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1

On a positive-feedback mechanism in intense atmospheric vortices  

NASA Astrophysics Data System (ADS)

Attention is focused on a positive feedback that may play a significant role in intense vortices, such as tornadoes and, probably, tropical cyclones: rotation suppresses turbulence which, in turn, may intensify rotation. Some simple models illustrate this phenomenon.

Ingel, L. Kh.

2014-01-01

2

Effects of sex steroids on the positive estrogen feedback mechanism in intact women and castrate men.  

PubMed

We studied the effects of prolonged testosterone treatment on ovulatory function and positive estrogen feedback in women and of prolonged estrogen priming on gonadotropin feedback in castrate men. An estrogen provocation test was carried out in 4 groups of transsexual subjects: 12 female transsexuals in their early follicular phase (days 3-5; group 1A), 8 females who had been treated with Depo-testosterone (T) for 3-6 months (group 1B), 11 men who had been castrated 3 months previously (group 2A), and 4 male castrates treated with oral estrogen for 3 months starting 3 months after castration (group 2B). The estrogen provocation test consisted of 3 GnRH tests (100 micrograms) carried out immediately before (0 h) and 44 and 92 h after an im injection of estradiol valerate (10 mg). Responses to the estrogen provocation test in women with normal menstrual cycles (group 1A) were typically female. After initial suppression at 44 h, a LH surge (positive feedback) occurred at 92 h. Pituitary responsiveness, however, was amplified both at 44 and 92 h. Prolonged T priming of women in group 1B did not inhibit the estrogen-induced LH surge, nor was the amplitude of the surge blunted. Removal of androgens and other testicular factors (group 2A) did not result in the appearance of an estrogen-induced LH surge. On the other hand, prolonged estrogen priming in male castrates (group 2B) resulted in activation of the positive feedback mechanism; a LH surge in response to the estrogen provocation occurred. The results of the present study imply that 1) contrary to an earlier suggestion, testosterone does not block or blunt the LH surge, indicating that it is probably not responsible for suppressing the LH surge in normal men; 2) testosterone can cause ovulatory failure without suppressing the LH surge in women; and 3) prolonged estrogen priming may be involved in activation of the positive feedback mechanism in humans. PMID:3932451

Goh, H H; Wong, P C; Ratnam, S S

1985-12-01

3

Collective Irrationality and Positive Feedback  

PubMed Central

Recent experiments on ants and slime moulds have assessed the degree to which they make rational decisions when presented with a number of alternative food sources or shelter. Ants and slime moulds are just two examples of a wide range of species and biological processes that use positive feedback mechanisms to reach decisions. Here we use a generic, experimentally validated model of positive feedback between group members to show that the probability of taking the best of options depends crucially on the strength of feedback. We show how the probability of choosing the best option can be maximized by applying an optimal feedback strength. Importantly, this optimal value depends on the number of options, so that when we change the number of options the preference of the group changes, producing apparent “irrationalities”. We thus reinterpret the idea that collectives show "rational" or "irrational" preferences as being a necessary consequence of the use of positive feedback. We argue that positive feedback is a heuristic which often produces fast and accurate group decision-making, but is always susceptible to apparent irrationality when studied under particular experimental conditions. PMID:21541321

Nicolis, Stamatios C.; Zabzina, Natalia; Latty, Tanya; Sumpter, David J. T.

2011-01-01

4

Neurobiological mechanisms underlying oestradiol negative and positive feedback regulation of gonadotropin-releasing hormone (GnRH) neurones  

PubMed Central

The feedback actions of ovarian oestradiol during the female reproductive cycle are among the most unique in physiology. During most of the cycle, oestradiol exerts homeostatic, negative feedback upon the release of gonadotropin-releasing hormone (GnRH). Upon exposure to sustained elevated oestradiol levels, however, there is a switch in the feedback effects of this hormone to positive, resulting in induction of a surge in the release of GnRH that serves as a neuroendocrine signal to initiate the ovulatory cascade. Here we review recent developments stemming from studies in an animal model exhibiting daily switches between positive and negative feedback that have probed the neurobiological mechanisms, including changes in neural networks and intrinsic properties of GnRH neurones, underlying this switch in oestradiol action. PMID:19207821

Moenter, Suzanne M.; Chu, Zhiguo; Christian, Catherine A.

2009-01-01

5

Studies Of Positive-Position-Feedback Control  

NASA Technical Reports Server (NTRS)

Report discusses theoretical and experimental studies of positive-position-feedback control for suppressing vibrations in large flexible structures. Positive-position-feedback control involves placement of actuators and sensors on structure; control voltages applied to actuators in response to outputs of sensors processed via compensator algorithm. Experiments demonstrate feasibility of suppressing vibrations by positive position feedback, and spillover of vibrational energy into uncontrolled modes has stabilizing effect if control gain sufficiently small.

Fanson, James L.; Caughey, Thomas K.

1992-01-01

6

A Positive Feedback Mechanism That Regulates Expression of miR-9 during Neurogenesis  

PubMed Central

MiR-9, a neuron-specific miRNA, is an important regulator of neurogenesis. In this study we identify how miR-9 is regulated during early differentiation from a neural stem-like cell. We utilized two immortalized rat precursor clones, one committed to neurogenesis (L2.2) and another capable of producing both neurons and non-neuronal cells (L2.3), to reproducibly study early neurogenesis. Exogenous miR-9 is capable of increasing neurogenesis from L2.3 cells. Only one of three genomic loci capable of encoding miR-9 was regulated during neurogenesis and the promoter region of this locus contains sufficient functional elements to drive expression of a luciferase reporter in a developmentally regulated pattern. Furthermore, among a large number of potential regulatory sites encoded in this sequence, Mef2 stood out because of its known pro-neuronal role. Of four Mef2 paralogs, we found only Mef2C mRNA was regulated during neurogenesis. Removal of predicted Mef2 binding sites or knockdown of Mef2C expression reduced miR-9-2 promoter activity. Finally, the mRNA encoding the Mef2C binding partner HDAC4 was shown to be targeted by miR-9. Since HDAC4 protein could be co-immunoprecipitated with Mef2C protein or with genomic Mef2 binding sequences, we conclude that miR-9 regulation is mediated, at least in part, by Mef2C binding but that expressed miR-9 has the capacity to reduce inhibitory HDAC4, stabilizing its own expression in a positive feedback mechanism. PMID:24714615

Oni, Eileen N.; Swerdel, Mavis R.; Toro-Ramos, Alana J.; Li, Jiali; Hart, Ronald P.

2014-01-01

7

Positive feedback within a kinase signaling complex functions as a switch mechanism for NF-?B activation.  

PubMed

A switchlike response in nuclear factor-?B (NF-?B) activity implies the existence of a threshold in the NF-?B signaling module. We show that the CARD-containing MAGUK protein 1 (CARMA1, also called CARD11)-TAK1 (MAP3K7)-inhibitor of NF-?B (I?B) kinase-? (IKK?) module is a switch mechanism for NF-?B activation in B cell receptor (BCR) signaling. Experimental and mathematical modeling analyses showed that IKK activity is regulated by positive feedback from IKK? to TAK1, generating a steep dose response to BCR stimulation. Mutation of the scaffolding protein CARMA1 at serine-578, an IKK? target, abrogated not only late TAK1 activity, but also the switchlike activation of NF-?B in single cells, suggesting that phosphorylation of this residue accounts for the feedback. PMID:24833394

Shinohara, Hisaaki; Behar, Marcelo; Inoue, Kentaro; Hiroshima, Michio; Yasuda, Tomoharu; Nagashima, Takeshi; Kimura, Shuhei; Sanjo, Hideki; Maeda, Shiori; Yumoto, Noriko; Ki, Sewon; Akira, Shizuo; Sako, Yasushi; Hoffmann, Alexander; Kurosaki, Tomohiro; Okada-Hatakeyama, Mariko

2014-05-16

8

Position feedback control system  

DOEpatents

Disclosed is a system and method for independently evaluating the spatial positional performance of a machine having a movable member, comprising an articulated coordinate measuring machine comprising: a first revolute joint; a probe arm, having a proximal end rigidly attached to the first joint, and having a distal end with a probe tip attached thereto, wherein the probe tip is pivotally mounted to the movable machine member; a second revolute joint; a first support arm serially connecting the first joint to the second joint; and coordinate processing means, operatively connected to the first and second revolute joints, for calculating the spatial coordinates of the probe tip; means for kinematically constraining the articulated coordinate measuring machine to a working surface; and comparator means, in operative association with the coordinate processing means and with the movable machine, for comparing the true position of the movable machine member, as measured by the true position of the probe tip, with the desired position of the movable machine member.

Bieg, Lothar F. (Albuquerque, NM); Jokiel, Jr., Bernhard (Albuquerque, NM); Ensz, Mark T. (Albuquerque, NM); Watson, Robert D. (Tijeras, NM)

2003-01-01

9

Depletion of Retinoic Acid Receptors Initiates a Novel Positive Feedback Mechanism that Promotes Teratogenic Increases in Retinoic Acid  

PubMed Central

Normal embryonic development and tissue homeostasis require precise levels of retinoic acid (RA) signaling. Despite the importance of appropriate embryonic RA signaling levels, the mechanisms underlying congenital defects due to perturbations of RA signaling are not completely understood. Here, we report that zebrafish embryos deficient for RA receptor ?b1 (RAR?b1), a conserved RAR splice variant, have enlarged hearts with increased cardiomyocyte (CM) specification, which are surprisingly the consequence of increased RA signaling. Importantly, depletion of RAR?b2 or concurrent depletion of RAR?b1 and RAR?b2 also results in increased RA signaling, suggesting this effect is a broader consequence of RAR depletion. Concurrent depletion of RAR?b1 and Cyp26a1, an enzyme that facilitates degradation of RA, and employment of a novel transgenic RA sensor line support the hypothesis that the increases in RA signaling in RAR deficient embryos are the result of increased embryonic RA coupled with compensatory RAR expression. Our results support an intriguing novel mechanism by which depletion of RARs elicits a previously unrecognized positive feedback loop that can result in developmental defects due to teratogenic increases in embryonic RA. PMID:23990796

D'Aniello, Enrico; Rydeen, Ariel B.; Anderson, Jane L.; Mandal, Amrita; Waxman, Joshua S.

2013-01-01

10

Positive feedback regulation of prothoracicotropic hormone secretion by ecdysteroid - A mechanism that determines the timing of metamorphosis.  

PubMed

When insect larvae have fully grown, prothoracicotropic hormone (PTTH) is released from the brain, triggering the initiation of metamorphic development through stimulation of ecdysteroid secretion by the prothoracic glands. The present study analyzes the mechanism that regulates the occurrence of this PTTH surge. In the silkworm Bombyx mori, the PTTH surge occurs on day 6 of the fifth instar and is preceded by a small rise in hemolymph ecdysteroid titer, which occurs late on day 5. We therefore hypothesized that this rise of ecdysteroid titer is involved in the induction of the PTTH surge. To test this hypothesis, two experiments were conducted. First, a small amount of 20-hydroxyecdysone was injected on day 4, two days before the expected day of the PTTH surge, to simulate the small rise in hemolymph ecdysteroid titer on day 5. This injection led to a precocious surge of PTTH the next day. Next, the hemolymph ecdysteroid titer on day 5 was artificially lowered by injecting ecdysteroid-22-oxidase, which inactivates 20-hydroxyecdysone. After this treatment, the PTTH surge did not occur on day 6 in 80% of the animals. These results indicate that a small rise of the hemolymph ecdysteroid titer plays a critical role in the induction of the PTTH surge. Since basal ecdysteroidogenic activity of the prothoracic glands increases with larval growth, a circulating level of ecdysteroids may convey information about larval maturity to the brain, to coordinate larval growth and metamorphosis. This is the first report in invertebrates to demonstrate positive feedback regulation of the surge of a tropic hormone by a downstream steroid hormone. PMID:25596092

Mizoguchi, Akira; Kamimura, Manabu; Kiuchi, Makoto; Kataoka, Hiroshi

2015-03-01

11

DAPK-HSF1 interaction as a positive-feedback mechanism stimulating TNF-induced apoptosis in colorectal cancer cells.  

PubMed

Death-associated protein kinase (DAPK) is a serine-threonine kinase with tumor suppressor function. Previously, we demonstrated that tumor necrosis factor (TNF) induced DAPK-mediated apoptosis in colorectal cancer. However, the protein-protein interaction network associated with TNF-DAPK signaling still remains unclear. We identified HSF1 as a new DAPK phosphorylation target in response to low concentrations of TNF and verified a physical interaction between DAPK and HSF1 both in vitro and in vivo. We show that HSF1 binds to the DAPK promoter. Transient overexpression of HSF1 protein led to an increase in DAPK mRNA level and consequently to an increase in the amount of apoptosis. By contrast, treatment with a DAPK-specific inhibitor as well as DAPK knockdown abolished the phosphorylation of HSF1 at Ser230 (pHSF1(Ser230)). Furthermore, translational studies demonstrated a positive correlation between DAPK and pHSF1(Ser230) protein expression in human colorectal carcinoma tissues. Taken together, our data define a novel link between DAPK and HSF1 and highlight a positive-feedback loop in DAPK regulation under mild inflammatory stress conditions in colorectal tumors. For the first time, we show that under TNF the pro-survival HSF1 protein can be redirected to a pro-apoptotic program. PMID:25380824

Benderska, Natalya; Ivanovska, Jelena; Rau, Tilman T; Schulze-Luehrmann, Jan; Mohan, Suma; Chakilam, Saritha; Gandesiri, Muktheshwar; Ziesché, Elisabeth; Fischer, Thomas; Söder, Stephan; Agaimy, Abbas; Distel, Luitpold; Sticht, Heinrich; Mahadevan, Vijayalakshmi; Schneider-Stock, Regine

2014-12-15

12

Positive feedback, memory, and the predictability of earthquakes.  

PubMed

We review the "critical point" concept for large earthquakes and enlarge it in the framework of so-called "finite-time singularities." The singular behavior associated with accelerated seismic release is shown to result from a positive feedback of the seismic activity on its release rate. The most important mechanisms for such positive feedback are presented. We solve analytically a simple model of geometrical positive feedback in which the stress shadow cast by the last large earthquake is progressively fragmented by the increasing tectonic stress. PMID:11875202

Sammis, C G; Sornette, D

2002-02-19

13

Positive feedback, memory, and the predictability of earthquakes  

PubMed Central

We review the “critical point” concept for large earthquakes and enlarge it in the framework of so-called “finite-time singularities.” The singular behavior associated with accelerated seismic release is shown to result from a positive feedback of the seismic activity on its release rate. The most important mechanisms for such positive feedback are presented. We solve analytically a simple model of geometrical positive feedback in which the stress shadow cast by the last large earthquake is progressively fragmented by the increasing tectonic stress. PMID:11875202

Sammis, C. G.; Sornette, D.

2002-01-01

14

Positive feedback in cellular control systems  

PubMed Central

Summary Feedback loops have been identified in a variety of regulatory systems and organisms. While feedback loops of the same type (negative or positive) tend to have properties in common, they can play distinctively diverse roles in different regulatory systems, where they can affect virulence in a pathogenic bacterium, maturation patterns of vertebrate oocytes and transitions through cell cycle phases in eukaryotic cells. This review focuses on the properties and functions of positive feedback in biological systems, including bistability, hysteresis and activation surges. PMID:18478531

Mitrophanov, Alexander Y.; Groisman, Eduardo A.

2008-01-01

15

Activation of apoptosis by caspase-3-dependent specific RelB cleavage in anticancer agent-treated cancer cells: Involvement of positive feedback mechanism.  

PubMed

DTCM-glutarimide (DTCM-G) is a newly found anti-inflammatory agent. In the course of experiments with lymphoma cells, we found that DTCM-G induced specific RelB cleavage. Anticancer agent vinblastine also induced the specific RelB cleavage in human fibrosarcoma HT1080 cells. The site-directed mutagenesis analysis revealed that the Asp205 site in RelB was specifically cleaved possibly by caspase-3 in vinblastine-treated HT1080 cells. Moreover, the cells stably overexpressing RelB Asp205Ala were resistant to vinblastine-induced apoptosis. Thus, the specific Asp205 cleavage of RelB by caspase-3 would be involved in the apoptosis induction by anticancer agents, which would provide the positive feedback mechanism. PMID:25511695

Kuboki, Mizuki; Ito, Ayumi; Simizu, Siro; Umezawa, Kazuo

2015-01-16

16

Elemental and Isotopic Evidence for Positive and Negative Feedback Mechanisms Governing Magmatic Flux in the Coast Mountains Batholith, British Columbia  

NASA Astrophysics Data System (ADS)

New REE data from 80 plutonic rocks from the southern Coast Mountains Batholith (CMB) ranging from 198 - 50 Ma form distinct populations of steeply ((La/Yb)N = 30 - 65) and shallowly dipping((La/Yb)N < 10) chondrite-normalized patterns. Nd and Sr isotopes have overall primitive characteristics with initial ? Nd from -2 to +8 and initial 87Sr/86Sr of 0.7030 - 0.7065. Periods of high magmatic flux (160-140 Ma, 120-80 Ma, and 60-50 Ma) when high (La/Yb)N was accompanied by less primitive Nd and Sr are preceded by low magmatic flux periods (200-160 Ma, 140- 120 Ma and 80-60 Ma) when (La/Yb)N was low and Nd and Sr appear more mantle-like. Magmatic flux in the CMB appears have been governed by shortening and thickening in the upper plate, which caused an increase in lower crustal melting. Continued crustal shortening eventually led to a negative feedback in CMB magmatic flux, as the combination of an over thickened crust and crowding of the wedge beneath the arc with igneous residues and lithospheric mantle inhibited underthrusting and the supply of fertile lithologies to the lower crust. Delamination or foundering of igneous residues and mantle lithosphere during low magmatic flux periods alleviates the space problem in the sub-arc wedge and allows renewed underthrusting to initiate the next period of high magmatic flux. This explains why CMB granitoids were generated deeper in the crust with garnet-rich residues (high (La/Yb)N) and less primitive initial ? Nd and 87Sr/86Sr during periods of high magmatic flux, while during periods of low magmatic flux granitoids were generated at a shallower depth with opposite signatures. Recognition of delamination events in the CMB has important implications for how continental arcs evolve through time.

Girardi, J. D.; Patchett, P.; Ducea, M. N.; Gehrels, G. E.; Manthei, C. D.; Pearson, D. M.; Rusmore, M. E.; Woodsworth, G. J.; Fan, J.; Kerrich, R. W.; Thole, J. T.; Wirth, K. R.

2008-12-01

17

Exotic herbivores directly facilitate the exotic grasses they graze: mechanisms for an unexpected positive feedback between invaders  

Microsoft Academic Search

The ability of an exotic species to establish in a system may depend not only on the invasibility of the native community,\\u000a but also on its interactions with other exotic species. Though examples of mutually beneficial interactions between exotic\\u000a species are known, few studies have quantified these effects or identified specific mechanisms. We used the co-invasion of\\u000a an endangered island

Rebecca J. Best; Peter Arcese

2009-01-01

18

Positive force feedback in bouncing gaits?  

PubMed Central

During bouncing gaits (running, hopping, trotting), passive compliant structures (e.g. tendons, ligaments) store and release part of the stride energy. Here, active muscles must provide the required force to withstand the developing tendon strain and to compensate for the inevitable energy losses. This requires an appropriate control of muscle activation. In this study, for hopping, the potential involvement of afferent information from muscle receptors (muscle spindles, Golgi tendon organs) is investigated using a two-segment leg model with one extensor muscle. It is found that: (i) positive feedbacks of muscle-fibre length and muscle force can result in periodic bouncing; (ii) positive force feedback (F+) stabilizes bouncing patterns within a large range of stride energies (maximum hopping height of 16.3 cm, almost twofold higher than the length feedback); and (iii) when employing this reflex scheme, for moderate hopping heights (up to 8.8 cm), an overall elastic leg behaviour is predicted (hopping frequency of 1.4-3 Hz, leg stiffness of 9-27 kN m(-1)). Furthermore, F+ could stabilize running. It is suggested that, during the stance phase of bouncing tasks, the reflex-generated motor control based on feedbacks might be an efficient and reliable alternative to central motor commands. PMID:14561282

Geyer, Hartmut; Seyfarth, Andre; Blickhan, Reinhard

2003-01-01

19

Potential macro-detritivore range expansion into the subarctic stimulates litter decomposition: a new positive feedback mechanism to climate change?  

PubMed

As a result of low decomposition rates, high-latitude ecosystems store large amounts of carbon. Litter decomposition in these ecosystems is constrained by harsh abiotic conditions, but also by the absence of macro-detritivores. We have studied the potential effects of their climate change-driven northward range expansion on the decomposition of two contrasting subarctic litter types. Litter of Alnus incana and Betula pubescens was incubated in microcosms together with monocultures and all possible combinations of three functionally different macro-detritivores (the earthworm Lumbricus rubellus, isopod Oniscus asellus, and millipede Julus scandinavius). Our results show that these macro-detritivores stimulated decomposition, especially of the high-quality A. incana litter and that the macro-detritivores tested differed in their decomposition-stimulating effects, with earthworms having the largest influence. Decomposition processes increased with increasing number of macro-detritivore species, and positive net diveristy effects occurred in several macro-detritivore treatments. However, after correction for macro-detritivore biomass, all interspecific differences in macro-detritivore effects, as well as the positive effects of species number on subarctic litter decomposition disappeared. The net diversity effects also appeared to be driven by variation in biomass, with a possible exception of net diversity effects in mass loss. Based on these results, we conclude that the expected climate change-induced range expansion of macro-detritivores into subarctic regions is likely to result in accelerated decomposition rates. Our results also indicate that the magnitude of macro-detritivore effects on subarctic decomposition will mainly depend on macro-detritivore biomass, rather than on macro-detritivore species number or identity. PMID:21735203

van Geffen, Koert G; Berg, Matty P; Aerts, Rien

2011-12-01

20

Ribosome flow model with positive feedback  

PubMed Central

Eukaryotic mRNAs usually form a circular structure; thus, ribosomes that terminatae translation at the 3? end can diffuse with increased probability to the 5? end of the transcript, initiating another cycle of translation. This phenomenon describes ribosomal flow with positive feedback—an increase in the flow of ribosomes terminating translating the open reading frame increases the ribosomal initiation rate. The aim of this paper is to model and rigorously analyse translation with feedback. We suggest a modified version of the ribosome flow model, called the ribosome flow model with input and output. In this model, the input is the initiation rate and the output is the translation rate. We analyse this model after closing the loop with a positive linear feedback. We show that the closed-loop system admits a unique globally asymptotically stable equilibrium point. From a biophysical point of view, this means that there exists a unique steady state of ribosome distributions along the mRNA, and thus a unique steady-state translation rate. The solution from any initial distribution will converge to this steady state. The steady-state distribution demonstrates a decrease in ribosome density along the coding sequence. For the case of constant elongation rates, we obtain expressions relating the model parameters to the equilibrium point. These results may perhaps be used to re-engineer the biological system in order to obtain a desired translation rate. PMID:23720534

Margaliot, Michael; Tuller, Tamir

2013-01-01

21

The progesterone positive feedback effect in women after ovariectomy.  

PubMed

Various ovarian substances regulate the secretion of gonadotrophins during the menstrual cycle, but there are still several unclarified issues. The aim of this study was to investigate the positive feedback effect of progesterone during the immediate period following ovariectomy. Experiments were performed in 12 normally cycling women (aged 39-49 years). Following abdominal hysterectomy plus bilateral ovariectomy performed on cycle day 3 (day 0), the women received either estradiol via skin patches (days 0-7, n = 6, group 1) or estradiol as above plus vaginal progesterone (days 1-7, n = 6, group 2). Serum estradiol values increased similarly in the two groups. After the operation, serum progesterone levels decreased significantly in group 1, while in group 2 they remained stable becoming higher than in group 1 (p < 0.05). An LH and an FSH surge occurred in group 2 with the values after the peak returning to the pre-surge baseline. In contrast, in group 1 LH and FSH levels following an initial decrease, increased gradually until the end of the experiment. These results demonstrate that, despite a variable response to estrogens, the positive feedback effect of progesterone remained intact immediately after ovariectomy in women. It is suggested that it is the combining action of estradiol and progesterone that can ensure the expression of a positive feedback mechanism in women. PMID:23153029

Zavos, Apostolos; Dafopoulos, Konstantinos; Messini, Christina I; Georgoulias, Panagiotis; Verikouki, Christina; Anifandis, George; Garas, Antonios; Messinis, Ioannis E

2013-03-01

22

Positive feedback, stochasticity and genetic competence  

NASA Astrophysics Data System (ADS)

A single gene, regulating its own expression via a positive feedback loop, constitutes a common motif in gene regulatory networks and signalling cascades. Recent experiments on the development of competence in the bacterial population B. subtilis show that the autoregulatory genetic module by itself can give rise to two types of cellular states. The states correspond to the low and high expression states of the master regulator ComK. The high expression state is attained when the ComK protein level exceeds a threshold value leading to a full activation of the autostimulatory loop. Stochasticity in gene expression drives the transitions between the two stable states. In this paper, we explain the appearance of bimodal protein distributions in B. subtilis cell population in the framework of three possible scenarios. In two of the cases, bistability provides the basis for binary gene expression. In the third case, the system is monostable in a deterministic description and stochasticity in gene expression is solely responsible for the appearance of the two expression states.

Karmakar, Rajesh; Bose, Indrani

2007-03-01

23

DC-SQUID electronics based on adaptive positive feedback; Experiments  

SciTech Connect

This paper demonstrates that the dc-SQUID read-out electronics can be realized utilizing positive feedback without deteriorating the SQUID noise performance. The required gain rise is achieved by interconnecting the SQUID output and a flux modulation coil via a cooled FET acting as a voltage-controlled resistor, different SQUIDs with different types of FETs have been studied experimentally. Possibilities to build an adaptive control of the feedback gain produced by the positive feedback are briefly discussed.

Seppa, H. (Metrology Research Inst., VTT, Technical Research Centre of Finland, Otakaari 7B, SF-02150 Espoo (FI)); Ahonen, A.; Knuutila, J.; Simola, J.; Vilkman, V. (Low Temperature Lab., Helsinki Univ. of Technology, SF-02150 Espoo (FI))

1991-03-01

24

Positively biased processing of self-relevant social feedback.  

PubMed

Receiving social feedback such as praise or blame for one's character traits is a key component of everyday human interactions. It has been proposed that humans are positively biased when integrating social feedback into their self-concept. However, a mechanistic description of how humans process self-relevant feedback is lacking. Here, participants received feedback from peers after a real-life interaction. Participants processed feedback in a positively biased way, i.e., they changed their self-evaluations more toward desirable than toward undesirable feedback. Using functional magnetic resonance imaging we investigated two feedback components. First, the reward-related component correlated with activity in ventral striatum and in anterior cingulate cortex/medial prefrontal cortex (ACC/MPFC). Second, the comparison-related component correlated with activity in the mentalizing network, including the MPFC, the temporoparietal junction, the superior temporal sulcus, the temporal pole, and the inferior frontal gyrus. This comparison-related activity within the mentalizing system has a parsimonious interpretation, i.e., activity correlated with the differences between participants' own evaluation and feedback. Importantly, activity within the MPFC that integrated reward-related and comparison-related components predicted the self-related positive updating bias across participants offering a mechanistic account of positively biased feedback processing. Thus, theories on both reward and mentalizing are important for a better understanding of how social information is integrated into the human self-concept. PMID:23175836

Korn, Christoph W; Prehn, Kristin; Park, Soyoung Q; Walter, Henrik; Heekeren, Hauke R

2012-11-21

25

Positive Feedback-Assisted Long-Range Cell Signalings in Mapk Cascades  

NASA Astrophysics Data System (ADS)

In this paper, we study potentials of positive feedback in spatial phosphoprotein signal propagation. For this, we consider a signaling pathway of four-tiered protein kinase cascades with each tier involving single (de)phosphorylation reactions only. In the case of a small cell, we propose a short positive feedback for short-range cell signaling, which can generate bistability to facilitate the phosphoprotein signal propagation from the plasma membrane to the periphery of cell nucleus. In contrast, in the case of a large cell for which the long-range signaling cannot be achieved by the short feedback, we propose a long positive feedback, and find that it can facilitate the propagation of phosphoprotein signal over a long distance. These results imply that positive-feedback mechanisms would be employed by living organisms for spatial information transfer and cellular decision-making processing.

Zhang, Yanbin; Chen, Kenian; Wang, Junwei; Chen, Aimin; Zhou, Tianshou

26

Alignment positioning mechanism  

NASA Technical Reports Server (NTRS)

An alignment positioning mechanism for correcting and compensating for misalignment of structures to be coupled is disclosed. The mechanism comprises a power screw with a base portion and a threaded shank portion. A mounting fixture is provided for rigidly coupling said base portion to the mounting interface of a supporting structure with the axis of the screw perpendicular thereto. A traveling ball nut threaded on the power screw is formed with an external annular arcuate surface configured in the form of a spherical segment and enclosed by a ball nut housing with a conforming arcuate surface for permitting gimballed motion thereon. The ball nut housing is provided with a mounting surface which is positionable in cooperable engagement with the mounting interface of a primary structure to be coupled to the supporting structure. Cooperative means are provided on the ball nut and ball nut housing, respectively, for positioning the ball nut and ball nut housing in relative gimballed position within a predetermined range of relative angular relationship whereby severe structural stresses due to unequal loadings and undesirable bending moments on the mechanism are avoided.

Fantasia, Peter M. (inventor)

1991-01-01

27

Feedback Mechanisms and constraints on Climate Sensitivity  

E-print Network

Feedback Mechanisms and constraints on Climate Sensitivity from a Perturbed Physics Ensemble and constraints on Climate Sensitivity from a Perturbed Physics Ensemble of General Circulation Models Benjamin is used to identify the dominant physical processes responsible for variation in climate sensitivity

28

Position feedback system for volume holographic storage media  

DOEpatents

A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g. voice coil motor) which respond to position feedback information and adjust the angular position of the reference angle of a reference beam to maximize SNR by reducing crosstalk, thereby improving storage capacity.

Hays, Nathan J. (San Francisco, CA); Henson, James A. (Morgan Hill, CA); Carpenter, Christopher M. (Sunnyvale, CA); Akin, Jr.. William R. (Morgan Hill, CA); Ehrlich, Richard M. (Saratoga, CA); Beazley, Lance D. (San Jose, CA)

1998-07-07

29

Cytokinesis through biochemical-mechanical feedback loops  

PubMed Central

Cytokinesis is emerging as a control system defined by interacting biochemical and mechanical modules, which form a system of feedback loops. This integrated system accounts for the regulation and kinetics of cytokinesis furrowing and demonstrates that cytokinesis is a whole-cell process in which the global and equatorial cortices and cytoplasm are active players in the system. Though originally defined in Dictyostelium, features of the control system are recognizable in other organisms, suggesting a universal mechanism for cytokinesis regulation and contractility. PMID:20709619

Surcel, Alexandra; Kee, Yee-Seir; Luo, Tianzhi; Robinson, Douglas N.

2010-01-01

30

Monotone Systems Under Positive Feedback: Multistability and a Reduction Theorem  

E-print Network

-01-1-0063 and NIH Grant R01 GM46383. Preprint submitted to Elsevier Science 17 July 2004 #12;This note is a follow-up to these two. In this paper, we deal with systems with inputs and outputs, as usual in control theory ([17]): xMonotone Systems Under Positive Feedback: Multistability and a Reduction Theorem German Enciso a,1

Enciso, Germán

31

High-Pass Filtered Positive Feedback. Decentralized Control of Cooperation  

Microsoft Academic Search

In a multilegged walking system, the legs, when in stance mode, have to cooperate to propel and support the body and, at the same time, to avoid unwanted forces across the body. As a simple method to control the joint movement, we propose to use local high-pass filtered positive feedback. This does not only make redundant the determination of equations

Holk Cruse; Christian Bartling; Thomas Kindermann

1995-01-01

32

Differential effects of aging on estrogen negative and positive feedback  

PubMed Central

Recent studies have demonstrated an age-related decline in gonadotropins and a decrease in pituitary responsiveness to GnRH, indicating that aging influences the neuroendocrine components of the female reproductive axis independently of changes in ovarian function. To determine whether aging might also affect the luteinizing hormone (LH) negative and positive feedback responses to gonadal steroids, we administered a controlled, graded sex steroid infusion to 11 younger (45–56 yr) and nine older (70–80 yr) postmenopausal women (PMW) in whom endogenous ovarian steroids and peptides are uniformly low. The doses of estradiol (E2) and progesterone (P) were chosen to mimic levels across the normal follicular phase and have been shown previously to induce negative followed by positive feedback on LH. Similar E2 and P levels were achieved in younger and older PMW (P = 0.4 and 0.3, respectively) and produced a biphasic LH response in all subjects. The early decline in LH to 53% of baseline was not different in older vs. younger PMW. However, the positive feedback effect was attenuated in older compared with younger PMW (peak LH 144.4 ± 19.5 vs. 226.8 ± 22.3 IU/l, respectively, P = 0.01). In conclusion, these studies in PMW demonstrate preservation of short-term steroid negative and positive feedback in response to exogenous E2 and P with aging. Attenuation of positive feedback in older compared with younger PMW is consistent with previous reports of declining GnRH responsiveness with aging. PMID:21558550

Shaw, N. D.; Srouji, S. S.; Histed, S. N.

2011-01-01

33

On feedback and stable price adjustment mechanisms  

NASA Astrophysics Data System (ADS)

Given an excess demand function of an economy, say Z(p), a stable price adjustment mechanism (SPAM) guarantees convergence of solution path p(t,p0) to an equilibrium peq solution of Z(p)=0. Besides, all equilibrium points of Z(p) are asymptotically stable. Some SPAMs have been proposed, including Newton and transpose Jacobian methods. Despite this powerful stability property of SPAMs, their acceptation in the economics community has been limited by a lack of interpretation. This paper focuses on this issue. Specifically, feedback control theory is used to link SPAMs and price dynamics models with control inputs, which match the economically intuitive Walrasian Hypothesis (i.e., prices change with excess demand sign). Under mild conditions, it is shown the existence of a feedback function that transforms the price dynamics into a desired SPAM. Hence, a SPAM is interpreted as a fundamental (e.g., Walrasian) price dynamics under the action of a feedback function aimed to stabilize the equilibrium set of the excess demand function.

Fernandez-Anaya, Guillermo; Alvarez-Ramirez, Jose; Ibarra-Valdez, Carlos

2007-04-01

34

Positive feedback regulation results in spatial clustering and fast spreading of active signaling molecules on a cell membrane  

PubMed Central

Positive feedback regulation is ubiquitous in cell signaling networks, often leading to binary outcomes in response to graded stimuli. However, the role of such feedbacks in clustering, and in spatial spreading of activated molecules, has come to be appreciated only recently. We focus on the latter, using a simple model developed in the context of Ras activation with competing negative and positive feedback mechanisms. We find that positive feedback, in the presence of slow diffusion, results in clustering of activated molecules on the plasma membrane, and rapid spatial spreading as the front of the cluster propagates with a constant velocity (dependent on the feedback strength). The advancing fronts of the clusters of the activated species are rough, with scaling consistent with the Kardar–Parisi–Zhang equation in one dimension. Our minimal model is general enough to describe signal transduction in a wide variety of biological networks where activity in the membrane-proximal region is subject to feedback regulation. PMID:19566183

Das, Jayajit; Kardar, Mehran; Chakraborty, Arup K.

2009-01-01

35

Improved Position Sensor for Feedback Control of Levitation  

NASA Technical Reports Server (NTRS)

An improved optoelectronic apparatus has been developed to provide the position feedback needed for controlling the levitation subsystem of a containerless-processing system. As explained, the advantage of this apparatus over prior optoelectronic apparatuses that have served this purpose stems from the use of an incandescent lamp, instead of a laser, to illuminate the levitated object. In containerless processing, a small object to be processed is levitated (e.g., by use of a microwave, low-frequency electromagnetic, electrostatic, or acoustic field) so that it is not in contact with the wall of the processing chamber or with any other solid object during processing. In the case of electrostatic or low-frequency electromagnetic levitation, real-time measurement of the displacement of the levitated object from its nominal levitation position along the vertical axis (and, in some cases, along one or two horizontal axes) is needed for feedback control of the levitating field.

Hyers, Robert; Savage, Larry; Rogers, Jan

2004-01-01

36

Positive feedback between future climate change and the carbon cycle  

Microsoft Academic Search

Future climate change due to increased atmospheric CO2 may affect land and ocean efficiency to absorb atmospheric CO2. Here, using climate and carbon three-dimensional models forced by a 1% per year increase in atmospheric CO2, we show that there is a positive feedback between the climate system and the carbon cycle. Climate change reduces land and ocean uptake of CO2,

Pierre Friedlingstein; Laurent Bopp; Philippe Ciais; Jean-Louis Dufresne; Laurent Fairhead; Hervé LeTreut; Patrick Monfray; James Orr

2001-01-01

37

Positive feedback, lock-in, and environmental policy  

Microsoft Academic Search

During the last several decades, modern economic methods have been brought to bear on problems of environmental policy, with powerful and influential results. However, this policy-making paradigm often relies on some of the most restrictive sets of assumptions of microeconomics: the convexity conditions required for competitive markets to be Pareto-efficient. When positive feedback or lock-inoccurs, these assumptions do not hold,

David Kline

2001-01-01

38

Reputation can enhance or suppress cooperation through positive feedback.  

PubMed

One possible explanation for the widespread existence of cooperation in nature is that individuals cooperate to establish reputations and so benefit in future interactions with others. We consider a class of games in which individuals contribute to a common good at a cost to themselves. Population members vary in type, that is, in the cost paid for a given level of contribution. We consider a form of indirect reciprocity in which the contribution of an individual depends on their partner's reputation and their own type. Here we show that for such games, reputation destabilizes the selfish equilibrium through a novel and robust feedback mechanism. For those games in which the selfish optimal contribution to the common good increases as the contribution of the partner increases, the feedback mechanism enhances cooperation levels. In contrast, when the optimal contribution decreases as partner's contribution increases, cooperation levels are reduced still further. PMID:25601004

McNamara, John M; Doodson, Polly

2015-01-01

39

The p53 pathway: positive and negative feedback loops.  

PubMed

The p53 pathway responds to stresses that can disrupt the fidelity of DNA replication and cell division. A stress signal is transmitted to the p53 protein by post-translational modifications. This results in the activation of the p53 protein as a transcription factor that initiates a program of cell cycle arrest, cellular senescence or apoptosis. The transcriptional network of p53-responsive genes produces proteins that interact with a large number of other signal transduction pathways in the cell and a number of positive and negative autoregulatory feedback loops act upon the p53 response. There are at least seven negative and three positive feedback loops described here, and of these, six act through the MDM-2 protein to regulate p53 activity. The p53 circuit communicates with the Wnt-beta-catenin, IGF-1-AKT, Rb-E2F, p38 MAP kinase, cyclin-cdk, p14/19 ARF pathways and the cyclin G-PP2A, and p73 gene products. There are at least three different ubiquitin ligases that can regulate p53 in an autoregulatory manner: MDM-2, Cop-1 and Pirh-2. The meaning of this redundancy and the relative activity of each of these feedback loops in different cell types or stages of development remains to be elucidated. The interconnections between signal transduction pathways will play a central role in our understanding of cancer. PMID:15838523

Harris, Sandra L; Levine, Arnold J

2005-04-18

40

A Positive Feedback Synapse from Retinal Horizontal Cells to Cone Photoreceptors  

PubMed Central

Cone photoreceptors and horizontal cells (HCs) have a reciprocal synapse that underlies lateral inhibition and establishes the antagonistic center-surround organization of the visual system. Cones transmit to HCs through an excitatory synapse and HCs feed back to cones through an inhibitory synapse. Here we report that HCs also transmit to cone terminals a positive feedback signal that elevates intracellular Ca2+ and accelerates neurotransmitter release. Positive and negative feedback are both initiated by AMPA receptors on HCs, but positive feedback appears to be mediated by a change in HC Ca2+, whereas negative feedback is mediated by a change in HC membrane potential. Local uncaging of AMPA receptor agonists suggests that positive feedback is spatially constrained to active HC-cone synapses, whereas the negative feedback signal spreads through HCs to affect release from surrounding cones. By locally offsetting the effects of negative feedback, positive feedback may amplify photoreceptor synaptic release without sacrificing HC-mediated contrast enhancement. PMID:21559323

Jackman, Skyler L.; Babai, Norbert; Chambers, James J.; Thoreson, Wallace B.; Kramer, Richard H.

2011-01-01

41

Active control of a flexible structure using a modal positive position feedback controller  

NASA Technical Reports Server (NTRS)

The feasibility of a new Modal Positive Position Feedback (MPPF) strategy in controlling the vibration of a complex flexible structure using a single piezo-electric active structural member is demonstrated. The control strategy generates its control forces by manipulating only the modal position signals of the structure to provide a damping action to undamped modes. This is in contrast to conventional modal controllers that rely in their operation on negative feedback of both the modal position and velocity. The proposed strategy is very simple to design and implement as it designs the controller at the uncoupled modal level and utilizes simple first order filters to achieve the Positive Position Feedback effect. The performance of the new strategy is enhanced by augmenting it with a time sharing strategy to share a small number of actuators between larger number of modes. The effectiveness of the new strategy is validated experimentally on a flexible box-type structure that has four bays and its first two bending modes are 2.015 and 6.535 Hz respectively. A single piezo-electric actuator is utilized as an active structural member to control several transverse bending modes of the structure. The performance of the active control system is determined in the time and the frequency domains. The results are compared with those obtained when using the Independent Modal Space Control (IMSC) of Meirovitch. The experimental results suggest the potential of the proposed strategy as a viable means for controlling the vibration of large flexible structures in real time.

Poh, S.; Baz, A.

1990-01-01

42

Blowin' in the Wind: Both "Negative" and "Positive" Feedback in an Obscured High-z Quasar  

NASA Astrophysics Data System (ADS)

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, preventing massive galaxies to overgrow and producing the red colors of ellipticals. On the other hand, some models are also requiring "positive" active galactic nucleus feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively driven winds are available. Here we present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z = 1.59 QSO detected in the XMM-COSMOS survey, in which we clearly resolve a fast (1500 km s-1) and extended (up to 13 kpc from the black hole) outflow in the [O III] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of H? emission and the rest frame U-band flux from Hubble Space Telescope/Advanced Camera for Surveys imaging enable to map the current star formation in the host galaxy: both tracers independently show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy ("negative feedback"), but also triggering star formation by outflow induced pressure at the edges ("positive feedback"). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work.

Cresci, G.; Mainieri, V.; Brusa, M.; Marconi, A.; Perna, M.; Mannucci, F.; Piconcelli, E.; Maiolino, R.; Feruglio, C.; Fiore, F.; Bongiorno, A.; Lanzuisi, G.; Merloni, A.; Schramm, M.; Silverman, J. D.; Civano, F.

2015-01-01

43

The Effect of Positive Feedback in a Constraint-Based Intelligent Tutoring System  

ERIC Educational Resources Information Center

Tutoring technologies for supporting learning from errors via negative feedback are highly developed and have proven their worth in empirical evaluations. However, observations of empirical tutoring dialogs highlight the importance of positive feedback in the practice of expert tutoring. We hypothesize that positive feedback works by reducing…

Mitrovic, Antonija; Ohlsson, Stellan; Barrow, Devon K.

2013-01-01

44

78 FR 13057 - Agency Information Collection Activities; Information Collection; IT Dashboard Feedback Mechanism  

Federal Register 2010, 2011, 2012, 2013, 2014

...Information Collection; IT Dashboard Feedback Mechanism AGENCY: Office of Innovative...collection requirement regarding IT Dashboard Feedback Mechanism. DATES: Submit comments on...Collection 3090- 0285, IT Dashboard Feedback Mechanism, by any of the following...

2013-02-26

45

78 FR 36190 - Agency Information Collection Activities; Submission for OMB Review; IT Dashboard Feedback Mechanism  

Federal Register 2010, 2011, 2012, 2013, 2014

...Submission for OMB Review; IT Dashboard Feedback Mechanism AGENCY: Office of Innovative...collection requirement regarding IT Dashboard Feedback Mechanism. A notice was published in...Collection 3090- 0285, IT Dashboard Feedback Mechanism, by any of the following...

2013-06-17

46

Making a commercial atomic force microscope more accurate and faster using positive position feedback control.  

PubMed

This paper presents experimental implementation of a positive position feedback (PPF) control scheme for vibration and cross-coupling compensation of a piezoelectric tube scanner in a commercial atomic force microscope (AFM). The AFM is a device capable of generating images with extremely high resolutions down to the atomic level. It is also being used in applications that involve manipulation of matter at a nanoscale. Early AFMs were operated in open loop. Consequently, they were susceptible to piezoelectric creep, thermal drift, hysteresis nonlinearity, and scan-induced vibration. These effects tend to distort the generated image and slow down the scanning speed of the device. Recently, a new generation of AFMs has emerged that utilizes position sensors to measure displacements of the scanner in three dimensions. These AFMs are equipped with feedback control loops that work to minimize the adverse effects of hysteresis, piezoelectric creep, and thermal drift on the obtained image using proportional-plus-integral (PI) controllers. These feedback controllers are often not designed to deal with the highly resonant nature of an AFM's scanner nor with the cross coupling between various axes. In this paper we illustrate the improvement in accuracy and imaging speed that can be achieved by using a properly designed feedback controller such as a PPF controller. Such controllers can be incorporated into most modern AFMs with minimal effort since they can be implemented in software with the existing hardware. Experimental results show that by implementing the PPF control scheme, relatively good images in comparison with a well-tuned PI controller can still be obtained up to line scan of 60 Hz. PMID:19566208

Mahmood, I A; Moheimani, S O Reza

2009-06-01

47

Climate sensitivity: analysis of feedback mechanisms  

Microsoft Academic Search

Abstract.,We study,climate,sensitivity,and feedback,processes,in three,independent,ways : (1) by using a three dimensional,(3-D) global cli- mate,model,for experiments,in which,solar irra- diance,, = 3-4, because either of these forcings would,cause,the,earth's surface,temperature,to

J Hansen; A Lacis; D Rind; G Russell; P Stone; I Fung; R Ruedy; J Lerner

1984-01-01

48

Positive Proprioceptive Feedback Elicited By Isometric Contractions of Ankle Flexors on Pretibial Motoneurons in Cats  

E-print Network

Positive Proprioceptive Feedback Elicited By Isometric Contractions of Ankle Flexors on Pretibial proprioceptive feedback elicited by isometric contractions of ankle flexors on pretibial motoneurons in cats. J inhibition. This contraction-induced Ia excitatory feedback in ankle flexors might either reinforce Ia

49

Comparison of negative and positive position feedback control of a flexible structure  

NASA Astrophysics Data System (ADS)

Two modal control techniques, negative position feedback (NPF) and positive position feedback (PPF), are applied to reduce multi-mode vibration of a lightly damped flexible beam using a piezoelectric sensor and piezoelectric actuators. The NPF and PPF controllers are constructed by respectively feeding back the generalized displacement response from the sensor in a negative and a positive sense to the actuators through second order high pass and low pass filters. PPF is well known while NPF is new for this application and is in fact an electrical realization of a dynamic vibration absorber. The choice of the parameters for controllers of both types is made easy by a robust modal control technique that offers an optimal performance for NPF control and a near-optimal performance for PPF control. Explicit forms of the controller parameters are presented. Experiments are conducted on a cantilever beam embedded with a matched pair of PZT (lead zirconate titanate) patch actuators and a collocated PVDF (polyvinylidene fluoride) patch sensor. The experiments demonstrate that it is possible to realize an electrical dynamic absorber using the generalized displacement sensor. It is further demonstrated that NPF can be a good alternative control strategy particularly when multiple modes are to be controlled.

Kim, Sang-Myeong; Wang, Semyung; Brennan, Michael J.

2011-01-01

50

Positive feedback and momentum growth during debris-flow entrainment of wet bed sediment  

USGS Publications Warehouse

Debris flows typically occur when intense rainfall or snowmelt triggers landslides or extensive erosion on steep, debris-mantled slopes. The flows can then grow dramatically in size and speed as they entrain material from their beds and banks, but the mechanism of this growth is unclear. Indeed, momentum conservation implies that entrainment of static material should retard the motion of the flows if friction remains unchanged. Here we use data from large-scale experiments to assess the entrainment of bed material by debris flows. We find that entrainment is accompanied by increased flow momentum and speed only if large positive pore pressures develop in wet bed sediments as the sediments are overridden by debris flows. The increased pore pressure facilitates progressive scour of the bed, reduces basal friction and instigates positive feedback that causes flow speed, mass and momentum to increase. If dryer bed sediment is entrained, however, the feedback becomes negative and flow momentum declines. We infer that analogous feedbacks could operate in other types of gravity-driven mass flow that interact with erodible beds. ?? 2011 Macmillan Publishers Limited. All rights reserved.

Iverson, R.M.; Reid, M.E.; Logan, M.; LaHusen, R.G.; Godt, J.W.; Griswold, J.P.

2011-01-01

51

Positive Force Feedback Control of Muscles ARTHUR PROCHAZKA, DEBORAH GILLARD, AND DAVID J. BENNETT  

E-print Network

on theoretical and empirical grounds to endow for the existence of positive force feedback in feline locomotor flexor Ib afferents tends to be much weaker andelicited by contact of the foot with the ground. MusclesPositive Force Feedback Control of Muscles ARTHUR PROCHAZKA, DEBORAH GILLARD, AND DAVID J. BENNETT

Prochazka, Arthur

52

Positive feedbacks of fire, climate, and vegetation and the conversion of tropical savanna  

E-print Network

Positive feedbacks of fire, climate, and vegetation and the conversion of tropical savanna William a positive feedback loop in which clearing of tropical savannas results in warmer and drier climate of tropical savannas increases temperatures and wind speeds and decreases precipitation and relative humidity

Jackson, Robert B.

53

On the utility of positive and negative feedback in a paired-associate learning task.  

PubMed

This study offers a neurophysiological examination of the relationship between feedback processing and learning. A two-choice paired-associate learning task borrowed and modified from Tricomi and Fiez [Tricomi, E., & Fiez, J. A. Feedback signals in the caudate reflect goal achievement on a declarative memory task. Neuroimage, 41, 1154-1167, 2008] was employed to examine the mediofrontal electrophysiological brain activity associated with the processing of performance feedback in a learning task and to elucidate the extent to which the processing of the initial informative feedback is related to learning outcomes. Twenty participants were tasked with learning to correctly pair 60 novel objects with their names by choosing on a trial-by-trial basis between two possible names and receiving feedback about the accuracy of their selection. The novel objects were presented in three blocks of trials (rounds), each of which presented the same set of 60 objects once. The rounds allowed the separation of the initial informative feedback in Round 1 from the other feedback stimuli in Rounds 2 and 3. The results indicated differences in the processing of initial informative and proceeding feedback stimuli. More specifically, the difference appeared to be driven by the change in the processing of positive feedback. Moreover, very first positive feedback provided in association with a particular new object was found associated with learning outcomes. The results imply that signs of successful and unsuccessful learning may be detected as early as the initial positive feedback provided in a learning task. The results suggest that the process giving rise to the feedback-related negativity is sensitive to the utility of the feedback and that the processing of the first informative positive feedback is associated with learning outcomes. PMID:24666164

Arbel, Yael; Murphy, Anthony; Donchin, Emanuel

2014-07-01

54

System justification and electrophysiological responses to feedback: support for a positivity bias.  

PubMed

Conservatives, compared to liberals, are consistently found to exhibit physiological sensitivity to aversive stimuli. However, it remains unknown whether conservatives are also sensitive to salient positively valenced stimuli. We therefore used event-related potentials to determine the relationship between system justification (SJ), a fundamental component of conservative political ideology, and neural processing of negative and positive feedback. Participants (N = 29) filled out questionnaire assessments of SJ. Feedback-related negativity (FRN), an event-related potential component thought to index activity in neural regions associated with reward processing, was assessed in response to positive and negative feedback on a time estimation task. A significant interaction was noted between SJ and feedback type in predicting FRN. Simple effects tests suggested that SJ predicted greater FRN in response to positive but not to negative feedback. Conservatives may experience salient positive information with a heightened intensity. PMID:24274321

Tritt, Shona M; Page-Gould, Elizabeth; Peterson, Jordan B; Inzlicht, Michael

2014-06-01

55

Blowin' in the wind: both `negative' and `positive' feedback in an outflowing quasar at z~1.6  

NASA Astrophysics Data System (ADS)

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation, preventing massive galaxies to over-grow and producing the red colors of ellipticals. On the other hand, some models are also requiring `positive' AGN feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively-driven winds are available. We present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z=1.59 QSO, in which we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black hole) outflow in the [OIII] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of H? emission and the rest frame U band flux show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy (`negative feedback'), but also triggering star formation by outflow induced pressure at the edges (`positive feedback'). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work.

Cresci, Giovanni

2015-02-01

56

Feedback mechanism for smart nozzles and nebulizers  

DOEpatents

Nozzles and nebulizers able to produce aerosol with optimum and reproducible quality based on feedback information obtained using laser imaging techniques. Two laser-based imaging techniques based on particle image velocimetry (PTV) and optical patternation map and contrast size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. Two pulses from thin laser sheet with known time difference illuminate droplets flow field. Charge coupled device (CCL)) captures scattering of laser light from droplets, providing two instantaneous particle images. Pointwise cross-correlation of corresponding images yields two-dimensional velocity map of aerosol velocity field. For droplet size distribution studies, solution is doped with fluorescent dye and both laser induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. Ratio of LIF/Mie images provides relative droplet size information, then scaled by point calibration method via phase Doppler particle analyzer.

Montaser, Akbar [Potomac, MD; Jorabchi, Kaveh [Arlington, VA; Kahen, Kaveh [Kleinburg, CA

2009-01-27

57

Through-wafer optical probe characterization for microelectromechanical systems positional state monitoring and feedback control  

NASA Astrophysics Data System (ADS)

Implementation of closed-loop microelectromechanical system (MEMS) control enables mechanical microsystems to adapt to the demands of the environment that they are actuating, opening a broad range of new opportunities for future MEMS applications. Integrated optical microsystems have the potential to enable continuous in situ optical interrogation of MEMS microstructure position fully decoupled from the means of mechanical actuation that is necessary for realization of feedback control. We present the results of initial research evaluating through-wafer optical microprobes for surface micromachined MEMS integrated optical position monitoring. Results from the through-wafer free-space optical probe of a lateral comb resonator fabricated using the multiuser MEMS process service (MUMPS) indicate significant positional information content with an achievable return probe signal dynamic range of up to 80% arising from film transmission contrast. Static and dynamic deflection analysis and experimental results indicate a through-wafer probe positional signal sensitivity of 40 mV/micrometers for the present setup or 10% signal change per micrometer. A simulation of the application of nonlinear sliding control is presented illustrating position control of the lateral comb resonator structure given the availability of positional state information.

Dawson, Jeremy M.; Chen, Jingdong; Brown, Kolin S.; Famouri, Parviz F.; Hornak, Lawrence A.

2000-12-01

58

Positive feedback can lead to dynamic nanometer-scale clustering on cell membranes  

NASA Astrophysics Data System (ADS)

Clustering of molecules on biological membranes is a widely observed phenomenon. A key example is the clustering of the oncoprotein Ras, which is known to be important for signal transduction in mammalian cells. Yet, the mechanism by which Ras clusters form and are maintained remains unclear. Recently, it has been discovered that activated Ras promotes further Ras activation. Here we show using particle-based simulation that this positive feedback is sufficient to produce persistent clusters of active Ras molecules at the nanometer scale via a dynamic nucleation mechanism. Furthermore, we find that our cluster statistics are consistent with experimental observations of the Ras system. Interestingly, we show that our model does not support a Turing regime of macroscopic reaction-diffusion patterning, and therefore that the clustering we observe is a purely stochastic effect, arising from the coupling of positive feedback with the discrete nature of individual molecules. These results underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.

Wehrens, Martijn; ten Wolde, Pieter Rein; Mugler, Andrew

2014-11-01

59

Blowin' in the wind: both `negative' and `positive' feedback in an obscured high-z Quasar  

E-print Network

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, preventing massive galaxies to over-grow and producing the red colors of ellipticals. On the other hand, some models are also requiring `positive' AGN feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively-driven winds are available. Here we present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z=1.59 QSO detected in the XMM-COSMOS survey, in which we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black hole) outflow in the [OIII] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Ha emission and the re...

Cresci, G; Brusa, M; Marconi, A; Perna, M; Mannucci, F; Piconcelli, E; Maiolino, R; Feruglio, C; Fiore, F; Bongiorno, A; Lanzuisi, G; Merloni, A; Schramm, M; Silverman, J D; Civano, F

2014-01-01

60

Multiversion Information Retrieval Systems and Feedback with Mechanism of Selection.  

ERIC Educational Resources Information Center

Discusses the design of multiversion information retrieval systems and provides a theoretical justification for the necessity of creating such systems to perform an optimal search for the user's information needs. Topics discussed include comparing query formulations; feedback algorithms; an experiment with a test collection; and the mechanism of…

Frants, Valery I.; And Others

1993-01-01

61

Cell Mechanics and Feedback Regulation of Actomyosin Networks  

NSDL National Science Digital Library

Actomyosin contractility is the major force-generating machinery that shapes cells and tissues during morphogenesis. New evidence from Drosophila demonstrates that these forces are spatially organized by a combination of biochemical and mechanical signals that provide dynamic feedback in a complex cellular environment.

Rodrigo Fernandez-Gonzalez (Sloan-Kettering Institute;Howard Hughes Medical Institute and the Developmental Biology Program REV); Jennifer A. Zallen (Sloan-Kettering Institute;Howard Hughes Medical Institute and the Developmental Biology Program REV)

2009-12-15

62

Alternative states and positive feedbacks in restoration ecology  

Microsoft Academic Search

There is increasing interest in developing better predictive tools and a broader conceptual framework to guide the restoration of degraded land. Traditionally, restoration efforts have focused on re-establishing historical disturbance regimes or abiotic conditions, relying on successional processes to guide the recovery of biotic communities. However, strong feedbacks between biotic factors and the physical environment can alter the efficacy of

Katharine N. Suding; Katherine L. Gross; Gregory R. Houseman

2004-01-01

63

Classical Estrogen Receptor ? Signaling Mediates Negative and Positive Feedback on Gonadotropin-Releasing Hormone Neuron Firing  

PubMed Central

During the female reproductive cycle, the neuroendocrine action of estradiol switches from negative feedback to positive feedback to initiate the preovulatory GnRH and subsequent LH surges. Estrogen receptor-? (ER?) is required for both estradiol negative and positive feedback regulation of LH. ER? may signal through estrogen response elements (EREs) in DNA and/or via ERE-independent pathways. Previously, a knock-in mutant allele (ER??/AA) that selectively restores ERE-independent signaling onto the ER??/? background was shown to confer partial negative but not positive estradiol feedback on serum LH. The current study investigated the roles of the ERE-dependent and ERE-independent ER? pathways for estradiol feedback at the level of GnRH neuron firing activity. The above ER? genetic models were crossed with GnRH-green fluorescent protein mice to enable identification of GnRH neurons in brain slices. Targeted extracellular recordings were used to monitor GnRH neuron firing activity using an ovariectomized, estradiol-treated mouse model that exhibits diurnal switches between negative and positive feedback. In wild-type mice, GnRH neuron firing decreased in response to estradiol during negative feedback and increased during positive feedback. In contrast, both positive and negative responses to estradiol were absent in GnRH neurons from ER??/? and ER??/AA mice. ERE-dependent signaling is thus required to increase GnRH neuron firing to generate a GnRH/LH surge. Furthermore, ERE-dependent and -independent ER? signaling pathways both appear necessary to mediate estradiol negative feedback on serum LH levels, suggesting central and pituitary estradiol feedback may use different combinations of ER? signaling pathways. PMID:18635656

Christian, Catherine A.; Glidewell-Kenney, Christine; Jameson, J. Larry; Moenter, Suzanne M.

2008-01-01

64

Understanding Informal Feedback Seeking in the Workplace: The Impact of the Position in the Organizational Hierarchy  

ERIC Educational Resources Information Center

Purpose: The purpose of this study is to investigate whether the position of employees in the organizational hierarchy is important in explaining their feedback seeking behaviour. Design/methodology/approach: This study takes a social network perspective by using an ego-centric network survey to investigate employees' feedback seeking behaviour…

van der Rijt, Janine; Van den Bossche, Piet; Segers, Mien S. R.

2013-01-01

65

Effects of endogenous proteins and microRNA target sequence in a positive feedback system.  

