The relation between circadian asynchrony, functional redundancy, and trophic performance in tropical ant communities.

PubMed

Houadria, Mickal; Blüthgen, Nico; Salas-Lopez, Alex; Schmitt, Mona-Isabel; Arndt, Johanna; Schneider, Eric; Orivel, Jérôme; Menzel, Florian

2016-01-01

The diversity-stability relationship has been under intense scrutiny for the past decades, and temporal asynchrony is recognized as an important aspect of ecosystem stability. In contrast to relatively well-studied interannual and seasonal asynchrony, few studies investigate the role of circadian cycles for ecosystem stability. Here, we studied multifunctional redundancy of diurnal and nocturnal ant communities in four tropical rain forest sites. We analyzed how it was influenced by species richness, functional performance, and circadian asynchrony. In two neotropical sites, species richness and functional redundancy were lower at night. In contrast, these parameters did not differ in the two paleotropical sites we studied. Circadian asynchrony between species was pronounced in the neotropical sites, and increased circadian functional redundancy. In general, species richness positively affected functional redundancy, but the effect size depended on the temporal and spatial breadth of the species with highest functional performance. Our analysis shows that high levels of trophic performance were only reached through the presence of such high-performing species, but not by even contributions of multiple, less-efficient species. Thus, these species can increase current functional performance, but reduce overall functional redundancy. Our study highlights that diurnal and nocturnal ecosystem properties of the very same habitat can markedly differ in terms of species richness and functional redundancy. Consequently, like the need to study multiple ecosystem functions, multiple periods of the circadian cycle need to be assessed in order to fully understand the diversity-stability relationship in an ecosystem.

Effects of visual feedback balance training on the balance and ankle instability in adult men with functional ankle instability.

PubMed

Nam, Seung-Min; Kim, Kyoung; Lee, Do Youn

2018-01-01

[Purpose] This study examined the effects of visual feedback balance training on the balance and ankle instability in adult men with functional ankle instability. [Subjects and Methods] Twenty eight adults with functional ankle instability, divided randomly into an experimental group, which performed visual feedback balance training for 20 minutes and ankle joint exercises for 10 minutes, and a control group, which performed ankle joint exercise for 30 minutes. Exercises were completed three times a week for 8 weeks. Bio rescue was used for balance ability. It measured limit of stability at one minute. For ankle instability was measured using Cumberland ankle instability tool (CAIT). This measure was performed before and after the experiments in each group. [Results] The experimental group had significant increase in the Limit of Stability and CAIT score. The control group had significant increase in CAIT score. While the Limit of Stability increased without significance. [Conclusion] In conclusion, visual feedback balance training can be recommended as a treatment method for patients with functional ankle instability.

Effects of special exercise programs on functional movement screen scores and injury prevention in preprofessional young football players.

PubMed

Dinc, Engin; Kilinc, Bekir Eray; Bulat, Muge; Erten, Yunus Turgay; Bayraktar, Bülent

2017-10-01

To increase movement capacity and to reduce injury risk in young soccer players by implementing a special functional exercise program based on functional movement screen (FMS) and correctives. 67 young male athletes 14-19 years of age from a Super League Football Club Academy participated in the study. Functional movement patterns were evaluated with FMS assessment protocol. Deep squat, hurdle step, inline lunge, shoulder mobility, active straight leg raise, trunk stability push-up, and rotatory stability were examined in FMS. Considering the FMS scores the number of intervention and control groups were defined as 24 and 43, respectively. Intervention program was composed of 1 hr twice a week sessions in total of 12 weeks with 4 weeks of mobility, 4 weeks of stability, and 4 weeks of integration exercises. At the end of 12-week intervention and control groups were re-evaluated with FMS protocol. Contact and noncontact sports injuries recorded during one season. In intervention group there was statistically significant difference in increase in total FMS scores ( P <0.01), deep squat ( P ≤0.001), hurdle step ( P <0.05), inline lunge ( P <0.01), and trunk stability push-up ( P <0.01). In control group total FMS, deep squat, and trunk stability push-up scores increased with a statistical difference ( P <0.01, P <0.05, P ≤0.01, respectively). The incidence of noncontact injury in control group was higher than intervention group ( P <0.05). Periodic movement screening and proper corrections with functional training is valuable in order to create better movement capacity to build better physical performance and more effective injury prevention.

Impact of a stance phase microprocessor-controlled knee prosthesis on level walking in lower functioning individuals with a transfemoral amputation.

PubMed

Eberly, Valerie J; Mulroy, Sara J; Gronley, JoAnne K; Perry, Jacquelin; Yule, William J; Burnfield, Judith M

2014-12-01

For individuals with transfemoral amputation, walking with a prosthesis presents challenges to stability and increases the demand on the hip of the prosthetic limb. Increasing age or comorbidities magnify these challenges. Computerized prosthetic knee joints improve stability and efficiency of gait, but are seldom prescribed for less physically capable walkers who may benefit from them. To compare level walking function while wearing a microprocessor-controlled knee (C-Leg Compact) prosthesis to a traditionally prescribed non-microprocessor-controlled knee prosthesis for Medicare Functional Classification Level K-2 walkers. Crossover. Stride characteristics, kinematics, kinetics, and electromyographic activity were recorded in 10 participants while walking with non-microprocessor-controlled knee and Compact prostheses. Walking with the Compact produced significant increase in velocity, cadence, stride length, single-limb support, and heel-rise timing compared to walking with the non-microprocessor-controlled knee prosthesis. Hip and thigh extension during late stance improved bilaterally. Ankle dorsiflexion, knee extension, and hip flexion moments of the prosthetic limb were significantly improved. Improvements in walking function and stability on the prosthetic limb were demonstrated by the K-2 level walkers when using the C-Leg Compact prosthesis. Understanding the impact of new prosthetic designs on gait mechanics is essential to improve prescription guidelines for deconditioned or older persons with transfemoral amputation. Prosthetic designs that improve stability for safety and walking function have the potential to improve community participation and quality of life. © The International Society for Prosthetics and Orthotics 2013.

Tighter Ligand Binding Can Compensate for Impaired Stability of an RNA-Binding Protein.

PubMed

Wallis, Christopher P; Richman, Tara R; Filipovska, Aleksandra; Rackham, Oliver

2018-06-15

It has been widely shown that ligand-binding residues, by virtue of their orientation, charge, and solvent exposure, often have a net destabilizing effect on proteins that is offset by stability conferring residues elsewhere in the protein. This structure-function trade-off can constrain possible adaptive evolutionary changes of function and may hamper protein engineering efforts to design proteins with new functions. Here, we present evidence from a large randomized mutant library screen that, in the case of PUF RNA-binding proteins, this structural relationship may be inverted and that active-site mutations that increase protein activity are also able to compensate for impaired stability. We show that certain mutations in RNA-protein binding residues are not necessarily destabilizing and that increased ligand-binding can rescue an insoluble, unstable PUF protein. We hypothesize that these mutations restabilize the protein via thermodynamic coupling of protein folding and RNA binding.

Experimental study of the effects of secondary air on the emissions and stability of a lean premixed combustor

NASA Technical Reports Server (NTRS)

Roffe, G.; Raman, R. S. V.

1981-01-01

Tests were run using a perforated plate flameholder with a relatively short attached recirculation zone and a vee gutter flameholder with a relatively long attached recirculation zone. Combustor streamlines were traced in cold flow tests at ambient pressure. The amount of secondary air entrainment in the recirculation zones of the flameholders was determined by tracer gas testing at cold flow ambient pressure conditions. Combustion tests were caried out at entrance conditions of 0.5 MPa/630K and emission of NOx, CO and unburned hydrocarbons were measured along with lean stability and flashback limits. The degree of entrainment increases as dilution air injection decreases. Flashback appears to be a function of overall equivalence ratio and resistance to flashback increases with increasing combustor entrance velocity. Lean stability limit appears to be a function of both primary zone and flameholder recirculation zone equivalence ratios and resistance to lean blowout increases with increasing combustor entrance velocity.

Postural Stability Margins as a Function of Support Surface Slopes.

PubMed

Dutt-Mazumder, Aviroop; Slobounov, Seymon M; Challis, John Henry; Newell, Karl Maxim

2016-01-01

This investigation examined the effects of slope of the surface of support (35°, 30°, 20°, 10° Facing(Toe) Down, 0° Flat and 10°, 20°, 25° Facing (Toe) Up) and postural orientation on the margins of postural stability in quiet standing of young adults. The findings showed that the center of pressure-CoP (displacement, area and length) had least motion at the baseline (0° Flat) platform condition that progressively increased as a function of platform angle in both facing up and down directions. The virtual time to collision (VTC) dynamics revealed that the spatio-temporal margins to the functional stability boundary were progressively smaller and the VTC time series also more regular (SampEn-Sample Entropy) as slope angle increased. Surface slope induces a restricted stability region with lower dimension VTC dynamics that is more constrained when postural orientation is facing down the slope. These findings provide further evidence that VTC acts as a control variable in standing posture that is influenced by the emergent dynamics of the individual-environment-task interaction.

Tyrosine Phosphorylation of the Human Serotonin Transporter: A Role in the Transporter Stability and Function

PubMed Central

Annamalai, Balasubramaniam; Mannangatti, Padmanabhan; Arapulisamy, Obulakshmi; Shippenberg, Toni S.; Jayanthi, Lankupalle D.

2012-01-01

The serotonin (5-HT) transporter (SERT) regulates serotoninergic neurotransmission by clearing 5-HT released into the synaptic space. Phosphorylation of SERT on serine and threonine mediates SERT regulation. Whether tyrosine phosphorylation regulates SERT is unknown. Here, we tested the hypothesis that tyrosine-phosphorylation of SERT regulates 5-HT transport. In support of this, alkali-resistant 32P-labeled SERT was found in rat platelets, and Src-tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo [3,4,d]pyrimidine (PP2) decreased platelet SERT function and expression. In human placental trophoblast cells expressing SERT, PP2 reduced transporter function, expression, and stability. Although siRNA silencing of Src expression decreased SERT function and expression, coexpression of Src resulted in PP2-sensitive increases in SERT function and expression. PP2 treatment markedly decreased SERT protein stability. Compared with WT-SERT, SERT tyrosine mutants Y47F and Y142F exhibited reduced 5-HT transport despite their higher total and cell surface expression levels. Moreover, Src-coexpression increased total and cell surface expression of Y47F and Y142F SERT mutants without affecting their 5-HT transport capacity. It is noteworthy that Y47F and Y142F mutants exhibited higher protein stability compared with WT-SERT. However, similar to WT-SERT, PP2 treatment decreased the stability of Y47F and Y142F mutants. Furthermore, compared with WT-SERT, Y47F and Y142F mutants exhibited lower basal tyrosine phosphorylation and no further enhancement of tyrosine phosphorylation in response to Src coexpression. These results provide the first evidence that SERT tyrosine phosphorylation supports transporter protein stability and 5HT transport. PMID:21992875

Mood stabilizer treatment increases serotonin type 1A receptor binding in bipolar depression

PubMed Central

Nugent, Allison C; Carlson, Paul J; Bain, Earle E; Eckelman, William; Herscovitch, Peter; Manji, Husseini; Zarate, Carlos A; Drevets, Wayne C

2013-01-01

Abnormal serotonin type 1A (5-HT1A) receptor function and binding have been implicated in the pathophysiology of mood disorders. Preclinical studies have consistently shown that stress decreases the gene expression of 5-HT1A receptors in experimental animals, and that the associated increase in hormone secretion plays a crucial role in mediating this effect. Chronic administration of the mood stabilizers lithium and divalproex (valproate semisodium) reduces glucocorticoid signaling and function in the hippocampus. Lithium has further been shown to enhance 5-HT1A receptor function. To assess whether these effects translate to human subject with bipolar disorder (BD), positron emission tomography (PET) and [18F]trans-4-fluoro-N-(2-[4-(2-methoxyphenyl) piperazino]-ethyl)-N-(2-pyridyl) cyclohexanecarboxamide ([18F]FCWAY) were used to acquire PET images of 5-HT1A receptor binding in 10 subjects with BD, before and after treatment with lithium or divalproex. Mean 5-HT1A binding potential (BPP) significantly increased following mood stabilizer treatment, most prominently in the mesiotemporal cortex (hippocampus plus amygdala). When mood state was also controlled for, treatment was associated with increases in BPP in widespread cortical areas. These preliminary findings are consistent with the hypothesis that these mood stabilizers enhance 5-HT1A receptor expression in BD, which may underscore an important component of these agents' mechanism of action. PMID:23926239

On increasing stability in the two dimensional inverse source scattering problem with many frequencies

NASA Astrophysics Data System (ADS)

Entekhabi, Mozhgan Nora; Isakov, Victor

2018-05-01

In this paper, we will study the increasing stability in the inverse source problem for the Helmholtz equation in the plane when the source term is assumed to be compactly supported in a bounded domain Ω with a sufficiently smooth boundary. Using the Fourier transform in the frequency domain, bounds for the Hankel functions and for scattering solutions in the complex plane, improving bounds for the analytic continuation, and the exact observability for the wave equation led us to our goals which are a sharp uniqueness and increasing stability estimate when the wave number interval is growing.

Mitochondria damage checkpoint in apoptosis and genome stability.

PubMed

Singh, Keshav K

2004-11-01

Mitochondria perform multiple cellular functions including energy production, cell proliferation and apoptosis. Studies described in this paper suggest a role for mitochondria in maintaining genomic stability. Genomic stability appears to be dependent on mitochondrial functions involved in maintenance of proper intracellular redox status, ATP-dependent transcription, DNA replication, DNA repair and DNA recombination. To further elucidate the role of mitochondria in genomic stability, I propose a mitochondria damage checkpoint (mitocheckpoint) that monitors and responds to damaged mitochondria. Mitocheckpoint can coordinate and maintain proper balance between apoptotic and anti-apoptotic signals. When mitochondria are damaged, mitocheckpoint can be activated to help cells repair damaged mitochondria, to restore normal mitochondrial function and avoid production of mitochondria-defective cells. If mitochondria are severely damaged, mitocheckpoint may not be able to repair the damage and protect cells. Such an event triggers apoptosis. If damage to mitochondria is continuous or persistent such as damage to mitochondrial DNA resulting in mutations, mitocheckpoint may fail which can lead to genomic instability and increased cell survival in yeast. In human it can cause cancer. In support of this proposal we provide evidence that mitochondrial genetic defects in both yeast and mammalian systems lead to impaired DNA repair, increased genomic instability and increased cell survival. This study reveals molecular genetic mechanisms underlying a role for mitochondria in carcinogenesis in humans.

Going, going, gone: predicting the fate of genomic insertions in plant RNA viruses.

PubMed

Willemsen, Anouk; Carrasco, José L; Elena, Santiago F; Zwart, Mark P

2018-05-10

Horizontal gene transfer is common among viruses, while they also have highly compact genomes and tend to lose artificial genomic insertions rapidly. Understanding the stability of genomic insertions in viral genomes is therefore relevant for explaining and predicting their evolutionary patterns. Here, we revisit a large body of experimental research on a plant RNA virus, tobacco etch potyvirus (TEV), to identify the patterns underlying the stability of a range of homologous and heterologous insertions in the viral genome. We obtained a wide range of estimates for the recombination rate-the rate at which deletions removing the insertion occur-and these appeared to be independent of the type of insertion and its location. Of the factors we considered, recombination rate was the best predictor of insertion stability, although we could not identify the specific sequence characteristics that would help predict insertion instability. We also considered experimentally the possibility that functional insertions lead to higher mutational robustness through increased redundancy. However, our observations suggest that both functional and non-functional increases in genome size decreased the mutational robustness. Our results therefore demonstrate the importance of recombination rates for predicting the long-term stability and evolution of viral RNA genomes and suggest that there are unexpected drawbacks to increases in genome size for mutational robustness.

Distinct Structural Elements Govern the Folding, Stability, and Catalysis in the Outer Membrane Enzyme PagP.

PubMed

Iyer, Bharat Ramasubramanian; Mahalakshmi, Radhakrishnan

2016-09-06

The outer membrane enzyme PagP is indispensable for lipid A palmitoylation in Gram-negative bacteria and has been implicated in resistance to host immune defenses. PagP possesses an unusual structure for an integral membrane protein, with a highly dynamic barrel domain that is tilted with respect to the membrane normal. In addition, it contains an N-terminal amphipathic helix. Recent functional and structural studies have shown that these molecular factors are critical for PagP to carry out its function in the challenging environment of the bacterial outer membrane. However, the precise contributions of the N-helix to folding and stability and residues that can influence catalytic rates remain to be addressed. Here, we identify a sequence-dependent stabilizing role for the N-terminal helix of PagP in the measured thermodynamic stability of the barrel. Using chimeric barrel sequences, we show that the Escherichia coli PagP N-terminal helix confers 2-fold greater stability to the Salmonella typhimurium barrel. Further, we find that the W78F substitution in S. typhimurium causes a nearly 20-fold increase in the specific activity in vitro for the phospholipase reaction, compared to that of E. coli PagP. Here, phenylalanine serves as a key regulator of catalysis, possibly by increasing the reaction rate. Through coevolution analysis, we detect an interaction network between seemingly unrelated segments of this membrane protein. Exchanging the structural and functional features between homologous PagP enzymes from E. coli and S. typhimurium has provided us with an understanding of the molecular factors governing PagP stability and function.

Influence of biopolymers on the solubility of branched-chain amino acids and stability of their solutions.

PubMed

Hong, Chi Rac; Lee, Gyu Whan; Paik, Hyun-Dong; Chang, Pahn-Shick; Choi, Seung Jun

2018-01-15

This study confirmed the possibility of biopolymer-type stabilizers to increase the saturation concentration of branched-chain amino acids by preventing their crystallization/precipitation. Although microfluidization increased the initial solubility, it failed to increase the saturation concentration of the branched-chain amino acids. The saturation concentration of the branched-chain amino acids increased from 3.81% to 4.42% and 4.85% after the incorporation of food hydrocolloids and proteins, respectively. However, the branched-chain amino acids:stabilizer ratio did not affect the solubility. In the case of food hydrocolloid-based solutions, crystal formation and growth of branched-chain amino acids occurred during storage, resulting in the precipitation of branched-chain amino acid crystals. However, food proteins effectively increased the stability of the solubilized branched-chain amino acids. The improved solubility and stability of the solubilized branched-chain amino acids could be attributed to interactions between the functional groups (carboxyl, amine, sulfate, aliphatic, aromatic, etc.) of the stabilizer and the branched-chain amino acid molecules. Copyright © 2017 Elsevier Ltd. All rights reserved.

Insight from first principles into the stability and magnetism of alkali-metal superoxide nanoclusters

NASA Astrophysics Data System (ADS)

Arcelus, Oier; Suaud, Nicolas; Katcho, Nebil A.; Carrasco, Javier

2017-05-01

Alkali-metal superoxides are gaining increasing interest as 2p magnetic materials for information and energy storage. Despite significant research efforts on bulk materials, gaps in our knowledge of the electronic and magnetic properties at the nanoscale still remain. Here, we focused on the role that structural details play in determining stability, electronic structure, and magnetic couplings of (MO2)n (M = Li, Na, and K, with n = 2-8) clusters. Using first-principles density functional theory based on the Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhof functionals, we examined the effect of atomic structure on the relative stability of different polymorphs within each investigated cluster size. We found that small clusters prefer to form planar-ring structures, whereas non-planar geometries become more stable when increasing the cluster size. However, the crossover point depends on the nature of the alkali metal. Our analysis revealed that electrostatic interactions govern the highly ionic M-O2 bonding and ultimately control the relative stability between 2-D and 3-D geometries. In addition, we analyzed the weak magnetic couplings between superoxide molecules in (NaO2)4 clusters comparing model Hamiltonian methods based on Wannier function projections onto πg states with wave function-based multi-reference calculations.

Conformational dynamics is key to understanding loss-of-function of NQO1 cancer-associated polymorphisms and its correction by pharmacological ligands

NASA Astrophysics Data System (ADS)

Encarnación, Medina-Carmona; Palomino-Morales, Rogelio J.; Fuchs, Julian E.; Esperanza, Padín-Gonzalez; Noel, Mesa-Torres; Salido, Eduardo; Timson, David J.; Pey, Angel L.

2016-02-01

Protein dynamics is essential to understand protein function and stability, even though is rarely investigated as the origin of loss-of-function due to genetic variations. Here, we use biochemical, biophysical, cell and computational biology tools to study two loss-of-function and cancer-associated polymorphisms (p.R139W and p.P187S) in human NAD(P)H quinone oxidoreductase 1 (NQO1), a FAD-dependent enzyme which activates cancer pro-drugs and stabilizes several oncosuppressors. We show that p.P187S strongly destabilizes the NQO1 dimer in vitro and increases the flexibility of the C-terminal domain, while a combination of FAD and the inhibitor dicoumarol overcome these alterations. Additionally, changes in global stability due to polymorphisms and ligand binding are linked to the dynamics of the dimer interface, whereas the low activity and affinity for FAD in p.P187S is caused by increased fluctuations at the FAD binding site. Importantly, NQO1 steady-state protein levels in cell cultures correlate primarily with the dynamics of the C-terminal domain, supporting a directional preference in NQO1 proteasomal degradation and the use of ligands binding to this domain to stabilize p.P187S in vivo. In conclusion, protein dynamics are fundamental to understanding loss-of-function in p.P187S, and to develop new pharmacological therapies to rescue this function.

Disordered Cold Regulated15 Proteins Protect Chloroplast Membranes during Freezing through Binding and Folding, But Do Not Stabilize Chloroplast Enzymes in Vivo1[W][OPEN

PubMed Central

Thalhammer, Anja; Bryant, Gary; Sulpice, Ronan; Hincha, Dirk K.

2014-01-01

Freezing can severely damage plants, limiting geographical distribution of natural populations and leading to major agronomical losses. Plants native to cold climates acquire increased freezing tolerance during exposure to low nonfreezing temperatures in a process termed cold acclimation. This involves many adaptative responses, including global changes in metabolite content and gene expression, and the accumulation of cold-regulated (COR) proteins, whose functions are largely unknown. Here we report that the chloroplast proteins COR15A and COR15B are necessary for full cold acclimation in Arabidopsis (Arabidopsis thaliana). They protect cell membranes, as indicated by electrolyte leakage and chlorophyll fluorescence measurements. Recombinant COR15 proteins stabilize lactate dehydrogenase during freezing in vitro. However, a transgenic approach shows that they have no influence on the stability of selected plastidic enzymes in vivo, although cold acclimation results in increased enzyme stability. This indicates that enzymes are stabilized by other mechanisms. Recombinant COR15 proteins are disordered in water, but fold into amphipathic α-helices at high osmolyte concentrations in the presence of membranes, a condition mimicking molecular crowding induced by dehydration during freezing. X-ray scattering experiments indicate protein-membrane interactions specifically under such crowding conditions. The COR15-membrane interactions lead to liposome stabilization during freezing. Collectively, our data demonstrate the requirement for COR15 accumulation for full cold acclimation of Arabidopsis. The function of these intrinsically disordered proteins is the stabilization of chloroplast membranes during freezing through a folding and binding mechanism, but not the stabilization of chloroplastic enzymes. This indicates a high functional specificity of these disordered plant proteins. PMID:25096979

Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity.

PubMed

Botelho, Danielle J; Leo, Bey Fen; Massa, Christopher B; Sarkar, Srijata; Tetley, Terry D; Chung, Kian Fan; Chen, Shu; Ryan, Mary P; Porter, Alexandra E; Zhang, Junfeng; Schwander, Stephan K; Gow, Andrew J

2016-01-01

Multiple studies have examined the direct cellular toxicity of silver nanoparticles (AgNPs). However, the lung is a complex biological system with multiple cell types and a lipid-rich surface fluid; therefore, organ level responses may not depend on direct cellular toxicity. We hypothesized that interaction with the lung lining is a critical determinant of organ level responses. Here, we have examined the effects of low dose intratracheal instillation of AgNPs (0.05 μg/g body weight) 20 and 110 nm diameter in size, and functionalized with citrate or polyvinylpyrrolidone. Both size and functionalization were significant factors in particle aggregation and lipid interaction in vitro. One day post-intratracheal instillation lung function was assessed, and bronchoalveolar lavage (BAL) and lung tissue collected. There were no signs of overt inflammation. There was no change in surfactant protein-B content in the BAL but there was loss of surfactant protein-D with polyvinylpyrrolidone (PVP)-stabilized particles. Mechanical impedance data demonstrated a significant increase in pulmonary elastance as compared to control, greatest with 110 nm PVP-stabilized particles. Seven days post-instillation of PVP-stabilized particles increased BAL cell counts, and reduced lung function was observed. These changes resolved by 21 days. Hence, AgNP-mediated alterations in the lung lining and mechanical function resolve by 21 days. Larger particles and PVP stabilization produce the largest disruptions. These studies demonstrate that low dose AgNPs elicit deficits in both mechanical and innate immune defense function, suggesting that organ level toxicity should be considered.

Development of Spexin-based Human Galanin Receptor Type II-Specific Agonists with Increased Stability in Serum and Anxiolytic Effect in Mice.

PubMed

Reyes-Alcaraz, Arfaxad; Lee, Yoo-Na; Son, Gi Hoon; Kim, Nam Hoon; Kim, Dong-Kyu; Yun, Seongsik; Kim, Dong-Hoon; Hwang, Jong-Ik; Seong, Jae Young

2016-02-24

The novel neuropeptide spexin (SPX) was discovered to activate galanin receptor 2 (GALR2) and 3 (GALR3) but not galanin receptor 1 (GALR1). Although GALR2 is known to display a function, particularly in anxiety, depression, and appetite regulation, the further determination of its function would benefit from a more stable and selective agonist that acts only at GALR2. In the present study, we developed a GALR2-specific agonist with increased stability in serum. As galanin (GAL) showed a low affinity to GALR3, the residues in SPX were replaced with those in GAL, revealing that particular mutations such as Gln5 → Asn, Met7 → Ala, Lys11 → Phe, and Ala13 → Pro significantly decreased potencies toward GALR3 but not toward GALR2. Quadruple (Qu) mutation of these residues still retained potency to GALR2 but totally abolished the potency to both GALR3 and GALR1. The first amino acid modifications or D-Asn1 substitution significantly increased the stability when they are incubated in 100% fetal bovine serum. Intracerebroventricular administration of the mutant peptide with D-Asn1 and quadruple substitution (dN1-Qu) exhibited an anxiolytic effect in mice. Taken together, the GALR2-specific agonist with increased stability can greatly help delineation of GALR2-mediated functions and be very useful for treatments of anxiety disorder.

Polarization Stability of Amorphous Piezoelectric Polyimides

NASA Technical Reports Server (NTRS)

Park, C.; Ounaies, Z.; Su, J.; Smith, J. G., Jr.; Harrison, J. S.

2000-01-01

Amorphous polyimides containing polar functional groups have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The thermal stability of the piezoelectric effect of one polyimide was evaluated as a function of various curing and poling conditions under dynamic and static thermal stimuli. First, the polymer samples were thermally cycled under strain by systematically increasing the maximum temperature from 50 C to 200 C while the piezoelectric strain coefficient was being measured. Second, the samples were isothermally aged at an elevated temperature in air, and the isothermal decay of the remanent polarization was measured at room temperature as a function of time. Both conventional and corona poling methods were evaluated. This material exhibited good thermal stability of the piezoelectric properties up to 100 C.

The development and use of SPIO Lycra compression bracing in children with neuromotor deficits.

PubMed

Hylton, N; Allen, C

1997-01-01

The use of flexible compression bracing in persons with neuromotor deficits offers improved possibilities for stability and movement control without severely limiting joint movement options. At the Children's Therapy Center in Kent, Washington, this treatment modality has been explored with increasing application in children with moderate to severe cerebral palsy and other neuromotor deficits over the past 6 years, with good success. Significant functional improvements using Neoprene shoulder/trunk/hip Bracing led us to experiment with much lighter compression materials. The stabilizing pressure input orthosis or SPIO bracing system (developed by Cheryl Allen, parent and Chief Designer, and Nancy Hylton, PT) is custom-fitted to the stability, movement control and sensory deficit needs of a specific individual. SPIO bracing developed for a specific child has often become part of a rapidly increasing group of flexible bracing options which appear to provide an improved base of support for functional gains in balance, dynamic stability, general and specific movement control with improved postural and muscle readiness. Both deep sensory and subtle biomechanical factors may account for the functional changes observed. This article discusses the development and current use of flexible compression SPIO bracing in this area.

The Effect of Core Stability Training on Functional Movement Patterns in Collegiate Athletes.

PubMed

Bagherian, Sajad; Ghasempoor, Khodayar; Rahnama, Nader; Wikstrom, Erik A

2018-02-06

Pre-participation examinations are the standard approach for assessing poor movement quality that would increase musculoskeletal injury risk. However, little is known about how core stability influences functional movement patterns. The primary purpose of this study was to determine the effect of an 8-week core stability program on functional movement patterns in collegiate athletes. The secondary purpose was to determine if the core stability training program would be more effective in those with worse movement quality (i.e. ≤14 baseline FMS score). Quasi-experimental design. Athletic Training Facility. One-hundred collegiate athletes. Functional movement patterns included the Functional Movement Screen (FMS), Lateral step down (LSD) and Y balance test (YBT) and were assessed before and after the 8-week program. Participants were placed into 1 of the 2 groups: intervention and control. The intervention group was required to complete a core stability training program that met 3 times per week for 8-week. Significant group x time interactions demonstrated improvements in FMS, LSD and YBT scores in the experimental group relative to the control group (p<0.001). Independent sample t-tests demonstrate that change scores were larger (greater improvement) for the FMS total score and Hurdle step (p<0.001) in athletes with worse movement quality. An 8-week core stability training program enhances functional movement patterns and dynamic postural control in collegiate athletes. The benefits are more pronounced in collegiate athletes with poor movement quality.

Electronic properties of graphene nanoribbons: A density functional investigation

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

Kumar, Sandeep, E-mail: skumar198712@gmail.com; Sharma, Hitesh, E-mail: dr.hitesh.phys@gmail.com

2015-05-15

Density functional theory calculations have been performed on graphene nano ribbons (GNRs) to investigate the electronic properties as a function of chirality, size and hydrogenation on the edges. The calculations were performed on GNRs with armchair and zigzag configurations with 28, 34, 36, 40, 50, 56, 62, 66 carbon atoms. The structural stability of AGNR and ZGNR increases with the size of nanoribbon where as hydrogenation of GNR tends to lowers their structural stability. All GNRs considered have shown semiconducting behavior with HOMO-LUMO gap decreasing with the increase in the GNR size. The hydrogenation of GNR decreases its HOMO-LUMO gapmore » significantly. The results are in agreement with the available experimental and theoretical results.« less

No beneficial effects of vitamin D supplementation on muscle function or quality of life in primary hyperparathyroidism: results from a randomized controlled trial.

PubMed

Rolighed, Lars; Rejnmark, Lars; Sikjaer, Tanja; Heickendorff, Lene; Vestergaard, Peter; Mosekilde, Leif; Christiansen, Peer

2015-05-01

Impairments of muscle function and strength in patients with primary hyperparathyroidism (PHPT) are rarely addressed, although decreased muscle function may contribute to increased fracture risk. We aimed to assess the changes in muscle strength, muscle function, postural stability, quality of life (QoL), and well-being during treatment with vitamin D or placebo before and after parathyroidectomy (PTX) in PHPT patients. A randomized placebo-controlled trial. We included 46 PHPT patients, mean age 58 (range 29-77) years and 35 (76%) were women. Daily treatment with 70 μg (2800 IU) cholecalciferol or placebo for 52 weeks. Treatment was administered 26 weeks before PTX and continued for 26 weeks after PTX. Changes in QoL and measures of muscle strength and function. Preoperatively, 25-hydroxyvitamin D (25OHD) increased significantly (50-94 nmol/l) compared with placebo (57-52 nmol/l). We did not measure any beneficial effects of supplementation with vitamin D compared with placebo regarding well-being, QoL, postural stability, muscle strength, or function. In all patients, we measured marked improvements in QoL, well-being (P<0.01), muscle strength in the knee flexion and extension (P<0.001), and muscle function tests (P<0.01) after surgical cure. Postural stability improved during standing with eyes closed (P<0.05), but decreased with eyes open (P<0.05). Patients with PHPT and 25OHD levels around 50 nmol/l did not benefit from vitamin D supplementation concerning muscle strength, muscle function, postural stability, well-being, or QoL. Independent of preoperative 25OHD levels, PTX improved these parameters. © 2015 European Society of Endocrinology.

Removal of the Side Chain at the Active-Site Serine by a Glycine Substitution Increases the Stability of a Wide Range of Serine β-Lactamases by Relieving Steric Strain

DOE PAGES

Stojanoski, Vlatko; Adamski, Carolyn J.; Hu, Liya; ...

