Venus - Impact Crater 'Jeanne

NASA Technical Reports Server (NTRS)

1991-01-01

This Magellan full-resolution image shows Jeanne crater, a 19.5 kilometer (12 mile) diameter impact crater. Jeanne crater is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The crater is surrounded by dark material of two types. The dark area on the southwest side of the crater is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the crater is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne crater also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt.

Contribution of peculiar shear motions to large-scale structure

NASA Technical Reports Server (NTRS)

Mueler, Hans-Reinhard; Treumann, Rudolf A.

1994-01-01

Self-gravitating shear flow instability simulations in a cold dark matter-dominated expanding Einstein-de Sitter universe have been performed. When the shear flow speed exceeds a certain threshold, self-gravitating Kelvin-Helmoholtz instability occurs, forming density voids and excesses along the shear flow layer which serve as seeds for large-scale structure formation. A possible mechanism for generating shear peculiar motions are velocity fluctuations induced by the density perturbations of the postinflation era. In this scenario, short scales grow earlier than large scales. A model of this kind may contribute to the cellular structure of the luminous mass distribution in the universe.

Dark Flow, Depression and Multiline Slot Machine Play.

PubMed

Dixon, Mike J; Stange, Madison; Larche, Chanel J; Graydon, Candice; Fugelsang, Jonathan A; Harrigan, Kevin A

2018-03-01

Multiline slot machines allow for a unique outcome type referred to as a loss disguised as a win (LDW). An LDW occurs when a player gains credits on a spin, but fewer credits than their original wager (e.g. 15-cent gain on a 20-cent wager). These outcomes alter the gambler's play experience by providing frequent, albeit smaller, credit gains throughout a playing session that are in fact net losses. Despite this negative overall value, research has shown that players physiologically respond to LDWs as if they are wins, not losses. These outcomes also create a "smoother" experience for the player that seems to promote a highly absorbing, flow-like state that we have called "dark flow". Past research has indicated that there may be a relationship between problem gambling status and dark flow, as well as between dark flow, depression, and gambling expectancies. In this study, we sought to further understand these relationships, while examining the influence of LDWs on game preference in the context of single versus multiline slots play. We used a realistic slot machine simulator equipped with a force transducer to measure how hard players pressed the spin button following different outcomes. This measure of arousal showed that LDWs were treated similarly to small wins. Participants overwhelmingly preferred the multiline game and experienced more positive affect while playing it, compared to the single-line game. Problem gambling severity index scores were related to dark flow in both games, but this relationship was stronger for the multiline game. Additionally, depression symptomatology and dark flow were strongly correlated in the multiline game, with significant relationships between depression and gambling expectancy, and gambling expectancy and dark flow ratings also emerging.

Venus - Impact Crater Jeanne

NASA Image and Video Library

1996-11-20

This full-resolution image from NASA Magellan spacecraft shows Jeanne crater, a 19.5 kilometer (12 mile) diameter impact crater. Jeanne crater is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The crater is surrounded by dark material of two types. The dark area on the southwest side of the crater is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the crater is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne crater also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt. http://photojournal.jpl.nasa.gov/catalog/PIA00472

Distribution and ultrastructural characteristics of dark cells in squamous metaplasias of the respiratory tract epithelium.

PubMed Central

Klein-Szanto, A. J.; Nettesheim, P.; Pine, A.; Martin, D.

1981-01-01

Dark epithelial basal cells were found in both carcinogen-induced and non-carcinogen-induced squamous metaplasias of the tracheal epithelium. Formaldehyde-induced squamous metaplasias exhibited 4% dark cells in the basal layer. Metaplasias induced by vitamin A deficiency and those induced by dimethylbenz(alpha)anthracene (DMBA) without atypia showed 18--20% basal dark cells. DMBA-induced metaplasias with moderate to severe atypia exhibited 50% basal dark cells. The labeling index of basal cells in metaplastic epithelia, regardless of the inducing agent, was 16--18%, ie, the same as that of the normal esophageal stratified squamous epithelium. The percentage of labeled dark basal cells per total dark cell population was approximately 19% in the non-carcinogen-induced metaplasias and in the DMBA-induced metaplasias without atypia. In the atypical metaplasias induced by DMA this percentage increased to 26. On the basis of ultrastructural observations, five types of dark epithelial cells could be distinguished in the metaplastic epithelia: Type I (ovoid or fusiform dark cell with abundant cytoplasmic filaments, desmosomes, and free ribosomes--dark keratinocyte type); Type II (ovoid or spherical small cell with scant cytoplasm with few organelles--basal respiratory type); Type III (irregular or ovoid, few cytoplasmic filaments and organelles and desmosomes, extremely abundant free ribosomes--dedifferentiated type); Type IV (fusiform or ovoid, large mitochondria, prominent ergastoplasm, secretion droplets--mucous cell type); and type V (irregular shape, organelle remnants, vacuoles, pyknotic nuclei--involutional-cell type). Type I was the predominant cell type in formaldehyde-induced metaplasias and was also commonly seen in DMBA-induced metaplasias without atypia. Type II predominated in metaplasias induced by vitamin A deficiency. Type III was seen in DMBA-induced metaplasias and was the predominant cell type in the atypical epithelial alterations. Type IV cells occurred only in the latter, and Type V cells were occasionally seen in formaldehyde- as well as in DMBA-induced atypical metaplasias. Each type of squamous metaplasia could thus be recognized by a determined numerical distribution of dark cells in the basal layer and a specific pattern of distribution of the ultrastructurally defined dark cell categories. Images Figure 3 Figure 4 Figure 5 Figure 1 Figure 2 Figure 6 Figure 7 PMID:6786102

Dark current of organic heterostructure devices with insulating spacer layers

NASA Astrophysics Data System (ADS)

Yin, Sun; Nie, Wanyi; Mohite, Aditya D.; Saxena, Avadh; Smith, Darryl L.; Ruden, P. Paul

2015-03-01

The dark current density at fixed voltage bias in donor/acceptor organic planar heterostructure devices can either increase or decrease when an insulating spacer layer is added between the donor and acceptor layers. The dominant current flow process in these systems involves the formation and subsequent recombination of an interfacial exciplex state. If the exciplex formation rate limits current flow, the insulating interface layer can increase dark current whereas, if the exciplex recombination rate limits current flow, the insulating interface layer decreases dark current. We present a device model to describe this behavior and illustrate it experimentally for various donor/acceptor systems, e.g. P3HT/LiF/C60.

Induced dark solitary pulse in an anomalous dispersion cavity fiber laser.

PubMed

Shao, Guodong; Song, Yufeng; Guo, Jun; Zhao, Luming; Shen, Deyuan; Tang, Dingyuan

2015-11-02

We report on the formation of induced dark solitary pulses in a net anomalous dispersion cavity fiber laser. In a weak birefringence cavity fiber laser simultaneous laser oscillation along the two orthogonal polarization directions of the cavity could be achieved. Under suitable conditions bright cavity solitons could be formed along one polarization direction while CW emission occurs along the orthogonal polarization direction. In a previous paper we have shown that under incoherent polarization coupling a bright soliton always induces a broad dark pulse on the CW beam. In the paper we further show that under coherent polarization coupling a bright soliton could further induce either a weak bright or a dark solitary pulse on the bottom of the broad dark pulse. Numerical simulations have also well reproduced the experimental observations, and further show whether a weak dark or bright solitary pulse is induced is determined by the presence or absence of a phase jump in the induced pulse.

Induction of a Longer Term Component of Isoprene Release in Darkened Aspen Leaves: Origin and Regulation under Different Environmental Conditions1

PubMed Central

Rasulov, Bahtijor; Hüve, Katja; Laisk, Agu; Niinemets, Ülo

2011-01-01

After darkening, isoprene emission continues for 20 to 30 min following biphasic kinetics. The initial dark release of isoprene (postillumination emission), for 200 to 300 s, occurs mainly at the expense of its immediate substrate, dimethylallyldiphosphate (DMADP), but the origin and controls of the secondary burst of isoprene release (dark-induced emission) between approximately 300 and 1,500 s, are not entirely understood. We used a fast-response gas-exchange system to characterize the controls of dark-induced isoprene emission by light, temperature, and CO2 and oxygen concentrations preceding leaf darkening and the effects of short light pulses and changing gas concentrations during dark-induced isoprene release in hybrid aspen (Populus tremula × Populus tremuloides). The effect of the 2-C-methyl-d-erythritol-4-phosphate pathway inhibitor fosmidomycin was also investigated. The integral of postillumination isoprene release was considered to constitute the DMADP pool size, while the integral of dark-induced emission was defined as the “dark” pool. Overall, the steady-state emission rate in light and the maximum dark-induced emission rate responded similarly to variations in preceding environmental drivers and atmospheric composition, increasing with increasing light, having maxima at approximately 40°C and close to the CO2 compensation point, and were suppressed by lack of oxygen. The DMADP and dark pool sizes were also similar through their environmental dependencies, except for high temperatures, where the dark pool significantly exceeded the DMADP pool. Isoprene release could be enhanced by short lightflecks early during dark-induced isoprene release, but not at later stages. Fosmidomycin strongly suppressed both the isoprene emission rates in light and in the dark, but the dark pool was only moderately affected. These results demonstrate a strong correspondence between the steady-state isoprene emission in light and the dark-induced emission and suggest that the dark pool reflects the total pool size of 2-C-methyl-d-erythritol-4-phosphate pathway metabolites upstream of DMADP. These metabolites are converted to isoprene as soon as ATP and NADPH become available, likely by dark activation of chloroplastic glycolysis and chlororespiration. PMID:21502186

Light-induced aggregation of microbial exopolymeric substances.

PubMed

Sun, Luni; Xu, Chen; Zhang, Saijin; Lin, Peng; Schwehr, Kathleen A; Quigg, Antonietta; Chiu, Meng-Hsuen; Chin, Wei-Chun; Santschi, Peter H

2017-08-01

Sunlight can inhibit or disrupt the aggregation process of marine colloids via cleavage of high molecular weight compounds into smaller, less stable fragments. In contrast, some biomolecules, such as proteins excreted from bacteria can form aggregates via cross-linking due to photo-oxidation. To examine whether light-induced aggregation can occur in the marine environment, we conducted irradiation experiments on a well-characterized protein-containing exopolymeric substance (EPS) from the marine bacterium Sagitulla stellata. Our results show that after 1 h sunlight irradiation, the turbidity level of soluble EPS was 60% higher than in the dark control. Flow cytometry also confirmed that more particles of larger sized were formed by sunlight. In addition, we determined a higher mass of aggregates collected on filter in the irradiated samples. This suggests light can induce aggregation of this bacterial EPS. Reactive oxygen species hydroxyl radical and peroxide played critical roles in the photo-oxidation process, and salts assisted the aggregation process. The observation that Sagitulla stellata EPS with relatively high protein content promoted aggregation, was in contrast to the case where no significant differences were found in the aggregation of a non-protein containing phytoplankton EPS between the dark and light conditions. This, together with the evidence that protein-to-carbohydrate ratio of aggregates formed under light condition is significantly higher than that formed under dark condition suggest that proteins are likely the important component for aggregate formation. Light-induced aggregation provides new insights into polymer assembly, marine snow formation, and the fate/transport of organic carbon and nitrogen in the ocean. Copyright © 2017 Elsevier Ltd. All rights reserved.

Venus - Lakshmi Region

NASA Technical Reports Server (NTRS)

1991-01-01

This Magellan image is centered at 55 degrees north latitude, 348.5 degrees longitude, in the eastern Lakshmi region of Venus. This image, which is of an area 300 kilometers (180 miles) in width and 230 kilometers (138 miles) in length, is a mosaic of orbits 458 through 484. The image shows a relatively flat plains region composed of many lava flows. The dark flows mostly likely represent smooth lava flows similar to 'pahoehoe' flows on Earth while the brighter lava flows are rougher flows similar to 'aa' flows on Earth. (The terms 'pahoehoe' and 'aa' refer to textures of lava with pahoehoe a smooth or ropey surface, and aa a rough, clinkery texture). The rougher flows are brighter because the rough surface returns more energy to the radar than the smooth flows. Situated on top of the lava flows are three dark splotches. Because of the thick Venusian atmosphere, the small impactors break up before they reached the surface. Only the fragments from the broken up impactor are deposited on the surface and these fragments produce the dark splotches in this image. The splotch at the far right (east) has a crater centered in it, indicating that the impactor was not completely destroyed during its journey through the atmosphere. The dark splotches in the center and to the far left in this image each represent an impactor that was broken up into small fragments that did not penetrate the surface to produce a crater. The dark splotch at the left has been modified by the wind. A southwest northeast wind flow has moved some of the debris making up the splotch to the northeast where it has piled up against some small ridges.

Dark energy in systems of galaxies

NASA Astrophysics Data System (ADS)

Chernin, A. D.

2013-11-01

The precise observational data of the Hubble Space Telescope have been used to study nearby galaxy systems. The main result is the detection of dark energy in groups, clusters, and flows of galaxies on a spatial scale of about 1-10 Mpc. The local density of dark energy in these systems, which is determined by various methods, is close to the global value or even coincides with it. A theoretical model of the nearby Universe has been constructed, which describes the Local Group of galaxies with the flow of dwarf galaxies receding from this system. The key physical parameter of the group-flow system is zero gravity radius, which is the distance at which the gravity of dark matter is compensated by dark-energy antigravity. The model predicts the existence of local regions of space where Einstein antigravity is stronger than Newton gravity. Six such regions have been revealed in the data of the Hubble space telescope. The nearest of these regions is at a distance of 1-3 Mpc from the center of the Milky Way. Antigravity in this region is several times stronger than gravity. Quasiregular flows of receding galaxies, which are accelerated by the dark-energy antigravity, exist in these regions. The model of the nearby Universe at the scale of groups of galaxies (˜1 Mpc) can be extended to the scale of clusters (˜10 Mpc). The systems of galaxies with accelerated receding flows constitute a new and probably widespread class of metagalactic populations. Strong dynamic effects of local dark energy constitute the main characteristic feature of these systems.

Gravity Does it: Redshift of Light from the Galaxies Yes, Expanding Universe NO!

NASA Astrophysics Data System (ADS)

Malhotra, Satish

2018-04-01

In the history of physics, ideas on space and time have changed the course of physics a number of times; this is another such event. We postulate 'space and time' as a flow of quantum gravity energy, having the absolute velocity c (same as velocity of light), where time is the delay in the spread of space (delay from infinite velocity flow, when there would be no time), such a flow has to have a reverse cycle, as energy creating it (howsoever large it might be has to be limited and limited energy can only create a limited space and time energy spread) and the reverse cycle is that of the creation of fundamental particles. This explanation of the universe tells us that the idea of an expanding universe is only an appearance, the argument, in brief, is as follows: One, the universe is so large that we cannot see the edges, light from the edges, the reality is non-observable. Two, the process is dark, it is beyond observation, the process of creation of charge (the reflection of light starts with it), the space energy flow process is in the range of invisible (before charge emerged); it is the elusive dark energy of the universe; we never connected space and time to flow of energy, and so did not find its connection either to its limitedness or to its dark nature (dark energy). Three, the space energy flow has a reverse process which leads to the formation of fundamental particles we have not included it in the totality of the processes of the universe, the former is the dark energy and the initial part of the reverse process—till it reaches the state of ionisation-- is dark matter. In the continuity of the cycle of space flow and its reversal to matter forms, ionisation happens at a particular point and visibility comes through along with; ionisation here is a later event (which is a part of the reverse process, enters visibility).It is this reverse process which creates fundamental particles (no big bang creation. With no idea of space as energy flow and no idea of the reverse process, physicists could never take the step in the direction of the correct understanding of the 'dark energy' or 'dark matter'.

Protective effects of flavanol-rich dark chocolate on endothelial function and wave reflection during acute hyperglycemia.

PubMed

Grassi, Davide; Desideri, Giovambattista; Necozione, Stefano; Ruggieri, Fabrizio; Blumberg, Jeffrey B; Stornello, Michele; Ferri, Claudio

2012-09-01

Nitric oxide plays a pivotal role in regulating vascular tone. Different studies show endothelial function is impaired during hyperglycemia. Dark chocolate increases flow-mediated dilation in healthy and hypertensive subjects with and without glucose intolerance; however, the effect of pretreatment with dark chocolate on endothelial function and other vascular responses to hyperglycemia has not been examined. Therefore, we aimed to investigate the effects of flavanol-rich dark chocolate administration on (1) flow-mediated dilation and wave reflections; (2) blood pressure, endothelin-1 and oxidative stress, before and after oral glucose tolerance test (OGTT). Twelve healthy volunteers (5 males, 28.2±2.7 years) randomly received either 100 g/d dark chocolate or flavanol-free white chocolate for 3 days. After 7 days washout period, volunteers were switched to the other treatment. Flow-mediated dilation, stiffness index, reflection index, peak-to-peak time, blood pressure, endothelin-1 and 8-iso-PGF(2α) were evaluated after each treatment phase and OGTT. Compared with white chocolate, dark chocolate ingestion improved flow-mediated dilation (P=0.03), wave reflections, endothelin-1 and 8-iso-PGF(2α) (P<0.05). After white chocolate ingestion, flow-mediated dilation was reduced after OGTT from 7.88±0.68 to 6.07±0.76 (P=0.027), 6.74±0.51 (P=0.046) at 1 and 2 h after the glucose load, respectively. Similarly, after white chocolate but not after dark chocolate, wave reflections, blood pressure, and endothelin-1 and 8-iso-PGF(2α) increased after OGTT. OGTT causes acute, transient impairment of endothelial function and oxidative stress, which is attenuated by flavanol-rich dark chocolate. These results suggest cocoa flavanols may contribute to vascular health by reducing the postprandial impairment of arterial function associated with the pathogenesis of atherosclerosis.

Light energy conservation processes in Halobacterium halobium cells

NASA Technical Reports Server (NTRS)

Bogomolni, R. A.

1977-01-01

Proton pumping driven by light or by respiration generates an electrochemical potential difference across the membrane in Halobacterium halobium. The pH changes induced by light or by respiration in cell suspensions are complicated by proton flows associated with the functioning of the cellular energy transducers. A proton-per-ATP ratio of about 3 is calculated from simultaneous measurements of phosphorylation and the proton inflow. This value is compatible with the chemiosmotic coupling hypothesis. The time course of the light-induced changes in membrane potential indicates that light-driven pumping increases a dark pre-existing potential of about 130 mV only by a small amount (20 to 30 mV). The complex kinetic features of the membrane potential changes do not closely follow those of the pH changes, which suggests that flows of ions other than protons are involved. A qualitative model consistent with the available data is presented.

Graviton fluctuations erase the cosmological constant

NASA Astrophysics Data System (ADS)

Wetterich, C.

2017-10-01

Graviton fluctuations induce strong non-perturbative infrared renormalization effects for the cosmological constant. The functional renormalization flow drives a positive cosmological constant towards zero, solving the cosmological constant problem without the need to tune parameters. We propose a simple computation of the graviton contribution to the flow of the effective potential for scalar fields. Within variable gravity, with effective Planck mass proportional to the scalar field, we find that the potential increases asymptotically at most quadratically with the scalar field. The solutions of the derived cosmological equations lead to an asymptotically vanishing cosmological "constant" in the infinite future, providing for dynamical dark energy in the present cosmological epoch. Beyond a solution of the cosmological constant problem, our simplified computation also entails a sizeable positive graviton-induced anomalous dimension for the quartic Higgs coupling in the ultraviolet regime, substantiating the successful prediction of the Higgs boson mass within the asymptotic safety scenario for quantum gravity.

Dark energy domination in the Virgocentric flow

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Karachentsev, I. D.; Nasonova, O. G.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.

2010-09-01

Context. The standard ΛCDM cosmological model implies that all celestial bodies are embedded in a perfectly uniform dark energy background, represented by Einstein's cosmological constant, and experience its repulsive antigravity action. Aims: Can dark energy have strong dynamical effects on small cosmic scales as well as globally? Continuing our efforts to clarify this question, we now focus on the Virgo Cluster and the flow of expansion around it. Methods: We interpret the Hubble diagram from a new database of velocities and distances of galaxies in the cluster and its environment, using a nonlinear analytical model, which incorporates the antigravity force in terms of Newtonian mechanics. The key parameter is the zero-gravity radius, the distance at which gravity and antigravity are in balance. Results: 1. The interplay between the gravity of the cluster and the antigravity of the dark energy background determines the kinematical structure of the system and controls its evolution. 2. The gravity dominates the quasi-stationary bound cluster, while the antigravity controls the Virgocentric flow, bringing order and regularity to the flow, which reaches linearity and the global Hubble rate at distances ⪆15 Mpc. 3. The cluster and the flow form a system similar to the Local Group and its outflow. In the velocity-distance diagram, the cluster-flow structure reproduces the group-flow structure with a scaling factor of about 10; the zero-gravity radius for the cluster system is also 10 times larger. Conclusions: The phase and dynamical similarity of the systems on the scales of 1-30 Mpc suggests that a two-component pattern may be universal for groups and clusters: a quasi-stationary bound central component and an expanding outflow around it, caused by the nonlinear gravity-antigravity interplay with the dark energy dominating in the flow component.

Exogenous energy supply to the plasma membrane of dark anaerobic cyanobacterium Anacystis nidulans: thermodynamic and kinetic characterization of the ATP synthesis effected by an artificial proton motive force.

PubMed

Peschek, G A; Hinterstoisser, B; Riedler, M; Muchl, R; Nitschmann, W H

1986-05-15

The net synthesis of ATP in dark anaerobic cells of Anacystis nidulans subjected to acid jumps and/or valinomycin pulses was characterized thermodynamically and kinetically. Maximum initial rates of 75 nmol ATP/min per mg dry weight at an applied proton motive force of -350 mV were obtained, the flow-force relationship (rate of ATP synthesis vs applied proton motive force) being linear between -240 and -320 mV irrespective of the source of the proton motive force. The pulse-induced ATP synthesis was inhibited by uncouplers (H+ ionophores) and F0F1-ATPase inhibitors but not by KCN or CO. In order to obtain maximum rates of pulse-induced ATP synthesis both a favorable stationary delta psi (-100 mV at pHo 9, preceding the acid jumps) and a favorable stationary delta pH (+2 units at pHo 4.1, preceding the valinomycin pulse) of the plasma membrane were obligatory, the effects of delta psi and delta pH being strictly additive. Moreover, the pulse-induced ATP synthesis required a minimum total proton motive force of -200 to -250 mV across the plasma membrane; it also required low preexisting phosphorylation potentials corresponding to -400 mV in dark anaerobic, i.e., energy-depleted, cells. The results are discussed in terms of both a reversible H+-ATPase and a respiratory electron transport system occurring in the plasma membrane of intact Anacystis nidulans.

Therapeutic perspectives for melatonin agonists and antagonists.

PubMed

Delagrange, P; Atkinson, J; Boutin, J A; Casteilla, L; Lesieur, D; Misslin, R; Pellissier, S; Pénicaud, L; Renard, P

2003-04-01

Melatonin is a neurohormone synthesized in the pineal gland during the dark period in all species, including humans. The diversity and differences in melatonin receptor distribution in the brain and extracerebral organs suggest multiple functional roles for melatonin. Administration of melatonin agonists reduces neophobia and treatment with a melatonin antagonist during the dark period reverses the anxiolytic-like effect of endogenous melatonin. Chronic treatment with agonists prevents various perturbations induced by chronic mild stress. Melatonin in vivo directly constricts cerebral arterioles in rats and decreases the lower limit of cerebral blood flow autoregulation, suggesting that melatonin may diminish the risk of hypoperfusion-induced cerebral ischemia. At the extracerebral level, melatonin regulates intestinal motility in rats. The intestinal postprandial motor response is shorter in the dark phase than in the light phase and this reduction is reversed in animals pretreated with a melatonin antagonist. Moreover, melatonin reduces the duration of cholecystokinin excitomotor effect. Endogenous melatonin may modulate intestinal motility to coordinate intestinal functions such as digestion and transit and control the metabolism of the animal. An adipocyte melatonin binding site may also participate in this control. Melatonin is involved in a wide range of physiological functions. The question remains as to whether evolution, adaptation and diurnal life have modified the physiological role of melatonin in humans. Moreover, the functional role of each of the receptor subtypes has to be characterized to design selective ligands to treat specific diseases.

JAZ7 negatively regulates dark-induced leaf senescence in Arabidopsis

PubMed Central

Yu, Juan; Zhang, Yixiang; Di, Chao; Zhang, Qunlian; Zhang, Kang; Wang, Chunchao; You, Qi; Yan, Hong; Dai, Susie Y.; Yuan, Joshua S; Xu, Wenying; Su, Zhen

2016-01-01

JASMONATE ZIM-domain (JAZ) proteins play important roles in plant defence and growth by regulating jasmonate signalling. Through data mining, we discovered that the JAZ7 gene was up-regulated in darkness. In the dark, the jaz7 mutant displayed more severe leaf yellowing, quicker chlorophyll degradation, and higher hydrogen peroxide accumulation compared with wild-type (WT) plants. The mutant phenotype of dark-induced leaf senescence could be rescued in the JAZ7-complemented and -overexpression lines. Moreover, the double mutants of jaz7 myc2 and jaz7 coi1 exhibited delayed leaf senescence. We further employed GeneChip analysis to study the molecular mechanism. Some key genes down-regulated in the triple mutant myc2 myc3 myc4 were up-regulated in the jaz7 mutant under darkness. The Gene Ontology terms ‘leaf senescence’ and ‘cell death’ were significantly enriched in the differentially expressed genes. Combining the genetic and transcriptomic analyses together, we proposed a model whereby darkness can induce JAZ7, which might further block MYC2 to suppress dark-induced leaf senescence. In darkness, the mutation of JAZ7 might partially liberate MYC2/MYC3/MYC4 from suppression, leading the MYC proteins to bind to the G-box/G-box-like motifs in the promoters, resulting in the up-regulation of the downstream genes related to indole-glucosinolate biosynthesis, sulphate metabolism, callose deposition, and JA-mediated signalling pathways. In summary, our genetic and transcriptomic studies established the JAZ7 protein as an important regulator in dark-induced leaf senescence. PMID:26547795

Compositional heterogeneity of the Sugarloaf melilite nephelinite flow, Honolulu Volcanics, Hawai'i

NASA Astrophysics Data System (ADS)

Clague, David A.; Frey, Frederick A.; Garcia, Michael O.; Huang, Shichun; McWilliams, Michael; Beeson, Melvin H.

2016-07-01

The Sugarloaf flow is a melilite nephelinite erupted from the Tantalus rift during rejuvenated-stage volcanism on O'ahu, the Honolulu Volcanics. The flow ponded in Mānoa Valley forming a ∼15 m thick flow which was cored and sampled in a quarry. Nepheline from a pegmatoid segregation in the flow yielded a 40Ar-39Ar age of 76 ka. This age, combined with others, indicates that the Tantalus rift eruptions are some of the youngest on O'ahu. Honolulu Volcanics erupt on average about every 35-40 ka indicating that future eruptions are possible. We evaluated the compositional variability of 19 samples from the flow, including 14 from the core. Twelve samples are representative of the bulk flow, four are dark- or light-colored variants, one is a heavy rare earth element (REE)-enriched pegmatoid, and two visually resemble the bulk flow, but have chemical characteristics of the dark and light variants. Our objective was to determine intraflow heterogeneity in mineralogy and composition. Variable abundances of Na2O, K2O, Sr, Ba, Rb, Pb and U in the flow were caused by post-eruptive mobility in a vapor phase, most likely during or soon after flow emplacement, and heterogeneous deposition of secondary calcite and zeolites. Relative to fine-grained samples, a pegmatoid vein that crosscuts the flow is enriched in incompatible trace elements except Sr and TiO2. Element mobility after eruption introduced scatter in trace element ratios including light-REE/heavy-REE, and all ratios involving mobile elements K, Rb, Ba, Sr, Pb, and U. Lavas from some of the 37 Honolulu Volcanics vents have crosscutting REE patterns in a primitive mantle-normalized plot. Such patterns have been interpreted to reflect variable amounts of residual garnet during partial melting. Previous studies of lavas from different vents concluded that garnet, phlogopite, amphibole, and Fe-Ti oxides were residual phases of the partial melting processes that created the Honolulu Volcanics (Clague and Frey, 1982; Yang et al., 2003). However post-eruptive processes in the Sugarloaf flow also produced crossing REE patterns. Eruptions on the Tantalus rift, including the Sugarloaf flow, produced volatile- and crystal-rich ash with interstitial glass and melt inclusions in olivine containing 4.2-6.4 wt% MgO compared to the flow average of 11.8 wt%. This flow erupted as a partially crystallized viscous magma at least 100 °C below its liquidus. The slow advance and cooling of the 15-m thick 'a' ā low promoted the segregation of pegmatoids, formation of light and dark bands with differing proportions of melilite and clinopyroxene, and induced volatile-enhanced mobility of incompatible elements.

Dark matter as a ghost free conformal extension of Einstein theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barvinsky, A.O., E-mail: barvin@td.lpi.ru

We discuss ghost free models of the recently suggested mimetic dark matter theory. This theory is shown to be a conformal extension of Einstein general relativity. Dark matter originates from gauging out its local Weyl invariance as an extra degree of freedom which describes a potential flow of the pressureless perfect fluid. For a positive energy density of this fluid the theory is free of ghost instabilities, which gives strong preference to stable configurations with a positive scalar curvature and trace of the matter stress tensor. Instabilities caused by caustics of the geodesic flow, inherent in this model, serve asmore » a motivation for an alternative conformal extension of Einstein theory, based on the generalized Proca vector field. A potential part of this field modifies the inflationary stage in cosmology, whereas its rotational part at the post inflationary epoch might simulate rotating flows of dark matter.« less

Influence of the variation potential on photosynthetic flows of light energy and electrons in pea.

PubMed

Sukhova, Ekaterina; Mudrilov, Maxim; Vodeneev, Vladimir; Sukhov, Vladimir

2018-05-01

Local damage (mainly burning, heating, and mechanical wounding) induces propagation of electrical signals, namely, variation potentials, which are important signals during the life of plants that regulate different physiological processes, including photosynthesis. It is known that the variation potential decreases the rate of CO 2 assimilation by the Calvin-Benson cycle; however, its influence on light reactions has been poorly investigated. The aim of our work was to investigate the influence of the variation potential on the light energy flow that is absorbed, trapped and dissipated per active reaction centre in photosystem II and on the flow of electrons through the chloroplast electron transport chain. We analysed chlorophyll fluorescence in pea leaves using JIP-test and PAM-fluorometry; we also investigated delayed fluorescence. The electrical signals were registered using extracellular electrodes. We showed that the burning-induced variation potential stimulated a nonphotochemical loss of energy in photosystem II under dark conditions. It was also shown that the variation potential gradually increased the flow of light energy absorbed, trapped and dissipated by photosystem II. These changes were likely caused by an increase in the fraction of absorbed light distributed to photosystem II. In addition, the variation potential induced a transient increase in electron flow through the photosynthetic electron transport chain. Some probable mechanisms for the influence of the variation potential on the light reactions of photosynthesis (including the potential role of intracellular pH decrease) are discussed in the work.

Antimycin A inhibits cytochrome b559-mediated cyclic electron flow within photosystem II.

PubMed

Takagi, Daisuke; Ifuku, Kentaro; Nishimura, Taishi; Miyake, Chikahiro

2018-05-22

The light reactions of photosynthesis are known to comprise both linear and cyclic electron flow in order to convert light energy into chemical energy in the form of NADPH and ATP. Antimycin A (AA) has been proposed as an inhibitor of ferredoxin-dependent cyclic electron flow around photosystem I (CEF-PSI) in photosynthesis research. However, its precise inhibitory mechanism and target site had not been elucidated yet. Here we show that AA inhibits the cyclic (alternative) electron flow via cytochrome b 559 (Cyt b 559 ) within photosystem II (CEF-PSII). When AA was applied to thylakoid membranes isolated from spinach leaves, the high potential form of Cyt b 559 , which was reduced in the dark, was transformed into the lower potential forms and readily oxidized by molecular oxygen. In the absence of AA, the reduced Cyt b 559 was oxidized by P680 + upon light illumination and re-reduced in the dark, mainly by the electron from the Q B site on the acceptor side of PSII. In contrast, AA suppressed the oxidation of Cyt b 559 and induced its reduction under the illumination. This inhibition of Cyt b 559 oxidation by AA enhanced photoinhibition of PSII. Based on the above results, we propose caution regarding the use of AA for evaluating CEF-PSI per se and concurrently propose that AA provides for new insights into, and interpretations of, the physiological importance of Cyt b 559 , rather than that of CEF-PSI in photosynthetic organisms.

Vortex Shedding in the Wake Induced by a Real Elephant Seal Whisker

NASA Astrophysics Data System (ADS)

Turk, Jodi; Omilion, Alexis; Zhang, Wei; Kim, Jeong-Jae; Kim, Jeong-Ju; Choi, Woo-Rak; Lee, Sang-Joon

2017-11-01

Biomimicry has been adopted to create innovative solutions in a vast range of applications. One such application is the design of seal-whisker-inspired flow sensors for autonomous underwater vehicles (AUVs). In dark, cramped, and unstable terrain AUVs are not able to maneuver using visual and sonar-based navigation. Hence, it is critical to use underwater flow sensors to accurately detect minute disturbances in the surroundings. Certain seal whiskers exhibit a unique undulating three-dimensional morphology that can reduce vortex induced vibrations (VIVs) if the major axis of the whisker cross-section is aligned to the inflow. This allows the seal to precisely track prey fish upstream using solely their whiskers. The current study aims to understand the effect of a real seal whisker's morphology on the vortex shedding behavior. Despite extensive studies of wake induced by scaled whisker-like models, the vortex shedding in the wake of a real seal whisker is not well understood. A series of experiments are conducted with a high-speed Particle Imaging Velocimetry (PIV) system in a water channel to examine the vortex shedding downstream from a smooth whisker and an undulating whisker at a Reynolds number of a few hundred. Results of the vortex shedding induced by real seal whiskers can provide insights on developing high-sensitivity underwater flow sensors for AUVs and other whisker-inspired structures.

Analysis of moving surface structures at a laser-induced boiling front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

2014-10-01

Recently ultra-high speed imaging enabled to observe moving wave patterns on metal melts that experience laser-induced boiling. In laser materials processing a vertical laser-induced boiling front governs processes like keyhole laser welding, laser remote fusion cutting, laser drilling or laser ablation. The observed waves originate from temperature variations that are closely related to the melt topology. For improved understanding of the essential front mechanisms and of the front topology, for the first time a deeper systematic analysis of the wave patterns was carried out. Seven geometrical shapes of bright or dark domains were distinguished and categorized, in particular bright peaks of three kinds and dark valleys, often inclined. Two categories describe special flow patterns at the top and bottom of the front. Dynamic and statistical analysis has revealed that the shapes often combine or separate from one category to another when streaming down the front. The brightness of wave peaks typically fluctuates during 20-50 μs. This variety of thermal wave observations is interpreted with respect to the accompanying surface topology of the melt and in turn for governing local mechanisms like absorption, shadowing, boiling, ablation pressure and melt acceleration. The findings can be of importance for understanding the key process mechanisms and for optimizing laser materials processing.

Singlet particles as cold dark matter in a noncommutative space-time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ettefaghi, M. M.

2009-03-15

We extend the noncommutative (NC) standard model to incorporate singlet particles as cold dark matter. In the NC space-time, the singlet particles can be coupled to the U(1) gauge field in the adjoint representation. We study the relic density of the singlet particles due to the NC induced interaction. Demanding either the singlet fermion or the singlet scalar to serve as cold dark matter and the NC induced interactions to be relevant to the dark matter production, we obtain the corresponding relations between the NC scale and the dark matter masses, which are consistent with some existing bounds.

Flavan-3-ol-enriched dark chocolate and white chocolate improve acute measures of platelet function in a gender-specific way--a randomized-controlled human intervention trial.

PubMed

Ostertag, Luisa M; Kroon, Paul A; Wood, Sharon; Horgan, Graham W; Cienfuegos-Jovellanos, Elena; Saha, Shikha; Duthie, Garry G; de Roos, Baukje

2013-02-01

We examined whether flavan-3-ol-enriched dark chocolate, compared with standard dark and white chocolate, beneficially affects platelet function in healthy subjects, and whether this relates to flavan-3-ol bioavailability. A total of 42 healthy subjects received an acute dose of flavan-3-ol-enriched dark, standard dark or white chocolate, in random order. Blood and urine samples were obtained just before and 2 and 6 h after consumption for measurements of platelet function, and bioavailability and excretion of flavan-3-ols. Flavan-3-ol-enriched dark chocolate significantly decreased adenosine diphosphate-induced platelet aggregation and P-selectin expression in men (all p ≤ 0.020), decreased thrombin receptor-activating peptide-induced platelet aggregation and increased thrombin receptor-activating peptide-induced fibrinogen binding in women (both p ≤ 0.041), and increased collagen/epinephrine-induced ex vivo bleeding time in men and women (p ≤ 0.042). White chocolate significantly decreased adenosine diphosphate-induced platelet P-selectin expression (p = 0.002) and increased collagen/epinephrine-induced ex vivo bleeding time (p = 0.042) in men only. Differences in efficacy by which flavan-3-ols affect platelet function were only partially explained by concentrations of flavan-3-ols and their metabolites in plasma or urine. Flavan-3-ols in dark chocolate, but also compounds in white chocolate, can improve platelet function, dependent on gender, and may thus beneficially affect atherogenesis. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dark Energy and the Hubble Law

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Dolgachev, V. P.; Domozhilova, L. M.

The Big Bang predicted by Friedmann could not be empirically discovered in the 1920th, since global cosmological distances (more than 300-1000 Mpc) were not available for observations at that time. Lemaitre and Hubble studied receding motions of galaxies at local distances of less than 20-30 Mpc and found that the motions followed the (nearly) linear velocity-distance relation, known now as Hubble's law. For decades, the real nature of this phenomenon has remained a mystery, in Sandage's words. After the discovery of dark energy, it was suggested that the dynamics of local expansion flows is dominated by omnipresent dark energy, and it is the dark energy antigravity that is able to introduce the linear velocity-distance relation to the flows. It implies that Hubble's law observed at local distances was in fact the first observational manifestation of dark energy. If this is the case, the commonly accepted criteria of scientific discovery lead to the conclusion: In 1927, Lemaitre discovered dark energy and Hubble confirmed this in 1929.

Direct Visualization of Planar Assembly of Plasmonic Nanoparticles Adjacent to Electrodes in Oscillatory Electric Fields.

PubMed

Ferrick, Adam; Wang, Mei; Woehl, Taylor J

2018-05-29

Electric field-directed assembly of colloidal nanoparticles (NPs) has been widely adopted for fabricating functional thin films and nanostructured surfaces. While first-order electrokinetic effects on NPs are well-understood in terms of classical models, effects of second-order electrokinetics that involve induced surface charge are still poorly understood. Induced charge electroosmotic phenomena, such as electrohydrodynamic (EHD) flow, have long been implicated in electric field-directed NP assembly with little experimental basis. Here, we use in situ dark-field optical microscopy and plasmonic NPs to directly observe the dynamics of planar assembly of colloidal NPs adjacent to a planar electrode in low-frequency (<1 kHz) oscillatory electric fields. We exploit the change in plasmonic NP color resulting from interparticle plasmonic coupling to visualize the assembly dynamics and assembly structure of silver NPs. Planar assembly of NPs is unexpected because of strong electrostatic repulsion between NPs and indicates that there are strong attractive interparticle forces oriented perpendicular to the electric field direction. A parametric investigation of the voltage- and frequency-dependent phase behavior reveals that planar NP assembly occurs over a narrow frequency range below which irreversible ballistic deposition occurs. Two key experimental observations are consistent with EHD flow-induced NP assembly: (1) NPs remain mobile during assembly and (2) electron microscopy observations reveal randomly close-packed planar assemblies, consistent with strong interparticle attraction. We interpret planar assembly in terms of EHD fluid flow and develop a scaling model that qualitatively agrees with the measured phase regions. Our results are the first direct in situ observations of EHD flow-induced NP assembly and shed light on long-standing unresolved questions concerning the formation of NP superlattices during electric field-induced NP deposition.

Duality between a dark state and a quasi-dark state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirokawa, Masao, E-mail: hirokawa@amath.hiroshima-u.ac.jp

We study a physical system coupled with two one-mode Bose fields. The physical system is a two-level system or a harmonic oscillator. We prove that each dark and quasi-dark state appears under a proper condition, and then, we derive a duality between the dark state and the quasi-dark state. This duality induces the switch between the dark state and the quasi-dark state.

Coupling effects for separate spatial solitons in a biased series centrosymmetric photorefractive crystal circuit considering grey solitons

NASA Astrophysics Data System (ADS)

Katti, Aavishkar; Yadav, Ram Anjore

2018-02-01

The existence and coupling of grey-grey, grey-bright and grey-dark separate spatial solitons in a biased series centrosymmetric photorefractive crystal circuit is investigated for the first time. The numerical solution of the separate spatial solitons is presented. The coupling between the two separate spatial solitons is analysed for all three cases of separate coupled solitons, namely grey-grey, grey-bright, and grey-dark. Changing the intensity of the soliton in one crystal affects the soliton in both crystals due to flow of the light induced current through the circuit. The effect of the background intensity of each crystal on both the spatial solitons is investigated. Also, the effect of changing the temperature of one crystal affects the soliton in both crystals due to the coupling effect. The soliton width dependence on the temperature is different for each crystal.

The Shift of ERG B-Wave Induced by Hours' Dark Exposure in Rodents.

PubMed

Li, Dake; Fang, Qi; Yu, Hongbo

2016-01-01

Dark adaptation can induce a rapid functional shift in the retina, and after that, the retinal function is believed to remain stable during the continuous dark exposure. However, we found that electroretinograms (ERG) b-waves gradually shifted during 24 hours' dark exposure in rodents. Detailed experiments were designed to explore this non-classical dark adaptation. In vivo ERG recording in adult and developing rodents after light manipulations. We revealed a five-fold decrease in ERG b-waves in adult rats that were dark exposed for 24 hours. The ERG b-waves significantly increased within the first hour's dark exposure, but after that decreased continuously and finally attained steady state after 1 day's dark exposure. After 3 repetitive, 10 minutes' light exposure, the dark exposed rats fully recovered. This recovery effect was eye-specific, and light exposure to one eye could not restore the ERGs in the non-exposed eye. The prolonged dark exposure-induced functional shift was also reflected in the down-regulation on the amplitude of intensity-ERG response curve, but the dynamic range of the responsive light intensity remained largely stable. Furthermore, the ERG b-wave shifts occurred in and beyond classical critical period, and in both rats and mice. Importantly, when ERG b-wave greatly shifted, the amplitude of ERG a-wave did not change significantly after the prolonged dark exposure. This rapid age-independent ERG change demonstrates a generally existing functional shift in the retina, which is at the entry level of visual system.

Constraints on interacting dark energy models from Planck 2015 and redshift-space distortion data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costa, André A.; Abdalla, E.; Xu, Xiao-Dong

2017-01-01

We investigate phenomenological interactions between dark matter and dark energy and constrain these models by employing the most recent cosmological data including the cosmic microwave background radiation anisotropies from Planck 2015, Type Ia supernovae, baryon acoustic oscillations, the Hubble constant and redshift-space distortions. We find that the interaction in the dark sector parameterized as an energy transfer from dark matter to dark energy is strongly suppressed by the whole updated cosmological data. On the other hand, an interaction between dark sectors with the energy flow from dark energy to dark matter is proved in better agreement with the available cosmologicalmore » observations. This coupling between dark sectors is needed to alleviate the coincidence problem.« less

Lepton flavor violation induced by dark matter

NASA Astrophysics Data System (ADS)

Arcadi, Giorgio; Ferreira, C. P.; Goertz, Florian; Guzzo, M. M.; Queiroz, Farinaldo S.; Santos, A. C. O.

2018-04-01

Guided by gauge principles we discuss a predictive and falsifiable UV complete model where the Dirac fermion that accounts for the cold dark matter abundance in our Universe induces the lepton flavor violation (LFV) decays μ →e γ and μ →e e e as well as μ -e conversion. We explore the interplay between direct dark matter detection, relic density, collider probes and lepton flavor violation to conclusively show that one may have a viable dark matter candidate yielding flavor violation signatures that can be probed in the upcoming experiments. In fact, keeping the dark matter mass at the TeV scale, a sizable LFV signal is possible, while reproducing the correct dark matter relic density and meeting limits from direct-detection experiments.

Dynamic freeze-in: impact of thermal masses and cosmological phase transitions on dark matter production

NASA Astrophysics Data System (ADS)

Baker, Michael J.; Breitbach, Moritz; Kopp, Joachim; Mittnacht, Lukas

2018-03-01

The cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values. We illustrate this point in three simple freeze-in models. The first one, which we call kinematically induced freeze-in, is based on the observation that the effective mass of a scalar temporarily becomes very small as the scalar potential undergoes a second order phase transition. This opens dark matter production channels that are otherwise forbidden. The second model we consider, dubbed vev-induced freeze-in, is a fermionic Higgs portal scenario. Its scalar sector is augmented compared to the Standard Model by an additional scalar singlet, S, which couples to dark matter and temporarily acquires a vacuum expectation value (a two-step phase transition or "vev flip-flop"). While < S> ≠ 0, the modified coupling structure in the scalar sector implies that dark matter production is significantly enhanced compared to the < S> = 0 phases realised at very early times and again today. The third model, which we call mixing-induced freeze-in, is similar in spirit, but here it is the mixing of dark sector fermions, induced by non-zero < S>, that temporarily boosts the dark matter production rate. For all three scenarios, we carefully dissect the evolution of the dark sector in the early Universe. We compute the DM relic abundance as a function of the model parameters, emphasising the importance of thermal corrections and the proper treatment of phase transitions in the calculation.

Dark-soliton collisions for a coupled AB system in the geophysical fluids or nonlinear optics

NASA Astrophysics Data System (ADS)

Xie, Xi-Yang; Meng, Gao-Qing

2018-02-01

Under investigation in this paper is a coupled AB system, which describes the marginally unstable baroclinic wave packets in the geophysical fluids or ultra-short pulses in nonlinear optics. As the dark solitons are more resistant against various perturbations than the bright ones, we aim to investigate the dark solitons in the geophysical fluids or nonlinear optics. Dark one- and two-soliton solutions for such a system are derived based on the bilinear forms and propagations of the one solitons and collisions between the two solitons are graphically illustrated and analyzed. Further, influences of the coefficients λ and σ on the solitons are discussed, where λ is a parameter measuring the state of the basic flow and σ is the group velocity. The dark-one solitons with invariant shapes and amplitudes are viewed, and elastic collisions between the dark-two solitons are observed. Also, elastic collision between the bright and dark solitons is viewed, and the dark soliton is found to possess two peaks. σ is found to affect the widths of the dark-one solitons and the travelling directions of the dark-two solitons. It is shown that λ cannot influence shapes of A1 and A2, but affect the plane of the one soliton for B, and the two-peak dark soliton for B changes to the single-peak one with the value of λ decreasing, where A1 and A2 are the packets of short waves and B is the mean flow.

DELLA proteins negatively regulate dark-induced senescence and chlorophyll degradation in Arabidopsis through interaction with the transcription factor WRKY6.

PubMed

Zhang, Yongqiang; Liu, Zhongjuan; Wang, Xiaoyun; Wang, Jianfeng; Fan, Kai; Li, Zhaowei; Lin, Wenxiong

2018-03-24

DELLA proteins' negative regulation of dark-induced senescence and chlorophyll degradation in Arabidopsis is through interaction with WRKY6 and thus repression of its transcriptional activities on senescence-related genes. Senescence is an intricate and highly orchestrated process regulated by numerous endogenous and environmental signals. Gibberellins (GAs) and their signaling components DELLA proteins have been known to participate in the regulation of senescence. However, the mechanism of the GA-DELLA system involved in the senescence process remains largely unclear. Darkness is a known environmental factor that induces plant senescence. In this study, exogenous GA 3 (an active form of GA) accelerated but paclobutrazol (a specific GA biosynthesis inhibitor) retarded dark-induced leaf yellowing in Arabidopsis. Moreover, the dark-triggered decrease in chlorophyll content, increase in cell membrane leakage, and upregulation of senescence-associated genes were notably impaired in both endogenous GA-decreased mutants ga3ox1/ga3ox2 and ga20ox1/ga20ox2 compared with those in wild-type Col-0. These effects of darkness were enhanced in the quintuple mutant of DELLA genes gai-t6/rga-t2/rgl1-1/rgl2-1/rgl3-1 and conversely attenuated in the gain-of-function mutant gai and transgenic plant 35S::TAP-RGAd17 compared with wild-type Ler. Subsequently, RGA interacted with the transcription factor WRKY6 in a yeast two-hybrid assay, as confirmed by bimolecular fluorescence complementation and pull-down analyses. In addition, mutation and overexpression of WRKY6 retarded and accelerated dark-induced senescence, respectively. Furthermore, transient expression assays in Arabidopsis protoplasts indicated that RGA and GAI weakened the transcriptional activities of WRKY6 on its downstream senescence-related genes, including SAG13 and SGR. Taken together, these results suggest that GAs positively and DELLAs negatively regulate dark-induced senescence and chlorophyll degradation in Arabidopsis. DELLAs function in this process, at least in part, by interacting with WRKY6.

Loop induced type-II seesaw model and GeV dark matter with U(1)B - L gauge symmetry

NASA Astrophysics Data System (ADS)

Nomura, Takaaki; Okada, Hiroshi

2017-11-01

We propose a model with U(1) B - L gauge symmetry and several new fermions in no conflict with anomaly cancellation where the neutrino masses are given by the vacuum expectation value of Higgs triplet induced at the one-loop level. The new fermions are odd under discrete Z2 symmetry and the lightest one becomes dark matter candidate. We find that the mass of dark matter is typically O (1)- O (10) GeV. Then relic density of the dark matter is discussed.

The Shift of ERG B-Wave Induced by Hours' Dark Exposure in Rodents

PubMed Central

Li, Dake; Fang, Qi; Yu, Hongbo

2016-01-01

Purpose Dark adaptation can induce a rapid functional shift in the retina, and after that, the retinal function is believed to remain stable during the continuous dark exposure. However, we found that electroretinograms (ERG) b-waves gradually shifted during 24 hours’ dark exposure in rodents. Detailed experiments were designed to explore this non-classical dark adaptation. Methods In vivo ERG recording in adult and developing rodents after light manipulations. Results We revealed a five-fold decrease in ERG b-waves in adult rats that were dark exposed for 24 hours. The ERG b-waves significantly increased within the first hour’s dark exposure, but after that decreased continuously and finally attained steady state after 1 day’s dark exposure. After 3 repetitive, 10 minutes’ light exposure, the dark exposed rats fully recovered. This recovery effect was eye-specific, and light exposure to one eye could not restore the ERGs in the non-exposed eye. The prolonged dark exposure-induced functional shift was also reflected in the down-regulation on the amplitude of intensity-ERG response curve, but the dynamic range of the responsive light intensity remained largely stable. Furthermore, the ERG b-wave shifts occurred in and beyond classical critical period, and in both rats and mice. Importantly, when ERG b-wave greatly shifted, the amplitude of ERG a-wave did not change significantly after the prolonged dark exposure. Conclusions This rapid age-independent ERG change demonstrates a generally existing functional shift in the retina, which is at the entry level of visual system. PMID:27517462

Circadian-dependent effect of melatonin on dopaminergic D2 antagonist-induced hypokinesia and agonist-induced stereotypies in rats.

PubMed

Sumaya, I C; Byers, D M; Irwin, L N; Del Val, S; Moss, D E

2004-08-01

Although a melatonin/dopamine relationship has been well established in nonmotor systems wherein dopamine and melatonin share an antagonist relationship, less clear is the role melatonin may play in extrapyramidal dopaminergic function. Therefore, the purpose of the present experiments was to examine the relationship between melatonin and the dopaminergic D2 receptor system and behavior. Hypokinesia was induced in male Sprague-Dawley rats with fluphenazine (D2 antagonist, 0.4 mg/kg ip) and stereotypies with apomorphine (D2 agonist, 0.6 mg/kg sc) during the light (1200 h) and dark (2200 h) phases. As expected, fluphenazine induced severe hypokinesia during the light phase (482 +/- 176 s); however, unexpectedly, fluphenazine-induced hypokinesia during the dark was almost nonexistent (25 +/- 6 s). Furthermore, melatonin treatment (30 mg/kg ip) produced a strong interaction with fluphenazine in that it reduced fluphenazine-induced hypokinesia by nearly 80% in the light (112 +/- 45 s) but paradoxically increased the minimal fluphenazine-induced hypokinesia in the dark by more than 60% (70 +/- 17 s). Melatonin also reduced apomorphine-induced stereotypies by nearly 40% in the light but had no effect in the dark. Taken together, these data show (1) a strong and unexpected nocturnal effect of fluphenazine on hypokinesia and (2) provide support for an antagonistic melatonin/dopaminergic interaction in the context of motor behavior and D2 receptor function which appears to be critically dependent on the light/dark status of the dopaminergic system. Copyright 2004 Elsevier Inc.

Levitating dark matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaloper, Nemanja; Padilla, Antonio, E-mail: kaloper@physics.ucdavis.edu, E-mail: antonio.padilla@nottingham.ac.uk

2009-10-01

A sizable fraction of the total energy density of the universe may be in heavy particles with a net dark U(1)' charge comparable to its mass. When the charges have the same sign the cancellation between their gravitational and gauge forces may lead to a mismatch between different measures of masses in the universe. Measuring galactic masses by orbits of normal matter, such as galaxy rotation curves or lensing, will give the total mass, while the flows of dark matter agglomerates may yield smaller values if the gauge repulsion is not accounted for. If distant galaxies which house light beaconsmore » like SNe Ia contain such dark particles, the observations of their cosmic recession may mistake the weaker forces for an extra 'antigravity', and infer an effective dark energy equation of state smaller than the real one. In some cases, including that of a cosmological constant, these effects can mimic w < −1. They can also lead to a local variation of galaxy-galaxy forces, yielding a larger 'Hubble Flow' in those regions of space that could be taken for a dynamical dark energy, or superhorizon effects.« less

Levitating dark matter

NASA Astrophysics Data System (ADS)

Kaloper, Nemanja; Padilla, Antonio

2009-10-01

A sizable fraction of the total energy density of the universe may be in heavy particles with a net dark U(1)' charge comparable to its mass. When the charges have the same sign the cancellation between their gravitational and gauge forces may lead to a mismatch between different measures of masses in the universe. Measuring galactic masses by orbits of normal matter, such as galaxy rotation curves or lensing, will give the total mass, while the flows of dark matter agglomerates may yield smaller values if the gauge repulsion is not accounted for. If distant galaxies which house light beacons like SNe Ia contain such dark particles, the observations of their cosmic recession may mistake the weaker forces for an extra `antigravity', and infer an effective dark energy equation of state smaller than the real one. In some cases, including that of a cosmological constant, these effects can mimic w < -1. They can also lead to a local variation of galaxy-galaxy forces, yielding a larger `Hubble Flow' in those regions of space that could be taken for a dynamical dark energy, or superhorizon effects.

Volcanism on Io: New insights from global geologic mapping

USGS Publications Warehouse

Williams, D.A.; Keszthelyi, L.P.; Crown, D.A.; Yff, J.A.; Jaeger, W.L.; Schenk, P.M.; Geissler, P.E.; Becker, T.L.

2011-01-01

We produced the first complete, 1:15M-scale global geologic map of Jupiter's moon Io, based on a set of monochrome and color Galileo-Voyager image mosaics produced at a spatial resolution of 1km/pixel. The surface of Io was mapped into 19 units based on albedo, color and surface morphology, and is subdivided as follows: plains (65.8% of surface), lava flow fields (28.5%), mountains (3.2%), and patera floors (2.5%). Diffuse deposits (DD) that mantle the other units cover ???18% of Io's surface, and are distributed as follows: red (8.6% of surface), white (6.9%), yellow (2.1%), black (0.6%), and green (???0.01%). Analyses of the geographical and areal distribution of these units yield a number of results, summarized below. (1) The distribution of plains units of different colors is generally geographically constrained: Red-brown plains occur >??30?? latitude, and are thought to result from enhanced alteration of other units induced by radiation coming in from the poles. White plains (possibly dominated by SO2+contaminants) occur mostly in the equatorial antijovian region (??30??, 90-230??W), possibly indicative of a regional cold trap. Outliers of white, yellow, and red-brown plains in other regions may result from long-term accumulation of white, yellow, and red diffuse deposits, respectively. (2) Bright (possibly sulfur-rich) flow fields make up 30% more lava flow fields than dark (presumably silicate) flows (56.5% vs. 43.5%), and only 18% of bright flow fields occur within 10km of dark flow fields. These results suggest that secondary sulfurous volcanism (where a bright-dark association is expected) could be responsible for only a fraction of Io's recent bright flows, and that primary sulfur-rich effusions could be an important component of Io's recent volcanism. An unusual concentration of bright flows at ???45-75??N, ???60-120??W could be indicative of more extensive primary sulfurous volcanism in the recent past. However, it remains unclear whether most bright flows are bright because they are sulfur flows, or because they are cold silicate flows covered in sulfur-rich particles from plume fallout. (3) We mapped 425 paterae (volcano-tectonic depressions), up from 417 previously identified by Radebaugh et al. (Radebaugh, J., Keszthelyi, L.P., McEwen, A.S., Turtle, E.P., Jaeger, W., Milazzo, M. [2001]. J. Geophys. Res. 106, 33005-33020). Although these features cover only 2.5% of Io's surface, they correspond to 64% of all detected hot spots; 45% of all hot spots are associated with the freshest dark patera floors, reflecting the importance of active silicate volcanism to Io's heat flow. (4) Mountains cover only ???3% of the surface, although the transition from mountains to plains is gradational with the available imagery. 49% of all mountains are lineated and presumably layered, showing evidence of linear structures supportive of a tectonic origin. In contrast, only 6% of visible mountains are mottled (showing hummocks indicative of mass wasting) and 4% are tholi (domes or shields), consistent with a volcanic origin. (5) Initial analyses of the geographic distributions of map units show no significant longitudinal variation in the quantity of Io's mountains or paterae, in contrast to earlier studies. This is because we use the area of mountain and patera materials as opposed to the number of structures, and our result suggests that the previously proposed anti-correlation of mountains and paterae (Schenk, P., Hargitai, H., Wilson, R., McEwen, A., Thomas, P. [2001]. J. Geophys. Res. 106, 33201-33222; Kirchoff, M.R., McKinnon, W.B., Schenk, P.M. [2011]. Earth Planet. Sci. Lett. 301, 22-30) is more complex than previously thought. There is also a slight decrease in surface area of lava flows toward the poles of Io, perhaps indicative of variations in volcanic activity. (6) The freshest bright and dark flows make up about 29% of all of Io's flow fields, suggesting active emplacement is occurring in less than a third of Io's

Implications of two-component dark matter induced by forbidden channels and thermal freeze-out

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Mayumi; Toma, Takashi, E-mail: mayumi@hep.s.kanazawa-u.ac.jp, E-mail: takashi.toma@tum.de

2017-01-01

We consider a model of two-component dark matter based on a hidden U(1) {sub D} symmetry, in which relic densities of the dark matter are determined by forbidden channels and thermal freeze-out. The hidden U(1) {sub D} symmetry is spontaneously broken to a residual Z{sub 4} symmetry, and the lightest Z{sub 4} charged particle can be a dark matter candidate. Moreover, depending on the mass hierarchy in the dark sector, we have two-component dark matter. We show that the relic density of the lighter dark matter component can be determined by forbidden annihilation channels which require larger couplings compared tomore » the normal freeze-out mechanism. As a result, a large self-interaction of the lighter dark matter component can be induced, which may solve small scale problems of ΛCDM model. On the other hand, the heavier dark matter component is produced by normal freeze-out mechanism. We find that interesting implications emerge between the two dark matter components in this framework. We explore detectabilities of these dark matter particles and show some parameter space can be tested by the SHiP experiment.« less

Function of the Golgi-located phosphate transporter PHT4;6 is critical for senescence-associated processes in Arabidopsis

PubMed Central

Hassler, Sebastian; Jung, Benjamin; Lemke, Lilia; Novák, Ondřej; Strnad, Miroslav; Martinoia, Enrico; Neuhaus, H. Ekkehard

2016-01-01

The phosphate transporter PHT4;6 locates to the trans-Golgi compartment, and its impaired activity causes altered intracellular phosphate compartmentation, leading to low cytosolic Pi levels, a blockage of Golgi-related processes such as protein glycosylation and hemicellulose biosynthesis, and a dwarf phenotype. However, it was unclear whether altered Pi homeostasis in pht4;6 mutants causes further cellular problems, typically associated with limited phosphate availability. Here we report that pht4;6 mutants exhibit a markedly increased disposition to induce dark-induced senescence. In control experiments, in which pht4;6 mutants and wild-type plants developed similarly, we confirmed that accelerated dark-induced senescence in mutants is not a ‘pleiotropic’ process associated with the dwarf phenotype. In fact, accelerated dark-induced senescence in pht4;6 mutants correlates strongly with increased levels of toxic NH4 + and higher sensitivity to ammonium, which probably contribute to the inability of pht4;6 mutants to recover from dark treatment. Experiments with modified levels of either salicylic acid (SA) or trans-zeatin (tZ) demonstrate that altered concentrations of these compounds in pht4;6 plants act as major cellular mediators for dark-induced senescence. This conclusion gained further support from the notion that the expression of the pht4;6 gene is, in contrast to genes coding for major phosphate importers, substantially induced by tZ. Taken together, our findings point to a critical function of PHT4;6 to control cellular phosphate levels, in particular the cytosolic Pi availability, required to energize plant primary metabolism for proper plant development. Phosphate and its allocation mediated by PHT4;6 is critical to prevent onset of dark-induced senescence. PMID:27325894

Quantitative laser speckle flowmetry of the in vivo microcirculation using sidestream dark field microscopy

PubMed Central

Nadort, Annemarie; Woolthuis, Rutger G.; van Leeuwen, Ton G.; Faber, Dirk J.

2013-01-01

We present integrated Laser Speckle Contrast Imaging (LSCI) and Sidestream Dark Field (SDF) flowmetry to provide real-time, non-invasive and quantitative measurements of speckle decorrelation times related to microcirculatory flow. Using a multi exposure acquisition scheme, precise speckle decorrelation times were obtained. Applying SDF-LSCI in vitro and in vivo allows direct comparison between speckle contrast decorrelation and flow velocities, while imaging the phantom and microcirculation architecture. This resulted in a novel analysis approach that distinguishes decorrelation due to flow from other additive decorrelation sources. PMID:24298399

In-Situ Characterization of Potential-Induced Degradation in Crystalline Silicon Photovoltaic Modules Through Dark I–V Measurements

DOE PAGES

Luo, Wei; Hacke, Peter; Singh, Jai Prakash; ...

2016-11-14

Here, a temperature correction methodology for in-situ dark I-V(DIV) characterization of conventional p-type crystalline silicon photovoltaic (PV) modules undergoing potential-induced degradation (PID) is proposed.

The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR

USGS Publications Warehouse

Soderblom, L.A.; Brown, R.H.; Soderblom, J.M.; Barnes, J.W.; Kirk, R.L.; Sotin, Christophe; Jaumann, R.; MacKinnon, D.J.; Mackowski, D.W.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

2009-01-01

Joint Cassini VIMS and RADAR SAR data of ???700-km-wide Hotei Regio reveal a rich collection of geological features that correlate between the two sets of images. The degree of correlation is greater than anywhere else seen on Titan. Central to Hotei Regio is a basin filled with cryovolcanic flows that are anomalously bright in VIMS data (in particular at 5 ??m) and quite variable in roughness in SAR. The edges of the flows are dark in SAR data and appear to overrun a VIMS-bright substrate. SAR-stereo topography shows the flows to be viscous, 100-200 m thick. On its southern edge the basin is ringed by higher (???1 km) mountainous terrain. The mountains show mixed texture in SAR data: some regions are extremely rough, exhibit low and spectrally neutral albedo in VIMS data and may be partly coated with darker hydrocarbons. Around the southern margin of Hotei Regio, the SAR image shows several large, dendritic, radar-bright channels that flow down from the mountainous terrain and terminate in dark blue patches, seen in VIMS images, whose infrared color is consistent with enrichment in water ice. The patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels. In the VIMS images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions. Conceivably the circular features are tectonic structures that are remnant from an ancient impact structure. We suggest that impact-generated structures may have simply served as zones of weakness; no direct causal connection, such as impact-induced volcanism, is implied. We also speculate that two large dark features lying on the northern margin of Hotei Regio could be calderas. In summary the preservation of such a broad suite of VIMS infrared color variations and the detailed correlation with features in the SAR image and SAR topography evidence a complex set of geological processes (pluvial, fluvial, tectonic, cryovolcanic, impact) that have likely remained active up to very recent geological time (<104 year). That the cryovolcanic flows are excessively bright in the infrared, particularly at 5 ??m, might signal ongoing geological activity. One study [Nelson, R.M., and 28 colleagues, 2009. Icarus 199, 429-441] reported significant 2-??m albedo changes in VIMS data for Hotei Arcus acquired between 2004 and 2006, that were interpreted as evidence for such activity. However in our review of that work, we do not agree that such evidence has yet been found.

Mated Drosophila melanogaster females consume more amino acids during the dark phase

PubMed Central

Uchizono, Shun; Tabuki, Yumi; Kawaguchi, Natsumi; Tanimura, Teiichi; Itoh, Taichi Q.

2017-01-01

To maintain homeostasis, animals must ingest appropriate quantities, determined by their internal nutritional state, of suitable nutrients. In the fruit fly Drosophila melanogaster, an amino acid deficit induces a specific appetite for amino acids and thus results in their increased consumption. Although multiple processes of physiology, metabolism, and behavior are under circadian control in many organisms, it is unclear whether the circadian clock also modulates such motivated behavior driven by an internal need. Differences in levels of amino acid consumption by flies between the light and dark phases of the day:night cycle were examined using a capillary feeder assay following amino acid deprivation. Female flies exhibited increased consumption of amino acids during the dark phase compared with the light phase. Investigation of mutants lacking a functional period gene (per0), a well-characterized clock gene in Drosophila, found no difference between the light and dark phases in amino acid consumption by per0 flies. Furthermore, increased consumption of amino acids during the dark phase was observed in mated but not in virgin females, which strongly suggested that mating is involved in the rhythmic modulation of amino acid intake. Egg production, which is induced by mating, did not affect the rhythmic change in amino acid consumption, although egg-laying behavior showed a per0-dependent change in rhythm. Elevated consumption of amino acids during the dark phase was partly induced by the action of a seminal protein, sex peptide (SP), on the sex peptide receptor (SPR) in females. Moreover, we showed that the increased consumption of amino acids during the dark phase is induced in mated females independently of their internal level of amino acids. These results suggest that a post-mating SP/SPR signal elevates amino acid consumption during the dark phase via the circadian clock. PMID:28241073

Mated Drosophila melanogaster females consume more amino acids during the dark phase.

PubMed

Uchizono, Shun; Tabuki, Yumi; Kawaguchi, Natsumi; Tanimura, Teiichi; Itoh, Taichi Q

2017-01-01

To maintain homeostasis, animals must ingest appropriate quantities, determined by their internal nutritional state, of suitable nutrients. In the fruit fly Drosophila melanogaster, an amino acid deficit induces a specific appetite for amino acids and thus results in their increased consumption. Although multiple processes of physiology, metabolism, and behavior are under circadian control in many organisms, it is unclear whether the circadian clock also modulates such motivated behavior driven by an internal need. Differences in levels of amino acid consumption by flies between the light and dark phases of the day:night cycle were examined using a capillary feeder assay following amino acid deprivation. Female flies exhibited increased consumption of amino acids during the dark phase compared with the light phase. Investigation of mutants lacking a functional period gene (per0), a well-characterized clock gene in Drosophila, found no difference between the light and dark phases in amino acid consumption by per0 flies. Furthermore, increased consumption of amino acids during the dark phase was observed in mated but not in virgin females, which strongly suggested that mating is involved in the rhythmic modulation of amino acid intake. Egg production, which is induced by mating, did not affect the rhythmic change in amino acid consumption, although egg-laying behavior showed a per0-dependent change in rhythm. Elevated consumption of amino acids during the dark phase was partly induced by the action of a seminal protein, sex peptide (SP), on the sex peptide receptor (SPR) in females. Moreover, we showed that the increased consumption of amino acids during the dark phase is induced in mated females independently of their internal level of amino acids. These results suggest that a post-mating SP/SPR signal elevates amino acid consumption during the dark phase via the circadian clock.

Current–voltage characteristics of organic heterostructure devices with insulating spacer layers

DOE PAGES

Yin, Sun; Nie, Wanyi; Mohite, Aditya D.; ...

2015-05-14

The dark current density in donor/acceptor organic planar heterostructure devices at a given forward voltage bias can either increase or decrease when an insulating spacer layer is added between the donor and acceptor layers. The dominant current flow process in these systems involves the formation and subsequent recombination of interfacial exciplex states. If the exciplex recombination rate limits current flow, an insulating interface layer decreases the dark current. However, if the exciplex formation rate limits the current, an insulating interface layer may increase the dark current. As a result, we present a device model to describe this behavior, and wemore » discuss relevant experimental data.« less

Local expansion flows of galaxies: quantifying acceleration effect of dark energy

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Teerikorpi, P.

2013-08-01

The nearest expansion flow of galaxies observed around the Local group is studied as an archetypical example of the newly discovered local expansion flows around groups and clusters of galaxies in the nearby Universe. The flow is accelerating due to the antigravity produced by the universal dark energy background. We introduce a new acceleration measure of the flow which is the dimensionless ``acceleration parameter" Q (x) = x - x-2 depending on the normalized distance x only. The parameter is zero at the zero-gravity distance x = 1, and Q(x) ∝ x, when x ≫ 1. At the distance x = 3, the parameter Q = 2.9. Since the expansion flows have a self-similar structure in normalized variables, we expect that the result is valid as well for all the other expansion flows around groups and clusters of galaxies on the spatial scales from ˜ 1 to ˜ 10 Mpc everywhere in the Universe.

Evolution of velocity dispersion along cold collisionless flows

DOE PAGES

Banik, Nilanjan; Sikivie, Pierre

2016-05-01

We found that the infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We also discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behaviour of the velocity dispersion near caustics. The results aremore » used to derive an upper limit on the energy dispersion of the Big Flow from the sharpness of its nearby caustic, and a prediction for the dispersions in its velocity components.« less

The detection of distant cooling flows and the formation of dark matter

NASA Technical Reports Server (NTRS)

Fabian, A. C.; Arnaud, K. A.; Nulsen, P. E. J.; Mushotzky, R. F.

1986-01-01

Cooling flows involving substantial mass inflow rates appear to be common in many nearby rich and poor clusters and in isolated galaxies. The extensive optical and ultraviolet filaments produced by the thermal instability of large flows are detectable out to redshifts greater than 1. It is proposed that this may explain the extended optical line emission reported in, and around, many distant radio galaxies, narrow-line quasars, and even nearby normal and active galaxies. An important diagnostic to distinguish cooling flows from other possible origins of emission line filaments is the presence of extensive regions at high thermal pressure. Other evidence for distant cooling flows and the resultant star formation is further discussed, together with the implications of cooling flow initial-mass functions for galaxy formation and the nature of 'dark' matter.

Phospholipase C mediated Suppression of Dark Noise Enables Single Photon Detection in Drosophila Photoreceptors

PubMed Central

Katz, Ben; Minke, Baruch

2012-01-01

Drosophila photoreceptor cells use the ubiquitous G-protein-mediated phospholipase C (PLC) cascade to achieve ultimate single photon sensitivity. This is manifested in the single photon responses (quantum bumps). In photoreceptor cells, dark activation of Gqα molecules occurs spontaneously and produces unitary dark events (dark bumps). A high rate of spontaneous Gqα activation and dark bump production potentially hampers single photon detection. We found that in wild type flies the in vivo rate of spontaneous Gqα activation is very high. Nevertheless, this high rate is not manifested in a substantially high rate of dark bumps. Therefore, it is unclear how phototransduction suppresses dark bump production, arising from spontaneous Gqα activation, while still maintaining high-fidelity representation of single photons. In this study we show that reduced PLC catalytic activity selectively suppressed production of dark bumps but not light-induced bumps. Manipulations of PLC activity using PLC mutant flies and Ca2+ modulations revealed that a critical level of PLC activity is required to induce bump production. The required minimal level of PLC activity, selectively suppressed random production of single Gqα-activated dark bumps despite a high rate of spontaneous Gqα activation. This minimal PLC activity level is reliably obtained by photon induced synchronized activation of several neighboring Gqα molecules activating several PLC molecules, but not by random activation of single Gqα molecules. We thus demonstrate how a G-protein-mediated transduction system, with PLC as its target, selectively suppresses its intrinsic noise while preserving reliable signaling. PMID:22357856

Numerical variation of dark cells in normal and chemically induced hyperplastic epidermis with age of animal and efficiency of tumor promoter. [Mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein-Szanto, A.J.P.; Slaga, T.J.

1981-11-01

The percentage of dark basal keratinocytes was quantitatively assessed in normal epidermis of Sencar mice before and after birth and in adult epidermis after topical application of several compounds of varying promoting efficiency. The percentage of dark keratinocytes reached a maximum at the 19th day of gestation (approx.40%) and fell abruptly after birth (approx.3%). Old animals exhibited a very low number of dark basal cells (0.2%). After topical application of the weak promoters resiniferotoxin, anthralin, ethylphenylpropiolate, and 12-deoxyphorbol-13-2,4,6-decatrienoate, the percentage of dark cells in young adult epidermis did not differ markedly from that in control (acetone-treated) specimens. The strong first-stagemore » promoters 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate and calcium ionophore A 23187, as well as the strong complete promoter 12-deoxyphorbol-13-deoxyphorbol-13-decanoate, induced the appearance of large numbers of dark keratinocytes, in a percentage similar to that seen after 12-O-tetra-decanoylphorbol-13-acetate application (approx.20%). The similarities between the dark keratinocytes seen after topical application of 12-O-tetradecanoylphorbol-13-acetate or other strong promoters and the dark cells observed in the fetal epidermis before the onset of the adult type of epidermal keratinization indicate that potent and/or first stage tumor promoters can be identified by their ability to induce cells resembling fetal-type dedifferentiated keratinocytes.« less

Generating cycle flow between dark and light zones with double paddlewheels to improve microalgal growth in a flat plate photo-bioreactor.

PubMed

Cheng, Jun; Xu, Junchen; Lu, Hongxiang; Ye, Qing; Liu, Jianzhong; Zhou, Junhu

2018-08-01

Double paddlewheels were proposed to generate cycle flow for increasing horizontal fluid velocity between dark and light zones in a flat plate photo-bioreactor, which strengthened the mass transfer and the mixing effect to improve microalgal growth with 15% CO 2 . Numerical fluid dynamics were used to simulate the cycle flow field with double paddlewheels. The local flow field measured with particle image velocimetry fitted well with the numerical simulation results. The horizontal fluid velocity in the photo-bioreactor was markedly increased from 5.8 × 10 -5  m/s to 0.45 m/s with the rotation of double paddlewheels, resulting in a decreased dark/light cycle period. Therefore, bubble formation time and diameter reduced by 24.4% and 27.4%, respectively. Meanwhile, solution mixing time reduced by 31.3% and mass transfer coefficient increased by 41.2%. The biomass yield of microalgae Nannochloropsis Oceanic increased by 127.1% with double paddlewheels under 15% CO 2 condition. Copyright © 2018 Elsevier Ltd. All rights reserved.

Evolution of separate screening soliton pairs in a biased series photorefractive crystal circuit.

PubMed

Liu, Jinsong; Hao, Zhonghua

2002-06-01

This paper presents calculations for an idea in photorefractive spatial soliton, namely, screening solitons form in a biased series photorefractive crystal circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. A system of two coupled equations is derived under appropriate conditions for two-beam propagation in the crystal circuit. The possibility of obtaining steady-state bright and dark screening soliton solutions is investigated in one dimension and, the existence of dark-dark, bright-dark, and bright-bright separate screening soliton pairs in such a circuit is proved. The numerical results show that the two solitons in a soliton pair can affect each other by the light-induced current and their coupling can affect their spatial profiles, dynamical evolutions, stabilities, and self-deflection. Under the limit in which the optical wave has a spatial extent much less than the width of the crystal, only the dark soliton can affect the other soliton by the light-induced current, but the bright soliton cannot. For a bright-dark or dark-dark soliton pair, the dark soliton in a weak input intensity can be obtained for a larger nonlinearity than for a stronger input intensity. For a bright-dark soliton pair, increasing the input intensity of the dark soliton can increase the bending angle of the bright soliton. Some potential applications are discussed.