PubMed

A positive feedback system, using GAL4-vp16 (a fusion protein of yeast GAL4 and herpes simplex virus vp16) as an activator and firefly luciferase as a reporter, maintained luciferase expression for 7?d in mice. However, the luciferase expression decreased after 7?d, and this phenomenon could be caused by immunoreactions against these exogenous proteins. This hypothesis was examined by the following three strategies, designed to avoid the putative immunoreactions: (i) use of the endogenous secreted alkaline phosphatase (SEAP) protein as a reporter, (ii) replacement of vp16 with endogenous transcription factors, and (iii) insertion of the target sequence of microRNA expressed in cells of hematopoietic origin, to suppress GAL4-vp16 expression in antigen-presenting cells. The results obtained in this study suggested that silencing would be induced by mechanism(s) besides immunoreactions against reporter and activator proteins. PMID:22975505

Kanda, Genki N; Togashi, Ryohei; Harashima, Hideyoshi; Kamiya, Hiroyuki

2012-01-01

66

Radiative and mechanical AGN feedback in galaxy evolution  

NASA Astrophysics Data System (ADS)

Accreting black holes are thought to inject energy into surrounding gas reservoirs via jets, outflows and radiation, inhibiting the build-up of massive galaxies and suppressing star formation. Active Galactic Nuclei (AGN) feedback can potentially starve the black hole, giving rise to a relation between the black hole mass and the stellar mass of galaxies. Many previous AGN feedback models, however, do not include all known and observed feedback processes. Since the importance of AGN-driven mass and momentum outflows in limiting the infall onto the black hole has been emphasized, we develop a numerical algorithm of AGN mechanical feedback via broad absorption line winds in a three-dimensional smoothed particle hydrodynamics code, modified with a pressure-entropy formulation, that better allows for contact discontinuities and implements improved fluid mixing. We also include the detailed treatment of radiative heating, radiation pressure, and the Eddington force and propose a unified model of AGN feedback. We investigate feedback effects in simulations of a single disk galaxy, major and minor mergers of galaxies, and the formation of elliptical galaxies in a cosmological context. We show that massive, non-relativistic outflows and X-ray heating are indeed a viable mechanism to regulate the black hole growth. While the thermal feedback model, where all the feedback energy is distributed as thermal heating, produces a factor of ~102-10 3 higher X-ray luminosity than expected for given stellar mass of the galaxy, our model can successfully reproduce both the observed L X-sigma* and MBH-sigma* relations. In our model, the AGN-induced outbursts result in strong galactic outflows with vw~2,000 km/s consistent with observed quasar properties. They also effectively quench star formation making ellipticals red and dead consistent with the observations. Our model shows large fluctuations in both radiant and wind outputs, naturally reproducing the two modes of AGN feedback: `wind' mode, where black holes grow rapidly near the Eddington limit and expel gas via high velocity winds and powerful radiation pressure; and a `maintenance' mode when the electromagnetic luminosity is considerably below the Eddington limit.

Choi, Ena

67

Positive and Negative Feedbacks and Free-Scale Pattern Distribution in Rural-Population Dynamics  

PubMed Central

Depopulation of rural areas is a widespread phenomenon that has occurred in most industrialized countries, and has contributed significantly to a reduction in the productivity of agro-ecological resources. In this study, we identified the main trends in the dynamics of rural populations in the Central Pyrenees in the 20th C and early 21st C, and used density independent and density dependent models and identified the main factors that have influenced the dynamics. In addition, we investigated the change in the power law distribution of population size in those periods. Populations exhibited density-dependent positive feedback between 1960 and 2010, and a long-term positive correlation between agricultural activity and population size, which has resulted in a free-scale population distribution that has been disrupted by the collapse of the traditional agricultural society and by emigration to the industrialized cities. We concluded that complex socio-ecological systems that have strong feedback mechanisms can contribute to disruptive population collapses, which can be identified by changes in the pattern of population distribution. PMID:25474704

Alados, Concepción L.; Errea, Paz; Gartzia, Maite; Saiz, Hugo; Escós, Juan

2014-01-01

68

Sensory feedback mechanisms in performance control: With special reference to the ideo-motor mechanism  

Microsoft Academic Search

Reviews 4 interpretations of the manner in which sensory feedback may be involved in regulation of skilled performance. For the serial chaining (SC) and closed-loop (CL) mechanisms, response selection is assumed to occur on the basis of peripheral feedback from preceding correct and incorrect responses, respectively; for the ideo-motor (IM) and fractional anticipatory goal response (rG-sG) mechanisms, it is assumed

Anthony G. Greenwald

1970-01-01

69

Predation risk suppresses the positive feedback between size structure and cannibalism.  

PubMed

1.?Cannibalism can play a prominent role in the structuring and dynamics of ecological communities. Previous studies have emphasized the importance of size structure and density of cannibalistic species in shaping short- and long-term cannibalism dynamics, but our understanding of how predators influence cannibalism dynamics is limited. This is despite widespread evidence that many prey species exhibit behavioural and morphological adaptations in response to predation risk. 2.?This study examined how the presence and absence of predation risk from larval dragonflies Aeshna nigroflava affected cannibalism dynamics in its prey larval salamanders Hynobius retardatus. 3.?We found that feedback dynamics between size structure and cannibalism depended on whether dragonfly predation risk was present. In the absence of dragonfly risk cues, a positive feedback between salamander size structure and cannibalism through time occurred because most of the replicates in this treatment contained at least one salamander larvae having an enlarged gape (i.e. cannibal). In contrast, this feedback and the emergence of cannibalism were rarely observed in the presence of the dragonfly risk cues. Once salamander size divergence occurred, experimental reversals of the presence or absence of dragonfly risk cues did not alter existing cannibalism dynamics as the experiment progressed. Thus, the effects of risk on the mechanisms driving cannibalism dynamics likely operated during the early developmental period of the salamander larvae. 4.?The effects of dragonfly predation risk on behavioural aspects of cannibalistic interactions among hatchlings may prohibit the initiation of dynamics between size structure and cannibalism. Our predation trials clearly showed that encounter rates among hatchlings and biting and ingestion rates of prospective prey by prospective cannibals were significantly lower in the presence vs. absence of dragonfly predation risk even though the size asymmetry between cannibals and victims was similar in both risk treatments. These results suggest that dragonfly risk cues first suppress cannibalism among hatchlings and then prevent size variation from increasing through time. 5.?We suggest that the positive feedback dynamics between size structure and cannibalism and their modification by predation risk may also operate in other systems to shape the population dynamics of cannibalistic prey species as well as overall community dynamics. PMID:21668893

Kishida, Osamu; Trussell, Geoffrey C; Ohno, Ayaka; Kuwano, Shinya; Ikawa, Takuya; Nishimura, Kinya

2011-11-01

70

Mechanical AGN feedback: controlling the thermodynamical evolution of elliptical galaxies  

NASA Astrophysics Data System (ADS)

A fundamental gap in the current understanding of galaxies concerns the thermodynamical evolution of ordinary, baryonic matter. On the one hand, radiative emission drastically decreases the thermal energy content of the interstellar plasma (ISM), inducing a slow cooling flow towards the centre. On the other hand, the active galactic nucleus (AGN) struggles to prevent the runaway cooling catastrophe, injecting huge amount of energy into the ISM. The present study intends to investigate thoroughly the role of mechanical AGN feedback in (isolated or massive) elliptical galaxies, extending and completing the mass range of tested cosmic environments. Our previously successful feedback models in galaxy clusters and groups demonstrated that AGN outflows, self-regulated by cold gas accretion, are able to quench the cooling flow properly without destroying the cool core. Via three-dimensional hydrodynamic simulations (FLASH 3.3), also including stellar evolution, we show that massive mechanical AGN outflows can indeed solve the cooling-flow problem for the entire life of the galaxy, at the same time reproducing typical observational features and constraints such as buoyant underdense bubbles, elliptical shock cocoons, sonic ripples, dredge-up of metals, subsonic turbulence and extended filamentary or nuclear cold gas. In order to avoid overheating and totally emptying the isolated galaxy, the frequent mechanical AGN feedback should be less powerful and efficient (?˜ 10-4) compared with the heating required for more massive and bound ellipticals surrounded by the intragroup medium (?˜ 10-3).

Gaspari, M.; Brighenti, F.; Temi, P.

2012-07-01

71

Adaptive Feedforward Compensation Algorithms for Active Vibration Control with Mechanical Coupling and Local Feedback -a unified approach  

E-print Network

Adaptive Feedforward Compensation Algorithms for Active Vibration Control with Mechanical Coupling an internal "positive" mechanical feedback between the compensation system and the reference source (a of a filter on observed data or a filtering of the residual acceleration in order to satisfy some passivity

Boyer, Edmond

72

EMG feedback tasks reduce reflexive stiffness during force and position perturbations.  

PubMed

Force and position perturbations are widely applied to identify muscular and reflexive contributions to posture maintenance of the arm. Both task instruction (force vs. position) and the inherently linked perturbation type (i.e., force perturbations-position task and position perturbations-force tasks) affect these contributions and their mutual balance. The goal of this study is to explore the modulation of muscular and reflexive contributions in shoulder muscles using EMG biofeedback. The EMG biofeedback provides a harmonized task instruction to facilitate the investigation of perturbation type effects irrespective of task instruction. External continuous force and position perturbations with a bandwidth of 0.5-20 Hz were applied at the hand while subjects maintained prescribed constant levels of muscular co-activation using visual feedback of an EMG biofeedback signal. Joint admittance and reflexive impedance were identified in the frequency domain, and parametric identification separated intrinsic muscular and reflexive feedback properties. In tests with EMG biofeedback, perturbation type (position and force) had no effect on joint admittance and reflexive impedance, indicating task as the dominant factor. A reduction in muscular and reflexive stiffness was observed when performing the EMG biofeedback task relative to the position task. Reflexive position feedback was effectively suppressed during the equivalent EMG biofeedback task, while velocity and acceleration feedback were both decreased by approximately 37%. This indicates that force perturbations with position tasks are a more effective paradigm to investigate complete dynamic motor control of the arm, while EMG tasks tend to reduce the reflexive contribution. PMID:21717098

Forbes, Patrick A; Happee, Riender; van der Helm, Frans C T; Schouten, Alfred C

2011-08-01

73

Physical mechanisms of low-latitude cloud feedback on climate change (Invited)  

NASA Astrophysics Data System (ADS)

Recent studies of the AR4 coupled climate models suggest that all have positive cloud feedbacks and that cloud feedbacks are still the dominant source of intermodel variability in climate sensitivity (Soden and Held 2006). Separation of the cloud response by latitude band and dynamical regime (Bony et al. 2006) shows that subtropical boundary-layer cloud induces most of the intermodel variability. We argue that overall cloud feedback is positive mainly because of the Hartmann-Larson (2002) Fixed Anvil Temperature (FAT) hypothesis. In both GCMs and CRMs, tropical deep convective cloudtops rise in a warmer climate, maintaining a constant temperature. This can be rationalized as a consequence of the strong dependence of saturation humidity and cloud microphysics on temperature. The result is a strong positive climate feedback. In most models, it is partly compensated by a slight decrease in high cloud amount as convection becomes more geographically focused. Most, but not all, GCMs predict a positive subtropical low cloud feedback as well, associated with decreased cloud cover in a warmer climate. Physical mechanisms of low-cloud sensitivity to climate change are poorly understood. It is argued that the diverse GCM responses reflect different parameterized responses to roughly the same changes in the large-scale environment of marine subtropical boundary layers as the climate warms. Two such robust changes are more warming above the boundary layer than at the surface (a strengthened trade inversion) due to the increased stratification of a moist adiabat in a warmer climate, and a reduction in boundary-layer radiative cooling due to the greenhouse effect of CO2. The strengthened inversion favors cloud increases, while reduced radiative cooling favors cloud decreases. An increased moisture jump across the inversion in a warmer climate has also been argued to destabilize inversion cloud, producing a positive feedback (Lock 2009). These uncertain and counteracting feedbacks are not represented well in most GCMs, and are even difficult to sort out in LES models. Lastly, we will critically discuss recent observational studies claiming relevance to cloud feedbacks on climate change and suggest some possible methodological improvements.

Bretherton, C. S.

2009-12-01

74

Positive and negative feedback learning and associated dopamine and serotonin transporter binding after methamphetamine.  

PubMed

Learning from mistakes and prospectively adjusting behavior in response to reward feedback is an important facet of performance monitoring. Dopamine (DA) pathways play an important role in feedback learning and a growing literature has also emerged on the importance of serotonin (5HT) in reward learning, particularly during punishment or reward omission (negative feedback). Cognitive impairments resulting from psychostimulant exposure may arise from altered patterns in feedback learning, which in turn may be modulated by DA and 5HT transmission. We analyzed long-term, off-drug changes in learning from positive and negative feedback and associated striatal DA transporter (DAT) and frontocortical 5HT transporter (SERT) binding in rats pretreated with methamphetamine (mAMPH). Specifically, we assessed the reversal phase of pairwise visual discrimination learning in rats receiving single dose- (mAMPHsingle) vs. escalating-dose exposure (mAMPHescal). Using fine-grained trial-by-trial analyses, we found increased sensitivity to and reliance on positive feedback in mAMPH-pretreated animals, with the mAMPHsingle group showing more pronounced use of this type of feedback. In contrast, overall negative feedback sensitivity was not altered following any mAMPH treatment. In addition to validating the enduring effects of mAMPH on early reversal learning, we found more consecutive error commissions before the first correct response in mAMPH-pretreated rats. This behavioral rigidity was negatively correlated with subregional frontocortical SERT whereas positive feedback sensitivity negatively correlated with striatal DAT binding. These results provide new evidence for the overlapping, yet dissociable roles of DA and 5HT systems in overcoming perseveration and in learning new reward rules. PMID:24959862

Stolyarova, Alexandra; O'Dell, Steve J; Marshall, John F; Izquierdo, Alicia

2014-09-01

75

On the magnitude of positive feedback between future climate change and the carbon cycle  

E-print Network

On the magnitude of positive feedback between future climate change and the carbon cycle J CO 2 will be 18% higher due to the climate change impact on the carbon cycle. Such a positive. They found a very large negative im- pact of climate change on land carbon cycle with a de- cline of tropical

Dufresne, Jean-Louis

76

Feedback loop design and experimental testing for integrated optics with micro-mechanical tuning  

E-print Network

I designed a capacitive sensor with feedback control for precision tuning of a MEMS controlled wavelength-selective switch. The implementation is based upon a customized feedback loop with a PID controller. The positional ...

Waller, Laura A. (Laura Ann)

2005-01-01

77

Position Sensor Performance in Nanometer Resolution Feedback Systems  

E-print Network

by the Australian Research Council Discovery Project (DP0986319) Expression of Uncertainty in Measurement (ISO (1994 standards for the measurement or reporting of position sensor per- formance, this article is aligned with the definitions and methods reported in the ISO/IEC 98:1993 Guide to the This research was supported

Fleming, Andrew J.

78

Faculty Position in Mechanical Engineering Additive Manufacturing  

E-print Network

Faculty Position in Mechanical Engineering Additive Manufacturing University of Kansas of additive manufacturing. Exceptional candidates with outstanding qualifications could be considered using additive manufacturing in applications such as, but not limited to the net shape manufacture of

79

Stabilizing PID controllers for a single-link biomechanical model with position, velocity, and force feedback.  

PubMed

In this paper we address the problem of PID stabilization of a single-link inverted pendulum-based biomechanical model with force feedback, two levels of position and velocity feedback, and with delays in all the feedback loops. The novelty of the proposed model lies in its physiological relevance, whereby both small and medium latency sensory feedbacks from muscle spindle (MS), and force feedback from Golgi tendon organ (GTO) are included in the formulation. The biomechanical model also includes active and passive viscoelastic feedback from Hill-type muscle model and a second-order low-pass function for muscle activation. The central nervous system (CNS) regulation of postural movement is represented by a proportional-integral-derivative (PID) controller. Padé approximation of delay terms is employed to arrive at an overall rational transfer function of the biomechanical model. The Hermite-Biehler theorem is then used to derive stability results, leading to the existence of stabilizing PID controllers. An algorithm for selection of stabilizing feedback gains is developed using the linear matrix inequality (LMI) approach. PMID:15796343

Iqbal, Kamran; Roy, Anindo

2004-12-01

80

Visual saliency computations: mechanisms, constraints, and the effect of feedback.  

PubMed

The primate visual system continuously selects spatial proscribed regions, features or objects for further processing. These selection mechanisms--collectively termed selective visual attention--are guided by intrinsic, bottom-up and by task-dependent, top-down signals. While much psychophysical research has shown that overt and covert attention is partially allocated based on saliency-driven exogenous signals, it is unclear how this is accomplished at the neuronal level. Recent electrophysiological experiments in monkeys point to the gradual emergence of saliency signals when ascending the dorsal visual stream and to the influence of top-down attention on these signals. To elucidate the neural mechanisms underlying these observations, we construct a biologically plausible network of spiking neurons to simulate the formation of saliency signals in different cortical areas. We find that saliency signals are rapidly generated through lateral excitation and inhibition in successive layers of neural populations selective to a single feature. These signals can be improved by feedback from a higher cortical area that represents a saliency map. In addition, we show how top-down attention can affect the saliency signals by disrupting this feedback through its action on the saliency map. While we find that saliency computations require dominant slow NMDA currents, the signal rapidly emerges from successive regions of the network. In conclusion, using a detailed spiking network model we find biophysical mechanisms and limitations of saliency computations which can be tested experimentally. PMID:20861387

Soltani, Alireza; Koch, Christof

2010-09-22

81

Positive and negative feedback by AGN jets in high-redshift galaxies  

NASA Astrophysics Data System (ADS)

Simulations of feedback by jets from active galactic nuclei (AGN) in the past mostly focused on the interaction at large scales as the circumgalactic medium or intra-cluster medium for clusters of galaxies. Only in recent years, simulations have included the interaction of jets with a highly inhomogeneous medium as required by a multi-phase interstellar medium (ISM). At the same time, feedback by AGN has become a common component for cosmological simulations of galaxy evolution to form massive galaxies compatible with observations. I will present some of our recent results and will put them into further context of other feedback simulations and how the opposing effects of positive and negative feedback by jets might be understood in terms of different properties of the ISM.

Gaibler, V.

82

VirB-Mediated Positive Feedback Control of the Virulence Gene Regulatory Cascade of Shigella flexneri  

PubMed Central

Shigella flexneri is a facultative intracellular pathogen that relies on a type III secretion system and its associated effector proteins to cause bacillary dysentery in humans. The genes that encode this virulence system are located on a 230-kbp plasmid and are transcribed in response to thermal, osmotic, and pH signals that are characteristic of the human lower gut. The virulence genes are organized within a regulatory cascade, and the nucleoid-associated protein H-NS represses each of the key promoters. Transcription derepression depends first on the VirF AraC-like transcription factor, a protein that antagonizes H-NS-mediated repression at the intermediate regulatory gene virB. The VirB protein in turn remodels the H-NS–DNA nucleoprotein complexes at the promoters of the genes encoding the type III secretion system and effector proteins, causing these genes to become derepressed. In this study, we show that the VirB protein also positively regulates the expression of its own gene (virB) via a cis-acting regulatory sequence. In addition, VirB positively regulates the gene coding for the VirF protein. This study reveals two hitherto uncharacterized feedback regulatory loops in the S. flexneri virulence cascade that provide a mechanism for the enhanced expression of the principal virulence regulatory genes. PMID:22821978

Kane, Kelly A.

2012-01-01

83

Marine Mechanical Engineer Full Time Position Wanted: Marine Mechanical Engineer  

E-print Network

Marine Mechanical Engineer Full Time Position Wanted: Marine Mechanical Engineer Boksa Marine Design, Inc. is a growing naval architecture and marine engineering firm specializing in the design in the industry. Qualified candidates should have a BSE or MSE in mechanical engineering or marine engineering

Eustice, Ryan

84

Positive feedback and alternative stable states in inbreeding, cooperation, sex roles and other evolutionary processes  

PubMed Central

A large proportion of studies in systems science focus on processes involving a mixture of positive and negative feedbacks, which are also common themes in evolutionary ecology. Examples of negative feedback are density dependence (population regulation) and frequency-dependent selection (polymorphisms). Positive feedback, in turn, plays a role in Fisherian ‘runaway’ sexual selection, the evolution of cooperation, selfing and inbreeding tolerance under purging of deleterious alleles, and the evolution of sex differences in parental care. All these examples feature self-reinforcing processes where the increase in the value of a trait selects for further increases, sometimes via a coevolutionary feedback loop with another trait. Positive feedback often leads to alternative stable states (evolutionary endpoints), making the interpretation of evolutionary predictions challenging. Here, we discuss conceptual issues such as the relationship between self-reinforcing selection and disruptive selection. We also present an extension of a previous model on parental care, focusing on the relationship between the operational sex ratio and sexual selection, and the influence of this relationship on the evolution of biparental or uniparental care. PMID:22144384

Lehtonen, Jussi; Kokko, Hanna

2012-01-01

85

Harnessing members' positive mood for team-directed learning behaviour and team innovation: The moderating role of perceived team feedback  

Microsoft Academic Search

This study examines the role of individual team members' positive mood and perceived team feedback for their team-directed learning behaviour. Results obtained in a sample of 186 members from 27 work teams showed that positive mood was positively associated with team-directed learning behaviour if individual members perceived that the feedback they received was based on the performance of the team

Frank Walter; Gerben S. van der Vegt

2012-01-01

86

Sensitivity analysis of the Nonlinear Integral Positive Position Feedback and Integral Resonant controllers on vibration suppression of nonlinear oscillatory systems  

NASA Astrophysics Data System (ADS)

A new Nonlinear Integral Positive Position Feedback (NIPPF) approach and the Integral Resonant Control (IRC) method are implemented and analyzed for nonlinear vibration control. The performances of both controllers are compared to the Positive Position Feedback (PPF) method. A comprehensive form of the nonlinear feedback controller that includes all three approaches is considered for the closed-loop system; this form is then solved innovatively using the Method of Multiple Scales. The particular form of the modulation equations for each controller is obtained via the calculated comprehensive solution. Sensitivity analysis is performed on the controller parameters of each approach, and the influence of the parameters on the system response is studied. Results demonstrate that controller structure has the most salient role in the suppression performance. Even by selecting the optimal control parameters for each approach, improvements in the control performances are limited. The NIPPF controller delivers superior results compared to the other two approaches in the frequency and time domains. Using this approach, not only is the vibration amplitude at the exact resonant frequency sufficiently suppressed, but the subsequent peaks in the frequency domain are also reduced significantly compared to the PPF method.

Omidi, Ehsan; Mahmoodi, S. Nima

2015-05-01

87

Effect of positive and negative emotion on stimulus-preceding negativity prior to feedback stimuli.  

PubMed

Stimulus-preceding negativity (SPN) was recorded to investigate the effect of positive and negative emotion on the SPN preceding feedback stimuli. In the time-estimation task in which an acoustic stimulus was presented 3 s after a voluntary movement, (1) the negative valence (aversive band noise and pure tone) and (2) the positive valence (reward and no-reward) of feedback stimuli were manipulated. During noise conditions, participants received the band noise as a feedback stimulus except when their time estimations were accurate. They received a monetary reward for accurate time estimations under the reward conditions. The prefeedback SPN was larger under reward than no-reward conditions. In addition, the prefeedback SPN in the noise condition was larger compared with the pure tone condition. Our results appear to suggest that emotional anticipation is important in eliciting the prefeedback SPN. PMID:12240663

Kotani, Y; Hiraku, S; Suda, K; Aihara, Y

2001-11-01

88

Switching between oscillations and homeostasis in competing negative and positive feedback motifs.  

PubMed

We analyze a class of network motifs in which a short, two-node positive feedback motif is inserted in a three-node negative feedback loop. We demonstrate that such networks can undergo a bifurcation to a state where a stable fixed point and a stable limit cycle coexist. At the bifurcation point the period of the oscillations diverges. Further, intrinsic noise can make the system switch between oscillatory state and the stationary state spontaneously. We find that this switching also occurs in previous models of circadian clocks that use this combination of positive and negative feedbacks. Our results suggest that real-life circadian systems may need specific regulation to prevent or minimize such switching events. PMID:22762992

Li, Weihan; Krishna, Sandeep; Pigolotti, Simone; Mitarai, Namiko; Jensen, Mogens H

2012-08-21

89

Mechanical feedback as a possible regulator of tissue growth  

NASA Astrophysics Data System (ADS)

Regulation of cell growth and proliferation has a fundamental role in animal and plant development and in the progression of cancer. In the context of development, it is important to understand the mechanisms that coordinate growth and patterning of tissues. Imaginal discs, which are larval precursors of fly limbs and organs, have provided much of what we currently know about these processes. Here, we consider the mechanism that is responsible for the observed uniformity of growth in wing imaginal discs, which persists in the presence of gradients in growth inducing morphogens in spite of the stochastic nature of cell division. The phenomenon of "cell competition," which manifests in apoptosis of slower-growing cells in the vicinity of faster growing tissue, suggests that uniform growth is not a default state but a result of active regulation. How can a patch of tissue compare its growth rate with that of its surroundings? A possible way is furnished by mechanical interactions. To demonstrate this mechanism, we formulate a mathematical model of nonuniform growth in a layer of tissue and examine its mechanical implications. We show that a clone growing faster or slower than the surrounding tissue is subject to mechanical stress, and we propose that dependence of the rate of cell division on local stress could provide an "integral-feedback" mechanism stabilizing uniform growth. The proposed mechanism of growth control is not specific to imaginal disc growth and could be of general relevance. Several experimental tests of the proposed mechanism are suggested. Drosophila melanogaster | imaginal disc | mechanics | stress

Shraiman, Boris I.

2005-03-01

90

UBTD1 induces cellular senescence through an UBTD1-Mdm2/p53 positive feedback loop.  

PubMed

The tumour suppressor p53 plays an important role in tumourigenesis. Besides inducing apoptosis, it regulates cellular senescence, which constitutes an important barrier to tumourigenesis. The mechanism of regulation of cellular senescence by p53 and its downstream pathway are poorly understood. Here, we report that the ubiquitin domain-containing 1 (UBTD1) gene, a new downstream target of p53, induces cellular senescence and acts as a novel tumour suppressor by a mechanism that depends on p53. Expression of UBTD1 increased upon cellular senescence induced by serial passageing of cultures, as well as by exposure to DNA-damageing drugs that induce premature senescence. Over-expression of UBTD1 induces senescence in human fibroblasts and cancer cells and attenuation of the transformed phenotype in cancer cells. UBTD1 is down-regulated in gastric and colorectal cancer tissues, and its lower expression correlates with a more aggressive phenotype and worse prognosis. Multivariate analysis revealed that UBTD1 expression was an independent prognostic factor for gastric cancer patients. Furthermore, UBTD1 increased the stability of p53 protein, by promoting the degradation of Mdm2 protein. Importantly, UBTD1 and p53 function mutually depend on each other in regulating cellular senescence and proliferation. Thus, our data suggest that, upon DNA damage, p53 induction by UBTD1 creates a positive feedback mechanism to further increase p53 expression. Our results establish UBTD1 as a regulator of cellular senescence that mediates p53 function, and provide insights into the mechanism of Mdm2 inhibition that impacts p53 dynamics during cellular senescence and tumourigenesis. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. PMID:25382750

Zhang, Xiao-Wei; Wang, Xiao-Feng; Ni, Su-Jie; Qin, Wei; Zhao, Li-Qin; Hua, Rui-Xi; Lu, You-Wei; Li, Jin; Dimri, Goberdhan P; Guo, Wei-Jian

2015-03-01

91

Positive feedbacks amplify rates of woody encroachment in mesic tallgrass prairie  

E-print Network

and fire limitation results in a positive feedback loop as clonal stems are able to extend into surrounding of evolutionary histories and climatic conditions (Archer 1995, Van Auken 2000, Roques et al. 2001, Knapp et al. 2008), resulting in changes in ecosystem structure and function (Scholes and Archer 1997, Van Auken

Nippert, Jesse

92

Transformed eddy-PV flux and positive synoptic eddy feedback onto low-frequency flow  

E-print Network

Transformed eddy-PV flux and positive synoptic eddy feedback onto low-frequency flow Hong-Li Ren Springer-Verlag 2010 Abstract Interaction between synoptic eddy and low- frequency flow (SELF) has been-hand side of the low-frequency flow in all vertical levels throughout the troposphere for monthly flow

Wang, Yuqing

93

Robotic hand biomimicry: The effect of finger force and position abduction feedback during contour interaction  

Microsoft Academic Search

The joint motion profiles of 10 human test subjects were recorded as they ran their hands over a flat surface and a convex surface. From this data, three controllers for a dexterous robotic hand were developed to mimic this behavior. Specifically, this work examines the role of finger abduction force and position feedback to motors that control finger extension. Experimental

Benjamin A. Kent; Erik D. Engeberg

2011-01-01

94

Robotic hand biomimicry: Lateral finger joint force and position feedback during contour interaction  

Microsoft Academic Search

The joint motion profiles of 10 human test subjects were recorded as they ran their hands over a flat surface and a convex surface. From this data, three controllers for a dexterous robotic hand were developed to mimic this behavior. Specifically, this work examines the role of finger abduction force and position feedback to motors that control finger extension. Experimental

Benjamin A. Kent; Erik D. Engeberg

2011-01-01

95

Positive Feedback in Hypogonadal Female Mice with Preoptic Area Brain Transplants  

Microsoft Academic Search

When fetal preoptic area (POA) brain grafts that contain gonadotropin-releasing hormone cells are transplanted into the third ventricle of adult female hypogonadal mice, the animals respond with sexual maturation, persistent estrus, and the ability to ovulate reflexively after mating. However, the absence of normal spontaneous ovulatory cyclicity suggests an impairment in positive feedback. We, therefore, studied the effect of administration

Marie J. Gibson; George J. Kokoris; Ann-Judith Silverman

1988-01-01

96

A Positive Feedback Synapse from Retinal Horizontal Cells to Cone Photoreceptors  

E-print Network

A Positive Feedback Synapse from Retinal Horizontal Cells to Cone Photoreceptors Skyler L. Jackman1 release without sacrificing HC-mediated contrast enhancement. Citation: Jackman SL, Babai N, Chambers JJ; Published May 3, 2011 Copyright: Ã? 2011 Jackman et al. This is an open-access article distributed under

Alford, Simon

97

A Positive Feedback Synapse from Retinal Horizontal Cells to Cone Photoreceptors  

Microsoft Academic Search

Cone photoreceptors and horizontal cells (HCs) have a reciprocal synapse that underlies lateral inhibition and establishes the antagonistic center-surround organization of the visual system. Cones transmit to HCs through an excitatory synapse and HCs feed back to cones through an inhibitory synapse. Here we report that HCs also transmit to cone terminals a positive feedback signal that elevates intracellular Ca2+

Skyler L. Jackman; Norbert Babai; James J. Chambers; Wallace B. Thoreson; Richard H. Kramer

2011-01-01

98

CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models  

NASA Astrophysics Data System (ADS)

CGILS—the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)—investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the "NESTS" negative cloud feedback and the "SCOPE" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence—Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations.

Zhang, Minghua; Bretherton, Christopher S.; Blossey, Peter N.; Austin, Phillip H.; Bacmeister, Julio T.; Bony, Sandrine; Brient, Florent; Cheedela, Suvarchal K.; Cheng, Anning; Genio, Anthony D.; Roode, Stephan R.; Endo, Satoshi; Franklin, Charmaine N.; Golaz, Jean-Christophe; Hannay, Cecile; Heus, Thijs; Isotta, Francesco Alessandro; Dufresne, Jean-Louis; Kang, In-Sik; Kawai, Hideaki; Köhler, Martin; Larson, Vincent E.; Liu, Yangang; Lock, Adrian P.; Lohmann, Ulrike; Khairoutdinov, Marat F.; Molod, Andrea M.; Neggers, Roel A. J.; Rasch, Philip; Sandu, Irina; Senkbeil, Ryan; Siebesma, A. Pier; Siegenthaler-Le Drian, Colombe; Stevens, Bjorn; Suarez, Max J.; Xu, Kuan-Man; Salzen, Knut; Webb, Mark J.; Wolf, Audrey; Zhao, Ming

2013-12-01

99

CGILS: Results from the First Phase of an International Project to Understand the Physical Mechanisms of Low Cloud Feedbacks in Single Column Models  

NASA Technical Reports Server (NTRS)

1] CGILS-the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)-investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the "NESTS" negative cloud feedback and the "SCOPE" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence-Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations

Zhang, Minghua; Bretherton, Christopher S.; Blossey, Peter N.; Austin, Phillip H.; Bacmeister, Julio T.; Bony, Sandrine; Brient, Florent; Cheedela, Suvarchal K.; Cheng, Anning; DelGenio, Anthony; DeRoode, Stephan R.; Endo, Satoshi; Franklin, Charmaine N.; Oolaz, Jean-Christophe; Hannay, Cecile; Heus, Thijs; Isotta, Francesco Alessandro; Dufresne, Jean-Louis; Kang, In-Sik; Kawai, Hideaki; Kiehler, Martin; Larson, Vincent E.; Liu, Yangang; Lock, Adrian P.; Lohmann, Ulrike; Molod, Andrea M.; Suarez, Max J.

2013-01-01

100

Meat as a bad habit: A case for positive feedback in consumption preferences leading to lock-in  

Microsoft Academic Search

The concepts of path dependence and lock-in have received growing acceptance but have generally been thought of as driven by positive feedback on the supply side of the economy. A case through example is made here of how endogenous preferences positive feedback in utility from consumption, social considerations, and institutional considerations can all lead to path dependence and the persistence

Joshua Frank

2007-01-01

101

An NF-?B pathway–mediated positive feedback loop amplifies Ras activity to pathological levels in mice  

PubMed Central

Genetic mutations that give rise to active mutant forms of Ras are oncogenic and found in several types of tumor. However, such mutations are not clear biomarkers for disease, since they are frequently detected in healthy individuals. Instead, it has become clear that elevated levels of Ras activity are critical for Ras-induced tumorigenesis. However, the mechanisms underlying the production of pathological levels of Ras activity are unclear. Here, we show that in the presence of oncogenic Ras, inflammatory stimuli initiate a positive feedback loop involving NF-?B that further amplifies Ras activity to pathological levels. Stimulation of Ras signaling by typical inflammatory stimuli was transient and had no long-term sequelae in wild-type mice. In contrast, these stimuli generated prolonged Ras signaling and led to chronic inflammation and precancerous pancreatic lesions (PanINs) in mice expressing physiological levels of oncogenic K-Ras. These effects of inflammatory stimuli were disrupted by deletion of inhibitor of NF-?B kinase 2 (IKK2) or inhibition of Cox-2. Likewise, expression of active IKK2 or Cox-2 or treatment with LPS generated chronic inflammation and PanINs only in mice expressing oncogenic K-Ras. The data support the hypothesis that in the presence of oncogenic Ras, inflammatory stimuli trigger an NF-?B–mediated positive feedback mechanism involving Cox-2 that amplifies Ras activity to pathological levels. Because a large proportion of the adult human population possesses Ras mutations in tissues including colon, pancreas, and lung, disruption of this positive feedback loop may be an important strategy for cancer prevention. PMID:22406536

Daniluk, Jaroslaw; Liu, Yan; Deng, Defeng; Chu, Jun; Huang, Haojie; Gaiser, Sebastian; Cruz-Monserrate, Zobeida; Wang, Huamin; Ji, Baoan; Logsdon, Craig D.

2012-01-01

102

An NF-?B pathway-mediated positive feedback loop amplifies Ras activity to pathological levels in mice.  

PubMed

Genetic mutations that give rise to active mutant forms of Ras are oncogenic and found in several types of tumor. However, such mutations are not clear biomarkers for disease, since they are frequently detected in healthy individuals. Instead, it has become clear that elevated levels of Ras activity are critical for Ras-induced tumorigenesis. However, the mechanisms underlying the production of pathological levels of Ras activity are unclear. Here, we show that in the presence of oncogenic Ras, inflammatory stimuli initiate a positive feedback loop involving NF-?B that further amplifies Ras activity to pathological levels. Stimulation of Ras signaling by typical inflammatory stimuli was transient and had no long-term sequelae in wild-type mice. In contrast, these stimuli generated prolonged Ras signaling and led to chronic inflammation and precancerous pancreatic lesions (PanINs) in mice expressing physiological levels of oncogenic K-Ras. These effects of inflammatory stimuli were disrupted by deletion of inhibitor of NF-?B kinase 2 (IKK2) or inhibition of Cox-2. Likewise, expression of active IKK2 or Cox-2 or treatment with LPS generated chronic inflammation and PanINs only in mice expressing oncogenic K-Ras. The data support the hypothesis that in the presence of oncogenic Ras, inflammatory stimuli trigger an NF-?B-mediated positive feedback mechanism involving Cox-2 that amplifies Ras activity to pathological levels. Because a large proportion of the adult human population possesses Ras mutations in tissues including colon, pancreas, and lung, disruption of this positive feedback loop may be an important strategy for cancer prevention. PMID:22406536

Daniluk, Jaroslaw; Liu, Yan; Deng, Defeng; Chu, Jun; Huang, Haojie; Gaiser, Sebastian; Cruz-Monserrate, Zobeida; Wang, Huamin; Ji, Baoan; Logsdon, Craig D

2012-04-01

103

On the feedback mechanism in supersonic cavity flows  

NASA Astrophysics Data System (ADS)

Self-sustained oscillations in supersonic cavity flows are investigated by implicit large-eddy simulations of a supersonic flow (M? = 2.0, ReD = 105) past a three-dimensional rectangular cavity with length-to-depth ratio of 2. Both turbulent and laminar inflows are considered, and a variation of boundary-layer thickness in the turbulent inflow case is conducted. An additional simulation of turbulent free shear layer is also performed to illustrate the relationship between shedding vortices and acoustic excitations. Feedback mechanism is identified as the dominant mechanism driving the self-sustained oscillations in supersonic open cavity flows, regardless of the upstream turbulent state and the boundary-layer thickness. The generation of discrete vortices in the cavity shear layer is shown to be highly associated with acoustic excitations rather than natural instabilities of the cavity shear layer. Simulation results support that the primary noise source arises from the successive passage of large-scale vortices over the cavity trailing edge. The effects of upstream boundary layer on the shear-layer characteristics and acoustic fields will also be discussed.

Li, Weipeng; Nonomura, Taku; Fujii, Kozo

2013-05-01

104

Eliminating the possibility at Chernobyl 4 of recriticality with positive feedback  

SciTech Connect

We have recently published an article in which we discuss means by which plutonium and other fissile material stored underground could reach criticality with positive feedback and therefore explosive potential. The Chernobyl rubble involving hundreds of tons of material is similar in some respects to the systems analyzed in the paper, and the practices there to control criticality may well increase the probability of a second event at Chernobyl 4. This paper explores the Chernobyl situation and remedial actions are recommended.

Bowman, C.D.

1996-04-29

105

Implementation of modified positive velocity feedback controller for active vibration control in smart structures  

NASA Astrophysics Data System (ADS)

This paper introduces the Modified Positive Velocity Feedback (MPVF) controller as an alternative to the conventional Positive Position Feedback (PPF) controller, with the goal of suppressing unwanted resonant vibrations in smart structures. The MPVF controller uses two parallel feedback compensators working on the fundamental modes of the structure. The vibration velocity is measured by a sensor or state estimator and is fed back to the controller as the input. To control n-modes, n sets of parallel compensators are required. MPVF controller gain selection in multimode cases highly affects the control results. This problem is resolved using the Linear Quadratic Regulator (LQR) and the M-norm optimization method, which are selected to form the desired performance of the MPVF controller. First, the controller is simulated for the two optimization approaches, and then, experimental investigation of the vibration suppression is performed. The LQR-optimized MPVF provides a better suppression in terms of vibration displacement. The M-normoptimized MPVF controller focuses on modes with higher magnitudes of velocity and provides a higher level of vibration velocity suppression than LQR-optimized method. Vibration velocity attenuation can be very important in preventing fatigue failures due to the fact that velocity can be directly related to stress.

Omidi, Ehsan; McCarty, Rachael; Mahmoodi, S. Nima

2014-03-01

106

A Novel TGF? Modulator that Uncouples R-Smad/I-Smad-Mediated Negative Feedback from R-Smad/Ligand-Driven Positive Feedback  

PubMed Central

As some of the most widely utilised intercellular signalling molecules, transforming growth factor ? (TGF?) superfamily members play critical roles in normal development and become disrupted in human disease. Establishing appropriate levels of TGF? signalling involves positive and negative feedback, which are coupled and driven by the same signal transduction components (R-Smad transcription factor complexes), but whether and how the regulation of the two can be distinguished are unknown. Genome-wide comparison of published ChIP-seq datasets suggests that LIM domain binding proteins (Ldbs) co-localise with R-Smads at a substantial subset of R-Smad target genes including the locus of inhibitory Smad7 (I-Smad7), which mediates negative feedback for TGF? signalling. We present evidence suggesting that zebrafish Ldb2a binds and directly activates the I-Smad7 gene, whereas it binds and represses the ligand gene, Squint (Sqt), which drives positive feedback. Thus, the fine tuning of TGF? signalling derives from positive and negative control by Ldb2a. Expression of ldb2a is itself activated by TGF? signals, suggesting potential feed-forward loops that might delay the negative input of Ldb2a to the positive feedback, as well as the positive input of Ldb2a to the negative feedback. In this way, precise gene expression control by Ldb2a enables an initial build-up of signalling via a fully active positive feedback in the absence of buffering by the negative feedback. In Ldb2a-deficient zebrafish embryos, homeostasis of TGF? signalling is perturbed and signalling is stably enhanced, giving rise to excess mesoderm and endoderm, an effect that can be rescued by reducing signalling by the TGF? family members, Nodal and BMP. Thus, Ldb2a is critical to the homeostatic control of TGF? signalling and thereby embryonic patterning. PMID:25665164

Gu, Wenchao; Monteiro, Rui; Zuo, Jie; Simões, Filipa Costa; Martella, Andrea; Andrieu-Soler, Charlotte; Grosveld, Frank; Sauka-Spengler, Tatjana; Patient, Roger

2015-01-01

107

Positive Feedback-Loop of Telomerase Reverse Transcriptase and 15-Lipoxygenase-2 Promotes Pulmonary Hypertension  

PubMed Central

Objective Pulmonary hypertension (PH) is characterized with pulmonary vasoconstriction and vascular remodeling mediated by 15-lipoxygenase (15-LO)/15-hydroxyeicosatetraenoic acid (15-HETE) according to our previous studies. Meanwhile, telomerase reverse transcriptase (TERT) activity is highly correlated with vascular injury and remodeling, suggesting that TERT may be an essential determinant in the development of PH. The aim of this study was to determine the contribution and molecular mechanisms of TERT in the pathogenesis of PH. Approach and Results We measured the right ventricular systolic pressure (RVSP) and ventricular weight, analyzed morphometric change of the pulmonary vessels in the hypoxia or monocrotaline treated rats. Bromodeoxyuridine incorporation, transwell assay and flow cytometry in pulmonary smooth muscle cells were performed to investigate the roles and relationship of TERT and 15-LO/15-HETE in PH. We revealed that the expression of TERT was increased in pulmonary vasculature of patients with PH and in the monocrotaline or hypoxia rat model of PH. The up-regulation of TERT was associated with experimental elevated RVSP and pulmonary vascular remodeling. Coimmunoprecipitation experiments identified TERT as a novel interacting partner of 15-LO-2. TERT and 15-LO-2 augmented protein expression of each other. In addition, the proliferation, migration and cell-cycle transition from G0/G1 phase to S phase induced by hypoxia were inhibited by TERT knockdown, which were rescued by 15-HETE addition. Conclusions These results demonstrate that TERT regulates pulmonary vascular remodeling. TERT and 15-LO-2 form a positive feedback loop and together promote proliferation and migration of pulmonary artery smooth muscle cells, creating a self-amplifying circuit which propels pulmonary hypertension. PMID:24376652

Shen, Tingting; Ma, Jun; Zhang, Lei; Yu, Xiufeng; Liu, Mengmeng; Hou, Yunlong; Wang, Yanyan; Ma, Cui; Li, Shuzhen; Zhu, Daling

2013-01-01

108

Two-axis antenna positioning mechanism  

NASA Technical Reports Server (NTRS)

The two-axis antenna positioning mechanism (TAAPM) is used to position three Ku-band and one C-band spot antennas on the INTELSAT 7 (I-7) spacecraft, which is a commercial telecommunications satellite purchased and operated by INTELSAT, an international consortium. The first I-7 was successfully launched on 22 Oct. 1993 from French Guiana on an Ariane launch vehicle. The TAAPM's on the first I-7 satellite successfully completed their in-orbit functional testing. The TAAPM was an entirely new design for Space Systems/Loral. This paper will describe the spacecraft/system requirements and application of the TAAPM and present the technical findings of TAAPM qualification and protoflight testing.

Herald, Michelle; Wai, Leilani C.

1994-01-01

109

Effect of position feedback during task-oriented upper-limb training after stroke: five-case pilot study  

Microsoft Academic Search

Feedback is an important element in motor learning during rehabilitation therapy following stroke. The objective of this pilot study was to better understand the effect of position feedback during task-oriented reach training of the upper limb in people with chronic stroke. Five subjects participated in the training for 30 minutes three times a week for 6 weeks. During training, subjects

Birgit I. Molier; Gerdienke B. Prange; Thijs Krabben; Arno H. A. Stienen; Kooij van der Herman; Jaap H. Buurke; Michiel J. A. Jannink; Hermie J. Hermens

2011-01-01

110

Enhanced Positive Water Vapor Feedback Associated with Tropical Deep Convection: New Evidence from Aura MLS  

NASA Technical Reports Server (NTRS)

Recent simultaneous observations of upper tropospheric (UT) water vapor and cloud ice from the Microwave Limb Sounder (MLS) on the Aura satellite provide new evidence for tropical convective influence on UT water vapor and its associated greenhouse effect. The observations show that UT water vapor increases as cloud ice water content increases. They also show that, when sea surface temperature (SST) exceeds approx.300 K, UT cloud ice associated with tropical deep convection increases sharply with increasing SST. The moistening of the upper troposphere by deep convection leads to an enhanced positive water vapor feedback, about 3 times that implied solely by thermodynamics. Over tropical oceans when SST greater than approx.300 K, the 'convective UT water vapor feedback' inferred from the MLS observations contributes approximately 65% of the sensitivity of the clear-sky greenhouse parameter to SST.

Su, Hui; Read, William G.; Jiang, Jonathan H.; Waters, Joe W.; Wu, Dong L.; Fetzer, Eric J.

2006-01-01

111

MICROBE SENSING, POSITIVE FEEDBACK LOOPS, AND THE PATHOGENESIS OF INFLAMMATORY DISEASES  

PubMed Central

Summary The molecular apparatus that protects us against infection can also injure us by causing autoimmune or autoinflammatory disease. It now seems that at times, defects within the sensing arm of innate immunity contribute to diseases of this type. The initiation of an immune response is often microbe dependent and, in many cases, Toll-like receptor (TLR) dependent. Positive feedback loops triggering immune activation may occur when TLR signaling pathways stimulate host cells in an unchecked manner. Or, immune activation may persist because of failure to eradicate an inciting infection. Or on occasion, endogenous DNA may trigger specific immune responses that beget further responses in a TLR-dependent autoamplification loop. Specific biochemical defects that cause loop-related autoimmunity have been revealed by random germline mutagenesis and by gene targeting. We have also developed some insight into critical points at which feedback loops can be interrupted. PMID:19120489

Beutler, Bruce

2009-01-01

112

Mutualism in a community context: the positive feedback between an ant-aphid mutualism and a gall-making midge.  

PubMed

Although mutualisms are widespread and often described in natural history accounts, their ecological influences on other community members remain largely unexplored. Many of these influences are likely a result of indirect effects. In this field study, we investigated the indirect effects of an ant-aphid mutualism on the abundance, survival rates and parasitism rates of a co-occurring herbivore. Rabdophaga salicisbrassicoides (Diptera: Cecidomyiidae) induces rosette galls on the developing shoots of Salix exigua trees, and populations can reach outbreak densities (up to 1,000 galls/stem) in central Washington State (USA). Ant-tended aphids feed on these same stems and often feed on gall tissue. In this study we used a combination of manipulative experiments and observational surveys to test the hypothesis that the abundances of aphids, ants, and galls have positive and reciprocal effects on one another, in a manner that would create a positive feedback loop in population growth. In addition, we examined whether the combined presence of ants and aphids reduces parasitism rates for the gallers. In support of the positive feedback loop hypothesis, aphids enjoyed higher population growth rates in the presence of ants and galls, the presence of ants and aphids resulted in increased abundance of galls, and the abundances of ants, aphids and galls were all positively correlated with one another. However, the mechanism underlying the positive effect of ants and aphids on galler density remains unknown, as the mutualism did not affect parasitism rates. More broadly, this study demonstrates that mutualisms can have significant and complex indirect effects on community and population ecology. PMID:17106723

Savage, Amy M; Peterson, Merrill A

2007-03-01

113

Control of a double impacting mechanical oscillator displacement feedback  

E-print Network

for this study was to understand the nature of non-linear resonances associated with the interaction of servo-hydraulic may be applicable to problems where physical objects must be manipulated by feedback assisted

Arrowsmith, David

114

Brown University School of Engineering Faculty Position in Solid Mechanics  

E-print Network

Brown University School of Engineering Faculty Position in Solid Mechanics The newly established School of Engineering at Brown University is seeking to fill a position in Solid Mechanics at any/nano-scale solid mechanics, mechanics of cells and biological systems, soft matter mechanics, mechanics

115

Movement goals and feedback and feedforward control mechanisms in speech production  

PubMed Central

Studies of speech motor control are described that support a theoretical framework in which fundamental control variables for phonemic movements are multi-dimensional regions in auditory and somatosensory spaces. Auditory feedback is used to acquire and maintain auditory goals and in the development and function of feedback and feedforward control mechanisms. Several lines of evidence support the idea that speakers with more acute sensory discrimination acquire more distinct goal regions and therefore produce speech sounds with greater contrast. Feedback modification findings indicate that fluently produced sound sequences are encoded as feedforward commands, and feedback control serves to correct mismatches between expected and produced sensory consequences. PMID:22661828

Perkell, Joseph S.

2010-01-01

116

Bistability, Probability Transition Rate and First-Passage Time in an Autoactivating Positive-Feedback Loop  

PubMed Central

A hallmark of positive-feedback regulation is bistability, which gives rise to distinct cellular states with high and low expression levels, and that stochasticity in gene expression can cause random transitions between two states, yielding bimodal population distribution (Kaern et al., 2005, Nat Rev Genet 6: 451-464). In this paper, the probability transition rate and first-passage time in an autoactivating positive-feedback loop with bistability are investigated, where the gene expression is assumed to be disturbed by both additive and multiplicative external noises, the bimodality in the stochastic gene expression is due to the bistability, and the bistability determines that the potential of the Fokker-Planck equation has two potential wells. Our main goal is to illustrate how the probability transition rate and first-passage time are affected by the maximum transcriptional rate, the intensities of additive and multiplicative noises, and the correlation of additive and multiplicative noises. Our main results show that (i) the increase of the maximum transcription rate will be useful for maintaining a high gene expression level; (ii) the probability transition rate from one potential well to the other one will increase with the increase of the intensity of additive noise; (iii) the increase of multiplicative noise strength will increase the amount of probability in the left potential well; and (iv) positive (or negative) cross-correlation between additive and multiplicative noises will increase the amount of probability in the left (or right) potential well. PMID:21445288

Zheng, Xiu-Deng; Yang, Xiao-Qian; Tao, Yi

2011-01-01

117

Valence-separated representation of reward prediction error in feedback-related negativity and positivity.  

PubMed

Feedback-related negativity (FRN) is an event-related brain potential (ERP) component elicited by errors and negative outcomes. Previous studies proposed that FRN reflects the activity of a general error-processing system that incorporates reward prediction error (RPE). However, other studies reported inconsistent results on this issue - namely, that FRN only reflects the valence of feedback and that the magnitude of RPE is reflected by the other ERP component called P300. The present study focused on the relationship between the FRN amplitude and RPE. ERPs were recorded during a reversal learning task performed by the participants, and a computational model was used to estimate trial-by-trial RPEs, which we correlated with the ERPs. The results indicated that FRN and P300 reflected the magnitude of RPE in negative outcomes and positive outcomes, respectively. In addition, the correlation between RPE and the P300 amplitude was stronger than the correlation between RPE and the FRN amplitude. These differences in the correlation between ERP and RPE components may explain the inconsistent results reported by previous studies; the asymmetry in the correlations might make it difficult to detect the effect of the RPE magnitude on the FRN and makes it appear that the FRN only reflects the valence of feedback. PMID:25634316

Bai, Yu; Katahira, Kentaro; Ohira, Hideki

2015-02-11

118

Spatial pattern formation of coastal vegetation in response to external gradients and positive feedbacks affecting soil porewater salinity: A model study  

USGS Publications Warehouse

Coastal vegetation of South Florida typically comprises salinity-tolerant mangroves bordering salinity-intolerant hardwood hammocks and fresh water marshes. Two primary ecological factors appear to influence the maintenance of mangrove/hammock ecotones against changes that might occur due to disturbances. One of these is a gradient in one or more environmental factors. The other is the action of positive feedback mechanisms, in which each vegetation community influences its local environment to favor itself, reinforcing the boundary between communities. The relative contributions of these two factors, however, can be hard to discern. A spatially explicit individual-based model of vegetation, coupled with a model of soil hydrology and salinity dynamics is presented here to simulate mangrove/hammock ecotones in the coastal margin habitats of South Florida. The model simulation results indicate that an environmental gradient of salinity, caused by tidal flux, is the key factor separating vegetation communities, while positive feedback involving the different interaction of each vegetation type with the vadose zone salinity increases the sharpness of boundaries, and maintains the ecological resilience of mangrove/hammock ecotones against small disturbances. Investigation of effects of precipitation on positive feedback indicates that the dry season, with its low precipitation, is the period of strongest positive feedback. ?? 2011 Springer Science+Business Media B.V. (outside the USA).

Jiang, J.; DeAngelis, D.L.; Smith, T. J., III; Teh, S.Y.; Koh, H.-L.

2012-01-01

119

Mechanisms of carbon monoxide attenuation of tubuloglomerular feedback.  

PubMed

Carbon monoxide (CO) is a physiological messenger with diverse functions in the kidney, including controlling afferent arteriole tone both directly and via tubuloglomerular feedback (TGF). We have reported that CO attenuates TGF, but the mechanisms underlying this effect remain unknown. We hypothesized that CO, acting via cGMP, cGMP-dependent protein kinase, and cGMP-stimulated phosphodiesterase 2, reduces cAMP in the macula densa, leading to TGF attenuation. In vitro, microdissected rabbit afferent arterioles and their attached macula densa were simultaneously perfused. TGF was measured as the decrease in afferent arteriole diameter elicited by switching macula densa NaCl from 10 to 80 mmol/L. Adding a CO-releasing molecule (CORM-3, 5 × 10(-5) mol/L) to the macula densa blunted TGF from 3.3 ± 0.3 to 2.0 ± 0.3 ?m (P<0.001). The guanylate cyclase inhibitor LY-83583 (10(-6) mol/L) enhanced TGF (5.8 ± 0.6 ?m; P<0.001 versus control) and prevented the effect of CORM-3 on TGF (LY-83583+CORM-3, 5.5 ± 0.3 ?m). Similarly, the cGMP-dependent protein kinase inhibitor KT-5823 (2 × 10(-6) mol/L) enhanced TGF and prevented the effect of CORM-3 on TGF (KT-5823, 6.0 ± 0.7 ?m; KT-5823+CORM-3, 5.9 ± 0.8 ?m). However, the phosphodiesterase 2 inhibitor BAY-60-7550 (10(-6) mol/L) did not prevent the effect of CORM-3 on TGF (BAY-60-7550, 4.07 ± 0.31 ?m; BAY-60-7550+CORM-3, 1.84 ± 0.31 ?m; P<0.001). Finally, the degradation-resistant cAMP analog dibutyryl-cAMP (10(-3) mol/L) prevented the attenuation of TGF by CORM-3 (dibutyryl-cAMP, 4.6 ± 0.5 ?m; dibutyryl-cAMP+CORM-3, 5.0 ± 0.6 ?m). We conclude that CO attenuates TGF by reducing cAMP via a cGMP-dependent pathway mediated by cGMP-dependent protein kinase rather than phosphodiesterase 2. Our results will lead to a better understanding of the mechanisms that control the renal microcirculation. PMID:22508834

Ren, Yilin; D'Ambrosio, Martin A; Wang, Hong; Falck, John R; Peterson, Edward L; Garvin, Jeffrey L; Carretero, Oscar A

2012-06-01

120

MECHANISMS OF CARBON MONOXIDE ATTENUATION OF TUBULOGLOMERULAR FEEDBACK (TGF)  

PubMed Central

Carbon monoxide (CO) is a physiological messenger with diverse functions in the kidney, including controlling afferent arteriole (Af-Art) tone both directly and via tubuloglomerular feedback (TGF). We have reported that CO attenuates TGF, but the mechanisms underlying this effect remain unknown. We hypothesized that CO, acting via cGMP, cGMP-dependent protein kinase (PKG), and cGMP-stimulated phosphodiesterase-2 (PDE2), reduces cAMP in the macula densa, leading to TGF attenuation. In vitro, microdissected rabbit Af-Arts and their attached macula densa were simultaneously perfused. TGF was measured as the decrease in Af-Art diameter elicited by switching macula densa NaCl from 10 to 80 mM. Adding a CO-releasing molecule (CORM-3, 5×10?5mol/L) to the macula densa blunted TGF from 3.3±0.3 to 2.0±0.3 µm (P<0.001). The guanylate cyclase inhibitor LY-83583 (10?6mol/L) enhanced TGF (5.8±0.6 µm; P<0.001 vs. control) and prevented the effect of CORM-3 on TGF (LY-83583 + CORM-3, 5.5±0.3 µm). Similarly, the PKG inhibitor KT-5823 (2×10?6mol/L) enhanced TGF and prevented the effect of CORM-3 on TGF (KT-5823, 6.0±0.7 µm; KT-5823 + CORM-3, 5.9±0.8 µm). However, the PDE2 inhibitor BAY-60-7550 (10?6mol/L) did not prevent the effect of CORM-3 on TGF (BAY-60-7550, 4.07±0.31 µm; BAY-60-7550 + CORM-3, 1.84±0.31 µm, P<0.001). Finally, the degradation-resistant cAMP analog dibutyryl-cAMP (db-cAMP, 10?3mol/L) prevented the attenuation of TGF by CORM-3 (db-cAMP, 4.6±0.5 µm; db-cAMP + CORM-3, 5.0±0.6 µm). We conclude that CO attenuates TGF by reducing cAMP via a cGMP-dependent pathway mediated by PKG, rather than PDE2. Our results will lead to a better understanding of the mechanisms that control the renal microcirculation. PMID:22508834

Ren, YiLin; D’Ambrosio, Martin A.; Wang, Hong; Falck, John R.; Peterson, Edward L.; Garvin, Jeffrey L.; Carretero, Oscar A.

2012-01-01

121

Rheological feedbacks between hydration, strain localization, and olivine deformation mechanisms in the oceanic lithosphere  

NASA Astrophysics Data System (ADS)

Transform faults in the oceanic lithosphere play a key role in the tectonic water cycle by enabling deep circulation of seawater into the shallow lithosphere. We investigate dredge peridotite mylonite samples from the transform fault section of the Shaka Fracture Zone, Southwest Indian Ridge, in order to evaluate the relationships between hydration state, strain localization, and olivine deformation mechanisms. Initial petrographic analyses reveal growth of hydrous amphibole phases and mineral fluid inclusions, as well as the development of heterogeneous strain localization. To further investigate these features, we performed integrated electron backscatter diffraction and energy dispersive spectroscopy characterization. These analyses constrain the amphibole phase as tremolite and document hydration reaction textures associated with orthopyroxene porphyroclast tails and exsolution lamellae. Additionally, detailed examination of mylonitized zones illustrates systematic relationships between hydrous phase fraction, olivine grain size, and lattice preferred orientation (LPO). In particular, localized grain size reduction and absence of any LPO correlate with high hydrous phase fraction, while relatively coarse grained olivine with strong LPO are found in essentially monomineralic regions, suggesting likely feedbacks between hydration reactions, transitions in olivine deformation mechanisms, and mylonitization. We assess these relationships to develop a conceptual model for the concomitant hydration and deformation of peridotite in the brittle-ductile transition zone and evaluate implications for the rheological evolution of faults in the oceanic lithosphere.; (Left) Electron backscatter diffraction phase map. Blue - Forsterite, Cyan - Tremolite, Green - Opx, Red - Chromite. (Center) Average forsterite grain size and tremolite fraction as functions of position calculated in 50 ?m bins. (Right) M-indices for forsterite and tremolite as functions of position calculated in 50 ?m bins. The strong correlation of forsterite fabric strength with average grain size and tremolite fraction illustrates feedbacks between hydration, strain localization, and olivine deformation mechanisms.

Kohli, A. H.; Warren, J. M.

2012-12-01

122

A positive feedback between magmatism and mantle upwelling in terrestrial planets: Implications for the Moon  

NASA Astrophysics Data System (ADS)

series of two-dimensional numerical models of magmatism and mantle convection in small planetary bodies are presented to discuss how the small size of the Moon exerts control over its mantle evolution. Mantle convection is modeled by a solid-state convection of internally heated materials with temperature-dependent viscosity. Magmatism is modeled as upward permeable flow of basaltic magma generated by decompression melting of upwelling mantle materials. Migration of the generated magma causes compaction/expansion of the coexisting matrix. The volume change of matrix and the buoyancy of magma induced by magmatism enhance the upwelling flow and hence the magmatism itself, when the Rayleigh number exceeds a threshold that is around the critical Rayleigh number for the onset of thermal convection. This positive feedback makes magmatism vigorous and episodic and causes efficient cooling and stirring of the mantle in large planets like Venus and the Earth. In small planetary bodies where the Rayleigh number is lower than the threshold, however, magmatism occurs more continuously with a characteristic time of several hundred million years, cooling and convective stirring of the mantle caused by magmatism are less important, and a compositionally stratified structure develops in the mantle. These features of magmatism and mantle structure fit in with the observations on the Moon. The positive feedback is a key to understanding why the evolution of the lunar mantle is so different from that of lager planets like the Earth and Venus.

