Sample records for biodegradation response variability

  1. Immunological Response to Biodegradable Magnesium Implants

    Pichler, Karin; Fischerauer, Stefan; Ferlic, Peter; Martinelli, Elisabeth; Brezinsek, Hans-Peter; Uggowitzer, Peter J.; Löffler, Jörg F.; Weinberg, Annelie-Martina


    The use of biodegradable magnesium implants in pediatric trauma surgery would render surgical interventions for implant removal after tissue healing unnecessary, thereby preventing stress to the children and reducing therapy costs. In this study, we report on the immunological response to biodegradable magnesium implants—as an important aspect in evaluating biocompatibility—tested in a growing rat model. The focus of this study was to investigate the response of the innate immune system to either fast or slow degrading magnesium pins, which were implanted into the femoral bones of 5-week-old rats. The main alloying element of the fast-degrading alloy (ZX50) was Zn, while it was Y in the slow-degrading implant (WZ21). Our results demonstrate that degrading magnesium implants beneficially influence the immune system, especially in the first postoperative weeks but also during tissue healing and early bone remodeling. However, rodents with WZ21 pins showed a slightly decreased phagocytic ability during bone remodeling when the degradation rate reached its maximum. This may be due to the high release rate of the rare earth-element yttrium, which is potentially toxic. From our results we conclude that magnesium implants have a beneficial effect on the innate immune system but that there are some concerns regarding the use of yttrium-alloyed magnesium implants, especially in pediatric patients.

  2. Effect of Ethanol and Methyl-tert-Butyl Ether on Monoaromatic Hydrocarbon Biodegradation: Response Variability for Different Aquifer Materials Under Various Electron-Accepting Conditions

    Ruiz-Aguilar, G L; Fernandez-Sanchez, J M; Kane, S R; Kim, D; Alvarez, P J


    Aquifer microcosms were used to determine how ethanol and methyl-tert-butyl ether (MtBE) affect monoaromatic hydrocarbon degradation under different electron-accepting conditions commonly found in contaminated sites experiencing natural attenuation. Response variability was investigated by using aquifer material from four sites with different exposure history. The lag phase prior to BTEX (benzene, toluene, ethylbenzene, and xylenes) and ethanol degradation was typically shorter in microcosms with previously contaminated aquifer material, although previous exposure did not always result in high degradation activity. Toluene was degraded in all aquifer materials and generally under a broader range of electron-accepting conditions compared to benzene, which was degraded only under aerobic conditions. MtBE was not degraded within 100 days under any condition, and it did not affect BTEX or ethanol degradation patterns. Ethanol was often degraded before BTEX compounds, and had a variable effect on BTEX degradation as a function of electron-accepting conditions and aquifer material source. An occasional enhancement of toluene degradation by ethanol occurred in denitrifying microcosms with unlimited nitrate; this may be attributable to the fortuitous growth of toluene-degrading bacteria during ethanol degradation. Nevertheless, experiments with flow-through aquifer columns showed that this beneficial effect could be eclipsed by an ethanol-driven depletion of electron acceptors, which significantly inhibited BTEX degradation and is probably the most important mechanism by which ethanol could hinder BTEX natural attenuation. A decrease in natural attenuation could increase the likelihood that BTEX compounds reach a receptor as well as the potential duration of exposure.

  3. Biodegradation of free cyanide and subsequent utilisation of biodegradation by-products by Bacillus consortia: optimisation using response surface methodology.

    Mekuto, Lukhanyo; Ntwampe, Seteno Karabo Obed; Jackson, Vanessa Angela


    A mesophilic alkali-tolerant bacterial consortium belonging to the Bacillus genus was evaluated for its ability to biodegrade high free cyanide (CN(-)) concentration (up to 500 mg CN(-)/L), subsequent to the oxidation of the formed ammonium and nitrates in a continuous bioreactor system solely supplemented with whey waste. Furthermore, an optimisation study for successful cyanide biodegradation by this consortium was evaluated in batch bioreactors (BBs) using response surface methodology (RSM). The input variables, that is, pH, temperature and whey-waste concentration, were optimised using a numerical optimisation technique where the optimum conditions were found to be as follows: pH 9.88, temperature 33.60 °C and whey-waste concentration of 14.27 g/L, under which 206.53 mg CN(-)/L in 96 h can be biodegraded by the microbial species from an initial cyanide concentration of 500 mg CN(-)/L. Furthermore, using the optimised data, cyanide biodegradation in a continuous mode was evaluated in a dual-stage packed-bed bioreactor (PBB) connected in series to a pneumatic bioreactor system (PBS) used for simultaneous nitrification, including aerobic denitrification. The whey-supported Bacillus sp. culture was not inhibited by the free cyanide concentration of up to 500 mg CN(-)/L, with an overall degradation efficiency of ≥ 99 % with subsequent nitrification and aerobic denitrification of the formed ammonium and nitrates over a period of 80 days. This is the first study to report free cyanide biodegradation at concentrations of up to 500 mg CN(-)/L in a continuous system using whey waste as a microbial feedstock. The results showed that the process has the potential for the bioremediation of cyanide-containing wastewaters. PMID:25721526

  4. Process and formulation variables in the preparation of injectable and biodegradable magnetic microspheres

    Zhao, Hong; Gagnon, Jeffrey; Häfeli, Urs O


    The aim of this study was to prepare biodegradable sustained release magnetite microspheres sized between 1 to 2 μm. The microspheres with or without magnetic materials were prepared by a W/O/W double emulsion solvent evaporation technique using poly(lactide-co-glycolide) (PLGA) as the biodegradable matrix forming polymer. Effects of manufacturing and formulation variables on particle size were investigated with non-magnetic microspheres. Microsphere size could be controlled by modification o...

  5. Spectral induced polarization (SIP) response of biodegraded oil in porous media

    Abdel Aal, Gamal Z.; Atekwana, Estella A.


    Laboratory experiments were conducted to investigate the effect of different oil saturation (0.2-0.8), wetting conditions (water-wet and oil-wet), and the addition of asphaltene on the spectral induced polarization (SIP) response of biodegraded and fresh crude oil in sand columns. In the water-wet case, no significant differences were observed for both the fresh and biodegraded oil and both displayed an increase in the magnitude of the phase (ϕ) and decrease in the magnitudes of the real (σ') and imaginary (σ'') conductivity components with increasing oil saturation. In this instance the SIP response is most likely controlled by the conduction and polarization of the electric double layer at the mineral-water interface. However, when oil is the wetting phase there were considerable differences in the magnitude of the SIP parameters between the fresh and biodegraded oil. The magnitude of ϕ and σ'' increased with increasing oil saturation, whereas σ' decreased. The magnitude of σ' and σ'' for the biodegraded oil-wetted sands were relatively higher compared to fresh oil-wetted sands. In experiments with fresh and biodegraded oil-wet sand, the addition of 1 per cent asphaltene increased σ' and σ'' with the biodegraded oil showing the highest magnitude. Asphaltenes are the most dipolar fraction of crude oil and increase in concentration with increasing biodegradation. Asphaltene creates a surface charge due to the ionization and complexation reactions of functional groups at interfaces. Therefore, the enhancement in the conduction and polarization observed with the biodegraded oil-wetted sands may be due to the increase in polar components (e.g. asphaltene) from the biodegradation process and the interactions of the polar components with the surfaces of water and mineral grains. Further studies are required to investigate the effect of other components in biodegraded oil such as resins, trace metals, biogenic metallic minerals (e.g. magnetite) and organic

  6. Response surface analysis to improve dispersed crude oil biodegradation

    Zahed, Mohammad A.; Aziz, Hamidi A.; Mohajeri, Leila [School of Civil Engineering, Universiti Sains Malaysia, Nibong Tebal, Penang (Malaysia); Isa, Mohamed H. [Civil Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak (Malaysia)


    In this research, the bioremediation of dispersed crude oil, based on the amount of nitrogen and phosphorus supplementation in the closed system, was optimized by the application of response surface methodology and central composite design. Correlation analysis of the mathematical-regression model demonstrated that a quadratic polynomial model could be used to optimize the hydrocarbon bioremediation (R{sup 2} = 0.9256). Statistical significance was checked by analysis of variance and residual analysis. Natural attenuation was removed by 22.1% of crude oil in 28 days. The highest removal on un-optimized condition of 68.1% were observed by using nitrogen of 20.00 mg/L and phosphorus of 2.00 mg/L in 28 days while optimization process exhibited a crude oil removal of 69.5% via nitrogen of 16.05 mg/L and phosphorus 1.34 mg/L in 27 days therefore optimization can improve biodegradation in shorter time with less nutrient consumption. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Surface characterization and cytotoxicity response of biodegradable magnesium alloys

    Magnesium alloys have raised an immense amount of interest to many researchers because of their evolution as a new kind of third generation materials. Due to their biocompatibility, density, and mechanical properties, magnesium alloys are frequently reported as prospective biodegradable implant materials. Moreover, magnesium alloys experience a natural phenomenon to biodegrade in aqueous solutions due to its corrosion activity, which is excellent for orthopedic and cardiovascular applications. However, a major concern with such alloys is fast and non-uniform corrosion degradation. Controlling the degradation rate in the physiological environment determines the success of biodegradable implants. In this investigation, three different grades of magnesium alloys: AZ31B, AZ91E and ZK60A were studied for their corrosion resistance and biocompatibility. Scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy and contact angle meter are used to study surface morphology, chemistry, roughness and wettability, respectively. Additionally, the cytotoxicity of the leached metal ions was evaluated by using a tetrazolium based bio-assay, MTS. - Highlights: • Micro-textured features formed after the anodization of magnesium alloys. • Contact angle increased and surface free energy decreased by anodization. • Corrosion rate increased for anodized surfaces compared to untreated samples. • Cell viability was greater than 75% implying the cytocompatibility of Mg alloys

  8. A phenomenological constitutive model for the nonlinear viscoelastic responses of biodegradable polymers

    Khan, Kamran


    We formulate a constitutive framework for biodegradable polymers that accounts for nonlinear viscous behavior under regimes with large deformation. The generalized Maxwell model is used to represent the degraded viscoelastic response of a polymer. The large-deformation, time-dependent behavior of viscoelastic solids is described using an Ogden-type hyperviscoelastic model. A deformation-induced degradation mechanism is assumed in which a scalar field depicts the local state of the degradation, which is responsible for the changes in the material\\'s properties. The degradation process introduces another timescale (the intrinsic material clock) and an entropy production mechanism. Examples of the degradation of a polymer under various loading conditions, including creep, relaxation and cyclic loading, are presented. Results from parametric studies to determine the effects of various parameters on the process of degradation are reported. Finally, degradation of an annular cylinder subjected to pressure is also presented to mimic the effects of viscoelastic arterial walls (the outer cylinder) on the degradation response of a biodegradable stent (the inner cylinder). A general contact analysis is performed. As the stiffness of the biodegradable stent decreases, stress reduction in the stented viscoelastic arterial wall is observed. The integration of the proposed constitutive model with finite element software could help a designer to predict the time-dependent response of a biodegradable stent exhibiting finite deformation and under complex mechanical loading conditions. © 2012 Springer-Verlag Wien.

  9. Biodegradable Poly(ester urethane)urea Elastomers with Variable Amino Content for Subsequent Functionalization with Phosphorylcholine

    Fang, Jun; Ye, Sang-Ho; Shankarraman, Venkat; Huang, Yixian; Mo, Xiumei; Wagner, William R.


    While surface modification is well suited for imparting biomaterials with specific functionality for favorable cell interactions, the modification of degradable polymers would be expected to provide only temporary benefit. Bulk modification by incorporating pendant reactive groups for subsequent functionalization of biodegradable polymers would provide a more enduring approach. Towards this end, a series of biodegradable poly(ester urethane)urea elastomers with variable amino content (PEUU-NH2 polymers) were developed. Carboxylated phosphorycholine was synthesized and conjugated to the PEUU-NH2 polymers for subsequent bulk functionalization to generate PEUU-PC polymers. Synthesis was verified by 1H NMR, X-ray photoelectron spectroscopy and ATR-FTIR. The impact of amine incorporation and phosphorylcholine conjugation was shown on mechanical, thermal and degradation properties. Water absorption increased with increasing amine content, and further with PC conjugation. In wet conditions, tensile strength and initial modulus generally decreased with increasing hydrophilicity, but remained in the range of 5–30 MPa and 10–20 MPa respectively. PC conjugation was associated with significantly reduced platelet adhesion in blood contact testing and the inhibition of rat vascular smooth muscle cell proliferation. These biodegradable PEUU-PC elastomers offer attractive properties for applications as non-thrombogenic, biodegradable coatings and for blood-contacting scaffold applications. Further, the PEUU-NH2 base polymers offer the potential to have multiple types of biofunctional groups conjugated onto the backbone to address a variety of design objectives. PMID:25132273

  10. Response and potential influence of Spartina alterniflora in the biodegradation of fuel oil

    A study was conducted to determine the tolerance of Spartina alterniflora to sediments contaminated with weathered No. 2 fuel oil and the possible impact of its growth on the rates of oil biodegradation. Pollutants can be converted via a plant's own metabolic activity, or by stimulation of microbial activity in the rhizosphere. In order for phytoremediation to be effective, plants must be able to tolerate the contaminant of concern. In this dose response experiment, a relationship of decreased plant growth with increased No. 2 fuel oil concentration was observed. Experimental concentration ranged from 2 to 137 g oil/kg of sediment. Oiling resulted in major depression in the density of the plant stem. The biodegradation rates of residual oil were quantified using gas chromatography-mass spectrometry to determine the concentration of target analytes. Significant biodegradation of both alkanes and PAH was observed at low concentrations where there was limited plant mortality. It was determined that Spartina alterniflora from a north temperate environment will grow in oiled sediments, but its tolerance level is surpassed at concentrations as low as 17 g/kg. This observation has significant implications for decision makers regarding the type and level of oil spill response options for salt marshes. 26 refs., 6 figs

  11. Variability of blowfly head optomotor responses.

    Rosner, R; Egelhaaf, M; Grewe, J; Warzecha, A K


    Behavioural responses of an animal are variable even when the animal experiences the same sensory input several times. This variability can arise from stochastic processes inherent to the nervous system. Also, the internal state of an animal may influence a particular behavioural response. In the present study, we analyse the variability of visually induced head pitch responses of tethered blowflies by high-speed cinematography. We found these optomotor responses to be highly variable in amplitude. Most of the variability can be attributed to two different internal states of the flies with high and low optomotor gain, respectively. Even within a given activity state, there is some variability of head optomotor responses. The amount of this variability differs for the two optomotor gain states. Moreover, these two activity states can be distinguished on a fine timescale and without visual stimulation, on the basis of the occurrence of peculiar head jitter movements. Head jitter goes along with high gain optomotor responses and haltere oscillations. Halteres are evolutionary transformed hindwings that oscillate when blowflies walk or fly. Their main function is to serve as equilibrium organs by detecting Coriolis forces and to mediate gaze stabilisation. However, their basic oscillating activity was also suggested to provide a gain-modulating signal. Our experiments demonstrate that halteres are not necessary for high gain head pitch to occur. Nevertheless, we find the halteres to be responsible for one component of head jitter movements. This component may be the inevitable consequence of their function as equilibrium and gaze-stabilising organs. PMID:19329750

  12. A ferulic acid (FA)-eluting system for biodegradable magnesium stent: Cells response of HUVECs.

    Zhang, Erlin; Shen, Feng


    A new drug-eluting system was designed for biodegradable magnesium stents, in which ferulic acid (FA) was used as drug due to its promotion function to endothelial cells and PHBHHx as drug delivery due to its biodegradability and biocompatibility. A 5 and 10% FA were added in PHBHHx to prepare FA containing PHBHHX films. The cell adhesion, spreading and proliferation on these films was investigated in order to assess cell response of HUVECs. It was also found that FA enhanced the adhesion, spreading and proliferation of HUVECs in a dose-dependent manner. Cell viability after H2 O2 injury and NO production of HUVECs were also studied. The results indicated that FA effectively inhibited H2 O2 -induced injury and promotes NO production. It was also shown that alkali treatment improved the cell adhesion, spreading and proliferation while the treatment reduces the FA release and in turn reduces the inhibition on H2 O2 -induced injury and NO production. However, alkali treatment itself had no influence on the H2 O2 induced injure and NO production. The tensile shear strength between the FA containing coating and Mg substrate was also tested. All results demonstrated that FA containing PHBHHx films exhibited strong promotion to the endothelialization and could be a choice for surface modification of magnesium stent. PMID:25630748

  13. Variability of soil potential for biodegradation of petroleum hydrocarbons in a heterogeneous subsurface

    Kristensen, Andreas Houlberg; Poulsen, Tjalfe; Mortensen, Lars;


    Quantifying the spatial variability of factors affecting natural attenuation of hydrocarbons in the unsaturated zone is important to (i) performing a reliable risk assessment and (ii) evaluating the possibility for bioremediation of petroleum-polluted sites. Most studies to date have focused on the...... shallow unsaturated zone. Based on a data set comprising analysis of about 100 soil samples taken in a 16-m-deep unsaturated zone polluted with volatile petroleum compounds, we statistically and geostatistically analyzed values of essential soil properties. The subsurface of the site was highly layered...

  14. Effect of Extraction Variables on the Biodegradable Chelant-Assisted Removal of Toxic Metals from Artificially Contaminated European Reference Soils

    Begum, Zinnat A.; Rahman, Ismail M. M.; Sawai, Hikaru; Mizutani, Satoshi; Maki, Teruya; Hasegawa, Hiroshi


    Development of aminopolycarboxylate chelants (APCs) having enhanced biodegradability is gaining increasing focus to replace the EDTA and its homologs with those used widely for the ex situ treatment of contaminated soils and are potential eco-threats. The paper reports the chelant-assisted extraction of the toxic metals (Cd, Cu, Pb, and Zn) from the metal-spiked European reference soils (Eurosoil 1 and Eurosoil 4) using biodegradable APCs, namely EDDS, GLDA, and HIDS. The effects of chelant-t...

  15. Acoustic response variability in automotive vehicles

    Hills, E.; Mace, B. R.; Ferguson, N. S.


    A statistical analysis of a series of measurements of the audio-frequency response of a large set of automotive vehicles is presented: a small hatchback model with both a three-door (411 vehicles) and five-door (403 vehicles) derivative and a mid-sized family five-door car (316 vehicles). The sets included vehicles of various specifications, engines, gearboxes, interior trim, wheels and tyres. The tests were performed in a hemianechoic chamber with the temperature and humidity recorded. Two tests were performed on each vehicle and the interior cabin noise measured. In the first, the excitation was acoustically induced by sets of external loudspeakers. In the second test, predominantly structure-borne noise was induced by running the vehicle at a steady speed on a rough roller. For both types of excitation, it is seen that the effects of temperature are small, indicating that manufacturing variability is larger than that due to temperature for the tests conducted. It is also observed that there are no significant outlying vehicles, i.e. there are at most only a few vehicles that consistently have the lowest or highest noise levels over the whole spectrum. For the acoustically excited tests, measured 1/3-octave noise reduction levels typically have a spread of 5 dB or so and the normalised standard deviation of the linear data is typically 0.1 or higher. Regarding the statistical distribution of the linear data, a lognormal distribution is a somewhat better fit than a Gaussian distribution for lower 1/3-octave bands, while the reverse is true at higher frequencies. For the distribution of the overall linear levels, a Gaussian distribution is generally the most representative. As a simple description of the response variability, it is sufficient for this series of measurements to assume that the acoustically induced airborne cabin noise is best described by a Gaussian distribution with a normalised standard deviation between 0.09 and 0.145. There is generally

  16. Biodegradable polyurethane ureas with variable polyester or polycarbonate soft segments: effects of crystallinity, molecular weight and composition on mechanical properties

    Ma, Zuwei; Hong, Yi; Nelson, Devin M.; Pichamuthu, Joseph E.; Leeson, Cory E.; Wagner, William R.


    Biodegradable polyurethane urea (PUU) elastomers are ideal candidates for fabricating tissue engineering scaffolds with mechanical properties akin to strong and resilient soft tissues. PUU with a crystalline poly(ε-caprolactone) (PCL) macrodiol soft segment (SS) showed good elasticity and resilience at small strains (

  17. pH-responsive and biodegradable polymeric nanoparticles with potential application as tumour-specific drug delivery containers

    Jäger, Eliezer; Giacomelli, F. C.; Jäger, Alessandro; Giacomelli, C.; Schmidt, V.; Ulbrich, Karel; Štěpánek, Petr

    Bratislava : Young Scientists Council of Polymer Institute of Slovak Academy of Sciences, 2012 - (Podhradská, S.; Šišková, A.). s. 65-66 ISBN 978-80-970923-2-0. [Bratislava Young Polymer Scientists Workshop /4./ - BYPOS 2012. 01.10.2012-05.10.2012, Liptovský Ján] R&D Projects: GA ČR GAP208/10/1600; GA AV ČR IAAX00500803 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : pH-responsive nanoparticles * biodegradable nanoparticles * drug-delivery Subject RIV: CD - Macromolecular Chemistry

  18. Topside ionospheric response to solar EUV variability

    Anderson, Phillip C.; Hawkins, Jessica M.


    We present an analysis of 23 years of thermal plasma measurements in the topside ionosphere from the Defense Meteorological Satellite Program (DMSP) spacecraft. The H+/O+ ratio and density vary dramatically with the solar cycle; cross-correlation coefficients between E10.7 and the daily averaged densities are greater than 0.85. The ionospheric parameters also vary dramatically with season, particularly at latitudes away from the equator where the solar zenith angle varies greatly with season. There are also 27 day solar rotation periodicities in the density, associated with periodicities in the directly measured solar EUV flux. Empirical orthogonal function analysis captures over 95% of the variation in the density in the first two principal components. The first principal component (PC1) is clearly associated with the solar EUV while the second principal component (PC2) is clearly associated with the solar zenith angle variation. The magnitude of the variation of the response of the topside ionosphere to solar EUV variability is shown to be closely related to the ionospheric composition. This is interpreted as the result of the effect of composition on the scale height in the topside ionosphere and the "pivot effect" in which the variation in density near the F2 peak is amplified by a factor of e at an altitude a scale height above the F2 peak. When the topside ionosphere is H+ dominated during solar minimum, DMSP may be much less than a scale height above the F2 peak while during solar maximum, when it is O+ dominated, DMSP may be several scale heights above the F2 peak.

  19. Biodegradable polycarbonate-based stimuli-responsive nanosystems for intracellular drug delivery

    Chen, Wei


    Biodegradable nanosystems based on functional polycarbonate-based polymers have propelled the development of targeted and controlled drug and gene delivery. Functional polycarbonate-based polymers have overcome many drawbacks which limited the application of the common polyester materials in this area. It is apparent that recently introduced novel functionalities in polycarbonate-based polymers allowed the preparation of novel nanocarriers, which are bioresponsive (i.e. pH, temperature, and r...

  20. Variability in Autistic Children's Social Responsiveness.

    Fein, Deborah; And Others

    This study attempted to systematically explore the range of variation in social response in 17 subjects (ages 5 to 15) with infantile autism. To collect observational data on social initiations, social responses, social monitoring with eye contact, and responses to specific types of social events, subjects were observed during free play in their…

  1. Multinomial Logit Models for Variable Response Categories Ordered

    Malika Chikhi; Thierry Moreau; Michel Chavance


    This paper present three type of logits for ordered response to c categories. We interpreted in term of distribution two logistics models: the cumulative and continuation-ratio logit for ordinal response variables to c categories.

  2. Brainstem response and state-trait variables

    Gilliland, Kirby


    A series of investigations are summarized from a personality research program that have relevance for mental state estimation. Of particular concern are those personality variables that are believed to have either a biological or perceptual basis and their relationship to human task performance and psychophysiology. These variables are among the most robust personality measures and include such dimensions as extraversion-introversion, sensation seeking, and impulsiveness. These dimensions also have the most distinct link to performance and psychophysiology. Through the course of many of these investigations two issues have emerged repeatedly: these personality dimensions appear to mediate mental state, and mental state appears to influence measures of performance or psychophysiology.

  3. Biodegradable Polymers

    Isabelle Vroman; Lan Tighzert


    Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources) or from biological resources (renewable resources). In general natural polymers offer fewer advantages than synthetic polymers. ...

  4. pH-responsive release of proteins from biocompatible and biodegradable reverse polymer micelles.

    Koyamatsu, Yuichi; Hirano, Taisuke; Kakizawa, Yoshinori; Okano, Fumiyoshi; Takarada, Tohru; Maeda, Mizuo


    A reverse polymer micelle with a diameter of 100nm was prepared for a protein carrier releasing payloads in a pH-dependent manner. The reverse polymer micelle was made from an amphiphilic diblock copolymer of biodegradable poly(d,l-lactic-co-glycolic acid) (PLGA) and biocompatible poly(ethylene glycol) (PEG). PLGA having a terminal carboxyl group was additionally embedded in the micelle's PLGA layer via hydrophobic interaction. The micelles encapsulating bovine serum albumin and streptavidin released the proteins under neutral and basic conditions, whereas the proteins remained in the interior at acidic pH. Using erythropoietin as a protein drug, it was also exemplified that the released protein retained its cell proliferation activity even after rigorous formulation processes, including water-in-oil emulsion. The present reverse polymer micelle could potentially find application as an oral protein drug delivery carrier. PMID:24200745

  5. Efficient MoS2 Exfoliation by Cross-β-Amyloid Nanotubes for Multistimuli-Responsive and Biodegradable Aqueous Dispersions.

    Kapil, Nidhi; Singh, Ashmeet; Singh, Manish; Das, Dibyendu


    Herein, we report the efficient exfoliation of MoS2 in aqueous medium by short cationic peptide nanotubes featuring the nucleating core (17) LVFFA(21) of β-amyloid (Aβ 1-42), a sequence associated with Alzheimer's disease. The role of morphology, length, and nature of the amyloid surface on exfoliation/dispersions of MoS2 were investigated through specific mutations of the amyloid sequences. Notably, owing to the properties of both the constituents, self-assembled soft nanostructures and MoS2 , the hybrid dispersions responded reversibly to various stimuli, including temperature, pH, and light. Addition of a protease resulted in loss of the dispersions, which are otherwise stable for months at ambient conditions. The design flexibility of the peptide sequences, along with the stimuli-responsiveness and biodegradability, can complement the applications of MoS2 in diverse fields. PMID:26880665

  6. Discerning biodegradation and adsorption of microcystin-LR in a shallow semi-enclosed bay and bacterial community shifts in response to associated process.

    Li, Jieming; Li, Ji; Shi, Ge; Mei, Zulin; Wang, Ruiping; Li, Dianyue


    Hepatotoxic microcystins (MCs) produced by cyanobacteria pose serious risks to aquatic ecosystems and human health, to understand elimination pathways and mechanisms for MCs, especially in a shallow and semi-enclosed eutrophic area, is of great significance. This study succeed in discerning biodegradation and adsorption of microcystin-LR (MCLR) mediated by water and/or sediment in northern part of Meiliang Bay in Lake Taihu, China, and among the first to reveal the shifts of indigenous bacterial community composition in response to MCLR-biodegradation in sediment by Illumina high-throughput sequencing (HTS). Results confirmed that biodegradation predominantly governed MCLR elimination as compared to adsorption in study area. Through faster biodegradation with a rate of 49.21μgL(-1)d(-1), lake water contributed more to overall MCLR removal than sediment. Sediment also played indispensable role in MCLR removal via primarily biodegradation by indigenous community (a rate of 17.27μgL(-1)d(-1)) and secondarily adsorption (safety in aquatic habitats. PMID:27294671

  7. Human genetic variability and HIV treatment response.

    Haas, David W


    Access to potent antiretroviral medications greatly reduces morbidity and mortality due to HIV/AIDS, but drug toxicity limits treatment success in many individuals. The field of pharmacogenomics strives to understand the influence of human genetic variants in response to medications. Investigators have begun to identify associations among human genetic variants, predisposition to HIV drug toxicities, and likelihood of virologic response. These include associations among abacavir hypersensitivity reactions, HLA type, and hsp70-hom genotypes, and among CYP2B6 polymorphisms, efavirenz pharmacokinetics, and central nervous system symptoms. Pharmacogenomics also holds great promise to suggest novel targets for drug development. The discovery that a naturally occurring, nonfunctional variant of the HIV receptor gene CCR5 protected against HIV infection encouraged the development of CCR5 antagonists. Through continued translational and applied research, pharmacogenomics will ultimately benefit persons living with HIV worldwide by identifying new therapeutic targets and through individualized drug prescribing that is informed by human genetic testing. PMID:16608660

  8. Multi-Wheat-Model Ensemble Responses to Interannual Climate Variability

    Ruane, Alex C.; Hudson, Nicholas I.; Asseng, Senthold; Camarrano, Davide; Ewert, Frank; Martre, Pierre; Boote, Kenneth J.; Thorburn, Peter J.; Aggarwal, Pramod K.; Angulo, Carlos


    We compare 27 wheat models' yield responses to interannual climate variability, analyzed at locations in Argentina, Australia, India, and The Netherlands as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Wheat Pilot. Each model simulated 1981e2010 grain yield, and we evaluate results against the interannual variability of growing season temperature, precipitation, and solar radiation. The amount of information used for calibration has only a minor effect on most models' climate response, and even small multi-model ensembles prove beneficial. Wheat model clusters reveal common characteristics of yield response to climate; however models rarely share the same cluster at all four sites indicating substantial independence. Only a weak relationship (R2 0.24) was found between the models' sensitivities to interannual temperature variability and their response to long-termwarming, suggesting that additional processes differentiate climate change impacts from observed climate variability analogs and motivating continuing analysis and model development efforts.

  9. Response of biodegradation characteristics of unacclimated activated sludge to moderate pressure in a batch reactor.

    Xu, Rui-Xiao; Li, Bing; Zhang, Yong; Si, Ling; Zhang, Xian-Qiu; Xie, Biao


    This study was aimed to investigate the effect of moderate pressure on unacclimated activated sludge. Process of organic degradation, variation of carbon dioxide (CO2) concentration of off-gas and characteristics of extracellular polymeric substances (EPS) of activated sludge were analyzed using pressure-atmospheric comparative experiments in bench-scale batch reactors. It was found that moderate pressure increased the degradation rate more dramatically when the biological process ran under a higher organic load with much more oxygen demand, which illuminated that applications of the pressurized method to high concentration organic wastewaters would be more reasonable and practicable. High oxygen transfer impetus increased utilization of oxygen which not only promoted the biodegradation of organics in wastewater, but also led to more EPS consumption in activated sludge. CO2 concentration of off-gas was lower in the earlier stage due to CO2 being pressed into the liquid phase and converted into inorganic carbon (IC). More CO2 emission was observed during the pressurized aerobic process 160 min later. EPS in pressurized reactor was much lower, which may be an important way of sludge reduction by pressurized technology. PMID:26802261

  10. Background Variables and Their Relationship to Stimulation Responses.

    Coulter, Richard J.

    Relevant variables for educational administrators in a problem solving, simulation situation were examined. The study analyzed choice selections (overt responses) and physiological activity (covert responses) as related to age, experience, and educational background. The physiological activities were defined as heart rate and galvanic skin…

  11. Multi-wheat-model ensemble responses to interannual climatic variability

    Ruane, A C; Hudson, N I; Asseng, S;


    common characteristics of yield response to climate; however models rarely share the same cluster at all four sites indicating substantial independence. Only a weak relationship (R2 ≤ 0.24) was found between the models' sensitivities to interannual temperature variability and their response to long......We compare 27 wheat models' yield responses to interannual climate variability, analyzed at locations in Argentina, Australia, India, and The Netherlands as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Wheat Pilot. Each model simulated 1981–2010 grain yield, and we...... evaluate results against the interannual variability of growing season temperature, precipitation, and solar radiation. The amount of information used for calibration has only a minor effect on most models' climate response, and even small multi-model ensembles prove beneficial. Wheat model clusters reveal...

  12. Random Forests for Ordinal Response Data: Prediction and Variable Selection

    Janitza, Silke; Tutz, Gerhard; Boulesteix, Anne-Laure


    The random forest method is a commonly used tool for classification with high-dimensional data that is able to rank candidate predictors through its inbuilt variable importance measures (VIMs). It can be applied to various kinds of regression problems including nominal, metric and survival response variables. While classification and regression problems using random forest methodology have been extensively investigated in the past, there seems to be a lack of literature on handling ordinal re...

  13. Enhancement of the optical response in a biodegradable polymer/azo-dye film by the addition of carbon nanotubes

    A new biodegradable photoresponsive material was developed using poly(lactic acid) (PLA) as the matrix material and Disperse Orange 3 (DO3) as photoisomerizable azo-dye. It was observed that the addition of multi-walled carbon nanotubes (MWCNTs) leads to a new phenomenon consisting of an enhancement of the optical anisotropy in a wide range of temperatures. In particular, the optical anisotropy increases 100% at room temperature. Moreover, the material containing MWCNTs shows a faster optical response that is evidenced as an increase in the growth rate of optical anisotropy. Spectroscopic data is provided to study the interaction among DO3, MWCNTs and PLA. The enhancement of optical anisotropy obtained with the addition of MWCNTs was related to the glass transition temperature (Tg) of each material. Maximum optical anisotropy was obtained 15 °C below the Tg for both materials. Results are interpreted in terms of the interactions among DO3, MWCNTs and PLA and the packing density of the dye into the polymer chains. (paper)

  14. Response-rate differences in variable-interval and variable-ratio schedules: An old problem revisited

    Cole, Mark R.


    In Experiment 1, a variable-ratio 10 schedule became, successively, a variable-interval schedule with only the minimum interreinforcement intervals yoked to the variable ratio, or a variable-interval schedule with both interreinforcement intervals and reinforced interresponse times yoked to the variable ratio. Response rates in the variable-interval schedule with both interreinforcement interval and reinforced interresponse time yoking fell between the higher rates maintained by the variable-...