2016-04-12

Serine β-lactamases are bacterial enzymes that hydrolyze β- lactam antibiotics. They utilize an active-site serine residue as a nucleophile, forming an acyl-enzyme intermediate during hydrolysis. Here, thermal denaturation experiments as well as X-ray crystallography were performed to test the effect of substitution of the catalytic serine with glycine on protein stability in serine β-lactamases. Six different enzymes comprising representatives from each of the three classes of serine β-lactamases were examined, including TEM-1, CTX-M- 14, and KPC-2 of class A, P99 of class C, and OXA-48 and OXA-163 of class D. For each enzyme, the wild type and a serine-to-glycine mutantmore » were evaluated for stability. The glycine mutants all exhibited enhanced thermostability compared to that of the wild type. In contrast, alanine substitutions of the catalytic serine in TEM-1, OXA-48, and OXA-163 did not alter stability, suggesting removal of the Cβ atom is key to the stability increase associated with the glycine mutants. The X-ray crystal structures of P99 S64G, OXA-48 S70G and S70A, and OXA-163 S70G suggest that removal of the side chain of the catalytic serine releases steric strain to improve enzyme stability. In addition, analysis of the torsion angles at the nucleophile position indicates that the glycine mutants exhibit improved distance and angular parameters of the intrahelical hydrogen bond network compared to those of the wild-type enzymes, which is also consistent with increased stability. The increased stability of the mutants indicates that the enzyme pays a price in stability for the presence of a side chain at the catalytic serine position but that the cost is necessary in that removal of the serine drastically impairs function. Our findings support the stability-function hypothesis, which states that active-site residues are optimized for substrate binding and catalysis but that the requirements for catalysis are often not consistent with the requirements for optimal stability.« less

Removal of the Side Chain at the Active-Site Serine by a Glycine Substitution Increases the Stability of a Wide Range of Serine β-Lactamases by Relieving Steric Strain

PubMed Central

Stojanoski, Vlatko; Adamski, Carolyn J.; Hu, Liya; Mehta, Shrenik C.; Sankaran, Banumathi; Zwart, Peter; Prasad, B.V. Venkataram; Palzkill, Timothy

2016-01-01

Serine β-lactamases are bacterial enzymes that hydrolyze β-lactam antibiotics. They utilize an active-site serine residue as a nucleophile, forming an acyl-enzyme intermediate during hydrolysis. In this study, thermal denaturation experiments as well as X-ray crystallography were performed to test the effect of substitution of the catalytic serine by glycine on protein stability in serine β-lactamases. Six different enzymes comprising representatives from each of the three classes of serine β-lactamases were examined including TEM-1, CTX-M-14, and KPC-2 of class A, P99 of class C, and OXA-48 and OXA-163 of class D. For each enzyme, the wild type and a serine-to-glycine mutant were evaluated for stability. The glycine mutants all exhibited enhanced thermostability compared to the wild type. In contrast, alanine substitutions of the catalytic serine in TEM-1, OXA-48 and OXA-163 did not alter stability, suggesting removal of the Cβ atom is key to the stability increase associated with the glycine mutants. The X-ray crystal structures of P99 S64G, OXA-48 S70G and S70A, and OXA-163 S70G suggest that removal of the side chain of the catalytic serine releases steric strain to improve enzyme stability. Additionally, analysis of the torsion angles at the nucleophile position indicates that the glycine mutants exhibit improved distance and angular parameters of the intra-helical hydrogen bond network compared to the wild-type enzymes, which is also consistent with increased stability. The increased stability of the mutants indicates that the enzyme pays a price in stability for the presence of a side chain at the catalytic serine position but that the cost is necessary in that removal of the serine drastically impairs function. These findings support the stability-function hypothesis, which states that active-site residues are optimized for substrate binding and catalysis but that the requirements for catalysis are often not consistent with the requirements for optimal stability. PMID:27073009

Removal of the Side Chain at the Active-Site Serine by a Glycine Substitution Increases the Stability of a Wide Range of Serine β-Lactamases by Relieving Steric Strain

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

Stojanoski, Vlatko; Adamski, Carolyn J.; Hu, Liya

Serine β-lactamases are bacterial enzymes that hydrolyze β- lactam antibiotics. They utilize an active-site serine residue as a nucleophile, forming an acyl-enzyme intermediate during hydrolysis. Here, thermal denaturation experiments as well as X-ray crystallography were performed to test the effect of substitution of the catalytic serine with glycine on protein stability in serine β-lactamases. Six different enzymes comprising representatives from each of the three classes of serine β-lactamases were examined, including TEM-1, CTX-M- 14, and KPC-2 of class A, P99 of class C, and OXA-48 and OXA-163 of class D. For each enzyme, the wild type and a serine-to-glycine mutantmore » were evaluated for stability. The glycine mutants all exhibited enhanced thermostability compared to that of the wild type. In contrast, alanine substitutions of the catalytic serine in TEM-1, OXA-48, and OXA-163 did not alter stability, suggesting removal of the Cβ atom is key to the stability increase associated with the glycine mutants. The X-ray crystal structures of P99 S64G, OXA-48 S70G and S70A, and OXA-163 S70G suggest that removal of the side chain of the catalytic serine releases steric strain to improve enzyme stability. In addition, analysis of the torsion angles at the nucleophile position indicates that the glycine mutants exhibit improved distance and angular parameters of the intrahelical hydrogen bond network compared to those of the wild-type enzymes, which is also consistent with increased stability. The increased stability of the mutants indicates that the enzyme pays a price in stability for the presence of a side chain at the catalytic serine position but that the cost is necessary in that removal of the serine drastically impairs function. Our findings support the stability-function hypothesis, which states that active-site residues are optimized for substrate binding and catalysis but that the requirements for catalysis are often not consistent with the requirements for optimal stability.« less

Improvement in the physiological function and standing stability based on kinect multimedia for older people

PubMed Central

Chen, Chih-Chen

2016-01-01

[Purpose] The increase in the Taiwanese older population is associated with age-related inconveniences. Finding adequate and simple physical activities to help the older people maintaining their physiological function and preventing them from falls has become an urgent social issue. [Subjects and Methods] This study aimed to design a virtual exercise training game suitable for Taiwanese older people. This system will allow for the maintenance of the physiological function and standing stability through physical exercise, while using a virtual reality game. The participants can easily exercise in a carefree, interactive environment. This study will use Kinect for Windows for physical movement detection and Unity software for virtual world development. [Results] Group A and B subjects were involved in the exercise training method of Kinect interactive multimedia for 12 weeks. The results showed that the functional reach test and the unipedal stance test improved significantly. [Conclusion] The physiological function and standing stability of the group A subjects were examined at six weeks post training. The results showed that these parameters remained constant. This proved that the proposed system provide substantial support toward the preservation of the Taiwanese older people’ physiological function and standing stability. PMID:27190480

Improvement in the physiological function and standing stability based on kinect multimedia for older people.

PubMed

Chen, Chih-Chen

2016-04-01

[Purpose] The increase in the Taiwanese older population is associated with age-related inconveniences. Finding adequate and simple physical activities to help the older people maintaining their physiological function and preventing them from falls has become an urgent social issue. [Subjects and Methods] This study aimed to design a virtual exercise training game suitable for Taiwanese older people. This system will allow for the maintenance of the physiological function and standing stability through physical exercise, while using a virtual reality game. The participants can easily exercise in a carefree, interactive environment. This study will use Kinect for Windows for physical movement detection and Unity software for virtual world development. [Results] Group A and B subjects were involved in the exercise training method of Kinect interactive multimedia for 12 weeks. The results showed that the functional reach test and the unipedal stance test improved significantly. [Conclusion] The physiological function and standing stability of the group A subjects were examined at six weeks post training. The results showed that these parameters remained constant. This proved that the proposed system provide substantial support toward the preservation of the Taiwanese older people' physiological function and standing stability.

Resilience and stability of a pelagic marine ecosystem

PubMed Central

Lindegren, Martin; Checkley, David M.; Ohman, Mark D.; Koslow, J. Anthony; Goericke, Ralf

2016-01-01

The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS. PMID:26763697

Mitochondrial ferritin affects mitochondria by stabilizing HIF-1α in retinal pigment epithelium: implications for the pathophysiology of age-related macular degeneration.

PubMed

Wang, Xiying; Yang, Hongkuan; Yanagisawa, Daijiro; Bellier, Jean-Pierre; Morino, Katsutaro; Zhao, Shiguang; Liu, Ping; Vigers, Piers; Tooyama, Ikuo

2016-11-01

Mitochondrial ferritin (FtMt) is believed to play an antioxidant role via iron regulation, and FtMt gene mutation has been reported in age-related macular degeneration (AMD). However, little is known about FtMt's functions in the retina and any links to AMD. In this study, we observed age-related increase in FtMt and hypoxia-inducible factor-1α (HIF-1α) in murine retinal pigment epithelium (RPE). FtMt overexpression in ARPE-19 cells stabilized HIF-1α, and increased the secretion of vascular endothelial growth factor. Conversely, HIF-1α stabilization reduced the protein level of the mature, functional form of FtMt. FtMt-overexpressing ARPE-19 cells exhibited less oxidative phosphorylation but unchanged production of adenosine triphosphate, enhanced mitochondrial fission, and triggered mitophagy in a HIF-1α-dependent manner. These findings suggest that increased FtMt in RPE may be protective via triggering mitophagy but cause wet AMD by inducing neovascularization due to increased vascular endothelial growth factor secretion. However, reduced level of functional FtMt in RPE under hypoxia may allow dry AMD through susceptibility to age-related stress. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

Enhancing vestibular function in the elderly with imperceptible electrical stimulation.

PubMed

Serrador, Jorge M; Deegan, Brian M; Geraghty, Maria C; Wood, Scott J

2018-01-10

Age-related loss of vestibular function can result in decrements in gaze stabilization and increased fall risk in the elderly. This study was designed to see if low levels of electrical stochastic noise applied transcutaneously to the vestibular system can improve a gaze stabilization reflex in young and elderly subject groups. Ocular counter-rolling (OCR) using a video-based technique was obtained in 16 subjects during low frequency passive roll tilts. Consistent with previous studies, there was a significant reduction in OCR gains in the elderly compared to the young group. Imperceptible stochastic noise significantly increased OCR in the elderly (Mean 23%, CI: 17-35%). Increases in OCR gain were greatest for those with lowest baseline gain and were negligible in those with normal gain. Since stimulation was effective at low levels undetectable to subjects, stochastic noise may provide a new treatment alternative to enhance vestibular function, specifically otolith-ocular reflexes, in the elderly or patient populations with reduced otolith-ocular function.

Increased functional properties and thermal stability of flexible cellulose nanocrystal/ZnO films.

PubMed

Lizundia, E; Urruchi, A; Vilas, J L; León, L M

2016-01-20

In this work we attempt to improve the functional properties and thermal stability of cellulose nanocrystal (CNC) films by means of eco-friendly materials and processes. Mechanically flexible films of closely packed CNCs with concentrations up to 5 wt.% of zinc oxide (ZnO) nanoparticles have been prepared by a simple, standard and environmentally friendly method using solely water. Results reveal that ultraviolet light is blocked by 98.5% at 1 wt.% ZnO while good transparency is maintained. A sharp hydrophobicity increase is observed with the addition of ZnO which would enhance the durability of films by decreasing the water diffusion through the material. The thermal degradation activation energy (E) presents an increase of 141%, denoting a high thermal stability of films, which would result beneficial for their potential application in the field of flexible electronics. Mechanical results demonstrate a high structural integrity of CNC/ZnO as a result of the occurring strong cellulosic inter- and intramolecular interactions within the closely packed CNC network. In overall, this work highlights the potential for environmentally friendly processing of sustainable nanostructured functional materials based on cellulose. Copyright © 2015 Elsevier Ltd. All rights reserved.

Linking soil bacterial biodiversity and soil carbon stability.

PubMed

Mau, Rebecca L; Liu, Cindy M; Aziz, Maliha; Schwartz, Egbert; Dijkstra, Paul; Marks, Jane C; Price, Lance B; Keim, Paul; Hungate, Bruce A

2015-06-01

Native soil carbon (C) can be lost in response to fresh C inputs, a phenomenon observed for decades yet still not understood. Using dual-stable isotope probing, we show that changes in the diversity and composition of two functional bacterial groups occur with this 'priming' effect. A single-substrate pulse suppressed native soil C loss and reduced bacterial diversity, whereas repeated substrate pulses stimulated native soil C loss and increased diversity. Increased diversity after repeated C amendments contrasts with resource competition theory, and may be explained by increased predation as evidenced by a decrease in bacterial 16S rRNA gene copies. Our results suggest that biodiversity and composition of the soil microbial community change in concert with its functioning, with consequences for native soil C stability.

Remarkable stabilization of a psychrotrophic RNase HI by a combination of thermostabilizing mutations identified by the suppressor mutation method.

PubMed

Tadokoro, Takashi; Matsushita, Kyoko; Abe, Yumi; Rohman, Muhammad Saifur; Koga, Yuichi; Takano, Kazufumi; Kanaya, Shigenori

2008-08-05

Ribonuclease HI from the psychrotrophic bacterium Shewanella oneidensis MR-1 (So-RNase HI) is much less stable than Escherichia coli RNase HI (Ec-RNase HI) by 22.4 degrees C in T m and 12.5 kJ mol (-1) in Delta G(H 2O), despite their high degrees of structural and functional similarity. To examine whether the stability of So-RNase HI increases to a level similar to that of Ec-RNase HI via introduction of several mutations, the mutations that stabilize So-RNase HI were identified by the suppressor mutation method and combined. So-RNase HI and its variant with a C-terminal four-residue truncation (154-RNase HI) complemented the RNase H-dependent temperature-sensitive (ts) growth phenotype of E. coli strain MIC3001, while 153-RNase HI with a five-residue truncation could not. Analyses of the activity and stability of these truncated proteins suggest that 153-RNase HI is nonfunctional in vivo because of a great decrease in stability. Random mutagenesis of 153-RNase HI using error-prone PCR, followed by screening for the revertants, allowed us to identify six single suppressor mutations that make 153-RNase HI functional in vivo. Four of them markedly increased the stability of the wild-type protein by 3.6-6.7 degrees C in T m and 1.7-5.2 kJ mol (-1) in Delta G(H 2O). The effects of these mutations were nearly additive, and combination of these mutations increased protein stability by 18.7 degrees C in T m and 12.2 kJ mol (-1) in Delta G(H 2O). These results suggest that several residues are not optimal for the stability of So-RNase HI, and their replacement with other residues strikingly increases it to a level similar to that of the mesophilic counterpart.

Antibody to human α-fetoprotein inhibits cell growth of human hepatocellular carcinoma cells by resuscitating the PTEN molecule: in vitro experiments.

PubMed

Ohkawa, Kiyoshi; Asakura, Tadashi; Tsukada, Yutaka; Matsuura, Tomokazu

2017-06-01

It has been proposed that α-fetoprotein (AFP) is a new member of the intracellular signaling molecule family of the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway via interaction with the phosphatase and tensin homolog (PTEN). In this study, the effects of anti-human AFP antibody on the functions of PTEN were examined using an AFP-producing human hepatoma cell line. The antibody caused significant inhibition of cell growth, compared to a normal IgG control, with the accumulation of intracellular immune complexes followed by significant reduction of cytosolic functional AFP. Decrease in the amount of AKT phosphorylated on serine (S) 473 indicated that PI3K/AKT signaling was suppressed in the cells. S380-phosphorylated PTEN increased markedly by the second day after antibody treatment, with slight but significant increase in the PTEN protein level. Since phosphorylation at S380 is critical for PTEN stability, the increase in S380-phosphorylated PTEN indicated maintenance of the number of PTEN molecules and the related potential to control PI3K/AKT signaling. p53 protein (P53) significantly, but slightly increased during antibody treatment, because PTEN expression increased the stability and function of P53 via both molecular interactions. P53 phosphorylated at S20 or at S392 dramatically increased, suggesting an increase in the stability, accumulation and activation of P53. Glucose transporter 1 (GLUT1) increased immediately after antibody treatment, pointing to a deficiency of glucose in the cells. Immunofluorescence cytology revealed that antibody-treatment re-distributed GLUT1 molecules throughout the cytoplasm with a reduction of their patchy localization on the cell surface. This suggested that translocation of GLUT1 depends on the PI3K/AKT pathway, in particular on PTEN expression. Antibody therapy targeted at AFP-producing tumor cells showed an inhibitory effect on the PI3K/AKT pathway via the liberation, restoration and functional stabilization of PTEN. PTEN simultaneously induced both P53 activation and intracellular translocation of GLUT1, since these are closely associated with PTEN.

N-Glycosylation enhances functional and structural stability of recombinant β-glucuronidase expressed in Pichia pastoris.

PubMed

Zou, Shuping; Huang, Shen; Kaleem, Imdad; Li, Chun

2013-03-10

Recombinant β-glucuronidase (GUS) expressed in Pichia pastoris GS115 is an important glycoprotein, encoded by a gene with four potential N-glycosylation sites. To investigate the impact of N-linked carbohydrate moieties on the stability of recombinant GUS, it was deglycosylated by peptide-N-glycosidase F (PNGase-F) under native conditions. The enzymatic activities of the glycosylated and deglycosylated GUS were compared under various conditions such as temperature, pH, organic solvents, detergents and chaotropic agent. The results demonstrated that the glycosylated GUS retained greater fraction of maximum enzymatic activity against various types of denaturants compared with the deglycosylated. The conformational stabilities of both GUS were analyzed by monitoring the unfolding equilibrium by using the denaturant guanidinium chloride (dn-HCl). The glycosylated GUS displayed a significant increase in its conformational stability than the deglycosylated counterpart. These results affirmed the key role of N-glycosylation on the structural and functional stability of β-glucuronidase and could have potential applications in the functional enhancement of industrial enzymes. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of dodecyl maltoside detergent on rhodopsin stability and function.

PubMed

Ramon, Eva; Marron, Jordi; del Valle, Luis; Bosch, Laia; Andrés, Anna; Manyosa, Joan; Garriga, Pere

2003-12-01

Detergent-solubilized bovine rhodopsin produces mixed detergent/lipid/protein micelles. The effect of dodecyl maltoside detergent on the thermal stability of dark-state rhodopsin, and upon formation of the different intermediates after rhodopsin photobleaching (metarhodopsin II and metarhodopsin III), and upon transducin activation has been studied. No significant effect is observed for the thermal stability of dark-state rhodopsin in the range of detergent concentrations studied, but a decrease in the stability of metarhodopsin II and an increase in metarhodopsin III formation is observed with decreasing detergent concentrations. The transducin activation process is also affected by the presence of detergent indicating that this process is dependent on the lipid micro-environment and membrane fluidity, and this stresses the importance of the native lipid environment in rhodopsin normal function.

Effects of McGill stabilization exercises and conventional physiotherapy on pain, functional disability and active back range of motion in patients with chronic non-specific low back pain.

PubMed

Ghorbanpour, Arsalan; Azghani, Mahmoud Reza; Taghipour, Mohammad; Salahzadeh, Zahra; Ghaderi, Fariba; Oskouei, Ali E

2018-04-01

[Purpose] The aim of this study was to compare the effects of "McGill stabilization exercises" and "conventional physiotherapy" on pain, functional disability and active back flexion and extension range of motion in patients with chronic non-specific low back pain. [Subjects and Methods] Thirty four patients with chronic non-specific low back pain were randomly assigned to McGill stabilization exercises group (n=17) and conventional physiotherapy group (n=17). In both groups, patients performed the corresponding exercises for six weeks. The visual analog scale (VAS), Quebec Low Back Pain Disability Scale Questionnaire and inclinometer were used to measure pain, functional disability, and active back flexion and extension range of motion, respectively. [Results] Statistically significant improvements were observed in pain, functional disability, and active back extension range of motion in McGill stabilization exercises group. However, active back flexion range of motion was the only clinical symptom that statistically increased in patients who performed conventional physiotherapy. There was no significant difference between the clinical characteristics while compared these two groups of patients. [Conclusion] The results of this study indicated that McGill stabilization exercises and conventional physiotherapy provided approximately similar improvement in pain, functional disability, and active back range of motion in patients with chronic non-specific low back pain. However, it appears that McGill stabilization exercises provide an additional benefit to patients with chronic non-specific low back, especially in pain and functional disability improvement.

Linking biodiversity to ecosystem function: Implications for conservation ecology

USGS Publications Warehouse

Schwartz, M.W.; Brigham, C.A.; Hoeksema, J.D.; Lyons, K.G.; Mills, M.H.; van Mantgem, P.

2000-01-01

We evaluate the empirical and theoretical support for the hypothesis that a large proportion of native species richness is required to maximize ecosystem stability and sustain function. This assessment is important for conservation strategies because sustenance of ecosystem functions has been used as an argument for the conservation of species. If ecosystem functions are sustained at relatively low species richness, then arguing for the conservation of ecosystem function, no matter how important in its own right, does not strongly argue for the conservation of species. Additionally, for this to be a strong conservation argument the link between species diversity and ecosystem functions of value to the human community must be clear. We review the empirical literature to quantify the support for two hypotheses: (1) species richness is positively correlated with ecosystem function, and (2) ecosystem functions do not saturate at low species richness relative to the observed or experimental diversity. Few empirical studies demonstrate improved function at high levels of species richness. Second, we analyze recent theoretical models in order to estimate the level of species richness required to maintain ecosystem function. Again we find that, within a single trophic level, most mathematical models predict saturation of ecosystem function at a low proportion of local species richness. We also analyze a theoretical model linking species number to ecosystem stability. This model predicts that species richness beyond the first few species does not typically increase ecosystem stability. One reason that high species richness may not contribute significantly to function or stability is that most communities are characterized by strong dominance such that a few species provide the vast majority of the community biomass. Rapid turnover of species may rescue the concept that diversity leads to maximum function and stability. The role of turnover in ecosystem function and stability has not been investigated. Despite the recent rush to embrace the linkage between biodiversity and ecosystem function, we find little support for the hypothesis that there is a strong dependence of ecosystem function on the full complement of diversity within sites. Given this observation, the conservation community should take a cautious view of endorsing this linkage as a model to promote conservation goals.

Higher order structural effects stabilizing the reverse Watson–Crick Guanine-Cytosine base pair in functional RNAs

PubMed Central

Chawla, Mohit; Abdel-Azeim, Safwat; Oliva, Romina; Cavallo, Luigi

2014-01-01

The G:C reverse Watson–Crick (W:W trans) base pair, also known as Levitt base pair in the context of tRNAs, is a structurally and functionally important base pair that contributes to tertiary interactions joining distant domains in functional RNA molecules and also participates in metabolite binding in riboswitches. We previously indicated that the isolated G:C W:W trans base pair is a rather unstable geometry, and that dicationic metal binding to the Guanine base or posttranscriptional modification of the Guanine can increase its stability. Herein, we extend our survey and report on other H-bonding interactions that can increase the stability of this base pair. To this aim, we performed a bioinformatics search of the PDB to locate all the occurencies of G:C trans base pairs. Interestingly, 66% of the G:C trans base pairs in the PDB are engaged in additional H-bonding interactions with other bases, the RNA backbone or structured water molecules. High level quantum mechanical calculations on a data set of representative crystal structures were performed to shed light on the structural stability and energetics of the various crystallographic motifs. This analysis was extended to the binding of the preQ1 metabolite to a preQ1-II riboswitch. PMID:24121683

Improvement of single domain antibody stability by disulfide bond introduction.

PubMed

Hagihara, Yoshihisa; Saerens, Dirk

2012-01-01

The successful medical application of single domain antibodies largely depends on their functionality. This feature is partly determined by the intrinsic stability of the single domain. Therefore a lot of research has gone into the elucidation of rules to uniformly increase stability of antibodies. Recently, a novel intra-domain disulfide bond was independently discovered by two research groups, after either rational design or careful investigation of the naturally occurring camelid antibody repertoire. By introducing this particular disulfide bond within a single domain antibody, the conformational stability can be increased in general. In this chapter it is described how to introduce this extra intra-domain disulfide bond and how to estimate the biophysical and biochemical impact of this cystine on the domain.

Thermodynamics-hydration relationships within loops that affect G-quadruplexes under molecular crowding conditions.

PubMed

Fujimoto, Takeshi; Nakano, Shu-ichi; Sugimoto, Naoki; Miyoshi, Daisuke

2013-01-31

We systematically investigated the effects of loop length on the conformation, thermodynamic stability, and hydration of DNA G-quadruplexes under dilute and molecular crowding conditions in the presence of Na(+). Structural analysis showed that molecular crowding induced conformational switches of oligonucleotides with the longer guanine stretch and the shorter thymine loop. Thermodynamic parameters further demonstrated that the thermodynamic stability of G-quadruplexes increased by increasing the loop length from two to four, whereas it decreased by increasing the loop length from four to six. Interestingly, we found by osmotic pressure analysis that the number of water molecules released from the G-quadruplex decreased with increasing thermodynamic stability. We assumed that base-stacking interactions within the loops not only stabilized the whole G-quadruplex structure but also created hydration sites by accumulating nucleotide functional groups. The molecular crowding effects on the stability of G-quadruplexes composed of abasic sites, which reduce the stacking interactions at the loops, further demonstrated that G-quadruplexes with fewer stacking interactions within the loops released a larger number of water molecules upon folding. These results showed that the stacking interactions within the loops determined the thermodynamic stability and hydration of the whole G-quadruplex.

Analysis of Core Stability Exercise Effect on the Physical and Psychological Function of Elderly Women Vulnerable to Falls during Obstacle Negotiation.

PubMed

Ko, Dae-Sik; Jung, Dae-In; Jeong, Mi-Ae

2014-11-01

[Purpose] The aim of the present study was to investigate the effects of core stability exercise (CSE) on the physical and psychological functions of elderly women while negotiating general obstacles. [Subjects and Methods] After allocating 10 elderly women each to the core stability training group and the control group, we carried out Performance-Oriented Mobility Assessment (POMA) and measured crossing velocity (CV), maximum vertical heel clearance (MVHC), and knee flexion angle for assessing physical performances. We evaluated depression and fear of falling for assessing psychological functions. [Results] Relative to the control group, the core stability training group showed statistically significant overall changes after the training session: an increase in POMA scores, faster CV, lower MVHC, and a decrease in knee flexion angle. Furthermore, depression and fear of falling decreased significantly. [Conclusion] CSE can have a positive effect on the improvement of physical and psychological performances of older women who are vulnerable to falls as they negotiate everyday obstacles.

Multi-muscle electrical stimulation and stand training: Effects on standing.

PubMed

Momeni, Kamyar; Ramanujam, Arvind; Garbarini, Erica L; Forrest, Gail F

2018-02-15

To examine the biomechanical and neuromuscular effects of a longitudinal multi-muscle electrical stimulation (submaximal intensities) training of the lower limbs combined with/without activity-based stand training, on the recovery of stability and function for one individual with spinal cord injury (SCI). Single-subject, longitudinal study. Neuroplasticity laboratory. A 34-year-old male, with sensory- and motor-complete SCI (C5/C6). Two consecutive interventions: 61 hours of supine, lower-limb ES (ES-alone) and 51 hours of ES combined with stand training using an overhead body-weight support system (ST + ES). Clinical measures, trunk stability, and muscle activity were assessed and compared across time points. Trunk Stability Limit (TSL) determined improvements in trunk independence. Functional clinical values increased after both interventions, with further increases post ST + ES. Post ES-alone, trunk stability was maintained at 81% body-weight (BW) loading before failure; post ST + ES, BW loading increased to 95%. TSL values decreased post ST + ES (TSL A/P =54.0 kg.cm, TSL M/L =14.5 kg.cm), compared to ES-alone (TSL A/P =8.5 kg.cm, TSL M/L =3.9 kg.cm). Trunk muscle activity decreased post ST + ES training, compared to ES-alone. Neuromuscular and postural trunk control dramatically improved following the multi-muscle ES of the lower limbs with stand training. Multi-muscle ES training paradigm of the lower limb, using traditional parameters, may contribute to the functional recovery of the trunk.

Acid azo dye remediation in anoxic-aerobic-anoxic microenvironment under periodic discontinuous batch operation: bio-electro kinetics and microbial inventory.

PubMed

Venkata Mohan, S; Suresh Babu, P; Naresh, K; Velvizhi, G; Madamwar, Datta

2012-09-01

Functional behavior of anoxic-aerobic-anoxic microenvironment on azo dye (C.I. Acid black 10B) degradation was evaluated in a periodic discontinuous batch mode operation for 26 cycles. Dye removal efficiency and azo-reductase activity (30.50 ± 1 U) increased with each feeding event until 13th cycle and further stabilized. Dehydrogenase activity also increased gradually and stabilized (2.0 ± 0.2 μg/ml) indicating the stable proton shuttling between metabolic intermediates providing higher number of reducing equivalents towards dye degradation. Voltammetric profiles showed drop in redox catalytic currents during stabilized phase also supports the consumption of reducing equivalents towards dye removal. Change in Tafel slopes, polarization resistance and other bioprocess parameters correlated well with the observed dye removal and biocatalyst behavior. Microbial community analysis documented the involvement of specific organism pertaining to aerobic and facultative functions with heterotrophic and autotrophic metabolism. Integrating anoxic microenvironment with aerobic operation might have facilitated effective dye mineralization due to the possibility of combining redox functions. Copyright © 2012 Elsevier Ltd. All rights reserved.

Attentional Focus Effects as a Function of Task Difficulty

ERIC Educational Resources Information Center

Wulf, Gabriele; Tollner, Thomas; Shea, Charles H.

2007-01-01

The purpose of the present study was to examine whether the advantages of adopting an external focus would be seen primarily for relatively challenging (postural stability) tasks but not less demanding tasks. To examine this, the authors used balance tasks that imposed increased challenges to maintaining stability. The present results support the…

Computational design of a pH stable enzyme: understanding molecular mechanism of penicillin acylase's adaptation to alkaline conditions.

PubMed

Suplatov, Dmitry; Panin, Nikolay; Kirilin, Evgeny; Shcherbakova, Tatyana; Kudryavtsev, Pavel; Svedas, Vytas

2014-01-01

Protein stability provides advantageous development of novel properties and can be crucial in affording tolerance to mutations that introduce functionally preferential phenotypes. Consequently, understanding the determining factors for protein stability is important for the study of structure-function relationship and design of novel protein functions. Thermal stability has been extensively studied in connection with practical application of biocatalysts. However, little work has been done to explore the mechanism of pH-dependent inactivation. In this study, bioinformatic analysis of the Ntn-hydrolase superfamily was performed to identify functionally important subfamily-specific positions in protein structures. Furthermore, the involvement of these positions in pH-induced inactivation was studied. The conformational mobility of penicillin acylase in Escherichia coli was analyzed through molecular modeling in neutral and alkaline conditions. Two functionally important subfamily-specific residues, Gluβ482 and Aspβ484, were found. Ionization of these residues at alkaline pH promoted the collapse of a buried network of stabilizing interactions that consequently disrupted the functional protein conformation. The subfamily-specific position Aspβ484 was selected as a hotspot for mutation to engineer enzyme variant tolerant to alkaline medium. The corresponding Dβ484N mutant was produced and showed 9-fold increase in stability at alkaline conditions. Bioinformatic analysis of subfamily-specific positions can be further explored to study mechanisms of protein inactivation and to design more stable variants for the engineering of homologous Ntn-hydrolases with improved catalytic properties.

Computational Design of a pH Stable Enzyme: Understanding Molecular Mechanism of Penicillin Acylase's Adaptation to Alkaline Conditions

PubMed Central

Suplatov, Dmitry; Panin, Nikolay; Kirilin, Evgeny; Shcherbakova, Tatyana; Kudryavtsev, Pavel; Švedas, Vytas

2014-01-01

Protein stability provides advantageous development of novel properties and can be crucial in affording tolerance to mutations that introduce functionally preferential phenotypes. Consequently, understanding the determining factors for protein stability is important for the study of structure-function relationship and design of novel protein functions. Thermal stability has been extensively studied in connection with practical application of biocatalysts. However, little work has been done to explore the mechanism of pH-dependent inactivation. In this study, bioinformatic analysis of the Ntn-hydrolase superfamily was performed to identify functionally important subfamily-specific positions in protein structures. Furthermore, the involvement of these positions in pH-induced inactivation was studied. The conformational mobility of penicillin acylase in Escherichia coli was analyzed through molecular modeling in neutral and alkaline conditions. Two functionally important subfamily-specific residues, Gluβ482 and Aspβ484, were found. Ionization of these residues at alkaline pH promoted the collapse of a buried network of stabilizing interactions that consequently disrupted the functional protein conformation. The subfamily-specific position Aspβ484 was selected as a hotspot for mutation to engineer enzyme variant tolerant to alkaline medium. The corresponding Dβ484N mutant was produced and showed 9-fold increase in stability at alkaline conditions. Bioinformatic analysis of subfamily-specific positions can be further explored to study mechanisms of protein inactivation and to design more stable variants for the engineering of homologous Ntn-hydrolases with improved catalytic properties. PMID:24959852

Motions and functional performance after supervised physical therapy program versus home-based program after arthroscopic anterior shoulder stabilization: a randomized clinical trial.