Ogawa, Masaki

2014-11-01

123

Efficient plant growth using automatic position-feedback laser light irradiation  

NASA Astrophysics Data System (ADS)

The plant growth based on the scanning laser beam is newly developed. Three semiconductor lasers with three primary colors, i.e., blue, green and red are used. Here, the laser scanned position is restricted only to the plant leaves, where the light illumination is needed. The feedback system based on the perspective projection is developed. The system consists of the automatic position correction from the camera image. The automatic image extraction of the leaf parts is also introduced. The electric power needed for this system is as small as 6.25% compared with the traditional white fluorescent lamp. Furthermore, experimental results show that the red-color laser light is particularly efficient for the growth of the radish sprouts.

Kakinoki, Yoshiaki; Kato, Yuya; Ogawa, Kosuke; Nakao, Akira; Okai, Zenshiro; Katsuyama, Toshio

2013-05-01

124

Epigenetic regulation of Kiss1 gene expression mediating estrogen-positive feedback action in the mouse brain.  

PubMed

This study aims to determine the epigenetic mechanism regulating Kiss1 gene expression in the anteroventral periventricular nucleus (AVPV) to understand the mechanism underlying estrogen-positive feedback action on gonadotropin-releasing hormone/gonadotropin surge. We investigated estrogen regulation of the epigenetic status of the mouse AVPV Kiss1 gene locus in comparison with the arcuate nucleus (ARC), in which Kiss1 expression is down-regulated by estrogen. Histone of AVPV Kiss1 promoter region was highly acetylated, and estrogen receptor ? was highly recruited at the region by estrogen. In contrast, the histone of ARC Kiss1 promoter region was deacetylated by estrogen. Inhibition of histone deacetylation up-regulated in vitro Kiss1 expression in a hypothalamic non-Kiss1-expressing cell line. Gene conformation analysis indicated that estrogen induced formation of a chromatin loop between Kiss1 promoter and the 3' intergenic region, suggesting that the intergenic region serves to enhance estrogen-dependent Kiss1 expression in the AVPV. This notion was proved, because transgenic reporter mice with a complete Kiss1 locus sequence showed kisspeptin neuron-specific GFP expression in both the AVPV and ARC, but the deletion of the 3' region resulted in greatly reduced GFP expression only in the AVPV. Taken together, these results demonstrate that estrogen induces recruitment of estrogen receptor ? and histone acetylation in the Kiss1 promoter region of the AVPV and consequently enhances chromatin loop formation of Kiss1 promoter and Kiss1 gene enhancer, resulting in an increase in AVPV-specific Kiss1 gene expression. These results indicate that epigenetic regulation of the Kiss1 gene is involved in estrogen-positive feedback to generate the gonadotropin-releasing hormone/gonadotropin surge. PMID:22505735

Tomikawa, Junko; Uenoyama, Yoshihisa; Ozawa, Makiko; Fukanuma, Tatsuya; Takase, Kenji; Goto, Teppei; Abe, Hitomi; Ieda, Nahoko; Minabe, Shiori; Deura, Chikaya; Inoue, Naoko; Sanbo, Makoto; Tomita, Koichi; Hirabayashi, Masumi; Tanaka, Satoshi; Imamura, Takuya; Okamura, Hiroaki; Maeda, Kei-ichiro; Tsukamura, Hiroko

2012-05-15

125

A simple negative interaction in the positive transcriptional feedback of a single gene is sufficient to produce reliable oscillations.  

PubMed

Negative and positive transcriptional feedback loops are present in natural and synthetic genetic oscillators. A single gene with negative transcriptional feedback needs a time delay and sufficiently strong nonlinearity in the transmission of the feedback signal in order to produce biochemical rhythms. A single gene with only positive transcriptional feedback does not produce oscillations. Here, we demonstrate that this single-gene network in conjunction with a simple negative interaction can also easily produce rhythms. We examine a model comprised of two well-differentiated parts. The first is a positive feedback created by a protein that binds to the promoter of its own gene and activates the transcription. The second is a negative interaction in which a repressor molecule prevents this protein from binding to its promoter. A stochastic study shows that the system is robust to noise. A deterministic study identifies that the dynamics of the oscillator are mainly driven by two types of biomolecules: the protein, and the complex formed by the repressor and this protein. The main conclusion of this paper is that a simple and usual negative interaction, such as degradation, sequestration or inhibition, acting on the positive transcriptional feedback of a single gene is a sufficient condition to produce reliable oscillations. One gene is enough and the positive transcriptional feedback signal does not need to activate a second repressor gene. This means that at the genetic level an explicit negative feedback loop is not necessary. The model needs neither cooperative binding reactions nor the formation of protein multimers. Therefore, our findings could help to clarify the design principles of cellular clocks and constitute a new efficient tool for engineering synthetic genetic oscillators. PMID:22205920

Miró-Bueno, Jesús M; Rodríguez-Patón, Alfonso

2011-01-01

126

A Simple Negative Interaction in the Positive Transcriptional Feedback of a Single Gene Is Sufficient to Produce Reliable Oscillations  

PubMed Central

Negative and positive transcriptional feedback loops are present in natural and synthetic genetic oscillators. A single gene with negative transcriptional feedback needs a time delay and sufficiently strong nonlinearity in the transmission of the feedback signal in order to produce biochemical rhythms. A single gene with only positive transcriptional feedback does not produce oscillations. Here, we demonstrate that this single-gene network in conjunction with a simple negative interaction can also easily produce rhythms. We examine a model comprised of two well-differentiated parts. The first is a positive feedback created by a protein that binds to the promoter of its own gene and activates the transcription. The second is a negative interaction in which a repressor molecule prevents this protein from binding to its promoter. A stochastic study shows that the system is robust to noise. A deterministic study identifies that the dynamics of the oscillator are mainly driven by two types of biomolecules: the protein, and the complex formed by the repressor and this protein. The main conclusion of this paper is that a simple and usual negative interaction, such as degradation, sequestration or inhibition, acting on the positive transcriptional feedback of a single gene is a sufficient condition to produce reliable oscillations. One gene is enough and the positive transcriptional feedback signal does not need to activate a second repressor gene. This means that at the genetic level an explicit negative feedback loop is not necessary. The model needs neither cooperative binding reactions nor the formation of protein multimers. Therefore, our findings could help to clarify the design principles of cellular clocks and constitute a new efficient tool for engineering synthetic genetic oscillators. PMID:22205920

Miró-Bueno, Jesús M.; Rodríguez-Patón, Alfonso

2011-01-01

127

Sahara Heat Low Perturbations and Water Vapor in the Sahel: A Positive Feedback System  

NASA Astrophysics Data System (ADS)

It is necessary to understand the drivers and feedbacks of global desertification, motivated by the increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change. Climate change and land dynamics are the perturbations that are major drivers of an ecosystem shift to a ';';desertified'' state. This shift is typically sustained by positive feedbacks, which stabilize the system in the new state. This research focuses on changes in precipitation resulting from land-atmosphere interactions and changes in vegetation cover. We concentrate on the Sahel region of Africa (a strip of land that is a transitional area between the Sahara desert to the North and the rain forest to the South). It is a dry land, semi arid environment and is a bistable ecosystem that can either be in the state of 'dry' or 'wet'. After an abnormally wet/high precipitation period in the 1950s the Sahel experienced terrible droughts and desertification which peaked in the 1980s. Since then, precipitation has gradually increased and a sinusoidal model has been shown run on a multi decadal cycle. Discrepancies in the data exist, however, and although the overall cycle has been modeled well, the large inter-annual fluctuations in precipitation have yet to be sufficiently modeled or explained. This research offers new evidence as to why such a phenomenon exists and attempts to attribute this behavior to a coupled land-atmosphere feedback system, linking together changes in vegetation cover and precipitation in the Sahel. Using the model output data from a high resolution Weather Research and Forecasting (WRF) model to look at Africa and compare the difference between perturbations and the mean, this research asserts that when the surface of the Saharan Heat Low (SHL) becomes extremely hot the pressure drops substantially. Subsequently, due to the West African Monsoon system, air rushes in from high-pressure areas, and pulls monsoon precipitation/humidity over the Sahel, causing abnormally wet seasons. The more rainfall the area receives, the more vegetation cover increases. Additionally, this increased water vapor coming from evapotranspiration from plants then blankets the SHL, further warming it and continuing the cycle of positive feedback. The reverse effect could also take place, causing an abnormally dry season. This is theorized to be the reason for the inter-annual variation in rainfall within the Sahel and preliminary results support this conclusion.

Caughman, L.; Evan, A. T.

2013-12-01

128

Chemical and mechanical feedback during reaction rim growth  

NASA Astrophysics Data System (ADS)

The system MgO-SiO2, including the mineral reaction quadruple periclase-forsterite-enstatite-quartz, has for several years become a favored target for laboratory and thought experiments on reaction rim growth, on the possible grain-scale pressure variability evolving during metamorphic reactions, and on the role of the local reaction volume in guiding kinetic pathways. Both isotope tracer and microstructure analyses indicate that the relative opposite fluxes of MgO and SiO2 components obey the limitations in space dictated by the stoichiometry of the local partial reactions. However, if the component's mobility is high, this implies local competition between mineral growth and the yield strength of the surrounding matrix, thus local pressure variation. Experimentally this is validated by the significant differences in Opx rim thickness, either forming around Ol in Qtz matrix, or around Qtz in Ol matrix, in one and the same experiment. Tantamount observations have been experimentally made in the CaO-SiO2 and CaO-MgO-SiO2 systems. In all these laboratory experiments, the presence of traces of water has been identified as a leading variable controlling the mobility of chemical species. Trace amounts of water follow local pressure gradients and speed up reaction rates where local volume change is negative. New results indicate that at least in coarse grained rocks, total water contents in the 10 ppm range might increase chemical fluxes along grain boundaries by orders of magnitude. The majority of metamorphic rocks in the Earth's crust is dominated by aluminuous silicates and quartz. Reaction rims in aluminosilicate lithologies have been studied in samples of high-pressure felsic granulites from the Bohemian Massif (Variscan belt of Central Europe). They show well developed plagioclase reaction rims around kyanite grains in two microstructural settings. Plagioclase rims around kyanite inclusions within large perthites have a radial thickness of up to 50 ?m, whereas the radial thickness of plagioclase rims around kyanites in the polycrystalline matrix is significantly larger, up to 200 ?m. The difference in the rim thickness for the two microstructural settings is ascribed to the complex interplay of the efficiency of chemical mass transfer and the mechanical response of the surrounding matrix next to the reaction site. Our data based on numerical modelling show that the microstructure may be generated and maintained on the geological time scale as a result of the mechanical feedback induced by the local reactions taking place in restricted space. In general, the observations from experimental and natural systems indicate that assumed equilibria in metamorphic rocks must be generally considered as local equilibria. This includes not only the chemical composition of metamorphic minerals, but also the strength of the surrounding matrix in which they form.

Milke, R.; Tajcmanova, L.

2012-12-01

129

Functional characteristics of a double positive feedback loop coupled with autorepression  

NASA Astrophysics Data System (ADS)

We study the functional characteristics of a two-gene motif consisting of a double positive feedback loop and an autoregulatory negative feedback loop. The motif appears in the gene regulatory network controlling the functional activity of pancreatic ?-cells. The model exhibits bistability and hysteresis in appropriate parameter regions. The two stable steady states correspond to low (OFF state) and high (ON state) protein levels, respectively. Using a deterministic approach, we show that the region of bistability increases in extent when the copy number of one of the genes is reduced from 2 to 1. The negative feedback loop has the effect of reducing the size of the bistable region. Loss of a gene copy, brought about by mutations, hampers the normal functioning of the ?-cells giving rise to the genetic disorder, maturity-onset diabetes of the young (MODY). The diabetic phenotype makes its appearance when a sizable fraction of the ?-cells is in the OFF state. Using stochastic simulation techniques we show that, on reduction of the gene copy number, there is a transition from the monostable ON to the ON state in the bistable region of the parameter space. Fluctuations in the protein levels, arising due to the stochastic nature of gene expression, can give rise to transitions between the ON and OFF states. We show that as the strength of autorepression increases, the ON ? OFF state transitions become less probable whereas the reverse transitions are more probable. The implications of the results in the context of the occurrence of MODY are pointed out.

Banerjee, Subhasis; Bose, Indrani

2008-12-01

130

Dynamics due to Non-Resonant Double Hopf Bifurcationin in Van Del Pol-Duffing System with Delayed Position Feedback  

Microsoft Academic Search

In this paper, the van der Pol-Duffing system with delayed position feedback is investigated A critical point with \\u000a 1:Ö<\\/font\\u000a>21:\\\\sqrt 2\\u000a frequency ratio is obtained. The center manifold reduction (CMR) is employed to classify various solutions bifurcating from\\u000a the point. The approximate expressions provided by the CMR are valid for values of the time delay and feedback gain close\\u000a to

J. Xu; M. S. Huang; Y. Y. Zhang

131

Better Bet-Hedging with coupled positive and negative feedback loops  

NASA Astrophysics Data System (ADS)

Bacteria use the phenotypic heterogeneity associated with bistable switches to distribute the risk of activating stress response strategies like sporulation and persistence. However bistable switches offer little control over the timing of phenotype switching and first passage times (FPT) for individual cells are found to be exponentially distributed. We show that a genetic circuit consisting of interlinked positive and negative feedback loops allows cells to control the timing of phenotypic switching. Using a mathematical model we find that in this system a stable high expression state and stable low expression limit cycle coexist and the FPT distribution for stochastic transitions between them shows multiple peaks at regular intervals. A multimodal FPT distribution allows cells to detect the persistence of stress and control the rate of phenotype transition of the population. We further show that extracellular signals from cell-cell communication that change the strength of the feedback loops can modulate the FPT distribution and allow cells even greater control in a bet-hedging strategy.

Narula, Jatin; Igoshin, Oleg

2011-03-01

132

A positive feedback regulation of ISL-1 in DLBCL but not in pancreatic ?-cells.  

PubMed

Insulin enhancer binding protein-1 (ISL-1), a LIM-homeodomain transcription factor, has been reported to play essential roles in promoting adult pancreatic ?-cells proliferation. Recent studies indicate that ISL-1 may also involve in the occurrence of a variety of tumors. However, whether ISL-1 has any functional effect on tumorigenesis, and what are the differences on ISL-1 function in distinct conditions, are completely unknown. In this study, we found that ISL-1 was highly expressed in human pancreatic ?-cells, as well as in diffuse large B cell lymphoma (DLBCL), but to a much less extent in other normal tissues or tumor specimens. Further study revealed that ISL-1 promoted the proliferation of pancreatic ?-cells and DLBCL cells, and also accelerated the tumorigenesis of DLBCL in vivo. We also found that ISL-1 could activate c-Myc transcription not only in pancreatic ?-cells but also in DLBCL cells. However, a cell-specific feedback regulation was detectable only in DLBCL cells. This auto-regulatory loop was established by the interaction of ISL-1 and c-Myc to form an ISL-1/c-Myc transcriptional complex, and synergistically to promote ISL-1 transcription through binding on the ISL-1 promoter. Taken together, our results demonstrate a positive feedback regulation of ISL-1 in DLBCL but not in pancreatic ?-cells, which might result in the functional diversities of ISL-1 in different physiological and pathological processes. PMID:24845569

Zhang, Qiao; Yang, Zhe; Wang, Weiping; Guo, Ting; Jia, Zhuqing; Ma, Kangtao; Zhou, Chunyan

2014-07-01

133

Self-Management of Patient Body Position, Pose, and Motion Using Wide-Field, Real-Time Optical Measurement Feedback: Results of a Volunteer Study  

SciTech Connect

Purpose: We present the results of a clinical feasibility study, performed in 10 healthy volunteers undergoing a simulated treatment over 3 sessions, to investigate the use of a wide-field visual feedback technique intended to help patients control their pose while reducing motion during radiation therapy treatment. Methods and Materials: An optical surface sensor is used to capture wide-area measurements of a subject's body surface with visualizations of these data displayed back to them in real time. In this study we hypothesize that this active feedback mechanism will enable patients to control their motion and help them maintain their setup pose and position. A capability hierarchy of 3 different level-of-detail abstractions of the measured surface data is systematically compared. Results: Use of the device enabled volunteers to increase their conformance to a reference surface, as measured by decreased variability across their body surfaces. The use of visual feedback also enabled volunteers to reduce their respiratory motion amplitude to 1.7 ± 0.6 mm compared with 2.7 ± 1.4 mm without visual feedback. Conclusions: The use of live feedback of their optically measured body surfaces enabled a set of volunteers to better manage their pose and motion when compared with free breathing. The method is suitable to be taken forward to patient studies.

Parkhurst, James M. [Developing Technologies, Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester (United Kingdom); Price, Gareth J., E-mail: gareth.price@christie.nhs.uk [Developing Technologies, Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester (United Kingdom); Faculty of Medical and Human Sciences, Manchester Academic Health Sciences Centre, University of Manchester, Manchester (United Kingdom); Sharrock, Phil J. [Developing Technologies, Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester (United Kingdom); Jackson, Andrew S.N. [Clinical Oncology, Southampton University Hospitals Foundation Trust, Southampton (United Kingdom); Stratford, Julie [Department of Radiotherapy, The Christie NHS Foundation Trust, Manchester (United Kingdom); Moore, Christopher J. [Developing Technologies, Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester (United Kingdom); Faculty of Medical and Human Sciences, Manchester Academic Health Sciences Centre, University of Manchester, Manchester (United Kingdom)

2013-12-01

134

Calculating the spontaneous magnetization and defining the Curie temperature using a positive-feedback model  

SciTech Connect

A positive-feedback mean-field modification of the classical Brillouin magnetization theory provides an explanation of the apparent persistence of the spontaneous magnetization beyond the conventional Curie temperature—the little understood “tail” phenomenon that occurs in many ferromagnetic materials. The classical theory is unable to resolve this apparent anomaly. The modified theory incorporates the temperature-dependent quantum-scale hysteretic and mesoscopic domain-scale anhysteretic magnetization processes and includes the effects of demagnetizing and exchange fields. It is found that the thermal behavior of the reversible and irreversible segments of the hysteresis loops, as predicted by the theory, is a key to the presence or absence of the “tails.” The theory, which permits arbitrary values of the quantum spin number J, generally provides a quantitative agreement with the thermal variations of both the spontaneous magnetization and the shape of the hysteresis loop.

Harrison, R. G., E-mail: rgh@doe.carleton.ca [Department of Electronics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada)

2014-01-21

135

Scattering and reflection positivity in relativistic Euclidean quantum mechanics  

E-print Network

Scattering and reflection positivity in relativistic Euclidean quantum mechanics W. N. Polyzou The University of Iowa, Iowa City, IA 52242 Abstract In this paper I exhibit a class of reflection positive mechanics where the dynamics is introduced through a collection of reflection positive Euclidean "Green

Polyzou, Wayne

136

Scattering and reflection positivity in relativistic Euclidean quantum mechanics  

E-print Network

Scattering and reflection positivity in relativistic Euclidean quantum mechanics W. N. Polyzou The University of Iowa, Iowa City, IA 52242 Abstract In this paper I exhibit a class of reflection positive mechanics where the dynamics is introduced through a collection of reflection positive Euclidean ``Green

Polyzou, Wayne

137

Laser-Machined Shape Memory Alloy Sensors for Position Feedback in Active Catheters  

PubMed Central

Catheter-based interventions are a form of minimally invasive surgery that can decrease hospitalization time and greatly lower patient morbidity compared to traditional methods. However, percutaneous catheter procedures are hindered by a lack of precise tip manipulation when actuation forces are transmitted over the length of the catheter. Active catheters with local shape-memory-alloy (SMA) actuation can potentially provide the desired manipulation of a catheter tip, but hysteresis makes it difficult to control the actuators. A method to integrate small-volume, compliant sensors on an active catheter to provide position feedback for control would greatly improve the viability of SMA-based active catheters. In this work, we describe the design, fabrication, and performance of resistance-based position sensors that are laser-machined from superelastic SMA tubing. Combining simple material models and rapid prototyping, we can develop sensors of appropriate stiffness and sensitivity with simple modifications in sensor geometry. The sensors exhibit excellent linearity over the operating range and are designed to be easily integrated onto an active catheter substrate. PMID:19759806

Tung, Alexander T.; Park, Byong-Ho; Liang, David H.; Niemeyer, Günter

2008-01-01

138

Visual Feedback of the Non-Moving Limb Improves Active Joint-Position Sense of the Impaired Limb in Spastic Hemiparetic Cerebral Palsy  

ERIC Educational Resources Information Center

This study examined the active joint-position sense in children with Spastic Hemiparetic Cerebral Palsy (SHCP) and the effect of static visual feedback and static mirror visual feedback, of the non-moving limb, on the joint-position sense. Participants were asked to match the position of one upper limb with that of the contralateral limb. The task…

Smorenburg, Ana R. P.; Ledebt, Annick; Deconinck, Frederik J. A.; Savelsbergh, Geert J. P.

2011-01-01

139

Local feedback mechanisms of the shallow water region around the Maritime Continent  

NASA Astrophysics Data System (ADS)

focus of this study is the local-scale air-sea feedback mechanisms over the shallow shelf water region (water depth <200 m) of the Maritime Continent (MC). MC was selected as a pilot study site for its extensive shallow water coverage, geographic complexity, and importance in the global climate system. To identify the local-scale air-sea feedback processes, we ran numerical experiments with perturbed surface layer water temperature using a coupled ocean-atmosphere model and an uncoupled ocean model. By examining the responses of the coupled and uncoupled models to the water temperature perturbation, we identify that, at a local-scale, a negative feedback process through the coupled dynamics that tends to restore the SST from its perturbation could dominate the shallow water region of the MC at a short time scale of several days. The energy budget shows that 38% of initial perturbation-induced heat energy was adjusted through the air-sea feedback mechanisms within 2 weeks, of which 58% is directly transferred into the atmosphere by the adjustment of latent heat flux due to the evaporative cooling mechanism. The increased inputs of heat and moisture into the lower atmosphere then modifies its thermal structure and increases the formation of low-level clouds, which act as a shield preventing incoming solar radiation from reaching the sea surface, accounts for 38% of the total adjustment of surface heat fluxes, serving as the second mechanism for the negative feedback process. The adjustment of sensible heat flux and net longwave radiation play a secondary role. The response of the coupled system to the SST perturbation suggests a response time scale of the coupled feedback process of about 3-5 days. The two-way air-sea feedback tightly links the surface heat fluxes, clouds and SST, and can play an important role in regulating the short-term variability of the SST over the shallow shelf water regions.

Xue, Pengfei; Eltahir, Elfatih A. B.; Malanotte-Rizzoli, Paola; Wei, Jun

2014-10-01

140

Positive feedback of dust aerosol via its impact on atmospheric stability during dust storms in the Eastern Mediterranean  

NASA Astrophysics Data System (ADS)

Aerosols affect the atmosphere through the aerosol-radiation and the aerosol-clouds interactions. In this paper we report on a new mechanism whereby the radiative effect of dust aerosol on surface fluxes acts to increase the dust loading of the atmosphere via modification of boundary-layer stability, thereby acting to enhance the radiative aerosol effect. This positive feedback between dust aerosol and boundary layer stability occurred during a series of dust storms in the Sahara and the Eastern Mediterranean in April 2012, which were studied using the Monitoring Atmospheric Composition and Climate - Interim Implementation (MACC-II) system. The radiative fluxes in the shortwave and long-wave spectra were both significantly affected by the prognostic aerosols-radiation interation, which strongly influenced the meteorological simulation. Reduced incoming solar radiation below the aerosol layers caused a decrease in maximum surface temperatures, and consequently a more stable thermal stratification of the lower atmosphere. The increased thermal stability led to decreased surface wind speeds and therefore to smaller amounts of dust aerosol emissions. Larger downwelling long-wave fluxes were associated with the opposite processes: less stable thermal stratification at night, brought mainly by higher minimum temperatures at the surface, caused stronger surface winds. Overall, the impact by the long-wave radiative forcing was more important than the short-wave contribution. This feedback was amplified when taken into account in the aerosol analysis of the MACC-II global system. It lead to a notable improvement in short term forecast of short and long-wave radiative fluxes, of surface temperature but also of the aerosol burden itself. Forecasts of radiative fluxes in the shortwave and long-wave spectrum were also improved. At a longer range the improvement were less important as the forecast error of the aerosol load increased, thereby highlighting the importance of accurate aerosol representation in the study of aerosol-radiation interaction.

Remy, S.; Benedetti, A.; Haiden, T.; Jones, L.; Razinger, M.; Flemming, J.; Engelen, R. J.; Peuch, V. H.; Thepaut, J. N.

2014-11-01

141

Feedback Inhibition of Ammonium Uptake by a Phospho-Dependent Allosteric Mechanism in Arabidopsis[W  

PubMed Central

The acquisition of nutrients requires tight regulation to ensure optimal supply while preventing accumulation to toxic levels. Ammonium transporter/methylamine permease/rhesus (AMT/Mep/Rh) transporters are responsible for ammonium acquisition in bacteria, fungi, and plants. The ammonium transporter AMT1;1 from Arabidopsis thaliana uses a novel regulatory mechanism requiring the productive interaction between a trimer of subunits for function. Allosteric regulation is mediated by a cytosolic C-terminal trans-activation domain, which carries a conserved Thr (T460) in a critical position in the hinge region of the C terminus. When expressed in yeast, mutation of T460 leads to inactivation of the trimeric complex. This study shows that phosphorylation of T460 is triggered by ammonium in a time- and concentration-dependent manner. Neither Gln nor l-methionine sulfoximine–induced ammonium accumulation were effective in inducing phosphorylation, suggesting that roots use either the ammonium transporter itself or another extracellular sensor to measure ammonium concentrations in the rhizosphere. Phosphorylation of T460 in response to an increase in external ammonium correlates with inhibition of ammonium uptake into Arabidopsis roots. Thus, phosphorylation appears to function in a feedback loop restricting ammonium uptake. This novel autoregulatory mechanism is capable of tuning uptake capacity over a wide range of supply levels using an extracellular sensory system, potentially mediated by a transceptor (i.e., transporter and receptor). PMID:19948793

Lanquar, Viviane; Loqué, Dominique; Hörmann, Friederike; Yuan, Lixing; Bohner, Anne; Engelsberger, Wolfgang R.; Lalonde, Sylvie; Schulze, Waltraud X.; von Wirén, Nicolaus; Frommer, Wolf B.

2009-01-01

142

Faculty Position in Mechanical Engineering Water Conservation in Industrial Processes  

E-print Network

Faculty Position in Mechanical Engineering Water Conservation in Industrial Processes University of Kansas The Department of Mechanical Engineering at the University of Kansas is seeking applications in industrial processes. Exceptional candidates with outstanding qualifications could be considered

143

Observer-based strict positive real (SPR) switching output feedback control  

Microsoft Academic Search

This paper considers switching output feedback control of linear systems and variable-structure systems. Theory for stability analysis and design for a class of observer-based feedback control systems is presented. It is shown how a circle-criterion approach can be used to design an observer-based state feedback control which yields a closed-loop system with specified robustness characteristics. The approach is relevant for

Rolf Johansson; Anders Robertsson; Anton Shiriaev

2004-01-01

144

Perceptions of Teachers' Positive Feedback and Perceived Threat to Sense of Self in Physical Education: A Longitudinal Study  

ERIC Educational Resources Information Center

This study examined the direction of causal flow between perceived positive general teacher feedback and perceived threat to sense of self in physical education (PE). The stability effect and stationarity of the relationship between these variables over the two-year period was tested. Students (N = 302) were administered questionnaire during class…

Koka, Andre; Hein, Vello

2006-01-01

145

PPAR and liver circadian clock Reciprocal regulation of BMAL1 and PPAR defines a novel positive feedback loop in  

E-print Network

PPAR and liver circadian clock Reciprocal regulation of BMAL1 and PPAR defines a novel positive feedback loop in the rodent liver circadian clock. Laurence Canaple*¶ , Juliette Rambaud*, Ouria Dkhissi.laudet@ens-lyon.fr The authors have nothing to declare. Running Title: PPAR and liver circadian clock Key words: PPAR, BMAL1

Boyer, Edmond

146

Construction and Modelling of an Inducible Positive Feedback Loop Stably Integrated in a Mammalian Cell-Line  

Microsoft Academic Search

Understanding the relationship between topology and dynamics of transcriptional regulatory networks in mammalian cells is essential to elucidate the biology of complex regulatory and signaling pathways. Here, we characterised, via a synthetic biology approach, a transcriptional positive feedback loop (PFL) by generating a clonal population of mammalian cells (CHO) carrying a stable integration of the construct. The PFL network consists

Velia Siciliano; Filippo Menolascina; Lucia Marucci; Chiara Fracassi; Immacolata Garzilli; Maria Nicoletta Moretti; Diego di Bernardo

2011-01-01

147

Intrinsic activity and positive feedback in motor circuits in organotypic spinal cord slice cultures.  

PubMed

In co-cultures of embryonic rat spinal cord slices and skeletal muscle, spinal motoneurons innervate muscle fibres and drive muscle contractions. However, multi-electrode array (MEA) recordings show that muscle contractions often appear in the absence of population activity in the spinal cord networks. Such uncorrelated muscle activity persists when the population bursts in the neuronal networks are prevented by un-coupling the network with the glutamatergic antagonists CNQX and D-APV. By contrast, the uncorrelated muscle activity is fully suppressed by the muscular nicotinic antagonist D-tubocurarine. Together, these findings confirm the previous finding that motoneurons drive muscle fibres in this preparation and suggest that they are intrinsically spiking in the absence of synaptic input. Intracellular recordings from spinal neurons support this suggestion. Analysing the correlated muscle activity, we found that in 15% of the population bursts, muscle activity appears at the beginning or before neuronal activity, suggesting that in these cases motoneurons initiate the population activity. Both the total number of population bursts and the percentage of such bursts that are initiated by muscle activity are reduced by a block of nicotinic receptors. Uncorrelated muscle and neuronal activity is reduced by the gap junction blocker carbenoxolone, suggesting that electrical coupling is involved in the generation of this activity. Together, these findings suggest that intrinsic firing of motoneurons may contribute to the activation of population bursts through cholinergic positive feedback loops in cultured spinal networks. PMID:19811528

Magloire, Vincent; Streit, Jürg

2009-10-01

148

Nur1 dephosphorylation confers positive feedback to mitotic exit phosphatase activation in budding yeast.  

PubMed

Substrate dephosphorylation by the cyclin-dependent kinase (Cdk)-opposing phosphatase, Cdc14, is vital for many events during budding yeast mitotic exit. Cdc14 is sequestered in the nucleolus through inhibitory binding to Net1, from which it is released in anaphase following Net1 phosphorylation. Initial Net1 phosphorylation depends on Cdk itself, in conjunction with proteins of the Cdc14 Early Anaphase Release (FEAR) network. Later on, the Mitotic Exit Network (MEN) signaling cascade maintains Cdc14 release. An important unresolved question is how Cdc14 activity can increase in early anaphase, while Cdk activity, that is required for Net1 phosphorylation, decreases and the MEN is not yet active. Here we show that the nuclear rim protein Nur1 interacts with Net1 and, in its Cdk phosphorylated form, inhibits Cdc14 release. Nur1 is dephosphorylated by Cdc14 in early anaphase, relieving the inhibition and promoting further Cdc14 release. Nur1 dephosphorylation thus describes a positive feedback loop in Cdc14 phosphatase activation during mitotic exit, required for faithful chromosome segregation and completion of the cell division cycle. PMID:25569132

Godfrey, Molly; Kuilman, Thomas; Uhlmann, Frank

2015-01-01

149

Nur1 Dephosphorylation Confers Positive Feedback to Mitotic Exit Phosphatase Activation in Budding Yeast  

PubMed Central

Substrate dephosphorylation by the cyclin-dependent kinase (Cdk)-opposing phosphatase, Cdc14, is vital for many events during budding yeast mitotic exit. Cdc14 is sequestered in the nucleolus through inhibitory binding to Net1, from which it is released in anaphase following Net1 phosphorylation. Initial Net1 phosphorylation depends on Cdk itself, in conjunction with proteins of the Cdc14 Early Anaphase Release (FEAR) network. Later on, the Mitotic Exit Network (MEN) signaling cascade maintains Cdc14 release. An important unresolved question is how Cdc14 activity can increase in early anaphase, while Cdk activity, that is required for Net1 phosphorylation, decreases and the MEN is not yet active. Here we show that the nuclear rim protein Nur1 interacts with Net1 and, in its Cdk phosphorylated form, inhibits Cdc14 release. Nur1 is dephosphorylated by Cdc14 in early anaphase, relieving the inhibition and promoting further Cdc14 release. Nur1 dephosphorylation thus describes a positive feedback loop in Cdc14 phosphatase activation during mitotic exit, required for faithful chromosome segregation and completion of the cell division cycle. PMID:25569132

Godfrey, Molly; Kuilman, Thomas; Uhlmann, Frank

2015-01-01

150

A Positive Feedback Loop Between Prolactin and STAT5 Promotes Angiogenesis.  

PubMed

The signal transduction events that orchestrate cellular activities required for angiogenesis remain incompletely understood. We and others recently described that proangiogenic mediators such as fibroblast growth factors can activate members of the signal transducers and activators of transcription (STAT) family. STAT5 activation is necessary and sufficient to induce migration, invasion and tube formation of endothelial cells. STAT5 effects on endothelial cells require the secretion of the prolactin (PRL) family member proliferin-1 (PLF1) in mice and PRL in humans. In human endothelial cells, PRL activates the PRL receptor (PRLR) resulting in MAPK and STAT5 activation, thus closing a positive feedback loop. In vivo, endothelial cell-derived PRL is expected to combine with PRL of tumor cell and pituitary origin to raise the concentration of this polypeptide hormone in the tumor microenvironment. Thus, PRL may stimulate tumor angiogenesis via autocrine, paracrine, and endocrine pathways. The disruption of tumor angiogenesis by interfering with PRL signaling may offer an attractive target for therapeutic intervention. PMID:25472543

Yang, Xinhai; Friedl, Andreas

2015-01-01

151

Distinct noise-controlling roles of multiple negative feedback mechanisms in a prokaryotic operon system.  

PubMed

Molecular fluctuations are known to affect dynamics of cellular systems in important ways. Studies aimed at understanding how molecular systems of certain regulatory architectures control noise therefore become essential. The interplay between feedback regulation and noise has been previously explored for cellular networks governed by a single negative feedback loop. However, similar issues within networks consisting of more complex regulatory structures remain elusive. The authors investigate how negative feedback loops manage noise within a biochemical cascade concurrently governed by multiple negative feedback loops, using the prokaryotic tryptophan (trp) operon system in Escherechia coli as the model system. To the authors knowledge, this is the first study of noise in the trp operon system. They show that the loops in the trp operon system possess distinct, even opposing, noise-controlling effects despite their seemingly analogous feedback structures. The enzyme inhibition loop, although controlling the last reaction of the cascade, was found to suppress noise not only for the tryptophan output but also for other upstream components. In contrast, the Repression (Rep) loop enhances noise for all systems components. Attenuation (Att) poses intermediate effects by attenuating noise for the upstream components but promoting noise for components downstream of its target. Regarding noise at the output tryptophan, Rep and Att can be categorised as noise-enhancing loops whereas Enzyme Inhibition as a noise-reducing loop. These findings suggest novel implications in how cellular systems with multiple feedback mechanisms control noise. [Includes supplementary material]. PMID:21405203

Nguyen, L K; Kulasiri, D

2011-03-01

152

Micro Position Control of a 3-RRR Compliant Mechanical Engineering  

E-print Network

Micro Position Control of a 3-RRR Compliant Mechanism Merve Acer Mechanical Engineering Istanbul as a micro positioning stage. The stage displacements are analyzed by using structural FEA. However important for micro/nano applications such as cell manipulation, surgery, aerospace, micro fluidics, optical

Yanikoglu, Berrin

153

Moisture transport across Central America as a positive feedback on abrupt climatic changes.  

PubMed

Moisture transport from the Atlantic to the Pacific ocean across Central America leads to relatively high salinities in the North Atlantic Ocean and contributes to the formation of North Atlantic Deep Water. This deep water formation varied strongly between Dansgaard/Oeschger interstadials and Heinrich events-millennial-scale abrupt warm and cold events, respectively, during the last glacial period. Increases in the moisture transport across Central America have been proposed to coincide with northerly shifts of the Intertropical Convergence Zone and with Dansgaard/Oeschger interstadials, with opposite changes for Heinrich events. Here we reconstruct sea surface salinities in the eastern equatorial Pacific Ocean over the past 90,000 years by comparing palaeotemperature estimates from alkenones and Mg/Ca ratios with foraminiferal oxygen isotope ratios that vary with both temperature and salinity. We detect millennial-scale fluctuations of sea surface salinities in the eastern equatorial Pacific Ocean of up to two to four practical salinity units. High salinities are associated with the southward migration of the tropical Atlantic Intertropical Convergence Zone, coinciding with Heinrich events and with Greenland stadials. The amplitudes of these salinity variations are significantly larger on the Pacific side of the Panama isthmus, as inferred from a comparison of our data with a palaeoclimate record from the Caribbean basin. We conclude that millennial-scale fluctuations of moisture transport constitute an important feedback mechanism for abrupt climate changes, modulating the North Atlantic freshwater budget and hence North Atlantic Deep Water formation. PMID:17314978

Leduc, Guillaume; Vidal, Laurence; Tachikawa, Kazuyo; Rostek, Frauke; Sonzogni, Corinne; Beaufort, Luc; Bard, Edouard

2007-02-22

154

Introduction: Mount Pinatubo as a test of climate feedback mechanisms  

NASA Astrophysics Data System (ADS)

The June 15, 1991 Mount Pinatubo eruption was a large but relatively shortlived shock to the Earth's atmosphere. It thus provided an excellent opportunity to study the workings of the climate system, to test climate models, and to examine the impacts of climate change on life. The largest eruption of the 20th Century inspired a large amount of research on the connection between volcanic eruptions and the Earth's atmosphere in the 12 years since that eruption, as exemplified by the chapters in this book. Here several additional examples of our new understanding of these connections are presented. While the global cooling after Pinatubo was not surprising, the observed winter warming over Northern Hemisphere continents in the two winters following the eruption is now understood as a dynamic response to volcanically produced temperature gradients in the lower stratosphere from aerosol heating and ozone depletion, and to reduced tropospheric storminess. Interactions of the Quasi-Biennial Oscillation of tropical stratospheric winds with the climate system are also now better understood by examining their role in the Pinatubo response. We have more confidence in the sensitivity of climate models used for attribution and projection of anthropogenic effects on climate because the strength of the water vapor feedback has been validated with Pinatubo simulations. The response of the biosphere to the Pinatubo eruption also illustrates its sensitivity to climate change and clarifies portions of the carbon cycle. Death of coral in the Red Sea in the winter of 1991-1992 and an unusually large number of polar bear cubs born in the summer of 1992 were two responses to the characteristic winter and summer temperature responses of the climate system. This strengthens our concern about negative impacts of global warming on polar bears and other wildlife. Enhanced vegetation growth from more diffuse and less direct solar radiation took more carbon dioxide out of the atmosphere than normal, temporarily reducing the observed long-term increase in carbon dioxide. Continued research on the Pinatubo eruption and its aftermath will undoubtedly enhance our understanding of the climate system.

Robock, Alan

155

Vacuum cryogenic wheel-driving mechanism with high positioning repeatability  

NASA Astrophysics Data System (ADS)

The repeatability of positioning of wheels carrying optical components can be critical for the performance of optical instruments. We present the cryogenic worm driven wheel positioning mechanism designed for Anglo-Australian Observatory's Infrared Imager and Spectrograph IRIS2. The mechanism, which was designed for a high vacuum environment and working temperature of 70-90K, utilized an aluminum worm and gearwheel, stepper motor and an encoding system based on infrared sensors. The mechanism has demonstrated repeatability of 1 arcmin.

Churilov, Vladimir; Smith, Greg; Hingley, Brian E.

2002-11-01

156

A computational study of background-induced flicker enhancement and feedback mechanisms in cat outer retina: temporal properties  

E-print Network

1 A computational study of background-induced flicker enhancement and feedback mechanisms in cat, Arizona State University, Tempe, AZ 85287 3 Neural Circuits Unit, Basic Neuroscience Program, NINDS, NIH, Bethesda, MD 20892 Running head: Temporal properties of flicker enhancement and feedback mechanisms Contact

Ringhofer, Christian

157

Positive effects of augmented verbal feedback on power production in NCAA Division I collegiate athletes.  

PubMed

The purpose of this study was to determine how augmented verbal feedback, specifically knowledge of performance during a countermovement vertical jump (CMVJ) protocol, would affect acute power output. Each subject (N = 14 [9 men and 5 women], 21.4 ± 0.8 years, 179.6 ± 6.1 cm, 87.5 ± 14.8 kg) completed the CMVJ protocol twice in a balanced randomized order, one trial with feedback and one without feedback. At least 48 hours were allowed between sessions for resting. Student-athletes were used because of their trained state and their familiarity with plyometrics and receiving and processing feedback during training. Each testing session began with a 10-minute warm-up consisting of a combination of dynamic stretching and submaximal jumps (no proprioceptive neuromuscular facilitation or static stretching). After completion of the warm-up, the subjects then began the CMVJ protocol. The CMVJ protocol consisted of 3 sets of 5 jumps on a calibrated force plate set to read at 200 Hz (Accupower). Subjects were instructed at the start of the protocol to give maximal effort on each jump. The standard set and repetition scheme for this protocol was 3 sets of 5 maximal repetitions with 3 minutes rest between sets. This was used to mimic the practice of training for maximal power. Before each jump, the subject was told the jump number and given a verbal start cue before the jump's initiation. The verbal performance feedback given consisted of the full kinetic numerical value of the peak power output in watts of the last completed jump. Significance in this study was set at p ? 0.05. There was a significant difference between mean power outputs (4,335 ± 366 W to 4,108 ± 345 W, p = 0.003) and the peak power outputs (4,567 ± 381 W to 4,319 ± 371 W, p = 0.018) when comparing feedback to no feedback, respectively. There was a significant difference in peak power output between the feedback and no feedback trials during set 2 (mean difference 361 ± 161 W, p = 0.043) and set 3 (mean difference 283 ± 109 W, p = 0.022). Also, there was a significant difference in mean power output between feedback and no feedback trials during set 2 (mean difference 240 ± 66 W, p = 0.003) and set 3 (mean difference 299 ± 93 W, p = 0.007). When training for maximal power in a plyometric training protocol, verbal feedback can be used as both a simple and effective aid in producing optimal power outputs. PMID:23207887

Staub, Joseph N; Kraemer, William J; Pandit, Ashley L; Haug, William B; Comstock, Brett A; Dunn-Lewis, Courtenay; Hooper, David R; Maresh, Carl M; Volek, Jeff S; Häkkinen, Keijo

2013-08-01

158

Balanced bridge feedback control system  

NASA Technical Reports Server (NTRS)

In a system having a driver, a motor, and a mechanical plant, a multiloop feedback control apparatus for controlling the movement and/or positioning of a mechanical plant, the control apparatus has a first local bridge feedback loop for feeding back a signal representative of a selected ratio of voltage and current at the output driver, and a second bridge feedback loop for feeding back a signal representative of a selected ratio of force and velocity at the output of the motor. The control apparatus may further include an outer loop for feeding back a signal representing the angular velocity and/or position of the mechanical plant.

Lurie, Boris J. (inventor)

1990-01-01

159

Landscape urbanization and economic growth in China: positive feedbacks and sustainability dilemmas.  

PubMed

Accelerating urbanization has been viewed as an important instrument for economic development and reducing regional income disparity in some developing countries, including China. Recent studies (Bloom et al. 2008) indicate that demographic urbanization level has no causal effect on economic growth. However, due to the varying and changing definition of urban population, the use of demographic indicators as a sole representing indicator for urbanization might be misleading. Here, we re-examine the causal relationship between urbanization and economic growth in Chinese cities and provinces in recent decades, using built-up areas as a landscape urbanization indicator. Our analysis shows that (1) larger cities, both in terms of population size and built-up area, and richer cities tend to gain more income, have larger built-up area expansion, and attract more population, than poorer cities or smaller cities; and (2) that there is a long-term bidirectional causality between urban built-up area expansion and GDP per capita at both city and provincial level, and a short-term bidirectional causality at provincial level, revealing a positive feedback between landscape urbanization and urban and regional economic growth in China. Our results suggest that urbanization, if measured by a landscape indicator, does have causal effect on economic growth in China, both within the city and with spillover effect to the region, and that urban land expansion is not only the consequences of economic growth in cities, but also drivers of such growth. The results also suggest that under its current economic growth model, it might be difficult for China to control urban expansion without sacrificing economic growth, and China's policy to stop the loss of agricultural land, for food security, might be challenged by its policy to promote economic growth through urbanization. PMID:22103244

Bai, Xuemei; Chen, Jing; Shi, Peijun

2012-01-01

160

Landscape Urbanization and Economic Growth in China: Positive Feedbacks and Sustainability Dilemmas  

PubMed Central

Accelerating urbanization has been viewed as an important instrument for economic development and reducing regional income disparity in some developing countries, including China. Recent studies (Bloom et al. 2008) indicate that demographic urbanization level has no causal effect on economic growth. However, due to the varying and changing definition of urban population, the use of demographic indicators as a sole representing indicator for urbanization might be misleading. Here, we re-examine the causal relationship between urbanization and economic growth in Chinese cities and provinces in recent decades, using built-up areas as a landscape urbanization indicator. Our analysis shows that (1) larger cities, both in terms of population size and built-up area, and richer cities tend to gain more income, have larger built-up area expansion, and attract more population, than poorer cities or smaller cities; and (2) that there is a long-term bidirectional causality between urban built-up area expansion and GDP per capita at both city and provincial level, and a short-term bidirectional causality at provincial level, revealing a positive feedback between landscape urbanization and urban and regional economic growth in China. Our results suggest that urbanization, if measured by a landscape indicator, does have causal effect on economic growth in China, both within the city and with spillover effect to the region, and that urban land expansion is not only the consequences of economic growth in cities, but also drivers of such growth. The results also suggest that under its current economic growth model, it might be difficult for China to control urban expansion without sacrificing economic growth, and China’s policy to stop the loss of agricultural land, for food security, might be challenged by its policy to promote economic growth through urbanization. PMID:22103244

2011-01-01

161

Positive Transcriptional Feedback Controls Hydrogenase Expression in Alcaligenes eutrophus H16  

PubMed Central

The protein HoxA is the central regulator of the Alcaligenes eutrophus H16 hox regulon, which encodes two hydrogenases, a nickel permease and several accessory proteins required for hydrogenase biosynthesis. Expression of the regulatory gene hoxA was analyzed. Screening of an 8-kb region upstream of hoxA with a promoter probe vector localized four promoter activities. One of these was found in the region immediately 5? of hoxA; the others were correlated with the nickel metabolism genes hypA1, hypB1, and hypX. All four activities were independent of HoxA and of the minor transcription factor ?54. Translational fusions revealed that hoxA is expressed constitutively at low levels. In contrast to these findings, immunoblotting studies revealed a clear fluctuation in the HoxA pool in response to conditions which induce the hox regulon. Quantitative transcript assays indicated elevated levels of hyp mRNA under hydrogenase-derepressing conditions. Using interposon mutagenesis, we showed that the activity of a remote promoter is required for hydrogenase expression and autotrophic growth. Site-directed mutagenesis revealed that PMBH, which directs transcription of the structural genes of the membrane-bound hydrogenase, contributes to the expression of hoxA under hydrogenase-derepressing conditions. Thus, expression of the hox regulon is governed by a positive feedback loop mediating amplification of the regulator HoxA. These results imply the existence of an unusually large (ca. 17,000-nucleotide) transcript. PMID:10482509

Schwartz, Edward; Buhrke, Thorsten; Gerischer, Ulrike; Friedrich, Bärbel

1999-01-01

162

A positive feedback between p53 and miR-34 miRNAs mediates tumor suppression.  

PubMed

As bona fide p53 transcriptional targets, miR-34 microRNAs (miRNAs) exhibit frequent alterations in many human tumor types and elicit multiple p53 downstream effects upon overexpression. Unexpectedly, miR-34 deletion alone fails to impair multiple p53-mediated tumor suppressor effects in mice, possibly due to the considerable redundancy in the p53 pathway. Here, we demonstrate that miR-34a represses HDM4, a potent negative regulator of p53, creating a positive feedback loop acting on p53. In a Kras-induced mouse lung cancer model, miR-34a deficiency alone does not exhibit a strong oncogenic effect. However, miR-34a deficiency strongly promotes tumorigenesis when p53 is haploinsufficient, suggesting that the defective p53-miR-34 feedback loop can enhance oncogenesis in a specific context. The importance of the p53/miR-34/HDM4 feedback loop is further confirmed by an inverse correlation between miR-34 and full-length HDM4 in human lung adenocarcinomas. In addition, human lung adenocarcinomas generate an elevated level of a short HDM4 isoform through alternative polyadenylation. This short HDM4 isoform lacks miR-34-binding sites in the 3' untranslated region (UTR), thereby evading miR-34 regulation to disable the p53-miR-34 positive feedback. Taken together, our results elucidated the intricate cross-talk between p53 and miR-34 miRNAs and revealed an important tumor suppressor effect generated by this positive feedback loop. PMID:24532687

Okada, Nobuhiro; Lin, Chao-Po; Ribeiro, Marcelo C; Biton, Anne; Lai, Gregory; He, Xingyue; Bu, Pengcheng; Vogel, Hannes; Jablons, David M; Keller, Andreas C; Wilkinson, J Erby; He, Biao; Speed, Terry P; He, Lin

2014-03-01

163

A positive feedback between p53 and miR-34 miRNAs mediates tumor suppression  

PubMed Central

As bona fide p53 transcriptional targets, miR-34 microRNAs (miRNAs) exhibit frequent alterations in many human tumor types and elicit multiple p53 downstream effects upon overexpression. Unexpectedly, miR-34 deletion alone fails to impair multiple p53-mediated tumor suppressor effects in mice, possibly due to the considerable redundancy in the p53 pathway. Here, we demonstrate that miR-34a represses HDM4, a potent negative regulator of p53, creating a positive feedback loop acting on p53. In a Kras-induced mouse lung cancer model, miR-34a deficiency alone does not exhibit a strong oncogenic effect. However, miR-34a deficiency strongly promotes tumorigenesis when p53 is haploinsufficient, suggesting that the defective p53–miR-34 feedback loop can enhance oncogenesis in a specific context. The importance of the p53/miR-34/HDM4 feedback loop is further confirmed by an inverse correlation between miR-34 and full-length HDM4 in human lung adenocarcinomas. In addition, human lung adenocarcinomas generate an elevated level of a short HDM4 isoform through alternative polyadenylation. This short HDM4 isoform lacks miR-34-binding sites in the 3? untranslated region (UTR), thereby evading miR-34 regulation to disable the p53-miR-34 positive feedback. Taken together, our results elucidated the intricate cross-talk between p53 and miR-34 miRNAs and revealed an important tumor suppressor effect generated by this positive feedback loop. PMID:24532687

Okada, Nobuhiro; Lin, Chao-Po; Ribeiro, Marcelo C.; Biton, Anne; Lai, Gregory; He, Xingyue; Bu, Pengcheng; Vogel, Hannes; Jablons, David M.; Keller, Andreas C.; Wilkinson, J. Erby; He, Biao; Speed, Terry P.; He, Lin

2014-01-01

164

Version pressure feedback mechanisms for speculative versioning caches  

DOEpatents

Mechanisms are provided for controlling version pressure on a speculative versioning cache. Raw version pressure data is collected based on one or more threads accessing cache lines of the speculative versioning cache. One or more statistical measures of version pressure are generated based on the collected raw version pressure data. A determination is made as to whether one or more modifications to an operation of a data processing system are to be performed based on the one or more statistical measures of version pressure, the one or more modifications affecting version pressure exerted on the speculative versioning cache. An operation of the data processing system is modified based on the one or more determined modifications, in response to a determination that one or more modifications to the operation of the data processing system are to be performed, to affect the version pressure exerted on the speculative versioning cache.

Eichenberger, Alexandre E.; Gara, Alan; O'Brien, Kathryn M.; Ohmacht, Martin; Zhuang, Xiaotong

2013-03-12

165

Mechanism with 6 DOF for position and orientation measurement  

NASA Astrophysics Data System (ADS)

This paper shows a new 6-DOF mechanism. It can measure 6 coordinate parameters of the position and orientation of a moving platform. The mechanism is comprised of a serial mechanism for position measurement and a parallel mechanism for orientation measurement. It is dexterous for a redundant DOF and a balancing weight in vertical direction. The parallel mechanism is designed by mechanical synthesis in order to avoid difficulty of forward solution, and the orientation parameters of the moving platform are obtained by analytical expressions. Therefore, the 6-DOF parameter values of a moving platform can be displayed in real time. The workspace of the mechanism is obtained by graphology and analytical method. The measuring error is analyzed by error modeling. The design-parameter values for the architecture of the parallel mechanism are optimized.

Yu, Xiaoliu; Chu, Liuhuo; Cen, Yuwan; Pan, Ziwei

2003-09-01

166

Positive and negative feedbacks to climate change associated with methane emissions from arctic permafrost systems (Invited)  

NASA Astrophysics Data System (ADS)

Arctic permafrost contains 950 billion tons of organic carbon (C) in the surface tens of meters, an amount comparable to the current atmospheric CO2 burden of 750 billion tons. This C pool, which accumulated in permafrost over tens of thousands of years, is a threat to global climate because of its vulnerability to rapid microbial decomposition upon thaw, resulting in the release of greenhouse gases CO2 and CH4 to the atmosphere. Greenhouse gas release from thawing permafrost constitutes one of the most important positive feedbacks of terrestrial ecosystems to climate warming in a warmer world. Based on patterns of permafrost degradation during the present interglacial period, estimates of the amount of C remaining in permafrost today, long term field measurements of CH4 and CO2 flux, laboratory incubation experiments, and mass balance calculations of the efficiency of CH4 production from thawed permafrost, we predict that at least 50 billion tons of CH4 (equivalent to 10 times the current atmospheric methane burden) will escape from thermokarst (thaw) lakes in Siberia’s Yedoma Ice Complex as it warms and thaws. Additional CH4 will be released from the remainder of arctic lakes. Under current projections of arctic warming of 7-8 deg C by 2100, widespread permafrost thaw will release 0.1-0.2 billion tons of CH4 yr-1 by 2100, an order of magnitude more than its current source strength, adding another 20-40% of all human and natural sources of CH4 to the atmosphere. Permafrost thaw may lead to an additional source of methane if expanding thaw bulbs beneath lakes and rivers intersect faults and unconsolidated sediments leading to the escape of CH4 from geological sources, such as those recently observed on the North Slope of Alaska with a flux of 60-100 kg CH4 m-2 d-1. Thermokarst lake dynamics play a pivotal role in permafrost degradation and aggradation in the Arctic such that the landscape resembles a palimpsest of lakes and drained lake basins. Analysis of remote sensing time series of thermokarst lakes on the Northern Seward Peninsula in Alaska revealed that while lakes are rapidly expanding, an unprecedented number of lakes drained during the past 55 years, suggesting that degradation of permafrost may be accelerating in some regions. Drained basins fill in with new terrestrial vegetation, often becoming wetlands. Although these are a source of methane to the atmosphere when their surface is unfrozen in summer, their total annual emissions are often lower than lakes because of refreezing of the lake thaw bulb. Plant productivity in basins, together with the buildup of peat, serve as a sink of atmospheric carbon and a negative feedback to permafrost thaw. Results presented here aim to improve understanding of microbial and geologic methane emission dynamics related to permafrost degradation in various regions of the Arctic in order to better constrain current and future atmospheric methane budgets and global climate models.

Walter Anthony, K. M.; Grosse, G.; Jones, B. M.

2009-12-01

167

30 CFR 33.23 - Mechanical positioning of parts.  

Code of Federal Regulations, 2012 CFR

...ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES Dust-Collector Requirements § 33.23 Mechanical positioning of parts. All parts of a...

2012-07-01

168

30 CFR 33.23 - Mechanical positioning of parts.  

Code of Federal Regulations, 2011 CFR

...ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES Dust-Collector Requirements § 33.23 Mechanical positioning of parts. All parts of a...

2011-07-01

169

30 CFR 33.23 - Mechanical positioning of parts.  

Code of Federal Regulations, 2013 CFR

...ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES Dust-Collector Requirements § 33.23 Mechanical positioning of parts. All parts of a...

2013-07-01

170

30 CFR 33.23 - Mechanical positioning of parts.  

Code of Federal Regulations, 2010 CFR

...ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES Dust-Collector Requirements § 33.23 Mechanical positioning of parts. All parts of a...

2010-07-01

171

30 CFR 33.23 - Mechanical positioning of parts.  

Code of Federal Regulations, 2014 CFR

...ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES Dust-Collector Requirements § 33.23 Mechanical positioning of parts. All parts of a...

2014-07-01

172

Agents' Privacy in Distributed Algorithmic Mechanisms (Position Paper)  

E-print Network

Agents' Privacy in Distributed Algorithmic Mechanisms (Position Paper) Joan Feigenbaum Noam Nisan@cs.huji.ac.il vijayr@cs.yale.edu Rahul Sami Scott Shenker Yale University ICSI sami@cs.yale.edu shenker

Feigenbaum, Joan

173

The positive feedback action of vasopressin on its own release from rat septal tissue in vitro is receptor-mediated.  

PubMed

The effect of arginine vasopressin (AVP) on its own septal release was evaluated using an in vitro superfusion procedure. As compared to basal release from septal fragments, pulses of synthetic AVP (15 pg/5 min) resulted in a 25-fold augmented release of endogenous AVP, indicating a positive feedback action. Both the basal and stimulated AVP release were significantly increased by 60 mM potassium and markedly reduced by omission of calcium. Preincubation of the septal fragments with the V2/V1 AVP receptor antagonist d(CH2)5 [D-Tyr (Et)2,Val4]AVP resulted in a dose-dependent inhibition of the positive feedback action of AVP which was nearly completely blocked at doses between 1.25 and 5 ng per 100 microliters incubation medium. As compared to this effect, the V1 antagonist d(CH2)5 Tyr (Me)2 AVP as well as oxytocin were significantly less potent. The results suggest that the positive feedback action of AVP on its own release from septal fragments is potassium-stimulated, calcium-dependent and mainly V2 receptor-mediated. The physiological significance of this phenomenon remains to be shown. PMID:1830507

Landgraf, R; Ramirez, A D; Ramirez, V D

1991-04-01

174

Antimicrobial Peptide Resistance Mechanisms of Gram-Positive Bacteria  

PubMed Central

Antimicrobial peptides, or AMPs, play a significant role in many environments as a tool to remove competing organisms. In response, many bacteria have evolved mechanisms to resist these peptides and prevent AMP-mediated killing. The development of AMP resistance mechanisms is driven by direct competition between bacterial species, as well as host and pathogen interactions. Akin to the number of different AMPs found in nature, resistance mechanisms that have evolved are just as varied and may confer broad-range resistance or specific resistance to AMPs. Specific mechanisms of AMP resistance prevent AMP-mediated killing against a single type of AMP, while broad resistance mechanisms often lead to a global change in the bacterial cell surface and protect the bacterium from a large group of AMPs that have similar characteristics. AMP resistance mechanisms can be found in many species of bacteria and can provide a competitive edge against other bacterial species or a host immune response. Gram-positive bacteria are one of the largest AMP producing groups, but characterization of Gram-positive AMP resistance mechanisms lags behind that of Gram-negative species. In this review we present a summary of the AMP resistance mechanisms that have been identified and characterized in Gram-positive bacteria. Understanding the mechanisms of AMP resistance in Gram-positive species can provide guidelines in developing and applying AMPs as therapeutics, and offer insight into the role of resistance in bacterial pathogenesis. PMID:25419466

McBride, Shonna M.

2014-01-01

175

Theoretical Models for the Mechanisms of Benign Paroxysmal Positional Vertigo  

Microsoft Academic Search

Benign paroxysmal positional vertigo (BPPV) is a common vestibular disorder resulting from a malfunction of the semicircular canal. Prior studies attempting to elucidate the mechanics of BPPV have focused on clinical and laboratory findings, and have discussed theoretical aspects only in qualitative terms. The goal of this study is to create a mathematical description of BPPV mechanics based on biophysical

Matthew G. House; Vicente Honrubia

2003-01-01

176

RhoA-mediated inhibition of vascular endothelial cell mobility: positive feedback through reduced cytosolic p21 and p27.  

PubMed

We previously identified that activation of the aryl hydrocarbon receptor (AhR) by 3-methylcholanthrene (3MC) exerts antiproliferative and antimigratory effects on human umbilical vein endothelial cells (HUVECs) through the upregulation of p21/p27 transcription and RhoA activation. In this study, we investigated the mechanisms of 3MC-mediated downregulation of cytosolic p21/ p27, and the effects of 3MC on RhoA activation and cell migration, in mouse cerebral vascular endothelial cells (MCVECs). Our results indicated that 3MC reduced the phosphorylation of p21/p27 through AhR/RhoA/PTEN-mediated PI3K/Akt inactivation, which reduced cytosolic p21/p27 retention, causing RhoA activation through positive feedback. Downregulation of p21/p27 by siRNA, and cytosolic p21/p27 by the nuclear export blocker leptomycin B, further reduced cell migration in the 3MC-treated cells. Reduced cytosolic p21/p27 expression led to reduced interaction between RhoA and the RhoA inhibitor p190RhoGAP, causing RhoA activation. Treatment with YS-49 activated PI3K/Akt, a downstream target of RhoA, to reduce RhoA/PTEN activation in the 3MC-treated cells, whereas treatment with wortmannin, a PI3K inhibitor, activated RhoA/PTEN. Gain- and loss-of-function analyses revealed that constitutively active (CA) Akt1, but not CA Akt2, inactivated RhoA and stimulated migratory activity. Considering the essential role of RhoA activation in cell migration, we evaluated the potential use of simvastatin, a RhoA inhibitor, as a therapeutic intervention in vivo using matrigel plug formation assays. Our results provide a molecular basis for the therapeutic application of simvastatin to reduce RhoA/PTEN activation, restore cytosolic levels of phosphorylated p21/p27, and induce angiogenic processes. PMID:24535918

Hsu, Yung-Ho; Chang, Chih-Cheng; Yang, Nian-Jie; Lee, Yi-Hsuan; Juan, Shu-Hui

2014-10-01

177

Positive Feedback Regulation of Type I IFN Production by the IFN-Inducible DNA Sensor cGAS.  