  15. Mahalanobis distance and variable selection to optimize dose response

    A battery of statistical techniques are combined to improve detection of low-level dose response. First, Mahalanobis distances are used to classify objects as normal or abnormal. Then the proportion classified abnormal is regressed on dose. Finally, a subset of regressor variables is selected which maximizes the slope of the dose response line. Use of the techniques is illustrated by application to mouse sperm damaged by low doses of x-rays

  16. Biodegradable polylactide microspheres enhance specific immune response induced by Hepatitis B surface antigen

    Qiu, Shaohui; Wei, Qiang (Ethan); Liang, Zhenglun; Ma, Guanghui; Wang, Lianyan; An, Wenqi; Ma, Xiaowei; Fang, Xin; He, Peng; Li, Hemin; Hu, Zhongyu


    Hepatitis B (HB) infection caused by Hepatitis B virus (HBV) is the most common liver disease in the world. HB vaccine, when administered in conjunction with alum adjuvants, induces Th2 immunity that confers protection against HBV. However, currently available vaccine formulations and adjuvants do not elicit adequate Th1 and CTL responses that are important for prevention of maternal transmission of the virus. Microspheres synthesized from poly (D, L-lactide-co-glycolide) (PLGA) or poly (D, L...

  17. Optimization of Process Variables by Response Surface Methodology

    Kashipeta Ravinder


    Full Text Available In the present study optimisation of the growth medium for the production of Cyclodextrin glucanotransferase (CGTase was carried out using response surface methodology. Four important parameters namely starch, yeast extract, K2HPO4 and MgSO4 concentrations were selected as the independent variables and the enzyme activity (CGTase activity U/mL was the dependent response variable. Each of these independent variables was studied at five different levels as per central composite design (CCD in four variables with a total of 28 experimental runs. The optimal calculated values of tested variables for maximal production of CGTase were found to be comprised of: starch, 2.16 %; yeast extract, 0.6 %; K2HPO4, 0.62 %; MgSO4, 0.04 % with a predicted CGTase activity of 150 U/ml. These predicted optimal parameters were tested in the laboratory and the final CGTase activity obtained was very close to the predicted value at 148.2 U/ml.

  18. Adaptive microbial population shifts in response to a continuous ethanol blend release increases biodegradation potential

    The fate of fuel releases largely depends on the poorly-understood response in microbial community structure and function. Here, we evaluate the impacts to the microbial community resulting from a pilot-scale continuous release (10 months) of a 10% v:v ethanol solution mixed with benzene and toluene (50 mg/L each). Microbial population shifts were characterized by pyrosequencing-based 16S rRNA analysis and by quantitative PCR targeting Bacteria, Archaea, and functional genes for methanogenesis (mcrA), acetogenesis (fhs) and aerobic degradation of aromatic hydrocarbons (PHE), which could occur in hypoxic micro-environments. The release stimulated microbial growth, increased species richness and diversity, and selected for genotypes involved in fermentative degradation (the relative abundance of mcrA and fhs increased 18- and 6-fold, respectively). The growth of putative hydrocarbon degraders and commensal anaerobes, and increases in microbial diversity and in degradation rates suggest an adaptive response that increases the potential for natural attenuation of ethanol blend releases. -- Highlights: •Pyrosequencing discerned microbial community changes after an ethanol blend release. •Adaptive microbial population shifts that enhance bioremediation were observed. •Hydrocarbon degraders and fermentation syntrophs proliferated. •Surprisingly, both species richness and taxonomic diversity increased. -- Pyrosequencing analysis discerned adaptive microbial population shifts that increase natural attenuation potential of an ethanol-blended fuel release

  19. Biodegradable polylactide microspheres enhance specific immune response induced by Hepatitis B surface antigen.

    Qiu, Shaohui; Wei, Qiang; Liang, Zhenglun; Ma, Guanghui; Wang, Lianyan; An, Wenqi; Ma, Xiaowei; Fang, Xin; He, Peng; Li, Hemin; Hu, Zhongyu


    Hepatitis B (HB) infection caused by Hepatitis B virus (HBV) is the most common liver disease in the world. HB vaccine, when administered in conjunction with alum adjuvants, induces Th2 immunity that confers protection against HBV. However, currently available vaccine formulations and adjuvants do not elicit adequate Th1 and CTL responses that are important for prevention of maternal transmission of the virus. Microspheres synthesized from poly (D, L-lactide-co-glycolide) (PLGA) or poly (D, L-lactide) (PLA) polymers have been considered as promising tools for in vivo delivery of antigens and drugs. Here we describe PLA microspheres synthesized by premix membrane emulsification method and their application in formulating a new microsphere based HB vaccine. To evaluate the immunogenicity of this microsphere vaccine, BALB/c mice were immunized with microsphere vaccine and a series of immunological assays were conducted. Results of Enzyme-linked ImmunoSpot (ELISPOT) assays revealed that the number of interferon-gamma (IFN-γ)-producing splenocytes and CD8(+) T cells increased significantly in the microsphere vaccine group. Microsphere vaccine group showed enhanced specific cell lysis when compared with HB surface antigen (HBsAg) only group in (51)Cr cytotoxicity assays. Moreover, microsphere vaccine elicited a comparable level of antibody production as that of HB vaccine administered with alum adjuvant. We show that phagocytosis of HBsAg by dendritic cells is more pronounced in microsphere vaccine group when compared with other control groups. These results clearly demonstrate the potential of using PLA microspheres as effective HB vaccine adjuvants for an enhanced Th1 immune response. PMID:25424942

  20. Qigong Effects on Heart Rate Variability and Peripheral Vasomotor Responses.

    Chang, Mei-Ying


    Population aging is occurring worldwide, and preventing cardiovascular event in older people is a unique challenge. The aim of this study was to examine the effects of a 12-week qigong (eight-form moving meditation) training program on the heart rate variability and peripheral vasomotor response of middle-aged and elderly people in the community. This was a quasi-experimental study that included the pre-test, post-test, and nonequivalent control group designs. Seventy-seven participants (experimental group = 47; control group = 30) were recruited. The experimental group performed 30 min of eight-form moving meditation 3 times per week for 12 weeks, and the control group continued their normal daily activities. After 12 weeks, the interaction effects indicated that compared with the control group, the experimental group exhibited significantly improved heart rate variability and peripheral vasomotor responses. PMID:24869492

  1. Binary regression with differentially misclassified response and exposure variables.

    Tang, Li; Lyles, Robert H; King, Caroline C; Celentano, David D; Lo, Yungtai


    Misclassification is a long-standing statistical problem in epidemiology. In many real studies, either an exposure or a response variable or both may be misclassified. As such, potential threats to the validity of the analytic results (e.g., estimates of odds ratios) that stem from misclassification are widely discussed in the literature. Much of the discussion has been restricted to the nondifferential case, in which misclassification rates for a particular variable are assumed not to depend on other variables. However, complex differential misclassification patterns are common in practice, as we illustrate here using bacterial vaginosis and Trichomoniasis data from the HIV Epidemiology Research Study (HERS). Therefore, clear illustrations of valid and accessible methods that deal with complex misclassification are still in high demand. We formulate a maximum likelihood (ML) framework that allows flexible modeling of misclassification in both the response and a key binary exposure variable, while adjusting for other covariates via logistic regression. The approach emphasizes the use of internal validation data in order to evaluate the underlying misclassification mechanisms. Data-driven simulations show that the proposed ML analysis outperforms less flexible approaches that fail to appropriately account for complex misclassification patterns. The value and validity of the method are further demonstrated through a comprehensive analysis of the HERS example data. PMID:25652841

  2. Examining Uncertainty in Demand Response Baseline Models and Variability in Automated Response to Dynamic Pricing

    Mathieu, Johanna L.; Callaway, Duncan S.; Kiliccote, Sila


    Controlling electric loads to deliver power system services presents a number of interesting challenges. For example, changes in electricity consumption of Commercial and Industrial (C&I) facilities are usually estimated using counterfactual baseline models, and model uncertainty makes it difficult to precisely quantify control responsiveness. Moreover, C&I facilities exhibit variability in their response. This paper seeks to understand baseline model error and demand-side variability in responses to open-loop control signals (i.e. dynamic prices). Using a regression-based baseline model, we define several Demand Response (DR) parameters, which characterize changes in electricity use on DR days, and then present a method for computing the error associated with DR parameter estimates. In addition to analyzing the magnitude of DR parameter error, we develop a metric to determine how much observed DR parameter variability is attributable to real event-to-event variability versus simply baseline model error. Using data from 38 C&I facilities that participated in an automated DR program in California, we find that DR parameter errors are large. For most facilities, observed DR parameter variability is likely explained by baseline model error, not real DR parameter variability; however, a number of facilities exhibit real DR parameter variability. In some cases, the aggregate population of C&I facilities exhibits real DR parameter variability, resulting in implications for the system operator with respect to both resource planning and system stability.

  3. Pavement Response to Variable Tyre Pressure of Heavy Vehicles

    Arshad Ahmad Kamil; Haron Hairol Anuar; Abd Rahman Zanariah; Abdul Halim A.G.


    In recent years, the effect of overinflated tyre pressure and increased heavy vehicles’ axle load on flexible pavements has become a subject of great concern because of the higher stress levels induced and damage caused to road pavements. This paper aims to evaluate the effect of variable tyre inflation pressures (using actual tyre contact/footprint area) to determine the responses of flexible pavement. A full scale experiment was conducted on a heavy vehicle with 1:1:2 axle configuration, 10...

  4. Response of closed basin lakes to interannual climate variability

    Huybers, Kathleen; Rupper, Summer; Roe, Gerard H.


    Lakes are key indicators of a region's hydrological cycle, directly reflecting the basin-wide balance between precipitation and evaporation. Lake-level records are therefore valuable repositories of climate history. However, the interpretation of such records is not necessarily straightforward. Lakes act as integrators of the year-to-year fluctuations in precipitation and evaporation that occur even in a constant climate. Therefore lake levels can exhibit natural, unforced fluctuations that persist on timescales of decades or more. This behavior is important to account for when distinguishing between true climate change and interannual variability as the cause of past lake-level fluctuations. We demonstrate the operation of this general principle for the particular case-study of the Great Salt Lake, which has long historical lake-level and climatological records. We employ both full water-balance and linear models. Both models capture the timing and size of the lake's historical variations. We then model the lake's response to much longer synthetic time series of precipitation and evaporation calibrated to the observations, and compare the magnitude and frequency of the modeled response to the Great Salt Lake's historical record. We find that interannual climate variability alone can explain much of the decadal-to-centennial variations in the lake-level record. Further, analytic solutions to the linear model capture much of the full model's behavior, but fail to predict the most extreme lake-level variations. We then apply the models to other lake geometries, and evaluate how the timing and amplitude of a lake-level response differs with climatic and geometric setting. A lake's response to a true climatic shift can only be understood in the context of these expected persistent lake-level variations. On the basis of these results, we speculate that lake response to interannual climate variability may play an important part in explaining much of Holocene lake

  5. Human Responses to Climate Variability: The Case of South Africa

    Oppenheimer, M.; Licker, R.; Mastrorillo, M.; Bohra-Mishra, P.; Estes, L. D.; Cai, R.


    Climate variability has been associated with a range of societal and individual outcomes including migration, violent conflict, changes in labor productivity, and health impacts. Some of these may be direct responses to changes in mean temperature or precipitation or extreme events, such as displacement of human populations by tropical cyclones. Others may be mediated by a variety of biological, social, or ecological factors such as migration in response to long-term changes in crops yields. Research is beginning to elucidate and distinguish the many channels through which climate variability may influence human behavior (ranging from the individual to the collective, societal level) in order to better understand how to improve resilience in the face of current variability as well as future climate change. Using a variety of data sets from South Africa, we show how climate variability has influenced internal (within country) migration in recent history. We focus on South Africa as it is a country with high levels of internal migration and dramatic temperature and precipitation changes projected for the 21st century. High poverty rates and significant levels of rain-fed, smallholder agriculture leave large portions of South Africa's population base vulnerable to future climate change. In this study, we utilize two complementary statistical models - one micro-level model, driven by individual and household level survey data, and one macro-level model, driven by national census statistics. In both models, we consider the effect of climate on migration both directly (with gridded climate reanalysis data) and indirectly (with agricultural production statistics). With our historical analyses of climate variability, we gain insights into how the migration decisions of South Africans may be influenced by future climate change. We also offer perspective on the utility of micro and macro level approaches in the study of climate change and human migration.

  6. The role of ethnocultural variables in response to terrorism.

    Walker, Katrina L; Chestnut, Dennis


    The threat of terrorism is having a profound impact on Americans. This study examined ethnocultural variables of ethnic background, gender, age, and educational background to better understand first reactions to, explanations for, and responses to what happened on September 11, 2001. Data were obtained from a sample of university students, church and civic group members, and people of the general community. Results suggest that ethnic background, gender, and age influence reactions to terrorism. Ethnic background and gender influenced causal explanations about the attacks. Strong gender differences were noted in how participants were affected by the attacks; strongest similarities were observed in reports of first reactions to news of the events, with most people experiencing shock and disbelief. Conclusions stress the importance of future mental health interventions and research giving strong consideration to ethnocultural variables when dealing with victims of terrorism. PMID:12971092

  7. Estimation of road profile variability from measured vehicle responses

    Fauriat, W.; Mattrand, C.; Gayton, N.; Beakou, A.; Cembrzynski, T.


    When assessing the statistical variability of fatigue loads acting throughout the life of a vehicle, the question of the variability of road roughness naturally arises, as both quantities are strongly related. For car manufacturers, gathering information on the environment in which vehicles evolve is a long and costly but necessary process to adapt their products to durability requirements. In the present paper, a data processing algorithm is proposed in order to estimate the road profiles covered by a given vehicle, from the dynamic responses measured on this vehicle. The algorithm based on Kalman filtering theory aims at solving a so-called inverse problem, in a stochastic framework. It is validated using experimental data obtained from simulations and real measurements. The proposed method is subsequently applied to extract valuable statistical information on road roughness from an existing load characterisation campaign carried out by Renault within one of its markets.

  8. Taking the pulse of mountains: Ecosystem responses to climatic variability

    Fagre, D.B.; Peterson, D.L.; Hessl, A.E.


    An integrated program of ecosystem modeling and field studies in the mountains of the Pacific Northwest (U.S.A.) has quantified many of the ecological processes affected by climatic variability. Paleoecological and contemporary ecological data in forest ecosystems provided model parameterization and validation at broad spatial and temporal scales for tree growth, tree regeneration and treeline movement. For subalpine tree species, winter precipitation has a strong negative correlation with growth; this relationship is stronger at higher elevations and west-side sites (which have more precipitation). Temperature affects tree growth at some locations with respect to length of growing season (spring) and severity of drought at drier sites (summer). Furthermore, variable but predictable climate-growth relationships across elevation gradients suggest that tree species respond differently to climate at different locations, making a uniform response of these species to future climatic change unlikely. Multi-decadal variability in climate also affects ecosystem processes. Mountain hemlock growth at high-elevation sites is negatively correlated with winter snow depth and positively correlated with the winter Pacific Decadal Oscillation (PDO) index. At low elevations, the reverse is true. Glacier mass balance and fire severity are also linked to PDO. Rapid establishment of trees in subalpine ecosystems during this century is increasing forest cover and reducing meadow cover at many subalpine locations in the western U.S.A. and precipitation (snow depth) is a critical variable regulating conifer expansion. Lastly, modeling potential future ecosystem conditions suggests that increased climatic variability will result in increasing forest fire size and frequency, and reduced net primary productivity in drier, east-side forest ecosystems. As additional empirical data and modeling output become available, we will improve our ability to predict the effects of climatic change

  9. Biodegradation of cyanide by a new isolated strain under alkaline conditions and optimization by response surface methodology (RSM)

    Mirizadeh, Shabnam; Yaghmaei, Soheila; Ghobadi Nejad, Zahra


    Background Biodegradation of free cyanide from industrial wastewaters has been proven as a viable and robust method for treatment of wastewaters containing cyanide. Results Cyanide degrading bacteria were isolated from a wastewater treatment plant for coke-oven-gas condensate by enrichment culture technique. Five strains were able to use cyanide as the sole nitrogen source under alkaline conditions and among them; one strain (C2) was selected for further studies on the basis of the higher eff...

  10. Biodegradation of Alachlor in Liquid and Soil Cultures Under Variable Carbon and Nitrogen Sources by Bacterial Consortium Isolated from Corn Field Soil

    Simin Nasseri


    Full Text Available Alachlor, an aniline herbicide widely used in corn production, is frequently detected in water resources. The main objectives of this research were focused on isolating bacterial consortium capable of alachlor biodegradation, assessing the effects of carbon and nitrogen sources on alachlor biodegradation and evaluating the feasibility of using bacterial consortium in soil culture. Kavar corn field soil with a long history of alachlor application in Fars province of Iran has been explored for their potential of alachlor biodegradation. The influence of different carbon compounds (glucose, sodium citrate, sucrose, starch and the combination of these compounds, the effect of nitrogen sources (ammonium nitrate and urea and different pH (5.5-8.5 on alachlor removal efficiency by the bacterial consortium in liquid culture were investigated. After a multi-step enrichment program 100 days of acclimation, a culture with the high capability of alachlor degradation was obtained (63%. Glucose and sodium citrate had the highest alachlor reduction rate (85%. Alachlor reduction rate increased more rapidly by the addition of ammonium nitrate (94% compare to urea. Based on the data obtained in the present study, pH of 7.5 is optimal for alachlor biodegradation. After 30 days of incubation, the percent of alachlor reduction were significantly enhanced in the inoculated soils (74% as compared to uninoculated control soils (17.67% at the soil moisture content of 25%. In conclusion, bioaugmentation of soil with bacterial consortium may enhance the rate of alachlor degradation in a polluted soil.

  11. Population variability complicates the accurate detection of climate change responses.

    McCain, Christy; Szewczyk, Tim; Bracy Knight, Kevin


    The rush to assess species' responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre- and post-CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species' range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate 'canaries in the coal mine' for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses. PMID:26725404

  12. In vitro responses of bone-forming MC3T3-E1 pre-osteoblasts to biodegradable Mg-based bulk metallic glasses.

    Li, Haifei; He, Wei; Pang, Shujie; Liaw, Peter K; Zhang, Tao


    In light of the superior property profile of favorable biocompatibility, proper corrosion/degradation behavior and good mechanical properties, Mg-based bulk metallic glasses (BMGs) are considered as potential biodegradable biomaterials. In the present study, in vitro responses of bone-forming MC3T3-E1 pre-osteoblasts to Mg-Zn-Ca-Sr BMGs were studied in order to assess their feasibility to serve as orthopedic implants. The Mg-Zn-Ca-Sr BMGs were much more capable of supporting cell adhesion and spreading in comparison with crystalline AZ31B Mg alloy. The Mg-Zn-Ca-Sr BMG extracts showed no cytotoxicity to and slightly stimulated the proliferation of pre-osteoblasts. The cells cultured in 100% BMG extracts exhibited lower alkaline phosphatase activity as compared with that in negative control, which could be mainly ascribed to the inhibition of high concentrations of Zn ions on cell differentiation. With decreasing the extract concentration, the inhibitory effect was diminished and the 5% BMG extract exhibited slight stimulation in cell differentiation and mineralization. The high corrosion resistance of BMGs contributed to smaller environmental variations, compared with AZ31B alloy, thus lowering the unfavorable influences on cellular responses. A comparison among the biodegradable Mg-, Ca- and Sr-based BMGs for their biomedical applications is presented. PMID:27524063

  13. The Atlantic Meridional Overturning Circulation's Response to Variable Buoyancy Forcing

    Butler, Edward; Oliver, Kevin; Hirschi, Joël


    The Meridional Overturning Circulation (MOC) is a large-scale global circulation of water (and heat) throughout the world's ocean. It is an integral part of the climate system, responsible for significant anomalous warming of the North Atlantic region. Much of our current understanding of the MOC is based on equilibrium theories. However, the MOC is not a steady circulation and exhibits variability across a broad range of timescales. We examine the transient response of global ocean overturning, with particular emphasis on the Atlantic MOC (AMOC), to periodic variations in the North Atlantic meridional density gradient on decadal, centennial, and millennial timescales within the Nucleus for European Modelling of the Ocean (NEMO) model framework. We use the ORCA2 global ocean configuration of NEMO (with realistic topography and a horizontal resolution of 2°) and impose periodic variations in air temperature over the North Atlantic. In response, we see large oscillations in the strength of the AMOC which peak in magnitude at 128-year timescales. A scaling relationship of the form Ψ ~ ΔρH2 (in which Δρ is a measure of meridional density gradient and H is the depth scale of maximal overturning) is found to hold for the AMOC in these transient simulations with strongest correlations observed at centennial timescales. We explore the validity of this scaling relationship across a broad range of spatial and temporal scales and discuss its validity in a global context.

  14. Synthesis and click chemistry of a new class of biodegradable polylactide towards tunable thermo-responsive biomaterials†

    Zhang, Quanxuan; Ren, Hong; Baker, Gregory L.


    A new class of clickable and biodegradable polylactide was designed and prepared via bulk polymerization of 3,6-dipropargyloxymethyl-1,4-dioxane-2,5-dione (1) which was synthesized from easily accessible propargyloxylactic acid (5). A homopolymer of 1 and random copolymer of 1 with l-lactide were obtained as amorphous materials and exhibit low Tg of 8.5 and 34 °C, respectively, indicating their promising potentials for biomedical applications. The statistical nature of random copolymers was i...

  15. Historical temperature variability affects coral response to heat stress.

    Jessica Carilli

    Full Text Available Coral bleaching is the breakdown of symbiosis between coral animal hosts and their dinoflagellate algae symbionts in response to environmental stress. On large spatial scales, heat stress is the most common factor causing bleaching, which is predicted to increase in frequency and severity as the climate warms. There is evidence that the temperature threshold at which bleaching occurs varies with local environmental conditions and background climate conditions. We investigated the influence of past temperature variability on coral susceptibility to bleaching, using the natural gradient in peak temperature variability in the Gilbert Islands, Republic of Kiribati. The spatial pattern in skeletal growth rates and partial mortality scars found in massive Porites sp. across the central and northern islands suggests that corals subject to larger year-to-year fluctuations in maximum ocean temperature were more resistant to a 2004 warm-water event. In addition, a subsequent 2009 warm event had a disproportionately larger impact on those corals from the island with lower historical heat stress, as indicated by lower concentrations of triacylglycerol, a lipid utilized for energy, as well as thinner tissue in those corals. This study indicates that coral reefs in locations with more frequent warm events may be more resilient to future warming, and protection measures may be more effective in these regions.

  16. Response of the bacterial community associated with a cosmopolitan marine diatom to crude oil shows a preference for the biodegradation of aromatic hydrocarbons.

    Mishamandani, Sara; Gutierrez, Tony; Berry, David; Aitken, Michael D


    Emerging evidence shows that hydrocarbonoclastic bacteria (HCB) may be commonly found associated with phytoplankton in the ocean, but the ecology of these bacteria and how they respond to crude oil remains poorly understood. Here, we used a natural diatom-bacterial assemblage to investigate the diversity and response of HCB associated with a cosmopolitan marine diatom, Skeletonema costatum, to crude oil. Pyrosequencing analysis and qPCR revealed a dramatic transition in the diatom-associated bacterial community, defined initially by a short-lived bloom of Methylophaga (putative oil degraders) that was subsequently succeeded by distinct groups of HCB (Marinobacter, Polycyclovorans, Arenibacter, Parvibaculum, Roseobacter clade), including putative novel phyla, as well as other groups with previously unqualified oil-degrading potential. Interestingly, these oil-enriched organisms contributed to the apparent and exclusive biodegradation of substituted and non-substituted polycyclic aromatic hydrocarbons (PAHs), thereby suggesting that the HCB community associated with the diatom is tuned to specializing in the degradation of PAHs. Furthermore, the formation of marine oil snow (MOS) in oil-amended incubations was consistent with its formation during the Deepwater Horizon oil spill. This work highlights the phycosphere of phytoplankton as an underexplored biotope in the ocean where HCB may contribute importantly to the biodegradation of hydrocarbon contaminants in marine surface waters. PMID:26184578

  17. Response time variability and response inhibition predict affective problems in adolescent girls, not in boys : the TRAILS study

    van Deurzen, Patricia A. M.; Buitelaar, Jan K.; Brunnekreef, J. Agnes; Ormel, Johan; Minderaa, Ruud B.; Hartman, Catharina A.; Huizink, Anja C.; Speckens, Anne E. M.; Oldehinkel, A. J.; Slaats-Willemse, Dorine I. E.


    The present study examines the relationship between neurocognitive functioning and affective problems through adolescence, in a cross-sectional and longitudinal perspective. Baseline response speed, response speed variability, response inhibition, attentional flexibility and working memory were asse

  18. Response of Thermospheric Hydrogen to Solar Variability and Greenhouse Gases

    Nossal, S. M.; Qian, L.; Solomon, S. C.; Burns, A. G.; Wang, W.; Mierkiewicz, E. J.; Roesler, F. L.; Woodward, R. C., Jr.


    Geocoronal hydrogen forms the upper boundary of the Earth's HOx chemisty and is a byproduct of methane and water vapor below. We will discuss observational and modeling studies of the upper atmospheric hydrogen response to the solar cycle and increases in greenhouse gases. The Wisconsin Northern hemisphere hydrogen airglow data set spans over two solar cycles. These data show a statistically significant solar cycle variation and a possible increase in intensity between successive solar maximum periods. We will discuss these data in the context of recent modeling studies with a single-column version of the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model. We investigate mechanisms associated with the solar cycle and greenhouse gas forcing of hydrogen by separately doubling carbon dioxide and methane, as well as doubling both together. These simulations indicate that carbon dioxide cooling, as well as methane changes to the source species for hydrogen, both lead to predicted increases in the upper thermospheric hydrogen density and that the response of hydrogen to greenhouse gases depends on the phase of the solar cycle. However, the effect of greenhouse gas doubling is not as large as the modeled solar cycle variability of thermospheric hydrogen. I will discuss results from these simulations and comparisons to observations.

  19. Proceedings of biodegradation

    This book contains the proceedings of Biodegradation. Topics include:biodegradation using the tools of biotechnology, basic science aspects of biodegradation, the physiological characteristics of microorganisms, the use of selective techniques that enhance the process of microbial evolution of biodegradative genes in nature, the genetic characteristics of microorganisms allowing them to biodegrade both natural and synthetic toxic chemicals, the molecular techniques that allow selective assembly of genetic segments form a variety of bacterial strains to a single strain, and methods needed to advance biodegradation research as well as the high-priority chemical problems important to the Department of Defense or to the chemical industry

  20. Avian community responses to variability in river hydrology.

    Alexander Royan

    Full Text Available River flow is a major driver of morphological structure and community dynamics in riverine-floodplain ecosystems. Flow influences in-stream communities through changes in water velocity, depth, temperature, turbidity and nutrient fluxes, and perturbations in the organisation of lower trophic levels are cascaded through the food web, resulting in shifts in food availability for consumer species. River birds are sensitive to spatial and phenological mismatches with aquatic prey following flow disturbances; however, the role of flow as a determinant of riparian ecological structure remains poorly known. This knowledge is crucial to help to predict if, and how, riparian communities will be influenced by climate-induced changes in river flow characterised by more extreme high (i.e. flood and/or low (i.e. drought flow events. Here, we combine national-scale datasets of river bird surveys and river flow archives to understand how hydrological disturbance has affected the distribution of riparian species at higher trophic levels. Data were analysed for 71 river locations using a Generalized Additive Model framework and a model averaging procedure. Species had complex but biologically interpretable associations with hydrological indices, with species' responses consistent with their ecology, indicating that hydrological-disturbance has implications for higher trophic levels in riparian food webs. Our quantitative analysis of river flow-bird relationships demonstrates the potential vulnerability of riparian species to the impacts of changing flow variability and represents an important contribution in helping to understand how bird communities might respond to a climate change-induced increase in the intensity of floods and droughts. Moreover, the success in relating parameters of river flow variability to species' distributions highlights the need to include river flow data in climate change impact models of species' distributions.

  1. Pavement Response to Variable Tyre Pressure of Heavy Vehicles

    Arshad Ahmad Kamil


    Full Text Available In recent years, the effect of overinflated tyre pressure and increased heavy vehicles’ axle load on flexible pavements has become a subject of great concern because of the higher stress levels induced and damage caused to road pavements. This paper aims to evaluate the effect of variable tyre inflation pressures (using actual tyre contact/footprint area to determine the responses of flexible pavement. A full scale experiment was conducted on a heavy vehicle with 1:1:2 axle configuration, 10 R 20 tyre size and attached trailer with constant axle load. Measurements were made for actual tyre-pavement contact area. KENPAVE linear elastic program was then used to analyse the effects of the measured actual tyre-pavement contact area and the results was compared using conventional circular tyre contact area. A comparative analysis was then made between the actual contact area and the conventional circular tyre contact area. It was found that high tyre inflation pressure produce smaller contact area, giving more detrimental effect on the flexible pavement. It was also found that the temperature of tyres when the heavy vehicles are operational give less significant impact on tyre inflation pressure for the Malaysian climate.

  2. Preparation of biodegradable PEGylated pH/reduction dual-stimuli responsive nanohydrogels for controlled release of an anti-cancer drug

    Zhou, Tingting; Zhao, Xubo; Liu, Lei; Liu, Peng


    A facile and efficient method was developed to prepare the monodisperse biodegradable PEGylated pH and reduction dual-stimuli sensitive poly[methacrylic acid-co-poly(ethylene glycol) methyl ether methacrylate-co-N,N-bis(acryloyl)cystamine] (PMPB) nanohydrogels with dried particle size below 200 nm via one-step distillation precipitation polymerization as a drug delivery system (DDS) for the controlled release of a wide-spectrum anti-cancer drug, doxorubicin hydrochloride (DOX). Under normal physiological media, the nanohydrogels possessed high drug encapsulation efficiency (more than 96%) within 48 h and exhibited good stability with a trifle premature drug release. However, rapid DOX release was achieved at lower pH or in the presence of reductive reagent glutathione (GSH) with a cumulative release of more than 85% within 30 h. Furthermore, the nanohydrogels manifested nontoxicity on HepG2 cells at a concentration of 10 μg mL-1 or lower. Based on the excellent characteristics of the nanohydrogels, such as low toxicity, impressive biodegradability, sharp dual responsiveness, adequate drug loading capacity and a high drug encapsulation efficiency, they were supposed to have potential application in the area of cancer therapy.A facile and efficient method was developed to prepare the monodisperse biodegradable PEGylated pH and reduction dual-stimuli sensitive poly[methacrylic acid-co-poly(ethylene glycol) methyl ether methacrylate-co-N,N-bis(acryloyl)cystamine] (PMPB) nanohydrogels with dried particle size below 200 nm via one-step distillation precipitation polymerization as a drug delivery system (DDS) for the controlled release of a wide-spectrum anti-cancer drug, doxorubicin hydrochloride (DOX). Under normal physiological media, the nanohydrogels possessed high drug encapsulation efficiency (more than 96%) within 48 h and exhibited good stability with a trifle premature drug release. However, rapid DOX release was achieved at lower pH or in the presence of

  3. Nanostructure controlled sustained delivery of human growth hormone using injectable, biodegradable, pH/temperature responsive nanobiohybrid hydrogel

    Singh, Narendra K.; Nguyen, Quang Vinh; Kim, Bong Sup; Lee, Doo Sung


    The clinical efficacy of a therapeutic protein, the human growth hormone (hGH), is limited by its short plasma half-life and premature degradation. To overcome this limitation, we proposed a new protein delivery system by the self-assembly and intercalation of a negatively charged hGH onto a positively charged 2D-layered double hydroxide nanoparticle (LDH). The LDH-hGH ionic complex, with an average particle size of approximately 100 nm, retards hGH diffusion. Nanobiohybrid hydrogels (PAEU/LDH-hGH) were prepared by dispersing the LDH-hGH complex into a cationic pH- and temperature-sensitive injectable PAEU copolymer hydrogel to enhance sustained hGH release by dual ionic interactions. Biodegradable copolymer hydrogels comprising poly(β-amino ester urethane) and triblock poly(ε-caprolactone-lactide)-poly(ethylene glycol)-poly-(ε-caprolactone-lactide) (PCLA-PEG-PCLA) were synthesized and characterized. hGH was self-assembled and intercalated onto layered LDH nanoparticles through an anion exchange technique. X-ray diffraction and zeta potential results showed that the LDH-hGH complex was prepared successfully and that the PAEU/LDH-hGH nanobiohybrid hydrogel had a disordered intercalated nanostructure. The biocompatibility of the nanobiohybrid hydrogel was confirmed by an in vitro cytotoxicity test. The in vivo degradation of pure PAEU and its nanobiohybrid hydrogels was investigated and it showed a controlled degradation of the PAEU/LDH nanobiohybrids compared with the pristine PAEU copolymer hydrogel. The LDH-hGH loaded injectable hydrogels suppressed the initial burst release of hGH and extended the release period for 13 days in vitro and 5 days in vivo. The developed nanohybrid hydrogel has the potential for application as a protein carrier to improve patient compliance.The clinical efficacy of a therapeutic protein, the human growth hormone (hGH), is limited by its short plasma half-life and premature degradation. To overcome this limitation, we proposed a new

  4. Microbial community evolution during simulated managed aquifer recharge in response to different biodegradable dissolved organic carbon (BDOC) concentrations

    Li, Dong


    This study investigates the evolution of the microbial community in laboratory-scale soil columns simulating the infiltration zone of managed aquifer recharge (MAR) systems and analogous natural aquifer sediment ecosystems. Parallel systems were supplemented with either moderate (1.1 mg/L) or low (0.5 mg/L) biodegradable dissolved organic carbon (BDOC) for a period of six months during which time, spatial (1 cm, 30 cm, 60 cm, 90 cm, and 120 cm) and temporal (monthly) analyses of sediment-associated microbial community structure were analyzed. Total microbial biomass associated with sediments was positively correlated with BDOC concentration where a significant decline in BDOC was observed along the column length. Analysis of 16S rRNA genes indicated dominance by Bacteria with Archaea comprising less than 1 percent of the total community. Proteobacteria was found to be the major phylum in samples from all column depths with contributions from Betaproteobacteria, Alphaproteobacteria and Gammaproteobacteria. Microbial community structure at all the phylum, class and genus levels differed significantly at 1 cm between columns receiving moderate and low BDOC concentrations; in contrast strong similarities were observed both between parallel column systems and across samples from 30 to 120 cm depths. Samples from 1 cm depth of the low BDOC columns exhibited higher microbial diversity (expressed as Shannon Index) than those at 1 cm of moderate BDOC columns, and both increased from 5.4 to 5.9 at 1 cm depth to 6.7-8.3 at 30-120 cm depths. The microbial community structure reached steady state after 3-4 months since the initiation of the experiment, which also resulted in an improved DOC removal during the same time period. This study suggested that BDOC could significantly influence microbial community structure regarding both composition and diversity of artificial MAR systems and analogous natural aquifer sediment ecosystems. © 2013 Elsevier Ltd.