PubMed

Ismail, M M; El Shorbagy, K M

2014-01-01

To compare the effects of a standardized supervised physical therapy versus a controlled home-based programs on the rate of shoulder motion and functional recovery after arthroscopic anterior shoulder stabilization. Twenty-seven patients (18-35years) underwent arthroscopic anterior shoulder stabilization. Patients were randomized into two groups. A supervised group (n=14) received a rehabilitation program, 3 sessions/week for 24 weeks and a controlled home treated group (n=13) who followed a home-based program for same period. Range of motion (ROM) of the shoulder was assessed 4 times after each phase of rehabilitation and function was assessed after the 3rd and 4th phase of rehabilitation. Both groups achieved a significant progressive increase in all shoulder motions throughout the study period. Patients in the supervised group achieved 92.6% and 94.2% of the contralateral side in abduction and forward elevation respectively. The controlled home-based group achieved 87.1% and 94.7% of abduction and forward elevation respectively. For external rotation, the percentage ROM achieved was 81.1% for the supervised group and 76.4% for the controlled home-based group. For function assessment, the two groups showed a significant improvement. However, the two groups were not significantly different from each other in all measured variables. A controlled home-based physical therapy program is as effective as a supervised program in increasing shoulder range of motion and function after arthroscopic anterior shoulder stabilization. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Diffusion and Stability of Hydrogen in Mg-Doped GaN: A Density Functional Study

NASA Astrophysics Data System (ADS)

Park, Ji-Sang; Chang, Kee Joo

2012-06-01

Using hybrid functional calculations, we study the diffusion and thermal stability of hydrogen in Mg-doped GaN. Compared with the generalized gradient approximation, we obtain a higher activation barrier for dissociating a Mg-H complex, which is attributed to the increase in the binding energy of Mg-H. Kinetic Monte Carlo simulations yield the annealing temperature of around 800 °C for activating Mg acceptors, close to the measured values. The results provide an insight to understanding the annealing effect such that the annealing temperature generally increases with the Mg-H concentration, and the retrapping of H is partly responsible for the low doping efficiencies at high Mg concentrations.

Variation in emulsion stabilization behavior of hybrid silicone polymers with change in molecular structure: Phase diagram study.

PubMed

Mehta, Somil C; Somasundaran, P; Kulkarni, Ravi

2009-05-15

Silicone oils are widely used in cosmetics and personal care applications to improve softness and condition skin and hair. Being insoluble in water and most hydrocarbons, a common mode of delivering them is in the form of emulsions. Currently most applications use polyoxyethylene (non-ionic) modified siloxanes as emulsifiers to stabilize silicone oil emulsions. However, ionically grafted silicone polymers have not received much attention. Ionic silicones have significantly different properties than the non-ionic counterpart. Thus considerable potential exists to formulate emulsions of silicones with different water/silicone oil ratios for novel applications. In order to understand the mechanisms underlying the effects of hydrophilic modifications on the ability of hybrid silicone polymers to stabilize various emulsions, this article focuses on the phase diagram studies for silicone emulsions. The emulsifying ability of functional silicones was seen to depend on a number of factors including hydrophilicity of the polymer, nature of the functional groups, the extent of modification, and the method of emulsification. It was observed that the region of stable emulsion in a phase diagram expanded with increase in shear rate. At a given shear rate, the region of stable emulsion and the nature of emulsion (water-in-oil or oil-in-water) was observed to depend on hydrophilic-hydrophobic balance of the hybrid silicone emulsifier. At a fixed amount of modification, the non-ionically modified silicone stabilized an oil-in-water emulsion, whereas the ionic silicones stabilized inverse water-in-oil emulsions. This was attributed to the greater hydrophilicity of the polyoxyethylene modified silicones than the ionic counterparts. In general, it is postulated that with progressive increase in hydrophilicity of hybrid silicone emulsifiers, their tendency to stabilize water-in-oil emulsion decreases with corresponding increase in oil-in-water emulsion. Further, this behavior is hypothesized to depend on the nature of modifying functional groups. Thus a hybrid silicone polymer can be tailored by selecting the nature and degree of hydrophilicity to obtain a desired silicone emulsion.

Mast cell stabilization decreases cardiomyocyte and LV function in dogs with isolated mitral regurgitation.

PubMed

Pat, Betty; Killingsworth, Cheryl; Chen, Yuanwen; Gladden, James D; Walcott, Greg; Powell, Pamela C; Denney, Thomas; Gupta, Himanshu; Desai, Ravi; Tillson, Michael; Dillon, A Ray; Dell'italia, Louis J

2010-09-01

Mast cells are increased in isolated mitral regurgitation (MR) in the dog and may mediate extracellular matrix loss and left ventricular (LV) dilatation. We tested the hypothesis that mast cell stabilization would attenuate LV remodeling and improve function in the MR dog. MR was induced in adult dogs randomized to no treatment (MR, n = 5) or to the mast cell stabilizer, ketotifen (MR + MCS, n = 4) for 4 months. LV hemodynamics were obtained at baseline and after 4 months of MR and magnetic resonance imaging (MRI) was performed at sacrifice. MRI-derived, serial, short-axis LV end-diastolic (ED) and end-systolic (ES) volumes, LVED volume/mass ratio, and LV 3-dimensional radius/wall thickness were increased in MR and MR + MCS dogs compared with normal dogs (n = 6) (P < .05). Interstitial collagen was decreased by 30% in both MR and MR + MCS versus normal dogs (P < .05). LV contractility by LV maximum time-varying elastance was significantly depressed in MR and MR + MCS dogs. Furthermore, cardiomyocyte fractional shortening was decreased in MR versus normal dogs and further depressed in MR + MCS dogs (P < .05). In vitro administration of ketotifen to normal cardiomyocytes also significantly decreased fractional shortening and calcium transients. Chronic mast cell stabilization did not attenuate eccentric LV remodeling or collagen loss in MR. However, MCS therapy had a detrimental effect on LV function because of a direct negative inotropic effect on cardiomyocyte function. Published by Elsevier Inc.

Effects of heat stress and probiotic supplementation on protein functionality and oxidative stability of ground chicken leg meat during display storage.

PubMed

Kim, Hyun-Wook; Kim, Ji-Han; Yan, Feifei; Cheng, Heng-Wei; Brad Kim, Yuan H

2017-12-01

The present study aimed to evaluate the effects of heat stress and probiotic supplementation on protein functionality and oxidative stability of ground chicken leg during display storage. Two hundred and forty, 1-day-old male chicks (5 birds per pen) were subjected to four treatments in a 2 (thermoneutral condition at 21 °C and cyclic heat stress at 32-21-32 °C for 10 h day -1 ) × 2 (regular diet with 0 or 0.25 g kg -1 Bacillus subtilis) factorial design. Chickens were harvested at day 46, and pairs of whole legs were collected at 1 day postmortem. The chicken legs were deboned, ground, tray-packaged with oxygen-permeable film, and displayed for 3 days. Heat stress and probiotic supplementation had no impact on pH, water-holding capacity, color, protein functionality, lipid lipolysis and lipid/protein oxidation stability (P > 0.05). Display storage increased the pH and lipid oxidation of ground chicken legs (P < 0.05). In addition, protein oxidation occurred during display storage, as determined via an increased carbonyl group (P = 0.0109) and reduced thiol group (P < 0.0001). The results of the present study indicate that chronic heat stress and probiotic supplementation had no practical adverse impact on protein functionality and oxidative stability of ground chicken leg meat. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Stabilization of enzymes in ionic liquids via modification of enzyme charge.

PubMed

Nordwald, Erik M; Kaar, Joel L

2013-09-01

Due to the propensity of ionic liquids (ILs) to inactivate enzymes, the development of strategies to improve enzyme utility in these solvents is critical to fully exploit ILs for biocatalysis. We have developed a strategy to broadly improve enzyme utility in ILs based on elucidating the effect of charge modifications on the function of enzymes in IL environments. Results of stability studies in aqueous-IL mixtures indicated a clear connection between the ratio of enzyme-containing positive-to-negative sites and enzyme stability in ILs. Stability studies of the effect of [BMIM][Cl] and [EMIM][EtSO4 ] on chymotrypsin specifically found an optimum ratio of positively-charged amine-to-negatively-charged acid groups (0.39). At this ratio, the half-life of chymotrypsin was increased 1.6- and 4.3-fold relative to wild-type chymotrypsin in [BMIM][Cl] and [EMIM][EtSO4 ], respectively. The half-lives of lipase and papain were similarly increased as much as 4.0 and 2.4-fold, respectively, in [BMIM][Cl] by modifying the ratio of positive-to-negative sites of each enzyme. More generally, the results of stability studies found that modifications that reduce the ratio of enzyme-containing positive-to-negative sites improve enzyme stability in ILs. Understanding the impact of charge modification on enzyme stability in ILs may ultimately be exploited to rationally engineer enzymes for improved function in IL environments. Copyright © 2013 Wiley Periodicals, Inc.

Poly(vinylbenzylchloride) Based Anion-Exchange Blend Membranes (AEBMs): Influence of PEG Additive on Conductivity and Stability

PubMed Central

Kerres, Jochen A.; Krieg, Henning M.

2017-01-01

In view of the many possible applications such as fuel cells and electrolysers, recent interest in novel anion exchange membranes (AEMs) has increased significantly. However, their low conductivity and chemical stability limits their current suitability. In this study, the synthesis and characterization of several three- and four-component anion exchange blend membranes (AEBMs) is described, where the compositions have been systematically varied to study the influence of the AEBM’s composition on the anion conductivities as well as chemical and thermal stabilities under strongly alkaline conditions. It was shown that the epoxide-functionalized poly(ethylene glycol)s that were introduced into the four-component AEBMs resulted in increased conductivity as well as a marked improvement in the stability of the AEBMs in an alkaline environment. In addition, the thermal stability of the novel AEBMs was excellent showing the suitability of these membranes for several electrochemical applications. PMID:28621717

C1orf106 is a colitis risk gene that regulates stability of epithelial adherens junctions.

PubMed

Mohanan, Vishnu; Nakata, Toru; Desch, A Nicole; Lévesque, Chloé; Boroughs, Angela; Guzman, Gaelen; Cao, Zhifang; Creasey, Elizabeth; Yao, Junmei; Boucher, Gabrielle; Charron, Guy; Bhan, Atul K; Schenone, Monica; Carr, Steven A; Reinecker, Hans-Christian; Daly, Mark J; Rioux, John D; Lassen, Kara G; Xavier, Ramnik J

2018-03-09

Polymorphisms in C1orf106 are associated with increased risk of inflammatory bowel disease (IBD). However, the function of C1orf106 and the consequences of disease-associated polymorphisms are unknown. Here we demonstrate that C1orf106 regulates adherens junction stability by regulating the degradation of cytohesin-1, a guanine nucleotide exchange factor that controls activation of ARF6. By limiting cytohesin-1-dependent ARF6 activation, C1orf106 stabilizes adherens junctions. Consistent with this model, C1orf106 -/- mice exhibit defects in the intestinal epithelial cell barrier, a phenotype observed in IBD patients that confers increased susceptibility to intestinal pathogens. Furthermore, the IBD risk variant increases C1orf106 ubiquitination and turnover with consequent functional impairments. These findings delineate a mechanism by which a genetic polymorphism fine-tunes intestinal epithelial barrier integrity and elucidate a fundamental mechanism of cellular junctional control. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

The stability of portfolio investment in stock crashes

NASA Astrophysics Data System (ADS)

Li, Yun-Xian; Qian, Zhen-Wei; Li, Jiang-Cheng; Tang, Nian-Sheng; Mei, Dong-Cheng

2016-08-01

The stability of portfolio investment in stock market crashes with Markowitz portfolio is investigated by the method of theoretical and empirical simulation. From numerical simulation of the mean escape time (MET), we conclude that: (i) The increasing number (Np) of stocks in Markowitz portfolio induces a maximum in the curve of MET versus the initial position; (ii) A critical value of Np in the behavior of MET versus the long-run variance or amplitude of volatility fluctuations maximumlly enhances the stability of portfolio investment. When Np takes value below the critical value, the increasing Np enhances the stability of portfolio investment, but restrains it when Np takes value above the critical value. In addition, a good agreement of both the MET and probability density functions of returns is found between real data and theoretical results.

Genetic and Environmental Stability in Attention Problems across the Lifespan: Evidence from the Netherlands Twin Register

ERIC Educational Resources Information Center

Kan, Kees-Jan; Dolan, Conor V.; Nivard, Michel G.; Middeldorp, Christel M.; van Beijsterveldt, Catharina E. M.; Willemsen, Gonneke; Boomsma, Dorret I.

2013-01-01

Objective: To review findings on attention-deficit/hyperactivity disorder and attention problems (AP) in children, adolescents, and adults, as established in the database of the Netherlands Twin Register and increase the understanding of stability in AP across the lifespan as a function of genetic and environmental influences. Method: A…

The effects of balance and postural stability exercises on spa based rehabilitation programme in patients with ankylosing spondylitis.

PubMed

Gunay, Selim M; Keser, Ilke; Bicer, Zemzem T

2018-01-01

Ankylosing spondylitis (AS) can cause severe functional disorders that lead to loss of balance. The aim of this study was to investigate the effects of balance and postural stability exercises on spa based rehabilitation programme in AS subjects. Twenty-one participants were randomized to the study (n= 11) and control groups (n= 10). Patients balance and stability were assessed with the Berg Balance Scale (BBS), Timed Up and Go (TUG) Test, Single Leg Stance Test (SLST) and Functional Reach Test (FRT). AS spesicied measures were used for assessing to other parameters. The treatment plan for both groups consisted of conventional transcutaneous electrical nerve stimulation (TENS), spa and land-based exercises 5 days per week for 3 weeks. The study group performed exercises based on postural stability and balance with routine physiotherapy practice in thermal water and in exercise room. The TUG, SLST and FUT scores were significantly increased in the study group. In both groups, the BASMI, BASFI, BASDAI and ASQoL scores decreased significantly by the end of the treatment period (p< 0.05). In AS rehabilitation, performing balance and stability exercises in addition to spa based routine approaches can increase the duration of maintaining balance and can improve the benefits of physiotherapy.

Maximizing detergent stability and functional expression of a GPCR by exhaustive recombination and evolution.

PubMed

Schlinkmann, Karola M; Hillenbrand, Matthias; Rittner, Alexander; Künz, Madeleine; Strohner, Ralf; Plückthun, Andreas

2012-09-21

To identify structural features in a G-protein-coupled receptor (GPCR) crucial for biosynthesis, stability in the membrane and stability in detergent micelles, we developed an evolutionary approach using expression in the inner membrane of Escherichia coli. From the analysis of 800,000 sequences of the rat neurotensin receptor 1, in which every amino acid had been varied to all 64 codons, we uncovered several "shift" positions, where the selected population focuses on a residue different from wild type. Here, we employed in vitro DNA recombination and a comprehensive synthetic binary library made by the Slonomics® technology, allowing us to uncover additive and synergistic effects in the structure that maximize both detergent stability and functional expression. We identified variants with >25,000 functional molecules per E. coli cell, a 50-fold increase over wild type, and observed strong coevolution of detergent stability. We arrived at receptor variants highly stable in short-chain detergents, much more so than those found by alanine scanning on the same receptor. These evolved GPCRs continue to be able to signal through the G-protein. We discuss the structural reasons for these improvements achieved through directed evolution. Copyright © 2012 Elsevier Ltd. All rights reserved.

Influence of age on the correlations of hematological and biochemical variables with the stability of erythrocyte membrane in relation to sodium dodecyl sulfate.

PubMed

de Freitas, Mariana V; Marquez-Bernardes, Liandra F; de Arvelos, Letícia R; Paraíso, Lara F; Gonçalves E Oliveira, Ana Flávia M; Mascarenhas Netto, Rita de C; Neto, Morun Bernardino; Garrote-Filho, Mario S; de Souza, Paulo César A; Penha-Silva, Nilson

2014-10-01

To evaluate the influence of age on the relationships between biochemical and hematological variables and stability of erythrocyte membrane in relation to the sodium dodecyl sulfate (SDS) in population of 105 female volunteers between 20 and 90 years. The stability of RBC membrane was determined by non-linear regression of the dependency of the absorbance of hemoglobin released as a function of SDS concentration, represented by the half-transition point of the curve (D50) and the variation in the concentration of the detergent to promote lysis (dD). There was an age-dependent increase in the membrane stability in relation to SDS. Analyses by multiple linear regression showed that this stability increase is significantly related to the hematological variable red cell distribution width (RDW) and the biochemical variables blood albumin and cholesterol. The positive association between erythrocyte stability and RDW may reflect one possible mechanism involved in the clinical meaning of this hematological index.

Hydrogel Tethering Enhances Interdomain Stabilization of Single-Chain Antibodies.

PubMed

Xiong, Yijia; Ford, Nicole R; Hecht, Karen A; Roesijadi, Guritno; Squier, Thomas C

2017-11-15

Here, we identify the importance of molecular crowding agents in the functional stabilization of scFv antibodies. Antibodies were tethered through an engineered calmodulin (CaM)-binding peptide into a stimulus-responsive hydrogel composed of poly(ethylene glycol) (PEG)-functionalized CaM. Macromolecular crowding is modulated by transient heating, which decreases effective pore sizes. Using a fluorescent ligand bound to the scFv, frequency-domain fluorescence spectroscopy was used to assess the structural coupling between the V H and the V L domains and relationships with functional stabilization. There is minimal structural coupling between the V H and the V L domains in solution, as is apparent from the substantial rotational mobility for the bound ligand, that is suggestive of an independent mobility for the V H and the V L domains. In comparison, the hydrogel matrix acts to structurally couple the V H and the V L domains, resulting in a reduction in rotational mobility and a retention of ligand binding in the presence of 8.0 M urea. Under these same conditions, ligand binding is disrupted for scFv antibodies in solution. Increases in the stabilization of scFv antibodies in hydrogels is not simply the result of molecular crowding because decreases in pore size act to destabilize ligand binding. Rather, our results suggest that the functional stabilization of the scFv antibody within the PEG hydrogel matrix includes important factors involving protein solvation that stabilize interdomain interactions between the V H and the V L domains necessary for ligand binding.

The Adenovirus Genome Contributes to the Structural Stability of the Virion

PubMed Central

Saha, Bratati; Wong, Carmen M.; Parks, Robin J.

2014-01-01

Adenovirus (Ad) vectors are currently the most commonly used platform for therapeutic gene delivery in human gene therapy clinical trials. Although these vectors are effective, many researchers seek to further improve the safety and efficacy of Ad-based vectors through detailed characterization of basic Ad biology relevant to its function as a vector system. Most Ad vectors are deleted of key, or all, viral protein coding sequences, which functions to not only prevent virus replication but also increase the cloning capacity of the vector for foreign DNA. However, radical modifications to the genome size significantly decreases virion stability, suggesting that the virus genome plays a role in maintaining the physical stability of the Ad virion. Indeed, a similar relationship between genome size and virion stability has been noted for many viruses. This review discusses the impact of the genome size on Ad virion stability and emphasizes the need to consider this aspect of virus biology in Ad-based vector design. PMID:25254384

DFT study on stability and H2 adsorption activity of bimetallic Au79-nPdn (n = 1-55) clusters

NASA Astrophysics Data System (ADS)

Liu, Xuejing; Tian, Dongxu; Meng, Changgong

2013-03-01

The stability and H2 adsorption activity of bimetallic Au79-nPdn (n = 1-55) clusters were studied by density functional theory with GGA-PW91 functional. The stability order for four Pd substitution types is face > mid-edge > corner > edge, and the stability is improved with increasing Pd content. In contrast with the stability order, H2 adsorption activity is corner ≈ edge > mid-edge > face. The Au36Pd43 (3) with Au:Pd ≈ 1:1 ratio and twenty-four Pd substitutions at (1 1 1) facets and nineteen Pd substitutions at subshell sites shows high stability and H2 non-activated dissociation activity. The partial density of d-states and d band center revealed that the electronic properties are closely associated with the geometric characteristic and adsorption activity. Correlating the d band center ɛd and the adsorption energies, the ɛd order agrees with the adsorption activity that the Pd substitution at edge and corner sites are more active than at face and mid-edge sites.

Large variability of biochar stability and biochar properties

NASA Astrophysics Data System (ADS)

Lehmann, J.; Nguyen, B.; Hanley, K.; Enders, A.

2008-12-01

In general, charring or purposeful pyrolysis increases the stability of biomass. It is less clear, however, to what extent biochar properties influence its stability. Chemical and physical properties of biochars and biomass-derived black carbons (BC) vary greatly as a function of the type of biomass it was generated from and of the production temperature. We show that these properties greatly affect the stability of BC is a function of both these factors, with highly significant interactions. BC produced from corn stalks produced at 350°C decomposed much quicker when incubated at field capacity at 30°C for one year than those produced at 600°C. In contrast, there was hardly a difference noted between those two temperatures if oak was the precursor biomass. Such differences in labile carbon not only affect the proportion of stable carbon in BC, but also influence the quantification of long-term stability. Extrapolation from short-term decay to long-term stability may require prior knowledge about the decay rate of the labile fraction of BC. Some indications are provided for the short-term oxidation of BC.

Multiscale model within-host and between-host for viral infectious diseases.

PubMed

Almocera, Alexis Erich S; Nguyen, Van Kinh; Hernandez-Vargas, Esteban A

2018-05-08

Multiscale models possess the potential to uncover new insights into infectious diseases. Here, a rigorous stability analysis of a multiscale model within-host and between-host is presented. The within-host model describes viral replication and the respective immune response while disease transmission is represented by a susceptible-infected model. The bridging of scales from within- to between-host considered transmission as a function of the viral load. Consequently, stability and bifurcation analyses were developed coupling the two basic reproduction numbers [Formula: see text] and [Formula: see text] for the within- and the between-host subsystems, respectively. Local stability results for each subsystem, including a unique stable equilibrium point, recapitulate classical approaches to infection and epidemic control. Using a Lyapunov function, global stability of the between-host system was obtained. Our main result was the derivation of the [Formula: see text] as an increasing function of [Formula: see text]. Numerical analyses reveal that a Michaelis-Menten form based on the virus is more likely to recapitulate the behavior between the scales than a form directly proportional to the virus. Our work contributes basic understandings of the two models and casts light on the potential effects of the coupling function on linking the two scales.

Influence of vision on head stabilization strategies in older adults during walking.

PubMed

Cromwell, Ronita L; Newton, Roberta A; Forrest, Gail

2002-07-01

Maintaining balance during dynamic activities is essential for preventing falls in older adults. Head stabilization contributes to dynamic balance, especially during the functional task of walking. Head stability and the role of vision in this process have not been studied during walking in older adults. Seventeen older adults (76.2 +/- 6.9 years) and 20 young adults (26.0 +/- 3.4 years) walked with their eyes open (EO), with their eyes closed (EC), and with fixed gaze (FG). Participants performed three trials of each condition. Sagittal plane head and trunk angular velocities in space were obtained using an infrared camera system with passive reflective markers. Frequency analyses of head-on-trunk with respect to trunk gains and phases were examined for head-trunk movement strategies used for head stability. Average walking velocity, cadence, and peak head velocity were calculated for each condition. Differences between age groups demonstrated that older adults decreased walking velocity in EO (p =.022). FG (p = .021), and EC (p = .022). and decreased cadence during EC (p = .007). Peak head velocity also decreased across conditions (p < .0001) for older adults. Movement patterns demonstrated increased head stability during EO. diminished head stability with EC, and improved head stability with FG as older adult patterns resembled those of young adults. Increased stability of the lower extremity outcome measures for older adults was indicated by reductions in walking velocity and cadence. Concomitant increases in head stability were related to visual tasks. Increased stability may serve as a protective mechanism to prevent falls. Further, vision facilitates the head stabilization process for older adults to compensate for age-related decrements in other sensory systems subserving dynamic balance.

Loss of functionally unique species may gradually undermine ecosystems

PubMed Central

O'Gorman, Eoin J.; Yearsley, Jon M.; Crowe, Tasman P.; Emmerson, Mark C.; Jacob, Ute; Petchey, Owen L.

2011-01-01

Functionally unique species contribute to the functional diversity of natural systems, often enhancing ecosystem functioning. An abundance of weakly interacting species increases stability in natural systems, suggesting that loss of weakly linked species may reduce stability. Any link between the functional uniqueness of a species and the strength of its interactions in a food web could therefore have simultaneous effects on ecosystem functioning and stability. Here, we analyse patterns in 213 real food webs and show that highly unique species consistently tend to have the weakest mean interaction strength per unit biomass in the system. This relationship is not a simple consequence of the interdependence of both measures on body size and appears to be driven by the empirical pattern of size structuring in aquatic systems and the trophic position of each species in the web. Food web resolution also has an important effect, with aggregation of species into higher taxonomic groups producing a much weaker relationship. Food webs with fewer unique and less weakly interacting species also show significantly greater variability in their levels of primary production. Thus, the loss of highly unique, weakly interacting species may eventually lead to dramatic state changes and unpredictable levels of ecosystem functioning. PMID:21106593

Large Field of View, Modular, Stabilized, Adaptive-Optics-Based Scanning Laser Ophthalmoscope

PubMed Central

Burns, Stephen A.; Tumbar, Remy; Elsner, Ann E.; Ferguson, Daniel; Hammer, Daniel X.

2007-01-01

We describe the design and performance of an adaptive optics retinal imager that is optimized for use during dynamic correction for eye movements. The system incorporates a retinal tracker and stabilizer, a wide field line scan Scanning Laser Ophthalmocsope (SLO), and a high resolution MEMS based adaptive optics SLO. The detection system incorporates selection and positioning of confocal apertures, allowing measurement of images arising from different portions of the double pass retinal point spread function (psf). System performance was excellent. The adaptive optics increased the brightness and contrast for small confocal apertures by more than 2x, and decreased the brightness of images obtained with displaced apertures, confirming the ability of the adaptive optics system to improve the pointspread function. The retinal image was stabilized to within 18 microns 90% of the time. Stabilization was sufficient for cross-correlation techniques to automatically align the images. PMID:17429477

Stability of glassy hierarchical networks

NASA Astrophysics Data System (ADS)

Zamani, M.; Camargo-Forero, L.; Vicsek, T.

2018-02-01

The structure of interactions in most animal and human societies can be best represented by complex hierarchical networks. In order to maintain close-to-optimal function both stability and adaptability are necessary. Here we investigate the stability of hierarchical networks that emerge from the simulations of an organization type with an efficiency function reminiscent of the Hamiltonian of spin glasses. Using this quantitative approach we find a number of expected (from everyday observations) and highly non-trivial results for the obtained locally optimal networks, including, for example: (i) stability increases with growing efficiency and level of hierarchy; (ii) the same perturbation results in a larger change for more efficient states; (iii) networks with a lower level of hierarchy become more efficient after perturbation; (iv) due to the huge number of possible optimal states only a small fraction of them exhibit resilience and, finally, (v) ‘attacks’ targeting the nodes selectively (regarding their position in the hierarchy) can result in paradoxical outcomes.

Regularized magnetotelluric inversion based on a minimum support gradient stabilizing functional

NASA Astrophysics Data System (ADS)

Xiang, Yang; Yu, Peng; Zhang, Luolei; Feng, Shaokong; Utada, Hisashi

2017-11-01

Regularization is used to solve the ill-posed problem of magnetotelluric inversion usually by adding a stabilizing functional to the objective functional that allows us to obtain a stable solution. Among a number of possible stabilizing functionals, smoothing constraints are most commonly used, which produce spatially smooth inversion results. However, in some cases, the focused imaging of a sharp electrical boundary is necessary. Although past works have proposed functionals that may be suitable for the imaging of a sharp boundary, such as minimum support and minimum gradient support (MGS) functionals, they involve some difficulties and limitations in practice. In this paper, we propose a minimum support gradient (MSG) stabilizing functional as another possible choice of focusing stabilizer. In this approach, we calculate the gradient of the model stabilizing functional of the minimum support, which affects both the stability and the sharp boundary focus of the inversion. We then apply the discrete weighted matrix form of each stabilizing functional to build a unified form of the objective functional, allowing us to perform a regularized inversion with variety of stabilizing functionals in the same framework. By comparing the one-dimensional and two-dimensional synthetic inversion results obtained using the MSG stabilizing functional and those obtained using other stabilizing functionals, we demonstrate that the MSG results are not only capable of clearly imaging a sharp geoelectrical interface but also quite stable and robust. Overall good performance in terms of both data fitting and model recovery suggests that this stabilizing functional is effective and useful in practical applications.[Figure not available: see fulltext.

Functional Trait Changes, Productivity Shifts and Vegetation Stability in Mountain Grasslands during a Short-Term Warming.

PubMed

Debouk, Haifa; de Bello, Francesco; Sebastià, Maria-Teresa

2015-01-01

Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i) how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii) whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland) in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland). The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM) for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM) than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i) the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii) the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term warming, compared to diversity effects. In summary, short-term climate warming can greatly alter vegetation functional structure and its relation to productivity.

Functional Trait Changes, Productivity Shifts and Vegetation Stability in Mountain Grasslands during a Short-Term Warming

PubMed Central

Debouk, Haifa; de Bello, Francesco; Sebastià, Maria-Teresa

2015-01-01

Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i) how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii) whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland) in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland). The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM) for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM) than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i) the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii) the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term warming, compared to diversity effects. In summary, short-term climate warming can greatly alter vegetation functional structure and its relation to productivity. PMID:26513148

Length-dependent structural stability of linear monatomic Cu wires

NASA Astrophysics Data System (ADS)

Singh, Gurvinder; Kumar, Krishan; Singh, Baljinder; Moudgil, R. K.

2018-05-01

We present first-principle calculations based on density functional theory for the finite-length monatomic Cu atom linear wires. The structure and its stability with increasing wire length in terms of number of atoms (N) is determined. Interestingly, the bond length is found to exhibit an oscillatory structure (the so-called magic length phenomenon), with a qualitative change in oscillatory behavior as one moves from even N wire to odd N wire. The even N wires follow simple even-odd oscillations whereas odd N wires show a phase change at the half length of the wires. The stability of the wire structure, determined in terms of the wire formation energy, also contains even-odd oscillation as a function of wire length. However, the oscillations in formation energy reverse its phase after the wire length is increased beyond N=12. Our findings are seen to be qualitatively consistent with recent simulations for a similar class finite-length metal atom wires.

Wnt/β-catenin signaling controls development of the blood–brain barrier

PubMed Central

Liebner, Stefan; Corada, Monica; Bangsow, Thorsten; Babbage, Jane; Taddei, Andrea; Czupalla, Cathrin J.; Reis, Marco; Felici, Angelina; Wolburg, Hartwig; Fruttiger, Marcus; Taketo, Makoto M.; von Melchner, Harald; Plate, Karl Heinz; Gerhardt, Holger; Dejana, Elisabetta

2008-01-01

The blood–brain barrier (BBB) is confined to the endothelium of brain capillaries and is indispensable for fluid homeostasis and neuronal function. In this study, we show that endothelial Wnt/β-catenin (β-cat) signaling regulates induction and maintenance of BBB characteristics during embryonic and postnatal development. Endothelial specific stabilization of β-cat in vivo enhances barrier maturation, whereas inactivation of β-cat causes significant down-regulation of claudin3 (Cldn3), up-regulation of plamalemma vesicle-associated protein, and BBB breakdown. Stabilization of β-cat in primary brain endothelial cells (ECs) in vitro by N-terminal truncation or Wnt3a treatment increases Cldn3 expression, BBB-type tight junction formation, and a BBB characteristic gene signature. Loss of β-cat or inhibition of its signaling abrogates this effect. Furthermore, stabilization of β-cat also increased Cldn3 and barrier properties in nonbrain-derived ECs. These findings may open new therapeutic avenues to modulate endothelial barrier function and to limit the devastating effects of BBB breakdown. PMID:18955553

Experimental and DFT study of thiol-stabilized Pt/CNTs catalysts.

PubMed

Li, L; Chen, S G; Wei, Z D; Qi, X Q; Xia, M R; Wang, Y Q

2012-12-28

Using a combination of experiments and density functional theory (DFT) calculations, we explored the mechanisms of the stabilization effect of the thiolized (-SH) group on the Pt/SH-CNTs catalyst. Pt particles supported on the hydroxyl functionalized CNTs (Pt/OH-CNTs) are synthesized as a baseline for comparison. Experimentally, the platinum on OH-CNTs has a stronger tendency for aggregation than that on SH-CNTs. The differences in the oxidation resistance, migration activation energy, and corrosion resistance between the Pt/SH-CNTs and Pt/OH-CNTs are calculated using DFT. The DFT calculations indicate that the -SH group enhances the oxidation resistance of the Pt cluster and CNTs and restricts Pt migration on the CNTs. DFT calculations also suggest that the enhanced stability of Pt/SH-CNTs originates from the increased interaction between Pt and SH-CNTs and the depressed d-band center of the Pt NPs. Thus, the functional groups on the CNTs used for stabilization of supported Pt NPs should provide a deposit and anchor site for Pt NPs and maintain the perfect structure of CNTs rather than destroying it.

Improving Thermo-Oxidative Stability of Nitrile Rubber Composites by Functional Graphene Oxide.