PubMed

Rapid and robust induction of type I IFN (IFN-I) is a critical event in host antiviral innate immune response. It has been well demonstrated that cyclic GMP-AMP (cGAMP) synthase (cGAS) plays an important role in sensing cytosolic DNA and triggering STING dependent signaling to induce IFN-I. However, it is largely unknown how cGAS itself is regulated during pathogen infection and IFN-I production. In this study, we show that pattern recognition receptor (PRR) ligands, including lipid A, LPS, poly(I:C), poly(dA:dT), and cGAMP, induce cGAS expression in an IFN-I-dependent manner in both mouse and human macrophages. Further experiments indicated that cGAS is an IFN-stimulated gene (ISG), and two adjacent IFN-sensitive response elements (ISREs) in the promoter region of cGAS mediate the induction of cGAS by IFN-I. Additionally, we show that optimal production of IFN-? triggered by poly (dA:dT) or HSV-1 requires IFNAR signaling. Knockdown of the constitutively expressed DNA sensor DDX41 attenuates poly(dA:dT)-triggered IFN-? production and cGAS induction. By analyzing the dynamic expression of poly(dA:dT)-induced IFN-? and cGAS transcripts, we have found that induction of IFN-? is earlier than cGAS. Furthermore, we have provided evidence that induction of cGAS by IFN-I meditates the subsequent positive feedback regulation of DNA-triggered IFN-I production. Thus, our study not only provides a novel mechanism of modulating cGAS expression, but also adds another layer of regulation in DNA-triggered IFN-I production by induction of cGAS. PMID:25609843

Ma, Feng; Li, Bing; Liu, Su-Yang; Iyer, Shankar S; Yu, Yongxin; Wu, Aiping; Cheng, Genhong

2015-02-15

178

Velocity and position control of a wheeled inverted pendulum by partial feedback linearization  

Microsoft Academic Search

In this paper, the dynamic model of a wheeled inverted pendulum (e.g., Segway, Quasimoro, and Joe) is analyzed from a controllability and feedback linearizability point of view. First, a dynamic model of this underactuated system is derived with respect to the wheel motor torques as inputs while taking the nonholonomic no-slip constraints into considerations. This model is compared with the

Kaustubh Pathak; Jaume Franch; Sunil Kumar Agrawal

2005-01-01

179

Early Detection of Online Auction Opportunistic Sellers through the Use of Negative-Positive Feedback  

ERIC Educational Resources Information Center

Apparently fraud is a growth industry. The monetary losses from Internet fraud have increased every year since first officially reported by the Internet Crime Complaint Center (IC3) in 2000. Prior research studies and third-party reports of fraud show rates substantially higher than eBay's reported negative feedback rate of less than 1%. The…

Reinert, Gregory J.

2010-01-01

180

Rapid Onset of the African Humid Period 14.5--11ka BP: External Forcing and Feedback Mechanisms.  

NASA Astrophysics Data System (ADS)

Using transient glacial-interglacial simulations conducted with two different climate-vegetation models we elucidate the mechanisms that control the onset of the African Humid Period (AHP) 14,500 to 11,000 years ago. Our analysis suggests that locally increased boreal summer solar radiation leads to a northward shift of the ITCZ. Vegetation in northern Africa adjusts to wetter conditions and provides a positive albedo-vegetation feedback that is further accelerating the northward migration of the ITCZ. Sensitivity experiments reveal that the albedo-vegetation feedback and its effect on the large-scale atmospheric circulation together with the CO2-fertilization effect provide a mechanism for generating multiple states of early to mid-Holocene vegetation over northern Africa. Our model simulations document that not only orbitally-driven insolation changes played a key role in controlling the onset of the AHP, but also the presence of the remnant ice-sheet over Europe, variations of the Atlantic Meridional Overturning circulation during the Younger Dryas and increasing levels atmospheric CO2. The model results presented here do not lend support to the notion that simple insolation thresholds govern the abrupt transitions of north African vegetation during the early to middle Holocene.

Timm, O.; Timmermann, A.; Koehler, P.; Menviel, L.

2008-12-01

181

Analysis of Links Positions in Landing Gear Mechanism  

NASA Astrophysics Data System (ADS)

This article contains a kinematic analysis of an aircraft chassis mechanism in a range of positions. The mechanism of the chassis is made up of several smaller subsystems with different functions. The first mechanism is used to eject the chassis before landing (touchdown) and fold it to hatchway after the lift off. The second mechanism is designed to perform rotation of the crossover with the wheel, in order to adjust the position of the wheel to fit it in the limited space in the hold. The third mechanism allows movement of the chassis resulting from the change in length of the damper. To determine the position of the following links of the mechanism calculus of vectors was applied in which unit vectors were used to represent the angular position of the links. The aim of the analysis is to determine the angle of convergence and the angle of heel wheels as a function of the variable length of hydraulic cylinder, length of the shock absorber, length of the regulations rods

Brewczy?ski, D.; Tora, G.

2014-08-01

182

Visual feedback of the non-moving limb improves active joint-position sense of the impaired limb in Spastic Hemiparetic Cerebral Palsy.  

PubMed

This study examined the active joint-position sense in children with Spastic Hemiparetic Cerebral Palsy (SHCP) and the effect of static visual feedback and static mirror visual feedback, of the non-moving limb, on the joint-position sense. Participants were asked to match the position of one upper limb with that of the contralateral limb. The task was performed in three visual conditions: without visual feedback (no vision); with visual feedback of the non-moving limb (screen); and with visual feedback of the non-moving limb and its mirror reflection (mirror). In addition to the proprioceptive measure, a functional test [Quality of Upper Extremity Skills Test (QUEST)] was performed and the amount of spasticity was determined in order to examine their relation with proprioceptive ability. The accuracy of matching was significantly influenced by the distance that had to be covered by the matching limb; a larger distance resulted in a lower matching accuracy. Moreover it was demonstrated that static (mirror) visual feedback improved the matching accuracy. A clear relation between functionality, as measured by the QUEST, and active joint-position sense was not found. This might be explained by the availability of visual information during the performance of the QUEST. It is concluded that static visual feedback improves matching accuracy in children with SHCP and that the initial distance between the limbs is an influential factor which has to be taken into account when measuring joint-position sense. PMID:21306868

Smorenburg, Ana R P; Ledebt, Annick; Deconinck, Frederik J A; Savelsbergh, Geert J P

2011-01-01

183

Design of a High Resolution Hexapod Positioning Mechanism  

NASA Technical Reports Server (NTRS)

This paper describes the development of a high resolution, six-degree of freedom positioning mechanism. This mechanism, based on the Stewart platform concept, was designed for use with the Developmental Comparative Active Optics Telescope Testbed (DCATT), a ground-based technology testbed for the Next Generation Space Telescope (NGST). The mechanism provides active control to the DCATT telescope's segmented primary mirror. Emphasis is on design decisions and technical challenges. Significant issues include undesirable motion properties of PZT-inchworm actuators, testing difficulties, dimensional stability, and use of advanced composite materials. Supporting test data from prototype mechanisms is presented.

Britt, Jamie

2001-01-01

184

Design of a High Resolution Hexapod Positioning Mechanism  

NASA Technical Reports Server (NTRS)

This paper describes the development of a high resolution, six-degree of freedom positioning mechanism. This mechanism, based on the Stewart platform concept, was designed for use with the Developmental Comparative Active Optics Telescope Testbed (DCATT), a ground-based technology testbed for the Next Generation Space Telescope (NGST). The mechanism provides active control to the DCATT telescope's segmented primary mirror. Emphasis is on design decisions and technical challenges. Significant issues include undesirable motion properties of PZT-inchworm actuators, testing difficulties, dimensional stability and use of advanced composite materials. Supporting test data from prototype mechanisms is presented.

Britt, Jamie; Brodeur, Stephen J. (Technical Monitor)

2001-01-01

185

Adaptation of hand movements to double-step targets and to distorted visual feedback: evidence for shared mechanisms.  

PubMed

Visuomotor adaptation of hand movements has been studied with two paradigms: double-step targets and distorted visual feedback. Here we investigate whether both procedures are based on a common adaptive mechanism. Subjects adapted either to double-step targets or to distorted feedback, each requiring a change of response angle by -15°. The magnitude of adaptation was larger with rotated feedback but magnitude of aftereffects was comparable, suggesting that the difference was due to strategic effects rather than visuomotor recalibration. Most importantly, subjects who adapted to double-step targets and were then exposed to rotated feedback performed as well as subjects who had fully adapted to rotated feedback, i.e., there was nearly 100% transfer from double-steps to rotations; likewise, the transfer from rotations to double-steps was almost 100%. From this we conclude that both types of adaptation share a common mechanism for recalibration. PMID:22154612

Schmitz, Gerd; Bock, Otmar; Grigorova, Valentina; Borisova, Steliana

2012-08-01

186

Basal Ganglia Engagement during Feedback Processing after a Substantial Delay  

PubMed Central

The striatum has been shown to play an important role in learning from performance-related feedback that is presented shortly after each response. However, less is known about the neural mechanisms supporting learning from feedback that is substantially delayed from the original response. Since the consequences of one’s actions often do not become known until after a delay, it is important to understand whether delayed feedback can produce neural responses similar to those elicited by immediate feedback presentation. We investigated this issue by using functional magnetic resonance imaging (fMRI) as participants performed a paired-associate learning task with 180 distinct trials. Feedback indicating response accuracy was presented immediately, after a delay of 25 minutes, or not at all. Both immediate and delayed feedback led to significant gains in accuracy on a post-test, relative to no feedback. Replicating previous work, we found that the caudate nuclei showed greater activation for positive feedback than negative feedback when the feedback was presented immediately. In addition, delayed feedback also led to differential caudate activity to positive versus negative feedback. Delayed negative feedback also produced significant activation of the putamen and globus pallidus (the lentiform nucleus), relative to no feedback and delayed positive feedback. This suggests that the caudate nucleus is sensitive to the affective nature of feedback, across different timescales, while the lentiform nucleus may be particularly involved in processing the information carried by negative feedback after a substantial delay. PMID:23817894

Dobryakova, Ekaterina; Tricomi, Elizabeth

2013-01-01

187

Basal ganglia engagement during feedback processing after a substantial delay.  

PubMed

The striatum has been shown to play an important role in learning from performance-related feedback that is presented shortly after each response. However, less is known about the neural mechanisms supporting learning from feedback that is substantially delayed from the original response. Since the consequences of one's actions often do not become known until after a delay, it is important to understand whether delayed feedback can produce neural responses similar to those elicited by immediate-feedback presentation. We investigated this issue by using functional magnetic resonance imaging (fMRI) as participants performed a paired-associate learning task with 180 distinct trials. Feedback indicating response accuracy was presented immediately, after a delay of 25 min, or not at all. Both immediate and delayed feedback led to significant gains in accuracy on a posttest, relative to no feedback. Replicating previous work, we found that the caudate nuclei showed greater activation for positive feedback than for negative feedback when the feedback was presented immediately. In addition, delayed feedback also led to differential caudate activity to positive versus negative feedback. Delayed negative feedback also produced significant activation of the putamen and globus pallidus (the lentiform nucleus), relative to no feedback and delayed positive feedback. This suggests that the caudate nucleus is sensitive to the affective nature of feedback, across different time scales, while the lentiform nucleus may be particularly involved in processing the information carried by negative feedback after a substantial delay. PMID:23817894

Dobryakova, Ekaterina; Tricomi, Elizabeth

2013-12-01

188

Essential role of Bmp signaling and its positive feedback loop in the early cell fate evolution of chordates.  

PubMed

In chordates, early separation of cell fate domains occurs prior to the final specification of ectoderm to neural and non-neural as well as mesoderm to dorsal and ventral during development. Maintaining such division with the establishment of an exact border between the domains is required for the formation of highly differentiated structures such as neural tube and notochord. We hypothesized that the key condition for efficient cell fate separation in a chordate embryo is the presence of a positive feedback loop for Bmp signaling within the gene regulatory network (GRN), underlying early axial patterning. Here, we therefore investigated the role of Bmp signaling in axial cell fate determination in amphioxus, the basal chordate possessing a centralized nervous system. Pharmacological inhibition of Bmp signaling induces dorsalization of amphioxus embryos and expansion of neural plate markers, which is consistent with an ancestral role of Bmp signaling in chordate axial patterning and neural plate formation. Furthermore, we provided evidence for the presence of the positive feedback loop within the Bmp signaling network of amphioxus. Using mRNA microinjections we found that, in contrast to vertebrate Vent genes, which promote the expression of Bmp4, amphioxus Vent1 is likely not responsible for activation of cephalochordate ortholog Bmp2/4. Cis-regulatory analysis of amphioxus Bmp2/4, Admp and Chordin promoters in medaka embryos revealed remarkable conservation of the gene regulatory information between vertebrates and basal chordates. Our data suggest that emergence of a positive feedback loop within the Bmp signaling network may represent a key molecular event in the evolutionary history of the chordate cell fate determination. PMID:23933491

Kozmikova, Iryna; Candiani, Simona; Fabian, Peter; Gurska, Daniela; Kozmik, Zbynek

2013-10-15

189

A satellite digital controller or 'play that PID tune again, Sam'. [Position, Integral, Derivative feedback control algorithm for design strategy  

NASA Technical Reports Server (NTRS)

The problem discussed is to design a digital controller for a typical satellite. The controlled plant is considered to be a rigid body acting in a plane. The controller is assumed to be a digital computer which, when combined with the proposed control algorithm, can be represented as a sampled-data system. The objective is to present a design strategy and technique for selecting numerical values for the control gains (assuming position, integral, and derivative feedback) and the sample rate. The technique is based on the parameter plane method and requires that the system be amenable to z-transform analysis.

Seltzer, S. M.

1976-01-01

190

The transition of boudinage into brittle low-angle faults - chemical and mechanical feedback mechanisms  

NASA Astrophysics Data System (ADS)

Slip on mid to upper crustal low-angle normal faults with maximum compressive sub-vertical stress trajectories represents a considerable mechanical problem. Their initiation and subsequent growth is commonly explained by unusual low fault friction caused by either high fluid pressure, weak fault-zone materials and/or aseismic deformation mechanisms. Recently, a reduction of the friction coefficient value of fault rocks has been suggested by fluid triggered phyllosilicate growth, which may lead to a significant fault weakening. On Serifos (Greece) dolomite/calcite mylonites are interlayered with some centimeter-thick quartz mylonites in the footwall of a ductile to brittle low-angle normal fault. Both mylonites have a strong shape and lattice preferred orientation of the mineral grains. Several tens of meters below the fault a reaction front developed between the dolomite/calcite and the quartzite mylonite consisting of fluid assisted stress-induced breakdown of dolomite and nucleation of talc and calcite. Locally also tremolite formed. The source of the fluid was most likely related to the intrusion of a nearby granodiorite pluton, which occurred during movement along the low-angle fault. Importantly, with the formation of this reaction zone the quartz layers started to develop layer perpendicular calcite-filled fractures which develop by antithetic slip co-rotating domino boudins. Where the rotated quartzite boudin necks were juxtaposed against the dolomite/calcite mylonite host, the talc-forming reaction continues. During ongoing co-rotation the boudins reoriented into a position, where the talc-coated top and bottom of two neighbouring boudins connected resulting into synthetic localization of deformation along these planes forming a shearband boudinage. This switch of domino to shearband boudinage leads to the isolation of the boudins and the formation of a continuous talc-rich layer, which developed into low-angle sc and scc'-type shear zones. Slip along numerous of these talc-rich zones continued during decreasing temperatures in the upper crust with cataclastic deformation of the dolomite. Based on these structural and petrological investigations we present a numerical mechanical finite element model, which tests the boudinage of a weaker layer (quartzite) in a stronger host rock (dolomite) by introducing a much weaker reaction zone (talc).

Tschegg, Cornelius; Grasemann, Bernhard; Frehner, Marcel

2010-05-01

191

Stochastic Gene Expression in a Lentiviral Positive Feedback Loop: HIV-1 Tat Fluctuations Drive Phenotypic Diversity  

E-print Network

Stochastic gene expression has been implicated in a variety of cellular processes, including cell differentiation and disease. In this issue of Cell, Weinberger et al. (2005) take an integrated computational-experimental approach to study the Tat transactivation feedback loop in HIV-1 and show that fluctuations in a key regulator, Tat, can result in a phenotypic bifurcation. This phenomenon is observed in an isogenic population where individual cells display two distinct expression states corresponding to latent and productive infection by HIV-1. These findings demonstrate the importance of stochastic gene expression in molecular "decision-making."

Leor S. Weinberger; John C. Burnett; Jared E. Toettcher; Adam P. Arkin; David V. Schaffer

2006-08-01

192

Nearly time-optimal feedback control of a magnetically levitated photolithography positioning system  

SciTech Connect

This paper focuses on the development of an approximate time-optimal feedback strategy for conducting rest-to-rest maneuvers of a magnetically levitated table. Classical switching curves are modified to account for the complexities of magnetic actuation as well as the coupling of the rigid body modes through the control. A smooth blend of time-optimal and proportional-derivative controls is realized near the destination point to correct for inaccuracies produced by the approximate time-optimal strategy. Detailed computer simulations of the system indicate that this hybrid control strategy provides a significant reduction in settling time as compared to proportional-derivative control alone.

Redmond, J.

1993-12-31

193

Tenure-Track Faculty Position: Mechanical Engineering School of Engineering  

E-print Network

engineering program. Interdisciplinary research collaborations will be valued. UVM recently identified threeTenure-Track Faculty Position: Mechanical Engineering School of Engineering College of Engineering & Mathematical Sciences The University of Vermont The School of Engineering at the University of Vermont (UVM

Hayden, Nancy J.

194

Positive Feedback Regulation of Proliferation in Vascular Smooth Muscle Cells Stimulated by Lipopolysaccharide Is Mediated through the TLR 4/Rac1/Akt Pathway  

PubMed Central

Toll-like receptor 4 (TLR4) are important in inflammation and regulating vascular smooth muscle cells (VSMCs) proliferation, which are related to atherosclerosis and restenosis. We have investigated the mechanisms involved in Lipopolysaccharide (LPS)-induced proliferation of VSMCs. Stimulation of rat aortic VSMCs with LPS significantly increases the proliferation of VSMCs. This effect is regulated by Rac1 (Ras-related C3 botulinum toxin substrate l), which mediates the activation of phosphatidylinositol 3-kinase/Akt (PI3K/Akt) signaling pathways. Inhibition of Rac1 activity by NSC23766 is associated with inhibition of Akt activity. Treatment with NSC23766 or LY294002 significantly decreases LPS-induced TLR4 protein and mRNA expression. The data show that positive feedback regulation of proliferation in VSMCs is mediated through the TLR4/Rac1/Akt pathway. PMID:24667766

Jiang, Dehua; Li, Dongye; Cao, Lijuan; Wang, Lele; Zhu, Shasha; Xu, Tongda; Wang, Cheng; Pan, Defeng

2014-01-01

195

Positive feedback regulation of proliferation in vascular smooth muscle cells stimulated by lipopolysaccharide is mediated through the TLR 4/Rac1/Akt pathway.  

PubMed

Toll-like receptor 4 (TLR4) are important in inflammation and regulating vascular smooth muscle cells (VSMCs) proliferation, which are related to atherosclerosis and restenosis. We have investigated the mechanisms involved in Lipopolysaccharide (LPS)-induced proliferation of VSMCs. Stimulation of rat aortic VSMCs with LPS significantly increases the proliferation of VSMCs. This effect is regulated by Rac1 (Ras-related C3 botulinum toxin substrate l), which mediates the activation of phosphatidylinositol 3-kinase/Akt (PI3K/Akt) signaling pathways. Inhibition of Rac1 activity by NSC23766 is associated with inhibition of Akt activity. Treatment with NSC23766 or LY294002 significantly decreases LPS-induced TLR4 protein and mRNA expression. The data show that positive feedback regulation of proliferation in VSMCs is mediated through the TLR4/Rac1/Akt pathway. PMID:24667766

Jiang, Dehua; Li, Dongye; Cao, Lijuan; Wang, Lele; Zhu, Shasha; Xu, Tongda; Wang, Cheng; Pan, Defeng

2014-01-01

196

Role of the Qinghai-Xizang plateau in feedback mechanisms affecting the planetary circulation  

SciTech Connect

It has been recognized for some time that the Qinghai-Xizang plateau is of great importance in generating planetary long-waves which, in resonance with similar waves induced by the Rocky Mountains, lead to the familiar pattern of quasi-stationary Rossby waves observed on monthly-mean upper level pressure charts. Seasonal forcing of flow patterns also appears to be particularly strong in the Qinghai-Xizang plateau region. Recent investigations suggest that the Qinghai-Xizang plateau may also be involved in feedback mechanisms which control in an important way the interannual variability of the general circulation of the atmosphere. It appears that the effects of the Qinghai-Xizang plateau on the interannual variability of the atmospheric circulation over Asia are but one important manifestation of a network of feedback mechanisms, ranging from the El Nino problems along the Peruvian coast to droughts in the Sahel region. A better understanding of each of the mechanisms involved will lead us closer to successful long-range forecasting of some of the weather phenomena which have a considerable effect on local and regional economics.

Reiter, E.R.; Yi-Hui, D.

1980-01-01

197

The Evolution of Different Forms of Sociality: Behavioral Mechanisms and Eco-Evolutionary Feedback  

PubMed Central

Different forms of sociality have evolved via unique evolutionary trajectories. However, it remains unknown to what extent trajectories of social evolution depend on the specific characteristics of different species. Our approach to studying such trajectories is to use evolutionary case-studies, so that we can investigate how grouping co-evolves with a multitude of individual characteristics. Here we focus on anti-predator vigilance and foraging. We use an individual-based model, where behavioral mechanisms are specified, and costs and benefits are not predefined. We show that evolutionary changes in grouping alter selection pressures on vigilance, and vice versa. This eco-evolutionary feedback generates an evolutionary progression from “leader-follower” societies to “fission-fusion” societies, where cooperative vigilance in groups is maintained via a balance between within- and between-group selection. Group-level selection is generated from an assortment that arises spontaneously when vigilant and non-vigilant foragers have different grouping tendencies. The evolutionary maintenance of small groups, and cooperative vigilance in those groups, is therefore achieved simultaneously. The evolutionary phases, and the transitions between them, depend strongly on behavioral mechanisms. Thus, integrating behavioral mechanisms and eco-evolutionary feedback is critical for understanding what kinds of intermediate stages are involved during the evolution of particular forms of sociality. PMID:25629313

van der Post, Daniel J.; Verbrugge, Rineke; Hemelrijk, Charlotte K.

2015-01-01

198

The evolution of different forms of sociality: behavioral mechanisms and eco-evolutionary feedback.  

PubMed

Different forms of sociality have evolved via unique evolutionary trajectories. However, it remains unknown to what extent trajectories of social evolution depend on the specific characteristics of different species. Our approach to studying such trajectories is to use evolutionary case-studies, so that we can investigate how grouping co-evolves with a multitude of individual characteristics. Here we focus on anti-predator vigilance and foraging. We use an individual-based model, where behavioral mechanisms are specified, and costs and benefits are not predefined. We show that evolutionary changes in grouping alter selection pressures on vigilance, and vice versa. This eco-evolutionary feedback generates an evolutionary progression from "leader-follower" societies to "fission-fusion" societies, where cooperative vigilance in groups is maintained via a balance between within- and between-group selection. Group-level selection is generated from an assortment that arises spontaneously when vigilant and non-vigilant foragers have different grouping tendencies. The evolutionary maintenance of small groups, and cooperative vigilance in those groups, is therefore achieved simultaneously. The evolutionary phases, and the transitions between them, depend strongly on behavioral mechanisms. Thus, integrating behavioral mechanisms and eco-evolutionary feedback is critical for understanding what kinds of intermediate stages are involved during the evolution of particular forms of sociality. PMID:25629313

van der Post, Daniel J; Verbrugge, Rineke; Hemelrijk, Charlotte K

2015-01-01

199

Thermospermine levels are controlled by an auxin-dependent feedback loop mechanism in Populus xylem.  

PubMed

Polyamines are small polycationic amines that are widespread in living organisms. Thermospermine, synthesized by thermospermine synthase ACAULIS5 (ACL5), was recently shown to be an endogenous plant polyamine. Thermospermine is critical for proper vascular development and xylem cell specification, but it is not known how thermospermine homeostasis is controlled in the xylem. We present data in the Populus model system supporting the existence of a negative feedback control of thermospermine levels in stem xylem tissues, the main site of thermospermine biosynthesis. While over-expression of the ACL5 homologue in Populus, POPACAULIS5, resulted in strong up-regulation of ACL5 expression and thermospermine accumulation in leaves, the corresponding levels in the secondary xylem tissues of the stem were similar or lower than those in the wild-type. POPACAULIS5 over-expression had a negative effect on accumulation of indole-3-acetic acid, while exogenous auxin had a positive effect on POPACAULIS5 expression, thus promoting thermospermine accumulation. Further, over-expression of POPACAULIS5 negatively affected expression of the class III homeodomain leucine zipper (HD-Zip III) transcription factor gene PttHB8, a homologue of AtHB8, while up-regulation of PttHB8 positively affected POPACAULIS5 expression. These results indicate that excessive accumulation of thermospermine is prevented by a negative feedback control of POPACAULIS5 transcript levels through suppression of indole-3-acetic acid levels, and that PttHB8 is involved in the control of POPACAULIS5 expression. We propose that this negative feedback loop functions to maintain steady-state levels of thermospermine, which is required for proper xylem development, and that it is dependent on the presence of high concentrations of endogenous indole-3-acetic acid, such as those present in the secondary xylem tissues. PMID:23647338

Milhinhos, Ana; Prestele, Jakob; Bollhöner, Benjamin; Matos, Andreia; Vera-Sirera, Francisco; Rambla, José L; Ljung, Karin; Carbonell, Juan; Blázquez, Miguel A; Tuominen, Hannele; Miguel, Célia M

2013-08-01

200

Positive water vapour feedback in climate models confirmed by satellite data  

NASA Technical Reports Server (NTRS)

It has recently been suggested that GCMs used to evaluate climate change overestimate the greenhouse effect due to increased concentrations of trace gases in the atmosphere. Here, new satellite-generated water vapor data are used to compare summer and winter moisture values in regions of the middle and upper troposphere that have previously been difficult to observe with confidence. It is found that, as the hemispheres warm, increased convection leads to increased water vapor above 500 mbar in approximate quantitative agreement with results from current climate models. The same conclusion is reached by comparing the tropical western and eastern Pacific regions. Thus, water vapor feedback is not overestimated in models and should amplify the climate response to increased trace-gas concentrations.

Rind, D.; Lerner, J.; Chiou, E.-W.; Chu, W.; Larsen, J.; Mccormick, M. P.; Mcmaster, L.

1991-01-01

201

Nonlinear output feedback control of dynamically positioned ships using vectorial observer backstepping  

Microsoft Academic Search

Dynamic positioning (DP) systems for ships are usually designed under the assumption that the kinematic equations be linearized about a constant yaw angle such that linear and gain scheduling techniques can be applied. This paper proposes a globally exponentially stable (GES) nonlinear control where this assumption is removed. A nonlinear observer is included in the design such that only position

Thor I. Fossen; A. Grovlen

1998-01-01

202

Creating a Positive Classroom Atmosphere: Teachers' Use of Effective Praise and Feedback  

ERIC Educational Resources Information Center

Creating a positive and engaging classroom atmosphere is one of the most powerful tools teachers can use to encourage children's learning and prevent problem behaviors from occurring. Teachers' responses to children's appropriate and problem behavior can help set the tone of the classroom environment. Creating positive interactions between a…

Conroy, Maureen A.; Sutherland, Kevin S.; Snyder, Angela; Al-Hendawi, Maha; Vo, Abigail

2009-01-01

203

RADIATIVE AND MOMENTUM-BASED MECHANICAL ACTIVE GALACTIC NUCLEUS FEEDBACK IN A THREE-DIMENSIONAL GALAXY EVOLUTION CODE  

SciTech Connect

We study the growth of black holes (BHs) in galaxies using three-dimensional smoothed particle hydrodynamic simulations with new implementations of the momentum mechanical feedback, and restriction of accreted elements to those that are gravitationally bound to the BH. We also include the feedback from the X-ray radiation emitted by the BH, which heats the surrounding gas in the host galaxies, and adds radial momentum to the fluid. We perform simulations of isolated galaxies and merging galaxies and test various feedback models with the new treatment of the Bondi radius criterion. We find that overall the BH growth is similar to what has been obtained by earlier works using the Springel, Di Matteo, and Hernquist algorithms. However, the outflowing wind velocities and mechanical energy emitted by winds are considerably higher (v{sub w} {approx} 1000-3000 km s{sup -1}) compared to the standard thermal feedback model (v{sub w} {approx} 50-100 km s{sup -1}). While the thermal feedback model emits only 0.1% of BH released energy in winds, the momentum feedback model emits more than 30% of the total energy released by the BH in winds. In the momentum feedback model, the degree of fluctuation in both radiant and wind output is considerably larger than in standard treatments. We check that the new model of BH mass accretion agrees with analytic results for the standard Bondi problem.

Choi, Ena; Ostriker, Jeremiah P. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Naab, Thorsten [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching (Germany); Johansson, Peter H. [Department of Physics, University of Helsinki, Gustaf Haellstroemin katu 2a, FI-00014 Helsinki (Finland)

2012-08-01

204

Positional Reproducibility of Pancreatic Tumors Under End-Exhalation Breath-Hold Conditions Using a Visual Feedback Technique  

SciTech Connect

Purpose: To assess positional reproducibility of pancreatic tumors under end-exhalation (EE) breath-hold (BH) conditions with a visual feedback technique based on computed tomography (CT) images. Methods and Materials: Ten patients with pancreatic cancer were enrolled in an institutional review board-approved trial. All patients were placed in a supine position on an individualized vacuum pillow with both arms raised. At the time of CT scan, they held their breath at EE with the aid of video goggles displaying their abdominal displacement. Each three-consecutive helical CT data set was acquired four times (sessions 1-4; session 1 corresponded to the time of CT simulation). The point of interest within or in proximity to a gross tumor volume was defined based on certain structural features. The positional variations in point of interest and margin size required to cover positional variations were assessed. Results: The means {+-} standard deviations (SDs) of intrafraction positional variations were 0.0 {+-} 1.1, 0.1 {+-} 1.2, and 0.1 {+-} 1.0 mm in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively (p = 0.726). The means {+-} SDs of interfraction positional variations were 0.3 {+-} 2.0, 0.8 {+-} 1.8, and 0.3 {+-} 1.8 mm in the LR, AP, and SI directions, respectively (p = 0.533). Population-based margin sizes required to cover 95th percentiles of the overall positional variations were 4.7, 5.3, and 4.9 mm in the LR, AP, and SI directions, respectively. Conclusions: A margin size of 5 mm was needed to cover the 95th percentiles of the overall positional variations under EE-BH conditions, using this noninvasive approach to motion management for pancreatic tumors.

Nakamura, Mitsuhiro, E-mail: m_nkmr@kuhp.kyoto-u.ac.j [Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto (Japan); Shibuya, Keiko [Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto (Japan); Shiinoki, Takehiro [Department of Nuclear Engineering, Graduate School of Engineering, Kyoto University, Kyoto (Japan); Matsuo, Yukinori; Nakamura, Akira [Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto (Japan); Nakata, Manabu [Clinical Radiology Service Division, Kyoto University Hospital, Kyoto (Japan); Sawada, Akira; Mizowaki, Takashi; Hiraoka, Masahiro [Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto (Japan)

2011-04-01

205

An ultrasonic contact-type position restoration mechanism.  

PubMed

An ultrasonic contact-type position restoration mechanism is proposed and investigated in this paper. In the mechanism, two driving points of an ultrasonic vibrator, excited by an AC voltage, produces a restoring force on a slider so that the slider can be pushed back to its equilibrium after it is perturbed away from its equilibrium. The restoring force is generated by the unbalance of ultrasonic frictional driving forces on the slider, which is caused by a pressure difference on the two driving points. A prototype of this mechanism is fabricated, and the effects of the driving voltage, preload between the slider and vibrator, and slider's size on the restoring characteristics are experimentally measured and analyzed. PMID:25554313

Lu, Xiaolong; Hu, Junhui; Bhuyan, Satyanarayan; Li, Shiyang

2014-12-01

206

An ultrasonic contact-type position restoration mechanism  

NASA Astrophysics Data System (ADS)

An ultrasonic contact-type position restoration mechanism is proposed and investigated in this paper. In the mechanism, two driving points of an ultrasonic vibrator, excited by an AC voltage, produces a restoring force on a slider so that the slider can be pushed back to its equilibrium after it is perturbed away from its equilibrium. The restoring force is generated by the unbalance of ultrasonic frictional driving forces on the slider, which is caused by a pressure difference on the two driving points. A prototype of this mechanism is fabricated, and the effects of the driving voltage, preload between the slider and vibrator, and slider's size on the restoring characteristics are experimentally measured and analyzed.

Lu, Xiaolong; Hu, Junhui; Bhuyan, Satyanarayan; Li, Shiyang

2014-12-01

207

Phytoplankton behavior affects ocean mixed layer dynamics through biological-physical feedback mechanisms  

NASA Astrophysics Data System (ADS)

Biologically induced changes in physical oceanic properties through phytoplankton provide potential positive and negative feedback loops. In particular, surface floating cyanobacteria, which are expected to be favored from future environmental conditions and can form large surface mats, can increase light absorption and the surface albedo and decrease momentum input from the atmosphere by wind. In this work we study the effect of a changing phytoplankton community composition to one dominated by buoyant cyanobacteria on the physical oceanic properties. We use the water column model General Ocean Turbulence Model and set up an idealized biological model taking into account the phytoplankton species' characteristics as well as the effects of biology on physics. The model results show that an increase of buoyant cyanobacteria leads to substantial changes in the seasonal cycle of the mixed layer. The results furthermore indicate that the effects due to altered absorption and biologically induced reduction of the wind drag are larger than contrary effects due to changes in the surface albedo. Overall, our model results suggest that the development of cyanobacterial surface blooms and their feedbacks on light absorption and wind drag need to be taken into account in ocean models used for climate scenarios in order to capture changes in the dynamics of the upper ocean.

Sonntag, S.; Hense, I.

2011-08-01

208

Hunger states switch a flip-flop memory circuit via a synaptic AMPK-dependent positive feedback loop  

PubMed Central

SUMMARY Synaptic plasticity in response to changes in physiologic state is coordinated by hormonal signals across multiple neuronal cell types. Here, we combine cell type-specific electrophysiological, pharmacological, and optogenetic techniques to dissect neural circuits and molecular pathways controlling synaptic plasticity onto AGRP neurons, a population that regulates feeding. We find that food deprivation elevates excitatory synaptic input, which is mediated by a presynaptic positive feedback loop involving AMP-activated protein kinase. Potentiation of glutamate release was triggered by the orexigenic hormone ghrelin and exhibited hysteresis, persisting for hours after ghrelin removal. Persistent activity was reversed by the anorexigenic hormone leptin, and optogenetic photostimulation demonstrated involvement of opioid release from POMC neurons. Based on these experiments, we propose a memory storage device for physiological state constructed from bistable synapses that are flipped between two sustained activity states by transient exposure to hormones signaling energy levels. PMID:21925320

Yang, Yunlei; Atasoy, Deniz; Su, Helen H.; Sternson, Scott M.

2011-01-01

209

Phospholipase D1 drives a positive feedback loop to reinforce the Wnt/beta-catenin/TCF signaling axis.  

PubMed

Activation of the Wnt signaling pathway occurs frequently in human cancers, but an understanding of the targets and regulation of this important pathway remains incomplete. In this study, we report that phospholipase D (PLD), a cell survival mediator that is upregulated in cancer, is an important target of the Wnt signaling pathway that functions in a positive feedback loop to reinforce pathway output. PLD1 expression and activity was enhanced by treatment with Wnt3a and glycogen synthase kinase-3 inhibitors, and the Wnt pathway-regulated transcription factors beta-catenin and TCF-4 were required for this effect. Three functional TCF-4-binding sites were identified within the PLD1 promoter. Interestingly, suppressing PLD1 blocked the ability of beta-catenin to transcriptionally activate PLD1 and other Wnt target genes by preventing beta-catenin/TCF-4 complex formation. Conversely, tactics to elevate intracellular levels of phosphatidic acid, the product of PLD1 enzyme activity, enhanced beta-catenin/TCF-4 complex formation as well as beta-catenin-dependent TCF transcriptional activity. In cell-based assays, PLD1 was necessary for the anchorage-independent growth driven by Wnt/beta-catenin signaling, whereas beta-catenin/TCF-4 was necessary for the anchorage-independent growth driven by PLD1 activation. Taken together, our findings define a function for PLD1 in a positive feedback loop of Wnt/beta-catenin/TCF-4 signaling that provides new mechanistic insights into cancer, with implications of novel strategies to disrupt Wnt signaling in cancer. PMID:20442281

Kang, Dong Woo; Lee, Soung-Hoon; Yoon, Jeong Whan; Park, Won-Sang; Choi, Kang-Yell; Min, Do Sik

2010-05-15

210

The positive effect of mirror visual feedback on arm control in children with spastic hemiparetic cerebral palsy is dependent on which arm is viewed.  

PubMed

Mirror visual feedback has previously been found to reduce disproportionate interlimb variability and neuromuscular activity in the arm muscles in children with Spastic Hemiparetic Cerebral Palsy (SHCP). The aim of the current study was to determine whether these positive effects are generated by the mirror per se (i.e. the illusory perception of two symmetrically moving limbs, irrespective of which arm generates the mirror visual feedback) or by the visual illusion that the impaired arm has been substituted and appears to move with less jerk and in synchrony with the less-impaired arm (i.e. by mirror visual feedback of the less-impaired arm only). Therefore, we compared the effect of mirror visual feedback from the impaired and the less-impaired upper limb on the bimanual coupling and neuromuscular activity during a bimanual coordination task. Children with SHCP were asked to perform a bimanual symmetrical circular movement in three different visual feedback conditions (i.e. viewing the two arms, viewing only one arm, and viewing one arm and its mirror image), combined with two head orientation conditions (i.e. looking from the impaired and looking from the less-impaired body side). It was found that mirror visual feedback resulted in a reduction in the eccentric activity of the Biceps Brachii Brevis in the impaired limb compared to the condition with actual visual feedback from the two arms. More specifically, this effect was exclusive to mirror visual feedback from the less-impaired arm and absent when mirror visual feedback from the impaired arm was provided. Across conditions, the less-impaired arm was the leading limb, and the nature of this coupling was independent from visual condition or head orientation. Also, mirror visual feedback did not affect the intensity of the mean neuromuscular activity or the muscle activity of the Triceps Brachii Longus. It was concluded that the positive effects of mirror visual feedback in children with SHCP are not just the result of the perception of two symmetrically moving limbs. Instead, in order to induce a decrease in eccentric neuromuscular activity in the impaired limb, mirror visual feedback from the 'unaffected' less-impaired limb is required. PMID:21766223

Smorenburg, Ana R P; Ledebt, Annick; Feltham, Max G; Deconinck, Frederik J A; Savelsbergh, Geert J P

2011-09-01

211

Iron-activated iron uptake: A positive feedback loop mediated by iron regulatory protein 1  

Microsoft Academic Search

The love-hate relationship between iron and living matter has generated mechanisms to maintain iron concentration in a narrow range, above and below which deleterious effects occur. At the cellular level, iron homeostasis is accomplished by the activity of the IRP proteins, which, under conditions of iron depletion, up-regulate the expression of the iron acquisition proteins TfR and DMT1. It has

Marto T. Núñez; Claudia Núñez-Millacura; Victoria Tapia; Patricia Muñoz; Dora Mazariegos; Miguel Arredondo; Pablo Muñoz; Casilda Mura; Ricardo B. Maccioni

2003-01-01

212

Ca2+ influx is an essential component of the positive-feedback loop that maintains leading-edge structure and activity in macrophages  

PubMed Central

In migrating eukaryotic cells, phosphatidylinositol 3-kinase (PI3K), filamentous actin (F-actin), and monomeric Rho GTPases are key components of a complex positive-feedback system that maintains and amplifies a phosphatidylinositol-3,4,5-trisphosphate signal at the leading edge of the cell. This lipid signal is required for cell polarization and movement. In leukocytes and Dictyostelium, activation or inhibition of any one of these components leads to the activation or inhibition, respectively, of the others via undefined feedback interactions. The role of Ca2+ signals in migrating leukocytes is controversial, and there has been no indication that Ca2+ participates in positive feedback. Here, we demonstrate that an extracellular Ca2+ influx is required for positive feedback at the leading edge of spontaneously polarized macrophages. Inhibition of extracellular Ca2+ influx leads to loss of leading-edge PI3K activity, disassembly of F-actin, cessation of ruffling, and decay of chemoattractant signals. Conversely, increasing cytosolic Ca2+ enhances membrane ruffling, PI3K activity, and F-actin accumulation. Overall, these findings demonstrate that an extracellular Ca2+ influx is an essential component, together with PI3K and F-actin, of the positive-feedback cycle that maintains leading-edge structure and ruffling activity and that supports the chemoattractant response. Strikingly, the Ca2+-sensitive enzyme protein kinase C? (PKC?) is enriched at the leading edge, and its enrichment is sensitive to blockade of Ca2+ influx, to inhibition of PI3K activity, and to F-actin depolymerization. These findings support the working hypothesis that a local, leading-edge Ca2+ signal recruits PKC? as a central player in the positive-feedback loop. PMID:17911247

Evans, John H.; Falke, Joseph J.

2007-01-01

213

Double-negative feedback loop between reprogramming factor LIN28 and microRNA let-7 regulates aldehyde dehydrogenase 1-positive cancer stem cells.  

PubMed

A relatively rare aldehyde dehydrogenase 1 (ALDH1)-positive "stem cell-like" subpopulation of tumor cells has the unique ability to initiate and perpetuate tumor growth; moreover, it is highly resistant to chemotherapy and significantly associated with poor clinical outcomes. The development of more effective therapies for cancer requires targeting of this cell population. Using cDNA microarray analysis, we identified that the expression of the Caenorhabditis elegans lin-28 homologue (LIN28) was positively correlated with the percentage of ALDH1+ tumor cells; this was further validated in an independent set of tissue arrays (n=197). Both loss-of-function and gain-of-function studies showed that LIN28 plays a critical role in the maintenance of ALDH1+ tumor cells. In addition, we found that there is a double-negative feedback loop between LIN28 and let-7 in tumor cells, and that let-7 negatively regulates ALDH1+ tumor cells. Finally, we report that a LIN28/let-7 loop modulates self-renewal and differentiation of mammary gland epithelial progenitor cells. Our data provide evidence that cancer stem cells may arise through a "reprogramming-like" mechanism. A rebalancing of the LIN28/let-7 regulatory loop could be a novel therapeutic strategy to target ALDH1+ cancer stem cells. PMID:21045151

Yang, Xiaojun; Lin, Xiaojuan; Zhong, Xiaomin; Kaur, Sippy; Li, Ning; Liang, Shun; Lassus, Heini; Wang, Liping; Katsaros, Dionyssios; Montone, Kathleen; Zhao, Xia; Zhang, Youcheng; Bützow, Ralf; Coukos, George; Zhang, Lin

2010-11-15

214

Double negative feedback loop between reprogramming factor LIN28 and microRNA let-7 regulates aldehyde dehydrogenase 1-positive cancer stem cells  

PubMed Central

A relatively rare aldehyde dehydrogenase 1 (ALDH1) positive “stem cell-like” subpopulation of tumor cells has the unique ability to initiate and perpetuate tumor growth; moreover it is highly resistant to chemotherapy and significantly associated with poor clinical outcomes. The development of more effective therapies for cancer requires targeting of this cell population. Using cDNA microarray analysis, we identified that the expression of the C. elegans lin-28 homolog (LIN28) was positively correlated with the percentage of ALDH1+ tumor cells; this was further validated in an independent set of tissue arrays (n=197). Both lose-of-function and gain-of-function studies demonstrated that LIN28 plays a critical role in the maintenance of ALDH1+ tumor cells. In addition, we found that there is a double negative feedback loop between LIN28 and let-7 in tumor cells, and that let-7 negatively regulates ALDH1+ tumor cells. Finally, we report that a LIN28/let-7 loop modulates self renewal and differentiation of mammary gland epithelial progenitor cells. Our data provide evidence that cancer stem cells may arise through a “reprogramming-like” mechanism. A rebalancing of the LIN28/let-7 regulatory loop could be a novel therapeutic strategy to target ALDH1+ cancer stem cells. PMID:21045151

Yang, Xiaojun; Lin, Xiaojuan; Zhong, Xiaomin; Kaur, Sippy; Li, Ning; Liang, Shun; Lassus, Heini; Wang, Liping; Katsaros, Dionyssios; Montone, Kathleen; Zhao, Xia; Zhang, Youcheng; Bützow, Ralf; Coukos, George; Zhang, Lin

2010-01-01

215

Evolution of Double Positive Autoregulatory Feedback Loops in CYCLOIDEA2 Clade Genes Is Associated with the Origin of Floral Zygomorphy[W  

PubMed Central

Members of the CYCLOIDEA2 (CYC2) clade of the TEOSINTE BRANCHED1, CYCLOIDEA, and PCF transcription factor genes are widely involved in controlling floral zygomorphy, a key innovation in angiosperm evolution, depending on their persistently asymmetric expression in the corresponding floral domains. However, it is unclear how this asymmetric expression is maintained throughout floral development. Selecting Primulina heterotricha as a model, we examined the expression and function of two CYC2 genes, CYC1C and CYC1D. We analyzed the role of their promoters in protein–DNA interactions and transcription activation using electrophoresis mobility shift assays, chromatin immunoprecipitation, and transient gene expression assays. We find that CYC1C and CYC1D positively autoregulate themselves and cross-regulate each other. Our results reveal a double positive autoregulatory feedback loop, evolved for a pair of CYC2 genes to maintain their expression in developing flowers. Further comparative genome analyses, together with the available expression and function data of CYC2 genes in the core eudicots, suggest that this mechanism might have led to the independent origins of floral zygomorphy, which are associated with plant–insect coevolution and the adaptive radiation of angiosperms. PMID:22649271

Yang, Xia; Pang, Hong-Bo; Liu, Bo-Ling; Qiu, Zhi-Jing; Gao, Qiu; Wei, Lai; Dong, Yang; Wang, Yin-Zheng

2012-01-01

216

Mechanisms for Generating False Positives for Extrasolar Life  

NASA Astrophysics Data System (ADS)

Future mission concepts designed to look for life generally plan to search for oxygen (O2), ozone (O3), and/or methane (CH4). However, mechanisms exist for generating each of these species abiotically. In this presentation, we will review these processes, and discuss the atmospheres that result from them. In general, false positives can form in atmospheres with severe redox imbalance. This redox imbalance can also be thought of as extreme elemental composition, skewed towards very high or very low O/H ratios. Specific examples of this include: 1) loss of H through the top of a planetary atmosphere that leads to high O/H and an atmosphere rich in O2 and O3 2) atmospheres whose volcanism is O-rich and H-poor (i.e., highly oxidized), which leads to an atmosphere that with high O/H that can accumulate O3 and potentially O2 3) atmospheres in which H escape is slow, leading to low O/H and accumulation of CH4 and 4) atmospheres in which volcanic outgassing is H-rich (highly reduced), leading to low O/H and potential accumulation of CH4. Each of these cases would constitute a 'false positive' for life if O2, O3, or CH4 were detected without obtaining the chemical atmospheric context that could indicate a severe redox imbalance exists.Methods exist for discriminating between these 'false positives' where the gases arise from abiotic sources, and 'true positives' where the gases arise by biological sources. The best means of doing this is to obtain measurements of both O-rich (O2/O3) and H-rich (CH4) species, allowing identification of non-extreme O/H ratios in the atmosphere, and eliminating this abiotic source of O2, O3, and CH4. Because this is the most likely cause of abiotic production of these species, the elimination of this explanation would indicate that these gases were instead likely produced by biology.More specific methods to identify each of these false positives mechanisms also exist, but will not be discussed in detail in this presentation.

Domagal-Goldman, Shawn; Meadows, Victoria; Schwieterman, Edward; Luger, Rodrigo; Wordsworth, Robin; Barnes, Rory; Segura, Antigona; Claire, Mark; Virtual Planetary Laboratory

2015-01-01

217

Mechanisms for Generating False Positives for Extrasolar Life  

NASA Astrophysics Data System (ADS)

Future mission concepts designed to look for life generally plan to search for oxygen (O2), ozone (O3), and/or methane (CH4). However, mechanisms exist for generating each of these species abiotically. In this presentation, we will review these processes, and discuss the atmospheres that result from them. In general, false positives can form in atmospheres with severe redox imbalance. This redox imbalance can also be thought of as extreme elemental composition, skewed towards very high or very low O/H ratios. Specific examples of this include: 1) loss of H through the top of a planetary atmosphere that leads to high O/H and an atmosphere rich in O2 and O3 2) atmospheres whose volcanism is O-rich and H-poor (i.e., highly oxidized), which leads to an atmosphere that with high O/H that can accumulate O3 and potentially O2 3) atmospheres in which H escape is slow, leading to low O/H and accumulation of CH4 and 4) atmospheres in which volcanic outgassing is H-rich (highly reduced), leading to low O/H and potential accumulation of CH4. Each of these cases would constitute a “false positive” for life if O2, O3, or CH4 were detected without obtaining the chemical atmospheric context that could indicate a severe redox imbalance exists.Methods exist for discriminating between these “false positives” where the gases arise from abiotic sources, and “true positives” where the gases arise by biological sources. The best means of doing this is to obtain measurements of both O-rich (O2/O3) and H-rich (CH4) species, allowing identification of non-extreme O/H ratios in the atmosphere, and eliminating this abiotic source of O2, O3, and CH4. Because this is the most likely cause of abiotic production of these species, the elimination of this explanation would indicate that these gases were instead likely produced by biology.More specific methods to identify each of these false positives mechanisms also exist, but will not be discussed in detail in this presentation.

Virtual Planetary Laboratory

2015-01-01

218

Water Vapor Feedback and Links to Mechanisms of Recent Tropical Climate Variations  

NASA Technical Reports Server (NTRS)

Recent variations of tropical climate on interannual to near-decadal scales have provided a useful target for studying feedback processes. A strong warm/cold ENSO couplet (e.g. 1997-2000) along with several subsequent weaker events are prominent interannual signals that are part of an apparent longer term strengthening of the Walker circulation during the mid to late1990 s with some weakening thereafter. Decadal scale changes in tropical SST structure during the 1990s are accompanied by focusing of precipitation over the Indo-Pacific warm pool and an increase in tropical ocean evaporation of order 1.0 %/decade. Here we use a number of diverse satellite measurements to explore connections between upper-tropospheric humidity (UTH) variations on these time scales and changes in other water and energy fluxes. Precipitation (GPCP, TRMM), turbulent fluxes (OAFlux), and radiative fluxes (ERBE / CERES, SRB) are use to analyze vertically-integrated divergence of moist static energy, divMSE, and its dry and moist components. Strong signatures of MSE flux transport linking ascending and descending regions of tropical circulations are found. Relative strengths of these transports compared to radiative flux changes are interpreted as a measure of efficiency in the overall process of heat rejection during episodes of warm or cold SST forcing. In conjunction with the diagnosed energy transports we explore frequency distributions of upper-tropospheric humidity as inferred from SSM/T-2 and AMSU-B passive microwave measurements. Relating these variations to SST changes suggests positive water vapor feedback, but at a level reduced from constant relative humidity.

Robertson, F. R.; Miller, Tim L.

2008-01-01

219

Investigating feedback mechanisms between stress and grain-size: preliminary findings from finite-element modelling  

NASA Astrophysics Data System (ADS)

It is widely accepted that changes in stress and grain size can induce a switch between grain-size insensitive (GSI) and sensitive (GSS) creep mechanisms. Under steady-state conditions, grains evolve to an equilibrium size in the boundary region between GSS and GSI, described by the paleopiezometer for a given material. Under these conditions, significant rheological weakening is not expected, as grain size reduction processes are balanced by grain growth processes. However, it has been shown that the stress field surrounding faults varies through the seismic cycle, with both rapid loading and unloading of stress possible in the co- and post-seismic stages. We propose that these changes in stress in the region of the brittle-ductile transition zone may be sufficient to force a deviation from the GSI-GSS boundary and thereby cause a change in grain size and creep mechanism prior to system re-equilibration. Here we present preliminary findings from numerical modelling of stress and grain size changes in response to loading of mechanical inhomogeneities. Our results are attained using a grain-size evolution (GSE) subroutine incorporated into the SULEC finite-element code developed by Susan Ellis and Susanne Buiter, which utilises an iterative approach of solving for spatial and temporal changes in differential stress, grain size and active creep mechanism. Preliminary models demonstrate that stress changes in response to the opening of a fracture in a flowing medium can be significant enough to cause a switch from GSI to GSS creep. These results are significant in the context of understanding spatial variations and feedback between stress, grain size and deformation mechanisms through the seismic cycle.

Cross, A. J.; Prior, D. J.; Ellis, S. M.

2012-12-01

220

Transglutaminase II/microRNA-218/-181a loop regulates positive feedback relationship between allergic inflammation and tumor metastasis.  

PubMed

The molecular mechanism of transglutaminase II (TGaseII)-mediated allergic inflammation remains largely unknown. TGaseII, induced by antigen stimulation, showed an interaction and co-localization with Fc?RI. TGaseII was necessary for in vivo allergic inflammation, such as triphasic cutaneous reaction, passive cutaneous anaphylaxis, and passive systemic anaphylaxis. TGaseII was necessary for the enhanced metastatic potential of B16F1 melanoma cells by passive systemic anaphylaxis. TGaseII was shown to be a secreted protein. Recombinant TGaseII protein increased the histamine release and ?-hexosaminidase activity, and enhanced the metastatic potential of B16F1 mouse melanoma cells. Recombinant TGaseII protein induced the activation of EGF receptor and an interaction between EGF receptor and Fc?RI. Recombinant TGaseII protein displayed angiogenic potential accompanied by allergic inflammation. R2 peptide, an inhibitor of TGaseII, exerted negative effects on in vitro and in vivo allergic inflammation by regulating the expression of TGaseII and Fc?RI signaling. MicroRNA (miR)-218 and miR-181a, decreased during allergic inflammation, were predicted as negative regulators of TGaseII by microRNA array and TargetScan analysis. miR-218 and miR-181a formed a negative feedback loop with TGaseII and regulated the in vitro and in vivo allergic inflammation. TGaseII was necessary for the interaction between mast cells and macrophages during allergic inflammation. Mast cells and macrophages, activated during allergic inflammation, were responsible for the enhanced metastatic potential of tumor cells that are accompanied by allergic inflammation. In conclusion, the TGaseII/miR-218/-181a feedback loop can be employed for the development of anti-allergy therapeutics. PMID:25202021

Eom, Sangkyung; Kim, Youngmi; Kim, Misun; Park, Deokbum; Lee, Hansoo; Lee, Yun Sil; Choe, Jongseon; Kim, Young Myeong; Jeoung, Dooil

2014-10-24

221

Rewiring Mitogen-Activated Protein Kinase Cascade by Positive Feedback Confers Potato Blight Resistance1  

PubMed Central

Late blight, caused by the notorious pathogen Phytophthora infestans, is a devastating disease of potato (Solanum tuberosum) and tomato (Solanum lycopersicum), and during the 1840s caused the Irish potato famine and over one million fatalities. Currently, grown potato cultivars lack adequate blight tolerance. Earlier cultivars bred for resistance used disease resistance genes that confer immunity only to some strains of the pathogen harboring corresponding avirulence gene. Specific resistance gene-mediated immunity and chemical controls are rapidly overcome in the field when new pathogen races arise through mutation, recombination, or migration from elsewhere. A mitogen-activated protein kinase (MAPK) cascade plays a pivotal role in plant innate immunity. Here we show that the transgenic potato plants that carry a constitutively active form of MAPK kinase driven by a pathogen-inducible promoter of potato showed high resistance to early blight pathogen Alternaria solani as well as P. infestans. The pathogen attack provoked defense-related MAPK activation followed by induction of NADPH oxidase gene expression, which is implicated in reactive oxygen species production, and resulted in hypersensitive response-like phenotype. We propose that enhancing disease resistance through altered regulation of plant defense mechanisms should be more durable and publicly acceptable than engineering overexpression of antimicrobial proteins. PMID:16407438

Yamamizo, Chihiro; Kuchimura, Kazuo; Kobayashi, Akira; Katou, Shinpei; Kawakita, Kazuhito; Jones, Jonathan D.G.; Doke, Noriyuki; Yoshioka, Hirofumi

2006-01-01

222

Positive feedback between p53 and TRF2 in telomere damage signaling and cellular senescence  

PubMed Central

The telomere-capping complex (shelterin) protects functional telomeres from initiating unwanted DNA damage response. Uncapped telomeres at the end of cellular replicative lifespan lose this protective mechanism and trigger DNA damage signaling to activate p53 and thereby induce replicative senescence. Here we identify a signaling pathway involving p53, Siah-1, a p53-inducible E3 ubiquitin ligase, and TRF2, a component of the shelterin complex. Endogenous Siah-1 and TRF2 were up- and down-regulated, respectively, at replicative senescence with activated p53. A series of experimental manipulations of p53 showed that p53 induced Siah-1 and repressed TRF2 protein levels. The p53-dependent ubiquitination and proteasomal degradation of TRF2 were attributed to the E3 ligase activity of Siah-1. Siah-1 knockdown stabilized TRF2 and delayed the onset of cellular replicative senescence, suggesting the role of Siah-1 and TRF2 in p53-regulated senescence. This study reveals that p53, a downstream effector of the telomere-initiated damage signaling, also functions upstream of the shelterin complex. PMID:21057505

Fujita, Kaori; Horikawa, Izumi; Mondal, Abdul M.; Miller Jenkins, Lisa M.; Appella, Ettore; Vojtesek, Borivoj; Bourdon, Jean-Christophe; Lane, David P.; Harris, Curtis C.

2012-01-01

223

Reward and Visual Feedback Relative to the Performance and Mechanical Efficiency of High School Girls in the Standing Broad Jump.  

ERIC Educational Resources Information Center

This study focuses on changes occurring in selected mechanical components of high school girls performing the standing broad jump, and collects data pertaining to the effects of monetary reward and videotape feedback upon the following components: (a) distance jumped, (b) maximum angle of knee flexion, (c) maximum angle of hip flexion, (d) hip…

Zebas, Carole J.

224

Revised Submission (R3) to `IEEE TNSRE' November 2009 Neural-Mechanical Feedback Control Scheme Generates Physiological  

E-print Network

Generates Physiological Ankle Torque Fluctuation during Quiet Stance Running Title: Neural and derivative (PD) feedback controller can regulate the active ankle torque during quiet stance and stabilize the active and passive ankle torque mechanisms and identify their contributions to the total ankle torque

Popovic, Milos R.

225

Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem  

Microsoft Academic Search

Ecosystem models that simulate biogeochemical processes usually ignore hydrological controls that govern them. It is quite possible that topographically driven water fluxes significantly influence the spatial distribution of C sources and sinks because of their large contribution to the local water balance. To investigate this, we simulated biogeochemical processes along with the associated feedback mechanisms in a boreal ecosystem using

Ajit Govind; Jing Ming Chen; Weimin Ju

2009-01-01

226

Neuron, Vol. 45, 447457, February 3, 2005, Copyright 2005 by Elsevier Inc. DOI 10.1016/j.neuron.2004.12.042 Positive Feedback in a Brainstem  

E-print Network

.neuron.2004.12.042 Positive Feedback in a Brainstem Tactile Sensorimotor Loop Quoc-Thang Nguyen1 and David (Erzurumlu and Killackey, 1979; Hattox et al., 2002) and indirect pathways within the brainstem via Summary-order The trigeminal loop in the brainstem comprises the loops involve collicular, cerebellar, and dorsal thalamic

Kleinfeld, David

227

Nonlinear state feedback controller design for underactuated mechanical system: a modified block backstepping approach.  