Local dark matter and dark energy as estimated on a scale of ~1 Mpc in a self-consistent way

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.

2009-12-01

Context: Dark energy was first detected from large distances on gigaparsec scales. If it is vacuum energy (or Einstein's Λ), it should also exist in very local space. Here we discuss its measurement on megaparsec scales of the Local Group. Aims: We combine the modified Kahn-Woltjer method for the Milky Way-M 31 binary and the HST observations of the expansion flow around the Local Group in order to study in a self-consistent way and simultaneously the local density of dark energy and the dark matter mass contained within the Local Group. Methods: A theoretical model is used that accounts for the dynamical effects of dark energy on a scale of ~1 Mpc. Results: The local dark energy density is put into the range 0.8-3.7ρv (ρv is the globally measured density), and the Local Group mass lies within 3.1-5.8×1012 M⊙. The lower limit of the local dark energy density, about 4/5× the global value, is determined by the natural binding condition for the group binary and the maximal zero-gravity radius. The near coincidence of two values measured with independent methods on scales differing by ~1000 times is remarkable. The mass ~4×1012 M⊙ and the local dark energy density ~ρv are also consistent with the expansion flow close to the Local Group, within the standard cosmological model. Conclusions: One should take into account the dark energy in dynamical mass estimation methods for galaxy groups, including the virial theorem. Our analysis gives new strong evidence in favor of Einstein's idea of the universal antigravity described by the cosmological constant.

Diffraction-induced instability of coupled dark solitary waves.

PubMed

Assanto, Gaetano; MacNeil, J Michael L; Smyth, Noel F

2015-04-15

We report on a novel instability arising from the propagation of coupled dark solitary beams governed by coupled defocusing nonlinear Schrödinger equations. Considering dark notches on backgrounds with different wavelengths, hence different diffraction coefficients, we find that the vector dark soliton solution is unstable to radiation modes. Using perturbation theory and numerical integration, we demonstrate that the component undergoing stronger diffraction radiates away, leaving a single dark soliton in the other mode/wavelength.

Chiral gravitational waves and baryon superfluid dark matter

NASA Astrophysics Data System (ADS)

Alexander, Stephon; McDonough, Evan; Spergel, David N.

2018-05-01

We develop a unified model of darkgenesis and baryogenesis involving strongly interacting dark quarks, utilizing the gravitational anomaly of chiral gauge theories. In these models, both the visible and dark baryon asymmetries are generated by the gravitational anomaly induced by the presence of chiral primordial gravitational waves. We provide a concrete model of an SU(2) gauge theory with two massless quarks. In this model, the dark quarks condense and form a dark baryon charge superfluid (DBS), in which the Higgs-mode acts as cold dark matter. We elucidate the essential features of this dark matter scenario and discuss its phenomenological prospects.

An experimental and theoretical study of the dark current and x-ray sensitivity of amorphous selenium x-ray photoconductors

NASA Astrophysics Data System (ADS)

Frey, Joel Brandon

Recently, the world of diagnostic radiography has seen the integration of digital flat panel x-ray image detectors into x-ray imaging systems, replacing analog film screens. These flat panel x-ray imagers (FPXIs) have been shown to produce high quality x-ray images and provide many advantages that are inherent to a fully digital technology. Direct conversion FPXIs based on a photoconductive layer of stabilized amorphous selenium (a-Se) have been commercialized and have proven particularly effective in the field of mammography. In the operation of these detectors, incident x-ray photons are converted directly to charge carriers in the a-Se layer and drifted to electrodes on either side of the layer by a large applied field (10 V/microm). The applied field causes a dark current to flow which is not due to the incident radiation and this becomes a source of noise which can reduce the dynamic range of the detector. The level of dark current in commercialized detectors has been reduced by the deposition of thin n- and p- type blocking layers between the electrodes and the bulk of the a-Se. Despite recent research into the dark current in metal/a-Se/metal sandwich structures, much is still unknown about the true cause and nature of this phenomenon. The work in this Ph.D. thesis describes an experimental and theoretical study of the dark current in these structures. Experiments have been performed on five separate sets of a-Se samples which approximate the photoconductive layer in an FPXI. The dark current has been measured as a function of time, sample structure, applied field, sample thickness and contact metal used. This work has conclusively shown that the dark current is almost entirely due to the injection of charge carriers from the contacts and the contribution of Poole-Frenkel enhanced bulk thermal generation is negligible. There is also evidence that while the dark current is initially controlled by the injection of holes from the positive contact, several minutes after the application of the bias, the dark current due to hole injection may decay to the point where the electron current becomes significant and even dominant. These conclusions are supported by numerical calculations of the dark current transients which have been calibrated to match experimental results. Work detailed in this Ph.D. thesis also focuses on Monte Carlo modeling of the x-ray sensitivity of a-Se FPXIs. The higher the x-ray sensitivity of a detector, the lower the radiation dose required to acquire an acceptable image. FPXIs can experience a decrease in the x-ray sensitivity of the photoconductive layer with accumulating exposure, leading to a phenomenon known as "ghosting". Modeling this decrease in sensitivity can uncover the reasons behind it. The Monte Carlo model described in this thesis is a continuation of a previous model which now considers the effects of the n- and p-like blocking layers and the flow of dark current between x-ray exposures. The simulation results explain how deep trapping of photogenerated charge carriers, and the resulting effect on the electric field distribution, contribute to sensitivity loss. The model has shown excellent agreement with experimental data and has accurately predicted a sensitivity recovery once exposure has ceased which is due to primarily to the relaxation of metastable x-ray-induced carrier trap states.

Evidence for Recent Extension and Volcanism inside the Southern Margin of Mare Frigoris

NASA Astrophysics Data System (ADS)

Albin, Edward F.; Harris, R. Scott

2014-11-01

We report the identification of possible recent volcanic activity inside the southern margin of Mare Frigoris. Evidence includes two elliptical constructs with associated dark flows found at 56.6° N, - 19.7° W, north of the La Condamine J impact crater. They were discovered on high resolution (0.5 m/pixel) LROC WAC and NAC imagery (e.g., M188379739R and M142393589L) by the first author while performing a systematic geologic overview of the area.The constructs occur along a 3.2 km lineament trending southwest to northwest. The southwestern construct is the largest, measuring approximately 1.4 km in diameter by 65 m in height while the northeastern structure measures 1.2 km wide by 40 m high. The summits appear to be concave and contain well-defined pits 190 m and 120 m in diameter, respectively, each encircled by a deposit of raised material. Distinct dark deposits, exhibiting flow lobes, emanate from the pits. In addition, rubbly, flow-like dark deposits are found sporadically along the flanks of each feature.We interpret these structures as low profile steep-sided volcanic domes. Hawke et al. (2014) discussed volcanic constructs in the eastern part of Mare Frigoris; however, the features described in this study appear to be significantly younger. The domes may represent upwelling along a localized rift. Continued extension on the flanks appears to have released discrete dark flows. Well-defined flows crossing the floors of summit pits appear to have flowed uphill. We suggest that the evacuation of the magma chambers beneath these flows caused subsidence, forming the pits and giving the illusion that the lava flowed up and over the rims. Although the age of these constructs and flows is unknown, the paucity of impact craters suggests that they are relatively young. These could represent very recent eruptions of evolved magma on the Moon, similar to those reported by Jolliff et al. (2011). References: B. R. Hawke et al., 2014, LPSC, 45, 1318. Jolliff et al., 2012, Nature Geoscience, 4, 566-571.

Study of Neutrino-Induced Neutrons in Dark Matter Detectors for Supernova Burst Neutrinos

NASA Astrophysics Data System (ADS)

Kwan, Newton; Scholberg, Kate

2017-09-01

When supernova burst neutrinos (1-50 MeV) pass through the Earth, they occasionally interact with the passive shielding surrounding dark matter detectors. When the neutrinos interact, one or two roughly 2 MeV neutrons are scattered isotropically and uniformly, often leaving undetected. Occasionally, these neutrino-induced neutrons (NINs) interact with the detector and leave a background signal similar to a WIMP. The purpose of this study is to understand the effects of NINs on active dark matter detectors during a supernova burst.

Good lamps are the best police: darkness increases dishonesty and self-interested behavior.

PubMed

Zhong, Chen-Bo; Bohns, Vanessa K; Gino, Francesca

2010-03-01

Darkness can conceal identity and encourage moral transgressions; it may also induce a psychological feeling of illusory anonymity that disinhibits dishonest and self-interested behavior regardless of actual anonymity. Three experiments provided empirical evidence supporting this prediction. In Experiment 1, participants in a room with slightly dimmed lighting cheated more and thus earned more undeserved money than those in a well-lit room. In Experiment 2, participants wearing sunglasses behaved more selfishly than those wearing clear glasses. Finally, in Experiment 3, an illusory sense of anonymity mediated the relationship between darkness and self-interested behaviors. Across all three experiments, darkness had no bearing on actual anonymity, yet it still increased morally questionable behaviors. We suggest that the experience of darkness, even when subtle, may induce a sense of anonymity that is not proportionate to actual anonymity in a given situation.

Dynamics of defect-induced dark solitons in an exciton-polariton condensate

NASA Astrophysics Data System (ADS)

Opala, Andrzej; Pieczarka, Maciej; Bobrovska, Nataliya; Matuszewski, Michał

2018-04-01

We study theoretically the emission of dark solitons induced by a moving defect in a nonresonantly pumped exciton-polariton condensate. The number of created dark solitons per unit of time is found to be strongly dependent on the pump power. We relate the observed dynamics of this process to the oscillations of the drag force experienced by the condensate. We investigate the stability of the polariton quantum fluid and present various types of dynamics depending on the condensate and moving obstacle parameters. Furthermore, we provide analytical expressions for dark soliton dynamics using the variational method adapted to the nonequilibrium polariton system. The determined dynamical equations are found to be in excellent agreement with the results of numerical simulations.

The dual effects of polar methanolic extract of Hypericum perforatum L. in bladder cancer cells

NASA Astrophysics Data System (ADS)

Nseyo, U. O.; Nseyo, O. U.; Shiverick, K. T.; Medrano, T.; Mejia, M.; Stavropoulos, N.; Tsimaris, I.; Skalkos, D.

2007-02-01

Introduction and background: We have reported on the polar methanolic fraction (PMF) of Hypericum Perforatum L as a novel photosensitizing agent for photodynamic therapy (PDT) and photodynamic diagnosis (PDD). PMF has been tested in human leukemic cells, HL-60 cells, cord blood hemopoietic progenitor cells, bladder cancers derived from metastatic lymph node (T-24) and primary papillary bladder lesion (RT-4). However, the mechanisms of the effects of PMF on these human cell lines have not been elucidated. We have investigated mechanisms of PMF + light versus PMF-alone (dark experiment) in T-24 human bladder cancer cells. Methods: PMF was prepared from an aerial herb of HPL which was brewed in methanol and extracted with ether and methanol. Stock solutions of PMF were made in DSMO and stored in dark conditions. PMF contains 0.57% hypericin and 2.52% hyperforin. The T24 cell line was obtained from American Type Culture Collection (ATCC). In PDT treatment, PMF (60μg/ml) was incubated with cells, which were excited with laser light (630nm) 24 hours later. Apoptosis was determined by DNA fragmentation/laddering assay. DNA isolation was performed according to the manufacture's instructions with the Kit (Oncogene Kit#AM41). Isolated DNA samples were separated by electrophoresis in 1.5% in agarose gels and bands were visualized by ethidium bromide labeling. The initial cell cycle analysis and phase distribution was by flow cytometry. DNA synthesis was measured by [3H] thymidine incorporation, and cell cycle regulatory proteins were assayed by Western immunoblot. Results: The results of the flow cytometry showed PMF +light induced significant (40%) apoptosis in T24 cells, whereas Light or PMF alone produced little apoptosis. The percentage of cells in G 0/G I phase was decreased by 25% and in G2/M phase by 38%. The main impact was observed on the S phase which was blocked by 78% from the specific photocytotoxic process. DNA laddering analysis showed that PMF (60μg/ml) + light at 630nm induced DNA fragmentation in a light dose-dependent manner; in contrast, PMF or light alone did not induce DNA fragmentation. In separate experiments, PMF alone treatment produced a dose-dependent DNA synthesis with a 90% inhibition at a concentration of 25μg/ml (IC90 = 25μg/ml). Expression of p53 and p27 cell cycle regulatory proteins was not altered by PMF alone, however, a dose-dependent increase in p21 expression was observed that correlates with PMF concentrations. Cyclin A and cyclin B protein levels showed a clear decrease inverse to the concentration of PMF. In the absence of light treatment, flow cytometry analysis showed that PMF alone results in G 0/G I cell cycle arrest, with a 2-fold increase in G 0/G I cells concomitant with 50% decrease in cells in both S and G II/M phases. However, flow cytometry on PMF alone-treated cells did not show sub G 0/G I peak, further evidence of the lack of apoptosis as a mechanism of effect of PMF in the dark. Conclusions: With respect to light treatment, apoptosis appears to play a vital role in PDT-induced cytotoxicity. The flow cytometry and DNA laddering results revealed that T24 cells demonstrated apoptotic responses in PMF-mediated PDT. Experiments conducted with PMF alone showed a dose-dependent inhibition of DNA synthesis associated with G 0/G I cell cycle arrest and the extract is able to coordinate changes in key cell cycle regulatory proteins in human bladder cancer cells. Both experimental conditions suggest PMF as a potent and effect anti-proliferative agent in cancer chemoprevention and therapy of human urothelial carcinoma cells.

New Views on Dark Matter from Emergent Gravity

NASA Astrophysics Data System (ADS)

Sun, Sichun; Zhang, Yun-Long

2018-01-01

We discuss a scenario that apparent dark matter comes from the induced gravity in the (3+1)- dimensional spacetime, which can be embedded into one higher dimensional flat spacetime. The stress tensor of dark energy and dark matter is identified with the Brown-York stress tensor on the hypersurface, and we find an interesting constraint relation between the dark matter and dark energy density parameter and baryonic density parameter. Our approach may show a new understanding for Verlinde's emergent gravity from higher dimensions. We also comment on some phenomenological implications, including gravitational wave solutions and MOND limit.

Creating and optimizing interfaces for electric-field and photon-induced charge transfer.

PubMed

Park, Byoungnam; Whitham, Kevin; Cho, Jiung; Reichmanis, Elsa

2012-11-27

We create and optimize a structurally well-defined electron donor-acceptor planar heterojunction interface in which electric-field and/or photon-induced charge transfer occurs. Electric-field-induced charge transfer in the dark and exciton dissociation at a pentacene/PCBM interface were probed by in situ thickness-dependent threshold voltage shift measurements in field-effect transistor devices during the formation of the interface. Electric-field-induced charge transfer at the interface in the dark is correlated with development of the pentacene accumulation layer close to PCBM, that is, including interface area, and dielectric relaxation time in PCBM. Further, we demonstrate an in situ test structure that allows probing of both exciton diffusion length and charge transport properties, crucial for optimizing optoelectronic devices. Competition between the optical absorption length and the exciton diffusion length in pentacene governs exciton dissociation at the interface. Charge transfer mechanisms in the dark and under illumination are detailed.

Constraints on the coupling between dark energy and dark matter from CMB data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murgia, R.; Gariazzo, S.; Fornengo, N., E-mail: riccardo.murgia@sissa.it, E-mail: gariazzo@to.infn.it, E-mail: fornengo@to.infn.it

2016-04-01

We investigate a phenomenological non-gravitational coupling between dark energy and dark matter, where the interaction in the dark sector is parameterized as an energy transfer either from dark matter to dark energy or the opposite. The models are constrained by a whole host of updated cosmological data: cosmic microwave background temperature anisotropies and polarization, high-redshift supernovae, baryon acoustic oscillations, redshift space distortions and gravitational lensing. Both models are found to be compatible with all cosmological observables, but in the case where dark matter decays into dark energy, the tension with the independent determinations of H{sub 0} and σ{sub 8}, alreadymore » present for standard cosmology, increases: this model in fact predicts lower H{sub 0} and higher σ{sub 8}, mostly as a consequence of the higher amount of dark matter at early times, leading to a stronger clustering during the evolution. Instead, when dark matter is fed by dark energy, the reconstructed values of H{sub 0} and σ{sub 8} nicely agree with their local determinations, with a full reconciliation between high- and low-redshift observations. A non-zero coupling between dark energy and dark matter, with an energy flow from the former to the latter, appears therefore to be in better agreement with cosmological data.« less

A taste of dark matter: Flavour constraints on pseudoscalar mediators

DOE PAGES

Dolan, Matthew J.; Kahlhoefer, Felix; McCabe, Christopher; ...

2015-03-31

Dark matter interacting via the exchange of a light pseudoscalar can induce observable signals in indirect detection experiments and experience large self-interactions while evading the strong bounds from direct dark matter searches. The pseudoscalar mediator will however induce flavour-changing interactions in the Standard Model, providing a promising alternative way to test these models. We investigate in detail the constraints arising from rare meson decays and fixed target experiments for different coupling structures between the pseudoscalar and Standard Model fermions. The resulting bounds are highly complementary to the information inferred from the dark matter relic density and the constraints from primordialmore » nucleosynthesis. We discuss the implications of our findings for the dark matter self-interaction cross section and the prospects of probing dark matter coupled to a light pseudoscalar with direct or indirect detection experiments. In particular, we find that a pseudoscalar mediator can only explain the Galactic Centre excess if its mass is above that of the B mesons, and that it is impossible to obtain a sufficiently large direct detection cross section to account for the DAMA modulation.« less

Electrophilic dark matter with dark photon: From DAMPE to direct detection

NASA Astrophysics Data System (ADS)

Gu, Pei-Hong; He, Xiao-Gang

2018-03-01

The electron-positron excess reported by the DAMPE collaboration recently may be explained by an electrophilic dark matter (DM). A standard model singlet fermion may play the role of such a DM when it is stabilized by some symmetries, such as a dark U(1)X gauge symmetry, and dominantly annihilates into the electron-positron pairs through the exchange of a scalar mediator. The model, with appropriate Yukawa couplings, can well interpret the DAMPE excess. Naively one expects that in this type of models the DM-nucleon cross section should be small since there is no tree-level DM-quark interactions. We however find that at one-loop level, a testable DM-nucleon cross section can be induced for providing ways to test the electrophilic model. We also find that a U (1) kinetic mixing can generate a sizable DM-nucleon cross section although the U(1)X dark photon only has a negligible contribution to the DM annihilation. Depending on the signs of the mixing parameter, the dark photon can enhance/reduce the one-loop induced DM-nucleon cross section.

Displacement damage effects on CMOS APS image sensors induced by neutron irradiation from a nuclear reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zujun, E-mail: wangzujun@nint.ac.cn; Huang, Shaoyan; Liu, Minbo

The experiments of displacement damage effects on CMOS APS image sensors induced by neutron irradiation from a nuclear reactor are presented. The CMOS APS image sensors are manufactured in the standard 0.35 μm CMOS technology. The flux of neutron beams was about 1.33 × 10{sup 8} n/cm{sup 2}s. The three samples were exposed by 1 MeV neutron equivalent-fluence of 1 × 10{sup 11}, 5 × 10{sup 11}, and 1 × 10{sup 12} n/cm{sup 2}, respectively. The mean dark signal (K{sub D}), dark signal spike, dark signal non-uniformity (DSNU), noise (V{sub N}), saturation output signal voltage (V{sub S}), and dynamic rangemore » (DR) versus neutron fluence are investigated. The degradation mechanisms of CMOS APS image sensors are analyzed. The mean dark signal increase due to neutron displacement damage appears to be proportional to displacement damage dose. The dark images from CMOS APS image sensors irradiated by neutrons are presented to investigate the generation of dark signal spike.« less

Electromagnetically induced transparency in sinusoidal modulated ring resonator

NASA Astrophysics Data System (ADS)

Malik, Jagannath; Oruganti, Sai Kiran; Song, Seongkyu; Ko, Nak Young; Bien, Franklin

2018-06-01

In the present work, we demonstrate controlling the excitation of bright mode (continuum mode) resonance and dark mode (discrete mode) resonance in a planar metasurface made of sinusoidal modulation inside a closed rectangular metallic ring placed over a dielectric substrate. Unlike asymmetrical breaking of a meta-atom (often referred to as the unit cell) to achieve the dark mode response in regular metamaterials, in the present structure, the bright or dark mode resonance is achieved using even or odd half cycle modulation. The achieved dark-mode shows a sharp resonance for a particular polarization of the incident electric field, which results in an electromagnetically induced transparency like spectrum. The electromagnetic behavior of the proposed meta-atom has been investigated in the frequency domain using commercially available software and validated through experiments in the gigahertz regime.

Study of material properties important for an optical property modulation-based radiation detection method for positron emission tomography.

PubMed

Tao, Li; Daghighian, Henry M; Levin, Craig S

2017-01-01

We compare the performance of two detector materials, cadmium telluride (CdTe) and bismuth silicon oxide (BSO), for optical property modulation-based radiation detection method for positron emission tomography (PET), which is a potential new direction to dramatically improve the annihilation photon pair coincidence time resolution. We have shown that the induced current flow in the detector crystal resulting from ionizing radiation determines the strength of optical modulation signal. A larger resistivity is favorable for reducing the dark current (noise) in the detector crystal, and thus the higher resistivity BSO crystal has a lower (50% lower on average) noise level than CdTe. The CdTe and BSO crystals can achieve the same sensitivity under laser diode illumination at the same crystal bias voltage condition while the BSO crystal is not as sensitive to 511-keV photons as the CdTe crystal under the same crystal bias voltage. The amplitude of the modulation signal induced by 511-keV photons in BSO crystal is around 30% of that induced in CdTe crystal under the same bias condition. In addition, we have found that the optical modulation strength increases linearly with crystal bias voltage before saturation. The modulation signal with CdTe tends to saturate at bias voltages higher than 1500 V due to its lower resistivity (thus larger dark current) while the modulation signal strength with BSO still increases after 3500 V. Further increasing the bias voltage for BSO could potentially further enhance the modulation strength and thus, the sensitivity.

Ruthenium porphyrin-induced photodamage in bladder cancer cells.

PubMed

Bogoeva, Vanya; Siksjø, Monica; Sæterbø, Kristin G; Melø, Thor Bernt; Bjørkøy, Astrid; Lindgren, Mikael; Gederaas, Odrun A

2016-06-01

Photodynamic therapy (PDT) is a noninvasive treatment for solid malignant and flat tumors. Light activated sensitizers catalyze photochemical reactions that produce reactive oxygen species which can cause cancer cell death. In this work we investigated the photophysical properties of the photosensitizer ruthenium(II) porphyrin (RuP), along with its PDT efficiency onto rat bladder cancer cells (AY27). Optical spectroscopy verified that RuP is capable to activate singlet oxygen via blue and red absorption bands and inter system crossing (ISC) to the triplet state. In vitro experiments on AY27 indicated increased photo-toxicity of RuP (20μM, 18h incubation) after cell illumination (at 435nm), as a function of blue light exposure. Cell survival fraction was significantly reduced to 14% after illumination of 20μM RuP with 15.6J/cm(2), whereas the "dark toxicity" of 20μM RuP was 17%. Structural and morphological changes of cells were observed, due to RuP accumulation, as well as light-dependent cell death was recorded by confocal microscopy. Flow cytometry verified that PDT-RuP (50μM) triggered significant photo-induced cellular destruction with a photoxicity of (93%±0.9%). Interestingly, the present investigation of RuP-PDT showed that the dominating mode of cell death is necrosis. RuP "dark toxicity" compared to the conventional chemotherapeutic drug cisplatin was higher, both evaluated by the MTT assay (24h). In conclusion, the present investigation shows that RuP with or without photoactivation induces cell death of bladder cancer cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Non-Friedmann cosmology for the Local Universe, significance of the universal Hubble constant, and short-distance indicators of dark energy

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Teerikorpi, P.; Baryshev, Yu. V.

2006-09-01

Based on the increasing evidence of the cosmological relevance of the local Hubble flow, we consider a simple analytical cosmological model for the Local Universe. This is a non-Friedmann model with a non-uniform static space-time. The major dynamical factor controlling the local expansion is the antigravity produced by the omnipresent and permanent dark energy of the cosmic vacuum (or the cosmological constant). The antigravity dominates at larger distances than 1-2 Mpc from the center of the Local group. The model gives a natural explanation of the two key quantitative characteristics of the local expansion flow, which are the local Hubble constant and the velocity dispersion of the flow. The observed kinematical similarity of the local and global flows of expansion is clarified by the model. We analytically demonstrate the efficiency of the vacuum cooling mechanism that allows one to see the Hubble law this close to the Local group. The "universal Hubble constant" HV (≈60 km s-1 Mpc-1), depending only on the vacuum density, has special significance locally and globally. The model makes a number of verifiable predictions. It also unexpectedly shows that the dwarf galaxies of the local flow with the shortest distances and lowest redshifts may be the most sensitive indicators of dark energy in our neighborhood.

Garden City Vein Complex, Gale Crater, Mars: Implications for Late Diagenetic Fluid Flow

NASA Astrophysics Data System (ADS)

Kronyak, R. E.; Kah, L. C.; Blaney, D. L.; Sumner, D. Y.; Fisk, M. R.; Rapin, W.; Nachon, M.; Mangold, N.; Grotzinger, J. P.; Wiens, R. C.

2015-12-01

Calcium sulfate filled fractures are observed in nearly all stratigraphic units encountered by the Mars Science Laboratory (MSL) Curiosity rover. The mm-scale of veins, however, provides little evidence for emplacement style. From sols 924-949, Curiosity observed a vein rich outcrop called Garden City, which shows variation in both thickness and complexity of veins. Extensive Mastcam and MAHLI imaging was conducted across the outcrop to provide textural detail that can be related to emplacement mechanisms. Additionally, Curiosity collected geochemical data on 17 ChemCam targets and 7 APXS targets, shedding light on the composition and variety of potential vein fluids. The Garden City vein system records (1) the presence of distinct dark-toned and light-toned (calcium sulfate) mineralization, and (2) the presence of laminated, epitaxial, and brecciated fabrics that suggest multiple emplacement modes. Dark-toned mineralization is observed as erosionally resistant ridges predominantly along fracture walls. Although erosional resistance may reflect the permeability of host rock to fracture-borne fluids, at Garden City, laminated textures suggest that at least some mineralization may have occurred as fracture-fill. Light-toned mineralization often bisects dark-toned material, indicating re-use of fluid pathways. Light-toned veinlets permeate fracture walls, and the largest veins entrain host rock and dark-toned material within calcium sulfate matrix. Such brecciation indicates high forces associated with fluid expulsion. Elsewhere, linear patterns occur broadly perpendicular to fracture walls, and are interpreted to represent epitaxial crystal growth, suggesting lower flow rates and fluid flow pressures within the fracture system. Together these observations indicate multiple episodes of fluid flow in the Gale Crater system.

280  GHz dark soliton fiber laser.

PubMed

Song, Y F; Guo, J; Zhao, L M; Shen, D Y; Tang, D Y

2014-06-15

We report on an ultrahigh repetition rate dark soliton fiber laser. We show both numerically and experimentally that by taking advantage of the cavity self-induced modulation instability and the dark soliton formation in a net normal dispersion cavity fiber laser, stable ultrahigh repetition rate dark soliton trains can be formed in a dispersion-managed cavity fiber laser. Stable dark soliton trains with a repetition rate as high as ∼280  GHz have been generated in our experiment. Numerical simulations have shown that the effective gain bandwidth limitation plays an important role on the stabilization of the formed dark solitons in the laser.

77 FR 2331 - Self-Regulatory Organizations; NYSE Arca, Inc.; Notice of Filing and Immediate Effectiveness of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-17

... trading systems (``ATSs''), including dark pools and electronic communication networks (``ECNs''). Each... data at no charge on its Web site in order to attract more order flow, and it uses market data revenue... users.\\19\\ A proliferation of dark pools and other [[Page 2335

Is there a field-theoretic explanation for precursor biopolymers?

PubMed

Rosen, Gerald

2002-08-01

A Hu-Barkana-Gruzinov cold dark matter scalar field phi may enter a weak isospin invariant derivative interaction that causes the flow of right-handed electrons to align parallel to (inverted delta phi). Hence, in the outer regions of galaxies where (inverted delta phi) is large, as in galactic halos, the derivative interaction may induce a chirality-imbued quantum chemistry. Such a chirality-imbued chemistry would in turn be conducive to the formation of abundant precursor biopolymers on interstellar dust grains, comets and meteors in galactic halo regions, with subsequent delivery to planets in the inner galactic regions where phi and (inverted delta phi) are concomitantly near zero and left-right symmetric terrestrial quantum chemistry prevails.

Morphologic and thermophysical characteristics of lava flows southwest of Arsia Mons, Mars

NASA Astrophysics Data System (ADS)

Crown, David A.; Ramsey, Michael S.

2017-08-01

The morphologic and thermophysical characteristics of part of the extensive lava flow fields southwest of Arsia Mons (22.5-27.5°S, 120-130°W) have been examined using a combination of orbital VNIR and TIR datasets. THEMIS images provide context for the regional geology and record diurnal temperature variability that is diverse and unusual for flow surfaces in such close proximity. CTX images were used to distinguish dominant flow types and assess local age relationships between individual lava flows. CTX and HiRISE images provide detailed information on flow surface textures and document aeolian effects as they reveal fine-grained deposits in many low-lying areas of the flow surfaces as well as small patches of transverse aeolian ridges. Although this region is generally dust-covered and has a lower overall thermal inertia, the THEMIS data indicate subtle spectral variations within the population of lava flows studied. These variations could be due to compositional differences among the flows or related to mixing of flow and aeolian materials. Specific results regarding flow morphology include: a) Two main lava flow types (bright, rugged and dark, smooth as observed in CTX images) dominate the southwest Arsia Mons/NE Daedalia Planum region; b) the bright, rugged flows have knobby, ridged, and/or platy surface textures, commonly have medial channel/levee systems, and may have broad distal lobes; c) the dark, smooth flows extend from distributary systems that consist of combinations of lava channels, lava tubes, and/or sinuous ridges and plateaus; and d) steep-sided, terraced margins, digitate breakout lobes, and smooth-surfaced plateaus along lava channel/tube systems are interpreted as signatures of flow inflation within the dark, smooth flow type. These flows exhibit smoother upper surfaces, are thinner, and have more numerous, smaller lobes, which, along with their the channel-/tube-fed nature, indicate a lower viscosity lava than for the bright, rugged flows. Flow patterns and local interfingering and overlapping relationships are delineated in CTX images and allow reconstruction of the complex flow field surfaces. Darker channel-/tube-fed flows are generally younger than adjacent thicker, bright, rugged flows; however, the diversity and complexity of temporal relationships observed, along with the thermophysical variability, suggests that lava sources with different eruptive styles and magnitudes and/or lavas that experienced different local emplacement conditions were active contemporaneously.

Improvement of sidestream dark field imaging with an image acquisition stabilizer.

PubMed

Balestra, Gianmarco M; Bezemer, Rick; Boerma, E Christiaan; Yong, Ze-Yie; Sjauw, Krishan D; Engstrom, Annemarie E; Koopmans, Matty; Ince, Can

2010-07-13

In the present study we developed, evaluated in volunteers, and clinically validated an image acquisition stabilizer (IAS) for Sidestream Dark Field (SDF) imaging. The IAS is a stainless steel sterilizable ring which fits around the SDF probe tip. The IAS creates adhesion to the imaged tissue by application of negative pressure. The effects of the IAS on the sublingual microcirculatory flow velocities, the force required to induce pressure artifacts (PA), the time to acquire a stable image, and the duration of stable imaging were assessed in healthy volunteers. To demonstrate the clinical applicability of the SDF setup in combination with the IAS, simultaneous bilateral sublingual imaging of the microcirculation were performed during a lung recruitment maneuver (LRM) in mechanically ventilated critically ill patients. One SDF device was operated handheld; the second was fitted with the IAS and held in position by a mechanic arm. Lateral drift, number of losses of image stability and duration of stable imaging of the two methods were compared. Five healthy volunteers were studied. The IAS did not affect microcirculatory flow velocities. A significantly greater force had to applied onto the tissue to induced PA with compared to without IAS (0.25 +/- 0.15 N without vs. 0.62 +/- 0.05 N with the IAS, p < 0.001). The IAS ensured an increased duration of a stable image sequence (8 +/- 2 s without vs. 42 +/- 8 s with the IAS, p < 0.001). The time required to obtain a stable image sequence was similar with and without the IAS. In eight mechanically ventilated patients undergoing a LRM the use of the IAS resulted in a significantly reduced image drifting and enabled the acquisition of significantly longer stable image sequences (24 +/- 5 s without vs. 67 +/- 14 s with the IAS, p = 0.006). The present study has validated the use of an IAS for improvement of SDF imaging by demonstrating that the IAS did not affect microcirculatory perfusion in the microscopic field of view. The IAS improved both axial and lateral SDF image stability and thereby increased the critical force required to induce pressure artifacts. The IAS ensured a significantly increased duration of maintaining a stable image sequence.

Readout technologies for directional WIMP Dark Matter detection

NASA Astrophysics Data System (ADS)

Battat, J. B. R.; Irastorza, I. G.; Aleksandrov, A.; Asada, T.; Baracchini, E.; Billard, J.; Bosson, G.; Bourrion, O.; Bouvier, J.; Buonaura, A.; Burdge, K.; Cebrián, S.; Colas, P.; Consiglio, L.; Dafni, T.; D'Ambrosio, N.; Deaconu, C.; De Lellis, G.; Descombes, T.; Di Crescenzo, A.; Di Marco, N.; Druitt, G.; Eggleston, R.; Ferrer-Ribas, E.; Fusayasu, T.; Galán, J.; Galati, G.; García, J. A.; Garza, J. G.; Gentile, V.; Garcia-Sciveres, M.; Giomataris, Y.; Guerrero, N.; Guillaudin, O.; Guler, A. M.; Harton, J.; Hashimoto, T.; Hedges, M. T.; Iguaz, F. J.; Ikeda, T.; Jaegle, I.; Kadyk, J. A.; Katsuragawa, T.; Komura, S.; Kubo, H.; Kuge, K.; Lamblin, J.; Lauria, A.; Lee, E. R.; Lewis, P.; Leyton, M.; Loomba, D.; Lopez, J. P.; Luzón, G.; Mayet, F.; Mirallas, H.; Miuchi, K.; Mizumoto, T.; Mizumura, Y.; Monacelli, P.; Monroe, J.; Montesi, M. C.; Naka, T.; Nakamura, K.; Nishimura, H.; Ochi, A.; Papevangelou, T.; Parker, J. D.; Phan, N. S.; Pupilli, F.; Richer, J. P.; Riffard, Q.; Rosa, G.; Santos, D.; Sawano, T.; Sekiya, H.; Seong, I. S.; Snowden-Ifft, D. P.; Spooner, N. J. C.; Sugiyama, A.; Taishaku, R.; Takada, A.; Takeda, A.; Tanaka, M.; Tanimori, T.; Thorpe, T. N.; Tioukov, V.; Tomita, H.; Umemoto, A.; Vahsen, S. E.; Yamaguchi, Y.; Yoshimoto, M.; Zayas, E.

2016-11-01

The measurement of the direction of WIMP-induced nuclear recoils is a compelling but technologically challenging strategy to provide an unambiguous signature of the detection of Galactic dark matter. Most directional detectors aim to reconstruct the dark-matter-induced nuclear recoil tracks, either in gas or solid targets. The main challenge with directional detection is the need for high spatial resolution over large volumes, which puts strong requirements on the readout technologies. In this paper we review the various detector readout technologies used by directional detectors. In particular, we summarize the challenges, advantages and drawbacks of each approach, and discuss future prospects for these technologies.

Local and global dynamical effects of dark energy

NASA Astrophysics Data System (ADS)

Chernin, A. D.

Local expansion flows of galaxies were discovered by Lemaitre and Hubble in 1927-29 at distances of less than 25-30 Mpc. The global expansion of the Universe as a whole was predicted theoretically by Friedmann in 1922-24 and discovered in the 1990s in observations at truly cosmological distances of more than 1 000 Mpc. On all these spatial scales, the flows follow a (nearly) linear velocity-distance relation, known now as Hubble's law. This similarity of local and global phenomena is due to the universal dark energy antigravity which dominates the cosmic dynamics on both local and global spatial scales.

Analysis of Dark Current in BRITE Nanostellite CCD Sensors †

PubMed Central

Popowicz, Adam

2018-01-01

The BRightest Target Explorer (BRITE) is the pioneering nanosatellite mission dedicated for photometric observations of the brightest stars in the sky. The BRITE charge coupled device (CCD) sensors are poorly shielded against extensive flux of energetic particles which constantly induce defects in the silicon lattice. In this paper we investigate the temporal evolution of the generation of the dark current in the BRITE CCDs over almost four years after launch. Utilizing several steps of image processing and employing normalization of the results, it was possible to obtain useful information about the progress of thermal activity in the sensors. The outcomes show a clear and consistent linear increase of induced damage despite the fact that only about 0.14% of CCD pixels were probed. By performing the analysis of temperature dependencies of the dark current, we identified the observed defects as phosphorus-vacancy (PV) pairs, which are common in proton irradiated CCD matrices. Moreover, the Meyer-Neldel empirical rule was confirmed in our dark current data, yielding EMN=24.8 meV for proton-induced PV defects. PMID:29415471

Contrasting effect of dark-chilling on chloroplast structure and arrangement of chlorophyll-protein complexes in pea and tomato: plants with a different susceptibility to non-freezing temperature.

PubMed

Garstka, Maciej; Venema, Jan Henk; Rumak, Izabela; Gieczewska, Katarzyna; Rosiak, Malgorzata; Koziol-Lipinska, Joanna; Kierdaszuk, Borys; Vredenberg, Wim J; Mostowska, Agnieszka

2007-10-01

The effect of dark-chilling and subsequent photoactivation on chloroplast structure and arrangements of chlorophyll-protein complexes in thylakoid membranes was studied in chilling-tolerant (CT) pea and in chilling-sensitive (CS) tomato. Dark-chilling did not influence chlorophyll content and Chl a/b ratio in thylakoids of both species. A decline of Chl a fluorescence intensity and an increase of the ratio of fluorescence intensities of PSI and PSII at 120 K was observed after dark-chilling in thylakoids isolated from tomato, but not from pea leaves. Chilling of pea leaves induced an increase of the relative contribution of LHCII and PSII fluorescence. A substantial decrease of the LHCII/PSII fluorescence accompanied by an increase of that from LHCI/PSI was observed in thylakoids from chilled tomato leaves; both were attenuated by photoactivation. Chlorophyll fluorescence of bright grana discs in chloroplasts from dark-chilled leaves, detected by confocal laser scanning microscopy, was more condensed in pea but significantly dispersed in tomato, compared with control samples. The chloroplast images from transmission-electron microscopy revealed that dark-chilling induced an increase of the degree of grana stacking only in pea chloroplasts. Analyses of O-J-D-I-P fluorescence induction curves in leaves of CS tomato before and after recovery from chilling indicate changes in electron transport rates at acceptor- and donor side of PS II and an increase in antenna size. In CT pea leaves these effects were absent, except for a small but irreversible effect on PSII activity and antenna size. Thus, the differences in chloroplast structure between CS and CT plants, induced by dark-chilling are a consequence of different thylakoid supercomplexes rearrangements.

Constraints on the interaction between dark matter and Baryons from cooling flow clusters.

PubMed

Qin, B; Wu, X P

2001-08-06

Other nongravitational heating processes are needed to resolve the disagreement between the absence of cool gas components in the centers of galaxy clusters revealed recently by Chandra and XMM observations and the expectations of conventional radiative cooling models. We propose that the interaction between dark matter and baryonic matter may act as an alternative for the reheating of intracluster medium (ICM) in the inner regions of clusters, in which kinetic energy of dark matter is transported to ICM to balance radiative cooling. Using the Chandra and XMM data, we set a useful constraint on the dark-matter-baryon cross section: sigma(xp)/m(x) approximately 1x10(-25) cm(2) GeV-1, where m(x) is the mass of dark matter particles.

Gene Expression Patterns during Light and Dark Infection of Prochlorococcus by Cyanophage

PubMed Central

Chisholm, Sallie W.

2016-01-01

Cyanophage infecting the marine cyanobacteria Prochlorococcus and Synechococcus require light and host photosystem activity for optimal reproduction. Many cyanophages encode multiple photosynthetic electron transport (PET) proteins, which are presumed to maintain electron flow and produce ATP and NADPH for nucleotide biosynthesis and phage genome replication. However, evidence suggests phage augment NADPH production via the pentose phosphate pathway (PPP), thus calling into question the need for NADPH production by PET. Genes implicated in cyclic PET have since been identified in cyanophage genomes. It remains an open question which mode of PET, cyclic or linear, predominates in infected cyanobacteria, and thus whether the balance is towards producing ATP or NADPH. We sequenced transcriptomes of a cyanophage (P-HM2) and its host (Prochlorococcus MED4) throughout infection in the light or in the dark, and analyzed these data in the context of phage replication and metabolite measurements. Infection was robust in the light, but phage were not produced in the dark. Host gene transcripts encoding high-light inducible proteins and two terminal oxidases (plastoquinol terminal oxidase and cytochrome c oxidase)—implicated in protecting the photosynthetic membrane from light stress—were the most enriched in light but not dark infection. Among the most diminished transcripts in both light and dark infection was ferredoxin–NADP+ reductase (FNR), which uses the electron acceptor NADP+ to generate NADPH in linear photosynthesis. The phage gene for CP12, which putatively inhibits the Calvin cycle enzyme that receives NADPH from FNR, was highly expressed in light infection. Therefore, both PET production of NADPH and its consumption by carbon fixation are putatively repressed during phage infection in light. Transcriptomic evidence is thus consistent with cyclic photophosphorylation using oxygen as the terminal electron acceptor as the dominant mode of PET under infection, with ATP from PET and NADPH from the PPP producing the energy and reducing equivalents for phage nucleotide biosynthesis and replication. PMID:27788196

Searching for dark matter with neutron star mergers and quiet kilonovae

NASA Astrophysics Data System (ADS)

Bramante, Joseph; Linden, Tim; Tsai, Yu-Dai

2018-03-01

We identify new astrophysical signatures of dark matter that implodes neutron stars (NSs), which could decisively test whether NS-imploding dark matter is responsible for missing pulsars in the Milky Way galactic center, the source of some r -process elements, and the origin of fast-radio bursts. First, NS-imploding dark matter forms ˜10-10 solar mass or smaller black holes inside neutron stars, which proceed to convert neutron stars into ˜1.5 solar mass black holes (BHs). This decreases the number of neutron star mergers seen by LIGO/Virgo (LV) and associated merger kilonovae seen by telescopes like DES, BlackGEM, and ZTF, instead producing a population of "black mergers" containing ˜1.5 solar mass black holes. Second, dark matter-induced neutron star implosions may create a new kind of kilonovae that lacks a detectable, accompanying gravitational signal, which we call "quiet kilonovae." Using DES data and the Milky Way's r-process abundance, we constrain quiet kilonovae. Third, the spatial distribution of neutron star merger kilonovae and quiet kilonovae in galaxies can be used to detect dark matter. NS-imploding dark matter destroys most neutron stars at the centers of disc galaxies, so that neutron star merger kilonovae would appear mostly in a donut at large radii. We find that as few as ten neutron star merger kilonova events, located to ˜1 kpc precision could validate or exclude dark matter-induced neutron star implosions at 2 σ confidence, exploring dark matter-nucleon cross-sections 4-10 orders of magnitude below current direct detection experimental limits. Similarly, NS-imploding dark matter as the source of fast radio bursts can be tested at 2 σ confidence once 20 bursts are located in host galaxies by radio arrays like CHIME and HIRAX.

Rapid dark-blood carotid vessel-wall imaging with random bipolar gradients in a radial SSFP acquisition.

PubMed

Lin, Hung-Yu; Flask, Chris A; Dale, Brian M; Duerk, Jeffrey L

2007-06-01

To investigate and evaluate a new rapid dark-blood vessel-wall imaging method using random bipolar gradients with a radial steady-state free precession (SSFP) acquisition in carotid applications. The carotid artery bifurcations of four asymptomatic volunteers (28-37 years old, mean age = 31 years) were included in this study. Dark-blood contrast was achieved through the use of random bipolar gradients applied prior to the signal acquisition of each radial projection in a balanced SSFP acquisition. The resulting phase variation for moving spins established significant destructive interference in the low-frequency region of k-space. This phase variation resulted in a net nulling of the signal from flowing spins, while the bipolar gradients had a minimal effect on the static spins. The net effect was that the regular SSFP signal amplitude (SA) in stationary tissues was preserved while dark-blood contrast was achieved for moving spins. In this implementation, application of the random bipolar gradient pulses along all three spatial directions nulled the signal from both in-plane and through-plane flow in phantom and in vivo studies. In vivo imaging trials confirmed that dark-blood contrast can be achieved with the radial random bipolar SSFP method, thereby substantially reversing the vessel-to-lumen contrast-to-noise ratio (CNR) of a conventional rectilinear SSFP "bright-blood" acquisition from bright blood to dark blood with only a modest increase in TR (approximately 4 msec) to accommodate the additional bipolar gradients. Overall, this sequence offers a simple and effective dark-blood contrast mechanism for high-SNR SSFP acquisitions in vessel wall imaging within a short acquisition time.

Circadian disruption induced by light-at-night accelerates aging and promotes tumorigenesis in rats

PubMed Central

Vinogradova, Irina A.; Anisimov, Vladimir N.; Bukalev, Andrey V.; Semenchenko, Anna V.; Zabezhinski, Mark A.

2009-01-01

We evaluated the effect of various light/dark regimens on the survival, life span and tumorigenesis in rats. Two hundred eight male and 203 females LIO rats were subdivided into 4 groups and kept at various light/dark regimens: standard 12:12 light/dark (LD); natural lighting of the North-West of Russia (NL); constant light (LL), and constant darkness (DD) since the age of 25 days until natural death. We found that exposure to NL and LL regimens accelerated development of metabolic syndrome and spontaneous tumorigenesis, shortened life span both in male and females rats as compared to the standard LD regimen. We conclude that circadian disruption induced by light-at-night accelerates aging and promotes tumorigenesis in rats. This observation supports the conclusion of the International Agency Research on Cancer that shift-work that involves circadian disruption is probably carcinogenic to humans. PMID:20157558

Surface evolution of two-component stone/ice bodies in the Jupiter region

NASA Astrophysics Data System (ADS)

Hartmann, W. K.

1980-11-01

Observational and theoretical data converge on the conclusion that planetesimals in Jupiter's region of the solar nebula were initially composed predominantly of a mixture of roughly 39-70% H2O ice by volume, and 30-61% dark stony material resembling carbonaceous chondrites. Recent observations emphasize a division of most asteroid and satellite surfaces in this region into two distinct groups: bright icy material and dark stony material. The present model accounts for these by two main processes: an impact-induced buildup of a dark stony regolith in the absence of surface thermal disturbance, and thermal-disturbance-induced eruption of 'water magmas' that create icy surfaces. 'Thermal disturbances' include tidal and radiative effects caused by nearness of a planet. A correlation of crater density and albedo, Ganymede's dark-ray craters, and other observed phenomena (listed in the summary) appear consistent with the model discussed here.

Dark matter, long-range forces, and large-scale structure

NASA Technical Reports Server (NTRS)

Gradwohl, Ben-Ami; Frieman, Joshua A.

1992-01-01

If the dark matter in galaxies and clusters is nonbaryonic, it can interact with additional long-range fields that are invisible to experimental tests of the equivalence principle. We discuss the astrophysical and cosmological implications of a long-range force coupled only to the dark matter and find rather tight constraints on its strength. If the force is repulsive (attractive), the masses of galaxy groups and clusters (and the mean density of the universe inferred from them) have been systematically underestimated (overestimated). We explore the consequent effects on the two-point correlation function, large-scale velocity flows, and microwave background anisotropies, for models with initial scale-invariant adiabatic perturbations and cold dark matter.

Particle-laden Thin Film Flow: An Alternating Direction Implicit Scheme and Comparison between Theory, Numerical Simulations, and Experiments

DTIC Science & Technology

2011-01-01

instability and a dark particle-rich ridge at the front of the fluid can be observed. Figure 5.3 contains a series of plots each taken two minutes into... dark ridge at the front. However, it is also clear that the model does not quantita- tively reproduce this departure from self-similarity of the fluid...behaviors cluster in these diagrams, forming distinct bands. We use color to label these regime bands: white for settled, light for well-mixed, and dark

Fast Parallel Tree Codes for Gravitational and Fluid Dynamical N-Body Problems

DTIC Science & Technology

1993-01-01

The particles represent the so-called " Dark Matter " eral times the the full message latency for every remote which is believed to dominate the mass...Katz, L. Herquist, and D. H. Weinberg. Galax- R. Acad. Sci. Paris, 306(I):739-742, 1988. ies and gas in a cold dark matter universe. Ap. J., [111 A...57(3):566-569, 1983. dark matter halos. Ap. J., 378:496, 1991. [30] G. Pedrizzetti. Insight into singular vortex flows. [17] C. C. Dyer and P. S. S

Dark soliton dynamics and interactions in continuous-wave-induced lattices.

PubMed

Tsopelas, Ilias; Kominis, Yannis; Hizanidis, Kyriakos

2007-10-01

The dynamics of dark spatial soliton beams and their interaction under the presence of a continuous wave (CW), which dynamically induces a photonic lattice, are investigated. It is shown that appropriate selection of the characteristic parameters of the CW result in controllable steering of a single soliton as well as controllable interaction between two solitons. Depending on the CW parameters, the soliton angle of propagation can be changed drastically, while two-soliton interaction can be either enhanced or reduced, suggesting a reconfigurable soliton control mechanism. Our analytical approach, based on the variational perturbation method, provides a dynamical system for the dark soliton evolution parameters. Analytical results are shown in good agreement with direct numerical simulations.

Light effects in the atomic-motion-induced Ramsey narrowing of dark resonances in wall-coated cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breschi, E.; Schori, C.; Di Domenico, G.

2010-12-15

We report on light shift and broadening in the atomic-motion-induced Ramsey narrowing of dark resonances prepared in alkali-metal vapors contained in wall-coated cells without buffer gas. The atomic-motion-induced Ramsey narrowing is due to the free motion of the polarized atomic spins in and out of the optical interaction region before spin relaxation. As a consequence of this effect, we observe a narrowing of the dark resonance linewidth as well as a reduction of the ground states' light shift when the volume of the interaction region decreases at constant optical intensity. The results can be intuitively interpreted as a dilution ofmore » the intensity effect similar to a pulsed interrogation due to the atomic motion. Finally the influence of this effect on the performance of compact atomic clocks is discussed.« less

Noise limitations of multiplier phototubes in the radiation environment of space

NASA Technical Reports Server (NTRS)

Viehmann, W.; Eubanks, A. G.

1976-01-01

The contributions of Cerenkov emission, luminescence, secondary electron emission, and bremsstrahlung to radiation-induced data current and noise of multiplier phototubes were analyzed quantitatively. Fluorescence and Cerenkov emission in the tube window are the major contributors and can quantitatively account for dark count levels observed in orbit. Radiation-induced noise can be minimized by shielding, tube selection, and mode of operation. Optical decoupling of windows and cathode (side-window tubes) leads to further reduction of radiation-induced dark counts, as does reducing the window thickness and effective cathode area, and selection of window/cathode combinations of low fluorescence efficiency. In trapped radiation-free regions of near-earth orbits and in free space, Cerenkov emission by relativistic particles contributes predominantly to the photoelectron yield per event. Operating multiplier phototubes in the photon (pulse) counting mode will discriminate against these large pulses and substantially reduce the dark count and noise to levels determined by fluorescence.

Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales

PubMed

Wittman; Tyson; Kirkman; Dell'Antonio; Bernstein

2000-05-11

Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting 'cosmic shear' can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model.

Involvement of the α1-adrenoceptor in sleep-waking and sleep loss-induced anxiety behavior in zebrafish.

PubMed

Singh, A; Subhashini, N; Sharma, S; Mallick, B N

2013-08-15

Sleep is a universal phenomenon in vertebrates, and its loss affects various behaviors. Independent studies have reported that sleep loss increases anxiety; however, the detailed mechanism is unknown. Because sleep deprivation increases noradrenalin (NA), which modulates many behaviors and induces patho-physiological changes, this study utilized zebrafish as a model to investigate whether sleep loss-induced increased anxiety is modulated by NA. Continuous behavioral quiescence for at least 6s was considered to represent sleep in zebrafish; although some authors termed it as a sleep-like state, in this study we have termed it as sleep. The activity of fish that signified sleep-waking was recorded in light-dark, during continuous dark and light; the latter induced sleep loss in fish. The latency, number of entries, time spent and distance travelled in the light chamber were assessed in a light-dark box test to estimate the anxiety behavior of normal, sleep-deprived and prazosin (PRZ)-treated fish. Zebrafish showed increased waking during light and complete loss of sleep upon continuous exposure to light for 24h. PRZ significantly increased sleep in normal fish. Sleep-deprived fish showed an increased preference for dark (expression of increased anxiety), and this effect was prevented by PRZ, which increased sleep as well. Our findings suggest that sleep loss-induced anxiety-like behavior in zebrafish is likely to be mediated by NA's action on the α1-adrenoceptor. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Mechanical contact induced transformation from the amorphous to the crystalline state in metallic glass

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1984-01-01

Friction and wear tests were conducted with 3.2- and 6.4-millimeter-diameter aluminum oxide spheres sliding, in reciprocating motion, on a Fe67Co18B14Si1 metallic foil. Crystallites with a size range of 10 to 150 nanometers were produced on the wear surface of the amorphous alloy. A strong interaction between transition metals and metalloids such as silicon and boron results in strong segregation during repeated sliding, provides preferential transition metal-metalloid clustering in the amorphous alloy, and subsequently produces the diffused honeycomb structure formed by dark grey bands and primary crystals, that is, alpha-Fe in the matrix. Large plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminum oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and/or powdery-whiskery oxide debris.

Interactive mixture of inhomogeneous dark fluids driven by dark energy: a dynamical system analysis

NASA Astrophysics Data System (ADS)

Izquierdo, Germán; Blanquet-Jaramillo, Roberto C.; Sussman, Roberto A.

2018-03-01

We examine the evolution of an inhomogeneous mixture of non-relativistic pressureless cold dark matter (CDM), coupled to dark energy (DE) characterised by the equation of state parameter w<-1/3, with the interaction term proportional to the DE density. This coupled mixture is the source of a spherically symmetric Lemaître-Tolman-Bondi (LTB) metric admitting an asymptotic Friedman-Lemaître-Robertson-Walker (FLRW) background. Einstein's equations reduce to a 5-dimensional autonomous dynamical system involving quasi-local variables related to suitable averages of covariant scalars and their fluctuations. The phase space evolution around the critical points (past/future attractors and five saddles) is examined in detail. For all parameter values and both directions of energy flow (CDM to DE and DE to CDM) the phase space trajectories are compatible with a physically plausible early cosmic times behaviour near the past attractor. This result compares favourably with mixtures with interaction driven by the CDM density, whose past evolution is unphysical for DE to CDM energy flow. Numerical examples are provided describing the evolution of an initial profile that can be associated with idealised structure formation scenarios.

Make dark matter charged again

NASA Astrophysics Data System (ADS)

Agrawal, Prateek; Cyr-Racine, Francis-Yan; Randall, Lisa; Scholtz, Jakub

2017-05-01

We revisit constraints on dark matter that is charged under a U(1) gauge group in the dark sector, decoupled from Standard Model forces. We find that the strongest constraints in the literature are subject to a number of mitigating factors. For instance, the naive dark matter thermalization timescale in halos is corrected by saturation effects that slow down isotropization for modest ellipticities. The weakened bounds uncover interesting parameter space, making models with weak-scale charged dark matter viable, even with electromagnetic strength interaction. This also leads to the intriguing possibility that dark matter self-interactions within small dwarf galaxies are extremely large, a relatively unexplored regime in current simulations. Such strong interactions suppress heat transfer over scales larger than the dark matter mean free path, inducing a dynamical cutoff length scale above which the system appears to have only feeble interactions. These effects must be taken into account to assess the viability of darkly-charged dark matter. Future analyses and measurements should probe a promising region of parameter space for this model.

Color-Coded Clues to Composition Superimposed on Martian Seasonal-Flow Image

NASA Image and Video Library

2014-02-10

This image from NASA Mar Reconnaissance Orbiter combines a photograph of seasonal dark flows on a Martian slope at Palikir Crater with a grid of colors based on data collected by a mineral-mapping spectrometer observing the same area.

Dark chocolate effect on platelet activity, C-reactive protein and lipid profile: a pilot study.

PubMed

Hamed, Miruais S; Gambert, Steven; Bliden, Kevin P; Bailon, Oscar; Singla, Anand; Anand, Singla; Antonino, Mark J; Hamed, Fatema; Tantry, Udaya S; Gurbel, Paul A

2008-12-01

Dark chocolate (DC) is one of the richest sources of flavonoids. Since DC has been demonstrated to have beneficial effects on the cardiovascular system, our study examined its effect on platelet reactivity, inflammation, and lipid levels in healthy subjects. In 28 healthy volunteers, we analyzed the effect of one week of DC (providing 700 mg of flavonoids/day). The primary outcome was to determine the effects of DC consumption on platelet activity measured by flow cytometry (adenosine diphosphate [ADP]- and arachidonic acid [AA]-induced total and activated glycoprotein (GP) IIb/IIIa as well as P-selectin expression). In addition to this, we measured the effect of DC on high-sensitivity C-reactive protein (hsCRP), high-density lipid cholesterol (HDL) and low-density lipid cholesterol (LDL) levels. Following seven days of regular DC ingestion, LDL fell by 6% (120 +/- 38 vs 112 +/- 37 mg/dL, P < 0.018) and HDL rose by 9% (66 +/- 23 vs 72 +/- 26 mg/dL, P < 0.0019). ADP- and AA-induced activated GPIIb/IIIa expression was reduced by DC [27.3 +/- 27.8 vs 17.4 +/- 20.5 mean fluorescence intensity (MFI), P < 0.006; and 9.2 +/- 6.5 vs. 6.1 +/- 2.2 MFI, P < 0.005, respectively]. DC reduced hsCRP levels in women (1.8 +/- 2.1 vs. 1.4 +/- 1.7 mg/dL, P < 0.04). One week of DC ingestion improved lipid profiles and decreased platelet reactivity within the total group while reducing inflammation only in women. Regular dark chocolate ingestion may have cardioprotective properties. Further long-term research is warranted to evaluate the effect of flavonoids on cardiovascular health and to determine whether DC's beneficial effects are related to flavonoids or some yet unknown component. This research is based on a larger study which was presented at the American Heart Association Scientific Sessions 2007.

SOI metal-oxide-semiconductor field-effect transistor photon detector based on single-hole counting.

PubMed

Du, Wei; Inokawa, Hiroshi; Satoh, Hiroaki; Ono, Atsushi

2011-08-01

In this Letter, a scaled-down silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistor (MOSFET) is characterized as a photon detector, where photogenerated individual holes are trapped below the negatively biased gate and modulate stepwise the electron current flowing in the bottom channel induced by the positive substrate bias. The output waveforms exhibit clear separation of current levels corresponding to different numbers of trapped holes. Considering this capability of single-hole counting, a small dark count of less than 0.02 s(-1) at room temperature, and low operation voltage of 1 V, SOI MOSFET could be a unique photon-number-resolving detector if the small quantum efficiency were improved. © 2011 Optical Society of America

Dopamine and noradrenaline efflux in the prefrontal cortex in the light and dark period: effects of novelty and handling and comparison to the nucleus accumbens.

PubMed

Feenstra, M G; Botterblom, M H; Mastenbroek, S

2000-01-01

We used on-line microdialysis measurements of dopamine and noradrenaline extracellular concentrations in the medial prefrontal cortex of awake, freely moving rats during the dark and the light period of the day to study whether (i) basal efflux would be higher in the active, dark period than in the inactive, light period; (ii) the activation induced by environmental stimuli would be dependent on these conditions. When determined one day after cannula placement, noradrenaline and dopamine levels were higher during the dark. Maximal relative increases induced by novelty and handling were 150% and 175-200%, respectively, and were very similar in the light and the dark, but the net increases were higher in the dark. Separate groups were tested one week after cannula placement to ensure recovery of possibly disturbed circadian rhythms. While basal levels in the dark were now approximately twice those in the light, the maximal relative and net increases after both novelty and handling were very similar. Basal levels of dopamine in the nucleus accumbens (one day after cannula placement) were not different in the light or dark, but were increased by novelty and handling to about 130% only in the light period, not in the dark. Thus, in the prefrontal cortex, dopamine strongly resembles noradrenaline, in that basal efflux was state dependent, whereas activation by stimuli was not. In the nucleus accumbens, basal dopamine efflux was not state dependent, but activation by stimuli was. These results suggest that there are differential effects of circadian phase on basal activity and responsiveness of the mesolimbic vs the mesocortical dopamine system.

[Blue-light induced expression of S-adenosy-L-homocysteine hydrolase-like gene in Mucor amphibiorum RCS1].

PubMed

Gao, Ya; Wang, Shu; Fu, Mingjia; Zhong, Guolin

2013-09-04

To determine blue-light induced expression of S-adenosyl-L-homocysteine hydrolase-like (sahhl) gene in fungus Mucor amphibiorum RCS1. In the random process of PCR, a sequence of 555 bp was obtained from M. amphibiorum RCS1. The 555 bp sequence was labeled with digoxin to prepare the probe for northern hybridization. By northern hybridization, the transcription of sahhl gene was analyzed in M. amphibiorum RCS1 mycelia culture process from darkness to blue light to darkness. Simultaneously real-time PCR method was used to the sahhl gene expression analysis. Compared with the sequence of sahh gene from Homo sapiens, Mus musculus and some fungi species, a high homology of the 555 bp sequence was confirmed. Therefore, the preliminary confirmation has supported that the 555 bp sequence should be sahhl gene from M. amphibiorum RCS1. Under the dark pre-culture in 24 h, a large amounts of transcript of sahhl gene in the mycelia can be detected by northern hybridization and real-time PCR in the condition of 24 h blue light. But a large amounts of transcript of sahhl gene were not found in other detection for the dark pre-culture of 48 h, even though M. amphibiorum RCS1 mycelia were induced by blue light. Blue light can induce the expression of sahhl gene in the vigorous growth of M. amphibiorum RCS1 mycelia.

Electronic transport in a long wavelength infrared quantum cascade detector under dark condition

NASA Astrophysics Data System (ADS)

Li, L.; Zhou, X. H.; Lin, T.; Li, N.; Zhu, Z. Q.; Liu, F. Q.

2016-09-01

We present a joint experimental and theoretical investigation on a long wavelength infrared quantum cascade detector to reveal its dark current paths. The temperature dependence of the dark current is measured. It is shown that there are two different transport mechanisms, namely resonant tunneling at low temperatures and thermal excitation at higher temperature, dominate the carrier flow, respectively. Moreover, the experimental intersubband transition energies obtained by the magneto-transport measurements matches the theoretical predictions well. With the aid of the calculated band structures, we can explain the observed oscillation phenomena of the dark current under the magnetic field very well. The obtained results provide insight into the transport properties of quantum cascade detectors thus providing a useful tool for device optimization.

CMB and matter power spectra with non-linear dark-sector interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marttens, R.F. vom; Casarini, L.; Zimdahl, W.

2017-01-01

An interaction between dark matter and dark energy, proportional to the product of their energy densities, results in a scaling behavior of the ratio of these densities with respect to the scale factor of the Robertson-Walker metric. This gives rise to a class of cosmological models which deviate from the standard model in an analytically tractable way. In particular, it becomes possible to quantify the role of potential dark-energy perturbations. We investigate the impact of this interaction on the structure formation process. Using the (modified) CAMB code we obtain the CMB spectrum as well as the linear matter power spectrum.more » It is shown that the strong degeneracy in the parameter space present in the background analysis is considerably reduced by considering Planck data. Our analysis is compatible with the ΛCDM model at the 2σ confidence level with a slightly preferred direction of the energy flow from dark matter to dark energy.« less

Improved hypocrellin A production in Shiraia bambusicola by light-dark shift.

PubMed

Sun, Chun Xiao; Ma, Yan Jun; Wang, Jian Wen

2018-05-01

Hypocrellin A (HA) is a major bioactive perylenequinone from the fruiting body of Shiraia bambusicola used for the treatment of skin diseases and developed as a photodynamic therapy (PDT) agent against cancers and viruses. The mycelial culture of S. bambusicola under dark is a biotechnological alternative for HA production but with low yield. In this study, light and dark conditions were investigated to develop effective elicitation on HA production in the cultures. Our results showed the constant light at 200 lx stimulated HA production without any growth retardation of mycelia. A light/dark shift (24: 24 h) not only increased HA content in mycelia by 65%, but stimulated HA release into the medium with the highest total HA production 181.67 mg/L on day 8, about 73% increase over the dark control. Moreover, light/dark shifting induced the formation of smaller and more compact fungal pellets, suggesting a new effective strategy for large-scale production of HA in mycelium cultures. The light/dark shift up-regulated the expression levels of two reactive oxygen species (ROS) related genes including superoxide-generating NADPH oxidase (Nox) and cytochrome c peroxidase (CCP), and induced the generation of ROS. With the treatment of vitamin C, we found that ROS was involved in the up-regulated expression of key biosynthetical genes for hypocrellins and improved HA production. These results provide a basis for understanding the influence of light/dark shift on fungal metabolism and the application of a novel strategy for enhancing HA production in submerged Shiraia cultures. Copyright © 2018 Elsevier B.V. All rights reserved.

Dark energy in six nearby galaxy flows: Synthetic phase diagrams and self-similarity

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Teerikorpi, P.; Dolgachev, V. P.; Kanter, A. A.; Domozhilova, L. M.; Valtonen, M. J.; Byrd, G. G.

2012-09-01

Outward flows of galaxies are observed around groups of galaxies on spatial scales of about 1 Mpc, and around galaxy clusters on scales of 10 Mpc. Using recent data from the Hubble Space Telescope (HST), we have constructed two synthetic velocity-distance phase diagrams: one for four flows on galaxy-group scales and the other for two flows on cluster scales. It has been shown that, in both cases, the antigravity produced by the cosmic dark-energy background is stronger than the gravity produced by the matter in the outflow volume. The antigravity accelerates the flows and introduces a phase attractor that is common to all scales, corresponding to a linear velocity-distance relation (the local Hubble law). As a result, the bundle of outflow trajectories mostly follow the trajectory of the attractor. A comparison of the two diagrams reveals the universal self-similar nature of the outflows: their gross phase structure in dimensionless variables is essentially independent of their physical spatial scales, which differ by approximately a factor of 10 in the two diagrams.

The Colorado River

NASA Technical Reports Server (NTRS)

2002-01-01

This Moderate-resolution Imaging Spectroradiometer (MODIS) true-color image shows the passage of the Colorado River through several southwestern states. The river begins, in this image, in Utah at the far upper right, where Lake Powell is visible as dark pixels surrounded by the salmon-colored rocks of the Colorado Plateau. The Colorado flows southwest through Glen Canyon, to the Glen Canyon Dam, on the Utah-Arizona border. From there it flows south into Arizona, and then turns sharply west where the Grand Canyon of the Colorado cuts through the mountains. The Colorado flows west to the Arizona-Nevada (upper left) border, where it is dammed again, this time by the Hoover Dam. The dark-colored pixels surrounding the bend in the river are Lake Mead. The river flows south along the border of first Nevada and Arizona and then California and Arizona. The Colorado River, which begins in Rocky Mountain National Park in Colorado, empties into the Gulf of California, seen at the bottom center of this image.

Effect of gravitational focusing on annual modulation in dark-matter direct-detection experiments.

PubMed

Lee, Samuel K; Lisanti, Mariangela; Peter, Annika H G; Safdi, Benjamin R

2014-01-10

The scattering rate in dark-matter direct-detection experiments should modulate annually due to Earth's orbit around the Sun. The rate is typically thought to be extremized around June 1, when the relative velocity of Earth with respect to the dark-matter wind is maximal. We point out that gravitational focusing can alter this modulation phase. Unbound dark-matter particles are focused by the Sun's gravitational potential, affecting their phase-space density in the lab frame. Gravitational focusing can result in a significant overall shift in the annual-modulation phase, which is most relevant for dark matter with low scattering speeds. The induced phase shift for light O(10)  GeV dark matter may also be significant, depending on the threshold energy of the experiment.

Revisiting the direct detection of dark matter in simplified models

NASA Astrophysics Data System (ADS)

Li, Tong

2018-07-01

In this work we numerically re-examine the loop-induced WIMP-nucleon scattering cross section for the simplified dark matter models and the constraint set by the latest direct detection experiment. We consider a fermion, scalar or vector dark matter component from five simplified models with leptophobic spin-0 mediators coupled only to Standard Model quarks and dark matter particles. The tree-level WIMP-nucleon cross sections in these models are all momentum-suppressed. We calculate the non-suppressed spin-independent WIMP-nucleon cross sections from loop diagrams and investigate the constrained space of dark matter mass and mediator mass by Xenon1T. The constraints from indirect detection and collider search are also discussed.

One-dimensional spatial dark soliton-induced channel waveguides in lithium niobate crystal.

PubMed

Zhang, Peng; Ma, Yanghua; Zhao, Jianlin; Yang, Dexing; Xu, Honglai

2006-04-01

The anisotropic dependence of the formation of one-dimensional (1-D) spatial dark solitons on the orientation of intensity gradients in lithium niobate crystal is numerically specified. Based on this, we propose an approach to fabricate channel waveguides by employing 1-D spatial dark solitons. By exposure of two 1-D dark solitons with different orientations, channel waveguides can be created. The structures of the channel waveguides can be tuned by adjustment of the widths of the solitons and/or the angles between the two exposures. A square channel waveguide is experimentally demonstrated in an iron-doped lithium niobate crystal by exposure of two orthogonal 1-D dark solitons in sequence.

The role of ANAC072 in the regulation of chlorophyll degradation during age- and dark-induced leaf senescence.

PubMed

Li, Shou; Gao, Jiong; Yao, Lingya; Ren, Guodong; Zhu, Xiaoyu; Gao, Shan; Qiu, Kai; Zhou, Xin; Kuai, Benke

2016-08-01

ANAC072 positively regulates both age- and dark-induced leaf senescence through activating the transcription of NYE1. Leaf senescence is integral to plant development, which is age-dependent and strictly regulated by internal and environmental signals. Although a number of senescence-related mutants and senescence-associated genes (SAGs) have been identified and characterized in the past decades, the general regulatory network of leaf senescence is still far from being elucidated. Here, we report the role of ANAC072, an SAG identified through bioinformatics analysis, in the regulation of chlorophyll degradation during natural and dark-induced leaf senescence. The expression of ANAC072 was increased with advancing leaf senescence in Arabidopsis. Leaf degreening was significantly delayed under normal or dark-induced conditions in anac072-1, a knockout mutant of ANAC072, with a higher chlorophyll level detected. In contrast, an overexpression mutant, anac072-2, with ANAC072 transcription markedly upregulated, showed an early leaf-yellowing phenotype. Consistently, senescent leaves of the loss-of-function mutant anac072-1 exhibited delays in the decrease of photosynthesis efficiency of photosystem II (F v/F m ratio) and the increase of plasma membrane ion leakage rate as compared with corresponding leaves of wild-type Col-0 plants, whereas the overexpression mutant anac072-2 showed opposite changes. Our data suggest that ANAC072 plays a positive role during natural and dark-induced leaf senescence. In addition, the transcript level of NYE1, a key regulatory gene in chlorophyll degradation, relied on the function of ANAC072. Combining these analyses with electrophoretic mobility shift assay and chromatin immunoprecipitation, we demonstrated that ANAC072 directly bound to the NYE1 promoter in vitro and in vivo, so ANAC072 may promote chlorophyll degradation by directly upregulating the expression of NYE1.

Nitrate and Ammonium Induced Photosynthetic Suppression in N-Limited Selenastrum minutum.

PubMed

Elrifi, I R; Turpin, D H

1986-05-01

Nitrate-limited chemostat cultures of Selenastrum minutum Naeg. Collins (Chlorophyta) were used to determine the effects of nitrogen addition on photosynthesis, dark respiration, and dark carbon fixation. Addition of NO(3) (-) or NH(4) (+) induced a transient suppression of photosynthetic carbon fixation (70 and 40% respectively). Intracellular ribulose bisphosphate levels decreased during suppression and recovered in parallel with photosynthesis. Photosynthetic oxygen evolution was decreased by N-pulsing under saturating light (650 microeinsteins per square meter per second). Under subsaturating light intensities (<165 microeinsteins per square meter per second) NH(4) (+) addition resulted in O(2) consumption in the light which was alleviated by the presence of the tricarboxylic acid cycle inhibitor fluoroacetate. Addition of NO(3) (-) or NH(4) (+) resulted in a large stimulation of dark respiration (67 and 129%, respectively) and dark carbon fixation (360 and 2080%, respectively). The duration of N-induced perturbations was dependent on the concentration of added N. Inhibition of glutamine 2-oxoglutarate aminotransferase by azaserine alleviated all these effects. It is proposed that suppression of photosynthetic carbon fixation in response to N pulsing was the result of a competition for metabolites between the Calvin cycle and nitrogen assimilation. Carbon skeletons required for nitrogen assimilation would be derived from tricarboxylic acid cycle intermediates. To maintain tricarboxylic acid cycle activity triose phosphates would be exported from the chloroplast. This would decrease the rate of ribulose bisphosphate regeneration and consequently decrease net photosynthetic carbon accumulation. Stoichiometric calculations indicate that the Calvin cycle is one source of triose phosphates for N assimilation; however, during transient N resupply the major demand for triose phosphates must be met by starch or sucrose breakdown. The effects of N-pulsing on O(2) evolution, dark respiration, and dark C-fixation are shown to be consistent with this model.

ASTROPHYSICS. Exclusion of leptophilic dark matter models using XENON100 electronic recoil data.

PubMed

2015-08-21

Laboratory experiments searching for galactic dark matter particles scattering off nuclei have so far not been able to establish a discovery. We use data from the XENON100 experiment to search for dark matter interacting with electrons. With no evidence for a signal above the low background of our experiment, we exclude a variety of representative dark matter models that would induce electronic recoils. For axial-vector couplings to electrons, we exclude cross sections above 6 × 10(-35) cm(2) for particle masses of m(χ) = 2 GeV/c(2). Independent of the dark matter halo, we exclude leptophilic models as an explanation for the long-standing DAMA/LIBRA signal, such as couplings to electrons through axial-vector interactions at a 4.4σ confidence level, mirror dark matter at 3.6σ, and luminous dark matter at 4.6σ. Copyright © 2015, American Association for the Advancement of Science.

Probing the stability of superheavy dark matter particles with high-energy neutrinos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esmaili, Arman; Peres, Orlando L.G.; Ibarra, Alejandro, E-mail: aesmaili@ifi.unicamp.br, E-mail: ibarra@tum.de, E-mail: orlando@ifi.unicamp.br

2012-11-01

Two of the most fundamental properties of the dark matter particle, the mass and the lifetime, are only weakly constrained by the astronomical and cosmological evidence of dark matter. We derive in this paper lower limits on the lifetime of dark matter particles with masses in the range 10TeV−10{sup 15}TeV from the non-observation of ultrahigh energy neutrinos in the AMANDA, IceCube, Auger and ANITA experiments. For dark matter particles which produce neutrinos in a two body or a three body leptonic decay, we find that the dark matter lifetime must be longer than O(10{sup 26}−10{sup 28})s for masses between 10more » TeV and the Grand Unification scale. Finally, we also calculate, for concrete particle physics scenarios, the limits on the strength of the interactions that induce the dark matter decay.« less

Diurnal behavioral and endocrine effects of chronic shaker stress in mice.

PubMed

Dubovicky, Michal; Mach, Mojmir; Key, Mary; Morris, Mariana; Paton, Sara; Lucot, James B

2007-12-01

Experiments were performed in C57BL/6J male mice to determine 1) light/dark effects of acute and chronic shaker stress on open field behavioral patterns and 2) light/dark effects of chronic stress on plasma corticosterone and oxytocin. Shaker stress was applied acutely (15 min) or chronically (3 or 7 days). Mice were tested in the open field in the light or dark phase of the circadian cycle. For the endocrine study, mice were exposed to 3 days of intermittent shaker stress and sacrificed after the last stress event (09:00 or 19:00 h). Acute or chronic shaker stress had no significant effects on intensity of motor activity and rearing of mice tested under either light condition. Mice tested in the dark phase had higher motor activity and exhibited lower anxiety-like behavior as expressed by central zone activities and had higher emotionality as expressed by increased defecation. Chronic stress increased corticosterone with a greater absolute increase in the dark period. However, the percentage stress-induced increase was not different between the day and night periods. The oxytocin response to stress was observed only during the light phase with no change seen at dark phase. These results show that there is a marked difference in the light/dark pituitary stress response with no alteration in stress induced behavioral changes. They also suggest that there are circadian interactions in the endocrine stress axis that are without consequences for open field behavior.