PubMed

Zhong, Rui; Zhang, Zhao; Zhao, Hongguo; He, Xianru; Wang, Xin; Zhang, Rui

2018-05-30

Graphene oxide (GO), modified with anti-aging agent p -phenylenediamine (PPD), was added into nitrile rubber (NBR) in order to improve the thermo-oxidative stability of NBR. The modification of GO and the transformation of functional groups were characterized by Fourier transform infrared spectroscopy (FTIR), Raman, and X-ray diffraction (XRD). Mechanical performances of NBR composites before and after the thermo-oxidative aging were recorded. The results of dynamic mechanical analysis (DMA) show an increased storage modulus (G') and a decreased value of area of tan δ peak after introducing modified GO into NBR. It indicates that filler particles show positive interaction with molecular chains. The thermo-oxidative stability of composites was investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Then, the thermo-oxidative aging kinetic parameters were obtained by the Flynn⁻Wall⁻Ozawa (FWO) equation. The results of aging tests show that the thermo-oxidative stability of rubber matrix increases obviously after introducing GO⁻PPD. In addition, mechanical properties (tensile strength and elongation at break) of both before and after aged NBR/GO⁻PPD composites were superior to that of NBR. This work provides meaningful guidance for achieving multifunction thermo-oxidative aging resistance rubber composites.

An extended heterogeneous car-following model accounting for anticipation driving behavior and mixed maximum speeds

NASA Astrophysics Data System (ADS)

Sun, Fengxin; Wang, Jufeng; Cheng, Rongjun; Ge, Hongxia

2018-02-01

The optimal driving speeds of the different vehicles may be different for the same headway. In the optimal velocity function of the optimal velocity (OV) model, the maximum speed vmax is an important parameter determining the optimal driving speed. A vehicle with higher maximum speed is more willing to drive faster than that with lower maximum speed in similar situation. By incorporating the anticipation driving behavior of relative velocity and mixed maximum speeds of different percentages into optimal velocity function, an extended heterogeneous car-following model is presented in this paper. The analytical linear stable condition for this extended heterogeneous traffic model is obtained by using linear stability theory. Numerical simulations are carried out to explore the complex phenomenon resulted from the cooperation between anticipation driving behavior and heterogeneous maximum speeds in the optimal velocity function. The analytical and numerical results all demonstrate that strengthening driver's anticipation effect can improve the stability of heterogeneous traffic flow, and increasing the lowest value in the mixed maximum speeds will result in more instability, but increasing the value or proportion of the part already having higher maximum speed will cause different stabilities at high or low traffic densities.

Thermochemical Stability Study of Alkyl-Tethered Quaternary Ammonium Cations for Anion Exchange Membrane Fuel Cells

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

Mohanty, Angela D.; Tignor, Steven E.; Sturgeon, Matthew R.

2017-01-01

The increased interest in the use of anion exchange membranes (AEMs) for applications in electrochemical devices has prompted significant efforts in designing materials with robust stability in alkaline media. Most reported AEMs suffer from polymer backbone degradation as well as cation functional group degradation. In this report, we provide comprehensive experimental investigations for the analysis of cation functional group stability under alkaline media. A silver oxide-mediated ion exchange method and an accelerated stability test in aqueous KOH solutions at elevated temperatures using a Parr reactor were used to evaluate a broad scope of quaternary ammonium (QA) cationic model compound structures,more » particularly focusing on alkyl-tethered cations. Additionally, byproduct analysis was employed to gain better understanding of degradation pathways and trends of alkaline stability. Experimental results under different conditions gave consistent trends in the order of cation stability of various QA small molecule model compounds. Overall, cations that are benzyl-substituted or that are near to electronegative atoms (such as oxygen) degrade faster in alkaline media in comparison to alkyl-tethered QAs. These comprehensive model compound stability studies provide valuable information regarding the relative stability of various cation structures and can help guide researchers towards designing new and promising candidates for AEM materials.« less

Exotic species enhance response diversity to land-use change but modify functional composition.

PubMed

Stavert, Jamie R; Pattemore, David E; Gaskett, Anne C; Beggs, Jacqueline R; Bartomeus, Ignasi

2017-08-16

Two main mechanisms may buffer ecosystem functions despite biodiversity loss. First, multiple species could share similar ecological roles, thus providing functional redundancy. Second, species may respond differently to environmental change (response diversity). However, ecosystem function would be best protected when functionally redundant species also show response diversity. This linkage has not been studied directly, so we investigated whether native and exotic pollinator species with similar traits (functional redundancy) differed in abundance (response diversity) across an agricultural intensification gradient. Exotic pollinator species contributed most positive responses, which partially stabilized overall abundance of the pollinator community. However, although some functionally redundant species exhibited response diversity, this was not consistent across functional groups and aggregate abundances within each functional group were rarely stabilized. This shows functional redundancy and response diversity do not always operate in concert. Hence, despite exotic species becoming increasingly dominant in human-modified systems, they cannot replace the functional composition of native species. © 2017 The Author(s).

Dual-Function Au@Y2O3:Eu3+ Smart Film for Enhanced Power Conversion Efficiency and Long-Term Stability of Perovskite Solar Cells.

PubMed

Kim, Chang Woo; Eom, Tae Young; Yang, In Seok; Kim, Byung Su; Lee, Wan In; Kang, Yong Soo; Kang, Young Soo

2017-07-28

In the present study, a dual-functional smart film combining the effects of wavelength conversion and amplification of the converted wave by the localized surface plasmon resonance has been investigated for a perovskite solar cell. This dual-functional film, composed of Au nanoparticles coated on the surface of Y 2 O 3 :Eu 3+ phosphor (Au@Y 2 O 3 :Eu 3+ ) nanoparticle monolayer, enhances the solar energy conversion efficiency to electrical energy and long-term stability of photovoltaic cells. Coupling between the Y 2 O 3 :Eu 3+ phosphor monolayer and ultraviolet solar light induces the latter to be converted into visible light with a quantum yield above 80%. Concurrently, the Au nanoparticle monolayer on the phosphor nanoparticle monolayer amplifies the converted visible light by up to 170%. This synergy leads to an increased solar light energy conversion efficiency of perovskite solar cells. Simultaneously, the dual-function film suppresses the photodegradation of perovskite by UV light, resulting in long-term stability. Introducing the hybrid smart Au@Y 2 O 3 :Eu 3+ film in perovskite solar cells increases their overall solar-to-electrical energy conversion efficiency to 16.1% and enhances long-term stability, as compared to the value of 15.2% for standard perovskite solar cells. The synergism between the wavelength conversion effect of the phosphor nanoparticle monolayer and the wave amplification by the localized surface plasmon resonance of the Au nanoparticle monolayer in a perovskite solar cell is comparatively investigated, providing a viable strategy of broadening the solar spectrum utilization.

Effect of infrared heating on the formation of sesamol and quality of defatted flours from Sesamum indicum L.

PubMed

Kumar, C Mahendra; Appu Rao, A G; Singh, Sridevi Annapurna

2009-01-01

Infrared (IR) heating offers several advantages over conventional heating in terms of heat transfer efficiency, compactness of equipment, and quality of the products. Roasting of sesame seeds degrades the lignan sesamolin to sesamol, which increases the oxidative stability of sesame oil synergistically with tocopherols. IR (near infrared, 1.1 to 1.3 microm, 6 kW power) roasting conditions were optimized for the conversion of sesamolin to sesamol. The resultant oil was evaluated for sesamol and tocopherol content as well as oxidative stability. The defatted flours were evaluated for their nutritional content and functionality. IR roasting of sesame seeds at 200 degrees C for 30 min increased the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The gamma-tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 degrees C for 30 min, respectively. There were no significant differences in the tocopherol content and oxidative stability of the oil. Methionine and cysteine content of the flours remained unchanged due to roasting. The functional properties of defatted flours obtained from either IR roasted or conventionally roasted sesame seeds remained the same. Practical Applications: Sesame oil is stable to oxidation compared to other vegetable oils. This stability can be attributed to the presence of tocopherols and the formation of sesamol, the thermal degradation product of sesamolin-a lignan present in sesame. Roasting of sesame seeds before oil extraction increases sesamol content which is a more potent antioxidant than the parent molecule. The conversion efficiency of sesamolin to sesamol is increased by 31% by infrared roasting of seeds compared to electric drum roasting. This can be used industrially to obtain roasted oil with greater oxidative stability.

Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method

PubMed Central

Segerström, Lova; Gustavsson, Jenny

2016-01-01

Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg6 (LARG), and Met-enkephalin-Arg6-Phe7 (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid peptide analysis. The result is improved diagnostic and research value of the samples with great benefits for basic research and clinical work. PMID:27007059

Clinical application of the Panjabi neutral zone hypothesis: the Stabilimax NZ posterior lumbar dynamic stabilization system.

PubMed

Yue, James J; Timm, Jens P; Panjabi, Manohar M; Jaramillo-de la Torre, Jorge

2007-01-15

The neutral zone (NZ) is a region of intervertebral motion around the neutral posture where little resistance is offered by the passive spinal column. The NZ appears to be a clinically important measure of spinal stability function. Its size may increase with injury to the spinal column, which in turn may result in spinal instability or low-back pain. Dynamic stabilization systems are designed to support and stabilize the spine while maintaining range of motion (ROM). The Stabilimax NZ device has been designed to reduce the NZ after spinal injury to treat pain while preserving ROM.

Effects of iron-aluminium oxides and organic carbon on aggregate stability of bauxite residues.

PubMed

Zhu, Feng; Li, Yubing; Xue, Shengguo; Hartley, William; Wu, Hao

2016-05-01

In order to successfully establish vegetation on bauxite residue, properties such as aggregate structure and stability require improvement. Spontaneous plant colonization on the deposits in Central China over the last 20 years has revealed that natural processes may improve the physical condition of bauxite residues. Samples from three different stacking ages were selected to determine aggregate formation and stability and its relationship with iron-aluminium oxides and organic carbon. The residue aggregate particles became coarser in both dry and wet sieving processes. The mean weight diameter (MWD) and geometry mean diameter (GMD) increased significantly, and the proportion of aggregate destruction (PAD) decreased. Natural stacking processes could increase aggregate stability and erosion resistant of bauxite residues. Free iron oxides and amorphous aluminium oxides were the major forms in bauxite residues, but there was no significant correlation between the iron-aluminium oxides and aggregate stability. Aromatic-C, alkanes-C, aliphatic-C and alkenes-C were the major functional groups present in the residues. With increasing stacking age, total organic carbon content and aggregate-associated organic carbon both increased. Alkanes-C, aliphatic-C and alkenes-C increased and were mainly distributed in macro-aggregates, whereas aromatic-C was mainly distributed in <0.05-mm aggregates. Organic carbon stability in micro-aggregates was higher than that in macro-aggregates and became more stable. Organic carbon contents in total residues, and within different aggregate sizes, were all negatively correlated with PAD. It indicated that organic materials had a more significant effect on macro-aggregate stability and the effects of iron-aluminium oxides maybe more important for stability of micro-aggregates.

'Trophic whales' as biotic buffers: weak interactions stabilize ecosystems against nutrient enrichment.

PubMed

Schwarzmüller, Florian; Eisenhauer, Nico; Brose, Ulrich

2015-05-01

Human activities may compromise biodiversity if external stressors such as nutrient enrichment endanger overall network stability by inducing unstable dynamics. However, some ecosystems maintain relatively high diversity levels despite experiencing continuing disturbances. This indicates that some intrinsic properties prevent unstable dynamics and resulting extinctions. Identifying these 'ecosystem buffers' is crucial for our understanding of the stability of ecosystems and an important tool for environmental and conservation biologists. In this vein, weak interactions have been suggested as stabilizing elements of complex systems, but their relevance has rarely been tested experimentally. Here, using network and allometric theory, we present a novel concept for a priori identification of species that buffer against externally induced instability of increased population oscillations via weak interactions. We tested our model in a microcosm experiment using a soil food-web motif. Our results show that large-bodied species feeding at the food web's base, so called 'trophic whales', can buffer ecosystems against unstable dynamics induced by nutrient enrichment. Similar to the functionality of chemical or mechanical buffers, they serve as 'biotic buffers' that take up stressor effects and thus protect fragile systems from instability. We discuss trophic whales as common functional building blocks across ecosystems. Considering increasing stressor effects under anthropogenic global change, conservation of these network-intrinsic biotic buffers may help maintain the stability and diversity of natural ecosystems. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

Linear and nonlinear stability criteria for compressible MHD flows in a gravitational field

NASA Astrophysics Data System (ADS)

Moawad, S. M.; Moawad

2013-10-01

The equilibrium and stability properties of ideal magnetohydrodynamics (MHD) of compressible flow in a gravitational field with a translational symmetry are investigated. Variational principles for the steady-state equations are formulated. The MHD equilibrium equations are obtained as critical points of a conserved Lyapunov functional. This functional consists of the sum of the total energy, the mass, the circulation along field lines (cross helicity), the momentum, and the magnetic helicity. In the unperturbed case, the equilibrium states satisfy a nonlinear second-order partial differential equation (PDE) associated with hydrodynamic Bernoulli law. The PDE can be an elliptic or a parabolic equation depending on increasing the poloidal flow speed. Linear and nonlinear Lyapunov stability conditions under translational symmetric perturbations are established for the equilibrium states.

A new methodology based on functional principal component analysis to study postural stability post-stroke.

PubMed

Sánchez-Sánchez, M Luz; Belda-Lois, Juan-Manuel; Mena-Del Horno, Silvia; Viosca-Herrero, Enrique; Igual-Camacho, Celedonia; Gisbert-Morant, Beatriz

2018-05-05

A major goal in stroke rehabilitation is the establishment of more effective physical therapy techniques to recover postural stability. Functional Principal Component Analysis provides greater insight into recovery trends. However, when missing values exist, obtaining functional data presents some difficulties. The purpose of this study was to reveal an alternative technique for obtaining the Functional Principal Components without requiring the conversion to functional data beforehand and to investigate this methodology to determine the effect of specific physical therapy techniques in balance recovery trends in elderly subjects with hemiplegia post-stroke. A randomized controlled pilot trial was developed. Thirty inpatients post-stroke were included. Control and target groups were treated with the same conventional physical therapy protocol based on functional criteria, but specific techniques were added to the target group depending on the subjects' functional level. Postural stability during standing was quantified by posturography. The assessments were performed once a month from the moment the participants were able to stand up to six months post-stroke. The target group showed a significant improvement in postural control recovery trend six months after stroke that was not present in the control group. Some of the assessed parameters revealed significant differences between treatment groups (P < 0.05). The proposed methodology allows Functional Principal Component Analysis to be performed when data is scarce. Moreover, it allowed the dynamics of recovery of two different treatment groups to be determined, showing that the techniques added in the target group increased postural stability compared to the base protocol. Copyright © 2018 Elsevier Ltd. All rights reserved.

The effects of 6-week training programs on throwing accuracy, proprioception, and core endurance in baseball.

PubMed

Lust, Kathleen R; Sandrey, Michelle A; Bulger, Sean M; Wilder, Nathan

2009-08-01

With a limited number of outcomes-based studies, only recommendations for strength-training and rehabilitation programs can be made. To determine the extent to which throwing accuracy, core stability, and proprioception improved after completion of a 6-week training program that included open kinetic chain (OKC), closed kinetic chain (CKC), and/or core-stability exercises. A 2 x 3 factorial design. Division III college. 19 healthy baseball athletes with a control group of 15. Two 6-week programs including OKC, CKC, and core-stabilization exercises that were progressed each week. Functional throwing-performance index, closed kinetic chain upper extremity stability test, back-extensor test, 45 degrees abdominal-fatigue test, and right- and left-side bridging test. There was no significant difference between groups. An increase was evident in all pretest-to-posttest results, with improvement ranging from 1.36% to 140%. Both of the 6-week training programs could be used to increase throwing accuracy, core stability, and proprioception in baseball.

Vav1-mediated scaffolding interactions stabilize SLP-76 microclusters and contribute to antigen-dependent T cell responses.

PubMed

Sylvain, Nicholas R; Nguyen, Ken; Bunnell, Stephen C

2011-03-08

The guanine nucleotide exchange factor (GEF) Vav1 synergizes with the adaptor protein SLP-76 (Src homology 2 domain--containing leukocyte phosphoprotein of 76 kD) to support T cell development and activation. In response to ligation of the T cell receptor (TCR), SLP-76 is assembled into microclusters that provide an essential platform for the signaling events that drive T cell activation. We found that Vav1 selectively entered SLP-76 microclusters, rather than TCR microclusters, influencing their stability and function. The carboxyl terminus of Vav1, which consists of Src homology domains, was both necessary and sufficient for the entry of Vav1 into SLP-76 microclusters; however, this fragment of Vav1 was insufficient to stabilize the microclusters, and it potently suppressed T cell activation. This indicated that the amino terminus of Vav1, which has the GEF domain, also contributed to the integrity of SLP-76 microclusters and thereby to T cell activation. These microcluster-stabilizing functions were independent of the GEF activity in the amino terminus of Vav1 and were unaffected if the GEF function of Vav1 was either inactivated or constitutively activated by mutation. In contrast, Vav1 deletion mutants lacking either the calponin homology domain or the catalytic core of the GEF exhibited mild scaffolding defects, but they differentially affected TCR-dependent calcium ion (Ca²+) responses. We conclude that multiple GEF-independent scaffolding functions distributed throughout the amino terminus of Vav1 contribute to the activation of T cells by acting synergistically to increase the stability and function of SLP-76 microclusters.

Chemical stability of insulin. 3. Influence of excipients, formulation, and pH.

PubMed

Brange, J; Langkjaer, L

1992-01-01

The influence of auxiliary substances and pH on the chemical transformations of insulin in pharmaceutical formulation, including various hydrolytic and intermolecular cross-linking reactions, was studied. Bacteriostatic agents had a profound stabilizing effect--phenol > m-cresol > methylparaben--on deamidation as well as on insulin intermolecular cross-linking reactions. Of the isotonicity substances, NaCl generally had a stabilizing effect whereas glycerol and glucose led to increased chemical deterioration. Phenol and sodium chloride exerted their stabilizing effect through independent mechanisms. Zinc ions, in concentrations that promote association of insulin into hexamers, increase the stability, whereas higher zinc content had no further influence. Protamine gave rise to additional formation of covalent protamine-insulin products which increased with increasing protamine concentration. The impact of excipients on the chemical processes seems to be dictated mainly via an influence on the three-dimensional insulin structure. The effect of the physical state of the insulin on the chemical stability was also complex, suggesting an intricate dependence of intermolecular proximity of involved functional groups. At pH values below five and above eight, insulin degrades relatively fast. At acid pH, deamidation at residue A21 and covalent insulin dimerization dominates, whereas disulfide reactions leading to covalent polymerization and formation of A- and B-chains prevailed in alkaline medium. Structure-reactivity relationship is proposed to be a main determinant for the chemical transformation of insulin.

Functional Stability of the Human Kappa Opioid Receptor Reconstituted in Nanodiscs Revealed by a Time-Resolved Scintillation Proximity Assay

PubMed Central

Hansen, Randi Westh; Wang, Xiaole; Golab, Agnieszka; Bornert, Olivier; Oswald, Christine; Wagner, Renaud; Martinez, Karen Laurence

2016-01-01

Long-term functional stability of isolated membrane proteins is crucial for many in vitro applications used to elucidate molecular mechanisms, and used for drug screening platforms in modern pharmaceutical industry. Compared to soluble proteins, the understanding at the molecular level of membrane proteins remains a challenge. This is partly due to the difficulty to isolate and simultaneously maintain their structural and functional stability, because of their hydrophobic nature. Here we show, how scintillation proximity assay can be used to analyze time-resolved high-affinity ligand binding to membrane proteins solubilized in various environments. The assay was used to establish conditions that preserved the biological function of isolated human kappa opioid receptor. In detergent solution the receptor lost high-affinity ligand binding to a radiolabelled ligand within minutes at room temperature. After reconstitution in Nanodiscs made of phospholipid bilayer the half-life of high-affinity ligand binding to the majority of receptors increased 70-fold compared to detergent solubilized receptors—a level of stability that is appropriate for further downstream applications. Time-resolved scintillation proximity assay has the potential to screen numerous conditions in parallel to obtain high levels of stable and active membrane proteins, which are intrinsically unstable in detergent solution, and with minimum material consumption. PMID:27035823

Monopoly models with time-varying demand function

NASA Astrophysics Data System (ADS)

Cavalli, Fausto; Naimzada, Ahmad

2018-05-01

We study a family of monopoly models for markets characterized by time-varying demand functions, in which a boundedly rational agent chooses output levels on the basis of a gradient adjustment mechanism. After presenting the model for a generic framework, we analytically study the case of cyclically alternating demand functions. We show that both the perturbation size and the agent's reactivity to profitability variation signals can have counterintuitive roles on the resulting period-2 cycles and on their stability. In particular, increasing the perturbation size can have both a destabilizing and a stabilizing effect on the resulting dynamics. Moreover, in contrast with the case of time-constant demand functions, the agent's reactivity is not just destabilizing, but can improve stability, too. This means that a less cautious behavior can provide better performance, both with respect to stability and to achieved profits. We show that, even if the decision mechanism is very simple and is not able to always provide the optimal production decisions, achieved profits are very close to those optimal. Finally, we show that in agreement with the existing empirical literature, the price series obtained simulating the proposed model exhibit a significant deviation from normality and large volatility, in particular when underlying deterministic dynamics become unstable and complex.

Transsynaptic Coordination of Synaptic Growth, Function, and Stability by the L1-Type CAM Neuroglian

PubMed Central

Moreno, Eliza; Stephan, Raiko; Boerner, Jana; Godenschwege, Tanja A.; Pielage, Jan

2013-01-01

The precise control of synaptic connectivity is essential for the development and function of neuronal circuits. While there have been significant advances in our understanding how cell adhesion molecules mediate axon guidance and synapse formation, the mechanisms controlling synapse maintenance or plasticity in vivo remain largely uncharacterized. In an unbiased RNAi screen we identified the Drosophila L1-type CAM Neuroglian (Nrg) as a central coordinator of synapse growth, function, and stability. We demonstrate that the extracellular Ig-domains and the intracellular Ankyrin-interaction motif are essential for synapse development and stability. Nrg binds to Ankyrin2 in vivo and mutations reducing the binding affinities to Ankyrin2 cause an increase in Nrg mobility in motoneurons. We then demonstrate that the Nrg–Ank2 interaction controls the balance of synapse growth and stability at the neuromuscular junction. In contrast, at a central synapse, transsynaptic interactions of pre- and postsynaptic Nrg require a dynamic, temporal and spatial, regulation of the intracellular Ankyrin-binding motif to coordinate pre- and postsynaptic development. Our study at two complementary model synapses identifies the regulation of the interaction between the L1-type CAM and Ankyrin as an important novel module enabling local control of synaptic connectivity and function while maintaining general neuronal circuit architecture. PMID:23610557

Transsynaptic coordination of synaptic growth, function, and stability by the L1-type CAM Neuroglian.

PubMed

Enneking, Eva-Maria; Kudumala, Sirisha R; Moreno, Eliza; Stephan, Raiko; Boerner, Jana; Godenschwege, Tanja A; Pielage, Jan

2013-01-01

The precise control of synaptic connectivity is essential for the development and function of neuronal circuits. While there have been significant advances in our understanding how cell adhesion molecules mediate axon guidance and synapse formation, the mechanisms controlling synapse maintenance or plasticity in vivo remain largely uncharacterized. In an unbiased RNAi screen we identified the Drosophila L1-type CAM Neuroglian (Nrg) as a central coordinator of synapse growth, function, and stability. We demonstrate that the extracellular Ig-domains and the intracellular Ankyrin-interaction motif are essential for synapse development and stability. Nrg binds to Ankyrin2 in vivo and mutations reducing the binding affinities to Ankyrin2 cause an increase in Nrg mobility in motoneurons. We then demonstrate that the Nrg-Ank2 interaction controls the balance of synapse growth and stability at the neuromuscular junction. In contrast, at a central synapse, transsynaptic interactions of pre- and postsynaptic Nrg require a dynamic, temporal and spatial, regulation of the intracellular Ankyrin-binding motif to coordinate pre- and postsynaptic development. Our study at two complementary model synapses identifies the regulation of the interaction between the L1-type CAM and Ankyrin as an important novel module enabling local control of synaptic connectivity and function while maintaining general neuronal circuit architecture.

Joint Stability in Total Knee Arthroplasty: What Is the Target for a Stable Knee?

PubMed

Wright, Timothy M

2017-02-01

Instability remains a common cause of failure in total knee arthroplasty. Although approaches for surgical treatment of instability exist, the target for initial stability remains elusive, increasing the likelihood that failures will persist because adequate stability is not restored when performing the primary arthroplasty. Although the mechanisms that stabilize the knee joint-contact between the articular surfaces, ligamentous constraints, and muscle forces-are well-defined, their relative importance and the interplay among them throughout functions of daily living are poorly understood. The problem is exacerbated by the complex multiplanar motions that occur across the joint and the large variations in these motions across the population, suggesting that stability targets may need to be patient-specific.

LMI-based stability and performance conditions for continuous-time nonlinear systems in Takagi-Sugeno's form.

PubMed

Lam, H K; Leung, Frank H F

2007-10-01

This correspondence presents the stability analysis and performance design of the continuous-time fuzzy-model-based control systems. The idea of the nonparallel-distributed-compensation (non-PDC) control laws is extended to the continuous-time fuzzy-model-based control systems. A nonlinear controller with non-PDC control laws is proposed to stabilize the continuous-time nonlinear systems in Takagi-Sugeno's form. To produce the stability-analysis result, a parameter-dependent Lyapunov function (PDLF) is employed. However, two difficulties are usually encountered: 1) the time-derivative terms produced by the PDLF will complicate the stability analysis and 2) the stability conditions are not in the form of linear-matrix inequalities (LMIs) that aid the design of feedback gains. To tackle the first difficulty, the time-derivative terms are represented by some weighted-sum terms in some existing approaches, which will increase the number of stability conditions significantly. In view of the second difficulty, some positive-definitive terms are added in order to cast the stability conditions into LMIs. In this correspondence, the favorable properties of the membership functions and nonlinear control laws, which allow the introduction of some free matrices, are employed to alleviate the two difficulties while retaining the favorable properties of PDLF-based approach. LMI-based stability conditions are derived to ensure the system stability. Furthermore, based on a common scalar performance index, LMI-based performance conditions are derived to guarantee the system performance. Simulation examples are given to illustrate the effectiveness of the proposed approach.

Plant species richness and functional traits affect community stability after a flood event.

PubMed

Fischer, Felícia M; Wright, Alexandra J; Eisenhauer, Nico; Ebeling, Anne; Roscher, Christiane; Wagg, Cameron; Weigelt, Alexandra; Weisser, Wolfgang W; Pillar, Valério D

2016-05-19

Climate change is expected to increase the frequency and magnitude of extreme weather events. It is therefore of major importance to identify the community attributes that confer stability in ecological communities during such events. In June 2013, a flood event affected a plant diversity experiment in Central Europe (Jena, Germany). We assessed the effects of plant species richness, functional diversity, flooding intensity and community means of functional traits on different measures of stability (resistance, resilience and raw biomass changes from pre-flood conditions). Surprisingly, plant species richness reduced community resistance in response to the flood. This was mostly because more diverse communities grew more immediately following the flood. Raw biomass increased over the previous year; this resulted in decreased absolute value measures of resistance. There was no clear response pattern for resilience. We found that functional traits drove these changes in raw biomass: communities with a high proportion of late-season, short-statured plants with dense, shallow roots and small leaves grew more following the flood. Late-growing species probably avoided the flood, whereas greater root length density might have allowed species to better access soil resources brought from the flood, thus growing more in the aftermath. We conclude that resource inputs following mild floods may favour the importance of traits related to resource acquisition and be less associated with flooding tolerance. © 2016 The Author(s).

Plant species richness and functional traits affect community stability after a flood event

PubMed Central

Fischer, Felícia M.; Wright, Alexandra J.; Eisenhauer, Nico; Ebeling, Anne; Roscher, Christiane; Wagg, Cameron; Weigelt, Alexandra; Weisser, Wolfgang W.; Pillar, Valério D.

2016-01-01

Climate change is expected to increase the frequency and magnitude of extreme weather events. It is therefore of major importance to identify the community attributes that confer stability in ecological communities during such events. In June 2013, a flood event affected a plant diversity experiment in Central Europe (Jena, Germany). We assessed the effects of plant species richness, functional diversity, flooding intensity and community means of functional traits on different measures of stability (resistance, resilience and raw biomass changes from pre-flood conditions). Surprisingly, plant species richness reduced community resistance in response to the flood. This was mostly because more diverse communities grew more immediately following the flood. Raw biomass increased over the previous year; this resulted in decreased absolute value measures of resistance. There was no clear response pattern for resilience. We found that functional traits drove these changes in raw biomass: communities with a high proportion of late-season, short-statured plants with dense, shallow roots and small leaves grew more following the flood. Late-growing species probably avoided the flood, whereas greater root length density might have allowed species to better access soil resources brought from the flood, thus growing more in the aftermath. We conclude that resource inputs following mild floods may favour the importance of traits related to resource acquisition and be less associated with flooding tolerance. PMID:27114578

A Note on Local Stability Conditions for Two Types of Monetary Models with Recursive Utility

NASA Astrophysics Data System (ADS)

Miyazaki, Kenji; Utsunomiya, Hitoshi

2009-09-01

This note explores local stability conditions for money-in-utility-function (MIUF) and transaction-costs (TC) models with recursive utility. Although Chen et al. [Chen, B.-L., M. Hsu, and C.-H. Lin, 2008, Inflation and growth: impatience and a qualitative equivalent, Journal of Money, Credit, and Banking, Vol. 40, No. 6, 1310-1323] investigated the relationship between inflation and growth in MIUF and TC models with recursive utility, they conducted only a comparative static analysis in a steady state. By establishing sufficient conditions for local stability, this note proves that impatience should be increasing in consumption and real balances. Increasing impatience, although less plausible from an empirical point of view, receives more support from a theoretical viewpoint.

Functional Properties of a High Protein Beverage Stabilized with Oat-β-Glucan.

PubMed

Vasquez-Orejarena, Eva; Simons, Christopher T; Litchfield, John H; Alvarez, Valente B

2018-05-01

This study evaluated the effect of oat flour and milk protein on the functional properties and sensory acceptability of shelf stable high protein dairy beverages containing at least 0.75 g of oat-β-glucan per serving size. Formulations adjusted to levels of 1.50% to 2.30% oat flour and 2.50% to 4.00% milk protein isolate (MPI) were thermal processed in a rotary retort. The finished product exhibited good suspension stability (>80%). The increase of oat and MPI contents lead to nectar-like beverages (51 to 100 mPas). However, oat flour was the component showing the highest effect on the viscosity coefficient values of the beverages. Sensory evaluation indicated that formulations with less than 1.9% oat flour and 2.5% MPI (thin liquid, <50 mPas) were the most accepted. Mouthfeel (perceived thickness), sweetness and aftertaste had the most influence on overall liking of the beverages. Overall, this study comprises the development of a functional food product. Supplementation of beverages with fiber from oats is an innovative approach to stabilize high protein beverages. Ready to drink protein beverage formulations use gums to stabilize the product and provide a desirable mouthfeel. The levels of oat-β-glucan used in the beverage increased the thickness and meet the requirement of the FDA approved health claim for reduction of the cardiovascular disease risk (21 CFR 101.81). © 2018 Institute of Food Technologists®.

Contribution of the Pubofemoral Ligament to Hip Stability: A Biomechanical Study.

PubMed

Martin, Hal D; Khoury, Anthony N; Schröder, Ricardo; Johnson, Eric; Gómez-Hoyos, Juan; Campos, Salvador; Palmer, Ian J

2017-02-01

To determine the isolated function of the pubofemoral ligament of the hip capsule and its contribution to hip stability in external/internal rotational motion during flexion greater than 30° and abduction. Thirteen hips from 7 fresh-frozen pelvis-to-toe cadavers were skeletonized from the lumbar spine to the distal femur with the capsular ligaments intact. Computed tomographic imaging was performed to ensure no occult pathological state existed, and assess bony anatomy. Specimens were placed on a surgical table in supine position with lower extremities resting on a custom-designed polyvinylchloride frame. Hip internal and external rotation was measured with the hip placed into a combination of the following motions: 30°, 60°, 110° hip flexion and 0°, 20°, 40° abduction. Testing positions were randomized. The pubofemoral ligament was released and measurements were repeated, followed by releasing the ligamentum teres. Analysis of the 2,106 measurements recorded demonstrates the pubofemoral ligament as a main controller of hip internal rotation during hip flexion beyond 30° and abduction. Hip internal rotation was increased up to 438.9% (P < .001) when the pubofemoral ligament was released and 412.9% (P < .001) when both the pubofemoral and teres ligament were released, compared with the native state. The hypothesis of the pubofemoral ligament as one of the contributing factors of anterior inferior hip stability by controlling external rotation of the hip in flexion beyond 30° and abduction was disproved. The pubofemoral ligament maintains a key function in limiting internal rotation in the position of increasing hip flexion beyond 30° and abduction. This cadaveric study concludes previous attempts at understanding the anatomical and biomechanical function of the capsular ligaments and their role in hip stability. The present study contributes to the understanding of hip stability and biomechanical function of the pubofemoral ligament. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Kinematics of Different Components of the Posterolateral Corner of the Knee in the Lateral Collateral Ligament-intact State: A Human Cadaveric Study.