  5. Cropping frequency and area response to climate variability can exceed yield response

    Cohn, Avery S.; Vanwey, Leah K.; Spera, Stephanie A.; Mustard, John F.


    The sensitivity of agricultural output to climate change has often been estimated by modelling crop yields under climate change scenarios or with statistical analysis of the impacts of year-to-year climatic variability on crop yields. However, the area of cropland and the number of crops harvested per growing season (cropping frequency) both also affect agricultural output and both also show sensitivity to climate variability and change. We model the change in agricultural output associated with the response of crop yield, crop frequency and crop area to year-to-year climate variability in Mato Grosso (MT), Brazil, a key agricultural region. Roughly 70% of the change in agricultural output caused by climate was determined by changes in frequency and/or changes in area. Hot and wet conditions were associated with the largest losses and cool and dry conditions with the largest gains. All frequency and area effects had the same sign as total effects, but this was not always the case for yield effects. A focus on yields alone may therefore bias assessments of the vulnerability of agriculture to climate change. Efforts to reduce climate impacts to agriculture should seek to limit production losses not only from crop yield, but also from changes in cropland area and cropping frequency.

  6. Biodegradability of Plastics

    Yutaka Tokiwa


    Full Text Available Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.. In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

  7. Future Climate Variability and Watershed Response in Southern California

    Lopez, Sonya Rita


    The current work focuses on assessing the impacts of future climate variability on water resources in southern California. Specifically, this dissertation work includes: (1) developing archetypal watersheds and climate scenarios to obtain regional changes to hydrology and sediment transport and (2) developing a statistical downscaling approach that considers regional climate heterogeneity (commonly neglected in downscaling methods) and using this data to drive hydrologic models. The archetypa...

  8. Response variability and reliability of systems with uncertain material property

    This study clearly shows that when the spatially varying bending flexibility is assumed to be a stochastic field, the beam response also constitutes the inhomogeneous stochastic field, and 'a reliability as a member' can exactly be evaluated by means of the classical first excursion theory. Although this study is very preliminary, it can help us to understand the response behavior of stochastic systems and also can give us a useful insight to estimating the reliability as a structural member. (author)

  9. Pharmacometabolomics Reveals That Serotonin Is Implicated in Aspirin Response Variability

    Ellero-Simatos, S; Lewis, JP; Georgiades, A; Yerges-Armstrong, LM; Beitelshees, AL; Horenstein, RB; Dane, A.; Harms, AC; Ramaker, R; Vreeken, RJ; Perry, CG; Zhu, H.; Sanchez, CL; Kühn, C.; ORTEL, TL


    While aspirin is generally effective for prevention of cardiovascular disease, considerable variation in drug response exists, resulting in some individuals displaying high on-treatment platelet reactivity. We used pharmacometabolomics to define pathways implicated in variation of response to treatment. We profiled serum samples from healthy subjects pre- and postaspirin (14 days, 81 mg/day) using mass spectrometry. We established a strong signature of aspirin exposure independent ...


    The influence of inorganic and organic amendments on the mineralization of ethylene dibromide, p-nitrophenol, phenol, and toluene was examined in subsurface soil samples from a pristine aquifer near Lula, Okla. The responses indicate that the metabolic abilities and nutrient requ...

  11. Stimuli-responsive protamine-based biodegradable nanocapsules for enhanced bioavailability and intracellular delivery of anticancer agents

    Enzyme- and pH-responsive polyelectrolyte nanocapsules having diameters in the range of 200 ± 20 nm were fabricated by means of Layer-by-Layer assembly of biopolymers, protamine, and heparin, and then loaded with anticancer drug doxorubicin. The incorporation of the FDA-approved peptide drug protamine as a wall component rendered the capsules responsive to enzyme stimuli. The stimuli-responsive drug release from these nanocapsules was evaluated, and further modulation of capsule permeability to avoid premature release was demonstrated by crosslinking the wall components. The interaction of the nanocapsules with cancer cells was studied using MCF-7 breast cancer cells. These capsules were readily internalized and disintegrated inside the cells, culminating in the release of the loaded doxorubicin and subsequent cell death as observed by confocal microscopy and MTT Assay. The bioavailability studies performed using BALB/c mice revealed that the encapsulated doxorubicin exhibited enhanced bioavailability compared to free doxorubicin. Our results indicate that this stimuli-responsive system fabricated from clinically used FDA-approved molecules and exhibiting minimal premature release has great potential for drug-delivery applications.

  12. Stimuli-responsive protamine-based biodegradable nanocapsules for enhanced bioavailability and intracellular delivery of anticancer agents

    Radhakrishnan, Krishna; Thomas, Midhun B.; Pulakkat, Sreeranjini [Indian Institute of Science, Department of Materials Engineering (India); Gnanadhas, Divya P.; Chakravortty, Dipshikha [Indian Institute of Science, Department of Microbiology and Cell Biology (India); Raichur, Ashok M., E-mail: [Indian Institute of Science, Department of Materials Engineering (India)


    Enzyme- and pH-responsive polyelectrolyte nanocapsules having diameters in the range of 200 ± 20 nm were fabricated by means of Layer-by-Layer assembly of biopolymers, protamine, and heparin, and then loaded with anticancer drug doxorubicin. The incorporation of the FDA-approved peptide drug protamine as a wall component rendered the capsules responsive to enzyme stimuli. The stimuli-responsive drug release from these nanocapsules was evaluated, and further modulation of capsule permeability to avoid premature release was demonstrated by crosslinking the wall components. The interaction of the nanocapsules with cancer cells was studied using MCF-7 breast cancer cells. These capsules were readily internalized and disintegrated inside the cells, culminating in the release of the loaded doxorubicin and subsequent cell death as observed by confocal microscopy and MTT Assay. The bioavailability studies performed using BALB/c mice revealed that the encapsulated doxorubicin exhibited enhanced bioavailability compared to free doxorubicin. Our results indicate that this stimuli-responsive system fabricated from clinically used FDA-approved molecules and exhibiting minimal premature release has great potential for drug-delivery applications.

  13. On Pearson's X^2 for categorical response variables

    Jeroen Weesie


    In this talk I discuss Pearson's X2 as a measure of goodness of fit for quantal response models, including binary outcome models (logit, probit, gompit), multinomial logistic regression (mlogit) and conditional logistic regression (clogit). Large sample results for X2 have been derived by a.o. McCullagh and Windmeijer. A Stata implementation of the test will be illustrated.

  14. Species response to environmental variables in Ayubia National Park, Pakistan using multivariate analysis

    A study was conducted in Ayubia National Park to explore the species response correlation with environmental gradients. Multivariate Analysis was applied to dataset to quantify the vegetation of study area. Vann Dobben circle analysis and T value Biplot was used with the help of Canonical Correspondence Analysis. Two zones were demarcated in Park. Results showed that Species Plantago major and Thlaspi griffthianum had positive and significant response towards environmental variables and few of species showed negative regression coefficient response to environmental variables. Similarly results of Attribute plot show the species response to particular environmental variable. Dominant spp of Zone 1 Hedera nepalensis showed negative association towards organic matter and Rumex nepalensis dominant species of Zone 2 Rumex nepalensis showed positive and significant response to environmental variables. (author)

  15. Influence of inorganic and organic nutrients on aerobic biodegradation and on the adaptation response of subsurface microbial communities.

    Swindoll, C M; Aelion, C M; Pfaender, F K


    The influence of inorganic and organic amendments on the mineralization of ethylene dibromide, p-nitrophenol, phenol, and toluene was examined in subsurface soil samples from a pristine aquifer near Lula, Okla. The responses indicate that the metabolic abilities and nutrient requirements of groundwater microorganisms vary substantially within an aquifer. In some samples, additions of inorganic nutrients resulted in a more rapid adaptation to the test substrate and a higher rate of metabolism,...

  16. Historical Temperature Variability Affects Coral Response to Heat Stress

    Jessica Carilli; Donner, Simon D.; Hartmann, Aaron C.


    Coral bleaching is the breakdown of symbiosis between coral animal hosts and their dinoflagellate algae symbionts in response to environmental stress. On large spatial scales, heat stress is the most common factor causing bleaching, which is predicted to increase in frequency and severity as the climate warms. There is evidence that the temperature threshold at which bleaching occurs varies with local environmental conditions and background climate conditions. We investigated the influence of...

  17. Acute psychological stress induces short-term variable immune response.

    Breen, Michael S; Beliakova-Bethell, Nadejda; Mujica-Parodi, Lilianne R; Carlson, Joshua M; Ensign, Wayne Y; Woelk, Christopher H; Rana, Brinda K


    In spite of advances in understanding the cross-talk between the peripheral immune system and the brain, the molecular mechanisms underlying the rapid adaptation of the immune system to an acute psychological stressor remain largely unknown. Conventional approaches to classify molecular factors mediating these responses have targeted relatively few biological measurements or explored cross-sectional study designs, and therefore have restricted characterization of stress-immune interactions. This exploratory study analyzed transcriptional profiles and flow cytometric data of peripheral blood leukocytes with physiological (endocrine, autonomic) measurements collected throughout the sequence of events leading up to, during, and after short-term exposure to physical danger in humans. Immediate immunomodulation to acute psychological stress was defined as a short-term selective up-regulation of natural killer (NK) cell-associated cytotoxic and IL-12 mediated signaling genes that correlated with increased cortisol, catecholamines and NK cells into the periphery. In parallel, we observed down-regulation of innate immune toll-like receptor genes and genes of the MyD88-dependent signaling pathway. Correcting gene expression for an influx of NK cells revealed a molecular signature specific to the adrenal cortex. Subsequently, focusing analyses on discrete groups of coordinately expressed genes (modules) throughout the time-series revealed immune stress responses in modules associated to immune/defense response, response to wounding, cytokine production, TCR signaling and NK cell cytotoxicity which differed between males and females. These results offer a spring-board for future research towards improved treatment of stress-related disease including the impact of stress on cardiovascular and autoimmune disorders, and identifies an immune mechanism by which vulnerabilities to these diseases may be gender-specific. PMID:26476140

  18. Glacier response to North Atlantic climate variability during the Holocene

    N. L. Balascio


    Full Text Available Small glaciers and ice caps respond rapidly to climate variations and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland, derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th Century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansions during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a

  19. Variability-based global sensitivity analysis of circuit response

    Opalski, Leszek J.


    The research problem of interest to this paper is: how to determine efficiently and objectively the most and the least influential parameters of a multimodule electronic system - given the system model f and the module parameter variation ranges. The author investigates if existing generic global sensitivity methods are applicable for electronic circuit design, even if they were developed (and successfully applied) in quite distant engineering areas. A photodiode detector analog front-end system response time is used to reveal capability of the selected global sensitivity approaches under study.

  20. Capturing the dynamics of response variability in the brain in ADHD

    Janna van Belle


    Full Text Available ADHD is characterized by increased intra-individual variability in response times during the performance of cognitive tasks. However, little is known about developmental changes in intra-individual variability, and how these changes relate to cognitive performance. Twenty subjects with ADHD aged 7–24 years and 20 age-matched, typically developing controls participated in an fMRI-scan while they performed a go-no-go task. We fit an ex-Gaussian distribution on the response distribution to objectively separate extremely slow responses, related to lapses of attention, from variability on fast responses. We assessed developmental changes in these intra-individual variability measures, and investigated their relation to no-go performance. Results show that the ex-Gaussian measures were better predictors of no-go performance than traditional measures of reaction time. Furthermore, we found between-group differences in the change in ex-Gaussian parameters with age, and their relation to task performance: subjects with ADHD showed age-related decreases in their variability on fast responses (sigma, but not in lapses of attention (tau, whereas control subjects showed a decrease in both measures of variability. For control subjects, but not subjects with ADHD, this age-related reduction in variability was predictive of task performance. This group difference was reflected in neural activation: for typically developing subjects, the age-related decrease in intra-individual variability on fast responses (sigma predicted activity in the dorsal anterior cingulate gyrus (dACG, whereas for subjects with ADHD, activity in this region was related to improved no-go performance with age, but not to intra-individual variability. These data show that using more sophisticated measures of intra-individual variability allows the capturing of the dynamics of task performance and associated neural changes not permitted by more traditional measures.

  1. Testing bronchial hyper-responsiveness: provocation or peak expiratory flow variability?

    Otter, J.J. den; Reijnen, G.M.W.; Bosch, W.J.H.M. van den; van Schayck, C. P.; Molema, J.; van Weel, C


    BACKGROUND: Assessing bronchial hyper-responsiveness (BHR) is a main diagnostic criterion of asthma. Provocation testing is not readily available in general practice, but peak expiratory flow (PEF) is. Several guidelines promote the use of PEF variability as a diagnostic tool for BHR. This study tested the agreement between histamine challenge testing and PEF variability, and the consequences for diagnosing asthma. AIM: To investigate the possibility of assessing BHR by PEF variability, using...

  2. Short term variability in FEV1 and bronchodilator responsiveness in patients with obstructive ventilatory defects.

    Tweeddale, P M; Alexander, F.; McHardy, G J


    Short term variability in FEV1 and responsiveness to inhaled bronchodilator were measured in 150 patients with obstructive ventilatory defects. The range of initial FEV1 was 0.5-4.71 and the natural variability over a 20 minute period when expressed in absolute terms was similar over the entire range, and differed insignificantly from that found in normal subjects. The increase in FEV1 and vital capacity (VC) required to exclude natural variability with 95% confidence in these patients was 16...

  3. Variable Selection for Varying-Coefficient Models with Missing Response at Random

    Pei Xin ZHAO; Liu Gen XUE


    In this paper, we present a variable selection procedure by combining basis function approximations with penalized estimating equations for varying-coefficient models with missing response at random. With appropriate selection of the tuning parameters, we establish the consistency of the variable selection procedure and the optimal convergence rate of the regularized estimators. A simulation study is undertaken to assess the finite sample performance of the proposed variable selection procedure.

  4. A latent class distance association model for cross-classified data with a categorical response variable

    Vera, J.F.; Rooij, M. de; Heiser, W.J.


    In this paper we propose a latent class distance association model for clustering in the predictor space of large contingency tables with a categorical response variable. The rows of such a table are characterized as profiles of a set of explanatory variables, while the columns represent a single ou

  5. A Composite Likelihood Inference in Latent Variable Models for Ordinal Longitudinal Responses

    Vasdekis, Vassilis G. S.; Cagnone, Silvia; Moustaki, Irini


    The paper proposes a composite likelihood estimation approach that uses bivariate instead of multivariate marginal probabilities for ordinal longitudinal responses using a latent variable model. The model considers time-dependent latent variables and item-specific random effects to be accountable for the interdependencies of the multivariate…

  6. Grey water biodegradability.

    Ghunmi, Lina Abu; Zeeman, Grietje; Fayyad, Manar; van Lier, Jules B


    Knowing the biodegradability characteristics of grey water constituents is imperative for a proper design and operation of a biological treatment system of grey water. This study characterizes the different COD fractions of dormitory grey water and investigates the effect of applying different conditions in the biodegradation test. The maximum aerobic and anaerobic biodegradability and conversion rate for the different COD fractions is determined. The results show that, on average, dormitory grey water COD fractions are 28% suspended, 32% colloidal and 40% dissolved. The studied factors incubation time, inoculum addition and temperature are influencing the determined biodegradability. The maximum biodegradability and biodegradation rate differ between different COD fractions, viz. COD(ss), COD(col) and COD(diss). The dissolved COD fraction is characterised by the lowest degradation rate, both for anaerobic and aerobic conditions. The maximum biodegradability for aerobic and anaerobic conditions is 86 and 70% respectively, whereas the first order conversion rate constant, k₂₀, is 0.119 and 0.005 day⁻¹, respectively. The anaerobic and aerobic conversion rates in relation to temperature can be described by the Arrhenius relation, with temperature coefficients of 1.069 and 1.099, respectively. PMID:20658309

  7. Factors influencing crude oil biodegradation by Yarrowia lipolytica

    Tatiana Felix Ferreira; Maria Alice Zarur Coelho; Maria Helena Miguez da Rocha-Leão


    Yarrowia lipolytica is unique strictly aerobic yeast with the ability to efficiently degrade hydrophobic substrates such as n-alkenes, fatty acids, glycerol and oils. In the present work, a 2(4) full factorial design was used to investigate the influence of the independent variables of temperature, agitation, initial cell concentration and initial petroleum concentration on crude oil biodegradation. The results showed that all variables studied had significant effects on the biodegradation pr...


    DEMİR, Rıza; TÜRKMEN, Erman


    Corporate Social Responsibility (CSR) can be defined as operating the organizations responsibly to internal and external environment. In the early 1980’s, CRS used to mean to manage activities of organizations without detriment to parties such as shareholders, employees, consumers and society, now it includes ethical and discretionary (philanthropic) responsibilities. This study aims to examine the perception of employees about corporate social responsibility in terms of demographic variables...

  9. Nile Delta vegetation response to Holocene climate variability

    Bernhardt, Christopher E.; Horton, Benjamin P.; Stanley, Jean-Daniel


    A 7000 yr palynologic record from Burullus Lagoon, Nile Delta, Egypt, is assessed to investigate changes in terrestrial vegetation in response to Nile flow. Previous studies in this region have shown that sea-level rise in the early to mid-Holocene, and markedly increased human land use during the past several centuries, altered vegetation in and around the lagoon. The pollen record from this study documents changes in delta vegetation that likely reflect variations in Nile flow. We suggest that Cyperaceae pollen is a sensitive marker of precipitation over the Nile headwaters and the resultant Nile flow. Decreases in Cyperaceae pollen, interpreted as a marker for diminished Nile flow, as well as the increase in relative abundance of microscopic charcoal, occurred at ca. 6000–5500, ca. 5000, ca. 4200, and ca. 3000 cal. yr B.P. (calibrated years before present). These correspond to extreme regional and global aridity events associated with a more southerly mean position of the Intertropical Convergence Zone. These changes, also recorded by other proxy studies, indicate that several marked regional drought events affected the Nile Delta region and impacted ancient Egyptian and Middle Eastern civilizations.

  10. Variable linesource response in attenuation corrected cardiac SPECT

    Full text: Varying line source response can result in errors due to the reference scan being inappropriate. The incidence of this problem and its effect on cardiac perfusion SPECT was investigated. Acquisitions of transmission data without the bed or a patient were used to determine the variation in global sensitivity and uniformity of the transmission with respect to camera position over a period of 4 months. The average variations for various parameters were: Influence of variations in regional sensitivity on the reconstructed attenuation map and ultimately the patient study was investigated. Counts in selected sections of patient transmission images were reduced by 5 to 30 percent and then reconstructed in the patient study with iterative reconstruction for 30 iterations (Butterworth 0.66 nyquist frequency order 10). The reconstructed scans were compared to the original study which had minimal linesource misalignment and the percentage differences were calculated to determine the effect of regional sensitivity differences with angle. At the level of variation of regional sensitivity (5-10%) it was found data varied by up to 20% in portions of the patient myocardium compared to the original data. Additional line source quality control is essential and variation in transmission counts with rotation minimised. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc

  11. Variable Selection for Semiparametric Varying-Coefficient Partially Linear Models with Missing Response at Random

    Pei Xin ZHAO; Liu Gen XUE


    In this paper,we present a variable selection procedure by combining basis function approximations with penalized estimating equations for semiparametric varying-coefficient partially linear models with missing response at random.The proposed procedure simultaneously selects significant variables in parametric components and nonparametric components.With appropriate selection of the tuning parameters,we establish the consistency of the variable selection procedure and the convergence rate of the regularized estimators.A simulation study is undertaken to assess the finite sample performance of the proposed variable selection procedure.

  12. Variability in Automated Responses of Commercial Buildings and Industrial Facilities to Dynamic Electricity Prices

    Mathieu, Johanna L.; Callaway, Duncan S.; Kiliccote, Sila


    Changes in the electricity consumption of commercial buildings and industrial facilities (C&I facilities) during Demand Response (DR) events are usually estimated using counterfactual baseline models. Model error makes it difficult to precisely quantify these changes in consumption and understand if C&I facilities exhibit event-to-event variability in their response to DR signals. This paper seeks to understand baseline model error and DR variability in C&I facilities facing dynamic electricity prices. Using a regression-based baseline model, we present a method to compute the error associated with estimates of several DR parameters. We also develop a metric to determine how much observed DR variability results from baseline model error rather than real variability in response. We analyze 38 C&I facilities participating in an automated DR program and find that DR parameter errors are large. Though some facilities exhibit real DR variability, most observed variability results from baseline model error. Therefore, facilities with variable DR parameters may actually respond consistently from event to event. Consequently, in DR programs in which repeatability is valued, individual buildings may be performing better than previously thought. In some cases, however, aggregations of C&I facilities exhibit real DR variability, which could create challenges for power system operation.

  13. Biodegradable modified Phba systems

    Compositions as well as production technology of ecologically sound biodegradable multicomponent polymer systems were developed. Our objective was to design some bio plastic based composites with required mechanical properties and biodegradability intended for use as biodegradable packaging. Significant characteristics required for food packaging such as barrier properties (water and oxygen permeability) and influence of γ-radiation on the structure and changes of main characteristics of some modified PHB matrices was evaluated. It was found that barrier properties were plasticizers chemical nature and sterilization with γ-radiation dependent and were comparable with corresponding values of typical polymeric packaging films. Low γ-radiation levels (25 kGy) can be recommended as an effective sterilization method of PHB based packaging materials. Purposely designed bio plastic packaging may provide an alternative to traditional synthetic packaging materials without reducing the comfort of the end-user due to specific qualities of PHB - biodegradability, Biocompatibility and hydrophobic nature

  14. pH-Responsive biodegradable polymeric micelles with anchors to interface magnetic nanoparticles for MR imaging in detection of cerebral ischemic area.

    Yang, Hong Yu; Jang, Moon-Sun; Gao, Guang Hui; Lee, Jung Hee; Lee, Doo Sung


    A novel type of pH-responsive biodegradable copolymer was developed based on methyloxy-poly(ethylene glycol)-block-poly[dopamine-2-(dibutylamino) ethylamine-l-glutamate] (mPEG-b-P(DPA-DE)LG) and applied to act as an intelligent nanocarrier system for magnetic resonance imaging (MRI). The mPEG-b-P(DPA-DE)LG copolymer was synthesized by a typical ring opening polymerization of N-carboxyanhydrides (NCAs-ROP) using mPEG-NH2 as a macroinitiator, and two types of amine-terminated dopamine groups and pH-sensitive ligands were grafted onto a side chain by a sequential aminolysis reaction. This design greatly benefits from the addition of the dopamine groups to facilitate self-assembly, as these groups can act as high-affinity anchors for iron oxide nanoparticles, thereby increasing long-term stability at physiological pH. The mPEG moiety in the copolymers helped the nanoparticles to remain well-dispersed in an aqueous solution, and pH-responsive groups could control the release of hydrophobic Fe3O4 nanoparticles in an acidic environment. The particle size of the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles was measured by dynamic light scattering (DLS) and cryo-TEM. The superparamagnetic properties of the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles were confirmed by a superconducting quantum interference device (SQUID). T2-weighted magnetic resonance imaging (MRI) of Fe3O4-loaded mPEG-b-P(DPA-DE)LG phantoms exhibited enhanced negative contrast with an r2 relaxivity of approximately 106.7 mM(-1) s(-1). To assess the ability of the Fe3O4-loaded mPEG-P(DE-DPA)LG micelles to act as MRI probes, we utilized a cerebral ischemia disease rat model with acidic tissue. We found that a gradual change in contrast in the cerebral ischemic area could be visualized by MRI after 1 h, and maximal signal loss was detected after 24 h post-injection. These results demonstrated that the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles can act as pH-triggered MRI probes for diagnostic imaging of acidic

  15. Response stability and variability induced in humans by different feedback contingenies

    Maes, J.H.R.


    In two experiments, the behavioral effects of different response-feedback contingencies were examined with a task requiring human subjects to repeatedly type three-key sequences on a computer keyboard. In Experiment 1, the subjects first received positive feedback for response variability, followed

  16. Progress of biodegradable metals

    Huafang Li


    Full Text Available Biodegradable metals (BMs are metals and alloys expected to corrode gradually in vivo, with an appropriate host response elicited by released corrosion products, then dissolve completely upon fulfilling the mission to assist with tissue healing with no implant residues. In the present review article, three classes of BMs have been systematically reviewed, including Mg-based, Fe-based and Zn-based BMs. Among the three BM systems, Mg-based BMs, which now have several systems reported the successful of clinical trial results, are considered the vanguards and main force. Fe-based BMs, with pure iron and Fe–Mn based alloys as the most promising, are still on the animal test stage. Zn-based BMs, supposed to have the degradation rate between the fast Mg-based BMs and the slow Fe-based BMs, are a rising star with only several reports and need much further research. The future research and development direction for the BMs are proposed, based on the clinical requirements on controllable degradation rate, prolonged mechanical stability and excellent biocompatibility, by optimization of alloy composition design, regulation on microstructure and mechanical properties, and following surface modification.

  17. Progress of biodegradable metals

    Huafang Li; Yufeng Zheng; Ling Qin


    Biodegradable metals (BMs) are metals and alloys expected to corrode gradually in vivo, with an appropriate host response elicited by released corrosion products, then dissolve completely upon fulfilling the mission to assist with tissue healing with no implant residues. In the present review article, three classes of BMs have been systematically reviewed, including Mg-based, Fe-based and Zn-based BMs. Among the three BM systems, Mg-based BMs, which now have several systems reported the successful of clinical trial results, are considered the vanguards and main force. Fe-based BMs, with pure iron and Fe–Mn based alloys as the most promising, are still on the animal test stage. Zn-based BMs, supposed to have the degradation rate between the fast Mg-based BMs and the slow Fe-based BMs, are a rising star with only several reports and need much further research. The future research and development direction for the BMs are proposed, based on the clinical requirements on controllable degradation rate, prolonged mechanical stability and excellent biocompat-ibility, by optimization of alloy composition design, regulation on microstructure and mechanical properties, and following surface modification.

  18. Green and biodegradable electronics

    Mihai Irimia-Vladu; Eric. D. Głowacki; Gundula Voss; Siegfried Bauer; Niyazi Serdar Sariciftci


    We live in a world where the lifetime of electronics is becoming shorter, now approaching an average of several months. This poses a growing ecological problem. This brief review will present some of the initial steps taken to address the issue of electronic waste with biodegradable organic electronic materials. Many organic materials have been shown to be biodegradable, safe, and nontoxic, including compounds of natural origin. Additionally, the unique features of such organic materials sugg...

  19. Evaluation of response variables in computer-simulated virtual cataract surgery

    Söderberg, Per G.; Laurell, Carl-Gustaf; Simawi, Wamidh; Nordqvist, Per; Skarman, Eva; Nordh, Leif


    We have developed a virtual reality (VR) simulator for phacoemulsification (phaco) surgery. The current work aimed at evaluating the precision in the estimation of response variables identified for measurement of the performance of VR phaco surgery. We identified 31 response variables measuring; the overall procedure, the foot pedal technique, the phacoemulsification technique, erroneous manipulation, and damage to ocular structures. Totally, 8 medical or optometry students with a good knowledge of ocular anatomy and physiology but naive to cataract surgery performed three sessions each of VR Phaco surgery. For measurement, the surgical procedure was divided into a sculpting phase and an evacuation phase. The 31 response variables were measured for each phase in all three sessions. The variance components for individuals and iterations of sessions within individuals were estimated with an analysis of variance assuming a hierarchal model. The consequences of estimated variabilities for sample size requirements were determined. It was found that generally there was more variability for iterated sessions within individuals for measurements of the sculpting phase than for measurements of the evacuation phase. This resulted in larger required sample sizes for detection of difference between independent groups or change within group, for the sculpting phase as compared to for the evacuation phase. It is concluded that several of the identified response variables can be measured with sufficient precision for evaluation of VR phaco surgery.

  20. pH-Responsive biodegradable polymeric micelles with anchors to interface magnetic nanoparticles for MR imaging in detection of cerebral ischemic area

    Yang, Hong Yu; Jang, Moon-Sun; Gao, Guang Hui; Lee, Jung Hee; Lee, Doo Sung


    A novel type of pH-responsive biodegradable copolymer was developed based on methyloxy-poly(ethylene glycol)-block-poly[dopamine-2-(dibutylamino) ethylamine-l-glutamate] (mPEG-b-P(DPA-DE)LG) and applied to act as an intelligent nanocarrier system for magnetic resonance imaging (MRI). The mPEG-b-P(DPA-DE)LG copolymer was synthesized by a typical ring opening polymerization of N-carboxyanhydrides (NCAs-ROP) using mPEG-NH2 as a macroinitiator, and two types of amine-terminated dopamine groups and pH-sensitive ligands were grafted onto a side chain by a sequential aminolysis reaction. This design greatly benefits from the addition of the dopamine groups to facilitate self-assembly, as these groups can act as high-affinity anchors for iron oxide nanoparticles, thereby increasing long-term stability at physiological pH. The mPEG moiety in the copolymers helped the nanoparticles to remain well-dispersed in an aqueous solution, and pH-responsive groups could control the release of hydrophobic Fe3O4 nanoparticles in an acidic environment. The particle size of the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles was measured by dynamic light scattering (DLS) and cryo-TEM. The superparamagnetic properties of the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles were confirmed by a superconducting quantum interference device (SQUID). T2-weighted magnetic resonance imaging (MRI) of Fe3O4-loaded mPEG-b-P(DPA-DE)LG phantoms exhibited enhanced negative contrast with an r2 relaxivity of approximately 106.7 mM-1 s-1. To assess the ability of the Fe3O4-loaded mPEG-P(DE-DPA)LG micelles to act as MRI probes, we utilized a cerebral ischemia disease rat model with acidic tissue. We found that a gradual change in contrast in the cerebral ischemic area could be visualized by MRI after 1 h, and maximal signal loss was detected after 24 h post-injection. These results demonstrated that the Fe3O4-loaded mPEG-b-P(DPA-DE)LG micelles can act as pH-triggered MRI probes for diagnostic imaging of acidic

  1. Spatial Representation and Cognitive Modulation of Response Variability in the Lateral Intraparietal Area Priority Map

    Falkner, Annegret L.; Goldberg, Michael E.; Krishna, B. Suresh


    The lateral intraparietal area (LIP) in the macaque contains a priority-based representation of the visual scene. We previously showed that the mean spike rate of LIP neurons is strongly influenced by spatially wide-ranging surround suppression in a manner that effectively sharpens the priority map. Reducing response variability can also improve the precision of LIP's priority map. We show that when a monkey plans a visually guided delayed saccade with an intervening distractor, variability (...

  2. Study on Short-term Variability of Ship Responses in Waves

    Iseki, Toshio; Nielsen, Ulrik Dam


    Short-term variability of ship responses is investigated from the view point of cross-spectrum analysis. In a steady state condition, it is well known that a certain length of sampled data are required for stable spectral analysis. However, the phase angle of the cross-spectra has not been discus...... concludes that the variability influences the accuracy of the wave buoy analogy....

  3. An adaptive search for the response time variability problem☆

    Salhi, S.; A García-Villoria


    The Response Time Variability Problem (RTVP) is an NP-hard combinatorial scheduling problem, which has recently been reported and formalised in the literature. This problem has a wide range of real-world applications in mixed-model assembly lines, multi-threaded computer systems, broadcast of commercial videotapes and others. The RTVP arises whenever products, clients or jobs need to be sequenced in such a way that the variability in the time between the points at which they receive the neces...

  4. Transmission Shifts Underlie Variability in Population Responses to Yersinia pestis Infection

    Buhnerkempe, Michael G; Eisen, Rebecca J.; Brandon Goodell; Gage, Kenneth L.; Antolin, Michael F.; Webb, Colleen T.


    Host populations for the plague bacterium, Yersinia pestis, are highly variable in their response to plague ranging from near deterministic extinction (i.e., epizootic dynamics) to a low probability of extinction despite persistent infection (i.e., enzootic dynamics). Much of the work to understand this variability has focused on specific host characteristics, such as population size and resistance, and their role in determining plague dynamics. Here, however, we advance the idea that the rel...