Insights into drying of non-circular sessile nanofluid droplet towards multi-scale surface patterning using a wall-less confinement architecture.

PubMed

Kabi, Prasenjit; Chaudhuri, Swetaprovo; Basu, Saptarshi

2016-10-04

Surface patterning with functional colloids is an important research area due to its widespread applicability in domains ranging from nano-electronics, pharmaceutics, semi-conductors, photovoltaics among others. To this endeavour, we propose a low-cost patterning technique that aspires to eliminate the more expensive methodologies presently in practise. Using a simple document stamp on which patterns of any geometry can be embossed, we are able to print two-dimensional mm-scale "wall-less confinement" using ink based hydrophobic fence on any plasma treated superhydrophilic surface. The confinement is subsequently filled with nanocolloidal liquid(s). Using the confinement geometry, we are able to control the 3D shape of the droplet to exhibit multiple interfacial curvatures. The droplet in the "wall-less confinements" evaporates naturally exhibiting unique geometry (curvature) induced flow structures which induce the nanoparticles to self-assemble into functional patterns. We have also shown that by modifying the geometry of the pattern, evaporation, flow and particle deposition dynamics get altered leading to precipitate topologies from macro to microscales. We, present two such geometrical designs which demonstrate the capability of modifying both the macroscopic as well as the microscopic features of the final precipitate. We have also provided a description of the physical mechanisms of the drying process by resolving the unique flow pattern using a combination of imaging and μPIV (micro particle image velocimetry). These provide insights into the coupled dynamics of evaporation and flow responsible for the evolution of particle deposition pattern. Precipitate characterization using SEM and dark-field microscopy highlight the transformation in the deposit morphology.

The signal transducer NPH3 integrates the phototropin1 photosensor with PIN2-based polar auxin transport in Arabidopsis root phototropism.

PubMed

Wan, Yinglang; Jasik, Jan; Wang, Li; Hao, Huaiqing; Volkmann, Dieter; Menzel, Diedrik; Mancuso, Stefano; Baluška, František; Lin, Jinxing

2012-02-01

Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone.

Phytochrome and Seed Germination. V. Changes of Phytochrome Content During the Germination of Cucumber Seeds 1

PubMed Central

Mancinelli, Alberto L.; Tolkowsky, Abby

1968-01-01

Cucumber seeds are light-sensitive, dark-germinating seeds. Inhibition of germination can be induced by prolonged exposure to continuous or intermittent FR. The dark germination process and the response to FR are phytochrome controlled. Phytochrome can be detected in these seeds by differential spectrophotometry in vivo. Spectrophotometrically measurable phytochrome increases during dark germination. The rate of increase is temperature dependent. Light treatments which are inhibitory for germination result in phytochrome contents lower than those of the seeds germinating in darkness. Treatments which restore germination also restore phytochrome formation. PMID:16656797

Soliton-dark pulse pair formation in birefringent cavity fiber lasers through cross phase coupling.

PubMed

Shao, Guodong; Song, Yufeng; Zhao, Luming; Shen, Deyuan; Tang, Dingyuan

2015-10-05

We report on the experimental observation of soliton-dark pulse pair formation in a birefringent cavity fiber laser. Temporal cavity solitons are formed in one polarization mode of the cavity. It is observed that associated with each of the cavity solitons a dark pulse is induced on the CW background of the orthogonal polarization mode. We show that the dark pulse formation is a result of the incoherent cross polarization coupling between the soliton and the CW beam and has a mechanism similar to that of the polarization domain formation observed in the fiber lasers.

Dark chocolate inhibits platelet aggregation in healthy volunteers.

PubMed

Innes, Andrew J; Kennedy, Gwen; McLaren, Margaret; Bancroft, Anne J; Belch, Jill J F

2003-08-01

Cardiovascular disease is a leading cause of death in the UK. The flavonoids found in cocoa may produce a cardio-protective role for chocolate with a high cocoa content. Thirty healthy volunteers were randomised to receive 100 g of white, milk or dark chocolate, and assessments of platelet function were undertaken on venous blood samples before and after chocolate consumption. White and milk chocolate had no significant effect on platelets. However dark chocolate inhibited collagen-induced platelet aggregation in platelet rich plasma. In the future dark chocolate may have a role in prevention of cardiovascular and thromboembolic diseases.

Magnetic annihilation of the dark mode in a strongly coupled bright-dark terahertz metamaterial.

PubMed

Manjappa, Manukumara; Turaga, Shuvan Prashant; Srivastava, Yogesh Kumar; Bettiol, Andrew Anthony; Singh, Ranjan

2017-06-01

Dark mode in metamaterials has become a vital component in determining the merit of the Fano type of interference in the system. Its strength dictates the enhancement and suppression in the amplitude and Q-factors of resulting resonance features. In this work, we experimentally probe the effect of strong near-field coupling on the strength of the dark mode in a concentrically aligned bright resonator and a dark split ring resonator (SRR) system exhibiting the classical analog of the electromagnetically induced transparency effect. An enhanced strong magnetic field between the bright-dark resonators destructively interferes with the inherent magnetic field of the dark mode to completely annihilate its effect in the coupled system. Moreover, the observed annihilation effect in the dark mode has a direct consequence on the disappearance of the SRR effect in the proposed system, wherein under the strong magnetic interactions, the LC resonance feature of the split ring resonator becomes invisible to the incident terahertz wave.

1.2-ps mode-locked semiconductor optical amplifier fiber laser pulses generated by 60-ps backward dark-optical comb injection and soliton compression.

PubMed

Lin, Gong-Ru; Chiu, I-Hsiang; Wu, Ming-Chung

2005-02-07

Optically harmonic mode-locking of a semiconductor optical amplifier fiber laser (SOAFL) induced by backward injecting a dark-optical comb is demonstrated for the first time. The dark-optical comb with 60-ps pulsewidth is generated from a Mach-Zehnder modulator, which is driven by an electrical comb at a DC offset of 0.3Vn. Theoretical simulation indicates that the backward injection of dark-optical comb results in a narrow gain window of 60 ps within one modulating period, providing a cross-gainmodulation induced mode-locking in the SOAFL with a shortest pulsewidth of 15 ps at repetition frequency of 1 GHz. The mode-locked SOAFL pulsewidth can be slightly shortened to 10.8 ps with a 200m-long dispersion compensating fiber. After nonlinearly soliton compression in a 5km-long single mode fiber, the pulsewidth, linewidth and time-bandwidth product become 1.2 ps, 2.06 nm and 0.31, respectively.

The NGC 1023 galaxy group: An anti-hubble flow?

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Dolgachev, V. P.; Domozhilova, L. M.

2010-10-01

We discuss recently published data indicating that the nearby galaxy group NGC 1023 includes an inner, virialized, quasi-stationary component together with an outer component comprising a flow of dwarf galaxies falling toward the center of the system. The inner component is similar to the Local Group of galaxies, but the Local Group is surrounded by a receding set of dwarf galaxies forming the local Hubble flow, rather than a system of approaching dwarfs. This clear difference in the structures of these two systems, which are very similar in other respects, may be associated with the dark energy in which they are immersed. Self-gravity dominates in the inner component of the Local Group, while the anti-gravity created by the cosmic dark-energy background dominates in the surrounding Hubble flow. In contrast, self-gravity likewise dominates throughout the NGC 1023 Group, both in its central component and in the surrounding “anti-Hubble” flow. NGC 1023 as a whole is apparently in an ongoing state of formation and virialization. We expect that there exists a receding flow similar to the local Hubble flow at distances of 1.4-3 Mpc from the center of the group, where anti-gravity should become stronger than the gravity of the system.

Re-examination of globally flat space-time.

PubMed

Feldman, Michael R

2013-01-01

In the following, we offer a novel approach to modeling the observed effects currently attributed to the theoretical concepts of "dark energy," "dark matter," and "dark flow." Instead of assuming the existence of these theoretical concepts, we take an alternative route and choose to redefine what we consider to be inertial motion as well as what constitutes an inertial frame of reference in flat space-time. We adopt none of the features of our current cosmological models except for the requirement that special and general relativity be local approximations within our revised definition of inertial systems. Implicit in our ideas is the assumption that at "large enough" scales one can treat objects within these inertial systems as point-particles having an insignificant effect on the curvature of space-time. We then proceed under the assumption that time and space are fundamentally intertwined such that time- and spatial-translational invariance are not inherent symmetries of flat space-time (i.e., observable clock rates depend upon both relative velocity and spatial position within these inertial systems) and take the geodesics of this theory in the radial Rindler chart as the proper characterization of inertial motion. With this commitment, we are able to model solely with inertial motion the observed effects expected to be the result of "dark energy," "dark matter," and "dark flow." In addition, we examine the potential observable implications of our theory in a gravitational system located within a confined region of an inertial reference frame, subsequently interpreting the Pioneer anomaly as support for our redefinition of inertial motion. As well, we extend our analysis into quantum mechanics by quantizing for a real scalar field and find a possible explanation for the asymmetry between matter and antimatter within the framework of these redefined inertial systems.

Re-Examination of Globally Flat Space-Time

NASA Astrophysics Data System (ADS)

Feldman, Michael R.

2013-11-01

In the following, we offer a novel approach to modeling the observed effects currently attributed to the theoretical concepts of "dark energy," "dark matter," and "dark flow." Instead of assuming the existence of these theoretical concepts, we take an alternative route and choose to redefine what we consider to be inertial motion as well as what constitutes an inertial frame of reference in flat space-time. We adopt none of the features of our current cosmological models except for the requirement that special and general relativity be local approximations within our revised definition of inertial systems. Implicit in our ideas is the assumption that at "large enough" scales one can treat objects within these inertial systems as point-particles having an insignificant effect on the curvature of space-time. We then proceed under the assumption that time and space are fundamentally intertwined such that time- and spatial-translational invariance are not inherent symmetries of flat space-time (i.e., observable clock rates depend upon both relative velocity and spatial position within these inertial systems) and take the geodesics of this theory in the radial Rindler chart as the proper characterization of inertial motion. With this commitment, we are able to model solely with inertial motion the observed effects expected to be the result of "dark energy," "dark matter," and "dark flow." In addition, we examine the potential observable implications of our theory in a gravitational system located within a confined region of an inertial reference frame, subsequently interpreting the Pioneer anomaly as support for our redefinition of inertial motion. As well, we extend our analysis into quantum mechanics by quantizing for a real scalar field and find a possible explanation for the asymmetry between matter and antimatter within the framework of these redefined inertial systems.

Dark Matter Decays from Nonminimal Coupling to Gravity.

PubMed

Catà, Oscar; Ibarra, Alejandro; Ingenhütt, Sebastian

2016-07-08

We consider the standard model extended with a dark matter particle in curved spacetime, motivated by the fact that the only current evidence for dark matter is through its gravitational interactions, and we investigate the impact on the dark matter stability of terms in the Lagrangian linear in the dark matter field and proportional to the Ricci scalar. We show that this "gravity portal" induces decay even if the dark matter particle only has gravitational interactions, and that the decay branching ratios into standard model particles only depend on one free parameter: the dark matter mass. We study in detail the case of a singlet scalar as a dark matter candidate, which is assumed to be absolutely stable in flat spacetime due to a discrete Z_{2} symmetry, but which may decay in curved spacetimes due to a Z_{2}-breaking nonminimal coupling to gravity. We calculate the dark matter decay widths and we set conservative limits on the nonminimal coupling parameter from experiments. The limits are very stringent and suggest that there must exist an additional mechanism protecting the singlet scalar from decaying via this gravity portal.

Make dark matter charged again

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Prateek; Cyr-Racine, Francis-Yan; Randall, Lisa

2017-05-01

We revisit constraints on dark matter that is charged under a U(1) gauge group in the dark sector, decoupled from Standard Model forces. We find that the strongest constraints in the literature are subject to a number of mitigating factors. For instance, the naive dark matter thermalization timescale in halos is corrected by saturation effects that slow down isotropization for modest ellipticities. The weakened bounds uncover interesting parameter space, making models with weak-scale charged dark matter viable, even with electromagnetic strength interaction. This also leads to the intriguing possibility that dark matter self-interactions within small dwarf galaxies are extremely large,more » a relatively unexplored regime in current simulations. Such strong interactions suppress heat transfer over scales larger than the dark matter mean free path, inducing a dynamical cutoff length scale above which the system appears to have only feeble interactions. These effects must be taken into account to assess the viability of darkly-charged dark matter. Future analyses and measurements should probe a promising region of parameter space for this model.« less

Generation and control of optical frequency combs using cavity electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Li, Jiahua; Qu, Ye; Yu, Rong; Wu, Ying

2018-02-01

We explore theoretically the generation and all-optical control of optical frequency combs (OFCs) in photon transmission based on a combination of single-atom-cavity quantum electrodynamics (CQED) and electromagnetically induced transparency (EIT). Here an external control field is used to form the cavity dark mode of the CQED system. When the strengths of the applied EIT control field are appropriately tuned, enhanced comb generation can be achieved. We discuss the properties of the dark mode and clearly show that the formation of the dark mode enables the efficient generation of OFCs. In our approach, the comb spacing is determined by the beating frequency between the driving pump and seed lasers. Our demonstrated theory may pave the way towards all-optical coherent control of OFCs using a CQED architecture.

Plasmonic EIT-like switching in bright-dark-bright plasmon resonators.

PubMed

Chen, Junxue; Wang, Pei; Chen, Chuncong; Lu, Yonghua; Ming, Hai; Zhan, Qiwen

2011-03-28

In this paper we report the study of the electromagnetically induced transparency (EIT)-like transmission in the bright-dark-bright plasmon resonators. It is demonstrated that the interferences between the dark plasmons excited by two bright plasmon resonators can be controlled by the incident light polarization. The constructive interference strengthens the coupling between the bright and dark resonators, leading to a more prominent EIT-like transparency window of the metamaterial. In contrary, destructive interference suppresses the coupling between the bright and dark resonators, destroying the interference pathway that forms the EIT-like transmission. Based on this observation, the plasmonic EIT switching can be realized by changing the polarization of incident light. This phenomenon may find applications in optical switching and plasmon-based information processing.

Reduction in the critical dark length for flower induction during aging in the short-day plant Pharbitis nil var. Kidachi.

PubMed

Hasegawa, Hiroshi; Yamada, Mizuki; Iwase, Yuiko; Wada, Kaede C; Takeno, Kiyotoshi

2010-12-01

The stress-sensitive short-day plant Pharbitis nil var. Kidachi flowers under a 16-h light and 8-h dark regime and non-stress conditions when grown for long periods of time. Such flowering was found to occur from the third week, and the floral buds were formed from the eighth node of the main stem. When young plants were grafted onto aged plants, the scions were induced to flower early. This flower induction by grafting was more effective when older plants were used as rootstocks. Grafting experiments using a single leaf as a donor revealed that younger leaves are more responsive to flower induction, suggesting that this age-mediated flowering response is not induced by aging or senescence of individual leaves. Rather, the plant may obtain the ability to flower as the whole plant ages. Flowering does not occur under continuous light conditions. A night break given in the 8-h dark period inhibits flowering. These results suggest that 8-h dark conditions, which are normally considered to be long-day conditions, actually correspond to short-day conditions for this plant. The 8-h dark conditions caused early flowering more efficiently in older plants. The critical dark length determined by a single treatment was 12 h in 0-week-old plants and was reduced to 6 h in 2- and 4-week-old plants. These results suggest that the critical dark length becomes shorter when plants get older. The expression of PnFT1 and PnFT2, orthologs of the flowering gene flowering locus T, was analyzed by reverse transcription-polymerase chain reaction revealing that the expression of PnFT at the end of dark period is correlated with flowering.

Induction of dark keratinocytes by 12-O-tetradecanoylphorbol-13-acetate and mezerein as an indicator of tumor-promoting efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein-Szanto, A.J.P.; Major, S.K.; Slaga, T.J.

1980-05-01

12-O-Tetradecanoylphorbol-13-acetate (TPA) and mezerein (MZ) are diterpene esters of similar structure and approximately equipotent on a molar basis as far as their hyperplasiogenic, inflammatogenic, and induction of ornithine decarboxylase activity effects in mouse skin are concerned. On the other hand, TPA is much more effective than MZ as a tumor promoter. The percentage of dark basal keratinocytes was determined in the interfollicular epidermis (IFE) of mice topically treated with 1, 2, or 4 ..mu..g of either TPA or MZ in a single application and studied at 12, 24, 48, 96, and 144 h thereafter. The results showed that TPA inducedmore » 2 to 3 times more dark cells than MZ in the IFE as well as in the infundibular portion of the hair follicle. The latter epithelium presented a larger number of dark keratinocytes than the IFE in all experimental and control situations, and the differences between the effects of TPA and MZ were even greater in the infundibular epidermis than in the IFE. TPA induced an increase of 5 to 11 times over the control number of dark cells (approx. 2% in IFE), reaching maximum values of 21% in the basal layer 24 h after topical application of 4 ..mu..g of TPA. MZ only produced a 3- to 6-fold increment. The labeling indices of the basal layer and of the dark basal cells were markedly and similarly increased with both compounds. The different dark-cell inducing characteristics seem to be the only detectable difference in early effects produced by TPA and MZ and would point to the importance of the production of the dedifferentiated dark cells during early stages of tumor promotion.« less

The Sahara's Diverse Landscape

NASA Technical Reports Server (NTRS)

2002-01-01

Vast stretches of uninterrupted sand are only one kind of Saharan landscape. This true-color MODIS image from November 9, 2001, reveals a diversity of land surface features, including ancient lava flows and volcanoes. Beginning at upper left and moving clockwise are the countries of Algeria, Tunisia, Libya, Chad, and Niger. Evidence of previous volcanic activity in the Sahara can be found in northeastern Chad, in particular, in a region known as Tibesti. Reaching up out of the surrounding desert, the dark rock of the Tibesti Plateau stands out in dark brown against the sand. Scattered throughout the region are the circular cones and calderas of several volcanoes. The dark remains of a lava flow mark the location of the Tousside volcano. North of Tibesti, in Libya, more dark-colored lava beds leave their mark on the landscape. Variety exists in Algeria, where the Grand Erg Oriental desert (far upper left) is hemmed in to the south by the Tinrhert Plateau. South of the Plateau, desert resumes briefly, only to give way to a mountainous region traced with impermanent rivers. In northern Niger, a sinuous gray-green line marks the edge of an escarpment that separates the Mangueni Plateau to the north from the rock deserts to the south. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Light-dependent expression of flg22-induced defense genes in Arabidopsis.

PubMed

Sano, Satoshi; Aoyama, Mayu; Nakai, Kana; Shimotani, Koji; Yamasaki, Kanako; Sato, Masa H; Tojo, Daisuke; Suwastika, I Nengah; Nomura, Hironari; Shiina, Takashi

2014-01-01

Chloroplasts have been reported to generate retrograde immune signals that activate defense gene expression in the nucleus. However, the roles of light and photosynthesis in plant immunity remain largely elusive. In this study, we evaluated the effects of light on the expression of defense genes induced by flg22, a peptide derived from bacterial flagellins which acts as a potent elicitor in plants. Whole-transcriptome analysis of flg22-treated Arabidopsis thaliana seedlings under light and dark conditions for 30 min revealed that a number of (30%) genes strongly induced by flg22 (>4.0) require light for their rapid expression, whereas flg22-repressed genes include a significant number of genes that are down-regulated by light. Furthermore, light is responsible for the flg22-induced accumulation of salicylic acid (SA), indicating that light is indispensable for basal defense responses in plants. To elucidate the role of photosynthesis in defense, we further examined flg22-induced defense gene expression in the presence of specific inhibitors of photosynthetic electron transport: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone (DBMIB). Light-dependent expression of defense genes was largely suppressed by DBMIB, but only partially suppressed by DCMU. These findings suggest that photosynthetic electron flow plays a role in controlling the light-dependent expression of flg22-inducible defense genes.

Experimental observation of the effect of generic singularities in polychromatic dark hollow beams.

PubMed

Yadav, Bharat Kumar; Joshi, Stuti; Kandpal, Hem Chandra

2014-08-15

This Letter presents the essence of our recent experimental study on generic singularities carrying spatially partially coherent, polychromatic dark hollow beams (PDHBs). To the best of our knowledge, this is the first experimental demonstration of generic singularities-induced wavefront tearing in focused polychromatic beams.

Interspecific and environmentally induced variation in foliar dark respiration among eighteen southeastern deciduous tree species

Treesearch

Katherine A. Mitchell; Paul V. Bolstad; James M. Vose

1999-01-01

We measured variations in leaf dark respiration rate (Rd) and leaf nitrogen (N) across species, canopy light environment, and elevation for 18 co-occurring deciduous hardwood species in the Southern Appalachian Mountains of Western North Carolina. Our overall objective was to estimate leaf...

Arecibo radar imagery of Mars: The major volcanic provinces

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, Michael C.; Husmann, Diana I.; Campbell, Bruce A.

2012-08-01

We present Earth-based radar images of Mars obtained with the upgraded Arecibo S-band (λ = 12.6 cm) radar during the 2005-2012 oppositions. The imaging was done using the same long-code delay-Doppler technique as for the earlier (pre-upgrade) imaging but at a much higher resolution (˜3 km) and, for some regions, a more favorable sub-Earth latitude. This has enabled us to make a more detailed and complete mapping of depolarized radar reflectivity (a proxy for small-scale surface roughness) over the major volcanic provinces of Tharsis, Elysium, and Amazonis. We find that vast portions of these regions are covered by radar-bright lava flows exhibiting circular polarization ratios close to unity, a characteristic that is uncommon for terrestrial lavas and that is a likely indicator of multiple scattering from extremely blocky or otherwise highly disrupted flow surfaces. All of the major volcanoes have radar-bright features on their shields, although the brightness distribution on Olympus Mons is very patchy and the summit plateau of Pavonis Mons is entirely radar-dark. The older minor shields (paterae and tholi) are largely or entirely radar-dark, which is consistent with mantling by dust or pyroclastic material. Other prominent radar-dark features include: the "fan-shaped deposits", possibly glacial, associated with the three major Tharsis Montes shields; various units of the Medusae Fossae Formation; a region south and west of Biblis Patera where "Stealth" deposits appear to obscure Tharsis flows; and a number of "dark-halo craters" with radar-absorbing ejecta blankets deposited atop surrounding bright flows. Several major bright features in Tharsis are associated with off-shield lava flows; these include the Olympus Mons basal plains, volcanic fields east and south of Pavonis Mons, the Daedalia Planum flows south of Arsia Mons, and a broad expanse of flows extending east from the Tharsis Montes to Echus Chasma. The radar-bright lava plains in Elysium are concentrated mainly in Cerberus and include the fluvio-volcanic channels of Athabasca Valles, Grjotá Valles, and Marte Valles, as well as an enigmatic region at the southern tip of the Cerberus basin. Some of the Cerberus bright features correspond to the distinctive "platy-ridged" flows identified in orbiter images. The radar-bright terrain in Amazonis Planitia comprises two distinct but contiguous sections: a northern section formed of lavas and sediments debouched from Marte Valles and a southern section whose volcanics may derive, in part, from local sources. This South Amazonis region shows perhaps the most complex radar-bright structure on Mars and includes features that correspond to platy-ridged flows similar to those in Cerberus.

Topography and geomorphology of the Huygens landing site on Titan

USGS Publications Warehouse

Soderblom, L.A.; Tomasko, M.G.; Archinal, B.A.; Becker, T.L.; Bushroe, M.W.; Cook, D.A.; Doose, L.R.; Galuszka, D.M.; Hare, T.M.; Howington-Kraus, E.; Karkoschka, E.; Kirk, R.L.; Lunine, J.I.; McFarlane, E.A.; Redding, B.L.; Rizk, B.; Rosiek, M.R.; See, C.; Smith, P.H.

2007-01-01

The Descent Imager/Spectral Radiometer (DISR) aboard the Huygens Probe took several hundred visible-light images with its three cameras on approach to the surface of Titan. Several sets of stereo image pairs were collected during the descent. The digital terrain models constructed from those images show rugged topography, in places approaching the angle of repose, adjacent to flatter darker plains. Brighter regions north of the landing site display two styles of drainage patterns: (1) bright highlands with rough topography and deeply incised branching dendritic drainage networks (up to fourth order) with dark-floored valleys that are suggestive of erosion by methane rainfall and (2) short, stubby low-order drainages that follow linear fault patterns forming canyon-like features suggestive of methane spring-sapping. The topographic data show that the bright highland terrains are extremely rugged; slopes of order of 30?? appear common. These systems drain into adjacent relatively flat, dark lowland terrains. A stereo model for part of the dark plains region to the east of the landing site suggests surface scour across this plain flowing from west to east leaving ???100-m-high bright ridges. Tectonic patterns are evident in (1) controlling the rectilinear, low-order, stubby drainages and (2) the "coastline" at the highland-lowland boundary with numerous straight and angular margins. In addition to flow from the highlands drainages, the lowland area shows evidence for more prolific flow parallel to the highland-lowland boundary leaving bright outliers resembling terrestrial sandbars. This implies major west to east floods across the plains where the probe landed with flow parallel to the highland-lowland boundary; the primary source of these flows is evidently not the dendritic channels in the bright highlands to the north. ?? 2007 Elsevier Ltd. All rights reserved.

Nonlinear spherical perturbations in quintessence models of dark energy

NASA Astrophysics Data System (ADS)

Pratap Rajvanshi, Manvendra; Bagla, J. S.

2018-06-01

Observations have confirmed the accelerated expansion of the universe. The accelerated expansion can be modelled by invoking a cosmological constant or a dynamical model of dark energy. A key difference between these models is that the equation of state parameter w for dark energy differs from ‑1 in dynamical dark energy (DDE) models. Further, the equation of state parameter is not constant for a general DDE model. Such differences can be probed using the variation of scale factor with time by measuring distances. Another significant difference between the cosmological constant and DDE models is that the latter must cluster. Linear perturbation analysis indicates that perturbations in quintessence models of dark energy do not grow to have a significant amplitude at small length scales. In this paper we study the response of quintessence dark energy to non-linear perturbations in dark matter. We use a fully relativistic model for spherically symmetric perturbations. In this study we focus on thawing models. We find that in response to non-linear perturbations in dark matter, dark energy perturbations grow at a faster rate than expected in linear perturbation theory. We find that dark energy perturbation remains localised and does not diffuse out to larger scales. The dominant drivers of the evolution of dark energy perturbations are the local Hubble flow and a supression of gradients of the scalar field. We also find that the equation of state parameter w changes in response to perturbations in dark matter such that it also becomes a function of position. The variation of w in space is correlated with density contrast for matter. Variation of w and perturbations in dark energy are more pronounced in response to large scale perturbations in matter while the dependence on the amplitude of matter perturbations is much weaker.

Colony-Forming Progenitor Cells in the Postnatal Mouse Liver and Pancreas Give Rise to Morphologically Distinct Insulin-Expressing Colonies in 3D Cultures

PubMed Central

Jin, Liang; Feng, Tao; Chai, Jing; Ghazalli, Nadiah; Gao, Dan; Zerda, Ricardo; Li, Zhuo; Hsu, Jasper; Mahdavi, Alborz; Tirrell, David A.; Riggs, Arthur D.; Ku, Hsun Teresa

2014-01-01

In our previous studies, colony-forming progenitor cells isolated from murine embryonic stem cell-derived cultures were differentiated into morphologically distinct insulin-expressing colonies. These colonies were small and not light-reflective when observed by phase-contrast microscopy (therefore termed “Dark” colonies). A single progenitor cell capable of giving rise to a Dark colony was termed a Dark colony-forming unit (CFU-Dark). The goal of the current study was to test whether endogenous pancreas, and its developmentally related liver, harbored CFU-Dark. Here we show that dissociated single cells from liver and pancreas of one-week-old mice give rise to Dark colonies in methylcellulose-based semisolid culture media containing either Matrigel or laminin hydrogel (an artificial extracellular matrix protein). CFU-Dark comprise approximately 0.1% and 0.03% of the postnatal hepatic and pancreatic cells, respectively. Adult liver also contains CFU-Dark, but at a much lower frequency (~0.003%). Microfluidic qRT-PCR, immunostaining, and electron microscopy analyses of individually handpicked colonies reveal the expression of insulin in many, but not all, Dark colonies. Most pancreatic insulin-positive Dark colonies also express glucagon, whereas liver colonies do not. Liver CFU-Dark require Matrigel, but not laminin hydrogel, to become insulin-positive. In contrast, laminin hydrogel is sufficient to support the development of pancreatic Dark colonies that express insulin. Postnatal liver CFU-Dark display a cell surface marker CD133+CD49flowCD107blow phenotype, while pancreatic CFU-Dark are CD133-. Together, these results demonstrate that specific progenitor cells in the postnatal liver and pancreas are capable of developing into insulin-expressing colonies, but they differ in frequency, marker expression, and matrix protein requirements for growth. PMID:25148366

Collider study on the loop-induced dark matter mediation

NASA Astrophysics Data System (ADS)

Tsai, Yuhsin

2016-06-01

Collider experiments are one of the most promising ways to constrain Dark Matter (DM) interactions. For DM couplings involving light mediators, especially for the loop-mediated interactions, a meaningful interpretation of the results requires to go beyond effective field theory. In this note we discuss the study of the magnetic dipole interacting DM, focusing on a model with anarchic dark flavor structure. By including the momentum-dependent form factors that mediate the coupling - given by the Dark Penguin - in collider processes, we study bounds from monophoton, diphoton, and non-pointing photon searches at the LHC. We also compare our results to constraints from the direct detection experiments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaplan, David E.; Krnjaic, Gordan Z.; Rehermann, Keith R.

We present a simple UV completion of Atomic Dark Matter (aDM) in which heavy right-handed neutrinos decay to induce both dark and lepton number densities. This model addresses several outstanding cosmological problems: the matter/anti-matter asymmetry, the dark matter abundance, the number of light degrees of freedom in the early universe, and the smoothing of small-scale structure. Additionally, this realization of aDM may reconcile the CoGeNT excess with recently published null results and predicts a signal in the CRESST Oxygen band. We also find that, due to unscreened long-range interactions, the residual un recombined dark ions settle into a diffuse isothermalmore » halo.« less

Trickle water and feeding system in plant culture and light-dark cycle effects on plant growth

NASA Technical Reports Server (NTRS)

Takano, T.; Inada, K.; Takanashi, J.

1987-01-01

Rockwool, as an inert medium covered or bagged with polyethylene film, can be effectively used for plant culture in space stations. The most important machine is the pump adjusting the dripping rate in the feeding system. Hydro-aeroponics may be adaptable to a space laboratory. The shortening of the light-dark cycles inhibits plant growth and induces an abnormal morphogenesis. A photoperiod of 12 hr dark may be needed for plant growth.

Image analysis of single event transient effects on charge coupled devices irradiated by protons

NASA Astrophysics Data System (ADS)

Wang, Zujun; Xue, Yuanyuan; Liu, Jing; He, Baoping; Yao, Zhibin; Ma, Wuying

2016-10-01

The experiments of single event transient (SET) effects on charge coupled devices (CCDs) irradiated by protons are presented. The radiation experiments have been carried out at the accelerator protons with the energy of 200 MeV and 60 MeV.The incident angles of the protons are at 30°and 90° to the plane of the CCDs to obtain the images induced by the perpendicularity and incline incident angles. The experimental results show that the typical characteristics of the SET effects on a CCD induced by protons are the generation of a large number of dark signal spikes (hot pixels) which are randomly distributed in the "pepper" images. The characteristics of SET effects are investigated by observing the same imaging area at different time during proton radiation to verify the transient effects. The experiment results also show that the number of dark signal spikes increases with increasing integration time during proton radiation. The CCDs were tested at on-line and off-line to distinguish the radiation damage induced by the SET effects or DD effects. The mechanisms of the dark signal spike generation induced by the SET effects and the DD effects are demonstrated respectively.

The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism[C][W

PubMed Central

Wan, Yinglang; Jasik, Jan; Wang, Li; Hao, Huaiqing; Volkmann, Dieter; Menzel, Diedrik; Mancuso, Stefano; Baluška, František; Lin, Jinxing

2012-01-01

Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone. PMID:22374399

Strigolactone Regulates Leaf Senescence in Concert with Ethylene in Arabidopsis.

PubMed

Ueda, Hiroaki; Kusaba, Makoto

2015-09-01

Leaf senescence is not a passive degenerative process; it represents a process of nutrient relocation, in which materials are salvaged for growth at a later stage or to produce the next generation. Leaf senescence is regulated by various factors, such as darkness, stress, aging, and phytohormones. Strigolactone is a recently identified phytohormone, and it has multiple functions in plant development, including repression of branching. Although strigolactone is implicated in the regulation of leaf senescence, little is known about its molecular mechanism of action. In this study, strigolactone biosynthesis mutant strains of Arabidopsis (Arabidopsis thaliana) showed a delayed senescence phenotype during dark incubation. The strigolactone biosynthesis genes MORE AXIALLY GROWTH3 (MAX3) and MAX4 were drastically induced during dark incubation and treatment with the senescence-promoting phytohormone ethylene, suggesting that strigolactone is synthesized in the leaf during leaf senescence. This hypothesis was confirmed by a grafting experiment using max4 as the stock and Columbia-0 as the scion, in which the leaves from the Columbia-0 scion senesced earlier than max4 stock leaves. Dark incubation induced the synthesis of ethylene independent of strigolactone. Strigolactone biosynthesis mutants showed a delayed senescence phenotype during ethylene treatment in the light. Furthermore, leaf senescence was strongly accelerated by the application of strigolactone in the presence of ethylene and not by strigolactone alone. These observations suggest that strigolactone promotes leaf senescence by enhancing the action of ethylene. Thus, dark-induced senescence is regulated by a two-step mechanism: induction of ethylene synthesis and consequent induction of strigolactone synthesis in the leaf. © 2015 American Society of Plant Biologists. All Rights Reserved.

Width-tunable pulse laser via optical injection induced gain modulation of semiconductor optical amplifiers

NASA Astrophysics Data System (ADS)

Pan, Honggang; Zhang, Ailing; Tong, Zhengrong; Zhang, Yue; Song, Hongyun; Yao, Yuan

2018-03-01

A width-tunable pulse laser via an optical injection induced gain modulation of a semiconductor optical amplifier (SOA) is demonstrated. When the pump current of the SOA is 330 mA or 400 mA and a continuous wave is injected into the laser cavity with different powers, bright or dark pulses with different pulse widths and frequency repetition rates are obtained. The bright and dark pulses are formed by the effect of gain dispersion and cross-gain modulation of the SOA.

Axion induced oscillating electric dipole moments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Christopher T.

In this study, the axion electromagnetic anomaly induces an oscillating electric dipole for any magnetic dipole. This is a low energy theorem which is a consequence of the space-time dependent cosmic background field of the axion. The electron will acquire an oscillating electric dipole of frequency m a and strength ~ 10-32 e-cm, within four orders of magnitude of the present standard model DC limit, and two orders of magnitude above the nucleon, assuming standard axion model and dark matter parameters. This may suggest sensitive new experimental venues for the axion dark matter search.

First results from the DarkSide-50 dark matter experiment at Laboratori Nazionali del Gran Sasso

NASA Astrophysics Data System (ADS)

Agnes, P.; Alexander, T.; Alton, A.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Cadonati, L.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; Cocco, A. G.; Crippa, L.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Deo, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M. Y.; Guardincerri, Y.; Hackett, B.; Herner, K.; Hungerford, E. V.; Ianni, Al.; Ianni, An.; Jollet, C.; Keeter, K.; Kendziora, C.; Kidner, S.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kurlej, A.; Li, P. X.; Loer, B.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Ma, Y. Q.; Machulin, I.; Mandarano, A.; Mari, S.; Maricic, J.; Marini, L.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P. D.; Milincic, R.; Montanari, D.; Monte, A.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Musico, P.; Nelson, A.; Odrowski, S.; Okounkova, M.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Papp, L.; Parmeggiano, S.; Parsells, R.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Renshaw, A.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, S.; Segreto, E.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, S.; Wojcik, M.; Wright, A.; Xiang, X.; Xu, J.; Yang, C. G.; Yoo, J.; Zavatarelli, S.; Zec, A.; Zhu, C.; Zuzel, G.

2015-04-01

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4 ± 0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (1422 ± 67) kgd exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1 ×10-44 cm2 for a WIMP mass of 100 Gev /c2.

Melt Flow before Crystal Seeding in Cz Si Growth with Transversal MF

NASA Astrophysics Data System (ADS)

Iizuka, Masaya; Mukaiyama, Yuji; Demina, S. E.; Kalaev, V. V.

2017-06-01

Industrial Cz growth of Si crystal of 300 mm and higher diameter usually requires DC magnetic fields (MFs) to suppress turbulence in the melt. We present 3D unsteady analysis of melt turbulent convection in an industrial Cz system coupled with the effect of the transversal MF for different argon gas flow rates for the stage before crystal seeding. We have performed detailed 2D axisymmetric modeling of global heat transfer in the whole Cz furnace. Radiative heat fluxes obtained in 2D modeling have been used in detailed 3D steady and unsteady modeling of crystallization zone. LES method is applied as a predictive approach for modeling of turbulent flow of silicon melt. We have obtained flow structure and temperature distribution in the melt, which were different from previously reported data. We have observed a well-fixed dark spike which includes low temperature melt area on the melt free surface in MF cases. These results indicates that MF and argon flow rate conditions are important to achieve stable positioning of the dark spike on the melt free surface for optimized crystal seeding without uncontrollable meltdown and single crystal structure loss.

Preserved vestibular evoked myogenic potentials (VEMP) in some patients with walking-induced oscillopsia due to bilateral vestibulopathy.

PubMed

Brantberg, Krister; Löfqvist, Lennart

2007-01-01

Bilateral vestibulopathy, i.e. decreased peripheral vestibular function affecting both ears, is characterized by unsteadiness of gait, particularly in darkness and by motion-induced oscillopsia. We have recently seen a few patients with severely impaired semicircular canal function albeit with rather normal vestibular evoked myogenic potentials (VEMP) suggesting normal saccular function. The five young patients, mean age 27 years (range 15-45), 4 males and 1 female, had severely impaired balance in darkness and they all reported walking-induced vertical oscillopsia. Hence, these patients with incomplete vestibular lesions had symptoms that were indistinguishable from the typical patient with bilateral vestibulopathy. Further, the findings in these patients suggest that saccular function probably contributes little to prevent walking-induced vertical oscillopsia.

Tunable electromagnetically induced absorption based on graphene

NASA Astrophysics Data System (ADS)

Cao, Maoyong; Wang, Tongling; Zhang, Huiyun; Zhang, Yuping

2018-04-01

In this paper, an electronically induced absorption (EIA) structure based on graphene at the infrared frequency is proposed. A pair of nanorods is coupled to a ring resonator, resulting in electronically induced transparency (EIT), and then, Babinet's principle is applied to transform the EIT structure into an EIA structure. Based on the bright and dark modes of the coupling schemes, the adjustment of the coupling strength between the dark and bright modes can be achieved by changing the asymmetry degree. In addition, the transparency window and the absorption peak can be tuned by changing the Fermi energy of graphene. This graphene-based EIA structure can develop the path in narrow-band filtering and, absorptive switching in the future.

Scale-invariant scalar field dark matter through the Higgs portal

NASA Astrophysics Data System (ADS)

Cosme, Catarina; Rosa, João G.; Bertolami, O.

2018-05-01

We discuss the dynamics and phenomenology of an oscillating scalar field coupled to the Higgs boson that accounts for the dark matter in the Universe. The model assumes an underlying scale invariance such that the scalar field only acquires mass after the electroweak phase transition, behaving as dark radiation before the latter takes place. While for a positive coupling to the Higgs field the dark scalar is stable, for a negative coupling it acquires a vacuum expectation value after the electroweak phase transition and may decay into photon pairs, albeit with a mean lifetime much larger than the age of the Universe. We explore possible astrophysical and laboratory signatures of such a dark matter candidate in both cases, including annihilation and decay into photons, Higgs decay, photon-dark scalar oscillations and induced oscillations of fundamental constants. We find that dark matter within this scenario will be generically difficult to detect in the near future, except for the promising case of a 7 keV dark scalar decaying into photons, which naturally explains the observed galactic and extra-galactic 3.5 keV X-ray line.

Dark-Bright Soliton Dynamics Beyond the Mean-Field Approximation

NASA Astrophysics Data System (ADS)

Katsimiga, Garyfallia; Koutentakis, Georgios; Mistakidis, Simeon; Kevrekidis, Panagiotis; Schmelcher, Peter; Theory Group of Fundamental Processes in Quantum Physics Team

2017-04-01

The dynamics of dark bright solitons beyond the mean-field approximation is investigated. We first examine the case of a single dark-bright soliton and its oscillations within a parabolic trap. Subsequently, we move to the setting of collisions, comparing the mean-field approximation to that involving multiple orbitals in both the dark and the bright component. Fragmentation is present and significantly affects the dynamics, especially in the case of slower solitons and in that of lower atom numbers. It is shown that the presence of fragmentation allows for bipartite entanglement between the distinguishable species. Most importantly the interplay between fragmentation and entanglement leads to the decay of each of the initial mean-field dark-bright solitons into fast and slow fragmented dark-bright structures. A variety of excitations including dark-bright solitons in multiple (concurrently populated) orbitals is observed. Dark-antidark states and domain-wall-bright soliton complexes can also be observed to arise spontaneously in the beyond mean-field dynamics. Deutsche Forschungsgemeinschaft (DFG) in the framework of the SFB 925 ``Light induced dynamics and control of correlated quantum systems''.

Applicability of quantitative optical imaging techniques for intraoperative perfusion diagnostics: a comparison of laser speckle contrast imaging, sidestream dark-field microscopy, and optical coherence tomography

NASA Astrophysics Data System (ADS)

Jansen, Sanne M.; de Bruin, Daniel M.; Faber, Dirk J.; Dobbe, Iwan J. G. G.; Heeg, Erik; Milstein, Dan M. J.; Strackee, Simon D.; van Leeuwen, Ton G.

2017-08-01

Patient morbidity and mortality due to hemodynamic complications are a major problem in surgery. Optical techniques can image blood flow in real-time and high-resolution, thereby enabling perfusion monitoring intraoperatively. We tested the feasibility and validity of laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), and sidestream dark-field microscopy (SDF) for perfusion diagnostics in a phantom model using whole blood. Microvessels with diameters of 50, 100, and 400 μm were constructed in a scattering phantom. Perfusion was simulated by pumping heparinized human whole blood at five velocities (0 to 20 mm/s). Vessel diameter and blood flow velocity were assessed with LSCI, OCT, and SDF. Quantification of vessel diameter was feasible with OCT and SDF. LSCI could only visualize the 400-μm vessel, perfusion units scaled nonlinearly with blood velocity. OCT could assess blood flow velocity in terms of inverse OCT speckle decorrelation time. SDF was not feasible to measure blood flow; however, for diluted blood the measurements were linear with the input velocity up to 1 mm/s. LSCI, OCT, and SDF were feasible to visualize blood flow. Validated blood flow velocity measurements intraoperatively in the desired parameter (mL·g-1) remain challenging.

Dynamics of a spherically symmetric inhomogeneous coupled dark energy model with coupling term proportional to non relatvistic matter

NASA Astrophysics Data System (ADS)

Izquierdo, Germán; Blanquet-Jaramillo, Roberto C.; Sussman, Roberto A.

2018-01-01

The quasi-local scalar variables approach is applied to a spherically symmetric inhomogeneous Lemaître-Tolman-Bondi metric containing a mixture of non-relativistic cold dark matter and coupled dark energy with constant equation of state. The quasi-local coupling term considered is proportional to the quasi-local cold dark matter energy density and a quasi-local Hubble factor-like scalar via a coupling constant α . The autonomous numerical system obtained from the evolution equations is classified for different choices of the free parameters: the adiabatic constant of the dark energy w and α . The presence of a past attractor in a non-physical region of the energy densities phase-space of the system makes the coupling term non physical when the energy flows from the matter to the dark energy in order to avoid negative values of the dark energy density in the past. On the other hand, if the energy flux goes from dark energy to dark matter, the past attractor lies in a physical region. The system is also numerically solved for some interesting initial profiles leading to different configurations: an ever expanding mixture, a scenario where the dark energy is completely consumed by the non-relativistic matter by means of the coupling term, a scenario where the dark energy disappears in the inner layers while the outer layers expand as a mixture of both sources, and, finally, a structure formation toy model scenario, where the inner shells containing the mixture collapse while the outer shells expand.

Induction of a carbon-starvation-related proteolysis in whole maize plants submitted to Light/Dark cycles and to extended darkness

PubMed

Brouquisse; Gaudillere; Raymond

1998-08-01

Three-week-old maize (Zea mays L.) plants were submitted to light/dark cycles and to prolonged darkness to investigate the occurrence of sugar-limitation effects in different parts of the whole plant. Soluble sugars fluctuated with light/dark cycles and dropped sharply during extended darkness. Significant decreases in protein level were observed after prolonged darkness in mature roots, root tips, and young leaves. Glutamine and asparagine (Asn) changed in opposite ways, with Asn increasing in the dark. After prolonged darkness the increase in Asn accounted for most of the nitrogen released by protein breakdown. Using polyclonal antibodies against a vacuolar root protease previously described (F. James, R. Brouquisse, C. Suire, A. Pradet, P. Raymond [1996] Biochem J 320: 283-292) or the 20S proteasome, we showed that the increase in proteolytic activities was related to an enrichment of roots in the vacuolar protease, with no change in the amount of 20S proteasome in either roots or leaves. Our results show that no significant net proteolysis is induced in any part of the plant during normal light/dark cycles, although changes in metabolism and growth appear soon after the beginning of the dark period, and starvation-related proteolysis probably appears in prolonged darkness earlier in sink than in mature tissues.

Dark matter, muon g -2 , electric dipole moments, and Z →ℓi+ℓj- in a one-loop induced neutrino model

NASA Astrophysics Data System (ADS)

Chiang, Cheng-Wei; Okada, Hiroshi; Senaha, Eibun

2017-07-01

We study a simple one-loop induced neutrino mass model that contains both bosonic and fermionic dark matter candidates and has the capacity to explain the muon anomalous magnetic moment anomaly. We perform a comprehensive analysis by taking into account the relevant constraints of charged lepton flavor violation, electric dipole moments, and neutrino oscillation data. We examine the constraints from lepton flavor-changing Z boson decays at the one-loop level, particularly when the involved couplings contribute to the muon g -2 . It is found that BR (Z →μ τ )≃(10-7- 10-6) while BR (τ →μ γ )≲10-11 in the fermionic dark matter scenario. The former can be probed by the precision measurement of the Z boson at future lepton colliders.

Lack of circadian regulation of melatonin rhythms in the sockeye salmon (Oncorhynchus nerka) in vivo and in vitro.

PubMed

Iigo, Masayuki; Azuma, Teruo; Iwata, Munehico

2007-01-01

Melatonin profiles were determined in the plasma in vivo and in the pineal organ in vitro of the sockeye salmon (Oncorhynchus nerka) under various light conditions to test whether they are under circadian regulation. When serial blood samples were taken at 4-h intervals for 3 days via a cannula inserted into the dorsal aorta, plasma melatonin exhibited significant fluctuation under a light-dark cycle, with higher levels during the dark phase than during the light phase. No rhythmic fluctuations persisted under either constant dark or constant light, with constant low and high levels, respectively. Melatonin release from the pineal organ in flow-through culture exhibited a similar pattern in response to the change in light conditions, with high and low release associated with the dark and light phases, respectively. These results indicate that melatonin production in the sockeye salmon is driven by light and darkness but lacks circadian regulation.

Physiological and Biochemical Mechanisms of Lifespan Regulation in Rats Kept Under Various Light Conditions.

PubMed

Khizhkin, Evgeniy A; Ilukha, Victor A; Vinogradova, Irina A; Uzenbaeva, Lyudmila B; Ilyina, Tatiana N; Yunash, Victoria D; Morozov, Artem V; Anisimov, Vladimir N

2017-01-01

The present study was aimed to identify how age-related changes in some physiological and biochemical systems are related to changes in the life span of rats with long-term pineal gland hypo- and hyperfunction induced by constant light and constant darkness, respectively. At the age of 25 days the rats were randomly divided into 3 groups: standard light/dark regimen (LD), constant light (LL) and constant darkness (DD). Age-related Antioxidant System (AOS) changes in liver tissues, alteration of immunoreactivity in blood smears were investigated, pubescence and lifespan of the animals were determined. Modification of the level of melatonin synthesis induced by constant light results in interrelated rearrangements in the functioning of the investigated physiological systems. Elevated activity of the antioxidant system extends the lifespan, while at the same time slowing down pubescence and altering the morpho-functional properties of leukocytes in blood. The absence of light/dark alternation (constant light and constant darkness) affects only those physiological indices that follow the organism's circadian rhythms (Activity of Antioxidant Enzymes (AOE), levels of individual immune system cell types), whereas changes in the parameters not governed by circadian fluctuations (vitamin concentrations, pubescence, and aging) depend on the level of melatonin produced by the pineal gland.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Bo; Jiang, Yunchun; Yang, Jiayan

Taking advantage of the high spatiotemporal resolution observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we present rare observations of the rapid formation of a filament caused by magnetic reconnection between two sets of dark threadlike structures. The two sets of dark threadlike structures belong to distinct flux systems with their adjacent ends anchored in an opposite-polarity magnetic field region, where the calculated photospheric velocity field shows that converging flows dominate there. Due to the converging flows, opposite-polarity magnetic flux converged and then canceled, leading to the formation ofmore » extreme ultraviolet (EUV) brightening that spread in opposite directions along the spine of the dark threadlike structures. Meanwhile, very weak remote brightening in the other terminals of the dark threadlike structures, as well as EUV loops, which rooted in the opposite-polarity magnetic field region, appeared. In addition, all of the AIA Fe line observations reveal that a flux rope was formed and underwent a rolling motion during the fadeaway of the EUV brightening. Soon after, as the EUV brightening disappeared, a filament that is very likely composed of two sets of intertwined dark threadlike structures was formed. Via differential emission measure (EM) analysis, it is found that both the EM and temperature of the plasma around the flux-canceling site increased during the brightening, implying that there, magnetic reconnection may occur to heat the plasma. These observations provide evidence that the filament is formed by magnetic reconnection associated with flux convergence and cancellation, and the magnetic structure of the filament is most likely a flux rope.« less

Analytical theory for the dark-soliton interaction in nonlocal nonlinear materials with an arbitrary degree of nonlocality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong Qian; Department of Physics, Shanghai University, Shanghai 200444; Wang, Q.

2010-07-15

We investigate theoretically the interaction of dark solitons in materials with a spatially nonlocal nonlinearity. In particular we do this analytically and for arbitrary degree of nonlocality. We employ the variational technique to show that nonlocality induces an attractive force in the otherwise repulsive soliton interaction.

Experiencing ownership over a dark-skinned body reduces implicit racial bias.

PubMed

Maister, Lara; Sebanz, Natalie; Knoblich, Günther; Tsakiris, Manos

2013-08-01

Previous studies have investigated how existing social attitudes towards other races affect the way we 'share' their bodily experiences, for example in empathy for pain, and sensorimotor mapping. Here, we ask whether it is possible to alter implicit racial attitudes by experimentally increasing self-other bodily overlap. Employing a bodily illusion known as the 'Rubber Hand Illusion', we delivered multisensory stimulation to light-skinned Caucasian participants to induce the feeling that a dark-skinned hand belonged to them. We then measured whether this could change their implicit racial biases against people with dark skin. Across two experiments, the more intense the participants' illusion of ownership over the dark-skinned rubber hand, the more positive their implicit racial attitudes became. Importantly, it was not the pattern of multisensory stimulation per se, but rather, it was the change in the subjective experience of body ownership that altered implicit attitudes. These findings suggest that inducing an overlap between the bodies of self and other through illusory ownership is an effective way to change and reduce negative implicit attitudes towards outgroups. Copyright © 2013 Elsevier B.V. All rights reserved.

Light-Induced Thickening of Photoreceptor Outer Segment Layer Detected by Ultra-High Resolution OCT Imaging.

PubMed

Li, Yichao; Fariss, Robert N; Qian, Jennifer W; Cohen, Ethan D; Qian, Haohua

2016-07-01

We examined if light induces changes in the retinal structure that can be observed using optical coherence tomography (OCT). Normal C57BL/6J mice (age 3-6 months) adapted to either room light (15 minutes to ∼5 hours, 50-500 lux) or darkness (overnight) were imaged using a Bioptigen UHR-OCT system. Confocal histologic images were obtained from mice killed under light- or dark-adapted conditions. The OCT image of eyes adapted to room light exhibited significant increases (6.1 ± 0.8 μm, n = 13) in total retina thickness compared to the same eyes after overnight dark adaptation. These light-adapted retinal thickness changes occurred mainly in the outer retina, with the development of a hyporeflective band between the RPE and photoreceptor-tip layers. Histologic analysis revealed a light-evoked elongation between the outer limiting membrane and Bruch's membrane from 45.8 ± 1.7 μm in the dark (n = 5) to 52.1 ± 3.7 μm (n = 5) in the light. Light-adapted retinas showed an increase of actin staining in RPE apical microvilli at the same location as the hyporeflective band observed in OCT images. Elongation of the outer retina could be detected even with brief light exposures, increasing 2.1 ± 0.3 μm after 15 minutes (n = 9), and 4.1 ± 1.0 μm after 2 hours (n = 6). Conversely, dark-adaptation caused outer retinal shortening of 1.4 ± 0.4 μm (n = 7) and 3.0 ± 0.5 μm (n = 8) after 15 minutes and 2 hours, respectively. Light-adaption induces an increase in the thickness of the outer retina and the appearance of a hyporeflective band in the OCT image. This is consistent with previous reports of light-induced fluid accumulation in the subretinal space.

Nano-sized TiO2 (nTiO2) induces metabolic perturbations in Physarum polycephalum macroplasmodium to counter oxidative stress under dark conditions.

PubMed

Zhang, Zhi; Liang, Zhi Cheng; Zhang, Jian Hua; Tian, Sheng Li; Le Qu, Jun; Tang, Jiao Ning; De Liu, Shi

2018-06-15

Nano-sized TiO 2 (nTiO 2 ) exerts an oxidative effect on cells upon exposure to solar or UV irradiation and ecotoxicity of the nTiO 2 is an urgent concern. Little information is available regarding the effect of TiO 2 on cells under dark conditions. Metabolomics is a unique approach to the discovery of biomarkers of nTiO 2 cytotoxicity, and leads to the identification of perturbed metabolic pathways and the mechanism underlying nTiO 2 toxicity. In the present study, gas chromatography mass spectrometry (GC/MS)-based metabolomics was performed to investigate the effect of nTiO 2 on sensitive cells (P. polycephalum macroplasmodium) under dark conditions. According to the multivariate pattern recognition analysis, at least 60 potential metabolic biomarkers related to sugar metabolism, amino acid metabolism, nucleotide metabolism, polyamine biosynthesis, and secondary metabolites pathways were significantly perturbed by nTiO 2 . Notably, many metabolic biomarkers and pathways were related to anti-oxidant mechanisms in the living organism, suggesting that nTiO 2 may induce oxidative stress, even under dark conditions. This speculation was further validated by the biochemical levels of reactive oxygen species (ROS), 8-hydroxy-2-deoxyguanosine (8-OHdG), and total soluble phenols (TSP). We inferred that the oxidative stress might be related to nTiO 2 -induced imbalance of cellular ROS. To the best of our knowledge, the present study is the first to investigate the nTiO 2 -induced metabolic perturbations in slime mold, provide a new perspective of the mechanism underlying nTiO 2 toxicity under dark conditions, and show that metabolomics can be employed as a rapid, reliable and powerful tool to investigate the interaction among organisms, the environment, and nanomaterials. Copyright © 2018 Elsevier Inc. All rights reserved.

Cognition Enhancing Activity of Sulforaphane Against Scopolamine Induced Cognitive Impairment in Zebra Fish (Danio rerio).

PubMed

Rajesh, Venugopalan; Ilanthalir, Sakthivel

2016-10-01

Several epidemiological studies have shown that consumption of large quantities of vegetables especially cruciferous vegetables (Broccoli and Brussels sprouts) can protect against chronic diseases. Sulforaphane, an isothiocynate found in cruciferous vegetables has been demonstrated to have neuroprotective effects in several experimental paradigms. This study was undertaken to examine the effect of sulforaphane on cognitive impairment in zebra fish model using a novel method of fear conditioning. Initially, the normal behaviour of zebra fishes was studied in light-dark tank for 10 min daily for 10 days. Fishes were then divided into seven groups of twelve in each. Group I served as normal, group II served as fear conditioned control, group III and group IV were sulforaphane (25 µM/L) and piracetam (200 mg/L) treated respectively. Group V served as scopolamine (400 µM/L) induced memory impairment fishes. Group VI and VII were sulforaphane (25 µM/L) and piracetam (200 mg/L) treated scopolamine induced memory impairment groups respectively. In normal behavioural analysis, fishes preferred to stay in dark compartment. The average number of entries into the dark and time spent in dark were significantly more. Fishes in group II to VII were individually subjected to fear conditioning passive avoidance task and evaluated for learned task memory. It was observed that the average number of entries into dark and time spent in dark were significantly decreased. After exposure to respective treatment fishes in group III to VII were subjected to cognitive evaluation. There was no significant difference in cognition of group III and IV fishes exposed to sulforaphane and piracetam alone respectively. Fishes exposed to scopolamine showed a significant cognitive impairment. Sulforaphane exposure prior to scopolamine significantly retained the memory of learned task. These findings suggest that sulforaphane might be a promising therapeutic agent for cognitive enhancement in Alzheimer's disease.

Relative effect of temperature and pH on diel cycling of dissolved trace elements in prickly pear creek, Montana

USGS Publications Warehouse

Jones, Clain A.; Nimick, D.A.; McCleskey, R. Blaine

2004-01-01

Diel (24 hr) cycles in dissolved metal and As concentrations have been documented in many northern Rocky Mountain streams in the U.S.A. The cause(s) of the cycles are unknown, although temperature- and pH-dependent sorption reactions have been cited as likely causes. A light/dark experiment was conducted to isolate temperature and pH as variables affecting diel metal cycles in Prickly Pear Creek, Montana. Light and dark chambers containing sediment and a strand of macrophyte were placed in the stream to simulate instream temperature oscillations. Photosynthesis-induced pH changes were allowed to proceed in the light chambers while photosynthesis was prevented in the dark chambers. Water samples were collected periodically for 22 hr in late July 2001 from all chambers and the stream. In the stream, dissolved Zn concentrations increased by 300% from late afternoon to early morning, while dissolved As concentrations exhibited the opposite pattern, increasing 33% between early morning and late afternoon. Zn and As concentrations in the light chambers showed similar, though less pronounced, diel variations. Conversely, Zn and As concentrations in the dark chambers had no obvious diel variation, indicating that light, or light-induced reactions, caused the variation. Temperature oscillations were nearly identical between light and dark chambers, strongly suggesting that temperature was not controlling the diel variations. As expected, pH was negatively correlated (P < 0.01) with dissolved Zn concentrations and positively correlated with dissolved As concentrations in both the light and dark chambers. From these experiments, photosynthesis-induced pH changes were determined to be the major cause of the diel dissolved Zn and As cycles in Prickly Pear Creek. Further research is necessary in other streams to verify that this finding is consistent among streams having large differences in trace-element concentrations and mineralogy of channel substrate. ?? 2004 Kluwer Academic Publishers.

Nitrate and Ammonium Induced Photosynthetic Suppression in N-Limited Selenastrum minutum1

PubMed Central

Elrifi, Ivor R.; Turpin, David H.

1986-01-01

Nitrate-limited chemostat cultures of Selenastrum minutum Naeg. Collins (Chlorophyta) were used to determine the effects of nitrogen addition on photosynthesis, dark respiration, and dark carbon fixation. Addition of NO3− or NH4+ induced a transient suppression of photosynthetic carbon fixation (70 and 40% respectively). Intracellular ribulose bisphosphate levels decreased during suppression and recovered in parallel with photosynthesis. Photosynthetic oxygen evolution was decreased by N-pulsing under saturating light (650 microeinsteins per square meter per second). Under subsaturating light intensities (<165 microeinsteins per square meter per second) NH4+ addition resulted in O2 consumption in the light which was alleviated by the presence of the tricarboxylic acid cycle inhibitor fluoroacetate. Addition of NO3− or NH4+ resulted in a large stimulation of dark respiration (67 and 129%, respectively) and dark carbon fixation (360 and 2080%, respectively). The duration of N-induced perturbations was dependent on the concentration of added N. Inhibition of glutamine 2-oxoglutarate aminotransferase by azaserine alleviated all these effects. It is proposed that suppression of photosynthetic carbon fixation in response to N pulsing was the result of a competition for metabolites between the Calvin cycle and nitrogen assimilation. Carbon skeletons required for nitrogen assimilation would be derived from tricarboxylic acid cycle intermediates. To maintain tricarboxylic acid cycle activity triose phosphates would be exported from the chloroplast. This would decrease the rate of ribulose bisphosphate regeneration and consequently decrease net photosynthetic carbon accumulation. Stoichiometric calculations indicate that the Calvin cycle is one source of triose phosphates for N assimilation; however, during transient N resupply the major demand for triose phosphates must be met by starch or sucrose breakdown. The effects of N-pulsing on O2 evolution, dark respiration, and dark C-fixation are shown to be consistent with this model. PMID:16664788

Prolonged dark period modulates the oxidative burst and enzymatic antioxidant systems in the leaves of salicylic acid-treated tomato.

PubMed

Poór, Péter; Takács, Zoltán; Bela, Krisztina; Czékus, Zalán; Szalai, Gabriella; Tari, Irma

2017-06-01

Salicylic acid (SA) is an important plant growth regulator playing a role in the hypersensitive reaction (HR) and the induction of systemic acquired resistance. Since the SA-mediated signalling pathways and the formation of reactive oxygen species (ROS) are light-dependent, the time- and concentration-specific induction of oxidative stress was investigated in leaves of tomato plants kept under light and dark conditions after treatments with 0.1mM and 1mM SA. The application of exogenous SA induced early superoxide- and H 2 O 2 production in the leaves, which was different in the absence or presence of light and showed time- and concentration-dependent changes. 1mM SA, which induced HR-like cell death resulted in two peaks in the H 2 O 2 production in the light but the first, priming peak was not detected in the dark. Unlike 0.1mM SA, 1mM SA application induced NADPH oxidase activity leading to increased superoxide production in the first hours of SA treatments in the light. Moreover, SA treatments inhibited catalase (CAT) activity and caused a transient decline in ascorbate peroxidase (APX), the two main enzymes responsible for H 2 O 2 degradation, which led to a fast H 2 O 2 burst in the light. Their activity as well as the expression of some isoenzymes of SOD and APX increased only from the 12th h in the illuminated samples. The activity of NADPH oxidase and expression SlRBOH1 gene encoding a NADPH oxidase subunit was much lower in the dark. In spite of low CAT and APX activity after SA treatments in the dark, the activation of guaiacol-dependent peroxidase (POD) could partially substitute H 2 O 2 scavenging activity of these enzymes in the dark, which reduced the ROS burst and development of lesion formation in the leaves. Copyright © 2017 Elsevier GmbH. All rights reserved.

Ultraviolet complete dark energy model

NASA Astrophysics Data System (ADS)

Narain, Gaurav; Li, Tianjun

2018-04-01

We consider a local phenomenological model to explain a nonlocal gravity scenario which has been proposed to address dark energy issues. This nonlocal gravity action has been seen to fit the data as well as Λ -CDM and therefore demands a more fundamental local treatment. The induced gravity model coupled with higher-derivative gravity is exploited for this proposal, as this perturbatively renormalizable model has a well-defined ultraviolet (UV) description where ghosts are evaded. We consider a generalized version of this model where we consider two coupled scalar fields and their nonminimal coupling with gravity. In this simple model, one of the scalar field acquires a vacuum expectation value (VEV), thereby inducing a mass for one of the scalar fields and generating Newton's constant. The induced mass however is seen to be always above the running energy scale thereby leading to its decoupling. The residual theory after decoupling becomes a platform for driving the accelerated expansion under certain conditions. Integrating out the residual scalar generates a nonlocal gravity action. The leading term of which is the nonlocal gravity action used to fit the data of dark energy.

Collider study on the loop-induced dark matter mediation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Yuhsin, E-mail: yhtsai@umd.edu

2016-06-21

Collider experiments are one of the most promising ways to constrain Dark Matter (DM) interactions. For DM couplings involving light mediators, especially for the loop-mediated interactions, a meaningful interpretation of the results requires to go beyond effective field theory. In this note we discuss the study of the magnetic dipole interacting DM, focusing on a model with anarchic dark flavor structure. By including the momentum-dependent form factors that mediate the coupling – given by the Dark Penguin – in collider processes, we study bounds from monophoton, diphoton, and non-pointing photon searches at the LHC. We also compare our results tomore » constraints from the direct detection experiments.« less

Differential role of ethylene and hydrogen peroxide in dark-induced stomatal closure.

PubMed

Kar, R K; Parvin, N; Laha, D

2013-12-15

Regulation of stomatal aperture is crucial in terrestrial plants for controlling water loss and gaseous exchange with environment. While much is known of signaling for stomatal opening induced by blue light and the role of hormones, little is known about the regulation of stomatal closing in darkness. The present study was aimed to verify their role in stomatal regulation in darkness. Epidermal peelings from the leaves of Commelina benghalensis were incubated in a defined medium in darkness for 1 h followed by a 1 h incubation in different test solutions [H2O2, propyl gallate, ethrel (ethylene), AgNO3, sodium orthovanadate, tetraethyl ammonium chloride, CaCl2, LaCl3, separately and in combination] before stomatal apertures were measured under the microscope. In the dark stomata remained closed under treatments with ethylene and propyl gallate but opened widely in the presence of H2O2 and AgNO3. The opening effect was largely unaffected by supplementing the treatment with Na-vanadate (PM H+ ATPase inhibitor) and tetraethyl ammonium chloride (K(+)-channel inhibitor) except that opening was significantly inhibited by the latter in presence of H2O2. On the other hand, H2O2 could not override the closing effect of ethylene at any concentrations while a marginal opening of stomata was found when Ag NO3 treatment was given together with propyl gallate. CaCl2 treatment opened stomata in the darkness while LaCl3 maintained stomata closed. A combination of LaCl3 and propyl gallate strongly promoted stomatal opening. A probable action of ethylene in closing stomata of Commelina benghalensis in dark has been proposed.

Effects of nicergoline on rabbit electroretinogram during recovery after ischaemia in light and dark.

PubMed

Blasco, G; Traversa, U; Drago, F

1997-11-01

Nicergoline is an ergot alkaloid derivative acting as a neuroprotective agent. In the present investigation, b-wave time-course recovery profiles under both light- and dark-adapted conditions, were studied in order to evaluate the possible effectiveness of nicergoline in the protection of the rabbit retina. Retinal ischaemia was induced by bilateral occlusion of common carotid artery in male rabbit of the Dutch strain. Groups of animals were subjected to 15-, 30- and 60-min periods of ischaemia under pentobarbital anaesthesia. Electroretinogram recordings were simultaneously obtained from both eyes, using, as the stimulus, the brightest flash from a stimulator positioned 15 cm in front of each eye. The treatment with nicergoline, administered immediately before the carotid occlusion, induced a significant protection only when the ischaemia seemed to cause retinal damage that the reperfusion alone was not able to recover completely. Nicergoline did not modify the recovery rate after 15-min or 30-min light-adapted and 15-min dark-adapted ischaemia; in these conditions the controls showed a full recovery. After 30-min dark-adapted ischaemia, the maximum recovery of the controls was 82%, and nicergoline significantly improved b-wave amplitude at all time points of reperfusion up to the complete recovery. Rabbit retina was irreversibly damaged by a 60-min ischaemia. In these conditions nicergoline significantly increased the percentage of b-wave recovery both in light- and dark-adapted ERG. Nicergoline, probably on the basis of its metabolic actions, seems to be effective in severe conditions of hypoxia and is more potent in dark than in light-adapted conditions. Its effectiveness in these experimental conditions could be justified by the different oxygen consumption of the photoreceptors in light and dark and the different sensitivity of cones and rods to the ischaemia.

Induced senescence promotes the feeding activities and nymph development of Myzus persicae (Hemiptera: Aphididae) on potato plants.

PubMed

Machado-Assefh, Cristina R; Lucatti, Alejandro F; Alvarez, Adriana E

2014-01-01

The effect of dark-induced senescence on Solanum tuberosum L. (Solanales: Solanaceae) plants was assessed on the feeding behavior and performance of the green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae). Senescence was induced by covering the basal part of the plant with a black cloth for 5 d, avoiding the light passage, but keeping the apical buds uncovered. The basal part of control plants was covered with a white nonwoven cloth. The degree of senescence was determined by measuring the chlorophyll content of the covered leaves. The performance and feeding behavior of M. persicae were studied on the uncovered nonsenescent apical leaves. The aphid's performance was evaluated by measuring nymphal mortality and prereproductive time. Aphid feeding behavior was monitored by the electrical penetration graph technique. In plants with dark-induced senescence, the aphids showed a reduction in their prereproductive time. Aphids also spent more time ingesting sap from the phloem than in control plants and performed more test probes after the first sustained ingestion of phloem sap. These data suggest that M. persicae's phloem activities and nymph development benefit from the nutritional enrichment of phloem sap, derived from dark-induced senescence on potato plants. The induced senescence improved plant acceptance by M. persicae through an increase in sap ingestion that likely resulted in a reduction in developmental time. © The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America.

"Wine-Dark Sea" in an Organic Flow Battery: Storing Negative Charge in 2,1,3-Benzothiadiazole Radicals Leads to Improved Cyclability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Wentao; Huang, Jinhua; Kowalski, Jeffrey A.

A highly soluble, readily accessible, redox-active organic material, 2,1,3-benzothiadiazole, is demonstrated as a novel anolyte material to enable exceptional cyclability in a full-cell organic redox flow battery. This material discovery represents a significant progress toward promising next-generation energy storage.

DARLA: Data Assimilation and Remote Sensing for Littoral Applications

DTIC Science & Technology

2013-09-30

of a hydraulic jump around Jetty A. We also obverse the signature of a soliton wave east of Jetty A ( ). West of the mouth, the orbital velocity of...surface flows. (B) Plan view of the bathymetry [Jesse McNinch] (color contours, red is 1 m depth, dark blue is 10 m depth) and near surface flows

Mt. Etna, Sicily as seen from STS-62

NASA Image and Video Library

1994-03-05

STS062-85-195 (4-18 March 1994) --- A thin plume of steam blows southward from the summit of Mt. Etna, the active volcano on the island of Sicily. The summit is capped with snow but the dark lava flow along the eastern flank (the 1991-93 flow) is clearly visible. The coastal city south of Etna is Catania.

Detecting ultralight axion dark matter wind with laser interferometers

NASA Astrophysics Data System (ADS)

Aoki, Arata; Soda, Jiro

The ultralight axion with mass around 10-22eV is known as a candidate of dark matter. A peculiar feature of the ultralight axion is oscillating pressure in time, which produces oscillation of gravitational potentials. Since the solar system moves through the dark matter halo at the velocity of about v ˜ 300km/s = 10-3, there exists axion wind, which looks like scalar gravitational waves for us. Hence, there is a chance to detect ultralight axion dark matter with a wide mass range by using laser interferometer detectors. We calculate the detector signal induced by the oscillating pressure of the ultralight axion field, which would be detected by future laser interferometer experiments. We also argue that the detector signal can be enhanced due to the resonance in modified gravity theory explaining the dark energy.

Evidence from Studies with Acifluorfen for Participation of a Flavin-Cytochrome Complex in Blue Light Photoreception for Phototropism of Oat Coleoptiles 12

PubMed Central

Leong, Ta-Yan; Briggs, Winslow R.

1982-01-01

The diphenyl ether acifluorfen enhances the blue light-induced absorbance change in Triton X100-solubilized crude membrane preparations from etiolated oat (Avena sativa L. cv. Lodi) coleoptiles. Enhancement of the spectral change is correlated with a change in rate of dark reoxidation of a b-type cytochrome. Similar, although smaller, enhancement was obtained with oxyfluorfen, nitrofen, and bifenox. Light-minus-dark difference spectra in the presence and absence of acifluorfen, and the dithionite-reduced-minus oxidized difference spectrum indicate that acifluorfen is acting specifically at a blue light-sensitive cytochrome-flavin complex. Sodium azide, a flavin inhibitor, decreases the light-induced absorbance change significantly, but does not affect the dark reoxidation of the cytochrome. Hence, it is acting on the light reaction, suggesting that the photoreceptor itself is a flavin. Acifluorfen sensitizes phototropism in dark-grown oat seedlings such that the first positive response occurs with blue light fluences as little as one-third of those required to elicit the same response in seedlings grown in the absence of the herbicide. Both this increase in sensitivity to light and the enhancement of the light-induced cytochrome reduction vary with the applied acifluorfen concentration in a similar manner. The herbicide is without effect either on elongation or on the geotropic response of dark-grown oat seedlings, indicating that acifluorfen is acting specifically close to, or at the photoreceptor end of, the stimulus-response chain. It seems likely that the flavin-cytochrome complex serves to transduce the light signal into curvature in phototropism in oats, with the flavin moiety itself serving as the photoreceptor. PMID:16662593

Prevention of duodenal ileus reveals functional differences in the duodenal response to luminal hypertonicity in Sprague-Dawley and Dark Agouti rats.

PubMed

Sedin, J; Sjöblom, M; Nylander, O

2014-03-01

The mechanism by which the duodenum adjusts the luminal osmolality remains unclear. The aim was to compare the duodenal osmoregulation in response to different hyperosmolar solutions in Sprague-Dawley and Dark Agouti rats and to elucidate whether cyclooxygenase-2 inhibition affects these responses. The duodenum was perfused in situ with a 700-milliosmolar solution (NaCl alone, D-glucose ± NaCl, D-mannitol ± NaCl or orange juice), and the effects on the duodenal motility, mucosal permeability, luminal alkalinization, fluid flux and osmoregulation were assessed in anaesthetized rats. The change in net fluid flux and luminal osmolality, in response to a given hyperosmolar solution, was almost identical in control rats of both strains. In control rats, hypertonic D-glucose-NaCl induced fluid secretion only in the presence of phlorizin, an inhibitor of SGLT1. Cyclooxygenase-2 inhibition potentiated the hypertonicity-induced fluid secretion and increased the osmolality-adjusting capability in both strains, but the responses were greater in Dark Agouti rats. While cyclooxygenase-2-inhibited Dark Agouti rats responded to the hyperosmolar solutions with depression of motility and increased mucosal permeability, these effects were absent or smaller in the Sprague-Dawley strain. In contrast, orange juice induced the same duodenal responses in cyclooxygenase-2-inhibited Dark Agouti and Sprague-Dawley rats. The duodenum possesses the ability to absorb fluid despite a very high luminal osmolality. Inhibition of cyclooxygenase-2 markedly enhanced the capability of the duodenum to secrete fluid and to decrease luminal osmolality, irrespective of the hyperosmolar solution or the rat strain used, and revealed notable differences between the two strains with regard to their osmolality-adjusting capability. © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Gene activity during germination of spores of the fern, Onoclea sensibilis: RNA and protein synthesis and the role of stored mRNA

NASA Technical Reports Server (NTRS)

Raghavan, V.

1991-01-01

Pattern of 3H-uridine incorporation into RNA of spores of Onoclea sensibilis imbibed in complete darkness (non-germinating conditions) and induced to germinate in red light was followed by oligo-dT cellulose chromatography, gel electrophoresis coupled with fluorography and autoradiography. In dark-imbibed spores, RNA synthesis was initiated about 24 h after sowing, with most of the label accumulating in the high mol. wt. poly(A) -RNA fraction. There was no incorporation of the label into poly(A) +RNA until 48 h after sowing. In contrast, photo-induced spores began to synthesize all fractions of RNA within 12 h after sowing and by 24 h, incorporation of 3H-uridine into RNA of irradiated spores was nearly 70-fold higher than that into dark-imbibed spores. Protein synthesis, as monitored by 3H-arginine incorporation into the acid-insoluble fraction and by autoradiography, was initiated in spores within 1-2 h after sowing under both conditions. Autoradiographic experiments also showed that onset of protein synthesis in the cytoplasm of the germinating spore is independent of the transport of newly synthesized nuclear RNA. One-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis of 35S-methionine-labelled proteins revealed a good correspondence between proteins synthesized in a cell-free translation system directed by poly(A) +RNA of dormant spores and those synthesized in vivo by dark-imbibed and photo-induced spores. These results indicate that stored mRNAs of O. sensibilis spores are functionally competent and provide templates for the synthesis of proteins during dark-imbibition and germination.