PubMed

Domnick, Christoph; Frosch, Karl-Heinz; Raschke, Michael J; Vogel, Nils; Schulze, Martin; von Glahn, Mathias; Drenck, Tobias C; Herbort, Mirco

2017-10-01

To determine the static stabilizing effects of different anatomical structures of the posterolateral corner (PLC) of the knee in the lateral collateral ligament (LCL)-intact state. Thirteen fresh-frozen human cadaveric knees were dissected and tested using an industrial robot with an optical tracking system. Kinematics were determined for 134 N anterior/posterior loads, 10 N m valgus/varus loads, and 5 N m internal/external rotatory loads in 0°, 20°, 30°, 60°, and 90° of knee flexion. The PLC structures were dissected and consecutively released: (I) intact knee joint, (II) with released posterior cruciate ligament (PCL), (III) popliteomeniscal fibers, (IV) popliteofibular ligament, (V) arcuat and popliteotibial fibers, (VI) popliteus tendon (PLT), and (VII) LCL. Repeated-measures analysis of variance was performed with significance set at P < .05. After releasing the PCL, posterior tibial translation increased by 5.2 mm at 20° to 9.4 mm at 90° of joint flexion (P < .0001). A mild 1.8° varus instability was measured in 0° of flexion (P = .0017). After releasing the PLC structures, posterior tibial translation further increased by 2.9 mm at 20° to 5.9 mm at 90° of flexion (P < .05) and external rotation angle increased by 2.6° at 0° to 7.9° at 90° of flexion (P < .05, vs II). Varus stability did not decrease. Mild differences between states V and VI were found in 60° and 90° external rotation tests (2.1° and 3.1°; P < .05). The connecting ligaments/fibers to the PLT act as a primary static stabilizer against external rotatory loads and a secondary stabilizer against posterior tibial loads (when PCL is injured). After releasing these structures, most static stabilizing function of the intact PLT is lost. The PLC has no varus-stabilizing function in the LCL-intact knee. Anatomy and function of these structures for primary and secondary joint stability should be considered for clinical diagnostics and when performing surgery in the PLC. Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

On Stabilizing the Variance of Dynamic Functional Brain Connectivity Time Series

PubMed Central

Fransson, Peter

2016-01-01

Abstract Assessment of dynamic functional brain connectivity based on functional magnetic resonance imaging (fMRI) data is an increasingly popular strategy to investigate temporal dynamics of the brain's large-scale network architecture. Current practice when deriving connectivity estimates over time is to use the Fisher transformation, which aims to stabilize the variance of correlation values that fluctuate around varying true correlation values. It is, however, unclear how well the stabilization of signal variance performed by the Fisher transformation works for each connectivity time series, when the true correlation is assumed to be fluctuating. This is of importance because many subsequent analyses either assume or perform better when the time series have stable variance or adheres to an approximate Gaussian distribution. In this article, using simulations and analysis of resting-state fMRI data, we analyze the effect of applying different variance stabilization strategies on connectivity time series. We focus our investigation on the Fisher transformation, the Box–Cox (BC) transformation and an approach that combines both transformations. Our results show that, if the intention of stabilizing the variance is to use metrics on the time series, where stable variance or a Gaussian distribution is desired (e.g., clustering), the Fisher transformation is not optimal and may even skew connectivity time series away from being Gaussian. Furthermore, we show that the suboptimal performance of the Fisher transformation can be substantially improved by including an additional BC transformation after the dynamic functional connectivity time series has been Fisher transformed. PMID:27784176

On Stabilizing the Variance of Dynamic Functional Brain Connectivity Time Series.

PubMed

Thompson, William Hedley; Fransson, Peter

2016-12-01

Assessment of dynamic functional brain connectivity based on functional magnetic resonance imaging (fMRI) data is an increasingly popular strategy to investigate temporal dynamics of the brain's large-scale network architecture. Current practice when deriving connectivity estimates over time is to use the Fisher transformation, which aims to stabilize the variance of correlation values that fluctuate around varying true correlation values. It is, however, unclear how well the stabilization of signal variance performed by the Fisher transformation works for each connectivity time series, when the true correlation is assumed to be fluctuating. This is of importance because many subsequent analyses either assume or perform better when the time series have stable variance or adheres to an approximate Gaussian distribution. In this article, using simulations and analysis of resting-state fMRI data, we analyze the effect of applying different variance stabilization strategies on connectivity time series. We focus our investigation on the Fisher transformation, the Box-Cox (BC) transformation and an approach that combines both transformations. Our results show that, if the intention of stabilizing the variance is to use metrics on the time series, where stable variance or a Gaussian distribution is desired (e.g., clustering), the Fisher transformation is not optimal and may even skew connectivity time series away from being Gaussian. Furthermore, we show that the suboptimal performance of the Fisher transformation can be substantially improved by including an additional BC transformation after the dynamic functional connectivity time series has been Fisher transformed.

PTH 1-34 Ameliorates the Osteopenia and Delayed Healing of Stabilized Tibia Fracture in Mice with Achondroplasia Resulting from Gain-Of-Function Mutation of FGFR3

PubMed Central

Chen, Hangang; Sun, Xianding; Yin, Liangjun; Chen, Shuai; Zhu, Ying; Huang, Junlan; Jiang, Wanling; Chen, Bo; Zhang, Ruobin; Chen, Lin; Nie, Mao; Xie, Yangli; Deng, Zhongliang

2017-01-01

Bone fracture healing is processed through multiple stages including the cartilaginous callus formation and its transition to bony callus. FGFR3 negatively regulates chondrogenesis and enhances osteogenesis during skeleton development. We previously found in mice carrying gain-of-function mutation of FGFR3 that FGFR3 delays the healing of un-stabilized fracture that heals mainly through endochondral ossification. Since fracture is regularly treated in clinics with rigid fixation, and stabilized fracture is healed largely through intramembranous ossification, we asked whether FGFR3, a key regulator of osteogenesis, also affect the regeneration of stabilized fracture. We found that gain-of-function mutation of FGFR3 inhibits the initiation of chondrogenesis and the subsequent bone formation. We further studied whether PTH1-34 can improve the osteopenia and delayed healing of the stabilized tibia fracture in mice with achondroplasia. Fracture healing was evaluated by radiography, micro-CT, biomechanical tests, histology, and real-time polymerase chain reaction (RT-PCR) analysis. We found that PTH 1-34 can alleviate the decreased bone mass and compromised architecture in ACH mice. Histological analysis revealed that administration of PTH1-34 increased the size of both the total callus and cartilaginous callus at 14 days after the surgery in ACH mice. RT-PCR data suggested that systemic PTH1-34 accelerated the initiation of chondrogenesis and chondrocyte maturation (earlier and higher levels of expression of chondrogenesis related markers) and enhanced the osteogenic differentiation in the fracture callus in ACH mice. These results indicate that the PTH1-34 administration resulted in an enhanced callus formation during bone fracture healing in ACH mice, which is at least in part mediated by an increase of cartilaginous callus at early stage and the promotion of bone formation in bony callus. In summary, in this study we revealed that FGFR3 delays the regeneration of stabilized fracture by inhibiting both the chondrogenesis and osteogenesis, and PTH1-34 treatment can improve the dysregulated bone metabolism and delayed bone injury healing resulting from gain-of-function mutation of FGFR3. PMID:29104492

Stabilized NADH as a Countermeasure for Jet Lag

NASA Technical Reports Server (NTRS)

Kay, Gary G.; Viirre, Erik; Clark, Jonathan

2001-01-01

Current remedies for jet lag (phototherapy, melatonin, stimulant, and sedative medications) are limited in efficacy and practicality. The efficacy of a stabilized, sublingual form of reduced nicotin amide adenine dinucleotide (NADH, ENADAlert, Menuco Corp.) as a countermeasure for jet lag was examined. Because NADH increases cellular production of ATP and facilitates dopamine synthesis, it may counteract the effects of jet lag on cognitive functioning and sleepiness. Thirty-five healthy, employed subjects participated in this double-blind, placebo-controlled study. Training and baseline testing were conducted on the West Coast before subjects flew overnight to the East Coast, where they would experience a 3-hour time difference. Upon arrival, individuals were randomly assigned to receive either 20 mg of sublingual stabilized ADH (n=18) or identical placebo tablets (n=17). All participants completed computer-administered tests (including CogScreen7) to assess changes in cognitive functioning, mood, and sleepiness in the morning and afternoon. Jet lag resulted in increased sleepiness for over half the participants and deterioration of cognitive functioning for approximately one third. The morning following the flight, subjects experienced lapses of attention in addition to disruptions in working memory, divided attention, and visual perceptual speed. Individuals who received NADH performed significantly better on 5 of 8 cognitive and psychomotor test measures (P less than or equal to 0.5) and showed a trend for better performance on the other three measures (P less than or equal to .l0). Subjects also reported less sleepiness compared with those who received placebo. No adverse effects were observed with NADH treatment. Stabilized NADH significantly reduced jet lag-induced disruptions of cognitive functioning, was easily administered, and was found to have no adverse side effects.

Enhancing stability and efficiency of perovskite solar cells with crosslinkable silane-functionalized and doped fullerene

DOE PAGES

Bai, Yang; Dong, Qingfeng; Shao, Yuchuan; ...

2016-10-05

The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p-i-n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, themore » perovskite devices deliver an efficiency of 19.5% with a high fill factor of 80.6%. Furthermore, a crosslinked silane-modified fullerene layer also enhances the water and moisture stability of the non-sealed perovskite devices by retaining nearly 90% of their original efficiencies after 30 days’ exposure in an ambient environment.« less

Enhancing stability and efficiency of perovskite solar cells with crosslinkable silane-functionalized and doped fullerene

PubMed Central

Bai, Yang; Dong, Qingfeng; Shao, Yuchuan; Deng, Yehao; Wang, Qi; Shen, Liang; Wang, Dong; Wei, Wei; Huang, Jinsong

2016-01-01

The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p–i–n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, the perovskite devices deliver an efficiency of 19.5% with a high fill factor of 80.6%. A crosslinked silane-modified fullerene layer also enhances the water and moisture stability of the non-sealed perovskite devices by retaining nearly 90% of their original efficiencies after 30 days' exposure in an ambient environment. PMID:27703136

Removal of a C-terminal serine residue proximal to the inter-chain disulfide bond of a human IgG1 lambda light chain mediates enhanced antibody stability and antibody dependent cell-mediated cytotoxicity

PubMed Central

Shen, Yang; Zeng, Lin; Zhu, Aiping; Blanc, Tim; Patel, Dipa; Pennello, Anthony; Bari, Amtul; Ng, Stanley; Persaud, Kris; Kang, Yun (Kenneth); Balderes, Paul; Surguladze, David; Hindi, Sagit; Zhou, Qinwei; Ludwig, Dale L.; Snavely, Marshall

2013-01-01

Optimization of biophysical properties is a critical success factor for the developability of monoclonal antibodies with potential therapeutic applications. The inter-domain disulfide bond between light chain (Lc) and heavy chain (Hc) in human IgG1 lends structural support for antibody scaffold stability, optimal antigen binding, and normal Fc function. Recently, human IgG1λ has been suggested to exhibit significantly greater susceptibility to reduction of the inter Lc-Hc disulfide bond relative to the same disulfide bond in human IgG1κ. To understand the molecular basis for this observed difference in stability, the sequence and structure of human IgG1λ and human IgG1κ were compared. Based on this Lc comparison, three single mutations were made in the λ Lc proximal to the cysteine residue, which forms a disulfide bond with the Hc. We determined that deletion of S214 (dS) improved resistance of the association between Lc and Hc to thermal stress. In addition, deletion of this terminal serine from the Lc of IgG1λ provided further benefit, including an increase in stability at elevated pH, increased yield from transient transfection, and improved in vitro antibody dependent cell-mediated cytotoxicity (ADCC). These observations support the conclusion that the presence of the terminal serine of the λ Lc creates a weaker inter-chain disulfide bond between the Lc and Hc, leading to slightly reduced stability and a potential compromise in IgG1λ function. Our data from a human IgG1λ provide a basis for further investigation of the effects of deleting terminal serine from λLc on the stability and function of other human IgG1λ antibodies. PMID:23567210

In-situ micro-FTIR Study of Thermal Changes of Organics in Tagish Lake Meteorite: Behavior of Aliphatic Oxygenated Functions and Effects of Minerals

NASA Technical Reports Server (NTRS)

Kebukawa, Yoko; Nakashima, Satoru; Nakamura-Messenger, Keiko; Zolensky, Michael E.

2007-01-01

Systematic in-situ FTIR heating experiments of Tagish Lake meteorite grains have been performed in order to study thermal stability of chondritic organics. Some aliphatic model organic substances have also been used to elucidate effects of hydrous phyllosilicate minerals on the thermal stability of organics. The experimental results indicated that organic matter in the Tagish Lake meteorite might contain oxygenated aliphatic hydrocarbons which are thermally stable carbonyls such as ester and/or C=O in ring compounds. The presence of hydrous phyllosilicate minerals has a pronounced effect on the increase of the thermal stability of aliphatic and oxygenated functions. These oxygenated aliphatic organics in Tagish Lake can be formed during the aqueous alteration in the parent body and the formation temperature condition might be less than 200 C, based especially on the thermal stability of C-O components. The hydrous phyllosilicates might provide sites for organic globule formation and protected some organic decomposition

Spectroscopic studies of Np(V) complexation

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

Stout, B.E.

The complexation of Np(V) with aliphatic (oxalic, malonic, succinic, glutaric, and maleic) and aromatic (phthalic, pyromellitic, hemimellitic, trimellitic, and mellitic) polycarboxylic acids was studied by spectrophotometry at 1 M ionic strength (NaClO{sub 4}) and 23 C. For the aliphatic systems, the stability of the neptunyl complexes was found to decrease as the carbon chain length of the ligand increased which was attributed to an entropy effect. In polycarboxylate systems, the stability constant decreased in the order hemimellitate > mellitate > pyromellitate > trimellitate, phthalate. With the exception of hemimellitate, this trend follows the order of decreasing basicity of the ligand.more » After correction of the stability constant for statistical effects, the stability of the mellitate, pyromellitate, trimellitate, and phthalate complexes were approximately the same. The unexpected strength the hemimellitate complexation was attributed to an increase in electron density at the binding site from the non-chelating carboxylate group through induction. The complexation of phthalate, trimellitate and hemimellitate and mellitate were studied as a function of pH. Trimellitate and mellitate were found to form ML as well as ML complexes while for phthalate and hemimellitate only ML species were observed. The stability constants of the cation-cation complexes Np(V)-U(VI) and Np(V)-Np(V), measured at 6 M ionic strength (HClO{sub 4}) and 25 C, were found to be 2.45 {+-} 0.05 and 1.41 {+-} 0.14, respectively. The change in enthalpy for the Np(V)-U(VI) system as determined by the measurement of the stability constant as function of temperature was -14.3 {+-} 1.6 kJ/mol.« less

Biodiversity and ecosystem stability in a decade-long grassland experiment.

PubMed

Tilman, David; Reich, Peter B; Knops, Johannes M H

2006-06-01

Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity, its effects on stability are debated. Here we present a long-term experimental field test of the diversity-stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.

Predator interference and stability of predator-prey dynamics.

PubMed

Přibylová, Lenka; Berec, Luděk

2015-08-01

Predator interference, that is, a decline in the per predator consumption rate as predator density increases, is generally thought to promote predator-prey stability. Indeed, this has been demonstrated in many theoretical studies on predator-prey dynamics. In virtually all of these studies, the stabilization role is demonstrated as a weakening of the paradox of enrichment. With predator interference, stable limit cycles that appear as a result of environmental enrichment occur for higher values of the environmental carrying capacity of prey, and even a complete absence of the limit cycles can happen. Here we study predator-prey dynamics using the Rosenzweig-MacArthur-like model in which the Holling type II functional response has been replaced by a predator-dependent family which generalizes many of the commonly used descriptions of predator interference. By means of a bifurcation analysis we show that sufficiently strong predator interference may bring about another stabilizing mechanism. In particular, hysteresis combined with (dis)appearance of stable limit cycles imply abrupt increases in both the prey and predator densities and enhanced persistence and resilience of the predator-prey system. We encourage refitting the previously collected data on predator consumption rates as well as for conducting further predation experiments to see what functional response from the explored family is the most appropriate.

Influence of bidentate ligand donor types on the formation and stability in 2 + 1 fac-[MI(CO)3]+ (M = Re, 99mTc) complexes.

PubMed

Hayes, Thomas R; Bottorff, Shalina C; Slocumb, Winston S; Barnes, Charles L; Clark, Aurora E; Benny, Paul D

2017-01-24

In the last two decades, a number of chelate strategies have been proposed for the fac-[M I (CO) 3 ] + (M = Re, 99m Tc) core in radiopharmaceutical applications. However, the development of new ligands/complexes with improved function and in vivo performance has been limited in recent years. Expanding on our previous studies using the 2 + 1 labeling strategy, a series of bidentate ligands (neutral vs. anionic) containing an aromatic amine in combination with monodentate pyridine analogs or imidazole were explored to determine the influence of the bidentate and monodentate ligands on the formation and stability of the respective complexes. The 2 + 1 complexes with Re and 99m Tc were synthesized in two steps and characterized by standard radio/chemical methods. X-ray characterization and density functional theory analysis of the Re 2 + 1 complexes with the complete bidentate series with 4-dimethylaminopyridine were conducted, indicating enhanced ligand binding energies of the neutral over anionic ligands. In the 99m Tc studies, anionic bidentate ligands had significantly higher formation yields of the 2 + 1 product, but neutral ligands appear to have increased stability in an amino acid challenge assay. Both bidentate series exhibited improved stability by increasing the basicity of the pyridine ligands.

Influence of Bidentate Ligand Donor Types on the Formation and Stability in 2+1 fac-[MI(CO)3]+ (M = Re, 99mTc) Complexes

PubMed Central

Hayes, Thomas R.; Bottorff, Shalina C.; Slocumb, Winston S.; Barnes, Charles L.; Clark, Aurora E.; Benny, Paul D.

2017-01-01

In the last two decades, a number of chelate strategies have been proposed for the fac-[MI(CO)3]+ (M = Re, 99mTc) core in radiopharmaceutical applications. However, the development of new ligands/complexes with improved function and in vivo performance has been limited in recent years. Expanding on our previous studies using the 2+1 labeling strategy, a series of bidentate ligands (neutral vs. anionic) containing an aromatic amine in combination with monodentate pyridine analogs or imidazole were explored to determine the influence of the bidentate and monodentate ligands on the formation and stability of the respective complexes. The 2+1 complexes with Re and 99mTc were synthesized in two steps and characterized by standard radio/chemical methods. X-ray characterization and density functional theory analysis of the Re 2+1 complexes with the complete bidentate series with 4-dimethylaminopyridine were conducted, indicating enhanced ligand binding energies of the neutral over anionic ligands. In the 99mTc studies, anionic bidentate ligands had significantly higher formation yields of the 2+1 product, but neutral ligands appear to have increased stability in an amino acid challenge assay. Both bidentate series exhibited improved stability by increasing the basicity of the pyridine ligands. PMID:28045466

Effects of Partial Beef Fat Replacement with Gelled Emulsion on Functional and Quality Properties of Model System Meat Emulsions

PubMed Central

2016-01-01

The objective of this study was to investigate the effects of partial beef fat replacement (0, 30, 50, 100%) with gelled emulsion (GE) prepared with olive oil on functional and quality properties of model system meat emulsion (MSME). GE consisted of inulin and gelatin as gelling agent and characteristics of gelled and model system meat emulsions were investigated. GE showed good initial stability against centrifugation forces and thermal stability at different temperatures. GE addition decreased the pH with respect to increase in GE concentration. Addition of GE increased lightness and yellowness but reduced redness compared to control samples. The results of the study showed that partial replacement of beef fat with GE could be used for improving cooking yield without negative effects on water holding capacity and emulsion stability compared to C samples when replacement level is up to 50%. The presence of GE significantly affected textural behaviors of samples (p<0.05). In conclusion, our study showed that GE have promising impacts on developing healthier meat product formulations besides improving technological characteristics. PMID:28115885

Effects of Partial Beef Fat Replacement with Gelled Emulsion on Functional and Quality Properties of Model System Meat Emulsions.

PubMed

Serdaroğlu, Meltem; Nacak, Berker; Karabıyıkoğlu, Merve; Keser, Gökçen

2016-01-01

The objective of this study was to investigate the effects of partial beef fat replacement (0, 30, 50, 100%) with gelled emulsion (GE) prepared with olive oil on functional and quality properties of model system meat emulsion (MSME). GE consisted of inulin and gelatin as gelling agent and characteristics of gelled and model system meat emulsions were investigated. GE showed good initial stability against centrifugation forces and thermal stability at different temperatures. GE addition decreased the pH with respect to increase in GE concentration. Addition of GE increased lightness and yellowness but reduced redness compared to control samples. The results of the study showed that partial replacement of beef fat with GE could be used for improving cooking yield without negative effects on water holding capacity and emulsion stability compared to C samples when replacement level is up to 50%. The presence of GE significantly affected textural behaviors of samples ( p <0.05). In conclusion, our study showed that GE have promising impacts on developing healthier meat product formulations besides improving technological characteristics.

Plasma membrane aquaporins mediates vesicle stability in broccoli

PubMed Central

Martínez-Ballesta, Maria del Carmen; García-Gomez, Pablo; Yepes-Molina, Lucía; Guarnizo, Angel L.; Teruel, José A.

2018-01-01

The use of in vitro membrane vesicles is attractive because of possible applications in therapies. Here we aimed to compare the stability and functionality of plasma membrane vesicles extracted from control and salt-treated broccoli. The impact of the amount of aquaporins was related to plasma membrane osmotic water permeability and the stability of protein secondary structure. Here, we describe for first time an increase in plant aquaporins acetylation under high salinity. Higher osmotic water permeability in NaCl vesicles has been related to higher acetylation, upregulation of aquaporins, and a more stable environment to thermal denaturation. Based on our findings, we propose that aquaporins play an important role in vesicle stability. PMID:29420651

Formation of diamond nanoparticle thin films by electrophoretic deposition

NASA Astrophysics Data System (ADS)

Goto, Yosuke; Ohishi, Fujio; Tanaka, Kuniaki; Usui, Hiroaki

2016-03-01

Thin films of diamond nanoparticles were prepared by electrophoretic deposition (EPD) using 0.5 wt % dispersions in water, ethanol, and 2-propanol. The film growth rate increased with increasing voltage applied to the electrodes. However, an excessive increase in voltage caused the degradation of film morphology. The optimum voltage was 4 V with an electrode separation of 5 mm. The film growth rate was higher in organic solvents than in water. The deposited film had a smooth surface with an average surface roughness comparable to the size of primary particles of the source material. It is notable that the EPD films had a considerably higher physical stability than spin-coated and cast films. The stability was further improved by thermally annealing the films. IR analysis revealed that the diamond nanoparticles have carboxy and amino groups on their surfaces. It is considered that the stability of the EPD films originate from a chemical reaction between these functional groups.

In Search of Functional Advantages of Knots in Proteins.

PubMed

Dabrowski-Tumanski, Pawel; Stasiak, Andrzej; Sulkowska, Joanna I

2016-01-01

We analysed the structure of deeply knotted proteins representing three unrelated families of knotted proteins. We looked at the correlation between positions of knotted cores in these proteins and such local structural characteristics as the number of intra-chain contacts, structural stability and solvent accessibility. We observed that the knotted cores and especially their borders showed strong enrichment in the number of contacts. These regions showed also increased thermal stability, whereas their solvent accessibility was decreased. Interestingly, the active sites within these knotted proteins preferentially located in the regions with increased number of contacts that also have increased thermal stability and decreased solvent accessibility. Our results suggest that knotting of polypeptide chains provides a favourable environment for the active sites observed in knotted proteins. Some knotted proteins have homologues without a knot. Interestingly, these unknotted homologues form local entanglements that retain structural characteristics of the knotted cores.

Mitochondrial Dysfunctions in Bipolar Disorder: Effect of the Disease and Pharmacotherapy.

PubMed

Cikankova, Tereza; Sigitova, Ekaterina; Zverova, Martina; Fisar, Zdenek; Raboch, Jiri; Hroudova, Jana

2017-01-01

Exact pathophysiological mechanisms of bipolar disorder have not been sufficiently clarified. We review the evidence of mitochondrial dysfunctions on the relation between both disease and pharmacotherapy. Mitochondria produce the most of energy-rich molecules of adenosine triphosphate (ATP), apart from energy production they are involved in other functions: regulation of free radicals, antioxidant defenses, lipid peroxidation, calcium metabolism and participate in the intrinsic pathway of apoptosis. According to increasing evidence dysfunctions of mitochondria are associated with affective disorders, a hypothesis of impaired mitochondrial functions has been proposed in bipolar disorder pathogenesis. Mitochondrial DNA mutations and/or polymorphisms, impaired phospholipid metabolism and glycolytic shift, decrease in ATP production, increased oxidative stress and changes of intracellular calcium are concerned in mood disorders and effects of mood stabilizers. Recent studies have also provided data about the positive effects of chronic treatment by mood stabilizers on mitochondrial functions. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Complexity study on the Cournot-Bertrand mixed duopoly game model with market share preference

NASA Astrophysics Data System (ADS)

Ma, Junhai; Sun, Lijian; Hou, Shunqi; Zhan, Xueli

2018-02-01

In this paper, a Cournot-Bertrand duopoly model with market share preference is established. Assume that there is a degree of product difference between the two firms, where one firm takes the price as a decision variable and the other takes the quantity. Both firms are bounded rational, with linear cost functions and demand functions. The stability of the equilibrium points is analyzed, and the effects of some parameters (α, β, d and v1) on the model stability are studied. Basins of attraction are investigated and the evolution process is shown with the increase in the output adjustment speed. The simulation results show that instability will lead to the increase in the average utility of the firm that determines the quantity and reduce the average utility of the firm that determines price.

Functional properties of protein isolates extracted from stabilized rice bran by microwave, dry heat, and parboiling.

PubMed

Khan, Saima Hafeez; Butt, Masood Sadiq; Sharif, Mian Kamran; Sameen, Ayesha; Mumtaz, Semee; Sultan, Muhammad Tauseef

2011-03-23

Protein isolates extracted from differently stabilized rice bran were analyzed to work out the food use potential. Bulk density remained higher for isolates obtained from heat stabilized bran, the treatments were found to have positive impact on the oil absorption properties, while the water absorption was slightly impaired owing to some possible configurational changes. Surface hydrophobicity and emulsion properties were improved with bran stabilization. Isolates exhibited better foaming properties owing to the flexible nature of protein molecules, with less intensive disulfide bonding, that were slightly affected by the stabilization treatment. Nitrogen solubility index followed a curved pattern with the least value near isoelectric point that showed an increasing trend toward basic pH, and parboiled protein isolates exhibited better gelling properties among the isolates.

Metabolic Cost of Lateral Stabilization during Walking in People with Incomplete Spinal Cord Injury

PubMed Central

Matsubara, J.H.; Wu, M.; Gordon, K.E.

2015-01-01

People with incomplete spinal cord injury (iSCI) expend considerable energy to walk, which can lead to rapid fatigue and limit community ambulation. Selecting locomotor patterns that enhance lateral stability may contribute to this population’s elevated cost of transport. The goal of the current study was to quantify the metabolic energy demands of maintaining lateral stability during gait in people with iSCI. To quantify this metabolic cost, we observed ten individuals with iSCI walking with and without external lateral stabilization. We hypothesized that with external lateral stabilization, people with iSCI would adapt their gait by decreasing step width, which would correspond with a substantial decrease in cost of transport. Our findings support this hypothesis. Subjects significantly (p < 0.05) decreased step width by 22%, step width variability by 18%, and minimum lateral margin of stability by 25% when they walked with external lateral stabilization compared to unassisted walking. Metabolic cost of transport also decreased significantly (p < 0.05) by 10% with external lateral stabilization. These findings suggest that this population is capable of adapting their gait to meet changing demands placed on balance. The percent reduction in cost of transport when walking with external lateral stabilization was strongly correlated with functional impairment level as assessed by subjects’ scores on the Berg Balance Scale (R = 0.778) and Lower Extremity Motor Score (R = 0.728). These relationships suggest that as functional balance and strength decrease, the amount of metabolic energy used to maintain lateral stability during gait will increase. PMID:25670651

Stability and thermal behavior of molybdenum disulfide nanotubes: Nonequilibrium molecular dynamics simulation using REBO potential

NASA Astrophysics Data System (ADS)

Ahadi, Zohreh; Shadman Lakmehsari, Muhammad; Kumar Singh, Sandeep; Davoodi, Jamal

2017-12-01

This study is an attempt to perform equilibrium molecular dynamics and non-equilibrium molecular dynamics (NEMD) to evaluate the stability and thermal behavior of molybdenum disulfide nanotubes (MoS2NTs) by reactive empirical bond order potential. The stability of nanotubes, cohesive energy, isobaric heat capacity, and enthalpies of fusion in armchair and zigzag structures with different radii were calculated. The observed results illustrate that SWMoS2NTs, which have larger diameters, are more stable with more negative energy than the smaller ones. Moreover, it was found that the melting point is increased with an increase in the nanotube's radius. During the melting process, the structural transformation of nanotubes was investigated using a mean-square displacement and radial distribution function diagrams. Afterwards, using a NEMD simulation, the thermal conductivity of nanotubes with various diameters was calculated at a constant nanotube length. The obtained results show that the thermal conductivity coefficient increases with increasing nanotube diameters when the nanotube length is constant.

Bivariate and multivariate analyses of the influence of blood variables of patients submitted to Roux-en-Y gastric bypass on the stability of erythrocyte membrane against the chaotropic action of ethanol.

PubMed

de Arvelos, Leticia Ramos; Rocha, Vanessa Custódio Afonso; Felix, Gabriela Pereira; da Cunha, Cleine Chagas; Bernardino Neto, Morun; da Silva Garrote Filho, Mario; de Fátima Pinheiro, Conceição; Resende, Elmiro Santos; Penha-Silva, Nilson

2013-03-01

The stability of the erythrocyte membrane, which is essential for the maintenance of cell functions, occurs in a critical region of fluidity, which depends largely on its composition and the composition and characteristics of the medium. As the composition of the erythrocyte membrane is influenced by several blood variables, the stability of the erythrocyte membrane must have relations with them. The present study aimed to evaluate, by bivariate and multivariate statistical analyses, the correlations and causal relationships between hematologic and biochemical variables and the stability of the erythrocyte membrane against the chaotropic action of ethanol. The validity of this type of analysis depends on the homogeneity of the population and on the variability of the studied parameters, conditions that can be filled by patients who undergo bariatric surgery by the technique of Roux-en-Y gastric bypass since they will suffer feeding restrictions that have great impact on their blood composition. Pathway analysis revealed that an increase in hemoglobin leads to decreased stability of the cell, probably through a process mediated by an increase in mean corpuscular volume. Furthermore, an increase in the mean corpuscular hemoglobin (MCH) leads to an increase in erythrocyte membrane stability, probably because higher values of MCH are associated with smaller quantities of red blood cells and a larger contact area between the cell membrane and ethanol present in the medium.

Mechanisms of anterior-posterior stability of the knee joint under load-bearing.

PubMed

Reynolds, Ryan J; Walker, Peter S; Buza, John

2017-05-24

The anterior-posterior (AP) stability of the knee is an important aspect of functional performance. Studies have shown that the stability increases when compressive loads are applied, as indicated by reduced laxity, but the mechanism has not been fully explained. A test rig was designed which applied combinations of AP shear and compressive forces, and measured the AP displacements relative to the neutral position. Five knees were evaluated at compressive loads of 0, 250, 500, and 750N, with the knee at 15° flexion. At each load, three cycles of shear force at ±100N were applied. For the intact knee under load, the posterior tibial displacement was close to zero, due to the upward slope of the anterior medial tibial surface. The soft tissues were then resected in sequence to determine their role in AP laxity. After anterior cruciate ligament (ACL) resection, the anterior tibial displacement increased significantly even under load, highlighting its importance in stability. Meniscal resection further increased displacement but also the vertical displacement increased, implying the meniscus was providing a buffering effect. The PCL had no effect on any of the displacements under load. Plowing cartilage deformation and surface friction were negligible. This work highlighted the particular importance of the upward slope of the anterior medial tibial surface and the ACL to AP knee stability under load. The results are relevant to the design of total knees which reproduce anatomic knee stability behavior. Copyright © 2017. Published by Elsevier Ltd.