  5. Optimization of fresh palm oil mill effluent biodegradation with Aspergillus niger and Trichoderma virens

    Jalaludin Noorbaizura


    Full Text Available In this work, response surface optimization strategy was employed to enhance the biodegradation process of fresh palm oil mill effluent (POME by Aspergillus niger and Trichoderma virens. A central composite design (CCD combined with response surface methodology (RSM were employed to study the effects of three independent variables: inoculum size (%, agitation rate (rpm and temperature (°C on the biodegradation processes and production of biosolids enriched with fungal biomass protein. The results achieved using A. niger were compared to those obtained using T. virens. The optimal conditions for the biodegradation processes in terms of total suspended solids (TSS, turbidity, chemical oxygen demand (COD, specific resistance to filtration (SRF and production of biosolids enriched with fungal biomass protein in fresh POME treated with A. niger and T. virens have been predicted by multiple response optimization and verified experimentally at 19% (v/v inoculum size, 100 rpm, 30.2°C and 5% (v/v inoculum size, 100 rpm, 33.3°C respectively. As disclosed by ANOVA and response surface plots, the effects of inoculum size and agitation rate on fresh POME treatment process by both fungal strains were significant.

  6. Which person variables predict how people benefit from True-False over Constructed Response items?

    Stella Bollmann


    Full Text Available The aim of this study was the investigation of the variable Benefit from TF, which we assumed to be additionally measured when using True-False instead of Constructed Response tests. Subjects who benefit from True-False have an advantage over other subjects in answering Multiple Choice or True-False exams. We expected it to be related to partial knowledge and examined its relation to other personal abilities and traits in a total of n = 106 psychology students. They completed a statistics exam in Constructed Response and True-False format and benefit items were defined as those to which the associated constructed response answer was not correct. Additionally, verbal intelligence and Big 5 measures were obtained. Results confirm the existence of the person variable Benefit from TF and its relation to partial knowledge. Furthermore, benefiters differed from others in conscientiousness and openness to experience variables. However, contrary to expectations, they did not differ in verbal IQ.

  7. Biodegradation of hydrocarbon cuts used for diesel oil formulation

    Penet, S.; Marchal, R.; Monot, F. [Departement de Biotechnologie et Chimie de la Biomasse, Institut Francais de Petrole, Rueil-Malmaison (France); Sghir, A. [Genoscope, CNRS UMR 8030, Structure et Evolution des Genomes, Evry (France)


    The biodegradability of various types of diesel oil (DO), such as straight-run DO, light-cycle DO, hydrocracking DO, Fischer-Tropsch DO and commercial DO, was investigated in biodegradation tests performed in closed-batch systems using two microflorae. The first microflora was an activated sludge from an urban wastewater treatment plant as commonly used in biodegradability tests of commercial products and the second was a microflora from a hydrocarbon-polluted soil with possible specific capacities for hydrocarbon degradation. Kinetics of CO{sub 2} production and extent of DO biodegradation were obtained by chromatographic procedures. Under optimised conditions, the polluted-soil microflora was found to extensively degrade all the DO types tested, the degradation efficiencies being higher than 88%. For all the DOs tested, the biodegradation capacities of the soil microflora were significantly higher than those of the activated sludge. Using both microflora, the extent of biodegradation was highly dependent upon the type of DO used, especially its hydrocarbon composition. Linear alkanes were completely degraded in each test, whereas identifiable branched alkanes such as farnesane, pristane or phytane were degraded to variable extents. Among the aromatics, substituted mono-aromatics were also variably biodegraded. (orig.)

  8. Spectral Kernel Approach to Study Radiative Response of Climate Variables and Interannual Variability of Reflected Solar Spectrum

    Jin, Zhonghai; Wielicki, Bruce A.; Loukachine, Constantin; Charlock, Thomas P.; Young, David; Noeel, Stefan


    The radiative kernel approach provides a simple way to separate the radiative response to different climate parameters and to decompose the feedback into radiative and climate response components. Using CERES/MODIS/Geostationary data, we calculated and analyzed the solar spectral reflectance kernels for various climate parameters on zonal, regional, and global spatial scales. The kernel linearity is tested. Errors in the kernel due to nonlinearity can vary strongly depending on climate parameter, wavelength, surface, and solar elevation; they are large in some absorption bands for some parameters but are negligible in most conditions. The spectral kernels are used to calculate the radiative responses to different climate parameter changes in different latitudes. The results show that the radiative response in high latitudes is sensitive to the coverage of snow and sea ice. The radiative response in low latitudes is contributed mainly by cloud property changes, especially cloud fraction and optical depth. The large cloud height effect is confined to absorption bands, while the cloud particle size effect is found mainly in the near infrared. The kernel approach, which is based on calculations using CERES retrievals, is then tested by direct comparison with spectral measurements from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) (a different instrument on a different spacecraft). The monthly mean interannual variability of spectral reflectance based on the kernel technique is consistent with satellite observations over the ocean, but not over land, where both model and data have large uncertainty. RMS errors in kernel ]derived monthly global mean reflectance over the ocean compared to observations are about 0.001, and the sampling error is likely a major component.

  9. Peri-implant tissue response and biodegradation performance of a Mg-1.0Ca-0.5Sr alloy in rat tibia.

    Berglund, Ida S; Jacobs, Brittany Y; Allen, Kyle D; Kim, Stanley E; Pozzi, Antonio; Allen, Josephine B; Manuel, Michele V


    Biodegradable magnesium (Mg) alloys combine the advantages of traditional metallic implants and biodegradable polymers, having high strength, low density, and a stiffness ideal for bone fracture fixation. A recently developed Mg-Ca-Sr alloy potentially possesses advantageous characteristics over other Mg alloys, such as slower degradation rates and minimal toxicity. In this study, the biocompatibility of this Mg-Ca-Sr alloy was investigated in a rat pin-placement model. Cylindrical pins were inserted in the proximal tibial metaphyses in pre-drilled holes orthogonal to the tibial axis. Implant and bone morphologies were investigated using μCT at 1, 3, and 6weeks after implant placement. At the same time points, the surrounding tissue was evaluated using H&E, TRAP and Goldner's trichrome staining. Although gas bubbles were observed around the degrading implant at early time points, the bone remained intact with no evidence of microfracture. Principle findings also include new bone formation in the area of the implant, suggesting that the alloy is a promising candidate for biodegradable orthopedic implants. PMID:26952400

  10. Variability of visual responses of superior colliculus neurons depends on stimulus velocity.

    Mochol, Gabriela; Wójcik, Daniel K; Wypych, Marek; Wróbel, Andrzej; Waleszczyk, Wioletta J


    Visually responding neurons in the superficial, retinorecipient layers of the cat superior colliculus receive input from two primarily parallel information processing channels, Y and W, which is reflected in their velocity response profiles. We quantified the time-dependent variability of responses of these neurons to stimuli moving with different velocities by Fano factor (FF) calculated in discrete time windows. The FF for cells responding to low-velocity stimuli, thus receiving W inputs, increased with the increase in the firing rate. In contrast, the dynamics of activity of the cells responding to fast moving stimuli, processed by Y pathway, correlated negatively with FF whether the response was excitatory or suppressive. These observations were tested against several types of surrogate data. Whereas Poisson description failed to reproduce the variability of all collicular responses, the inclusion of secondary structure to the generating point process recovered most of the observed features of responses to fast moving stimuli. Neither model could reproduce the variability of low-velocity responses, which suggests that, in this case, more complex time dependencies need to be taken into account. Our results indicate that Y and W channels may differ in reliability of responses to visual stimulation. Apart from previously reported morphological and physiological differences of the cells belonging to Y and W channels, this is a new feature distinguishing these two pathways. PMID:20203179

  11. Schedule-Induced and Operant Mechanisms that Influence Response Variability: A Review and Implications for Future Investigations

    Lee, Ronald; Sturmey, Peter; Fields, Lanny


    Response variability, a fundamental characteristic of behavior, may be in some cases an induced effect of reinforcement schedules. Research on schedule-induced response variability has shown that continuous reinforcement results in less variability than intermittent reinforcement schedules. Studies on the effects of intermittency of reinforcement,…

  12. Green and biodegradable electronics

    Mihai Irimia-Vladu


    Full Text Available We live in a world where the lifetime of electronics is becoming shorter, now approaching an average of several months. This poses a growing ecological problem. This brief review will present some of the initial steps taken to address the issue of electronic waste with biodegradable organic electronic materials. Many organic materials have been shown to be biodegradable, safe, and nontoxic, including compounds of natural origin. Additionally, the unique features of such organic materials suggest they will be useful in biofunctional electronics; demonstrating functions that would be inaccessible for traditional inorganic compounds. Such materials may lead to fully biodegradable and even biocompatible/biometabolizable electronics for many low-cost applications. This review highlights recent progress in these classes of material, covering substrates and insulators, semiconductors, and finally conductors.

  13. System-wide contribution to frequency response from variable speed wind turbines

    Ruttledge, Lisa; Flynn, Damian


    Due to the differing electromechanical characteristics of modern variable speed wind turbines to conventional generators, the provision of ancillary services from wind generation is likely to change the nature of the frequency response of power systems to contingency events. This paper explores the aggregate contribution from wind turbines to the frequency response of future power systems, considering both emulated inertial and governor controls. In particular, the potential issues that may a...

  14. CRMS vegetation analytical team framework: Methods for collection, development, and use of vegetation response variables

    Cretini, Kari F.; Visser, Jenneke M.; Krauss, Ken W.; Steyer, Gregory D.


    This document identifies the main objectives of the Coastwide Reference Monitoring System (CRMS) vegetation analytical team, which are to provide (1) collection and development methods for vegetation response variables and (2) the ways in which these response variables will be used to evaluate restoration project effectiveness. The vegetation parameters (that is, response variables) collected in CRMS and other coastal restoration projects funded under the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) are identified, and the field collection methods for these parameters are summarized. Existing knowledge on community and plant responses to changes in environmental drivers (for example, flooding and salinity) from published literature and from the CRMS and CWPPRA monitoring dataset are used to develop a suite of indices to assess wetland condition in coastal Louisiana. Two indices, the floristic quality index (FQI) and a productivity index, are described for herbaceous and forested vegetation. The FQI for herbaceous vegetation is tested with a long-term dataset from a CWPPRA marsh creation project. Example graphics for this index are provided and discussed. The other indices, an FQI for forest vegetation (that is, trees and shrubs) and productivity indices for herbaceous and forest vegetation, are proposed but not tested. New response variables may be added or current response variables removed as data become available and as our understanding of restoration success indicators develops. Once indices are fully developed, each will be used by the vegetation analytical team to assess and evaluate CRMS/CWPPRA project and program effectiveness. The vegetation analytical teams plan to summarize their results in the form of written reports and/or graphics and present these items to CRMS Federal and State sponsors, restoration project managers, landowners, and other data users for their input.

  15. Editorial: Biodegradable Materials

    Carl Schaschke


    Full Text Available This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment.

  16. Study on Short-term Variability of Ship Responses in Waves

    Nielsen, Ulrik Dam; Iseki, Toshio


    Short-term variability of ship responses is investigated by cross-spectrum analysis. In a steady state condition, it is well known that a certain length of sampled data is required for stable results of the spectral analysis. However, the phase lag between responses, in terms of the phase angle of...... the cross-spectra, has not been discussed in detail. Using long stationary time series, the transition of amplitudes and relative phase angles of the cross-spectra has been investigated by iterative analyzes with a few seconds of time shifting. In the results, the short-term variability of the...... relative phase angle was observed. In effect, the variability may compromise the accuracy of the wave buoy analogy....

  17. Biodegradation of clofibric acid and identification of its metabolites

    Salgado, R. [REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); ESTS-IPS, Escola Superior de Tecnologia de Setubal do Instituto Politecnico de Setubal, Rua Vale de Chaves, Campus do IPS, Estefanilha, 2910-761 Setubal (Portugal); Oehmen, A. [REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Carvalho, G. [REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Instituto de Biologia Experimental e Tecnologica (IBET), Av. da Republica (EAN), 2784-505 Oeiras (Portugal); Noronha, J.P. [REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Reis, M.A.M., E-mail: [REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)


    Graphical abstract: Metabolites produced during clofibric acid biodegradation. Highlights: Black-Right-Pointing-Pointer Clofibric acid is biodegradable. Black-Right-Pointing-Pointer Mainly heterotrophic bacteria degraded the clofibric acid. Black-Right-Pointing-Pointer Metabolites of clofibric acid biodegradation were identified. Black-Right-Pointing-Pointer The metabolic pathway of clofibric acid biodegradation is proposed. - Abstract: Clofibric acid (CLF) is the pharmaceutically active metabolite of lipid regulators clofibrate, etofibrate and etofyllinclofibrate, and it is considered both environmentally persistent and refractory. This work studied the biotransformation of CLF in aerobic sequencing batch reactors (SBRs) with mixed microbial cultures, monitoring the efficiency of biotransformation of CLF and the production of metabolites. The maximum removal achieved was 51% biodegradation (initial CLF concentration = 2 mg L{sup -1}), where adsorption and abiotic removal mechanisms were shown to be negligible, showing that CLF is indeed biodegradable. Tests showed that the observed CLF biodegradation was mainly carried out by heterotrophic bacteria. Three main metabolites were identified, including {alpha}-hydroxyisobutyric acid, lactic acid and 4-chlorophenol. The latter is known to exhibit higher toxicity than the parent compound, but it did not accumulate in the SBRs. {alpha}-Hydroxyisobutyric acid and lactic acid accumulated for a period, where nitrite accumulation may have been responsible for inhibiting their degradation. A metabolic pathway for the biodegradation of CLF is proposed in this study.

  18. Resistance to Change and Preference for Variable versus Fixed Response Sequences

    Arantes, Joana; Berg, Mark E.; Le, Dien; Grace, Randolph C.


    In Experiment 1, 4 pigeons were trained on a multiple chain schedule in which the initial link was a variable-interval (VI) 20-s schedule signalled by a red or green center key, and terminal links required four responses made to the left (L) and/or right (R) keys. In the REPEAT component, signalled by red keylights, only LRLR terminal-link…

  19. Amygdala and heart rate variability responses from listening to emotionally intense parts of a story

    Wallentin, Mikkel; Nielsen, Andreas Højlund; Vuust, Peter;


    . In this fMRI study we investigated BOLD-responses to naturally fluctuating emotions evoked by listening to a story. The emotional intensity profile of the text was found through a rating study. The validity of this profile was supported by heart rate variability (HRV) data showing a significant...

  20. Convergence of Dynamic Vegetation Net Productivity Responses to Precipitation Variability from 10 Years of MODIS EVI

    According to Global Climate Models (GCMs) the occurrence of extreme events of precipitation will be more frequent in the future. Therefore, important challenges arise regarding climate variability, which are mainly related to the understanding of ecosystem responses to changes in precipitation patte...

  1. Does Response Variability Predict Distractibility among Adults with Attention-Deficit/Hyperactivity Disorder?

    Adams, Zachary W.; Roberts, Walter M.; Milich, Richard; Fillmore, Mark T.


    Increased intraindividual variability in response time (RTSD) has been observed reliably in attention-deficit/hyperactivity disorder (ADHD) and has often been used as a measure of inattention. RTSD is assumed to reflect attentional lapses and distractibility, though evidence for the validity of this connection is lacking. We assessed whether RTSD…

  2. Vegetation response to climate variability in India from 2001 to 2010

    Hashimoto, H.; Milesi, C.; Wang, W.; Ganguly, S.; Michaelis, A.; Nemani, R.


    Food supply in India is a critical issue in sustaining a large population, and more accurate predictability of agricultural productivity is necessary for policy makers. After the Green revolution, the productivity in India has increased dramatically, but the leveling-off of the productivity was expected in the near future. Decreasing of ground water was already observed and some climate models predict a higher frequency of drought in the 21st century. For a better understanding of vegetation response to climate change, we analyzed the satellite images of India from 2001 to 2010. MODIS satellite imagery shows high spatial variability in vegetation indices in response to climate variability. In this study we scrutinize the cause and mechanism of the spatial variability in vegetation growth in India. First, we tried to find the corresponding climate variability from re-analysis data (MERRA and NCEP-NCAR reanalysis data) and satellite imagery such as TRMM, GIMMS, and MODIS, as well as interpolated climate observation data (CRU). Although the precipitation variability due to ENSO has the strongest impact on vegetation growth, the other climate variability, such as shortwave radiation, also perturbed the vegetation response to climate changes. Second, we proved our hypothesis explaining the vegetation growth trend by running the Terrestrial Observation and Prediction System (TOPS) model. The model results were compared with satellite images and showed reasonable spatial pattern of net primary production to explain the observed vegetation growth variability to climate change. Those results can contribute to a more profound understanding of the mechanism of vegetation growth in India toward future prediction in food supply.

  3. Computer Optimization of Biodegradable Nanoparticles Fabricated by Dispersion Polymerization.

    Akala, Emmanuel O; Adesina, Simeon; Ogunwuyi, Oluwaseun


    Quality by design (QbD) in the pharmaceutical industry involves designing and developing drug formulations and manufacturing processes which ensure predefined drug product specifications. QbD helps to understand how process and formulation variables affect product characteristics and subsequent optimization of these variables vis-à-vis final specifications. Statistical design of experiments (DoE) identifies important parameters in a pharmaceutical dosage form design followed by optimizing the parameters with respect to certain specifications. DoE establishes in mathematical form the relationships between critical process parameters together with critical material attributes and critical quality attributes. We focused on the fabrication of biodegradable nanoparticles by dispersion polymerization. Aided by a statistical software, d-optimal mixture design was used to vary the components (crosslinker, initiator, stabilizer, and macromonomers) to obtain twenty nanoparticle formulations (PLLA-based nanoparticles) and thirty formulations (poly-ɛ-caprolactone-based nanoparticles). Scheffe polynomial models were generated to predict particle size (nm), zeta potential, and yield (%) as functions of the composition of the formulations. Simultaneous optimizations were carried out on the response variables. Solutions were returned from simultaneous optimization of the response variables for component combinations to (1) minimize nanoparticle size; (2) maximize the surface negative zeta potential; and (3) maximize percent yield to make the nanoparticle fabrication an economic proposition. PMID:26703678

  4. Population variability in biological adaptive responses to DNA damage and the shapes of carcinogen dose-response curves

    Carcinogen dose-response curves for both ionizing radiation and chemicals are typically assumed to be linear at environmentally relevant doses. This assumption is used to ensure protection of the public health in the absence of relevant dose-response data. A theoretical justification for the assumption has been provided by the argument that low dose linearity is expected when an exogenous agent adds to an ongoing endogenous process. Here, we use computational modeling to evaluate (1) how two biological adaptive processes, induction of DNA repair and cell cycle checkpoint control, may affect the shapes of dose-response curves for DNA-damaging carcinogens and (2) how the resulting dose-response behaviors may vary within a population. Each model incorporating an adaptive process was capable of generating not only monotonic dose-responses but also nonmonotonic (J-shaped) and threshold responses. Monte Carlo analysis suggested that all these dose-response behaviors could coexist within a population, as the spectrum of qualitative differences arose from quantitative changes in parameter values. While this analysis is largely theoretical, it suggests that (a) accurate prediction of the qualitative form of the dose-response requires a quantitative understanding of the mechanism (b) significant uncertainty is associated with human health risk prediction in the absence of such quantitative understanding and (c) a stronger experimental and regulatory focus on biological mechanisms and interindividual variability would allow flexibility in regulatory treatment of environmental carcinogens without compromising human health

  5. Inter-individual variability of stone marten behavioral responses to a highway.

    Fernando Ascensão

    Full Text Available Efforts to reduce the negative impacts of roads on wildlife may be hindered if individuals within the population vary widely in their responses to roads and mitigation strategies ignore this variability. This knowledge is particularly important for medium-sized carnivores as they are vulnerable to road mortality, while also known to use available road passages (e.g., drainage culverts for safely crossing highways. Our goal in this study was to assess whether this apparently contradictory pattern of high road-kill numbers associated with a regular use of road passages is attributable to the variation in behavioral responses toward the highway between individuals. We investigated the responses of seven radio-tracked stone martens (Martes foina to a highway by measuring their utilization distribution, response turning angles and highway crossing patterns. We compared the observed responses to simulated movement parameterized by the observed space use and movement characteristics of each individual, but naïve to the presence of the highway. Our results suggested that martens demonstrate a diversity of responses to the highway, including attraction, indifference, or avoidance. Martens also varied in their highway crossing patterns, with some crossing repeatedly at the same location (often coincident with highway passages. We suspect that the response variability derives from the individual's familiarity of the landscape, including their awareness of highway passage locations. Because of these variable yet potentially attributable responses, we support the use of exclusionary fencing to guide transient (e.g., dispersers individuals to existing passages to reduce the road-kill risk.

  6. Deconstructing an Atmospheric Model: Variability and Response, Unstable Periodic Orbits, and the Fluctuation-Dissipation Theorem

    Gritsun, Andrei; Lucarini, Valerio


    Unstable periodic orbits (UPOs) provide the so-called skeletal dynamics of a sufficiently well-behaved chaotic dynamical system and provide a powerful tool for relating the response of the system to its variability. In fact, UPOs constitute natural modes of variability of the system, and resonant behaviour of the response of the system to can be associated to good correspondence between the geometry of one UPO and of the forcing term and between their periodicities. We have here analyzed a simple barotropic model of the atmosphere and constructed and found algorithmically a large number of UPOs. We have then studied the change in the climate resulting from changes in the forcing, in the orography, and in the Eckman friction. The most interesting result is the presence of a strong resonance in the orographic response on time scales of the order of about 3 days, corresponding to forced waves. Interestingly, such a spectral feature is entirely absent from the natural variability of the system and correspond to the excitation of a specific group of UPOs. This clarifies the fact that, as opposed to the case of quasi-equilibrium systems, it is far from obvious to associate forced and free variability in the spirit of the fluctuation-dissipation theorem (FDT). Reassuringly, ysing the complementary point of view of covariant Lyapunov vectors, we discover that the forcing projects substantially in the stable direction of the flow, which is exactly the mathematical setting under which the FDT cannot be applied.

  7. The contribution of interindividual factors to variability of response in transcranial direct current stimulation studies

    Lucia M Li


    Full Text Available There has been an explosion of research using transcranial direct current stimulation (tDCS for investigating and modulating human cognitive and motor function in healthy populations. It has also been used in many studies seeking to improve deficits in disease populations. With the slew of studies reporting ‘promising results’ for everything from motor recovery after stroke to boosting memory function, one could be easily seduced by the idea of tDCS being the next panacea for all neurological ills. However, huge variability exists in the reported effects of tDCS, with great variability in the effect sizes and even contradictory results reported. In this review, we consider the interindividual factors that may contribute to this variability. In particular, we discuss the importance of baseline neuronal state and features, anatomy, age and the inherent variability in the injured brain. We additionally consider how interindividual variability affects the results of motor evoked potential (MEP testing with transcranial magnetic stimulation (TMS, which, in turn, can lead to apparent variability in response to tDCS in motor studies.

  8. Response of fish communities to various environmental variables across multiple spatial scales.

    Kwon, Yong-Su; Li, Fengqing; Chung, Namil; Bae, Mi-Jung; Hwang, Soon-Jin; Byoen, Myeong-Seop; Park, Sang-Jung; Park, Young-Seuk


    A better understanding of the relative importance of different spatial scale determinants on fish communities will eventually increase the accuracy and precision of their bioassessments. Many studies have described the influence of environmental variables on fish communities on multiple spatial scales. However, there is very limited information available on this topic for the East Asian monsoon region, including Korea. In this study, we evaluated the relationship between fish communities and environmental variables at multiple spatial scales using self-organizing map (SOM), random forest, and theoretical path models. The SOM explored differences among fish communities, reflecting environmental gradients, such as a longitudinal gradient from upstream to downstream, and differences in land cover types and water quality. The random forest model for predicting fish community patterns that used all 14 environmental variables was more powerful than a model using any single variable or other combination of environmental variables, and the random forest model was effective at predicting the occurrence of species and evaluating the contribution of environmental variables to that prediction. The theoretical path model described the responses of different species to their environment at multiple spatial scales, showing the importance of altitude, forest, and water quality factors to fish assemblages. PMID:23202766

  9. Response of Fish Communities to Various Environmental Variables across Multiple Spatial Scales

    Sang-Jung Park


    Full Text Available A better understanding of the relative importance of different spatial scale determinants on fish communities will eventually increase the accuracy and precision of their bioassessments. Many studies have described the influence of environmental variables on fish communities on multiple spatial scales. However, there is very limited information available on this topic for the East Asian monsoon region, including Korea. In this study, we evaluated the relationship between fish communities and environmental variables at multiple spatial scales using self-organizing map (SOM, random forest, and theoretical path models. The SOM explored differences among fish communities, reflecting environmental gradients, such as a longitudinal gradient from upstream to downstream, and differences in land cover types and water quality. The random forest model for predicting fish community patterns that used all 14 environmental variables was more powerful than a model using any single variable or other combination of environmental variables, and the random forest model was effective at predicting the occurrence of species and evaluating the contribution of environmental variables to that prediction. The theoretical path model described the responses of different species to their environment at multiple spatial scales, showing the importance of altitude, forest, and water quality factors to fish assemblages.

  10. Plant Functional Variability in Response to Late-Quaternary Climate Change Recorded in Ancient Packrat Middens

    Holmgren, C. A.; Potts, D. L.


    Responses of plant functional traits to environmental variability are of enduring interest because they constrain organism performance and ecosystem function. However, most inferences regarding plant functional trait response to climatic variability have been limited to the modern period. To better understand plant functional response to long-term climate variability and how adjustments in leaf morphology may contribute to patterns of species establishment, persistence, or extirpation, we measured specific leaf area (SLA) from macrofossils preserved in ancient packrat middens collected along the Arizona/New Mexico border, USA. Our record spanned more than 32,000 years and included six woodland and Chihuahuan Desert species: Berberis cf. haematocarpa, Juniperus cf. coahuilensis, Juniperus osteosperma, Larrea tridentata, Prosopis glandulosa and Parthenium incanum. We predicted that regional climatic warming and drying since the late Pleistocene would result in intraspecific decreases in SLA. As predicted, SLA was positively correlated with midden age for three of the six species (L. tridentata, J. osteosperma, B. cf. haematocarpa). SLA was also negatively correlated with December (L. tridentata, J. cf. coahuilensis) or June (B. cf. haematocarpa, J. osteosperma) insolation. A unique record of vegetation community dynamics, plant macrofossils preserved in packrat middens also represent a rich and largely untapped source of information on long-term trends in species functional response to environmental change.

  11. Response variability of frontal eye field neurons modulates with sensory input and saccade preparation but not visual search salience.

    Purcell, Braden A; Heitz, Richard P; Cohen, Jeremiah Y; Schall, Jeffrey D


    Discharge rate modulation of frontal eye field (FEF) neurons has been identified with a representation of visual search salience (physical conspicuity and behavioral relevance) and saccade preparation. We tested whether salience or saccade preparation are evident in the trial-to-trial variability of discharge rate. We quantified response variability via the Fano factor in FEF neurons recorded in monkeys performing efficient and inefficient visual search tasks. Response variability declined following stimulus presentation in most neurons, but despite clear discharge rate modulation, variability did not change with target salience. Instead, we found that response variability was modulated by stimulus luminance and the number of items in the visual field independently of attentional demands. Response variability declined to a minimum before saccade initiation, and presaccadic response variability was directionally tuned. In addition, response variability was correlated with the response time of memory-guided saccades. These results indicate that the trial-by-trial response variability of FEF neurons reflects saccade preparation and the strength of sensory input, but not visual search salience or attentional allocation. PMID:22956785

  12. Characterizing climate predictability and model response variability from multiple initial condition and multi-model ensembles

    Kumar, Devashish


    Climate models are thought to solve boundary value problems unlike numerical weather prediction, which is an initial value problem. However, climate internal variability (CIV) is thought to be relatively important at near-term (0-30 year) prediction horizons, especially at higher resolutions. The recent availability of significant numbers of multi-model (MME) and multi-initial condition (MICE) ensembles allows for the first time a direct sensitivity analysis of CIV versus model response variability (MRV). Understanding the relative agreement and variability of MME and MICE ensembles for multiple regions, resolutions, and projection horizons is critical for focusing model improvements, diagnostics, and prognosis, as well as impacts, adaptation, and vulnerability studies. Here we find that CIV (MICE agreement) is lower (higher) than MRV (MME agreement) across all spatial resolutions and projection time horizons for both temperature and precipitation. However, CIV dominates MRV over higher latitudes generally an...

  13. Responses of Montane Forest to Climate Variability in the Central Himalayas of Nepal

    Janardan Mainali


    Full Text Available Climate changes are having dramatic ecological impacts in mid- to high-latitude mountain ranges where growth conditions are limited by climatic variables such as duration of growing season, moisture, and ambient temperature. We document patterns of forest vegetative response for 5 major alpine forest communities to current climate variability in the central Himalayas of Nepal to provide a baseline for assessment of future changes, as well as offer some insight into the trajectory of these changes over time. We used mean monthly surface air temperature and rainfall and the monthly averaged normalized difference vegetation index (NDVI to compare relative vegetation productivity among forest types and in relation to both climatic variables. Because changes in temperature and precipitation are directly manifested as changes in phenology, we examined current vegetative responses to climate variability in an effort to determine which climate variable is most critical for different alpine forest types. Our results show that correlations differ according to vegetation type and confirm that both precipitation and temperature affect monthly NDVI values, though more significant correlations were found with temperature data. The temperature response was more consistent because at the maximum increased temperatures, there was still an ongoing increase in vegetative vigor. This indicates that temperature is still the major limiting factor for plant growth at higher-elevation sites. This part of the Himalayas has abundant moisture, and some forest types are already saturated in terms of growth in relation to precipitation. Clear increases in productivity are documented on the upper treeline ecotones, and these systems are likely to continue to have increasing growth rates.

  14. Long-term successional forest dynamics: species and community responses to climatic variability

    Kardol, Paul [ORNL; Todd Jr, Donald E [ORNL; Hanson, Paul J [ORNL; Mulholland, Patrick J [ORNL


    Question: Are tree dynamics sensitive to climatic variability, and do tree species differ in their responses to climatic variability? Hence, is vulnerability of forest communities to climatic variability depending on stand composition? Location: Mixed young forest at Walker Branch Watershed near Oak Ridge, East-Tennessee, USA. Methods: Using a long-term data set (1967-2006), we analyzed temporal forest dynamics at the tree and species level, and we analyzed community dynamics for forest stands that different in their initial species composition (i.e., Chestnut Oak, Oak-Hickory, Pine, and Yellow poplar stands). Using summer drought and growing season temperature as defined climate drivers, we evaluated relationships between forest dynamics and climate across levels of organization. Results: Over the 4-decade studied period, forest communities underwent successional change and substantially increased their biomass. Variation in summer drought and growing season temperature contributed to temporal biomass dynamics for some tree species, but not for others. Stand-level responses to climatic variability were shown to be related to responses of specific component species; however, not for Pine stands. Pinus echinata, the dominant species in stands initially identified as Pine stands, decreased over time due to periodical outbreaks of the pine bark beetle (Dendroctonus frontalis). The outbreaks on Walker Branch could not be directly related to climatic conditions. Conclusions: Our results imply that vulnerability of developing forests to predicted climate conditions is stand-type dependent, and hence, is a function of species composition. Autogenic successional processes (or insect outbreaks) were found to prevail over climatic variability in determining long-term forest dynamics for stands dominated by sensitive species, emphasizing the importance of studying interactions between forest succession and climate change.

  15. Decreased reaction time variability is associated with greater cardiovascular responses to acute stress.

    Wawrzyniak, Andrew J; Hamer, Mark; Steptoe, Andrew; Endrighi, Romano


    Cardiovascular (CV) responses to mental stress are prospectively associated with poor CV outcomes. The association between CV responses to mental stress and reaction times (RTs) in aging individuals may be important but warrants further investigation. The present study assessed RTs to examine associations with CV responses to mental stress in healthy, older individuals using robust regression techniques. Participants were 262 men and women (mean age = 63.3 ± 5.5 years) from the Whitehall II cohort who completed a RT task (Stroop) and underwent acute mental stress (mirror tracing) to elicit CV responses. Blood pressure, heart rate, and heart rate variability were measured at baseline, during acute stress, and through a 75-min recovery. RT measures were generated from an ex-Gaussian distribution that yielded three predictors: mu-RT, sigma-RT, and tau-RT, the mean, standard deviation, and mean of the exponential component of the normal distribution, respectively. Decreased intraindividual RT variability was marginally associated with greater systolic (B = -.009, SE = .005, p = .09) and diastolic (B = -.004, SE = .002, p = .08) blood pressure reactivity. Decreased intraindividual RT variability was associated with impaired systolic blood pressure recovery (B = -.007, SE = .003, p = .03) and impaired vagal tone (B = -.0047, SE = .0024, p = .045). Study findings offer tentative support for an association between RTs and CV responses. Despite small effect sizes and associations not consistent across predictors, these data may point to a link between intrinsic neuronal plasticity and CV responses. PMID:26894967

  16. Separation of multiple evoked responses using differential amplitude and latency variability

    Knuth, K H; Bressler, S L; Ding, M; Knuth, Kevin H.; Truccolo, Wilson A.; Bressler, Steven L.; Ding, Mingzhou


    In neuroelectrophysiology one records electric potentials or magnetic fields generated by ensembles of synchronously active neurons in response to externally presented stimuli. These evoked responses are often produced by multiple generators in the presence of ongoing background activity. While source localization techniques or current source density estimation are usually used to identify generators, application of blind source separation techniques to obtain independent components has become more popular. We approach this problem by applying the Bayesian methodology to a more physiologically-realistic source model. As it is generally accepted that single trials vary in amplitude and latency, we incorporate this variability into the model. Rather than making the unrealistic assumption that these cortical components are independent of one another, our algorithm utilizes the differential amplitude and latency variability of the evoked waveforms to identify the cortical components. The algorithm is applied to i...