QUIESCENT PROMINENCE DYNAMICS OBSERVED WITH THE HINODE SOLAR OPTICAL TELESCOPE. I. TURBULENT UPFLOW PLUMES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal

2010-06-20

Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) 'arches' or 'bubbles' that 'inflate' from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate verticallymore » from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex 'roll-up' of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) 'optical flow' code to derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s{sup -1}, which is supersonic for a {approx}10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s{sup -1}. Typical lifetimes range from 300 to 1000 s ({approx}5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km{sup 2} s{sup -1} reaching maximum projected areas from 2 to 15 Mm{sup 2}. Maximum contrast of the dark flows relative to the bright prominence plasma in SOT images is negative and ranges from -10% for smaller flows to -50% for larger flows. Passive scalar 'cork movies' derived from NAVE measurements show that prominence plasma is entrained by the upflows, helping to counter the ubiquitous downflow streams in the prominence. Plume formation shows no clear temporal periodicity. However, it is common to find 'active cavities' beneath prominences that can spawn many upflows in succession before going dormant. The mean flow recurrence time in these active locations is roughly 300-500 s (5-8 minutes). Locations remain active on timescales of tens of minutes up to several hours. Using a column density ratio measurement and reasonable assumptions on plume and prominence geometries, we estimate that the mass density in the dark cavities is at most 20% of the visible prominence density, implying that a single large plume could supply up to 1% of the mass of a typical quiescent prominence. We hypothesize that the plumes are generated from a Rayleigh-Taylor instability taking place on the boundary between the buoyant cavities and the overlying prominence. Characteristics, such as plume size and frequency, may be modulated by the strength and direction of the cavity magnetic field relative to the prominence magnetic field. We conclude that buoyant plumes are a source of quiescent prominence mass as well as a mechanism by which prominence plasma is advected upward, countering constant gravitational drainage.« less

Quiescent Prominence Dynamics Observed with the Hinode Solar Optical Telescope. I. Turbulent Upflow Plumes

NASA Astrophysics Data System (ADS)

Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine, Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto, Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya; Suematsu, Yoshinori; Shimizu, Toshifumi

2010-06-01

Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) "arches" or "bubbles" that "inflate" from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate vertically from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex "roll-up" of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) "optical flow" code to derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s-1, which is supersonic for a ~10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s-1. Typical lifetimes range from 300 to 1000 s (~5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km2 s-1 reaching maximum projected areas from 2 to 15 Mm2. Maximum contrast of the dark flows relative to the bright prominence plasma in SOT images is negative and ranges from -10% for smaller flows to -50% for larger flows. Passive scalar "cork movies" derived from NAVE measurements show that prominence plasma is entrained by the upflows, helping to counter the ubiquitous downflow streams in the prominence. Plume formation shows no clear temporal periodicity. However, it is common to find "active cavities" beneath prominences that can spawn many upflows in succession before going dormant. The mean flow recurrence time in these active locations is roughly 300-500 s (5-8 minutes). Locations remain active on timescales of tens of minutes up to several hours. Using a column density ratio measurement and reasonable assumptions on plume and prominence geometries, we estimate that the mass density in the dark cavities is at most 20% of the visible prominence density, implying that a single large plume could supply up to 1% of the mass of a typical quiescent prominence. We hypothesize that the plumes are generated from a Rayleigh-Taylor instability taking place on the boundary between the buoyant cavities and the overlying prominence. Characteristics, such as plume size and frequency, may be modulated by the strength and direction of the cavity magnetic field relative to the prominence magnetic field. We conclude that buoyant plumes are a source of quiescent prominence mass as well as a mechanism by which prominence plasma is advected upward, countering constant gravitational drainage.

The effect of fast and regeneration in light versus dark on regulation in the hydra-algal symbiosis

NASA Technical Reports Server (NTRS)

Bossert, P.; Slobodkin, L. B.

1983-01-01

Green hydra are able to regenerate tentacles after fast durations which cause brown, i.e., asymbiotic, hydra to fail completely, but the presence of endosymbiotic algae does not always enhance regeneration in fasted hydra. Green hydra whose nutritional state falls below some threshold, exhibit a light induced inhibition of regeneration. That is, hydra, fasted in the light, then randomly assigned to light or dark after decapitation, regenerate better in the dark. This effect of light does not appear to be present either in brown hydra or in normally green hydra from which the algae were removed. In a large strain of Chlorohydra viridissima, after fasts of intermediate duration (10 and 15 days), this light induced inhibition of regeneration is associated with an increase in the number of algae per gastric cell in regenerating hydra relative to non-regenerating controls.

Lidar and Radar Measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study

NASA Astrophysics Data System (ADS)

Di Girolamo, Paolo; Summa, Donato; Bhawar, Rohini; Di Iorio, Tatiana; Vaughan, Geraint; Norton, Emily; Peters, Gerhard

2009-03-01

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark bands were observed by the Univ. of BASILicata Raman lidar system (BASIL) on several IOPs and SOPs (among others, 23 July, 15 August, 17 August). Dark band signatures appear in the lidar measurements of particle backscattering at 355, 532 and 1064 nm and particle extinction at 355 and 532 nm, as well as in particle depolarization measurements. Lidar data are supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester Radio UHF clear air wind profiler (1.29 GHz). Results from BASIL and the radars are illustrated and discussed to support in the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar dark band and radar bright band.

Radiatively induced neutrino mass model with flavor dependent gauge symmetry

NASA Astrophysics Data System (ADS)

Lee, SangJong; Nomura, Takaaki; Okada, Hiroshi

2018-06-01

We study a radiative seesaw model at one-loop level with a flavor dependent gauge symmetry U(1) μ - τ, in which we consider bosonic dark matter. We also analyze the constraints from lepton flavor violations, muon g - 2, relic density of dark matter, and collider physics, and carry out numerical analysis to search for allowed parameter region which satisfy all the constraints and to investigate some predictions. Furthermore we find that a simple but adhoc hypothesis induces specific two zero texture with inverse mass matrix, which provides us several predictions such as a specific pattern of Dirac CP phase.

The 11 years solar cycle as the manifestation of the dark Universe

DOE PAGES

Zioutas, K.; Semertzidis, Y.; Tsagri, M.; ...

2014-11-26

Sun’s luminosity in the visible changes at the 10 -3 level, following an 11 years period. In X-rays, which should not be there, the amplitude varies even ~10 5 times stronger, making their mysterious origin since the discovery in 1938 even more puzzling, and inspiring. We suggest that the multifaceted mysterious solar cycle is due to some kind of dark matter streams hitting the Sun. Planetary gravitational lensing enhances (occasionally) slow moving flows of dark constituents towards the Sun, giving rise to the periodic behaviour. Jupiter provides the driving oscillatory force, though its 11.8 years orbital period appears slightly decreased,more » just as 11 years, if the lensing impact of other planets is included. Then, the 11 years solar clock may help to decipher (overlooked) signatures from the dark sector in laboratory experiments or observations in space.« less

Enhanced solution velocity between dark and light areas with horizontal tubes and triangular prism baffles to improve microalgal growth in a flat-panel photo-bioreactor.

PubMed

Yang, Zongbo; Cheng, Jun; Xu, Xiaodan; Zhou, Junhu; Cen, Kefa

2016-07-01

Novel horizontal tubes and triangular prism (HTTP) baffles that generate flow vortices were developed to increase solution velocity between dark and light areas and thus improve microalgal growth in a flat-panel photo-bioreactor. Solution velocity, mass-transfer coefficient, and mixing time were measured with a particle-imaging velocimeter, dissolved oxygen probes, and pH probes. The solution mass-transfer coefficient increased by 30% and mixing time decreased by 21% when the HTTP baffles were used. The solution velocity between dark and light areas increased from ∼0.9cm/s to ∼3.5cm/s, resulting in a decreased dark-light cycle period to one-fourth. This enhanced flashing light effect with the HTTP baffles dramatically increased microalgae biomass yield by 70% in the flat-panel photo-bioreactor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Alterations in circadian and meal-induced gut peptide levels in lean and obese rats.

PubMed

Moghadam, Alexander A; Moran, Timothy H; Dailey, Megan J

2017-12-01

Alterations in gut hormone signaling are a likely contributing factor to the metabolic disturbances associated with overweight/obesity as they coordinate the timing of feeding behavior, absorption, and utilization of nutrients. These hormones are released in response to food intake, or follow a circadian or anticipatory pattern of secretion that is independent of nutrient stimulation. The aim of this study was to identify the degree to which high-fat diet-induced obesity would alter the daily rhythm of gut peptide plasma levels (glucagon-like peptide-1 [GLP-1], peptide YY [PYY], insulin or amylin [AMY]) or meal-induced levels in the middle of the light or dark cycle. Male Sprague-Dawley rats were fed a high-fat diet (OBESE) or chow (LEAN), implanted with jugular catheters, and blood samples were taken every 2 h throughout the light/dark cycle while freely feeding or after an Ensure liquid meal. We found that even when OBESE and LEAN animals ate the same kcals and have a similar pattern of food intake, there is a difference in both the levels and rhythm of plasma gut peptides. GLP-1 and PYY are higher during the light cycle in LEAN animals and AMY is higher in the OBESE group throughout the light/dark cycle. There was also a differential response of plasma gut signals after the Ensure meal, even though the composition and amount of intake of the meal were the same in both groups. These changes occur prior to the high-fat diet induced loss of glycemic control and may be a target for early intervention. Impact statement The aim of this study was to test if obesity would alter the daily rhythm of gut peptides or meal-induced levels in the middle of the light or dark cycle. We found that even when animals are eating the same amount (in kcal) of food that the obese animals have altered daily rhythms and meal-induced gut peptide levels. In particular, we are the first to show that obesity induces increases in peptide YY levels during the light cycle and amylin remains high throughout the light and dark cycle in obese animals. These changes occurred prior to a loss of glycemic control. Thus, the rhythm of gut peptides could be used as an early indicator of later and more serious metabolic disturbances and may be a target for early intervention.

Aspects of Clock Resetting in Flowering of Xanthium 1

PubMed Central

Papenfuss, Herbert D.; Salisbury, Frank B.

1967-01-01

Flowering is induced in Xanthium strumarium by a single dark period exceeding about 8.3 hours in length (the critical night). To study the mechanism which measures this dark period, plants were placed in growth chambers for about 2 days under constant light and temperature, given a phasing dark period terminated by an intervening light period (1 min to several hrs in duration), and finally a test dark period long enough normally to induce flowering. In some experiments, light interruptions during the test dark period were given to establish the time of maximum sensitivity. If the phasing dark period was less than 5 hours long, its termination by a light flash only broadened the subsequent time of maximum sensitivity to a light flash, but the critical night was delayed. In causing the delay, the end of the intervening light period was acting like the dusk signal which initiated time measurement at the beginning of the phasing dark period. If the phasing dark period was 6 hours or longer, time of maximum sensitivity during the subsequent test dark period was shifted by as much as 10 to 14 hours. In this case the light terminating the phasing dark period acted as a rephaser or a dawn signal. Following a 7.5-hour phasing dark period, intervening light periods of 1 minute to 5 hours did not shift the subsequent time of maximum sensitivity, but with intervening light periods longer than 5 hours, termination of the light acts clearly like a dusk signal. The clock appears to be suspended during intervening light periods longer than 5 to 15 hours. It is restarted by a dusk signal. There is an anomaly with intervening light periods of 10 to 13 hours, following which time of maximum sensitivity is actually less than the usual 8 hours after dusk. Ability of the clock in Xanthium to be rephased, suspended, restarted, or delayed, depending always upon conditions of the experiment, is characteristic of an oscillating timer and may confer upon this plant its ability to respond to a single inductive cycle. It is suggested that phytochrome may influence only the phase of the clock and not other aspects of flowering such as synthesis of flowering hormone. PMID:16656693

Gravitational waves from dark first order phase transitions and dark photons

NASA Astrophysics Data System (ADS)

Addazi, Andrea; Marcianò, Antonino

2018-01-01

Cold Dark Matter particles may interact with ordinary particles through a dark photon, which acquires a mass thanks to a spontaneous symmetry breaking mechanism. We discuss a dark photon model in which the scalar singlet associated to the spontaneous symmetry breaking has an effective potential that induces a first order phase transition in the early Universe. Such a scenario provides a rich phenomenology for electron-positron colliders and gravitational waves interferometers, and may be tested in several different channels. The hidden first order phase transition implies the emission of gravitational waves signals, which may constrain the dark photon’s space of parameters. Compared limits from electron-positron colliders, astrophysics, cosmology and future gravitational waves interferometers such as eLISA, U-DECIGO and BBO are discussed. This highly motivates a cross-checking strategy of data arising from experiments dedicated to gravitational waves, meson factories, the International Linear Collider (ILC), the Circular Electron Positron Collider (CEPC) and other underground direct detection experiments of cold dark matter candidates. Supported by the Shanghai Municipality (KBH1512299) and Fudan University (JJH1512105)

First results from the DarkSide-50 dark matter experiment at Laboratori Nazionali del Gran Sasso

DOE PAGES

Agnes, P.

2015-03-11

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4 ± 0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter searchmore » for a (1422 ± 67) kg d exposure with an atmospheric argon fill. As a result, this is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1×10 -44 cm 2 for a WIMP mass of 100 Gev/c 2.« less

Specific dietary preferences are linked to differing gut microbial metabolic activity in response to dark chocolate intake.

PubMed

Martin, Francois-Pierre J; Montoliu, Ivan; Nagy, Kornél; Moco, Sofia; Collino, Sebastiano; Guy, Philippe; Redeuil, Karine; Scherer, Max; Rezzi, Serge; Kochhar, Sunil

2012-12-07

Systems biology approaches are providing novel insights into the role of nutrition for the management of health and disease. In the present study, we investigated if dietary preference for dark chocolate in healthy subjects may lead to different metabolic response to daily chocolate consumption. Using NMR- and MS-based metabolic profiling of blood plasma and urine, we monitored the metabolic response of 10 participants stratified as chocolate desiring and eating regularly dark chocolate (CD) and 10 participants stratified as chocolate indifferent and eating rarely dark chocolate (CI) to a daily consumption of 50 g of dark chocolate as part of a standardized diet over a one week period. We demonstrated that preference for chocolate leads to different metabolic response to chocolate consumption. Daily intake of dark chocolate significantly increased HDL cholesterol by 6% and decreased polyunsaturated acyl ether phospholipids. Dark chocolate intake could also induce an improvement in the metabolism of long chain fatty acid, as noted by a compositional change in plasma fatty acyl carnitines. Moreover, a relationship between regular long-term dietary exposure to a small amount of dark chocolate, gut microbiota, and phenolics was highlighted, providing novel insights into biological processes associated with cocoa bioactives.

Re-Examination of Globally Flat Space-Time

PubMed Central

Feldman, Michael R.

2013-01-01

In the following, we offer a novel approach to modeling the observed effects currently attributed to the theoretical concepts of “dark energy,” “dark matter,” and “dark flow.” Instead of assuming the existence of these theoretical concepts, we take an alternative route and choose to redefine what we consider to be inertial motion as well as what constitutes an inertial frame of reference in flat space-time. We adopt none of the features of our current cosmological models except for the requirement that special and general relativity be local approximations within our revised definition of inertial systems. Implicit in our ideas is the assumption that at “large enough” scales one can treat objects within these inertial systems as point-particles having an insignificant effect on the curvature of space-time. We then proceed under the assumption that time and space are fundamentally intertwined such that time- and spatial-translational invariance are not inherent symmetries of flat space-time (i.e., observable clock rates depend upon both relative velocity and spatial position within these inertial systems) and take the geodesics of this theory in the radial Rindler chart as the proper characterization of inertial motion. With this commitment, we are able to model solely with inertial motion the observed effects expected to be the result of “dark energy,” “dark matter,” and “dark flow.” In addition, we examine the potential observable implications of our theory in a gravitational system located within a confined region of an inertial reference frame, subsequently interpreting the Pioneer anomaly as support for our redefinition of inertial motion. As well, we extend our analysis into quantum mechanics by quantizing for a real scalar field and find a possible explanation for the asymmetry between matter and antimatter within the framework of these redefined inertial systems. PMID:24250790

Quantum many-body dynamics of dark solitons in optical lattices

NASA Astrophysics Data System (ADS)

Mishmash, R. V.; Danshita, I.; Clark, Charles W.; Carr, L. D.

2009-11-01

We present a fully quantum many-body treatment of dark solitons formed by ultracold bosonic atoms in one-dimensional optical lattices. Using time-evolving block decimation to simulate the single-band Bose-Hubbard Hamiltonian, we consider the quantum dynamics of density and phase engineered dark solitons as well as the quantum evolution of mean-field dark solitons injected into the quantum model. The former approach directly models how one may create quantum entangled dark solitons in experiment. While we have already presented results regarding the latter approach elsewhere [R. V. Mishmash and L. D. Carr, Phys. Rev. Lett. 103, 140403 (2009)], we expand upon those results in this work. In both cases, quantum fluctuations cause the dark soliton to fill in and may induce an inelasticity in soliton-soliton collisions. Comparisons are made to the Bogoliubov theory which predicts depletion into an anomalous mode that fills in the soliton. Our many-body treatment allows us to go beyond the Bogoliubov approximation and calculate explicitly the dynamics of the system’s natural orbitals.

Ultra Light Axionic Dark Matter: Galactic Halos and Implications for Observations with Pulsar Timing Arrays

NASA Astrophysics Data System (ADS)

de Martino, Ivan; Broadhurst, Tom; Tye, S.-H. Henry; Chiueh, Tzihong; Shive, Hsi-Yu; Lazkoz, Ruth

2018-01-01

The cold dark matter (CDM) paradigm successfully explains the cosmic structure over an enormous span of redshifts. However, it fails when probing the innermost regions of dark matter halos and the properties of the Milky Way's dwarf galaxy satellites. Moreover, the lack of experimental detection of Weakly Interacting Massive Particle (WIMP) favors alternative candidates such as light axionic dark matter that naturally arise in string theory. Cosmological N-body simulations have shown that axionic dark matter forms a solitonic core of size of ≃ 150 pc in the innermost region of the galactic halos. The oscillating scalar field associated to the axionic dark matter halo produces an oscillating gravitational potential that induces a time dilation of the pulse arrival time of ≃ 400 ns/(m_B/10^{-22} eV) for pulsar within such a solitonic core. Over the whole galaxy, the averaged predicted signal may be detectable with current and forthcoming pulsar timing array telescopes.

The inert doublet model in the light of Fermi-LAT gamma-ray data: a global fit analysis

NASA Astrophysics Data System (ADS)

Eiteneuer, Benedikt; Goudelis, Andreas; Heisig, Jan

2017-09-01

We perform a global fit within the inert doublet model taking into account experimental observables from colliders, direct and indirect dark matter searches and theoretical constraints. In particular, we consider recent results from searches for dark matter annihilation-induced gamma-rays in dwarf spheroidal galaxies and relax the assumption that the inert doublet model should account for the entire dark matter in the Universe. We, moreover, study in how far the model is compatible with a possible dark matter explanation of the so-called Galactic center excess. We find two distinct parameter space regions that are consistent with existing constraints and can simultaneously explain the excess: One with dark matter masses near the Higgs resonance and one around 72 GeV where dark matter annihilates predominantly into pairs of virtual electroweak gauge bosons via the four-vertex arising from the inert doublet's kinetic term. We briefly discuss future prospects to probe these scenarios.

Limits on Momentum-Dependent Asymmetric Dark Matter with CRESST-II.

PubMed

Angloher, G; Bento, A; Bucci, C; Canonica, L; Defay, X; Erb, A; Feilitzsch, F V; Ferreiro Iachellini, N; Gorla, P; Gütlein, A; Hauff, D; Jochum, J; Kiefer, M; Kluck, H; Kraus, H; Lanfranchi, J-C; Loebell, J; Münster, A; Pagliarone, C; Petricca, F; Potzel, W; Pröbst, F; Reindl, F; Schäffner, K; Schieck, J; Schönert, S; Seidel, W; Stodolsky, L; Strandhagen, C; Strauss, R; Tanzke, A; Trinh Thi, H H; Türkoğlu, C; Uffinger, M; Ulrich, A; Usherov, I; Wawoczny, S; Willers, M; Wüstrich, M; Zöller, A

2016-07-08

The usual assumption in direct dark matter searches is to consider only the spin-dependent or spin-independent scattering of dark matter particles. However, especially in models with light dark matter particles O(GeV/c^{2}), operators which carry additional powers of the momentum transfer q^{2} can become dominant. One such model based on asymmetric dark matter has been invoked to overcome discrepancies in helioseismology and an indication was found for a particle with a preferred mass of 3  GeV/c^{2} and a cross section of 10^{-37}  cm^{2}. Recent data from the CRESST-II experiment, which uses cryogenic detectors based on CaWO_{4} to search for nuclear recoils induced by dark matter particles, are used to constrain these momentum-dependent models. The low energy threshold of 307 eV for nuclear recoils of the detector used, allows us to rule out the proposed best fit value above.

Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current.

PubMed

DeRose, Christopher T; Trotter, Douglas C; Zortman, William A; Starbuck, Andrew L; Fisher, Moz; Watts, Michael R; Davids, Paul S

2011-12-05

We present a compact 1.3 × 4 μm2 Germanium waveguide photodiode, integrated in a CMOS compatible silicon photonics process flow. This photodiode has a best-in-class 3 dB cutoff frequency of 45 GHz, responsivity of 0.8 A/W and dark current of 3 nA. The low intrinsic capacitance of this device may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications.

Image-based Modeling of Biofilm-induced Calcium Carbonate Precipitation

NASA Astrophysics Data System (ADS)

Connolly, J. M.; Rothman, A.; Jackson, B.; Klapper, I.; Cunningham, A. B.; Gerlach, R.

2013-12-01

Pore scale biological processes in the subsurface environment are important to understand in relation to many engineering applications including environmental contaminant remediation, geologic carbon sequestration, and petroleum production. Specifically, biofilm induced calcium carbonate precipitation has been identified as an attractive option to reduce permeability in a lasting way in the subsurface. This technology may be able to replace typical cement-based grouting in some circumstances; however, pore-scale processes must be better understood for it to be applied in a controlled manor. The work presented will focus on efforts to observe biofilm growth and ureolysis-induced mineral precipitation in micro-fabricated flow cells combined with finite element modelling as a tool to predict local chemical gradients of interest (see figure). We have been able to observe this phenomenon over time using a novel model organism that is able to hydrolyse urea and express a fluorescent protein allowing for non-invasive observation over time with confocal microscopy. The results of this study show the likely existence of a wide range of local saturation indices even in a small (1 cm length scale) experimental system. Interestingly, the locations of high predicted index do not correspond to the locations of higher precipitation density, highlighting the need for further understanding. Figure 1 - A micro-fabricated flow cell containing biofilm-induced calcium carbonate precipitation. (A) Experimental results: Active biofilm is in green and dark circles are calcium carbonate crystals. Note the channeling behavior in the top of the image, leaving a large hydraulically inactive area in the biofilm mass. (B) Finite element model: The prediction of relative saturation of calcium carbonate (as calcite). Fluid enters the system at a low saturation state (blue) but areas of high supersaturation (red) are predicted within the hydraulically inactive area in the biofilm. If only effluent saturation was measured, precipitation may not even be predicted but we see local, pore-scale behavior dictating system behavior in this case. The flow cell is 1 cm in length and the porous media elements are 100 μm.

Rats fed only during the light period are resistant to stress-induced weight loss.

PubMed

Harris, Ruth B S; Zhou, Jun; Mitchell, Tiffany; Hebert, Sadie; Ryan, Donna H

2002-08-01

Repeated restraint stress (3 h/day for 3 days) causes a chronic down-regulation of body weight in rats. This study determined whether weight loss was influenced by the time of day that rats had access to food or that stress was applied. Groups of male Sprague-Dawley rats were fed a 40% kcal fat diet with food given ad libitum, only during the light phase or only during the dark phase. After 2 weeks of adaptation, rats within each feeding treatment were divided into four groups. One was exposed to repeated restraint at the start of the light phase, another was restrained at the start of the dark phase and the remaining groups were nonstressed controls for restrained rats. Body weight was significantly reduced in ad libitum- and dark-fed restrained rats, compared with nonstressed controls, from Day 2 of restraint, regardless of the time of day that they were stressed. There was no significant effect of restraint on weight change of light-fed rats. Food intake was inhibited by stress in ad libitum- and dark-fed rats, but it was not changed in light-fed rats. Serum corticosterone was increased by restraint in all rats irrespective of feeding schedule. This study demonstrates that stress-induced weight loss only occurs when rats have food available during their normal feeding period (dark phase) and is not determined by increased corticosterone release.

β-Glucan and dark chocolate: a randomized crossover study on short-term satiety and energy intake.

PubMed

Akyol, Asli; Dasgin, Halil; Ayaz, Aylin; Buyuktuncer, Zehra; Besler, H Tanju

2014-09-23

The aims of this study were to adapt a traditional recipe into a healthier form by adding 3 g of oat β-glucan, substituting milk chocolate to dark chocolate with 70% cocoa, and to examine the effect of these alterations on short-term satiety and energy intake. Study subjects (n = 25) were tested in a randomized, crossover design with four products closely matched for energy content. Four different versions of a traditional recipe including milk chocolate-control (CON), oat β-glucan (B-GLU), dark chocolate (DARK) or oat β-glucan and dark chocolate (B-GLU + DARK) were given to subjects on different test days. After subjects were asked to report visual analog scale (VAS) scores on sensory outcomes and related satiety for four hours ad libitum, lunch was served and energy intake of individuals was measured. VAS scores indicated that none of the test foods exerted an improved effect on satiety feelings. However, energy intake of individuals during ad libitum lunch was significantly lower in dark chocolate groups (CON: 849.46 ± 47.45 kcal versus DARK: 677.69 ± 48.45 kcal and B-GLU + DARK: 691.08 ± 47.45 kcal, p = 0.014). The study demonstrated that substituting dark chocolate for milk chocolate is more effective in inducing satiety during subsequent food intake in healthy subjects.

β-Glucan and Dark Chocolate: A Randomized Crossover Study on Short-Term Satiety and Energy Intake

PubMed Central

Akyol, Asli; Dasgin, Halil; Ayaz, Aylin; Buyuktuncer, Zehra; Besler, H. Tanju

2014-01-01

Aim: The aims of this study were to adapt a traditional recipe into a healthier form by adding 3 g of oat β-glucan, substituting milk chocolate to dark chocolate with 70% cocoa, and to examine the effect of these alterations on short-term satiety and energy intake. Materials and Methods: Study subjects (n = 25) were tested in a randomized, crossover design with four products closely matched for energy content. Four different versions of a traditional recipe including milk chocolate-control (CON), oat β-glucan (B-GLU), dark chocolate (DARK) or oat β-glucan and dark chocolate (B-GLU + DARK) were given to subjects on different test days. After subjects were asked to report visual analog scale (VAS) scores on sensory outcomes and related satiety for four hours ad libitum, lunch was served and energy intake of individuals was measured. Results: VAS scores indicated that none of the test foods exerted an improved effect on satiety feelings. However, energy intake of individuals during ad libitum lunch was significantly lower in dark chocolate groups (CON: 849.46 ± 47.45 kcal versus DARK: 677.69 ± 48.45 kcal and B-GLU + DARK: 691.08 ± 47.45 kcal, p = 0.014). Conclusion: The study demonstrated that substituting dark chocolate for milk chocolate is more effective in inducing satiety during subsequent food intake in healthy subjects. PMID:25251294

Irradiation-induced precipitation and mechanical properties of vanadium alloys at <430 C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, H.M.; Gazda, J.; Smith, D.L.

Recent attention to V-base alloys has focused on the effect of low-temperature (<430 C) irradiation on tensile and impact properties of V-4Cr-4Ti. In previous studies, dislocation channeling, which causes flow localization and severe loss of work-hardening capability, has been attributed to dense, irradiation-induced precipitation of very fine particles. However, efforts to identify the precipitates were unsuccessful until now. In this study, analysis by transmission electron microscopy (TEM) was conducted on unalloyed V, V-5Ti, V-3Ti-1Si, and V-4Cr-4Ti specimens that were irradiated at <430 C in conventional and dynamic helium charging experiments. By means of dark-field imaging and selected-area-diffraction analysis, the characteristicmore » precipitates were identified to be (V,Ti{sub 1{minus}x})(C,O,N). In V-3Ti-1Si, precipitation of (V,Ti{sub 1{minus}x})(C,O,N) was negligible at <430 C, and as a result, dislocation channeling did not occur and work-hardening capability was high.« less

Gravitationally neutral dark matter-dark antimatter universe crystal with epochs of decelerated and accelerated expansion

NASA Astrophysics Data System (ADS)

Gribov, I. A.; Trigger, S. A.

2016-11-01

A large-scale self-similar crystallized phase of finite gravitationally neutral universe (GNU)—huge GNU-ball—with spherical 2D-boundary immersed into an endless empty 3D- space is considered. The main principal assumptions of this universe model are: (1) existence of stable elementary particles-antiparticles with the opposite gravitational “charges” (M+gr and M -gr), which have the same positive inertial mass M in = |M ±gr | ≥ 0 and are equally presented in the universe during all universe evolution epochs; (2) the gravitational interaction between the masses of the opposite charges” is repulsive; (3) the unbroken baryon-antibaryon symmetry; (4) M+gr-M-gr “charges” symmetry, valid for two equally presented matter-antimatter GNU-components: (a) ordinary matter (OM)-ordinary antimatter (OAM), (b) dark matter (DM)-dark antimatter (DAM). The GNU-ball is weightless crystallized dust of equally presented, mutually repulsive (OM+DM) clusters and (OAM+DAM) anticlusters. Newtonian GNU-hydrodynamics gives the observable spatial flatness and ideal Hubble flow. The GNU in the obtained large-scale self-similar crystallized phase preserves absence of the cluster-anticluster collisions and simultaneously explains the observable large-scale universe phenomena: (1) the absence of the matter-antimatter clusters annihilation, (2) the self-similar Hubble flow stability and homogeneity, (3) flatness, (4) bubble and cosmic-net structures as 3D-2D-1D decrystallization phases with decelerative (a ≤ 0) and accelerative (a ≥ 0) expansion epochs, (5) the dark energy (DE) phenomena with Λ VACUUM = 0, (6) the DE and DM fine-tuning nature and predicts (7) evaporation into isolated huge M±gr superclusters without Big Rip.

Cerberus Wind Streaks

NASA Technical Reports Server (NTRS)

2002-01-01

(Released 6 May 2002) The Science Cerberus is a dark region on Mars that has shrunk down from a continuous length of about 1000 km to roughly three discontinuous spots a few 100 kms in length in less than 20 years. There are two competing processes at work in the Cerberus region that produce the bright and dark features seen in this THEMIS image. Bright dust settles out of the atmosphere, especially after global dust storms, depositing a layer just thick enough to brighten the dark surfaces. Deposition occurs preferentially in the low wind 'shadow zones' within craters and downwind of crater rims, producing the bright streaks. The direction of the streaks clearly indicates that the dominant winds come from the northeast. Dust deposition would completely blot out the dark areas if it were not for the action of wind-blown sand grains scouring the surface and lifting the dust back into the atmosphere. Again, the shadow zones are protected from the blowing sand, preserving the bright layer of dust. Also visible in this image are lava flow features extending from the flanks of the huge Elysium volcanoes to the northwest. Two shallow channels and a raised flow lobe are just barely discernable. The lava channel in the middle of the image crosses the boundary of the bright and dark surfaces without any obvious change in its morphology. This demonstrates that the bright dust layer is very thin in this location, perhaps as little as a few millimeters. The Story Mars is an ever-changing land of spectacular contrasts. This THEMIS image shows the Cerberus region of Mars, a dark area located near the Elysium volcanoes and fittingly named after the three-headed, dragon-tailed dog who guards the door of the underworld. Two opposing processes are at work here: a thin layer of dust falling from the atmosphere and/or dust storms creating brighter surface areas (e.g. the top left portion of this image) and dust being scoured away by the action of the Martian wind disturbing the sand grains and freeing the lighter dust to fly away once more (the darker portions of this image). There are, however, some darker areas that are somewhat shielded and protected from the wind that have yielded bright, dusty crater floors and wind streaks that trail out behind the craters. These wind streaks tell a story all their own as to the prevailing wind direction coming from the northeast. This, added to the fact that this dark region was once 1000 km in length and has dwindled to just a few isolated dark splotches of 100 kilometers in the past 20 years, help us to see that the Martian environment is still quite dynamic and capable of changing. Finally, this being a volcanic region, a lobe of a lava flow from the immense Elysium volcanoes to the northwest is visible stretching across the bottom one-quarter of the image.

Relative roles of temperature and photoperiod as drivers of metabolic flexibility in dark-eyed juncos.

PubMed

Swanson, David; Zhang, Yufeng; Liu, Jin-Song; Merkord, Christopher L; King, Marisa O

2014-03-15

Seasonal phenotypic flexibility in small birds produces a winter phenotype with elevated maximum cold-induced metabolic rates (=summit metabolism, Msum). Temperature and photoperiod are candidates for drivers of seasonal phenotypes, but their relative impacts on metabolic variation are unknown. We examined photoperiod and temperature effects on Msum, muscle masses and activities of key catabolic enzymes in winter dark-eyed juncos (Junco hyemalis). We randomly assigned birds to four treatment groups varying in temperature (cold=3°C; warm=24°C) and photoperiod [short day (SD)=8 h:16 h light:dark; long day (LD)=16 h:8 h light:dark] in a two-by-two design. We measured body mass (Mb), flight muscle width and Msum before and after 3 and 6 weeks of acclimation, and flight muscle and heart masses after 6 weeks. Msum increased for cold-exposed, but not for warm-exposed, birds. LD birds gained more Mb than SD birds, irrespective of temperature. Flight muscle size and mass did not differ significantly among groups, but heart mass was larger in cold-exposed birds. Citrate synthase, carnitine palmitoyl transferase and β-hydroxyacyl Co-A dehydrogenase activities in the pectoralis were generally higher for LD and cold groups. The cold-induced changes in Msum and heart mass parallel winter changes for small birds, but the larger Mb and higher catabolic enzyme activities in LD birds suggest photoperiod-induced changes associated with migratory disposition. Temperature appears to be a primary driver of flexibility in Msum in juncos, but photoperiod-induced changes in Mb and catabolic enzyme activities, likely associated with migratory disposition, interact with temperature to contribute to seasonal phenotypes.

Self-interacting spin-2 dark matter

NASA Astrophysics Data System (ADS)

Chu, Xiaoyong; Garcia-Cely, Camilo

2017-11-01

Recent developments in bigravity allow one to construct consistent theories of interacting spin-2 particles that are free of ghosts. In this framework, we propose an elementary spin-2 dark matter candidate with a mass well below the TeV scale. We show that, in a certain regime where the interactions induced by the spin-2 fields do not lead to large departures from the predictions of general relativity, such a light dark matter particle typically self-interacts and undergoes self-annihilations via 3-to-2 processes. We discuss its production mechanisms and also identify the regions of the parameter space where self-interactions can alleviate the discrepancies at small scales between the predictions of the collisionless dark matter paradigm and cosmological N-body simulations.

The Higgs seesaw induced neutrino masses and dark matter

DOE PAGES

Cai, Yi; Chao, Wei

2015-08-12

In this study we propose a possible explanation of the active neutrino Majorana masses with the TeV scale new physics which also provide a dark matter candidate. We extend the Standard Model (SM) with a local U(1)' symmetry and introduce a seesaw relation for the vacuum expectation values (VEVs) of the exotic scalar singlets, which break the U(1)' spontaneously. The larger VEV is responsible for generating the Dirac mass term of the heavy neutrinos, while the smaller for the Majorana mass term. As a result active neutrino masses are generated via the modified inverse seesaw mechanism. The lightest of themore » new fermion singlets, which are introduced to cancel the U(1)' anomalies, can be a stable particle with ultra flavor symmetry and thus a plausible dark matter candidate. We explore the parameter space with constraints from the dark matter relic abundance and dark matter direct detection.« less

Cooling Flows

NASA Astrophysics Data System (ADS)

Fabian, A.; Murdin, P.

2000-11-01

A subsonic cooling flow occurs when the hot gaseous atmosphere of a galaxy, group or cluster of galaxies cools slowly. Such atmospheres occur as a result of gas having fallen into the DARK MATTER well of the object and heated by gravitational energy release. A dominant cooling process is the emission of radiation by the gas. As cooling proceeds the gas sinks further in the potential well, giving ...

First Imaging Results from the Iapetus B/C Flyby of the Cassini Spacecraft

NASA Technical Reports Server (NTRS)

Denk, T.; Neukum, G.; Roatsch, T.; McEwen, A. S.; Turtle, E. P.; Thomas, P. C.; Helfenstein, P.; Wagner, R. J.; Porco, C.C.; Perry, J. E.

2005-01-01

The first of two relatively close Iapetus flybys in Cassini's primary mission occured on Dec 31, 2004 18:49 UTC near apoapsis from orbit "B" to "C" at an altitude of approximately 123,400 km over the northern leading hemisphere, resulting in a minimum pixel scale of 740 m for the ISS narrow angle camera (NAC). Data revealed details of a greater than 1300-km-long ridge that had been discovered just one week earlier in optical navigation images. Individual mountains within the western part of the ridge reach heights of approximately 20 km over surrounding terrain. The data set provides constraints on the origin of the albedo dichotomy. It appears very likely that the dark material is overlying an ice crust, but no evidence for emplacement of dark material via surface flows is apparent. Instead, signs for dark-material emplacement through processes that included ballistic transportation are visible. No bright-floor ("punch-through") craters have been found on the dark hemisphere. The ridge discovery may revive the idea of an endogenic origin of the dark side.

Characterization of electrically-active defects in ultraviolet light-emitting diodes with laser-based failure analysis techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Mary A.; Tangyunyong, Paiboon; Cole, Edward I.

2016-01-14

Laser-based failure analysis techniques demonstrate the ability to quickly and non-intrusively screen deep ultraviolet light-emitting diodes (LEDs) for electrically-active defects. In particular, two laser-based techniques, light-induced voltage alteration and thermally-induced voltage alteration, generate applied voltage maps (AVMs) that provide information on electrically-active defect behavior including turn-on bias, density, and spatial location. Here, multiple commercial LEDs were examined and found to have dark defect signals in the AVM indicating a site of reduced resistance or leakage through the diode. The existence of the dark defect signals in the AVM correlates strongly with an increased forward-bias leakage current. This increased leakage ismore » not present in devices without AVM signals. Transmission electron microscopy analysis of a dark defect signal site revealed a dislocation cluster through the pn junction. The cluster included an open core dislocation. Even though LEDs with few dark AVM defect signals did not correlate strongly with power loss, direct association between increased open core dislocation densities and reduced LED device performance has been presented elsewhere [M. W. Moseley et al., J. Appl. Phys. 117, 095301 (2015)].« less

Characterization of electrically-active defects in ultraviolet light-emitting diodes with laser-based failure analysis techniques

DOE PAGES

Miller, Mary A.; Tangyunyong, Paiboon; Edward I. Cole, Jr.

2016-01-12

In this study, laser-based failure analysis techniques demonstrate the ability to quickly and non-intrusively screen deep ultraviolet light-emitting diodes(LEDs) for electrically-active defects. In particular, two laser-based techniques, light-induced voltage alteration and thermally-induced voltage alteration, generate applied voltage maps (AVMs) that provide information on electrically-active defect behavior including turn-on bias, density, and spatial location. Here, multiple commercial LEDs were examined and found to have dark defect signals in the AVM indicating a site of reduced resistance or leakage through the diode. The existence of the dark defect signals in the AVM correlates strongly with an increased forward-bias leakage current. This increasedmore » leakage is not present in devices without AVM signals. Transmission electron microscopyanalysis of a dark defect signal site revealed a dislocation cluster through the pn junction. The cluster included an open core dislocation. Even though LEDs with few dark AVM defect signals did not correlate strongly with power loss, direct association between increased open core dislocation densities and reduced LED device performance has been presented elsewhere [M. W. Moseley et al., J. Appl. Phys. 117, 095301 (2015)].« less

Lidar and radar measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study: observations of dark and bright band phenomena

NASA Astrophysics Data System (ADS)

di Girolamo, P.; Summa, D.; Bhawar, R.; di Iorio, T.; Norton, E. G.; Peters, G.; Dufournet, Y.

2011-11-01

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark and bright bands were observed by the University of BASILicata Raman lidar system (BASIL) during several intensive (IOPs) and special (SOPs) observation periods (among others, 23 July, 15 August, and 17 August 2007). Lidar data were supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Results from BASIL and the radars for 23 July 2007 are illustrated and discussed to support the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar and radar dark and bright bands. Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE.

Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra

USGS Publications Warehouse

Baines, K.H.; Delitsky, M.L.; Momary, T.W.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

2009-01-01

Thunderstorm activity on Saturn is associated with optically detectable clouds that are atypically dark throughout the near-infrared. As observed by Cassini/VIMS, these clouds are ~20% less reflective than typical neighboring clouds throughout the spectral range from 0.8 ??m to at least 4.1 ??m. We propose that active thunderstorms originating in the 10-20 bar water-condensation region vertically transport dark materials at depth to the ~1 bar level where they can be observed. These materials in part may be produced by chemical processes associated with lightning, likely within the water clouds near the ~10 bar freezing level of water, as detected by the electrostatic discharge of lightning flashes observed by Cassini/RPWS (e.g., Fischer et al. 2008, Space Sci. Rev., 137, 271-285). We review lightning-induced pyrolytic chemistry involving a variety of Saturnian constituents, including hydrogen, methane, ammonia, hydrogen sulfide, phosphine, and water. We find that the lack of absorption in the 1-2 ??m spectral region by lightning-generated sulfuric and phosphorous condensates renders these constituents as minor players in determining the color of the dark storm clouds. Relatively small particulates of elemental carbon, formed by lightning-induced dissociation of methane and subsequently upwelled from depth - perhaps embedded within and on the surface of spectrally bright condensates such as ammonium hydrosulfide or ammonia - may be a dominant optical material within the dark thunderstorm-related clouds of Saturn. ?? 2009 Elsevier Ltd. All rights reserved.

System-on-fluidics immunoassay device integrating wireless radio-frequency-identification sensor chips.

PubMed

Yazawa, Yoshiaki; Oonishi, Tadashi; Watanabe, Kazuki; Shiratori, Akiko; Funaoka, Sohei; Fukushima, Masao

2014-09-01

A simple and sensitive point-of-care-test (POCT) device for chemiluminescence (CL) immunoassay was devised and tested. The device consists of a plastic flow-channel reactor and two wireless-communication sensor chips, namely, a photo-sensor chip and a temperature-sensor chip. In the flow-channel reactor, a target antigen is captured by an antibody immobilized on the inner wall of the flow-channel and detected with enzyme labeled antibody by using CL substrate. The CL signal corresponding to the amount of antigen is measured by a newly developed radio-frequency-identification (RFID) sensor, which enables batteryless operation and wireless data communication with an external reader. As for the POCT device, its usage environment, especially temperature, varies for each measurement. Hence, temperature compensation is a key issue in regard to eliminating dark-signal fluctuation, which is a major factor in deterioration of the precision of the POCT device. A two-stage temperature-compensation scheme was adopted. As for the first stage, the signals of two photodiodes, one with an open window and one with a sealed window, integrated on the photo-sensor chip are differentiated to delete the dark signal. As for the second stage, the differentiated signal fluctuation caused by a temperature variation is compensated by using the other sensor chip (equipped with a temperature sensor). The dark-level fluctuation caused by temperature was reduced from 0.24 to 0.02 pA/°C. The POCT device was evaluated as a CL immunoassay of thyroid-stimulating hormone (TSH). The flow rate of the CL reagent in the flow channel was optimized. As a result, the detection limit of the POCT device was 0.08 ng/ml (i.e., 0.4 μIU/ml). Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

[Molecular responses of photosynthetic apparatus of plants to long term irradiance changes].

PubMed

Adamiec, Małgorzata; Jackowski, Grzegorz

2008-01-01

In response to long term (at least 1-3 h) irradiance changes the responses are elicited at the level of structure and function of photosynthetic apparatus of plants which are thought to be aimed to keep the balance between the level of excitation energy funneled to the reaction centers of the photosystems by energetic antennae and the utilization of this energy in the form of photosynthetic electron transfer and dark reactions. At high vs medium irradiances the rate of excitation energy transfer via LHCII is reduced while the rate of electron flow and photosynthetic dark reactions is increased. The reaction at LHCII level stems from the reduction of its pool per PSII reaction center and the regulatory events comprise changes in the expression of LHCII apoproteins and/or chi b biosynthesis. The basis for higher electron flow capabilities lies in significant increases in the content of some electron carriers and the catalytic activity of ATP synthase. The upregulation of photosynthetic dark reaction in turn is due to the activation of signaling pathways leading to the increase in the pool and catalytic activities of rubisco and other Calvin cycle enzymes.

The veto system of the DarkSide-50 experiment

DOE PAGES

Agnes, P.

2016-03-16

Here, nuclear recoil events produced by neutron scatters form one of the most important classes of background in WIMP direct detection experiments, as they may produce nuclear recoils that look exactly like WIMP interactions. In DarkSide-50, we both actively suppress and measure the rate of neutron-induced background events using our neutron veto, composed of a boron-loaded liquid scintillator detector within a water Cherenkov detector. This paper is devoted to the description of the neutron veto system of DarkSide-50, including the detector structure, the fundamentals of event reconstruction and data analysis, and basic performance parameters.

The veto system of the DarkSide-50 experiment

NASA Astrophysics Data System (ADS)

Agnes, P.; Agostino, L.; Albuquerque, I. F. M.; Alexander, T.; Alton, A. K.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Bottino, B.; Brigatti, A.; Brodsky, J.; Budano, F.; Bussino, S.; Cadeddu, M.; Cadonati, L.; Cadoni, M.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Carlini, M.; Catalanotti, S.; Cavalcante, P.; Chepurnov, A.; Cocco, A. G.; Covone, G.; Crippa, L.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Cecco, S.; De Deo, M.; De Vincenzi, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Foster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Giganti, C.; Goretti, A. M.; Granato, F.; Grandi, L.; Gromov, M.; Guan, M.; Guardincerri, Y.; Hackett, B. R.; Herner, K. R.; Hungerford, E. V.; Ianni, Aldo; Ianni, Andrea; James, I.; Johnson, T.; Jollet, C.; Keeter, K.; Kendziora, C. L.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Li, X.; Lissia, M.; Lombardi, P.; Luitz, S.; Ma, Y.; Machulin, I. N.; Mandarano, A.; Mari, S. M.; Maricic, J.; Marini, L.; Martoff, C. J.; Meregaglia, A.; Meyers, P. D.; Miletic, T.; Milincic, R.; Montanari, D.; Monte, A.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B. J.; Muratova, V. N.; Musico, P.; Napolitano, J.; Nelson, A.; Odrowski, S.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D. A.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Renshaw, A. L.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, S.; Savarese, C.; Segreto, E.; Semenov, D. A.; Shields, E.; Singh, P. N.; Skorokhvatov, M. D.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Trinchese, P.; Unzhakov, E. V.; Vishneva, A.; Vogelaar, R. B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, J.; Wojcik, M. M.; Xiang, X.; Xu, J.; Yang, C.; Yoo, J.; Zavatarelli, S.; Zec, A.; Zhong, W.; Zhu, C.; Zuzel, G.

2016-03-01

Nuclear recoil events produced by neutron scatters form one of the most important classes of background in WIMP direct detection experiments, as they may produce nuclear recoils that look exactly like WIMP interactions. In DarkSide-50, we both actively suppress and measure the rate of neutron-induced background events using our neutron veto, composed of a boron-loaded liquid scintillator detector within a water Cherenkov detector. This paper is devoted to the description of the neutron veto system of DarkSide-50, including the detector structure, the fundamentals of event reconstruction and data analysis, and basic performance parameters.

"Dark energy" in the Local Void

NASA Astrophysics Data System (ADS)

Villata, M.

2012-05-01

The unexpected discovery of the accelerated cosmic expansion in 1998 has filled the Universe with the embarrassing presence of an unidentified "dark energy", or cosmological constant, devoid of any physical meaning. While this standard cosmology seems to work well at the global level, improved knowledge of the kinematics and other properties of our extragalactic neighborhood indicates the need for a better theory. We investigate whether the recently suggested repulsive-gravity scenario can account for some of the features that are unexplained by the standard model. Through simple dynamical considerations, we find that the Local Void could host an amount of antimatter (˜5×1015 M ⊙) roughly equivalent to the mass of a typical supercluster, thus restoring the matter-antimatter symmetry. The antigravity field produced by this "dark repulsor" can explain the anomalous motion of the Local Sheet away from the Local Void, as well as several other properties of nearby galaxies that seem to require void evacuation and structure formation much faster than expected from the standard model. At the global cosmological level, gravitational repulsion from antimatter hidden in voids can provide more than enough potential energy to drive both the cosmic expansion and its acceleration, with no need for an initial "explosion" and dark energy. Moreover, the discrete distribution of these dark repulsors, in contrast to the uniformly permeating dark energy, can also explain dark flows and other recently observed excessive inhomogeneities and anisotropies of the Universe.

Increase in nitrate uptake by soybean plants during interruption of the dark period with low intensity light

NASA Technical Reports Server (NTRS)

Raper, C. D. Jr; Vessey, J. K.; Henry, L. T.

1991-01-01

Diurnal patterns of net NO3- uptake by nonnodulated soybean [Glycine max (L.) Merr. cv. Ransom] plants growing in flowing hydroponic culture at 26 and 16 degrees C root temperatures were measured at hourly intervals during alternate days of a 12-day growth period. Ion chromatography was used to determine removal of NO3- from the culture solution. Day and night periods of 9 and 15 h were used during growth. The night period included two 6-h dark periods and an intervening 3-h period of night interruption by incandescent lamps to effect a long-day photoperiod and repress floral initiation. At both root temperatures, the average specific rates of NO3- uptake were twice as great during the night interruption period as during the day period; they were greater during the day period than during the dark periods; and they were greater during the dark period immediately following the day period than during the later dark period that followed the night interruption. While these average patterns were repetitious among days, measured rates of uptake varied hourly and included intervals of net efflux scattered through the day period and more frequently through the 2 dark periods. Root temperature did not affect the average daily specific rates of uptake or the qualitative relationships among day, dark and night interruption periods of the diurnal cycle.

Low-frequency electroacupuncture suppresses focal epilepsy and improves epilepsy-induced sleep disruptions.

PubMed

Yi, Pei-Lu; Lu, Chin-Yu; Jou, Shuo-Bin; Chang, Fang-Chia

2015-07-07

The positive effects of acupuncture at Feng-Chi acupoints on treating epilepsy and insomnia have been well-documented in ancient Chinese literature. However, there is a lack of scientific evidence to elucidate the underlying mechanisms behind these effects. Our previous study demonstrated that high-frequency (100 Hz) electroacupuncture (EA) at Feng-Chi acupoints deteriorates both pilocarpine-induced focal epilepsy and sleep disruptions. This study investigated the effects of low-frequency (10 Hz) EA on epileptic activities and epilepsy-induced sleep disruptions. In rats, the Feng-Chi acupoint is located 3 mm away from the center of a line between the two ears. Rats received 30 min of 10 Hz EA stimuli per day before each day's dark period for three consecutive days. Our results indicated that administration of pilocarpine into the left CeA at the beginning of the dark period induced focal epilepsy and decreased both rapid eye movement (REM) sleep and non-REM (NREM) sleep during the consequent light period. Low-frequency (10 Hz) EA at Feng-Chi acupoints suppressed pilocarpine-induced epileptiform EEGs, and this effect was in turn blocked by naloxone (a broad-spectrum opioid receptor antagonist), but not by naloxonazine (a μ-receptor antagonist), naltrindole (a δ-receptor antagonist) and nor-binaltorphimine (a κ-receptor antagonist). Ten Hz EA enhanced NREM sleep during the dark period, and this enhancement was blocked by all of the opioid receptor antagonists. On the other hand, 10 Hz EA reversed pilocarpine-induced NREM suppression during the light period, and the EA's effect on the sleep disruption was only blocked by naloxonazine. These results indicate that low-frequency EA stimulation of Feng-Chi acupoints is beneficial in improving epilepsy and epilepsy-induced sleep disruptions, and that opioid receptors in the CeA mediate EA's therapeutic effects.

The inhibition of nitric oxide-activated poly(ADP-ribose) synthetase attenuates transsynaptic alteration of spinal cord dorsal horn neurons and neuropathic pain in the rat.

PubMed

Mao, J; Price, D D; Zhu, J; Lu, J; Mayer, D J

1997-09-01

Transsynaptic alteration of spinal cord dorsal horn neurons characterized by hyperchromatosis of cytoplasm and nucleoplasm (so-called 'dark' neurons) occurs in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the common sciatic nerve. The incidence of dark neurons in CCI rats has been proposed to be mediated by glutamate-induced neurotoxicity. In the present study, we examined whether the inhibition of the nitric oxide (NO)-activated poly(ADP-ribose) synthetase (PARS), a nuclear enzyme critical to glutamate-induced neurotoxicity, would both reduce the incidence of dark neurons and attenuate behavioral manifestations of neuropathic pain in CCI rats. Dark neurons were observed bilaterally (with ipsilateral predominance) within the spinal cord dorsal horn, particularly in laminae I-II, of rats 8 days after unilateral sciatic nerve ligation as compared to sham operated rats. The number of dark neurons in the dorsal horn was dose-dependently reduced in CCI rats receiving once daily intrathecal (i.t.) treatment with the PARS inhibitor benzamide (200 or 400 nmol, but not 100 nmol benzamide or saline) for 7 days. Consistent with the histological improvement, thermal hyperalgesia, mechanical hyperalgesia, and low threshold mechano-allodynia also were reliably reduced in CCI rats treated with either 200 or 400 nmol benzamide. Neither dark neurons nor neuropathic pain behaviors were reliably affected by i.t. administration of either 800 nmol novobiocin (a mono(ADP-ribose) synthetase) or 800 nmol benzoic acid (the backbone structure of benzamide), indicating a selective effect of benzamide. Intrathecal treatment with an NO synthase inhibitor NG-nitro-L-arginine methyl ester (40 nmol, but not its inactive D-isomer) utilizing the same benzamide treatment regimen resulted in similar reductions of both dark neurons and neuropathic pain behaviors in CCI rats. These results provide, for the first time, in vivo evidence indicating that benzamide is neuroprotective and that the PARS-mediated transsynaptic alteration of spinal cord dorsal horn neurons contributes to behavioral manifestations of neuropathic pain in CCI rats. These observations may have general implications beyond treatment of neuropathic pain in that PARS-mediated neuronal alterations may play a significant role in glutamate-mediated neurotoxicity under many other circumstances.

Transcriptomics reveals the molecular processes of light-induced rapid darkening of the non-obligate cave dweller Oreolalax rhodostigmatus (Megophryidae, Anura) and their genetic basis of pigmentation strategy.

PubMed

Zhu, Wei; Liu, Lusha; Wang, Xungang; Gao, Xinyu; Jiang, Jianping; Wang, Bin

2018-05-31

Vertebrates use different pigmentation strategies to adapt to various environments. A large amount of research has been done on disclosing the mechanisms of pigmentation strategies in vertebrates either under light, or, living in constant darkness. However, less attention has been paid to non-obligate, darkness dwellers. Red-spotted toothed toads Oreolalax rhodostigmatus (Megophryidae; Anura) from the karst mountainous region of southwestern China are non-obligate cave dwellers. Most tadpoles of the species possess transparent skin as they inhabit the dark karst caves. But remarkably, the transparent tadpoles can darken just within 15 h once exposed to light. Obviously, it is very significant to reveal molecular mechanisms of the unexpected rapid-darkening phenomenon. We compared the transcriptomes of O. rhodostigmatus tadpoles with different durations of light exposure to investigate the cellular processes and potential regulation signals for their light-induced rapid darkening. Genes involved in melanogenesis (i.e. TYR, TYRP1 and DCT) and melanocyte proliferation, as well as their transcriptional factor (MITF), showed light-induced transcription, suggesting a dominating role of morphological color change (MCC) in this process. Transcription of genes related to growth factor, MAPK and PI3K-Akt pathways increased with time of light exposure, suggesting that light could induce significant growth signal, which might facilitate the rapid skin darkening. Most importantly, an in-frame deletion of four residues was identified in O. rhodostigmatus melanocortin-1 receptor (MC1R), a critical receptor in MCC. This deletion results in a more negatively charged ligand pocket with three stereo-tandem aspartate residues. Such structural changes likely decrease the constitutive activity of MC1R, but increase its ligands-dependent activity, thus coordinating pigment regression and rapid melanogenesis in the dark and light, respectively. Our study suggested that rapid MCC was responsible for the light-induced rapid darkening of O. rhodostigmatus tadpoles. Genetic mutations of MC1R in them could explain how these non-obligate cave dwellers coordinate pigment regression and robust melanogenesis in darkness and light, respectively. To our knowledge, this is the first study that reports the association between pigmentation phenotype adaptation and MC1R mutations in amphibians and/or in non-obligate cave dwellers.

Current Status of the dark matter experiment DarkSide-50

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marini, L.; Pagani, Ioanna; Agnes, P.

2016-07-12

DarkSide-50 is a dark matter direct search experiment at LNGS, searching for rare nuclear recoils possibly induced by WIMPs. It has two nested vetoes and a dual phase liquid argon TPC as dark matter detector. Key features of this experiment are the use of underground argon as radio-pure target and of muon and neutron active vetoes to suppress the background. The first data-taking campaign was running from November 2013 to April 2015 with an atmospheric argon target and a reduced efficiency neutron veto due to internal contamination. However, an upper limit on the WIMP-nucleon cross section of 6.1×10-44 cm2 atmore » 90% CL was obtained for a WIMP mass of 100 GeV/c2 and an exposure of (1422 ± 67) kg·d. At present DarkSide-50 started a 3 years run, intended to be background-free because the neutron veto was successfully recovered and underground argon replaced the atmospheric one. Additionally calibration campaigns for both the TPC and the neutron veto were completed. Thanks to the good performance of the background rejection, the results obtained so far suggest the scalability of DarkSide-50 to a ton-scale detector, which will play a key role into the dark matter search scenario.« less

A fresh look into the interacting dark matter scenario

NASA Astrophysics Data System (ADS)

Escudero, Miguel; Lopez-Honorez, Laura; Mena, Olga; Palomares-Ruiz, Sergio; Villanueva-Domingo, Pablo

2018-06-01

The elastic scattering between dark matter particles and radiation represents an attractive possibility to solve a number of discrepancies between observations and standard cold dark matter predictions, as the induced collisional damping would imply a suppression of small-scale structures. We consider this scenario and confront it with measurements of the ionization history of the Universe at several redshifts and with recent estimates of the counts of Milky Way satellite galaxies. We derive a conservative upper bound on the dark matter-photon elastic scattering cross section of σγ DM < 8 × 10‑10 σT (mDM/GeV) at 95% CL, about one order of magnitude tighter than previous constraints from satellite number counts. Due to the strong degeneracies with astrophysical parameters, the bound on the dark matter-photon scattering cross section derived here is driven by the estimate of the number of Milky Way satellite galaxies. Finally, we also argue that future 21 cm probes could help in disentangling among possible non-cold dark matter candidates, such as interacting and warm dark matter scenarios. Let us emphasize that bounds of similar magnitude to the ones obtained here could be also derived for models with dark matter-neutrino interactions and would be as constraining as the tightest limits on such scenarios.

Current status of the dark matter experiment DarkSide-50

NASA Astrophysics Data System (ADS)

Marini, L.; Pagani, L.; Agnes, P.; Alexander, T.; Alton, A.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Cadonati, L.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; Cocco, A. G.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Deo, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M. Y.; Guardincerri, Y.; Hackett, B.; Herner, K.; Humble, P.; Hungerford, E. V.; Ianni, Al.; Ianni, An.; Jollet, C.; Keeter, K.; Kendziora, C.; Kidner, S.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kurlej, A.; Li, P. X.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Ma, Y. Q.; Machulin, I.; Mandarano, A.; Mari, S.; Maricic, J.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P. D.; Milincic, R.; Montanari, D.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Musico, P.; Nelson, A.; Odrowski, S.; Okounkova, M.; Orsini, M.; Ortica, F.; Pallavicini, M.; Pantic, E.; Papp, L.; Parmeggiano, S.; Parsells, R.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Renshaw, A.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, S.; Segreto, E.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, S.; Wojcik, M.; Wright, A.; Xiang, X.; Xu, J.; Yang, C. G.; Yoo, J.; Zavatarelli, S.; Zec, A.; Zhu, C.; Zuzel, G.; DarkSide Collaboration

2016-01-01

DarkSide-50 is a dark matter direct search experiment at LNGS, searching for rare nuclear recoils possibly induced by WIMPs. It has two nested vetoes and a dual phase liquid argon TPC as dark matter detector. Key features of this experiment are the use of underground argon as radio-pure target and of muon and neutron active vetoes to suppress the background. The first data-taking campaign was running from November 2013 to April 2015 with an atmospheric argon target and a reduced efficiency neutron veto due to internal contamination. However, an upper limit on the WIMP-nucleon cross section of 6.1×10-44 cm2 at 90% CL was obtained for a WIMP mass of 100 GeV/c2 and an exposure of (1422±67) kg . d . At present DarkSide-50 started a 3 years run, intended to be background-free because the neutron veto was successfully recovered and underground argon replaced the atmospheric one. Additionally calibration campaigns for both the TPC and the neutron veto were completed. Thanks to the good performance of the background rejection, the results obtained so far suggest the scalability of DarkSide-50 to a ton-scale detector, which will play a key role into the dark matter search scenario.

The DarkSide experiment

NASA Astrophysics Data System (ADS)

Bottino, B.; Aalseth, C. E.; Acconcia, G.; Acerbi, F.; Agnes, P.; Agostino, L.; Albuquerque, I. F. M.; Alexander, T.; Alton, A.; Ampudia, P.; Ardito, R.; Arisaka, K.; Arnquist, I. J.; Asner, D. M.; Back, H. O.; Baldin, B.; Batignani, G.; Biery, K.; Bisogni, M. G.; Bocci, V.; Bondar, A.; Bonfini, G.; Bonivento, W.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Bunker, R.; Bussino, S.; Buttafava, M.; Buzulutskov, A.; Cadeddu, M.; Cadoni, M.; Calandri, N.; Calaprice, F.; Calvo, J.; Campajola, L.; Canci, N.; Candela, A.; Cantini, C.; Cao, H.; Caravati, M.; Cariello, M.; Carlini, M.; Carpinelli, M.; Castellani, A.; Catalanotti, S.; Cavalcante, P.; Chepurnov, A.; Cicalò, C.; Citterio, M.; Cocco, A. G.; Corgiolu, S.; Covone, G.; Crivelli, P.; D'Angelo, D.; D'Incecco, M.; Daniel, M.; Davini, S.; De Cecco, S.; De Deo, M.; De Guido, G.; De Vincenzi, M.; Demontis, P.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Dolgov, A.; Dromia, I.; Dussoni, S.; Edkins, E.; Empl, A.; Fan, A.; Ferri, A.; Filip, C. O.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Froudakis, G. E.; Gabriele, F.; Gabrieli, A.; Galbiati, C.; Gendotti, A.; Ghioni, M.; Ghisi, A.; Giagu, S.; Gibertoni, G.; Giganti, C.; Giorgi, M.; Giovannetti, G. K.; Gligan, M. L.; Gola, A.; Goretti, A.; Granato, F.; Grassi, M.; Grate, J. W.; Gromov, M.; Guan, M.; Guardincerri, Y.; Gulinatti, A.; Haaland, R. K.; Hackett, B.; Harrop, B.; Herner, K.; Hoppe, E. W.; Horikawa, S.; Hungerford, E.; Ianni, Al.; Ianni, An.; Ivashchuk, O.; James, I.; Johnson, T. N.; Jollet, C.; Keeter, K.; Kendziora, C.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Kuss, M. W.; Lissia, M.; Li, X.; Lodi, G. U.; Lombardi, P.; Longo, G.; Loverre, P.; Luitz, S.; Lussana, R.; Luzzi, L.; Ma, Y.; Machado, A. A.; Machulin, I.; Mais, L.; Mandarano, A.; Mapelli, L.; Marcante, M.; Mari, S.; Mariani, M.; Maricic, J.; Marinelli, M.; Marini, L.; Martoff, C. J.; Mascia, M.; Meregaglia, A.; Meyers, P. D.; Miletic, T.; Milincic, R.; Miller, J. D.; Moioli, S.; Monasterio, S.; Montanari, D.; Monte, A.; Montuschi, M.; Monzani, M. E.; Morrocchi, M.; Mosteiro, P.; Mount, B.; Mu, W.; Muratova, V. N.; Murphy, S.; Musico, P.; Napolitano, J.; Nelson, A.; Nosov, V.; Nurakhov, N. N.; Odrowski, S.; Oleinik, A.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Palmas, S.; Pantic, E.; Paoloni, E.; Parmeggiano, S.; Paternoster, G.; Pazzona, F.; Pelczar, K.; Pellegrini, L. A.; Pelliccia, N.; Perasso, S.; Peronio, P.; Perotti, F.; Perruzza, R.; Piemonte, C.; Pilo, F.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Radics, B.; Randle, K.; Ranucci, G.; Razeti, M.; Razeto, A.; Rech, I.; Regazzoni, V.; Regenfus, C.; Reinhold, B.; Renshaw, A.; Rescigno, M.; Ricotti, M.; Riffard, Q.; Rizzardini, S.; Romani, A.; Romero, L.; Rossi, B.; Rossi, N.; Rountree, D.; Rubbia, A.; Ruggeri, A.; Sablone, D.; Saggese, P.; Salatino, P.; Salemme, L.; Sands, W.; Sangiorgio, S.; Sant, M.; Santorelli, R.; Sanzaro, M.; Savarese, C.; Sechi, E.; Segreto, E.; Semenov, D.; Shchagin, A.; Shekhtman, L.; Shemyakina, E.; Shields, E.; Simeone, M.; Singh, P. N.; Skorokhvatov, M.; Smallcomb, M.; Smirnov, O.; Sokolov, A.; Sotnikov, A.; Stanford, C.; Suffritti, G. B.; Suvorov, Y.; Tamborini, D.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Tosi, A.; Trinchese, P.; Unzhakov, E.; Vacca, A.; Verducci, M.; Viant, T.; Villa, F.; Vishneva, A.; Vogelaar, B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, S.; Wilhelmi, J.; Wojcik, M.; Wu, S.; Xiang, X.; Xu, J.; Yang, C.; Yoo, J.; Zappa, F.; Zappalà, G.; Zavatarelli, S.; Zec, A.; Zhong, W.; Zhu, C.; Zullo, A.; Zullo, M.; Zuzel, G.

2017-01-01

DarkSide is a dark matter direct search experiment at Laboratori Nazionali del Gran Sasso (LNGS). DarkSide is based on the detection of rare nuclear recoils possibly induced by hypothetical dark matter particles, which are supposed to be neutral, massive (m>10{ GeV}) and weakly interactive (WIMP). The dark matter detector is a two-phase time projection chamber (TPC) filled with ultra-pure liquid argon. The TPC is placed inside a muon and a neutron active vetoes to suppress the background. Using argon as active target has many advantages, the key features are the strong discriminant power between nuclear and electron recoils, the spatial reconstruction and easy scalability to multi-tons size. At the moment DarkSide-50 is filled with ultra-pure argon, extracted from underground sources, and from April 2015 it is taking data in its final configuration. When combined with the preceding search with an atmospheric argon target, it is possible to set a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 2.0×10^{-44} cm ^2 for a WIMP mass of 100 GeV/ c^2 . The next phase of the experiment, DarkSide-20k, will be the construction of a new detector with an active mass of ˜20 tons.

Gabaculine does not inhibit cytokinin-stimulated biosynthesis of chlorophyll in Pinus nigra seedlings in the dark.

PubMed

Drazic; Bogdanovic

2000-05-15

Chlorophyll (Chl) accumulation was monitored during black pine (Pinus nigra L.) seed germination for 14 days in the light and in the dark in the presence of gabaculine (GAB) and cytokinin in order to elucidate the regulation of gymnosperm seedling greening in the dark, primarily at the level of aminolevulinic acid formation. In the light, GAB inhibited chlorophyll accumulation in a manner dependent on concentration and developmental stage, and in the dark it showed no effect. Cytokinin, 10(-5) M benzyl adenine (BA) partly overcame GAB-induced inhibition in the light, mainly during earlier developmental stages. In the seedlings grown in the dark, an equal quantity of Chl accumulated in the presence of cytokinin with and without GAB and it was approximately 20-40% higher than in the control seedlings or in the seedlings grown only in the presence of GAB. 5-Amino-levulinic acid (ALA) synthesis was equal in the light and in the dark in seedlings of the same age and seedlings treated with GAB grown in the dark. In the light, GAB inhibited ALA synthetic activity. The results indicate that ALA synthesis is not a rate-limiting step within Chl biosynthesis in pine seedlings grown in the dark.

X-ray dark-field radiography facilitates the diagnosis of pulmonary fibrosis in a mouse model.

PubMed

Hellbach, Katharina; Yaroshenko, Andre; Willer, Konstantin; Conlon, Thomas M; Braunagel, Margarita B; Auweter, Sigrid; Yildirim, Ali Ö; Eickelberg, Oliver; Pfeiffer, Franz; Reiser, Maximilian F; Meinel, Felix G

2017-03-23

The aim of this study was to evaluate whether diagnosing pulmonary fibrosis with projection radiography can be improved by using X-ray dark-field radiograms. Pulmonary X-ray transmission and dark-field images of C57Bl/6N mice, either treated with bleomycin to induce pulmonary fibrosis or PBS to serve as controls, were acquired with a prototype grating-based small-animal scanner. Two blinded readers, both experienced radiologists and familiar with dark-field imaging, had to assess dark-field and transmission images for the absence or presence of fibrosis. Furthermore readers were asked to grade their stage of diagnostic confidence. Histological evaluation of the lungs served as the standard of reference in this study. Both readers showed a notably higher diagnostic confidence when analyzing the dark-field radiographs (p < 0.001). Diagnostic accuracy improved significantly when evaluating the lungs in dark-field images alone (p = 0.02) or in combination with transmission images (p = 0.01) compared to sole analysis of absorption images. Interreader agreement improved from good when assessing only transmission images to excellent when analyzing dark-field images alone or in combination with transmission images. Adding dark-field images to conventional transmission images in a murine model of pulmonary fibrosis leads to an improved diagnosis of this disease on chest radiographs.

Effects of dark chocolate on azoxymethane-induced colonic aberrant crypt foci.

PubMed

Hong, Mee Young; Nulton, Emily; Shelechi, Mahshid; Hernández, Lisa M; Nemoseck, Tricia

2013-01-01

Epidemiologic evidence supports that diets rich in polyphenols promote health and may delay the onset of colon cancer. Cocoa and chocolate products have some of the highest polyphenolic concentrations compared to other polyphenolic food sources. This study tested the hypothesis that a diet including dark chocolate can protect against colon cancer by inhibiting aberrant crypt foci (ACF) formation, downregulating gene expression of inflammatory mediators, and favorably altering cell kinetics. We also investigated whether bloomed dark chocolate retains the antioxidant capacity and protects against colon cancer. Forty-eight rats received either a diet containing control (no chocolate), regular dark chocolate, or bloomed dark chocolate and were injected subcutaneously with saline or azoxymethane. Relative to control, both regular and bloomed dark chocolate diets lowered the total number of ACF (P = 0.022). Chocolate diet-fed animals downregulated transcription levels of COX-2 (P = 0.035) and RelA (P = 0.045). Both chocolate diets lowered the proliferation index (P = 0.001). These results suggest that a diet including dark chocolate can reduce cell proliferation and some gene expression involving inflammation, which may explain the lower number of early preneoplastic lesions. These results provide new insight on polyphenol-rich chocolate foods and colon cancer prevention.

Proteomic and Metabolomic Analyses of Leaf from Clematis terniflora DC. Exposed to High-Level Ultraviolet-B Irradiation with Dark Treatment.

PubMed

Yang, Bingxian; Wang, Xin; Gao, Cuixia; Chen, Meng; Guan, Qijie; Tian, Jingkui; Komatsu, Setsuko

2016-08-05

Clematis terniflora DC. has potential pharmaceutical value; on the contrary, high-level UV-B irradiation with dark treatment led to the accumulation of secondary metabolites. Metabolomic and proteomic analyses of leaf of C. terniflora were performed to investigate the systematic response mechanisms to high-level UV-B irradiation with dark treatment. Metabolites related to carbohydrates, fatty acids, and amino acids and/or proteins related to stress, cell wall, and amino acid metabolism were gradually increased in response to high-level UV-B irradiation with dark treatment. On the basis of cluster analysis and mapping of proteins related to amino acid metabolism, the abundances of S-adenosylmethionine synthetase and cysteine synthase as well as 1,1-diphenyl-2-picrylhydrazyl scavenging activity were gradually increased in response to high-level UV-B irradiation with dark treatment. Furthermore, the abundance of dihydrolipoyl dehydrogenase/glutamate dehydrogenase and the content of γ-aminobutyric acid were also increased following high-level UV-B irradiation with dark treatment. Taken together, these results suggest that high-level UV-B irradiation with dark treatment induces the activation of reactive oxygen species scavenging system and γ-aminobutyric acid shunt pathway in leaf of C. terniflora.

Direct detection with dark mediators

DOE PAGES

Curtin, David; Surujon, Ze'ev; Tsai, Yuhsin

2014-10-16

We introduce dark mediator Dark Matter (dmDM) where the dark and visible sectors are connected by at least one light mediator Φ carrying the same dark charge that stabilizes DM. Φ is coupled to the Standard Model via an operator q¯qΦΦ*/Λ, and to dark matter via a Yukawa coupling y χX¯ cXΦ. Direct detection is realized as the 2 → 3 process χN → χ¯NΦ at tree-level for m Φ≲10 keV and small Yukawa coupling, or alternatively as a loop-induced 2 → 2 process χN → χN. We explore the direct-detection consequences of this scenario and find that a heavymore » O(100 GeV) dmDM candidate fakes different O(10 GeV) standard WIMPs in different experiments. Large portions of the dmDM parameter space are detectable above the irreducible neutrino background and not yet excluded by any bounds. Interestingly, for the m Φ range leading to novel direct detection phenomenology, dmDM is also a form of Self-Interacting Dark Matter (SIDM), which resolves inconsistencies between dwarf galaxy observations and numerical simulations.« less

Form factors for dark matter capture by the Sun in effective theories

NASA Astrophysics Data System (ADS)

Catena, Riccardo; Schwabe, Bodo

2015-04-01

In the effective theory of isoscalar and isovector dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle, 8 isotope-dependent nuclear response functions can be generated in the dark matter scattering by nuclei. We compute the 8 nuclear response functions for the 16 most abundant elements in the Sun, i.e. H, 3He, 4He, 12C, 14N, 16O, 20Ne, 23Na, 24Mg, 27Al, 28Si, 32S, 40Ar, 40Ca, 56Fe, and 59Ni, through numerical shell model calculations. We use our response functions to compute the rate of dark matter capture by the Sun for all isoscalar and isovector dark matter-nucleon effective interactions, including several operators previously considered for dark matter direct detection only. We study in detail the dependence of the capture rate on specific dark matter-nucleon interaction operators, and on the different elements in the Sun. We find that a so far neglected momentum dependent dark matter coupling to the nuclear vector charge gives a larger contribution to the capture rate than the constant spin-dependent interaction commonly included in dark matter searches at neutrino telescopes. Our investigation lays the foundations for model independent analyses of dark matter induced neutrino signals from the Sun. The nuclear response functions obtained in this study are listed in analytic form in an appendix, ready to be used in other projects.

Perturbations from cosmic strings in cold dark matter

NASA Technical Reports Server (NTRS)

Albrecht, Andreas; Stebbins, Albert

1992-01-01

A systematic linear analysis of the perturbations induced by cosmic strings in cold dark matter is presented. The power spectrum is calculated and it is found that the strings produce a great deal of power on small scales. It is shown that the perturbations on interesting scales are the result of many uncorrelated string motions, which indicates a much more Gaussian distribution than was previously supposed.

Perturbations from cosmic strings in cold dark matter

NASA Technical Reports Server (NTRS)

Albrecht, Andreas; Stebbins, Albert

1991-01-01

A systematic linear analysis of the perturbations induced by cosmic strings in cold dark matter is presented. The power spectrum is calculated and it is found that the strings produce a great deal of power on small scales. It is shown that the perturbations on interesting scales are the result of many uncorrelated string motions, which indicates a much more Gaussian distribution than was previously supposed.