PubMed

This paper presents the formulation of a novel block-backstepping based control algorithm to address the stabilization problem for a generalized nonlinear underactuated mechanical system. For the convenience of compact design, first, the state model of the underactuated system has been converted into the block-strict feedback form. Next, we have incorporated backstepping control action to derive the expression of the control input for the generic nonlinear underactuated system. The proposed block backstepping technique has further been enriched by incorporating an integral action additionally for enhancing the steady state performance of the overall system. Asymptotic stability of the overall system has been analyzed using Lyapunov stability criteria. Subsequently, the stability of the zero dynamics has also been analyzed to ensure the global asymptotic stability of the entire nonlinear system at its desired equilibrium point. The proposed control algorithm has been applied for the stabilization of a benchmarked underactuated mechanical system to verify the effectiveness of the proposed control law in real-time environment. PMID:24434123

Rudra, Shubhobrata; Barai, Ranjit Kumar; Maitra, Madhubanti

2014-03-01

228

Mechanisms and Feedbacks Causing Changes in Upper Stratospheric Ozone in the 21st Century  

NASA Technical Reports Server (NTRS)

Stratospheric ozone is expected to increase during the 21st century as the abundance of halogenated ozone-depleting substances decrease to 1960 values. However, climate change will likely alter this "recovery" of stratospheric ozone by changing stratospheric temperatures, circulation, and abundance of reactive chemical species. Here we quantity the contribution of different mechanisms to changes in upper stratospheric ozone from 1960 to 2100 in the Goddard Earth Observing System Chemistry-Climate Model (GEOS CCM), using multiple linear regression analysis applied to simulations using either Alb or A2 greenhouse gas (GHG) scenarios. In both these scenarios upper stratospheric ozone has a secular increase over the 21st century. For the simulation using the Alb GHG scenario, this increase is determined by the decrease in halogen amounts and the greenhouse gas induced cooling, with roughly equal contributions from each mechanism. There is a larger cooling in the simulation using the A2 GHG scenario, but also enhanced loss from higher NOy and HOx concentrations, which nearly offsets the increase due to cooler temperatures. The resulting ozone evolutions are similar in the A2 and Alb simulations. The response of ozone due to feedbacks from temperature and HOx changes, related to changing halogen concentrations, are also quantified using simulations with fixed halogen concentrations.

Oman, Luke; Waugh, D. W.; Kawa, S. R.; Stolarski, R. S.; Douglass, A. R.; Newman, P. A.

2009-01-01

229

The small GTPase HRas shapes local PI3K signals through positive feedback and regulates persistent membrane extension in migrating fibroblasts  

PubMed Central

Self-amplification of phosphoinositide 3-kinase (PI3K) signaling is believed to regulate asymmetric membrane extension and cell migration, but the molecular organization of the underlying feedback circuit is elusive. Here we use an inducible approach to synthetically activate PI3K and interrogate the feedback circuitry governing self-enhancement of 3?-phosphoinositide (3-PI) signals in NIH3T3 fibroblasts. Synthetic activation of PI3K initially leads to uniform production of 3-PIs at the plasma membrane, followed by the appearance of asymmetric and highly amplified 3-PI signals. A detailed spatiotemporal analysis shows that local self-amplifying 3-PI signals drive rapid membrane extension with remarkable directional persistence and initiate a robust migratory response. This positive feedback loop is critically dependent on the small GTPase HRas. Silencing of HRas abrogates local amplification of 3-PI signals upon synthetic PI3K activation and results in short-lived protrusion events that do not support cell migration. Finally, our data indicate that this feedback circuit is likely to operate during platelet-derived growth factor–induced random cell migration. We conclude that positive feedback between PI3K and HRas is essential for fibroblasts to spontaneously self-organize and generate a productive migratory response in the absence of spatial cues. PMID:23676667

Thevathasan, Jervis Vermal; Tan, Elisabeth; Zheng, Hui; Lin, Yu-Chun; Li, Yang; Inoue, Takanari; Fivaz, Marc

2013-01-01

230

Augmented Feedback Supports Skill Transfer and Reduces High-Risk Injury Landing Mechanics  

PubMed Central

Background There is a current need to produce a simple, yet effective method for screening and targeting possible deficiencies related to increased anterior cruciate ligament (ACL) injury risk. Hypothesis Frontal plane knee angle (FPKA) during a drop vertical jump will decrease upon implementing augmented feedback into a standardized sport training program. Study Design Controlled laboratory study. Methods Thirty-seven female participants (mean ± SD: age, 14.7 ±1.5 years; height, 160.9 ± 6.8 cm; weight, 54.5 ± 7.2 kg) were trained over 8 weeks. During each session, each participant received standardized training consisting of strength training, plyometrics, and conditioning. They were also videotaped running on a treadmill at a standardized speed and performing a repeated tuck jump for 10 seconds. Study participants were randomized into 2 groups and received augmented feedback on either their jumping (AF) or sprinting (CTRL) form. Average (mean of 3 trials) and most extreme (trial with greatest knee abduction) FPKA were calculated from 2-dimensional video captured during performance of the drop vertical jump. Results After testing, a main effect of time was noted, with the AF group reducing their FPKA average by 37.9% over the 3 trials while the CTRL group demonstrated a 26.7% reduction average across the 3 trials (P < .05). Conversely, in the most extreme drop vertical jump trial, a significant time-by-group interaction was noted (P < .05). The AF group reduced their most extreme FPKA by 6.9° (pretest, 18.4° ± 12.3°; posttest, 11.4° ± 10.1°) on their right leg and 6.5° (pretest, 16.3° ± 14.5°; posttest, 9.8° ± 10.7°) on their left leg, which represented a 37.7% and 40.1 % reduction in FPKA, respectively. In the CTRL group, no similar changes were noted in the right (pretest, 16.9° ± 14.3°; posttest, 14.0° ± 12.3°) or left leg (pretest, 9.8° ± 11.1°; posttest, 7.2° ± 9.2°) after training. Conclusion Providing athletes with augmented feedback on deficits identified by the tuck jump assessment has a positive effect on their biomechanics during a different drop vertical jump task that is related to increased ACL injury risk. The ability of the augmented feedback to support the transfer of skills and injury risk factor reductions across different tasks provides exciting new evidence related to how neuromuscular training may ultimately cross over into retained biomechanics that reduce ACL injuries during sport. Clinical Relevance The tuck jump assessment’s ease of use makes it a timely and economically favorable method to support ACL prevention strategies in young girls. PMID:23371471

Myer, Gregory D.; Stroube, Benjamin W.; DiCesare, Christopher A.; Brent, Jensen L.; Ford, Kevin R.; Heidt, Robert S.; Hewett, Timothy E.

2014-01-01

231

Positive feedback loop between introductions of non-native marine species and cultivation of oysters in Europe.  

PubMed

With globalization, agriculture and aquaculture activities are increasingly affected by diseases that are spread through movement of crops and stock. Such movements are also associated with the introduction of non-native species via hitchhiking individual organisms. The oyster industry, one of the most important forms of marine aquaculture, embodies these issues. In Europe disease outbreaks affecting cultivated populations of the naturalized oyster Crassostrea gigas caused a major disruption of production in the late 1960s and early 1970s. Mitigation procedures involved massive imports of stock from the species' native range in the northwestern Pacific from 1971 to 1977. We assessed the role stock imports played in the introduction of non-native marine species (including pathogens) from the northwestern Pacific to Europe through a methodological and critical appraisal of record data. The discovery rate of non-native species (a proxy for the introduction rate) from 1966 to 2012 suggests a continuous vector activity over the entire period. Disease outbreaks that have been affecting oyster production since 2008 may be a result of imports from the northwestern Pacific, and such imports are again being considered as an answer to the crisis. Although successful as a remedy in the short and medium terms, such translocations may bring new diseases that may trigger yet more imports (self-reinforcing or positive feedback loop) and lead to the introduction of more hitchhikers. Although there is a legal framework to prevent or reduce these introductions, existing procedures should be improved. PMID:25047099

Mineur, Frederic; Le Roux, Auguste; Maggs, Christine A; Verlaque, Marc

2014-12-01

232

Elastin-derived peptides stimulate trophoblast migration and invasion: a positive feedback loop to enhance spiral artery remodelling.  

PubMed

Elastin breakdown in the walls of uterine spiral arteries during early pregnancy facilitates their transformation into dilated, high-flow, low-resistance channels. Elastin-derived peptides (EDP) can influence cell migration, invasion and protease activity, and so we hypothesized that EDP released during elastolysis promote extravillous trophoblast (EVT) invasion and further elastin breakdown. Treatment of the trophoblast cell line SGHPL4 with the elastin-derived matrikine VGVAPG (1 ?g/ml) significantly increased total elastase activity, promoted migration in a wound healing assay and increased invasion through Matrigel-coated transwells compared with vehicle control (0.1% DMSO) or the scrambled sequence VVGPGA. Furthermore, treatment of first-trimester placental villous explants with this EDP significantly increased both the area of trophoblast outgrowth and distance of migration away from the villous tips. Primary first-trimester cytotrophoblast exposed to VGVAPG (1 ?g/ml) for 30 min showed increased phosphorylation of endothelial nitric oxide synthase and activation of the mitogen activated protein kinase pathway, events also associated with tumour cell migration and invasion. These in vitro observations suggest liberation of bioactive EDP during induction of elastolysis in the uterine spiral arteries may orchestrate a positive feedback loop that promotes EVT invasion and further elastin breakdown, contributing to the process of vascular remodelling. PMID:25245255

Desforges, Michelle; Harris, Lynda K; Aplin, John D

2015-01-01

233

Ecological consequences of body size decline in harvested fish species: positive feedback loops in trophic interactions amplify human impact.  

PubMed

Humans are changing marine ecosystems worldwide, both directly through fishing and indirectly through climate change. One of the little explored outcomes of human-induced change involves the decreasing body sizes of fishes. We use a marine ecosystem model to explore how a slow (less than 0.1% per year) decrease in the length of five harvested species could affect species interactions, biomasses and yields. We find that even small decreases in fish sizes are amplified by positive feedback loops in the ecosystem and can lead to major changes in natural mortality. For some species, a total of 4 per cent decrease in length-at-age over 50 years resulted in 50 per cent increase in predation mortality. However, the magnitude and direction in predation mortality changes differed among species and one shrinking species even experienced reduced predation pressure. Nevertheless, 50 years of gradual decrease in body size resulted in 1-35% decrease in biomasses and catches of all shrinking species. Therefore, fisheries management practices that ignore contemporary life-history changes are likely to overestimate long-term yields and can lead to overfishing. PMID:23365151

Audzijonyte, Asta; Kuparinen, Anna; Gorton, Rebecca; Fulton, Elizabeth A

2013-04-23

234

Investigation of the MBL cloud feedback mechanism with a hierarchy of models  

NASA Astrophysics Data System (ADS)

Marine boundary layer (MBL) clouds strongly influence the Earth's radiation budget, and their response to climate changes is one of the central uncertainties in climate models. To study this response, we use a hierarchical modeling framework spanning an idealized GCM, a single-column model (SCM), and a large-eddy simulation (LES) model. The idealized GCM has an eddy diffusion/mass flux (EDMF) closure and a PDF-based cloud scheme to represent the turbulent and cloud processes in a unified and physically well-founded way. The subtropical MBL clouds are simulated in a wide range of model climates. Their coverage strongly decreases as the climate warms, suggesting a positive climate feedback. The SCM with the same parameterizations is run with idealized yet climatically plausible forcing terms representing the large-scale processes. The statistical equilibrium states from the SCM are comparable to the GCM results. Controlled experiments are performed in the SCM to separate dynamic and thermodynamic effects. The processes primarily responsible for the cloud response to warming are discussed in the context of a further simplified SCM, on the basis of which scaling results are derived. The SCM results are also validated with the LES model.

Tan, Zhihong; Schneider, Tapio; Teixeira, João; Pressel, Kyle G.; Lam, Rémi

2013-04-01

235

A MDM2-dependent positive-feedback loop is involved in inhibition of miR-375 and miR-106b induced by Helicobacter pylori lipopolysaccharide.  

PubMed

Dysregulation of microRNAs (miRNAs) has been linked to virulence factors of Helicobacter pylori and shown to contribute to the progression of gastric cancer. However, the mechanisms of these processes remain poorly understood. The aim of this study was to investigate the mechanisms by which lipopolysaccharide (LPS), a virulence factor of H. pylori, regulates miR-375 and miR-106b expression in gastric epithelial cells. The results show that LPS from H. pylori 26695 downregulated the expression of miR-375 and miR-106b in gastric epithelial cells, and low levels of Dicer were also observed. Downregulation of miR-375 was found to increase expression of MDM2 with SP1 activation. Overexpression of MDM2 inhibited Dicer by repressing p63 to create a positive-feedback loop involving SP1/MDM2/p63/Dicer that leads to inhibition of miR-375 and miR-106b expression. In addition, we demonstrated that JAK1 and STAT3 were downstream target genes of miR-106b. H. pylori LPS also enhanced the tyrosine phosphorylation of JAK1, JAK2 and STAT3. Together, these results provide insight into the regulatory mechanisms of MDM2 on H. pylori LPS-induced specific miRNAs, and furthermore, suggest that gastric epithelial cells treated with H. pylori LPS may be susceptible to JAK/STAT3 signal pathway activation via inhibition of miR-375 and miR-106b. PMID:25307786

Ye, Feng; Tang, Chunli; Shi, Weijia; Qian, Juan; Xiao, Shuping; Gu, Min; Dang, Yini; Liu, Jianping; Chen, Yan; Shi, Ruihua; Zhang, Guoxin

2015-05-01

236

Separable Neural Mechanisms Contribute to Feedback Processing in a Rule-Learning Task  

ERIC Educational Resources Information Center

To adjust performance appropriately to environmental demands, it is important to monitor ongoing action and process performance feedback for possible errors. In this study, we used fMRI to test whether medial prefrontal cortex (PFC)/anterior cingulate cortex (ACC) and dorsolateral (DL) PFC have different roles in feedback processing. Twenty adults…

Zanolie, K.; Van Leijenhorst, L.; Rombouts, S. A. R. B.; Crone, E. A.

2008-01-01

237

The role of feedback mechanisms in historic channel changes of the lower Rio Grande in the Big Bend region  

NASA Astrophysics Data System (ADS)

Over the last century, large-scale water development of the upper Rio Grande in the U.S. and Mexico, and of the Rio Conchos in Mexico, has resulted in progressive channel narrowing of the lower Rio Grande in the Big Bend region. We used methods operating at multiple spatial and temporal scales to analyze the rate, magnitude, and processes responsible for channel narrowing. These methods included: hydrologic analysis of historic stream gage data, analysis of notes of measured discharges, historic oblique and aerial photograph analysis, and stratigraphic and dendrogeomorphic analysis of inset floodplain deposits. Our analyses indicate that frequent large floods between 1900 and the mid-1940s acted as a negative feedback mechanism and maintained a wide, sandy, multi-threaded river. Declines in mean and peak flow in the mid-1940s resulted in progressive channel narrowing. Channel narrowing has been temporarily interrupted by occasional large floods that widened the channel, however, channel narrowing has always resumed. After large floods in 1990 and 1991, the active channel width of the lower Rio Grande has narrowed by 36-52%. Narrowing has occurred by the vertical accretion of fine-grained deposits on top of sand and gravel bars, inset within natural levees. Channel narrowing by vertical accretion occurred simultaneously with a rapid invasion of non-native riparian vegetation ( Tamarix spp., Arundo donax) which created a positive feedback and exacerbated the processes of channel narrowing and vertical accretion. In two floodplain trenches, we measured 2.75 and 3.5 m of vertical accretion between 1993 and 2008. In some localities, nearly 90% of bare, active channel bars were converted to vegetated floodplain during the same period. Upward shifts of stage-discharge relations occurred resulting in over-bank flooding at lower discharges, and continued vertical accretion despite a progressive reduction in stream flow. Thus, although the magnitude of the average annual flood was reduced between 40 and 50%, over-bank flooding continued. These changes reflect a shift in the geomorphic nature of the Rio Grande from a wide, laterally unstable, multi-thread river, to a laterally stable, single-thread channel with cohesive, vertical banks, and few active in-channel bars.

Dean, David J.; Schmidt, John C.

2011-03-01

238

IL-18 levels and the outcome of innate immune response to lipopolysaccharide: importance of a positive feedback loop with caspase-1 in IL-18 expression.  

PubMed

LPS enhanced antibacterial host defenses (ABHD) when given at low (75 micro g) doses (16 of 19 mice survived 3x LD(50) Escherichia coli vs 3 of 19 LPS-naive mice; p = 0.0001), but induced lethal inflammation at high (500 micro g) doses (5 of 5 died). Differences in the cytokine profiles induced by these LPS doses may provide insight into the mechanism(s) of transition from beneficial to lethal LPS responses. The 75 micro g LPS induced 5.9 +/- 0.9 ng/ml serum IL-18 at 8 h, which decreased to 2.3 +/- 0.4 ng/ml by 24 h, whereas 500 micro g LPS induced 11.1 +/- 1.6 ng/ml serum IL-18 levels at 8 h, which increased until death. Compared with 75 micro g, higher but sublethal (150 micro g) doses of LPS induced greater serum IL-18 levels and less effectively induced ABHD (3 of 8 survived). Reduction of serum IL-18 with neutralizing Ab improved the ABHD induced by 150 micro g, but reduced that produced by 75 micro g LPS, suggesting an optimal range of serum IL-18 level was essential for efficient ABHD. Increased expression of caspase-1 mRNA in response to the higher IL-18 levels induced at the 150 and 500 micro g, but not at the 75 micro g doses of LPS may represent a positive feedback regulatory loop leading to sustained serum IL-18 levels. We conclude that the regulation of serum IL-18 expression is critical to the outcome of innate immune responses to LPS. PMID:12193723

Joshi, Vishwas D; Kalvakolanu, Dhananjaya V; Hasday, Jeffrey D; Hebel, Richard J; Cross, Alan S

2002-09-01

239

MECHANISM OF INHIBITION OF TUBULOGLOMERULAR FEEDBACK (TGF) BY CARBON MONOXIDE AND cGMP  

PubMed Central

Tubuloglomerular feedback (TGF) is a mechanism that senses NaCl in the macula densa (MD) and causes constriction of the afferent arteriole (Af-Art). Carbon monoxide (CO), either endogenous or exogenous, inhibits TGF at least in part via cGMP. We hypothesize that CO in the MD, acting via both cGMP-dependent and - independent mechanisms, attenuates TGF by acting downstream from depolarization and Ca entry into the MD cells. In vitro, microdissected rabbit Af-Arts and their MD were simultaneously perfused and TGF was measured as the decrease in Af-Art diameter. MD depolarization was induced with ionophores, while adding the CO-releasing molecule CORM-3 to the MD perfusate at non-toxic concentrations. CORM-3 blunted depolarization-induced TGF at 50 ?M, from 3.6±0.4 to 2.5±0.4 ?m (P<0.01), and abolished it at 100 ?M, to 0.1±0.1 ?m (P<0.001, n=6). When cGMP generation was blocked by guanylyl cyclase inhibitor LY-83583 added to the MD, CORM-3 no longer affected depolarization-induced TGF at 50 ?M (2.9±0.4 vs. 3.0±0.4 ?m), but partially inhibited TGF at 100 ?M (to 1.3±0.2 ?m, P<0.05, n=9). Experiments using ETYA and indomethacin suggest arachidonic acid metabolites do not mediate the cGMP-independent effect of CO. We then added the calcium ionophore A23187 to the macula densa, which caused TGF (4.1±0.6 ?M); A23187-induced TGF was inhibited by CORM-3 at 50 ?M (1.9±0.6 ?M, P<0.01) and 100 ?M (0.2±0.5 ?M, P<0.001, n=6). We conclude that CO inhibits TGF acting downstream from depolarization and calcium entry, acting via cGMP at low concentrations, but additional mechanisms of action may be involved at higher concentrations. PMID:23648700

Ren, YiLin; D’Ambrosio, Martin A.; Garvin, Jeffrey L.; Wang, Hong; Carretero, Oscar A.

2013-01-01

240

Acetylcholine Promotes Ca2+and NO-Oscillations in Adipocytes Implicating Ca2+?NO?cGMP?cADP-ribose?Ca2+ Positive Feedback Loop - Modulatory Effects of Norepinephrine and Atrial Natriuretic Peptide  

PubMed Central

Purpose This study investigated possible mechanisms of autoregulation of Ca2+ signalling pathways in adipocytes responsible for Ca2+ and NO oscillations and switching phenomena promoted by acetylcholine (ACh), norepinephrine (NE) and atrial natriuretic peptide (ANP). Methods Fluorescent microscopy was used to detect changes in Ca2+ and NO in cultures of rodent white adipocytes. Agonists and inhibitors were applied to characterize the involvement of various enzymes and Ca2+-channels in Ca2+ signalling pathways. Results ACh activating M3-muscarinic receptors and G?? protein dependent phosphatidylinositol 3 kinase induces Ca2+ and NO oscillations in adipocytes. At low concentrations of ACh which are insufficient to induce oscillations, NE or ?1, ?2-adrenergic agonists act by amplifying the effect of ACh to promote Ca2+ oscillations or switching phenomena. SNAP, 8-Br-cAMP, NAD and ANP may also produce similar set of dynamic regimes. These regimes arise from activation of the ryanodine receptor (RyR) with the implication of a long positive feedback loop (PFL): Ca2+? NO?cGMP?cADPR?Ca2+, which determines periodic or steady operation of a short PFL based on Ca2+-induced Ca2+ release via RyR by generating cADPR, a coagonist of Ca2+ at the RyR. Interplay between these two loops may be responsible for the observed effects. Several other PFLs, based on activation of endothelial nitric oxide synthase or of protein kinase B by Ca2+-dependent kinases, may reinforce functioning of main PFL and enhance reliability. All observed regimes are independent of operation of the phospholipase C/Ca2+-signalling axis, which may be switched off due to negative feedback arising from phosphorylation of the inositol-3-phosphate receptor by protein kinase G. Conclusions This study presents a kinetic model of Ca2+-signalling system operating in adipocytes and integrating signals from various agonists, which describes it as multivariable multi feedback network with a family of nested positive feedback. PMID:23696827

Turovsky, Egor A.; Turovskaya, Mariya V.; Dolgacheva, Ludmila P.; Zinchenko, Valery P.; Dynnik, Vladimir V.

2013-01-01

241

Convective-Radiative Feedback Mechanisms By Dusty Convective Plumes And Vortices  

NASA Astrophysics Data System (ADS)

We have been conducting field campaigns in Arizona to quantify the role of convective plumes and vortices on the content and vertical distribution of atmospheric dust aerosols. Data collected during our field campaigns show that coherent (organized over their vertical extension) convective vortices produce dust fluxes of nearly 1 g m-2 s-1 (Renno et al., 2004). Thus, very large dust devils of ~100 m in diameter can pump nearly 15,000 kg of dust in their lifetime of about 30 minutes. We used a combination of observational data and theory to determine the role of convective plumes and vortices on the global aerosol budget and show that they contribute to about 35% of the global budget of mineral dust (Koch and Renno, in press). This value was based on theoretical predictions of the fractional area covered by dusty plumes and vortices during the convectively active period of the diurnal cycle. We use measurements made during our field campaigns in Arizona to refine this calculation by detecting dust events based on heat flux and surface velocities intense enough to lift dust. We also use data from our field campaigns to better understand the radiative-convective feedback mechanisms due to convective plumes and vortices. We observed strong oscillations in surface temperature and solar flux. These oscillations, with a frequency of about 30 minutes, are of the order of the convective time scale. We speculate that intense boundary layer convection produces an increase in the concentration of atmospheric dust, which absorbs and scatters solar radiation, decreasing surface temperature and stabilizing the atmosphere, therefore causing a decrease in the intensity of atmospheric convection and surface dust flux. Therefore, we expect to see a correlation between the variability in the surface temperature and dust flux with the frequency of convective plumes and vortices on a regional scale.

Koch, J.; Renno, N. O.

2005-12-01

242

Elimination of Negative Feedback Control Mechanisms Along the Insulin Signaling Pathway Improves ?-Cell Function Under Stress  

PubMed Central

OBJECTIVE Cellular stress and proinflammatory cytokines induce phosphorylation of insulin receptor substrate (IRS) proteins at Ser sites that inhibit insulin and IGF-1 signaling. Here, we examined the role of Ser phosphorylation of IRS-2 in mediating the inhibitory effects of proinflammatory cytokines and cellular stress on ?-cell function. RESEARCH DESIGN AND METHODS Five potential inhibitory Ser sites located proximally to the P-Tyr binding domain of IRS-2 were mutated to Ala. These IRS-2 mutants, denoted IRS-25A, and their wild-type controls (IRS-2WT) were introduced into adenoviral constructs that were infected into Min6 cells or into cultured murine islets. RESULTS When expressed in cultured mouse islets, IRS-25A was better than IRS-2WT in protecting ?-cells from apoptosis induced by a combination of IL-1?, IFN-?, TNF-?, and Fas ligand. Cytokine-treated islets expressing IRS25A secreted significantly more insulin in response to glucose than did islets expressing IRS-2WT. This could be attributed to the higher transcription of Pdx1 in cytokine-treated islets that expressed IRS-25A. Accordingly, transplantation of 200 islets expressing IRS25A into STZ-induced diabetic mice restored their ability to respond to a glucose load similar to naïve mice. In contrast, mice transplanted with islets expressing IRS2WT maintained sustained hyperglycemia 3 days after transplantation. CONCLUSIONS Elimination of a physiological negative feedback control mechanism along the insulin-signaling pathway that involves Ser/Thr phosphorylation of IRS-2 affords protection against the adverse effects of proinflammatory cytokines and improves ?-cell function under stress. Genetic approaches that promote IRS25A expression in pancreatic ?-cells, therefore, could be considered a rational treatment against ?-cell failure after islet transplantation. PMID:20547979

Gurevitch, Diana; Boura-Halfon, Sigalit; Isaac, Roi; Shahaf, Galit; Alberstein, Moti; Ronen, Denise; Lewis, Eli C.; Zick, Yehiel

2010-01-01

243

Semaphorin 3E–Plexin-D1 signaling regulates VEGF function in developmental angiogenesis via a feedback mechanism  

PubMed Central

Blood vessel networks are typically formed by angiogenesis, a process in which new vessels form by sprouting of endothelial cells from pre-existing vessels. This process is initiated by vascular endothelial growth factor (VEGF)-mediated tip cell selection and subsequent angiogenic sprouting. Surprisingly, we found that VEGF directly controls the expression of Plexin-D1, the receptor for the traditional repulsive axon guidance cue, semaphorin 3E (Sema3E). Sema3E–Plexin-D1 signaling then negatively regulates the activity of the VEGF-induced Delta-like 4 (Dll4)–Notch signaling pathway, which controls the cell fate decision between tip and stalk cells. Using the mouse retina as a model system, we show that Plexin-D1 is selectively expressed in endothelial cells at the front of actively sprouting blood vessels and its expression is tightly controlled by VEGF secreted by surrounding tissues. Therefore, although the Sema3E secreted by retinal neurons is evenly distributed throughout the retina, Sema3E–Plexin-D1 signaling is spatially controlled by VEGF through its regulation of Plexin-D1. Moreover, we show that gain and loss of function of Sema3E and Plexin-D1 disrupts normal Dll4 expression, Notch activity, and tip/stalk cell distribution in the retinal vasculature. Finally, the retinal vasculature of mice lacking sema3E or plexin-D1 has an uneven growing front, a less-branched vascular network, and abnormal distribution of dll4-positive cells. Lowering Notch activity in the mutant mice can reverse this defect, solidifying the observation that Dll4–Notch signaling is regulated by Sema3E–Plexin-D1 and is required for its function in vivo. Together, these data reveal a novel role of Sema3E–Plexin-D1 function in modulating angiogenesis via a VEGF-induced feedback mechanism. PMID:21724832

Kim, Jiha; Oh, Won-Jong; Gaiano, Nicholas; Yoshida, Yutaka; Gu, Chenghua

2011-01-01

244

Pulsed Feedback Defers Cellular Differentiation  

PubMed Central

Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable “polyphasic” positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a “timer” that operates over timescales much longer than a cell cycle. PMID:22303282

Levine, Joe H.; Fontes, Michelle E.; Dworkin, Jonathan; Elowitz, Michael B.

2012-01-01

245

Quantum-Mechanical Position Operator in Extended Systems  

Microsoft Academic Search

The position operator (defined within the Schrödinger representation in the standard way) becomes meaningless when periodic boundary conditions are adopted for the wave function, as usual in condensed matter physics. I show how to define the position expectation value by means of a simple many-body operator acting on the wave function of the extended system. The relationships of the present

Raffaele Resta; Fisica Teorica; Strada Costiera

1998-01-01

246

Carriage-rail assembly for high-resolution mechanical positioning  

NASA Technical Reports Server (NTRS)

Carriage-rail assembly effects extreme resolution and position accuracy with little friction, and is applicable to such apparatus as optical benches, inspection fixtures, machine tools, and photographic equipment. Directions for assembly construction are given.

Bosworth, R. H.; Roney, B. W.

1970-01-01

247

Feedbacks of phytoplankton surface mats on ocean physics  

NASA Astrophysics Data System (ADS)

The effects of phytoplankton on ocean physics through the feedback by light absorption have been investigated repeatedly. In contrast, additional feedback mechanisms involving positively buoyant phytoplankton have been largely ignored. However, extensive surface mats of buoyant cyanobacteria, as they occur regularly in the Baltic Sea in summer, may have significant effects on wind drag and albedo. Using an ecosystem model that is embedded in a water column or an ocean circulation model, we study the relative importance of all three feedback mechanisms. We show that surface floating cyanobacteria substantially alter their environment. The light absorption and wind drag feedbacks, however, are stronger than the albedo feedback. Overall, we find that the increase of sea surface temperatures and cooling subsurface mediated by cyanobacteria also modify ocean circulation patterns. Since the abundance of surface floating cyanobacteria is expected to increase in future, we recommend to include these biological-physical feedback mechanisms in the next generation of ocean climate models.

Hense, Inga; Sonntag, Sebastian

2014-05-01

248

A Distal ABA Responsive Element in AtNCED3 Promoter Is Required for Positive Feedback Regulation of ABA Biosynthesis in Arabidopsis  

PubMed Central

The plant hormone abscisic acid (ABA) plays a crucial role in plant development and responses to abiotic stresses. Recent studies indicate that a positive feedback regulation by ABA exists in ABA biosynthesis in plants under dehydration stress. To understand the molecular basis of this regulation, we analyzed the cis-elements of the AtNCED3 promoter in Arabidopsis. AtNCED3 encodes the first committed and highly regulated dioxygenase in the ABA biosynthetic pathway. Through delineated and mutagenesis analyses in stable-transformed Arabidopsis, we revealed that a distal ABA responsive element (ABRE: GGCACGTG, -2372 to -2364 bp) is required for ABA-induced AtNCED3 expression. By analyzing the AtNCED3 expression in ABRE binding protein ABF3 over-expression transgenic plants and knock-out mutants, we provide evidence that the ABA feedback regulation of AtNCED3 expression is not mediated by ABF3. PMID:24475264

Yang, Yan-Zhuo; Tan, Bao-Cai

2014-01-01

249

Simple mechanism combines positive locking and quick-release features  

NASA Technical Reports Server (NTRS)

For secure locking and quick release of two objects, this device uses a spring-loaded slotted bolt, locked in position by two retainer arms. When these retainer arms are freed from contact, the bolt is ejected and the objects released.

Clayton, L. B.

1964-01-01

250

A Positive Feedback Loop Links Opposing Functions of P-TEFb/Cdk9 and Histone H2B Ubiquitylation to Regulate Transcript Elongation in Fission Yeast  

PubMed Central

Transcript elongation by RNA polymerase II (RNAPII) is accompanied by conserved patterns of histone modification. Whereas histone modifications have established roles in transcription initiation, their functions during elongation are not understood. Mono-ubiquitylation of histone H2B (H2Bub1) plays a key role in coordinating co-transcriptional histone modification by promoting site-specific methylation of histone H3. H2Bub1 also regulates gene expression through an unidentified, methylation-independent mechanism. Here we reveal bidirectional communication between H2Bub1 and Cdk9, the ortholog of metazoan positive transcription elongation factor b (P-TEFb), in the fission yeast Schizosaccharomyces pombe. Chemical and classical genetic analyses indicate that lowering Cdk9 activity or preventing phosphorylation of its substrate, the transcription processivity factor Spt5, reduces H2Bub1 in vivo. Conversely, mutations in the H2Bub1 pathway impair Cdk9 recruitment to chromatin and decrease Spt5 phosphorylation. Moreover, an Spt5 phosphorylation-site mutation, combined with deletion of the histone H3 Lys4 methyltransferase Set1, phenocopies morphologic and growth defects due to H2Bub1 loss, suggesting independent, partially redundant roles for Cdk9 and Set1 downstream of H2Bub1. Surprisingly, mutation of the histone H2B ubiquitin-acceptor residue relaxes the Cdk9 activity requirement in vivo, and cdk9 mutations suppress cell-morphology defects in H2Bub1-deficient strains. Genome-wide analyses by chromatin immunoprecipitation also demonstrate opposing effects of Cdk9 and H2Bub1 on distribution of transcribing RNAPII. Therefore, whereas mutual dependence of H2Bub1 and Spt5 phosphorylation indicates positive feedback, mutual suppression by cdk9 and H2Bub1-pathway mutations suggests antagonistic functions that must be kept in balance to regulate elongation. Loss of H2Bub1 disrupts that balance and leads to deranged gene expression and aberrant cell morphologies, revealing a novel function of a conserved, co-transcriptional histone modification. PMID:22876190

Jacques, Pierre-Étienne; Pagé, Viviane; Nagy, Stephen; Racine, Ariane; St. Amour, Courtney V.; Zhang, Chao; Shokat, Kevan M.; Schwer, Beate; Robert, François; Fisher, Robert P.; Tanny, Jason C.

2012-01-01

251

Cloud CCN feedback  

SciTech Connect

Cloud microphysics affects cloud albedo precipitation efficiency and the extent of cloud feedback in response to global warming. Compared to other cloud parameters, microphysics is unique in its large range of variability and the fact that much of the variability is anthropogenic. Probably the most important determinant of cloud microphysics is the spectra of cloud condensation nuclei (CCN) which display considerable variability and have a large anthropogenic component. When analyzed in combination three field observation projects display the interrelationship between CCN and cloud microphysics. CCN were measured with the Desert Research Institute (DRI) instantaneous CCN spectrometer. Cloud microphysical measurements were obtained with the National Center for Atmospheric Research Lockheed Electra. Since CCN and cloud microphysics each affect the other a positive feedback mechanism can result.

Hudson, J.G.

1992-12-31

252

Academic Job Opportunities Multiple Faculty Positions in Mechanical Engineering  

E-print Network

of particular interest include, but are not limited to, high strain rate, impact dynamics, wave propagation of mechanics in biology, with emphasis on translational aspects of biomechanics in health and disease. Current strength of the department include fundamental aspects of cell, tissue and organismal biomechanics

Mofrad, Mohammad R. K.

253

Modeling the relativistic runaway electron avalanche and the feedback mechanism with GEANT4  

NASA Astrophysics Data System (ADS)