Radiation Power as Function of Current in Wall-stabilized AC Arc of Water-cooled Vortex Type with Small Caliber

NASA Astrophysics Data System (ADS)

Iwao, Toru; Naito, Yuto; Shimizu, Yuta; Yamamoto, Shinji

2016-10-01

The problem of an emergency large-scale lighting with the high-intensity discharge (HID) lamp is the lack of radiation intensity because of inappropriate energy balance. Some researchers have researched that the radiation power depended on the arc temperature increases with increasing the current. However, the heat loss and the erosion of the electrode as well as the radiation power increases with increasing the current excessively. AC current replaces alternately the cathode and the anode. Thus, it is possible to avoid the concentration of the heat transfer to the anode. Moreover, the lamp efficiency decreases with increasing the current excessively because of ultra violet rays increment. It is necessary to control the temperature distribution with controlling the current and radius. In this paper, the radiation power as a function of the current in the wall-stabilized AC arc of water-cooled vortex type with small caliber was measured. As a result, the radiation power increased with increasing the current and appropriate wall radius. The radiation of AC arc is smaller than it of DC arc. And, the erosion of electrode decreases.

Age-Related Differences in Test-Retest Reliability in Resting-State Brain Functional Connectivity

PubMed Central

Song, Jie; Desphande, Alok S.; Meier, Timothy B.; Tudorascu, Dana L.; Vergun, Svyatoslav; Nair, Veena A.; Biswal, Bharat B.; Meyerand, Mary E.; Birn, Rasmus M.; Bellec, Pierre; Prabhakaran, Vivek

2012-01-01

Resting-state functional MRI (rs-fMRI) has emerged as a powerful tool for investigating brain functional connectivity (FC). Research in recent years has focused on assessing the reliability of FC across younger subjects within and between scan-sessions. Test-retest reliability in resting-state functional connectivity (RSFC) has not yet been examined in older adults. In this study, we investigated age-related differences in reliability and stability of RSFC across scans. In addition, we examined how global signal regression (GSR) affects RSFC reliability and stability. Three separate resting-state scans from 29 younger adults (18–35 yrs) and 26 older adults (55–85 yrs) were obtained from the International Consortium for Brain Mapping (ICBM) dataset made publically available as part of the 1000 Functional Connectomes project www.nitrc.org/projects/fcon_1000. 92 regions of interest (ROIs) with 5 cubic mm radius, derived from the default, cingulo-opercular, fronto-parietal and sensorimotor networks, were previously defined based on a recent study. Mean time series were extracted from each of the 92 ROIs from each scan and three matrices of z-transformed correlation coefficients were created for each subject, which were then used for evaluation of multi-scan reliability and stability. The young group showed higher reliability of RSFC than the old group with GSR (p-value = 0.028) and without GSR (p-value <0.001). Both groups showed a high degree of multi-scan stability of RSFC and no significant differences were found between groups. By comparing the test-retest reliability of RSFC with and without GSR across scans, we found significantly higher proportion of reliable connections in both groups without GSR, but decreased stability. Our results suggest that aging is associated with reduced reliability of RSFC which itself is highly stable within-subject across scans for both groups, and that GSR reduces the overall reliability but increases the stability in both age groups and could potentially alter group differences of RSFC. PMID:23227153

Molecular Dynamics Simulations and Structural Analysis to Decipher Functional Impact of a Twenty Residue Insert in the Ternary Complex of Mus musculus TdT Isoform

PubMed Central

Mutt, Eshita; Sowdhamini, Ramanathan

2016-01-01

Insertions/deletions are common evolutionary tools employed to alter the structural and functional repertoire of protein domains. An insert situated proximal to the active site or ligand binding site frequently impacts protein function; however, the effect of distal indels on protein activity and/or stability are often not studied. In this paper, we have investigated a distal insert, which influences the function and stability of a unique DNA polymerase, called terminal deoxynucleotidyl transferase (TdT). TdT (EC:2.7.7.31) is a monomeric 58 kDa protein belonging to family X of eukaryotic DNA polymerases and known for its role in V(D)J recombination as well as in non-homologous end-joining (NHEJ) pathways. Two murine isoforms of TdT, with a length difference of twenty residues and having different biochemical properties, have been studied. All-atom molecular dynamics simulations at different temperatures and interaction network analyses were performed on the short and long-length isoforms. We observed conformational changes in the regions distal to the insert position (thumb subdomain) in the longer isoform, which indirectly affects the activity and stability of the enzyme through a mediating loop (Loop1). A structural rationale could be provided to explain the reduced polymerization rate as well as increased thermosensitivity of the longer isoform caused by peripherally located length variations within a DNA polymerase. These observations increase our understanding of the roles of length variants in introducing functional diversity in protein families in general. PMID:27311013

Dynamic stability requirements during gait and standing exergames on the wii fit® system in the elderly

PubMed Central

2012-01-01

Background In rehabilitation, training intensity is usually adapted to optimize the trained system to attain better performance (overload principle). However, in balance rehabilitation, the level of intensity required during training exercises to optimize improvement in balance has rarely been studied, probably due to the difficulty in quantifying the stability level during these exercises. The goal of the present study was to test whether the stabilizing/destabilizing forces model could be used to analyze how stability is challenged during several exergames, that are more and more used in balance rehabilitation, and a dynamic functional task, such as gait. Methods Seven healthy older adults were evaluated with three-dimensional motion analysis during gait at natural and fast speed, and during three balance exergames (50/50 Challenge, Ski Slalom and Soccer). Mean and extreme values for stabilizing force, destabilizing force and the ratio of the two forces (stability index) were computed from kinematic and kinetic data to determine the mean and least level of dynamic, postural and overall balance stability, respectively. Results Mean postural stability was lower (lower mean destabilizing force) during the 50/50 Challenge game than during all the other tasks, but peak postural instability moments were less challenging during this game than during any of the other tasks, as shown by the minimum destabilizing force values. Dynamic stability was progressively more challenged (higher mean and maximum stabilizing force) from the 50/50 Challenge to the Soccer and Slalom games, to the natural gait speed task and to the fast gait speed task, increasing the overall stability difficulty (mean and minimum stability index) in the same manner. Conclusions The stabilizing/destabilizing forces model can be used to rate the level of balance requirements during different tasks such as gait or exergames. The results of our study showed that postural stability did not differ much between the evaluated tasks (except for the 50/50 Challenge), compared to dynamic stability, which was significantly less challenged during the games than during the functional tasks. Games with greater centre of mass displacements and changes in the base of support are likely to stimulate balance control enough to see improvements in balance during dynamic functional tasks, and could be tested in pathological populations with the approach used here. PMID:22607025

Bloom syndrome ortholog HIM-6 maintains genomic stability in C. elegans.

PubMed

Grabowski, Melissa M; Svrzikapa, Nenad; Tissenbaum, Heidi A

2005-12-01

Bloom syndrome is caused by mutation of the Bloom helicase (BLM), a member of the RecQ helicase family. Loss of BLM function results in genomic instability that causes a high incidence of cancer. It has been demonstrated that BLM is important for maintaining genomic stability by playing a role in DNA recombination and repair; however, the exact function of BLM is not clearly understood. To determine the mechanism by which BLM controls genomic stability in vivo, we examined the phenotypes caused by mutation of the C. elegans BLM helicase ortholog, HIM-6. We find that the loss of HIM-6 leads to genomic instability as evidenced by an increased number of genomic insertions and deletions, which results in visible random mutant phenotypes. In addition to the mutator phenotype, him-6 mutants have a low brood size, a high incidence of males, a shortened life span, and an increased amount of germ line apoptosis. Upon exposure to high temperature, him-6 mutants that are serially passed become sterile demonstrating a mortal germ line phenotype. Our data suggest a model in which loss of HIM-6 results in genomic instability due to an increased number of DNA lesions, which either cannot be repaired and/or are introduced by low fidelity recombination events. The increased level of genomic instability that leads to him-6(ok412) mutants having a shortened life span.

CO binding improves the structural, functional, physical and anti-oxidation properties of the PEGylated hemoglobin.

PubMed

Wang, Qingqing; Hu, Tao; Sun, Lijing; Ji, Shaoyang; Zhao, Dawei; Liu, Jiaxin; Ma, Guanghui; Su, Zhiguo

2015-02-01

PEGylated hemoglobin (Hb) is a promising oxygen therapeutic agent for clinical application. However, it suffered from structural perturbation, functional instability and methemoglobin (metHb) formation. To improve the structural, functional, physical and anti-oxidation properties of the PEGylated Hb. PEGylation of Hb with CO binding (HbCO) was conducted using maleimide and acylation chemistry, respectively. Physical and chemical parameters were measured for Hb samples. The circular dichroism spectra, dynamic light scattering and analytical ultracentrifugation were used to investigate the structure and conformation of PEGylated HbCO. CO binding can inhibit the autoxidation of the PEGylated Hb, structurally stabilize its tetramer and improve its thermal and pH stability. Importantly, the circular dichroism spectra showed that CO binding can decrease the structural perturbation of Hb induced by PEGylation. The PEGylated HbCO with CO release showed slightly higher oxygen-delivery capacity than the PEGylated Hb. The PEGylated HbCO did not show metHb formation after 30-day storage at 4°C. CO binding structurally stabilized the PEGylated Hb, abolished its metHb formation, and significantly increased its physical stability. In particular, it also avoided the perturbation of PEG chains on the heme microenvironment. The functional property of the PEGylated HbCO can be maintained during its long-term storage, which is of great significance for field transfusion.

Temporal variation in development of ecosystem services from oyster reef restoration

USGS Publications Warehouse

LaPeyre, Megan K.; Humphries, Austin T.; Casas, Sandra M.; La Peyre, Jerome F.

2014-01-01

Restoration ecology relies heavily on ecosystem development theories that generally assume development of fully functioning natural systems over time, but often fail to identify the time-frame required for provision of desired functions, or acknowledge different pathways of functional development. In estuaries, a decline of overall habitat quality and functioning has led to significant efforts to restore critical ecosystem services, recently through the creation and restoration of oyster reefs. Oyster reef restoration generally occurs with goals of (1) increasing water quality via filtration through sustainable oyster recruitment, (2) stabilizing shorelines, and (3) creating and enhancing critical estuarine habitat for fish and invertebrates. We restored over 260 m2 of oyster reef habitat in coastal Louisiana and followed the development and provision of these ecosystem services from 2009 through 2012. Oysters recruited to reefs immediately, with densities of oysters greater than 75 mm exceeding 80 ind m−2 after 3 years, and provision of filtration rates of 1002 ± 187 L h−1 m−2; shoreline stabilization effects of the created reefs were minimal over the three years of monitoring, with some evidence of positive shoreline stabilization during higher wind/energy events only; increased nekton abundance of resident, but not larger transient fish was immediately measurable at the reefs, however, this failed to increase through time. Our results provide critical insights into the development trajectories of ecosystem services provided by restored oyster reefs, as well as the mechanisms mediating these changes. This is critical both ecologically to understand how and where a reef thrives, and for policy and management to guide decision-making related to oyster reef restoration and the crediting and accounting of ecosystem services.

Stability of rhombohedral phases in vanadium at high-pressure and high-temperature: first-principles investigations

NASA Astrophysics Data System (ADS)

Wang, Yi X.; Wu, Q.; Chen, Xiang R.; Geng, Hua Y.

2016-09-01

The pressure-induced transition of vanadium from BCC to rhombohedral structures is unique and intriguing among transition metals. In this work, the stability of these phases is revisited by using density functional theory. At finite temperatures, a novel transition of rhombohedral phases back to BCC phase induced by thermal electrons is discovered. This reentrant transition is found not driven by phonons, instead it is the electronic entropy that stabilizes the latter phase, which is totally out of expectation. Parallel to this transition, we find a peculiar and strong increase of the shear modulus C44 with increasing temperature. It is counter-intuitive in the sense that it suggests an unusual harding mechanism of vanadium by temperature. With these stability analyses, the high-pressure and finite-temperature phase diagram of vanadium is proposed. Furthermore, the dependence of the stability of RH phases on the Fermi energy and chemical environment is investigated. The results demonstrate that the position of the Fermi level has a significant impact on the phase stability, and follows the band-filling argument. Besides the Fermi surface nesting, we find that the localization/delocalization of the d orbitals also contributes to the instability of rhombohedral distortions in vanadium.

Insights into the redox components of dissolved organic matters during stabilization process.

PubMed

Yuan, Ying; Xi, Bei-Dou; He, Xiao-Song; Ma, Yan; Zhang, Hui; Li, Dan; Zhao, Xin-Yu

2018-05-01

The changes of dissolved organic matter (DOM) components during stabilization process play significant effects on its redox properties but are little reported. Composting is a stabilization process of DOM, during which both the components and electron transfer capacities (ETCs) of DOM change. The redox components within compost-derived DOM during the stabilization process are investigated in this study. The results show that compost-derived DOM contained protein-like, fulvic-like, and humic-like components. The protein-like component decreases during composting, whereas the fulvic- and humic-like components increase during the process. The electron-donating capacity (EDC), electron-accepting capacity (EAC), and ETC of compost-derived DOM all increase during composting but their correlations with the components presented significant difference. The humic-like components were the main functional component responsible for both EDC and ETC, whereas the protein- and fluvic-like components show negative effects with the EAC, EDC, and ETC, suggesting that the components within DOM have specific redox properties during the stabilization process. These findings are very meaningful for better understanding the geochemical behaviors of DOM in the environment.

Amino-Functionalized Ceramic Capillary Membranes for Controlled Virus Retention.

PubMed

Bartels, Julia; Souza, Marina N; Schaper, Amelie; Árki, Pál; Kroll, Stephen; Rezwan, Kurosch

2016-02-16

A straightforward chemical functionalization strategy using aminosilanes for high-flux yttria-stabilized zirconia capillary membranes is presented (macroporous, d50 = 144 nm, open porosity =49%, membrane flux ∼150 L/(m(2)hbar)). Three different aminosilanes with one, two or three amino groups per silane molecule, namely 3-aminopropyltriethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AE-APTES) and N-(3-trimethoxysilylpropyl)diethylenetriamine (TPDA), are used to generate the amino-functionalized membranes. With a higher number of amino groups per silane molecule increased loading capacities between 0.44 and 1.01 accessible amino groups/nm(2) membrane are achieved. Streaming potential measurements confirm that the zeta-potential of the membrane surface is converted from negative (non-functionalized) to positive (amino-functionalized). By operation in dead-end filtration mode using the model virus MS2 (diameter = 25 nm, IEP = 3.9) the virus retention capacity of the amino-functionalized membranes is significantly increased and log reduction values (LRVs) of up to 9.6 ± 0.3 (TPDA) are obtained whereas a LRV < 0.3 is provided by the non-functionalized membranes. Long-term dead-end filtration experiments for 1 week reveal a high stability of immobilized aminosilanes (TPDA), being robust against leaching. By iterative backflushing with desorption buffer MS2-loaded membranes are successfully regenerated being reusable for a new filtration cycle. The presented functionalization platform is highly promising for controlled virus retention.

Monitoring bisphosphonate surface functionalization and acid stability of hierarchically porous titanium zirconium oxides.

PubMed

Ide, Andreas; Drisko, Glenna L; Scales, Nicholas; Luca, Vittorio; Schiesser, Carl H; Caruso, Rachel A

2011-11-01

To take advantage of the full potential of functionalized transition metal oxides, a well-understood nonsilane based grafting technique is required. The functionalization of mixed titanium zirconium oxides was studied in detail using a bisphosphonic acid, featuring two phosphonic acid groups with high surface affinity. The bisphosphonic acid employed was coupled to a UV active benzamide moiety in order to track the progress of the surface functionalization in situ. Using different material compositions, altering the pH environment, and looking at various annealing conditions, key features of the functionalization process were identified that consequently will allow for intelligent material design. Loading with bisphosphonic acid was highest on supports calcined at 650 °C compared to lower calcination temperatures: A maximum capacity of 0.13 mmol g(-1) was obtained and the adsorption process could be modeled with a pseudo-second-order rate relationship. Heating at 650 °C resulted in a phase transition of the mixed binary oxide to a ternary oxide, titanium zirconium oxide in the srilankite phase. This phase transition was crucial in order to achieve high loading of the bisphosphonic acid and enhanced chemical stability in highly acidic solutions. Due to the inert nature of phosphorus-oxygen-metal bonds, materials functionalized by bisphosphonic acids showed increased chemical stability compared to their nonfunctionalized counterparts in harshly acidic solutions. Leaching studies showed that the acid stability of the functionalized material was improved with a partially crystalline srilankite phase. The materials were characterized using nitrogen sorption, X-ray powder diffraction, and UV-vis spectroscopy; X-ray photoelectron spectroscopy was used to study surface coverage with the bisphosphonic acid molecules.

Enhanced Luminescent Stability through Particle Interactions in Silicon Nanocrystal Aggregates

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

Miller, Joseph B.; Dandu, Naveen; Velizhanin, Kirill A.

2015-10-27

Close-packed assemblies of ligand-passivated colloidal nanocrystals can exhibit enhanced photoluminescent stability, but the origin of this effect is unclear. Here, we use experiment, simulation, and ab initio computation to examine the influence of interparticle interactions on the photoluminescent stability of silicon nanocrystal aggregates. The time-dependent photoluminescence emitted by structures ranging in size from a single quantum dot to agglomerates of more than a thousand is compared with Monte Carlo simulations of noninteracting ensembles using measured single-particle blinking data as input. In contrast to the behavior typically exhibited by the metal chalcogenides, the measured photoluminescent stability shows an enhancement with respectmore » to the noninteracting scenario with increasing aggregate size. We model this behavior using time-dependent density functional theory calculations of energy transfer between neighboring nanocrystals as a function of nanocrystal size, separation, and the presence of charge and/or surface-passivation defects. Our results suggest that rapid exciton transfer from “bright” nanocrystals to surface trap states in nearest-neighbors can efficiently fill such traps and enhance the stability of emission by promoting the radiative recombination of slowly diffusing excited electrons.« less

Inviscid linear stability analysis of two vertical columns of different densities in a gravitational acceleration field

DOE PAGES

Prathama, Aditya Heru; Pantano, Carlos

2017-08-09

Here, we study the inviscid linear stability of a vertical interface separating two fluids of different densities and subject to a gravitational acceleration field parallel to the interface. In this arrangement, the two free streams are constantly accelerated, which means that the linear stability analysis is not amenable to Fourier or Laplace solution in time. Instead, we derive the equations analytically by the initial-value problem method and express the solution in terms of the well-known parabolic cylinder function. The results, which can be classified as an accelerating Kelvin–Helmholtz configuration, show that even in the presence of surface tension, the interfacemore » is unconditionally unstable at all wavemodes. This is a consequence of the ever increasing momentum of the free streams, as gravity accelerates them indefinitely. The instability can be shown to grow as the exponential of a quadratic function of time.« less

Towards Extending Solar Cell Lifetimes: Addition of a Fluorous Cation to Triple Cation-Based Perovskite Films.

PubMed

Salado, Manuel; Fernández, M Asunción; Holgado, Juan P; Kazim, Samrana; Nazeeruddin, Mohammad Khaja; Dyson, Paul J; Ahmad, Shahzada

2017-10-09

Organohalide perovskites have emerged as highly promising replacements for thin-film solar cells. However, their poor stability under ambient conditions remains problematic, hindering commercial exploitation. The addition of a fluorous-functionalized imidazolium cation during the preparation of a highly stable cesium-based mixed perovskite material Cs 0.05 (MA 0.15 FA 0.85 ) 0.95 Pb(I 0.85 Br 0.15 ) 3 (MA=methylammonium; FA=formamidinium) has been shown to influence its stability. The resulting materials, which vary according to the amount of the fluorous-functionalized imidazolium cation present during fabrication, display a prolonged tolerance to atmospheric humidity (>100 days) along with power conversion efficiencies exceeding 16 %. This work provides a general route that can be implemented in a variety of perovskites and highlights a promising way to increase perovskite solar cell stability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Correlation of structural stability with functional remodeling of high-density lipoproteins: the importance of being disordered.

PubMed

Guha, Madhumita; Gao, Xuan; Jayaraman, Shobini; Gursky, Olga

2008-11-04

High-density lipoproteins (HDLs) are protein-lipid assemblies that remove excess cell cholesterol and prevent atherosclerosis. HDLs are stabilized by kinetic barriers that decelerate protein dissociation and lipoprotein fusion. We propose that similar barriers modulate metabolic remodeling of plasma HDLs; hence, changes in particle composition that destabilize HDLs and accelerate their denaturation may accelerate their metabolic remodeling. To test this notion, we correlate existing reports on HDL-mediated cell cholesterol efflux and esterification, which are obligatory early steps in cholesterol removal, with our kinetic studies of HDL stability. The results support our hypothesis and show that factors accelerating cholesterol efflux and esterification in model discoidal lipoproteins (including reduced protein size, reduced fatty acyl chain length, and/or increased level of cis unsaturation) destabilize lipoproteins and accelerate their fusion and apolipoprotein dissociation. Oxidation studies of plasma spherical HDLs show a similar trend: mild oxidation by Cu(2+) or OCl(-) accelerates cell cholesterol efflux, protein dissociation, and HDL fusion, while extensive oxidation inhibits these reactions. Consequently, moderate destabilization may be beneficial for HDL functions by facilitating insertion of cholesterol and lipophilic enzymes, promoting dissociation of lipid-poor apolipoproteins, which are primary acceptors of cell cholesterol, and thereby accelerating HDL metabolism. Therefore, HDL stability must be delicately balanced to maintain the structural integrity of the lipoprotein assembly and ensure structural specificity necessary for interactions of HDL with its metabolic partners, while facilitating rapid HDL remodeling and turnover at key junctures of cholesterol transport. The inverse correlation between HDL stability and remodeling illustrates the functional importance of structural disorder in macromolecular assemblies stabilized by kinetic barriers.

Successful Stabilization of Graphene Oxide in Electrolyte Solutions: Enhancement of Bio-functionalization and Cellular Uptake

PubMed Central

Hong, Bong Jin; Compton, Owen C.; An, Zhi; Eryzazici, Ibrahim; Nguyen, SonBinh T.

2013-01-01

Aqueous dispersions of graphene oxide are inherently unstable in the presence of electrolytes, which screen the electrostatic surface charge on these nanosheets and induce irreversible aggregation. Two complementary strategies, utilizing either electrostatic or steric stabilization, have been developed to enhance the stability of graphene oxide in electrolyte solutions, allowing it to stay dispersed in cell culture media and serum. The electrostatic stabilization approach entails further oxidation of graphene oxide to low C/O ratio (~1.03) and increases ionic tolerance of these nanosheets. The steric stabilization technique employs an amphiphilic block copolymer that serves as a non-covalently bound surfactant to minimize the aggregate-induced nanosheets-nanosheet interactions. Both strategies can stabilize graphene oxide nanosheets with large dimensions (>300 nm) in biological media, allowing for an enhancement of >250% in the bioconjugation efficiency of streptavidin in comparison to untreated nanosheets. Notably, both strategies allow the stabilized nanosheets to be readily uptake by cells, demonstrating their excellent performance as potential drug delivery vehicles. PMID:22017285

Material Innovation in Advancing Organometal Halide Perovskite Functionality.

PubMed

Zheng, Fan; Saldana-Greco, Diomedes; Liu, Shi; Rappe, Andrew M

2015-12-03

Organometal halide perovskites (OMHPs) have garnered much attention recently for their unprecedented rate of increasing power conversion efficiency (PCE), positioning them as a promising basis for the next-generation photovoltaic devices. However, the gap between the rapid increasing PCE and the incomplete understanding of the structure-property-performance relationship prevents the realization of the true potential of OMHPs. This Perspective aims to provide a concise overview of the current status of OMHP research, highlighting the unique properties of OMHPs that are critical for solar applications but still not adequately explained. Stability and performance challenges of OMHP solar cells are discussed, calling upon combined experimental and theoretical efforts to address these challenges for pioneering commercialization of OMHP solar cells. Various material innovation strategies for improving the performance and stability of OMHPs are surveyed, showing that the OMHP architecture can serve as a promising and robust platform for the design and optimization of materials with desired functionalities.

Density-functional theory computer simulations of CZTS0.25Se0.75 alloy phase diagrams

NASA Astrophysics Data System (ADS)

Chagarov, E.; Sardashti, K.; Haight, R.; Mitzi, D. B.; Kummel, A. C.

2016-08-01

Density-functional theory simulations of CZTS, CZTSe, and CZTS0.25Se0.75 photovoltaic compounds have been performed to investigate the stability of the CZTS0.25Se0.75 alloy vs. decomposition into CZTS, CZTSe, and other secondary compounds. The Gibbs energy for vibrational contributions was estimated by calculating phonon spectra and thermodynamic properties at finite temperatures. It was demonstrated that the CZTS0.25Se0.75 alloy is stabilized not by enthalpy of formation but primarily by the mixing contributions to the Gibbs energy. The Gibbs energy gains/losses for several decomposition reactions were calculated as a function of temperature with/without intermixing and vibration contributions to the Gibbs energy. A set of phase diagrams was built in the multidimensional space of chemical potentials at 300 K and 900 K temperatures to demonstrate alloy stability and boundary compounds at various chemical conditions. It demonstrated for CZTS0.25Se0.75 that the chemical potentials for stability differ between typical processing temperature (˜900 K) and operating temperature (300 K). This implies that as cooling progresses, the flux/concentration of S should be increased in MBE growth to maintain the CZTS0.25Se0.75 in a thermodynamically stable state to minimize phase decomposition.

Improvement of the Thermal and Optical Performances of Protective Polydimethylsiloxane Space Coatings with Cellulose Nanocrystal Additives.

PubMed

Planes, Mikael; Brand, Jérémie; Lewandowski, Simon; Remaury, Stéphanie; Solé, Stéphane; Le Coz, Cédric; Carlotti, Stéphane; Sèbe, Gilles

2016-10-07

This work investigates the possibility of using cellulose nanocrystals (CNCs) as biobased nanoadditives in protective polydimethylsiloxane (PDMS) space coatings, to improve the thermal and optical performances of the material. CNCs produced from wood pulp were functionalized in different conditions with the objective to improve their dispersibility in the PDMS matrix, increase their thermal stability and provide photoactive functions. Polysiloxane, cinnamate, chloroacetate and trifluoroacetate moieties were accordingly anchored at the CNCs surface by silylation, using two different approaches, or acylation with different functional vinyl esters. The modified CNCs were thoroughly characterized by FT-IR spectroscopy, solid-state NMR spectroscopy and thermogravimetric analysis, before being incorporated into a PDMS space coating formulation in low concentration (0.5 to 4 wt %). The cross-linked PDMS films were subsequently investigated with regards to their mechanical behavior, thermal stability and optical properties after photoaging. Results revealed that the CNC additives could significantly improve the thermal stability of the PDMS coating, up to 140 °C, depending on the treatment and CNC concentration, without affecting the mechanical properties and transparency of the material. In addition, the PDMS films loaded with as low as 1 wt % halogenated nanoparticles, exhibited an improved UV-stability after irradiation in geostationary conditions.

Novel functional Renilla luciferase mutant provides long-term serum stability and high luminescence activity.

PubMed

Song, Woo Chul; Sung, Hye-Jin; Park, Kyung Soo; Choi, Jeong-Woo; Cho, Je-Yeol; Um, Soong Ho

2013-10-01

Fluorescent and luminescent chemical probes are essential in recent medical diagnostics. However, the use of these probes in vivo has raised concerns due to their low sensitivity, background signal interference, and non-biocompatibility. Therefore, biological chromophores have received much attention as new alternatives. In particular, luciferase, a class of oxidative enzyme with bioluminescence, has emerged as a promising fluorophore due to its improved biocompatibility. However, the enzyme usually possesses weaker luminescence and stability relative to its chemically-based competitors. Here, we report a novel functional mutant luciferase with both enhanced luminescence and long-term serum stability. For the preparation of the modified Renilla luciferase, a new bacterial subcloning design was established. The luciferase coding DNA sequence was redesigned so that mutant luciferase could be easily expressed in an Escherichia coli system. The mutant Renilla luciferase, which we called "m-Rluc," demonstrated characteristic enzymatic functions and showed a 5.6-fold increase in luminescence activity. In addition, the enzyme's physiological stability remained >80% for more than 5days, in contrast to conventional luciferase, termed "hrluc," which disappeared within a few hours. We suggest that this novel biological luciferase probe may be a great tool for both in vitro and in vivo medical diagnostics. Copyright © 2013 Elsevier Inc. All rights reserved.

Foams prepared from whey protein isolate and egg white protein: 2. Changes associated with angel food cake functionality.

PubMed

Berry, Tristan K; Yang, Xin; Foegeding, E Allen

2009-06-01

The effects of sucrose on the physical properties and thermal stability of foams prepared from 10% (w/v) protein solutions of whey protein isolate (WPI), egg white protein (EWP), and their combinations (WPI/EWP) were investigated in wet foams and angel food cakes. Incorporation of 12.8 (w/v) sucrose increased EWP foam stability (drainage 1/2 life) but had little effect on the stability of WPI and WPI/EWP foams. Increased stability was not due to viscosity alone. Sucrose increased interfacial elasticity (E ') of EWP and decreased E' of WPI and WPI/EWP combinations, suggesting that altered interfacial properties increased stability in EWP foams. Although 25% WPI/75% EWP cakes had similar volumes as EWP cakes, cakes containing WPI had larger air cells. Changes during heating showed that EWP foams had network formation starting at 45 degrees C, which was not observed in WPI and WPI/EWP foams. Moreover, in batters, which are foams with additional sugar and flour, a stable foam network was observed from 25 to 85 degrees C for batters made from EWP foams. Batters containing WPI or WPI/EWP mixtures showed signs of destabilization starting at 25 degrees C. These results show that sucrose greatly improved the stability of wet EWP foams and that EWP foams form network structures that remain stable during heating. In contrast, sucrose had minimal effects on stability of WPI and WPI/EWP wet foams, and batters containing these foams showed destabilization prior to heating. Therefore, destabilization processes occurring in the wet foams and during baking account for differences in angel food cake quality.

Phytoplankton Diversity Effects on Community Biomass and Stability along Nutrient Gradients in a Eutrophic Lake.

PubMed

Tian, Wang; Zhang, Huayong; Zhao, Lei; Zhang, Feifan; Huang, Hai

2017-01-20

The relationship between biodiversity and ecosystem functioning is a central issue in ecology, but how this relationship is affected by nutrient stress is still unknown. In this study, we analyzed the phytoplankton diversity effects on community biomass and stability along nutrient gradients in an artificial eutrophic lake. Four nutrient gradients, varying from slightly eutrophic to highly eutrophic states, were designed by adjusting the amount of polluted water that flowed into the lake. Mean phytoplankton biomass, species richness, and Shannon diversity index all showed significant differences among the four nutrient gradients. Phytoplankton community biomass was correlated with diversity (both species richness and Shannon diversity index), varying from positive to negative along the nutrient gradients. The influence of phytoplankton species richness on resource use efficiency (RUE) also changed from positive to negative along the nutrient gradients. However, the influence of phytoplankton Shannon diversity on RUE was not significant. Both phytoplankton species richness and Shannon diversity had a negative influence on community turnover (measured as community dissimilarity), i.e., a positive diversity-stability relationship. Furthermore, phytoplankton spatial stability decreased along the nutrient gradients in the lake. With increasing nutrient concentrations, the variability (standard deviation) of phytoplankton community biomass increased more rapidly than the average total biomass. Results in this study will be helpful in understanding the phytoplankton diversity effects on ecosystem functioning and how these effects are influenced by nutrient conditions in aquatic ecosystems.

Hierarchical functional organization of formal biological systems: a dynamical approach. II. The concept of non-symmetry leads to a criterion of evolution deduced from an optimum principle of the (O-FBS) sub-system.

PubMed

Chauvet, G A

1993-03-29

In paper I a theory of functional organization in terms of functional interactions was proposed for a formal biological system (FBS). A functional interaction was defined as the product emitted by a structural unit, i.e. an assembly of molecules, cells, tissues or organs, which acts on another. We have shown that a self-association hypothesis could be an explanation for the source of these functional interactions because it is consistent with increased stability of the system after association. The construction of the set of interactions provides the topology of the biological system, called (O-FBS), in contrast to the (D-FBS) which describes the dynamics of the processes associated with the functional interactions. In this paper, an optimum principle is established, due to the non-symmetry of functional interactions, which could explain the stability of an FBS, and a criterion of evolution for the hierarchical topological organization of a FBS during development is deduced from that principle. The combinatorics of the (O-FBS) leads to the topological stability of the related graph. It is shown that this problem can be expressed as the re-distribution of sources and sinks, when one of them is suppressed, given the constraint of the invariance of the physiological function. Such an optimum principle could be called a 'principle of increase in functional order by hierarchy'. The first step is the formulation of a 'potential' for the functional organization, which describes the ability of the system to combine functional interactions, such that the principle of vital coherence (paper I) is satisfied. This function measures the number of potential functional interactions. The second step is to discover the maximum of this function. Biological systems in such a state of maximum organization are shown to satisfy particular dynamics, which can be experimentally verified: either the number of sinks decreases, or this number increases, in a monotonic way. The class of systems considered here is assumed to satisfy such an extremum hypothesis. The third step is a study of the variation of the degree of organization (paper I), i.e. the number of structural units when the biological system is growing. We establish an optimum principle for a new function called 'orgatropy'. By adding a criterion of specialization to the system we show the emergence of a level of organization with a re-organization of the system.(ABSTRACT TRUNCATED AT 400 WORDS)

Urban ecosystem services: tree diversity and stability of tropospheric ozone removal.