Probing leptophilic dark sectors with hadronic processes

NASA Astrophysics Data System (ADS)

D'Eramo, Francesco; Kavanagh, Bradley J.; Panci, Paolo

2017-08-01

We study vector portal dark matter models where the mediator couples only to leptons. In spite of the lack of tree-level couplings to colored states, radiative effects generate interactions with quark fields that could give rise to a signal in current and future experiments. We identify such experimental signatures: scattering of nuclei in dark matter direct detection; resonant production of lepton-antilepton pairs at the Large Hadron Collider; and hadronic final states in dark matter indirect searches. Furthermore, radiative effects also generate an irreducible mass mixing between the vector mediator and the Z boson, severely bounded by ElectroWeak Precision Tests. We use current experimental results to put bounds on this class of models, accounting for both radiatively induced and tree-level processes. Remarkably, the former often overwhelm the latter.

Gravitationally bound BCS state as dark matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexander, Stephon; Cormack, Sam, E-mail: stephon_alexander@brown.edu, E-mail: samuel.c.cormack.gr@dartmouth.edu

2017-04-01

We explore the possibility that fermionic dark matter undergoes a BCS transition to form a superfluid. This requires an attractive interaction between fermions and we describe a possible source of this interaction induced by torsion. We describe the gravitating fermion system with the Bogoliubov-de Gennes formalism in the local density approximation. We solve the Poisson equation along with the equations for the density and gap energy of the fermions to find a self-gravitating, superfluid solution for dark matter halos. In order to produce halos the size of dwarf galaxies, we require a particle mass of ∼ 200 eV. We findmore » a maximum attractive coupling strength before the halo becomes unstable. If dark matter halos do have a superfluid component, this raises the possibility that they contain vortex lines.« less

Statics and dynamics of atomic dark-bright solitons in the presence of impurities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achilleos, V.; Frantzeskakis, D. J.; Kevrekidis, P. G.

2011-11-15

Adopting a mean-field description for a two-component atomic Bose-Einstein condensate, we study the statics and dynamics of dark-bright solitons in the presence of localized impurities. We use adiabatic perturbation theory to derive an equation of motion for the dark-bright soliton center. We show that, counterintuitively, an attractive (repulsive) delta-like impurity, acting solely on the bright-soliton component, induces an effective localized barrier (well) in the effective potential felt by the soliton; this way, dark-bright solitons are reflected from (transmitted through) attractive (repulsive) impurities. Our analytical results for the small-amplitude oscillations of solitons are found to be in good agreement with resultsmore » obtained via a Bogoliubov-de Gennes analysis and direct numerical simulations.« less

Probing leptophilic dark sectors with hadronic processes

DOE PAGES

D'Eramo, Francesco; Kavanagh, Bradley J.; Panci, Paolo

2017-05-29

We study vector portal dark matter models where the mediator couples only to leptons. In spite of the lack of tree-level couplings to colored states, radiative effects generate interactions with quark fields that could give rise to a signal in current and future experiments. We identify such experimental signatures: scattering of nuclei in dark matter direct detection; resonant production of lepton–antilepton pairs at the Large Hadron Collider; and hadronic final states in dark matter indirect searches. Furthermore, radiative effects also generate an irreducible mass mixing between the vector mediator and the Z boson, severely bounded by ElectroWeak Precision Tests. Wemore » use current experimental results to put bounds on this class of models, accounting for both radiatively induced and tree-level processes. Remarkably, the former often overwhelm the latter.« less

Harbor seal vibrissa morphology suppresses vortex-induced vibrations.

PubMed

Hanke, Wolf; Witte, Matthias; Miersch, Lars; Brede, Martin; Oeffner, Johannes; Michael, Mark; Hanke, Frederike; Leder, Alfred; Dehnhardt, Guido

2010-08-01

Harbor seals (Phoca vitulina) often live in dark and turbid waters, where their mystacial vibrissae, or whiskers, play an important role in orientation. Besides detecting and discriminating objects by direct touch, harbor seals use their whiskers to analyze water movements, for example those generated by prey fish or by conspecifics. Even the weak water movements left behind by objects that have passed by earlier can be sensed and followed accurately (hydrodynamic trail following). While scanning the water for these hydrodynamic signals at a swimming speed in the order of meters per second, the seal keeps its long and flexible whiskers in an abducted position, largely perpendicular to the swimming direction. Remarkably, the whiskers of harbor seals possess a specialized undulated surface structure, the function of which was, up to now, unknown. Here, we show that this structure effectively changes the vortex street behind the whiskers and reduces the vibrations that would otherwise be induced by the shedding of vortices from the whiskers (vortex-induced vibrations). Using force measurements, flow measurements and numerical simulations, we find that the dynamic forces on harbor seal whiskers are, by at least an order of magnitude, lower than those on sea lion (Zalophus californianus) whiskers, which do not share the undulated structure. The results are discussed in the light of pinniped sensory biology and potential biomimetic applications.

Characterization of tub4P287L, a β‐tubulin mutant, revealed new aspects of microtubule regulation in shade

PubMed Central

Yu, Jie; Qiu, Hong; Liu, Xin; Wang, Meiling; Gao, Yongli; Chory, Joanne

2015-01-01

Abstract When sun plants, such as Arabidopsis thaliana, are under canopy shade, elongation of stems/petioles will be induced as one of the most prominent responses. Plant hormones mediate the elongation growth. However, how environmental and hormonal signals are translated into cell expansion activity that leads to the elongation growth remains elusive. Through forward genetic study, we identified shade avoidance2 (sav2) mutant, which contains a P287L mutation in β‐TUBULIN 4. Cortical microtubules (cMTs) play a key role in anisotropic cell growth. Hypocotyls of sav2 are wild type‐like in white light, but are short and highly swollen in shade and dark. We showed that shade not only induces cMT rearrangement, but also affects cMT stability and dynamics of plus ends. Even though auxin and brassinosteroids are required for shade‐induced hypocotyl elongation, they had little effect on shade‐induced rearrangement of cMTs. Blocking auxin transport suppressed dark phenotypes of sav2, while overexpressing EB1b‐GFP, a microtubule plus‐end binding protein, rescued sav2 in both shade and dark, suggesting that tub4P287L represents a unique type of tubulin mutation that does not affect cMT function in supporting cell elongation, but may affect the ability of cMTs to respond properly to growth promoting stimuli. PMID:25899068

Dark Flows in Newton Crater Extending During Summer Six-Image Sequence

NASA Image and Video Library

2011-08-04

This image comes from observations of Newton crater by the HiRISE camera onboard NASA Mars Reconnaissance Orbiter where features appear and incrementally grow during warm seasons and fade in cold seasons.

A Direct Dark Matter Search with the MAJORANA Low-Background Broad Energy Germanium Detector

NASA Astrophysics Data System (ADS)

Finnerty, Padraic Seamus

It is well established that a significant portion of our Universe is comprised of invisible, non-luminous matter, commonly referred to as dark matter. The detection and characterization of this missing matter is an active area of research in cosmology and particle astrophysics. A general class of candidates for non-baryonic particle dark matter is weakly interacting massive particles (WIMPs). WIMPs emerge naturally from supersymmetry with predicted masses between 1--1000 GeV. There are many current and near-future experiments that may shed light on the nature of dark matter by directly detecting WIMP-nucleus scattering events. The MAJORANA experiment will use p-type point contact (PPC) germanium detectors as both the source and detector to search for neutrinoless double-beta decay in 76Ge. These detectors have both exceptional energy resolution and low-energy thresholds. The low-energy performance of PPC detectors, due to their low-capacitance point-contact design, makes them suitable for direct dark matter searches. As a part of the research and development efforts for the MAJORANA experiment, a custom Canberra PPC detector has been deployed at the Kimballton Underground Research Facility in Ripplemead, Virginia. This detector has been used to perform a search for low-mass (< 10 GeV) WIMP induced nuclear recoils using a 221.49 live-day exposure. It was found that events originating near the surface of the detector plague the signal region, even after all cuts. For this reason, only an upper limit on WIMP induced nuclear recoils was placed. This limit is inconsistent with several recent claims to have observed light WIMP based dark matter.

Activation of violaxanthin cycle in darkness is a common response to different abiotic stresses: a case study in Pelvetia canaliculata

PubMed Central

2011-01-01

Background In the violaxanthin (V) cycle, V is de-epoxidized to zeaxanthin (Z) when strong light or light combined with other stressors lead to an overexcitation of photosystems. However, plants can also suffer stress in darkness and recent reports have shown that dehydration triggers V-de-epoxidation in the absence of light. In this study, we used the highly stress-tolerant brown alga Pelvetia canaliculata as a model organism, due to its lack of lutein and its non-photochemical quenching independent of the transthylakoidal-ΔpH, to study the triggering of the V-cycle in darkness induced by abiotic stressors. Results We have shown that besides desiccation, other factors such as immersion, anoxia and high temperature also induced V-de-epoxidation in darkness. This process was reversible once the treatments had ceased (with the exception of heat, which caused lethal damage). Irrespective of the stressor applied, the resulting de-epoxidised xanthophylls correlated with a decrease in Fv/Fm, suggesting a common function in the down-regulation of photosynthetical efficiency. The implication of the redox-state of the plastoquinone-pool and of the differential activity of V-cycle enzymes on V-de-epoxidation in darkness was also examined. Current results suggest that both violaxanthin de-epoxidase (VDE) and zeaxanthin-epoxidase (ZE) have a basal constitutive activity even in darkness, being ZE inhibited under stress. This inhibition leads to Z accumulation. Conclusion This study demonstrates that V-cycle activity is triggered by several abiotic stressors even when they occur in an absolute absence of light, leading to a decrease in Fv/Fm. This finding provides new insights into an understanding of the regulation mechanism of the V-cycle and of its ecophysiological roles. PMID:22269024

Dark matter maps reveal cosmic scaffolding.

PubMed

Massey, Richard; Rhodes, Jason; Ellis, Richard; Scoville, Nick; Leauthaud, Alexie; Finoguenov, Alexis; Capak, Peter; Bacon, David; Aussel, Hervé; Kneib, Jean-Paul; Koekemoer, Anton; McCracken, Henry; Mobasher, Bahram; Pires, Sandrine; Refregier, Alexandre; Sasaki, Shunji; Starck, Jean-Luc; Taniguchi, Yoshi; Taylor, Andy; Taylor, James

2007-01-18

Ordinary baryonic particles (such as protons and neutrons) account for only one-sixth of the total matter in the Universe. The remainder is a mysterious 'dark matter' component, which does not interact via electromagnetism and thus neither emits nor reflects light. As dark matter cannot be seen directly using traditional observations, very little is currently known about its properties. It does interact via gravity, and is most effectively probed through gravitational lensing: the deflection of light from distant galaxies by the gravitational attraction of foreground mass concentrations. This is a purely geometrical effect that is free of astrophysical assumptions and sensitive to all matter--whether baryonic or dark. Here we show high-fidelity maps of the large-scale distribution of dark matter, resolved in both angle and depth. We find a loose network of filaments, growing over time, which intersect in massive structures at the locations of clusters of galaxies. Our results are consistent with predictions of gravitationally induced structure formation, in which the initial, smooth distribution of dark matter collapses into filaments then into clusters, forming a gravitational scaffold into which gas can accumulate, and stars can be built.

Heat shock protein 70 and heat shock protein 90 expression in light- and dark-adapted adult octopus retinas.

PubMed

Ochoa, Gina H; Clark, Ying Mei; Matsumoto, Brian; Torres-Ruiz, Jose A; Robles, Laura J

2002-02-01

Light- and dark-adaptation leads to changes in rhabdom morphology and photopigment distribution in the octopus retina. Molecular chaperones, including heat shock proteins (Hsps), may be involved in specific signaling pathways that cause changes in photoreceptor actin- and tubulin-based cytoskeletons and movement of the photopigments, rhodopsin and retinochrome. In this study, we used immunoblotting, in situ RT-PCR, immunofluorescence and confocal microscopy to localize the inducible form of Hsp70 and the larger Hsp90 in light- and dark-adapted and dorsal and ventral halves of adult octopus retinas. The Hsps showed differences in distribution between the light and dark and in dorsal vs. ventral position in the retina. Double labeling confocal microscopy co-localized Hsp70 with actin and tubulin, and Hsp90 with the photopigment, retinochrome. Our results demonstrate the presence of Hsp70 and Hsp90 in otherwise non-stressed light- and dark-adapted octopus retinas. These Hsps may help stabilize the cytoskeleton, important for rhabdom structure, and are perhaps involved in the redistribution of retinochrome in conditions of light and dark.

Exercise effects on the size and metabolic properties of soleus fibers in hindlimb-suspended rats

NASA Technical Reports Server (NTRS)

Graham, Scot C.; Roy, Roland R.; West, Steve P.; Thomason, Don; Baldwin, Kenneth M.

1989-01-01

The effects of four-week-long hind-limb suspension (HS) of rats on the size the soleus muscle fibers and the activity of succinate dehydrogenase (SDH) in dark and light ATPase fibers were investigated together with the efficacy of an endurance exercise (EX) program (daily treadmill exercise for 1.5 h/day at 20 m/min and a 30-percent grade) in ameliorating HS-induced changes. It was found that, in comparison to age-matched controls, the soleus wet weight decreased by 69 and 30 percent in HS and HS-EX rats, respectively, and the percent of dark ATPase fibers increased from 10 percent in controls to 19 and 17 percent, respectively. The values of the integrated fiber activity (activity/min times muscle area) showed a net loss of SDH in both the light and dark ATPase fibers of HS rats, but only in the light ATPase fibers of the HS-EX rats, indicating that exercise ameliorated but did not prevent the muscle fiber atrophy induced by HS.

Osmotic Stress-Induced Polyamine Accumulation in Cereal Leaves 1

PubMed Central

Flores, Hector E.; Galston, Arthur W.

1984-01-01

Arginine decarboxylase activity increases 2- to 3-fold in osmotically stressed oat leaves in both light and dark, but putrescine accumulation in the dark is only one-third to one-half of that in light-stressed leaves. If arginine or ornithine are supplied to dark-stressed leaves, putrescine rises to levels comparable to those obtained by incubation under light. Thus, precursor amino acid availability is limiting to the stress response. Amino acid levels change rapidly upon osmotic treatment; notably, glutamic acid decreases with a corresponding rise in glutamine. Difluoromethylarginine (0.01-0.1 millimolar), the enzyme-activated irreversible inhibitor of arginine decarboxylase, prevents the stress-induced putrescine rise, as well as the incorporation of label from [14C]arginine, with the expected accumulation of free arginine, but has no effect on the rest of the amino acid pool. The use of specific inhibitors such as α-difluoromethylarginine is suggested as probes for the physiological significance of stress responses by plant cells. PMID:16663552

Lake Eyre, Simpson Desert, South Australia, Australia

NASA Image and Video Library

1990-12-10

STS035-501-007 (2-10 Dec. 1990) --- The STS-35 crewmembers aboard the Earth-orbiting Space Shuttle Columbia photographed this view of the Arid Simpson Desert of Australia with a handheld Rolleiflex camera. Lake Eyre is normally dry; however, the STS-35 crew was able to recognize water in the lowest parts of the lake (dark pink area) and possibly in Lake Blanche east of Lake Eyre. Lake Frome lies in the distance separated from Lake Torrens (top right) by dark hills of Flinders Range. The Finke River (bottom left to middle) flows into the Eyre basin from the northwest. Although it is the largest river entering the basin, Finke's floods seldom reach Lake Eyre. The dark brown patch in the foreground is an area of ancient, brown lateritic soils partly covered by dunes.

Sonodynamic action of pyropheophorbide-a methyl ester in liver cancer cells.

PubMed

Xu, Jing; Xia, Xinshu; Wang, Xinna; Xu, Chuanshan; Wang, Ping; Xiang, Junyan; Jiang, Yuan; Leung, Albert Wingnang

2010-07-01

This study aimed to investigate the sonodynamic action of pyropheophorbide-a methyl ester (MPPa) in liver cancer cells to explore a novel therapeutic modality. H22 cells were chosen as model cells to investigate the sonodynamic action of MPPa on liver cancer. The MPPa concentration was kept constant at 2 micromol/L, and the cells were subjected to ultrasound exposure at an intensity of 0.97 W/cm(2). Cytotoxicity was investigated 24 hours after ultrasound exposure. Apoptosis was evaluated using flow cytometry with annexin V-fluorescein isothiocyanate and propidium iodine staining and nuclear staining with Hoechst 33258. Reactive oxygen species (ROS) were analyzed using flow cytometry with 2,7-dichlorodihydrofluorescein diacetate staining. No significant dark cytotoxicity of MPPa was shown in the H22 cells at the concentration of 2 micromol/L. The cell death rate induced by ultrasound treatment was significantly higher in the presence of MPPa than in the absence of it (P < .05). Flow cytometry showed that the sonodynamic action of MPPa significantly increased the early and late apoptotic rates of the H22 cells. Nuclear condensation and an ROS increase were found after sonodynamic treatment. Our findings showed that MPPa-mediated sonodynamic action significantly enhanced death of H22 cells and the ROS level, suggesting that MPPa is a novel sonosensitizer and the sonodynamic action of MPPa might be a potential therapeutic modality in the management of liver cancer.

Geologic mapping of the Amirani-Gish Bar region of Io: Implications for the global geologic mapping of Io

USGS Publications Warehouse

Williams, D.A.; Keszthelyi, L.P.; Crown, D.A.; Jaeger, W.L.; Schenk, P.M.

2007-01-01

We produced the first geologic map of the Amirani-Gish Bar region of Io, the last of four regional maps generated from Galileo mission data. The Amirani-Gish Bar region has five primary types of geologic materials: plains, mountains, patera floors, flows, and diffuse deposits. The flows and patera floors are thought to be compositionally similar, but are subdivided based on interpretations regarding their emplacement environments and mechanisms. Our mapping shows that volcanic activity in the Amirani-Gish Bar region is dominated by the Amirani Eruptive Center (AEC), now recognized to be part of an extensive, combined Amirani-Maui flow field. A mappable flow connects Amirani and Maui, suggesting that Maui is fed from Amirani, such that the post-Voyager designation "Maui Eruptive Center" should be revised. Amirani contains at least four hot spots detected by Galileo, and is the source of widespread bright (sulfur?) flows and active dark (silicate?) flows being emplaced in the Promethean style (slowly emplaced, compound flow fields). The floor of Gish Bar Patera has been partially resurfaced by dark lava flows, although other parts of its floor are bright and appeared unchanged during the Galileo mission. This suggests that the floor did not undergo complete resurfacing as a lava lake as proposed for other ionian paterae. There are several other hot spots in the region that are the sources of both active dark flows (confined within paterae), and SO2- and S2-rich diffuse deposits. Mapped diffuse deposits around fractures on mountains and in the plains appear to serve as the source for gas venting without the release of magma, an association previously unrecognized in this region. The six mountains mapped in this region exhibit various states of degradation. In addition to gaining insight into this region of Io, all four maps are studied to assess the best methodology to use to produce a new global geologic map of Io based on the newly released, combined Galileo-Voyager global mosaics. To convey the complexity of ionian surface geology, we find that a new global geologic map of Io should include a map sheet displaying the global abundances and types of surface features as well as a complementary GIS database as a means to catalog the record of surface changes observed since the Voyager flybys and during the Galileo mission. ?? 2006 Elsevier Inc. All rights reserved.

Efficient removal of cyclobutane pyrimidine dimers in barley: differential contribution of light-dependent and dark DNA repair pathways.

PubMed

Manova, Vasilissa; Georgieva, Ralitsa; Borisov, Borislav; Stoilov, Lubomir

2016-10-01

Barley stress response to ultraviolet radiation (UV) has been intensively studied at both the physiological and morphological level. However, the ability of barley genome to repair UV-induced lesions at the DNA level is far less characterized. In this study, we have investigated the relative contribution of light-dependent and dark DNA repair pathways for the efficient elimination of cyclobutane pyrimidine dimers (CPDs) from the genomic DNA of barley leaf seedlings. The transcriptional activity of barley CPD photolyase gene in respect to the light-growth conditions and UV-C irradiation of the plants has also been analyzed. Our results show that CPDs induced in the primary barley leaf at frequencies potentially damaging DNA at the single-gene level are removed efficiently and exclusively by photorepair pathway, whereas dark repair is hardly detectable, even at higher CPD frequency. A decrease of initially induced CPDs under dark is observed but only after prolonged incubation, suggesting the activation of light-independent DNA damage repair and/or tolerance mechanisms. The green barley seedlings possess greater capacity for CPD photorepair than the etiolated ones, with efficiency of CPD removal dependent on the intensity and quality of recovering light. The higher repair rate of CPDs measured in the green leaves correlates with the higher transcriptional activity of barley CPD photolyase gene. Visible light and UV-C radiation affect differentially the expression of CPD photolyase gene particularly in the etiolated leaves. We propose that the CPD repair potential of barley young seedlings may influence their response to UV-stress. © 2016 Scandinavian Plant Physiology Society.

Electrical signals as mechanism of photosynthesis regulation in plants.

PubMed

Sukhov, Vladimir

2016-12-01

This review summarizes current works concerning the effects of electrical signals (ESs) on photosynthesis, the mechanisms of the effects, and its physiological role in plants. Local irritations of plants induce various photosynthetic responses in intact leaves, including fast and long-term inactivation of photosynthesis, and its activation. Irritation-induced ESs, including action potential, variation potential, and system potential, probably causes the photosynthetic responses in intact leaves. Probable mechanisms of induction of fast inactivation of photosynthesis are associated with Ca 2+ - and (or) H + -influxes during ESs generation; long-term inactivation of photosynthesis might be caused by Ca 2+ - and (or) H + -influxes, production of abscisic and jasmonic acids, and inactivation of phloem H + -sucrose symporters. It is probable that subsequent development of inactivation of photosynthesis is mainly associated with decreased CO 2 influx and inactivation of the photosynthetic dark reactions, which induces decreased photochemical quantum yields of photosystems I and II and increased non-photochemical quenching of photosystem II fluorescence and cyclic electron flow around photosystem I. However, other pathways of the ESs influence on the photosynthetic light reactions are also possible. One of them might be associated with ES-connected acidification of chloroplast stroma inducing ferredoxin-NADP + reductase accumulation at the thylakoids in Tic62 and TROL complexes. Mechanisms of ES-induced activation of photosynthesis require further investigation. The probable ultimate effect of ES-induced photosynthetic responses in plant life is the increased photosynthetic machinery resistance to stressors, including high and low temperatures, and enhanced whole-plant resistance to environmental factors at least during 1 h after irritation.

ASTER Images Merapi Continuing Eruption

NASA Image and Video Library

2010-11-18

This thermal infrared image from NASA Terra spacecraft of Merapi continuing eruption has been processed to reveal the dominant presence of volcanic ash in the eruption plume and clouds, displayed in dark red. The warm volcanic flow appears bright.

Light-Induced Alterations in Basil Ganglia Kynurenic Acid Levels

NASA Technical Reports Server (NTRS)

Sroufe, Angela E.; Whittaker, J. A.; Patrickson, J. W.; Orr, M. C.

1997-01-01

The metabolic synthesis, release and breakdown of several known CNS neurotransmitters have been shown to follow a circadian pattern entrained to the environmental light/dark cycle. The levels of excitatory amino acid (EAA) transmitters such as glutamate, have been shown to vary with environmental lighting conditions. Kynurenic Acid (KA), an endogenous tryptophan metabolite and glutamate receptor antagonist, has been reported to have neuroprotective effects against EAA-induced excitotoxic cell damage. Changes in KA's activity within the mammalian basal ganglia has been proposed as being contributory to neurotoxicity in Huntington's Disease. It is not known whether CNS KA levels follow a circadian pattern or exhibit light-induced fluctuations. However, because the symptoms of certain degenerative motor disorders seem to fluctuate with daily 24 hour rhythm, we initiated studies to determine if basal ganglia KA were influenced by the daily light/dark cycle and could influence motor function. Therefore in this study, HPLC-EC was utilized to determine if basal ganglia KA levels in tissue extracts from adult male Long-Evans rats (200-250g) entrained to 24 and 48 hours constant light and dark conditions, respectively. Samples were taken one hour before the onset of the subjective day and one hour prior to the onset of the subjective night in order to detect possible phase differences in KA levels and to allow for accumulation of factors expressed in association with the light or dark phase. Data analysis revealed that KA levels in the basal ganglia vary with environmental lighting conditions; being elevated generally during the dark. Circadian phase differences in KA levels were also evident during the subjective night and subjective day, respectively. Results from these studies are discussed with respect to potential cyclic changes in neuronal susceptibility to excitotoxic damage during the daily 24 hour cycle and its possible relevance to future therapeutic approaches in treating neurodegenerative disorders.

Hidden U (1 ) gauge symmetry realizing a neutrinophilic two-Higgs-doublet model with dark matter

NASA Astrophysics Data System (ADS)

Nomura, Takaaki; Okada, Hiroshi

2018-04-01

We propose a neutrinophilic two-Higgs-doublet model with hidden local U (1 ) symmetry, where active neutrinos are Dirac type, and a fermionic dark matter (DM) candidate is naturally induced as a result of remnant symmetry even after the spontaneous symmetry breaking. In addition, a physical Goldstone boson arises as a consequence of two types of gauge singlet bosons and contributes to the DM phenomenologies as well as an additional neutral gauge boson. Then, we analyze the relic density of DM within the safe range of direct detection searches and show the allowed region of dark matter mass.

A radiative neutrino mass model in light of DAMPE excess with hidden gauged U(1) symmetry

NASA Astrophysics Data System (ADS)

Nomura, Takaaki; Okada, Hiroshi; Wu, Peiwen

2018-05-01

We propose a one-loop induced neutrino mass model with hidden U(1) gauge symmetry, in which we successfully involve a bosonic dark matter (DM) candidate propagating inside a loop diagram in neutrino mass generation to explain the e+e‑ excess recently reported by the DArk Matter Particle Explorer (DAMPE) experiment. In our scenario dark matter annihilates into four leptons through Z' boson as DM DM → Z' Z' (Z' → l+ l‑) and Z' decays into leptons via one-loop effect. We then investigate branching ratios of Z' taking into account lepton flavor violations and neutrino oscillation data.

Topology and dark energy: testing gravity in voids.

PubMed

Spolyar, Douglas; Sahlén, Martin; Silk, Joe

2013-12-13

Modified gravity has garnered interest as a backstop against dark matter and dark energy (DE). As one possible modification, the graviton can become massive, which introduces a new scalar field--here with a Galileon-type symmetry. The field can lead to a nontrivial equation of state of DE which is density and scale dependent. Tension between type Ia supernovae and Planck could be reduced. In voids, the scalar field dramatically alters the equation of state of DE, induces a soon-observable gravitational slip between the two metric potentials, and develops a topological defect (domain wall) due to a nontrivial vacuum structure for the field.

Baryogenesis via dark matter-induced symmetry breaking in the early Universe

NASA Astrophysics Data System (ADS)

Sakstein, Jeremy; Trodden, Mark

2017-11-01

We put forward a new proposal for generating the baryon asymmetry of the universe by making use of the dynamics of a U (1) scalar field coupled to dark matter. High dark matter densities cause the U (1) symmetry to break spontaneously so that the field acquires a large vacuum expectation value. The symmetry is restored when the density redshifts below a critical value, resulting in the coherent oscillation of the scalar field. A net B - L number can be generated either via baryon number-conserving couplings to the standard model or through small symmetry-violating operators and the subsequent decay of the scalar condensate.

Effects of Displacement Damage on the Time-Resolved Gain and Bandwidth of a Low Breakdown Voltage Si Avalanche Photodiode

NASA Technical Reports Server (NTRS)

Laird, Jamie S.; Onoda, Shinobu; Hirao, Toshio; Becker, Heidi; Johnston, Allan; Laird, Jamie S.; Itoh, Hisayoshi

2006-01-01

Effects of displacement damage and ionization damage induced by gamma irradiation on the dark current and impulse response of a high-bandwidth low breakdown voltage Si Avalanche Photodiode has been investigated using picosecond laser microscopy. At doses as high as 10Mrad (Si) minimal alteration in the impulse response and bandwidth were observed. However, dark current measurements also performed with and without biased irradiation exhibit anomalously large damage factors for applied biases close to breakdown. The absence of any degradation in the impulse response is discussed as are possible mechanisms for higher dark current damage factors observed for biased irradiation.

Regulation of respiration and the oxygen diffusion barrier in soybean protect symbiotic nitrogen fixation from chilling-induced inhibition and shoots from premature senescence.

PubMed

van Heerden, Philippus D R; Kiddle, Guy; Pellny, Till K; Mokwala, Phatlane W; Jordaan, Anine; Strauss, Abram J; de Beer, Misha; Schlüter, Urte; Kunert, Karl J; Foyer, Christine H

2008-09-01

Symbiotic nitrogen fixation is sensitive to dark chilling (7 degrees C-15 degrees C)-induced inhibition in soybean (Glycine max). To characterize the mechanisms that cause the stress-induced loss of nodule function, we examined nodule structure, carbon-nitrogen interactions, and respiration in two soybean genotypes that differ in chilling sensitivity: PAN809 (PAN), which is chilling sensitive, and Highveld Top (HT), which is more chilling resistant. Nodule numbers were unaffected by dark chilling, as was the abundance of the nitrogenase and leghemoglobin proteins. However, dark chilling decreased nodule respiration rates, nitrogenase activities, and NifH and NifK mRNAs and increased nodule starch, sucrose, and glucose in both genotypes. Ureide and fructose contents decreased only in PAN nodules. While the chilling-induced decreases in nodule respiration persisted in PAN even after return to optimal temperatures, respiration started to recover in HT by the end of the chilling period. The area of the intercellular spaces in the nodule cortex and infected zone was greatly decreased in HT after three nights of chilling, an acclimatory response that was absent from PAN. These data show that HT nodules are able to regulate both respiration and the area of the intercellular spaces during chilling and in this way control the oxygen diffusion barrier, which is a key component of the nodule stress response. We conclude that chilling-induced loss of symbiotic nitrogen fixation in PAN is caused by the inhibition of respiration coupled to the failure to regulate the oxygen diffusion barrier effectively. The resultant limitations on nitrogen availability contribute to the greater chilling-induced inhibition of photosynthesis in PAN than in HT.

Regulation of Respiration and the Oxygen Diffusion Barrier in Soybean Protect Symbiotic Nitrogen Fixation from Chilling-Induced Inhibition and Shoots from Premature Senescence1[W][OA

PubMed Central

van Heerden, Philippus D.R.; Kiddle, Guy; Pellny, Till K.; Mokwala, Phatlane W.; Jordaan, Anine; Strauss, Abram J.; de Beer, Misha; Schlüter, Urte; Kunert, Karl J.; Foyer, Christine H.

2008-01-01

Symbiotic nitrogen fixation is sensitive to dark chilling (7°C–15°C)-induced inhibition in soybean (Glycine max). To characterize the mechanisms that cause the stress-induced loss of nodule function, we examined nodule structure, carbon-nitrogen interactions, and respiration in two soybean genotypes that differ in chilling sensitivity: PAN809 (PAN), which is chilling sensitive, and Highveld Top (HT), which is more chilling resistant. Nodule numbers were unaffected by dark chilling, as was the abundance of the nitrogenase and leghemoglobin proteins. However, dark chilling decreased nodule respiration rates, nitrogenase activities, and NifH and NifK mRNAs and increased nodule starch, sucrose, and glucose in both genotypes. Ureide and fructose contents decreased only in PAN nodules. While the chilling-induced decreases in nodule respiration persisted in PAN even after return to optimal temperatures, respiration started to recover in HT by the end of the chilling period. The area of the intercellular spaces in the nodule cortex and infected zone was greatly decreased in HT after three nights of chilling, an acclimatory response that was absent from PAN. These data show that HT nodules are able to regulate both respiration and the area of the intercellular spaces during chilling and in this way control the oxygen diffusion barrier, which is a key component of the nodule stress response. We conclude that chilling-induced loss of symbiotic nitrogen fixation in PAN is caused by the inhibition of respiration coupled to the failure to regulate the oxygen diffusion barrier effectively. The resultant limitations on nitrogen availability contribute to the greater chilling-induced inhibition of photosynthesis in PAN than in HT. PMID:18667725

The mitochondrial electron transfer flavoprotein complex is essential for survival of Arabidopsis in extended darkness.

PubMed

Ishizaki, Kimitsune; Schauer, Nicolas; Larson, Tony R; Graham, Ian A; Fernie, Alisdair R; Leaver, Christopher J

2006-09-01

In mammals, the electron transfer flavoprotein (ETF) is a heterodimeric protein composed of two subunits, alpha and beta, that is responsible for the oxidation of at least nine mitochondrial matrix flavoprotein dehydrogenases. Electrons accepted by ETF are further transferred to the main respiratory chain via the ETF ubiquinone oxide reductase (ETFQO). Sequence analysis of the unique Arabidopsis homologues of two subunits of ETF revealed their high similarity to both subunits of the mammalian ETF. Yeast two-hybrid experiments showed that the Arabidopsis ETFalpha and ETFbeta can form a heteromeric protein. Isolation and characterization of two independent T-DNA insertional Arabidopsis mutants of the ETFbeta gene revealed accelerated senescence and early death compared to wild-type during extended darkness. Furthermore in contrast to wild-type, the etfb mutants demonstrated a significant accumulation of several amino acids, isovaleryl CoA and phytanoyl CoA during dark-induced carbohydrate deprivation. These phenotypic characteristics of etfb mutants are broadly similar to those that we observed previously in Arabidopsis etfqo mutants, suggesting functional association between ETF and ETFQO in Arabidopsis, and confirming the essential roles of the ETF/ETFQO electron transfer complex in the catabolism of leucine and involvement in the chlorophyll degradation pathway activated during dark-induced carbohydrate deprivation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnes, P.

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4 ± 0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter searchmore » for a (1422 ± 67) kg d exposure with an atmospheric argon fill. As a result, this is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1×10 -44 cm 2 for a WIMP mass of 100 Gev/c 2.« less

Regulation of Carbon Flow by Nitrogen and Light in the Red Alga, Gelidium coulteri.

PubMed

Macler, B A

1986-09-01

The red alga Gelidium coulteri Harv. photosynthetically fixed [(14)C] bicarbonate at high rates under defined conditions in unialgal laboratory culture. The fixation rate and flow of photosynthate into various end products were dependent on the nitrogen status of the tissue. Plants fed luxury levels of nitrogen (approximately 340 micromolar) showed fixation rates several-fold higher than those seen for plants starved for nitrogen. The addition of NO(3) (-) or NH(4) (+) to such starved plants further inhibited fixation over at least the first several hours after addition. The majority of (14)C after incubations of 30 minutes to 8 hours was found in the compounds floridoside, agar and floridean starch. In addition, amino acids and intermediate compounds of the reductive pentose phosphate pathway, glycolytic pathway and tricarboxylic acid cycle were detected. Nitrogen affected the partitioning of labeled carbon into these compounds. Plants under luxury nitrogen conditions had higher floridoside levels and markedly lower amounts of agar and starch than found in plants limited for nitrogen. Amino acid, phycobiliprotein and chlorophyll levels were also significantly higher in nitrogen-enriched plants. Addition of NO(3) (-) to starved plants led to an increase in floridoside, tricarboxylic acid cycle intermediates and amino acids within 1 hour and inhibited carbon flow into agar and starch. Carbon fixation in the dark was only 1 to 7% of that seen in the light. Dark fixation of [(14)C]bicarbonate yielded label primarily in tricarboxylic acid cycle intermediates, amino acids and polysaccharides. Nitrogen stimulated amino acid synthesis at the expense of agar and starch. Floridoside was only a minor component in the dark. Pulse-chase experiments, designed to show carbon turnover, indicated a 2-fold increase in labeling of agar over 96 hours of chase in the light. No increases were seen in the dark. Low molecular weight pools, including floridoside, decreased 2- to 5-fold over this period under both light and dark conditions. Nitrogen status did not influence turnover. There was little or no organic carbon released into the culture medium over this period. The results are consistent with biosynthetic pathways to floridoside and agar that share the common intermediate UDP-d-galactose. It is hypothesized that synthesis of floridoside is regulated by nitrogen and light at the enzymic level.

Regulation of Carbon Flow by Nitrogen and Light in the Red Alga, Gelidium coulteri1

PubMed Central

Macler, Bruce A.

1986-01-01

The red alga Gelidium coulteri Harv. photosynthetically fixed [14C] bicarbonate at high rates under defined conditions in unialgal laboratory culture. The fixation rate and flow of photosynthate into various end products were dependent on the nitrogen status of the tissue. Plants fed luxury levels of nitrogen (approximately 340 micromolar) showed fixation rates several-fold higher than those seen for plants starved for nitrogen. The addition of NO3− or NH4+ to such starved plants further inhibited fixation over at least the first several hours after addition. The majority of 14C after incubations of 30 minutes to 8 hours was found in the compounds floridoside, agar and floridean starch. In addition, amino acids and intermediate compounds of the reductive pentose phosphate pathway, glycolytic pathway and tricarboxylic acid cycle were detected. Nitrogen affected the partitioning of labeled carbon into these compounds. Plants under luxury nitrogen conditions had higher floridoside levels and markedly lower amounts of agar and starch than found in plants limited for nitrogen. Amino acid, phycobiliprotein and chlorophyll levels were also significantly higher in nitrogen-enriched plants. Addition of NO3− to starved plants led to an increase in floridoside, tricarboxylic acid cycle intermediates and amino acids within 1 hour and inhibited carbon flow into agar and starch. Carbon fixation in the dark was only 1 to 7% of that seen in the light. Dark fixation of [14C]bicarbonate yielded label primarily in tricarboxylic acid cycle intermediates, amino acids and polysaccharides. Nitrogen stimulated amino acid synthesis at the expense of agar and starch. Floridoside was only a minor component in the dark. Pulse-chase experiments, designed to show carbon turnover, indicated a 2-fold increase in labeling of agar over 96 hours of chase in the light. No increases were seen in the dark. Low molecular weight pools, including floridoside, decreased 2- to 5-fold over this period under both light and dark conditions. Nitrogen status did not influence turnover. There was little or no organic carbon released into the culture medium over this period. The results are consistent with biosynthetic pathways to floridoside and agar that share the common intermediate UDP-d-galactose. It is hypothesized that synthesis of floridoside is regulated by nitrogen and light at the enzymic level. PMID:16664980

Dark-matter production through loop-induced processes at the LHC: the s-channel mediator case.

PubMed

Mattelaer, Olivier; Vryonidou, Eleni

We show how studies relevant for mono-X searches at the LHC in simplified models featuring a dark-matter candidate and an s -channel mediator can be performed within the MadGraph5_aMC@NLO framework. We focus on gluon-initiated loop-induced processes, mostly relevant to the case where the mediator couples preferentially to third generation quarks and in particular to the top quark. Our implementation allows us to study signatures at hadron colliders involving missing transverse energy plus jets or plus neutral bosons ([Formula: see text]), possibly including the effects of extra radiation by multi-parton merging and matching to the parton shower.

Dark chocolate and vascular function in patients with peripheral artery disease: a randomized, controlled cross-over trial.

PubMed

Hammer, Alexandra; Koppensteiner, Renate; Steiner, Sabine; Niessner, Alexander; Goliasch, Georg; Gschwandtner, Michael; Hoke, Matthias

2015-01-01

Flavonoid-rich dark chocolate has positive effects on vascular function in healthy subjects and in patients at risk of atherosclerosis. The impact of dark chocolate on endothelial and microvascular function in patients with symptomatic peripheral artery disease (PAD) has not been investigated so far. In an investigator blinded, randomized, controlled, cross-over trial we assessed the effect of flavonoid-rich dark chocolate and cocoa-free control chocolate on flow-mediated dilatation (FMD) of the brachial artery and on microvascular function (assessed by Laser Doppler fluxmetry) in 21 patients with symptomatic (Fontaine stage II) PAD. Measurements were done in each patient on 2 single days, with an interval of 7 days, at baseline and at 2 hours after ingestion of 50 g dark chocolate or 50 g white chocolate, respectively. FMD remained unchanged after intake of dark chocolate (baseline and 2 hours after ingestion, %: 5.1 [IQR 4.4 to 7.3] and 5.5 [IQR 3.9 to 10.4]; p = 0.57, and after intake of white chocolate (baseline and 2 hours after ingestion, %: 6.4 [IQR 4.5 to 11.4] and 4.4 [IQR 2.6 to 8.7]; p = 0.14. Similarly, microcirculatory parameters were not significantly altered after intake of any chocolate compared with the respective baseline values. In conclusion, a single consumption of 50 g dark chocolate has no effect on endothelial and microvascular function in patients with symptomatic PAD.

Sleep deprivation decreases phase-shift responses of circadian rhythms to light in the mouse: role of serotonergic and metabolic signals.

PubMed

Challet, E; Turek, F W; Laute, M; Van Reeth, O

2001-08-03

The circadian pacemaker in the suprachiasmatic nuclei is primarily synchronized to the daily light-dark cycle. The phase-shifting and synchronizing effects of light can be modulated by non-photic factors, such as behavioral, metabolic or serotonergic cues. The present experiments examine the effects of sleep deprivation on the response of the circadian pacemaker to light and test the possible involvement of serotonergic and/or metabolic cues in mediating the effects of sleep deprivation. Photic phase-shifting of the locomotor activity rhythm was analyzed in mice transferred from a light-dark cycle to constant darkness, and sleep-deprived for 8 h from Zeitgeber Time 6 to Zeitgeber Time 14. Phase-delays in response to a 10-min light pulse at Zeitgeber Time 14 were reduced by 30% in sleep-deprived mice compared to control mice, while sleep deprivation without light exposure induced no significant phase-shifts. Stimulation of serotonin neurotransmission by fluoxetine (10 mg/kg), a serotonin reuptake inhibitor that decreases light-induced phase-delays in non-deprived mice, did not further reduce light-induced phase-delays in sleep-deprived mice. Impairment of serotonin neurotransmission with p-chloroamphetamine (three injections of 10 mg/kg), which did not increase light-induced phase-delays in non-deprived mice significantly, partially normalized light-induced phase-delays in sleep-deprived mice. Injections of glucose increased light-induced phase-delays in control and sleep-deprived mice. Chemical damage of the ventromedial hypothalamus by gold-thioglucose (600 mg/kg) prevented the reduction of light-induced phase-delays in sleep-deprived mice, without altering phase-delays in control mice. Taken together, the present results indicate that sleep deprivation can reduce the light-induced phase-shifts of the mouse suprachiasmatic pacemaker, due to serotonergic and metabolic changes associated with the loss of sleep.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catena, Riccardo; Schwabe, Bodo, E-mail: riccardo.catena@theorie.physik.uni-goettingen.de, E-mail: bodo.schwabe@theorie.physik.uni-goettingen.de

In the effective theory of isoscalar and isovector dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle, 8 isotope-dependent nuclear response functions can be generated in the dark matter scattering by nuclei. We compute the 8 nuclear response functions for the 16 most abundant elements in the Sun, i.e. H, {sup 3}He, {sup 4}He, {sup 12}C, {sup 14}N, {sup 16}O, {sup 20}Ne, {sup 23}Na, {sup 24}Mg, {sup 27}Al, {sup 28}Si, {sup 32}S, {sup 40}Ar, {sup 40}Ca, {sup 56}Fe, and {sup 59}Ni, through numerical shell model calculations. We use our response functions to compute the rate of dark mattermore » capture by the Sun for all isoscalar and isovector dark matter-nucleon effective interactions, including several operators previously considered for dark matter direct detection only. We study in detail the dependence of the capture rate on specific dark matter-nucleon interaction operators, and on the different elements in the Sun. We find that a so far neglected momentum dependent dark matter coupling to the nuclear vector charge gives a larger contribution to the capture rate than the constant spin-dependent interaction commonly included in dark matter searches at neutrino telescopes. Our investigation lays the foundations for model independent analyses of dark matter induced neutrino signals from the Sun. The nuclear response functions obtained in this study are listed in analytic form in an appendix, ready to be used in other projects.« less

Dark chocolate improves coronary vasomotion and reduces platelet reactivity.

PubMed

Flammer, Andreas J; Hermann, Frank; Sudano, Isabella; Spieker, Lukas; Hermann, Matthias; Cooper, Karen A; Serafini, Mauro; Lüscher, Thomas F; Ruschitzka, Frank; Noll, Georg; Corti, Roberto

2007-11-20

Dark chocolate has potent antioxidant properties. Coronary atherosclerosis is promoted by impaired endothelial function and increased platelet activation. Traditional risk factors, high oxidative stress, and reduced antioxidant defenses play a crucial role in the pathogenesis of atherosclerosis, particularly in transplanted hearts. Thus, flavonoid-rich dark chocolate holds the potential to have a beneficial impact on graft atherosclerosis. We assessed the effect of flavonoid-rich dark chocolate compared with cocoa-free control chocolate on coronary vascular and platelet function in 22 heart transplant recipients in a double-blind, randomized study. Coronary vasomotion was assessed with quantitative coronary angiography and cold pressor testing before and 2 hours after ingestion of 40 g of dark (70% cocoa) chocolate or control chocolate, respectively. Two hours after ingestion of flavonoid-rich dark chocolate, coronary artery diameter was increased significantly (from 2.36+/-0.51 to 2.51+/-0.59 mm, P<0.01), whereas it remained unchanged after control chocolate. Endothelium-dependent coronary vasomotion improved significantly after dark chocolate (4.5+/-11.4% versus -4.3+/-11.7% in the placebo group, P=0.01). Platelet adhesion decreased from 4.9+/-1.1% to 3.8+/-0.8% (P=0.04) in the dark chocolate group but remained unchanged in the control group. Dark chocolate induces coronary vasodilation, improves coronary vascular function, and decreases platelet adhesion 2 hours after consumption. These immediate beneficial effects were paralleled by a significant reduction of serum oxidative stress and were positively correlated with changes in serum epicatechin concentration.

Form factors for dark matter capture by the Sun in effective theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catena, Riccardo; Schwabe, Bodo

2015-04-24

In the effective theory of isoscalar and isovector dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle, 8 isotope-dependent nuclear response functions can be generated in the dark matter scattering by nuclei. We compute the 8 nuclear response functions for the 16 most abundant elements in the Sun, i.e. H, {sup 3}He, {sup 4}He, {sup 12}C, {sup 14}N, {sup 16}O, {sup 20}Ne, {sup 23}Na, {sup 24}Mg, {sup 27}Al, {sup 28}Si, {sup 32}S, {sup 40}Ar, {sup 40}Ca, {sup 56}Fe, and {sup 59}Ni, through numerical shell model calculations. We use our response functions to compute the rate of dark mattermore » capture by the Sun for all isoscalar and isovector dark matter-nucleon effective interactions, including several operators previously considered for dark matter direct detection only. We study in detail the dependence of the capture rate on specific dark matter-nucleon interaction operators, and on the different elements in the Sun. We find that a so far neglected momentum dependent dark matter coupling to the nuclear vector charge gives a larger contribution to the capture rate than the constant spin-dependent interaction commonly included in dark matter searches at neutrino telescopes. Our investigation lays the foundations for model independent analyses of dark matter induced neutrino signals from the Sun. The nuclear response functions obtained in this study are listed in analytic form in an appendix, ready to be used in other projects.« less

Search for magnetic inelastic dark matter with XENON100

NASA Astrophysics Data System (ADS)

Aprile, E.; Aalbers, J.; Agostini, F.; Alfonsi, M.; Amaro, F. D.; Anthony, M.; Arneodo, F.; Barrow, P.; Baudis, L.; Bauermeister, B.; Benabderrahmane, M. L.; Berger, T.; Breur, P. A.; Brown, A.; Brown, E.; Bruenner, S.; Bruno, G.; Budnik, R.; Bütikofer, L.; Calvén, J.; Cardoso, J. M. R.; Cervantes, M.; Cichon, D.; Coderre, D.; Colijn, A. P.; Conrad, J.; Cussonneau, J. P.; Decowski, M. P.; de Perio, P.; Di Gangi, P.; Di Giovanni, A.; Diglio, S.; Eurin, G.; Fei, J.; Ferella, A. D.; Fieguth, A.; Franco, D.; Fulgione, W.; Gallo Rosso, A.; Galloway, M.; Gao, F.; Garbini, M.; Geis, C.; Goetzke, L. W.; Greene, Z.; Grignon, C.; Hasterok, C.; Hogenbirk, E.; Itay, R.; Kaminsky, B.; Kessler, G.; Kish, A.; Landsman, H.; Lang, R. F.; Lellouch, D.; Levinson, L.; Lin, Q.; Lindemann, S.; Lindner, M.; Lombardi, F.; Lopes, J. A. M.; Manfredini, A.; Maris, I.; Marrodán Undagoitia, T.; Masbou, J.; Massoli, F. V.; Masson, D.; Mayani, D.; Messina, M.; Micheneau, K.; Molinario, A.; Murra, M.; Naganoma, J.; Ni, K.; Oberlack, U.; Pakarha, P.; Pelssers, B.; Persiani, R.; Piastra, F.; Pienaar, J.; Pizzella, V.; Piro, M.-C.; Plante, G.; Priel, N.; Rauch, L.; Reichard, S.; Reuter, C.; Rizzo, A.; Rosendahl, S.; Rupp, N.; dos Santos, J. M. F.; Sartorelli, G.; Scheibelhut, M.; Schindler, S.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Selvi, M.; Shagin, P.; Silva, M.; Simgen, H.; Sivers, M. v.; Stein, A.; Thers, D.; Tiseni, A.; Trinchero, G.; Tunnell, C.; Vargas, M.; Wang, H.; Wei, Y.; Weinheimer, C.; Wulf, J.; Ye, J.; Zhang, Y.

2017-10-01

We present the first search for dark matter-induced delayed coincidence signals in a dual-phase xenon time projection chamber, using the 224.6 live days of the XENON100 science run II. This very distinct signature is predicted in the framework of magnetic inelastic dark matter which has been proposed to reconcile the modulation signal reported by the DAMA/LIBRA collaboration with the null results from other direct detection experiments. No candidate event has been found in the region of interest and upper limits on the WIMP's magnetic dipole moment are derived. The scenarios proposed to explain the DAMA/LIBRA modulation signal by magnetic inelastic dark matter interactions of WIMPs with masses of 58.0 GeV/c2 and 122.7 GeV/c2 are excluded at 3.3 σ and 9.3 σ, respectively.

Bent dark soliton dynamics in two spatial dimensions beyond the mean field approximation

NASA Astrophysics Data System (ADS)

Mistakidis, Simeon; Katsimiga, Garyfallia; Koutentakis, Georgios; Kevrekidis, Panagiotis; Schmelcher, Peter; Theory Group of Fundamental Processes in Quantum Physics Team

2017-04-01

The dynamics of a bented dark soliton embedded in two spatial dimensions beyond the mean-field approximation is explored. We examine the case of a single bented dark soliton comparing the mean-field approximation to a correlated approach that involves multiple orbitals. Fragmentation is generally present and significantly affects the dynamics, especially in the case of stronger interparticle interactions and in that of lower atom numbers. It is shown that the presence of fragmentation allows for the appearance of solitonic and vortex structures in the higher-orbital dynamics. In particular, a variety of excitations including dark solitons in multiple orbitals and vortex-antidark complexes is observed to arise spontaneously within the beyond mean-field dynamics. Deutsche Forschungsgemeinschaft (DFG) in the framework of the SFB 925 ``Light induced dynamics and control of correlated quantum systems''.

Making beam splitters with dark soliton collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steiglitz, Ken

2010-10-15

We show with numerical simulations that for certain simple choices of parameters, the waveguides induced by colliding dark solitons in a Kerr medium yield a complete family of beam splitters for trapped linear waves, ranging from total transmission to total deflection. The way energy is transferred from one waveguide to another is similar to that of a directional coupler, but no special fabrication is required. Dark soliton beam splitters offer potential advantages over their bright soliton counterparts: Their transfer characteristics do not depend on the relative phase or speed of the colliding solitons; dark solitons are generally more robust thanmore » bright solitons; and the probe peaks at nulls of the pump, enhancing the signal-to-noise ratio for probe detection. The last factor is especially important for possible application to quantum information processing.« less

Chemiexcitation of Melanin Derivatives Induces DNA Photoproducts Long after UV Exposure

PubMed Central

Premi, Sanjay; Wallisch, Silvia; Mano, Camila M.; Weiner, Adam B.; Bacchiocchi, Antonella; Wakamatsu, Kazumasa; Bechara, Etelvino J. H.; Halaban, Ruth; Douki, Thierry; Brash, Douglas E.

2015-01-01

Mutations in sunlight-induced melanoma arise from cyclobutane pyrimidine dimers (CPD), DNA photoproducts that are typically created picoseconds after an ultraviolet (UV) photon is absorbed at thymine or cytosine. Here we show that in melanocytes, CPD are generated for >3 hours after exposure to UVA, a major component of the radiation in sunlight and in tanning beds. These “dark CPD” constitute the majority of CPD and include the cytosine-containing CPD that initiate UV-signature C→T mutations. Dark CPD arise when UV-induced reactive oxygen and nitrogen species combine to excite an electron in fragments of the pigment melanin. This creates a quantum triplet state that has the energy of a UV photon but that induces CPD by energy transfer to DNA in a radiation-independent manner. Melanin may thus be carcinogenic as well as protective against cancer. These findings also validate the long-standing suggestion that chemically-generated excited electronic states are relevant to mammalian biology. PMID:25700512

The ribokinases of Arabidopsis thaliana and Saccharomyces cerevisiae are required for ribose recycling from nucleotide catabolism, which in plants is not essential to survive prolonged dark stress.

PubMed

Schroeder, Rebekka Y; Zhu, Anting; Eubel, Holger; Dahncke, Kathleen; Witte, Claus-Peter

2018-01-01

Nucleotide catabolism in Arabidopsis thaliana and Saccharomyces cerevisiae leads to the release of ribose, which requires phosphorylation to ribose-5-phosphate mediated by ribokinase (RBSK). We aimed to characterize RBSK in plants and yeast, to quantify the contribution of plant nucleotide catabolism to the ribose pool, and to investigate whether ribose carbon contributes to dark stress survival of plants. We performed a phylogenetic analysis and determined the kinetic constants of plant-expressed Arabidopsis and yeast RBSKs. Using mass spectrometry, several metabolites were quantified in AtRBSK mutants and double mutants with genes of nucleoside catabolism. Additionally, the dark stress performance of several nucleotide metabolism mutants and rbsk was compared. The plant PfkB family of sugar kinases forms nine major clades likely representing distinct biochemical functions, one of them RBSK. Nucleotide catabolism is the dominant ribose source in plant metabolism and is highly induced by dark stress. However, rbsk cannot be discerned from the wild type in dark stress. Interestingly, the accumulation of guanosine in a guanosine deaminase mutant strongly enhances dark stress symptoms. Although nucleotide catabolism contributes to carbon mobilization upon darkness and is the dominant source of ribose, the contribution appears to be of minor importance for dark stress survival. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Depiction of pneumothoraces in a large animal model using x-ray dark-field radiography.

PubMed

Hellbach, Katharina; Baehr, Andrea; De Marco, Fabio; Willer, Konstantin; Gromann, Lukas B; Herzen, Julia; Dmochewitz, Michaela; Auweter, Sigrid; Fingerle, Alexander A; Noël, Peter B; Rummeny, Ernst J; Yaroshenko, Andre; Maack, Hanns-Ingo; Pralow, Thomas; van der Heijden, Hendrik; Wieberneit, Nataly; Proksa, Roland; Koehler, Thomas; Rindt, Karsten; Schroeter, Tobias J; Mohr, Juergen; Bamberg, Fabian; Ertl-Wagner, Birgit; Pfeiffer, Franz; Reiser, Maximilian F

2018-02-08

The aim of this study was to assess the diagnostic value of x-ray dark-field radiography to detect pneumothoraces in a pig model. Eight pigs were imaged with an experimental grating-based large-animal dark-field scanner before and after induction of a unilateral pneumothorax. Image contrast-to-noise ratios between lung tissue and the air-filled pleural cavity were quantified for transmission and dark-field radiograms. The projected area in the object plane of the inflated lung was measured in dark-field images to quantify the collapse of lung parenchyma due to a pneumothorax. Means and standard deviations for lung sizes and signal intensities from dark-field and transmission images were tested for statistical significance using Student's two-tailed t-test for paired samples. The contrast-to-noise ratio between the air-filled pleural space of lateral pneumothoraces and lung tissue was significantly higher in the dark-field (3.65 ± 0.9) than in the transmission images (1.13 ± 1.1; p = 0.002). In case of dorsally located pneumothoraces, a significant decrease (-20.5%; p > 0.0001) in the projected area of inflated lung parenchyma was found after a pneumothorax was induced. Therefore, the detection of pneumothoraces in x-ray dark-field radiography was facilitated compared to transmission imaging in a large animal model.

Dark adaptation-induced changes in rod, cone and intrinsically photosensitive retinal ganglion cell (ipRGC) sensitivity differentially affect the pupil light response (PLR).

PubMed

Wang, Bin; Shen, Chao; Zhang, Lei; Qi, Linsong; Yao, Lu; Chen, Jianzhang; Yang, Guoqing; Chen, Tao; Zhang, Zuoming

2015-11-01

Our purpose was to explore pupil light response (PLR) with respect to the change in sensitivity of photoreceptors during various dark adaptation phases and to determine the optimal duration of dark adaptation time before the PLR. The PLR was recorded in 15 healthy subjects and three patients with neural or retinal vision loss after 1-sec blue and red light stimuli of 1, 10, and 100 cd/m(2). The PLR was repeated nine times at different checkpoints during the 40-minute dark adaptation. The transient contraction amplitude, sustained contraction amplitude, and relative sustained contraction ratio of the PLR were analyzed. The increase in the transient contraction amplitude during the entire dark adaptation process was significant (changing up to 45.1 %) in the initial phase of dark adaptation under different stimulus conditions. The changes in the sustained contraction amplitude and the relative sustained contraction ratio were substantial (changing up to 71.0 % and 37.2 % from 1 to 20 minutes of dark adaptation, respectively) under high-intensity blue illumination. The inflection point of the contraction curves in the dark adaptation was 15 or 20 minutes. The patients' PLR results changed in a similar manner. The changes in the sensitivity of different photoreceptors occurred at different rates, and the contraction amplitude of the PLR was significantly affected by the dark adaptation duration. So 20 minutes of dark adaptation before PLR testing was suggested to achieve a consistent and stable pupil response. The dark adaptation effect should be put into consideration when comparing the results from different phases of the PLR test.

Effects of dark chocolate and cocoa consumption on endothelial function and arterial stiffness in overweight adults.

PubMed

West, Sheila G; McIntyre, Molly D; Piotrowski, Matthew J; Poupin, Nathalie; Miller, Debra L; Preston, Amy G; Wagner, Paul; Groves, Lisa F; Skulas-Ray, Ann C

2014-02-01

The consumption of cocoa and dark chocolate is associated with a lower risk of CVD, and improvements in endothelial function may mediate this relationship. Less is known about the effects of cocoa/chocolate on the augmentation index (AI), a measure of vascular stiffness and vascular tone in the peripheral arterioles. We enrolled thirty middle-aged, overweight adults in a randomised, placebo-controlled, 4-week, cross-over study. During the active treatment (cocoa) period, the participants consumed 37 g/d of dark chocolate and a sugar-free cocoa beverage (total cocoa = 22 g/d, total flavanols (TF) = 814 mg/d). Colour-matched controls included a low-flavanol chocolate bar and a cocoa-free beverage with no added sugar (TF = 3 mg/d). Treatments were matched for total fat, saturated fat, carbohydrates and protein. The cocoa treatment significantly increased the basal diameter and peak diameter of the brachial artery by 6% (+2 mm) and basal blood flow volume by 22%. Substantial decreases in the AI, a measure of arterial stiffness, were observed in only women. Flow-mediated dilation and the reactive hyperaemia index remained unchanged. The consumption of cocoa had no effect on fasting blood measures, while the control treatment increased fasting insulin concentration and insulin resistance (P= 0·01). Fasting blood pressure (BP) remained unchanged, although the acute consumption of cocoa increased resting BP by 4 mmHg. In summary, the high-flavanol cocoa and dark chocolate treatment was associated with enhanced vasodilation in both conduit and resistance arteries and was accompanied by significant reductions in arterial stiffness in women.

Anaerobic Carbon Metabolism by the Tricarboxylic Acid Cycle : Evidence for Partial Oxidative and Reductive Pathways during Dark Ammonium Assimilation.

PubMed

Vanlerberghe, G C; Horsey, A K; Weger, H G; Turpin, D H

1989-12-01

Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH(4) (+) in the dark under anaerobic conditions. Addition of NH(4) (+) to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO(2) efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenolpyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H(14)CO(3) (-) to anaerobic cells assimilating NH(4) (+) results in the incorporation of radiolabel into the alpha-carboxyl carbon of glutamic acid. Incorporation of radiolabel into glutamic acid is not simply a short-term phenomenon following NH(4) (+) addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply alpha-ketoglutarate for glutamate production. During dark aerobic NH(4) (+) assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH(4) (+) assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH(4) (+) assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity.

Examination pf Potential Anti-Tumor Activity of N-Thiolated B-Lactam Antibiotics in Nude Mice Bearing Human Breast Tumors

DTIC Science & Technology

2005-08-01

temperature in the dark, and then analyzed by flow cytometry within 3 hr of staining. 2.7. Caspase-3/-7 activity assay To measure cell-free caspase-3/-7...were treated with 50 mM of lactam 12 for the indicated hours. (A) Measurement of sub-G1 DNA content by flow cytometry analysis. The percentage of sub...Daniel for critical reading of the manuscript. We also appreciate the assistance of the Flow Cytometry Core at H. Lee Moffitt Cancer Center

Dwarfs and Giants in the local flows of galaxies.

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Emelyanov, N. V.; Karachentsev, I. D.

We use recent Hubble Space Telescope data on nearby dwarf and giant galaxies to study the dynamical structure and evolutionary trends of the local expansion flows of galaxies. It is found that antigravity of dark energy dominates the force field of the flows and makes them expand with acceleration. It also cools the flows and introduces to them the nearly linear velocity-distance relation with the time-rate close to the global Hubble's factor. There are grounds to expect that this is the universal physical regularity that is common not only for the nearby flows we studied here, but also for all the expansion flows of various spatial scales from the 1 Mpc scale and up to the scale of the global cosmological expansion.

Exotic dark spinor fields

NASA Astrophysics Data System (ADS)

Da Rocha, Roldão; Bernardini, Alex E.; da Silva, J. M. Hoff

2011-04-01

Exotic dark spinor fields are introduced and investigated in the context of inequivalent spin structures on arbitrary curved spacetimes, which induces an additional term on the associated Dirac operator, related to a Čech cohomology class. For the most kinds of spinor fields, any exotic term in the Dirac operator can be absorbed and encoded as a shift of the electromagnetic vector potential representing an element of the cohomology group {H^1}( {M,{{Z}_2}} ) . The possibility of concealing such an exotic term does not exist in case of dark (ELKO) spinor fields, as they cannot carry electromagnetic charge, so that the full topological analysis must be evaluated. Since exotic dark spinor fields also satisfy Klein-Gordon propagators, the dynamical constraints related to the exotic term in the Dirac equation can be explicitly calculated. It forthwith implies that the non-trivial topology associated to the spacetime can drastically engender — from the dynamics of dark spinor fields — constraints in the spacetime metric structure. Meanwhile, such constraints may be alleviated, at the cost of constraining the exotic spacetime topology. Besides being prime candidates to the dark matter problem, dark spinor fields are shown to be potential candidates to probe non-trivial topologies in spacetime, as well as probe the spacetime metric structure.

Acute dark chocolate ingestion is beneficial for hemodynamics via enhancement of erythrocyte deformability in healthy humans.

PubMed

Radosinska, Jana; Horvathova, Martina; Frimmel, Karel; Muchova, Jana; Vidosovicova, Maria; Vazan, Rastislav; Bernatova, Iveta

2017-03-01

Erythrocyte deformability is an important property of erythrocytes that considerably affects blood flow and hemodynamics. The high content of polyphenols present in dark chocolate has been reported to play a protective role in functionality of erythrocytes. We hypothesized that chocolate might influence erythrocytes not only after repeated chronic intake, but also immediately after its ingestion. Thus, we determined the acute effect of dark chocolate and milk (with lower content of biologically active substances) chocolate intake on erythrocyte deformability. We also focused on selected factors that may affect erythrocyte deformability, specifically nitric oxide production in erythrocytes and total antioxidant capacity of plasma. We determined posttreatment changes in the mentioned parameters 2hours after consumption of chocolate compared with their levels before consumption of chocolate. In contrast to milk chocolate intake, the dark chocolate led to a significantly higher increase in erythrocyte deformability. Nitric oxide production in erythrocytes was not changed after dark chocolate intake, but significantly decreased after milk chocolate. The plasma total antioxidant capacity remained unaffected after ingestion of both chocolates. We conclude that our hypothesis was confirmed. Single ingestion of dark chocolate improved erythrocyte deformability despite unchanged nitric oxide production and antioxidant capacity of plasma. Increased deformability of erythrocytes may considerably improve rheological properties of blood and thus hemodynamics in humans, resulting in better tissue oxygenation. Copyright © 2017 Elsevier Inc. All rights reserved.

Endogenous alpha-ketol linolenic acid levels in short day-induced cotyledons are closely related to flower induction in Pharbitis nil.

PubMed

Suzuki, Masayuki; Yamaguchi, Shoko; Iida, Toshii; Hashimoto, Ikue; Teranishi, Hiromi; Mizoguchi, Masaya; Yano, Fumihiko; Todoroki, Yasushi; Watanabe, Naoharu; Yokoyama, Mineyuki

2003-01-01

Alpha-ketol linolenic acid [KODA, 9,10-ketol-octadecadienoic acid, that is 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid] is a signal compound found in Lemna paucicostata after exposure to stress, such as drought, heat or osmotic stress. KODA reacts with catecholamines to generate products that strongly induce flowering, although KODA itself is inactive [Yokoyama et al. (2000) Plant Cell Physiol. 41: 110; Yamaguchi et al. (2001) Plant Cell Physiol. 42: 1201]. We examined the role of KODA in the flower-induction process of Pharbitis nil (violet). KODA was identified for the first time in seedlings of P. nil grown under a flower-inductive condition (16-h dark exposure), by means of LC-SIM and LC-MS/MS. In addition, the changes in endogenous KODA levels (evaluated after esterification of KODA with 9-anthryldiazomethane) during the flower-inductive phase in short day-induced cotyledons were closely related to flower induction. The KODA concentration sharply increased in seedlings during the last 2 h of a 16-h dark period, while the KODA level showed no significant elevation under continuous light. The increase of KODA level occurred in cotyledonal blades, but not in other parts (petiole, hypocotyls and shoot tip). When the 16-h dark period was interrupted with a 10-min light exposure at the 8th h, flower induction was blocked and KODA level also failed to increase. The degree of elevation of KODA concentration in response to 16-h dark exposure was the highest when the cotyledons had just unfolded, and gradually decreased in seedlings grown under continuous light for longer periods, reaching the basal level at the 3rd day after unfolding. Flower-inducing ability also decreased in a similar manner. These results suggest that KODA may be involved in flower induction in P. nil.

An enhancing effect of visible light and UV radiation on phenolic compounds and various antioxidants in broad bean seedlings.

PubMed

Younis, Mahmoud El-Baz; Hasaneen, Mohammed Naguib Abdel-Ghany; Abdel-Aziz, Heba Mahmoud Mohammed

2010-10-01

Exposure of dark- or ambient visible light-grown broad bean seedlings to low (LL) and high (HL) visible light intensities, UV-A or UV-C, either alone or in combination, induced significant increases in total phenolic compounds as well as in anthocyanins content, throughout the germination period, as compared with the respective levels in control seedlings. In general, as compared with control levels, exposure of both dark- or light-grown broad bean seedlings to LL, HL, UV-A or UV-C, induced significant increases in the contents of non-enzymatic antioxidants (total ascorbate; ASA-DASA and total glutathione; GSSG-GSH) and enzymatic antioxidant activities (superoxide dismutase; SOD, catalase; CAT, ascorbate peroxidase; APO and glutathione reductase; GR). The obtained results are discussed in relation to induced mechanisms of protection and repair from the inevitable exposure to damaging visible light and UV-radiation. © 2010 Landes Bioscience

An enhancing effect of visible light and UV radiation on phenolic compounds and various antioxidants in broad bean seedlings

PubMed Central

Hasaneen, Mohammed Naguib Abdel-Ghany; Abdel-Aziz, Heba Mahmoud Mohammed

2010-01-01

Exposure of dark- or ambient visible light-grown broad bean seedlings to low (LL) and high (HL) visible light intensities, UV-A or UV-C, either alone or in combination, induced significant increases in total phenolic compounds as well as in anthocyanins content, throughout the germination period, as compared with the respective levels in control seedlings. In general, as compared with control levels, exposure of both dark- or light-grown broad bean seedlings to LL, HL, UV-A or UV-C, induced significant increases in the contents of non-enzymatic antioxidants (total ascorbate; ASA-DASA and total glutathione; GSSG-GSH) and enzymatic antioxidant activities (superoxide dismutase; SOD, catalase; CAT, ascorbate peroxidase; APO and glutathione reductase; GR). The obtained results are discussed in relation to induced mechanisms of protection and repair from the inevitable exposure to damaging visible light and UV radiation. PMID:20505357

Dynamically tunable electromagnetically induced transparency analogy in terahertz metamaterial

NASA Astrophysics Data System (ADS)

Liu, Chenxi; Liu, Peiguo; Bian, Lian; Zhou, Qihui; Li, Gaosheng; Liu, Hanqin

2018-03-01

A metamaterial analogy of tunable electromagnetically induced transparency (EIT) is theoretically investigated in terahertz regime. The proposed metamaterial consists of vertical gold strips and horizontal graphene wires, which perform as bright elements and dark elements, respectively. The EIT-like phenomenon can be induced by bright-dark mode coupling on condition of structural lateral displacement. Numerical result reveals that the EIT-like effect remains noticeable with a wide range of incidence polarization angles. Most importantly, by manipulating gate voltages, the EIT window can be dynamically controlled without refabricating the structure. The amplitude modulation depth can reach 81%, 79%, and 68% respectively at three characteristic frequencies as Fermi energy changes in the scope of 0.8-1.0 eV. Furthermore, a sensitivity of 0.95 THz per refractive index unit (RIU) is realized varying the refractive index in the surrounding medium. This structure provides potential applications for detectors, sensors, and modulators.

Arabidopsis RabF1 (ARA6) Is Involved in Salt Stress and Dark-Induced Senescence (DIS)

PubMed Central

Yin, Congfei; Karim, Sazzad; Zhang, Hongsheng; Aronsson, Henrik

2017-01-01

Arabidopsis small GTPase RabF1 (ARA6) functions in endosomal vesicle transport and may play a crucial role in recycling and degradation of molecules, thus involved in stress responses. Here we have reported that complementary overexpression lines RabF1OE (overexpression), GTPase mutants RabF1Q93L (constitutively active) and RabF1S47N (dominant negative) lines show longer root growth than wild-type, rabF1 knockout and N-myristoylation deletion (Δ1−29, N-terminus) complementary overexpression mutant plants under salt induced stress, which indicates that N-myristoylation of RabF1 is indispensable for salt tolerance. Moreover, RabF1 is highly expressed during senescence and RabF1OE lines were more tolerant of dark-induced senescence (DIS) than wild-type and rabF1. PMID:28157156

Induction of conidiation by endogenous volatile compounds in Trichoderma spp.

PubMed

Nemcovic, Marek; Jakubíková, Lucia; Víden, Ivan; Farkas, Vladimír

2008-07-01

Light and starvation are two principal environmental stimuli inducing conidiation in the soil micromycete Trichoderma spp. We observed that volatiles produced by conidiating colonies of Trichoderma spp. elicited conidiation in colonies that had not been induced previously by exposure to light. The inducing effect of volatiles was both intra- and interspecific. Chemical profiles of the volatile organic compounds (VOCs) produced by the nonconidiated colonies grown in the dark and by the conidiating colonies were compared using solid-phase microextraction of headspace samples followed by tandem GC-MS. The conidiation was accompanied by increased production of eight-carbon compounds 1-octen-3-ol and its analogs 3-octanol and 3-octanone. When vapors of these compounds were applied individually to dark-grown colonies, they elicited their conidiation already at submicromolar concentrations. It is concluded that the eight-carbon VOCs act as signaling molecules regulating development and mediating intercolony communication in Trichoderma.

Interacting Dark Resonances with Plasmonic Meta-Molecules

DTIC Science & Technology

2014-09-17

different K-subsystems, as seen in Fig. 1(b). Within the transparency window, of the K-configuration atomic electromagnetic induced transparency ( EIT ...exhibits EIT -type phenomena as seen by a reduction in absorbance at x 264 THz. The basic physical mechanism behind this EIT -type phenomena can be...radiative plasmonic atom.5 However, in the presence of a second dark plasmonic atom, the EIT -type transparency at FIG. 1. (a) Atomic four-level system

A NAP-AAO3 Regulatory Module Promotes Chlorophyll Degradation via ABA Biosynthesis in Arabidopsis Leaves[W][OPEN

PubMed Central

Yang, Jiading; Worley, Eric

2014-01-01

Chlorophyll degradation is an important part of leaf senescence, but the underlying regulatory mechanisms are largely unknown. Excised leaves of an Arabidopsis thaliana NAC-LIKE, ACTIVATED BY AP3/PI (NAP) transcription factor mutant (nap) exhibited lower transcript levels of known chlorophyll degradation genes, STAY-GREEN1 (SGR1), NON-YELLOW COLORING1 (NYC1), PHEOPHYTINASE (PPH), and PHEIDE a OXYGENASE (PaO), and higher chlorophyll retention than the wild type during dark-induced senescence. Transcriptome coexpression analysis revealed that abscisic acid (ABA) metabolism/signaling genes were disproportionately represented among those positively correlated with NAP expression. ABA levels were abnormally low in nap leaves during extended darkness. The ABA biosynthetic genes 9-CIS-EPOXYCAROTENOID DIOXYGENASE2, ABA DEFICIENT3, and ABSCISIC ALDEHYDE OXIDASE3 (AAO3) exhibited abnormally low transcript levels in dark-treated nap leaves. NAP transactivated the promoter of AAO3 in mesophyll cell protoplasts, and electrophoretic mobility shift assays showed that NAP can bind directly to a segment (−196 to −162 relative to the ATG start codon) of the AAO3 promoter. Exogenous application of ABA increased the transcript levels of SGR1, NYC1, PPH, and PaO and suppressed the stay-green phenotype of nap leaves during extended darkness. Overexpression of AAO3 in nap leaves also suppressed the stay-green phenotype under extended darkness. Collectively, the results show that NAP promotes chlorophyll degradation by enhancing transcription of AAO3, which leads to increased levels of the senescence-inducing hormone ABA. PMID:25516602

The Critical Role of Arabidopsis Electron-Transfer Flavoprotein:Ubiquinone Oxidoreductase during Dark-Induced StarvationW⃞

PubMed Central

Ishizaki, Kimitsune; Larson, Tony R.; Schauer, Nicolas; Fernie, Alisdair R.; Graham, Ian A.; Leaver, Christopher J.

2005-01-01

In mammals, electron-transfer flavoprotein:ubiquinone oxidoreductase (ETFQO) and electron-transfer flavoprotein (ETF) are functionally associated, and ETF accepts electrons from at least nine mitochondrial matrix flavoprotein dehydrogenases and transfers them to ubiquinone in the inner mitochondrial membrane. In addition, the mammalian ETF/ETFQO system plays a key role in β-oxidation of fatty acids and catabolism of amino acids and choline. By contrast, nothing is known of the function of ETF and ETFQO in plants. Sequence analysis of the unique Arabidopsis thaliana homologue of ETFQO revealed high similarity to the mammalian ETFQO protein. Moreover, green fluorescent protein cellular localization experiments suggested a mitochondrial location for this protein. RNA gel blot analysis revealed that Arabidopsis ETFQO transcripts accumulated in long-term dark-treated leaves. Analysis of three independent insertional mutants of Arabidopsis ETFQO revealed a dramatic reduction in their ability to withstand extended darkness, resulting in senescence and death within 10 d after transfer, whereas wild-type plants remained viable for at least 15 d. Metabolite profiling of dark-treated leaves of the wild type and mutants revealed a dramatic decline in sugar levels. In contrast with the wild type, the mutants demonstrated a significant accumulation of several amino acids, an intermediate of Leu catabolism, and, strikingly, high-level accumulation of phytanoyl-CoA. These data demonstrate the involvement of a mitochondrial protein, ETFQO, in the catabolism of Leu and potentially of other amino acids in higher plants and also imply a novel role for this protein in the chlorophyll degradation pathway activated during dark-induced senescence and sugar starvation. PMID:16055629

Electromagnetic waves propagating in the string axiverse

NASA Astrophysics Data System (ADS)

Yoshida, Daiske; Soda, Jiro

2018-04-01

It is widely believed that axions are ubiquitous in string theory and could be dark matter. The peculiar features of axion dark matter are coherent oscillations and a coupling to the electromagnetic field through the Chern-Simons term. In this letter, we study the consequences of these two features of axions with mass in the range 10^{-13} eV to 103 eV. First, we study the parametric resonance of electromagnetic waves induced by the coherent oscillation of the axion. Since the resonance frequency is determined by the mass of the axion dark matter, if we detect this signal, we can get information on the mass of the axion dark matter. Second, we study the velocity of light in the background of the axion dark matter. In the presence of the Chern-Simons term, the dispersion relation is modified and the speed of light will oscillate in time. It turns out that the change in the speed of light would be difficult to observe. We argue that future radio wave observations of the resonance can give rise to a stronger constraint on the coupling constant and/or the density of the axion dark matter.