AbstractThis paper presents the first study that uses the GEometry ANd Tracking 4 (GEANT4) toolkit to do quantitative comparisons with other modeling results related to the production of terrestrial gamma ray flashes and high-energy particle emission from thunderstorms. We will study the relativistic runaway electron avalanche (RREA) and the relativistic <span class="hlt">feedback</span> process, as well as the production of bremsstrahlung photons from runaway electrons. The Monte Carlo simulations take into account the effects of electron ionization, electron by electron (Møller), and electron by positron (Bhabha) scattering as well as the bremsstrahlung process and pair production, in the 250 eV to 100 GeV energy range. Our results indicate that the multiplication of electrons during the development of RREAs and under the influence of <span class="hlt">feedback</span> are consistent with previous estimates. This is important to validate GEANT4 as a tool to model RREAs and <span class="hlt">feedback</span> in homogeneous electric fields. We also determine the ratio of bremsstrahlung photons to energetic electrons N?/Ne. We then show that the ratio has a dependence on the electric field, which can be expressed by the avalanche time ?(E) and the bremsstrahlung coefficient ?(?). In addition, we present comparisons of GEANT4 simulations performed with a "standard" and a "low-energy" physics list both validated in the 1 keV to 100 GeV energy range. This comparison shows that the choice of physics list used in GEANT4 simulations has a significant effect on the results.</p> <div class="credits"> <p class="dwt_author">Skeltved, Alexander Broberg; Østgaard, Nikolai; Carlson, Brant; Gjesteland, Thomas; Celestin, Sebastien</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">254</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://research.sabanciuniv.edu/22058/1/2013_RA394_ASC2013_0513_Merve.pdf"> <span id="translatedtitle">Micro <span class="hlt">Position</span> Control of a Designed 3-PRR Compliant <span class="hlt">Mechanism</span> Using Experimental Models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">Micro <span class="hlt">Position</span> Control of a Designed 3-PRR Compliant <span class="hlt">Mechanism</span> Using Experimental Models Merve Acer stage based on 3-PRR kinematic structure is designed to be used as a planar micro positioner, which is the accuracy of the dual laser <span class="hlt">position</span> sensor. Keywords-- compliant <span class="hlt">mechanism</span>, micro motion</p> <div class="credits"> <p class="dwt_author">Yanikoglu, Berrin</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">255</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2015IAUS..309..182C"> <span id="translatedtitle">Models of AGN <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The physical processes responsible of sweeping up the surrounding gas in the host galaxy of an AGN, and able in some circumstances to expel it from the galaxy, are not yet well known. The various <span class="hlt">mechanisms</span> are briefly reviewed: quasar or radio modes, either momentum-conserving outflows, energy-conserving outflows, or intermediate. They are confronted to observations, to know whether they can explain the M-sigma relation, quench the star formation or whether they can also provide some <span class="hlt">positive</span> <span class="hlt">feedback</span> and how the black hole accretion history is related to that of star formation.</p> <div class="credits"> <p class="dwt_author">Combes, Françcoise</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">256</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24996180"> <span id="translatedtitle">Serine phosphorylation on <span class="hlt">position</span> 1033 of vinculin impacts cellular <span class="hlt">mechanics</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">This study evaluates the influence of S1033 vinculin phosphorylation on the <span class="hlt">mechanical</span> properties of cells. We demonstrate that MEFvcl KO cells transfected with the non-phosphorylatable eGFP-vinculin mutant S1033A are of lower stiffness compared to MEFvcl Rescue and phospho-mimicking mutant S1033D cells, which were of similar stiffness. Analogous, 2D traction microscopy indicates that MEFvcl Rescue and MEF mutant S1033D cells generate similar strain energy, but mutant S1033A cells display ?50% less strain energy. Fluorescence recovery after photobleaching demonstrates that the recovery time for mutant S1033A was significantly lower compared to MEFvcl Rescue and mutant S1033D and that the mobile fraction was smaller for MEFvcl Rescue and mutant S1033D than for mutant S1033A cells. This indicates that serine phosphorylation is required for the activation of vinculin and force transmission in focal adhesions. PMID:24996180</p> <div class="credits"> <p class="dwt_author">Auernheimer, Vera; Goldmann, Wolfgang H</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-25</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">257</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/1012585"> <span id="translatedtitle">RHIC 10 Hz global orbit <span class="hlt">feedback</span> system</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the horizontal beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including a local beam <span class="hlt">feedback</span> system at each of the two experimental areas, reinforcing the magnet base support assembly, and a <span class="hlt">mechanical</span> servo <span class="hlt">feedback</span> system. However, the local <span class="hlt">feedback</span> system was insufficient because perturbation amplitudes outside the experimental areas were still problematic, and the <span class="hlt">mechanical</span> solutions are very expensive. A global 10 Hz orbit <span class="hlt">feedback</span> system consisting of 36 beam <span class="hlt">position</span> monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two 3.8 km circumference counter-rotating rings has been developed and commissioned in February 2011. A description of the system architecture and results with beam will be discussed.</p> <div class="credits"> <p class="dwt_author">Michnoff, R.; Arnold, L.; Carboni, L.; Cerniglia, P; Curcio, A.; DeSanto, L.; Folz, C.; Ho, C.; Hoff, L.; Hulsart, R.; Karl, R.; Luo, Y.; Liu, C.; MacKay, W.; Mahler, G.; Meng, W.; Mernick, K.; Minty, M.; Montag, C.; Olsen, R.; Piacentino, J.; Popken, P.; Przybylinski, R.; Ptitsyn, V.; Ritter, J.; Schoenfeld, R.; Thieberger, P.; Tuozzolo, J.; Weston, A.; White, J.; Ziminski, P.; Zimmerman, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-03-28</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">258</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://arxiv.org/pdf/1501.05655.pdf"> <span id="translatedtitle">Towards simulating star formation in turbulent high-z galaxies with <span class="hlt">mechanical</span> supernova <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary"><span class="hlt">Feedback</span> from supernovae is essential to understanding the self-regulation of star formation in galaxies. However, the efficacy of the process in a cosmological context remains unclear due to excessive radiative losses during the shock propagation. To better understand the impact of SN explosions on the evolution of galaxies, we perform a suite of high-resolution (12 pc), zoom-in cosmological simulations of a Milky Way-like galaxy at z=3 with adaptive mesh refinement. We find that SN explosions can efficiently regulate star formation, leading to the stellar mass and metallicity consistent with the observed mass-metallicity relation and stellar mass-halo mass relation at z~3. This is achieved by making three important changes to the classical <span class="hlt">feedback</span> scheme: i) the different phases of SN blast waves are modelled directly by injecting radial momentum expected at each stage, ii) the realistic time delay of SNe, commencing at as early as 3 Myr, is required to disperse very dense gas before a runaway collapse set...</p> <div class="credits"> <p class="dwt_author">Kimm, Taysun; Devriendt, Julien; Dubois, Yohan; Slyz, Adrianne</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">259</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25219309"> <span id="translatedtitle">The Arabidopsis NAC transcription factor NTL4 participates in a <span class="hlt">positive</span> <span class="hlt">feedback</span> loop that induces programmed cell death under heat stress conditions.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Programmed cell death (PCD) is an integral component of plant development and adaptation under adverse environmental conditions. Reactive oxygen species (ROS) are one of the most important players that trigger PCD in plants, and ROS-generating machinery is activated in plant cells undergoing PCD. The membrane-bound NAC transcription factor NTL4 has recently been proven to facilitate ROS production in response to drought stress in Arabidopsis. In this work, we show that NTL4 participates in a <span class="hlt">positive</span> <span class="hlt">feedback</span> loop that bursts ROS accumulation to modulate PCD under heat stress conditions. Heat stress induces NTL4 gene transcription and NTL4 protein processing. The level of hydrogen peroxide (H2O2) was elevated in 35S:4?C transgenic plants that overexpress a transcriptionally active nuclear NTL4 form but significantly reduced in NTL4-deficient ntl4 mutants under heat stress conditions. In addition, heat stress-induced cell death was accelerated in the 35S:4?C transgenic plants but decreased in the ntl4 mutants. Notably, H2O2 triggers NTL4 gene transcription and NTL4 protein processing under heat stress conditions. On the basis of these findings, we conclude that NTL4 modulates PCD through a ROS-mediated <span class="hlt">positive</span> <span class="hlt">feedback</span> control under heat stress conditions, possibly providing an adaptation strategy by which plants ensure their survival under extreme heat stress conditions. PMID:25219309</p> <div class="credits"> <p class="dwt_author">Lee, Sangmin; Lee, Hyo-Jun; Huh, Sung Un; Paek, Kyung-Hee; Ha, Jun-Ho; Park, Chung-Mo</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">260</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4077591"> <span id="translatedtitle">A novel bidirectional <span class="hlt">positive-feedback</span> loop between Wnt–?-catenin and EGFR–ERK plays a role in context-specific modulation of epithelial tissue regeneration</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">ABSTRACT By operating as both a subunit of the cadherin complex and a key component of Wnt signalling, ?-catenin acts as the lynchpin between cell–cell contact and transcriptional regulation of proliferation, coordinating epithelial tissue homeostasis and regeneration. The integration of multiple growth-regulatory inputs with ?-catenin signalling has been observed in cancer-derived cells, yet the existence of pathway crosstalk in normal cells is unknown. Using a highly regenerative normal human epithelial culture system that displays contact inhibition, we demonstrate that the receptor tyrosine kinase (RTK)-driven MAPK and Wnt–?-catenin signalling axes form a bidirectional <span class="hlt">positive-feedback</span> loop to drive cellular proliferation. We show that ?-catenin both drives and is regulated by proliferative signalling cues, and its downregulation coincides with the switch from proliferation to contact-inhibited quiescence. We reveal a novel contextual interrelationship whereby <span class="hlt">positive</span> and negative <span class="hlt">feedback</span> between three major signalling pathways – EGFR–ERK, PI3K–AKT and Wnt–?-catenin – enable autocrine-regulated tissue homeostasis as an emergent property of physical interactions between cells. Our work has direct implications for normal epithelial tissue homeostasis and provides insight as to how dysregulation of these pathways could drive excessive and sustained cellular growth in disease. PMID:24816560</p> <div class="credits"> <p class="dwt_author">Georgopoulos, Nikolaos T.; Kirkwood, Lisa A.; Southgate, Jennifer</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_12");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return 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title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">261</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1130271"> <span id="translatedtitle">CGILS: Results from the First Phase of an International Project to Understand the Physical <span class="hlt">Mechanisms</span> of Low Cloud <span class="hlt">Feedbacks</span> in Single Column Models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Large Eddy Models (LES) and Single Column Models (SCM) are used in a surrogate climate change 101 to investigate the physical <span class="hlt">mechanism</span> of low cloud <span class="hlt">feedbacks</span> in climate models. Enhanced surface-102 driven boundary layer turbulence and shallow convection in a warmer climate are found to be 103 dominant <span class="hlt">mechanisms</span> in SCMs.</p> <div class="credits"> <p class="dwt_author">Zhang, Minghua; Bretherton, Christopher S.; Blossey, Peter; Austin, Phillip A.; Bacmeister, J.; Bony, Sandrine; Brient, Florent; Cheedela, Suvarchal K.; Cheng, Anning; Del Genio, Anthony D.; De Roode, Stephan R.; Endo , Satoshi; Franklin, Charmaine N.; Golaz, Jean-Christophe; Hannay, Cecile; Heus, Thijs; Isotta, Francesco A.; Jean-Louis, Dufresne; Kang, In-Sik; Kawai, Hideaki; Koehler, M.; Larson, Vincent E.; Liu, Yangang; Lock, Adrian; Lohmann, U.; Khairoutdinov, Marat; Molod, Andrea M.; Neggers, Roel; Rasch, Philip J.; Sandu, Irina; Senkbeil, Ryan; Siebesma, A. P.; Siegenthaler-Le Drian, Colombe; Stevens, Bjorn; Suarez, Max; Xu, Kuan-Man; Von Salzen, Knut; Webb, Mark; Wolf, Audrey; Zhao, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-26</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">262</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20060054397&hterms=feedback&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dfeedback"> <span id="translatedtitle">The Role of Possible <span class="hlt">Feedback</span> <span class="hlt">Mechanisms</span> in the Effects of Altered Gravity on Formation and Function of Gravireceptors of Mollusks and Fish</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The variety of the effects of altered gravity (AG) on development and function of gravireceptors cannot be explained by simple <span class="hlt">feedback</span> <span class="hlt">mechanism</span> that correlates gravity level and weight of test mass. The reaction of organisms to the change of gravity depends on the phase of their development. To predict this reaction we need to know the details of the <span class="hlt">mechanisms</span> of gravireceptor formation</p> <div class="credits"> <p class="dwt_author">Kondrachuk, Alexander V.; Boyle, Richard D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">263</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24552238"> <span id="translatedtitle">Cognitive <span class="hlt">mechanisms</span> linking low trait <span class="hlt">positive</span> affect to depressive symptoms: a prospective diary study.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Low trait <span class="hlt">positive</span> affect represents an affective vulnerability to depression, but little research has examined <span class="hlt">mechanisms</span> linking low trait <span class="hlt">positive</span> affect to depressive symptoms. The current study investigated whether the cognitive strategies of dampening and <span class="hlt">positive</span> rumination mediated the prospective association between low trait <span class="hlt">positive</span> affect and depressive symptoms. Participants were 209 undergraduate students who participated in an eight-week online study. Depressive symptoms and trait temperament were assessed at baseline, followed by seven weekly questionnaires which assessed cognitive strategies in response to weekly events and weekly depressive symptoms. Data were analysed using multilevel modelling following the mediation approach proposed by Nezlek. Results indicated that low trait <span class="hlt">positive</span> affect significantly predicted less <span class="hlt">positive</span> rumination but not greater dampening in response to weekly <span class="hlt">positive</span> events. Less <span class="hlt">positive</span> rumination in response to weekly <span class="hlt">positive</span> events partially mediated the association between low trait <span class="hlt">positive</span> affect and greater depressive symptoms across the study. PMID:24552238</p> <div class="credits"> <p class="dwt_author">Harding, Kaitlin A; Hudson, Melissa R; Mezulis, Amy</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">264</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/913701"> <span id="translatedtitle"><span class="hlt">Mechanism</span> of <span class="hlt">Positive</span> Allosteric Modulators Acting on AMPA Receptors</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Ligand-gated ion channels involved in the modulation of synaptic strength are the AMPA, kainate, and NMDA glutamate receptors. Small molecules that potentiate AMPA receptor currents relieve cognitive deficits caused by neurodegenerative diseases such as Alzheimer's disease and show promise in the treatment of depression. Previously, there has been limited understanding of the molecular <span class="hlt">mechanism</span> of action for AMPA receptor potentiators. Here we present cocrystal structures of the glutamate receptor GluR2 S1S2 ligand-binding domain in complex with aniracetam [1-(4-methoxybenzoyl)-2-pyrrolidinone] or CX614 (pyrrolidino-1, 3-oxazino benzo-1, 4-dioxan-10-one), two AMPA receptor potentiators that preferentially slow AMPA receptor deactivation. Both potentiators bind within the dimer interface of the nondesensitized receptor at a common site located on the twofold axis of molecular symmetry. Importantly, the potentiator binding site is adjacent to the 'hinge' in the ligand-binding core 'clamshell' that undergoes conformational rearrangement after glutamate binding. Using rapid solution exchange, patch-clamp electrophysiology experiments, we show that point mutations of residues that interact with potentiators in the cocrystal disrupt potentiator function. We suggest that the potentiators slow deactivation by stabilizing the clamshell in its closed-cleft, glutamate-bound conformation.</p> <div class="credits"> <p class="dwt_author">Jin,R.; Clark, S.; Weeks, A.; Dudman, J.; Gouaux, E.; Partin, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">265</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3237626"> <span id="translatedtitle">Effects of dynein on microtubule <span class="hlt">mechanics</span> and centrosome <span class="hlt">positioning</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">To determine forces on intracellular microtubules, we measured shape changes of individual microtubules following laser severing in bovine capillary endothelial cells. Surprisingly, regions near newly created minus ends increased in curvature following severing, whereas regions near new microtubule plus ends depolymerized without any observable change in shape. With dynein inhibited, regions near severed minus ends straightened rapidly following severing. These observations suggest that dynein exerts a pulling force on the microtubule that buckles the newly created minus end. Moreover, the lack of any observable straightening suggests that dynein prevents lateral motion of microtubules. To explain these results, we developed a model for intracellular microtubule <span class="hlt">mechanics</span> that predicts the enhanced buckling at the minus end of a severed microtubule. Our results show that microtubule shapes reflect a dynamic force balance in which dynein motor and friction forces dominate elastic forces arising from bending moments. A centrosomal array of microtubules subjected to dynein pulling forces and resisted by dynein friction is predicted to center on the experimentally observed time scale, with or without the pushing forces derived from microtubule buckling at the cell periphery. PMID:22013075</p> <div class="credits"> <p class="dwt_author">Wu, Jun; Misra, Gaurav; Russell, Robert J.; Ladd, Anthony J. C.; Lele, Tanmay P.; Dickinson, Richard B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">266</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=feedback&id=EJ1032053"> <span id="translatedtitle">Audio <span class="hlt">Feedback</span> -- Better <span class="hlt">Feedback</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">National Student Survey (NSS) results show that many students are dissatisfied with the amount and quality of <span class="hlt">feedback</span> they get for their work. This study reports on two case studies in which we tried to address these issues by introducing audio <span class="hlt">feedback</span> to one undergraduate (UG) and one postgraduate (PG) class, respectively. In case study one…</p> <div class="credits"> <p class="dwt_author">Voelkel, Susanne; Mello, Luciane V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">267</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013ExFl...54.1480P"> <span id="translatedtitle">Experimental investigations of a trailing edge noise <span class="hlt">feedback</span> <span class="hlt">mechanism</span> on a NACA 0012 airfoil</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Discrete frequency tones in the trailing edge noise spectra of NACA 0012 airfoils are investigated with the Coherent Particle Velocity method. The Reynolds number and angle of attack range, in which these discrete frequency tones are present, are consistent with published results. The discrete tones are composed of a main tone and a set of regularly spaced side peaks resulting in a ladder-type structure for the dependency on the free stream velocity. The occurrence of this discrete frequency noise could be attributed to the presence of a laminar boundary layer on the pressure side opening up into a separation bubble near the trailing edge, which was visualized using oil flow. Wall pressure measurements close to the trailing edge revealed a strong spanwise and streamwise coherence of the flow structures inside this laminar separation bubble. The laminar vortex shedding frequencies inferred from the streamwise velocity fluctuations, which were evaluated from hot-wire measurements at the trailing edge, were seen to coincide with the discrete tone frequencies observed in the trailing edge noise spectra. Previous findings on discrete frequency tones for airfoils with laminar boundary layers up to the trailing edge hint at the existence of a global <span class="hlt">feedback</span> loop. Hence, sound waves generated at the trailing edge feed back into the laminar boundary layer upstream by receptivity and are, then, convectively amplified downstream. The most dominant amplification of these disturbance modes is observed inside the laminar separation bubble. Therefore, the frequencies of the most pronounced tones in the trailing edge noise spectra are in the frequency range of the convectively most amplified disturbance modes. Modifying the receptivity behavior of the laminar boundary layer on the pressure side by means of very thin, two-dimensional roughness elements considerably changes the discrete tone frequencies. For roughness elements placed closer to the trailing edge, the main tone frequency was seen to decrease, while the frequency spacing in-between two successive tones increased. Based on the stability characteristics of the laminar boundary layer and the characteristics of the upstream traveling sound wave, a method for predicting the discrete tone frequencies was developed showing good agreement with the measured results. Hence, with a controlled modification of the laminar boundary layer receptivity behavior, the existence of the proposed <span class="hlt">feedback</span> loop could be confirmed. At the same time, no significant influence of a second <span class="hlt">feedback</span> loop previously proposed for the suction side of the NACA 0012 airfoil was observed neither by influencing the boundary layer with a receptivity-roughness element nor by tripping the boundary layer at the leading edge.</p> <div class="credits"> <p class="dwt_author">Plogmann, B.; Herrig, A.; Würz, W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">268</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53369977"> <span id="translatedtitle">Large-Area Phase-Contrast X-ray Imaging System Using a Two-Crystal X-ray Interferometer-Development of an Interference-Pattern-Based <span class="hlt">Feedback</span> <span class="hlt">Positioning</span> System</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">To more accurately suppress the phase fluctuation of the interference beams of a large-area phase-contrast X-ray imaging system using a two-crystal X-ray interferometer, a new <span class="hlt">feedback</span> <span class="hlt">positioning</span> system (FPS) has been developed and applied. The motion of interference patterns replaces the intensity of the interference beam in a small region as the <span class="hlt">feedback</span> signal used in controlling the rotation of</p> <div class="credits"> <p class="dwt_author">A. Yoneyama; T. Takeda; Y. Tsuchiya; J. Wu; T. T. Lwin; K. Hyodo</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">269</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1851915"> <span id="translatedtitle">A 3-SYNAPSE <span class="hlt">POSITIVE</span> <span class="hlt">FEEDBACK</span> LOOP REGULATES THE EXCITABILITY OF AN INTERNEURON CRITICAL FOR SENSITIZATION IN THE LEECH</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Sensitization of reflexive shortening in the leech has been linked to serotonin (5-HT)-induced changes in the excitability of a single interneuron, the S cell. This neuron is necessary for sensitization and complete dishabituation of reflexive shortening, during which it contributes to the sensory-motor reflex. The S cell does not contain 5-HT, which is released primarily from the Retzius (R) cells, whose firing enhances S-cell excitability. Here we show that the S cell excites the R cells, mainly via a fast disynaptic pathway in which the first synapse is the electrical junction between the S cell and the coupling interneurons, and the second synapse is a glutamatergic synapse of the coupling interneurons onto the R cells. The S cell-triggered excitatory postsynaptic potential in the R cell diminishes and nearly disappears in elevated concentrations of divalent cations because the coupling interneurons become inexcitable under these conditions. Serotonin released from the R cells feeds back upon the S cell and increases its excitability by activating a 5-HT7-like receptor; 5-methoxytryptamine (5-MeOT; 10 ?M) mimics the effects of 5-HT on S cell excitability, and effects of both 5-HT and 5-MeOT are blocked by pimozide (10 ?M) and SB-269970 (5 ?M). This <span class="hlt">feedback</span> loop may be critical for the full expression of sensitization of reflexive shortening. PMID:16571760</p> <div class="credits"> <p class="dwt_author">Crisp, Kevin M.; Muller, Kenneth J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">270</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012GeoRL..39.4701K"> <span id="translatedtitle">Warm Eocene climate enhanced petroleum generation from Cretaceous source rocks: A potential climate <span class="hlt">feedback</span> <span class="hlt">mechanism</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Earth surface temperatures, including in the deep sea increased by 5-10°C from the late Paleocene ca. 58 Myr ago to the Early Eocene Climatic Optimum (EECO) centered at about 51 Myr ago. A large (˜2.5‰) drop in ?13C of carbonate spans much of this interval. This suggests a long-term increase in the net flux of 13C-depleted carbon to the ocean and atmosphere that is difficult to explain by changes in surficial carbon cycling alone. We reveal a relationship between surface temperature increase and increased petroleum generation in sedimentary basins operating on 100 kyr to Myr time scales. We propose that early Eocene warming has led to a synchronization of periods of maximum petroleum generation and enhanced generation in otherwise unproductive basins through extension of the volume of source rock within the oil and gas window across hundreds of sedimentary basins globally. Modelling the thermal evolution of four sedimentary basins in the southwest Pacific predicted an up to 50% increase in petroleum generation that would have significantly increased leakage of light hydrocarbons and oil degeneration products into the atmosphere. Extrapolating our modelling results to hundreds of sedimentary basins worldwide suggests that globally increased leakage could have caused a climate <span class="hlt">feedback</span> effect, driving or enhancing early Eocene climate warming.</p> <div class="credits"> <p class="dwt_author">Kroeger, K. F.; Funnell, R. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">271</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23385367"> <span id="translatedtitle">Plant-soil <span class="hlt">feedbacks</span> and soil sickness: from <span class="hlt">mechanisms</span> to application in agriculture.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Negative plant-soil <span class="hlt">feedbacks</span> play an important role in soil sickness, which is one of the factors limiting the sustainable development of intensive agriculture. Various factors, such as the buildup of pests in the soil, disorder in physico-chemical soil properties, autotoxicity, and other unknown factors may contribute to soil sickness. A range of autotoxins have been identified, and these exhibit their allelopathic potential by influencing cell division, water and ion uptake, dark respiration, ATP synthesis, redox homeostasis, gene expression, and defense responses. Meanwhile, there are great interspecific and intraspecific differences in the uptake and accumulation of autotoxins, which contribute to the specific differences in growth in response to different autotoxins. Importantly, the autotoxins also influence soil microbes and vice versa, leading to an increased or decreased degree of soil sickness. In many cases, autotoxins may enhance soilborne diseases by predisposing the roots to infection by soilborne pathogens through a direct biochemical and physiological effect. Some approaches, such as screening for low autotoxic potential and disease-resistant genotypes, proper rotation and intercropping, proper soil and plant residue management, adoption of resistant plant species as rootstocks, introduction of beneficial microbes, physical removal of phytotoxins, and soil sterilization, are proposed. We discuss the challenges that we are facing and possible approaches to these. PMID:23385367</p> <div class="credits"> <p class="dwt_author">Huang, Li-Feng; Song, Liu-Xia; Xia, Xiao-Jian; Mao, Wei-Hua; Shi, Kai; Zhou, Yan-Hong; Yu, Jing-Quan</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">272</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.knmi.nl/~siebesma/PUBS/zhang_siebesma_13_JAMES.pdf"> <span id="translatedtitle">CGILS: Results from the first phase of an international project to understand the physical <span class="hlt">mechanisms</span> of low cloud <span class="hlt">feedbacks</span> in single</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">: shallow cumulus, cumulus under stratocumulus, and well- mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated simulated negative cloud <span class="hlt">feedback</span> in the well- mixed coastal stratus/stratocumulus regime, and <span class="hlt">positive</span></p> <div class="credits"> <p class="dwt_author">Siebesma, Pier</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">273</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49994936"> <span id="translatedtitle">Design of <span class="hlt">mechanisms</span> for cooperation among multiple <span class="hlt">position</span>-controlled robots</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper proposes a strategy for handling a single object by cooperation of multiple robots controlled by PID <span class="hlt">position</span> controllers. Since such a cooperative system has <span class="hlt">mechanical</span> closed loops, installation of free joints or flexibility among robots is necessary to avoid excessive inner forces caused by the <span class="hlt">positioning</span> error of each robot. First, the essential kinematic conditions to achieve the</p> <div class="credits"> <p class="dwt_author">Hisashi OSUMI; Tamio ARAI</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">274</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/279716"> <span id="translatedtitle">Low noise YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} SQUID magnetometers operated with additional <span class="hlt">positive</span> <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Three magnetometers based on dc superconducting quantum interference devices (SQUIDs) fabricated from YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} have been operated in a magnetically shielded room using a flux-locked loop involving additional <span class="hlt">positive</span> <span class="hlt">feedback</span> with bias current reversal. Two of these devices, integrated multiloop dc SQUIDs with outer diameters of 7 mm, achieved white noise levels of 10 fT/{radical}Hz for bicrystal junctions and 30 fT/{radical}Hz for step-edge junctions. The third magnetometer involved a flux transformer with a 10{times}10 mm{sup 2} pickup coil connected to a 16-turn input coil which was inductively coupled to a bicrystal SQUID. This device achieved a white noise of 16.2 fT/{radical}Hz. High quality magnetocardiograms were obtained without signal averaging. {copyright} {ital 1996 American Institute of Physics.}</p> <div class="credits"> <p class="dwt_author">Drung, D.; Dantsker, E.; Ludwig, F.; Koch, H. [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, 10587 Berlin (Germany)] [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, 10587 Berlin (Germany); Kleiner, R.; Clarke, J. [Department of Physics, University of California, Berkeley] [Department of Physics, University of California, Berkeley; [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Krey, S.; Reimer, D. [Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany)] [Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); David, B.; Doessel, O. [Philips Research Laboratories, Dept. Technical Systems, Roentgenstrasse 24-26, 22335 Hamburg (Germany)] [Philips Research Laboratories, Dept. Technical Systems, Roentgenstrasse 24-26, 22335 Hamburg (Germany)</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">275</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.3804K"> <span id="translatedtitle">Warm Eocene climate enhanced petroleum generation from Cretaceous source rocks - a potential climate <span class="hlt">feedback</span> <span class="hlt">mechanism</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Surface and deep sea temperatures from late Paleocene to early Eocene until the Early Eocene climatic Optimum increased by 5 - 10° C. This change was associated with a negative ?13C trend which implies major changes in global carbon cycling and enrichment of surface systems in isotopically light carbon. The degree of change in sedimentary ?13C requires emission of >10,000 gigatonnes of isotopically light carbon into the ocean. We reveal a relationship between global warming and increased petroleum generation in sedimentary basins operating on 100 kyr to Myr time scales that may explain the observed isotope shift. We use TEX86-based surface temperature data1 to predict how change in surface temperature influences the temperature evolution and resultant petroleum generation in four southwest Pacific sedimentary basins. Models predict an up to 50% increase in oil and gas expulsion rates in response to the increase in temperatures from late Paleocene to early Eocene in the region. Such an increase in petroleum generation would have significantly increased leakage of light hydrocarbons and oil degeneration products into surface systems. We propose that our modelling results are representative of a large number of sedimentary basins world-wide and that early Eocene warming has led to a synchronization of periods of maximum petroleum generation and enhanced generation in otherwise unproductive basins through extension of the volume of source rock within the oil and gas window. Extrapolating our modelling results to hundreds of sedimentary basins worldwide suggests that globally increased leakage could have led to the release of an amount of CH4, CO2 and light petroleum components into surface systems compatible with the observed changes in ?13C. We further suggest that this is a significant <span class="hlt">feedback</span> effect, enhancing early Eocene climate warming. 1Bijl, P. K., S. Schouten, A. Sluijs, G.-J. Reichart, J. C. Zachos, and H. Brinkhuis (2009), Early Palaeogene temperature evolution of the southwest Pacific Ocean, Nature, 461, 776-779.</p> <div class="credits"> <p class="dwt_author">Kroeger, K. F.; Funnell, R. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">276</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19890017188&hterms=ri+yun&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dri%2Byun"> <span id="translatedtitle">Nonlinear <span class="hlt">feedback</span> control of multiple robot arms</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Multiple coordinated robot arms are modeled by considering the arms: (1) as closed kinematic chains, and (2) as a force constrained <span class="hlt">mechanical</span> system working on the same object simultaneously. In both formulations a new dynamic control method is discussed. It is based on a <span class="hlt">feedback</span> linearization and simultaneous output decoupling technique. Applying a nonlinear <span class="hlt">feedback</span> and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, by choosing a general output equation, researchers can superimpose the <span class="hlt">position</span> and velocity error <span class="hlt">feedback</span> with the force-torque error <span class="hlt">feedback</span> in the task space simultaneously.</p> <div class="credits"> <p class="dwt_author">Tarn, T. J.; Yun, X.; Bejczy, A. K.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">277</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://cdsweb.cern.ch/record/1700221"> <span id="translatedtitle">How Community <span class="hlt">Feedback</span> Shapes User Behavior</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">Social media systems rely on user <span class="hlt">feedback</span> and rating <span class="hlt">mechanisms</span> for personalization, ranking, and content filtering. However, when users evaluate content contributed by fellow users (e.g., by liking a post or voting on a comment), these evaluations create complex social <span class="hlt">feedback</span> effects. This paper investigates how ratings on a piece of content affect its author's future behavior. By studying four large comment-based news communities, we find that negative <span class="hlt">feedback</span> leads to significant behavioral changes that are detrimental to the community. Not only do authors of negatively-evaluated content contribute more, but also their future posts are of lower quality, and are perceived by the community as such. Moreover, these authors are more likely to subsequently evaluate their fellow users negatively, percolating these effects through the community. In contrast, <span class="hlt">positive</span> <span class="hlt">feedback</span> does not carry similar effects, and neither encourages rewarded authors to write more, nor improves the quality of their posts. Interes...</p> <div class="credits"> <p class="dwt_author">Cheng, Justin; Leskovec, Jure</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">278</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/16086302"> <span id="translatedtitle">Whole-body magnetic resonance imaging featuring moving table continuous data acquisition with high-precision <span class="hlt">position</span> <span class="hlt">feedback</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A novel setup for whole-body MR imaging with moving table continuous data acquisition has been developed and evaluated. The setup features a manually <span class="hlt">positioned</span> moving table platform with integrated phased-array surface radiofrequency coils. A high-precision laser <span class="hlt">position</span> sensor was integrated into the system to provide real-time <span class="hlt">positional</span> data that were used to compensate for nonlinear manual table translation. This setup enables continuous 2D and 3D whole-body data acquisition during table movement with surface coil image quality. The concept has been successfully evaluated with whole-body steady-state free precession (TrueFISP) anatomic imaging in five healthy volunteers. Seamless coronal and sagittal slices of continually acquired whole-body data during table movement were accurately reconstructed. The proposed strategy is potentially useful for a variety of applications, including whole-body metastasis screening, whole-body MR angiography, large field-of-view imaging in short bore systems, and for moving table applications during MR-guided interventions. PMID:16086302</p> <div class="credits"> <p class="dwt_author">Zenge, Michael O; Ladd, Mark E; Vogt, Florian M; Brauck, Katja; Barkhausen, Joerg; Quick, Harald H</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">279</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://lgmacweb.env.uea.ac.uk/ajw/Reprints/Ridgwell_and_Watson_Paleoceanogr_2002.pdf"> <span id="translatedtitle"><span class="hlt">Feedback</span> between aeolian dust, climate, and atmospheric CO2 in glacial time</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">, in turn, climate is responsive to the dust due to iron fertilization. This <span class="hlt">positive</span> <span class="hlt">feedback</span> may mean. The <span class="hlt">mechanism</span> for this is ``iron fertil- ization'' of the biota in the Southern Ocean [Watson et al., 2000</p> <div class="credits"> <p class="dwt_author">Watson, Andrew</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">280</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19910015297&hterms=HRAM&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHRAM"> <span id="translatedtitle">SIRTF/IRS cryogenic grating drive <span class="hlt">mechanism</span> (ARC second <span class="hlt">positioning</span> at 4 K)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The requirements, design, and test results of a grating drive <span class="hlt">mechanism</span> for the Infrared Spectrograph (IRS) science instrument on the proposed superfluid helium-cooled Space Infrared Telescope Facility (SIRTF) are described. The IRS grating drive <span class="hlt">mechanism</span>, tested in the fall of 1989, satisfied all performance requirements in vacuum at 4 K. Measured <span class="hlt">mechanism</span> performance included: 1.4 arc sec root-mean-square (rms) error <span class="hlt">positioning</span> resolution; 2.2 arc sec rms <span class="hlt">position</span> repeatability error, less than 10 millijoules/deg dissipated power; and 170 deg angular range of travel. <span class="hlt">Mechanisms</span> that precisely <span class="hlt">position</span> optical elements at very low cryogenic temperatures (at/below 4 K) are vital to the operating success of a number of proposed infrared scientific instruments like those in SIRTF.</p> <div class="credits"> <p class="dwt_author">Kubitschek, Michael J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1991-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" 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<div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www4.ncsu.edu/~msolufse/olufsenIFAC2.pdf"> <span id="translatedtitle">On the Track of Syncope induced by Orthostatic Stress -<span class="hlt">Feedback</span> <span class="hlt">Mechanisms</span> Regulating the Cardiovascular System</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">the Cardiovascular System Ottesen JT.* and Olufsen MS.** *Roskilde University, 4000 Roskilde, Denmark (Tel: (+45 4674-mail: msolufse@unity.ncsu.edu) Abstract: A physiological realistic model of the controlled cardiovascular system. It turns out that this <span class="hlt">mechanical</span> effect is significant. Keywords: Cardiovascular, control, sit</p> <div class="credits"> <p class="dwt_author">Olufsen, Mette Sofie</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">282</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25121971"> <span id="translatedtitle"><span class="hlt">Mechanical</span> cell-matrix <span class="hlt">feedback</span> explains pairwise and collective endothelial cell behavior in vitro.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">In vitro cultures of endothelial cells are a widely used model system of the collective behavior of endothelial cells during vasculogenesis and angiogenesis. When seeded in an extracellular matrix, endothelial cells can form blood vessel-like structures, including vascular networks and sprouts. Endothelial morphogenesis depends on a large number of chemical and <span class="hlt">mechanical</span> factors, including the compliancy of the extracellular matrix, the available growth factors, the adhesion of cells to the extracellular matrix, cell-cell signaling, etc. Although various computational models have been proposed to explain the role of each of these biochemical and biomechanical effects, the understanding of the <span class="hlt">mechanisms</span> underlying in vitro angiogenesis is still incomplete. Most explanations focus on predicting the whole vascular network or sprout from the underlying cell behavior, and do not check if the same model also correctly captures the intermediate scale: the pairwise cell-cell interactions or single cell responses to ECM <span class="hlt">mechanics</span>. Here we show, using a hybrid cellular Potts and finite element computational model, that a single set of biologically plausible rules describing (a) the contractile forces that endothelial cells exert on the ECM, (b) the resulting strains in the extracellular matrix, and (c) the cellular response to the strains, suffices for reproducing the behavior of individual endothelial cells and the interactions of endothelial cell pairs in compliant matrices. With the same set of rules, the model also reproduces network formation from scattered cells, and sprouting from endothelial spheroids. Combining the present <span class="hlt">mechanical</span> model with aspects of previously proposed <span class="hlt">mechanical</span> and chemical models may lead to a more complete understanding of in vitro angiogenesis. PMID:25121971</p> <div class="credits"> <p class="dwt_author">van Oers, René F M; Rens, Elisabeth G; LaValley, Danielle J; Reinhart-King, Cynthia A; Merks, Roeland M H</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">283</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4133044"> <span id="translatedtitle"><span class="hlt">Mechanical</span> Cell-Matrix <span class="hlt">Feedback</span> Explains Pairwise and Collective Endothelial Cell Behavior In Vitro</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">In vitro cultures of endothelial cells are a widely used model system of the collective behavior of endothelial cells during vasculogenesis and angiogenesis. When seeded in an extracellular matrix, endothelial cells can form blood vessel-like structures, including vascular networks and sprouts. Endothelial morphogenesis depends on a large number of chemical and <span class="hlt">mechanical</span> factors, including the compliancy of the extracellular matrix, the available growth factors, the adhesion of cells to the extracellular matrix, cell-cell signaling, etc. Although various computational models have been proposed to explain the role of each of these biochemical and biomechanical effects, the understanding of the <span class="hlt">mechanisms</span> underlying in vitro angiogenesis is still incomplete. Most explanations focus on predicting the whole vascular network or sprout from the underlying cell behavior, and do not check if the same model also correctly captures the intermediate scale: the pairwise cell-cell interactions or single cell responses to ECM <span class="hlt">mechanics</span>. Here we show, using a hybrid cellular Potts and finite element computational model, that a single set of biologically plausible rules describing (a) the contractile forces that endothelial cells exert on the ECM, (b) the resulting strains in the extracellular matrix, and (c) the cellular response to the strains, suffices for reproducing the behavior of individual endothelial cells and the interactions of endothelial cell pairs in compliant matrices. With the same set of rules, the model also reproduces network formation from scattered cells, and sprouting from endothelial spheroids. Combining the present <span class="hlt">mechanical</span> model with aspects of previously proposed <span class="hlt">mechanical</span> and chemical models may lead to a more complete understanding of in vitro angiogenesis. PMID:25121971</p> <div class="credits"> <p class="dwt_author">LaValley, Danielle J.; Reinhart-King, Cynthia A.; Merks, Roeland M. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">284</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/12614273"> <span id="translatedtitle">Eventum <span class="hlt">Mechanics</span> of Quantum Trajectories: Continual Measurements, Quantum Predictions and <span class="hlt">Feedback</span> Control</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Quantum <span class="hlt">mechanical</span> systems exhibit an inherently probabilistic nature upon\\u000ameasurement which excludes in principle the singular direct observability\\u000acontinual case. Quantum theory of time continuous measurements and quantum\\u000aprediction theory, developed by the author on the basis of an\\u000aindependent-increment model for quantum noise and nondemolition causality\\u000aprinciple in the 80's, solves this problem allowing continual quantum\\u000apredictions and reducing</p> <div class="credits"> <p class="dwt_author">VIACHESLAV P BELAVKIN</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">285</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4177813"> <span id="translatedtitle">SPDEF Inhibits Prostate Carcinogenesis by Disrupting a <span class="hlt">Positive</span> <span class="hlt">Feedback</span> Loop in Regulation of the Foxm1 Oncogene</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">SAM-pointed domain-containing ETS transcription factor (SPDEF) is expressed in normal prostate epithelium. While its expression changes during prostate carcinogenesis (PCa), the role of SPDEF in prostate cancer remains controversial due to the lack of genetic mouse models. In present study, we generated transgenic mice with the loss- or gain-of-function of SPDEF in prostate epithelium to demonstrate that SPDEF functions as tumor suppressor in prostate cancer. Loss of SPDEF increased cancer progression and tumor cell proliferation, whereas over-expression of SPDEF in prostate epithelium inhibited carcinogenesis and reduced tumor cell proliferation in vivo and in vitro. Transgenic over-expression of SPDEF inhibited mRNA and protein levels of Foxm1, a transcription factor critical for tumor cell proliferation, and reduced expression of Foxm1 target genes, including Cdc25b, Cyclin B1, Cyclin A2, Plk-1, AuroraB, CKS1 and Topo2alpha. Deletion of SPDEF in transgenic mice and cultures prostate tumor cells increased expression of Foxm1 and its target genes. Furthermore, an inverse correlation between SPDEF and Foxm1 levels was found in human prostate cancers. The two-gene signature of low SPDEF and high FoxM1 predicted poor survival in prostate cancer patients. Mechanistically, SPDEF bound to, and inhibited transcriptional activity of Foxm1 promoter by interfering with the ability of Foxm1 to activate its own promoter through auto-regulatory site located in the ?745/?660 bp Foxm1 promoter region. Re-expression of Foxm1 restored cellular proliferation in the SPDEF-<span class="hlt">positive</span> cancer cells and rescued progression of SPDEF-<span class="hlt">positive</span> tumors in mouse prostates. Altogether, SPDEF inhibits prostate carcinogenesis by preventing Foxm1-regulated proliferation of prostate tumor cells. The present study identified novel crosstalk between SPDEF tumor suppressor and Foxm1 oncogene and demonstrated that this crosstalk is required for tumor cell proliferation during progression of prostate cancer in vivo. PMID:25254494</p> <div class="credits"> <p class="dwt_author">Ustiyan, Vladimir; Le, Tien; Fulford, Logan; Sridharan, Anusha; Medvedovic, Mario; Kalinichenko, Vladimir V.; Whitsett, Jeffrey A.; Kalin, Tanya V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">286</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4294389"> <span id="translatedtitle">STAT3 inhibition suppresses proliferation of retinoblastoma through down-regulation of <span class="hlt">positive</span> <span class="hlt">feedback</span> loop of STAT3/miR-17-92 clusters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Retinoblastoma, the most common intraocular malignant tumor in children, is characterized by the loss of both functional alleles of RB1 gene, which however alone cannot maintain malignant characteristics of retinoblastoma cells. Nevertheless, the investigation of other molecular aberrations such as matrix metalloproteinases (MMPs) and miRNAs is still lacking. In this study, we demonstrate that STAT3 is activated in retinoblastoma cells, Ki67-<span class="hlt">positive</span> areas of in vivo orthotopic tumors in BALB/c nude mice, and human retinoblastoma tissues of the advanced stage. Furthermore, target genes of STAT3 including BCL2, BCL2L1, BIRC5, and MMP9 are up-regulated in retinoblastoma cells compared to other retinal constituent cells. Interestingly, STAT3 inhibition by targeted siRNA suppresses the proliferation of retinoblastoma cells and the formation of in vivo orthotopic tumors. In line with these results, STAT3 siRNA effectively induces down-regulation of target genes of STAT3. In addition, miRNA microarray analysis and further real-time PCR experiments with STAT3 siRNA treatment show that STAT3 activation is related to the up-regulation of miR-17-92 clusters in retinoblastoma cells via <span class="hlt">positive</span> <span class="hlt">feedback</span> loop between them. In conclusion, we suggest that STAT3 inhibition could be a potential therapeutic approach in retinoblastoma through the suppression of tumor proliferation. PMID:25359779</p> <div class="credits"> <p class="dwt_author">Jo, Dong Hyun; Kim, Jin Hyoung; Cho, Chang Sik; Cho, Young-Lai; Jun, Hyoung Oh; Yu, Young Suk; Min, Jeong-Ki; Kim, Jeong Hun</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">287</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25359779"> <span id="translatedtitle">STAT3 inhibition suppresses proliferation of retinoblastoma through down-regulation of <span class="hlt">positive</span> <span class="hlt">feedback</span> loop of STAT3/miR-17-92 clusters.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Retinoblastoma, the most common intraocular malignant tumor in children, is characterized by the loss of both functional alleles of RB1 gene, which however alone cannot maintain malignant characteristics of retinoblastoma cells. Nevertheless, the investigation of other molecular aberrations such as matrix metalloproteinases (MMPs) and miRNAs is still lacking. In this study, we demonstrate that STAT3 is activated in retinoblastoma cells, Ki67-<span class="hlt">positive</span> areas of in vivo orthotopic tumors in BALB/c nude mice, and human retinoblastoma tissues of the advanced stage. Furthermore, target genes of STAT3 including BCL2, BCL2L1, BIRC5, and MMP9 are up-regulated in retinoblastoma cells compared to other retinal constituent cells. Interestingly, STAT3 inhibition by targeted siRNA suppresses the proliferation of retinoblastoma cells and the formation of in vivo orthotopic tumors. In line with these results, STAT3 siRNA effectively induces down-regulation of target genes of STAT3. In addition, miRNA microarray analysis and further real-time PCR experiments with STAT3 siRNA treatment show that STAT3 activation is related to the up-regulation of miR-17-92 clusters in retinoblastoma cells via <span class="hlt">positive</span> <span class="hlt">feedback</span> loop between them. In conclusion, we suggest that STAT3 inhibition could be a potential therapeutic approach in retinoblastoma through the suppression of tumor proliferation. PMID:25359779</p> <div class="credits"> <p class="dwt_author">Jo, Dong Hyun; Kim, Jin Hyoung; Cho, Chang Sik; Cho, Young-Lai; Jun, Hyoung Oh; Yu, Young Suk; Min, Jeong-Ki; Kim, Jeong Hun</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-30</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">288</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/2107543"> <span id="translatedtitle">Time-varying <span class="hlt">Feedback</span> Stabilization of Car-like Wheeled Mobile Robots</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Many nonholonomic <span class="hlt">mechanical</span> systems, such as common wheeled mobile robots, are controllable but cannot be stabilized to given <span class="hlt">positions</span> and orientations bv using smooth pure-state <span class="hlt">feedback</span> control. However, as shown in Samson (1990), such systems may still be stabilized by using smooth time-varying <span class="hlt">feedbacks</span>,—i.e., <span class="hlt">feedbacks</span> that explicitly depend on the time variable. This possibility is here applied to the stabilization</p> <div class="credits"> <p class="dwt_author">Claude Samson</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">289</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25412730"> <span id="translatedtitle">Prestin is an anion transporter dispensable for <span class="hlt">mechanical</span> <span class="hlt">feedback</span> amplification in Drosophila hearing.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">In mammals, the membrane-based protein Prestin confers unique electromotile properties to cochlear outer hair cells, which contribute to the cochlear amplifier. Like mammals, the ears of insects, such as those of Drosophila melanogaster, <span class="hlt">mechanically</span> amplify sound stimuli and have also been reported to express Prestin homologs. To determine whether the D. melanogaster Prestin homolog (dpres) is required for auditory amplification, we generated and analyzed dpres mutant flies. We found that dpres is robustly expressed in the fly's antennal ear. However, dpres mutant flies show normal auditory nerve responses, and intact non-linear amplification. Thus we conclude that, in D. melanogaster, auditory amplification is independent of Prestin. This finding resonates with prior phylogenetic analyses, which suggest that the derived motor function of mammalian Prestin replaced, or amended, an ancestral transport function. Indeed, we show that dpres encodes a functional anion transporter. Interestingly, the acquired new motor function in the phylogenetic lineage leading to birds and mammals coincides with loss of the mechanotransducer channel NompC (=TRPN1), which has been shown to be required for auditory amplification in flies. The advent of Prestin (or loss of NompC, respectively) may thus mark an evolutionary transition from a transducer-based to a Prestin-based <span class="hlt">mechanism</span> of auditory amplification. PMID:25412730</p> <div class="credits"> <p class="dwt_author">Kavlie, Ryan G; Fritz, Janice L; Nies, Florian; Göpfert, Martin C; Oliver, Dominik; Albert, Joerg T; Eberl, Daniel F</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">290</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014A%26A...564A.126R"> <span id="translatedtitle">Radiative and <span class="hlt">mechanical</span> <span class="hlt">feedback</span> into the molecular gas of NGC 253</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Starburst galaxies are galaxies or regions of galaxies undergoing intense periods of star formation. Understanding the heating and cooling <span class="hlt">mechanisms</span> in these galaxies can give us insight to the driving <span class="hlt">mechanisms</span> that fuel the starburst. Molecular emission lines play a crucial role in the cooling of the excited gas. With Herschel Spectral and Photometric Imaging Receiver we have been able to observe the rich molecular spectrum towards the central region of NGC 253. Carbon monoxide (CO, J = 4 - 3 to 13-12) is the brightest molecule in the Herschel wavelength range and together with ground-based low-J observations, the line fluxes trace the excitation of CO. By studying the CO excitation ladder and comparing the intensities to models, we investigate whether the gas is excited by UV radiation, X-rays, cosmic rays, or turbulent heating. Comparing the 12CO and 13CO observations to large velocity gradient models and photon-dominated region (PDR) models we find three main interstellar medium (ISM) phases. We estimate the density, temperature, and masses of these ISM phases. By adding 13CO, HCN, and HNC line intensities, we are able to constrain these degeneracies and determine the heating sources. The first ISM phase responsible for the low-J CO lines is excited by PDRs, but the second and third phases, responsible for the mid to high-J CO transitions, require an additional heating source. We find three possible combinations of models that can reproduce our observed molecular emission. Although we cannot determine which of these is preferable, we can conclude that <span class="hlt">mechanical</span> heating is necessary to reproduce the observed molecular emission and cosmic ray heating is a negligible heating source. We then estimate the mass of each ISM phase; 6 × 107M? for phase 1 (low-J CO lines), 3 × 107M? for phase 2 (mid-J CO lines), and 9 × 106M? for phase 3 (high-J CO lines) for a total system mass of 1 × 108M?.</p> <div class="credits"> <p class="dwt_author">Rosenberg, M. J. F.; Kazandjian, M. V.; van der Werf, P. P.; Israel, F. P.; Meijerink, R.; Weiß, A.; Requena-Torres, M. A.; Güsten, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">291</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2674525"> <span id="translatedtitle">Memory without <span class="hlt">Feedback</span> in a Neural Network</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Summary Memory storage on short time scales is thought to be maintained by neuronal activity that persists after the remembered stimulus is removed. Although previous work suggested that <span class="hlt">positive</span> <span class="hlt">feedback</span> is necessary to maintain persistent activity, here it is demonstrated how neuronal responses can instead be maintained by a purely feedforward <span class="hlt">mechanism</span> in which activity is passed sequentially through a chain of network states. This feedforward form of memory storage is shown to occur both in architecturally feedforward networks and in recurrent networks that nevertheless function in a feedforward manner. The networks can be tuned to be perfect integrators of their inputs, or to reproduce the time-varying firing patterns observed during some working memory tasks but not easily reproduced by <span class="hlt">feedback</span>-based attractor models. This work illustrates a new <span class="hlt">mechanism</span> for maintaining short-term memory in which both feedforward and <span class="hlt">feedback</span> processes interact to govern network behavior. PMID:19249281</p> <div class="credits"> <p class="dwt_author">Goldman, Mark S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">292</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25354164"> <span id="translatedtitle">Inhibitory and toxic effects of extracellular self-DNA in litter: a <span class="hlt">mechanism</span> for negative plant-soil <span class="hlt">feedbacks</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Plant-soil negative <span class="hlt">feedback</span> (NF) is recognized as an important factor affecting plant communities. The objectives of this work were to assess the effects of litter phytotoxicity and autotoxicity on root proliferation, and to test the hypothesis that DNA is a driver of litter autotoxicity and plant-soil NF. The inhibitory effect of decomposed litter was studied in different bioassays. Litter biochemical changes were evaluated with nuclear magnetic resonance (NMR) spectroscopy. DNA accumulation in litter and soil was measured and DNA toxicity was assessed in laboratory experiments. Undecomposed litter caused nonspecific inhibition of root growth, while autotoxicity was produced by aged litter. The addition of activated carbon (AC) removed phytotoxicity, but was ineffective against autotoxicity. Phytotoxicity was related to known labile allelopathic compounds. Restricted (13) C NMR signals related to nucleic acids were the only ones negatively correlated with root growth on conspecific substrates. DNA accumulation was observed in both litter decomposition and soil history experiments. Extracted total DNA showed evident species-specific toxicity. Results indicate a general occurrence of litter autotoxicity related to the exposure to fragmented self-DNA. The evidence also suggests the involvement of accumulated extracellular DNA in plant-soil NF. Further studies are needed to further investigate this unexpected function of extracellular DNA at the ecosystem level and related cellular and molecular <span class="hlt">mechanisms</span>. PMID:25354164</p> <div class="credits"> <p class="dwt_author">Mazzoleni, Stefano; Bonanomi, Giuliano; Incerti, Guido; Chiusano, Maria Luisa; Termolino, Pasquale; Mingo, Antonio; Senatore, Mauro; Giannino, Francesco; Cartenì, Fabrizio; Rietkerk, Max; Lanzotti, Virginia</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">293</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014WRR....50.8084Z"> <span id="translatedtitle">Numerical study of evaporation-induced salt accumulation and precipitation in bare saline soils: <span class="hlt">Mechanism</span> and <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">from bare saline soils in coastal wetlands causes salt precipitation in the form of efflorescence and subflorescence. However, it is not clear how much the precipitated salt in turn affects the water transport in the soil and hence the evaporation rate. We hypothesized that efflorescence exerts a mulching resistance to evaporation, while subflorescence reduces the pore space for water vapor to move through the soil. A numerical model is developed to simulate the transport of water, solute, and heat in the soil, and resulting evaporation and salt precipitation with the hypothesized <span class="hlt">feedback</span> <span class="hlt">mechanism</span> incorporated. The model was applied to simulate four evaporation experiments in soil columns with and without a fixed shallow water table, and was found to replicate well the experimental observations. The simulated results indicated that as long as the hydraulic connection between the near surface soil layer and the water source in the interior soil layer exists, vaporization occurs near the surface, and salt precipitates exclusively as efflorescence. When such hydraulic connection is absent, the vaporization plane develops downward and salt precipitates as subflorescence. Being more substantial in quantity, efflorescent affects more significantly evaporation than subflorescence during the soil-drying process. Different evaporation stages based on the location of the vaporization plane and the state of salt accumulation can be identified for characterizing the process of evaporation from bare saline soils with or without a fixed shallow water table.</p> <div class="credits"> <p class="dwt_author">Zhang, Chenming; Li, Ling; Lockington, David</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">294</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25253801"> <span id="translatedtitle">A Tradeoff Between Accuracy and Flexibility in a Working Memory Circuit Endowed with Slow <span class="hlt">Feedback</span> <span class="hlt">Mechanisms</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Recent studies have shown that reverberation underlying mnemonic persistent activity must be slow, to ensure the stability of a working memory system and to give rise to long neural transients capable of accumulation of information over time. Is the slower the underlying process, the better? To address this question, we investigated 3 slow biophysical <span class="hlt">mechanisms</span> that are activity-dependent and prominently present in the prefrontal cortex: Depolarization-induced suppression of inhibition (DSI), calcium-dependent nonspecific cationic current (ICAN), and short-term facilitation. Using a spiking network model for spatial working memory, we found that these processes enhance the memory accuracy by counteracting noise-induced drifts, heterogeneity-induced biases, and distractors. Furthermore, the incorporation of DSI and ICAN enlarges the range of network's parameter values required for working memory function. However, when a progressively slower process dominates the network, it becomes increasingly more difficult to erase a memory trace. We demonstrate this accuracy-flexibility tradeoff quantitatively and interpret it using a state-space analysis. Our results supports the scenario where N-methyl-d-aspartate receptor-dependent recurrent excitation is the workhorse for the maintenance of persistent activity, whereas slow synaptic or cellular processes contribute to the robustness of mnemonic function in a tradeoff that potentially can be adjusted according to behavioral demands. PMID:25253801</p> <div class="credits"> <p class="dwt_author">Pereira, Jacinto; Wang, Xiao-Jing</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-24</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">295</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=Journal+AND+Positive+AND+Behavior+AND+Interventions&id=EJ1042115"> <span id="translatedtitle">Increasing Induction-Level Teachers' <span class="hlt">Positive</span>-to-Negative Communication Ratio and Use of Behavior-Specific Praise through E-Mailed Performance <span class="hlt">Feedback</span> and Its Effect on Students' Task Engagement</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">The purpose of this study was to examine the effects of e-mailed specific performance <span class="hlt">feedback</span> that included progress monitoring graphs on induction-level teachers' ratios of <span class="hlt">positive</span>-to-negative communication behaviors and their use of behavior-specific praise in classrooms for students with emotional and behavioral disorders, mild…</p> <div class="credits"> <p class="dwt_author">Rathel, Jeanna M.; Drasgow, Erik; Brown, William H.; Marshall, Kathleen J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">296</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16.5157D"> <span id="translatedtitle">The role of thermo-<span class="hlt">mechanical</span> <span class="hlt">feedback</span> in the generation of shear zones in the lithosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The collision between continental plates results in the development of orogenic belts. Ongoing collision is responsible for the localisation of deformation and the development of shear zones. The presence of shear zones is well documented within orogens and their importance for the exhumation of high-grade (HG) metamorphic rocks is well accepted; their role in the formation of HG units is however debated. State of the art geodynamic modelling of continental collision is often used to model the genesis and exhumation of HG rocks. Nevertheless, it is a common approach to model collision by predefining shear zones and/or by employing constitutive models that can introduce mesh dependency. Mesh size dependency leads to difficult comparison between physical models and natural data since pressure and temperature cannot be accurately computed within the modelled shear zones. In this contribution, we employ thermo-<span class="hlt">mechanical</span> modelling to study the formation of shear zones in the lithosphere. Our approach takes into account the coupling between momentum and energy balance by including viscous dissipation and temperature/stress dependant viscosity. We show that this methodology allows for the spontaneous development of shear zones around a cylindrical weak heterogeneity. Systematic simulations showed that this approach produces mesh-insensitive results. The modelled shear zones are hence characterised by a finite-width, which is independent on the numerical mesh resolution. Additional test were performed to constrain the physical parameters that control shear band thicknesses, the results highlight the role of thermal transport properties rather than the initial heterogeneity dimensions. Moreover, we demonstrate that these results can be achieved by using two different numerical methods, which are both popular methods in the geodynamic modelling community (Lagrangian finite elements and Eulerian-Lagrangian finite differences). Such models may therefore be reliably used to quantify stresses, pressure and strain rates within shear zones in numerical models of continental collision and may bring new insights in the processes that drive the formation of HG metamorphic rocks.</p> <div class="credits"> <p class="dwt_author">Duretz, Thibault; Schmalholz, Stefan M.; Podladchikov, Yuri Y.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">297</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFMEP13C0884M"> <span id="translatedtitle">Coevolution of topography, soils, and vegetation in upland landscapes: Using cinder cones to elucidate ecohydrogeomorphic <span class="hlt">feedback</span> <span class="hlt">mechanisms</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The study of landscape evolution in upland environments requires analysis of complex interactions among topography, soil development, and vegetation cover under changing climatic conditions. Earth surface scientists lack a comprehensive understanding of these interactions in part due to their interdisciplinary nature, our limited ability to reconstruct the progression of landscape states through time, and the limited spatially-distributed data available for paleoclimate conditions. In this study, we investigate the interactions and <span class="hlt">feedbacks</span> among topography, soil development, and vegetation cover in upland environments using remote sensing, geochemistry, and numerical modeling. We focus on quantifying the evolution of late Quaternary cinder cones within several volcanic fields, spanning a range of climates, as a function of age and microclimate, which varies with elevation and slope aspect. Cinder cones are excellent natural laboratories for studying the evolution of upland landscapes because they begin their evolution at a known time in the past (i.e. many cinder cones have been radiometrically dated) and because they often have unusually uniform initial conditions (i.e. they form close to the angle of repose and are comprised of well-sorted volcaniclastic parent materials). As such, cinder cones of different ages with similar size and climatic history can provide an approximate time progression illustrating how a dated hillslope has evolved over geologic time scales. Data suggest that rates of soil development and fluvial erosion are low on younger cones, which have surfaces consisting mostly of permeable cinders, but increase significantly after eolian deposits reduce the permeability of the cone surface. Further, data demonstrate that microclimatic differences between north and south facing slopes lead to systematic variations in biomass. Additionally, north-facing slopes on cinder cones are found to be steeper than corresponding south-facing slopes. The observed asymmetries in hillslope morphology are not present initially, but appear to develop over time as a result of differences in post-emplacement processes that may be attributed to aspect-induced microclimatic effects on long-term sediment transport rates. Results provide additional constraints on the timing and magnitude of <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> among topography, biomass, and soil development as well as improve our understanding of cinder cone evolution within different climates.</p> <div class="credits"> <p class="dwt_author">McGuire, L.; Pelletier, J. D.; Rasmussen, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">298</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncsu.edu/crsc/reports/ftp/crsc-tr01-29.ps.gz"> <span id="translatedtitle">Model Development for the <span class="hlt">Positioning</span> <span class="hlt">Mechanisms</span> in an Atomic Force Microscope</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">. Two common con#12;gurations for <span class="hlt">positioning</span> <span class="hlt">mechanisms</span> employ stacked actuators utilizing d 33 motion displacements exhibits hysteresis and constitutive nonlinearities due to the ferroelectric nature. In the second step, system models based on these constitutive equations are developed for the stacked actuator</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">299</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/35343339"> <span id="translatedtitle">Home <span class="hlt">mechanical</span> ventilation for amyotrophic lateral sclerosis: nasal compared to tracheostomy-intermittent <span class="hlt">positive</span> pressure ventilation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">People with amyotrophic lateral sclerosis (ALS) usually die from respiratory failure unless they use <span class="hlt">mechanical</span> ventilation (MV). Many die of respiratory failure without being adequately informed about the available options, such as MV, that can provide symptomatic relief and prolong survival. The traditional method of MV used for persons with ALS has been tracheostomy-intermittent <span class="hlt">positive</span> pressure ventilation (IPPV). However, the</p> <div class="credits"> <p class="dwt_author">Pamela A. Cazzolli; Edward A. Oppenheimer</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">300</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4042281"> <span id="translatedtitle">A similar correction <span class="hlt">mechanism</span> in slow and fluent readers after suboptimal landing <span class="hlt">positions</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The present eye movements study investigated the optimal viewing <span class="hlt">position</span> (OVP) and inverted-optimal viewing <span class="hlt">position</span> (I-OVP) effects in slow readers. The basis of these effects is a phenomenon called corrective re-fixations, which describes a short saccade from a suboptimal landing <span class="hlt">position</span> (word beginning or end) to the center of the word. The present study found corrective re-fixations in slow readers, which was evident from the I-OVP effects in first fixation durations, the OVP effect in number of fixations and the OVP effect in re-fixation probability. The main result is that slow readers, despite being characterized by a fragmented eye movement pattern during reading, nevertheless share an intact <span class="hlt">mechanism</span> for performing corrective re-fixations. This correction <span class="hlt">mechanism</span> is not linked to linguistic processing, but to visual and oculomotor processes, which suggests the integrity of oculomotor and visual processes in slow readers. PMID:24917801</p> <div class="credits"> <p class="dwt_author">Gagl, Benjamin; Hawelka, Stefan; Hutzler, Florian</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_14");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_15");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a style="font-weight: bold;">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_17");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">301</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19880050737&hterms=Greenhouse+effect+Atmospheric&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2528%2528Greenhouse%2Beffect%2529%2BAtmospheric%2529"> <span id="translatedtitle">Cloud-radiation interactions - Effects of cirrus optical thickness <span class="hlt">feedbacks</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The paper is concerned with a cloud-radiation <span class="hlt">feedback</span> <span class="hlt">mechanism</span> which may be an important component of the climate changes expected from increased atmospheric concentrations of carbon dioxide and other trace greenhouse gases. A major result of the study is that cirrus cloud optical thickness <span class="hlt">feedbacks</span> may indeed tend to increase the surface warming due to trace gas increases. However, the <span class="hlt">positive</span> <span class="hlt">feedback</span> from cirrus appears to be generally weaker than the negative effects due to lower clouds. The results just confirm those of earlier research indicating that the net effect of cloud optical thickness <span class="hlt">feedbacks</span> may be a negative <span class="hlt">feedback</span> which may substantially (by a factor of about 2) reduce the surface warming due to the doubling of CO2, even in the presence of cirrus clouds.</p> <div class="credits"> <p class="dwt_author">Somerville, Richard C. J.; Iacobellis, Sam</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">302</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/38486951"> <span id="translatedtitle">Terrorism: A <span class="hlt">Positive</span> <span class="hlt">Feedback</span> Game</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This article offers an approach to political systems in enclaves (i.e. closed, dissident minorities) from the standpoint of Cultural Theory; it seeks to identify different kinds of organized dissent, as well as the constraints facing them, most especially those deriving from manipulation and control of information. In this latter case, the resulting choices have implications with regard to both structure</p> <div class="credits"> <p class="dwt_author">Mary Douglas; Gerald Mars</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">303</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/16839308"> <span id="translatedtitle">Performance <span class="hlt">feedback</span> drives caudate activation in a phonological learning task.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Adults have difficulty discriminating nonnative phonetic contrasts, but under certain circumstances training can lead to improvement in this ability. Despite the ubiquitous use of performance <span class="hlt">feedback</span> in training paradigms in this and many other domains, the <span class="hlt">mechanisms</span> by which <span class="hlt">feedback</span> affects learning are not well understood. In this event-related functional magnetic resonance imaging study, we examined how performance <span class="hlt">feedback</span> is processed during perceptual learning. Thirteen Japanese speakers for whom the English phonemes [r] and [l] were nondistinct performed an identification task of the words "road" and "load" that has been shown to be effective in inducing learning only when performance <span class="hlt">feedback</span> is present. Each subject performed alternating runs of training with and without <span class="hlt">feedback</span>, followed by performance of a card-guessing task with monetary reward and punishment outcomes. We found that the caudate nucleus was more robustly activated bilaterally when performing the perceptual identification task with <span class="hlt">feedback</span> than without <span class="hlt">feedback</span>, and the right caudate nucleus also showed a differential response to <span class="hlt">positive</span> and negative <span class="hlt">feedback</span>. Moreover, using a within-subjects design, we found that the caudate nucleus also showed a similar activation pattern to monetary reward and punishment outcomes in the card-guessing task. These results demonstrate that the caudate responds to <span class="hlt">positive</span> and negative <span class="hlt">feedback</span> during learning in a manner analogous to its processing of extrinsic affective reinforcers and indicate that this region may be a critical moderator of the influence of <span class="hlt">feedback</span> on learning. These findings impact our broader understanding of the <span class="hlt">mechanisms</span> underlying nondeclarative learning and language acquisition. PMID:16839308</p> <div class="credits"> <p class="dwt_author">Tricomi, Elizabeth; Delgado, Mauricio R; McCandliss, Bruce D; McClelland, James L; Fiez, Julie A</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">304</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25284585"> <span id="translatedtitle">P-REX1 creates a <span class="hlt">positive</span> <span class="hlt">feedback</span> loop to activate growth factor receptor, PI3K/AKT and MEK/ERK signaling in breast cancer.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Phosphatidylinositol 3-kinase (PI3K) promotes cancer cell survival, migration, growth and proliferation by generating phosphatidylinositol 3,4,5-trisphosphate (PIP3) in the inner leaflet of the plasma membrane. PIP3 recruits pleckstrin homology domain-containing proteins to the membrane to activate oncogenic signaling cascades. Anticancer therapeutics targeting the PI3K/AKT/mTOR (mammalian target of rapamycin) pathway are in clinical development. In a mass spectrometric screen to identify PIP3-regulated proteins in breast cancer cells, levels of the Rac activator PIP3-dependent Rac exchange factor-1 (P-REX1) increased in response to PI3K inhibition, and decreased upon loss of the PI3K antagonist phosphatase and tensin homolog (PTEN). P-REX1 mRNA and protein levels were <span class="hlt">positively</span> correlated with ER expression, and inversely correlated with PI3K pathway activation in breast tumors as assessed by gene expression and phosphoproteomic analyses. P-REX1 increased activation of Rac1, PI3K/AKT and MEK/ERK signaling in a PTEN-independent manner, and promoted cell and tumor viability. Loss of P-REX1 or inhibition of Rac suppressed PI3K/AKT and MEK/ERK, and decreased viability. P-REX1 also promoted insulin-like growth factor-1 receptor activation, suggesting that P-REX1 provides <span class="hlt">positive</span> <span class="hlt">feedback</span> to activators upstream of PI3K. In support of a model where PIP3-driven P-REX1 promotes both PI3K/AKT and MEK/ERK signaling, high levels of P-REX1 mRNA (but not phospho-AKT or a transcriptomic signature of PI3K activation) were predictive of sensitivity to PI3K inhibitors among breast cancer cell lines. P-REX1 expression was highest in estrogen receptor-<span class="hlt">positive</span> breast tumors compared with many other cancer subtypes, suggesting that neutralizing the P-REX1/Rac axis may provide a novel therapeutic approach to selectively abrogate oncogenic signaling in breast cancer cells.Oncogene advance online publication, 6 October 2014; doi:10.1038/onc.2014.328. PMID:25284585</p> <div class="credits"> <p class="dwt_author">Dillon, L M; Bean, J R; Yang, W; Shee, K; Symonds, L K; Balko, J M; McDonald, W H; Liu, S; Gonzalez-Angulo, A M; Mills, G B; Arteaga, C L; Miller, T W</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">305</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AdWR...51..326D"> <span id="translatedtitle">Global desertification: Drivers and <span class="hlt">feedbacks</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Desertification is a change in soil properties, vegetation or climate, which results in a persistent loss of ecosystem services that are fundamental to sustaining life. Desertification affects large dryland areas around the world and is a major cause of stress in human societies. Here we review recent research on the drivers, <span class="hlt">feedbacks</span>, and impacts of desertification. A multidisciplinary approach to understanding the drivers and <span class="hlt">feedbacks</span> of global desertification is motivated by our increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change. Classic desertification theories look at this process as a transition between stable states in bistable ecosystem dynamics. Climate change (i.e., aridification) and land use dynamics are the major drivers of an ecosystem shift to a “desertified” (or “degraded”) state. This shift is typically sustained by <span class="hlt">positive</span> <span class="hlt">feedbacks</span>, which stabilize the system in the new state. Desertification <span class="hlt">feedbacks</span> may involve land degradation processes (e.g., nutrient loss or salinization), changes in rainfall regime resulting from land-atmosphere interactions (e.g., precipitation recycling, dust emissions), or changes in plant community composition (e.g., shrub encroachment, decrease in vegetation cover). We analyze each of these <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> and discuss their possible enhancement by interactions with socio-economic drivers. Large scale effects of desertification include the emigration of “environmental refugees” displaced from degraded areas, climatic changes, and the alteration of global biogeochemical cycles resulting from the emission and long-range transport of fine mineral dust. Recent research has identified some possible early warning signs of desertification, which can be used as indicators of resilience loss and imminent shift to desert-like conditions. We conclude with a brief discussion on some desertification control strategies implemented in different regions around the world.