  17. Comparison between genomic predictions using daughter yield deviation and conventional estimated breeding value as response variables

    Guo, Gang; Lund, Mogens Sandø; Zhang, Y;


    This study compared genomic predictions using conventional estimated breeding values (EBV) and daughter yield deviations (DYD) as response variables based on simulated data. Eight scenarios were simulated in regard to heritability (0.05 and 0.30), number of daughters per sire (30, 100, and unequal...... scenarios, the EBV approach was as effective as or slightly better than the DYD approach at predicting breeding value, dependent on simulated scenarios and statistical models. Applying a Bayesian common prior model (the same prior distribution of marker effect variance) and a linear mixed model (GBLUP), the...... index combining GEBV and PA in most scenarios. These results indicate that EBV can be used as an alternative response variable for genomic prediction....

  18. Land surface phenological response to decadal climate variability across Australia using satellite remote sensing

    M. Broich


    Full Text Available Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative information on phenological cycles and their variability is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually reoccurring patterns. Yet, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e. drylands received much less attention, despite the fact that they cover more than 30% of the global land surface. Here we focused on Australia, the driest inhabited continent with one of the most variable rainfall climates in the world and vast areas of dryland systems. Detailed and internally consistent studies investigating phenological cycles and their response to climate variability across the entire continent designed specifically for Australian dryland conditions are missing. To fill this knowledge gap and to advance phenological research, we used existing methods more effectively to study geographic and climate-driven variability in phenology over Australia. We linked derived phenological metrics with rainfall and the Southern Oscillation Index (SOI. We based our analysis on Enhanced Vegetation Index (EVI data from the MODerate Resolution Imaging Spectroradiometer (MODIS from 2000 to 2013, which included extreme drought and wet years. We conducted a continent-wide investigation of the link between phenology and climate variability and a more detailed investigation over the Murray–Darling Basin (MDB, the primary agricultural area and largest river catchment of Australia. Results showed high inter- and intra-annual variability in phenological cycles. Phenological cycle peaks occurred not only during the austral summer but at any time of the year, and their timing varied by more than a month in

  19. Biodegradation of natural oils in seawater

    Al-Darbi, M.M.; Saeed, N.O.; Islam, M.R. [Dalhousie University, Halifax, NS (Canada). Faculty of Engineering; Lee, K. [Bedford Institute of Oceanography, Dartmouth, NS (Canada)


    Spills of non-petroleum hydrocarbons including oils and fish oils are of environmental concern because of their potential to cause serious effects on marine life and coastal environments. Biodegradation by indigenous microorganisms is an important and potentially ubiquitous process affecting both the chemical composition and physical properties of contaminant oils. Data on the environmental persistence of non-petroleum oils is now required for risk assessments and decision making by spill responders. This article investigates the biodegradability of various vegetable and fish oils under the influence of natural bacteria in seawater. The influence of nutrients and microbial environment on changes in bacterial numbers and the extent and rate of degradation for various test oils (olive, mustard, canola and cod liver oils) were studied over time. Time-series visual and microscopic observations were made to characterize physical changes in the residual oils, formation of floating and precipitate particles, oil droplets and dispersion. The biodegradation process was significantly influenced by environmental conditions, with a higher rate and extent of biodegradation observed in seawater amended with nutrients and wastewater that contained elevated numbers of bacteria and nutrients. It was observed that different oils respond in different rates and extents to biodegradation depending on their stability, viscosity and compositions. All results clearly revealed a significant response of the oil-contaminated samples to both the seawater and wastewater environments. Observations on changes in the physical properties of the residual oil may be important in the context of oil spill response strategies. For example, simple physical recovery methods may be used to recover polymeric lumps at the sea surface. (author)

  20. ltm: An R Package for Latent Variable Modeling and Item Response Analysis

    Dimitris Rizopoulos


    Full Text Available The R package ltm has been developed for the analysis of multivariate dichotomous and polytomous data using latent variable models, under the Item Response Theory approach. For dichotomous data the Rasch, the Two-Parameter Logistic, and Birnbaum's Three-Parameter models have been implemented, whereas for polytomous data Semejima's Graded Response model is available. Parameter estimates are obtained under marginal maximum likelihood using the Gauss-Hermite quadrature rule. The capabilities and features of the package are illustrated using two real data examples.

  1. Arrestin Competition Influences the Kinetics and Variability of the Mammalian Rod's Single-Photon Responses

    Doan, Thuy; Azevedo, Anthony W.; Hurley, James B; Rieke, Fred


    Reliable signal transduction via G-protein coupled receptors requires proper receptor inactivation. For example, signals originating from single rhodopsin molecules vary little from one to the next, requiring reproducible inactivation of rhodopsin by phosphorylation and arrestin binding. We determined how reduced concentrations of rhodopsin kinase (GRK1) and/or arrestin1 influenced the kinetics and variability of the single-photon responses of mouse rods. These experiments revealed that arres...

  2. Eddy heat flux in the Southern Ocean: response to variable wind forcing

    Hogg, Andrew Mcc.; Meredith, Michael P; Blundell, Jeffrey R.; Wilson, Christopher


    We assess the role of time-dependent eddy variability in the Antarctic Circumpolar Current (ACC) in influencing warming of the Southern Ocean. For this, we use an eddy-resolving quasigeostrophic model of the wind-driven circulation, and quantify the response of circumpolar transport, eddy kinetic energy and eddy heat transport to changes in winds. On interannual timescales, the model exhibits the behaviour of an "eddy saturated" ocean state, where increases in wind stress do not signicantly ...

  3. Coccolithophore responses to environmental variability in the South China Sea: species composition and calcite content

    Jin, X. B.; C. L. Liu; Poulton, A. J.; M. H. Dai; X.H. Guo


    Coccolithophore contributions to the global marine carbon cycle are regulated by the calcite content of their scales (coccoliths), and the relative cellular levels of photosynthesis and calcification. All three of these factors vary between coccolithophore species, and with response to the growth environment. Here, water samples were collected in the northern basin of the South China Sea (SCS) during summer 2014 in order to examine how environmental variability influenced species composition ...

  4. Modelling studies on soil-mediated response to acid deposition and climate variability

    Holmberg, Maria


    The impact of acidifying atmospheric precipitation and climate variability on forest soil was studied using three approaches: (i) dynamic process-oriented modelling, (ii) static vulnerability assessment, and (iii) non-linear response pattern identification. The dynamic soil acidification model MIDAS is presented, with applications at the plot and catchment scale in Norway, Sweden and Finland, which show that growing vegetation contributes to soil acidification and which illustrate that the re...

  5. Topographic position modulates the mycorrhizal response of oak trees to interannual rainfall variability

    Querejeta Mercader, José Ignacio; Egerton-Warburton, L. M.; Allen, Michael F.


    California coast live oak (Quercus agrifolia) forms tripartite symbiotic associations with arbuscular (AMF) and ectomycorrhizal (EMF) fungi. We selected oak individuals differing in topographic position and depth to groundwater (mesic valley vs. xeric hill sites) to investigate changes of tree mycorrhizal status in response to interannual rainfall variability. EMF root colonization, as well as hyphal abundance and viability in upper rhizosphere soil (0–30 cm), were negatively affected by seve...

  6. Responses of the circumpolar boreal forest to 20th century climate variability

    We examined relationships between tree ring-width and climate at 232 sites around the circumpolar boreal forest to explore variability in two types of response to temperature: a browning response characterized by inverse correlations between growth and temperature, and a greening response characterized by positive correlations between growth and temperature. We used moving-window correlation analysis for eight 30-year time windows, lagged by 10 years, to characterize the climate response at each site from 1902 to 2002. Inverse growth responses to temperature were widespread, occurring in all species, all time periods, and in nearly all geographic areas. The frequency of the browning response increased after 1942, while the frequency of the greening response declined. Browning was concentrated in five species (Picea abies, Picea glauca, Picea mariana, Picea obovata and Pinus banksiana), and occurred more frequently in the warmer parts of species' ranges, suggesting that direct temperature stress might be a factor. In some species, dry sites were also more likely to experience browning; moisture stress might thus be an additional explanation in some cases. As inverse responses to temperature are widespread, and occur in a broad array of species, there is unlikely to be any single explanation for their occurrence

  7. Mass Market Demand Response and Variable Generation Integration Issues: A Scoping Study

    Cappers, Peter; Mills, Andrew; Goldman, Charles; Wiser, Ryan; Eto, Joseph H.


    This scoping study focuses on the policy issues inherent in the claims made by some Smart Grid proponents that the demand response potential of mass market customers which is enabled by widespread implementation of Advanced Metering Infrastructure (AMI) through the Smart Grid could be the “silver bullet” for mitigating variable generation integration issues. In terms of approach, we will: identify key issues associated with integrating large amounts of variable generation into the bulk power system; identify demand response opportunities made more readily available to mass market customers through widespread deployment of AMI systems and how they can affect the bulk power system; assess the extent to which these mass market Demand Response (DR) opportunities can mitigate Variable Generation (VG) integration issues in the near-term and what electricity market structures and regulatory practices could be changed to further expand the ability for DR to mitigate VG integration issues over the long term; and provide a qualitative comparison of DR and other approaches to mitigate VG integration issues.

  8. A case study of alternative site response explanatory variables in Parkfield, California

    Thompson, E.M.; Baise, L.G.; Kayen, R.E.; Morgan, E.C.; Kaklamanos, J.


    The combination of densely-spaced strong-motion stations in Parkfield, California, and spectral analysis of surface waves (SASW) profiles provides an ideal dataset for assessing the accuracy of different site response explanatory variables. We judge accuracy in terms of spatial coverage and correlation with observations. The performance of the alternative models is period-dependent, but generally we observe that: (1) where a profile is available, the square-root-of-impedance method outperforms VS30 (average S-wave velocity to 30 m depth), and (2) where a profile is unavailable, the topographic-slope method outperforms surficial geology. The fundamental site frequency is a valuable site response explanatory variable, though less valuable than VS30. However, given the expense and difficulty of obtaining reliable estimates of VS30 and the relative ease with which the fundamental site frequency can be computed, the fundamental site frequency may prove to be a valuable site response explanatory variable for many applications. ?? 2011 ASCE.

  9. Variability in the Responsiveness to Low-Dose Aspirin: Pharmacological and Disease-Related Mechanisms

    Bianca Rocca


    Full Text Available The main pharmacological aspects of pharmacodynamics (PD and pharmacokinetics (PK of aspirin as antiplatelet agent were unravelled between the late sixties and the eighties, and low-dose aspirin given once daily has been shown to be a mainstay in the current treatment and prevention of cardiovascular disorders. Nevertheless, several PD and PK aspects of aspirin in selected clinical conditions have recently emerged and deserve future clinical attention. In 1994, the term “aspirin resistance” was used for the first time, but, until now, no consensus exists on definition, standardized assay, underlying mechanisms, clinical impact, and possible efficacy of alternative therapeutic interventions. At variance with an undefined aspirin-resistant status, in the last 5 years, the concept of variability in response to aspirin due to specific pathophysiological mechanisms and based on PK and/or PD of the drug has emerged. This growing evidence highlights the existence and possible clinical relevance of an interindividual variability of pharmacological aspirin response and calls for new, large studies to test new low-dose aspirin-based regimens which may ameliorate platelet acetylation, reduce variability in drug responsiveness, and improve clinical efficacy on selected populations.

  10. Absorbable and biodegradable polymers

    Shalaby, Shalaby W


    INTRODUCTION NOTES: Absorbable/Biodegradable Polymers: Technology Evolution. DEVELOPMENT AND APPLICATIONOF NEW SYSTEMS: Segmented Copolyesters with Prolonged Strength Retention Profiles. Polyaxial Crystalline Fiber-Forming Copolyester. Polyethylene Glycol-Based Copolyesters. Cyanoacrylate-Based Systems as Tissue Adhesives. Chitosan-Based Systems. Hyaluronic Acid-Based Systems. DEVELOPMENTS IN PREPARATIVE, PROCESSING, AND EVALUATION METHODS: New Approaches to the Synthesis of Crystalline. Fiber-Forming Aliphatic Copolyesters. Advances in Morphological Development to Tailor the Performance of Me

  11. A general approach to simultaneous model fitting and variable elimination in response models for biological data with many more variables than observations

    Kiiveri Harri T


    Full Text Available Abstract Background With the advent of high throughput biotechnology data acquisition platforms such as micro arrays, SNP chips and mass spectrometers, data sets with many more variables than observations are now routinely being collected. Finding relationships between response variables of interest and variables in such data sets is an important problem akin to finding needles in a haystack. Whilst methods for a number of response types have been developed a general approach has been lacking. Results The major contribution of this paper is to present a unified methodology which allows many common (statistical response models to be fitted to such data sets. The class of models includes virtually any model with a linear predictor in it, for example (but not limited to, multiclass logistic regression (classification, generalised linear models (regression and survival models. A fast algorithm for finding sparse well fitting models is presented. The ideas are illustrated on real data sets with numbers of variables ranging from thousands to millions. R code implementing the ideas is available for download. Conclusion The method described in this paper enables existing work on response models when there are less variables than observations to be leveraged to the situation when there are many more variables than observations. It is a powerful approach to finding parsimonious models for such datasets. The method is capable of handling problems with millions of variables and a large variety of response types within the one framework. The method compares favourably to existing methods such as support vector machines and random forests, but has the advantage of not requiring separate variable selection steps. It is also works for data types which these methods were not designed to handle. The method usually produces very sparse models which make biological interpretation simpler and more focused.

  12. Behavioral variability, elimination of responses, and delay-of-reinforcement gradients in SHR and WKY rats

    Killeen Peter R


    Full Text Available Abstract Background Attention-deficit/hyperactivity disorder (ADHD is characterized by a pattern of inattention, hyperactivity, and impulsivity that is cross-situational, persistent, and produces social and academic impairment. Research has shown that reinforcement processes are altered in ADHD. The dynamic developmental theory has suggested that a steepened delay-of-reinforcement gradient and deficient extinction of behavior produce behavioral symptoms of ADHD and increased behavioral variability. Method The present study investigated behavioral variability and elimination of non-target responses during acquisition in an animal model of ADHD, the spontaneously hypertensive rat (SHR, using Wistar Kyoto (WKY rats as controls. The study also aimed at providing a novel approach to measuring delay-of-reinforcement gradients in the SHR and the WKY strains. The animals were tested in a modified operant chamber presenting 20 response alternatives. Nose pokes in a target hole produced water according to fixed interval (FI schedules of reinforcement, while nose pokes in the remaining 19 holes either had no consequences or produced a sound or a short flickering of the houselight. The stimulus-producing holes were included to test whether light and sound act as sensory reinforcers in SHR. Data from the first six sessions testing FI 1 s were used for calculation of the initial distribution of responses. Additionally, Euclidean distance (measured from the center of each hole to the center of the target hole and entropy (a measure of variability were also calculated. Delay-of-reinforcement gradients were calculated across sessions by dividing the fixed interval into epochs and determining how much reinforcement of responses in one epoch contributed to responding in the next interval. Results Over the initial six sessions, behavior became clustered around the target hole. There was greater initial variability in SHR behavior, and slower elimination of

  13. Comparative Study on Response Surfaces for Reliability Analysis of Spatially Variable Soil Slope

    李亮; 褚雪松


    This paper focuses on the performance of the second-order polynomial-based response surfaces on the reliability of spatially variable soil slope. A single response surface constructed to approximate the slope system failure performance functionG(X) (called single RS) and multiple response surfaces constructed on finite number of slip surfaces (called multiple RS) are developed, respectively. Single RS and multiple RS are applied to evaluate the system failure probability pf for a cohesive soil slope together with Monte Carlo simulation (MCS). It is found thatpf calculated by single RS deviates significantly from that obtained by searching a large number of potential slip surfaces, and this deviation becomes insignificant with the decrease of the number of random variables or the increase of the scale of fluctuation. In other words, single RS cannot approximateG(X) with reasonable accuracy. The value ofpf from multiple response surfaces fits well with that obtained by searching a large number of potential slip surfaces. That is, multiple RS can estimateG(X) with reasonable accuracy.

  14. Variable postpartum responsiveness among humans and other primates with "cooperative breeding": A comparative and evolutionary perspective.

    Hrdy, Sarah B


    This article is part of a Special Issue "Parental Care".Until recently, evolutionists reconstructing mother-infant bonding among human ancestors relied on nonhuman primate models characterized by exclusively maternal care, overlooking the highly variable responsiveness exhibited by mothers in species with obligate reliance on allomaternal care and provisioning. It is now increasingly recognized that apes as large-brained, slow maturing, and nutritionally dependent for so long as early humans were, could not have evolved unless "alloparents" (group members other than genetic parents), in addition to parents, had helped mothers to care for and provision offspring, a rearing system known as "cooperative breeding." Here I review situation-dependent maternal responses ranging from highly possessive to permissive, temporarily distancing, rejecting, or infanticidal, documented for a small subset of cooperatively breeding primates. As in many mammals, primate maternal responsiveness is influenced by physical condition, endocrinological priming, prior experience and local environments (especially related to security). But mothers among primates who evolved as cooperative breeders also appear unusually sensitive to cues of social support. In addition to more "sapient" or rational decision-making, humankind's deep history of cooperative breeding must be considered when trying to understand the extremely variable responsiveness of human mothers. PMID:26518662

  15. Low voltage RF MEMS variable capacitor with linear C-V response

    Elshurafa, Amro M.


    An RF MEMS variable capacitor, fabricated in the PolyMUMPS process and tuned electrostatically, possessing a linear capacitance-voltage response is reported. The measured quality factor of the device was 17 at 1GHz, while the tuning range was 1.2:1 and was achieved at an actuation DC voltage of 8V only. Further, the linear regression coefficient was 0.98. The variable capacitor was created such that it has both vertical and horizontal capacitances present. As the top suspended plate moves towards the bottom fixed plate, the vertical capacitance increases whereas the horizontal capacitance decreases simultaneously such that the sum of the two capacitances yields a linear capacitance-voltage relation. © 2012 The Institution of Engineering and Technology.

  16. Monsoonal variability in abiotic parameters in coastal waters off Trivandrum evokes press and pulse response in biotic variables

    Subina, N.S.; Bhosle, S.; Nair, S.; Lokabharathi, P.A.

    ANOVA showed significant variation in environmental parameters with time during monsoon. Principal component analysis of the abiotic variables revealed salinity, nitrite and nitrate to be the three driving attributes of the coastal waters during...

  17. Complex response of white pines to past environmental variability increases understanding of future vulnerability.

    Virginia Iglesias

    Full Text Available Ecological niche models predict plant responses to climate change by circumscribing species distributions within a multivariate environmental framework. Most projections based on modern bioclimatic correlations imply that high-elevation species are likely to be extirpated from their current ranges as a result of rising growing-season temperatures in the coming decades. Paleoecological data spanning the last 15,000 years from the Greater Yellowstone region describe the response of vegetation to past climate variability and suggest that white pines, a taxon of special concern in the region, have been surprisingly resilient to high summer temperature and fire activity in the past. Moreover, the fossil record suggests that winter conditions and biotic interactions have been critical limiting variables for high-elevation conifers in the past and will likely be so in the future. This long-term perspective offers insights on species responses to a broader range of climate and associated ecosystem changes than can be observed at present and should be part of resource management and conservation planning for the future.

  18. Biodegradation of halogenated organic compounds.

    Chaudhry, G R; Chapalamadugu, S


    In this review we discuss the degradation of chlorinated hydrocarbons by microorganisms, emphasizing the physiological, biochemical, and genetic basis of the biodegradation of aliphatic, aromatic, and polycyclic compounds. Many environmentally important xenobiotics are halogenated, especially chlorinated. These compounds are manufactured and used as pesticides, plasticizers, paint and printing-ink components, adhesives, flame retardants, hydraulic and heat transfer fluids, refrigerants, solvents, additives for cutting oils, and textile auxiliaries. The hazardous chemicals enter the environment through production, commercial application, and waste. As a result of bioaccumulation in the food chain and groundwater contamination, they pose public health problems because many of them are toxic, mutagenic, or carcinogenic. Although synthetic chemicals are usually recalcitrant to biodegradation, microorganisms have evolved an extensive range of enzymes, pathways, and control mechanisms that are responsible for catabolism of a wide variety of such compounds. Thus, such biological degradation can be exploited to alleviate environmental pollution problems. The pathways by which a given compound is degraded are determined by the physical, chemical, and microbiological aspects of a particular environment. By understanding the genetic basis of catabolism of xenobiotics, it is possible to improve the efficacy of naturally occurring microorganisms or construct new microorganisms capable of degrading pollutants in soil and aquatic environments more efficiently. Recently a number of genes whose enzyme products have a broader substrate specificity for the degradation of aromatic compounds have been cloned and attempts have been made to construct gene cassettes or synthetic operons comprising these degradative genes. Such gene cassettes or operons can be transferred into suitable microbial hosts for extending and custom designing the pathways for rapid degradation of recalcitrant

  19. Large-basin hydrological response to climate model outputs: uncertainty caused by the internal atmospheric variability

    A. Gelfan


    Full Text Available An approach is proposed to assess hydrological simulation uncertainty originating from internal atmospheric variability. The latter is one of three major factors contributing to the uncertainty of simulated climate change projections (along with so-called "forcing" and "climate model" uncertainties. Importantly, the role of the internal atmospheric variability is the most visible over the spatial–temporal scales of water management in large river basins. The internal atmospheric variability is represented by large ensemble simulations (45 members with the ECHAM5 atmospheric general circulation model. The ensemble simulations are performed using identical prescribed lower boundary conditions (observed sea surface temperature, SST, and sea ice concentration, SIC, for 1979–2012 and constant external forcing parameters but different initial conditions of the atmosphere. The ensemble of the bias-corrected ECHAM5-outputs as well as ensemble averaged ECHAM5-output are used as the distributed input for ECOMAG and SWAP hydrological models. The corresponding ensembles of runoff hydrographs are calculated for two large rivers of the Arctic basin: the Lena and the Northern Dvina rivers. A number of runoff statistics including the mean and the SD of the annual, monthly and daily runoff, as well as the annual runoff trend are assessed. The uncertainties of runoff statistics caused by the internal atmospheric variability are estimated. It is found that the uncertainty of the mean and SD of the runoff has a distinguished seasonal dependence with maximum during the periods of spring-summer snowmelt and summer-autumn rainfall floods. A noticeable non-linearity of the hydrological models' response to the ensemble ECHAM5 output is found most strongly expressed for the Northern Dvine River basin. It is shown that the averaging over ensemble members effectively filters stochastic term related to internal atmospheric variability. The simulated trends are close to

  20. Which person variables predict how people benefit from True-False over Constructed Response items?

    Stella Bollmann; Eva Böbel; Moritz Heene


    The aim of this study was the investigation of the variable Benefit from TF, which we assumed to be additionally measured when using True-False instead of Constructed Response tests. Subjects who benefit from True-False have an advantage over other subjects in answering Multiple Choice or True-False exams. We expected it to be related to partial knowledge and examined its relation to other personal abilities and traits in a total of n = 106 psychology students. They completed a statistics exa...

  1. Pastoral mobility as a response to climate variability in African drylands

    Adriansen, Hanne Kirstine


    The article outlines aspects of ‘the new paradigm’ for dryland ecosystems and pastoral production systems. Rationality of pastoralism was claimed by parts of the research community for decades, but especially among policy and development planners pastoralism was perceived as an irrational and des...... West Africa. In an example from Ferlo, Senegal, different types of pastoral mobility are discussed with special focus on the importance of scale. It is concluded that pastoral mobility is a rational response to climate variability and unpredictability in African drylands....

  2. Hair follicle response to the variable l.e.t. of a helium ion beam

    A homogeneous population of hair follicles in the rat tail has been used to analyse the in vivo response of a biological system to heavy particle irradiation. The conical configuration of the rat tail gives rise to a variable energy degradation of the beam thus yielding information on the damage elicited by the increasing l.e.t. of the helium beam at different sites on the same sample. By means of scanning electron microscopy three different zones were observed as direct evidence of helium ion penetration in the tail. Quantitative evaluation of radiation damage yielded results concerning hair follicle damage after increasing doses for different regions of the ionization curve. (author)

  3. Highly variable response to cytotoxic chemotherapy in carcinoma-associated fibroblasts (CAFs) from lung and breast

    Carcinoma-associated fibroblasts (CAFs) can promote carcinogenesis and tumor progression. Only limited data on the response of CAFs to chemotherapy and their potential impact on therapy outcome are available. This study was undertaken to analyze the influence of chemotherapy on carcinoma-associated fibroblasts (CAFs) in vitro and in vivo. The in vivo response of stromal cells to chemotherapy was investigated in 22 neoadjuvant treated breast tumors on tissue sections before and after chemotherapy. Response to chemotherapy was analyzed in vitro in primary cultures of isolated CAFs from 28 human lung and 9 breast cancer tissues. The response was correlated to Mdm2, ERCC1 and TP53 polymorphisms and TP53 mutation status. Additionally, the cytotoxic effects were evaluated in an ex vivo experiment using cultured tissue slices from 16 lung and 17 breast cancer specimens. Nine of 22 tumors showed a therapy-dependent reduction of stromal activity. Pathological response of tumor or stroma cells did not correlate with clinical response. Isolated CAFs showed little sensitivity to paclitaxel. In contrast, sensitivity of CAFs to cisplatinum was highly variable with a GI50 ranging from 2.8 to 29.0 μM which is comparable to the range observed in tumor cell lines. No somatic TP53 mutation was detected in any of the 28 CAFs from lung cancer tissue. In addition, response to cisplatinum was not significantly associated with the genotype of TP53 nor Mdm2 and ERCC1 polymorphisms. However, we observed a non-significant trend towards decreased sensitivity in the presence of TP53 variant genotype. In contrast to the results obtained in isolated cell culture, in tissue slice culture breast cancer CAFs responded to paclitaxel within their microenvironment in the majority of cases (9/14). The opposite was observed in lung cancer tissues: only few CAFs were sensitive to cisplatinum within their microenvironment (2/15) whereas a higher proportion responded to cisplatinum in isolated culture

  4. Development and Validation of Culture-Specific Variable Response Inconsistency and True Response Inconsistency Scales for Use with the Korean MMPI-2

    Ketterer, Holly L.; Han, Kyunghee; Hur, Jaehong; Moon, Kyungjoo


    In response to the concern that Minnesota Multiphasic Personality Inventory-2 (MMPI-2; J. N. Butcher, W. Dahlstrom, J. R. Graham, A. Tellegen, & B. Kaemmer, 1989; J. N. Butcher et al., 2001) Variable Response Inconsistency (VRIN) and True Response Inconsistency (TRIN) score invalidity criteria recommended for use with American samples results in…

  5. Time Course and Variability of Polycythemic Response in Men at High Altitude

    Grover, R. F.; Seiland, M.; McCullough, R. G.; Greenleaf, J. E.; Dahms, T. E.; Wolfel, E.; Reeves, J. T.


    Ten young men were exposed to 4,300 m (PB 460 Torr) for three weeks. Plasma volume (PV, Evans Blue dye). and blood volume (BV, carbon monoxide) measured simultaneously, and red cell volume (RCV) calculated from hematocrit, were determined twice at sea level and after 9-11 and 19-20 days at high altitude. After 19-20 days. half the subjects increased RCV +19.4 +/- 1.8% (paltitude. Consequently, compared with sea level values, BV was unchanged (-3.1 +/- 1.8%) in the group with increased RCV, but BV decreased significantly (-12.2 +/- 1.4%, p<0.05) in the other group. Variability in RCV response was not explained by differences, in hypoxemic stimulus or the erythropoictin and reticulocyte responses. Since RCV reflects the balance between red cell. production and destruction, accelerated red cell destruction may have occurred in those individuals with no net change in RCV.

  6. Wintertime atmospheric response to Atlantic multidecadal variability: effect of stratospheric representation and ocean-atmosphere coupling

    Peings, Yannick; Magnusdottir, Gudrun


    The impact of the Atlantic multidecadal variability (AMV) on the wintertime atmosphere circulation is investigated using three different configurations of the Community Atmospheric Model version 5 (CAM5). Realistic SST and sea ice anomalies associated with the AMV in observations are prescribed in CAM5 (low-top model) and WACCM5 (high-top model) to assess the dependence of the results on the representation of the stratosphere. In a third experiment, the role of ocean-atmosphere feedback is investigated by coupling CAM5 to a slab-ocean model in which the AMV forcing is prescribed through oceanic heat flux anomalies. The three experiments give consistent results concerning the response of the NAO in winter, with a negative NAO signal in response to a warming of the North Atlantic ocean. This response is found in early winter when the high-top model is used, and in late winter with the low-top model. With the slab-ocean, the negative NAO response is more persistent in winter and shifted eastward over the continent due to the damping of the atmospheric response over the North Atlantic ocean. Additional experiments suggest that both tropical and extratropical SST anomalies are needed to obtain a significant modulation of the NAO, with small influence of sea ice anomalies. Warm tropical SST anomalies induce a northward shift of the ITCZ and a Rossby-wave response that is reinforced in the mid-latitudes by the extratropical SST anomalies through eddy-mean flow interactions. This modeling study supports that the positive phase of the AMV promotes the negative NAO in winter, while illustrating the impacts of the stratosphere and of the ocean-atmosphere feedbacks in the spatial pattern and timing of this response.

  7. Ecosystem responses to recent oceanographic variability in high-latitude Northern Hemisphere ecosystems

    Mueter, Franz J.; Broms, Cecilie; Drinkwater, Kenneth F.; Friedland, Kevin D.; Hare, Jonathan A.; Hunt, George L., Jr.; Melle, Webjørn; Taylor, Maureen


    As part of the international MENU collaboration, we compared and contrasted ecosystem responses to climate-forced oceanographic variability across several high latitude regions of the North Pacific (Eastern Bering Sea (EBS) and Gulf of Alaska (GOA)) and North Atlantic Oceans (Gulf of Maine/Georges Bank (GOM/GB) and the Norwegian/Barents Seas (NOR/BAR)). Differences in the nitrate content of deep source waters and incoming solar radiation largely explain differences in average primary productivity among these ecosystems. We compared trends in productivity and abundance at various trophic levels and their relationships with sea-surface temperature. Annual net primary production generally increases with annual mean sea-surface temperature between systems and within the EBS, BAR, and GOM/GB. Zooplankton biomass appears to be controlled by both top-down (predation by fish) and bottom-up forcing (advection, SST) in the BAR and NOR regions. In contrast, zooplankton in the GOM/GB region showed no evidence of top-down forcing but appeared to control production of major fish populations through bottom-up processes that are independent of temperature variability. Recruitment of several fish stocks is significantly and positively correlated with temperature in the EBS and BAR, but cod and pollock recruitment in the EBS has been negatively correlated with temperature since the 1977 shift to generally warmer conditions. In each of the ecosystems, fish species showed a general poleward movement in response to warming. In addition, the distribution of groundfish in the EBS has shown a more complex, non-linear response to warming resulting from internal community dynamics. Responses to recent warming differ across systems and appear to be more direct and more pronounced in the higher latitude systems where food webs and trophic interactions are simpler and where both zooplankton and fish species are often limited by cold temperatures.

  8. Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability

    Zhang, Jinlun; Steele, Michael; Schweiger, Axel


    Numerical experiments are conducted to project arctic sea ice responses to varying levels of future anthropogenic warming and climate variability over 2010-2050. A summer ice-free Arctic Ocean is likely by the mid-2040s if arctic surface air temperature (SAT) increases 4°C by 2050 and climate variability is similar to the past relatively warm two decades. If such a SAT increase is reduced by one-half or if a future Arctic experiences a range of SAT fluctuation similar to the past five decades, a summer ice-free Arctic Ocean would be unlikely before 2050. If SAT increases 4°C by 2050, summer ice volume decreases to very low levels (10-37% of the 1978-2009 summer mean) as early as 2025 and remains low in the following years, while summer ice extent continues to fluctuate annually. Summer ice volume may be more sensitive to warming while summer ice extent more sensitive to climate variability. The rate of annual mean ice volume decrease relaxes approaching 2050. This is because, while increasing SAT increases summer ice melt, a thinner ice cover increases winter ice growth. A thinner ice cover also results in a reduced ice export, which helps to further slow ice volume loss. Because of enhanced winter ice growth, arctic winter ice extent remains nearly stable and therefore appears to be a less sensitive climate indicator.

  9. Variable selection for distribution-free models for longitudinal zero-inflated count responses.

    Chen, Tian; Wu, Pan; Tang, Wan; Zhang, Hui; Feng, Changyong; Kowalski, Jeanne; Tu, Xin M


    Zero-inflated count outcomes arise quite often in research and practice. Parametric models such as the zero-inflated Poisson and zero-inflated negative binomial are widely used to model such responses. Like most parametric models, they are quite sensitive to departures from assumed distributions. Recently, new approaches have been proposed to provide distribution-free, or semi-parametric, alternatives. These methods extend the generalized estimating equations to provide robust inference for population mixtures defined by zero-inflated count outcomes. In this paper, we propose methods to extend smoothly clipped absolute deviation (SCAD)-based variable selection methods to these new models. Variable selection has been gaining popularity in modern clinical research studies, as determining differential treatment effects of interventions for different subgroups has become the norm, rather the exception, in the era of patent-centered outcome research. Such moderation analysis in general creates many explanatory variables in regression analysis, and the advantages of SCAD-based methods over their traditional counterparts render them a great choice for addressing this important and timely issues in clinical research. We illustrate the proposed approach with both simulated and real study data. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26844819

  10. Application and Refinement of a Method to Achieve Uniform Convective Response on Variable-Resolution Meshes

    Walko, R. L.; Medvigy, D.; Avissar, R.