The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

PubMed

Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

2016-01-01

For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to 'internal photons' inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350-700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation.

Cocoa and Dark Chocolate Polyphenols: From Biology to Clinical Applications

PubMed Central

Magrone, Thea; Russo, Matteo Antonio; Jirillo, Emilio

2017-01-01

It is well known that cocoa and dark chocolate possess polyphenols as major constituents whose dietary consumption has been associated to beneficial effects. In fact, cocoa and dark chocolate polyphenols exert antioxidant and anti-inflammatory activities switching on some important signaling pathways such as toll-like receptor 4/nuclear factor κB/signal transducer and activator of transcription. In particular, cocoa polyphenols induce release of nitric oxide (NO) through activation of endothelial NO synthase which, in turn, accounts for vasodilation and cardioprotective effects. In the light of the above described properties, a number of clinical trials based on the consumption of cocoa and dark chocolate have been conducted in healthy subjects as well as in different categories of patients, such as those affected by cardiovascular, neurological, intestinal, and metabolic pathologies. Even if data are not always concordant, modifications of biomarkers of disease are frequently associated to improvement of clinical manifestations. Quite interestingly, following cocoa and dark chocolate ingestion, cocoa polyphenols also modulate intestinal microbiota, thus leading to the growth of bacteria that trigger a tolerogenic anti-inflammatory pathway in the host. Finally, many evidences encourage the consumption of cocoa and dark chocolate by aged people for the recovery of the neurovascular unit. PMID:28649251

Light-dark cycle memory in the mammalian suprachiasmatic nucleus.

PubMed

Ospeck, Mark C; Coffey, Ben; Freeman, Dave

2009-09-16

The mammalian circadian oscillator, or suprachiasmatic nucleus (SCN), contains several thousand clock neurons in its ventrolateral division, many of which are spontaneous oscillators with period lengths that range from 22 to 28 h. In complete darkness, this network synchronizes through the exchange of action potentials that release vasoactive intestinal polypeptide, striking a compromise, free-running period close to 24 h long. We entrained Siberian hamsters to various light-dark cycles and then tracked their activity into constant darkness to show that they retain a memory of the previous light-dark cycle before returning to their own free-running period. Employing Leloup-Goldbeter mammalian clock neurons we model the ventrolateral SCN network and show that light acting weakly upon a strongly rhythmic vasoactive intestinal polypeptide oscillation can explain the observed light-dark cycle memory. In addition, light is known to initiate a mitogen-activated protein kinase signaling cascade that induces transcription of both per and mkp1 phosphatase. We show that the ensuing phosphatase-kinase interaction can account for the dead zone in the mammalian phase response curve and hypothesize that the SCN behaves like a lock-in amplifier to entrain to the light edges of the circadian day.

Strongly self-interacting vector dark matter via freeze-in

NASA Astrophysics Data System (ADS)

Duch, Mateusz; Grzadkowski, Bohdan; Huang, Da

2018-01-01

We study a vector dark matter (VDM) model in which the dark sector couples to the Standard Model sector via a Higgs portal. If the portal coupling is small enough the VDM can be produced via the freeze-in mechanism. It turns out that the electroweak phase transition have a substantial impact on the prediction of the VDM relic density. We further assume that the dark Higgs boson which gives the VDM mass is so light that it can induce strong VDM self-interactions and solve the small-scale structure problems of the Universe. As illustrated by the latest LUX data, the extreme smallness of the Higgs portal coupling required by the freeze-in mechanism implies that the dark matter direct detection bounds are easily satisfied. However, the model is well constrained by the indirect detections of VDM from BBN, CMB, AMS-02, and diffuse γ/X-rays. Consequently, only when the dark Higgs boson mass is at most of O (keV) does there exist a parameter region which leads to a right amount of VDM relic abundance and an appropriate VDM self-scattering while satisfying all other constraints simultaneously.

Cocoa and Dark Chocolate Polyphenols: From Biology to Clinical Applications.

PubMed

Magrone, Thea; Russo, Matteo Antonio; Jirillo, Emilio

2017-01-01

It is well known that cocoa and dark chocolate possess polyphenols as major constituents whose dietary consumption has been associated to beneficial effects. In fact, cocoa and dark chocolate polyphenols exert antioxidant and anti-inflammatory activities switching on some important signaling pathways such as toll-like receptor 4/nuclear factor κB/signal transducer and activator of transcription. In particular, cocoa polyphenols induce release of nitric oxide (NO) through activation of endothelial NO synthase which, in turn, accounts for vasodilation and cardioprotective effects. In the light of the above described properties, a number of clinical trials based on the consumption of cocoa and dark chocolate have been conducted in healthy subjects as well as in different categories of patients, such as those affected by cardiovascular, neurological, intestinal, and metabolic pathologies. Even if data are not always concordant, modifications of biomarkers of disease are frequently associated to improvement of clinical manifestations. Quite interestingly, following cocoa and dark chocolate ingestion, cocoa polyphenols also modulate intestinal microbiota, thus leading to the growth of bacteria that trigger a tolerogenic anti-inflammatory pathway in the host. Finally, many evidences encourage the consumption of cocoa and dark chocolate by aged people for the recovery of the neurovascular unit.

Pathway for recovery of photo-degraded polymer solar cells by post degradation thermal anneal

DOE PAGES

Bhattacharya, J.; Joshi, P. H.; Biswas, Rana; ...

2017-02-16

The photo-degradation of polymer solar cells is a critical challenge preventing its commercial deployment. We experimentally fabricate organic solar cells and characterize their degradation under solar simulators in an environmental chamber under nitrogen flow, without exposure to oxygen and moisture. We have developed a thermally stable inverted organic solar cell architecture in which light induced degradation of device characteristics can be reversibly annealed to the pristine values. The stable inverted cells utilized MoO x layers that are thermally treated immediately after their deposition on the organic layer, and before metal cathode deposition. Organic solar cells that are photo-degraded in themore » presence of oxygen, however show irreversible degradation that cannot be thermally recovered. The decrease of organic solar cell characteristics correlates with increases in mid-gap electronic states, measured using capacitance spectroscopy and dark current. It is likely the photo-induced defect states caused by local H motion from the alkyl chains to the aromatic backbone, can be reversibly annealed at elevated temperatures after photo-degradation. Finally, our results provide a pathway for improving the stability of organic photovoltaics.« less

Pathway for recovery of photo-degraded polymer solar cells by post degradation thermal anneal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, J.; Joshi, P. H.; Biswas, Rana

The photo-degradation of polymer solar cells is a critical challenge preventing its commercial deployment. We experimentally fabricate organic solar cells and characterize their degradation under solar simulators in an environmental chamber under nitrogen flow, without exposure to oxygen and moisture. We have developed a thermally stable inverted organic solar cell architecture in which light induced degradation of device characteristics can be reversibly annealed to the pristine values. The stable inverted cells utilized MoO x layers that are thermally treated immediately after their deposition on the organic layer, and before metal cathode deposition. Organic solar cells that are photo-degraded in themore » presence of oxygen, however show irreversible degradation that cannot be thermally recovered. The decrease of organic solar cell characteristics correlates with increases in mid-gap electronic states, measured using capacitance spectroscopy and dark current. It is likely the photo-induced defect states caused by local H motion from the alkyl chains to the aromatic backbone, can be reversibly annealed at elevated temperatures after photo-degradation. Finally, our results provide a pathway for improving the stability of organic photovoltaics.« less

MC-13 Syrtis Major Region

NASA Technical Reports Server (NTRS)

1994-01-01

Mars digital-image mosaic merged with color of the MC-13 quadrangle, Syrtis Major region of Mars. The central part is dominated by dark dust and lava flows of the Syrtis Major Planitia region. These lava flows are partly bounded to the east by a large depression, Isidis basin, which contains smooth plains, and to the west and north by heavily cratered and moderately faulted highlands. Latitude range 0 to 30 degrees, longitude range -90 to -45 degrees.

Quantisation of the holographic Ricci dark energy model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albarran, Imanol; Bouhmadi-López, Mariam, E-mail: imanol@ubi.pt, E-mail: mbl@ubi.pt

2015-08-01

While general relativity is an extremely robust theory to describe the gravitational interaction in our Universe, it is expected to fail close to singularities like the cosmological ones. On the other hand, it is well known that some dark energy models might induce future singularities; this can be the case for example within the setup of the Holographic Ricci Dark Energy model (HRDE). On this work, we perform a cosmological quantisation of the HRDE model and obtain under which conditions a cosmic doomsday can be avoided within the quantum realm. We show as well that this quantum model not onlymore » avoid future singularities but also the past Big Bang.« less

Origin of large dark current increase in InGaAs/InP avalanche photodiode

NASA Astrophysics Data System (ADS)

Wen, J.; Wang, W. J.; Chen, X. R.; Li, N.; Chen, X. S.; Lu, W.

2018-04-01

The large dark current increase near the breakdown voltage of an InGaAs/InP avalanche photodiode is observed and analyzed from the aspect of bulk defects in the device materials. The trap level information is extracted from the temperature-dependent electrical characteristics of the device and the low temperature photoluminescence spectrum of the materials. Simulation results with the extracted trap level taken into consideration show that the trap is in the InP multiplication layer and the trap assisted tunneling current induced by the trap is the main cause of the large dark current increase with the bias from the punch-through voltage to 95% breakdown voltage.

Do stochastic inhomogeneities affect dark-energy precision measurements?

PubMed

Ben-Dayan, I; Gasperini, M; Marozzi, G; Nugier, F; Veneziano, G

2013-01-11

The effect of a stochastic background of cosmological perturbations on the luminosity-redshift relation is computed to second order through a recently proposed covariant and gauge-invariant light-cone averaging procedure. The resulting expressions are free from both ultraviolet and infrared divergences, implying that such perturbations cannot mimic a sizable fraction of dark energy. Different averages are estimated and depend on the particular function of the luminosity distance being averaged. The energy flux being minimally affected by perturbations at large z is proposed as the best choice for precision estimates of dark-energy parameters. Nonetheless, its irreducible (stochastic) variance induces statistical errors on Ω(Λ)(z) typically lying in the few-percent range.

Light-mediated host searching strategies in a fish ectoparasite, Argulus foliaceus L. (crustacea: branchiura).

PubMed

Mikheev, V N; Mikheev, A V; Pasternak, A F; Valtonen, E T

2000-04-01

Argulus foliaceus, an obligate fish ectoparasite, can search for its hosts in both light and dark conditions and uses vision in the light. We have examined what searching mode is used at night, when the infection rate was at its highest, and which stimuli produced by the fish are most important. A change of illumination produced a clear difference in the searching behaviour of adult Argulus females. The mean swimming speed and the area explored were 3-4 times higher in the dark, when the parasite employed a cruising search strategy. This changed to an ambush (hover-and-wait) strategy in the light. The swimming activity is accompanied by changes in metabolic costs; the activity of the electron transport system being approximately 25 % lower in the light. The most pronounced light-induced differences in host-searching behaviour took place in moderately hungry parasites (starved for 24-96 h). Less motivated (just having left a fish) or exhausted animals did not exhibit any clear differences in swimming speed. Among the external signals tested, fish smell, from both perch (Perca fluviatilis) and roach (Rutilus rutilus), induced an elevated swimming speed of the parasite. Periodic water movements caused similar but weaker effects. The effects of these stimuli were observed under both light and dark conditions. We conclude that host-searching behaviour of A. foliaceus is under internal (state of hunger) and external (illumination and host-induced signals) control and involves all its sensory equipment (vision, olfaction and mechano-reception). Perch (but not roach) reduced their swimming speed in the dark, which make them more susceptible to cruising Argulus. Thus the behavioural interplay between hosts and parasites can also influence the infection rate of A. foliaceus found on perch and roach in Finnish lakes.

Rapid development of semistarvation-induced hyperactivity in Dark Agouti rats. Excessive wheel running and effect of 3,4-methylenedioxymethamphetamine (MDMA).

PubMed

Vidal, Pedro; Pérez-Padilla, Ángeles; Pellón, Ricardo

2013-02-01

Clinical studies have found that patients with anorexia develop high activity levels. These data suggest a possible implication of activity in the aetiology of anorexia and are in line with findings obtained in animals during experimental procedures to model interactions between activity and weight loss. Activity-based anorexia (ABA) and semistarvation-induced hyperactivity (SIH) develop when laboratory rats have food access restricted to a single period in the day and are given free access to an activity wheel. This experiment sought to show the effect on weight loss of the excessive activity normally seen in Dark Agouti rats and of hyperactivity induced by 3,4-methylenedioxymethamphetamine (MDMA). To this end, 32 female rats of the Dark Agouti strain were selected and divided into four groups in accordance with a 2 × 2 factorial design, in which one factor was treatment (saline or MDMA) and the other was access or lack of access to an activity wheel. Animals with wheel running access displayed a marked increase in running combined with accelerated weight loss. Although pharmacological treatment resulted in no observable effect on weight loss, rats treated with 12.5mg/kg MDMA generally registered more wheel running than did those treated with saline. Analysis of data on the temporal distribution of wheel running revealed an alteration in circadian activity patterns as a consequence of MDMA. These results, by showing a general high level of wheel running in Dark Agouti rats, once again emphasise the close relationship between activity and weight loss in the development of SIH and related phenomena such as ABA. Copyright © 2012 Elsevier Ltd. All rights reserved.

Hunting Down Massless Dark Photons in Kaon Physics

NASA Astrophysics Data System (ADS)

Fabbrichesi, M.; Gabrielli, E.; Mele, B.

2017-07-01

If dark photons are massless, they couple to standard-model particles only via higher dimensional operators, while direct (renormalizable) interactions induced by kinetic mixing, which motivates most of the current experimental searches, are absent. We consider the effect of possible flavor-changing magnetic-dipole couplings of massless dark photons in kaon physics. In particular, we study the branching ratio for the process K+→π+π0γ ¯ with a simplified-model approach, assuming the chiral quark model to evaluate the hadronic matrix element. Possible effects in the K0-K¯ 0 mixing are taken into account. We find that branching ratios up to O (10-7) are allowed—depending on the dark-sector masses and couplings. Such large branching ratios for K+→π+π0γ ¯ could be of interest for experiments dedicated to rare K+ decays like NA62 at CERN, where γ ¯ can be detected as a massless invisible system.

Search for magnetic inelastic dark matter with XENON100

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aprile, E.; Anthony, M.; Aalbers, J.

2017-10-01

We present the first search for dark matter-induced delayed coincidence signals in a dual-phase xenon time projection chamber, using the 224.6 live days of the XENON100 science run II. This very distinct signature is predicted in the framework of magnetic inelastic dark matter which has been proposed to reconcile the modulation signal reported by the DAMA/LIBRA collaboration with the null results from other direct detection experiments. No candidate event has been found in the region of interest and upper limits on the WIMP's magnetic dipole moment are derived. The scenarios proposed to explain the DAMA/LIBRA modulation signal by magnetic inelasticmore » dark matter interactions of WIMPs with masses of 58.0 GeV/c{sup 2} and 122.7 GeV/c{sup 2} are excluded at 3.3 σ and 9.3 σ, respectively.« less

Broadband and Resonant Approaches to Axion Dark Matter Detection.

PubMed

Kahn, Yonatan; Safdi, Benjamin R; Thaler, Jesse

2016-09-30

When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. We propose a new experiment to detect this axion effective current. In the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. We consider both resonant and broadband readout circuits and show that a broadband approach has advantages at small axion masses. We estimate the reach of this design, taking into account the irreducible sources of noise, and demonstrate potential sensitivity to axionlike dark matter with masses in the range of 10^{-14}-10^{-6}  eV. In particular, both the broadband and resonant strategies can probe the QCD axion with a GUT-scale decay constant.

Periodically modulated dark states

NASA Astrophysics Data System (ADS)

Han, Yingying; Zhang, Jun; Zhang, Wenxian

2018-04-01

Phenomena of electromagnetically induced transparency (PEIT) may be interpreted by the Autler-Townes Splitting (ATS), where the coupled states are split by the coupling laser field, or by the quantum destructive interference (QDI), where the atomic phases caused by the coupling laser and the probe laser field cancel. We propose modulated experiments to explore the PEIT in an alternative way by periodically modulating the coupling and the probe fields in a Λ-type three-level system initially in a dark state. Our analytical and numerical results rule out the ATS interpretation and show that the QDI interpretation is more appropriate for the modulated experiments. Interestingly, dark state persists in the double-modulation situation where control and probe fields never occur simultaneously, which is significant difference from the traditional dark state condition. The proposed experiments are readily implemented in atomic gases, artificial atoms in superconducting quantum devices, or three-level meta-atoms in meta-materials.

Electroweak baryogenesis from a dark sector

NASA Astrophysics Data System (ADS)

Cline, James M.; Kainulainen, Kimmo; Tucker-Smith, David

2017-06-01

Adding an extra singlet scalar S to the Higgs sector can provide a barrier at tree level between a false vacuum with restored electroweak symmetry and the true one. This has been demonstrated to readily give a strong phase transition as required for electroweak baryogenesis. We show that with the addition of a fermionic dark matter particle χ coupling to S , a simple UV-complete model can realize successful electroweak baryogenesis. The dark matter gets a C P asymmetry that is transferred to the standard model through a C P portal interaction, which we take to be a coupling of χ to τ leptons and an inert Higgs doublet. The C P asymmetry induced in left-handed τ leptons biases sphalerons to produce the baryon asymmetry. The model has promising discovery potential at the LHC, while robustly providing a large enough baryon asymmetry and correct dark matter relic density with reasonable values of the couplings.

Topical nutraceutical Optixcare EH ameliorates experimental ocular oxidative stress in rats.

PubMed

Kador, Peter F; Guo, Changmei; Kawada, Hiroyoshi; Randazzo, James; Blessing, Karen

2014-09-01

Based on the hypothesis that oral nutraceuticals do not adequately reach all ocular tissues in the anterior segment, we evaluated the ability of a 3% concentration of the ingredients in a topical nutraceutical antioxidant formulation called Optixcare Eye Health (Optixcare EH) to ameliorate oxidative stress in rat models of age-related ocular diseases. Diabetes was induced by tail-vein injection of streptozotocin, and the development of cataracts was monitored by slit lamp. Young rats were exposed to ultraviolet (UV) light, and the reduction in lens glutathione (GSH) levels and increase in 4-hydroxynonenol (4-HNE) were measured. Oxidative stress in the neural retina was generated by exposure of dark-adapted rats to 1,000 lx of light, and oxidative stress markers were measured. Dry eye was induced in rats by twice daily (b.i.d.) subcutaneous scopolamine injections. Topical Optixcare EH was administered b.i.d. and compared in select experiments to the multifunctional antioxidant JHX-4, the topical aldose reductase inhibitor (ARI) Kinostat™, oral Ocu-GLO™, and the topical ocular comfort agents Optixcare Eye Lube, Optixcare Eye Lube + Hyaluron, and Idrop Vet Plus hyaluronic acid. In diabetic rats, topical ARI treatment prevented cataract formation while the nutraceuticals delayed their development with Optixcare EH>Ocu-GLO. In UV-exposed rats, the reduction of GSH and increase in 4-HNE in the lens were normalized in order JHX-4>Optixcare EH>Ocu-GLO. In the retina, oxidative stress markers were reduced better by oral JHX-4 compared with topical Optixcare EH. In the scopolamine-induced dry-eye rats, tear flow was maintained by Optixcare EH treatment, while none of the comfort agents examined altered tear flow. Topical administration of a 3% concentration of the ingredients in Optixcare EH reduces experimentally induced reactive oxygen species in rats exposed to several sources of ocular oxidative stress. In addition, Optixcare EH maintains tear volume in scopolamine-induced dry eye. This suggests that in the anterior segment, the ingredients in Optixcare EH may have clinical potential against ocular oxidative stress.

Tunable photonic band gaps and optical nonreciprocity by an RF-driving ladder-type system in moving optical lattice

NASA Astrophysics Data System (ADS)

Ba, Nuo; Zhong, Xin; Wang, Lei; Fei, Jin-You; Zhang, Yan; Bao, Qian-Qian; Xiao, Li

2018-03-01

We investigate photonic transport properties of the 1D moving optical lattices filled with vast cold atoms driven into a four-level ladder-type system and obtain dynamically controlled photonic bandgaps and optical nonreciprocity. It is found that the two obvious optical nonreciprocity can be generated at two well-developed photonic bandgaps based on double dark states in the presence of a radio-frequency field. However, when the radio-frequency field is absence, the only one induced photonic bandgaps with distinguishing optical nonreciprocity can be opened up via single dark state. Dynamic control of the induced photonic bandgaps and optical nonreciprocity could be exploited to achieve all-optical diodes and routing for quantum information networks.

Spin-0± portal induced Dark Matter

NASA Astrophysics Data System (ADS)

Dutta, Sukanta; Goyal, Ashok; Saini, Lalit Kumar

2018-02-01

Standard model (SM) spin-zero singlets are constrained through their di-Bosonic decay channels via an effective coupling induced by a vector-like quark (VLQ) loop at the LHC for √{s}=13 TeV. These spin-zero resonances are then considered as portals for scalar, vector or fermionic dark matter particle interactions with SM gauge bosons. We find that the model is validated with respect to the observations from LHC data and from cosmology, indirect and direct detection experiments for an appreciable range of scalar, vector and fermionic DM masses greater than 300 GeV and VLQ masses ≥ 400 GeV, corresponding to the three choice of portal masses 270 GeV, 500 GeV and 750 GeV respectively.

Geoengineering Research for a Deep Underground Science and Engineering Laboratory in Sedimentary Rock

NASA Astrophysics Data System (ADS)

Mauldon, M.

2004-12-01

A process to identify world-class research for a Deep Underground Science and Engineering Laboratory (DUSEL) in the USA has been initiated by NSF. While allowing physicists to study, inter alia, dark matter and dark energy, this laboratory will create unprecedented opportunities for biologists to study deep life, geoscientists to study crustal processes and geoengineers to study the behavior of rock, fluids and underground cavities at depth, on time scales of decades. A substantial portion of the nation's future infrastructure is likely to be sited underground because of energy costs, urban crowding and vulnerability of critical surface facilities. Economic and safe development of subsurface space will require an improved ability to engineer the geologic environment. Because of the prevalence of sedimentary rock in the upper continental crust, much of this subterranean infrastructure will be hosted in sedimentary rock. Sedimentary rocks are fundamentally anisotropic due to lithology and bedding, and to discontinuities ranging from microcracks to faults. Fractures, faults and bedding planes create structural defects and hydraulic pathways over a wide range of scales. Through experimentation, observation and monitoring in a sedimentary rock DUSEL, in conjunction with high performance computational models and visualization tools, we will explore the mechanical and hydraulic characteristics of layered rock. DUSEL will permit long-term experiments on 100 m blocks of rock in situ, accessed via peripheral tunnels. Rock volumes will be loaded to failure and monitored for post-peak behavior. The response of large rock bodies to stress relief-driven, time-dependent strain will be monitored over decades. Large block experiments will be aimed at measurement of fluid flow and particle/colloid transport, in situ mining (incl. mining with microbes), remediation technologies, fracture enhancement for resource extraction and large scale long-term rock mass response to induced stresses - with parallel geophysical imaging of the rock mass (and subsequent verification) flow and transport processes, and time-dependent stress and strain. An experimental advantage of sedimentary rock is the presence of pervasive mechanical interfaces (bedding planes), which suggest a host of experimental designs on large rock blocks and slabs (induced flexure, shear strength of interfaces, etc). Thus DUSEL will enable fundamental research about the behavior of a layered rock mass - the dominant structural architecture in near-surface environments worldwide. A further benefit is the natural suitability of sedimentary rocks for experiments related to oil and gas production, or to CO2 sequestration. For example, fluid-induced fracturing of sedimentary rock has long been used by the hydrocarbon industry to improve oil and coal bed methane recovery. Since some fracturing agents are potential contaminants, a major concern and legal responsibility in the US is ensuring the integrity of nearby aquifers. Hydraulic fracturing from a sedimentary rock DUSEL will be followed by injection of low viscosity grout. The rock mass will then be mined back to expose network characteristics of the induced hydraulic fractures. Key questions related to hydrocarbon extraction, CO2 sequestration, waste isolation, and remediation of subsurface contaminants depend critically on the connectivity and architecture of fractures and on coupled thermal, hydrological, mechanical and chemical processes. Fluid flow, particle transport and reaction transport processes are coupled to the stress across fractures, and to thermal, chemical and hydraulic gradients. All can best be studied via large block tests in a subterranean laboratory, ideally in a sedimentary environment.

Dark adaptation during systemic hypoxia induced by chronic respiratory insufficiency.

PubMed

Thylefors, Joakim; Piitulainen, Eeva; Havelius, Ulf

2009-03-01

To investigate dark adaptation during hypoxia in patients with chronic respiratory failure. At three visits, dark adaptation was recorded by computerized dark adaptometry in 13 patients with chronic respiratory insufficiency treated by long-term oxygen therapy. At visits 1 and 3, the patients were administered their usual oxygen supplement. At visit 2, no oxygen was given. At each visit, an analysis of arterial blood gases measured pH, partial pressure of O(2) (Pao(2)), partial pressure of CO(2) (Paco(2)), base excess (BE), standard bicarbonate (HCO(3)), and arterial oxygen saturation. Pulse oximetry (POX) was also recorded. Significant differences were recorded between visits 1 and 2 and between visits 2 and 3 for Pao(2), arterial oxygen saturation, and POX; no differences were found for pH, Paco(2), BE, or HCO(3). No differences were seen between visits 1 and 3 for any of the laboratory parameters. All patients had normal and unchanged dark adaptation at the three visits. Hypoxia in chronic respiratory insufficiency was associated with normal dark adaptation, in contrast to hypoxia in healthy persons at high altitudes, which is known to produce impaired dark adaptation. The result may partly reflect the influence of Paco(2) on the lumen of choroidal and retinal vessels. At high altitudes, with hypocapnic vasoconstriction the oxygen supply to the retina is further compromised, resulting in reduced dark adaptation. The authors hypothesize that respiratory insufficiency with hypercapnia or normocapnia will have larger choroidal and retinal vessel lumens, added to by further dilation of retinal vessels during hypoxia. The tentative net effect would be preserved dark adaptation.

Radial dependence of the dark matter distribution in M33

NASA Astrophysics Data System (ADS)

López Fune, E.; Salucci, P.; Corbelli, E.

2017-06-01

The stellar and gaseous mass distributions, as well as the extended rotation curve, in the nearby galaxy M33 are used to derive the radial distribution of dark matter density in the halo and to test cosmological models of galaxy formation and evolution. Two methods are examined to constrain the dark mass density profiles. The first method deals directly with fitting the rotation curve data in the range of galactocentric distances 0.24 ≤ r ≤ 22.72 kpc. Using the results of collisionless Λ cold dark matter numerical simulations, we confirm that the Navarro-Frenkel-White (NFW) dark matter profile provides a better fit to the rotation curve data than the cored Burkert profile (BRK) profile. The second method relies on the local equation of centrifugal equilibrium and on the rotation curve slope. In the aforementioned range of distances, we fit the observed velocity profile, using a function that has a rational dependence on the radius, and we derive the slope of the rotation curve. Then, we infer the effective matter densities. In the radial range 9.53 ≤ r ≤ 22.72 kpc, the uncertainties induced by the luminous matter (stars and gas) become negligible, because the dark matter density dominates, and we can determine locally the radial distribution of dark matter. With this second method, we tested the NFW and BRK dark matter profiles and we can confirm that both profiles are compatible with the data, even though in this case the cored BRK density profile provides a more reasonable value for the baryonic-to-dark matter ratio.

Anxiolytic-like effects of restraint during the dark cycle in adolescent mice.

PubMed

Ota, Yuki; Ago, Yukio; Tanaka, Tatsunori; Hasebe, Shigeru; Toratani, Yui; Onaka, Yusuke; Hashimoto, Hitoshi; Takuma, Kazuhiro; Matsuda, Toshio

2015-05-01

Stress during developmental stage may cause psychological morbidities, and then the studies on stress are important in adolescent rodents. Restraint is used as a common stressor in rodents and the effects of restraint during the light cycle have been studied, but those of restraint during the dark cycle have not. The present study examined the effects of restraint during the light and dark cycles on anxiety behaviors in adolescent mice. Restraint for 3h during either the light or dark cycle impaired memory function in the fear conditioning test, but did not affect locomotor activity. In the elevated plus-maze test, restraint during the dark cycle reduced anxiety-like behaviors in mice. Repeated exposure to a 3-h period dark cycle restraint for 2 weeks had a similar anxiolytic-like effect. In contrast, restraint for 3h during the light cycle produced anxiety behavior in adolescent, but not adult, mice. The light cycle stress increased plasma corticosterone levels, and elevated c-Fos expression in the prefrontal cortex, paraventricular hypothalamic nucleus, basolateral amygdala and dentate gyrus, and enhanced serotonin turnover in the hippocampus and striatum, while the dark cycle stress did not. There was no difference in the stress-mediated reduction in pentobarbital-induced sleeping time between dark and light cycle restraint. These findings suggest that the anxiolytic effect of dark cycle restraint is mediated by corticosterone, serotonin or γ-aminobutyric acid-independent mechanisms, although the anxiogenic effect of light cycle restraint is associated with changes in plasma corticosterone levels and serotonin turnover in specific brain regions. Copyright © 2015 Elsevier B.V. All rights reserved.

THE NUMBER OF TIDAL DWARF SATELLITE GALAXIES IN DEPENDENCE OF BULGE INDEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

López-Corredoira, Martín; Kroupa, Pavel, E-mail: martinlc@iac.es, E-mail: pavel@astro.uni-bonn.de

We show that a significant correlation (up to 5σ) emerges between the bulge index, defined to be larger for a larger bulge/disk ratio, in spiral galaxies with similar luminosities in the Galaxy Zoo 2 of the Sloan Digital Sky Survey and the number of tidal-dwarf galaxies in the catalog by Kaviraj et al. In the standard cold or warm dark matter cosmological models, the number of satellite galaxies correlates with the circular velocity of the dark matter host halo. In generalized gravity models without cold or warm dark matter, such a correlation does not exist, because host galaxies cannot capture infalling dwarfmore » galaxies due to the absence of dark-matter-induced dynamical friction. However, in such models, a correlation is expected to exist between the bulge mass and the number of satellite galaxies because bulges and tidal-dwarf satellite galaxies form in encounters between host galaxies. This is not predicted by dark matter models in which bulge mass and the number of satellites are a priori uncorrelated because higher bulge/disk ratios do not imply higher dark/luminous ratios. Hence, our correlation reproduces the prediction of scenarios without dark matter, whereas an explanation is not found readily from the a priori predictions of the standard scenario with dark matter. Further research is needed to explore whether some application of the standard theory may explain this correlation.« less

Dark-mediated dormancy release in stratified Lolium rigidum seeds is associated with higher activities of cell wall-modifying enzymes and an apparent increase in gibberellin sensitivity.

PubMed

Goggin, Danica E; Powles, Stephen B; Toorop, Peter E; Steadman, Kathryn J

2011-04-15

Dormancy release in freshly matured, imbibed annual ryegrass (Lolium rigidum) seeds is inhibited by light and involves a decrease in seed sensitivity to abscisic acid. Other processes involved in dormancy release in the dark were investigated by measuring seed storage compound mobilisation and the activity of cell wall-degrading enzymes. Activities of endo-β-mannanase and total peroxidase were higher in dark-stratified compared to light-stratified seeds, indicating that weakening of the structures constraining the embryo was accelerated in the dark. A dramatic degradation of storage proteins in light-stratified seeds, accompanied by induction of a high molecular mass protease, suggests that maintenance of storage(-like) proteins is also important in dark-mediated dormancy release. α-Amylase activity was induced in dark-stratified seeds at least 48 h prior to radicle emergence upon transfer to conditions permitting germination, or in light-stratified seeds supplied with exogenous gibberellin A(4). This suggests that (a) α-amylase is involved in stimulation of germination of non-dormant L. rigidum seeds, and (b) dark-stratified seeds have an increased sensitivity to gibberellins which permits the rapid induction of α-amylase activity upon exposure to germination conditions. Overall, it appears that a number of processes, although possibly minor in themselves, occur in concert during dark-stratification to contribute to dormancy release. Copyright © 2010 Elsevier GmbH. All rights reserved.

Dark and bright blocker soliton interaction in defocusing waveguide arrays.

PubMed

Smirnov, Eugene; Rüter, Christian E; Stepić, Milutin; Shandarov, Vladimir; Kip, Detlef

2006-11-13

We experimentally demonstrate the interaction of an optical probe beam with both bright and dark blocker solitons formed with low optical light power in a saturable defocusing waveguide array in photorefractive lithium niobate. A phase insensitive interaction of the beams is achieved by means of counterpropagating light waves. Partial and full reflection (blocking) of the probe beam on the positive or negative light-induced defect is obtained, respectively, in good agreement with numerical simulations.

Direct perturbation theory for the dark soliton solution to the nonlinear Schroedinger equation with normal dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu Jialu; Yang Chunnuan; Cai Hao

2007-04-15

After finding the basic solutions of the linearized nonlinear Schroedinger equation by the method of separation of variables, the perturbation theory for the dark soliton solution is constructed by linear Green's function theory. In application to the self-induced Raman scattering, the adiabatic corrections to the soliton's parameters are obtained and the remaining correction term is given as a pure integral with respect to the continuous spectral parameter.

Dynamics of Carbon-Concentrating Mechanism Induction and Protein Relocalization during the Dark-to-Light Transition in Synchronized Chlamydomonas reinhardtii1[W][OPEN

PubMed Central

Mitchell, Madeline C.; Meyer, Moritz T.; Griffiths, Howard

2014-01-01

In the model green alga Chlamydomonas reinhardtii, a carbon-concentrating mechanism (CCM) is induced under low CO2 in the light and comprises active inorganic carbon transport components, carbonic anhydrases, and aggregation of Rubisco in the chloroplast pyrenoid. Previous studies have focused predominantly on asynchronous cultures of cells grown under low versus high CO2. Here, we have investigated the dynamics of CCM activation in synchronized cells grown in dark/light cycles compared with induction under low CO2. The specific focus was to undertake detailed time course experiments comparing physiology and gene expression during the dark-to-light transition. First, the CCM could be fully induced 1 h before dawn, as measured by the photosynthetic affinity for inorganic carbon. This occurred in advance of maximum gene transcription and protein accumulation and contrasted with the coordinated induction observed under low CO2. Between 2 and 1 h before dawn, the proportion of Rubisco and the thylakoid lumen carbonic anhydrase in the pyrenoid rose substantially, coincident with increased CCM activity. Thus, other mechanisms are likely to activate the CCM before dawn, independent of gene transcription of known CCM components. Furthermore, this study highlights the value of using synchronized cells during the dark-to-light transition as an alternative means of investigating CCM induction. PMID:25106822

Investigation of Mixing a Supersonic Stream with the Flow Downstream of a Wedge

NASA Technical Reports Server (NTRS)

Sheeley, Joseph

1997-01-01

The flow characteristics in the base region of a two-dimensional supersonic compression ramp are investigated. A stream-wise oriented air jet, M = 1.75, is injected through a thin horizontal slot into a supersonic air main flow, M = 2.3, at the end of a two-dimensional compression ramp. The velocity profile and basic characteristics of the flow in the base region immediately following the ramp are determined. Visualization of the flowfield for qualitative observations is accomplished via Dark Central Ground Interferometry (DCGI). Two-dimensional velocity profiles are obtained using Laser Doppler Velocimetry (LDV). The study is the initial phase of a four-year investigation of base flow mixing. The current study is to provide more details of the flowfield.

Pine Island Bay movie

Atmospheric Science Data Center

2014-08-01

... between successive frames is not uniform. The flow of the glacier, widening of the rift, and subsequent break-off of the iceberg are ... a gap in image acquisition during Antarctic winter, when the glacier was in continuous darkness. MISR was built and is managed by NASA's ...

Metabolomic Responses of Arabidopsis Suspension Cells to Bicarbonate under Light and Dark Conditions

PubMed Central

Misra, Biswapriya B.; Yin, Zepeng; Geng, Sisi; de Armas, Evaldo; Chen, Sixue

2016-01-01

Global CO2 level presently recorded at 400 ppm is expected to reach 550 ppm in 2050, an increment likely to impact plant growth and productivity. Using targeted LC-MS and GC-MS platforms we quantified 229 and 29 metabolites, respectively in a time-course study to reveal short-term responses to different concentrations (1, 3, and 10 mM) of bicarbonate (HCO3−) under light and dark conditions. Results indicate that HCO3− treatment responsive metabolomic changes depend on the HCO3− concentration, time of treatment, and light/dark. Interestingly, 3 mM HCO3− concentration treatment induced more significantly changed metabolites than either lower or higher concentrations used. Flavonoid biosynthesis and glutathione metabolism were common to both light and dark-mediated responses in addition to showing concentration-dependent changes. Our metabolomics results provide insights into short-term plant cellular responses to elevated HCO3− concentrations as a result of ambient increases in CO2 under light and dark. PMID:27762345

Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect

NASA Astrophysics Data System (ADS)

Park, Kyoung-Duck; Jiang, Tao; Clark, Genevieve; Xu, Xiaodong; Raschke, Markus B.

2018-01-01

Excitons, Coulomb-bound electron-hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (XD) show anti-parallel spin configuration with generally forbidden radiative emission. Because of their long lifetimes, these dark excitons are appealing candidates for quantum computing and optoelectronics. However, optical read-out and control of XD states has remained challenging due to their decoupling from light. Here, we present a tip-enhanced nano-optical approach to induce, switch and programmably modulate the XD emission at room temperature. Using a monolayer transition metal dichalcogenide (TMD) WSe2 on a gold substrate, we demonstrate 6 × 105-fold enhancement in dark exciton photoluminescence quantum yield achieved through coupling of the antenna-tip to the dark exciton out-of-plane optical dipole moment, with a large Purcell factor of ≥2 × 103 of the tip-sample nano-cavity. Our approach provides a facile way to harness excitonic properties in low-dimensional semiconductors offering new strategies for quantum optoelectronics.

Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect.

PubMed

Park, Kyoung-Duck; Jiang, Tao; Clark, Genevieve; Xu, Xiaodong; Raschke, Markus B

2018-01-01

Excitons, Coulomb-bound electron-hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (X D ) show anti-parallel spin configuration with generally forbidden radiative emission. Because of their long lifetimes, these dark excitons are appealing candidates for quantum computing and optoelectronics. However, optical read-out and control of X D states has remained challenging due to their decoupling from light. Here, we present a tip-enhanced nano-optical approach to induce, switch and programmably modulate the X D emission at room temperature. Using a monolayer transition metal dichalcogenide (TMD) WSe 2 on a gold substrate, we demonstrate ~6 × 10 5 -fold enhancement in dark exciton photoluminescence quantum yield achieved through coupling of the antenna-tip to the dark exciton out-of-plane optical dipole moment, with a large Purcell factor of ≥2 × 10 3 of the tip-sample nano-cavity. Our approach provides a facile way to harness excitonic properties in low-dimensional semiconductors offering new strategies for quantum optoelectronics.

Spin precession experiments for light axionic dark matter

NASA Astrophysics Data System (ADS)

Graham, Peter W.; Kaplan, David E.; Mardon, Jeremy; Rajendran, Surjeet; Terrano, William A.; Trahms, Lutz; Wilkason, Thomas

2018-03-01

Axionlike particles are promising candidates to make up the dark matter of the Universe, but it is challenging to design experiments that can detect them over their entire allowed mass range. Dark matter in general, and, in particular, axionlike particles and hidden photons, can be as light as roughly 10-22 eV (˜10-8 Hz ), with astrophysical anomalies providing motivation for the lightest masses ("fuzzy dark matter"). We propose experimental techniques for direct detection of axionlike dark matter in the mass range from roughly 10-13 eV (˜102 Hz ) down to the lowest possible masses. In this range, these axionlike particles act as a time-oscillating magnetic field coupling only to spin, inducing effects such as a time-oscillating torque and periodic variations in the spin-precession frequency with the frequency and direction of these effects set by the axion field. We describe how these signals can be measured using existing experimental technology, including torsion pendulums, atomic magnetometers, and atom interferometry. These experiments demonstrate a strong discovery capability, with future iterations of these experiments capable of pushing several orders of magnitude past current astrophysical bounds.

Light-Induced Translocation of RGS9-1 and Gβ5L in Mouse Rod Photoreceptors

PubMed Central

Tian, Mei; Zallocchi, Marisa; Wang, Weimin; Chen, Ching-Kang; Palczewski, Krzysztof; Delimont, Duane; Cosgrove, Dominic; Peng, You-Wei

2013-01-01

The transducin GTPase-accelerating protein complex, which determines the photoresponse duration of photoreceptors, is composed of RGS9-1, Gβ5L and R9AP. Here we report that RGS9-1 and Gβ5L change their distribution in rods during light/dark adaptation. Upon prolonged dark adaptation, RGS9-1 and Gβ5L are primarily located in rod inner segments. But very dim-light exposure quickly translocates them to the outer segments. In contrast, their anchor protein R9AP remains in the outer segment at all times. In the dark, Gβ5L's interaction with R9AP decreases significantly and RGS9-1 is phosphorylated at S475 to a significant degree. Dim light exposure leads to quick de-phosphorylation of RGS9-1. Furthermore, after prolonged dark adaptation, RGS9-1 and transducin Gα are located in different cellular compartments. These results suggest a previously unappreciated mechanism by which prolonged dark adaptation leads to increased light sensitivity in rods by dissociating RGS9-1 from R9AP and redistributing it to rod inner segments. PMID:23555598

Acute dark chocolate and cocoa ingestion and endothelial function: a randomized controlled crossover trial.

PubMed

Faridi, Zubaida; Njike, Valentine Yanchou; Dutta, Suparna; Ali, Ather; Katz, David L

2008-07-01

Studies suggest cardioprotective benefits of dark chocolate containing cocoa. This study examines the acute effects of solid dark chocolate and liquid cocoa intake on endothelial function and blood pressure in overweight adults. Randomized, placebo-controlled, single-blind crossover trial of 45 healthy adults [mean age: 53 y; mean body mass index (in kg/m(2)): 30]. In phase 1, subjects were randomly assigned to consume a solid dark chocolate bar (containing 22 g cocoa powder) or a cocoa-free placebo bar (containing 0 g cocoa powder). In phase 2, subjects were randomly assigned to consume sugar-free cocoa (containing 22 g cocoa powder), sugared cocoa (containing 22 g cocoa powder), or a placebo (containing 0 g cocoa powder). Solid dark chocolate and liquid cocoa ingestion improved endothelial function (measured as flow-mediated dilatation) compared with placebo (dark chocolate: 4.3 +/- 3.4% compared with -1.8 +/- 3.3%; P < 0.001; sugar-free and sugared cocoa: 5.7 +/- 2.6% and 2.0 +/- 1.8% compared with -1.5 +/- 2.8%; P < 0.001). Blood pressure decreased after the ingestion of dark chocolate and sugar-free cocoa compared with placebo (dark chocolate: systolic, -3.2 +/- 5.8 mm Hg compared with 2.7 +/- 6.6 mm Hg; P < 0.001; and diastolic, -1.4 +/- 3.9 mm Hg compared with 2.7 +/- 6.4 mm Hg; P = 0.01; sugar-free cocoa: systolic, -2.1 +/- 7.0 mm Hg compared with 3.2 +/- 5.6 mm Hg; P < 0.001; and diastolic: -1.2 +/- 8.7 mm Hg compared with 2.8 +/- 5.6 mm Hg; P = 0.014). Endothelial function improved significantly more with sugar-free than with regular cocoa (5.7 +/- 2.6% compared with 2.0 +/- 1.8%; P < 0.001). The acute ingestion of both solid dark chocolate and liquid cocoa improved endothelial function and lowered blood pressure in overweight adults. Sugar content may attenuate these effects, and sugar-free preparations may augment them.

Citrulline Supplementation Improves Organ Perfusion and Arginine Availability under Conditions with Enhanced Arginase Activity

PubMed Central

Wijnands, Karolina A.P.; Meesters, Dennis M.; van Barneveld, Kevin W.Y.; Visschers, Ruben G.J.; Briedé, Jacob J.; Vandendriessche, Benjamin; van Eijk, Hans M.H.; Bessems, Babs A.F.M.; van den Hoven, Nadine; von Wintersdorff, Christian J.H.; Brouckaert, Peter; Bouvy, Nicole D.; Lamers, Wouter H.; Cauwels, Anje; Poeze, Martijn

2015-01-01

Enhanced arginase-induced arginine consumption is believed to play a key role in the pathogenesis of sickle cell disease-induced end organ failure. Enhancement of arginine availability with l-arginine supplementation exhibited less consistent results; however, l-citrulline, the precursor of l-arginine, may be a promising alternative. In this study, we determined the effects of l-citrulline compared to l-arginine supplementation on arginine-nitric oxide (NO) metabolism, arginine availability and microcirculation in a murine model with acutely-enhanced arginase activity. The effects were measured in six groups of mice (n = 8 each) injected intraperitoneally with sterile saline or arginase (1000 IE/mouse) with or without being separately injected with l-citrulline or l-arginine 1 h prior to assessment of the microcirculation with side stream dark-field (SDF)-imaging or in vivo NO-production with electron spin resonance (ESR) spectroscopy. Arginase injection caused a decrease in plasma and tissue arginine concentrations. l-arginine and l-citrulline supplementation both enhanced plasma and tissue arginine concentrations in arginase-injected mice. However, only the citrulline supplementation increased NO production and improved microcirculatory flow in arginase-injected mice. In conclusion, the present study provides for the first time in vivo experimental evidence that l-citrulline, and not l-arginine supplementation, improves the end organ microcirculation during conditions with acute arginase-induced arginine deficiency by increasing the NO concentration in tissues. PMID:26132994

Pyroclastic Flow Remnants at Shiveluch Volcano

NASA Image and Video Library

2017-12-08

NASA image acquired February 25, 2011 Pyroclastic flows are some of the most fearsome hazards posed by erupting volcanoes. These avalanches of superheated ash, gas, and rock are responsible for some of the most famous volcanic disasters in history, including the burial of the ancient Roman city of Pompei and the destruction of Saint-Pierre in 1902. More recently, pyroclastic flows from Mount Merapi in Indonesia caused most of the casualties during the volcano’s 2010 eruption. The intense heat—over 1,000° Celsius (1800° Fahrenheit)—the terrific speed—up to 720 kilometers (450 miles) per hour—and the mixture of toxic gases all contribute to the deadly potential. Pyroclastic flows can incinerate, burn, or asphyxiate people who cannot get out of the flow path. This false-color satellite image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the Terra satellite shows the remnants of a large pyroclastic flow on the slopes of Shiveluch Volcano. Fortunately, no one was hurt during the eruption and flow in the sparsely-populated area. ASTER detected heat from the flow during or shortly after an event on January 25, 2011. Note how the heat signatures from January line up with the dark surface deposits visible on February 25; those deposits cover more than 10 square kilometers (4 square miles). Light brown ash covers the snow above the flow deposits, and a tiny plume rises from Shiveluch’s growing lava dome. Vegetation surrounding the volcano is colored dark red. NASA Earth Observatory image by Robert Simmon, using data from the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Caption by Robert Simmon. Instrument: Terra - ASTER Credit: NASA Earth Observatory NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

Dark septate endophyte decreases stress on rice plants.

PubMed

Santos, Silvana Gomes Dos; Silva, Paula Renata Alves da; Garcia, Andres Calderin; Zilli, Jerri Édson; Berbara, Ricardo Luis Louro

Abiotic stress is one of the major limiting factors for plant development and productivity, which makes it important to identify microorganisms capable of increasing plant tolerance to stress. Dark septate endophytes can be symbionts of plants. In the present study, we evaluated the ability of dark septate endophytes isolates to reduce the effects of water stress in the rice varieties Nipponbare and Piauí. The experiments were performed under gnotobiotic conditions, and the water stress was induced with PEG. Four dark septate endophytes were isolated from the roots of wild rice (Oryza glumaepatula) collected from the Brazilian Amazon. Plant height as well as shoot and root fresh and dry matter were measured. Leaf protein concentrations and antioxidant enzyme activity were also estimated. The dark septate endophytes were grown in vitro in Petri dishes containing culture medium; they exhibited different levels of tolerance to salinity and water stress. The two rice varieties tested responded differently to inoculation with dark septate endophytes. Endophytes promoted rice plant growth both in the presence and in the absence of a water deficit. Decreased oxidative stress in plants in response to inoculation was observed in nearly all inoculated treatments, as indicated by the decrease in antioxidant enzyme activity. Dark septate endophytes fungi were shown to increase the tolerance of rice plants to stress caused by water deficiency. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Photovoltaic Retinal Prosthesis for Restoring Sight to Patients Blinded by Retinal Injury or Degeneration

DTIC Science & Technology

2016-02-01

are rapidly expanding [1][2]. Cochlear implants [3] have seen the most remarkable success in sensory neuroprosthetics, while retinal implants [4][5...intensities: Imax (bright pixels) and Imin (dark pixels). In the common return configurations (connected and monopolar), the current flowing through the...array forces the injected current to flow to the back side, which results in a potential build-up in front of the device. Near each pixel (within

Noise-induced hearing loss induces loudness intolerance in a rat Active Sound Avoidance Paradigm (ASAP).

PubMed

Manohar, Senthilvelan; Spoth, Jaclyn; Radziwon, Kelly; Auerbach, Benjamin D; Salvi, Richard

2017-09-01

Hyperacusis is a loudness hypersensitivity disorder in which moderate-intensity sounds are perceived as extremely loud, aversive and/or painful. To assess the aversive nature of sounds, we developed an Active Sound Avoidance Paradigm (ASAP) in which rats altered their place preference in a Light/Dark shuttle box in response to sound. When no sound (NS) was present, rats spent more than 95% of the time in the Dark Box versus the transparent Light Box. However, when a 60 or 90 dB SPL noise (2-20 kHz, 2-8 kHz, or 16-20 kHz bandwidth) was presented in the Dark Box, the rats'' preference for the Dark Box significantly decreased. Percent time in the dark decreased as sound intensity in the Dark Box increased from 60 dB to 90 dB SPL. Interestingly, the magnitude of the decrease was not a monotonic function of intensity for the 16-20 kHz noise and not related to the bandwidth of the 2-20 kHz and 2-8 kHz noise bands, suggesting that sound avoidance is not solely dependent on loudness but the aversive quality of the noise as well. Afterwards, we exposed the rats for 28 days to a 16-20 kHz noise at 102 dB SPL; this exposure produced a 30-40 dB permanent threshold shift at 16 and 32 kHz. Following the noise exposure, the rats were then retested on the ASAP paradigm. High-frequency hearing loss did not alter Dark Box preference in the no-sound condition. However, when the 2-20 kHz or 2-8 kHz noise was presented at 60 or 90 dB SPL, the rats avoided the Dark Box significantly more than they did before the exposure, indicating these two noise bands with energy below the region of hearing loss were perceived as more aversive. In contrast, when the 16-20 kHz noise was presented at 60 or 90 dB SPL, the rats remained in the Dark Box presumably because the high-frequency hearing loss made 16-20 kHz noise less audible and less aversive. These results indicate that when rats develop a high-frequency hearing loss, they become less tolerant of low frequency noise, i.e., high intensity sounds are perceived as more aversive and should be avoided. Published by Elsevier B.V.

A giant protogalactic disk linked to the cosmic web

NASA Astrophysics Data System (ADS)

Martin, D. Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D.; Moore, Anna; Cantalupo, Sebastiano; Prochaska, J. Xavier; Chang, Daphne

2015-08-01

The specifics of how galaxies form from, and are fuelled by, gas from the intergalactic medium remain uncertain. Hydrodynamic simulations suggest that `cold accretion flows'--relatively cool (temperatures of the order of 104 kelvin), unshocked gas streaming along filaments of the cosmic web into dark-matter halos--are important. These flows are thought to deposit gas and angular momentum into the circumgalactic medium, creating disk- or ring-like structures that eventually coalesce into galaxies that form at filamentary intersections. Recently, a large and luminous filament, consistent with such a cold accretion flow, was discovered near the quasi-stellar object QSO UM287 at redshift 2.279 using narrow-band imaging. Unfortunately, imaging is not sufficient to constrain the physical characteristics of the filament, to determine its kinematics, to explain how it is linked to nearby sources, or to account for its unusual brightness, more than a factor of ten above what is expected for a filament. Here we report a two-dimensional spectroscopic investigation of the emitting structure. We find that the brightest emission region is an extended rotating hydrogen disk with a velocity profile that is characteristic of gas in a dark-matter halo with a mass of 1013 solar masses. This giant protogalactic disk appears to be connected to a quiescent filament that may extend beyond the virial radius of the halo. The geometry is strongly suggestive of a cold accretion flow.

A giant protogalactic disk linked to the cosmic web.

PubMed

Martin, D Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D; Moore, Anna; Cantalupo, Sebastiano; Prochaska, J Xavier; Chang, Daphne

2015-08-13

The specifics of how galaxies form from, and are fuelled by, gas from the intergalactic medium remain uncertain. Hydrodynamic simulations suggest that 'cold accretion flows'--relatively cool (temperatures of the order of 10(4) kelvin), unshocked gas streaming along filaments of the cosmic web into dark-matter halos--are important. These flows are thought to deposit gas and angular momentum into the circumgalactic medium, creating disk- or ring-like structures that eventually coalesce into galaxies that form at filamentary intersections. Recently, a large and luminous filament, consistent with such a cold accretion flow, was discovered near the quasi-stellar object QSO UM287 at redshift 2.279 using narrow-band imaging. Unfortunately, imaging is not sufficient to constrain the physical characteristics of the filament, to determine its kinematics, to explain how it is linked to nearby sources, or to account for its unusual brightness, more than a factor of ten above what is expected for a filament. Here we report a two-dimensional spectroscopic investigation of the emitting structure. We find that the brightest emission region is an extended rotating hydrogen disk with a velocity profile that is characteristic of gas in a dark-matter halo with a mass of 10(13) solar masses. This giant protogalactic disk appears to be connected to a quiescent filament that may extend beyond the virial radius of the halo. The geometry is strongly suggestive of a cold accretion flow.

Intracellular pH of symbiotic dinoflagellates

NASA Astrophysics Data System (ADS)

Gibbin, E. M.; Davy, S. K.

2013-09-01

Intracellular pH (pHi) is likely to play a key role in maintaining the functional success of cnidarian-dinoflagellate symbiosis, yet until now the pHi of the symbiotic dinoflagellates (genus Symbiodinium) has never been quantified. Flow cytometry was used in conjunction with the ratiometric fluorescent dye BCECF to monitor changes in pHi over a daily light/dark cycle. The pHi of Symbiodinium type B1 freshly isolated from the model sea anemone Aiptasia pulchella was 7.25 ± 0.01 (mean ± SE) in the light and 7.10 ± 0.02 in the dark. A comparable effect of irradiance was seen across a variety of cultured Symbiodinium genotypes (types A1, B1, E1, E2, F1, and F5) which varied between pHi 7.21-7.39 in the light and 7.06-7.14 in the dark. Of note, there was a significant genotypic difference in pHi, irrespective of irradiance.

A Comparison of Photo-Induced Hysteresis Between Hydrogenated Amorphous Silicon and Amorphous IGZO Thin-Film Transistors.

PubMed

Ha, Tae-Jun; Cho, Won-Ju; Chung, Hong-Bay; Koo, Sang-Mo

2015-09-01

We investigate photo-induced instability in thin-film transistors (TFTs) consisting of amorphous indium-gallium-zinc-oxide (a-IGZO) as active semiconducting layers by comparing with hydrogenated amorphous silicon (a-Si:H). An a-IGZO TFT exhibits a large hysteresis window in the illuminated measuring condition but no hysteresis window in the dark condition. On the contrary, a large hysteresis window measured in the dark condition in a-Si:H was not observed in the illuminated condition. Even though such materials possess the structure of amorphous phase, optical responses or photo instability in TFTs looks different from each other. Photo-induced hysteresis results from initially trapped charges at the interface between semiconductor and dielectric films or in the gate dielectric which possess absorption energy to interact with deep trap-states and affect the movement of Fermi energy level. In order to support our claim, we also perform CV characteristics in photo-induced hysteresis and demonstrate thermal-activated hysteresis. We believe that this work can provide important information to understand different material systems for optical engineering which includes charge transport and band transition.

Epidermal Phytochrome B Inhibits Hypocotyl Negative Gravitropism Non-Cell-Autonomously.

PubMed

Kim, Jaewook; Song, Kijong; Park, Eunae; Kim, Keunhwa; Bae, Gabyong; Choi, Giltsu

2016-11-01

Seedling hypocotyls display negative gravitropism in the dark but agravitropism in the light. The Arabidopsis thaliana pif quadruple mutant (pifQ), which lacks four PHYTOCHROME-INTERACTING FACTORS (PIFs), is agravitropic in the dark. Endodermis-specific expression of PIF1 rescues gravitropism in pifQ mutant seedlings. Since phytochromes induce light responses by inhibiting PIFs and the COP1-SPA ubiquitin E3 ligase complex in the nucleus, we asked whether phyB can cell autonomously inhibit hypocotyl negative gravitropism in the endodermis. We found that while epidermis-specific expression of PHYB rescues hypocotyl negative gravitropism and all other phyB mutant phenotypes, endodermis-specific expression of PHYB does not. Epidermal phyB induces the phosphorylation and degradation of endodermal PIFs in response to red light. This induces a global gene expression pattern similar to that induced by red light treatment of seedlings expressing PHYB under the control of its own endogenous promoter. Our results imply that epidermal phyB generates an unidentified mobile signal that travels to the endodermis where it promotes PIF degradation and inhibits hypocotyl negative gravitropism. © 2016 American Society of Plant Biologists. All rights reserved.

Epidermal Phytochrome B Inhibits Hypocotyl Negative Gravitropism Non-Cell-Autonomously

PubMed Central

Kim, Jaewook; Song, Kijong; Park, Eunae; Kim, Keunhwa; Choi, Giltsu

2016-01-01

Seedling hypocotyls display negative gravitropism in the dark but agravitropism in the light. The Arabidopsis thaliana pif quadruple mutant (pifQ), which lacks four PHYTOCHROME-INTERACTING FACTORS (PIFs), is agravitropic in the dark. Endodermis-specific expression of PIF1 rescues gravitropism in pifQ mutant seedlings. Since phytochromes induce light responses by inhibiting PIFs and the COP1-SPA ubiquitin E3 ligase complex in the nucleus, we asked whether phyB can cell autonomously inhibit hypocotyl negative gravitropism in the endodermis. We found that while epidermis-specific expression of PHYB rescues hypocotyl negative gravitropism and all other phyB mutant phenotypes, endodermis-specific expression of PHYB does not. Epidermal phyB induces the phosphorylation and degradation of endodermal PIFs in response to red light. This induces a global gene expression pattern similar to that induced by red light treatment of seedlings expressing PHYB under the control of its own endogenous promoter. Our results imply that epidermal phyB generates an unidentified mobile signal that travels to the endodermis where it promotes PIF degradation and inhibits hypocotyl negative gravitropism. PMID:27758895

Chemically induced and light-independent cryptochrome photoreceptor activation.

PubMed

Rosenfeldt, Gesa; Viana, Rafael Muñoz; Mootz, Henning D; von Arnim, Albrecht G; Batschauer, Alfred

2008-01-01

The cryptochrome photoreceptors of higher plants are dimeric proteins. Their N-terminal photosensory domain mediates dimerization, and the unique C-terminal extension (CCT) mediates signaling. We made use of the human FK506-binding protein (FKBP) that binds with high affinity to rapamycin or rapamycin analogs (rapalogs). The FKBP-rapamycin complex is recognized by another protein, FRB, thus allowing rapamycin-induced dimerization of two target proteins. Here we demonstrate by bioluminescence resonance energy transfer (BRET) assays the applicability of this regulated dimerization system to plants. Furthermore, we show that fusion proteins consisting of the C-terminal domain of Arabidopsis cryptochrome 2 fused to FKBP and FRB and coexpressed in Arabidopsis cells specifically induce the expression of cryptochrome-controlled reporter and endogenous genes in darkness upon incubation with the rapalog. These results demonstrate that the activation of cryptochrome signal transduction can be chemically induced in a dose-dependent fashion and uncoupled from the light signal, and provide the groundwork for gain-of-function experiments to study specifically the role of photoreceptors in darkness or in signaling cross-talk even under light conditions that activate members of all photoreceptor families.

ARC-1990-A90-3001

NASA Image and Video Library

1990-08-21

This portion of a Magellan radar image strip shows a small region on Venus 20 km (12.4 mi.) wide and 75 km (50 mi.) long on the east flank of a major volcanic upland called Beta Regio. The image is centerd at 23 degrees north latitude and 286.7 degrees east longitude. The ridge and valley networkin the middle part of the image is formed by intersection faults which have broken the Venusian crust into a clomplex, deformed type of surface called tessera, the Latin word for tile. The parallel mountains and valleys resemble the Basin and Range Province in the western United States. The irregular dark patch near the top of the image is a smooth surface, probably formed by lava flows in a region about 10 km (6 mi.) across. Similar dark surfaces within the valleys indicate lava flows that are younger than the tessera giving an indication of the geologic time relationships of the events that formed the present surface. The image has a resolution of 120 meters (400 feet).

Cold exposure impairs dark-pulse capacity to induce REM sleep in the albino rat.

PubMed

Baracchi, Francesca; Zamboni, Giovanni; Cerri, Matteo; Del Sindaco, Elide; Dentico, Daniela; Jones, Christine Ann; Luppi, Marco; Perez, Emanuele; Amici, Roberto

2008-06-01

In the albino rat, a REM sleep (REMS) onset can be induced with a high probability and a short latency when the light is suddenly turned off (dark pulse, DP) during non-REM sleep (NREMS). The aim of this study was to investigate to what extent DP delivery could overcome the integrative thermoregulatory mechanisms that depress REMS occurrence during exposure to low ambient temperature (Ta). To this aim, the efficiency of a non-rhythmical repetitive DP (3 min each) delivery during the first 6-h light period of a 12 h:12 h light-dark cycle in inducing REMS was studied in the rat, through the analysis of electroencephalogram, electrocardiogram, hypothalamic temperature and motor activity at different Tas. The results showed that DP delivery triggers a transition from NREMS to REMS comparable to that which occurs spontaneously. However, the efficiency of DP delivery in inducing REMS was reduced during cold exposure to an extent comparable with that observed in spontaneous REMS occurrence. Such impairment was associated with low Delta activity and high sympathetic tone when DPs were delivered. Repetitive DP administration increased REMS amount during the delivery period and a subsequent negative REMS rebound was observed. In conclusion, DP delivery did not overcome the integrative thermoregulatory mechanisms that depress REMS in the cold. These results underline the crucial physiological meaning of the mutual exclusion of thermoregulatory activation and REMS occurrence, and support the hypothesis that the suspension of the central control of body temperature is a prerequisite for REMS occurrence.

Direct perturbation theory for the dark soliton solution to the nonlinear Schrödinger equation with normal dispersion.

PubMed

Yu, Jia-Lu; Yang, Chun-Nuan; Cai, Hao; Huang, Nian-Ning

2007-04-01

After finding the basic solutions of the linearized nonlinear Schrödinger equation by the method of separation of variables, the perturbation theory for the dark soliton solution is constructed by linear Green's function theory. In application to the self-induced Raman scattering, the adiabatic corrections to the soliton's parameters are obtained and the remaining correction term is given as a pure integral with respect to the continuous spectral parameter.

Coupled field induced conversion between destructive and constructive quantum interference

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Xiangqian, E-mail: xqjiang@hit.edu.cn; Sun, Xiudong

2016-12-15

We study the control of quantum interference in a four-level atom driven by three coherent fields forming a closed loop. The spontaneous emission spectrum shows two sets of peaks which are dramatically influenced by the fields. Due to destructive quantum interference, a dark line can be observed in the emission spectrum, and the condition of the dark line is given. We found that the conversion between destructive and constructive quantum interference can be achieved through controlling the Rabi frequency of the external fields.

LOW-MASS SUPPRESSION OF THE SATELLITE LUMINOSITY FUNCTION DUE TO THE SUPERSONIC BARYON-COLD-DARK-MATTER RELATIVE VELOCITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bovy, Jo; Dvorkin, Cora

We study the effect of the supersonic baryon-cold-dark-matter (CDM) flow, which has recently been shown to have a large effect on structure formation during the dark ages 10 {approx}< z {approx}< 1000, on the abundance of luminous, low-mass satellite galaxies around galaxies like the Milky Way. As the supersonic baryon-CDM flow significantly suppresses both the number of halos formed and the amount of baryons accreted onto such halos of masses 10{sup 6} < M{sub halo}/M{sub Sun} < 10{sup 8} at z {approx}> 10, a large effect results on the stellar luminosity function before reionization. As halos of these masses aremore » believed to have very little star formation after reionization due to the effects of photoheating by the ultraviolet background, this effect persists to the present day. We calculate that the number of low-mass 10{sup 6} < M{sub halo}/M{sub Sun} < 5 Multiplication-Sign 10{sup 7} halos that host luminous satellite galaxies today is typically suppressed by 50%, with values ranging up to 90% in regions where the initial supersonic velocity is high. We show that this previously ignored cosmological effect resolves some of the tension between the observed and predicted number of low-mass satellites in the Milky Way, reducing the need for other mass-dependent star-formation suppression before reionization.« less

Homeostatic response to sleep/rest deprivation by constant water flow in larval zebrafish in both dark and light conditions.

PubMed

Aho, Vilma; Vainikka, Maija; Puttonen, Henri A J; Ikonen, Heidi M K; Salminen, Tiia; Panula, Pertti; Porkka-Heiskanen, Tarja; Wigren, Henna-Kaisa

2017-06-01

Sleep-or sleep-like states-have been reported in adult and larval zebrafish using behavioural criteria. These reversible quiescent periods, displaying circadian rhythmicity, have been used in pharmacological, genetic and neuroanatomical studies of sleep-wake regulation. However, one of the important criteria for sleep, namely sleep homeostasis, has not been demonstrated unequivocally. To study rest homeostasis in zebrafish larvae, we rest-deprived 1-week-old larvae with a novel, ecologically relevant method: flow of water. Stereotyped startle responses to sensory stimuli were recorded after the rest deprivation to study arousal threshold using a high-speed camera, providing an appropriate time resolution to detect species-specific behavioural responses occurring in a millisecond time-scale. Rest-deprived larvae exhibited fewer startle responses than control larvae during the remaining dark phase and the beginning of the light phase, which can be interpreted as a sign of rest homeostasis-often used as equivalent of sleep homeostasis. To address sleep homeostasis further, we probed the adenosinergic system, which in mammals regulates sleep homeostasis. The adenosine A1 receptor agonist, cyclohexyladenosine, administered during the light period, decreased startle responses and increased immobility bouts, while the adenosine antagonist, caffeine, administered during the dark period, decreased immobility bouts. These results suggest that the regulation of sleep homeostasis in zebrafish larvae consists of the same elements as that of other species. © 2017 European Sleep Research Society.

Sensitivity of Atom Interferometry to Ultralight Scalar Field Dark Matter.

PubMed

Geraci, Andrew A; Derevianko, Andrei

2016-12-23

We discuss the use of atom interferometry as a tool to search for dark matter (DM) composed of virialized ultralight fields (VULFs). Previous work on VULF DM detection using accelerometers has considered the possibility of equivalence-principle-violating effects whereby gradients in the dark matter field can directly produce relative accelerations between media of differing composition. In atom interferometers, we find that time-varying phase signals induced by coherent oscillations of DM fields can also arise due to changes in the atom rest mass that can occur between light pulses throughout the interferometer sequence as well as changes in Earth's gravitational field. We estimate that several orders of magnitude of unexplored phase space for VULF DM couplings can be probed due to these new effects.

Recognising Axionic Dark Matter by Compton and de-Broglie Scale Modulation of Pulsar Timing

NASA Astrophysics Data System (ADS)

De Martino, Ivan; Broadhurst, Tom; Tye, S.-H. Henry; Chiueh, Tzihong; Schive, Hsi-Yu; Lazkoz, Ruth

2017-11-01

Light Axionic Dark Matter, motivated by string theory, is increasingly favored for the "no-WIMP era". Galaxy formation is suppressed below a Jeans scale, of ≃ 10^8 M_⊙ by setting the axion mass to, m_B ˜ 10^{-22}eV, and the large dark cores of dwarf galaxies are explained as solitons on the de-Broglie scale. This is persuasive, but detection of the inherent scalar field oscillation at the Compton frequency, ω_B= (2.5 months)^{-1}(m_B/10^{-22}eV), would be definitive. By evolving the coupled Schrödinger-Poisson equation for a Bose-Einstein condensate, we predict the dark matter is fully modulated by de-Broglie interference, with a dense soliton core of size ≃ 150pc, at the Galactic center. The oscillating field pressure induces General Relativistic time dilation in proportion to the local dark matter density and pulsars within this dense core have detectably large timing residuals, of ≃ 400nsec/(m_B/10^{-22}eV). This is encouraging as many new pulsars should be discovered near the Galactic center with planned radio surveys. More generally, over the whole Galaxy, differences in dark matter density between pairs of pulsars imprints a pairwise Galactocentric signature that can be distinguished from an isotropic gravitational wave background.

The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

PubMed Central

Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

2016-01-01

For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to ‘internal photons’ inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350–700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation. PMID:26950936

Direct probe of dark energy through gravitational lensing effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Hong-Jian; Zhang, Zhen, E-mail: hjhe@tsinghua.edu.cn, E-mail: zh.zhang@pku.edu.cn

We show that gravitational lensing can provide a direct method to probe the nature of dark energy at astrophysical scales. For lensing system as an isolated astrophysical object, we derive the dark energy contribution to gravitational potential as a repulsive power-law term, containing a generic equation of state parameter w . We find that it generates w -dependent and position-dependent modification to the conventional light orbital equation of w =−1. With post-Newtonian approximation, we compute its direct effect for an isolated lensing system at astrophysical scales and find that the dark energy force can deflect the path of incident lightmore » rays. We demonstrate that the dark-energy-induced deflection angle Δα{sub DE}∝ M {sup (1+1/3} {sup w} {sup )} (with 1+1/3 w > 0), which increases with the lensing mass M and consistently approaches zero in the limit M → 0. This effect is distinctive because dark energy tends to diffuse the rays and generates concave lensing effect . This is in contrast to the conventional convex lensing effect caused by both visible and dark matter. Measuring such concave lensing effect can directly probe the existence and nature of dark energy. We estimate this effect and show that the current gravitational lensing experiments are sensitive to the direct probe of dark energy at astrophysical scales. For the special case w =−1, our independent study favors the previous works that the cosmological constant can affect light bending, but our prediction qualitatively and quantitatively differ from the literature, including our consistent realization of Δα{sub DE} → 0 (under 0 M → ) at the leading order.« less

Tunable phonon-induced transparency in bilayer graphene nanoribbons.

PubMed

Yan, Hugen; Low, Tony; Guinea, Francisco; Xia, Fengnian; Avouris, Phaedon

2014-08-13

In the phenomenon of plasmon-induced transparency, which is a classical analogue of electromagnetically induced transparency (EIT) in atomic gases, the coherent interference between two plasmon modes results in an optical transparency window in a broad absorption spectrum. With the requirement of contrasting lifetimes, typically one of the plasmon modes involved is a dark mode that has limited coupling to the electromagnetic radiation and possesses relatively longer lifetime. Plasmon-induced transparency not only leads to light transmission at otherwise opaque frequency regions but also results in the slowing of light group velocity and enhanced optical nonlinearity. In this article, we report an analogous behavior, denoted as phonon-induced transparency (PIT), in AB-stacked bilayer graphene nanoribbons. Here, light absorption due to the plasmon excitation is suppressed in a narrow window due to the coupling with the infrared active Γ-point optical phonon, whose function here is similar to that of the dark plasmon mode in the plasmon-induced transparency. We further show that PIT in bilayer graphene is actively tunable by electrostatic gating and estimate a maximum slow light factor of around 500 at the phonon frequency of 1580 cm(-1), based on the measured spectra. Our demonstration opens an avenue for the exploration of few-photon nonlinear optics and slow light in this novel two-dimensional material.

Long-Term Effects of (–)-Epigallocatechin Gallate (EGCG) on Pristane-Induced Arthritis (PIA) in Female Dark Agouti Rats

PubMed Central

Leichsenring, Anna; Bäcker, Ingo; Furtmüller, Paul G.; Obinger, Christian; Lange, Franziska; Flemmig, Jörg

2016-01-01

Rheumatoid arthritis (RA)—a widespread chronic inflammatory disease in industrialized countries—is characterized by a persistent and progressive joint destruction. The chronic pro-inflammatory state results from a mutual activation of the innate and the adaptive immune system, while the exact pathogenesis mechanism is still under discussion. New data suggest a role of the innate immune system and especially polymorphonuclear granulocytes (PMNs, neutrophils) not only during onset and the destructive phase of RA but also at the chronification of the disease. Thereby the enzymatic activity of myeloperoxidase (MPO), a peroxidase strongly abundant in neutrophils, may be important: While its peroxidase activity is known to contribute to cartilage destruction at later stages of RA the almost MPO-specific oxidant hypochlorous acid (HOCl) is also discussed for certain anti-inflammatory effects. In this study we used pristane-induced arthritis (PIA) in Dark Agouti rats as a model for the chronic course of RA in man. We were able to shown that a specific detection of the HOCl-producing MPO activity provides a sensitive new marker to evaluate the actual systemic inflammatory status which is only partially detectable by the evaluation of clinical symptoms (joint swelling and redness measurements). Moreover, we evaluated the long-term pharmacological effect of the well-known anti-inflammatory flavonoid epigallocatechin gallate (EGCG). Thereby only upon early and continuous oral application of this polyphenol the arthritic symptoms were considerably diminished both in the acute and in the chronic phase of the disease. The obtained results were comparable to the treatment control (application of methotrexate, MTX). As revealed by stopped-flow kinetic measurements, EGCG may regenerate the HOCl-production of MPO which is known to be impaired at chronic inflammatory diseases like RA. It can be speculated that this MPO activity-promoting effect of EGCG may contribute to the pharmacological mode of action of this polyphenol. PMID:27023113

Flow visualization V; Proceedings of the 5th International Symposium, Prague, Czechoslovakia, Aug. 21-25, 1989

NASA Astrophysics Data System (ADS)

Reznicek, R.

The present conference on flow visualization encompasses methods exploiting tracing particles, surface tracing methods, methods exploiting the effects of streaming fluid on passing radiation/field, computer-aided flow visualization, and applications to fluid mechanics, aerodynamics, flow devices, shock tubes, and heat/mass transfer. Specific issues include visualizing velocity distribution by stereo photography, dark-field Fourier quasiinterferometry, speckle tomography of an open flame, a fast eye for real-time image analysis, and velocity-field determination based on flow-image analysis. Also addressed are flows around rectangular prisms with oscillating flaps at the leading edges, the tomography of aerodynamic objects, the vapor-screen technique applied to a delta-wing aircraft, flash-lamp planar imaging, IR-thermography applications in convective heat transfer, and the visualization of marangoni effects in evaporating sessile drops.

Dissipative hidden sector dark matter

NASA Astrophysics Data System (ADS)

Foot, R.; Vagnozzi, S.

2015-01-01

A simple way of explaining dark matter without modifying known Standard Model physics is to require the existence of a hidden (dark) sector, which interacts with the visible one predominantly via gravity. We consider a hidden sector containing two stable particles charged under an unbroken U (1 )' gauge symmetry, hence featuring dissipative interactions. The massless gauge field associated with this symmetry, the dark photon, can interact via kinetic mixing with the ordinary photon. In fact, such an interaction of strength ε ˜10-9 appears to be necessary in order to explain galactic structure. We calculate the effect of this new physics on big bang nucleosynthesis and its contribution to the relativistic energy density at hydrogen recombination. We then examine the process of dark recombination, during which neutral dark states are formed, which is important for large-scale structure formation. Galactic structure is considered next, focusing on spiral and irregular galaxies. For these galaxies we modeled the dark matter halo (at the current epoch) as a dissipative plasma of dark matter particles, where the energy lost due to dissipation is compensated by the energy produced from ordinary supernovae (the core-collapse energy is transferred to the hidden sector via kinetic mixing induced processes in the supernova core). We find that such a dynamical halo model can reproduce several observed features of disk galaxies, including the cored density profile and the Tully-Fisher relation. We also discuss how elliptical and dwarf spheroidal galaxies could fit into this picture. Finally, these analyses are combined to set bounds on the parameter space of our model, which can serve as a guideline for future experimental searches.