PubMed

Manes, Fausto; Incerti, Guido; Salvatori, Elisabetta; Vitale, Marcello; Ricotta, Carlo; Costanza, Robert

2012-01-01

Urban forests provide important ecosystem services, such as urban air quality improvement by removing pollutants. While robust evidence exists that plant physiology, abundance, and distribution within cities are basic parameters affecting the magnitude and efficiency of air pollution removal, little is known about effects of plant diversity on the stability of this ecosystem service. Here, by means of a spatial analysis integrating system dynamic modeling and geostatistics, we assessed the effects of tree diversity on the removal of tropospheric ozone (O3) in Rome, Italy, in two years (2003 and 2004) that were very different for climatic conditions and ozone levels. Different tree functional groups showed complementary uptake patterns, related to tree physiology and phenology, maintaining a stable community function across different climatic conditions. Our results, although depending on the city-specific conditions of the studied area, suggest a higher function stability at increasing diversity levels in urban ecosystems. In Rome, such ecosystem services, based on published unitary costs of externalities and of mortality associated with O3, can be prudently valued to roughly US$2 and $3 million/year, respectively.

Structure-Activity Relationship of the Antimalarial Ozonide Artefenomel (OZ439).

PubMed

Dong, Yuxiang; Wang, Xiaofang; Kamaraj, Sriraghavan; Bulbule, Vivek J; Chiu, Francis C K; Chollet, Jacques; Dhanasekaran, Manickam; Hein, Christopher D; Papastogiannidis, Petros; Morizzi, Julia; Shackleford, David M; Barker, Helena; Ryan, Eileen; Scheurer, Christian; Tang, Yuanqing; Zhao, Qingjie; Zhou, Lin; White, Karen L; Urwyler, Heinrich; Charman, William N; Matile, Hugues; Wittlin, Sergio; Charman, Susan A; Vennerstrom, Jonathan L

2017-04-13

Building on insights gained from the discovery of the antimalarial ozonide arterolane (OZ277), we now describe the structure-activity relationship (SAR) of the antimalarial ozonide artefenomel (OZ439). Primary and secondary amino ozonides had higher metabolic stabilities than tertiary amino ozonides, consistent with their higher pK a and lower log D 7.4 values. For primary amino ozonides, addition of polar functional groups decreased in vivo antimalarial efficacy. For secondary amino ozonides, additional functional groups had variable effects on metabolic stability and efficacy, but the most effective members of this series also had the highest log D 7.4 values. For tertiary amino ozonides, addition of polar functional groups with H-bond donors increased metabolic stability but decreased in vivo antimalarial efficacy. Primary and tertiary amino ozonides with cycloalkyl and heterocycle substructures were superior to their acyclic counterparts. The high curative efficacy of these ozonides was most often associated with high and prolonged plasma exposure, but exposure on its own did not explain the presence or absence of either curative efficacy or in vivo toxicity.

Enhanced stability of a chimeric hepatitis B core antigen virus-like-particle (HBcAg-VLP) by a C-terminal linker-hexahistidine-peptide.

PubMed

Schumacher, Jens; Bacic, Tijana; Staritzbichler, René; Daneschdar, Matin; Klamp, Thorsten; Arnold, Philipp; Jägle, Sabrina; Türeci, Özlem; Markl, Jürgen; Sahin, Ugur

2018-04-13

Virus-like-particles (VLPs) are attractive nanoparticulate scaffolds for broad applications in material/biological sciences and medicine. Prior their functionalization, specific adaptations have to be carried out. These adjustments frequently lead to disordered particles, but the particle integrity is an essential factor for the VLP suitability. Therefore, major requirements for particle stabilization exist. The objective of this study was to evaluate novel stabilizing elements for functionalized chimeric hepatitis B virus core antigen virus-like particles (HBcAg-VLP), with beneficial characteristics for vaccine development, imaging or delivery. The effects of a carboxy-terminal polyhistidine-peptide and an intradimer disulfide-bridge on the stability of preclinically approved chimeric HBcAg-VLPs were assessed. We purified recombinant chimeric HBcAg-VLPs bearing different modified C-termini and compared their physical and chemical particle stability by quantitative protein-biochemical and biophysical techniques. We observed lower chemical resistance of T = 3- compared to T = 4-VLP (triangulation number) capsids and profound impairment of accessibility of hexahistidine-peptides in assembled VLPs. Histidines attached to the C-terminus were associated with superior mechanical and/or chemical particle stability depending on the number of histidine moieties. A molecular modeling approach based on cryo-electron microscopy and biolayer interferometry revealed the underlying structural mechanism for the strengthening of the integrity of VLPs. Interactions triggering capsid stabilization occur on a highly conserved residue on the basis of HBcAg-monomers as well as on hexahistidine-peptides of adjacent monomers. This new stabilization mechanism appears to mimic an evolutionary conserved stabilization concept for hepadnavirus core proteins. These findings establish the genetically simply transferable C-terminal polyhistidine-peptide as a general stabilizing element for chimeric HBcAg-VLPs to increase their suitability.

The differential role of motor cortex in the stretch reflex modulation induced by changes in environmental mechanics and verbal instruction

PubMed Central

Shemmell, Jonathan; An, Je Hi; Perreault, Eric J.

2009-01-01

The motor cortex assumes an increasingly important role in higher mammals relative to that in lower mammals. This is true to such an extent that the human motor cortex is deeply involved in reflex regulation and it is common to speak of “transcortical reflex loops”. Such loops appear to add flexibility to the human stretch reflex, once considered to be immutable, allowing it to adapt across a range of functional tasks. However, the purpose of this adaptation remains unclear. A common proposal is that stretch reflexes contribute to the regulation of limb stability; increased reflex sensitivity during tasks performed in unstable environments supports this hypothesis. Alternatively, prior to movement onset, stretch reflexes can assist an imposed stretch, opposite to what would be expected from a stabilizing response. Here we show that stretch reflex modulation in tasks that require changes in limb stability is mediated by motor cortical pathways, and that these differ from pathways contributing to reflex modulation that depends on how the subject is instructed to react to an imposed perturbation. By timing muscle stretches such that the modulated portion of the reflex occurred within a cortical silent period induced by transcranial magnetic stimulation, we abolished the increase in reflex sensitivity observed when individuals stabilized arm posture within a compliant environment. Conversely, reflex modulation caused by altered task instruction was unaffected by cortical silence. These results demonstrate that task-dependent changes in reflex function can be mediated through multiple neural pathways and that these pathways have task specific roles. PMID:19846713

The differential role of motor cortex in stretch reflex modulation induced by changes in environmental mechanics and verbal instruction.

PubMed

Shemmell, Jonathan; An, Je Hi; Perreault, Eric J

2009-10-21

The motor cortex assumes an increasingly important role in higher mammals relative to that in lower mammals. This is true to such an extent that the human motor cortex is deeply involved in reflex regulation and it is common to speak of "transcortical reflex loops." Such loops appear to add flexibility to the human stretch reflex, once considered to be immutable, allowing it to adapt across a range of functional tasks. However, the purpose of this adaptation remains unclear. A common proposal is that stretch reflexes contribute to the regulation of limb stability; increased reflex sensitivity during tasks performed in unstable environments supports this hypothesis. Alternatively, before movement onset, stretch reflexes can assist an imposed stretch, opposite to what would be expected from a stabilizing response. Here we show that stretch reflex modulation in tasks that require changes in limb stability is mediated by motor cortical pathways, and that these differ from pathways contributing to reflex modulation that depend on how the subject is instructed to react to an imposed perturbation. By timing muscle stretches such that the modulated portion of the reflex occurred within a cortical silent period induced by transcranial magnetic stimulation, we abolished the increase in reflex sensitivity observed when individuals stabilized arm posture within a compliant environment. Conversely, reflex modulation caused by altered task instruction was unaffected by cortical silence. These results demonstrate that task-dependent changes in reflex function can be mediated through multiple neural pathways and that these pathways have task-specific roles.

Long-term efficiency of soil stabilization with apatite and Slovakite: the impact of two earthworm species (Lumbricus terrestris and Dendrobaena veneta) on lead bioaccessibility and soil functioning.

PubMed

Tica, D; Udovic, M; Lestan, D

2013-03-01

Remediation soil is exposed to various environmental factors over time that can affect the final success of the operation. In the present study, we assessed Pb bioaccessibility and microbial activity in industrially polluted soil (Arnoldstein, Austria) stabilized with 5% (w/w) of Slovakite and 5% (w/w) of apatite soil after exposure to two earthworm species, Lumbricus terrestris and Dendrobaena veneta, used as model environmental biotic soil factors. Stabilization resulted in reduced Pb bioaccessibility, as assessed with one-step extraction tests and six-step sequential extraction, and improved soil functioning, mirrored in reduced β-glucosidase activity in soil. Both earthworm species increased Pb bioaccessibility, thus decreasing the initial stabilization efficacy and indicating the importance of considering the long-term fate of remediated soil. The earthworm species had different effects on soil enzyme activity, which can be attributed to species-specific microbial populations in earthworm gut acting on the ingested soil. Copyright © 2012 Elsevier Ltd. All rights reserved.

Polymorphism and metal-induced structural transformation in 5,5'-bis(4-pyridyl)(2,2'-bispyrimidine) adlayers on Au(111).

PubMed

Hötger, Diana; Carro, Pilar; Gutzler, Rico; Wurster, Benjamin; Chandrasekar, Rajadurai; Klyatskaya, Svetlana; Ruben, Mario; Salvarezza, Roberto C; Kern, Klaus; Grumelli, Doris

2018-05-31

Metal-organic coordination networks self-assembled on surfaces have emerged as functional low-dimensional architectures with potential applications ranging from the fabrication of functional nanodevices to electrocatalysis. Among them, bis-pyridyl-bispyrimidine (PBP) and Fe-PBP on noble metal surfaces appear as interesting systems in revealing the details of the molecular self-assembly and the effect of metal incorporation on the organic network arrangement. Herein, we report a combined STM, XPS, and DFT study revealing polymorphism in bis-pyridyl-bispyrimidine adsorbed adlayers on the reconstructed Au(111) surface. The polymorphic structures are converted by the addition of Fe adatoms into one unique Fe-PBP surface structure. DFT calculations show that while all PBP phases exhibit a similar thermodynamic stability, metal incorporation selects the PBP structure that maximizes the number of metal-N close contacts. Charge transfer from the Fe adatoms to the Au substrate and N-Fe interactions stabilize the Fe-PBP adlayer. The increased thermodynamic stability of the metal-stabilized structure leads to its sole expression on the surface.

Bivariate and multivariate analyses of the correlations between stability of the erythrocyte membrane, serum lipids and hematological variables.

PubMed

Bernardino Neto, M; de Avelar, E B; Arantes, T S; Jordão, I A; da Costa Huss, J C; de Souza, T M T; de Souza Penha, V A; da Silva, S C; de Souza, P C A; Tavares, M; Penha-Silva, N

2013-01-01

The observation that the fluidity must remain within a critical interval, outside which the stability and functionality of the cell tends to decrease, shows that stability, fluidity and function are related and that the measure of erythrocyte stability allows inferences about the fluidity or functionality of these cells. This study determined the biochemical and hematological variables that are directly or indirectly related to erythrocyte stability in a population of 71 volunteers. Data were evaluated by bivariate and multivariate analysis. The erythrocyte stability showed a greater association with hematological variables than the biochemical variables. The RDW stands out for its strong correlation with the stability of erythrocyte membrane, without being heavily influenced by other factors. Regarding the biochemical variables, the erythrocyte stability was more sensitive to LDL-C. Erythrocyte stability was significantly associated with RDW and LDL-C. Thus, the level of LDL-C is a consistent link between stability and functionality, suggesting that a measure of stability could be more one indirect parameter for assessing the risk of degenerative processes associated with high levels of LDL-C.

Design and Characterization of DNA Strand-Displacement Circuits in Serum-Supplemented Cell Medium.

PubMed

Fern, Joshua; Schulman, Rebecca

2017-09-15

The functional stability and lifetimes of synthetic molecular circuits in biological environments are important for long-term, stable sensors or controllers of cell or tissue behavior. DNA-based molecular circuits, in particular DNA strand-displacement circuits, provide simple and effective biocompatible control mechanisms and sensors, but are vulnerable to digestion by nucleases present in living tissues and serum-supplemented cell culture. The stability of double-stranded and single-stranded DNA circuit components in serum-supplemented cell medium and the corresponding effect of nuclease-mediated degradation on circuit performance were characterized to determine the major routes of degradation and DNA strand-displacement circuit failure. Simple circuit design choices, such as the use of 5' toeholds within the DNA complexes used as reactants in the strand-displacement reactions and the termination of single-stranded components with DNA hairpin domains at the 3' termini, significantly increase the functional lifetime of the circuit components in the presence of nucleases. Simulations of multireaction circuits, guided by the experimentally measured operation of single-reaction circuits, enable predictive realization of multilayer and competitive-reaction circuit behavior. Together, these results provide a basic route to increased DNA circuit stability in cell culture environments.

Design and Characterization of DNA Strand-Displacement Circuits in Serum-Supplemented Cell Medium

DOE PAGES

Fern, Joshua; Schulman, Rebecca

2017-05-30

The functional stability and lifetimes of synthetic molecular circuits in biological environments are important for long-term, stable sensors or controllers of cell or tissue behavior. DNA-based molecular circuits, particularly DNA strand-displacement circuits, provide simple and effective biocompatible control mechanisms and sensors, but are vulnerable to digestion by nucleases present in living tissues and serum-supplemented cell culture. The stability of double-stranded and single-stranded DNA circuit components in serum-supplemented cell medium and the corresponding effect of nuclease-mediated degradation on circuit performance were characterized to determine the major routes of degradation and DNA strand-displacement circuit failure. Simple circuit design choices, such as themore » use of 5' toeholds within the DNA complexes used as reactants in the strand-displacement reactions and the termination of single-stranded components with DNA hairpin domains at the 3' termini, significantly increase the functional lifetime of the circuit components in the presence of nucleases. Furthermore, simulations of multireaction circuits, guided by the experimentally measured operation of single-reaction circuits, enable predictive realization of multilayer and competitive-reaction circuit behavior. Altogether, these results provide a basic route to increased DNA circuit stability in cell culture environments.« less

Design and Characterization of DNA Strand-Displacement Circuits in Serum-Supplemented Cell Medium

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

Fern, Joshua; Schulman, Rebecca

The functional stability and lifetimes of synthetic molecular circuits in biological environments are important for long-term, stable sensors or controllers of cell or tissue behavior. DNA-based molecular circuits, particularly DNA strand-displacement circuits, provide simple and effective biocompatible control mechanisms and sensors, but are vulnerable to digestion by nucleases present in living tissues and serum-supplemented cell culture. The stability of double-stranded and single-stranded DNA circuit components in serum-supplemented cell medium and the corresponding effect of nuclease-mediated degradation on circuit performance were characterized to determine the major routes of degradation and DNA strand-displacement circuit failure. Simple circuit design choices, such as themore » use of 5' toeholds within the DNA complexes used as reactants in the strand-displacement reactions and the termination of single-stranded components with DNA hairpin domains at the 3' termini, significantly increase the functional lifetime of the circuit components in the presence of nucleases. Furthermore, simulations of multireaction circuits, guided by the experimentally measured operation of single-reaction circuits, enable predictive realization of multilayer and competitive-reaction circuit behavior. Altogether, these results provide a basic route to increased DNA circuit stability in cell culture environments.« less

Legal Nature and Functions of Referendum in Constitutional Law Theory

ERIC Educational Resources Information Center

Kucherenko, Petr A.; Sangadzhiev, Badma.V.; Velibekov, Murad C.

2016-01-01

The relevance of the study of the legal nature and functions of the referendum is conditioned by the increasing dynamics of development of direct democracy in the developed countries and the needs to legalize it in constitutional and legal norms to ensure stability in society. The purpose of this paper is to define the legal nature of the…

Structural and optical properties of electron beam evaporated yttria stabilized zirconia thin films

NASA Astrophysics Data System (ADS)

Kirubaharan, A. Kamalan; Kuppusami, P.; Singh, Akash; Dharini, T.; Ramachandran, D.; Mohandas, E.

2015-06-01

Yttria stabilized zirconia (10 mole % Y2O3) thin films were deposited on quartz substrates using electron beam physical vapor deposition at the substrate temperatures in the range 300 - 973 K. XRD analysis showed cubic crystalline phase of YSZ films with preferred orientation along (111). The surface roughness was found to increase with the increase of deposition temperatures. The optical band gap of ˜5.7 eV was calculated from transmittance curves. The variation in the optical properties is correlated with the changes in the microstructural features of the films prepared as a function of substrate temperature.

EX4 stabilizes and activates Nrf2 via PKCδ, contributing to the prevention of oxidative stress-induced pancreatic beta cell damage

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

Kim, Mi-Hwi; Kim, Eung-Hwi

Oxidative stress in pancreatic beta cells can inhibit insulin secretion and promote apoptotic cell death. Exendin-4 (EX4), a glucagon-like peptide-1 receptor agonist, can suppress beta cell apoptosis, improve beta cell function and protect against oxidative damage. In this study, we investigated the molecular mechanisms for antioxidative effects of EX4 in pancreatic beta cells. INS-1 cells, a rat insulinoma cell line, were pretreated with EX4 and exposed to palmitate or H{sub 2}O{sub 2}. Reactive oxygen species (ROS) production, and glutathione and insulin secretion were measured. The mRNA and protein expression levels of antioxidant genes were examined. The level of nuclear factormore » erythroid 2-related factor 2 (Nrf2), its binding to antioxidant response element (ARE), and its ubiquination in the presence of EX4 were determined. The Nrf2 signaling pathway was determined using rottlerin (protein kinase [PK]Cδ inhibitor), H89 (PKA inhibitor) and LY294002 (phosphatidylinositide 3-kinase [PI3K] inhibitor). EX4 treatment decreased ROS production, recovered cellular glutathione levels and insulin secretion in the presence of oxidative stress in INS-1 cells. The expression levels of glutamate-cysteine ligase catalytic subunit and heme oxygenase-1 were increased by EX4 treatment. EX4 promoted Nrf2 translocation, ARE binding activity and enhanced stabilization of Nrf2 by inhibition of ubiquitination. Knockdown of Nrf2 abolished the effect of EX4 on increased insulin secretion. Inhibition of PKCδ attenuated Nrf2 translocation and antioxidative gene expression by EX4 treatment. We suggest that EX4 activates and stabilizes Nrf2 through PKCδ activation, contributing to the increase of antioxidant gene expression and consequently improving beta cell function in the presence of oxidative stress. - Highlights: • EX4 protects against oxidative stress-induced pancreatic beta cell dysfunction. • EX4 increases antioxidant gene expression. • Antioxidative effect of EX4 is mediated by Nrf2. • EX4 increases Nrf2 level by stabilizing Nrf2 protein. • EX4 stabilizes Nrf2 by activation of PKCδ.« less

Surface functionalization of microwave plasma-synthesized silica nanoparticles for enhancing the stability of dispersions

NASA Astrophysics Data System (ADS)

Sehlleier, Yee Hwa; Abdali, Ali; Schnurre, Sophie Marie; Wiggers, Hartmut; Schulz, Christof

2014-08-01

Gas phase-synthesized silica nanoparticles were functionalized with three different silane coupling agents (SCAs) including amine, amine/phosphonate and octyltriethoxy functional groups and the stability of dispersions in polar and non-polar dispersing media such as water, ethanol, methanol, chloroform, benzene, and toluene was studied. Fourier transform infrared spectroscopy showed that all three SCAs are chemically attached to the surface of silica nanoparticles. Amine-functionalized particles using steric dispersion stabilization alone showed limited stability. Thus, an additional SCA with sufficiently long hydrocarbon chains and strong positively charged phosphonate groups was introduced in order to achieve electrosteric stabilization. Steric stabilization was successful with hydrophobic octyltriethoxy-functionalized silica nanoparticles in non-polar solvents. The results from dynamic light scattering measurements showed that in dispersions of amine/phosphonate- and octyltriethoxy-functionalized silica particles are dispersed on a primary particle level. Stable dispersions were successfully prepared from initially agglomerated nanoparticles synthesized in a microwave plasma reactor by designing the surface functionalization.

E2-EPF UCP regulates stability and functions of missense mutant pVHL via ubiquitin mediated proteolysis.

PubMed

Park, Kyeong-Su; Kim, Ju Hee; Shin, Hee Won; Chung, Kyung-Sook; Im, Dong-Soo; Lim, Jung Hwa; Jung, Cho-Rok

2015-10-26

Missense mutation of VHL gene is frequently detected in type 2 VHL diseases and linked to a wide range of pVHL functions and stability. Certain mutant pVHLs retain ability to regulate HIFs but lose their function by instability. In this case, regulating of degradation of mutant pVHLs, can be postulated as therapeutic method. The stability and cellular function of missense mutant pVHLs were determine in HEK293T transient expressing cell and 786-O stable cell line. Ubiquitination assay of mutant VHL proteins was performed in vitro system. Anticancer effect of adenovirus mediated shUCP expressing was evaluated using ex vivo mouse xenograft assay. Three VHL missense mutants (V155A, L158Q, and Q164R) are directly ubiquitinated by E2-EPF UCP (UCP) in vitro. Mutant pVHLs are more unstable than wild type in cell. Missense mutant pVHLs interact with UCP directly in both in vitro and cellular systems. Lacking all of lysine residues of pVHL result in resistance to ubiquitination thereby increase its stability. Missense mutant pVHLs maintained the function of E3 ligase to ubiquitinate HIF-1α in vitro. In cells expressing mutant pVHLs, Glut-1 and VEGF were relatively upregulated compared to their levels in cells expressing wild-type. Depletion of UCP restored missense mutant pVHLs levels and inhibited cell growth. Adenovirus-mediated shUCP RNA delivery inhibited tumor growth in ex vivo mouse xenograft model. These data suggest that targeting of UCP can be one of therapeutic method in type 2 VHL disease caused by unstable but functional missense mutant pVHL.

Mammalian Sterile 20-like Kinase 1 (Mst1) Enhances the Stability of Forkhead Box P3 (Foxp3) and the Function of Regulatory T Cells by Modulating Foxp3 Acetylation.

PubMed

Li, Jiang; Du, Xingrong; Shi, Hao; Deng, Kejing; Chi, Hongbo; Tao, Wufan

2015-12-25

Regulatory T cells (Tregs) play crucial roles in maintaining immune tolerance. The transcription factor Foxp3 is a critical regulator of Treg development and function, and its expression is regulated at both transcriptional and post-translational levels. Acetylation by lysine acetyl transferases/lysine deacetylases is one of the main post-translational modifications of Foxp3, which regulate Foxp3's stability and transcriptional activity. However, the mechanism(s) by which the activities of these lysine acetyl transferases/lysine deacetylases are regulated to preserve proper Foxp3 acetylation during Treg development and maintenance of Treg function remains to be determined. Here we report that Mst1 can enhance Foxp3 stability, its transcriptional activity, and Treg function by modulating the Foxp3 protein at the post-translational level. We discovered that Mst1 could increase the acetylation of Foxp3 by inhibiting Sirt1 activity, which requires the Mst1 kinase activity. We also found that Mst1 could attenuate Sirt1-mediated deacetylation of Foxp3 through directly interacting with Foxp3 to prevent or interfere the interaction between Sirt1 and Foxp3. Therefore, Mst1 can regulate Foxp3 stability in kinase-dependent and kinase-independent manners. Finally, we showed that treatment of Mst1(-/-) Tregs with Ex-527, a Sirt1-specific inhibitor, partially restored the suppressive function of Mst1(-/-) Tregs. Our studies reveal a novel mechanism by which Mst1 enhances Foxp3 expression and Treg function at the post-translational level. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Evaluation of nanostructural, mechanical, and biological properties of collagen-nanotube composites.

PubMed

Tan, Wei; Twomey, John; Guo, Dongjie; Madhavan, Krishna; Li, Min

2010-06-01

Collagen I is an essential structural and mechanical building block of various tissues, and it is often used as tissue-engineering scaffolds. However, collagen-based constructs reconstituted in vitro often lacks robust fiber structure, mechanical stability, and molecule binding capability. To enhance these performances, the present study developed 3-D collagen-nanotube composite constructs with two types of functionalized carbon nanotubes, carboxylated nanotubes and covalently functionalized nanotubes (CFNTs). The influences of nanotube functionalization and loading concentration on the collagen fiber structure, mechanical property, biocompatibility, and molecule binding were examined. Results revealed that surface modification and loading concentration of nanotubes determined the interactions between nanotubes and collagen fibrils, thus altering the structure and property of nanotube-collagen composites. Scanning electron microscopy and confocal microscopy revealed that the incorporation of CFNT in collagen-based constructs was an effective means of restructuring collagen fibrils because CFNT strongly bound to collagen molecules inducing the formation of larger fibril bundles. However, increased nanotube loading concentration caused the formation of denser fibril network and larger aggregates. Static stress-strain tests under compression showed that the addition of nanotube into collagen-based constructs did not significantly increase static compressive moduli. Creep/recovery testing under compression revealed that CFNT-collagen constructs showed improved mechanical stability under continuous loading. Testing with endothelial cells showed that biocompatibility was highly dependent on nanotube loading concentration. At a low loading level, CFNT-collagen showed higher endothelial coverage than the other tested constructs or materials. Additionally, CFNT-collagen showed capability of binding to other biomolecules to enhance the construct functionality. In conclusion, functionalized nanotube-collagen composites, particularly CFNT-collagen composites, could be promising materials, which provide structural support showing bundled fibril structure, biocompatibility, multifunctionality, and mechanical stability, but rigorous control over chemical modification, loading concentration, and nanotube dispersion are needed.

Formation, antioxidant property and oxidative stability of cold pressed rice bran oil emulsion.

PubMed

Thanonkaew, Amonrat; Wongyai, Surapote; Decker, Eric A; McClements, David J

2015-10-01

Cold pressed rice bran oil (CPRBO) is used in foods, cosmetics, and pharmaceuticals due to its desirable health and functional attributes. The purpose of this work was to study the formation, antioxidant property and oxidative stability of oil-in-water emulsion of CPRBO. The influence of oil (10-40 % CPRBO) and surfactant (1-5 % glyceryl monostearate (GMS)) concentration on the properties of emulsions were studied. The lightness (L*) and yellowness (b*) of CPRBO emulsions decreased as GMS concentration increased, which was attributed to a decrease in droplet size after homogenization. The CPRBO emulsion was stable during storage at room temperature for 30 days. Increasing the oil concentration in the CPRBO emulsions increased their antioxidant activity, which can be attributed to the corresponding increase in phytochemical content. However, GMS concentration had little impact on the antioxidant activity of CPRBO emulsions. The storage of CPRBO emulsion at room temperature showed that lipid oxidation markers gradually increased after 30 days of storage, which was correlated to a decrease in gamma oryzanol content and antioxidant activity. These results have important implications for the utilization of rice bran oil (RBO) as a function ingredient in food, cosmetic, and pharmaceutical products.

Network structure shapes spontaneous functional connectivity dynamics.

PubMed

Shen, Kelly; Hutchison, R Matthew; Bezgin, Gleb; Everling, Stefan; McIntosh, Anthony R

2015-04-08

The structural organization of the brain constrains the range of interactions between different regions and shapes ongoing information processing. Therefore, it is expected that large-scale dynamic functional connectivity (FC) patterns, a surrogate measure of coordination between brain regions, will be closely tied to the fiber pathways that form the underlying structural network. Here, we empirically examined the influence of network structure on FC dynamics by comparing resting-state FC (rsFC) obtained using BOLD-fMRI in macaques (Macaca fascicularis) to structural connectivity derived from macaque axonal tract tracing studies. Consistent with predictions from simulation studies, the correspondence between rsFC and structural connectivity increased as the sample duration increased. Regions with reciprocal structural connections showed the most stable rsFC across time. The data suggest that the transient nature of FC is in part dependent on direct underlying structural connections, but also that dynamic coordination can occur via polysynaptic pathways. Temporal stability was found to be dependent on structural topology, with functional connections within the rich-club core exhibiting the greatest stability over time. We discuss these findings in light of highly variable functional hubs. The results further elucidate how large-scale dynamic functional coordination exists within a fixed structural architecture. Copyright © 2015 the authors 0270-6474/15/355579-10$15.00/0.

Full-frame video stabilization with motion inpainting.

PubMed

Matsushita, Yasuyuki; Ofek, Eyal; Ge, Weina; Tang, Xiaoou; Shum, Heung-Yeung

2006-07-01

Video stabilization is an important video enhancement technology which aims at removing annoying shaky motion from videos. We propose a practical and robust approach of video stabilization that produces full-frame stabilized videos with good visual quality. While most previous methods end up with producing smaller size stabilized videos, our completion method can produce full-frame videos by naturally filling in missing image parts by locally aligning image data of neighboring frames. To achieve this, motion inpainting is proposed to enforce spatial and temporal consistency of the completion in both static and dynamic image areas. In addition, image quality in the stabilized video is enhanced with a new practical deblurring algorithm. Instead of estimating point spread functions, our method transfers and interpolates sharper image pixels of neighboring frames to increase the sharpness of the frame. The proposed video completion and deblurring methods enabled us to develop a complete video stabilizer which can naturally keep the original image quality in the stabilized videos. The effectiveness of our method is confirmed by extensive experiments over a wide variety of videos.

Bonded functional esthetic prototype: an alternative pre-treatment mock-up technique and cost-effective medium-term esthetic solution.

PubMed

McLaren, Edward A

2013-09-01

As the economy has receded in recent years, many patients have been inclined to reject dental treatment beyond what they feel is the minimal amount necessary. Increasingly, there has been reluctance to take on the expense of full-mouth restorations and time-consuming procedures. Consequently, clinicians can benefit from innovative, conservative, interim solutions that enable them to provide segment treatment with long-term stability and esthetics, with lower initial cost. The bonded functional esthetic prototype (BFEP) allows fabrication of up to 14 teeth from composite in 1 hour, providing either a pre-treatment restoration or a long-term provisional solution until further treatment can be completed. As demonstrated herein, the BFEP enables superb function, stability, and esthetics in the interim while dispersing the cost of definitive treatment over time.

Predicting the Influence of Nano-Scale Material Structure on the In-Plane Buckling of Orthotropic Plates

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Odegard, Gregory M.; Nemeth, Michael P.; Frankland, Sarah-Jane V.

2004-01-01

A multi-scale analysis of the structural stability of a carbon nanotube-polymer composite material is developed. The influence of intrinsic molecular structure, such as nanotube length, volume fraction, orientation and chemical functionalization, is investigated by assessing the relative change in critical, in-plane buckling loads. The analysis method relies on elastic properties predicted using the hierarchical, constitutive equations developed from the equivalent-continuum modeling technique applied to the buckling analysis of an orthotropic plate. The results indicate that for the specific composite materials considered in this study, a composite with randomly orientated carbon nanotubes consistently provides the highest values of critical buckling load and that for low volume fraction composites, the non-functionalized nanotube material provides an increase in critical buckling stability with respect to the functionalized system.

Microencapsulation structures based on protein-coated liposomes obtained through electrospraying for the stabilization and improved bioaccessibility of curcumin.

PubMed

Gómez-Mascaraque, Laura G; Casagrande Sipoli, Caroline; de La Torre, Lucimara Gaziola; López-Rubio, Amparo

2017-10-15

Novel food-grade hybrid encapsulation structures based on the entrapment of phosphatidylcholine liposomes, within a WPC matrix through electrospraying, were developed and used as delivery vehicles for curcumin. The loading capacity and encapsulation efficiency of the proposed system was studied, and the suitability of the approach to stabilize curcumin and increase its bioaccessibility was assessed. Results showed that the maximum loading capacity of the liposomes was around 1.5% of curcumin, although the loading capacity of the hybrid microencapsulation structures increased with the curcumin content by incorporation of curcumin microcrystals upon electrospraying. Microencapsulation of curcumin within the proposed hybrid structures significantly increased its bioaccessibility (∼1.7-fold) compared to the free compound, and could successfully stabilize it against degradation in PBS (pH=7.4). The proposed approach thus proved to be a promising alternative to produce powder-like functional ingredients. Copyright © 2017 Elsevier Ltd. All rights reserved.

Full-Body Gaze Control Mechanisms Elicited During Locomotion: Effects Of VOR Adaptation

NASA Technical Reports Server (NTRS)

Mulavara, A. P.; Houser, J.; Peters, B.; Miller, C.; Richards, J.; Marshburn, A.; Brady, R.; Cohen, H.; Bloomberg, J. J.