    Variable-resolution computational grids can substantially improve the benefit-to-cost ratio in many environmental modeling applications, but they can also introduce unwanted and unrealistic numerical anomalies if not properly utilized. For example, we showed in previous studies that resolved (non-parameterized) atmospheric convection develops more quickly as resolution increases. Furthermore, on variable grids that transition from resolved to parameterized convection, timing and intensity of the convection in both regimes is generally disparate unless special care is taken to tune the parameterization. In both cases, the convection that develops first (due to purely numerical reasons) tends to suppress convection elsewhere by inducing subsidence in the surrounding environment. This highly nonlinear competition, while desirable when induced by natural causes such as surface inhomogeneity, is highly undesirable when it is a numerical artifact of variable grid resolution and/or selective application of convective parameterization. Our current research is aimed at leveling the playing field for convection across a variable resolution grid so that the above problems are avoided. The underlying idea is to apply the same or very similar 'convective machinery' to all areas of the grid. For convection-resolving regions of the grid, this machinery is simply the model grid itself, along with explicit representation of dynamics and a bulk microphysics parameterization. For coarser regions of the grid, the local environment is sampled from one or more grid columns (depending on local resolution) and fed to a separate 'convective processor', which determines the convective response to that environment and feeds the result back to the host grid. The convective processor chooses to either (1) explicitly resolve convective activity in the given environment on a separate (independent) limited-area 3D computational grid of comparable resolution to the convection-resolving part of the

  11. The evaluation of storm rainfall variability and its influence on runoff response at a catchment scale

    David, Vaclav; Davidová, Tereza


    Storm rainfall events are usually very dynamic processes which are characterized by high spatial and temporal variability. It can influence the catchment response to the event a lot in terms of the shape and volume of response hydrographs. In this contribution, the variability of selected rainfall events is presented. It is assessed in terms of total volumes of precipitation which are an input to rainfall-runoff process. As a source of precipitation information, data from precipitation gauging stations were used which have one hour time step. Additionally, data originated from weather radar were used to describe spatial variability in more detail. Measured reflectivity data were transformed into the values of precipitation intensities which were compared to station data to make a check on the reliability of radar originated data. The assessment was carried out by the comparison of total precipitation to a catchment based on different extent of source data. Precipitation totals were calculated from station data using different methods including Thiessen polygons and different interpolation techniques. As a study area, the catchment of Blanice River was selected. This catchment is located in Central Bohemia Region and smaller part extends beyond it to South Bohemia Region. Its total area to the confluence to Sázava River is 543 km2. In this catchment, agricultural lands predominates but the percentage of forests is also not negligible. The area is in general hilly with important presence of steep slopes. The results of obtained by the analyses carried out show the high importance of the amount of available precipitation data and their quality. Despite the fact that the variability of precipitation can affect the distribution of runoff and consecutively the shape of response hydrograph, it can affect also the accuracy and representativeness of the information provided by point measurements of precipitation by gauges and by weather radars. Acknowledgement The research

  12. Experimental Investigation and Optimization of Response Variables in WEDM of Inconel - 718

    Karidkar, S. S.; Dabade, U. A.


    Effective utilisation of Wire Electrical Discharge Machining (WEDM) technology is challenge for modern manufacturing industries. Day by day new materials with high strengths and capabilities are being developed to fulfil the customers need. Inconel - 718 is similar kind of material which is extensively used in aerospace applications, such as gas turbine, rocket motors, and spacecraft as well as in nuclear reactors and pumps etc. This paper deals with the experimental investigation of optimal machining parameters in WEDM for Surface Roughness, Kerf Width and Dimensional Deviation using DoE such as Taguchi methodology, L9 orthogonal array. By keeping peak current constant at 70 A, the effect of other process parameters on above response variables were analysed. Obtained experimental results were statistically analysed using Minitab-16 software. Analysis of Variance (ANOVA) shows pulse on time as the most influential parameter followed by wire tension whereas spark gap set voltage is observed to be non-influencing parameter. Multi-objective optimization technique, Grey Relational Analysis (GRA), shows optimal machining parameters such as pulse on time 108 Machine unit, spark gap set voltage 50 V and wire tension 12 gm for optimal response variables considered for the experimental analysis.

  13. Dynamic Response in Transient Operation of a Variable Geometry Turbine Stage: Influence of the Aerodynamic Performance

    Nicolas Binder


    Full Text Available The transient response of a radial turbine stage with a variable geometry system is evaluated. Mainly, the consequences of the variations of the aerodynamic performance of the stage on the response time are checked. A simple quasi-steady model is derived in order to formalize the expected dependences. Then an experimental campaign is conducted: a brutal step in the feeding conditions of the stage is imposed, and the response time in terms of rotational speed is measured. This has been reproduced on different declinations of the same stage, through the variation of the stator geometry, and correlated to the steady-state performance of the initial and final operating points of the transient phase. The matching between theoretical expectation and results is surprisingly good for some configurations, less for others. The most important factor identified is the mass-flow level during the transient phase. It increases the reactivity, even far above the theoretical expectation for some configurations. For those cases, it is demonstrated that the quasi-steady approach may not be sufficient to explain how the transient response is set.

  14. The contribution of pre-stimulus neural oscillatory activity to spontaneous response time variability.

    Bompas, Aline; Sumner, Petroc; Muthumumaraswamy, Suresh D; Singh, Krish D; Gilchrist, Iain D


    Large variability between individual response times, even in identical conditions, is a ubiquitous property of animal behavior. However, the origins of this stochasticity and its relation to action decisions remain unclear. Here we focus on the state of the perception-action network in the pre-stimulus period and its influence on subsequent saccadic response time and choice in humans. We employ magnetoencephalography (MEG) and a correlational source reconstruction approach to identify the brain areas where pre-stimulus oscillatory activity predicted saccadic response time to visual targets. We find a relationship between future response time and pre-stimulus power, but not phase, in occipital (including V1), parietal, posterior cingulate and superior frontal cortices, consistently across alpha, beta and low gamma frequencies, each accounting for between 1 and 4% of the RT variance. Importantly, these correlations were not explained by deterministic sources of variance, such as experimental factors and trial history. Our results further suggest that occipital areas mainly reflect short-term (trial to trial) stochastic fluctuations, while the frontal contribution largely reflects longer-term effects such as fatigue or practice. Parietal areas reflect fluctuations at both time scales. We found no evidence of lateralization: these effects were indistinguishable in both hemispheres and for both saccade directions, and non-predictive of choice - a finding with fundamental consequences for models of action decision, where independent, not coupled, noise is normally assumed. PMID:25482267

  15. Human inter-individual variability in metabolism and genotoxic response to zidovudine

    A mainstay of the antiretroviral drugs used for therapy of HIV-1, zidovudine (AZT) is genotoxic and becomes incorporated into DNA. Here we explored host inter-individual variability in AZT-DNA incorporation, by AZT radioimmunoassay (RIA), using 19 different strains of normal human mammary epithelial cells (NHMECs) exposed for 24 h to 200 μM AZT. Twelve of the 19 NHMEC strains showed detectable AZT-DNA incorporation levels (16 to 259 molecules of AZT/106 nucleotides), while 7 NHMEC strains did not show detectable AZT-DNA incorporation. In order to explore the basis for this variability, we compared the 2 NHMEC strains that showed the highest levels of AZT-DNA incorporation (H1 and H2) with 2 strains showing no detectable AZT-DNA incorporation (L1 and L2). All 4 strains had similar (≥ 80%) cell survival, low levels of accumulation of cells in S-phase, and no relevant differences in response to the direct-acting mutagen bleomycin (BLM). Finally, when levels of thymidine kinase 1 (TK1), the first enzyme in the pathway for incorporation of AZT into DNA, were determined by Western blot analysis in all 19 NHMEC strains at 24 h of AZT exposure, higher TK1 protein levels were found in the 12 strains showing AZT-DNA incorporation, compared to the 7 showing no incorporation (p = 0.0005, Mann-Whitney test). Furthermore, strains L1 and L2, which did not show AZT-DNA incorporation at 24 h, did have measurable incorporation by 48 and 72 h. These data suggest that variability in AZT-DNA incorporation may be modulated by inter-individual differences in the rate of induction of TK1 in response to AZT exposure

  16. Multi-scale responses of scattering layers to environmental variability in Monterey Bay, California

    Urmy, Samuel S.; Horne, John K.


    A 38 kHz upward-facing echosounder was deployed on the seafloor at a depth of 875 m in Monterey Bay, CA, USA (36° 42.748‧N, 122° 11.214‧W) from 27 February 2009 to 18 August 2010. This 18-month record of acoustic backscatter was compared to oceanographic time series from a nearby data buoy to investigate the responses of animals in sound-scattering layers to oceanic variability at seasonal and sub-seasonal time scales. Pelagic animals, as measured by acoustic backscatter, moved higher in the water column and decreased in abundance during spring upwelling, attributed to avoidance of a shoaling oxycline and advection offshore. Seasonal changes were most evident in a non-migrating scattering layer near 500 m depth that disappeared in spring and reappeared in summer, building to a seasonal maximum in fall. At sub-seasonal time scales, similar responses were observed after individual upwelling events, though they were much weaker than the seasonal relationship. Correlations of acoustic backscatter with oceanographic variability also differed with depth. Backscatter in the upper water column decreased immediately following upwelling, then increased approximately 20 days later. Similar correlations existed deeper in the water column, but at increasing lags, suggesting that near-surface productivity propagated down the water column at 10-15 m d-1, consistent with sinking speeds of marine snow measured in Monterey Bay. Sub-seasonal variability in backscatter was best correlated with sea-surface height, suggesting that passive physical transport was most important at these time scales.

  17. Spatial patterns of simulated transpiration response to climate variability in a snow dominated mountain ecosystem

    Christensen, L.; Tague, C.L.; Baron, J.S.


    Transpiration is an important component of soil water storage and stream-flow and is linked with ecosystem productivity, species distribution, and ecosystem health. In mountain environments, complex topography creates heterogeneity in key controls on transpiration as well as logistical challenges for collecting representative measurements. In these settings, ecosystem models can be used to account for variation in space and time of the dominant controls on transpiration and provide estimates of transpiration patterns and their sensitivity to climate variability and change. The Regional Hydro-Ecological Simulation System (RHESSys) model was used to assess elevational differences in sensitivity of transpiration rates to the spatiotemporal variability of climate variables across the Upper Merced River watershed, Yosemite Valley, California, USA. At the basin scale, predicted annual transpiration was lowest in driest and wettest years, and greatest in moderate precipitation years (R2 = 0.32 and 0.29, based on polynomial regression of maximum snow depth and annual precipitation, respectively). At finer spatial scales, responsiveness of transpiration rates to climate differed along an elevational gradient. Low elevations (1200-1800 m) showed little interannual variation in transpiration due to topographically controlled high soil moistures along the river corridor. Annual conifer stand transpiration at intermediate elevations (1800-2150 m) responded more strongly to precipitation, resulting in a unimodal relationship between transpiration and precipitation where highest transpiration occurred during moderate precipitation levels, regardless of annual air temperatures. Higher elevations (2150-2600 m) maintained this trend, but air temperature sensitivities were greater. At these elevations, snowfall provides enough moisture for growth, and increased temperatures influenced transpiration. Transpiration at the highest elevations (2600-4000 m) showed strong sensitivity to

  18. Spatial representation and cognitive modulation of response variability in the lateral intraparietal area priority map.

    Falkner, Annegret L; Goldberg, Michael E; Krishna, B Suresh


    The lateral intraparietal area (LIP) in the macaque contains a priority-based representation of the visual scene. We previously showed that the mean spike rate of LIP neurons is strongly influenced by spatially wide-ranging surround suppression in a manner that effectively sharpens the priority map. Reducing response variability can also improve the precision of LIP's priority map. We show that when a monkey plans a visually guided delayed saccade with an intervening distractor, variability (measured by the Fano factor) decreases both for neurons representing the saccade goal and for neurons representing the broad spatial surround. The reduction in Fano factor is maximal for neurons representing the saccade goal and steadily decreases for neurons representing more distant locations. LIP Fano factor changes are behaviorally significant: increasing expected reward leads to lower variability for the LIP representation of both the target and distractor locations, and trials with shorter latency saccades are associated with lower Fano factors in neurons representing the surround. Thus, the LIP Fano factor reflects both stimulus and behavioral engagement. Quantitative modeling shows that the interaction between mean spike count and target-receptive field (RF) distance in the surround during the predistractor epoch is multiplicative: the Fano factor increases more steeply with mean spike count further away from the RF. A negative-binomial model for LIP spike counts captures these findings quantitatively, suggests underlying mechanisms based on trial-by-trial variations in mean spike rate or burst-firing patterns, and potentially provides a principled framework to account simultaneously for the previously observed unsystematic relationships between spike rate and variability in different brain areas. PMID:24107945

  19. Increased Intrasubject Variability in Response Time in Youths with Bipolar Disorder and At-Risk Family Members

    Brotman, Melissa A.; Rooney, Melissa H.; Skup, Martha; Pine, Daniel S.; Leibenluft, Ellen


    Intrasubject variability in response time (ISV-RT) was higher in youths with bipolar disorder (BD) and those with first-degree relatives with BD compared to youths without BD. ISV-RT may be a risk marker for BD.

  20. Intraclass Correlation Coefficients in Hierarchical Design Studies with Discrete Response Variables: A Note on a Direct Interval Estimation Procedure

    Raykov, Tenko; Marcoulides, George A.


    A latent variable modeling procedure that can be used to evaluate intraclass correlation coefficients in two-level settings with discrete response variables is discussed. The approach is readily applied when the purpose is to furnish confidence intervals at prespecified confidence levels for these coefficients in setups with binary or ordinal…

  1. Preparation of a biodegradable oil absorber and its biodegradation.

    Yoo, Su-Yong; Daud, Wan Mohd Ashri Wan; Lee, Min-Gyu


    The biodegradable oil absorption resin (B-PEHA) was prepared by suspension polymerization, and its preparation was confirmed by Fourier transform infrared analysis. The oil absorption capacities of the prepared B-PEHA were: chloroform 30.88, toluene 19.75, xylene, 18.78, THF 15.96, octane 11.43, hexane 9.5, diesel oil 12.80, and kerosene 13.79 g/g. The biodegradation of the prepared B-PEHA was also investigated by determination of reduced sugar produced after enzymatic hydrolysis, thermogravimetric analysis, and incubation with Aspergillus niger. The biodegradation of B-PEHA was ~18%. PMID:21909668

  2. Continental-scale impacts of intra-seasonal rainfall variability on simulated ecosystem responses in Africa

    Guan, K.; Good, S. P.; Caylor, K. K.; Sato, H.; Wood, E. F.; Li, H.


    Climate change is expected to modify intra-seasonal rainfall variability, arising from shifts in rainfall frequency, intensity and seasonality. These intra-seasonal changes are likely to have important ecological impacts on terrestrial ecosystems. Yet, quantifying these impacts across biomes and large climate gradients is largely missing. This gap hinders our ability to better predict ecosystem services and their responses to climate change, especially for arid and semi-arid ecosystems. Here we use a synthetic weather generator and an independently validated vegetation dynamic model (SEIB-Dynamic Global Vegetation Model, DGVM) to virtually conduct a series of "rainfall manipulation experiments" to study how changes in the intra-seasonal rainfall variability affect continent-scale ecosystem responses across Africa. We generate different rainfall scenarios with fixed total annual rainfall but shifts in (i) frequency vs. intensity, (ii) rainy season length vs. frequency, (iii) intensity vs. rainy season length. These scenarios are fed into SEIB-DGVM to investigate changes in biome distributions and ecosystem productivity. We find a loss of ecosystem productivity with increased rainfall frequency and decreased intensity at very low rainfall regimes (year-1) and low frequency (benefit from increased frequency and decreased intensity, except in the wet tropics (>1800 mm year-1) where radiation limitation prevents further productivity gains. This result reconciles seemingly contradictory findings in previous field studies on the impact of rainfall frequency/intensity on ecosystem productivity. We also find that changes in rainy season length can yield more dramatic ecosystem responses compared with similar percentage changes in rainfall frequency or intensity, with the largest impacts in semi-arid woodlands. This study demonstrates that intra-seasonal rainfall characteristics play a significant role in influencing ecosystem function and structure through controls on

  3. Biodegradation of Polypropylene Nonwovens

    Keene, Brandi Nechelle

    The primary aim of the current research is to document the biodegradation of polypropylene nonwovens and filament under composting environments. To accelerate the biodegradat ion, pre-treatments and additives were incorporated into polypropylene filaments and nonwovens. The initial phase (Chapter 2) of the project studied the biodegradation of untreated polypropylene with/without pro-oxidants in two types of composting systems. Normal composting, which involved incubation of samples in food waste, had little effect on the mechanical properties of additive-free spunbond nonwovens in to comparison prooxidant containing spunbond nonwovens which were affected significantly. Modified composting which includes the burial of samples with food and compressed air, the polypropylene spunbond nonwovens with/without pro-oxidants displayed an extreme loss in mechanical properties and cracking on the surface cracking. Because the untreated spunbond nonwovens did not completely decompose, the next phase of the project examined the pre-treatment of gamma-irradiation or thermal aging prior to composting. After exposure to gamma-irradiation and thermal aging, polypropylene is subjected to oxidative degradation in the presence of air and during storage after irradiat ion. Similar to photo-oxidation, the mechanism of gamma radiation and thermal oxidative degradation is fundamentally free radical in nature. In Chapter 3, the compostability of thermal aged spunbond polypropylene nonwovens with/without pro-oxidant additives. The FTIR spectrum confirmed oxidat ion of the polypropylene nonwovens with/without additives. Cracking on both the pro-oxidant and control spunbond nonwovens was showed by SEM imaging. Spunbond polypropylene nonwovens with/without pro-oxidants were also preirradiated by gamma rays followed by composting. Nonwovens with/without pro-oxidants were severely degraded by gamma-irradiation after up to 20 kGy exposure as explained in Chapter 4. Furthermore (Chapter 5), gamma

  4. Calibrations between the variables of microbial TTI response and ground pork qualities.

    Kim, Eunji; Choi, Dong Yeol; Kim, Hyun Chul; Kim, Keehyuk; Lee, Seung Ju


    A time-temperature indicator (TTI) based on a lactic acid bacterium, Weissella cibaria CIFP009, was applied to ground pork packaging. Calibration curves between TTI response and pork qualities were obtained from storage tests at 2°C, 10°C, and 13°C. The curves of the TTI vs. total cell number at different temperatures coincided to the greatest extent, indicating the highest representativeness of calibration, by showing the least coefficient of variance (CV=11%) of the quality variables at a given TTI response (titratable acidity) on the curves, followed by pH (23%), volatile basic nitrogen (VBN) (25%), and thiobarbituric acid-reactive substances (TBARS) (47%). Similarity of Arrhenius activation energy (Ea) could also reflect the representativeness of calibration. The total cell number (104.9 kJ/mol) was found to be the most similar to that of the TTI response (106.2 kJ/mol), followed by pH (113.6 kJ/mol), VBN (77.4 kJ/mol), and TBARS (55.0 kJ/mol). PMID:23747630

  5. Putative role of aquaporins in variable hydraulic conductance of leaves in response to light.

    Cochard, Hervé; Venisse, Jean-Stéphane; Barigah, Têtè Sévérien; Brunel, Nicole; Herbette, Stéphane; Guilliot, Agnès; Tyree, Melvin T; Sakr, Soulaiman


    Molecular and physiological studies in walnut (Juglans regia) are combined to establish the putative role of leaf plasma membrane aquaporins in the response of leaf hydraulic conductance (K(leaf)) to irradiance. The effects of light and temperature on K(leaf) are described. Under dark conditions, K(leaf) was low, but increased by 400% upon exposure to light. In contrast to dark conditions, K(leaf) values of light-exposed leaves responded to temperature and 0.1 mm cycloheximide treatments. Furthermore, K(leaf) was not related to stomatal aperture. Data of real-time reverse transcription-polymerase chain reaction showed that K(leaf) dynamics were tightly correlated with the transcript abundance of two walnut aquaporins (JrPIP2,1 and JrPIP2,2). Low K(leaf) in the dark was associated with down-regulation, whereas high K(leaf) in the light was associated with up-regulation of JrPIP2. Light responses of K(leaf) and aquaporin transcripts were reversible and inhibited by cycloheximide, indicating the importance of de novo protein biosynthesis in this process. Our results indicate that walnut leaves can rapidly change their hydraulic conductance and suggest that these changes can be explained by regulation of plasma membrane aquaporins. Model simulation suggests that variable leaf hydraulic conductance in walnut might enhance leaf gas exchanges while buffering leaf water status in response to ambient light fluctuations. PMID:17114274

  6. Variability of glycemic and insulin response to a standard meal, within and between healthy subjects

    Sandra Hirsch


    Full Text Available Aim: To test the variability within and between subject of glycemic response test following the ingestion of a standard food. Material and methods: Glucose and insulin response of a standard meal (white bread was performed in ten healthy volunteers and repeated under identical conditions for 6 times. Blood glucose and insulin levels were measured in the fasted state and over the 180 min following commencement of consumption of the foods The Area Under the Curve (AUC for glucose and insulin was calculated for the values above baseline for the 3hour period following the standard meal. Within and between coefficient of variation was calculated. Results: The total intra-individual variation of the gAUC was 51.8% range 24.9 to 91.4%. The inter-individual variation of the gAUC in the complete study was 75.2% . The total intra-individual variation of the iAUC was 51.9%. ranged: 7.7 to 103%. The inter-individual variation in the complete study was 86%. Conclusion: Glucose and insulin response to a reference food has low reliability, therefore limits its clinical utility for individual dietary prescription.

  7. Biodegradable micromechanical sensors

    Keller, Stephan Sylvest; Greve, Anders; Schmid, Silvan;

    The development of biopolymers for food packaging, medical engineering or drug delivery is a growing field of research [1]. At the same time, the interest in methods for detailed analysis of biopolymers is increasing. Micromechanical sensors are versatile tools for the characterization of mechani......The development of biopolymers for food packaging, medical engineering or drug delivery is a growing field of research [1]. At the same time, the interest in methods for detailed analysis of biopolymers is increasing. Micromechanical sensors are versatile tools for the characterization...... of biopolymers to microfabrication is challenging, as these polymers are affected by common processes such as photolithography or wet etching. Here, we present two methods for fabrication of biodegradable micromechanical sensors. First, we fabricated bulk biopolymer microcantilevers using nanoimprint lithography...

  8. Biodegradation of biodiesel fuels

    Biodiesel fuel test substances Rape Ethyl Ester (REE), Rape Methyl Ester (RME), Neat Rape Oil (NR), Say Methyl Ester (SME), Soy Ethyl Ester (SEE), Neat Soy Oil (NS), and proportionate combinations of RME/diesel and REE/diesel were studied to test the biodegradability of the test substances in an aerobic aquatic environment using the EPA 560/6-82-003 Shake Flask Test Method. A concurrent analysis of Phillips D-2 Reference Diesel was also performed for comparison with a conventional fuel. The highest rates of percent CO2 evolution were seen in the esterified fuels, although no significant difference was noted between them. Ranges of percent CO2 evolution for esterified fuels were from 77% to 91%. The neat rape and neat soy oils exhibited 70% to 78% CO2 evolution. These rates were all significantly higher than those of the Phillips D-2 reference fuel which evolved from 7% to 26% of the organic carbon to CO2. The test substances were examined for BOD5 and COD values as a relative measure of biodegradability. Water Accommodated Fraction (WAF) was experimentally derived and BOD5 and COD analyses were carried out with a diluted concentration at or below the WAF. The results of analysis at WAF were then converted to pure substance values. The pure substance BOD5 and COD values for test substances were then compared to a control substance, Phillips D-2 Reference fuel. No significant difference was noted for COD values between test substances and the control fuel. (p > 0.20). The D-2 control substance was significantly lower than all test substances for BCD, values at p 5 value

  9. Mesoscale disturbance and ecological response to decadal climatic variability in the American Southwest

    Swetnam, T.W.; Betancourt, J.L.


    Ecological responses to climatic variability in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and tree demography reveal climatic effects across scales, from annual to decadal, and from local (Climate-disturbance relations are more variable and complex than previously assumed. During the past three centuries, mesoscale outbreaks of the western spruce budworm (Choristoneura occidentalis) were associated with wet, not dry episodes, contrary to conventional wisdom. Regional fires occur during extreme droughts but, in some ecosystems, antecedent wet conditions play a secondary role by regulating accumulation of fuels. Interdecadal changes in fire-climate associations parallel other evidence for shifts in the frequency or amplitude of the Southern Oscillation (SO) during the past three centuries. High interannual, fire-climate correlations (r = 0.7 to 0.9) during specific decades (i.e., circa 1740-80 and 1830-60) reflect periods of high amplitude in the SO and rapid switching from extreme wet to dry years in the Southwest, thereby entraining fire occurrence across the region. Weak correlations from 1780 to 1830 correspond with a decrease in SO frequency or amplitude inferred from independent tree-ring width, ice core, and coral isotope reconstructions. Episodic dry and wet episodes have altered age structures and species composition of woodland and conifer forests. The scarcity of old, living conifers established before circa 1600 suggests that the extreme drought of 1575-95 had pervasive effects on tree populations. The most extreme drought of the past 400 years occurred in the mid-twentieth century (1942-57). This drought resulted in broadscale plant dieoffs in shrublands, woodlands, and forests and accelerated shrub invasion of grasslands. Drought conditions were broken by the post-1976 shift to the negative SO phase and

  10. Dynamic sensorimotor planning during long-term sequence learning: the role of variability, response chunking and planning errors.

    Timothy Verstynen

    Full Text Available Many everyday skills are learned by binding otherwise independent actions into a unified sequence of responses across days or weeks of practice. Here we looked at how the dynamics of action planning and response binding change across such long timescales. Subjects (N = 23 were trained on a bimanual version of the serial reaction time task (32-item sequence for two weeks (10 days total. Response times and accuracy both showed improvement with time, but appeared to be learned at different rates. Changes in response speed across training were associated with dynamic changes in response time variability, with faster learners expanding their variability during the early training days and then contracting response variability late in training. Using a novel measure of response chunking, we found that individual responses became temporally correlated across trials and asymptoted to set sizes of approximately 7 bound responses at the end of the first week of training. Finally, we used a state-space model of the response planning process to look at how predictive (i.e., response anticipation and error-corrective (i.e., post-error slowing processes correlated with learning rates for speed, accuracy and chunking. This analysis yielded non-monotonic association patterns between the state-space model parameters and learning rates, suggesting that different parts of the response planning process are relevant at different stages of long-term learning. These findings highlight the dynamic modulation of response speed, variability, accuracy and chunking as multiple movements become bound together into a larger set of responses during sequence learning.

  11. Correcting scan-to-scan response variability for a radiochromic film-based reference dosimetry system

    Purpose: In radiochromic film dosimetry systems, measurements are usually obtained from film images acquired on a CCD-based flatbed scanner. The authors investigated factors affecting scan-to-scan response variability leading to increased dose measurement uncertainty. Methods: The authors used flatbed document scanners to repetitively scan EBT3 radiochromic films exposed to doses 0–1000 cGy, together with three neutral density filters and three blue optical filters. Scanning was performed under two conditions: scanner lid closed and scanner lid opened/closed between scans. The authors also placed a scanner in a cold room at 9 °C and later in a room at 22 °C and scanned EBT3 films to explore temperature effects. Finally, the authors investigated the effect of altering the distance between the film and the scanner’s light source. Results: Using a measurement protocol to isolate the contribution of the CCD and electronic circuitry of the scanners, the authors found that the standard deviation of response measurements for the EBT3 film model was about 0.17% for one scanner and 0.09% for the second. When the lid of the first scanner was opened and closed between scans, the average scan-to-scan difference of responses increased from 0.12% to 0.27%. Increasing the sample temperature during scanning changed the RGB response values by about −0.17, −0.14, and −0.05%/°C, respectively. Reducing the film-to-light source distance increased the RBG response values about 1.1, 1.3, and 1.4%/mm, respectively. The authors observed that films and film samples were often not flat with some areas up to 8 mm away from the scanner’s glass window. Conclusions: In the absence of measures to deal with the response irregularities, each factor the authors investigated could lead to dose uncertainty >2%. Those factors related to the film-to-light source distance could be particularly impactful since the authors observed many instances where the curl of film samples had the

  12. Dynamic Crushing Response of Closed-cell Aluminium Foam at Variable Strain Rates

    Islam, M. A.; Kader, M. A.; Escobedo, J. P.; Hazell, P. J.; Appleby-Thomas, G. J.; Quadir, M. Z.


    The impact response of aluminium foams is essential for assessing their crashworthiness and energy absorption capacity for potential applications. The dynamic compactions of closed-cell aluminium foams (CYMAT) have been tested at variable strain rates. Microstructural characterization has also been carried out. The low strain rate impact test has been carried out using drop weight experiments while the high strain compaction test has been carried out via plate impact experiments. The post impacted samples have been examined using optical and electron microscopy to observe the microstructural changes during dynamic loading. This combination of dynamic deformation during impact and post impact microstructural analysis helped to evaluate the pore collapse mechanism and impact energy absorption characteristics.

  13. Detection of outliers in the response and explanatory variables of the simple circular regression model

    Mahmood, Ehab A.; Rana, Sohel; Hussin, Abdul Ghapor; Midi, Habshah


    The circular regression model may contain one or more data points which appear to be peculiar or inconsistent with the main part of the model. This may be occur due to recording errors, sudden short events, sampling under abnormal conditions etc. The existence of these data points "outliers" in the data set cause lot of problems in the research results and the conclusions. Therefore, we should identify them before applying statistical analysis. In this article, we aim to propose a statistic to identify outliers in the both of the response and explanatory variables of the simple circular regression model. Our proposed statistic is robust circular distance RCDxy and it is justified by the three robust measurements such as proportion of detection outliers, masking and swamping rates.

  14. Origins of Total-Dose Response Variability in Linear Bipolar Microcircuits

    LM1ll voltage comparators exhibit a wide range of total-dose-induced degradation. Simulations show this variability may be a natural consequence of the low base doping of the substrate PNP (SPNP) input transistors. Low base doping increases the SPNP's collector to base breakdown voltage, current gain, and sensitivity to small fluctuations in the radiation-induced oxide defect densities. The build-up of oxide trapped charge (Not) and interface traps (Nit) is shown to be a function of pre-irradiation bakes. Experimental data indicate that, despite its structural similarities to the LM111, irradiated input transistors of the LM124 operational amplifier do not exhibit the same sensitivity to variations in pre-irradiation thermal cycles. Further disparities in LM111 and LM124 responses may result from a difference in the oxide defect build-up in the two part types. Variations in processing, packaging, and circuit effects are suggested as potential explanations

  15. Urban heat island impacts on plant phenology: intra-urban variability and response to land cover

    Zipper, Samuel C.; Schatz, Jason; Singh, Aditya; Kucharik, Christopher J.; Townsend, Philip A.; Loheide, Steven P., II


    Despite documented intra-urban heterogeneity in the urban heat island (UHI) effect, little is known about spatial or temporal variability in plant response to the UHI. Using an automated temperature sensor network in conjunction with Landsat-derived remotely sensed estimates of start/end of the growing season, we investigate the impacts of the UHI on plant phenology in the city of Madison WI (USA) for the 2012–2014 growing seasons. Median urban growing season length (GSL) estimated from temperature sensors is ∼5 d longer than surrounding rural areas, and UHI impacts on GSL are relatively consistent from year-to-year. Parks within urban areas experience a subdued expression of GSL lengthening resulting from interactions between the UHI and a park cool island effect. Across all growing seasons, impervious cover in the area surrounding each temperature sensor explains >50% of observed variability in phenology. Comparisons between long-term estimates of annual mean phenological timing, derived from remote sensing, and temperature-based estimates of individual growing seasons show no relationship at the individual sensor level. The magnitude of disagreement between temperature-based and remotely sensed phenology is a function of impervious and grass cover surrounding the sensor, suggesting that realized GSL is controlled by both local land cover and micrometeorological conditions.

  16. The High Variability of Hydrologic Response in Mountain Watersheds: Snowy Range, Wyoming

    Miller, S. N.


    Three adjacent mountain streams that coalesce to form a single river have been monitored with a nested watershed design comprised of ten runoff stations for the past three years. Some of the stations are co-located on previous monitoring sites that allow for an extended period of record. Stage-discharge relationships have been built with high degrees of confidence at each station, and stream isotope data have been taken to better determine sources of water and fractionation of precipitation into runoff components. In addition to runoff observations we have multiple weather stations and use geophysical methods to investigate the subsurface and better characterize potential flow pathways and remote sensing and field methods to characterize the watersheds. From these data we have observed a high degree in variability in runoff characteristics among these sites, including significant differences in annual runoff, proportion of baseflow, rainfall/runoff efficiency, and hydrologic regime. Analyses of nested runoff data reveal longitudinal and seasonal changes in surface and subsurface flow, which allow us to identify the timing and location of groundwater contributions and channel transmission to regional aquifers. Differences among the watershed responses are augmented by precipitation, and we identify stream reaches that change from effluent to influent depending on timing and magnitude of runoff. We explored physical interpretations for the observed variability, including management, beetle impacts, and subsurface characteristics as inferred from geophysical data.