Re-Form: FPGA-Powered True Codesign Flow for High-Performance Computing In The Post-Moore Era

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cappello, Franck; Yoshii, Kazutomo; Finkel, Hal

Multicore scaling will end soon because of practical power limits. Dark silicon is becoming a major issue even more than the end of Moore’s law. In the post-Moore era, the energy efficiency of computing will be a major concern. FPGAs could be a key to maximizing the energy efficiency. In this paper we address severe challenges in the adoption of FPGA in HPC and describe “Re-form,” an FPGA-powered codesign flow.

NR-code: Nonlinear reconstruction code

NASA Astrophysics Data System (ADS)

Yu, Yu; Pen, Ue-Li; Zhu, Hong-Ming

2018-04-01

NR-code applies nonlinear reconstruction to the dark matter density field in redshift space and solves for the nonlinear mapping from the initial Lagrangian positions to the final redshift space positions; this reverses the large-scale bulk flows and improves the precision measurement of the baryon acoustic oscillations (BAO) scale.

Knowledge Engineering (Or, Catching Black Cats in Dark Rooms).

ERIC Educational Resources Information Center

Ruyle, Kim E.

1993-01-01

Discusses knowledge engineering, its relationship to artificial intelligence, and possible applications to developing expert systems, job aids, and technical training. The educational background of knowledge engineers is considered; the role of subject matter experts is described; and examples of flow charts, lists, and pictorial representations…

Dark energy in the environments of the Local Group, the M 81 group, and the CenA group: the normalized Hubble diagram

NASA Astrophysics Data System (ADS)

Teerikorpi, P.; Chernin, A. D.; Karachentsev, I. D.; Valtonen, M. J.

2008-05-01

Context: Type Ia supernova observations on scales of thousands of Mpc show that the global expansion of the universe is accelerated by antigravity produced by the enigmatic dark energy contributing 3/4 of the total energy of the universe. Aims: Does antigravity act on small scales as well as large? As a continuation of our efforts to answer this crucial question we combine high accuracy observations of the galaxy flows around the Local Group and the nearby M 81 and CenA groups to observe the effect of the dark energy density on local scales of a few Mpc. Methods: We use an analytical model to describe non-uniform static space-time regions around galaxy groups. In this context it is useful to present the Hubble flow in a normalized Hubble diagram V/Hv Rv vs. r/R_v, where the vacuum Hubble constant Hv depends only on the cosmological vacuum density and the zero-gravity distance Rv depends on the vacuum density and on the mass of the galaxy group. We have prepared the normalized Hubble diagrams for the LG, M 81 and CenA group environments for different values of the assumed vacuum energy density, using a total of about 150 galaxies, for almost all of which the distances have been measured by the HST. Results: The normalized Hubble diagram, where we identify dynamically different regions, is in agreement with the standard vacuum density (Ωv = 0.77~h_70-2), the out-flow of galaxies clearly being controlled by the minimum energy condition imposed by the central mass plus the vacuum density. A high vacuum density 1.6~h_70-2 violates the minimum energy limit, while a low density 0.1~h_70-2 leaves the start of the Hubble flow around 1-2 Mpc with the slope close to the global value obscure. We also consider the subtle relation of the zero-gravity radius Rv to the zero-velocity distance R0 appearing in the usual retarded expansion around a mass M: in a vacuum-dominated flat universe R0 ≈ 0.76 R_v. Conclusions: The normalized Hubble diagram appears to be a good way to present and analyze physically different regions around mass clumps embedded in cosmological vacuum. The most natural interpretation of the diagram is that the local density of the dark energy is approximately equal to the density known from studies on global scales.

Temperature dependence of alpha-induced scintillation in the 1,1,4,4-tetraphenyl-1,3-butadiene wavelength shifter

NASA Astrophysics Data System (ADS)

Veloce, L. M.; Kuźniak, M.; Di Stefano, P. C. F.; Noble, A. J.; Boulay, M. G.; Nadeau, P.; Pollmann, T.; Clark, M.; Piquemal, M.; Schreiner, K.

2016-06-01

Liquid noble based particle detectors often use the organic wavelength shifter 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) which shifts UV scintillation light to the visible regime, facilitating its detection, but which also can scintillate on its own. Dark matter searches based on this type of detector commonly rely on pulse-shape discrimination (PSD) for background mitigation. Alpha-induced scintillation therefore represents a possible background source in dark matter searches. The timing characteristics of this scintillation determine whether this background can be mitigated through PSD. We have therefore characterized the pulse shape and light yield of alpha induced TPB scintillation at temperatures ranging from 300 K down to 4 K, with special attention given to liquid noble gas temperatures. We find that the pulse shapes and light yield depend strongly on temperature. In addition, the significant contribution of long time constants above ~50 K provides an avenue for discrimination between alpha decay events in TPB and nuclear-recoil events in noble liquid detectors.

Soliton resonance in bose-einstein condensate

NASA Technical Reports Server (NTRS)

Zak, Michail; Kulikov, I.

2002-01-01

A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

Possible molecular mechanism underlying cadmium-induced circadian rhythms disruption in zebrafish

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Bo; Chen, Tian-Ming; Zhong, Yingbin

This study was aimed to explore the mechanisms underlying cadmium-induced circadian rhythms disruption. Two groups of zebrafish larvae treated with or without 5 ppm CdCl{sub 2} were incubated in a photoperiod of 14-h light/10-h dark conditions. The mRNA levels of clock1a, bmal1b, per2 and per1b in two groups were determined. Microarray data were generated in two group of samples. Differential expression of genes were identified and the changes in expression level for some genes were validated by RT-PCR. Finally, Gene Ontology functional and KEGG pathway enrichment analysis of differentially expressed genes (DEGs) were performed. In comparison with normal group, the mRNAmore » levels of clock1a, bmal1b, and per2 were significantly changed and varied over the circadian cycle in CdCl2-treated group. DEGs were obtained from the light (84 h, ZT12) and dark (88 h, ZT16) phase. In addition, G-protein coupled receptor protein signaling pathway and immune response were both enriched by DEGs in both groups. While, proteolysis and amino acid metabolism were found associated with DEGs in light phase, and Neuroactive ligand-receptor interaction and oxidation-reduction process were significantly enriched by DEGs in dark phase. Besides, the expression pattern of genes including hsp70l and or115-11 obtained by RT-PCR were consistent with those obtained by microarray analysis. As a consequence, cadmium could make significant effects on circadian rhythms through immune response and G protein-coupled receptor signaling pathway. Besides, between the dark and the light phase, the mechanism by which cadmium inducing disruption of circadian rhythms were different to some extent. - Highlights: • Cadmium could affect the expression levels of circadian rhythm-related genes. • Genes expression in microarray data were consistent with those in RT-PCR analysis. • Immune response and G protein-coupled receptor signaling pathway were identified. • Cadmium induces circadian rhythm disruption by different mechanism in day and night.« less

UAVSAR for the Management of Natural Disasters

NASA Astrophysics Data System (ADS)

Lou, Y.; Hensley, S.; Jones, C. E.

2014-12-01

The unique capabilities of imaging radar to penetrate cloud cover and collect data in darkness over large areas at high resolution makes it a key information provider for the management and mitigation of natural and human-induced disasters such as earthquakes, volcanoes, landslides, floods, and wildfires. Researchers have demonstrated the use of UAVSAR's fully polarimetric data to determine flood extent, forest fire extent, lava flow, and landslide. The ability for UAVSAR to provide high accuracy repeated flight tracks and precise imaging geometry for measuring surface deformation to a few centimeter accuracy using InSAR techniques. In fact, UAVSAR's repeat-pass interferometry capability unleashed new potential approaches to manage the risk of natural disasters prior to the occurrence of these events by modeling and monitoring volcano inflation, earthquake fault movements, landslide rate and extent, and sink hole precursory movement. In this talk we will present examples of applications of UAVSAR for natural disaster management. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Hunting Down Massless Dark Photons in Kaon Physics.

PubMed

Fabbrichesi, M; Gabrielli, E; Mele, B

2017-07-21

If dark photons are massless, they couple to standard-model particles only via higher dimensional operators, while direct (renormalizable) interactions induced by kinetic mixing, which motivates most of the current experimental searches, are absent. We consider the effect of possible flavor-changing magnetic-dipole couplings of massless dark photons in kaon physics. In particular, we study the branching ratio for the process K^{+}→π^{+}π^{0}γ[over ¯] with a simplified-model approach, assuming the chiral quark model to evaluate the hadronic matrix element. Possible effects in the K^{0}-K[over ¯]^{0} mixing are taken into account. We find that branching ratios up to O(10^{-7}) are allowed-depending on the dark-sector masses and couplings. Such large branching ratios for K^{+}→π^{+}π^{0}γ[over ¯] could be of interest for experiments dedicated to rare K^{+} decays like NA62 at CERN, where γ[over ¯] can be detected as a massless invisible system.

Z boson mediated dark matter beyond the effective theory

DOE PAGES

Kearney, John; Orlofsky, Nicholas; Pierce, Aaron

2017-02-17

Here, direct detection bounds are beginning to constrain a very simple model of weakly interacting dark matter—a Majorana fermion with a coupling to the Z boson. In a particularly straightforward gauge-invariant realization, this coupling is introduced via a higher-dimensional operator. While attractive in its simplicity, this model generically induces a large ρ parameter. An ultraviolet completion that avoids an overly large contribution to ρ is the singlet-doublet model. We revisit this model, focusing on the Higgs blind spot region of parameter space where spin-independent interactions are absent. This model successfully reproduces dark matter with direct detection mediated by the Zmore » boson but whose cosmology may depend on additional couplings and states. Future direct detection experiments should effectively probe a significant portion of this parameter space, aside from a small coannihilating region. As such, Z-mediated thermal dark matter as realized in the singlet-doublet model represents an interesting target for future searches.« less

Dark Matter Elastic Scattering Through Higgs Loops [Everything you always wanted to know but were afraid to ask

DOE PAGES

Berlin, Asher; Hooper, Dan; McDermott, Samuel D.

2015-12-28

We consider a complete list of simplifieed models in which Majorana dark matter particles annihilate at tree level to hh or hZ finnal states, and calculate the loop-induced elastic scattering cross section with nuclei in each case. Expressions for these annihilation and elastic scattering cross sections are provided, and can be easily applied to a variety of UV complete models. We identify several phenomenologically viable scenarios, including dark matter that annihilates through the s-channel exchange of a spin-zero mediator or through the t-channel exchange of a fermion. Although the elastic scattering cross sections predicted in this class of models aremore » generally quite small, XENON1Tand LZ should be sensitive to significant regions of this parameter space. Models in which the dark matter annihilates to hh or hZ can also generate a gamma-ray signal that is compatible with the excess observed from the Galactic Center.« less

Dark Matter Elastic Scattering Through Higgs Loops [Everything you always wanted to know but were afraid to ask

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berlin, Asher; Hooper, Dan; McDermott, Samuel D.

We consider a complete list of simplifieed models in which Majorana dark matter particles annihilate at tree level to hh or hZ finnal states, and calculate the loop-induced elastic scattering cross section with nuclei in each case. Expressions for these annihilation and elastic scattering cross sections are provided, and can be easily applied to a variety of UV complete models. We identify several phenomenologically viable scenarios, including dark matter that annihilates through the s-channel exchange of a spin-zero mediator or through the t-channel exchange of a fermion. Although the elastic scattering cross sections predicted in this class of models aremore » generally quite small, XENON1Tand LZ should be sensitive to significant regions of this parameter space. Models in which the dark matter annihilates to hh or hZ can also generate a gamma-ray signal that is compatible with the excess observed from the Galactic Center.« less

The Hubble IR cutoff in holographic ellipsoidal cosmologies

NASA Astrophysics Data System (ADS)

Cataldo, Mauricio; Cruz, Norman

2018-01-01

It is well known that for spatially flat FRW cosmologies, the holographic dark energy disfavors the Hubble parameter as a candidate for the IR cutoff. For overcoming this problem, we explore the use of this cutoff in holographic ellipsoidal cosmological models, and derive the general ellipsoidal metric induced by a such holographic energy density. Despite the drawbacks that this cutoff presents in homogeneous and isotropic universes, based on this general metric, we developed a suitable ellipsoidal holographic cosmological model, filled with a dark matter and a dark energy components. At late time stages, the cosmic evolution is dominated by a holographic anisotropic dark energy with barotropic equations of state. The cosmologies expand in all directions in accelerated manner. Since the ellipsoidal cosmologies given here are not asymptotically FRW, the deviation from homogeneity and isotropy of the universe on large cosmological scales remains constant during all cosmic evolution. This feature allows the studied holographic ellipsoidal cosmologies to be ruled by an equation of state ω =p/ρ , whose range belongs to quintessence or even phantom matter.

A correlation between the cosmic microwave background and large-scale structure in the Universe.

PubMed

Boughn, Stephen; Crittenden, Robert

2004-01-01

Observations of distant supernovae and the fluctuations in the cosmic microwave background (CMB) indicate that the expansion of the Universe may be accelerating under the action of a 'cosmological constant' or some other form of 'dark energy'. This dark energy now appears to dominate the Universe and not only alters its expansion rate, but also affects the evolution of fluctuations in the density of matter, slowing down the gravitational collapse of material (into, for example, clusters of galaxies) in recent times. Additional fluctuations in the temperature of CMB photons are induced as they pass through large-scale structures and these fluctuations are necessarily correlated with the distribution of relatively nearby matter. Here we report the detection of correlations between recent CMB data and two probes of large-scale structure: the X-ray background and the distribution of radio galaxies. These correlations are consistent with those predicted by dark energy, indicating that we are seeing the imprint of dark energy on the growth of structure in the Universe.

Proteomic analyses bring new insights into the effect of a dark stress on lipid biosynthesis in Phaeodactylum tricornutum

PubMed Central

Bai, Xiaocui; Song, Hao; Lavoie, Michel; Zhu, Kun; Su, Yiyuan; Ye, Hanqi; Chen, Si; Fu, Zhengwei; Qian, Haifeng

2016-01-01

Microalgae biosynthesize high amount of lipids and show high potential for renewable biodiesel production. However, the production cost of microalgae-derived biodiesel hampers large-scale biodiesel commercialization and new strategies for increasing lipid production efficiency from algae are urgently needed. Here we submitted the marine algae Phaeodactylum tricornutum to a 4-day dark stress, a condition increasing by 2.3-fold the total lipid cell quotas, and studied the cellular mechanisms leading to lipid accumulation using a combination of physiological, proteomic (iTRAQ) and genomic (qRT-PCR) approaches. Our results show that the expression of proteins in the biochemical pathways of glycolysis and the synthesis of fatty acids were induced in the dark, potentially using excess carbon and nitrogen produced from protein breakdown. Treatment of algae in the dark, which increased algal lipid cell quotas at low cost, combined with optimal growth treatment could help optimizing biodiesel production. PMID:27147218

Lensing of Fast Radio Bursts as a Probe of Compact Dark Matter

NASA Astrophysics Data System (ADS)

Muñoz, Julian B.; Kovetz, Ely D.; Dai, Liang; Kamionkowski, Marc

2016-08-01

The possibility that part of the dark matter is made of massive compact halo objects (MACHOs) remains poorly constrained over a wide range of masses, and especially in the 20 - 100 M⊙ window. We show that strong gravitational lensing of extragalactic fast radio bursts (FRBs) by MACHOs of masses larger than ˜20 M⊙ would result in repeated FRBs with an observable time delay. Strong lensing of a FRB by a lens of mass ML induces two images, separated by a typical time delay ˜few×(ML/30 M⊙) msec . Considering the expected FRB detection rate by upcoming experiments, such as canadian hydrogen intensity mapping experiment (CHIME), of 1 04 FRBs per year, we should observe from tens to hundreds of repeated bursts yearly, if MACHOs in this window make up all the dark matter. A null search for echoes with just 1 04 FRBs would constrain the fraction fDM of dark matter in MACHOs to fDM≲0.08 for ML≳20 M⊙ .

Quantum logic between remote quantum registers

NASA Astrophysics Data System (ADS)

Yao, N. Y.; Gong, Z.-X.; Laumann, C. R.; Bennett, S. D.; Duan, L.-M.; Lukin, M. D.; Jiang, L.; Gorshkov, A. V.

2013-02-01

We consider two approaches to dark-spin-mediated quantum computing in hybrid solid-state spin architectures. First, we review the notion of eigenmode-mediated unpolarized spin-chain state transfer and extend the analysis to various experimentally relevant imperfections: quenched disorder, dynamical decoherence, and uncompensated long-range coupling. In finite-length chains, the interplay between disorder-induced localization and decoherence yields a natural optimal channel fidelity, which we calculate. Long-range dipolar couplings induce a finite intrinsic lifetime for the mediating eigenmode; extensive numerical simulations of dipolar chains of lengths up to L=12 show remarkably high fidelity despite these decay processes. We further briefly consider the extension of the protocol to bosonic systems of coupled oscillators. Second, we introduce a quantum mirror based architecture for universal quantum computing that exploits all of the dark spins in the system as potential qubits. While this dramatically increases the number of qubits available, the composite operations required to manipulate dark-spin qubits significantly raise the error threshold for robust operation. Finally, we demonstrate that eigenmode-mediated state transfer can enable robust long-range logic between spatially separated nitrogen-vacancy registers in diamond; disorder-averaged numerics confirm that high-fidelity gates are achievable even in the presence of moderate disorder.

Endogenous Abscisic Acid Promotes Hypocotyl Growth and Affects Endoreduplication during Dark-Induced Growth in Tomato (Solanum lycopersicum L.)

PubMed Central

Humplík, Jan F.; Bergougnoux, Véronique; Jandová, Michaela; Šimura, Jan; Pěnčík, Aleš; Tomanec, Ondřej; Rolčík, Jakub; Novák, Ondřej; Fellner, Martin

2015-01-01

Dark-induced growth (skotomorphogenesis) is primarily characterized by rapid elongation of the hypocotyl. We have studied the role of abscisic acid (ABA) during the development of young tomato (Solanum lycopersicum L.) seedlings. We observed that ABA deficiency caused a reduction in hypocotyl growth at the level of cell elongation and that the growth in ABA-deficient plants could be improved by treatment with exogenous ABA, through which the plants show a concentration dependent response. In addition, ABA accumulated in dark-grown tomato seedlings that grew rapidly, whereas seedlings grown under blue light exhibited low growth rates and accumulated less ABA. We demonstrated that ABA promotes DNA endoreduplication by enhancing the expression of the genes encoding inhibitors of cyclin-dependent kinases SlKRP1 and SlKRP3 and by reducing cytokinin levels. These data were supported by the expression analysis of the genes which encode enzymes involved in ABA and CK metabolism. Our results show that ABA is essential for the process of hypocotyl elongation and that appropriate control of the endogenous level of ABA is required in order to drive the growth of etiolated seedlings. PMID:25695830

Model-based confirmation of alternative substrates of mitochondrial electron transport chain.

PubMed

Kleessen, Sabrina; Araújo, Wagner L; Fernie, Alisdair R; Nikoloski, Zoran

2012-03-30

Discrimination of metabolic models based on high throughput metabolomics data, reflecting various internal and external perturbations, is essential for identifying the components that contribute to the emerging behavior of metabolic processes. Here, we investigate 12 different models of the mitochondrial electron transport chain (ETC) in Arabidopsis thaliana during dark-induced senescence in order to elucidate the alternative substrates to this metabolic pathway. Our findings demonstrate that the coupling of the proposed computational approach, based on dynamic flux balance analysis, with time-resolved metabolomics data results in model-based confirmations of the hypotheses that, during dark-induced senescence in Arabidopsis, (i) under conditions where the main substrate for the ETC are not fully available, isovaleryl-CoA dehydrogenase and 2-hydroxyglutarate dehydrogenase are able to donate electrons to the ETC, (ii) phytanoyl-CoA does not act even as an indirect substrate of the electron transfer flavoprotein/electron-transfer flavoprotein:ubiquinone oxidoreductase complex, and (iii) the mitochondrial γ-aminobutyric acid transporter has functional significance in maintaining mitochondrial metabolism. Our study provides a basic framework for future in silico studies of alternative pathways in mitochondrial metabolism under extended darkness whereby the role of its components can be computationally discriminated based on available molecular profile data.

Morphology, stratigraphy, and surface roughness properties of Venusian lava flow fields

NASA Astrophysics Data System (ADS)

Byrnes, Jeffrey M.; Crown, David A.

2002-10-01

Morphologic characteristics, flow stratigraphy, and radar backscatter properties of five lava flow fields on Venus (Turgmam Fluctus, Zipaltonal Fluctus, Tuli Mons/Uilata Fluctus, Var Mons, and Mylitta Fluctus) were examined to understand flow field emplacement mechanisms and relationships to other surface processes. These analyses indicate that the flow fields studied developed through emplacement of numerous, thin flow units, presumably over extended periods of time. Although the Venusian fields display flow morphologies similar to those observed within terrestrial flow fields, the Venusian flow units are significantly larger and have a larger range of radar backscatter coefficients. Both simple and compound flow emplacement appear to have occurred within the flow fields. A potential correlation between flow rheology and radar brightness is suggested by differences in planform morphology, apparent flow thickness, and apparent sensitivity to topography between bright and dark flows. Distributary flow morphologies may result from tube-fed flows, and postemplacement modification by processes such as flow inflation and crustal foundering is consistent with discrete zones of increased radar brightness within individual flow lobes. Mapping of these flow fields does not indicate any simple evolutionary trend in eruptive/resurfacing style within the flow fields, or any consistent temporal sequence relative to other tectonic and volcanic features.

The Baryonic and Dark Matter Distributions in Abell 401

NASA Astrophysics Data System (ADS)

Nevalainen, J.; Markevitch, M.; Forman, W.

1999-11-01

We combine spatially resolved ASCA temperature data with ROSAT imaging data to constrain the total mass distribution in the cluster A401, assuming that the cluster is in hydrostatic equilibrium, but without the assumption of gas isothermality. We obtain a total mass within the X-ray core (290 h-150 kpc) of 1.2+0.1-0.5×1014 h-150 Msolar at the 90% confidence level, 1.3 times larger than the isothermal estimate. The total mass within r500 (1.7 h-150 Mpc) is M500=0.9+0.3-0.2×1015 h-150 Msolar at 90% confidence, in agreement with the optical virial mass estimate, and 1.2 times smaller than the isothermal estimate. Our M500 value is 1.7 times smaller than that estimated using the mass-temperature scaling law predicted by simulations. The best-fit dark matter density profile scales as r-3.1 at large radii, which is consistent with the Navarro, Frenk & White (NFW) ``universal profile'' as well as the King profile of the galaxy density in A401. From the imaging data, the gas density profile is shallower than the dark matter profile, scaling as r-2.1 at large radii, leading to a monotonically increasing gas mass fraction with radius. Within r500 the gas mass fraction reaches a value of fgas=0.21+0.06-0.05 h-3/250 (90% confidence errors). Assuming that fgas (plus an estimate of the stellar mass) is the universal value of the baryon fraction, we estimate the 90% confidence upper limit of the cosmological matter density to be Ωm<0.31, in conflict with an Einstein-deSitter universe. Even though the NFW dark matter density profile is statistically consistent with the temperature data, its central temperature cusp would lead to convective instability at the center, because the gas density does not have a corresponding peak. One way to reconcile a cusp-shaped total mass profile with the observed gas density profile, regardless of the temperature data, is to introduce a significant nonthermal pressure in the center. Such a pressure must satisfy the hydrostatic equilibrium condition without inducing turbulence. Alternately, significant mass drop-out from the cooling flow would make the temperature less peaked and the NFW profile acceptable. However, the quality of data is not adequate to test this possibility.

Dark Matter Ignition of Type Ia Supernovae.

PubMed

Bramante, Joseph

2015-10-02

Recent studies of low redshift type Ia supernovae (SN Ia) indicate that half explode from less than Chandrasekhar mass white dwarfs, implying ignition must proceed from something besides the canonical criticality of Chandrasekhar mass SN Ia progenitors. We show that 1-100 PeV mass asymmetric dark matter, with imminently detectable nucleon scattering interactions, can accumulate to the point of self-gravitation in a white dwarf and collapse, shedding gravitational potential energy by scattering off nuclei, thereby heating the white dwarf and igniting the flame front that precedes SN Ia. We combine data on SN Ia masses with data on the ages of SN Ia-adjacent stars. This combination reveals a 2.8σ inverse correlation between SN Ia masses and ignition ages, which could result from increased capture of dark matter in 1.4 vs 1.1 solar mass white dwarfs. Future studies of SN Ia in galactic centers will provide additional tests of dark-matter-induced type Ia ignition. Remarkably, both bosonic and fermionic SN Ia-igniting dark matter also resolve the missing pulsar problem by forming black holes in ≳10  Myr old pulsars at the center of the Milky Way.

Electron Transport Controls Glutamine Synthetase Activity in the Facultative Heterotrophic Cyanobacterium Synechocystis sp. PCC 6803.

PubMed Central

Reyes, J. C.; Crespo, J. L.; Garcia-Dominguez, M.; Florencio, F. J.

1995-01-01

Glutamine synthetase (GS) from Synechocystis sp. PCC 6803 was inactivated in vivo by transferring cells from light to darkness or by incubation with the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea but not with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone. Addition of glucose prevented both dark and 3-(3,4-dichlorophenyl)-1,1-dimethylurea GS inactivation. In a Synechocystis psbE-psbF mutant (T1297) lacking photosystem II, glucose was required to maintain active GS, even in the light. However, in nitrogen-starved T1297 cells the removal of glucose did not affect GS activity. The fact that dark-inactivated GS was reactivated in vitro by the same treatments that reactivate the ammonium-inactivated GS points out that both nitrogen metabolism and redox state of the cells lead to the same molecular regulatory mechanism in the control of GS activity. Using GS antibodies we detected that dark-inactivated GS displayed a different electrophoretic migration with respect to the active form in nondenaturing polyacrylamide gel electrophoresis but not in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The possible pathway to modulate GS activity by the electron transport flow in Synechocystis cells is discussed. PMID:12228640

Multi-stream portrait of the Cosmic web

NASA Astrophysics Data System (ADS)

Ramachandra, Nesar; Shandarin, Sergei

2016-03-01

We report the results of the first study of the multi-stream environment of dark matter haloes in cosmological N-body simulations in the ΛCDM cosmology. The full dynamical state of dark matter can be described as a three-dimensional sub-manifold in six-dimensional phase space - the dark matter sheet. In our study we use a Lagrangian sub-manifold x = x (q , t) (where x and q are co-moving Eulerian and Lagrangian coordinates respectively), which is dynamically equivalent to the dark matter sheet but is more convenient for numerical analysis. Our major results can be summarized as follows. At the resolution of the simulation, the cosmic web represents a hierarchical structure: each halo is embedded in the filamentary framework of the web predominantly at the filament crossings, and each filament is embedded in the wall like fabric of the web at the wall crossings. Locally, each halo or sub-halo is a peak in the number of streams field. The number of streams in the neighbouring filaments is higher than in the neighbouring walls. The walls are regions where number of streams is equal to three or a few. Voids are uniquely defined by the local condition requiring to be a single-stream flow region.

Development of the photosynthetic apparatus of Cunninghamia lanceolata in light and darkness.

PubMed

Xue, Xian; Wang, Qi; Qu, Yanli; Wu, Hongyang; Dong, Fengqin; Cao, Haoyan; Wang, Hou-Ling; Xiao, Jianwei; Shen, Yingbai; Wan, Yinglang

2017-01-01

Here, we compared the development of dark- and light-grown Chinese fir (Cunninghamia lanceolata) cotyledons, which synthesize chlorophyll in the dark, representing a different phenomenon from angiosperm model plants. We determined that the grana lamellar membranes were well developed in both chloroplasts and etiochloroplasts. The accumulation of thylakoid membrane protein complexes was similar between chloroplasts and etiochloroplasts. Measurement of chlorophyll fluorescence parameters indicated that photosystem II (PSII) had low photosynthetic activities, whereas the photosystem I (PSI)-driven cyclic electron flow (CEF) rate exceeded the rate of PSII-mediated photon harvesting in etiochloroplasts. Analysis of the protein contents in etiochloroplasts indicated that the light-harvesting complex II remained mostly in its monomeric conformation. The ferredoxin NADP + oxidoreductase and NADH dehydrogenase-like complexes were relatively abundantly expressed in etiochloroplasts for Chinese fir. Our transcriptome analysis contributes a global expression database for Chinese fir cotyledons, providing background information on the regulatory mechanisms of different genes involved in the development of dark- and light-grown cotyledons. In conclusion, we provide a novel description of the early developmental status of the light-dependent and light-independent photosynthetic apparatuses in gymnosperms. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Transient Slope Lineae Formation in a Well-Preserved Crater

NASA Image and Video Library

2017-11-20

This enhanced color image from NASA's Mars Reconnaissance Orbiter (MRO) shows what are called "recurring slope lineae"s in Tivat Crater. The narrow, dark flows descend downhill (towards the upper left). Analysis shows that the flows all end at approximately the same slope, which is similar to the angle of repose for sand. RSL are mostly found on steep rocky slopes in dark regions of Mars, such as the southern mid-latitudes, Valles Marineris near the equator, and in Acidalia Planitia on the northern plains. The appearance and growth of these features resemble seeping liquid water, but how they form remains unclear, and this research demonstrated that the RSL flows seen by HiRISE are likely moving granular material like sand and dust. These findings indicate that present-day Mars may not have a significant volume of liquid water. The water-restricted conditions that exist on Mars would make it difficult for Earth-like life to exist near the surface of the planet. The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25.6 centimeters (10.8 inches) per pixel (with 1 x 1 binning); objects on the order of 77 centimeters (30.3 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA22114

Separate spatial Holographic-Hamiltonian soliton pairs and solitons interaction in an unbiased series photorefractive crystal circuit.

PubMed

Cai, Xin; Liu, Jinsong; Wang, Shenglie

2009-02-16

This paper presents calculations for an idea in photorefractive spatial soliton, namely, a dissipative holographic soliton and a Hamiltonian soliton in one dimension form in an unbiased series photorefractive crystal circuit consisting of two photorefractive crystals of which at least one must be photovoltaic. The two solitons are known collectively as a separate Holographic-Hamiltonian spatial soliton pair and there are two types: dark-dark and bright-dark if only one crystal of the circuit is photovoltaic. The numerical results show that the Hamiltonian soliton in a soliton pair can affect the holographic one by the light-induced current whereas the effect of the holographic soliton on the Hamiltonian soliton is too weak to be ignored, i.e., the holographic soliton cannot affect the Hamiltonian one.

NEWSdm: Nuclear Emulsions for WIMP Search with directional measurement

NASA Astrophysics Data System (ADS)

Di Crescenzo, A.

2017-12-01

Direct Dark Matter searches are nowadays one of the most exciting research topics. Several experimental efforts are concentrated on the development, construction, and operation of detectors looking for the scattering of target nuclei with Weakly Interactive Massive Particles (WIMPs). The measurement of the direction of WIMP-induced nuclear recoils is a challenging strategy to extend dark matter searches beyond the neutrino floor and provide an unambiguous signature of the detection of Galactic dark matter. Current directional experiments are based on the use of gas TPC whose sensitivity is strongly limited by the small achievable detector mass. We present an innovative directional experiment based on the use of a solid target made by newly developed nuclear emulsions and read-out systems reaching a position resolution of the order of 10 nm.

Internal flows and force matrices in axial flow inducers

NASA Astrophysics Data System (ADS)

Bhattacharyya, Abhijit

1994-01-01

Axial flow inducers such as those used in high speed rocket engine turbopumps are subject to complex internal flows and fluid-induced lateral and rotordynamic forces. An investigation of these internal flows was conducted using boundary layer flow visualization on the blades, hub and housing of unshrouded and shrouded inducers. Results showed that the blade boundary layer flows have strong radial components at off-design conditions and remain attached to the blade surface at all flow coefficients tested. The origin of upstream swirling backflow was found to be at the discharge plane of the inducer. In addition, flow reversal was observed at the suction side blade tip near the leading edge in a shrouded inducer. Re-entry of the hub boundary layer flow, a downstream backflow, into the blade passage area was observed at flow coefficients below design. For unshrouded inducers the radially outward flow near the blade tip mixed with the leakage flow to form the upstream backflow. The lateral and rotordynamic forces acting on an inducer due to an imposed whirl motion was also investigated at various flow coefficients. It was found that the rotordynamic force data at various whirl frequency ratios does not allow a normal quadratic fit; consequently the conventional inertial, stiffness and damping coefficients cannot be obtained and a definite whirl ratio describing the instability region does not result. Application of an actuator disk theory proved to be inaccurate in estimating the rotordynamic tangential force in a non-whirling inducer. The effect of upstream and downstream flow distortions on the rotordynamic and lateral forces on an inducer were studied. It was found that at flow coefficients below design, large lateral forces occurred in the presence of a downstream asymmetry. Results of inlet distortion experiments show that a strong inlet shear causes a significant increase in the lateral force. Cavitation was found to have important consequences for fluid-induced rotordynamic forces. These forces become destabilizing for both forward and reverse whirl. Decreasing cavitation numbers caused an increase in the magnitudes of the destabilizing forces.

Nitrogen remobilisation facilitates adventitious root formation on reversible dark-induced carbohydrate depletion in Petunia hybrida.

PubMed

Zerche, Siegfried; Haensch, Klaus-Thomas; Druege, Uwe; Hajirezaei, Mohammad-Reza

2016-10-10

Adventitious root (AR) formation in axillary shoot tip cuttings is a crucial physiological process for ornamental propagation that is utilised in global production chains for young plants. In this process, the nitrogen and carbohydrate metabolisms of a cutting are regulated by its total nitrogen content (N t ), dark exposure during transport and irradiance levels at distinct production sites and phases through a specific plasticity to readjust metabolite pools. Here, we examined how elevated N t contents with a combined dark exposure of cuttings influence their internal N-pools including free amino acids and considered early anatomic events of AR formation as well as further root development in Petunia hybrida cuttings. Enhanced N t contents of unrooted cuttings resulted in elevated total free amino acid levels and in particular glutamate (glu) and glutamine (gln) in leaf and basal stem. N-allocation to mobile N-pools increased whereas the allocation to insoluble protein-N declined. A dark exposure of cuttings conserved initial N t and nitrate-N, while it reduced insoluble protein-N and increased soluble protein, amino- and amide-N. The increase of amino acids mainly comprised asparagine (asn), aspartate (asp) and arginine (arg) in the leaves, with distinct tissue specific responses to an elevated N supply. Dark exposure induced an early transient rise of asp followed by a temporary increase of glu. A strong positive N effect of high N t contents of cuttings on AR formation after 384 h was observed. Root meristematic cells developed at 72 h with a negligible difference for two N t levels. After 168 h, an enhanced N t accelerated AR formation and gave rise to first obvious fully developed roots while only meristems were formed with a low N t . However, dark exposure for 168 h promoted AR formation particularly in cuttings with a low N t to such an extent so that the benefit of the enhanced N t was almost compensated. Combined dark exposure and low N t of cuttings strongly reduced shoot growth during AR formation. The results indicate that both enhanced N t content and dark exposure of cuttings reinforced N signals and mobile N resources in the stem base facilitated by senescence-related proteolysis in leaves. Based on our results, a model of N mobilisation concomitant with carbohydrate depletion and its significance for AR formation is postulated.

A uniform laminar air plasma plume with large volume excited by an alternating current voltage

NASA Astrophysics Data System (ADS)

Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

2015-12-01

Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii.

PubMed

Godaux, Damien; Bailleul, Benjamin; Berne, Nicolas; Cardol, Pierre

2015-06-01

The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP(+) oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. © 2015 American Society of Plant Biologists. All Rights Reserved.

Effect of Light Availability on the Interaction between Maritime Pine and the Pine Weevil: Light Drives Insect Feeding Behavior But Also the Defensive Capabilities of the Host

PubMed Central

Suárez-Vidal, Estefanía; López-Goldar, Xosé; Sampedro, Luis; Zas, Rafael

2017-01-01

Light is a major environmental factor that may determine the interaction between plants and herbivores in several ways, including top-down effects through changes in herbivore behavior and bottom-up effects mediated by alterations of plant physiology. Here we explored the relative contribution of these two regulation processes to the outcome of the interaction of pine trees with a major forest pest, the pine weevil (Hylobius abietis). We studied to what extent light availability influence insect feeding behavior and/or the ability of pines to produce induced defenses in response to herbivory. For this purpose, 3-year old Pinus pinaster plants from three contrasting populations were subjected to 6 days of experimental herbivory by the pine weevil under two levels of light availability (complete darkness or natural sunlight) independently applied to the plant and to the insect in a fully factorial design. Light availability strongly affected the pine weevil feeding behavior. The pine weevil fed more and caused larger feeding scars in darkness than under natural sunlight. Besides, under the more intense levels of weevil damage (i.e., those registered with insects in darkness), light availability also affected the pine’s ability to respond to insect feeding by producing induced resin defenses. These results were consistent across the three studied populations despite they differed in weevil susceptibility and inducibility of defenses. Morocco was the most damaged population and the one that induced more defensive compounds. Overall, results indicate that light availability modulates the outcome of the pine–weevil interactions through both bottom-up and top-down regulation mechanisms. PMID:28912787

Investigation of light-induced conformation changes in spiropyran-modified succinylated poly(L-lysine).

PubMed

Cooper, T M; Stone, M O; Natarajan, L V; Crane, R L

1995-08-01

To determine the maximum range of coupling between side-chain photochromism and polypeptide conformation change, we modified the carboxylate side chains of succinylated poly(L-lysine) with a spiropyran to form polypeptide I. The extent of modification was determined to be 35.5%. The spacer group length between the polypeptide alpha-carbon and the dye was 12 atoms, providing minimum polypeptide-dye interaction. Conformation changes were monitored by circular dichroism as a function of light adaptation and solvent composition (hexafluoroisopropanol [HFIP] vs trifluoroethanol [TFE]). Under all solvent compositions, the dark-adapted dye was in the merocyanine form. Light adaptation by visible light converted the dye to the spiropyran form. When dissolved in TFE, I adopted a helical conformation insensitive to light adaptation. With increasing percentage HFIP, a solvent-induced helix-to-coil transition was observed around 80% (vol/vol) HFIP. At 100% HFIP, both light- and dark-adapted forms of I were in the coil state. Near the midpoint of the solvent-induced helix-to-coil transition, light adaptation caused conformation changes. Applying helix-to-coil transition theory, we measured a statistically significant difference in coil segment-HFIP binding constant for light- vs dark-adapted solutions (6.38 +/- 0.03 M-1 vs 6.56 +/- 0.03 M-1), but not for the nucleation parameter sigma (1.2 +/- 0.4 10(-3) vs 1.3 +/- 0.3 x 10(-3). The small binding constant difference translated to a light-induced binding energy difference of 17 cal/mol/monomer. Near the midpoint of the helix-to-coil transition, collective interactions between monomer units made possible the translation of a small energy difference (less than RT) into large macromolecular conformation changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Light at night acutely impairs glucose tolerance in a time-, intensity- and wavelength-dependent manner in rats.

PubMed

Opperhuizen, Anne-Loes; Stenvers, Dirk J; Jansen, Remi D; Foppen, Ewout; Fliers, Eric; Kalsbeek, Andries

2017-07-01

Exposure to light at night (LAN) has increased dramatically in recent decades. Animal studies have shown that chronic dim LAN induced obesity and glucose intolerance. Furthermore, several studies in humans have demonstrated that chronic exposure to artificial LAN may have adverse health effects with an increased risk of metabolic disorders, including type 2 diabetes. It is well-known that acute exposure to LAN affects biological clock function, hormone secretion and the activity of the autonomic nervous system, but data on the effects of LAN on glucose homeostasis are lacking. This study aimed to investigate the acute effects of LAN on glucose metabolism. Male Wistar rats were subjected to i.v. glucose or insulin tolerance tests while exposed to 2 h of LAN in the early or late dark phase. In subsequent experiments, different light intensities and wavelengths were used. LAN exposure early in the dark phase at ZT15 caused increased glucose responses during the first 20 min after glucose infusion (p < 0.001), whereas LAN exposure at the end of the dark phase, at ZT21, caused increased insulin responses during the first 10 min (p < 0.01), indicating that LAN immediately induces glucose intolerance in rats. Subsequent experiments demonstrated that the effect of LAN was both intensity- and wavelength-dependent. White light of 50 and 150 lx induced greater glucose responses than 5 and 20 lx, whereas all intensities other than 5 lx reduced locomotor activity. Green light induced glucose intolerance, but red and blue light did not, suggesting the involvement of a specific retina-brain pathway. Together, these data show that exposure to LAN has acute adverse effects on glucose metabolism in a time-, intensity- and wavelength-dependent manner.

The efficacy of (+)-Naltrexone on alcohol preference and seeking behaviour is dependent on light-cycle.

PubMed

Jacobsen, Jonathan Henry W; Buisman-Pijlman, Femke T A; Mustafa, Sanam; Rice, Kenner C; Hutchinson, Mark R

2018-01-01

Circadian rhythm affects drug-induced reward behaviour and the innate immune system. Peaks in reward-associated behaviour and immune responses typically occur during the active (dark) phase of rodents. While the role of the immune system, specifically, Toll-like receptor 4 (TLR4, an innate immune receptor) in drug-induced reward is becoming increasingly appreciated, it is unclear whether its effects vary according to light-cycle. Therefore, the aim of this study was to characterise the effects of the phase of the light-cycle and the state of the innate immune system on alcohol reward behaviour and subsequently determine whether the efficacy of targeting the immune component of drug reward depends upon the light-cycle. This study demonstrates that mice exhibit greater alcohol-induced conditioned place preference and alcohol two-bottle choice preference during the dark cycle. This effect overlapped with elevations in reward-, thirst- and immune-related genes. Administration of (+)-Naltrexone, a TLR4 antagonist, reduced immune-related gene mRNA expression and alcohol preference with its effects most pronounced during the dark cycle. However, (+)-Naltrexone, like other TLR4 antagonists exhibited off-target side effects, with a significant reduction in overall saccharin intake - an effect likely attributable to a reduction in tyrosine hydroxylase (Th) mRNA expression levels. Collectively, the study highlights a link between a time-of-day dependent influence of TLR4 on natural and alcohol reward-like behaviour in mice. Copyright © 2017 Elsevier Inc. All rights reserved.

η2-SO2 Linkage Photoisomer of an Osmium Coordination Complex.

PubMed

Cole, Jacqueline M; Velazquez-Garcia, Jose de J; Gosztola, David J; Wang, SuYin Grass; Chen, Yu-Sheng

2018-03-05

We report the discovery of an η 2 -SO 2 linkage photoisomer in the osmium pentaammine coordination complex, [Os(NH 3 ) 5 (SO 2 )][Os(NH 3 ) 5 (HSO 3 )]Cl 4 (1). Its dark- and light-induced crystal structures are determined via synchrotron X-ray crystallography, at 100 K, where the photoinduced state is metastable in a single crystal that has been stimulated by 505 nm light for 2.5 h. The SO 2 photoisomer in the [Os(NH 3 ) 5 (SO 2 )] 2+ cation contrasts starkly with the photoinactivity of the HSO 3 ligand in its companion [Os(NH 3 ) 5 (HSO 3 )] + cation within the crystallographic asymmetric unit of this single crystal. Panchromatic optical absorption characteristics of this single crystal are revealed in both dark- and light-induced states, using concerted absorption spectroscopy and optical microscopy. Its absorption halves across most of its visible spectrum, upon exposure to 505 nm light. The SO 2 ligand seems to be responsible for this photoinduced bleaching effect, judging from a comparison of the dark- and light-induced crystal structures of 1. The SO 2 photoisomerism is found to be thermally reversible, and so 1 presents a rare example of an osmium-based solid-state optical switch. Such switching in an osmium complex is significant because bottom-row transition metals stand to offer linkage photoisomerism with the greatest photoconversion levels and thermal stability. The demonstration of η 2 -SO 2 bonding in this complex also represents a fundamental contribution to osmium coordination chemistry.

Toxicity and deficiency of copper in Elsholtzia splendens affect photosynthesis biophysics, pigments and metal accumulation.

PubMed

Peng, Hongyun; Kroneck, Peter M H; Küpper, Hendrik

2013-06-18

Elsholtzia splendens is a copper-tolerant plant species growing on copper deposits in China. Spatially and spectrally resolved kinetics of in vivo absorbance and chlorophyll fluorescence in mesophyll of E. splendens were used to investigate the copper-induced stress from deficiency and toxicity as well as the acclimation to excess copper stress. The plants were cultivated in nutrient solutions containing either Fe(III)-EDTA or Fe(III)-EDDHA. Copper toxicity affected light-acclimated electron flow much stronger than nonphotochemical quenching (NPQ) or dark-acclimated photochemical efficiency of PSIIRC (Fv/Fm). It also changed spectrally resolved Chl fluorescence kinetics, in particular by strengthening the short-wavelength (<700 nm) part of NPQ altering light harvesting complex II (LHCII) aggregation. Copper toxicity reduced iron accumulation, decreased Chls and carotenoids in leaves. During acclimation to copper toxicity, leaf copper decreased but leaf iron increased, with photosynthetic activity and pigments recovering to normal levels. Copper tolerance in E. splendens was inducible; acclimation seems be related to homeostasis of copper and iron in E. splendens. Copper deficiency appeared at 10 mg copper per kg leaf DW, leading to reduced growth and decreased photosynthetic parameters (F0, Fv/Fm, ΦPSII). The importance of these results for evaluating responses of phytoremediation plants to stress in their environment is discussed.

Sleep Deprivation and Caffeine Treatment Potentiate Photic Resetting of the Master Circadian Clock in a Diurnal Rodent.

PubMed

Jha, Pawan Kumar; Bouâouda, Hanan; Gourmelen, Sylviane; Dumont, Stephanie; Fuchs, Fanny; Goumon, Yannick; Bourgin, Patrice; Kalsbeek, Andries; Challet, Etienne

2017-04-19

Circadian rhythms in nocturnal and diurnal mammals are primarily synchronized to local time by the light/dark cycle. However, nonphotic factors, such as behavioral arousal and metabolic cues, can also phase shift the master clock in the suprachiasmatic nuclei (SCNs) and/or reduce the synchronizing effects of light in nocturnal rodents. In diurnal rodents, the role of arousal or insufficient sleep in these functions is still poorly understood. In the present study, diurnal Sudanian grass rats, Arvicanthis ansorgei , were aroused at night by sleep deprivation (gentle handling) or caffeine treatment that both prevented sleep. Phase shifts of locomotor activity were analyzed in grass rats transferred from a light/dark cycle to constant darkness and aroused in early night or late night. Early night, but not late night, sleep deprivation induced a significant phase shift. Caffeine on its own induced no phase shifts. Both sleep deprivation and caffeine treatment potentiated light-induced phase delays and phase advances in response to a 30 min light pulse, respectively. Sleep deprivation in early night, but not late night, potentiated light-induced c-Fos expression in the ventral SCN. Caffeine treatment in midnight triggered c-Fos expression in dorsal SCN. Both sleep deprivation and caffeine treatment potentiated light-induced c-Fos expression in calbindin-containing cells of the ventral SCN in early and late night. These findings indicate that, in contrast to nocturnal rodents, behavioral arousal induced either by sleep deprivation or caffeine during the sleeping period potentiates light resetting of the master circadian clock in diurnal rodents, and activation of calbindin-containing suprachiasmatic cells may be involved in this effect. SIGNIFICANCE STATEMENT Arousing stimuli have the ability to regulate circadian rhythms in mammals. Behavioral arousal in the sleeping period phase shifts the master clock in the suprachiasmatic nuclei and/or slows down the photic entrainment in nocturnal animals. How these stimuli act in diurnal species remains to be established. Our study in a diurnal rodent, the Grass rat, indicates that sleep deprivation in the early rest period induces phase delays of circadian locomotor activity rhythm. Contrary to nocturnal rodents, both sleep deprivation and caffeine-induced arousal potentiate the photic entrainment in a diurnal rodent. Such enhanced light-induced circadian responses could be relevant for developing chronotherapeutic strategies. Copyright © 2017 the authors 0270-6474/17/374343-16$15.00/0.

Basal Ganglia Dopamine-gamma-Aminobutyric Acid-Acetylcholine Interaction in Organophosphate-Induced Neurotoxicity. Appendices

DTIC Science & Technology

1982-12-01

Animals were maintained ad llbltua on standard laboratory chow and tap water and were housed in a room with automatic 12 hour light and dark cycles and...supernatant fluid was centrl- fuged at 20,000 x g for 20 min to obtain a crude mitochondria ! pellet. The crude mitochondrlal pellet was resuspended...chow and tap water and wer- housed in a room with automatic 12 hour light and dark cycles and temperature set at 25.5 ± 1.8°C. DUsopropylfli’oro

Neutrino mass in flavor dependent gauged lepton model

NASA Astrophysics Data System (ADS)

Nomura, Takaaki; Okada, Hiroshi

2018-03-01

We study a neutrino model introducing an additional nontrivial gauged lepton symmetry where the neutrino masses are induced at two-loop level, while the first and second charged-leptons of the standard model are done at one-loop level. As a result of the model structure, we can predict one massless active neutrino, and there is a dark matter candidate. Then we discuss the neutrino mass matrix, muon anomalous magnetic moment, lepton flavor violations, oblique parameters, and relic density of dark matter, taking into account the experimental constraints.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuo, Y.S.; Smith, E.B.; Deb, S.K.

A Kaufman ion beam source was used to implant hydrogen atoms into glow-discharge-deposited amorphous silicon materials in which the hydrogen content had been driven out by heating. We found that the hydrogen atoms introduced by this low-energy (less than 700 eV) ion implantation method bonded predominantly as SiH. An air mass one, photo-to-dark-conductivity ratio as high as 5.6 x 10/sup 5/ has been obtained with hydrogen-implanted materials. No light-induced reduction of the photo- and dark conductivities has been observed in these materials after 20 h of AMl illumnination.

Possible interaction between baryons and dark-matter particles revealed by the first stars

NASA Astrophysics Data System (ADS)

Barkana, Rennan

2018-03-01

The cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from Lyman-α radiation from some of the earliest stars. By observing this 21-centimetre signal—either its sky-averaged spectrum or maps of its fluctuations, obtained using radio interferometers—we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. The recent detection of the global 21-centimetre spectrum reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3.8 standard deviations. Here we report that this absorption can be explained by the combination of radiation from the first stars and excess cooling of the cosmic gas induced by its interaction with dark matter. Our analysis indicates that the spatial fluctuations of the 21-centimetre signal at cosmic dawn could be an order of magnitude larger than previously expected and that the dark-matter particle is no heavier than several proton masses, well below the commonly predicted mass of weakly interacting massive particles. Our analysis also confirms that dark matter is highly non-relativistic and at least moderately cold, and primordial velocities predicted by models of warm dark matter are potentially detectable. These results indicate that 21-centimetre cosmology can be used as a dark-matter probe.

Possible interaction between baryons and dark-matter particles revealed by the first stars.

PubMed

Barkana, Rennan

2018-02-28

The cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from Lyman-α radiation from some of the earliest stars. By observing this 21-centimetre signal-either its sky-averaged spectrum or maps of its fluctuations, obtained using radio interferometers-we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. The recent detection of the global 21-centimetre spectrum reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3.8 standard deviations. Here we report that this absorption can be explained by the combination of radiation from the first stars and excess cooling of the cosmic gas induced by its interaction with dark matter. Our analysis indicates that the spatial fluctuations of the 21-centimetre signal at cosmic dawn could be an order of magnitude larger than previously expected and that the dark-matter particle is no heavier than several proton masses, well below the commonly predicted mass of weakly interacting massive particles. Our analysis also confirms that dark matter is highly non-relativistic and at least moderately cold, and primordial velocities predicted by models of warm dark matter are potentially detectable. These results indicate that 21-centimetre cosmology can be used as a dark-matter probe.

Recognizing Axionic Dark Matter by Compton and de Broglie Scale Modulation of Pulsar Timing.

PubMed

De Martino, Ivan; Broadhurst, Tom; Tye, S-H Henry; Chiueh, Tzihong; Schive, Hsi-Yu; Lazkoz, Ruth

2017-12-01

Light axionic dark matter, motivated by string theory, is increasingly favored for the "no weakly interacting massive particle era". Galaxy formation is suppressed below a Jeans scale of ≃10^{8}  M_{⊙} by setting the axion mass to m_{B}∼10^{-22}  eV, and the large dark cores of dwarf galaxies are explained as solitons on the de Broglie scale. This is persuasive, but detection of the inherent scalar field oscillation at the Compton frequency ω_{B}=(2.5  months)^{-1}(m_{B}/10^{-22}  eV) would be definitive. By evolving the coupled Schrödinger-Poisson equation for a Bose-Einstein condensate, we predict the dark matter is fully modulated by de Broglie interference, with a dense soliton core of size ≃150  pc, at the Galactic center. The oscillating field pressure induces general relativistic time dilation in proportion to the local dark matter density and pulsars within this dense core have detectably large timing residuals of ≃400  nsec/(m_{B}/10^{-22}  eV). This is encouraging as many new pulsars should be discovered near the Galactic center with planned radio surveys. More generally, over the whole Galaxy, differences in dark matter density between pairs of pulsars imprints a pairwise Galactocentric signature that can be distinguished from an isotropic gravitational wave background.

Improved diagnosis of pulmonary emphysema using in vivo dark-field radiography.

PubMed

Meinel, Felix G; Yaroshenko, Andre; Hellbach, Katharina; Bech, Martin; Müller, Mark; Velroyen, Astrid; Bamberg, Fabian; Eickelberg, Oliver; Nikolaou, Konstantin; Reiser, Maximilian F; Pfeiffer, Franz; Yildirim, Ali Ö

2014-10-01

The purpose of this study was to assess whether the recently developed method of grating-based x-ray dark-field radiography can improve the diagnosis of pulmonary emphysema in vivo. Pulmonary emphysema was induced in female C57BL/6N mice using endotracheal instillation of porcine pancreatic elastase and confirmed by in vivo pulmonary function tests, histopathology, and quantitative morphometry. The mice were anesthetized but breathing freely during imaging. Experiments were performed using a prototype small-animal x-ray dark-field scanner that was operated at 35 kilovolt (peak) with an exposure time of 5 seconds for each of the 10 grating steps. Images were compared visually. For quantitative comparison of signal characteristics, regions of interest were placed in the upper, middle, and lower zones of each lung. Receiver-operating-characteristic statistics were performed to compare the effectiveness of transmission and dark-field signal intensities and the combined parameter "normalized scatter" to differentiate between healthy and emphysematous lungs. A clear visual difference between healthy and emphysematous mice was found for the dark-field images. Quantitative measurements of x-ray dark-field signal and normalized scatter were significantly different between the mice with pulmonary emphysema and the control mice and showed good agreement with pulmonary function tests and quantitative histology. The normalized scatter showed a significantly higher discriminatory power (area under the receiver-operating-characteristic curve [AUC], 0.99) than dark-field (AUC, 0.90; P = 0.01) or transmission signal (AUC, 0.69; P < 0.001) alone did, allowing for an excellent discrimination of healthy and emphysematous lung regions. In a murine model, x-ray dark-field radiography is technically feasible in vivo and represents a substantial improvement over conventional transmission-based x-ray imaging for the diagnosis of pulmonary emphysema.

The Planar Satellite Distributions around Andromeda, the Milky Way and Other Galaxies, and Their Implications for Fundamental Physics

NASA Astrophysics Data System (ADS)

Kroupa, P.

2014-05-01

The existence of dark matter particles is a key hypothesis in present-day cosmology and galactic dynamics. The validity of this hypothesis is challenged significantly by two independent arguments. 1) The dual dwarf galaxy theorem must be true in any realistic cosmological model. But it is found to be falsified when the dark-matter-based model is applied to the observational data. A consistency check of this conclusion comes from the observed significantly disk-like distributions of satellite populations which orbit in the same direction around their hosting galaxy and which cannot be derived from dark-matter models. 2) The action of dynamical friction due to expansive and massive dark matter halos must be evident in the galaxy population. The evidence however for dynamical friction is void or meagre at best. The M81 group fo galaxies already appears to rule out the existence of dynamical friction through dark matter halos, and the Milky Way satellite galaxies have been shown to challenge dark-matter-induced dynamical friction. The implication of this deduction for fundamental physics would be that exotic dark matter particles do not exist and that consequently gravitational physics on the scales of galaxies and beyond ought to be non-Newtonian/Einsteinian. An analysis of the kinematical data in galaxies shows them to be described excellently by scale-invariant dynamics, as discovered by Milgrom. This leads to a natural emergence of laws that galaxies are observed to obey. Such success has not been forthcoming in the dark-matter-based models. A consequence of this novel understanding of galactic astrophysics is that most dwarf satellite galaxies are formed as tidal dwarf galaxies in galaxy-galaxy encounters and that galactic mergers are rare.

Pigmentation plasticity enhances crypsis in larval newts: associated metabolic cost and background choice behaviour

PubMed Central

Polo-Cavia, Nuria; Gomez-Mestre, Ivan

2017-01-01

In heterogeneous environments, the capacity for colour change can be a valuable adaptation enhancing crypsis against predators. Alternatively, organisms might achieve concealment by evolving preferences for backgrounds that match their visual traits, thus avoiding the costs of plasticity. Here we examined the degree of plasticity in pigmentation of newt larvae (Lissotriton boscai) in relation to predation risk. Furthermore, we tested for associated metabolic costs and pigmentation-dependent background choice behaviour. Newt larvae expressed substantial changes in pigmentation so that light, high-reflecting environment induced depigmentation whereas dark, low-reflecting environment induced pigmentation in just three days of exposure. Induced pigmentation was completely reversible upon switching microhabitats. Predator cues, however, did not enhance cryptic phenotypes, suggesting that environmental albedo induces changes in pigmentation improving concealment regardless of the perceived predation risk. Metabolic rate was higher in heavily pigmented individuals from dark environments, indicating a high energetic requirement of pigmentation that could impose a constraint to larval camouflage in dim habitats. Finally, we found partial evidence for larvae selecting backgrounds matching their induced phenotypes. However, in the presence of predator cues, larvae increased the time spent in light environments, which may reflect a escape response towards shallow waters rather than an attempt at increasing crypsis. PMID:28051112

Short-term regulation and alternative pathways of photosynthetic electron transport in Hibiscus rosa-sinensis leaves.

PubMed

Trubitsin, Boris V; Vershubskii, Alexey V; Priklonskii, Vladimir I; Tikhonov, Alexander N

2015-11-01

In this work, using the EPR and PAM-fluorometry methods, we have studied induction events of photosynthetic electron transport in Hibiscus rosa-sinensis leaves. The methods used are complementary, providing efficient tools for in situ monitoring of P700 redox transients and photochemical activity of photosystem II (PSII). The induction of P700(+) in dark-adapted leaves is characterized by the multiphase kinetics with a lag-phase, which duration elongates with the dark-adaptation time. Analyzing effects of the uncoupler monensin and artificial electron carrier methylviologen (MV) on photooxidation of P700 and slow induction of chlorophyll a fluorescence (SIF), we could ascribe different phases of transient kinetics of electron transport processes in dark-adapted leaves to the following regulatory mechanisms: (i) acceleration of electron transfer on the acceptor side of PSI, (ii) pH-dependent modulation of the intersystem electron flow, and (iii) re-distribution of electron fluxes between alternative (linear, cyclic, and pseudocyclic) pathways. Monensin significantly decreases a level of P700(+) and inhibits SIF. MV, which mediates electron flow from PSI to O2 with consequent formation of H2O2, promotes a rapid photooxidation of P700 without any lag-phase peculiar to untreated leaves. MV-mediated water-water cycle (H2O→PSII→PSI→MV→O2→H2O2→H2O) is accompanied by generation of ascorbate free radicals. This suggests that the ascorbate peroxidase system of defense against reactive oxygen species is active in chloroplasts of H. rosa-sinensis leaves. In DCMU-treated chloroplasts with inhibited PSII, the contribution of cyclic electron flow is insignificant as compared to linear electron flow. For analysis of induction events, we have simulated electron transport processes within the framework of our generalized mathematical model of oxygenic photosynthesis, which takes into account pH-dependent mechanisms of electron transport control and re-distribution of electron fluxes between alternative pathways. The model adequately describes the main peculiarities of P700(+) induction and dynamics of the intersystem electron transport. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of Milk vs Dark Chocolate Consumption on Visual Acuity and Contrast Sensitivity Within 2 Hours: A Randomized Clinical Trial.

PubMed

Rabin, Jeff C; Karunathilake, Nirmani; Patrizi, Korey

2018-04-26

Consumption of dark chocolate can improve blood flow, mood, and cognition in the short term, but little is known about the possible effects of dark chocolate on visual performance. To compare the short-term effects of consumption of dark chocolate with those of milk chocolate on visual acuity and large- and small-letter contrast sensitivity. A randomized, single-masked crossover design was used to assess short-term visual performance after consumption of a dark or a milk chocolate bar. Thirty participants without pathologic eye disease each consumed dark and milk chocolate in separate sessions, and within-participant paired comparisons were used to assess outcomes. Testing was conducted at the Rosenberg School of Optometry from June 25 to August 15, 2017. Visual acuity (in logMAR units) and large- and small-letter contrast sensitivity (in the log of the inverse of the minimum detectable contrast [logCS units]) were measured 1.75 hours after consumption of dark and milk chocolate bars. Among the 30 participants (9 men and 21 women; mean [SD] age, 26 [5] years), small-letter contrast sensitivity was significantly higher after consumption of dark chocolate (mean [SE], 1.45 [0.04] logCS) vs milk chocolate (mean [SE], 1.30 [0.05] logCS; mean improvement, 0.15 logCS [95% CI, 0.08-0.22 logCS]; P < .001). Large-letter contrast sensitivity was slightly higher after consumption of dark chocolate (mean [SE], 2.05 [0.02] logCS) vs milk chocolate (mean [SE], 2.00 [0.02] logCS; mean improvement, 0.05 logCS [95% CI, 0.00-0.10 logCS]; P = .07). Visual acuity improved slightly after consumption of dark chocolate (mean [SE], -0.22 [0.01] logMAR; visual acuity, approximately 20/12) and milk chocolate (mean [SE], -0.18 [0.01] logMAR; visual acuity, approximately 20/15; mean improvement, 0.04 logMAR [95% CI, 0.02-0.06 logMAR]; P = .05). Composite scores combining results from all tests showed significant improvement after consumption of dark compared with milk chocolate (mean improvement, 0.20 log U [95% CI, 0.10-0.30 log U]; P < .001). Contrast sensitivity and visual acuity were significantly higher 2 hours after consumption of a dark chocolate bar compared with a milk chocolate bar, but the duration of these effects and their influence in real-world performance await further testing. clinicaltrials.gov Identifier: NCT03326934.

Test of the decaying dark matter hypothesis using the Hopkins Ultraviolet Telescope

NASA Technical Reports Server (NTRS)

Davidsen, A. F.; Kriss, G. A.; Ferguson, H. C.; Blair, W. P.; Bowers, C. W.; Kimble, R. A.

1991-01-01

Sciama's hypothesis that the dark matter associated with galaxies, galaxy clusters, and the intergalactic medium consists of tau neutrinos of rest mass 28-30 eV whose decay generates ultraviolet photons of energy roughly 14-15 eV, has been tested using the Hopkins Ultraviolet Telescope flows aboard the Space Shuttle Columbia. A straightforward application of Sciama's model predicts that a spectral line from neutrino decay photons should be observed from the rich galaxy cluster Abell 665 with an SNR of about 30. No such emission was detected. For neutrinos in the mass range 27.2-32.1 eV, the observations set a lower lifetime limit significantly greater than Sciama's model requires.

Polarimetry and spectroscopy of a simple sunspot. I - On the magnetic field of a sunspot penumbra

NASA Technical Reports Server (NTRS)

Schmidt, W.; Hofmann, A.; Balthasar, H.; Tarbell, T. D.; Frank, Z. A.

1992-01-01

We investigate the magnetic field structure of a medium sized sunspot using high resolution magnetograms and spectrograms and derive a relationship between the brightness of penumbral structures and the inclination of the magnetic field. The field inclination to the spot normal is larger in the dark structures than in the bright ones. We show that the field strength does not vary between dark and bright structures. At the inner penumbral boundary the field strength is 2000 Gauss and about 1000 Gauss at the outer penumbral edge. The line-of sight component of the material flow decreases rapidly within one arcsecond at the photospheric boundary of the spot.

Analysis of a Gene Regulatory Cascade Mediating Circadian Rhythm in Zebrafish

PubMed Central

Wang, Haifang; Du, Jiulin; Yan, Jun

2013-01-01

In the study of circadian rhythms, it has been a puzzle how a limited number of circadian clock genes can control diverse aspects of physiology. Here we investigate circadian gene expression genome-wide using larval zebrafish as a model system. We made use of a spatial gene expression atlas to investigate the expression of circadian genes in various tissues and cell types. Comparison of genome-wide circadian gene expression data between zebrafish and mouse revealed a nearly anti-phase relationship and allowed us to detect novel evolutionarily conserved circadian genes in vertebrates. We identified three groups of zebrafish genes with distinct responses to light entrainment: fast light-induced genes, slow light-induced genes, and dark-induced genes. Our computational analysis of the circadian gene regulatory network revealed several transcription factors (TFs) involved in diverse aspects of circadian physiology through transcriptional cascade. Of these, microphthalmia-associated transcription factor a (mitfa), a dark-induced TF, mediates a circadian rhythm of melanin synthesis, which may be involved in zebrafish's adaptation to daily light cycling. Our study describes a systematic method to discover previously unidentified TFs involved in circadian physiology in complex organisms. PMID:23468616

Anticonvulsant and neuroprotective effects of Pimpinella anisum in rat brain

PubMed Central

2012-01-01

Background Essential oil of Pimpinella anisum L. Apiaceae (anise oil) has been widely used in traditional Persian medicine to treat a variety of diseases, including some neurological disorders. This study was aimed to test the possible anti-seizure and anti-hypoxia effects of anise oil. Methods The effects of different concentrations of anise oil were tested on seizure attacks induced by pentylenetetrazol (PTZ) injection and neuronal hypoxia induced by oxygen withdrawal as well as on production of dark neurons and induction of long-term potentiation (LTP) in in vivo and in vitro experimental models of rat brain. Results Anise oil significantly prolonged the latency of seizure attacks and reduced the amplitude and duration of epileptiform burst discharges induced by injection of intraperitoneal PTZ. In addition, anise oil significantly inhibited production of dark neurons in different regions of the brain in epileptic rats. Anise oil also significantly enhanced the duration of the appearance of anoxic terminal negativity induced by oxygen withdrawal and inhibited induction of LTP in hippocampal slices. Conclusions Our data indicate the anticonvulsant and neuroprotective effects of anise oil, likely via inhibition of synaptic plasticity. Further evaluation of anise oil to use in the treatment of neurological disorders is suggested. PMID:22709243

In Vivo Dark-Field Radiography for Early Diagnosis and Staging of Pulmonary Emphysema.

PubMed

Hellbach, Katharina; Yaroshenko, Andre; Meinel, Felix G; Yildirim, Ali Ö; Conlon, Thomas M; Bech, Martin; Mueller, Mark; Velroyen, Astrid; Notohamiprodjo, Mike; Bamberg, Fabian; Auweter, Sigrid; Reiser, Maximilian; Eickelberg, Oliver; Pfeiffer, Franz

2015-07-01

The aim of this study was to evaluate the suitability of in vivo x-ray dark-field radiography for early-stage diagnosis of pulmonary emphysema in mice. Furthermore, we aimed to analyze how the dark-field signal correlates with morphological changes of lung architecture at distinct stages of emphysema. Female 8- to 10-week-old C57Bl/6N mice were used throughout all experiments. Pulmonary emphysema was induced by orotracheal injection of porcine pancreatic elastase (80-U/kg body weight) (n = 30). Control mice (n = 11) received orotracheal injection of phosphate-buffered saline. To monitor the temporal patterns of emphysema development over time, the mice were imaged 7, 14, or 21 days after the application of elastase or phosphate-buffered saline. X-ray transmission and dark-field images were acquired with a prototype grating-based small-animal scanner. In vivo pulmonary function tests were performed before killing the animals. In addition, lungs were obtained for detailed histopathological analysis, including mean cord length (MCL) quantification as a parameter for the assessment of emphysema. Three blinded readers, all of them experienced radiologists and familiar with dark-field imaging, were asked to grade the severity of emphysema for both dark-field and transmission images. Histopathology and MCL quantification confirmed the introduction of different stages of emphysema, which could be clearly visualized and differentiated on the dark-field radiograms, whereas early stages were not detected on transmission images. The correlation between MCL and dark-field signal intensities (r = 0.85) was significantly higher than the correlation between MCL and transmission signal intensities (r = 0.37). The readers' visual ratings for dark-field images correlated significantly better with MCL (r = 0.85) than visual ratings for transmission images (r = 0.36). Interreader agreement and the diagnostic accuracy of both quantitative and visual assessment were significantly higher for dark-field imaging than those for conventional transmission images. X-ray dark-field radiography can reliably visualize different stages of emphysema in vivo and demonstrates significantly higher diagnostic accuracy for early stages of emphysema than conventional attenuation-based radiography.

Rapid changes in protein phosphorylation associated with light-induced gravity perception in corn roots

NASA Technical Reports Server (NTRS)

McFadden, J. J.; Poovaiah, B. W.

1988-01-01

The effect of light and calcium depletion on in vivo protein phosphorylation was tested using dark-grown roots of Merit corn. Light caused rapid and specific promotion of phosphorylation of three polypeptides. Pretreatment of roots with ethylene glycol bis N,N,N',N' tetraacetic acid and A23187 prevented light-induced changes in protein phosphorylation. We postulate that these changes in protein phosphorylation are involved in the light-induced gravity response.

Volcanic Constructs on Ganymede and Enceladus: Topographic Evidence from Stereo Images and Photoclinometry

NASA Technical Reports Server (NTRS)

Schenk, Paul M.; Moore, Jeffrey M.

1995-01-01

The morphology of volcanic features on Ganymede differs significantly from that on the terrestrial planets. Few if any major volcanic landforms, such as thick flows or shield volcanoes, have been identified to date. Using new stereo Voyager images, we have searched Ganymede for relief-generating volcanic constructs. We observed seven major types of volcanic structures, including several not previously recognized. The oldest are broad flat-topped domes partially filling many older craters in dark terrain. Similar domes occur on Enceladus. Together with smooth dark deposits, these domes indicate that the volcanic history of the dark terrain is complex. Bright terrain covers vast areas, although the style of emplacement remains unclear. Smooth bright materials embay and flood older terrains, and may have been emplaced as low- viscosity fluids. Associated with smooth bright material are a number of scalloped-shaped, semi- enclosed scarps that cut into preexisting terrain. In planform these structures resemble terrestrial calderas. The youngest volcanic materials identified are a series of small flows that may have flooded the floor of the multiring impact structure Gilgamesh, forming a broad dome, The identification of volcanic constructs up to I km thick is the first evidence for extrusion of moderate-to-high viscosity material on Ganymede. Viscosity and yield strength estimates for these materials span several orders of magnitude, indicating that volcanic materials on Ganymede have a range of compositions and/or were extruded under a wide range of conditions and/or eruptive styles.

[Characteristics of soil water infiltration in sub-alpine dark coniferous ecosystem of upper reaches of Yangtze River].

PubMed

Yu, Xinxiao; Zhao, Yutao; Zhang, Zhiqiang; Cheng, Genwei

2003-01-01

Dark coniferous forest is the predominant type of vegetation in the upper reaches of Yangtze River. Difference among different types of soil exists. The sand content of soil is higher and the soil texture is coarser in the early stage of forest succession. The sand content of soil decreases with the advancement of the forest succession while that of soil in Abies fabri over-mature forest is the lowest. In slope wash soil, the sand content of soil decreases with the increasing soil depth. The soil porosity and soil water-holding capacity increases and soil bulk density decreases with the advancement of forest succession and decrease of soil depth. The deeper soil depth or the smaller soil water content are, the smaller the unsaturated hydraulic conductivity of soil measured by CGA method. Moreover, the correlation of soil water content with unsaturated hydraulic conductivity of soil can be simulated by an exponential function. The saturated hydraulic conductivity of soil decreases exponentially with the increasing soil depth. The time to attain the stable infiltration rate is different among different soil depth, while the deeper the soil depth is, the longer the time needs. The variation in soil texture, soil physical properties and the high infiltration rate of soil there implicated that there are scarce surface runoff, but abundant in subsurface flow, return flow and seepage, which is the result of regulation by dark coniferous forest on hydrological processes.

Anaerobic Carbon Metabolism by the Tricarboxylic Acid Cycle 1

PubMed Central

Vanlerberghe, Greg C.; Horsey, Anne K.; Weger, Harold G.; Turpin, David H.

1989-01-01

Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH4+ in the dark under anaerobic conditions. Addition of NH4+ to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO2 efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenolpyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H14CO3− to anaerobic cells assimilating NH4+ results in the incorporation of radiolabel into the α-carboxyl carbon of glutamic acid. Incorporation of radiolabel into glutamic acid is not simply a short-term phenomenon following NH4+ addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply α-ketoglutarate for glutamate production. During dark aerobic NH4+ assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH4+ assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH4+ assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity. PMID:16667215

Pb-Induced Avoidance-Like Chloroplast Movements in Fronds of Lemna trisulca L.

PubMed Central

Samardakiewicz, Sławomir; Krzeszowiec-Jeleń, Weronika; Bednarski, Waldemar; Jankowski, Artur; Suski, Szymon; Gabryś, Halina; Woźny, Adam

2015-01-01

Lead ions are particularly dangerous to the photosynthetic apparatus, but little is known about the effects of trace metals, including Pb, on regulation of chloroplast redistribution. In this study a new effect of lead on chloroplast distribution patterns and movements was demonstrated in mesophyll cells of a small-sized aquatic angiosperm Lemna trisulca L. (star duckweed). An analysis of confocal microscopy images of L. trisulca fronds treated with lead (15 μM Pb2+, 24 h) in darkness or in weak white light revealed an enhanced accumulation of chloroplasts in the profile position along the anticlinal cell walls, in comparison to untreated plants. The rearrangement of chloroplasts in their response to lead ions in darkness was similar to the avoidance response of chloroplasts in plants treated with strong white light. Transmission electron microscopy X-ray microanalysis showed that intracellular chloroplast arrangement was independent of the location of Pb deposits, suggesting that lead causes redistribution of chloroplasts, which looks like a light-induced avoidance response, but is not a real avoidance response to the metal. Furthermore, a similar redistribution of chloroplasts in L. trisulca cells in darkness was observed also under the influence of exogenously applied hydrogen peroxide (H2O2). In addition, we detected an enhanced accumulation of endogenous H2O2 after treatment of plants with lead. Interestingly, H2O2-specific scavenger catalase partly abolished the Pb-induced chloroplast response. These results suggest that H2O2 can be involved in the avoidance-like movement of chloroplasts induced by lead. Analysis of photometric measurements revealed also strong inhibition (but not complete) of blue-light-induced chloroplast movements by lead. This inhibition may result from disturbances in the actin cytoskeleton, as we observed fragmentation and disappearance of actin filaments around chloroplasts. Results of this study show that the mechanisms of the toxic effect of lead on chloroplasts can include disturbances in their movement and distribution pattern. PMID:25646776

Dark, Recurring Streaks on Walls of Garni Crater

NASA Image and Video Library

2015-09-28

Dark narrow streaks, called "recurring slope lineae," emanate from the walls of Garni Crater on Mars, in this view constructed from observations by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The dark streaks here are up to few hundred yards, or meters, long. They are hypothesized to be formed by flow of briny liquid water on Mars. The image was produced by first creating a 3-D computer model (a digital terrain map) of the area based on stereo information from two HiRISE observations, and then draping an image over the land-shape model. The vertical dimension is exaggerated by a factor of 1.5 compared to horizontal dimensions. The draped image is a red waveband (monochrome) product from HiRISE observation ESP_031059_1685, taken on March 12, 2013 at 11.5 degrees south latitude, 290.3 degrees east longitude. Other image products from this observation are at http://hirise.lpl.arizona.edu/ESP_031059_1685. http://photojournal.jpl.nasa.gov/catalog/PIA19917

Featured Image: A New Dark Vortex on Neptune

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

This remarkable series of images by the Hubble Space Telescope (click for the full view) track a dark vortex only the fifth ever observed on Neptune as it evolves in Neptunes atmosphere. These Hubble images, presented in a recent study led by Michael Wong (University of California, Berkeley), were taken in 2015 September, 2016 May, 2016 October, and 2017 October; the observations have monitored the evolution of the vortex as it has gradually weakened and drifted polewards. Confirmation of the vortex solved a puzzle that arose in 2015, when astronomers spotted an unexplained outburst of cloud activity on Neptune. This outburst was likely a group of bright companion clouds that form as air flows over high-pressure dark vortices, causing gases to freeze into methane ice crystals. To learn more about what the authors have since learned by studying this vortex, check out the paper below.CitationMichael H. Wong et al 2018 AJ 155 117. doi:10.3847/1538-3881/aaa6d6

Analytical and experimental study of mean flow and turbulence characteristics inside the passages of an axial flow inducer

NASA Technical Reports Server (NTRS)

Gorton, C. A.; Lakshminarayana, B.