</p> <div class="credits"> <p class="dwt_author">D'Odorico, Paolo; Bhattachan, Abinash; Davis, Kyle F.; Ravi, Sujith; Runyan, Christiane W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">306</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5614405"> <span id="translatedtitle">The <span class="hlt">positional</span> isotope exchange technique as a probe of enzymatic <span class="hlt">mechanisms</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The <span class="hlt">positional</span> isotope exchange (PIX) technique has been used to investigate the <span class="hlt">mechanisms</span> of five enzymes: uridine diphosphoglucose pyrophosphorylase, galactose 1-phosphate uridyltransferase, sucrose synthetase, D-alanyl-D-alanine ligase and carbamyl phosphate synthetase. Applications of the technique have been expanded to include determination of kinetic <span class="hlt">mechanisms</span> (ordered or random), partitioning ratios of binary and ternary enzyme complexes, and individual rate constants. Combination of the PIX technique and traditional steady state kinetics allowed the determination of the lower limit of release of substrates from the binary and ternary enzyme complexes in the reaction catalyzed by uridine diphosphoglucose pyrophosphorylase. Because it was possible to follow a <span class="hlt">positional</span> isotope exchange in both the forward and reverse direction, values for all of the individual rate constants were estimated. A <span class="hlt">positional</span> isotope exchange method was developed for the analysis of enzyme catalyzed reactions which have ping-pong kinetic <span class="hlt">mechanisms</span>. The application involves the recyclization of the modified enzyme form by inclusion of the unlabeled product. The methodology was applied to galactose-1-phosphate uridyltransferase. The relative rate of product dissociation from the enzyme-product complex was determined. The timing of intermediate formation was probed in the reactions catalyzed by sucrose synthetase and D-alanyl-D-alanine ligase. For both enzymes, the formation of an intermediate prior to the binding of the last substrate was investigated. The reaction of sucrose synthetase has been proposed to proceed by a two step <span class="hlt">mechanism</span> in which the scissile bond of UDP-glucose is cleaved to form an intermediate which would then react with fructose. No <span class="hlt">positional</span> isotope exchange in the absence of fructose could be detected for sucrose synthetase.</p> <div class="credits"> <p class="dwt_author">Mullins, L.S.H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">307</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.charlydmiller.com/lib07/1998effectsofproneonrespmechgasexch.pdf"> <span id="translatedtitle">Effects of the Prone <span class="hlt">Position</span> on Respiratory <span class="hlt">Mechanics</span> and Gas Exchange during Acute Lung Injury</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We studied 16 patients with acute lung injury receiving volume-controlled ventilation to assess the relationships between gas exchange and respiratory <span class="hlt">mechanics</span> before, during, and after 2 h in the prone <span class="hlt">position</span>. We measured the end-expiratory lung volume (EELV, helium dilution), the total respi- ratory system (Cst,rs), the lung (Cst,L) and the thoracoabdominal cage (Cst,w) compliances (end- inspiratory occlusion technique and</p> <div class="credits"> <p class="dwt_author">PAOLO PELOSI; DANIELA TUBIOLO; DANIELE MASCHERONI; PIERLUIGI VICARDI; STEFANIA CROTTI; FRANCO VALENZA; LUCIANO GATTINONI</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">308</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/9476848"> <span id="translatedtitle">Effects of the prone <span class="hlt">position</span> on respiratory <span class="hlt">mechanics</span> and gas exchange during acute lung injury.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">We studied 16 patients with acute lung injury receiving volume-controlled ventilation to assess the relationships between gas exchange and respiratory <span class="hlt">mechanics</span> before, during, and after 2 h in the prone <span class="hlt">position</span>. We measured the end-expiratory lung volume (EELV, helium dilution), the total respiratory system (Cst,rs), the lung (Cst,L) and the thoracoabdominal cage (Cst,w) compliances (end-inspiratory occlusion technique and esophageal balloon), the hemodynamics, and gas exchange. In the prone <span class="hlt">position</span>, PaO2 increased from 103.2 +/- 23.8 to 129.3 +/- 32.9 mm Hg (p < 0.05) without significant changes of Cst,rs and EELV. However, Cst,w decreased from 204.8 +/- 97.4 to 135.9 +/- 52.5 ml/cm H2O (p < 0.01) and the decrease was correlated with the oxygenation increase (r = 0.62, p < 0.05). Furthermore, the greater the baseline supine Cst,w, the greater its decrease in the prone <span class="hlt">position</span> (r = 0.82, p < 0.01). Consequently, the oxygenation changes in the prone <span class="hlt">position</span> were predictable from baseline supine Cst,w (r = 0.80, p < 0.01). Returning to the supine <span class="hlt">position</span>, Cst,rs increased compared with baseline (42.3 +/- 14.4 versus 38.4 +/- 13.7 ml/cm H2O; p < 0.01), mainly because of the lung component (57.5 +/- 25.1 versus 52.4 +/- 23.3 ml/cm H2O; p < 0.01). Thus, (1) baseline Cst,w and its changes may play a role in determining the oxygenation response in the prone <span class="hlt">position</span>; (2) the prone <span class="hlt">position</span> improves Cst,rs and Cst,L when the supine <span class="hlt">position</span> is resumed. PMID:9476848</p> <div class="credits"> <p class="dwt_author">Pelosi, P; Tubiolo, D; Mascheroni, D; Vicardi, P; Crotti, S; Valenza, F; Gattinoni, L</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">309</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23746506"> <span id="translatedtitle"><span class="hlt">Mechanical</span> consequences of cell-wall turnover in the elongation of a Gram-<span class="hlt">positive</span> bacterium.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A common feature of walled organisms is their exposure to osmotic forces that challenge the <span class="hlt">mechanical</span> integrity of cells while driving elongation. Most bacteria rely on their cell wall to bear osmotic stress and determine cell shape. Wall thickness can vary greatly among species, with Gram-<span class="hlt">positive</span> bacteria having a thicker wall than Gram-negative bacteria. How wall dimensions and <span class="hlt">mechanical</span> properties are regulated and how they affect growth have not yet been elucidated. To investigate the regulation of wall thickness in the rod-shaped Gram-<span class="hlt">positive</span> bacterium Bacillus subtilis, we analyzed exponentially growing cells in different media. Using transmission electron and epifluorescence microscopy, we found that wall thickness and strain were maintained even between media that yielded a threefold change in growth rate. To probe <span class="hlt">mechanisms</span> of elongation, we developed a biophysical model of the Gram-<span class="hlt">positive</span> wall that balances the <span class="hlt">mechanical</span> effects of synthesis of new material and removal of old material through hydrolysis. Our results suggest that cells can vary their growth rate without changing wall thickness or strain by maintaining a constant ratio of synthesis and hydrolysis rates. Our model also indicates that steady growth requires wall turnover on the same timescale as elongation, which can be driven primarily by hydrolysis rather than insertion. This perspective of turnover-driven elongation provides mechanistic insight into previous experiments involving mutants whose growth rate was accelerated by the addition of lysozyme or autolysin. Our approach provides a general framework for deconstructing shape maintenance in cells with thick walls by integrating wall <span class="hlt">mechanics</span> with the kinetics and regulation of synthesis and turnover. PMID:23746506</p> <div class="credits"> <p class="dwt_author">Misra, Gaurav; Rojas, Enrique R; Gopinathan, Ajay; Huang, Kerwyn Casey</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">310</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://hal.inria.fr/docs/00/88/11/64/PDF/on_acceleration_feedback.pdf"> <span id="translatedtitle">Acceleration <span class="hlt">Feedback</span> via an algebraic state estimation method Romain Delpoux, Hebertt Sira-Ramirez and Thierry Floquet</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">Acceleration <span class="hlt">Feedback</span> via an algebraic state estimation method Romain Delpoux, Hebertt Sira-Ram´irez and Thierry Floquet Abstract-- In many <span class="hlt">mechanical</span> systems, only accelerations are available for <span class="hlt">feedback</span> with the trajectory tracking problem for a second order <span class="hlt">position</span> system on which only the acceleration is available</p> <div class="credits"> <p class="dwt_author">Boyer, Edmond</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">311</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5291582"> <span id="translatedtitle">The Nature and Role of <span class="hlt">Feedback</span> Text Comments in Online Marketplaces: Implications for Trust Building, Price Premiums, and Seller Differentiation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">ABSTRACT For online marketplaces to succeed and prevent a market of lemons, their <span class="hlt">feedback</span> <span class="hlt">mechanism</span> (reputation system) must differentiate among sellers and create price premiumsfor trustworthy ones as returns to their reputation. However, the literature has solely focused on numerical (<span class="hlt">positive</span> and negative) <span class="hlt">feedback</span> ratings, alas ignoring the role offeedback text comments. These text comments are proposed to convey useful</p> <div class="credits"> <p class="dwt_author">Paul A. Pavlou; Angelika Dimoka</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">312</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/16569109"> <span id="translatedtitle">Expressive disclosure and benefit finding among breast cancer patients: <span class="hlt">mechanisms</span> for <span class="hlt">positive</span> health effects.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A randomized trial (n = 60; A. L. Stanton, S. Danoff-Burg, L. A. Sworowski, et al., 2002) revealed that 4 sessions of written expressive disclosure or benefit finding produced lower physical symptom reports and medical appointments for cancer-related morbidities at 3-month follow-up among breast cancer patients relative to a fact-control condition. The goal of this article is to investigate <span class="hlt">mechanisms</span> underlying these effects. Within-session heart rate habituation mediated effects of expressive disclosure on physical symptoms, and greater use of negative emotion words in essays predicted a decline in physical symptoms. Postwriting mood and use of <span class="hlt">positive</span> emotion and cognitive <span class="hlt">mechanism</span> words in essays were not significant mediators, although greater cognitive <span class="hlt">mechanism</span> word use was related to greater heart rate habituation and negative emotion word use. PMID:16569109</p> <div class="credits"> <p class="dwt_author">Low, Carissa A; Stanton, Annette L; Danoff-Burg, Sharon</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">313</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=feedback&pg=3&id=EJ1036078"> <span id="translatedtitle"><span class="hlt">Feedback</span> Sandwiches Affect Perceptions but Not Performance</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">The <span class="hlt">feedback</span> sandwich technique-make <span class="hlt">positive</span> comments; provide critique; end with <span class="hlt">positive</span> comments-is commonly recommended to <span class="hlt">feedback</span> givers despite scant evidence of its efficacy. These two studies (N = 20; N = 350) of written peer <span class="hlt">feedback</span> with third-year medical students on clinical patient note-writing assignments indicate that students…</p> <div class="credits"> <p class="dwt_author">Parkes, Jay; Abercrombie, Sara; McCarty, Teresita</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">314</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/28079049"> <span id="translatedtitle">A <span class="hlt">positive</span> <span class="hlt">feedback</span> <span class="hlt">mechanism</span> in the transcriptional activation of Apaf1 by p53 and the coactivator Zac-1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">p53 exerts its tumor suppressor effects by activating genes involved in cell growth arrest and programmed cell death. The p53 target genes inducing growth arrest are well defined whereas those inducing apoptosis are not fully characterized. Proapoptotic activity of p53 was shown to involve several genes like Bax, Noxa and Puma, which may function in the release of cytochrome c</p> <div class="credits"> <p class="dwt_author">Galit Rozenfeld-Granot; Janakiraman Krishnamurthy; Karuppiah Kannan; Amos Toren; Ninette Amariglio; David Givol; Gideon Rechavi</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">315</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://arxiv.org/pdf/astro-ph/0604446v2"> <span id="translatedtitle">Flux-transport dynamos with Lorentz force <span class="hlt">feedback</span> on differential rotation and meridional flow: Saturation <span class="hlt">mechanism</span> and torsional oscillations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">In this paper we discuss a dynamic flux-transport dynamo model that includes the <span class="hlt">feedback</span> of the induced magnetic field on differential rotation and meridional flow. We consider two different approaches for the <span class="hlt">feedback</span>: meanfield Lorentz force and quenching of transport coefficients such as turbulent viscosity and heat conductivity. We find that even strong <span class="hlt">feedback</span> on the meridional flow does not change the character of the flux-transport dynamo significantly; however it leads to a significant reduction of differential rotation. To a large degree independent from the dynamo parameters, the saturation takes place when the toroidal field at the base of the convection zone reaches between 1.2 an 1.5 T, the energy converted intomagnetic energy corresponds to about 0.1 to 0.2% of the solar luminosity. The torsional oscillations produced through Lorentz force <span class="hlt">feedback</span> on differential rotation show a dominant poleward propagating branch with the correct phase relation to the magnetic cycle. We show that incorporating enhanced surface cooling of the active region belt (as proposed by Spruit) leads to an equatorward propagating branch in good agreement with observations.</p> <div class="credits"> <p class="dwt_author">Matthias Rempel</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-26</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">316</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://cds.cern.ch/record/943721/files/0604446.pdf"> <span id="translatedtitle">Flux-transport dynamos with Lorentz force <span class="hlt">feedback</span> on differential rotation and meridional flow: Saturation <span class="hlt">mechanism</span> and torsional oscillations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">In this paper we discuss a dynamic flux-transport dynamo model that includes the <span class="hlt">feedback</span> of the induced magnetic field on differential rotation and meridional flow. We consider two different approaches for the <span class="hlt">feedback</span>: meanfield Lorentz force and quenching of transport coefficients such as turbulent viscosity and heat conductivity. We find that even strong <span class="hlt">feedback</span> on the meridional flow does not change the character of the flux-transport dynamo significantly; however it leads to a significant reduction of differential rotation. To a large degree independent from the dynamo parameters, the saturation takes place when the toroidal field at the base of the convection zone reaches between 1.2 an 1.5 T, the energy converted intomagnetic energy corresponds to about 0.1 to 0.2% of the solar luminosity. The torsional oscillations produced through Lorentz force <span class="hlt">feedback</span> on differential rotation show a dominant poleward propagating branch with the correct phase relation to the magnetic cycle. We show that incorporat...</p> <div class="credits"> <p class="dwt_author">Rempel, M</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">317</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25355957"> <span id="translatedtitle">Reward <span class="hlt">feedback</span> accelerates motor learning.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Recent findings have demonstrated that reward <span class="hlt">feedback</span> alone can drive motor learning. However, it is not yet clear whether reward <span class="hlt">feedback</span> alone can lead to learning when a perturbation is introduced abruptly, or how a reward gradient can modulate learning. Here, we provide reward <span class="hlt">feedback</span> that decays continuously with increasing error. We asked whether it is possible to learn an abrupt visuomotor rotation by reward alone, and if the learning process could be modulated by combining reward and sensory <span class="hlt">feedback</span> and/or by using different reward landscapes. We designed a novel visuomotor learning protocol during which subjects experienced an abruptly introduced rotational perturbation. Subjects received either visual <span class="hlt">feedback</span>, reward <span class="hlt">feedback</span>, or a combination of the two. Two different reward landscapes, where the reward decayed either linearly or cubically with distance from the target, were tested. Results demonstrate that it is possible to learn from reward <span class="hlt">feedback</span> alone and that the combination of reward and sensory <span class="hlt">feedback</span> accelerates learning. An analysis of the underlying <span class="hlt">mechanisms</span> revealed that while reward <span class="hlt">feedback</span> alone does not allow for sensorimotor remapping, it can nonetheless lead to broad generalization, highlighting a dissociation between remapping and generalization. Secondly, the combination of reward and sensory <span class="hlt">feedback</span> accelerates learning without compromising sensorimotor remapping. These findings suggest that the use of reward <span class="hlt">feedback</span> is a promising approach to either supplement or substitute sensory <span class="hlt">feedback</span>, in the development of improved neurorehabilitation techniques. More generally, they point to an important role played by reward in the motor learning process. PMID:25355957</p> <div class="credits"> <p class="dwt_author">Asadi Nikooyan, Ali; Ahmed, Alaa A</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-29</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">318</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=507571"> <span id="translatedtitle">Endogenous interleukin 6 production in multiple myeloma patients treated with chimeric monoclonal anti-IL6 antibodies indicates the existence of a <span class="hlt">positive</span> <span class="hlt">feed-back</span> loop.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">In vitro as well as in vivo observations have shown that IL6 plays a key role in the pathogenesis of multiple myeloma. Therefore we started a phase I/II dose escalating study with chimeric monoclonal anti-IL6 antibodies (cMab) in multiple myeloma (MM) patients resistant to second-line chemotherapy. Here we describe the pharmacological data as well as a new method for calculating the endogenous IL6 production. The cMab (CLB IL6/8; Kd: 6.25 x 10(-12) M) was given in two cycles of 14 daily infusions, starting on day 1 and day 28. Daily dose: 5 mg in patients 1-3, 10 mg in patients 4-6, and 20 mg in patients 7-9 (total dose 140, 280, and 560 mg of anti-IL6, respectively). Using the pharmacokinetic data of free IL6 and the binding characteristics of the cMab, the endogenous IL6 production could be calculated from day to day using a one-compartment open model. The median half-life time of this antibody was 17.6 d. No human antichimeric antibodies were induced. Pre-treatment median endogenous IL6 production in the MM patients was 60 micrograms/d (range 13.8-230; normal controls < 7 micrograms/d). During treatment with anti-IL6 cMabs, the endogenous IL6 production immediately decreased in all patients to below 3 micrograms/d and never reached the pre-treatment value during the treatment period, except in two patients who developed an active infection, resulting in an IL6 production of 128 and 1,208 micrograms/d, respectively. We concluded that in MM patients endogenous IL6 production is 2-30 times higher than in healthy individuals. The anti-IL6 cMab strongly suppress this endogenous IL6 production, probably by blocking a <span class="hlt">positive</span> <span class="hlt">feed-back</span> loop, but this cMab does not prevent infection-induced IL6 production. The chimeric anti-IL6 Mabs have a long half-life time, a low immunogenicity, and are able to block IL6-dependent processes in vivo. PMID:8823310</p> <div class="credits"> <p class="dwt_author">van Zaanen, H C; Koopmans, R P; Aarden, L A; Rensink, H J; Stouthard, J M; Warnaar, S O; Lokhorst, H M; van Oers, M H</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">319</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011RAA....11..725Y"> <span id="translatedtitle">Panel <span class="hlt">positioning</span> error and support <span class="hlt">mechanism</span> for a 30-m THz radio telescope</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A 30-m TeraHertz (THz) radio telescope is proposed to operate at 200 ?m with an active primary surface. This paper presents sensitivity analysis of active surface panel <span class="hlt">positioning</span> errors with optical performance in terms of the Strehl ratio. Based on Ruze's surface error theory and using a Monte Carlo simulation, the effects of six rigid panel <span class="hlt">positioning</span> errors, such as piston, tip, tilt, radial, azimuthal and twist displacements, were directly derived. The optical performance of the telescope was then evaluated using the standard Strehl ratio. We graphically illustrated the various panel error effects by presenting simulations of complete ensembles of full reflector surface errors for the six different rigid panel <span class="hlt">positioning</span> errors. Study of the panel error sensitivity analysis revealed that the piston error and tilt/tip errors are dominant while the other rigid errors are much less important. Furthermore, as indicated by the results, we conceived of an alternative Master-Slave Concept-based (MSC-based) active surface by implementating a special Series-Parallel Concept-based (SPC-based) hexapod as the active panel support <span class="hlt">mechanism</span>. A new 30-m active reflector based on the two concepts was demonstrated to achieve correction for all the six rigid panel <span class="hlt">positioning</span> errors in an economically feasible way.</p> <div class="credits"> <p class="dwt_author">Yang, De-Hua; Okoh, Daniel; Zhou, Guo-Hua; Li, Ai-Hua; Li, Guo-Ping; Cheng, Jing-Quan</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">320</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/935785"> <span id="translatedtitle">Thermal-chemical-<span class="hlt">mechanical</span> <span class="hlt">feedback</span> during fluid-rock interactions: Implications for chemical transport and scales of equilibria in the crust</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Our research evaluates the hypothesis that <span class="hlt">feedback</span> amongst thermal-chemical-<span class="hlt">mechanical</span> processes operative in fluid-rock systems alters the fluid flow dynamics of the system which, in turn, affects chemical transport and temporal and spatial scales of equilibria, thus impacting the resultant mineral textural development of rocks. Our methods include computational experimentation and detailed analyses of fluid-infiltrated rocks from well-characterized terranes. This work focuses on metamorphic rocks and hydrothermal systems where minerals and their textures are utilized to evaluate pressure (P), temperature (T), and time (t) paths in the evolution of mountain belts and ore deposits, and to interpret tectonic events and the timing of these events. Our work on coupled processes also extends to other areas where subsurface flow and transport in porous media have consequences such as oil and gas movement, geothermal system development, transport of contaminants, nuclear waste disposal, and other systems rich in fluid-rock reactions. Fluid-rock systems are widespread in the geologic record. Correctly deciphering the products resulting from such systems is important to interpreting a number of geologic phenomena. These systems are characterized by complex interactions involving time-dependent, non-linear processes in heterogeneous materials. While many of these interactions have been studied in isolation, they are more appropriately analyzed in the context of a system with <span class="hlt">feedback</span>. When one process impacts another process, time and space scales as well as the overall outcome of the interaction can be dramatically altered. Our goals to test this hypothesis are: to develop and incorporate algorithms into our 3D heat and mass transport code to allow the effects of <span class="hlt">feedback</span> to be investigated numerically, to analyze fluid infiltrated rocks from a variety of terranes at differing P-T conditions, to identify subtle features of the infiltration of fluids and/or <span class="hlt">feedback</span>, and to quantify the importance of <span class="hlt">feedback</span> in complex fluid-rock systems and its affects on time and space scales and rates of reaction. We have made significant contributions toward understanding <span class="hlt">feedback</span> and its impacts by numerical experimentation using 3D computational modeling of fluid-rock systems and by chemical and textural analyses of fluid-infiltrated rocks.</p> <div class="credits"> <p class="dwt_author">Dutrow, Barbara</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-08-13</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_15");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" 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showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_18");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">321</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23499266"> <span id="translatedtitle">Everolimus in hormone receptor-<span class="hlt">positive</span> advanced breast cancer: targeting receptor-based <span class="hlt">mechanisms</span> of resistance.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Although patients with hormone receptor (HR)-<span class="hlt">positive</span> breast cancer are successfully treated with endocrine therapy, many tumors go on to develop resistance to these agents. Studies have determined that <span class="hlt">mechanisms</span> of resistance to endocrine therapy are quite complex and can involve a multitude of signal transduction pathways, either through direct association with the estrogen receptor or through cross-talk with other pathways. Preclinical studies have suggested the therapeutic importance of the mammalian target of rapamycin (mTOR) pathway and that inhibiting this pathway may restore sensitivity to endocrine therapy. The oral mTOR inhibitor everolimus has been extensively studied for breast cancer. Clinical studies suggest that everolimus in combination with endocrine therapy improves progression-free survival and is well tolerated. A combined approach, targeting both mTOR signal transduction and the HR pathways, promises to take clinical research in a new direction for the treatment of HR-<span class="hlt">positive</span> advanced breast cancer. PMID:23499266</p> <div class="credits"> <p class="dwt_author">Shtivelband, Mikhail I</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">322</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/22157104"> <span id="translatedtitle"><span class="hlt">Position</span> measurements in the de Broglie-Bohm interpretation of quantum <span class="hlt">mechanics</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The de Broglie-Bohm interpretation of quantum <span class="hlt">mechanics</span> assigns <span class="hlt">positions</span> and trajectories to particles. We analyze the validity of a formula for the velocities of Bohmian particles which makes the analysis of these trajectories particularly simple. We apply it to particle detectors of four different types and show that the detectors of three of these types lead to 'surrealistic trajectories', i.e., leave a trace where the Bohmian particle was not present. - Highlights: Black-Right-Pointing-Pointer We perform computer simulation of Bohmian trajectories for <span class="hlt">position</span> detectors. Black-Right-Pointing-Pointer A simplified velocity formula provides very precise (or exact) Bohmian trajectories. Black-Right-Pointing-Pointer Spin, phase, and Bohmian velocity type detectors exhibit surrealistic trajectories.</p> <div class="credits"> <p class="dwt_author">Naaman-Marom, Gillie; Erez, Noam; Vaidman, Lev, E-mail: vaidman@post.tau.ac.il</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-10-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">323</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/26347081"> <span id="translatedtitle"><span class="hlt">Feedback</span> strategies for visual search in airframe structural inspection</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Feedback</span> of information has consistently shown <span class="hlt">positive</span> results in human inspection, provided it is given in a timely and appropriate manner. <span class="hlt">Feedback</span> serves as the basis of most training schemes; traditionally this has been performance <span class="hlt">feedback</span>. Other forms of <span class="hlt">feedback</span> which provide strategy information rather than performance information may have a role in improving inspection. This study compared performance <span class="hlt">feedback</span></p> <div class="credits"> <p class="dwt_author">Anand K. Gramopadhye; Colin G. Drury; Joseph Sharit</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">324</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4287604"> <span id="translatedtitle">Activation of Parallel Fiber <span class="hlt">Feedback</span> by Spatially Diffuse Stimuli Reduces Signal and Noise Correlations via Independent <span class="hlt">Mechanisms</span> in a Cerebellum-Like Structure</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Correlations between the activities of neighboring neurons are observed ubiquitously across systems and species and are dynamically regulated by several factors such as the stimulus' spatiotemporal extent as well as by the brain's internal state. Using the electrosensory system of gymnotiform weakly electric fish, we recorded the activities of pyramidal cell pairs within the electrosensory lateral line lobe (ELL) under spatially localized and diffuse stimulation. We found that both signal and noise correlations were markedly reduced (>40%) under the latter stimulation. Through a network model incorporating key anatomical features of the ELL, we reveal how activation of diffuse parallel fiber <span class="hlt">feedback</span> from granule cells by spatially diffuse stimulation can explain both the reduction in signal as well as the reduction in noise correlations seen experimentally through independent <span class="hlt">mechanisms</span>. First, we show that burst-timing dependent plasticity, which leads to a negative image of the stimulus and thereby reduces single neuron responses, decreases signal but not noise correlations. Second, we show trial-to-trial variability in the responses of single granule cells to sensory input reduces noise but not signal correlations. Thus, our model predicts that the same <span class="hlt">feedback</span> pathway can simultaneously reduce both signal and noise correlations through independent <span class="hlt">mechanisms</span>. To test this prediction experimentally, we pharmacologically inactivated parallel fiber <span class="hlt">feedback</span> onto ELL pyramidal cells. In agreement with modeling predictions, we found that inactivation increased both signal and noise correlations but that there was no significant relationship between magnitude of the increase in signal correlations and the magnitude of the increase in noise correlations. The <span class="hlt">mechanisms</span> reported in this study are expected to be generally applicable to the cerebellum as well as other cerebellum-like structures. We further discuss the implications of such decorrelation on the neural coding strategies used by the electrosensory and by other systems to process natural stimuli. PMID:25569283</p> <div class="credits"> <p class="dwt_author">Simmonds, Benjamin; Chacron, Maurice J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">325</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013SPIE.8863E..06L"> <span id="translatedtitle">Cryogenic optical <span class="hlt">position</span> encoders for <span class="hlt">mechanisms</span> in the JWST optical telescope element simulator (OSIM)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The JWST Optical Telescope Element Simulator (OSIM) is a configurable, cryogenic, optical stimulus for high fidelity ground characterization and calibration of JWST's flight instruments. OSIM and its associated Beam Image Analyzer (BIA) contain several ultra-precise, cryogenic <span class="hlt">mechanisms</span> that enable OSIM to project point sources into the instruments according to the same optical prescription as the flight telescope will image stars - correct in focal surface <span class="hlt">position</span> and chief ray angle. OSIM's and BIA's fifteen axes of <span class="hlt">mechanisms</span> navigate according to redundant, cryogenic, absolute, optical encoders - 32 in all operating at or below 100 K. OSIM's encoder subsystem, the engineering challenges met in its development, and the encoders' sub-micron and sub-arcsecond performance are discussed.</p> <div class="credits"> <p class="dwt_author">Leviton, Douglas B.; Anderjaska, Thomas; Badger, James; Capon, Tom; Davis, Clinton; Dicks, Brent; Eichhorn, William; Garza, Mario; Guishard, Corina; Haghani, Shadan; Hakun, Claef; Haney, Paul; Happs, David; Hovmand, Lars; Kadari, Madhu; Kirk, Jeffrey; Nyquist, Richard; Robinson, F. David; Sullivan, Joseph; Wilson, Erin</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">326</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4069743"> <span id="translatedtitle">A cfr-<span class="hlt">positive</span> clinical staphylococcal isolate from India with multiple <span class="hlt">mechanisms</span> of linezolid-resistance</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Background & objectives: Linezolid, a member of the oxazolidinone class of antibiotics, has been an effective therapeutic option to treat severe infections caused by multidrug resistant Gram <span class="hlt">positive</span> bacteria. Emergence of linezolid resistant clinical strains is a serious issue in the healthcare settings worldwide. We report here the molecular characterization of a linezolid resistant clinical isolate of Staphylococcus haemolyticus from India. Methods: The species of the clinical isolate was identified by 16S rRNA gene sequencing. The minimum inhibitory concentrations (MICs) of linezolid, clindamycin, chloramphenicol and oxacillin were determined by E-test method. To elucidate the <span class="hlt">mechanism</span> of linezolid-resistance, presence of cfr gene (chloramphenicol florfenicol resistance) and mutations in 23S rRNA and ribosomal proteins (L3, L4 and L22) were investigated. Staphylococcal Cassette Chromosome mec (SCCmec) typing was performed by multiplex PCR. Results: The study documented a rare clinical S. haemolyticus strain with three independent <span class="hlt">mechanisms</span> of linezolid-resistance. The strain carried cfr gene, the only known transmissible <span class="hlt">mechanism</span> of linezolid-resistance. The strain also possessed resistance-conferring mutations such as G2576T in domain V of 23S rRNA gene and Met156Thr in L3 ribosomal protein. The other ribosomal proteins (L4 and L22) did not exhibit mutations accountable for linezolid-resistance. Restriction digestion by NheI revealed that all the alleles of 23S rRNA gene were mutated. The isolate showed elevated MIC values (>256 ?g ml-1 of linezolid, clindamycin, chloramphenicol and oxacillin. Methicillin resistance was conferred by type I SCCmec element. The strain also harboured lsa(B) gene which encodes an ABC transporter that can efflux clindamycin. Interpretation & conclusions: The present study reports the first clinical strain from India with transmissible and multiple <span class="hlt">mechanisms</span> of linezolid-resistance. Judicious use of linezolid in clinical practice and proper surveillance of cfr-<span class="hlt">positive</span> strains are of utmost importance to safeguard the efficacy of linezolid. PMID:24820843</p> <div class="credits"> <p class="dwt_author">Rajan, Vineeth; Kumar, Vijay Gowdara Shankarappa; Gopal, Shubha</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">327</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3982761"> <span id="translatedtitle">A <span class="hlt">Positive</span> <span class="hlt">Feedback</span> Loop between HEAT SHOCK PROTEIN101 and HEAT STRESS-ASSOCIATED 32-KD PROTEIN Modulates Long-Term Acquired Thermotolerance Illustrating Diverse Heat Stress Responses in Rice Varieties1[W][OPEN</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Heat stress is an important factor that has a negative impact on rice (Oryza sativa) production. To alleviate this problem, it is necessary to extensively understand the genetic basis of heat tolerance and adaptability to heat stress in rice. Here, we report the molecular <span class="hlt">mechanism</span> underlying heat acclimation memory that confers long-term acquired thermotolerance (LAT) in this monocot plant. Our results showed that a <span class="hlt">positive</span> <span class="hlt">feedback</span> loop formed by two heat-inducible genes, HEAT SHOCK PROTEIN101 (HSP101) and HEAT STRESS-ASSOCIATED 32-KD PROTEIN (HSA32), at the posttranscriptional level prolongs the effect of heat acclimation in rice seedlings. The interplay between HSP101 and HSA32 also affects basal thermotolerance of rice seeds. These findings are similar to those reported for the dicot plant Arabidopsis (Arabidopsis thaliana), suggesting a conserved function in plant heat stress response. Comparison between two rice cultivars, japonica Nipponbare and indica N22 showed opposite performance in basal thermotolerance and LAT assays. ‘N22’ seedlings have a higher basal thermotolerance level than cv Nipponbare and vice versa at the LAT level, indicating that these two types of thermotolerance can be decoupled. The HSP101 and HSA32 protein levels were substantially higher in cv Nipponbare than in cv N22 after a long recovery following heat acclimation treatment, at least partly explaining the difference in the LAT phenotype. Our results point out the complexity of thermotolerance diversity in rice cultivars, which may need to be taken into consideration when breeding for heat tolerance for different climate scenarios. PMID:24520156</p> <div class="credits"> <p class="dwt_author">Lin, Meng-yi; Chai, Kuo-hsing; Ko, Swee-suak; Kuang, Lin-yun; Lur, Huu-Sheng; Charng, Yee-yung</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">328</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AdSpR..48..488K"> <span id="translatedtitle">Formation <span class="hlt">mechanism</span> of great <span class="hlt">positive</span> TEC disturbances prior to Wenchuan earthquake on May 12, 2008</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The problems of physical explanation and possible <span class="hlt">mechanisms</span> of the seismo-ionospheric effects formation are under discussion now. There are proposed different <span class="hlt">mechanisms</span> of such effects, for example, large- and small-scale internal gravity waves (IGWs), atmospheric electric field, electromagnetic fields and emissions. However, the appearance of local large-scale seismo-ionospheric anomalies in Total Electron Content ( TEC) is possible to explain only by two <span class="hlt">mechanisms</span>: an atmospheric electric field and/or small-scale IGWs. In this paper, the simulation results for reproduction of the observed seismo-ionospheric great <span class="hlt">positive</span> effects in TEC prior to strong Wenchuan earthquake are presented. The obtained results confirm the proposed <span class="hlt">mechanism</span> of seismo-ionospheric effects formation by the penetration of the seismogenic electric field from the atmosphere into the ionosphere. It is suggested that so great TEC enhancement observed 3 days prior to Wenchuan earthquake could be explained by combined action of seismogenic vertical electric field and IGWs generated by the solar terminator.</p> <div class="credits"> <p class="dwt_author">Klimenko, M. V.; Klimenko, V. V.; Zakharenkova, I. E.; Pulinets, S. A.; Zhao, B.; Tsidilina, M. N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">329</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://repository.tamu.edu/handle/1969.1/ETD-TAMU-1188"> <span id="translatedtitle">You must be creative! The effect of performance <span class="hlt">feedback</span> on intrinsic motivation and creativity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">the effect of perceived competence on interest. Creative answers to open-ended problems were assessed after time 2 (before <span class="hlt">feedback</span>), and after time 3 (after <span class="hlt">feedback</span>). <span class="hlt">Feedback</span> style (autonomous, controlled, and neutral) and <span class="hlt">Feedback</span> sign (<span class="hlt">positive</span>, negative...</p> <div class="credits"> <p class="dwt_author">Benzer, Justin Kane</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">330</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008APS..MAR.B7002M"> <span id="translatedtitle">Using DNA <span class="hlt">mechanics</span> to predict intrinsic and extrinsic nucleosome <span class="hlt">positioning</span> signals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In eukaryotic genomes, nucleosomes function to compact DNA and to regulate access to it both by simple physical occlusion and by providing the substrate for numerous covalent epigenetic tags. While nucleosome <span class="hlt">positions</span> in vitro are determined by sequence alone, in vivo competition with other DNA-binding factors and action of chromatin remodeling enzymes play a role that needs to be quantified. We developed a biophysical, DNA <span class="hlt">mechanics</span>-based model for the sequence dependence of DNA bending energies, and validated it against a collection of in vitro free energies of nucleosome formation and a nucleosome crystal structure; we also successfully designed both strong and poor histone binding sequences ab initio. For in vivo data from S.cerevisiae, the strongest <span class="hlt">positioning</span> signal came from the competition with other factors rather than intrinsic nucleosome sequence preferences. Based on sequence alone, our model predicts that functional transcription factor binding sites tend to be covered by nucleosomes, yet are uncovered in vivo because functional sites cluster within a single nucleosome footprint and thus make transcription factors bind cooperatively. Similarly a weak enhancement of nucleosome binding in the TATA region becomes a strong depletion when the TATA-binding protein is included, in quantitative agreement with experiment. Our model distinguishes multiple ways in which genomic sequence influences nucleosome <span class="hlt">positions</span>, and thus provides alternative explanations for several genome-wide experimental findings. In the future our approach will be used to rationally alter gene expression levels in model systems through redesign of nucleosome occupancy profiles.</p> <div class="credits"> <p class="dwt_author">Morozov, Alexandre</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">331</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24416216"> <span id="translatedtitle">A double <span class="hlt">mechanism</span> for the mesenchymal stem cells' <span class="hlt">positive</span> effect on pancreatic islets.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The clinical usability of pancreatic islet transplantation for the treatment of type I diabetes, despite some encouraging results, is currently hampered by the short lifespan of the transplanted tissue. In vivo studies have demonstrated that co-transplantation of Mesenchymal Stem Cells (MSCs) with transplanted pancreatic islets is more effective with respect to pancreatic islets alone in ensuring glycemia control in diabetic rats, but the molecular <span class="hlt">mechanisms</span> of this action are still unclear. The aim of this study was to elucidate the molecular <span class="hlt">mechanisms</span> of the <span class="hlt">positive</span> effect of MSCs on pancreatic islet functionality by setting up direct, indirect and mixed co-cultures. MSCs were both able to prolong the survival of pancreatic islets, and to directly differentiate into an "insulin-releasing" phenotype. Two distinct <span class="hlt">mechanisms</span> mediated these effects: i) the survival increase was observed in pancreatic islets indirectly co-cultured with MSCs, probably mediated by the trophic factors released by MSCs; ii) MSCs in direct contact with pancreatic islets started to express Pdx1, a pivotal gene of insulin production, and then differentiated into insulin releasing cells. These results demonstrate that MSCs may be useful for potentiating pancreatic islets' functionality and feasibility. PMID:24416216</p> <div class="credits"> <p class="dwt_author">Scuteri, Arianna; Donzelli, Elisabetta; Rodriguez-Menendez, Virginia; Ravasi, Maddalena; Monfrini, Marianna; Bonandrini, Barbara; Figliuzzi, Marina; Remuzzi, Andrea; Tredici, Giovanni</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">332</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24846339"> <span id="translatedtitle">Offering effective <span class="hlt">feedback</span> to trainees.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Abstract Effective <span class="hlt">feedback</span> on performance is an integral part of clinical training. It allows the trainee to critically reflect on their development, as well as enable the teacher to chart progress and detect areas for development. In order to provide effective <span class="hlt">feedback</span>, we need to take into account the performance itself, but also the setting where <span class="hlt">feedback</span> is offered, and the expected outcomes of the encounter. As ever, negative <span class="hlt">feedback</span> remains more difficult to give and receive, and as such requires a greater degree of delicacy to produce a <span class="hlt">positive</span> result. PMID:24846339</p> <div class="credits"> <p class="dwt_author">Iskander, Morkos</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">333</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014PApGe.tmp..162X"> <span id="translatedtitle">Dynamic Ruptures on a Frictional Interface with Off-Fault Brittle Damage: <span class="hlt">Feedback</span> <span class="hlt">Mechanisms</span> and Effects on Slip and Near-Fault Motion</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The spontaneous generation of brittle rock damage near and behind the tip of a propagating rupture can produce dynamic <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> that modify significantly the rupture properties, seismic radiation, and generated fault zone structure. In this work, we study such <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> for single rupture events and their consequences for earthquake physics and various possible observations. This is done through numerical simulations of in-plane dynamic ruptures on a frictional fault with bulk behavior governed by a brittle damage rheology that incorporates reduction of elastic moduli in off-fault yielding regions. The model simulations produce several features that modify key properties of the ruptures, local wave propagation, and fault zone damage. These include (1) dynamic generation of near-fault regions with lower elastic properties, (2) dynamic changes of normal stress on the fault, (3) rupture transition from crack-like to a detached pulse, (4) emergence of a rupture mode consisting of a train of pulses, (5) quasi-periodic modulation of slip rate on the fault, and (6) asymmetric near-fault ground motion with higher amplitude and longer duration on the side with reduced elastic moduli. The results can have significant implications to multiple topics ranging from rupture directivity and local amplification of seismic motion to near-fault tremor-like signals.</p> <div class="credits"> <p class="dwt_author">Xu, Shiqing; Ben-Zion, Yehuda; Ampuero, Jean-Paul; Lyakhovsky, Vladimir</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">334</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JGRD..119.1796D"> <span id="translatedtitle">Interactive ozone induces a negative <span class="hlt">feedback</span> in CO2-driven climate change simulations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Interactively coupled climate chemistry models (CCMs) extend the number of <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> in climate change simulations by including chemical <span class="hlt">feedback</span>. In this study the radiative <span class="hlt">feedback</span> from ozone changes on climate response and climate sensitivity is quantified for a series of simulations driven by CO2 increases on top of a present-day reference concentration level. Other possibly relevant <span class="hlt">feedback</span> via atmospheric chemistry, e.g., via CH4 and N2O, is not fully quantified in the CCM setup as their concentrations are essentially fixed at the surface. In case of a CO2-doubling simulation, the ozone <span class="hlt">feedback</span> reduces the climate sensitivity parameter by 3.4%, from 0.70 K/(W m-2) without interactive chemistry to 0.68 K/(W m-2). In case of a 4*CO2 simulation, the reduction of the climate sensitivity parameter increases to 8.4%. An analysis of <span class="hlt">feedback</span> reveals that the negative <span class="hlt">feedback</span> of stratospheric ozone and the associated negative <span class="hlt">feedback</span> change in stratospheric water vapor are mainly responsible for this damping. The <span class="hlt">feedback</span> from tropospheric ozone changes is <span class="hlt">positive</span> but much smaller. The nonlinearity in the climate sensitivity damping with increased CO2 concentrations is shown to be due to nonlinear <span class="hlt">feedback</span> of ozone and stratospheric water vapor.</p> <div class="credits"> <p class="dwt_author">Dietmüller, S.; Ponater, M.; Sausen, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">335</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3385767"> <span id="translatedtitle">Regulation of oscillation dynamics in biochemical systems with dual negative <span class="hlt">feedback</span> loops</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary"><span class="hlt">Feedback</span> controls are central to cellular regulation. Negative-<span class="hlt">feedback</span> <span class="hlt">mechanisms</span> are well known to underline oscillatory dynamics. However, the presence of multiple negative-<span class="hlt">feedback</span> <span class="hlt">mechanisms</span> is common in oscillatory cellular systems, raising intriguing questions of how they cooperate to regulate oscillations. In this work, we studied the dynamical properties of a set of general biochemical motifs with dual, nested negative-<span class="hlt">feedback</span> structures. We showed analytically and then confirmed numerically that, in these motifs, each negative-<span class="hlt">feedback</span> loop exhibits distinctly different oscillation-controlling functions. The longer, outer <span class="hlt">feedback</span> loop was found to promote oscillations, whereas the short, inner loop suppresses and can even eliminate oscillations. We found that the <span class="hlt">position</span> of the inner loop within the coupled motifs affects its repression strength towards oscillatory dynamics. Bifurcation analysis indicated that emergence of oscillations may be a strict parametric requirement and thus evolutionarily tricky. Investigation of the quantitative features of oscillations (i.e. frequency, amplitude and mean value) revealed that coupling negative <span class="hlt">feedback</span> provides robust tuning of the oscillation dynamics. Finally, we demonstrated that the mitogen-activated protein kinase (MAPK) cascades also display properties seen in the general nested <span class="hlt">feedback</span> motifs. The findings and implications in this study provide novel understanding of biochemical negative-<span class="hlt">feedback</span> regulation in a mixed wiring context. PMID:22417908</p> <div class="credits"> <p class="dwt_author">Nguyen, Lan K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">336</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012HESSD...911161K"> <span id="translatedtitle">A model of hydrological and <span class="hlt">mechanical</span> <span class="hlt">feedbacks</span> of preferential fissure flow in a slow-moving landslide</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The importance of hydrological processes for landslide activity is generally accepted. However, the relationship between precipitation, hydrological responses and movement is not straightforward. Groundwater recharge is mostly controlled by the hydrological material properties and the structure (e.g. layering, preferential flow paths such as fissures) of the unsaturated zone. In slow-moving landslides, differential displacements caused by the bedrock structure complicate the hydrological regime due to continuous opening and closing of the fissures, creating temporary preferential flow paths systems for infiltration and groundwater drainage. The consecutive opening and closing of fissure aperture control the formation of a critical pore water pressure by creating dynamic preferential flow paths for infiltration and groundwater drainage. This interaction may explain the seasonal nature of the slow-moving landslide activity, including the often observed shifts and delays in hydrological responses when compared to timing, intensity and duration of precipitation. The main objective of this study is to model the influence of fissures on the hydrological dynamics of slow-moving landslide and the dynamic <span class="hlt">feedbacks</span> between fissures, hydrology and slope stability. For this we adapt the spatially distributed hydrological and slope stability model (STARWARS) to account for geotechnical and hydrological <span class="hlt">feedbacks</span>, linking between hydrological response of the landside and the dynamics of the fissure network and applied the model to the hydrologically controlled Super-Sauze landslide (South French Alps).</p> <div class="credits"> <p class="dwt_author">Krzeminska, D. M.; Bogaard, T. A.; Malet, J.-P.; van Beek, L. P. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">337</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013HESS...17..947K"> <span id="translatedtitle">A model of hydrological and <span class="hlt">mechanical</span> <span class="hlt">feedbacks</span> of preferential fissure flow in a slow-moving landslide</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The importance of hydrological processes for landslide activity is generally accepted. However, the relationship between precipitation, hydrological responses and movement is not straightforward. Groundwater recharge is mostly controlled by the hydrological material properties and the structure (e.g., layering, preferential flow paths such as fissures) of the unsaturated zone. In slow-moving landslides, differential displacements caused by the bedrock structure complicate the hydrological regime due to continuous opening and closing of the fissures, creating temporary preferential flow paths systems for infiltration and groundwater drainage. The consecutive opening and closing of fissure aperture control the formation of a critical pore water pressure by creating dynamic preferential flow paths for infiltration and groundwater drainage. This interaction may explain the seasonal nature of the slow-moving landslide activity, including the often observed shifts and delays in hydrological responses when compared to timing, intensity and duration of precipitation. The main objective of this study is to model the influence of fissures on the hydrological dynamics of slow-moving landslide and the dynamic <span class="hlt">feedbacks</span> between fissures, hydrology and slope stability. For this we adapt the spatially distributed hydrological and slope stability model (STARWARS) to account for geotechnical and hydrological <span class="hlt">feedbacks</span>, linking between hydrological response of the landside and the dynamics of the fissure network and applied the model to the hydrologically controlled Super-Sauze landslide (South French Alps).</p> <div class="credits"> <p class="dwt_author">Krzeminska, D. M.; Bogaard, T. A.; Malet, J.-P.; van Beek, L. P. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">338</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011ArTh...32..263K"> <span id="translatedtitle">Optimization of guide vane <span class="hlt">positions</span> in bended inflow of <span class="hlt">mechanical</span> draft wet-cooling tower</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Optimization of vane <span class="hlt">positions</span> in a <span class="hlt">mechanical</span> draft wet-cooling tower is presented in this paper. The originally installed, equally spaced, vanes produced non-uniform air velocity distribution reducing the performance of the fill of the cooling tower. A 2D CFD model of the tower has been created. The model has then been used to determine the objective function in the optimization procedure. The selected objective function was the standard deviation of the velocity of air entering the fill. The Goal Driven Optimization tools of the ANSYSWorkbench 2.0 have been used for the optimization and the ANSYS Fluent 13.0 as a flow solver. The optimization allowed reduction of the objective function and producing a more uniform air flow.</p> <div class="credits"> <p class="dwt_author">Klimanek, Adam; Musio?, Tomasz; Stechman, Adam</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">339</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/22217738"> <span id="translatedtitle">Solutions to <span class="hlt">position</span>-dependent mass quantum <span class="hlt">mechanics</span> for a new class of hyperbolic potentials</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">We analytically solve the <span class="hlt">position</span>-dependent mass (PDM) 1D Schrödinger equation for a new class of hyperbolic potentials V{sub q}{sup p}(x)=?V{sub 0}(sinh{sup p}x/cosh{sup q}x),?p=?2,0,?q?[see C. A. Downing, J. Math. Phys. 54, 072101 (2013)] among several hyperbolic single- and double-wells. For a solitonic mass distribution, m(x)=m{sub 0}?sech{sup 2}(x), we obtain exact analytic solutions to the resulting differential equations. For several members of the class, the quantum <span class="hlt">mechanical</span> problems map into confluent Heun differential equations. The PDM Poschl-Teller potential is considered and exactly solved as a particular case.</p> <div class="credits"> <p class="dwt_author">Christiansen, H. R. [Physics Department, State University Vale do Acaraú, Av. da Universidade 850, 62040-370 Sobral-CE (Brazil) [Physics Department, State University Vale do Acaraú, Av. da Universidade 850, 62040-370 Sobral-CE (Brazil); Grupo de Física Teórica, State University of Ceara (UECE), Av. Paranjana 1700, 60740-903 Fortaleza-CE (Brazil); Cunha, M. S. [Grupo de Física Teórica, State University of Ceara (UECE), Av. Paranjana 1700, 60740-903 Fortaleza-CE (Brazil)] [Grupo de Física Teórica, State University of Ceara (UECE), Av. Paranjana 1700, 60740-903 Fortaleza-CE (Brazil)</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">340</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=tv+AND+broadcasting&pg=6&id=EJ094943"> <span id="translatedtitle">Video <span class="hlt">Feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">Author states that participation in TV becomes video <span class="hlt">feedback</span> to teachers and parents. If radical approaches to TV become the norm, video will be the content of a new awareness that is being generated by this new visual culture. (Author)</p> <div class="credits"> <p class="dwt_author">Jonassen, David H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1974-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_16");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return 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<a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a style="font-weight: bold;">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_19");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">341</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2014JAP...116u3301F"> <span id="translatedtitle">Initiation process and propagation <span class="hlt">mechanism</span> of <span class="hlt">positive</span> streamer discharge in water</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The aim of this study was to clarify the initiation process and the propagation <span class="hlt">mechanism</span> of <span class="hlt">positive</span> underwater streamers under the application of pulsed voltage with a duration of 10 ?s, focusing on two different theories of electrical discharges in liquids: the bubble theory and the direct ionization theory. The initiation process, which is the time lag from the beginning of voltage application to streamer inception, was found to be related to the bubble theory. In this process, Joule heating resulted in the formation of a bubble cluster at the tip of a needle electrode. Streamer inception was observed from the tip of a protrusion on the surface of this bubble cluster, which acted as a virtual sharp electrode to enhance the local electric field to a level greater than 10 MV/cm. Streak imaging of secondary streamer propagation showed that luminescence preceded gas channel generation, suggesting a <span class="hlt">mechanism</span> of direct ionization in water. Streak imaging of primary streamer propagation revealed intermittent propagation, synchronized with repetitive pulsed currents. Shadowgraph imaging of streamers synchronized with the light emission signal indicated the possibility of direct ionization in water for primary streamer propagation as well as for secondary streamer propagation.</p> <div class="credits"> <p class="dwt_author">Fujita, Hidemasa; Kanazawa, Seiji; Ohtani, Kiyonobu; Komiya, Atsuki; Kaneko, Toshiro; Sato, Takehiko</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">342</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23600658"> <span id="translatedtitle">Prediction of clathrate structure type and guest <span class="hlt">position</span> by molecular <span class="hlt">mechanics</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The clathrate hydrates occur in various types in which the number, size, and shape of the various cages differ. Usually the clathrate type of a specific guest is predicted by the size and shape of the molecular guest. We have developed a methodology to determine the clathrate type employing molecular <span class="hlt">mechanics</span> with the MMFF force field employing a strategy to calculate the energy of formation of the clathrate from the sum of the guest/cage energies. The clathrate type with the most negative (most stable) energy of formation would be the type predicted (we mainly focused on type I, type II, or bromine type). This strategy allows for a calculation to predict the clathrate type for any cage guest in a few minutes on a laptop computer. It proved successful in predicting the clathrate structure for 46 out of 47 guest molecules. The molecular <span class="hlt">mechanics</span> calculations also provide a prediction of the guest <span class="hlt">position</span> within the cage and clathrate structure. These predictions are generally consistent with the X-ray and neutron diffraction studies. By supplementing the diffraction study with molecular <span class="hlt">mechanics</span>, we gain a more detailed insight regarding the details of the structure. We have also compared MM calculations to studies of the multiple occupancy of the cages. Finally, we present a density functional calculation that demonstrates that the inside of the clathrates cages have a relatively uniform and low electrostatic potential in comparison with the outside oxygen and hydrogen atoms. This implies that van der Waals forces will usually be dominant in the guest-cage interactions. PMID:23600658</p> <div class="credits"> <p class="dwt_author">Fleischer, Everly B; Janda, Kenneth C</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-16</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">343</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=bifurcation&pg=3&id=EJ834234"> <span id="translatedtitle"><span class="hlt">Positive</span> Maladjustment as a Transition from Chaos to Order</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">Dabrowski's theory of <span class="hlt">positive</span> disintegration describes patterns and explains <span class="hlt">mechanisms</span> of human development and has been successfully applied to understanding of gifted individuals. This article shows how the concepts of chaos theory and self-organization such as the sensitivity to initial conditions, <span class="hlt">positive</span> and negative <span class="hlt">feedback</span>, bifurcation…</p> <div class="credits"> <p class="dwt_author">Laycraft, Krystyna</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">344</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24967742"> <span id="translatedtitle">Mechanistic, mathematical model to predict the dynamics of tissue genesis in bone defects via <span class="hlt">mechanical</span> <span class="hlt">feedback</span> and mediation of biochemical factors.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The link between <span class="hlt">mechanics</span> and biology in the generation and the adaptation of bone has been well studied in context of skeletal development and fracture healing. Yet, the prediction of tissue genesis within - and the spatiotemporal healing of - postnatal defects, necessitates a quantitative evaluation of mechano-biological interactions using experimental and clinical parameters. To address this current gap in knowledge, this study aims to develop a mechanistic mathematical model of tissue genesis using bone morphogenetic protein (BMP) to represent of a class of factors that may coordinate bone healing. Specifically, we developed a mechanistic, mathematical model to predict the dynamics of tissue genesis by periosteal progenitor cells within a long bone defect surrounded by periosteum and stabilized via an intramedullary nail. The emergent material properties and <span class="hlt">mechanical</span> environment associated with nascent tissue genesis influence the strain stimulus sensed by progenitor cells within the periosteum. Using a <span class="hlt">mechanical</span> finite element model, periosteal surface strains are predicted as a function of emergent, nascent tissue properties. Strains are then input to a mechanistic mathematical model, where <span class="hlt">mechanical</span> regulation of BMP-2 production mediates rates of cellular proliferation, differentiation and tissue production, to predict healing outcomes. A parametric approach enables the spatial and temporal prediction of endochondral tissue regeneration, assessed as areas of cartilage and mineralized bone, as functions of radial distance from the periosteum and time. Comparing model results to histological outcomes from two previous studies of periosteum-mediated bone regeneration in a common ovine model, it was shown that mechanistic models incorporating <span class="hlt">mechanical</span> <span class="hlt">feedback</span> successfully predict patterns (spatial) and trends (temporal) of bone tissue regeneration. The novel model framework presented here integrates a mechanistic <span class="hlt">feedback</span> system based on the mechanosensitivity of periosteal progenitor cells, which allows for modeling and prediction of tissue regeneration on multiple length and time scales. Through combination of computational, physical and engineering science approaches, the model platform provides a means to test new hypotheses in silico and to elucidate conditions conducive to endogenous tissue genesis. Next generation models will serve to unravel intrinsic differences in bone genesis by endochondral and intramembranous <span class="hlt">mechanisms</span>. PMID:24967742</p> <div class="credits"> <p class="dwt_author">Moore, Shannon R; Saidel, Gerald M; Knothe, Ulf; Knothe Tate, Melissa L</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">345</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4072518"> <span id="translatedtitle">Mechanistic, Mathematical Model to Predict the Dynamics of Tissue Genesis in Bone Defects via <span class="hlt">Mechanical</span> <span class="hlt">Feedback</span> and Mediation of Biochemical Factors</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The link between <span class="hlt">mechanics</span> and biology in the generation and the adaptation of bone has been well studied in context of skeletal development and fracture healing. Yet, the prediction of tissue genesis within - and the spatiotemporal healing of - postnatal defects, necessitates a quantitative evaluation of mechano-biological interactions using experimental and clinical parameters. To address this current gap in knowledge, this study aims to develop a mechanistic mathematical model of tissue genesis using bone morphogenetic protein (BMP) to represent of a class of factors that may coordinate bone healing. Specifically, we developed a mechanistic, mathematical model to predict the dynamics of tissue genesis by periosteal progenitor cells within a long bone defect surrounded by periosteum and stabilized via an intramedullary nail. The emergent material properties and <span class="hlt">mechanical</span> environment associated with nascent tissue genesis influence the strain stimulus sensed by progenitor cells within the periosteum. Using a <span class="hlt">mechanical</span> finite element model, periosteal surface strains are predicted as a function of emergent, nascent tissue properties. Strains are then input to a mechanistic mathematical model, where <span class="hlt">mechanical</span> regulation of BMP-2 production mediates rates of cellular proliferation, differentiation and tissue production, to predict healing outcomes. A parametric approach enables the spatial and temporal prediction of endochondral tissue regeneration, assessed as areas of cartilage and mineralized bone, as functions of radial distance from the periosteum and time. Comparing model results to histological outcomes from two previous studies of periosteum-mediated bone regeneration in a common ovine model, it was shown that mechanistic models incorporating <span class="hlt">mechanical</span> <span class="hlt">feedback</span> successfully predict patterns (spatial) and trends (temporal) of bone tissue regeneration. The novel model framework presented here integrates a mechanistic <span class="hlt">feedback</span> system based on the mechanosensitivity of periosteal progenitor cells, which allows for modeling and prediction of tissue regeneration on multiple length and time scales. Through combination of computational, physical and engineering science approaches, the model platform provides a means to test new hypotheses in silico and to elucidate conditions conducive to endogenous tissue genesis. Next generation models will serve to unravel intrinsic differences in bone genesis by endochondral and intramembranous <span class="hlt">mechanisms</span>. PMID:24967742</p> <div class="credits"> <p class="dwt_author">Moore, Shannon R.; Saidel, Gerald M.; Knothe, Ulf; Knothe Tate, Melissa L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">346</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3572190"> <span id="translatedtitle">Senescence sensitivity of breast cancer cells is defined by <span class="hlt">positive</span> <span class="hlt">feedback</span> loop between CIP2A and E2F1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Senescence induction contributes to cancer therapy responses and is crucial for p53-mediated tumor suppression. However, whether p53 inactivation actively suppresses senescence induction has been unclear. Here we demonstrate that E2F1 overexpression, due to p53 or p21 inactivation, promotes expression of human oncoprotein CIP2A, which in turn, by inhibiting PP2A activity, increases stabilizing serine 364 phosphorylation of E2F1. Several lines of evidence demonstrate that increased activity of E2F1-CIP2A <span class="hlt">feedback</span> renders breast cancer cells resistant to senescence induction. Importantly, mammary tumorigenesis is impaired in a CIP2A deficient mouse model, and CIP2A deficient tumors display markers of senescence induction. Moreover, high CIP2A expression predicts for poor prognosis in a subgroup of breast cancer patients treated with senescence-inducing chemotherapy. Together these results implicate E2F1-CIP2A <span class="hlt">feedback</span> loop as a key determinant of breast cancer cell sensitivity to senescence induction. It also constitutes a promising pro-senescence target for therapy of cancers with inactivated p53-p21 pathway. PMID:23306062</p> <div class="credits"> <p class="dwt_author">Laine, Anni; Sihto, Harri; Come, Christophe; Rosenfeldt, Mathias T.; Zwolinska, Aleksandra; Niemelä, Minna; Khanna, Anchit; Chan, Edward K.; Kähäri, Veli-Matti; Kellokumpu-Lehtinen, Pirkko-Liisa; Sansom, Owen J.; Evan, Gerard I.; Junttila, Melissa R.; Ryan, Kevin M.; Marine, Jean-Christophe; Joensuu, Heikki; Westermarck, Jukka</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">347</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.1550P"> <span id="translatedtitle">On the role of temperature <span class="hlt">feedbacks</span> for Arctic amplification</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The amplification of global climate changes at the poles is a well-known feature of the climate system mentioned already by Arrhenius (1896). It has been linked to the surface-albedo <span class="hlt">feedback</span>, changes in atmospheric and oceanic heat convergence, water vapour and cloud <span class="hlt">feedbacks</span> and the albedo effect of black carbon on snow (Serreze and Barry, 2011). We here focus on the role of temperature <span class="hlt">feedbacks</span>, which have received rather little attention in recent debates. The basic temperature <span class="hlt">feedback</span> is the Planck <span class="hlt">feedback</span> or the increase in the Earth's blackbody radiation due to a uniform temperature increase. Since the blackbody radiation scales with the fourth power of temperature, stronger warming is necessary in cold regions to balance a globally uniform radiative forcing. The second temperature <span class="hlt">feedback</span> is caused by changes in the vertical atmospheric temperature structure: In the Tropics, deep convection leads to warming aloft being larger than at the surface, which causes a greater increase in outgoing longwave radiation compared a vertically uniform forcing and thus constitutes a negative <span class="hlt">feedback</span> <span class="hlt">mechanism</span>. In the Arctic, where warming is amplified at the surface, the lapse-rate <span class="hlt">feedback</span> is <span class="hlt">positive</span> (Wetherald and Manabe, 1975). We use CMIP5 model output and radiative Kernels to investigate the zonal distribution of temperature <span class="hlt">feedbacks</span>. Arrhenius, S. (1896). On the influence of carbonic acid in the air upon the temperature of the ground Philos. Mag. J. Sci., 5, pp. 237-276 Serreze, M.C. and Barry, R.G. (2011) . Processes and impacts of Arctic amplification: A research synthesis, Global and Planetary Change, 77(1-2), pp. 85-96 Wetherald, R. and Manabe, S. (1975). The effects of changing the solar constant on the climate of a general circulation model. J. Atmos. Sci., 23 pp 2044-2059</p> <div class="credits"> <p class="dwt_author">Pithan, Felix; Mauritsen, Thorsten</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">348</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/12466332"> <span id="translatedtitle">Applications of <span class="hlt">Feedback</span> Control in Quantum Systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We give an introduction to <span class="hlt">feedback</span> control in quantum systems, as well as an overview of the variety of applications which have been explored to date. This introductory review is aimed primarily at control theorists unfamiliar with quantum <span class="hlt">mechanics</span>, but should also be useful to quantum physicists interested in applications of <span class="hlt">feedback</span> control. We explain how <span class="hlt">feedback</span> in quantum systems</p> <div class="credits"> <p class="dwt_author">Kurt Jacobs</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">349</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24376030"> <span id="translatedtitle">Qualitative tissue differentiation by analysing the intensity ratios of atomic emission lines using laser induced breakdown spectroscopy (LIBS): prospects for a <span class="hlt">feedback</span> <span class="hlt">mechanism</span> for surgical laser systems.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The research work presented in this paper focuses on qualitative tissue differentiation by monitoring the intensity ratios of atomic emissions using 'Laser Induced Breakdown Spectroscopy' (LIBS) on the plasma plume created during laser tissue ablation. The background of this study is to establish a real time <span class="hlt">feedback</span> control <span class="hlt">mechanism</span> for clinical laser surgery systems during the laser ablation process. Ex-vivo domestic pig tissue samples (muscle, fat, nerve and skin) were used in this experiment. Atomic emission intensity ratios were analyzed to find a characteristic spectral line for each tissue. The results showed characteristic elemental emission intensity ratios for the respective tissues. The spectral lines and intensity ratios of these specific elements varied among the different tissue types. The main goal of this study is to qualitatively and precisely identify different tissue types for tissue specific laser surgery. (© 2013 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim). PMID:24376030</p> <div class="credits"> <p class="dwt_author">Kanawade, Rajesh; Mahari, Fanuel; Klämpfl, Florian; Rohde, Maximilian; Knipfer, Christian; Tangermann-Gerk, Katja; Adler, Werner; Schmidt, Michael; Stelzle, Florian</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">350</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4164001"> <span id="translatedtitle">Primary motor cortex and fast <span class="hlt">feedback</span> responses to <span class="hlt">mechanical</span> perturbations: a primer on what we know now and some suggestions on what we should find out next</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Many researchers have drawn a clear distinction between fast <span class="hlt">feedback</span> responses to <span class="hlt">mechanical</span> perturbations (e.g., stretch responses) and voluntary control processes. But this simple distinction is difficult to reconcile with growing evidence that long-latency stretch responses share most of the defining capabilities of voluntary control. My general view—and I believe a growing consensus—is that the functional similarities between long-latency stretch responses and voluntary control processes can be readily understood based on their shared neural circuitry, especially a transcortical pathway through primary motor cortex. Here I provide a very brief and selective account of the human and monkey studies linking a transcortical pathway through primary motor cortex to the generation and functional sophistication of the long-latency stretch response. I then lay out some of the notable issues that are ready to be answered. PMID:25309359</p> <div class="credits"> <p class="dwt_author">Pruszynski, J. Andrew</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">351</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2015JSV...334..296M"> <span id="translatedtitle">Analysis and synthesis of modal and non-modal self-excited oscillations in a class of <span class="hlt">mechanical</span> systems with nonlinear velocity <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Many devices and processes utilize self-excited oscillations either as the working principle or as the performance enhancer. The present paper investigates a nonlinear velocity <span class="hlt">feedback</span> control method for generating artificial self-excited oscillations in a class of two degrees-of-freedom <span class="hlt">mechanical</span> systems. The paper derives the conditions of existence and stability of the modal oscillations and numerically corroborates this. It also proposes a methodology to design the control system for inducing natural oscillations in one of the desired modes. Other than modal oscillations, the system can also be designed to oscillate in a non-modal state with the desired frequency and amplitude-ratio within a specific range (depending on the system). Numerical simulations confirm the analytical results. Further analysis shows that for each frequency of excitation, the control cost is minimum when the system operates at an optimal amplitude-ratio.</p> <div class="credits"> <p class="dwt_author">Malas, Anindya; Chatterjee, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">352</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1203579"> <span id="translatedtitle"><span class="hlt">Mechanisms</span> of Mutagenesis by a Bulky DNA Lesion at the Guanine N7 <span class="hlt">Position</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">In order to examine the <span class="hlt">mechanisms</span> of mutagenesis by a bulky DNA lesion at the guanine N7 <span class="hlt">position</span>, the replicative form DNA of phage M13AB28 (mp8 without the amber codons in phage genes) was modified in vitro with aflatoxin B(1)-2,3-dichloride and transfected into appropriate Escherichia coli cells. Forward mutations in the lacZ ?-complementing gene segment were identified as light blue or colorless plaques on appropriate indicator plates, isolated, and defined by DNA sequencing. Transfection of modified DNA into uvrA(-)/mucAB(+) cells without prior UV (SOS) induction increased mutation frequency eight-fold over untreated DNA, whereas this increase was 12-fold upon SOS induction. Transfection of modified DNA after conversion of the primary guanine-aflatoxin lesions to the stable imidazole ring-opened formamidopyrimidine-aflatoxin suggested that these lesions were nearly equally mutagenic. A majority of point mutations under all conditions affected G:C bp. Base substitutions were in the majority, but significant frameshift mutagenesis was also detected in SOS-induced cells. Both G-to-T transversions and G-to-A transitions were produced at equal efficiency and together accounted for virtually all of the base substitutions induced by the primary lesions. Point mutations occurred predominantly at predicted damage hotspots. The characteristics of base substitution and frameshift mutations, together with available information point to multiple <span class="hlt">mechanisms</span> of mutagenesis by this class of mutagens. The data indicate that primary lesions have the properties of both a noninstructional and pseudo-instructional lesion. In addition, the sequence context appears to play a role in determining whether a frameshift or a base substitution is induced by this bulky lesion. PMID:3147220</p> <div class="credits"> <p class="dwt_author">Sambamurti, K.; Callahan, J.; Luo, X.; Perkins, C. P.; Jacobsen, J. S.; Humayun, M. Z.