  17. Optimization and Modeling of Process Variables of Biodiesel Production from Marula Oil using Response Surface Methodology

    This paper presents an optimization study in the production of biodiesel production from Marula oil. The study was carried out using a central composite design of experiments under response surface methodology. A mathematical model was developed to correlate the transesterification process variables to biodiesel yield. The transesterification reaction variables were methanol to oil ratio, x /sub 1/ (10-50 wt percentage), reaction time, x /sub 2/ (30-90 min), reaction temperature, x /sub 3/ (30-90 Degree C) stirring speed, x /sub 4/ (100-400 rpm) and amount of catalyst, x /sub 5/ (0.5-1.5 g). The optimum conditions for the production of the biodiesel were found to be methanol to oil ratio (29.43 wt percentage), reaction time (59.17 minutes), reaction temperature (58.80 Degree C), stirring speed (325 rpm) and amount of catalyst (1.02 g). The optimum yield of biodiesel that can be produced was 95 percentage. The results revealed that the crucial fuel properties of the biodiesel produced at the optimum conditions met the ASTM biodiesel specifications. (author)

  18. The response of the North Pacific Decadal Variability to strong tropical volcanic eruptions

    Wang, Tao [Chinese Academy of Sciences, Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Beijing (China); Otteraa, Odd Helge [Uni Bjerknes Centre, Uni Research, Bergen (Norway); Bjerknes Center for Climate Research, Bergen (Norway); Gao, Yongqi [Chinese Academy of Sciences, Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Beijing (China); Bjerknes Center for Climate Research, Bergen (Norway); Nansen Environmental and Remote Sensing Center, Bergen (Norway); Wang, Huijun [Chinese Academy of Sciences, Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Beijing (China); Chinese Academy of Sciences, Climate Change Research Center, Institute of Atmospheric Physics, Beijing (China)


    In this study, the effects of volcanic forcing on North Pacific climate variability, on interannual to decadal time scales, are examined using climate model simulations covering the last 600 years. The model used is the Bergen Climate Model, a fully coupled atmosphere-ocean general circulation model. It is found that natural external forcings, such as tropical strong volcanic eruptions (SVEs) and variations in total solar irradiance, play an important role in regulating North Pacific Decadal Variability (NPDV). In response to tropical SVEs the lower stratospheric pole-to-equator temperature gradient is enhanced. The North polar vortex is strengthened, which forces a significant positive Arctic Oscillation. At the same time, dipole zonal wind anomalies associated with strong polar vortex propagate downward from the lower stratosphere. Through positive feedbacks in the troposphere, the surface westerly winds across the central North Pacific are significantly weakened, and positive sea level pressure anomalies are formed in the North Pacific. This anomalous surface circulation results in changes in the net heat fluxes and the oceanic advection across the North Pacific. As a result of this, warm water converges in the subtropical western North Pacific, where the surface waters in addition are heated by significantly reduced latent and sensible heat fluxes from the ocean. In the eastern and high-latitude North Pacific the ocean loses more heat, and large-scale decreases in sea surface temperatures are found. The overall response of this chain of events is that the North Pacific enters a negative phase of the Pacific decadal oscillation (PDO), and this negative phase of the PDO is maintained for several years. It is thus concluded that the volcanic forcing plays a key role in the phasing of the PDO. The model results furthermore highlight the important role of troposphere-stratosphere coupling, tropical-extratropical teleconnections and extratropical ocean

  19. Androgen responsiveness to competition in humans: the role of cognitive variables

    Oliveira GA


    Full Text Available Gonçalo A Oliveira,1 Rui F Oliveira1,2 1Unidade de Investigação em Eco-Etologia, ISPA – Instituto Universitário, Lisbon, Portugal; 2Champalimaud Neuroscience Program, Instituto Gulbenkian de Ciência, Oeiras, Portugal Abstract: Although androgens are commonly seen as male sex hormones, it has been established over the years that in both sexes, androgens also respond to social challenges. To explain the socially driven changes in androgens, two theoretical models have been proposed: the biosocial model and the challenge hypothesis. These models are typically seen as partly overlapping; however, they generate different predictions that are clarified here. In humans, sports competition and nonmetabolic competitive tasks have been used in the laboratory setting, as a proxy for agonistic interactions in animals. The results reviewed here show that the testosterone (T response to competition in humans is highly variable – the studies present postcompetition T levels and changes in T that depend on the contest outcome and that cannot be predicted by the current theoretical models. These conflicting results bring to the foreground the importance of considering cognitive factors that could moderate the androgen response to competition. Among these variables, we elect cognitive appraisal and its components as a key candidate modulating factor. It is known that T also modulates the cognitive processes that are relevant to performance in competition. In this article, we reviewed the evidence arising from studies investigating the effect of administering exogenous T and compare those results with the findings from studies that measured endogenous T levels. Finally, we summarized the importance of also considering the interaction between androgens and other hormones, such as cortisol, when investigating the social modulation of T, as proposed by the dual-hormone hypothesis. Keywords: testosterone, challenge hypothesis, biosocial model, cognitive

  20. Evaluation of simulated photolysis rates and their response to solar irradiance variability

    Sukhodolov, Timofei; Rozanov, Eugene; Ball, William T.; Bais, Alkiviadis; Tourpali, Kleareti; Shapiro, Alexander I.; Telford, Paul; Smyshlyaev, Sergey; Fomin, Boris; Sander, Rolf; Bossay, Sébastien; Bekki, Slimane; Marchand, Marion; Chipperfield, Martyn P.; Dhomse, Sandip; Haigh, Joanna D.; Peter, Thomas; Schmutz, Werner


    The state of the stratospheric ozone layer and the temperature structure of the atmosphere are largely controlled by the solar spectral irradiance (SSI) through its influence on heating and photolysis rates. This study focuses on the uncertainties in the photolysis rate response to solar irradiance variability related to the choice of SSI data set and to the performance of the photolysis codes used in global chemistry-climate models. To estimate the impact of SSI uncertainties, we compared several photolysis rates calculated with the radiative transfer model libRadtran, using SSI calculated with two models and observed during the Solar Radiation and Climate Experiment (SORCE) satellite mission. The importance of the calculated differences in the photolysis rate response for ozone and temperature changes has been estimated using 1-D a radiative-convective-photochemical model. We demonstrate that the main photolysis reactions, responsible for the solar signal in the stratosphere, are highly sensitive to the spectral distribution of SSI variations. Accordingly, the ozone changes and related ozone-temperature feedback are shown to depend substantially on the SSI data set being used, which highlights the necessity of obtaining accurate SSI variations. To evaluate the performance of photolysis codes, we compared the results of eight, widely used, photolysis codes against two reference schemes. We show that, in most cases, absolute values of the photolysis rates and their response to applied SSI changes agree within 30%. However, larger errors may appear in specific atmospheric regions because of differences, for instance, in the treatment of Rayleigh scattering, quantum yields, or absorption cross sections.

  1. Compared in vivo toxicity in mice of lung delivered biodegradable and non-biodegradable nanoparticles.

    Aragao-Santiago, Letícia; Hillaireau, Hervé; Grabowski, Nadège; Mura, Simona; Nascimento, Thais L; Dufort, Sandrine; Coll, Jean-Luc; Tsapis, Nicolas; Fattal, Elias


    To design nanoparticle (NP)-based drug delivery systems for pulmonary administration, biodegradable materials are considered safe, but their potential toxicity is poorly explored. We here explore the lung toxicity in mice of biodegradable nanoparticles (NPs) and compare it to the toxicity of non-biodegradable ones. NP formulations of poly(d,l-lactide-co-glycolide) (PLGA) coated with chitosan (CS), poloxamer 188 (PF68) or poly(vinyl alcohol) (PVA), which renders 200 nm NPs of positive, negative or neutral surface charge respectively, were analyzed for their biodistribution by in vivo fluorescence imaging and their inflammatory potential after single lung nebulization in mice. After exposure, analysis of bronchoalveolar lavage (BAL) cell population, protein secretion and cytokine release as well as lung histology were carried out. The inflammatory response was compared to the one induced by non-biodegradable counterparts, namely, TiO2 of rutile and anatase crystal form and polystyrene (PS). PLGA NPs were mostly present in mice lungs, with little passage to other organs. An increase in neutrophil recruitment was observed in mice exposed to PS NPs 24 h after nebulization, which declined at 48 h. This result was supported by an increase in interleukin (IL)-6 and tumor necrosis factor α (TNFα) in BAL supernatant at 24 h. TiO2 anatase NPs were still present in lung cells 48 h after nebulization and induced the expression of pro-inflammatory cytokines and the recruitment of polymorphonuclear cells to BAL. In contrast, regardless of their surface charge, PLGA NPs did not induce significant changes in the inflammation markers analyzed. In conclusion, these results point out to a safe use of PLGA NPs regardless of their surface coating compared to non-biodegradable ones. PMID:26573338

  2. Using Bayesian inference for parameter estimation when the system response and experimental conditions are measured with error and some variables are considered as nuisance variables

    Emery, A. F.; Valenti, E.; Bardot, D.


    Parameter estimation is generally based upon the maximum likelihood approach and often involves regularization. Typically it is desired that the results be unbiased and of minimum variance. However, it is often better to accept biased estimates that have minimum mean square error. Bayesian inference is an attractive approach that achieves this goal and incorporates regularization automatically. More importantly, it permits us to analyse experiments in which both the system response and the independent variables (time, sensor position, experimental conditions, etc) are corrupted by noise and in which the model includes nuisance variables. This paper describes the use of Bayesian inference for an apparently simple experiment which is, in fact, fundamentally difficult and is compounded by a nuisance variable. By presenting this analysis we hope that members of the inverse community will see the value of applying Bayesian inference.


    Natural processes of biodegradation, that return carbon from its various organic forms to the inorganic state, are increasingly screened for bioremediation applications. ariety of microbial systems capable of degrading synthetic organic chemicals, from pesticides to polychlorinat...

  4. Reef fish dynamic response to climatic variability in a warm eastern Mediterranean semi-enclosed basin

    Agiadi, K.; Koskeridou, E.; Giamali, Ch.; Karakitsios, V.


    Recent studies on the effects of global warming on fish populations reveal that the resulting hypoxia-based habitat compression due to the expansion of the oxygen minimum zone may lead to the restriction of fish depth distributions to the oxygenated near-surface layer1. Here we postulate that similar phenomena may have affected the fish distribution in the early Pliocene Heraklion semi-enclosed sea (Crete, eastern Mediterranean). Fish otoliths from Voutes section are systematically identified and the data is examined from a palaeoecologic perspective in response to the Pliocene climatic variability. Bregmaceros and Diaphus taaningi otoliths' relative abundances are used as reliable palaeoclimatic indicators2. The Voutes section sediments contain a very rich fish fauna. Diaphus spp., Bregmaceros sp., Sardinella maderensis, Phosichthyidae and Sternoptychyidae form the pelagic component. Mesopelagic taxa belong mostly to Myctophids. The benthopelagic and benthic component of the fish fauna is very well diversified and is comprised of Gobiids, such as Gobius cf. niger, Callogobius sp., Lesueurigobius aff. sanzoi, and Aphya sp., as well as Gadiculus labiatus, Laemonema sp., Oblada melanura, Parascombrus mutinensis, Barbourisia rufa, Blennius sp., Ammodytes sp., Solea aff. solea. The presence of Oligopus sp., Spratelloides sp., and Brotula cf. mutlibarbata in the middle part of the section indicate the development of a reef in the study area. The palaeoecologic analysis of the surface, intermediate and deep water faunal groups indicate that the pelagic fish populations in the semi-enclosed early Pliocene Heraklion basin directly reflect the climatic variability. However, the intermediate and deep water fish did not respond to climate change in the same manner. Indeed, two dysoxic events are recorded in this section, where the pelagic component of the fauna is almost exclusively comprised of Bregmaceros sp., few Myctophids are present, and the benthic and benthopelagic

  5. Variability of Sea Surface Temperature Response to Tropical Cyclones along the NEC Bifurcation Latitude

    Fernandez, I.; Villanoy, C. L.


    The east of the Philippines serves as an entry point to an annual average of 20 tropical cyclones. The ocean is dynamic where the North Equatorial Current (NEC) bifurcates into the Kurushio Current to the north and Mindanao Current to the south. The displacement and intensity of NEC bifurcation in the region varies seasonally and interannually driven by local monsoons and ENSO. The variability of the NEC bifurcation latitude may alter the origins of the Kuroshio and modify the sea surface temperature field, which can alter the strength of the typhoons and upper ocean response. This paper aims to characterize the variability of Sea Surface Temperature (SST) Response to Tropical Cyclones along with the NEC Bifurcation latitude using daily merged product of the TRMM Microwave Imager (TMI) and Advanced Microwave Scanning Radiometer (AMSR-E), Sea Surface Height (SSH) and SSH Anomaly (SSHA) from AVISO and background climatological D26 (depth of 26 °C) and T100 (depth integrated temperature up to 100 meters) from ARGO profiles and CTD data from WOA09 from 2003 to 2012. SSH measurements from this period were used as a proxy for determining the bifurcation latitude (YB). Characteristics of the meridional distribution from 0° to 30°N of D26 is homogenous along 10-15°N. Monthly mean D26 along 10-15°N, 125-145°E shows high correlation with YB . Variations of the D26 and T100 showed deepening and warming along with YB. Two regions were derived from meridional distribution of T100 namely BSouth (15°N), where background climatological condition is shallow (D26) and varies seasonally. These regions where used to compare variability with respect to SST recovery time and the SST maximum change (ΔSSTmax) along with other factors such as TCs translation speed (TS) and intensity based on the Saffir-Simpson Hurricane Scale. Results showed that in both regions SST Recovery time is described as fast (5days). Difference between both regions can be described with respect to the

  6. Anaerobic biodegradability of kitchen waste

    Neves, L.; Oliveira, Rosário; M. Mota; Alves, M.M.


    Biodegradability of synthetic and real kitchen wastes was assessed in batch assays, under different solid contents between 1,8 and 24% and waste/inoculum ratios between 0,2 and 29 VSwaste/Vsseed sludge. Methanization rate and cumulative methane production from synthetic wastes simulated with different blends of protein, carbohydrates, fat and cellulose were compared. Although the excess of protein, carbohydrates and cellulose enhanced the biodegradability by 16 to 48%, the excess of fat re...

  7. Governmental responses and smallholders' adaptations to climatic variability in southeastern Mexico

    Mardero Jimenez, Silvia Sofia; Schmook, Birgit; Christman, Zachary; Radel, Claudia


    Maize agriculture comprises a third of the area under cultivation in Mexico (75 million hectares), with only a quarter of this crop irrigated artificially. With the great dependence of the country's dominant crop on natural rainfall, there is potential for major losses in maize production due to climatic events, such as irregular rainfalls, droughts, and hurricanes. In 2012, droughts alone caused losses of 16 billion Mexican pesos nationwide in the agricultural sector. Over the last decades, political and economic pressures in the agrarian sector have further stressed Mexican smallholder farmers, as they have to respond to a combination of economic and climatic factors. This interdisciplinary study first documents local climate changes and then explores smallholder farmers' adaptations and governmental policy responses to the variable and changing precipitation and temperature patterns across southeastern Mexico. To assess local climate changes, we analyzed precipitation and temperature data from the land-based weather station network of CONAGUA for the 1973-2012 period. Precipitation anomalies were estimated to evaluate the annual and seasonal stability, deficit, or surplus; and linear regressions used to evaluate precipitation and temperature trends. Climatic analysis demonstrated, 1) a considerable increase in temperature across the study area; 2) a decline in precipitation across a sub-section; 3) increased drought frequency; and 4) an increase in negative anomalies in recent years. We then combine findings from our previous research (Mardero et al. 2014 and Mardero et al. 2015), based on interviews with 150 swidden maize smallholders in 10 communities, to new data from in-depth interviews with managers of local and regional agricultural associations and with members of governmental institutions in charge of climate policy implementation (n=19). The new data allow us to explore governmental responses to climatic variability in the agricultural sector in direct

  8. Dendrogeomorphically derived slope response to decadal and centennial scale climate variability: Black Mesa, Arizona, USA

    L. A. Scuderi


    Full Text Available A major impediment to an understanding of the links between climate and landscape change, has been the relatively coarse resolution of landscape response measures (rates of weathering, sediment production, erosion and transport relative to the higher resolution of the climatic signal (precipitation and temperature on hourly to annual time scales. A combination of high temporal and spatial resolution dendroclimatic and dendrogeomorphic approaches were used to study relationships between climatic variability and hillslope and valley floor dynamics in a small drainage basin in the Colorado Plateau of northeastern Arizona, USA Dendrogeomorphic and vegetation evidence from slopes and valley bottoms, including root exposure, bending of trunks, change in plant cover and burial and exhumation of valley bottom trees and shrubs, suggest that the currently observed process of root colonization and rapid breakdown of the weakly cemented bedrock by subaerial weathering, related to periodic dry/wet cycle induced changes in vegetation cover, has lead to a discontinuous, climate-controlled production of sediment from these slopes. High-amplitude precipitation shifts over the last 2000-years may exert the largest control on landscape processes and may be as, or more, important than other hypothesized causal mechanisms (e.g. ENSO frequency and intensity, flood frequency in eroding slopes and producing sediments that ultimately impact higher order drainages in the region. Current vegetation response to a prolonged drought over the past decade suggests that another major transition, incorporating vegetation change, slope erosion, sediment production and subsequent valley floor deposition, may be in its initial phase.

  9. Biodegradable and edible gelatine actuators for use as artificial muscles

    Chambers, L. D.; Winfield, J.; Ieropoulos, I.; Rossiter, J.


    The expense and use of non-recyclable materials often requires the retrieval and recovery of exploratory robots. Therefore, conventional materials such as plastics and metals in robotics can be limiting. For applications such as environmental monitoring, a fully biodegradable or edible robot may provide the optimum solution. Materials that provide power and actuation as well as biodegradability provide a compelling dimension to future robotic systems. To highlight the potential of novel biodegradable and edible materials as artificial muscles, the actuation of a biodegradable hydrogel was investigated. The fabricated gelatine based polymer gel was inexpensive, easy to handle, biodegradable and edible. The electro-mechanical performance was assessed using two contactless, parallel stainless steel electrodes immersed in 0.1M NaOH solution and fixed 40 mm apart with the strip actuator pinned directly between the electrodes. The actuation displacement in response to a bias voltage was measured over hydration/de-hydration cycles. Long term (11 days) and short term (1 hour) investigations demonstrated the bending behaviour of the swollen material in response to an electric field. Actuation voltage was low (robotics.

  10. Dissociation of response variability from firing rate effects in frontal eye field neurons during visual stimulation, working memory, and attention.

    Chang, Mindy H; Armstrong, Katherine M; Moore, Tirin


    Recent studies suggest that trial-to-trial variability of neuronal spiking responses may provide important information about behavioral state. Observed changes in variability during sensory stimulation, attention, motor preparation, and visual discrimination suggest that variability may reflect the engagement of neurons in a behavioral task. We examined changes in spiking variability of frontal eye field (FEF) neurons in a change detection task requiring monkeys to remember a visually cued location and direct attention to that location while ignoring distracters elsewhere. In this task, the firing rates (FRs) of FEF neurons not only continuously reflect the location of the remembered cue and select targets, but also predict detection performance on a trial-by-trial basis. Changes in FEF response variability, as measured by the Fano factor (FF), showed clear dissociations from changes in FR. The FF declined in response to visual stimulation at all tested locations, even in the opposite hemifield, indicating much broader spatial tuning of the FF compared with the FR. Furthermore, despite robust spatial modulation of the FR throughout all epochs of the task, spatial tuning of the FF did not persist throughout the delay period, nor did it show attentional modulation. These results indicate that changes in variability, at least in the FEF, are most effectively driven by visual stimulation, while behavioral engagement is not sufficient. Instead, changes in variability may reflect shifts in the balance between feedforward and recurrent sources of excitatory drive. PMID:22323732

  11. Himalayan River Terraces as A Landscape Response to Quaternary Summer Monsoon Variability

    Jonell, T. N.; Clift, P. D.


    In order to interpret marine sedimentary archives as records of the erosional response to Asian monsoon variability, we must first recognize how transport processes affect the storage and release of sediment to the ocean. River terraces, such as found in the Greater Himalaya, provide a pivotal role in the source-to-sink story, because this is where sediment storage occurs and is likely modulated. We investigate the role that climate plays in controlling erosion and sediment flux to the Indus delta and fan by looking at the Indus River system, which is dominated by the strong forcing of the Asian monsoon, as well as winter Westerly winds. Paleoceanographic, speleothem, and lacustrine records indicate that summer monsoon intensity was strong from 29 to 37 ka, decreased after that time until ~16 ka, reached maximum intensity from 8 to 10 ka, and then weakened until ~3 ka. Some lacustrine records, however, indicate a more complex pattern of monsoon variability in the Greater Himalaya, which contrasts with monsoonal forcing in central India. This disagreement suggests that floodplains of major river systems may not experience the same climatic conditions as their mountain sources, resulting in contrasting landscape responses to climate change. High altitude river valleys, at least north ofthe Greater Himalaya, appear to be sensitive to monsoon strength because they lie on the periphery of the present rainfall maximum, in the Himalayan rain shadow. These steep river valleys may be affected by landslide damming during periods of increase moisture transport and strong monsoonal precipitation, where damming provides sediment storage through valley-filling and later sediment release through gradual incision or dam-bursting. The Zanskar River, a major tributary to the upper Indus River, provides a record of the erosional response of mountain river valleys to these extreme phases through river terracing. New OSL ages from alluvial terraces indicate reworking of sediment and

  12. Investigating Biodegradation of Heavy Fuel Oil by Kinetic Models and New Third Parametric Equation

    Ali-Reza Chackoshian Khorasani


    Conclusion: Ch equation by reason of using two variables for computation of third variable and correctly selecting variables could describe various changes in mazut biodegradation under different conditions via mathematical statements. Moreover, it is possible that this equation can be used to study other various phenomena in future.

  13. A simple model for the spatially-variable coastal response to hurricanes

    Stockdon, H.F.; Sallenger, A.H., Jr.; Holman, R.A.; Howd, P.A.


    The vulnerability of a beach to extreme coastal change during a hurricane can be estimated by comparing the relative elevations of storm-induced water levels to those of the dune or berm. A simple model that defines the coastal response based on these elevations was used to hindcast the potential impact regime along a 50-km stretch of the North Carolina coast to the landfalls of Hurricane Bonnie on August 27, 1998, and Hurricane Floyd on September 16, 1999. Maximum total water levels at the shoreline were calculated as the sum of modeled storm surge, astronomical tide, and wave runup, estimated from offshore wave conditions and the local beach slope using an empirical parameterization. Storm surge and wave runup each accounted for ∼ 48% of the signal (the remaining 4% is attributed to astronomical tides), indicating that wave-driven process are a significant contributor to hurricane-induced water levels. Expected water levels and lidar-derived measures of pre-storm dune and berm elevation were used to predict the spatially-varying storm-impact regime: swash, collision, or overwash. Predictions were compared to the observed response quantified using a lidar topography survey collected following hurricane landfall. The storm-averaged mean accuracy of the model in predicting the observed impact regime was 55.4%, a significant improvement over the 33.3% accuracy associated with random chance. Model sensitivity varied between regimes and was highest within the overwash regime where the accuracies were 84.2% and 89.7% for Hurricanes Bonnie and Floyd, respectively. The model not only allows for prediction of the general coastal response to storms, but also provides a framework for examining the longshore-variable magnitudes of observed coastal change. For Hurricane Bonnie, shoreline and beach volume changes within locations that experienced overwash or dune erosion were two times greater than locations where wave runup was confined to the foreshore (swash regime

  14. A comparison of stratospheric photochemical response to different reconstructions of solar ultraviolet radiative variability

    Bolduc, Cassandra; Bourqui, Michel S.; Charbonneau, Paul


    We present calculations of stratospheric chemical abundances variations between different levels of solar activity using a simple photochemistry model in transient chemistry mode. Different models for the reconstruction of the solar spectrum, as well as observations from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irradiance Monitor (SIM) on the SOlar Radiation and Climate Experiment (SORCE) satellite, are used as inputs to the calculations. We put the emphasis on the MOnte CArlo Spectral Solar Irradiance Model (MOCASSIM) reconstructions, which cover the spectral interval from 150 to 400 nm and extend from 1610 to present. We compare our results with those obtained with the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) model as well as with the Magnesium-Neutron Monitor (MGNM) model over a period of time spanning the ascending phase of Cycle 22. We also perform the calculations using SORCE composite spectra for the descending phase of Cycle 23 and with the reconstructed MOCASSIM, NRLSSI and MGNM spectra for the same period for comparison. Finally, we compare the chemical abundances obtained for the Maunder Minimum with those obtained for the Cycle 23 minimum (in March 2009) and find that stratospheric ozone concentration was slightly higher during the recent minimum, consequent to the small positive variability between the MOCASSIM spectra for both epochs, especially below 260 nm. We find that the response in stratospheric ozone is not only dependent on the variability amplitude in the solar spectrum (especially in the 200-240 nm band), but also significantly on the base level of the minimum solar spectrum.

  15. Biodegradation of polyethoxylated nonylphenols.

    Ruiz, Yassellis; Medina, Luis; Borusiak, Margarita; Ramos, Nairalith; Pinto, Gilberto; Valbuena, Oscar


    Polyethoxylated nonylphenols, with different ethoxylation degrees (NPEO x ), are incorporated into many commercial and industrial products such as detergents, domestic disinfectants, emulsifiers, cosmetics, and pesticides. However, the toxic effects exerted by their degradation products, which are persistent in natural environments, have been demonstrated in several animal and invertebrate aquatic species. Therefore, it seems appropriate to look for indigenous bacteria capable of degrading native NPEO x and its derivatives. In this paper, the isolation of five bacterial strains, capable of using NPEO 15 , as unique carbon source, is described. The most efficient NPEO 15 degrader bacterial strains were identified as Pseudomonas fluorescens (strain Yas2) and Klebsiella pneumoniae (strain Yas1). Maximal growth rates were reached at pH 8, 27°C in a 5% NPEO 15 medium. The NPEO 15 degradation extension, followed by viscometry assays, reached 65% after 54.5 h and 134 h incubation times, while the COD values decreased by 95% and 85% after 24 h for the Yas1 and Yas2 systems, respectively. The BOD was reduced by 99% and 99.9% levels in 24 h and 48 h incubations. The viscosity data indicated that the NPEO 15 biodegradation by Yas2 follows first-order kinetics. Kinetic rate constant (k) and half life time (τ) for this biotransformation were estimated to be 0.0072 h(-1) and 96.3 h, respectively. PMID:23936727

  16. Effect of high-resolution spatial soil moisture variability on simulated runoff response using a distributed hydrologic model

    Minet, J; Laloy, E.; Lambot, S; Vanclooster, M


    The importance of the spatial variability of antecedent soil moisture conditions on runoff response is widely acknowledged in hillslope hydrology. Using a distributed hydrologic model, this paper aims at investigating the effects of soil moisture spatial variability on runoff in various field conditions and at finding the structure of the soil moisture pattern that approaches the measured soil moisture pattern in terms of field scale runoff. High spatial resolution soil moisture was surveyed ...

  17. Effect of GPR-derived within-field soil moisture variability on the runoff response using a distributed hydrologic model

    Minet, J; Laloy, E.; Lambot, S; Vanclooster, M


    The importance of the spatial variability of the antecedent soil moisture conditions on the runoff response is widely acknowledged in hillslope hydrology. Using a distributed hydrologic model, this paper aims at investigating the effects of soil moisture spatial variability on the runoff in various field conditions and at finding the soil moisture scenario that behaves the most closely as the measured soil moisture pattern in term of runoff hydrograph. Soil moisture was surveyed in ten differ...

  18. Forest tree growth response to hydroclimate variability in the southern Appalachians.

    Elliott, Katherine J; Miniat, Chelcy F; Pederson, Neil; Laseter, Stephanie H


    Climate change will affect tree species growth and distribution; however, under the same climatic conditions species may differ in their response according to site conditions. We evaluated the climate-driven patterns of growth for six dominant deciduous tree species in the southern Appalachians. We categorized species into two functional groups based on their stomatal regulation and xylem architecture: isohydric, diffuse porous and anisohydric, ring porous. We hypothesized that within the same climatic regime: (i) species-specific differences in growth will be conditional on topographically mediated soil moisture availability; (ii) in extreme drought years, functional groups will have markedly different growth responses; and (iii) multiple hydroclimate variables will have direct and indirect effects on growth for each functional group. We used standardized tree-ring chronologies to examine growth of diffuse-porous (Acer, Liriodendron, and Betula) and ring-porous (Quercus) species vs. on-site climatic data from 1935 to 2003. Quercus species growing on upslope sites had higher basal area increment (BAI) than Quercus species growing on mesic, cove sites; whereas, Acer and Liriodendron had lower BAI on upslope compared to cove sites. Diffuse-porous species were more sensitive to climate than ring porous, especially during extreme drought years. Across functional groups, radial growth was more sensitive to precipitation distribution, such as small storms and dry spell length (DSL), rather than the total amount of precipitation. Based on structural equation modeling, diffuse-porous species on upslope sites were the most sensitive to multiple hydroclimate variables (r(2)  = 0.46), while ring-porous species on upslope sites were the least sensitive (r(2)  = 0.32). Spring precipitation, vapor pressure deficit, and summer storms had direct effects on summer AET/P, and summer AET/P, growing season small storms and DSL partially explained growth. Decreasing numbers of

  19. Ecohydrological responses of dense canopies to environmental variability: 1. Interplay between vertical structure and photosynthetic pathway

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.


    Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and ecophysiological functioning of leaves and the structural components of the canopy. These responses have the potential to significantly modify plant carbon uptake and surface energy partitioning, and have been attributed with large-scale changes in surface hydrology over recent decades. While the aggregated effects of vegetation acclimation can be pronounced, they often result from subtle changes in canopy properties that require the resolution of physical, biochemical and ecophysiological processes through the canopy for accurate estimation. In this paper, the first of two, a multilayer canopy-soil-root system model developed to capture the emergent vegetation responses to environmental change is presented. The model incorporates both C3 and C4 photosynthetic pathways, and resolves the vertical radiation, thermal, and environmental regimes within the canopy. The tight coupling between leaf ecophysiological functioning and energy balance determines vegetation responses to climate states and perturbations, which are modulated by soil moisture states through the depth of the root system. The model is validated for three growing seasons each for soybean (C3) and maize (C4) using eddy-covariance fluxes of CO2, latent, and sensible heat collected at the Bondville (Illinois) Ameriflux tower site. The data set provides an opportunity to examine the role of important environmental drivers and model skill in capturing variability in canopy-atmosphere exchange. Vertical variation in radiative states and scalar fluxes over a mean diurnal cycle are examined to understand the role of canopy structure on the patterns of absorbed radiation and scalar flux magnitudes and the consequent differences in sunlit and shaded source/sink locations through the canopies. An analysis is made of the impact of

  20. Spatial uncoupling of biodegradation, soil respiration, and PAH concentration in a creosote contaminated soil

    Hotspots and coldspots of concentration and biodegradation of polycyclic aromatic hydrocarbons (PAHs) marginally overlapped at the 0.5-100 m scale in a creosote contaminated soil in southern Sweden, suggesting that concentration and biodegradation had little spatial co-variation. Biodegradation was substantial and its spatial variability considerable and highly irregular, but it had no spatial autocorrelation. The soil concentration of PAHs explained only 20-30% of the variance of their biodegradation. Soil respiration was spatially autocorrelated. The spatial uncoupling between biodegradation and soil respiration seemed to be governed by the aging of PAHs in the soil, since biodegradation of added 13C phenanthrene covaried with both soil respiration and microbial biomass. The latter two were also correlated with high concentrations of phospholipid fatty acids (PLFAs) that are common in gram-negative bacteria. However, several of the hotspots of biodegradation coincided with hotspots for the distribution of a PLFA indicative of fungal biomass. - Hotspots of PAH biodegradation in a creosote contaminated soil do not coincide with hotspots of PAH concentration, microbial biomass and respiration.

  1. Biodegradation of plastics in soil and effects on nitrification activity. A laboratory approach.

    Giulia eBettas Ardisson


    Full Text Available The progressive application of new biodegradable plastics in agriculture calls for improved testing approaches to assure their environmental safety. Full biodegradation (≥ 90% prevents accumulation in soil, which is the first tier of testing. The application of specific ecotoxicity tests is the second tier of testing needed to show safety for the soil ecosystem. Soil microbial nitrification is widely used as a bioindicator for evaluating the impact of chemicals on soil but it is not applied for evaluating the impact of biodegradable plastics. In this work the International Standard test for biodegradation of plastics in soil (ISO 17556, 2012 was applied both to measure biodegradation and to prepare soil samples needed for a subsequent nitrification test based on another International Standard (ISO 14238, 2012. The plastic mulch film tested in this work showed full biodegradability and no inhibition of the nitrification potential of the soil in comparison with the controls. The laboratory approach suggested in this Technology Report enables (i to follow the course of biodegradation, (ii a strict control of variables and environmental conditions, (iii the application of very high concentrations of test material (to maximize the possible effects. This testing approach could be taken into consideration in improved testing schemes aimed at defining the biodegradability of plastics in soil.

  2. Responses of carbon isotope discrimination in C4 plant to variable N and water supply

    Yang, Hao; Li, Shenggong


    Understanding variations and underlying mechanisms of carbon isotope discrimination (Δ) in C4 species is critical for predicting the effects of change in C3/C4 ratio of plant community on ecosystem processes and functionning. However, little is known about the effects of soil resource gradients on Δ of C4 plants. To address Δ responses to drought and nitrogen supply, the leaf carbon isotope composition, bundle sheath leakiness (BLS), and leaf gas exchange (A, gs, Ci/Ca) were measured on Cleistogenes squarrosa, a dominant C4 species in the Inner Mongolia grassland. C. squarrosa were grown in controlled-environment pots from seed under a combination of water and N supply. High N availability and drought stimulated photosynthetic rate (A) and further decreased the ratio of internal and ambient CO2 concentrations (Ci/Ca) through increasing leaf N content. BLS was higher under high N supply and was unchanged by drought. There was significant interaction between N and water supply to affect BLS and Ci/Ca. Δ was negatively related to Ci/Ca and was positively related to BLS. Tradeoff between the responses of BLS and Ci/Ca to changing environmental conditions kept leaf Δ relatively stable, which was also supported by a field N addition experiment. Our results suggested leaf Δ of C4 plant was unchanged under variable water and N environment conditions although the operating efficiency of C4 pathway and CO2 concentration in photosynthesis were changed. Our findings have implications for predicting the change of C3/C4 ratio of plant community and understanding ecosystem processes and functionning.