1980-01-01

The inviscid and viscid effects existing within the passages of a three bladed axial flow inducer operating at a flow coefficient of 0.065 are investigated. The blade static pressure and blade limiting streamline angle distributions were determined and the three components of mean velocity, turbulence intensities, and turbulence stresses were measured at locations inside the inducer blade passage utilizing a rotating three sensor hotwire probe. Applicable equations were derived for the hotwire data reduction analysis and solved numerically to obtain the appropriate flow parameters. The three dimensional inviscid flow in the inducer was predicted by numerically solving the exact equations of motion, and the three dimensional viscid flow was predicted by incorporating the dominant viscous terms into the exact equations. The analytical results are compared with the experimental measurements and design values where appropriate. Radial velocities are found to be of the same order as axial velocities within the inducer passage, confirming the highly three dimensional characteristic of inducer flow. Total relative velocity distribution indicate a substantial velocity deficiency near the tip at mid-passage which expands significantly as the flow proceeds toward the inducer trailing edge. High turbulence intensities and turbulence stresses are concentrated within this core region. Considerable wake diffusion occurs immediately downstream of the inducer trailing edge to decay this loss core. Evidence of boundary layer interactions, blade blockage effects, radially inward flows, annulus wall effects, and backflows are all found to exist within the long, narrow passages of the inducer.

Mapping of the Culann-Tohil region of Io from Galileo imaging data

USGS Publications Warehouse

Williams, D.A.; Schenk, P.M.; Moore, Johnnie N.; Keszthelyi, L.P.; Turtle, E.P.; Jaeger, W.L.; Radebaugh, J.; Milazzo, M.P.; Lopes, R.M.C.; Greeley, R.

2004-01-01

We have used Galileo spacecraft data to produce a geomorphologic map of the Culann-Tohil region of Io's antijovian hemisphere. This region includes a newly discovered shield volcano, Tsu??i Goab Tholus and a neighboring bright flow field, Tsu??i Goab Fluctus, the active Culann Patera and the enigmatic Tohil Mons-Radegast Patera-Tohil Patera complex. Analysis of Voyager global color and Galileo Solid-State Imaging (SSI) high-resolution, regional (50-330 m/pixel), and global color (1.4 km/pixel) images, along with available Galileo Near-Infrared Mapping Spectrometer (NIMS) data, suggests that 16 distinct geologic units can be defined and characterized in this region, including 5 types of diffuse deposits. Tsu??i Goab Fluctus is the center of a low-temperature hotspot detected by NIMS late during the Galileo mission, and could represent the best case for active effusive sulfur volcanism detected by Galileo. The Culann volcanic center has produced a range of explosive and effusive deposits, including an outer yellowish ring of enhanced sulfur dioxide (SO2), an inner red ring of SO2 with short-chain sulfur (S3-S4) contaminants, and two irregular green diffuse deposits (one in Tohil Patera) apparently produced by the interaction of dark, silicate lava flows with sulfurous contaminants ballistically-emplaced from Culann's eruption plume(s). Fresh and red-mantled dark lava flows west of the Culann vent can be contrasted with unusual red-brown flows east of the vent. These red-brown flows have a distinct color that is suggestive of a compositional difference, although whether this is due to surface alteration or distinct lava compositions cannot be determined. The main massif of Tohil Mons is covered with ridges and grooves, defining a unit of tectonically disrupted crustal materials. Tohil Mons also contains a younger unit of mottled crustal materials that were displaced by mass wasting processes. Neighboring Radegast Patera contains a NIMS hotspot and a young lava lake of dark silicate flows, whereas the southwest portion of Tohil Patera contains white flow-like units, perhaps consisting of 'ponds' of effusively emplaced SO2. From 0?? -15?? S the hummocky bright plains unit away from volcanic centers contains scarps, grooves, pits, graben, and channel-like features, some of which have been modified by erosion. Although the most active volcanic centers appear to be found in structural lows (as indicated by mapping of scarps), DEMs derived from stereo images show that, with the exception of Tohil Mons, there is less than 1 km of relief in the Culann-Tohil region. There is no discernable correlation between centers of active volcanism and topography. ?? 2003 Elsevier Inc. All rights reserved.

The Zamama-Thor region of Io: Insights from a synthesis of mapping, topography, and Galileo spacecraft data

USGS Publications Warehouse

Williams, D.A.; Keszthelyi, L.P.; Schenk, P.M.; Milazzo, M.P.; Lopes, R.M.C.; Rathbun, J.A.; Greeley, R.

2005-01-01

We have studied data from the Galileo spacecraft's three remote sensing instruments (Solid-State Imager (SSI), Near-Infrared Mapping Spectrometer (NIMS), and Photopolarimeter-Radiometer (PPR)) covering the Zamama - Thor region of Io's antijovian hemisphere, and produced a geomorphological map of this region. This is the third of three regional maps we are producing from the Galileo spacecraft data. Our goal is to assess the variety of volcanic and tectonic materials and their interrelationships on Io using planetary mapping techniques, supplemented with all available Galileo remote sensing data. Based on the Galileo data analysis and our mapping, we have determined that the most recent geologic activity in the Zamama - Thor region has been dominated by two sites of large-scale volcanic surface changes. The Zamama Eruptive Center is a site of both explosive and effusive eruptions, which emanate from two relatively steep edifices (Zamama Tholi A and B) that appear to be built by both silicate and sulfur volcanism. A ???100-km long flow field formed sometime after the 1979 Voyager flybys, which appears to be a site of promethean-style compound flows, flow-front SO2 plumes, and adjacent sulfur flows. Larger, possibly stealthy, plumes have on at least one occasion during the Galileo mission tapped a source that probably includes S and/or Cl to produce a red pyroclastic deposit from the same vent from which silicate lavas were erupted. The Thor Eruptive Center, which may have been active prior to Voyager, became active again during the Galileo mission between May and August 2001. A pillanian-style eruption at Thor included the tallest plume observed to date on Io (at least 500 km high) and new dark lava flows. The plume produced a central dark pyroclastic deposit (probably silicate-rich) and an outlying white diffuse ring that is SO2-rich. Mapping shows that several of th000e new dark lava flows around the plume vent have reoccupied sites of earlier flows. Unlike most of the other pillanian eruptions observed during the Galileo mission, the 2001 Thor eruption did not produce a large red ring deposit, indicating a relative lack of S and/or Cl gases interacting with the magma during that eruption. Between these two eruptive centers are two paterae, Thomagata and Reshef. Thomagata Patera is located on a large shield-like mesa and shows no signs of activity. In contrast, Reshef Patera is located on a large, irregular mesa that is apparently undergoing degradation through erosion (perhaps from SO2 -sapping or chemical decomposition of sulfur-rich material) from multiple secondary volcanic centers. ?? 2005 Elsevier Inc. All rights reserved.

The development of a cryogenic over-pressure pump

NASA Astrophysics Data System (ADS)

Alvarez, M.; Cease, H.; Flaugher, B.; Flores, R.; Garcia, J.; Lathrop, A.; Ruiz, F.

2014-01-01

A cryogenic over-pressure pump (OPP) was tested in the prototype telescope liquid nitrogen (LN2) cooling system for the Dark Energy Survey (DES) Project. This OPP consists of a process cylinder (PC), gas generator, and solenoid operated valves (SOVs). It is a positive displacement pump that provided intermittent liquid nitrogen (LN2) flow to an array of charge couple devices (CCDs) for the prototype Dark Energy Camera (DECam). In theory, a heater submerged in liquid would generate the drive gas in a closed loop cooling system. The drive gas would be injected into the PC to displace that liquid volume. However, due to limitations of the prototype closed loop nitrogen system (CCD cooling system) for DECam, a quasiclosed-loop nitrogen system was created. During the test of the OPP, the CCD array was cooled to its designed set point temperature of 173K. It was maintained at that temperature via electrical heaters. The performance of the OPP was captured in pressure, temperature, and flow rate in the CCD LN2 cooling system at Fermi National Accelerator Laboratory (FNAL).

Exposed Bedrock in the Koval'sky Impact Basin

NASA Image and Video Library

2017-06-27

This image shows partially exposed bedrock within the Koval'sky impact basin, which is on the outskirts of the extensive lava field of Daedalia Planum. Daedalia Planum is located southwest of Arsia Mons, which may be the source responsible for filling the crater with lava flows and ash deposits. On one side, bright bedrock with scattered dark blue spots are seen. The dark blue spots are boulders shedding from the outcrops. The color range of the bedrock provides some information on its composition. The blue color is indicative of the presence of iron-rich minerals that are generally not oxidized (i.e., rusted), unlike most of the ruddy Martian surface. Volcanic rocks are common on Mars. Possible candidate minerals for the bluish materials are often consistent with iron-rich minerals, such as pyroxene and olivine. The ridges may represent remnants of the original surface of the lava flows that filled the Koval'sky impact basin. NB: The region is named for M. A. Koval'sky, a Russian astronomer. https://photojournal.jpl.nasa.gov/catalog/PIA21765

From Science To Design: Systems Engineering For The Lsst

NASA Astrophysics Data System (ADS)

Claver, Chuck F.; Axelrod, T.; Fouts, K.; Kantor, J.; Nordby, M.; Sebag, J.; LSST Collaboration

2009-01-01

The LSST is a universal-purpose survey telescope that will address scores of scientific missions. To assist the technical teams to convergence to a specific engineering design, the LSST Science Requirements Document (SRD) selects four stressing principle scientific missions: 1) Constraining Dark Matter and Dark Energy; 2) taking an Inventory of the Solar System; 3) Exploring the Transient Optical Sky; and 4) mapping the Milky Way. From these 4 missions the SRD specifies the needed requirements for single images and the full 10 year survey that enables a wide range of science beyond the 4 principle missions. Through optical design and analysis, operations simulation, and throughput modeling the systems engineering effort in the LSST has largely focused on taking the SRD specifications and deriving system functional requirements that define the system design. A Model Based Systems Engineering approach with SysML is used to manage the flow down of requirements from science to system function to sub-system. The rigor of requirements flow and management assists the LSST in keeping the overall scope, hence budget and schedule, under control.

Light-Dependent OCT Structure Changes in Photoreceptor Degenerative rd 10 Mouse Retina

PubMed Central

Li, Yichao; Zhang, Yikui; Chen, Sonia; Vernon, Gregory; Wong, Wai T.

2018-01-01

Purpose Using optical coherence tomography (OCT) to analyze the effects of light/dark adaptation in a mouse model of inherited photoreceptor degeneration (rd10), and to study dynamics of subretinal fluid during the progress of retinal degeneration. Methods rd10 and wild-type (WT) C57BL/6J mice were reared in cyclic light or darkness and imaged with Bioptigen UHR-OCT or Spectralis HRA+OCT after adaptation to either light or darkness. Results OCT images from rd10 mice were analyzed at three progressive stages of degeneration. After light-adaptation, stage I (postnatal age [P]26–29) eyes demonstrated no apparent subretinal fluid. At stage II (P32–38), subretinal fluid was present and restricted to parapapillary area, while at stage III (P44–45) extensive subretinal fluid was present across many retinal areas. Following overnight dark-adaptation, WT eyes showed a large reduction in outer retinal thickness (4.6 ± 1.4 μm, n = 16), whereas this change was significantly smaller in stage I rd10 eyes (1.5 ± 0.5 μm, n = 14). In stage II rd10 eyes, dark-adaptation significantly reduced the extent of subretinal fluid, with the amount of reduction correlating with the amount of fluid pre-existing in the light-adapted state. However, dark-adaptation did not significantly alter the amount of subretinal fluid observed in stage III rd10 mice. In addition, dark-rearing of rd10 mice from P6 to P30 slowed retinal degeneration. Conclusions Visual experience in the form of light/dark adaptation exerts a significant effect on outer retinal structure in the context of photoreceptor degeneration. This effect may arise from light-dependent alterations in fluid transport across the RPE monolayer, and promote photoreceptor survival as induced by dark-rearing. PMID:29490345

DarkSide-20k: A 20 tonne two-phase LAr TPC for direct dark matter detection at LNGS

NASA Astrophysics Data System (ADS)

Aalseth, C. E.; Acerbi, F.; Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; Alici, A.; Alton, A. K.; Antonioli, P.; Arcelli, S.; Ardito, R.; Arnquist, I. J.; Asner, D. M.; Ave, M.; Back, H. O.; Barrado Olmedo, A. I.; Batignani, G.; Bertoldo, E.; Bettarini, S.; Bisogni, M. G.; Bocci, V.; Bondar, A.; Bonfini, G.; Bonivento, W.; Bossa, M.; Bottino, B.; Boulay, M.; Bunker, R.; Bussino, S.; Buzulutskov, A.; Cadeddu, M.; Cadoni, M.; Caminata, A.; Canci, N.; Candela, A.; Cantini, C.; Caravati, M.; Cariello, M.; Carlini, M.; Carpinelli, M.; Castellani, A.; Catalanotti, S.; Cataudella, V.; Cavalcante, P.; Cavuoti, S.; Cereseto, R.; Chepurnov, A.; Cicalò, C.; Cifarelli, L.; Citterio, M.; Cocco, A. G.; Colocci, M.; Corgiolu, S.; Covone, G.; Crivelli, P.; D'Antone, I.; D'Incecco, M.; D'Urso, D.; Da Rocha Rolo, M. D.; Daniel, M.; Davini, S.; de Candia, A.; De Cecco, S.; De Deo, M.; De Filippis, G.; De Guido, G.; De Rosa, G.; Dellacasa, G.; Della Valle, M.; Demontis, P.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Dolgov, A.; Dormia, I.; Dussoni, S.; Empl, A.; Fernandez Diaz, M.; Ferri, A.; Filip, C.; Fiorillo, G.; Fomenko, K.; Franco, D.; Froudakis, G. E.; Gabriele, F.; Gabrieli, A.; Galbiati, C.; Garcia Abia, P.; Gendotti, A.; Ghisi, A.; Giagu, S.; Giampa, P.; Gibertoni, G.; Giganti, C.; Giorgi, M. A.; Giovanetti, G. K.; Gligan, M. L.; Gola, A.; Gorchakov, O.; Goretti, A. M.; Granato, F.; Grassi, M.; Grate, J. W.; Grigoriev, G. Y.; Gromov, M.; Guan, M.; Guerra, M. B. B.; Guerzoni, M.; Gulino, M.; Haaland, R. K.; Hallin, A.; Harrop, B.; Hoppe, E. W.; Horikawa, S.; Hosseini, B.; Hughes, D.; Humble, P.; Hungerford, E. V.; Ianni, An.; Jillings, C.; Johnson, T. N.; Keeter, K.; Kendziora, C. L.; Kim, S.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Kuss, M.; Kuźniak, M.; La Commara, M.; Lehnert, B.; Li, X.; Lissia, M.; Lodi, G. U.; Loer, B.; Longo, G.; Loverre, P.; Lussana, R.; Luzzi, L.; Ma, Y.; Machado, A. A.; Machulin, I. N.; Mandarano, A.; Mapelli, L.; Marcante, M.; Margotti, A.; Mari, S. M.; Mariani, M.; Maricic, J.; Martoff, C. J.; Mascia, M.; Mayer, M.; McDonald, A. B.; Messina, A.; Meyers, P. D.; Milincic, R.; Moggi, A.; Moioli, S.; Monroe, J.; Monte, A.; Morrocchi, M.; Mount, B. J.; Mu, W.; Muratova, V. N.; Murphy, S.; Musico, P.; Nania, R.; Navrer Agasson, A.; Nikulin, I.; Nosov, V.; Nozdrina, A. O.; Nurakhov, N. N.; Oleinik, A.; Oleynikov, V.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Palmas, S.; Pandola, L.; Pantic, E.; Paoloni, E.; Paternoster, G.; Pavletcov, V.; Pazzona, F.; Peeters, S.; Pelczar, K.; Pellegrini, L. A.; Pelliccia, N.; Perotti, F.; Perruzza, R.; Pesudo, V.; Piemonte, C.; Pilo, F.; Pocar, A.; Pollmann, T.; Portaluppi, D.; Pugachev, D. A.; Qian, H.; Radics, B.; Raffaelli, F.; Ragusa, F.; Razeti, M.; Razeto, A.; Regazzoni, V.; Regenfus, C.; Reinhold, B.; Renshaw, A. L.; Rescigno, M.; Retière, F.; Riffard, Q.; Rivetti, A.; Rizzardini, S.; Romani, A.; Romero, L.; Rossi, B.; Rossi, N.; Rubbia, A.; Sablone, D.; Salatino, P.; Samoylov, O.; Sánchez García, E.; Sands, W.; Sanfilippo, S.; Sant, M.; Santorelli, R.; Savarese, C.; Scapparone, E.; Schlitzer, B.; Scioli, G.; Segreto, E.; Seifert, A.; Semenov, D. A.; Shchagin, A.; Shekhtman, L.; Shemyakina, E.; Sheshukov, A.; Simeone, M.; Singh, P. N.; Skensved, P.; Skorokhvatov, M. D.; Smirnov, O.; Sobrero, G.; Sokolov, A.; Sotnikov, A.; Speziale, F.; Stainforth, R.; Stanford, C.; Suffritti, G. B.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Tonazzo, A.; Tosi, A.; Trinchese, P.; Unzhakov, E. V.; Vacca, A.; Vázquez-Jáuregui, E.; Verducci, M.; Viant, T.; Villa, F.; Vishneva, A.; Vogelaar, B.; Wada, M.; Wahl, J.; Walding, J.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Williams, R.; Wojcik, M. M.; Wu, S.; Xiang, X.; Xiao, X.; Yang, C.; Ye, Z.; Yllera de Llano, A.; Zappa, F.; Zappalà, G.; Zhu, C.; Zichichi, A.; Zullo, M.; Zullo, A.; Zuzel, G.

2018-03-01

Building on the successful experience in operating the DarkSide-50 detector, the DarkSide Collaboration is going to construct DarkSide-20k, a direct WIMP search detector using a two-phase Liquid Argon Time Projection Chamber (LAr TPC) with an active (fiducial) mass of 23 t (20 t). This paper describes a preliminary design for the experiment, in which the DarkSide-20k LAr TPC is deployed within a shield/veto with a spherical Liquid Scintillator Veto (LSV) inside a cylindrical Water Cherenkov Veto (WCV). This preliminary design provides a baseline for the experiment to achieve its physics goals, while further development work will lead to the final optimization of the detector parameters and an eventual technical design. Operation of DarkSide-50 demonstrated a major reduction in the dominant 39Ar background when using argon extracted from an underground source, before applying pulse shape analysis. Data from DarkSide-50, in combination with MC simulation and analytical modeling, shows that a rejection factor for discrimination between electron and nuclear recoils of >3 × 109 is achievable. This, along with the use of the veto system and utilizing silicon photomultipliers in the LAr TPC, are the keys to unlocking the path to large LAr TPC detector masses, while maintaining an experiment in which less than < 0.1 events (other than ν-induced nuclear recoils) is expected to occur within the WIMP search region during the planned exposure. DarkSide-20k will have ultra-low backgrounds than can be measured in situ, giving sensitivity to WIMP-nucleon cross sections of 1.2 × 10^{-47} cm2 (1.1 × 10^{-46} cm2) for WIMPs of 1 TeV/c 2 (10 TeV/c 2) mass, to be achieved during a 5 yr run producing an exposure of 100 t yr free from any instrumental background.

Activation of G proteins mediates flow-induced prostaglandin E2 production in osteoblasts

NASA Technical Reports Server (NTRS)

Reich, K. M.; McAllister, T. N.; Gudi, S.; Frangos, J. A.

1997-01-01

Interstitial fluid flow may play a role in load-induced bone remodeling. Previously, we have shown that fluid flow stimulates osteoblast production of cAMP inositol trisphosphate (IP3), and PGE2. Flow-induced increases in cAMP and IP3 were shown to be a result of PG production. Thus, PGE2 production appears to be an important component in fluid flow induced signal transduction. In the present study, we investigated the mechanism of flow-induced PGE2 synthesis. Flow-induced a 20-fold increase in PGE2 production in osteoblasts. Increases were also observed with ALF4-(10mM) (98-fold), an activator of guanidine nucleotide-binding proteins (G proteins), and calcium ionophore A23187 (2 microM) (100-fold) in stationary cells. We then investigated whether flow stimulation is mediated by G proteins and increases in intracellular calcium. Flow-induced PGE2 production was inhibited by the G protein inhibitors GDP beta S (100 microM) and pertussis toxin (1 microgram/ml) by 83% and 72%, respectively. Chelation of extracellular calcium by EGTA (2 mM) and intracellular calcium by quin-2/AM (30 microM) blocked flow stimulation by 87% and 67%, respectively. These results suggest that G proteins and calcium play an important role in mediating mechanochemical signal transduction in osteoblasts.

In vitro propagation of the Garden Heliotrope, Valeriana officinalis L.: influence of pre-chilling and light on seed germination.

PubMed

Bhat, B; Sharma, V D

2015-03-01

Valeriana officinalis is an important medicinal herb commonly found in Kashmir valley. This study forms an important preliminary step for in-vitro micro propagation of V. officinalis from breaking the seed dormancy, inducing rapid seed germination and its subsequent micro propagation. We investigated the influence of pretreatment of V. officinalis seeds with reduced temperature and light on seed germination and in-vitro propagation. Culture of explants from cultivated seeds have demonstrated its potential for in vitro propagation and plantlet regeneration. Individual as well as combinations of treatments such as temperature and light availability influenced the germination of seeds variedly. Unchilled seeds of V. officinalis were given dip in GA3 (200 ppm) for 24, 48 and 120 h. Seeds treated with GA3 for 24 h and kept in darkness showed the best results, i.e. 48%. Seeds pretreated with GA3 for 120 h and incubated in dark showed 40% germination. Pre-chilling up to 72 h and kept in light showed maximum germination of 60% followed by 40% kept in darkness. Pre-chilling for 48 h resulted in 40 and 25% seed germination in light and darkness, respectively. GA3 pre-treatment for 72 h and 24 h pre chilling were most effective in inducing seed germination. Maximum shoot response was obtained on MS enriched with BAP (1 mg/L) + IAA (0.1 mg/L) combinations using shoot tips as explants. Multiple shoot regeneration from shoot apices was recorded on BAP (1 mg/L) and BAP (1 mg/L) + IAA (0.1 mg/L).

Dynamical behavior of psb gene transcripts in greening wheat seedlings. I. Time course of accumulation of the pshA through psbN gene transcripts during light-induced greening.

PubMed

Kawaguchi, H; Fukuda, I; Shiina, T; Toyoshima, Y

1992-11-01

The time course of the accumulation of the transcripts from 13 psb genes encoding a major part of the proteins composing photosystem II during light-induced greening of dark-grown wheat seedlings was examined focusing on early stages of plastid development (0.5 h through 72 h). The 13 genes can be divided into three groups. (1) The psbA gene is transcribed as a single transcript of 1.3 kb in the dark-grown seedlings, but its level increases 5- to 7-fold in response to light due to selective increase in RNA stability as well as in transcription activity. (2) The psbE-F-L-J operon, psbM and psbN genes are transcribed as a single transcript of 1.1 kb, two transcripts of 0.5 and 0.7 kb and a single transcript of 0.3 kb, respectively, in the dark-grown seedlings. The levels of accumulation of every transcript remain unchanged or rather decrease during plastid development under illumination. (3) The psbK-I-D-C gene cluster and psbB-H operon exhibit fairly complicated northern hybridization patterns during the greening process. When a psbC or psbD gene probe was used for northern hybridization, five transcripts differing in length were detected in the etioplasts from 5-day old dark-grown seedlings. After 2 h illumination, two new transcripts of different length appeared. Light induction of new transcripts was also observed in the psbB-H operon.

Mechanisms of flow and ACh-induced dilation in rat soleus arterioles are altered by hindlimb unweighting

NASA Technical Reports Server (NTRS)

Schrage, William G.; Woodman, Christopher R.; Laughlin, M. Harold

2002-01-01

The purpose of this study was to test the hypothesis that endothelium-dependent dilation (flow-induced dilation and ACh-induced dilation) in rat soleus muscle arterioles is impaired by hindlimb unweighting (HLU). Male Sprague-Dawley rats (approximately 300 g) were exposed to HLU or weight-bearing control (Con) conditions for 14 days. Soleus first-order (1A) and second-order (2A) arterioles were isolated, cannulated, and exposed to step increases in luminal flow at constant pressure. Flow-induced dilation was not impaired by HLU in 1A or 2A arterioles. The cyclooxygenase inhibitor indomethacin (Indo; 50 microM) did not alter flow-induced dilation in 1As or 2As. Inhibition of nitric oxide synthase (NOS) with N(omega)-nitro-L-arginine (L-NNA; 300 microM) reduced flow-induced dilation by 65-70% in Con and HLU 1As. In contrast, L-NNA abolished flow-induced dilation in 2As from Con rats but had no effect in HLU 2As. Combined treatment with L-NNA + Indo reduced tone in 1As and 2As from Con rats, but flow-induced dilation in the presence of L-NNA + Indo was not different from responses without inhibitors in either Con or HLU 1As or 2As. HLU also did not impair ACh-induced dilation (10(-9)-10(-4) M) in soleus 2As. L-NNA reduced ACh-induced dilation by approximately 40% in Con 2As but abolished dilation in HLU 2As. Indo did not alter ACh-induced dilation in Con or HLU 2As, whereas combined treatment with L-NNA + Indo abolished ACh-induced dilation in 2As from both groups. We conclude that flow-induced dilation (1As and 2As) was preserved after 2 wk HLU, but HLU decreased the contribution of NOS in mediating flow-induced dilation and increased the contribution of a NOS- and cyclooxygenase-independent mechanism (possibly endothelium-derived hyperpolarizing factor). In soleus 2As, ACh-induced dilation was preserved after 2-wk HLU but the contribution of NOS in mediating ACh-induced dilation was increased.

CASIMIR Effect in a Supersymmetry-Breaking Brane-World as Dark Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, P

2004-09-29

A new model for the origin of dark energy is proposed based on the Casimir effect in a supersymmetry-breaking brane-world. Supersymmetry is assumed to be preserved in the bulk while broken on a 3-brane. Due to the boundary conditions imposed on the compactified extra dimensions, there is an effective Casimir energy induced on the brane. The net Casimir energy contributed from the graviton and the gravitino modes as a result of supersymmetry-breaking on the brane is identified as the observed dark energy, which in our construction is a cosmological constant. We show that the smallness of the cosmological constant, whichmore » results from the huge contrast in the extra-dimensional volumes between that associated with the 3-brane and that of the bulk, is attainable under very relaxed condition.« less

Dark matter versus Mach's principle.

NASA Astrophysics Data System (ADS)

von Borzeszkowski, H.-H.; Treder, H.-J.

1998-02-01

Empirical and theoretical evidence show that the astrophysical problem of dark matter might be solved by a theory of Einstein-Mayer type. In this theory up to global Lorentz rotations the reference system is determined by the motion of cosmic matter. Thus one is led to a "Riemannian space with teleparallelism" realizing a geometric version of the Mach-Einstein doctrine. The field equations of this gravitational theory contain hidden matter terms where the existence of hidden matter is inferred safely from its gravitational effects. It is argued that in the nonrelativistic mechanical approximation they provide an inertia-free mechanics where the inertial mass of a body is induced by the gravitational action of the comic masses. Interpreted form the Newtonian point of view this mechanics shows that the effective gravitational mass of astrophysical objects depends on r such that one expects the existence of dark matter.

Collisional phase shifts of ring dark solitons in inhomogeneous Bose Einstein condensates

NASA Astrophysics Data System (ADS)

Peng, Ping; Li, Guan-Qiang; Xue, Ju-Kui

2007-06-01

The head-on collisions of two ring dark solitons in inhomogeneous Bose Einstein condensates (BECs) with thin disk-shaped potential are studied by the extended Poincaré Lighthill Kuo (PLK) perturbation method. The result shows that the system admits a solution with two concentric ring solitons, one moving inwards and the other moving outwards, which in small-amplitude limit, are described by two modified cylindrical KdV equations in the respective reference frames. In particular, the analytical phase shifts induced by the head-on collisions between two ring dark solitary waves are derived, and the result shows that the phase shifts change with the radial coordinate r according to the (1+σr)r law (where σ˜ωr2/ωz2), which are quite different with the homogeneous case.

Induction of Secondary Dormancy in Chenopodium bonus-henricus L. Seeds by Osmotic and High Temperature Treatments and Its Prevention by Light and Growth Regulators 1

PubMed Central

Khan, Anwar A.; Karssen, C. M.

1980-01-01

Factors controlling the establishment and removal of secondary dormancy in Chenopodium bonus-henricus L. seeds were investigated. Unchilled seeds required light for germination. A moist-chilling treatment at 4 C for 28 to 30 days removed this primary dormancy. Chilled seeds now germinated in the dark. When chilled seeds were held in the dark in −8.6 bars polyethylene glycol 6000 solution at 15 C or in water at 29 C a secondary dormancy was induced which increased progressively with time as determined by subsequent germination. These seeds now failed to germinate under the condition (darkness) which previously allowed their germination. Continuous light or daily brief red light irradiations during prolonged imbibition in polyethylene glycol solution at 15 C or in water at 29 C prevented the establishment of the secondary dormancy and caused an advancement of subsequent germination. Far red irradiations immediately following red irradiation reestablished the secondary dormancy indicating phytochrome participation in “pregerminative” processes. The growth regulator combination, kinetin + ethephon + gibberellin A4+A7 (GA4+7), and to a relatively lesser extent GA4+7, was effective in preventing the establishment of the secondary dormancy and in advancing the germination or emergence time. Following the establishment of the secondary dormancy by osmotic or high temperature treatments the regulator combination was relatively more active than light or GA4+7 in removing the dormancy. Prolonged dark treatment at 29 C seemed to induce changes that were partially independent of light or GA4+7 control. The data presented here indicate that changes during germination preventing dark treatment determine whether the seed will germinate, show an advancement effect, or will become secondarily dormant. These changes appear to be modulated by light and hormones. PMID:16661382

Factors controlling charge recombination under dark and light conditions in dye sensitised solar cells.

PubMed

Barnes, Piers R F; Anderson, Assaf Y; Juozapavicius, Mindaugas; Liu, Lingxuan; Li, Xiaoe; Palomares, Emilio; Forneli, Amparo; O'Regan, Brian C

2011-02-28

A simple and powerful approach for assessing the recombination losses in dye sensitised solar cells (DSSCs) across the current voltage curve (j-V) as a function of TiO(2) electron concentration (n) is demonstrated. The total flux of electrons recombining with iodine species in the electrolyte and oxidised dye molecules can be thought of as a recombination current density, defined as j(rec) = j(inj)-j where j(inj) is the current of electrons injected from optically excited dye states and j is the current density collected at cell voltage (V). The electron concentration at any given operating conditions is determined by charge extraction. This allows comparison of factors influencing electron recombination rates at matched n. We show that j(rec) is typically 2-3 times higher under 1 sun equivalent illumination (j(inj) > 0) relative to dark (j(inj) = 0) conditions. This difference was increased by increasing light intensity, electrolyte iodine concentration and electrolyte solvent viscosity. The difference was reduced by increasing the electrolyte iodide concentration and increasing the temperature. These results allowed us to verify a numerical model of complete operational cells (Barnes et al., Phys. Chem. Chem. Phys., DOI: 10.1039/c0cp01554g) and to relate the differences in j(rec) to physical processes in the devices. The difference between j(rec) in the light and dark can be explained by two factors: (1) an increase in the concentration of electron acceptor species (I(3)(-) and/or I(2)) when current is flowing under illumination relative to dark conditions where the current is flowing in the opposite direction, and (2) a non-trivial contribution from electron recombination to oxidised dye molecules under light conditions. More generally, the technique helps to assign the observed relationship between the components, processing and performance of DSSCs to more fundamental physical processes.

Does epicatechin contribute to the acute vascular function effects of dark chocolate? A randomized, crossover study.

PubMed

Dower, James I; Geleijnse, Johanna M; Kroon, Paul A; Philo, Mark; Mensink, Marco; Kromhout, Daan; Hollman, Peter C H

2016-11-01

Cocoa, rich in flavan-3-ols, improves vascular function, but the contribution of specific flavan-3-ols is unknown. We compared the effects of pure epicatechin, a major cocoa flavan-3-ol, and chocolate. In a randomized crossover study, twenty healthy men (40-80 years) were supplemented with: (1) 70g dark chocolate (150 mg epicatechin) with placebo capsules; (2) pure epicatechin capsules (2 × 50 mg epicatechin) with 75g white chocolate; and (3) placebo capsules with 75 g white chocolate (0 mg epicatechin). Vascular function (flow-mediated dilation (FMD) and augmentation index (AIx)) were measured before and 2 hours after interventions. Epicatechin metabolites time-profiles were measured in blood to calculate the bioavailability. Pure epicatechin did not significantly improve FMD (+0.75%; p = 0.10) or AIx (-2.2%; p = 0.23) compared to placebo. Dark chocolate significantly improved FMD (+0.96%; p = 0.04) and AIx (-4.6%; p = 0.02). Differences in improvements in FMD (+ 0.21%; p = 0.65) or Aix (-2.4%; p = 0.20) between pure epicatechin and dark chocolate were not significant. The bioavailability of epicatechin did not differ between pure epicatechin and dark chocolate (p = 0.14). Despite differences in epicatechin dose, improvements in vascular function after pure epicatechin and chocolate were similar and the bioavailability did not differ, suggesting a role for epicatechin. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tunable electromagnetically induced transparency from a superconducting terahertz metamaterial

NASA Astrophysics Data System (ADS)

Zhang, Caihong; Wu, Jingbo; Jin, Biaobing; Jia, Xiaoqing; Kang, Lin; Xu, Weiwei; Wang, Huabing; Chen, Jian; Tonouchi, Masoyoshi; Wu, Peiheng

2017-06-01

We demonstrate in this paper the tunable electromagnetically induced transparency (EIT) made from a superconducting (SC) niobium nitride (NbN) film induced by an intense terahertz (THz) field. As the variation of the incident THz field alters the intrinsic ohmic loss of the SC NbN film, the field-dependent transmittance is observed. To elaborate the role of the bright and dark modes, a hybrid coupling model is introduced to fit the experimental transmission spectra and extract the characteristic parameters of each mode. It is shown that the resonator for the bright mode is altered greatly due to strong direct coupling to the incident intense THz field, whereas the dark mode resonator has little interaction with the incident THz field via a weak near-filed coupling to the bright-mode resonator. This implies that we can partially control a mode or a part of metamaterial by introducing the intense THz field, which offers an effective manner to selectively control the electromagnetic property of the metamaterial. This work may bring many potential applications for the tunable EIT-like metamaterial.

Interaction of clumpy dark matter with interstellar medium in astrophysical systems

NASA Astrophysics Data System (ADS)

Baushev, A. N.

2012-02-01

Contemporary cosmological conceptions suggest that the dark matter in haloes of galaxies and galaxy clusters has most likely a clumpy structure. If a stream of gas penetrates through it, a small-scale gravitational field created by the clumps disturbs the flow resulting in momentum exchange between the stream and the dark matter. In this article, we perform an analysis of this effect, based on the hierarchical halo model of the dark matter structure and Navarro-Frenk-White density profiles. We consider the clumps of various masses, from the smallest up to the highest ones M≥ 109 M⊙. It has been found that in any event the effect grows with the mass of the clump: not only the drag force ? acting on the clump but also its acceleration ? increases. We discuss various astrophysical systems. The mechanism proved to be ineffective in the case of galaxy or galaxy cluster collisions. On the other hand, it played an important role during the process of galaxy formation. As a result, the dark matter should have formed a more compact, oblate and faster rotating substructure in the halo of our Galaxy. We have shown that this thick disc should be more clumpy than the halo. This fact is very important for the indirect detection experiments since it is the clumps that give the main contribution to the annihilation signal. Our calculations show that the mechanism of momentum exchange between the dark and baryon matter is ineffective on the outskirts of the galactic halo. It means that the clumps from there were not transported to the thick disc, and this region should be more clumpy than the halo on the average.

Melanopsin Phototransduction Contributes to Light-Evoked Choroidal Expansion and Rod L-Type Calcium Channel Function In Vivo.

PubMed

Berkowitz, Bruce A; Schmidt, Tiffany; Podolsky, Robert H; Roberts, Robin

2016-10-01

In humans, rodents, and pigeons, the dark → light transition signals nonretinal brain tissue to increase choroidal thickness, a major control element of choroidal blood flow, and thus of photoreceptor and retinal pigment epithelium function. However, it is unclear which photopigments in the retina relay the light signal to the brain. Here, we test the hypothesis that melanopsin (Opn4)-regulated phototransduction modulates light-evoked choroidal thickness expansion in mice. Two-month-old C57Bl/6 wild-type (B6), 4- to 5-month-old C57Bl/6/129S6 wild-type (B6 + S6), and 2-month-old melanopsin knockout (Opn4-/-) on a B6 + S6 background were studied. Retinal anatomy was evaluated in vivo by optical coherence tomography and MRI. Choroidal thickness in dark and light were measured by diffusion-weighted MRI. Rod cell L-type calcium channel (LTCC) function in dark and light (manganese-enhanced MRI [MEMRI]) was also measured. Opn4-/- mice did not show the light-evoked expansion of choroidal thickness observed in B6 and B6 + S6 controls. Additionally, Opn4-/- mice had lower than normal rod cell and inner retinal LTCC function in the dark but not in the light. These deficits were not due to structural abnormalities because retinal laminar architecture and thickness, and choroidal thickness in the Opn4-/- mice were similar to controls. First time evidence is provided that melanopsin phototransduction contributes to dark → light control of murine choroidal thickness. The data also highlight a contribution in vivo of melanopsin phototransduction to rod cell and inner retinal depolarization in the dark.

Diel variation of the cellular carbon to nitrogen ratio of Chlorella autotrophica (Chlorophyta) growing in phosphorus- and nitrogen-limited continuous cultures.

PubMed

Ng, Wai Ho Albert; Liu, Hongbin

2015-02-01

We investigated the relationship between daily growth rates and diel variation of carbon (C) metabolism and C to nitrogen (N) ratio under P- and N-limitation in the green algae Chlorella autotrophica. To do this, continuous cultures of C. autotrophica were maintained in a cyclostat culture system under 14:10 light:dark cycle over a series of P- and N-limited growth rates. Cell abundance, together with cell size, as reflected by side scatter signal from flow cytometric analysis demonstrated a synchronized diel pattern with cell division occurring at night. Under either type of nutrient limitation, the cellular C:N ratio increased through the light period and decreased through the dark period over all growth rates, indicating a higher diel variation of C metabolism than that of N. Daily average cellular C:N ratios were higher at lower dilution rates under both types of nutrient limitation but cell enlargement was only observed at lower dilution rates under P-limitation. Carbon specific growth rates during the dark period positively correlated with cellular daily growth rates (dilution rates), with net loss of C during night at the lowest growth rates under N-limitation. Under P-limitation, dark C specific growth rates were close to zero at low dilution rates but also exhibited an increasing trend at high dilution rates. In general, diel variations of cellular C:N were low when dark C specific growth rates were high. This result indicated that the fast growing cells performed dark C assimilation at high rates, hence diminished the uncoupling of C and N metabolism at night. © 2014 Phycological Society of America.

Effects of adsorbed pyridine derivatives and ultrathin atomic-layer-deposited alumina coatings on the conduction band-edge energy of TiO2 and on redox-shuttle-derived dark currents.

PubMed

Katz, Michael J; Vermeer, Michael J D; Farha, Omar K; Pellin, Michael J; Hupp, Joseph T

2013-01-15

Both the adsorption of t-butylpyridine and the atomic-layer deposition of ultrathin conformal coatings of insulators (such as alumina) are known to boost open-circuit photovoltages substantially for dye-sensitized solar cells. One attractive interpretation is that these modifiers significantly shift the conduction-edge energy of the electrode, thereby shifting the onset potential for dark current arising from the interception of injected electrons by solution-phase redox shuttle components such as Co(phenanthroline)(3)(3+) and triiodide. For standard, high-area, nanoporous photoelectrodes, band-edge energies are difficult to measure directly. In contrast, for flat electrodes they are readily accessible from Mott-Schottky analyses of impedance data. Using such electrodes (specifically TiO(2)), we find that neither organic nor inorganic electrode-surface modifiers shift the conduction-band-edge energy sufficiently to account fully for the beneficial effects on electrode behavior (i.e., the suppression of dark current). Additional experiments reveal that the efficacy of ultrathin coatings of Al(2)O(3) arises chiefly from the passivation of redox-catalytic surface states. In contrast, adsorbed t-butylpyridine appears to suppress dark currents mainly by physically blocking access of shuttle molecules to the electrode surface. Studies with other derivatives of pyridine, including sterically and/or electronically diverse derivatives, show that heterocycle adsorption and the concomitant suppression of dark current does not require the coordination of surface Ti(IV) or Al(III) atoms. Notably, the favorable (i.e., negative) shifts in onset potential for the flow of dark current engendered by organic and inorganic surface modifiers are additive. Furthermore, they appear to be largely insensitive to the identity of shuttle molecules.

Effects of light and growth regulators on adventitious bud formation in horseradish (Armoracia rusticana).

PubMed

Kamada, H; Tachikawa, Y; Saitou, T; Harada, H

1995-07-01

To clarify that the presence of Ri T-DNA genes are not prerequisite for the light-induced bud formation in horseradish (Armoracia rusticana) hairy roots, leaf and root segments of nontransformed horseradish plants were used as explants. Bud formation from nontransformed tissues was observed in hormone-free medium under 16 h daylight conditions, but not under continuous darkness. To investigate the effects of growth regulators on bud formation, leaf and root explants were treated with auxin (1-naphthaleneacetic acid; NAA) and / or cytokinin (6-benzyl-aminopurine; BA). The most effective treatment in the dark to stimulate bud formation was BA at 1 mg·1(-1). These results show that adventitious bud formation in horseradish can be induced by light and growth regulators, and especially cytokinin, may be involved in bud formation, irrespective of whether the tissues were transformed with Ri T-DNA.

Soot Precursor Material: Spatial Location via Simultaneous LIF-LII Imaging and Characterization via TEM

NASA Technical Reports Server (NTRS)

VanderWal, Randall L.

1996-01-01

The chemical and physical transformation between gaseous fuel pyrolysis products and solid carbonaceous soot represents a critical step in soot formation. In this paper, simultaneous two-dimensional LIF-LII (laser-induced fluorescence - laser-induced incandescence) images identify the spatial location where the earliest identifiable chemical and physical transformation of material towards solid carbonaceous soot occurs along the axial streamline in a normal diffusion flame. The identification of the individual LIF and LII signals is achieved by examining both the excitation wavelength dependence and characteristic temporal decay of each signal. Spatially precise thermophoretic sampling measurements are guided by the LIF-LII images with characterization of the sampled material accomplished via both bright and dark field TEM. Both bright and dark field TEM measurements support the observed changes in photophysical properties which account for conversion of fluorescence to incandescence as fuel pyrolysis products evolve towards solid carbonaceous soot.

Dark and antidark soliton interactions in the nonlocal nonlinear Schrödinger equation with the self-induced parity-time-symmetric potential.

PubMed

Li, Min; Xu, Tao

2015-03-01

Via the Nth Darboux transformation, a chain of nonsingular localized-wave solutions is derived for a nonlocal nonlinear Schrödinger equation with the self-induced parity-time (PT) -symmetric potential. It is found that the Nth iterated solution in general exhibits a variety of elastic interactions among 2N solitons on a continuous-wave background and each interacting soliton could be the dark or antidark type. The interactions with an arbitrary odd number of solitons can also be obtained under different degenerate conditions. With N=1 and 2, the two-soliton and four-soliton interactions and their various degenerate cases are discussed in the asymptotic analysis. Numerical simulations are performed to support the analytical results, and the stability analysis indicates that the PT-symmetry breaking can also destroy the stability of the soliton interactions.

An engineered CARS substrate with giant field enhancement in crisscross dimer nanostructure.

PubMed

Zhang, Jia; Chen, Shu; Wang, Junqiao; Mu, Kaijun; Fan, Chunzhen; Liang, Erjun; Ding, Pei

2018-01-15

We theoretically investigate the optical properties of a nanostructure consisting of the two identical and symmetrically arranged crisscrosses. A plasmonic Fano resonance is induced by a strong interplay between bright mode and dark modes, where the bright mode is due to electric dipole resonance while dark modes originate from the magnetic dipole induced by LC resonances. In this article, we find that the electric field "hotspots" corresponding to three different wavelengths can be positioned at the same spatial position, and its spectral tunability is achieved by changing geometric parameters. The crisscrosses system can be designed as a plasmonic substrate for enhancing Coherent Anti-Stokes Raman Scattering (CARS) signal. This discovery provides a new method to achieve single molecule detection. At the same time, it also has many important applications for multi-photon imaging and other nonlinear optical processes, such as four-wave mixing and stimulated Raman scattering.

Intrinsic neutron background of nuclear emulsions for directional Dark Matter searches

NASA Astrophysics Data System (ADS)

Alexandrov, A.; Asada, T.; Buonaura, A.; Consiglio, L.; D'Ambrosio, N.; De Lellis, G.; Di Crescenzo, A.; Di Marco, N.; Di Vacri, M. L.; Furuya, S.; Galati, G.; Gentile, V.; Katsuragawa, T.; Laubenstein, M.; Lauria, A.; Loverre, P. F.; Machii, S.; Monacelli, P.; Montesi, M. C.; Naka, T.; Pupilli, F.; Rosa, G.; Sato, O.; Strolin, P.; Tioukov, V.; Umemoto, A.; Yoshimoto, M.

2016-07-01

Recent developments of the nuclear emulsion technology led to the production of films with nanometric silver halide grains suitable to track low energy nuclear recoils with submicrometric length. This improvement opens the way to a directional Dark Matter detection, thus providing an innovative and complementary approach to the on-going WIMP searches. An important background source for these searches is represented by neutron-induced nuclear recoils that can mimic the WIMP signal. In this paper we provide an estimation of the contribution to this background from the intrinsic radioactive contamination of nuclear emulsions. We also report the neutron-induced background as a function of the read-out threshold, by using a GEANT4 simulation of the nuclear emulsion, showing that it amounts to about 0.06 per year per kilogram, fully compatible with the design of a 10 kg × year exposure.

Storage and retrieval of electromagnetic waves with orbital angular momentum via plasmon-induced transparency.

PubMed

Bai, Zhengyang; Xu, Datang; Huang, Guoxiang

2017-01-23

We propose a scheme to realize the storage and retrieval of high-dimensional electromagnetic waves with orbital angular momentum (OAM) via plasmon-induced transparency (PIT) in a metamaterial, which consists of an array of meta-atoms constructed by a metallic structure loaded with two varactors. We show that due to PIT effect the system allows the existence of shape-preserving dark-mode plasmonic polaritons, which are mixture of electromagnetic-wave modes and dark oscillatory modes of the meta-atoms and may carry various OAMs. We demonstrate that the slowdown, storage and retrieval of multi-mode electromagnetic waves with OAMs can be achieved through the active manipulation of a control field. Our work raises the possibility for realizing PIT-based spatial multi-mode memory of electromagnetic waves and is promising for practical application of information processing with large capacity by using room-temperature metamaterials.

High-order corrections on the laser cooling limit in the Lamb-Dicke regime.

PubMed

Yi, Zhen; Gu, Wen-Ju

2017-01-23

We investigate corrections on the cooling limit of high-order Lamb-Dicke (LD) parameters in the double electromagnetically induced transparency (EIT) cooling scheme. Via utilizing quantum interferences, the single-phonon heating mechanism vanishes and the system evolves to a double dark state, from which we will obtain the mechanical occupation on the single-phonon excitation state. In addition, the further correction induced by two-phonon heating transitions is included to achieve a more accurate cooling limit. There exist two pathways of two-phonon heating transitions: direct two-phonon excitation from the dark state and further excitation from the single-phonon excited state. By adding up these two parts of correction, the obtained analytical predictions show a well consistence with numerical results. Moreover, we find that the two pathways can destructively interfere with each other, leading to the elimination of two-phonon heating transitions and achieving a lower cooling limit.

Dark Agouti rat model of chemotherapy-induced mucositis: establishment and current state of the art.

PubMed

Vanhoecke, Barbara; Bateman, Emma; Mayo, Bronwen; Vanlancker, Eline; Stringer, Andrea; Thorpe, Daniel; Keefe, Dorothy

2015-06-01

Mucositis is a major oncological problem. The entire gastrointestinal and genitourinary tract and also other mucosal surfaces can be affected in recipients of radiotherapy, and/or chemotherapy. Major progress has been made in recent years in understanding the mechanisms of oral and small intestinal mucositis, which appears to be more prominent than colonic damage. This progress is largely due to the development of representative laboratory animal models of mucositis. This review focuses on the development and establishment of the Dark Agouti rat mammary adenocarcinoma model by the Mucositis Research Group of the University of Adelaide over the past 20 years to characterize the mechanisms underlying methotrexate-, 5-fluorouracil-, and irinotecan-induced mucositis. It also aims to summarize the results from studies using different animal model systems to identify new molecular and cellular markers of mucositis. © 2015 by the Society for Experimental Biology and Medicine.

Optimal descriptor as a translator of eclectic data into prediction of cytotoxicity for metal oxide nanoparticles under different conditions.

PubMed

Toropova, Alla P; Toropov, Andrey A; Rallo, Robert; Leszczynska, Danuta; Leszczynski, Jerzy

2015-02-01

The Monte Carlo technique has been used to build up quantitative structure-activity relationships (QSARs) for prediction of dark cytotoxicity and photo-induced cytotoxicity of metal oxide nanoparticles to bacteria Escherichia coli (minus logarithm of lethal concentration for 50% bacteria pLC50, LC50 in mol/L). The representation of nanoparticles include (i) in the case of the dark cytotoxicity a simplified molecular input-line entry system (SMILES), and (ii) in the case of photo-induced cytotoxicity a SMILES plus symbol '^'. The predictability of the approach is checked up with six random distributions of available data into the visible training and calibration sets, and invisible validation set. The statistical characteristics of these models are correlation coefficient 0.90-0.94 (training set) and 0.73-0.98 (validation set). Copyright © 2014 Elsevier Inc. All rights reserved.

Flow induced force of labyrinth seal

NASA Technical Reports Server (NTRS)

Iwatsubo, T.; Motooka, N.; Kawai, R.

1982-01-01

Flow induced instability force due to a labyrinth seal is analyzed. An approximate solution is given for the partial differential equation representing the flow in labyrinth seal and it is compared with the finite difference method in order to verify the accuracy of both methods. The effects of difference of inlet and outlet pressures of the seal, deflection of pressure and mass flow from the steady state, rotor diameter, seal clearance, seal interval and seal number on the flow induced force of the seal are investigated and it is known that some of these factors are very influential on the flow induced force.

Bicarbonate trigger for inducing lipid accumulation in algal systems

DOEpatents

Gardner, Robert; Peyton, Brent; Cooksey, Keith E.

2015-08-04

The present invention provides bicarbonate containing and/or bicarbonate-producing compositions and methods to induce lipid accumulation in an algae growth system, wherein the algae growth system is under light-dark cycling condition. By adding said compositions at a specific growth stage, said methods lead to much higher lipid accumulation and/or significantly reduced total time required for accumulating lipid in the algae growth system.

Noxious heat and scratching decrease histamine-induced itch and skin blood flow.

PubMed

Yosipovitch, Gil; Fast, Katharine; Bernhard, Jeffrey D

2005-12-01

The aim of this study was to assess the effect of thermal stimuli or distal scratching on skin blood flow and histamine-induced itch in healthy volunteers. Twenty-one healthy volunteers participated in the study. Baseline measurements of skin blood flow were obtained on the flexor aspect of the forearm. These measurements were compared with skin blood flow after various stimuli: heating the skin, cooling the skin, noxious cold 2 degrees C, noxious heat 49 degrees C, and scratching via a brush with controlled pressure. Afterwards histamine iontophoresis was performed and skin blood flow and itch intensity were measured immediately after the above-mentioned stimuli. Scratching reduced mean histamine-induced skin blood flow and itch intensity. Noxious heat pain increased basal skin blood flow but reduced histamine-induced maximal skin blood flow and itch intensity. Cold pain and cooling reduced itch intensity, but neither affected histamine-induced skin blood flow. Sub-noxious warming the skin did not affect the skin blood flow or itch intensity. These findings suggest that heat pain and scratching may inhibit itch through a neurogenic mechanism that also affects skin blood flow.

Detection of light-induced changes of intracellular ionized calcium concentration in Limulus ventral photoreceptors using arsenazo III

PubMed Central

Brown, J. E.; Brown, P. K.; Pinto, L. H.

1977-01-01

1. The metallochromic indicator dye, arsenazo III, was injected intracellularly into Limulus ventral photoreceptor cells to concentrations greater than 1 mM. 2. The absorption spectrum (450-750 nm) of the dye in single dark-adapted cells was measured by a scanning microspectrophotometer. When a cell was light-adapted, the absorption of the dye changed; the difference spectrum had two maxima at about 610 and 660 nm, a broad minimum at about 540 nm and an isosbestic point at about 585 nm. 3. When intracellular calcium concentration was raised in dark-adapted cells previously injected with arsenazo III, the difference spectum had two maxima at about 610 and 660 nm, a broad minimum at about 530 nm and an isosbestic point at about 585 nm. The injection of Mg2+ into dark-adapted cells previously injected with the dye induced a difference spectrum that had a single maximum at about 620 nm. Also, decreasing the intracellular pH of cells previously injected with the dye induced a difference spectrum that had a minimum at about 620 nm. The evidence suggests that there is a rise of intracellular ionized calcium when a Limulus ventral photoreceptor is light-adapted. 4. The intracellular calcium concentration, [Ca2+]1, in light-adapted photoreceptors was estimated to reach at least 10-4 M by compaing the light-induced difference spectra measured in ventral photoreceptors with a standard curve determined in microcuvettes containing 2mM arsenazo III in 400 mM-KCl, 1 mM-MgCl2 and 25 mM MOPS at pH 7·0. 5. In cells injected to less than 3 mM arsenazo III, light induced a transient decrease in optical transmission at 660 nm (T660). This decrease in T660 indicates that illumination of a ventral photoreceptor normally causes a transient increase of [Ca2+]1. 6. Arsenazo III was found to be sensitive, selective and rapid enough to measure light-induced changes of intracellular ionized calcium in Limulus ventral photoreceptor cells. PMID:17732

A Micromegas-based Directional Dark Matter Detector for Use with Negative Ion Gases

NASA Astrophysics Data System (ADS)

Nicoloff, Catherine; Battat, James

2017-01-01

Directional dark matter detectors seek to measure the direction of WIMP-induced nuclear recoils. The angular distribution of these recoils provides a unique signature that is not mimicked by any known background population. Low-pressure gas time projection chambers (TPCs) have a long and successful history in directional dark matter searches. The benefit of the low-pressure gas target is that nuclear recoils from dark matter extend long enough to be reliably reconstructed. For the last decade, the DRIFT collaboration has employed a MWPC-based negative-ion TPC for directional dark matter detection. DRIFT recently published the leading limit from a directional detector on the spin-dependent WIMP-proton interaction (1.1 pb at a WIMP mass of 100 GeV/c2) . Although the effective spatial granularity along the drift direction is 60 um, the MWPC wire spacing of 2 mm limits DRIFT's track reconstruction. DRIFT is now exploring TPC readouts that offer higher spatial resolution. Here, we report on one such effort that uses a Micromegas for gas amplification with orthogonal strips for charge signal readout. The detector can be used with both electron drift and negative ion gases. We will describe the detector design and present preliminary commissioning data taken in a surface laboratory. Research Corporation, NSF, and MA Space Grant.

Dark matter vs. neutrinos: the effect of astrophysical uncertainties and timing information on the neutrino floor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Jonathan H., E-mail: jonathan.h.m.davis@gmail.com

2015-03-01

Future multi-tonne Direct Detection experiments will be sensitive to solar neutrino induced nuclear recoils which form an irreducible background to light Dark Matter searches. Indeed for masses around 6 GeV the spectra of neutrinos and Dark Matter are so similar that experiments are said to run into a neutrino floor, for which sensitivity increases only marginally with exposure past a certain cross section. In this work we show that this floor can be overcome using the different annual modulation expected from solar neutrinos and Dark Matter. Specifically for cross sections below the neutrino floor the DM signal is observable throughmore » a phase shift and a smaller amplitude for the time-dependent event rate. This allows the exclusion power to be improved by up to an order of magnitude for large exposures. In addition we demonstrate that, using only spectral information, the neutrino floor exists over a wider mass range than has been previously shown, since the large uncertainties in the Dark Matter velocity distribution make the signal spectrum harder to distinguish from the neutrino background. However for most velocity distributions it can still be surpassed using timing information, and so the neutrino floor is not an absolute limit on the sensitivity of Direct Detection experiments.« less

Dark matter vs. neutrinos: the effect of astrophysical uncertainties and timing information on the neutrino floor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Jonathan H.

2015-03-09

Future multi-tonne Direct Detection experiments will be sensitive to solar neutrino induced nuclear recoils which form an irreducible background to light Dark Matter searches. Indeed for masses around 6 GeV the spectra of neutrinos and Dark Matter are so similar that experiments are said to run into a neutrino floor, for which sensitivity increases only marginally with exposure past a certain cross section. In this work we show that this floor can be overcome using the different annual modulation expected from solar neutrinos and Dark Matter. Specifically for cross sections below the neutrino floor the DM signal is observable throughmore » a phase shift and a smaller amplitude for the time-dependent event rate. This allows the exclusion power to be improved by up to an order of magnitude for large exposures. In addition we demonstrate that, using only spectral information, the neutrino floor exists over a wider mass range than has been previously shown, since the large uncertainties in the Dark Matter velocity distribution make the signal spectrum harder to distinguish from the neutrino background. However for most velocity distributions it can still be surpassed using timing information, and so the neutrino floor is not an absolute limit on the sensitivity of Direct Detection experiments.« less

Evidence that Ribulose 1,5-Bisphosphate (RuBP) Binds to Inactive Sites of RuBP Carboxylase in Vivo and an Estimate of the Rate Constant for Dissociation 1

PubMed Central

Cardon, Zoe G.; Mott, Keith A.

1989-01-01

The binding of ribulose 1,5-bisphosphate (RuBP) to inactive (noncarbamylated) sites of the enzyme RuBP carboxylase in vivo was investigated in Spinacia oleracea and Helianthus annuus. The concentrations of RuBP and inactive sites were determined in leaf tissue as a function of time after a change to darkness. RuBP concentrations fell rapidly after the change to darkness and were approximately equal to the concentration of inactive sites after 60 s. Variations in the concentration of inactive sites, which were induced by differences in the light intensity before the light-dark transition, correlated with the concentration of RuBP between 60 and 120 s after the change to darkness. These data are discussed as evidence that RuBP binds to inactive sites of RuBP carboxylase in vivo. After the concentration of RuBP fell below that of inactive sites (at times longer than 60 s of darkness), the decline in RuBP was logarithmic with time. This would be expected if the dissociation of RuBP from inactive sites controlled the decline in RuBP concentration. These data were used to estimate the rate constant for dissociation of RuBP from inactive sites in vivo. PMID:16666692

Comparison of Measured Dark Current Distributions with Calculated Damage Energy Distributions in HgCdTe

NASA Technical Reports Server (NTRS)

Marshall, C. J.; Marshall, P. W.; Howe, C. L.; Reed, R. A.; Weller, R. A.; Mendenhall, M.; Waczynski, A.; Ladbury, R.; Jordan, T. M.

2007-01-01

This paper presents a combined Monte Carlo and analytic approach to the calculation of the pixel-to-pixel distribution of proton-induced damage in a HgCdTe sensor array and compares the results to measured dark current distributions after damage by 63 MeV protons. The moments of the Coulombic, nuclear elastic and nuclear inelastic damage distributions were extracted from Monte Carlo simulations and combined to form a damage distribution using the analytic techniques first described in [1]. The calculations show that the high energy recoils from the nuclear inelastic reactions (calculated using the Monte Carlo code MCNPX [2]) produce a pronounced skewing of the damage energy distribution. While the nuclear elastic component (also calculated using the MCNPX) contributes only a small fraction of the total nonionizing damage energy, its inclusion in the shape of the damage across the array is significant. The Coulombic contribution was calculated using MRED [3-5], a Geant4 [4,6] application. The comparison with the dark current distribution strongly suggests that mechanisms which are not linearly correlated with nonionizing damage produced according to collision kinematics are responsible for the observed dark current increases. This has important implications for the process of predicting the on-orbit dark current response of the HgCdTe sensor array.

Structure of the apoptosome: mechanistic insights into activation of an initiator caspase from Drosophila

PubMed Central

Pang, Yuxuan; Bai, Xiao-chen; Yan, Chuangye; Hao, Qi; Chen, Zheqin; Wang, Jia-Wei

2015-01-01

Apoptosis is executed by a cascade of caspase activation. The autocatalytic activation of an initiator caspase, exemplified by caspase-9 in mammals or its ortholog, Dronc, in fruit flies, is facilitated by a multimeric adaptor complex known as the apoptosome. The underlying mechanism by which caspase-9 or Dronc is activated by the apoptosome remains unknown. Here we report the electron cryomicroscopic (cryo-EM) structure of the intact apoptosome from Drosophila melanogaster at 4.0 Å resolution. Analysis of the Drosophila apoptosome, which comprises 16 molecules of the Dark protein (Apaf-1 ortholog), reveals molecular determinants that support the assembly of the 2.5-MDa complex. In the absence of dATP or ATP, Dronc zymogen potently induces formation of the Dark apoptosome, within which Dronc is efficiently activated. At 4.1 Å resolution, the cryo-EM structure of the Dark apoptosome bound to the caspase recruitment domain (CARD) of Dronc (Dronc-CARD) reveals two stacked rings of Dronc-CARD that are sandwiched between two octameric rings of the Dark protein. The specific interactions between Dronc-CARD and both the CARD and the WD40 repeats of a nearby Dark protomer are indispensable for Dronc activation. These findings reveal important mechanistic insights into the activation of initiator caspase by the apoptosome. PMID:25644603

Lensing of Fast Radio Bursts as a Probe of Compact Dark Matter.

PubMed

Muñoz, Julian B; Kovetz, Ely D; Dai, Liang; Kamionkowski, Marc

2016-08-26

The possibility that part of the dark matter is made of massive compact halo objects (MACHOs) remains poorly constrained over a wide range of masses, and especially in the 20-100  M_{⊙} window. We show that strong gravitational lensing of extragalactic fast radio bursts (FRBs) by MACHOs of masses larger than ∼20  M_{⊙} would result in repeated FRBs with an observable time delay. Strong lensing of a FRB by a lens of mass M_{L} induces two images, separated by a typical time delay ∼few×(M_{L}/30  M_{⊙})  msec. Considering the expected FRB detection rate by upcoming experiments, such as canadian hydrogen intensity mapping experiment (CHIME), of 10^{4} FRBs per year, we should observe from tens to hundreds of repeated bursts yearly, if MACHOs in this window make up all the dark matter. A null search for echoes with just 10^{4} FRBs would constrain the fraction f_{DM} of dark matter in MACHOs to f_{DM}≲0.08 for M_{L}≳20  M_{⊙}.

Rotary blood pump

NASA Technical Reports Server (NTRS)

Benkowski, Robert J. (Inventor); Kiris, Cetin (Inventor); Kwak, Dochan (Inventor); Rosenbaum, Bernard J. (Inventor); Bacak, James W. (Inventor); DeBakey, Michael E. (Inventor)

1999-01-01

A blood pump that comprises a pump housing having a blood flow path therethrough, a blood inlet, and a blood outlet; a stator mounted to the pump housing, the stator having a stator field winding for producing a stator magnetic field; a flow straightener located within the pump housing, and comprising a flow straightener hub and at least one flow straightener blade attached to the flow straightener hub; a rotor mounted within the pump housing for rotation in response to the stator magnetic field, the rotor comprising an inducer and an impeller; the inducer being located downstream of the flow straightener, and comprising an inducer hub and at least one inducer blade attached to the inducer hub; the impeller being located downstream of the inducer, and comprising an impeller hub and at least one impeller blade attached to the impeller hub; and preferably also comprising a diffuser downstream of the impeller, the diffuser comprising a diffuser hub and at least one diffuser blade. Blood flow stagnation and clot formation within the pump are minimized by, among other things, providing the inducer hub with a diameter greater than the diameter of the flow straightener hub; by optimizing the axial spacing between the flow straightener hub and the inducer hub, and between the impeller hub and the diffuser hub; by optimizing the inlet angle of the diffuser blades; and by providing fillets or curved transitions between the upstream end of the inducer hub and the shaft mounted therein, and between the impeller hub and the shaft mounted therein.

Electromagnetic near-field coupling induced polarization conversion and asymmetric transmission in plasmonic metasurfaces

NASA Astrophysics Data System (ADS)

Peng, Yu-Xiang; Wang, Kai-Jun; He, Meng-Dong; Luo, Jian-Hua; Zhang, Xin-Min; Li, Jian-Bo; Tan, Shi-Hua; Liu, Jian-Qiang; Hu, Wei-Da; Chen, Xiaoshuang

2018-04-01

In this paper, we demonstrate the effect of polarization conversion in a plasmonic metasurface structure, in which each unit cell consists of a metal bar and four metal split-ring resonators (SRRs). Such effect is attributed to the fact that the dark plasmon mode of SRRs (bar), which radiates cross-polarized component, is induced by the bright plasmon mode of bar (SRRs) due to the electromagnetic near-field coupling between bar and SRRs. We find that there are two ways to achieve a large cross-polarized component in our proposed metasurface structure. The first way is realized when the dark plasmon mode of bar (SRRs) is in resonance, while at this time the bright plasmon mode of SRRs (bar) is not at resonant state. The second way is realized when the bright plasmon mode of SRRs (bar) is resonantly excited, while the dark plasmon mode of bar (SRRs) is at nonresonant state. It is also found that the linearly polarized light can be rotated by 56.50 after propagation through the metasurface structure. Furthermore, our proposed metasurface structure exhibits an asymmetric transmission for circularly polarized light. Our findings take a further step in developing integrated metasurface-based photonics devices for polarization manipulation and modulation.

Daily regulation of body temperature rhythm in the camel (Camelus dromedarius) exposed to experimental desert conditions

PubMed Central

Bouâouda, Hanan; Achâaban, Mohamed R.; Ouassat, Mohammed; Oukassou, Mohammed; Piro, Mohamed; Challet, Etienne; El Allali, Khalid; Pévet, Paul

2014-01-01

Abstract In the present work, we have studied daily rhythmicity of body temperature (Tb) in Arabian camels challenged with daily heat, combined or not with dehydration. We confirm that Arabian camels use heterothermy to reduce heat gain coupled with evaporative heat loss during the day. Here, we also demonstrate that this mechanism is more complex than previously reported, because it is characterized by a daily alternation (probably of circadian origin) of two periods of poikilothermy and homeothermy. We also show that dehydration induced a decrease in food intake plays a role in this process. Together, these findings highlight that adaptive heterothermy in the Arabian camel varies across the diurnal light–dark cycle and is modulated by timing of daily heat and degrees of water restriction and associated reduction of food intake. The changed phase relationship between the light–dark cycle and the Tb rhythm observed during the dehydration process points to a possible mechanism of internal desynchronization during the process of adaptation to desert environment. During these experimental conditions mimicking the desert environment, it will be possible in the future to determine if induced high‐amplitude ambient temperature (Ta) rhythms are able to compete with the zeitgeber effect of the light–dark cycle. PMID:25263204

Effects of high flavanol dark chocolate on cardiovascular function and platelet aggregation.

PubMed

Rull, Gurvinder; Mohd-Zain, Zetty N; Shiel, Julian; Lundberg, Martina H; Collier, David J; Johnston, Atholl; Warner, Timothy D; Corder, Roger

2015-08-01

Regular consumption of chocolate and cocoa products has been linked to reduced cardiovascular mortality. This study compared the effects of high flavanol dark chocolate (HFDC; 1064mg flavanols/day for 6weeks) and low flavanol dark chocolate (LFDC; 88mg flavanols/day for 6weeks) on blood pressure, heart rate, vascular function and platelet aggregation in men with pre-hypertension or mild hypertension. Vascular function was assessed by pulse wave analysis using radial artery applanation tonometry in combination with inhaled salbutamol (0.4mg) to assess changes due to endothelium-dependent vasodilatation. HFDC did not significantly reduce blood pressure compared to baseline or LFDC. Heart rate was increased by LFDC compared to baseline, but not by HFDC. Vascular responses to salbutamol tended to be greater after HFDC. Platelet aggregation induced by collagen or the thromboxane analogue U46619 was unchanged after LFDC or HFDC, whereas both chocolates reduced responses to ADP and the thrombin receptor activator peptide, SFLLRNamide (TRAP6), relative to baseline. Pre-incubation of platelets with theobromine also attenuated platelet aggregation induced by ADP or TRAP6. We conclude that consumption of HFDC confers modest improvements in cardiovascular function. Platelet aggregation is modulated by a flavanol-independent mechanism that is likely due to theobromine. Copyright © 2015 Elsevier Inc. All rights reserved.

Model-based Confirmation of Alternative Substrates of Mitochondrial Electron Transport Chain

PubMed Central

Kleessen, Sabrina; Araújo, Wagner L.; Fernie, Alisdair R.; Nikoloski, Zoran

2012-01-01

Discrimination of metabolic models based on high throughput metabolomics data, reflecting various internal and external perturbations, is essential for identifying the components that contribute to the emerging behavior of metabolic processes. Here, we investigate 12 different models of the mitochondrial electron transport chain (ETC) in Arabidopsis thaliana during dark-induced senescence in order to elucidate the alternative substrates to this metabolic pathway. Our findings demonstrate that the coupling of the proposed computational approach, based on dynamic flux balance analysis, with time-resolved metabolomics data results in model-based confirmations of the hypotheses that, during dark-induced senescence in Arabidopsis, (i) under conditions where the main substrate for the ETC are not fully available, isovaleryl-CoA dehydrogenase and 2-hydroxyglutarate dehydrogenase are able to donate electrons to the ETC, (ii) phytanoyl-CoA does not act even as an indirect substrate of the electron transfer flavoprotein/electron-transfer flavoprotein:ubiquinone oxidoreductase complex, and (iii) the mitochondrial γ-aminobutyric acid transporter has functional significance in maintaining mitochondrial metabolism. Our study provides a basic framework for future in silico studies of alternative pathways in mitochondrial metabolism under extended darkness whereby the role of its components can be computationally discriminated based on available molecular profile data. PMID:22334689

Fluoxetine and WAY 100,635 dissociate increases in scototaxis and analgesia induced by conspecific alarm substance in zebrafish (Danio rerio Hamilton 1822).

PubMed

Maximino, Caio; Lima, Monica Gomes; Costa, Carina Cardoso; Guedes, Iêda Maria Louzada; Herculano, Anderson Manoel

2014-09-01

Alarm reactions to a substance secreted by the damaged skin of conspecifics and closely-related species are increasingly being recognized as fear-like responses in fish. The neurochemical underpinnings of these effects are so far unknown; however, given the role of the serotonergic system on defensive behavior, it is possible that the alarm reaction is mediated by this monoamine. Exposure to conspecific alarm substance (CAS) increased anxiety-like behavior in the light/dark test in zebrafish and decreased nocifensive behavior. These effects were accompanied by increases in blood glucose, hemoglobin, epinephrine and norepinephrine levels, as well as extracellular levels of serotonin in the brain. Pretreatment with fluoxetine blocked the anxiogenic effects of CAS on the light/dark test as well as all physiological parameters and the increase in extracellular brain 5-HT, but not the reduction in nocifensive behavior. Conversely, pretreatment with the 5-HT1AR antagonist WAY 100635 blocked the effects on nocifensive behavior, but not the effects on anxiety-like behavior nor on physiological parameters. These results point to an important and complex role of the serotonergic system in the mediation of fear-potentiated behavior in the light/dark test and in fear-induced analgesia in zebrafish. Copyright © 2014 Elsevier Inc. All rights reserved.

Dark chocolate acutely improves walking autonomy in patients with peripheral artery disease.

PubMed

Loffredo, Lorenzo; Perri, Ludovica; Catasca, Elisa; Pignatelli, Pasquale; Brancorsini, Monica; Nocella, Cristina; De Falco, Elena; Bartimoccia, Simona; Frati, Giacomo; Carnevale, Roberto; Violi, Francesco

2014-07-02

NOX-2, the catalytic subunit of NADPH oxidase, has a key role in the formation of reactive oxidant species and is implicated in impairing flow-mediated dilation (FMD). Dark chocolate exerts artery dilatation via down-regulating NOX2-mediated oxidative stress. The aim of this study was to investigate whether dark chocolate improves walking autonomy in peripheral artery disease (PAD) patients via an oxidative stress-mediated mechanism. FMD, serum levels of isoprostanes, nitrite/nitrate (NOx) and sNOX2-dp, a marker of blood NOX2 activity, maximal walking distance (MWD) and maximal walking time (MWT) were studied in 20 PAD patients (14 males and 6 females, mean age: 69±9 years) randomly allocated to 40 g of dark chocolate (>85% cocoa) or 40 g of milk chocolate (≤35% cocoa) in a single blind, cross-over design. The above variables were assessed at baseline and 2 hours after chocolate ingestion. Dark chocolate intake significantly increased MWD (+11%; P<0.001), MWT (+15%; P<0.001), serum NOx (+57%; P<0.001) and decreased serum isoprostanes (-23%; P=0.01) and sNOX2-dp (-37%; P<0.001); no changes of the above variables were observed after milk chocolate intake. Serum epicatechin and its methylated metabolite significantly increased only after dark chocolate ingestion. Multiple linear regression analysis showed that Δ of MWD was independently associated with Δ of MWT (P<0.001) and Δ of NOx (P=0.018). In vitro study demonstrated that HUVEC incubated with a mixture of polyphenols significantly increased nitric oxide (P<0.001) and decreased E-selectin (P<0.001) and VCAM1 (P<0.001). In PAD patients dark but not milk chocolate acutely improves walking autonomy with a mechanism possibly related to an oxidative stress-mediated mechanism involving NOX2 regulation. http://www.clinicaltrials.gov. Unique identifier: NCT01947712. © 2014 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Dust Mantle Near Pavonis Mons

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-356, 10 May 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a thick mantle of dust covering lava flows north of Pavonis Mons so well that the flows are no longer visible. Flows are known to occur here because of the proximity to the volcano, and such flows normally have a very rugged surface. Fine dust, however, has settled out of the atmosphere over time and obscured the flows from view. The cliff at the top of the image faces north (up), the cliff in the middle of the image faces south (down), and the rugged slope at the bottom of the image faces north (up). The dark streak at the center-left was probably caused by an avalanche of dust sometime in the past few decades. The image is located near 4.1oN, 111.3oW. Sunlight illuminates the scene from the right/lower right.

Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation

NASA Astrophysics Data System (ADS)

Bourke, Michael F.; Marriott, Philip J.; Glud, Ronnie N.; Hasler-Sheetal, Harald; Kamalanathan, Manoj; Beardall, John; Greening, Chris; Cook, Perran L. M.

2017-01-01

Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to bacteria and archaea. Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H2 production rates, suggesting the presence of fermentation. The production of both dissolved inorganic carbon and H2 persisted following administration of broad spectrum bactericidal antibiotics, but ceased following treatment with metronidazole. Metronidazole inhibits the ferredoxin/hydrogenase pathway of fermentative eukaryotic H2 production, suggesting that pathway as the source of H2 and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae. Cell counts revealed a predominance of microalgae in the sediments. H2 production was observed in dark anoxic cultures of diatoms (Fragilariopsis sp.) and a chlorophyte (Pyramimonas) isolated from the study site, substantiating the hypothesis that microalgae undertake fermentation. We conclude that microalgal dark fermentation could be an important energy-conserving pathway in permeable sediments.