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">353</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4274697"> <span id="translatedtitle">The pilot experience upon surgical ablation of large liver tumor by microwave system with tissue permittivity <span class="hlt">feedback</span> control <span class="hlt">mechanism</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Background Microwave ablation (MWA) is used to treat patients with unresectable liver cancer. Our institution applied a novel microwave generator capable of automatically adjusting energy levels based on <span class="hlt">feedback</span> related to tissue permittivity. This approach is meant to facilitate ablations over larger areas and provide results of greater predictablility. This paper reports on the safety, efficacy, and feasibility of this new system in the treatment of patients with large liver tumors. Methods Between July 2012 and December 2012, a total of 23 patients with malignant liver tumors exceeding 4 cm in diameter underwent surgical MWA using a 902–928 MHz generator. The proposed system used a 14-gauge antenna without internal-cooling. Follow up on tumor recurrence was performed using contrast-enhanced computed tomography or magnetic resonance imaging at 1 month and then at 3 month intervals for a period of at least 12 months following ablation. Results Among the cancers treated, 10 were primary hepatocellular carcinomas (HCCs) and 13 were metastatic lesions from primary colorectal cancer (CRLM). The mean tumor size was 5.40 cm (range of 4.0-7.0 cm). A total of 18 patients underwent MWA via open surgery, and 5 received laparoscopic MWA. The mean ablation time was 1982 seconds, with a range of 900-3600 seconds, and the median number of ablation sessions was 2.0 (range of 1–4 sessions). The rate of complete ablation, as defined by a total loss of contrast-enhancement one month post-treatment, was 82.6% (19 of 23 patients), and the rate of local recurrence was 26.3% (5 of 19 patients). For tumors with a diameter of 4.0-7.0 cm, the technical success rate of MWA was higher for HCC patients (70%) than for metastatic liver cancer (53.8%) patients; however, the difference was not statistically significant. All patients survived throughout the observation period, and the morbidity rate was 8.6%. Conclusions MWA treatment using the proposed system with tissue permittivity <span class="hlt">feedback</span> control resulted in a high rate of complete ablation and reduced morbidity. This approach proved to be a fast, easy, and effective option for the ablation of large liver cancers, particularly HCCs. PMID:25336074</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">354</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3216642"> <span id="translatedtitle">Clustering in Cell Cycle Dynamics with General Response/Signaling <span class="hlt">Feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Motivated by experimental and theoretical work on autonomous oscillations in yeast, we analyze ordinary differential equations models of large populations of cells with cell-cycle dependent <span class="hlt">feedback</span>. We assume a particular type of <span class="hlt">feedback</span> that we call Responsive/Signaling (RS), but do not specify a functional form of the <span class="hlt">feedback</span>. We study the dynamics and emergent behaviour of solutions, particularly temporal clustering and stability of clustered solutions. We establish the existence of certain periodic clustered solutions as well as “uniform” solutions and add to the evidence that cell-cycle dependent <span class="hlt">feedback</span> robustly leads to cell-cycle clustering. We highlight the fundamental differences in dynamics between systems with negative and <span class="hlt">positive</span> <span class="hlt">feedback</span>. For <span class="hlt">positive</span> <span class="hlt">feedback</span> systems the most important <span class="hlt">mechanism</span> seems to be the stability of individual isolated clusters. On the other hand we find that in negative <span class="hlt">feedback</span> systems, clusters must interact with each other to reinforce coherence. We conclude from various details of the mathematical analysis that negative <span class="hlt">feedback</span> is most consistent with observations in yeast experiments. PMID:22001733</p> <div class="credits"> <p class="dwt_author">Young, Todd R.; Fernandez, Bastien; Buckalew, Richard; Moses, Gregory; Boczko, Erik M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">355</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19940017168&hterms=jensen+wake+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Djensen%2Bwake%2Bmodel"> <span id="translatedtitle">Climate forcings and <span class="hlt">feedbacks</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Global temperature has increased significantly during the past century. Understanding the causes of observed global temperature change is impossible in the absence of adequate monitoring of changes in global climate forcings and radiative <span class="hlt">feedbacks</span>. Climate forcings are changes imposed on the planet's energy balance, such as change of incoming sunlight or a human-induced change of surface properties due to deforestation. Radiative <span class="hlt">feedbacks</span> are radiative changes induced by climate change, such as alteration of cloud properties or the extent of sea ice. Monitoring of global climate forcings and <span class="hlt">feedbacks</span>, if sufficiently precise and long-term, can provide a very strong constraint on interpretation of observed temperature change. Such monitoring is essential to eliminate uncertainties about the relative importance of various climate change <span class="hlt">mechanisms</span> including tropospheric sulfate aerosols from burning of coal and oil smoke from slash and burn agriculture, changes of solar irradiance changes of several greenhouse gases, and many other <span class="hlt">mechanisms</span>. The considerable variability of observed temperature, together with evidence that a substantial portion of this variability is unforced indicates that observations of climate forcings and <span class="hlt">feedbacks</span> must be continued for decades. Since the climate system responds to the time integral of the forcing, a further requirement is that the observations be carried out continuously. However, precise observations of forcings and <span class="hlt">feedbacks</span> will also be able to provide valuable conclusions on shorter time scales. For example, knowledge of the climate forcing by increasing CFC's relative to the forcing by changing ozone is important to policymakers, as is information on the forcing by CO2 relative to the forcing by sulfate aerosols. It will also be possible to obtain valuable tests of climate models on short time scales, if there is precise monitoring of all forcings and <span class="hlt">feedbacks</span> during and after events such as a large volcanic eruption or an El Nino.</p> <div class="credits"> <p class="dwt_author">Hansen, James</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">356</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.cs.ubc.ca/cgi-bin/tr/2006/TR-2006-14.pdf"> <span id="translatedtitle">Captured Dynamics Data of 5 <span class="hlt">Mechanical</span> Knobs</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">1 Captured Dynamics Data of 5 <span class="hlt">Mechanical</span> Knobs Torque models are presented for five <span class="hlt">mechanical</span> fitting was used to estimate model parameters for <span class="hlt">position</span>, velocity, and acceleration model parts the rendering of feelings on a force-<span class="hlt">feedback</span> knob. This haptic camera is an extension of similar <span class="hlt">mechanical</span></p> <div class="credits"> <p class="dwt_author">MacLean, Karon</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">357</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.sciencemag.org/content/322/5900/390.full?sid=ecdf6360-7e23-482a-b322-4571c6a3cb51"> <span id="translatedtitle"><span class="hlt">Feedback</span> Loops Shape Cellular Signals in Space and Time</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This article discusses the study of <span class="hlt">feedback</span> loops in biological systems. <span class="hlt">Positive</span> and negative <span class="hlt">feedback</span> loops are common regulatory elements in biological signaling systems. We discuss core <span class="hlt">feedback</span> motifs that have distinct roles in shaping signaling responses in space and time. We also discuss approaches to experimentally investigate <span class="hlt">feedback</span> loops in signaling systems.</p> <div class="credits"> <p class="dwt_author">Onn Brandman (University of California-San Francisco and Howard Hughes Medical Institute;Department of Cellular and Molecular Pharmacology); Tobias Meyer (Stanford University Medical Center;Department of Chemical and Systems Biology)</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-10-17</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">358</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25074501"> <span id="translatedtitle">Social closeness and <span class="hlt">feedback</span> modulate susceptibility to the framing effect.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Although we often seek social <span class="hlt">feedback</span> (SFB) from others to help us make decisions, little is known about how SFB affects decisions under risk, particularly from a close peer. We conducted two experiments using an established framing task to probe how decision-making is modulated by SFB valence (<span class="hlt">positive</span>, negative) and the level of closeness with <span class="hlt">feedback</span> provider (friend, confederate). Participants faced mathematically equivalent decisions framed as either an opportunity to keep (gain frame) or lose (loss frame) part of an initial endowment. Periodically, participants were provided with <span class="hlt">positive</span> (e.g., "Nice!") or negative (e.g., "Lame!") <span class="hlt">feedback</span> about their choices. Such <span class="hlt">feedback</span> was provided by either a confederate (Experiment 1) or a gender-matched close friend (Experiment 2). As expected, the framing effect was observed in both experiments. Critically, an individual's susceptibility to the framing effect was modulated by the valence of the SFB, but only when the <span class="hlt">feedback</span> provider was a close friend. This effect was reflected in the activation patterns of ventromedial prefrontal cortex and posterior cingulate cortex, regions involved in complex decision-making. Taken together, these results highlight social closeness as an important factor in understanding the impact of SFB on neural <span class="hlt">mechanisms</span> of decision-making. PMID:25074501</p> <div class="credits"> <p class="dwt_author">Sip, Kamila E; Smith, David V; Porcelli, Anthony J; Kar, Kohitij; Delgado, Mauricio R</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">359</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1997JAP....81.4293G"> <span id="translatedtitle">Sensing <span class="hlt">position</span> and speed by recording magnetization transitions on <span class="hlt">mechanically</span> functional machine members (abstract)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Conventional means of sensing <span class="hlt">position</span> and speed of moving machine members for control purposes typically requires the use of supplementary, ad hoc devices. Many <span class="hlt">mechanically</span> functional moving machine members are fabricated from ferromagnetic steels and may, thus, provide an opportunity to themselves carry <span class="hlt">positionally</span> relevant information in the form of local regions of deliberately instilled remanent magnetization, Mr. To avoid ambiguities associated with the imprecise borders of such regions as well as their possibly preexisting presence, information is more reliably carried in the form of local transitions in the polarity of Mr from a quiescent bias. The presence and physical location of such transitions relative to reference features either on the member itself or on other members undergoing correlated motion constitutes stored information. The presence of a transition is signaled by the transitory appearance of the external field associated with ??Mr as the transition containing region passes by a magnetic-field detecting device fixed to the machine frame. Implanting and removing transitions from parts while in motion is readily accomplished by pulsed currents and biasing magnets. While the whole process of storing, reading, and erasing bits of information in magnetic form follows the concepts and principles of conventional magnetic recording, profoundly different quantitative factors, conditions, and performance requirements affect the implementation of the described sensing system. In particular, the coercivity, Hc, of commonly used steels is 3-30 Oe versus 300-1200 Oe in recording media and both the thickness of the media and the air gaps separating the media surface from the heads used in conventional systems are each 2-3 orders of magnitude smaller than their counterparts in the described system, where speed may also be variable down to zero. While the combined effect of these factors is to greatly diminish the attainable density of recorded information, this has only modest impact on the ability of the system to fulfill its purpose by effectively providing a dynamically adjustable "magnetic cam." The magnetic and operational details of an experimental sensing system were explored using a "timing" belt as the <span class="hlt">mechanically</span> functional member. The molded polyurethane belt incorporated cabled steel wires (nine cold drawn carbon steel 0.08 mm diam) wound in an 0.8 mm pitch helix around the belt circumference; 13 full turns in the 10 mm wide belt. An isolated cable showed 4?M=15 kG in a 100 Oe field, 4?Mr=11.9 kG with Hc=17 Oe. The belt was driven at surface speeds from 0-10 m/s. Bias was provided by a small barium ferrite magnet, magnetic transitions were recorded by current pulses through a coil wound on a gapped core and detected by a Hall-effect field sensor located at a fixed distance downstream. Fields of ±10 Oe with gradients >1 Oe/mm were detected at distances of 1.5 mm from the belt surface. Speed was determined from the elapsed time between a recording pulse and its detection.</p> <div class="credits"> <p class="dwt_author">Garshelis, I. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">360</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://arxiv.org/pdf/gr-qc/0312005v5"> <span id="translatedtitle">A Graph Model for the quantum <span class="hlt">mechanics</span> of a moving cyclic disturbance interacting at a spatial <span class="hlt">position</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">An analysis is made of a moving disturbance using a directed cyclic graph. A statistical approach is used to calculate the alternative <span class="hlt">positions</span> in space and state of the disturbance with a defined observed time. The probability for a freely moving entity interacting in a particular spatial <span class="hlt">position</span> is calculated and a formulation is derived for the minimum locus of uncertainty in <span class="hlt">position</span> and momentum. This is found to accord with calculations for quantum <span class="hlt">mechanics</span>. The model has proven amenable to computer modelling; a copy of the "SimulTime" program is available on request.</p> <div class="credits"> <p class="dwt_author">Daniel Brown</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-03-24</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_17");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' 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showDiv("page_20");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">361</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/984409"> <span id="translatedtitle">Global Orbit <span class="hlt">Feedback</span> in RHIC</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">For improved reproducibility of good operating conditions and ramp commissioning efficiency, new dual-plane slow orbit <span class="hlt">feedback</span> during the energy ramp was implemented during run-10 in the Relativistic Heavy Ion Collider (RHIC). The orbit <span class="hlt">feedback</span> is based on steering the measured orbit, after subtraction of the dispersive component, to either a design orbit or to a previously saved reference orbit. Using multiple correctors and beam <span class="hlt">position</span> monitors, an SVD-based algorithm is used for determination of the applied corrections. The online model is used as a basis for matrix computations. In this report we describe the <span class="hlt">feedback</span> design, review the changes made to realize its implementation, and assess system performance.</p> <div class="credits"> <p class="dwt_author">Minty, M.; Hulsart, R.; Marusic, A.; Michnoff, R.; Ptitsyn, V.; Robert-Demolaize, G.; Satogata, T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-05-23</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">362</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23457492"> <span id="translatedtitle">VCP Is an integral component of a novel <span class="hlt">feedback</span> <span class="hlt">mechanism</span> that controls intracellular localization of catalase and H2O2 Levels.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Catalase is a key antioxidant enzyme that catalyzes the decomposition of hydrogen peroxide (H2O2) to water and oxygen, and it appears to shuttle between the cytoplasm and peroxisome via unknown <span class="hlt">mechanisms</span>. Valosin-containing protein (VCP) belongs to the AAA class of ATPases and is involved in diverse cellular functions, e.g. cell cycle and protein degradation, etc. Here we show that VCP and PEX19, a protein essential for peroxisome biogenesis, interact with each other. Knockdown of either VCP or PEX19 resulted in a predominantly cytoplasmic redistribution of catalase, and loss of VCP ATPase activity also increased its cytoplasmic redistribution. Moreover, VCP knockdown decreased intracellular ROS levels in normal and H2O2-treated cells, and an oxidation-resistant VCP impaired the ROS-induced cytoplasmic redistribution of catalase. These observations reveal a novel <span class="hlt">feedback</span> <span class="hlt">mechanism</span>, in which VCP can sense H2O2 levels, and regulates them by controlling the localization of catalase. PMID:23457492</p> <div class="credits"> <p class="dwt_author">Murakami, Katsuhiro; Ichinohe, Yuzuru; Koike, Masaaki; Sasaoka, Norio; Iemura, Shun-ichiro; Natsume, Tohru; Kakizuka, Akira</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">363</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25223703"> <span id="translatedtitle">Profiling human protein degradome delineates cellular responses to proteasomal inhibition and reveals a <span class="hlt">feedback</span> <span class="hlt">mechanism</span> in regulating proteasome homeostasis.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Global change in protein turnover (protein degradome) constitutes a central part of cellular responses to intrinsic or extrinsic stimuli. However, profiling protein degradome remains technically challenging. Recently, inhibition of the proteasome, e.g., by using bortezomib (BTZ), has emerged as a major chemotherapeutic strategy for treating multiple myeloma and other human malignancies, but systematic understanding of the <span class="hlt">mechanisms</span> for BTZ drug action and tumor drug resistance is yet to be achieved. Here we developed and applied a dual-fluorescence-based Protein Turnover Assay (ProTA) to quantitatively profile global changes in human protein degradome upon BTZ-induced proteasomal inhibition. ProTA and subsequent network analyses delineate potential molecular basis for BTZ action and tumor drug resistance in BTZ chemotherapy. Finally, combined use of BTZ with drugs targeting the ProTA-identified key genes or pathways in BTZ action reduced BTZ resistance in multiple myeloma cells. Remarkably, BTZ stabilizes proteasome subunit PSMC1 and proteasome assembly factor PSMD10, suggesting a previously under-appreciated <span class="hlt">mechanism</span> for regulating proteasome homeostasis. Therefore, ProTA is a novel tool for profiling human protein degradome to elucidate potential <span class="hlt">mechanisms</span> of drug action and resistance, which might facilitate therapeutic development targeting proteostasis to treat human disorders. PMID:25223703</p> <div class="credits"> <p class="dwt_author">Yu, Tao; Tao, Yonghui; Yang, Meiqiang; Chen, Peng; Gao, Xiaobo; Zhang, Yanbo; Zhang, Tao; Chen, Zi; Hou, Jian; Zhang, Yan; Ruan, Kangcheng; Wang, Hongyan; Hu, Ronggui</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">364</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=trivia&pg=2&id=EJ871430"> <span id="translatedtitle">Learning from <span class="hlt">Feedback</span>: Spacing and the Delay-Retention Effect</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">Most modern research on the effects of <span class="hlt">feedback</span> during learning has assumed that <span class="hlt">feedback</span> is an error correction <span class="hlt">mechanism</span>. Recent studies of <span class="hlt">feedback</span>-timing effects have suggested that <span class="hlt">feedback</span> might also strengthen initially correct responses. In an experiment involving cued recall of trivia facts, we directly tested several theories of…</p> <div class="credits"> <p class="dwt_author">Smith, Troy A.; Kimball, Daniel R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">365</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4208176"> <span id="translatedtitle">Detecting Both the Mass and <span class="hlt">Position</span> of an Accreted Particle by a Micro/Nano-<span class="hlt">Mechanical</span> Resonator Sensor</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">In the application of a micro-/nano-<span class="hlt">mechanical</span> resonator, the <span class="hlt">position</span> of an accreted particle and the resonant frequencies are measured by two different physical systems. Detecting the particle <span class="hlt">position</span> sometimes can be extremely difficult or even impossible, especially when the particle is as small as an atom or a molecule. Using the resonant frequencies to determine the mass and <span class="hlt">position</span> of an accreted particle formulates an inverse problem. The Dirac delta function and Galerkin method are used to model and formulate an eigenvalue problem of a beam with an accreted particle. An approximate method is proposed by ignoring the off-diagonal elements of the eigenvalue matrix. Based on the approximate method, the mass and <span class="hlt">position</span> of an accreted particle can be decoupled and uniquely determined by measuring at most three resonant frequencies. The approximate method is demonstrated to be very accurate when the particle mass is small, which is the application scenario for much of the mass sensing of micro-/nano-<span class="hlt">mechanical</span> resonators. By solving the inverse problem, the <span class="hlt">position</span> measurement becomes unnecessary, which is of some help to the mass sensing application of a micro-/nano-<span class="hlt">mechanical</span> resonator by reducing two measurement systems to one. How to apply the method to the general scenario of multiple accreted particles is also discussed. PMID:25184493</p> <div class="credits"> <p class="dwt_author">Zhang, Yin; Liu, Yun</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">366</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/r6g5w3tt54528137.pdf"> <span id="translatedtitle">Neocognitron: A self-organizing neural network model for a <span class="hlt">mechanism</span> of pattern recognition unaffected by shift in <span class="hlt">position</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A neural network model for a <span class="hlt">mechanism</span> of visual pattern recognition is proposed in this paper. The network is self-organized by “learning without a teacher”, and acquires an ability to recognize stimulus patterns based on the geometrical similarity (Gestalt) of their shapes without affected by their <span class="hlt">positions</span>. This network is given a nickname “neocognitron”. After completion of self-organization, the network</p> <div class="credits"> <p class="dwt_author">Kunihiko Fukushima</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">367</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/29066641"> <span id="translatedtitle">Supine body <span class="hlt">position</span> as a risk factor for nosocomial pneumonia in <span class="hlt">mechanically</span> ventilated patients: a randomised trial</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">1851 Summary Background Risk factors for nosocomial pneumonia, such as gastro-oesophageal reflux and subsequent aspiration, can be reduced by semirecumbent body <span class="hlt">position</span> in intensive-care patients. The objective of this study was to assess whether the incidence of nosocomial pneumonia can also be reduced by this measure. Methods This trial was stopped after the planned interim analysis. 86 intubated and <span class="hlt">mechanically</span></p> <div class="credits"> <p class="dwt_author">Mitra B Drakulovic; Antoni Torres; Torsten T Bauer; Jose M Nicolas; Santiago Nogué; Miquel Ferrer</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">368</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3580957"> <span id="translatedtitle">Furosemide Alters Organ of Corti <span class="hlt">Mechanics</span>: Evidence for <span class="hlt">Feedback</span> of Outer Hair Cells upon the Basilar Membrane</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">A widely held hypothesis of mammalian cochlear function is that the <span class="hlt">mechanical</span> responses to sound of the basilar membrane depend on transduction by the outer hair cells. We have tested this hypothesis by studying the effect upon basilar membrane vibrations (measured by means of either the Mössbauer technique or Doppler-shift laser velocimetry) of systemic injection of furosemide, a loop diuretic that decreases transduction currents in hair cells. Furosemide reversibly altered the responses to tones and clicks of the chinchilla basilar membrane, causing response-magnitude reductions that were largest (up to 61 dB, averaging 25-30 dB) at low stimulus intensities at the characteristic frequency (CF) and small or nonexistent at high intensities and at frequencies far removed from CF. Furosemide also induced response-phase lags that were largest at low stimulus intensities (averaging 77°) and were confined to frequencies close to CF. These results constitute the most definitive demonstration to date that <span class="hlt">mechanical</span> responses of the basilar membrane are dependent on the normal function of the organ of Corti and strongly implicate the outer hair cells as being responsible for the high sensitivity and frequency selectivity of basilar membrane responses. A corollary of these findings is that sensorineural hearing deficits in humans due to outer hair cell loss reflect pathologically diminished vibrations of the basilar membrane. PMID:2010805</p> <div class="credits"> <p class="dwt_author">Ruggero, Mario A.; Rich, Nola C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">369</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3004135"> <span id="translatedtitle">Downregulation of Friend Leukemia Virus Integration 1 as a <span class="hlt">Feedback</span> <span class="hlt">Mechanism</span> That Restrains Lipopolysaccharide Induction of Matrix Metalloproteases and Interleukin-10 in Human Macrophages</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The E26 transformation-specific (Ets) proteins are a family of transcription factors with important roles in a variety of cellular processes ranging from proliferation and differentiation to transformation and metastasis. Tissue-specific expression of Ets proteins and their ability to interact with other families of transcription factors contribute to their versatility. In this study, we investigated the regulation of Ets factors in primary human monocytes and macrophages, and their role in matrix metalloprotease (MMP) and cytokine production. The macrophage-activating Toll-like receptor ligand, lipopolysaccharide (LPS), induced the expression of Ets family members epithelium-specific Ets factor 3 (ESE-3) and TEL-2 but rapidly suppressed Friend leukemia virus integration 1 (FLI-1) expression. Modulation of FLI-1 expression using either RNA interference or forced expression identified a <span class="hlt">positive</span> role for FLI-1 in contributing to LPS-induced expression of MMP-1, MMP-3, MMP-10, and interleukin-10 (IL-10). Thus, the rapid downregulation of FLI-1 expression after LPS stimulation attenuates the induction of various MMPs and IL-10 under inflammatory conditions. In contrast, the expression of IL-6 and TNF? and the effects of interferon (IFN)? on LPS responses were not dependent on FLI-1. Our results define a novel FLI-1-mediated self-regulatory <span class="hlt">feedback</span> loop that limits MMP expression and thus may attenuate extent of tissue destruction associated with inflammatory responses. PMID:20879862</p> <div class="credits"> <p class="dwt_author">Ho, Hao H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">370</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007JNEng...4..234B"> <span id="translatedtitle">Asymmetric interjoint <span class="hlt">feedback</span> contributes to postural control of redundant multi-link systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Maintaining the postural configuration of a limb such as an arm or leg is a fundamental neural control task that involves the coordination of multiple linked body segments. Biological systems are known to use a complex network of inter- and intra-joint <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> arising from muscles, spinal reflexes and higher neuronal structures to stabilize the limbs. While previous work has shown that a small amount of asymmetric heterogenic <span class="hlt">feedback</span> contributes to the behavior of these systems, a satisfactory functional explanation for this non-conservative <span class="hlt">feedback</span> structure has not been put forth. We hypothesized that an asymmetric multi-joint control strategy would confer both an energetic and stability advantage in maintaining endpoint <span class="hlt">position</span> of a kinematically redundant system. We tested this hypothesis by using optimal control models incorporating symmetric versus asymmetric <span class="hlt">feedback</span> with the goal of maintaining the endpoint location of a kinematically redundant, planar limb. Asymmetric <span class="hlt">feedback</span> improved endpoint control performance of the limb by 16%, reduced energetic cost by 21% and increased interjoint coordination by 40% compared to the symmetric <span class="hlt">feedback</span> system. The overall effect of the asymmetry was that proximal joint motion resulted in greater torque generation at distal joints than vice versa. The asymmetric organization is consistent with heterogenic stretch reflex gains measured experimentally. We conclude that asymmetric <span class="hlt">feedback</span> has a functionally relevant role in coordinating redundant degrees of freedom to maintain the <span class="hlt">position</span> of the hand or foot.</p> <div class="credits"> <p class="dwt_author">Bunderson, Nathan E.; Ting, Lena H.; Burkholder, Thomas J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">371</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=%22reinforcement+learning%22&id=EJ793233"> <span id="translatedtitle">The Human Ventromedial Frontal Lobe Is Critical for Learning from Negative <span class="hlt">Feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">Are <span class="hlt">positive</span> and negative <span class="hlt">feedback</span> weighed in a common balance in the brain, or do they influence behaviour through distinct neural <span class="hlt">mechanisms</span>? Recent neuroeconomic studies in both human and non-human primates indicate that the ventromedial frontal lobe carries information about both losses and gains, suggesting that this region may encode value…</p> <div class="credits"> <p class="dwt_author">Wheeler, Elizabeth Z.; Fellows, Lesley K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">372</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dspace.mit.edu/handle/1721.1/40943"> <span id="translatedtitle">Design and manufacture of an electro-<span class="hlt">mechanical</span> hand <span class="hlt">position</span> tracker</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">This thesis discusses the conceptual design, manufacture, and assembly of a device that tracks the movements and <span class="hlt">position</span> of a user's hand. This device will be used for stroke patients undergoing rehabilitation using robotic ...</p> <div class="credits"> <p class="dwt_author">Tan, Nicola</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">373</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://repository.tamu.edu/handle/1969.1/ETD-TAMU-2001-THESIS-B45"> <span id="translatedtitle">Participant/assessor personality characteristics that influence <span class="hlt">feedback</span> acceptance in developmental assessment centers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p class="result-summary">(<span class="hlt">positive</span> or negative) and magnitude of the <span class="hlt">feedback</span>. Results indicated that (a) <span class="hlt">feedback</span> acceptance was multidimensional in nature; (b) magnitude, but not <span class="hlt">feedback</span> direction, shared a significant, negative relationship with these dimensions; (c...</p> <div class="credits"> <p class="dwt_author">Bell, Suzanne Tamara</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-07</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">374</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/25223550"> <span id="translatedtitle">Glucose-driven chemo-<span class="hlt">mechanical</span> autonomous drug-release system with multi-enzymatic amplification toward <span class="hlt">feedback</span> control of blood glucose in diabetes.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A second-generation novel chemo-<span class="hlt">mechanical</span> autonomous drug release system, incorporating various improvements over our first-generation system, was fabricated and evaluated. Enhanced oxygen uptake by the enzyme membrane of the organic engine was facilitated by optimizing the quantity of enzyme immobilizer, PVA-SbQ, and by hydrophobizing the membrane surface. Various quantities of PVA-SbQ were evaluated in the organic engine by measuring the decompression rate, with 1.5mg/cm(2) yielding optimum results. When fluororesin was used as a hydrophobizing coating, the time to reach the peak decompression rate was shortened 2.3-fold. The optimized elements of the system were evaluated as a unit, first in an open loop and then in a closed loop setting, using a mixture of glucose solution (25mmol/L), ATP and MgCI2 with glucose hexokinase enzyme (HK) as a glucose reducer. In conclusion, <span class="hlt">feedback</span>-control of physiologically relevant glucose concentration was demonstrated by the second-generation drug release system without any requirement for external energy. PMID:25223550</p> <div class="credits"> <p class="dwt_author">Munkhjargal, Munkhbayar; Hatayama, Kohdai; Matsuura, Yuki; Toma, Koji; Arakawa, Takahiro; Mitsubayashi, Kohji</p> <p class="dwt_publisher"></p> <p class="publishDate">2015-05-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">375</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4178494"> <span id="translatedtitle">A <span class="hlt">Feedback</span> <span class="hlt">Mechanism</span> to Control Apoptosis Occurs in the Digestive Gland of the Oyster Crassostrea gigas Exposed to the Paralytic Shellfish Toxins Producer Alexandrium catenella</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">To better understand the effect of Paralytic Shellfish Toxins (PSTs) accumulation in the digestive gland of the Pacific oyster, Crassostrea gigas, we experimentally exposed individual oysters for 48 h to a PSTs producer, the dinoflagellate Alexandrium catenella. In comparison to the effect of the non-toxic Alexandrium tamarense, on the eight apoptotic related genes tested, Bax and BI.1 were significantly upregulated in oysters exposed 48 h to A. catenella. Among the five detoxification related genes tested, the expression of cytochrome P450 (CYP1A) was shown to be correlated with toxin concentration in the digestive gland of oysters exposed to the toxic dinoflagellate. Beside this, we observed a significant increase in ROS production, a decrease in caspase-3/7 activity and normal percentage of apoptotic cells in this tissue. Taken together, these results suggest a <span class="hlt">feedback</span> <span class="hlt">mechanism</span>, which may occur in the digestive gland where BI.1 could play a key role in preventing the induction of apoptosis by PSTs. Moreover, the expression of CYP1A, Bax and BI.1 were found to be significantly correlated to the occurrence of natural toxic events, suggesting that the expression of these genes together could be used as biomarker to assess the biological responses of oysters to stress caused by PSTs. PMID:25257788</p> <div class="credits"> <p class="dwt_author">Rolland, Jean-Luc; Medhioub, Walid; Vergnes, Agnes; Abi-khalil, Celina; Savar, Véronique; Abadie, Eric; Masseret, Estelle; Amzil, Zouher; Laabir, Mohamed</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">376</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22750459"> <span id="translatedtitle">Testosterone interacts with the <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> engaged by Tyr985 of the leptin receptor and diet-induced obesity.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Inhibitory signaling through Tyr985 of the leptin receptor contributes to the attenuation of anorectic leptin action in obese animals. Leptin receptor (LEPR-B) Tyr985Leu homozygote mutant mice (termed l/l) were previously generated to study Tyr985's contributions to inhibition of LEPR-B signaling; young female l/l mice display a lean, leptin-sensitive phenotype, while young male l/l are not significantly different from wild-type. We report here that testosterone (but not estrogen) determines the sex-specificity of the l/l phenotype. This provides additional insight into the cellular <span class="hlt">mechanism</span> by which gonadal hormones determine central sensitivity to leptin, and may help elucidate the long-noted sex differences in leptin sensitivity. Additionally, we observed that Tyr985 signaling protects against a diet-dependent switch that exacerbates obesity with high fat feeding, such that the enhanced leptin sensitivity of l/l mice on a normal diet leads to increased adiposity in the face of chronic high-fat diet. PMID:22750459</p> <div class="credits"> <p class="dwt_author">Johnson, Joshua A; Calo, Sal; Nair, Lekshmi; IglayReger, Heidi B; Greenwald-Yarnell, Megan; Skorupski, Josh; Myers, Martin G; Bodary, Peter F</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">377</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70033433"> <span id="translatedtitle">A laboratory study of particle ploughing and pore-pressure <span class="hlt">feedback</span>: A velocity-weakening <span class="hlt">mechanism</span> for soft glacier beds</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">If basal-water discharge and pressure are sufficiently high, a soft-bedded glacier will slip over its bed by ploughing, the process in which particles that span the ice-bed interface are dragged across the bed surface. Results of laboratory experiments indicate that resistance to ploughing can decrease with increasing ploughing velocity (velocity weakening). During ploughing at various velocities (15-400 ma-1), till was compacted in front of idealized particles, causing pore pressures there that were orders of magnitude higher than the ambient value. This excess pore pressure locally weakened the till in shear, thereby decreasing ploughing resistance by a factor of 3.0-6.6 with a six-fold increase in ploughing velocity. Characteristic timescales of pore-pressure diffusion and compaction down-glacier from ploughing particles depend on till diffusivity, ploughing velocity and sizes of ploughing particles. These timescales accurately predict the ranges of these variables over which excess pore pressure and velocity weakening occurred. Existing ploughing models do not account for velocity weakening. A new ploughing model with no adjustable parameters predicts ploughing resistance to no worse than 38% but requires that excess pore pressures be measured. Velocity weakening by this <span class="hlt">mechanism</span> may affect fast glacier flow, sediment transport by bed deformation and basal seismicity.</p> <div class="credits"> <p class="dwt_author">Thomason, J.F.; Iverson, N.R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">378</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3954254"> <span id="translatedtitle">Coress <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">This issue highlights the importance of anatomical orientation, which can sometimes be difficult during bowel anastomosis and stoma formation. The need for good medical communication and an adequate handover, particularly at night and at weekends for patients with medical co-morbidities or following complex surgery, is emphasised in another case. We are grateful to the clinicians who have provided the material for these reports. The online reporting form is on our website, www.coress.org.uk, which also includes all previous <span class="hlt">feedback</span> reports. Published contributions will be acknowledged by a ‘Certificate of Contribution’, which may be included in the contributor’s record of continuing professional development.</p> <div class="credits"> <p class="dwt_author">Smith, Frank CT</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">379</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20130013061&hterms=feedback&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfeedback"> <span id="translatedtitle">Inverse Compton X-Ray Halos Around High-z Radio Galaxies: A <span class="hlt">Feedback</span> <span class="hlt">Mechanism</span> Powered by Far-Infrared Starbursts or the Cosmic Microwave Background?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">We report the detection of extended X-ray emission around two powerful radio galaxies at z approx. 3.6 (4C 03.24 and 4C 19.71) and use these to investigate the origin of extended, inverse Compton (IC) powered X-ray halos at high redshifts. The halos have X-ray luminosities of L(sub X) approx. 3 x 10(exp 44) erg/s and sizes of approx.60 kpc. Their morphologies are broadly similar to the approx.60 kpc long radio lobes around these galaxies suggesting they are formed from IC scattering by relativistic electrons in the radio lobes, of either cosmic microwave background (CMB) photons or far-infrared photons from the dust-obscured starbursts in these galaxies. These observations double the number of z > 3 radio galaxies with X-ray-detected IC halos. We compare the IC X-ray-to-radio luminosity ratios for the two new detections to the two previously detected z approx. 3.8 radio galaxies. Given the similar redshifts, we would expect comparable X-ray IC luminosities if millimeter photons from the CMB are the dominant seed field for the IC emission (assuming all four galaxies have similar ages and jet powers). Instead we see that the two z approx. 3.6 radio galaxies, which are 4 fainter in the far-infrared than those at z 3.8, also have approx.4x fainter X-ray IC emission. Including data for a further six z > or approx. 2 radio sources with detected IC X-ray halos from the literature, we suggest that in the more compact, majority of radio sources, those with lobe sizes < or approx.100-200 kpc, the bulk of the IC emission may be driven by scattering of locally produced far-infrared photons from luminous, dust-obscured starbursts within these galaxies, rather than millimeter photons from the CMB. The resulting X-ray emission appears sufficient to ionize the gas on approx.100-200 kpc scales around these systems and thus helps form the extended, kinematically quiescent Ly(alpha) emission line halos found around some of these systems. The starburst and active galactic nucleus activity in these galaxies are thus combining to produce an even more effective and widespread "<span class="hlt">feedback</span>" process, acting on the long-term gas reservoir for the galaxy, than either individually could achieve. If episodic radio activity and co-eval starbursts are common in massive, high-redshift galaxies, then this IC-<span class="hlt">feedback</span> <span class="hlt">mechanism</span> may play a role in affecting the star formation histories of the most massive galaxies at the present day.</p> <div class="credits"> <p class="dwt_author">Small, Ian; Blundell, Katherine M.; Lehmer, B. D.; Alexander, D. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">380</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012ERL.....7a1005L"> <span id="translatedtitle">Shrub expansion and climate <span class="hlt">feedbacks</span> in Arctic tundra</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Arctic tundra ecosystems stand to play a substantial role in both the magnitude and rate of global climate warming over the coming decades and centuries. The exact nature of this role will be determined by the combined effects of currently amplified rates of climate warming in the Arctic (Serreze et al 2000) and a series of related <span class="hlt">positive</span> climate <span class="hlt">feedbacks</span> that include mobilization of permafrost carbon (Schuur et al 2008), decreases in surface albedo (Chapin et al 2005) and evapotranspiration (ET) mediated increases in atmospheric water vapor (Swann et al 2010). Conceptually, these <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> are intuitive and readily comprehensible: warming-induced permafrost thaw will make new soil carbon pools accessible for microbial respiration, and increased vegetation productivity, expansion of shrubs in particular, will lower surface reflectance and increase ET. However, our current understanding of these <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> relies largely on limited and local field studies and, as such, the quantitative estimates of <span class="hlt">feedback</span> effects on regional and global climate require spatial upscaling and uncertainty estimates derived from models. Moreover, the <span class="hlt">feedback</span> <span class="hlt">mechanisms</span> interact and their combined net effect on climate is highly variable and not well characterized. A recent study by Bonfils et al (2012) is among the first to explicitly examine how shrub expansion in tundra ecosystems will impact regional climate. Using an Earth system model, Bonfils et al find that an idealized 20% increase in shrub cover north of 60°N latitude will lead to annual temperature increases of 0.66?°C and 1.84?°C, respectively, when the shrubs are 0.5 m and 2 m tall. The modeled temperature increases arise from atmospheric heating as a combined consequence of decreased albedo and increased ET. The primary difference between the two cases is associated with the fact that tall shrubs protrude above the snow, thus reducing albedo year round, whereas short shrubs are completely covered by the snowpack for part of the year. These results support evidence that shrub expansion in Arctic tundra will feed back <span class="hlt">positively</span> to ongoing climate warming but, perhaps more importantly, illustrate the significance of shrub height in dictating the <span class="hlt">feedback</span> strength. While differences in albedo associated with vegetation stature have been previously documented in these ecosystems (Loranty et al 2011, Sturm et al 2005a), the magnitudes of the <span class="hlt">feedbacks</span> on regional climate were unknown. These findings highlight a pressing need to understand the rate and spatial extent at which shrub expansion is occurring. While increases in vegetation productivity inferred from satellite data have been observed across the Arctic (Bunn and Goetz 2006, Goetz et al 2005, Walker et al 2009), recent analyses suggest that the observed trends are a result of general increases in productivity across all vegetation types (Beck and Goetz 2011). Another important finding reported by Bonfils et al (2012) is the <span class="hlt">positive</span> correlation between shrub height and modeled active layer depth (i.e. permafrost thaw). Results from a field study (Blok et al 2010) showed that the shading effects of shrub canopies reduce ground heat flux, which in turn leads to a decrease in active layer depth. Bonfils et al's (2012) results indicate that regional warming as a consequence of albedo and ET <span class="hlt">feedbacks</span> will offset the local cooling effects of increased shrub cover, thus the net climate <span class="hlt">feedback</span> associated with shrub expansion could be greater than reported (owing to biogeochemical processes and related <span class="hlt">feedbacks</span>). A similar study by Lawrence and Swenson (2011) found that snow redistribution to shrub covered areas (Sturm et al 2005b) simultaneously reduced the albedo <span class="hlt">feedback</span> by covering shrubs with snow and introduced a soil warming <span class="hlt">feedback</span> through insulation provided by additional snow cover, with a net result of increased active layer depth under shrubs. When shrub cover (1 m tall canopy) was increased by 20% and less snow was available for redistribution over a greater shrub covered area, the insul</p> <div class="credits"> <p class="dwt_author">Loranty, Michael M.; Goetz, Scott J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-03-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_18");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" 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id="NextPageLink" onclick='return showDiv("page_21");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">381</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21584866"> <span id="translatedtitle">ESTIMATE OF THE TOTAL <span class="hlt">MECHANICAL</span> <span class="hlt">FEEDBACK</span> ENERGY FROM GALAXY CLUSTER-CENTERED BLACK HOLES: IMPLICATIONS FOR BLACK HOLE EVOLUTION, CLUSTER GAS FRACTION, AND ENTROPY</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The total <span class="hlt">feedback</span> energy injected into hot gas in galaxy clusters by central black holes can be estimated by comparing the potential energy of observed cluster gas profiles with the potential energy of non-radiating, <span class="hlt">feedback</span>-free hot gas atmospheres resulting from gravitational collapse in clusters of the same total mass. <span class="hlt">Feedback</span> energy from cluster-centered black holes expands the cluster gas, lowering the gas-to-dark-matter mass ratio below the cosmic value. <span class="hlt">Feedback</span> energy is unnecessarily delivered by radio-emitting jets to distant gas far beyond the cooling radius where the cooling time equals the cluster lifetime. For clusters of mass (4-11) x 10{sup 14} M{sub sun}, estimates of the total <span class="hlt">feedback</span> energy, (1-3) x 10{sup 63} erg, far exceed <span class="hlt">feedback</span> energies estimated from observations of X-ray cavities and shocks in the cluster gas, energies gained from supernovae, and energies lost from cluster gas by radiation. The time-averaged mean <span class="hlt">feedback</span> luminosity is comparable to those of powerful quasars, implying that some significant fraction of this energy may arise from the spin of the black hole. The universal entropy profile in <span class="hlt">feedback</span>-free gaseous atmospheres in Navarro-Frenk-White cluster halos can be recovered by multiplying the observed gas entropy profile of any relaxed cluster by a factor involving the gas fraction profile. While the <span class="hlt">feedback</span> energy and associated mass outflow in the clusters we consider far exceed that necessary to stop cooling inflow, the time-averaged mass outflow at the cooling radius almost exactly balances the mass that cools within this radius, an essential condition to shut down cluster cooling flows.</p> <div class="credits"> <p class="dwt_author">Mathews, William G.; Guo Fulai, E-mail: mathews@ucolick.org [University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-09-10</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">382</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://nar.oxfordjournals.org/cgi/screenpdf/37/14/4707.pdf"> <span id="translatedtitle">Using DNA <span class="hlt">mechanics</span> to predict in vitro nucleosome <span class="hlt">positions</span> and formation energies</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">In eukaryotic genomes, nucleosomes function to compact DNA and to regulate access to it both by simple physical occlusion and by providing the sub- strate for numerous covalent epigenetic tags. While competition with other DNA-binding factors and action of chromatin remodeling enzymes signifi- cantly affect nucleosome formation in vivo, nucleo- some <span class="hlt">positions</span> in vitro are determined by steric exclusion and</p> <div class="credits"> <p class="dwt_author">Alexandre V. Morozov; Karissa Fortney; Daria A. Gaykalova; Vasily M. Studitsky; Jonathan Widom; Eric D. Siggia</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">383</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2000845"> <span id="translatedtitle">A Novel ‘Roll-and-Slide’ <span class="hlt">Mechanism</span> of DNA Folding in Chromatin. Implications for Nucleosome <span class="hlt">Positioning</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">How eukaryotic genomes encode the folding of DNA into nucleosomes and how this intrinsic organization of chromatin guides biological function are questions of wide interest. The physical basis of nucleosome <span class="hlt">positioning</span> lies in the sequence-dependent propensity of DNA to adopt the tightly bent configuration imposed by the binding of the histone proteins. Traditionally, only DNA bending and twisting deformations are considered, while the effects of the lateral displacements of adjacent base pairs are neglected. We demonstrate, however, that these displacements play a much more important structural role than ever imagined. Specifically, the lateral Slide deformations observed at sites of local anisotropic bending of DNA define its superhelical trajectory in chromatin. Furthermore, the computed cost of deforming DNA on the nucleosome is sequence specific: in optimally <span class="hlt">positioned</span> sequences the most easily deformed base-pair steps (CA:TG and TA) occur at sites of large <span class="hlt">positive</span> Slide and negative Roll (where the DNA bends into the minor groove). These conclusions rest upon a treatment of DNA that goes beyond the conventional ribbon model, incorporating all essential degrees of freedom of ‘real’ duplexes in the estimation of DNA deformation energies. Indeed, only after lateral Slide displacements are considered, are we able to account for the sequence-specific folding of DNA found in nucleosome structures. The close correspondence between the predicted and observed nucleosome locations demonstrates the potential advantage of our 'structural' approach in the computer mapping of nucleosome <span class="hlt">positioning</span>. PMID:17585938</p> <div class="credits"> <p class="dwt_author">Tolstorukov, Michael Y.; Colasanti, Andrew V.; McCandlish, David; Olson, Wilma K.; Zhurkin, Victor B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">384</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JASTP..81...59M"> <span id="translatedtitle">Two types of <span class="hlt">positive</span> disturbances in the daytime mid-latitude F2-layer: Morphology and formation <span class="hlt">mechanisms</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Morphological analysis of foF2 variations for the periods of daytime <span class="hlt">positive</span> disturbances over three ionospheric stations St. Petersburg (sub-auroral zone), Slough (middle latitudes), and Alma-Ata (middle-low latitudes) has confirmed the existence of two types of <span class="hlt">positive</span> F2-layer disturbances with different morphology. Type I is referred to those followed by quiet or <span class="hlt">positively</span> disturbed ionospheric conditions. They occur under low or moderate level of geomagnetic activity. <span class="hlt">Positive</span> disturbances of type II are related to strong geomagnetic storms and they are followed by negative ionospheric disturbances. The two types manifest different occurrence frequency distribution and its dependence on latitude and level of geomagnetic activity. They also exhibit different duration and magnitude. This tells that two types of disturbances belong to different classes of events and may have different formation <span class="hlt">mechanisms</span>. Millstone Hill ISR and digisonde hmF2 and foF2 observations for some selected periods of F2-layer <span class="hlt">positive</span> disturbances of both types were analyzed. The original earlier developed self-consistent method to extract thermospheric parameters from ISR observations was used to estimate the contribution of various aeronomic parameters to the observed storm time F2-layer variations. Our analysis of a well-pronounced <span class="hlt">positive</span> disturbances of type II on December 14, 2006 has confirmed the well-known concept by Prölss (1993a,b, 1995)—daytime midlatitude <span class="hlt">positive</span> disturbances of type II are mainly produced by TADs and following them disturbed equatorward winds. However our calculations have shown that about half of the observed <span class="hlt">positive</span> storm effect may be attributed to thermospheric parameter (neutral composition and temperature) variations. The type II of <span class="hlt">positive</span> disturbances presents the first phase of a two-phase (<span class="hlt">positive</span>/negative) ionospheric storm. For this reason their occurrence frequency distribution is similar to that for negative disturbances. The driving force for both disturbances is the same—the thermosphere heating in the auroral zone. Situation with <span class="hlt">positive</span> disturbances of type I is more complicated. Electric fields on April 03, 2004, and neutral composition (mainly atomic oxygen) variations on April 11, 2000 were shown to be responsible for the observed <span class="hlt">positive</span> storm effect. The difference in the two cases is presumably related with the localization (longitudinal sector) of the auroral heating.</p> <div class="credits"> <p class="dwt_author">Mikhailov, A. V.; Perrone, L.; Smirnova, N. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">385</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48403279"> <span id="translatedtitle">Output <span class="hlt">feedback</span> tracking control for ships</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">For most ships, measurements of the ship velocities are not available. For <span class="hlt">feedback</span> control of the ship, estimates of the velocities must therefore be computed from the <span class="hlt">position</span> and heading measurements. The ship <span class="hlt">position</span> is typically measured using the Navstar differential global <span class="hlt">positioning</span> systern (DGPS), while the heading is usually measured by a gyro compass. As the <span class="hlt">position</span> measurements are</p> <div class="credits"> <p class="dwt_author">K. Y. Pettersen; H. Nijmeijer</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">386</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1999SPIE.3878..281D"> <span id="translatedtitle">Through-wafer interrogation of microstructure motion for MEMS <span class="hlt">feedback</span> control</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Closed-loop MEMS control enables <span class="hlt">mechanical</span> microsystems to adapt to the demands of the environment which they are actuating opening a new window of opportunity for future MEMS applications. Planar diffractive optical microsystems have the potential to enable the integrated optical interrogation of MEMS microstructure <span class="hlt">position</span> fully decoupled from the means of <span class="hlt">mechanical</span> actuation which is central to realization of <span class="hlt">feedback</span> control. This paper presents the results of initial research evaluating through-wafer optical microsystems for MEMS integrated optical monitoring. <span class="hlt">Positional</span> monitoring results obtained from a 1.3 micrometer wavelength through- wafer free-space optical probe of a lateral comb resonator fabricated using the Multi-User MEMS Process Service (MUMPS) are presented. Given the availability of <span class="hlt">positional</span> information via probe signal <span class="hlt">feedback</span>, a simulation of the application of nonlinear sliding control is presented illustrating <span class="hlt">position</span> control of the lateral comb resonator structure.</p> <div class="credits"> <p class="dwt_author">Dawson, Jeremy M.; Chen, Jingdong; Brown, Kolin S.; Famouri, Parviz F.; Hornak, Lawrence A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">387</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/934887"> <span id="translatedtitle">Detecting vegetation-precipitation <span class="hlt">feedbacks</span> in mid-Holocene North Africa from two climate models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Using two climate-vegetation model simulations from the Fast Ocean Atmosphere Model (FOAM) and the Community Climate System Model (CCSM, version 2), we investigate vegetation-precipitation <span class="hlt">feedbacks</span> across North Africa during the mid-Holocene. From mid-Holocene snapshot runs of FOAM and CCSM2, we detect a negative <span class="hlt">feedback</span> at the annual timescale with our statistical analysis. Using the Monte- Carlo bootstrap method, the annual negative <span class="hlt">feedback</span> is further confirmed to be significant in both simulations. Additional analysis shows that this negative interaction is partially caused by the competition between evaporation and transpiration in North African grasslands. Furthermore, we find the <span class="hlt">feedbacks</span> decrease with increasing timescales, and change signs from <span class="hlt">positive</span> to negative at increasing timescales in FOAM. The proposed <span class="hlt">mechanism</span> for this sign switch is associated with the different persistent timescales of upper and lower soil water contents, and their interactions with vegetation and atmospheric precipitation.</p> <div class="credits"> <p class="dwt_author">Wang, Yi; Notaro, Michael; Liu, Zhengyu; Gallimore, Robert; Levis, Samuel; Kutzbach, John E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-03-31</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">388</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/2373713"> <span id="translatedtitle">Glenohumeral muscle force and moment <span class="hlt">mechanics</span> in a <span class="hlt">position</span> of shoulder instability.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The three-dimensional orientation of the shoulder girdle musculature was studied in five cadaver shoulders in the <span class="hlt">position</span> of function at 90 degrees of abduction and 90 degrees of external rotation using a method of computer assisted gross muscle cross-section analysis. The muscle volume, muscle fiber length, and physiological cross-sectional area were obtained by dissecting two specimens. The line of action, the magnitude and orientation of the moment were calculated for each muscle crossing the shoulder joint. The quantitative description of the moment potential of muscle forces influencing shoulder function was thus obtained. The most effective flexors of the shoulder which also appear to resist anterior dislocation in the <span class="hlt">position</span> studied are the pectoral, the short head of the biceps, coracobrachialis, anterior deltoid, and the subscapularis. Most of the rotator cuff muscles and the posterior deltoid acted as adductors, while the anterior deltoid, long and short head of the biceps, and supraspinatus were abductors. In this <span class="hlt">position</span>, external rotation was effected by the long head of the biceps, coracobrachialis, and the posterior deltoid, while the majority of the remaining muscles acted as internal rotators. PMID:2373713</p> <div class="credits"> <p class="dwt_author">Bassett, R W; Browne, A O; Morrey, B F; An, K N</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">389</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23030358"> <span id="translatedtitle">Extending the biotic ligand model to account for <span class="hlt">positive</span> and negative <span class="hlt">feedback</span> interactions between cadmium and zinc in a freshwater alga.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Low concentrations of essential trace metals such as zinc (Zn) were recently shown to strongly modulate cadmium (Cd) uptake in the freshwater alga Chlamydomonas reinhardtii. Here we studied the <span class="hlt">mechanisms</span> of Cd and Zn acquisition by this alga, using metal uptake kinetics experiments. Cadmium uptake rates fitted a three transport site model characterized by the affinity constants K(Cd–1)(Cd) = 10(5.0), K(Cd–2)(Cd) = 10(7.6), and K(Cd–3)(Cd) = 10(8.8). Similar uptake kinetics were obtained for Zn with K(Zn–1)(Zn) = 10(5.0), K(Zn–2)(Zn) = 10(7.4), and K(Zn–3)(Zn) > 10(9). Competitive binding experiments suggest that Zn and Cd share the same three transport systems. The capacities of the transport systems were modulated by as much as 10-fold following preacclimation to high or low Zn(2+) and Cd(2+) concentrations. We conclude that the strong protective effect of Zn on Cd accumulation is mainly due to the reduction of the maximal uptake rate of the high-affinity Zn–2 (or Cd–2) transport system. A biotic ligand model was developed to incorporate the effects of both chemical speciation and physiological regulation of Cd transport systems. The model successfully predicts the experimentally measured steady-state Cd content of C. reinhardtii in the presence of low or high [Zn(2+)]. PMID:23030358</p> <div class="credits"> <p class="dwt_author">Lavoie, Michel; Campbell, Peter G C; Fortin, Claude</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">390</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19950005141&hterms=hydraulic+manipulator&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhydraulic%2Bmanipulator"> <span id="translatedtitle">Control of parallel manipulators using force <span class="hlt">feedback</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Two control schemes are compared for parallel robotic <span class="hlt">mechanisms</span> actuated by hydraulic cylinders. One scheme, the 'rate based scheme', uses the <span class="hlt">position</span> and rate information only for <span class="hlt">feedback</span>. The second scheme, the 'force based scheme' feeds back the force information also. The force control scheme is shown to improve the response over the rate control one. It is a simple constant gain control scheme better suited to parallel <span class="hlt">mechanisms</span>. The force control scheme can be easily modified for the dynamic forces on the end effector. This paper presents the results of a computer simulation of both the rate and force control schemes. The gains in the force based scheme can be individually adjusted in all three directions, whereas the adjustment in just one direction of the rate based scheme directly affects the other two directions.</p> <div class="credits"> <p class="dwt_author">Nanua, Prabjot</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">391</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/11432949"> <span id="translatedtitle">Stomatal oscillations at small apertures: indications for a fundamental insufficiency of stomatal <span class="hlt">feedback</span>-control inherent in the stomatal turgor <span class="hlt">mechanism</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Continuous measurements of stomatal aperture simultaneously with gas exchange during periods of stomatal oscillations are reported for the first time. Measurements were performed in the field on attached leaves of undisturbed Sambucus nigra L. plants which were subjected to step-wise increases of PPFD. Oscillations only occurred when stomatal apertures were small under high water vapour mole fraction difference between leaf and atmosphere (DeltaW). They consisted of periodically repeated opening movements transiently leading to very small apertures. Measurements of the area of the stomatal complex in parallel to the determination of aperture were used to record volume changes of guard cells even if stomata were closed. Stomatal opening upon a light stimulus required an antecedent guard cell swelling before a slit occurred. After opening of the slit the guard cells again began to shrink which, with some delay, led to complete closure. Opening and closing were rhythmically repeated. The time-lag until initial opening was different for each individual stoma. This led to counteracting movements of closely adjacent stomata. The tendency to oscillate at small apertures is interpreted as being a failure of smoothly damped <span class="hlt">feedback</span> regulation at the point of stomatal opening: Volume changes are ineffective for transpiration if stomata are still closed; however, at the point of initial opening transpiration rate rises steeply. This discontinuity together with the rather long time constants inherent in the stomatal turgor <span class="hlt">mechanism</span> makes oscillatory overshooting responses likely if at high DeltaW the 'nominal value' of gas exchange demands a small aperture. PMID:11432949</p> <div class="credits"> <p class="dwt_author">Kaiser, H; Kappen, L</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">392</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21182698"> <span id="translatedtitle">Alterations in glucocorticoid negative <span class="hlt">feedback</span> following maternal Pb, prenatal stress and the combination: A potential biological unifying <span class="hlt">mechanism</span> for their corresponding disease profiles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Combined exposures to maternal lead (Pb) and prenatal stress (PS) can act synergistically to enhance behavioral and neurochemical toxicity in offspring. Maternal Pb itself causes permanent dysfunction of the body's major stress system, the hypothalamic pituitary adrenal (HPA) axis. The current study sought to determine the potential involvement of altered negative glucocorticoid <span class="hlt">feedback</span> as a mechanistic basis of the effects in rats of maternal Pb (0, 50 or 150 ppm in drinking water beginning 2 mo prior to breeding), prenatal stress (PS; restraint on gestational days 16-17) and combined maternal Pb + PS in 8 mo old male and female offspring. Corticosterone changes were measured over 24 h following an i.p. injection stress containing vehicle or 100 or 300 {mu}g/kg (females) or 100 or 150 {mu}g/kg (males) dexamethasone (DEX). Both Pb and PS prolonged the time course of corticosterone reduction following vehicle injection stress. Pb effects were non-monotonic, with a greater impact at 50 vs. 150 ppm, particularly in males, where further enhancement occurred with PS. In accord with these findings, the efficacy of DEX in suppressing corticosterone was reduced by Pb and Pb + PS in both genders, with Pb efficacy enhanced by PS in females, over the first 6 h post-administration. A marked prolongation of DEX effects was found in males. Thus, Pb, PS and Pb + PS, sometimes additively, produced hypercortisolism in both genders, followed by hypocortisolism in males, consistent with HPA axis dysfunction. These findings may provide a plausible unifying biological <span class="hlt">mechanism</span> for the reported links between Pb exposure and stress-associated diseases and disorders mediated via the HPA axis, including obesity, hypertension, diabetes, anxiety, schizophrenia and depression. They also suggest broadening of Pb screening programs to pregnant women in high stress environments.</p> <div class="credits"> <p class="dwt_author">Rossi-George, A.; Virgolini, M.B. [Environmental and Occupational Health Sciences Institute, a Joint Institute of the Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey and Rutgers, the State University of New Jersey, Piscataway, NJ 08854 (United States); Weston, D. [Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States); Cory-Slechta, D.A. [Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States)], E-mail: deborah_cory-slechta@urmc.rochester.edu</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">393</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/750533"> <span id="translatedtitle">Design of a high-resolution high-stability <span class="hlt">positioning</span> <span class="hlt">mechanism</span> for crystal optics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The authors present a novel miniature multi-axis driving structure that will allow <span class="hlt">positioning</span> of two crystals with better than 50-nrad angular resolution and nanometer linear driving sensitivity.The precision and stability of this structure allow the user to align or adjust an assembly of crystals to achieve the same performance as does a single channel-cut crystal, so they call it an artificial channel-cut crystal. In this paper, the particular designs and specifications, as well as the test results,for a two-axis driving structure for a high-energy-resolution artificial channel-cut crystal monochromator are presented</p> <div class="credits"> <p class="dwt_author">Shu, D.; Toellner, T. S.; Alp, E. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-10-11</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">394</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3457184"> <span id="translatedtitle">Symmetry-Related Clustering of <span class="hlt">Positive</span> Charges Is a Common <span class="hlt">Mechanism</span> for Heparan Sulfate Binding in Enteroviruses</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Coxsackievirus A9 (CAV9), a member of the Picornaviridae family, uses an RGD motif in the VP1 capsid protein to bind to integrin ?v?6 during cell entry. Here we report that two CAV9 isolates can bind to the heparan sulfate/heparin class of proteoglycans (HSPG). Sequence analysis identified an arginine (R) at <span class="hlt">position</span> 132 in VP1 in these two isolates, rather than a threonine (T) as seen in the nonbinding strains tested. We introduced a T132R substitution into the HSPG-nonbinding strain Griggs and recovered infectious virus capable of binding to immobilized heparin, unlike the parental Griggs strain. The known CAV9 structure was used to identify the location of VP1 <span class="hlt">position</span> 132, 5 copies of which were found to cluster around the 5-fold axis of symmetry, presumably producing a region of <span class="hlt">positive</span> charge which can interact with the negatively charged HSPG. Analysis of several enteroviruses of the same species as CAV9, Human enterovirus B (HEV-B), identified examples from 5 types in which blocking of infection by heparin was coincident with an arginine (or another basic amino acid, lysine) at a <span class="hlt">position</span> corresponding to 132 in VP1 in CAV9. Together, these data show that membrane-associated HSPG can serve as a (co)receptor for some CAV9 and other HEV-B strains and identify symmetry-related clustering of <span class="hlt">positive</span> charges as one <span class="hlt">mechanism</span> by which HSPG binding can be achieved. This is a potentially powerful <span class="hlt">mechanism</span> by which a single amino acid change could generate novel receptor binding capabilities, underscoring the plasticity of host-cell interactions in enteroviruses. PMID:22855495</p> <div class="credits"> <p class="dwt_author">McLeish, Nigel J.; Williams, Çi?dem H.; Kaloudas, Dimitrios; Roivainen, Merja M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">395</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/21336078"> <span id="translatedtitle">Minimal <span class="hlt">position</span>-velocity uncertainty wave packets in relativistic and non-relativistic quantum <span class="hlt">mechanics</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">We consider wave packets of free particles with a general energy-momentum dispersion relation E(p). The spreading of the wave packet is determined by the velocity v={partial_derivative}{sub p}E. The <span class="hlt">position</span>-velocity uncertainty relation {delta}x{delta}v{>=}1/2 |<{partial_derivative}{sub p}{sup 2}E>| is saturated by minimal uncertainty wave packets {phi}(p)=Aexp(-{alpha}E(p)+{beta}p). In addition to the standard minimal Gaussian wave packets corresponding to the non-relativistic dispersion relation E(p)=p{sup 2}/2m, analytic calculations are presented for the spreading of wave packets with minimal <span class="hlt">position</span>-velocity uncertainty product for the lattice dispersion relation E(p)=-cos(pa)/ma{sup 2} as well as for the relativistic dispersion relation E(p)={radical}(p{sup 2}+m{sup 2}). The boost properties of moving relativistic wave packets as well as the propagation of wave packets in an expanding Universe are also discussed.</p> <div class="credits"> <p class="dwt_author">Al-Hashimi, M.H. [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Bern University, Sidlerstrasse 5, CH-3012 Bern (Switzerland)], E-mail: hashimi@itp.unibe.ch; Wiese, U.-J. [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Bern University, Sidlerstrasse 5, CH-3012 Bern (Switzerland)</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">396</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009ems..confE.509X"> <span id="translatedtitle">Low Cloud <span class="hlt">Feedback</span> Diagnosed from Observations and LES Modeling</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The negative cloud optical depth <span class="hlt">feedback</span> (Somerville and Remer 1984) was based upon the increase of liquid water content with the ambient temperature (T) inferred from in situ observations. Recent satellite observations from ISCCP, AVHRR and CERES (Tselioudis et al. 1992; Chang and Coakley 2007; Eitzen et al. 2008) indicate that cloud optical depth may decrease with T, instead of increase with T, thereby suggesting a <span class="hlt">positive</span> cloud optical depth <span class="hlt">feedback</span> to a climate warming. We have analyzed the monthly gridded cloud and radiative property data from CERES (Clouds and the Earth's Radiant Energy System) and examined the rate of changes in cloud and radiative properties with sea surface temperature (SST) anomaly from the annual mean SST. It is found in the boundary-layer cloud regions that the cloud radiative cooling effect, cloud fraction and cloud optical depth decrease with the increase of SST anomaly. All of these trends imply a <span class="hlt">positive</span> cloud <span class="hlt">feedback</span>. However, these rates of change are mostly contributed by changes in dynamic and thermodynamic state of the atmosphere, which can be represented by the mean rates projected to the joint lower tropospheric stability vs. vertical velocity at 700hPa distribution. The residual rates are close to nearly neutral, compared to the original rates, thereby suggesting that the <span class="hlt">positive</span> cloud <span class="hlt">feedback</span> is unlikely to occur. An LES (large-eddy simulation) model is used to understand the low cloud <span class="hlt">feedback</span> <span class="hlt">mechanisms</span>, based upon the configuration designed by the Cloud <span class="hlt">Feedback</span> Model Intercomparison Project (CFMIP). Three CFMIP configurations (cases) are simulated, corresponding to shallow cumulus, stratocumulus and solid stratus clouds. The UCLA LES is run for 30 days in order to reach cloud-radiative equilibrium. The SST increases by 2 K in the perturbed simulation from that in the control simulation. The last ten days of the integrations are analyzed. The cloud <span class="hlt">feedback</span> effect is negative (0.4 - 6.0 W m-2 K-1) for all three cases, which is consistent with prior modeling results, while the clearsky <span class="hlt">feedback</span> effect is <span class="hlt">positive</span>, due to large increase in lower-tropospheric water vapor. The clearsky <span class="hlt">feedback</span> effect is the largest for the shallow cumulus simulation, arising from the largest increase in water vapor related to the highest SST among the three configurations. The increase of liquid water path and cloud optical depth, which is related to the increase of cloud thickness and liquid water content, is caused by the increase of surface latent heat flux and precipitable water in the warmer climate. The increased surface latent heat flux is the major driver for the negative cloud <span class="hlt">feedback</span> <span class="hlt">mechanism</span>. The changes in cloud fraction do not contribute to the negative cloud <span class="hlt">feedback</span> in the stratocumulus case, but somewhat do in the cumulus case. The increase in cloud thickness in the perturbed simulations is resulted from a larger increase in cloud top altitude than in cloud base altitude in the stratocumulus case but the cloud thickness does not change much in the cumulus case.</p> <div class="credits"> <p class="dwt_author">Xu, K.-M.; Cheng, A.; Eitzen, Z. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">397</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/20818493"> <span id="translatedtitle">The endocytic penetration <span class="hlt">mechanism</span> of iron oxide magnetic nanoparticles with <span class="hlt">positively</span> charged cover: a morphological approach.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">In this study we present a morphological approach in observing the interaction of cationic magnetic nanoparticles with A-549 cells (human lung adenocarcinoma). Under our experimental conditions, nanoparticles easily penetrated cells and were observed in vivo, using bright light microscopy. In fixed cells, nanoparticles remained inside cells, showing quantity and distribution patterns similar to those in unfixed cells. The presence of nanoparticles did not affect cell viability or the morphologic parameters assessed. We determined the potential internalization <span class="hlt">mechanism</span> of nanoparticles into cells using endocytosis inhibitors. The results suggest that nanoparticles used in this study penetrate A-549 cells mainly through a macropinocytosis process. PMID:20818493</p> <div class="credits"> <p class="dwt_author">Cañete, Magdalena; Soriano, Jorge; Villanueva, Angeles; Roca, Alejandro G; Veintemillas, Sabino; Serna, Carlos J; Miranda, Rodolfo; Del Puerto Morales, Maria</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">398</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=339961"> <span id="translatedtitle"><span class="hlt">Mechanisms</span> of DNA sequence selective alkylation of guanine-N7 <span class="hlt">positions</span> by nitrogen mustards.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Quantitative determinations were carried out of the relative reaction rates of several nitrogen mustards at various guanine-N7 <span class="hlt">positions</span> in DNA fragments of known sequence. The findings suggest structural hypotheses of the origins of the reaction selectivities. End-labeled DNA fragments were reacted with nitrogen mustards, and the guanine-N7 alkylation sites were analyzed by gel electrophoresis. Relative reaction intensities were determined by computer analysis of digitized densitometer scans. The differences in reaction intensities at different G's were in part attributable to the effects of nearest neighbor base pairs on the molecular electrostatic potential near the reaction site. Uracil and quinacrine mustards have specific sequence preferences for reaction that differ from other mustards. The nature of the specific sequence preferences were determined and hypotheses are proposed to explain their origin. PMID:3697095</p> <div class="credits"> <p class="dwt_author">Kohn, K W; Hartley, J A; Mattes, W B</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">399</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23066027"> <span id="translatedtitle">STAT3 protein up-regulates G?-interacting vesicle-associated protein (GIV)/Girdin expression, and GIV enhances STAT3 activation in a <span class="hlt">positive</span> <span class="hlt">feedback</span> loop during wound healing and tumor invasion/metastasis.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">G?-interacting vesicle-associated protein (GIV) is a guanine nucleotide exchange factor that modulates key signaling pathways during a diverse set of biological processes, e.g. wound healing, macrophage chemotaxis, tumor angiogenesis, vascular repair, and cancer invasion/metastasis. We recently demonstrated that GIV is a metastasis-related protein, which serves both as a therapeutic target and as a biomarker for prognostication in cancer patients. Here we report the discovery that GIV is a direct target of the transcription factor signal transducer and activator of transcription-3 (STAT3), which is commonly known as a central regulator of tumor metastasis. We identified a single STAT3-binding site on the GIV promoter that was necessary and sufficient for transcriptional activation of GIV during wound healing and cancer invasion. Immunohistochemical analysis of breast carcinomas showed significant correlation between STAT3 activation and elevated GIV expression. Furthermore, we provide evidence that GIV <span class="hlt">positively</span> autoregulates its own transcription by enhancing STAT3 activation via its guanine nucleotide exchange factor activity. Our findings provide mechanistic insights into how STAT3 activation is directly integrated with the receptor tyrosine kinase-GIV-G protein signaling axis. The forward <span class="hlt">feedback</span> regulation we describe here between GIV and STAT3 may have profound therapeutic implications for cancer and epithelial regeneration/repair and could help invent novel approaches in treating and prognosticating cancer. PMID:23066027</p> <div class="credits"> <p class="dwt_author">Dunkel, Ying; Ong, Andrew; Notani, Dimple; Mittal, Yash; Lam, Michael; Mi, Xiaoyi; Ghosh, Pradipta</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">400</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3270997"> <span id="translatedtitle">Epidermal Growth Factor Receptor (EGFR)-mediated <span class="hlt">Positive</span> <span class="hlt">Feedback</span> of Protein-tyrosine Phosphatase ? (PTP?) on ERK1/2 and AKT Protein Pathways Is Required for Survival of Human Breast Cancer Cells*</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Increased tyrosine phosphorylation has been correlated with human cancer, including breast cancer. In general, the activation of tyrosine kinases (TKs) can be antagonized by the action of protein-tyrosine phosphatases (PTPs). However, in some cases PTPs can potentiate the activation of TKs. In this study, we have investigated the functional role of PTP? in human breast cancer cell lines. We found the up-regulation and activation of receptor PTP? (RPTP?) in MCF-7 cells and MDA-MB-231 upon PMA, FGF, and serum stimulation, which depended on EGFR and ERK1/2 activity. Diminishing the expression of PTP? in human breast cancer cells abolished ERK1/2 and AKT activation, and decreased the viability and anchorage-independent growth of the cells. Conversely, stable MCF-7 cell lines expressing inducible high levels of ectopic PTP? displayed higher activation of ERK1/2 and anchorage-independent growth. Our results demonstrate that expression of PTP? is up-regulated and activated in breast cancer cell lines, through EGFR, by sustained activation of the ERK1/2 pathway, generating a <span class="hlt">positive</span> <span class="hlt">feedback</span> regulatory loop required for survival of human breast cancer cells. PMID:22117074</p> <div class="credits"> <p class="dwt_author">Nunes-Xavier, Caroline E.; Elson, Ari; Pulido, Rafael</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_19");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a style="font-weight: bold;">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_21");' href="#" titl