  3. Muscle activation, blood lactate, and perceived exertion responses to changing resistance training programming variables.

    Hiscock, Daniel J; Dawson, Brian; Donnelly, Cyril J; Peeling, Peter


    Ratings of perceived exertion (RPE: 0-10) during resistance training with varying programming demands were examined. Blood lactate (BLa) and muscle activation (using surface electromyography: EMG) were measured as potential mediators of RPE responses. Participants performed three sets of single arm (preferred side) bicep curls at 70% of 1 repetition maximum over 4 trials: Trial (A) 3 sets × 8 repetitions × 120 s recovery between sets; (B) 3 sets × 8 repetitions × 240 s recovery; (C) 3 sets × maximum number of repetitions (MNR) × 120 s recovery; (D) 3 sets × MNR × 240 s recovery. Overall body (RPE-O) and active muscle (RPE-AM) perceptual responses were assessed following each set in each trial. Biceps brachii and brachioradialis muscle EMG was measured during each set for each trial. RPE-O and RPE-AM were not different between Trial A (3.5 ± 1 and 6 ± 1, respectively) and Trial B (3.5 ± 1 and 5.5 ± 1, respectively) (p < .05). However, RPE-AM was significantly greater in Trial C (7.5 ± 1.5) and Trial D (7.5 ± 1.5) than in Trial B (p < .05). There were no significant differences in muscle activation or BLa between trials; however, work rate (tonnage/min) was greater in Trials C and D compared to Trial B. In conclusion, BLa and muscle activation were not related to RPE, but resistance training variables, such as work rate, may impact on RPE when intensity (%1RM) and the number of sets completed remain constant. PMID:26267339

  4. Effects of the Biodegradation on Biodegradable Polymer Blends and Polypropylene

    Pereira, R. C. T.; Franchetti, S. M. M.; Agnelli, J. A. M.; Mattoso, L. H. C.


    The large use of plastics in the world generates a large amount of waste which persists around 200 years in the environment. To minimize this effect is important to search some new polymer materials: the blends of biodegradable polymers with synthetic polymers. It is a large area that needs an intensive research to investigate the blends properties and its behavior face to the different treatments to aim at the biodegradation. The blends used in this work are: some biodegradable polymers such as: poly(hydroxybutyrate) (PHB) and poly(ɛ-polycaprolactone) (PCL) with a synthetic polymer, polypropylene (PP), in lower concentration. These blends were prepared using an internal mixer (Torque Rheometer), and pressed. These films were submitted to fungus biotreatment. The films analyses will be carried out by Fourier Transform Infrared (FTIR), UV-Vis absorption (UV-Vis), Scanning Electronic Microscopy (SEM), DSC and TGA.

  5. Temperature and pH Responsive Microfibers for Controllable and Variable Ibuprofen Delivery

    Toan Tran


    Full Text Available Electrospun microfibers (MFs composed of pH and temperature responsive polymers can be used for controllable and variable delivery of ibuprofen. First, electrospinning technique was employed to prepare poly(ε-caprolactone (PCL and poly(N-isopropylacrylamide-co-methacrylic acid (pNIPAM-co-MAA MFs containing ibuprofen. It was found that drug release rates from PCL MFs cannot be significantly varied by either temperature (22–40°C or pH values (1.7–7.4. In contrast, the ibuprofen (IP diffusion rates from pNIPAM-co-MAA MFs were very sensitive to changes in both temperature and pH. The IP release from pNIPAM-co-MAA MFs was highly linear and controllable when the temperature was above the lower critical solution temperature (LCST of pNIPAM-co-MAA (33°C and the pH was lower than the pKa of carboxylic acids (pH 2. At room temperature, however, the release rate was dramatically increased by nearly ten times compared to that at higher temperature and lower pH. Such a unique and controllable drug delivery system could be naturally envisioned to find many practical applications in biomedical and pharmaceutical sciences such as programmable transdermal drug delivery.

  6. Biodegradable and radically polymerized elastomers with enhanced processing capabilities

    Ifkovits, Jamie L; Burdick, Jason A [Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104 (United States); Padera, Robert F [Department of Pathology, Brigham and Women' s Hospital, Harvard Medical School, Boston, MA 02115 (United States)], E-mail:


    The development of biodegradable materials with elastomeric properties is beneficial for a variety of applications, including for use in the engineering of soft tissues. Although others have developed biodegradable elastomers, they are restricted by their processing at high temperatures and under vacuum, which limits their fabrication into complex scaffolds. To overcome this, we have modified precursors to a tough biodegradable elastomer, poly(glycerol sebacate) (PGS) with acrylates to impart control over the crosslinking process and allow for more processing options. The acrylated-PGS (Acr-PGS) macromers are capable of crosslinking through free radical initiation mechanisms (e.g., redox and photo-initiated polymerizations). Alterations in the molecular weight and % acrylation of the Acr-PGS led to changes in formed network mechanical properties. In general, Young's modulus increased with % acrylation and the % strain at break increased with molecular weight when the % acrylation was held constant. Based on the mechanical properties, one macromer was further investigated for in vitro and in vivo degradation and biocompatibility. A mild to moderate inflammatory response typical of implantable biodegradable polymers was observed, even when formed as an injectable system with redox initiation. Moreover, fibrous scaffolds of Acr-PGS and a carrier polymer, poly(ethylene oxide), were prepared via an electrospinning and photopolymerization technique and the fiber morphology was dependent on the ratio of these components. This system provides biodegradable polymers with tunable properties and enhanced processing capabilities towards the advancement of approaches in engineering soft tissues.

  7. Reliability analysis for aeroengine turbine disc fatigue life with multiple random variables based on distributed collaborative response surface method

    高海峰; 白广忱; 高阳; 鲍天未


    The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables, such as applied load, working temperature, geometrical dimensions and material properties. In order to ameliorate reliability analysis efficiency without loss of reliability, the distributed collaborative response surface method (DCRSM) was proposed, and its basic theories were established in this work. Considering the failure dependency among the failure modes, the distributed response surface was constructed to establish the relationship between the failure mode and the relevant random variables. Then, the failure modes were considered as the random variables of system response to obtain the distributed collaborative response surface model based on structure failure criterion. Finally, the given turbine disc structure was employed to illustrate the feasibility and validity of the presented method. Through the comparison of DCRSM, Monte Carlo method (MCM) and the traditional response surface method (RSM), the results show that the computational precision for DCRSM is more consistent with MCM than RSM, while DCRSM needs far less computing time than MCM and RSM under the same simulation conditions. Thus, DCRSM is demonstrated to be a feasible and valid approach for improving the computational efficiency of reliability analysis for aeroengine turbine disc fatigue life with multiple random variables, and has great potential value for the complicated mechanical structure with multi-component and multi-failure mode.

  8. Response variability in Attention-Deficit/Hyperactivity Disorder: a neuronal and glial energetics hypothesis

    Auerbach Judith G


    Full Text Available 1. Abstract Background Current concepts of Attention-Deficit/Hyperactivity Disorder (ADHD emphasize the role of higher-order cognitive functions and reinforcement processes attributed to structural and biochemical anomalies in cortical and limbic neural networks innervated by the monoamines, dopamine, noradrenaline and serotonin. However, these explanations do not account for the ubiquitous findings in ADHD of intra-individual performance variability, particularly on tasks that require continual responses to rapid, externally-paced stimuli. Nor do they consider attention as a temporal process dependent upon a continuous energy supply for efficient and consistent function. A consideration of this feature of intra-individual response variability, which is not unique to ADHD but is also found in other disorders, leads to a new perspective on the causes and potential remedies of specific aspects of ADHD. The hypothesis We propose that in ADHD, astrocyte function is insufficient, particularly in terms of its formation and supply of lactate. This insufficiency has implications both for performance and development: H1 In rapidly firing neurons there is deficient ATP production, slow restoration of ionic gradients across neuronal membranes and delayed neuronal firing; H2 In oligodendrocytes insufficient lactate supply impairs fatty acid synthesis and myelination of axons during development. These effects occur over vastly different time scales: those due to deficient ATP (H1 occur over milliseconds, whereas those due to deficient myelination (H2 occur over months and years. Collectively the neural outcomes of impaired astrocytic release of lactate manifest behaviourally as inefficient and inconsistent performance (variable response times across the lifespan, especially during activities that require sustained speeded responses and complex information processing. Testing the hypothesis Multi-level and multi-method approaches are required. These include

  9. Adhesion of biocompatible and biodegradable micropatterned surfaces

    Kaiser, J.S.; Kamperman, M.M.G.; Souza, E.J.; Schick, B.; Arzt, E.


    We studied the effects of pillar dimensions and stiffness of biocompatible and biodegradable micropatterned surfaces on adhesion on different compliant substrates. The micropatterned adhesives were based on biocompatible polydimethylsiloxane (PDMS) and biodegradable poly(lactic-co-glycolic) acid (PL

  10. Using climate response functions in analyzing electricity production variables. A case study from Norway.

    Tøfte, Lena S.; Martino, Sara; Mo, Birger


    representation of hydropower is included and total hydro power production for each area is calculated, and the production is distributed among all available plants within each area. During simulation, the demand is affected by prices and temperatures. 6 different infrastructure scenarios of wind and power line development are analyzed. The analyses are done by running EMPS calibrated for today's situation for 11*11*8 different combinations of altered weather variables (temperature, precipitation and wind) describing different climate change scenarios, finding the climate response function for every EMPS-variable according the electricity production, such as prices and income, energy balances (supply, consumption and trade), overflow losses, probability of curtailment etc .

  11. Poly (3-Hydroxyalkanoates: Biodegradable Plastics

    Surbhi Jain


    Full Text Available During the 1920’s, a polyester called poly (3-hydroxybutyrate was discovered in bacterial cells. This compound, otherwise known as PHB, is part of a polyester family called polyhydroxyalkanoates (PHAs. Polyhydroxyalkanoates are used as an energy and carbon sto rage compound within certain bacterial cells. Polyhydroxyalkanoates (PHAs are thermoplastic, biodegradable polyesters synthesized by some bacteria from renewable carbon sources. However, their application is limited by high production cost. Polyhydroxyalkanoates (PHAs have attracted research and commercial interests worldwide because they can be used as biodegradable thermoplastics and also because they can be produced from renewable resources. This review will present an overview on synthesis and degradation of polyhydroxyalkanoates (PHAs, development as biodegradable plastics and its potential production from renewable resources such as palm oil products.

  12. The identification of hydrological indices for the characterization of macroinvertebrate community response to flow regime variability

    Worrall, T.P; M. J. Dunbar; Extence, C.A.; C. L. R. Laize; Monk, W.A.; Wood, P J


    The importance of flow regime variability for maintaining ecological functioning and integrity of river ecosystems has been firmly established in both natural and anthropogenically modified systems. In this paper we examine river flow regimes across lowland catchments in eastern England using 47 variables, including those derived using the Indicators of Hydrologic Alteration (IHA) software. A Principal Components Analysis (PCA) method was used to identify redundant hydrological variables and ...

  13. Soil microbial community response to drought and precipitation variability in the Chihuahuan Desert.

    Clark, Jeb S; Campbell, James H; Grizzle, Heath; Acosta-Martìnez, Veronica; Zak, John C


    Increases in the magnitude and variability of precipitation events have been predicted for the Chihuahuan Desert region of West Texas. As patterns of moisture inputs and amounts change, soil microbial communities will respond to these alterations in soil moisture windows. In this study, we examined the soil microbial community structure within three vegetation zones along the Pine Canyon Watershed, an elevation and vegetation gradient in Big Bend National Park, Chihuahuan Desert. Soil samples at each site were obtained in mid-winter (January) and in mid-summer (August) for 2 years to capture a component of the variability in soil temperature and moisture that can occur seasonally and between years along this watershed. Precipitation patterns and amounts differed substantially between years with a drought characterizing most of the second year. Soils were collected during the drought period and following a large rainfall event and compared to soil samples collected during a relatively average season. Structural changes within microbial community in response to site, season, and precipitation patterns were evaluated using fatty acid methyl ester (FAME) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses. Fungal FAME amounts differed significantly across seasons and sites and greatly outweighed the quantity of bacterial and actinomycete FAME levels for all sites and seasons. The highest fungal FAME levels were obtained in the low desert scrub site and not from the high elevation oak-pine forests. Total bacterial and actinomycete FAME levels did not differ significantly across season and year within any of the three locations along the watershed. Total bacterial and actinomycete FAME levels in the low elevation desert-shrub and grassland sites were slightly higher in the winter than in the summer. Microbial community structure at the high elevation oak-pine forest site was strongly correlated with levels of NH4+-N, % soil moisture

  14. Streamflow response to climate variability and human activities in the upper catchment of the Yellow River Basin

    ZHAO FangFang; XU ZongXue; ZHANG Lu; ZUO DePeng


    Both sensitivity-based method and simulation method are used to analyze the streamflow response to climate variability and human activities in the upper catchment of the Yellow River Basin (UYRB) in this study.The separation regime of effects from climate variability and human activities is investigated.Results show that the changes of streamflow are more sensitive to precipitation than potential evapotranspiration (PET).Effect of climate variability on streamflow estimated using the sensitiv-ity-based method is weak in the upper catchment of Jimai station, and strong in the upper catchment of Lanzhou station, where the climate effects accounted for about 50% of total streamflow changes.Effects of human activities on streamflow accounted for about 40% in the UYRB, with weaker effects in the upper catchment of Tangnaihai station than those in the upper catchment of Lanzhou station.Both climate variability and human activities are main factors to affect the changes of streamflow in the UYRB.

  15. Streamflow response to climate variability and human activities in the upper catchment of the Yellow River Basin


    Both sensitivity-based method and simulation method are used to analyze the streamflow response to climate variability and human activities in the upper catchment of the Yellow River Basin (UYRB) in this study. The separation regime of effects from climate variability and human activities is investigated. Results show that the changes of streamflow are more sensitive to precipitation than potential evapotranspiration (PET). Effect of climate variability on streamflow estimated using the sensitivity-based method is weak in the upper catchment of Jimai station, and strong in the upper catchment of Lanzhou station, where the climate effects accounted for about 50% of total streamflow changes. Effects of human activities on streamflow accounted for about 40% in the UYRB, with weaker effects in the upper catchment of Tangnaihai station than those in the upper catchment of Lanzhou station. Both climate variability and human activities are main factors to affect the changes of streamflow in the UYRB.

  16. Microtopographic hydrologic variability change resulting from vegetation acclimation response to elevated atmospheric CO2

    Le, P. V.; Kumar, P.


    The elevated concentration of atmospheric CO2 increases the ratio of carbon fixation to water loss from plants or water use efficiency, which reduces transpiration. However, the magnitude of the effects of this vegetation acclimation on hydrologic dynamics, such as soil moisture content and surface runoff controlled by microtopographic variability on the land surface, remains unclear. Here we integrate a multi-layer canopy-root-soil model (MLCan) with a coupled surface-subsurface flow model (GCSFlow) to capture the acclimation responses of vegetation to climate change and predict how these changes affect hydrologic dynamics on landscapes at fine scales. The model is implemented on a hybrid CPU-GPU parallel computing environment to overcome challenges associated with the high density of computational grid and nonlinear solvers. The model is capable of simulating large-scale heterogeneities due to both microtopography and soils and lateral water fluxes at emerging lidar-scale resolutions (~1m). We demonstrate that hybrid computing is feasible for detailed, large-scale ecohydrologic modeling, which has been previously assumed to be an intractable computational problem. Simulations are performed for corn crop in the Goose Creek watershed in central Illinois, USA at present and projected higher concentrations of atmospheric CO2, 400 ppm and 550 ppm, respectively. The results show a net decrease of 11% for the average annual evapotranspiration of corn, which increases water content in the soil and at the land surface. These results highlight the critical role of a warming climate on atmospheric-soil-vegetation interactions and the need to understand other dynamics near the soil surface associated with water and vegetation.

  17. Loss of lag-response curvilinearity of indices of heart rate variability in congestive heart failure

    Smith Michael L


    Full Text Available Abstract Background Heart rate variability (HRV is known to be impaired in patients with congestive heart failure (CHF. Time-domain analysis of ECG signals traditionally relies heavily on linear indices of an essentially non-linear phenomenon. Poincaré plots are commonly used to study non-linear behavior of physiologic signals. Lagged Poincaré plots incorporate autocovariance information and analysis of Poincaré plots for various lags can provide interesting insights into the autonomic control of the heart. Methods Using Poincaré plot analysis, we assessed whether the relation of the lag between heart beats and HRV is altered in CHF. We studied the influence of lag on estimates of Poincaré plot indices for various lengths of beat sequence in a public domain data set (PhysioNet of 29 subjects with CHF and 54 subjects with normal sinus rhythm. Results A curvilinear association was observed between lag and Poincaré plot indices (SD1, SD2, SDLD and SD1/SD2 ratio in normal subjects even for a small sequence of 50 beats (p value for quadratic term 3 × 10-5, 0.002, 3.5 × 10-5 and 0.0003, respectively. This curvilinearity was lost in patients with CHF even after exploring sequences up to 50,000 beats (p values for quadratic term > 0.5. Conclusion Since lagged Poincaré plots incorporate autocovariance information, these analyses provide insights into the autonomic control of heart rate that is influenced by the non-linearity of the signal. The differences in lag-response in CHF patients and normal subjects exist even in the face of the treatment received by the CHF patients.

  18. Developmental models for estimating ecological responses to environmental variability: structural, parametric, and experimental issues.

    Moore, Julia L; Remais, Justin V


    Developmental models that account for the metabolic effect of temperature variability on poikilotherms, such as degree-day models, have been widely used to study organism emergence, range and development, particularly in agricultural and vector-borne disease contexts. Though simple and easy to use, structural and parametric issues can influence the outputs of such models, often substantially. Because the underlying assumptions and limitations of these models have rarely been considered, this paper reviews the structural, parametric, and experimental issues that arise when using degree-day models, including the implications of particular structural or parametric choices, as well as assumptions that underlie commonly used models. Linear and non-linear developmental functions are compared, as are common methods used to incorporate temperature thresholds and calculate daily degree-days. Substantial differences in predicted emergence time arose when using linear versus non-linear developmental functions to model the emergence time in a model organism. The optimal method for calculating degree-days depends upon where key temperature threshold parameters fall relative to the daily minimum and maximum temperatures, as well as the shape of the daily temperature curve. No method is shown to be universally superior, though one commonly used method, the daily average method, consistently provides accurate results. The sensitivity of model projections to these methodological issues highlights the need to make structural and parametric selections based on a careful consideration of the specific biological response of the organism under study, and the specific temperature conditions of the geographic regions of interest. When degree-day model limitations are considered and model assumptions met, the models can be a powerful tool for studying temperature-dependent development. PMID:24443079

  19. Factors influencing crude oil biodegradation by Yarrowia lipolytica

    Tatiana Felix Ferreira


    Full Text Available Yarrowia lipolytica is unique strictly aerobic yeast with the ability to efficiently degrade hydrophobic substrates such as n-alkenes, fatty acids, glycerol and oils. In the present work, a 2(4 full factorial design was used to investigate the influence of the independent variables of temperature, agitation, initial cell concentration and initial petroleum concentration on crude oil biodegradation. The results showed that all variables studied had significant effects on the biodegradation process. Temperature, agitation speed and initial cell concentration had positive effects, and initial petroleum concentration had a negative effect. Among the crude oil removal conditions studied, the best temperature and agitation conditions were 28ºC and 250 rpm, respectively.

  20. Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability.

    Medvigy, David; Wofsy, Steven C; Munger, J William; Moorcroft, Paul R


    We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model version 2 in conjunction with the long-term record of carbon fluxes measured at Harvard Forest. We find that fluctuations of sunlight and precipitation are strongly and nonlinearly coupled to ecosystem function, with effects that accumulate through annual and decadal timescales. Increasing variability in sunlight and precipitation leads to lower rates of carbon sequestration and favors broad-leaved deciduous trees over conifers. Temperature variability has only minor impacts by comparison. We also find that projected changes in sunlight and precipitation variability have important implications for carbon storage and ecosystem structure and composition. Based on Intergovernmental Panel on Climate Change model estimates for changes in high-frequency meteorological variability over the next 100 years, we expect that terrestrial ecosystems will be affected by changes in variability almost as much as by changes in mean climate. We conclude that terrestrial ecosystems are highly sensitive to high-frequency meteorological variability, and that accurate knowledge of the statistics of this variability is essential for realistic predictions of ecosystem structure and functioning. PMID:20404190

  1. Biodegradable polycaprolactone-chitosan three-dimensional scaffolds fabricated by melt stretching and multilayer deposition for bone tissue engineering: assessment of the physical properties and cellular response

    Fabrication of polycaprolactone (PCL)-chitosan (CS) three-dimensional (3D) scaffolds using the novel technique of melt stretching and multilayer deposition was introduced. In brief, firstly, the PCL-CS monofilaments containing 0% (pure PCL), 10%, 20% and 30% CS by weight were fabricated by melting and stretching processes. Secondly, the desired multilayer (3D) scaffolds were fabricated by arranging and depositing the filaments. Physical properties of the filaments and the scaffolds were evaluated. MC3T3-E1 cell lines were seeded on the scaffolds to assess their proliferation. A typical micro-groove pattern was found on the surfaces of pure PCL filaments due to stretching. The filaments of PCL-30%CS had the highest tendency of fracture during stretching and could not be used to form the scaffold. Increasing CS proportions tended to reduce the micro-groove pattern, surface roughness, tensile strength and elasticity of the filaments, whilst compressive strength of the PCL-CS scaffolds was not affected. The average pore size and porosity of the scaffolds were 536.90 ± 17.91 μm and 45.99 ± 2.8% respectively. Over 60 days, degradation of the scaffolds gradually increased (p > 0.05). The more CS containing scaffolds were found to increase in water uptake, but decrease in degradation rate. During the culture period, the growth of the cells in PCL-CS groups was significantly higher than in the pure PCL group (p < 0.05). On culture-day 21, the growth in the PCL-20%CS group was significantly higher than the other groups (p < 0.05). In conclusion, the PCL-20%CS scaffolds obtained the optimum results in terms of physical properties and cellular response.

  2. Biodegradable polycaprolactone-chitosan three-dimensional scaffolds fabricated by melt stretching and multilayer deposition for bone tissue engineering: assessment of the physical properties and cellular response

    Thuaksuban, Nuttawut; Nuntanaranont, Thongchai; Suttapreyasri, Srisurang [Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Prince of Songkla University, Kanjanavanij Road, Hatyai, Songkhla, 90112 (Thailand); Pattanachot, Wachirapan [Polymer Science Program, Faculty of Science, Prince of Songkla University, Kanjanavanij Road, Hatyai, Songkhla, 90112 (Thailand); Cheung, Lim Kwong, E-mail: [Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, the University of Hong Kong, Hong Kong (China)


    Fabrication of polycaprolactone (PCL)-chitosan (CS) three-dimensional (3D) scaffolds using the novel technique of melt stretching and multilayer deposition was introduced. In brief, firstly, the PCL-CS monofilaments containing 0% (pure PCL), 10%, 20% and 30% CS by weight were fabricated by melting and stretching processes. Secondly, the desired multilayer (3D) scaffolds were fabricated by arranging and depositing the filaments. Physical properties of the filaments and the scaffolds were evaluated. MC3T3-E1 cell lines were seeded on the scaffolds to assess their proliferation. A typical micro-groove pattern was found on the surfaces of pure PCL filaments due to stretching. The filaments of PCL-30%CS had the highest tendency of fracture during stretching and could not be used to form the scaffold. Increasing CS proportions tended to reduce the micro-groove pattern, surface roughness, tensile strength and elasticity of the filaments, whilst compressive strength of the PCL-CS scaffolds was not affected. The average pore size and porosity of the scaffolds were 536.90 {+-} 17.91 {mu}m and 45.99 {+-} 2.8% respectively. Over 60 days, degradation of the scaffolds gradually increased (p > 0.05). The more CS containing scaffolds were found to increase in water uptake, but decrease in degradation rate. During the culture period, the growth of the cells in PCL-CS groups was significantly higher than in the pure PCL group (p < 0.05). On culture-day 21, the growth in the PCL-20%CS group was significantly higher than the other groups (p < 0.05). In conclusion, the PCL-20%CS scaffolds obtained the optimum results in terms of physical properties and cellular response.

  3. Variability in lateralised blood flow response to language is associated with language development in children aged 1-5 years.

    Kohler, M; Keage, H A D; Spooner, R; Flitton, A; Hofmann, J; Churches, O F; Elliott, S; Badcock, N A


    The developmental trajectory of language lateralisation over the preschool years is unclear. We explored the relationship between lateralisation of cerebral blood flow velocity response to object naming and cognitive performance in children aged 1-5 years. Functional transcranial Doppler ultrasound was used to record blood flow velocity bilaterally from middle cerebral arteries during a naming task in 58 children (59% male). At group level, the Lateralisation Index (LI) revealed a greater relative increase in cerebral blood flow velocity within the left as compared to right middle cerebral artery. After controlling for maternal IQ, left-lateralised children displayed lower expressive language scores compared to right- and bi-lateralised children, and reduced variability in LI. Supporting this, greater variability in lateralised response, rather than mean response, was indicative of greater expressive language ability. Findings suggest that a delayed establishment of language specialisation is associated with better language ability in the preschool years. PMID:25950747

  4. Biodegradable congress 2012; Bioschmierstoff-Kongress 2012



    Within the Guelzower expert discussions at 5th and 6th June, 2012 in Oberhausen (Federal Republic of Germany) the following lectures were held: (1) Promotion of biodegradable lubricants by means of research and development as well as public relations (Steffen Daebeler); (2) Biodegradable lubricants - An overview of the advantages and disadvantages of the engaged product groups (Hubertus Murrenhoff); (3) Standardization of biodegradable lubricants - CEN/DIN standard committees - state of the art (Rolf Luther); (4) Market research for the utilization of biodegradable lubricants and means of proof of sustainability (Norbert Schmitz); (5) Fields of application for high performance lubricants and requirements upon the products (Gunther Kraft); (6) Investigations of biodegradable lubricants in rolling bearings and gears (Christoph Hentschke); (7) Biodegradable lubricants in central lubrication systems Development of gears and bearings of offshore wind power installations (Reiner Wagner); (8) Investigations towards environmental compatibility of biodegradable lubricants used in offshore wind power installations (Tolf Schneider); (9) Development of glycerine based lubricants for the industrial metalworking (Harald Draeger); (10) Investigations and utilization of biodegradable oils as electroinsulation oils in transformers (Stefan Tenbohlen); (11) Operational behaviour of lubricant oils in vegetable oil operation and Biodiesel operation (Horst Hamdorf); (12) Lubrication effect of lubricating oil of the third generation (Stefan Heitzig); (13) Actual market development from the view of a producer of biodegradable lubricants (Frank Lewen); (14) Utilization of biodegradable lubricants in forestry harvesters (Guenther Weise); (15) New biodegradable lubricants based on high oleic sunflower oil (Otto Botz); (16) Integrated fluid concept - optimized technology and service package for users of biodegradable lubricants (Juergen Baer); (17) Utilization of a bio oil sensor to control

  5. Long-term release of clodronate from biodegradable microspheres

    Perugini, Paola; Genta, Ida; Conti, Bice; Modena, Tiziana; Pavanetto, Franca


    This paper describes the formulation of a biodegradable microparticulate drug delivery system containing clodronate, a bisphosphonate intended for the treatment of bone diseases. Microspheres were prepared with several poly(D,L-lactide-co-glycolide) (PLGA) copolymers of various molecular weights and molar compositions and 1 poly(D,L-lactide) (PDLLA) homopolymer by a water-in-oil-in-water (w/o/w) double emulsion solvent evaporation procedure. Critical process parameters and formulation variabl...

  6. PEF variability, bronchial responsiveness and their relation to allergy markers in a random population (20-70 yr).

    Boezen, H M; Postma, D S; Schouten, J P; Kerstjens, H A; Rijcken, B


    We investigated the coherence of bronchial hyperresponsiveness (BHR) and peak expiratory flow (PEF) variability in their relation to allergy markers and respiratory symptoms in 399 subjects (20-70 yr). Bronchial hyperresponsiveness to methacholine was defined by both the provocative dose causing a fall in FEV1 of 20%, and the dose-response slope. PEF variability was determined as diurnal PEF variation (amplitude percent mean) and between-day PEF variation. Skin tests positivity, serum total IgE, and specific IgE (RAST) for house-dust mite (HDM), cat, timothy grass, and birch ("pollen") were determined, as well as the number of peripheral blood eosinophils. Wheeze and nocturnal dyspnea were defined as asthma-like symptoms; dyspnea > or = grade 3, cough and phlegm as chronic obstructive pulmonary disease (COPD)-like symptoms. The reciprocal of the dose-response slope and PEF variability were significantly correlated (r = -0.39). Subjects with a positive skin test for HDM (odds ratio [OR] = 3.9), cat (OR = 8.3), or pollen (OR = 3.6), or specific IgE for HDM (OR = 2.3), cat (OR = 3.4), or pollen (OR = 1.9) had increased risk of BHR compared with the reference group (all p values blood eosinophils. There are different associations of BHR and PEF variability with allergy markers. Although BHR and PEF variability are significantly correlated, they cannot be used interchangeably in epidemiologic settings. PMID:8680695

  7. Enzymatic oxidative biodegradation of nanoparticles: Mechanisms, significance and applications.

    Vlasova, Irina I; Kapralov, Alexandr A; Michael, Zachary P; Burkert, Seth C; Shurin, Michael R; Star, Alexander; Shvedova, Anna A; Kagan, Valerian E


    Biopersistence of carbon nanotubes, graphene oxide (GO) and several other types of carbonaceous nanomaterials is an essential determinant of their health effects. Successful biodegradation is one of the major factors defining the life span and biological responses to nanoparticles. Here, we review the role and contribution of different oxidative enzymes of inflammatory cells - myeloperoxidase, eosinophil peroxidase, lactoperoxidase, hemoglobin, and xanthine oxidase - to the reactions of nanoparticle biodegradation. We further focus on interactions of nanomaterials with hemoproteins dependent on the specific features of their physico-chemical and structural characteristics. Mechanistically, we highlight the significance of immobilized peroxidase reactive intermediates vs diffusible small molecule oxidants (hypochlorous and hypobromous acids) for the overall oxidative biodegradation process in neutrophils and eosinophils. We also accentuate the importance of peroxynitrite-driven pathways realized in macrophages via the engagement of NADPH oxidase- and NO synthase-triggered oxidative mechanisms. We consider possible involvement of oxidative machinery of other professional phagocytes such as microglial cells, myeloid-derived suppressor cells, in the context of biodegradation relevant to targeted drug delivery. We evaluate the importance of genetic factors and their manipulations for the enzymatic biodegradation in vivo. Finally, we emphasize a novel type of biodegradation realized via the activation of the "dormant" peroxidase activity of hemoproteins by the nano-surface. This is exemplified by the binding of GO to cyt c causing the unfolding and 'unmasking' of the peroxidase activity of the latter. We conclude with the strategies leading to safe by design carbonaceous nanoparticles with optimized characteristics for mechanism-based targeted delivery and regulatable life-span of drugs in circulation. PMID:26768553

  8. Global signal modulation of single-trial fMRI response variability: Effect on positive vs negative BOLD response relationship.

    Mayhew, S D; Mullinger, K J; Ostwald, D; Porcaro, C; Bowtell, R; Bagshaw, A P; Francis, S T


    In functional magnetic resonance imaging (fMRI), the relationship between positive BOLD responses (PBRs) and negative BOLD responses (NBRs) to stimulation is potentially informative about the balance of excitatory and inhibitory brain responses in sensory cortex. In this study, we performed three separate experiments delivering visual, motor or somatosensory stimulation unilaterally, to one side of the sensory field, to induce PBR and NBR in opposite brain hemispheres. We then assessed the relationship between the evoked amplitudes of contralateral PBR and ipsilateral NBR at the level of both single-trial and average responses. We measure single-trial PBR and NBR peak amplitudes from individual time-courses, and show that they were positively correlated in all experiments. In contrast, in the average response across trials the absolute magnitudes of both PBR and NBR increased with increasing stimulus intensity, resulting in a negative correlation between mean response amplitudes. Subsequent analysis showed that the amplitude of single-trial PBR was positively correlated with the BOLD response across all grey-matter voxels and was not specifically related to the ipsilateral sensory cortical response. We demonstrate that the global component of this single-trial response modulation could be fully explained by voxel-wise vascular reactivity, the BOLD signal standard deviation measured in a separate resting-state scan (resting state fluctuation amplitude, RSFA). However, bilateral positive correlation between PBR and NBR regions remained. We further report that modulations in the global brain fMRI signal cannot fully account for this positive PBR-NBR coupling and conclude that the local sensory network response reflects a combination of superimposed vascular and neuronal signals. More detailed quantification of physiological and noise contributions to the BOLD signal is required to fully understand the trial-by-trial PBR and NBR relationship compared with that of

  9. Biodegradation kinetics at low concentrations (

    Toräng, Lars; Albrechtsen, Hans-Jørgen; Nyholm, Niels

    Aerobic biodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in groundwater added sediment fines. At concentrations at or below 1 mu g/L of 2,4-D degradation kinetic was of true first order without significant growth of specific degraders and with half-life for mineralization in the...

  10. Biodegradable Pectin/clay Aerogels

    Biodegradable, foamlike materials based on renewable pectin and sodium montmorillonite clay were fabricated through a simple, environmentally friendly freeze-drying process. Addition of multivalent cations (Ca2+ and Al3+) resulted in apparent crosslinking of the polymer, and enhancement of aerogel p...