2004-01-01

Control of locomotion requires precise interaction between several sensorimotor subsystems. During locomotion the performer must satisfy two performance criteria: maintain stable forward translation and to stabilize gaze (McDonald, et al., 1997). Precise coordination demands integration of multiple sensorimotor subsystems for fulfilling both criteria. In order to test the general hypothesis that the whole body can serve as an integrated gaze stabilization system, we have previously investigated how the multiple, interdependent full-body sensorimotor subsystems respond to changes in gaze stabilization task constraints during locomotion (Mulavara and Bloomberg, 2003). The results suggest that the full body contributes to gaze stabilization during locomotion, and that its different functional elements respond to changes in visual task constraints. The goal of this study was to determine how the multiple, interdependent, full-body sensorimotor subsystems aiding gaze stabilization during locomotion are functionally coordinated after the vestibulo-ocular reflex (VOR) gain has been altered. We investigated the potential of adaptive remodeling of the full-body gaze control system following exposure to visual-vestibular conflict known to adaptively reduce the VOR. Subjects (n=14) walked (6.4 km/h) on the treadmill before and after they were exposed to 0.5X manifying lenses worn for 30 minutes during self-generated sinusoidal vertical head rotations performed while seated. In this study we measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, shank and foot, accelerations along the vertical axis at the head and the shank, and the vertical forces acting on the support surface. Results indicate that, following exposure to the 0.5X minifying lenses, there was a significant increase in the duration of stance and stride times, alteration in the amplitude of head movement with respect to space and a significant increase in the amount of knee flexion during the initial stance phase of the gait cycle. This study provides further evidence that the full body contributes to gaze stabilization during locomotion, and that different functional elements are responsive to changes in visual task constraints and are subject to adaptive alteration following exposure to visual-vestibular conflict.

Intraspecific functional diversity of common species enhances community stability

USGS Publications Warehouse

Wood, Connor M.; McKinney, Shawn T.; Loftin, Cynthia S.

2017-01-01

Common species are fundamental to the structure and function of their communities and may enhance community stability through intraspecific functional diversity (iFD). We measured among-habitat and within-habitat iFD (i.e., among- and within-plant community types) of two common small mammal species using stable isotopes and functional trait dendrograms, determined whether iFD was related to short-term population stability and small mammal community stability, and tested whether spatially explicit trait filters helped explain observed patterns of iFD. Southern red-backed voles (Myodes gapperi) had greater iFD than deer mice (Peromyscus maniculatus), both among habitats, and within the plant community in which they were most abundant (their “primary habitat”). Peromyscus maniculatus populations across habitats differed significantly between years and declined 78% in deciduous forests, their primary habitat, as did the overall deciduous forest small mammal community. Myodes gapperi populations were stable across habitats and within coniferous forest, their primary habitat, as was the coniferous forest small mammal community. Generalized linear models representing internal trait filters (e.g., competition), which increase within-habitat type iFD, best explained variation in M. gapperidiet, while models representing internal filters and external filters (e.g., climate), which suppress within-habitat iFD, best explained P. maniculatus diet. This supports the finding that M. gapperi had higher iFD than P. maniculatus and is consistent with the theory that internal trait filters are associated with higher iFD than external filters. Common species with high iFD can impart a stabilizing influence on their communities, information that can be important for conserving biodiversity under environmental change.

Engineering Copper Carboxylate Functionalities on Water Stable Metal–Organic Frameworks for Enhancement of Ammonia Removal Capacities

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

Joshi, Jayraj N.; Garcia-Gutierrez, Erika Y.; Moran, Colton M.

Functionalization of copper carboxylate groups on a series of UiO-66 metal organic framework (MOF) analogues and their corresponding impact on humid and dry ammonia adsorption behavior were studied. Relative locations of possible carboxylic acid binding sites for copper on the MOF analogues were varied on ligand and missing linker defect sites. Materials after copper incorporation exhibited increased water vapor and ammonia affinity during isothermal adsorption and breakthrough experiments, respectively. The introduction of copper markedly increased ammonia adsorption capacities for all adsorbents possessing carboxyl binding sites. In particular, the new MOF UiO-66-(COOCu)2 displayed the highest ammonia breakthrough capacities of 6.38 andmore » 6.84 mmol g–1 under dry and humid conditions, respectively, while retaining crystallinity and porosity. Relative carboxylic acid site locations were also found to impact sorbent stability, as missing linker defect functionalized materials degraded under humid conditions after copper incorporation. Postsynthetic metal insertion provides a method for adding sites that are analogous to open metal sites while maintaining good structural stability.« less

Evolution and resilience of the nuclear nonproliferation regime

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

Pregenzer, Arian L.

2014-05-09

This paper introduces the concept of systems resilience as a new framework for thinking about the future of the nonproliferation regime. Resilience refers to the ability of a system to maintain its vital functions in the face of continuous and unpredictable change. First, I make the case that the nonproliferation regime can be viewed as a complex system. Next, I discuss key themes from the literature on systems resilience and apply them to the nonproliferation system: the difference between resilience and stability; the need for evolution to maintain function; the importance of functional diversity; and the concept of the adaptivemore » cycle. I show that most existing nonproliferation strategies are aimed at stability rather than resilience and that the current nonproliferation system may be over-constrained by the cumulative evolution of strategies. According to the literature on systems resilience, this increases its vulnerability to collapse. I argue that the resilience of the nonproliferation system can be enhanced by increasing international participation in setting the nonproliferation agenda, developing general international response capabilities, focusing on non-coercive approaches to decreasing demand, and applying systems thinking more rigorously to nonproliferation.« less

Purple-bacterial photosynthetic reaction centers and quantum-dot hybrid-assemblies in lecithin liposomes and thin films.

PubMed

Lukashev, Eugeny P; Knox, Petr P; Gorokhov, Vladimir V; Grishanova, Nadezda P; Seifullina, Nuranija Kh; Krikunova, Maria; Lokstein, Heiko; Paschenko, Vladimir Z

2016-11-01

Quantum dots (QDs) absorb ultraviolet and long-wavelength visible light energy much more efficiently than natural bacterial light-harvesting proteins and can transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion of RCs combined with QDs as antennae into liposomes opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components or inorganic components alone. RCs from Rhodobacter sphaeroides and QDs (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased. The efficiency of energy transfer between QDs and RCs and conditions of long-term stability of function of such hybrid complexes in film preparations were investigated as well. It was found that dry films containing RCs and QDs, maintained at atmospheric humidity, are capable of maintaining their functional activity for at least some months as judged by measurements of their spectral characteristics, efficiency of energy transfer from QDs to RCs and RC electron transport activity. Addition of trehalose to the films increases the stability further, especially for films maintained at low humidity. These stable hybrid film structures are promising for further studies towards developing new phototransformation devices for biotechnological applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Tests of Dorsolateral Frontal Function Correlate with Objective Tests of Postural Stability in Early to Moderate Stage Parkinson’s Disease

PubMed Central

Nocera, Joe R.; Price, Catherine; Fernandez, Hubert H.; Amano, Shinichi; Vallabhajosula, Srikant; Okun, Michael S.; Hwynn, Nelson; Hass, Chris J.

2010-01-01

A substantial number of individuals with Parkinson’s disease who display impaired postural stability experience accelerated cognitive decline and an increased prevalence of dementia. To date, studies suggest that this relationship, believed to be due to involvement of nondopaminergic circuitry, occurs later in the disease process. Research has yet to adequately investigate this cognitive-posturomotor relationship especially when examining earlier disease states. To gain greater understanding of the relationship between postural stability and cognitive function/dysfunction we evaluated a more stringent, objective measure of postural stability (center of pressure displacement), and also more specific measures of cognition in twenty-two patients with early to moderate stage Parkinson’s disease. The magnitude of the center of pressure displacement in this cohort was negatively correlated with performance on tests known to activate dorsolateral frontal regions. Additionally, the postural stability item of the UPDRS exhibited poor correlation with the more objective measure of center of pressure displacement and all specific measures of cognition. These results may serve as rationale for a more thorough evaluation of postural stability and cognition especially in individuals with mild Parkinson’s disease. Greater understanding of the relationship between motor and cognitive processes in Parkinson’s disease will be critical for understanding the disease process and its potential therapeutic possibilities. PMID:20829093

Combined Spectroscopic and Calorimetric Studies to Reveal Absorption Mechanisms and Conformational Changes of Protein on Nanoporous Biomaterials

PubMed Central

Ahmadi, Saharnaz; Farokhi, Maryam; Padidar, Parisa; Falahati, Mojtaba

2015-01-01

In this study the effect of surface modification of mesoporous silica nanoparticles (MSNs) on its adsorption capacities and protein stability after immobilization of beta-lactoglobulin B (BLG-B) was investigated. For this purpose, non-functionalized (KIT-6) and aminopropyl-functionalized cubic Ia3d mesoporous silica ([n-PrNH2-KIT-6]) nanoparticles were used as nanoporous supports. Aminopropyl-functionalized mesoporous nanoparticles exhibited more potential candidates for BLG-B adsorption and minimum BLG leaching than non-functionalized nanoparticles. It was observed that the amount of adsorbed BLG is dependent on the initial BLG concentration for both KIT-6 and [n-PrNH2-KIT-6] mesoporous nanoparticles. Also larger amounts of BLG-B on KIT-6 was immobilized upon raising the temperature of the medium from 4 to 55 °C while such increase was undetectable in the case of immobilization of BLG-B on the [n-PrNH2-KIT-6]. At temperatures above 55 °C the amounts of adsorbed BLG on both studied nanomaterials decreased significantly. By Differential scanning calorimetry or DSC analysis the heterogeneity of the protein solution and increase in Tm may indicate that immobilization of BLG-B onto the modified KIT-6 results in higher thermal stability compared to unmodified one. The obtained results provide several crucial factors in determining the mechanism(s) of protein adsorption and stability on the nanostructured solid supports and the development of engineered nano-biomaterials for controlled drug-delivery systems and biomimetic interfaces for the immobilization of living cells. PMID:26230687

Effects of Kaolin Clay on the Mechanical Properties of Asphaltic Concrete AC14

NASA Astrophysics Data System (ADS)

Abdullah, M. E.; Ramadhansyah, P. J.; Rafsanjani, M. H.; Norhidayah, A. H.; Yaacob, H.; Hainin, M. R.; Warid, M. N. Mohd; Satar, M. K. I. Mohd; Aziz, Md Maniruzzaman A.; Mashros, N.

2018-04-01

This study investigated the effect of kaolin clay on the mechanical properties of asphaltic concrete AC14 through Marshall Stability, resilient modulus, and dynamic creep tests. Four replacement levels of kaolin clay (2%, 4%, 6%, and 8% by weight of the binder) were considered. Kaolin clay functioned as an effective filler replacement material to increase the mechanical properties of asphalt mixtures. Asphaltic concrete with 2% to 4% kaolin clay replacement level exhibited excellent performance with good stability, resilient modulus, and creep stiffness.

Structural and electronic properties of rectangular CdTe nanowire: A DST study

NASA Astrophysics Data System (ADS)

Khan, Md. Shahzad; Bhatia, Manjeet; Srivastava, Anurag

2018-05-01

CdTe rectangular nanowire of different diameter in zinc-blende phase is investigated using density functional theory. Enhancement of diameter increased stability and improved electronic qualities suitable for device purpose applications. Cohesive energy per atom enhanced on enlarging diameter advocating the stability. Large diameter nanowire (22.62Å) exhibits bandgap of 1.21eV and electronic effective mass is observed to be 0.51me. The bonding between Cd-Te atoms are predominantly observed as covalent assuring its inertness towards moisture.

Role of Buffers in Protein Formulations.

PubMed

Zbacnik, Teddy J; Holcomb, Ryan E; Katayama, Derrick S; Murphy, Brian M; Payne, Robert W; Coccaro, Richard C; Evans, Gabriel J; Matsuura, James E; Henry, Charles S; Manning, Mark Cornell

2017-03-01

Buffers comprise an integral component of protein formulations. Not only do they function to regulate shifts in pH, they also can stabilize proteins by a variety of mechanisms. The ability of buffers to stabilize therapeutic proteins whether in liquid formulations, frozen solutions, or the solid state is highlighted in this review. Addition of buffers can result in increased conformational stability of proteins, whether by ligand binding or by an excluded solute mechanism. In addition, they can alter the colloidal stability of proteins and modulate interfacial damage. Buffers can also lead to destabilization of proteins, and the stability of buffers themselves is presented. Furthermore, the potential safety and toxicity issues of buffers are discussed, with a special emphasis on the influence of buffers on the perceived pain upon injection. Finally, the interaction of buffers with other excipients is examined. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Stability of rhombohedral phases in vanadium at high-pressure and high-temperature: first-principles investigations

PubMed Central

Wang, Yi X.; Wu, Q.; Chen, Xiang R.; Geng, Hua Y.

2016-01-01

The pressure-induced transition of vanadium from BCC to rhombohedral structures is unique and intriguing among transition metals. In this work, the stability of these phases is revisited by using density functional theory. At finite temperatures, a novel transition of rhombohedral phases back to BCC phase induced by thermal electrons is discovered. This reentrant transition is found not driven by phonons, instead it is the electronic entropy that stabilizes the latter phase, which is totally out of expectation. Parallel to this transition, we find a peculiar and strong increase of the shear modulus C44 with increasing temperature. It is counter-intuitive in the sense that it suggests an unusual harding mechanism of vanadium by temperature. With these stability analyses, the high-pressure and finite-temperature phase diagram of vanadium is proposed. Furthermore, the dependence of the stability of RH phases on the Fermi energy and chemical environment is investigated. The results demonstrate that the position of the Fermi level has a significant impact on the phase stability, and follows the band-filling argument. Besides the Fermi surface nesting, we find that the localization/delocalization of the d orbitals also contributes to the instability of rhombohedral distortions in vanadium. PMID:27581551

[The effect of hydrophobic surface properties of protein on its resistance to denaturation by organic solvents (using modified alpha-chymotrypsin as an example].

PubMed

Kudriashova, E V; Belova, A B; Vinogradov, A A; Mozhaev, V V

1994-03-01

Catalytic activity of covalently modified alpha-chymotrypsin in water/cosolvent solutions was investigated. The stability of chymotrypsin increases upon modification with hydrophilic reagents, such as glyceraldehyde, pyrometallic and succinic anhydrides, and glucosamine. Correlation was observed between the protein's stability in organic solvents and the degree of hydrophilization of the protein's surface. The protein is the more stable, the higher are the modification degree and the hydrophilicity of the modifying residue. At a certain critical hydrophilization degree of chymotrypsin a limit of stability is achieved. The stabilization effect can be accounted for by the fact that the interaction between water molecules on the surface and protein's functional groups become stronger in the hydrophilized protein.

Effects of Cordyceps militaris (L.) Fr. fermentation on the nutritional, physicochemical, functional properties and angiotensin I converting enzyme inhibitory activity of red bean (Phaseolus angularis [Willd.] W.F. Wight.) flour.

PubMed

Xiao, Yu; Sun, Mingmei; Zhang, Qiuqin; Chen, Yulian; Miao, Junqing; Rui, Xin; Dong, Mingsheng

2018-04-01

The effects of solid-state fermentation with Cordyceps militaris (L.) Fr. on the nutritional, physicochemical, and functional properties as well as angiotensin I converting enzyme (ACE) inhibitory activity of red bean ( Phaseolus angularis [Willd.] W.F. Wight.) flour were determined. Fermentation increased the amount of small peptides but significantly decreased large peptides. Fermentation also increased proteins and essential amino acids (by 9.31 and 13.89%, respectively) and improved the in vitro protein digestibility (6.54%) of red beans. Moreover, fermentation increased the water holding capacity (from 2.36 to 2.59 mL/g), fat absorption capacity (from 84.65 to 114.55%), emulsion activity (from 10.96 to 52.77%), emulsion stability (from 5.43 to 53.82%), and foaming stability (from 11.95 to 20.68%). Fermented red bean flour achieved a lower least gelation concentration of 14% than that of the control (18%). In contrast to the non-fermented red bean, the fermented red bean showed ACE inhibitory activity, with IC 50 value of 0.63 mg protein/mL. Overall, fermentation improved the nutritional, physicochemical, and functional properties as well as the biological activity of red bean flour. Thus, fermented red bean flour may serve as a novel nutritional and functional ingredient for applications in food design.

Gait ataxia in humans: vestibular and cerebellar control of dynamic stability.

PubMed

Schniepp, Roman; Möhwald, Ken; Wuehr, Max

2017-10-01

During human locomotion, vestibular feedback control is fundamental for maintaining dynamic stability and adapting the gait pattern to external circumstances. Within the supraspinal locomotor network, the cerebellum represents the key site for the integration of vestibular feedback information. The cerebellum is further important for the fine-tuning and coordination of limb movements during walking. The aim of this review article is to highlight the shared structural and functional sensorimotor principles in vestibular and cerebellar locomotion control. Vestibular feedback for the maintenance of dynamic stability is integrated into the locomotor pattern via midline, caudal cerebellar structures (vermis, flocculonodular lobe). Hemispheric regions of the cerebellum facilitate feed-forward control of multi-joint coordination and higher locomotor functions. Characteristic features of the gait disorder in patients with vestibular deficits or cerebellar ataxia are increased levels of spatiotemporal gait variability in the fore-aft and the medio-lateral gait dimension. In the fore-aft dimension, pathologic increases of gait fluctuations critically depend on the locomotion speed and predominantly manifest during slow walking velocities. This feature is associated with an increased risk of falls in both patients with vestibular hypofunction as well as patients with cerebellar ataxia. Pharmacological approaches for the treatment of vestibular or cerebellar gait ataxia are currently not available. However, new promising options are currently tested in randomized, controlled trials (fampridine/FACEG; acetyl-DL-leucine/ALCAT).

Deletion of internal structured repeats increases the stability of a leucine-rich repeat protein, YopM

PubMed Central

Barrick, Doug

2011-01-01

Mapping the stability distributions of proteins in their native folded states provides a critical link between structure, thermodynamics, and function. Linear repeat proteins have proven more amenable to this kind of mapping than globular proteins. C-terminal deletion studies of YopM, a large, linear leucine-rich repeat (LRR) protein, show that stability is distributed quite heterogeneously, yet a high level of cooperativity is maintained [1]. Key components of this distribution are three interfaces that strongly stabilize adjacent sequences, thereby maintaining structural integrity and promoting cooperativity. To better understand the distribution of interaction energy around these critical interfaces, we studied internal (rather than terminal) deletions of three LRRs in this region, including one of these stabilizing interfaces. Contrary to our expectation that deletion of structured repeats should be destabilizing, we find that internal deletion of folded repeats can actually stabilize the native state, suggesting that these repeats are destabilizing, although paradoxically, they are folded in the native state. We identified two residues within this destabilizing segment that deviate from the consensus sequence at a position that normally forms a stacked leucine ladder in the hydrophobic core. Replacement of these nonconsensus residues with leucine is stabilizing. This stability enhancement can be reproduced in the context of nonnative interfaces, but it requires an extended hydrophobic core. Our results demonstrate that different LRRs vary widely in their contribution to stability, and that this variation is context-dependent. These two factors are likely to determine the types of rearrangements that lead to folded, functional proteins, and in turn, are likely to restrict the pathways available for the evolution of linear repeat proteins. PMID:21764506

A Report of Undergraduates' Bonding Misconceptions.

ERIC Educational Resources Information Center

Nicoll, Gayle

2001-01-01

Describes misconceptions related to electronegativity, bonding, geometry, and microscopic representations that undergraduate students hold. Investigates the stability of misconceptions as a function of educational level, indicating that some students' misconceptions relating to bonding are resistant to change despite increased chemistry education.…

Evans function computation for the stability of travelling waves

NASA Astrophysics Data System (ADS)

Barker, B.; Humpherys, J.; Lyng, G.; Lytle, J.

2018-04-01

In recent years, the Evans function has become an important tool for the determination of stability of travelling waves. This function, a Wronskian of decaying solutions of the eigenvalue equation, is useful both analytically and computationally for the spectral analysis of the linearized operator about the wave. In particular, Evans-function computation allows one to locate any unstable eigenvalues of the linear operator (if they exist); this allows one to establish spectral stability of a given wave and identify bifurcation points (loss of stability) as model parameters vary. In this paper, we review computational aspects of the Evans function and apply it to multidimensional detonation waves. This article is part of the theme issue `Stability of nonlinear waves and patterns and related topics'.

Influence of functionalized nanoparticles on conformational stability of type I collagen for possible biomedical applications.

PubMed

Kandamchira, Aswathy; Selvam, Sangeetha; Marimuthu, Nidhin; Janardhanan, Sreeram Kalarical; Fathima, Nishter Nishad

2013-12-01

Collagen-nanoparticle interactions are vital for many biomedical applications including drug delivery and tissue engineering applications. Iron oxide nanoparticles synthesized using starch template according to our earlier reported procedures were functionalized by treating them with Gum Arabic (GA), a biocompatible polysaccharide, so as to enhance the interaction between nanoparticle surfaces and collagen. Viscosity, circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) techniques have been used to study the collagen-nanoparticle interactions. The relative viscosity for collagen-nanoparticle conjugate was found to increase with increase in concentration of the nanoparticle within the concentration range investigated, which is due to the aggregation of protein onto the surface of nanoparticle. The CD spectra for the collagen-nanoparticle at different concentration ratios do not have much variation in the Rpn values (ratio of positive peak intensity over negative peak intensity) after functionalization with GA. The variation of molar ellipticity values for collagen-nanoparticle is due to the glycoprotein present in GA. The collagen triple helical structure is maintained after interaction with nanoparticles. The FTIR spectra of native collagen, Coll-Fs (nanoparticle without functionalization) and Coll-FsG (nanoparticle functionalized with GA) show clearly the amide I, II, III bands, with respect to collagen. The ability of polysaccharide stabilized/functionalized nanoparticles to maintain the collagen properties would help in its biomedical applications. © 2013.

Genome Stability Pathways in Head and Neck Cancers

PubMed Central

O'Byrne, Kenneth J.; Panizza, Benedict; Richard, Derek J.

2013-01-01

Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies. PMID:24364026

Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

NASA Astrophysics Data System (ADS)

Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

2016-02-01

Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

PubMed Central

Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

2016-01-01

Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology. PMID:26861509

Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion.

PubMed

Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W; Liu, Yan; Walter, Nils G; Yan, Hao

2016-02-10

Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

Magnetic Fe3O4@MCM-41 core-shell nanoparticles functionalized with thiol silane for efficient l-asparaginase immobilization.

PubMed

Ulu, Ahmet; Noma, Samir Abbas Ali; Koytepe, Suleyman; Ates, Burhan

2018-06-06

l-Asparaginase (l-ASNase) is a vital enzyme for medical treatment and food industry. Here, we assessed the use of Fe 3 O 4 @Mobil Composition of Matter No. 41 (MCM-41) magnetic nanoparticles as carrier matrix for l-ASNase immobilization. In addition, surface of Fe 3 O 4 @MCM-41 magnetic nanoparticles was functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) to enhance stability of l-ASNase. The chemical structure, thermal properties, magnetic profile and morphology of the thiol-functionalized Fe 3 O 4 @MCM-41 magnetic nanoparticles were characterized with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy and zeta-potential measurement. l-ASNase was covalently immobilized onto the thiol-functionalized Fe 3 O 4 @MCM-41 magnetic nanoparticles. The properties of the immobilized enzyme, including optimum pH, temperature, kinetic parameters, thermal stability, reusability and storage stability were investigated and compared to free one. Immobilized enzyme was found to be stable over a wide range of pH and temperature range than free enzyme. The immobilized l-ASNase also showed higher thermal stability after 180 min incubation at 50 °C. The immobilized enzyme still retained 63% of its original activity after 16 times of reuse. The Km value for the immobilized enzyme was 1.15-fold lower than the free enzyme, which indicates increased affinity for the substrate. Additionally, the immobilized enzyme was active over 65% and 53% after 30 days of storage at 4 °C and room temperature (∼25 °C), respectively. Thereby, the results confirmed that thiol-functionalized Fe 3 O 4 @MCM-41 magnetic nanoparticles had high efficiency for l-ASNase immobilization and improved stability of L-ASNase.

System and method for determining stability of a neural system

NASA Technical Reports Server (NTRS)

Curtis, Steven A. (Inventor)

2011-01-01

Disclosed are methods, systems, and computer-readable media for determining stability of a neural system. The method includes tracking a function world line of an N element neural system within at least one behavioral space, determining whether the tracking function world line is approaching a psychological stability surface, and implementing a quantitative solution that corrects instability if the tracked function world line is approaching the psychological stability surface.

Concentration Dependent Effects of Bovine Serum Albumin on Graphene Oxide Colloidal Stability in Aquatic Environment.

PubMed

Sun, Binbin; Zhang, Yinqing; Chen, Wei; Wang, Kunkun; Zhu, Lingyan

2018-06-22

The impacts of a model globular protein (bovine serum albumin, BSA) on aggregation kinetics of graphene oxide (GO) in aquatic environment were investigated through time-resolved dynamic light scattering at pH 5.5. Aggregation kinetics of GO without BSA as a function of electrolyte concentrations (NaCl, MgCl 2 , and CaCl 2 ) followed the traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and the critical coagulation concentration (CCC) was 190, 5.41, and 1.61 mM, respectively. As BSA was present, it affected the GO stability in a concentration dependent manner. At fixed electrolyte concentrations below the CCC values, for example 120 mM NaCl, the attachment efficiency of GO increased from 0.08 to 1, then decreased gradually and finally reached up to zero as BSA concentration increased from 0 to 66.5 mg C/L. The low-concentration BSA depressed GO stability mainly due to electrostatic binding between the positively charged lysine groups of BSA and negatively charged groups of GO, as well as double layer compression effect. With the increase of BSA concentration, more and more BSA molecules were adsorbed on GO, leading to strong steric repulsion which finally predominated and stabilized the GO. These results provided significant information about the concentration dependent effects of natural organic matters on GO stability under environmentally relevant conditions.

Nanoporous microbead supported bilayers: stability, physical characterization, and incorporation of functional transmembrane proteins.

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

Davis, Ryan W.; Brozik, James A.; Brozik, Susan Marie

2007-03-01

The introduction of functional transmembrane proteins into supported bilayer-based biomimetic systems presents a significant challenge for biophysics. Among the various methods for producing supported bilayers, liposomal fusion offers a versatile method for the introduction of membrane proteins into supported bilayers on a variety of substrates. In this study, the properties of protein containing unilamellar phosphocholine lipid bilayers on nanoporous silica microspheres are investigated. The effects of the silica substrate, pore structure, and the substrate curvature on the stability of the membrane and the functionality of the membrane protein are determined. Supported bilayers on porous silica microspheres show a significant increasemore » in surface area on surfaces with structures in excess of 10 nm as well as an overall decrease in stability resulting from increasing pore size and curvature. Comparison of the liposomal and detergent-mediated introduction of purified bacteriorhodopsin (bR) and the human type 3 serotonin receptor (5HT3R) are investigated focusing on the resulting protein function, diffusion, orientation, and incorporation efficiency. In both cases, functional proteins are observed; however, the reconstitution efficiency and orientation selectivity are significantly enhanced through detergent-mediated protein reconstitution. The results of these experiments provide a basis for bulk ionic and fluorescent dye-based compartmentalization assays as well as single-molecule optical and single-channel electrochemical interrogation of transmembrane proteins in a biomimetic platform.« less

Identification of mild cognitive impairment in ACTIVE: algorithmic classification and stability.

PubMed

Cook, Sarah E; Marsiske, Michael; Thomas, Kelsey R; Unverzagt, Frederick W; Wadley, Virginia G; Langbaum, Jessica B S; Crowe, Michael

2013-01-01

Rates of mild cognitive impairment (MCI) have varied substantially, depending on the criteria used and the samples surveyed. The present investigation used a psychometric algorithm for identifying MCI and its stability to determine if low cognitive functioning was related to poorer longitudinal outcomes. The Advanced Cognitive Training of Independent and Vital Elders (ACTIVE) study is a multi-site longitudinal investigation of long-term effects of cognitive training with older adults. ACTIVE exclusion criteria eliminated participants at highest risk for dementia (i.e., Mini-Mental State Examination < 23). Using composite normative for sample- and training-corrected psychometric data, 8.07% of the sample had amnestic impairment, while 25.09% had a non-amnestic impairment at baseline. Poorer baseline functional scores were observed in those with impairment at the first visit, including a higher rate of attrition, depressive symptoms, and self-reported physical functioning. Participants were then classified based upon the stability of their classification. Those who were stably impaired over the 5-year interval had the worst functional outcomes (e.g., Instrumental Activities of Daily Living performance), and inconsistency in classification over time also appeared to be associated increased risk. These findings suggest that there is prognostic value in assessing and tracking cognition to assist in identifying the critical baseline features associated with poorer outcomes.

Role of ankle foot orthoses in functional stability of individuals with stroke.

PubMed

Rao, N; Aruin, A S

2016-10-01

Ankle foot orthoses (AFOs) are frequently prescribed to improve ambulation in individuals with stroke. However, the role of AFOs in balance control is not completely understood. The aim of the study was to evaluate the contribution of the AFOs in functional stability of individuals with stroke. Twenty three individuals with unilateral hemiparesis due to stroke were assessed using the Functional Reach Test. The subjects performed reaches forward, left and right while standing with or without an AFO. When provided with AFO, individuals with stroke improved the maximal reaching distance in all the directions (p < 0.05). The study found that individuals with unilateral stroke clearly demonstrated improvements in functional stability when they were provided with AFOs. This outcome could be used in the optimization of balance rehabilitation of individuals with stroke. Implications for Rehabilitation Functional stability is impaired in individuals with stroke. Functional Reach Test (FRT) was used to assess the role of ankle foot orthoses (AFOs) in balance control. Individuals with stroke improved their functional stability while they were provided with AFOs. Functional Reach Test could assist clinicians in the evaluation of postural stability associated with the use of AFOs.

Influence of xanthan, guar, CMC and gum acacia on functional properties of water chestnut (Trapa bispinosa) starch.

PubMed

Lutfi, Zubala; Nawab, Anjum; Alam, Feroz; Hasnain, Abid; Haider, Syed Zia

2017-10-01

This study was performed to determine the effect of xanthan, guar, CMC and gum acacia on functional and pasting properties of starch isolated from water chestnut (Trapa bispinosa). Morphological properties of water chestnut starch with CMC were studied by scanning electron microscopy (SEM). The addition of hydrocolloids significantly enhanced the solubility of water chestnut starch (WCS) while reduced swelling power and freeze-thaw stability. The hydrophilic tendency of WCS was increased by xanthan gum; however, with addition of gum acacia it decreased significantly. Starch was modified with guar and gum acacia exhibited highest% syneresis. Guar gum was found to be effective in increasing the clarity of water chestnut starch paste. The addition of CMC significantly reduced the pasting temperature of WCS indicating ease of gelatinization. The setback was accelerated in the presence of xanthan gum but gum acacia delayed this effect during the cooling of the starch paste. Only xanthan gum was found to be effective in increasing breakdown showing good paste stability of WCS. Copyright © 2017 Elsevier B.V. All rights reserved.

Inactivation of Semicircular Canals Causes Adaptive Increases in Otolith-driven Tilt Responses

NASA Technical Reports Server (NTRS)

Angelaki, Dora E.; Newlands, Shawn D.; Dickman, J. David

2002-01-01

Growing experimental and theoretical evidence suggests a functional synergy in the processing of otolith and semicircular canal signals for the generation of the vestibulo-ocular reflexes (VORs). In this study we have further tested this functional interaction by quantifying the adaptive changes in the otolith-ocular system during both rotational and translational movements after surgical inactivation of the semicircular canals. For 0.1- 0.5 Hz (stimuli for which there is no recovery of responses from the plugged canals), pitch and roll VOR gains recovered during earth- horizontal (but not earth-vertical) axis rotations. Corresponding changes were also observed in eye movements elicited by translational motion (0.1 - 5 Hz). Specifically, torsional eye movements increased during lateral motion, whereas vertical eye movements increased during fore-aft motion. The findings indicate that otolith signals can be adapted according to compromised strategy that leads to improved gaze stabilization during motion. Because canal-plugged animals permanently lose the ability to discriminate gravitoinertial accelerations, adapted animals can use the presence of gravity through otolith-driven tilt responses to assist gaze stabilization during earth-horizontal axis rotations.

Increasing Accuracy of Tissue Shear Modulus Reconstruction Using Ultrasonic Strain Tensor Measurement

NASA Astrophysics Data System (ADS)

Sumi, C.

Previously, we developed three displacement vector measurement methods, i.e., the multidimensional cross-spectrum phase gradient method (MCSPGM), the multidimensional autocorrelation method (MAM), and the multidimensional Doppler method (MDM). To increase the accuracies and stabilities of lateral and elevational displacement measurements, we also developed spatially variant, displacement component-dependent regularization. In particular, the regularization of only the lateral/elevational displacements is advantageous for the lateral unmodulated case. The demonstrated measurements of the displacement vector distributions in experiments using an inhomogeneous shear modulus agar phantom confirm that displacement-component-dependent regularization enables more stable shear modulus reconstruction. In this report, we also review our developed lateral modulation methods that use Parabolic functions, Hanning windows, and Gaussian functions in the apodization function and the optimized apodization function that realizes the designed point spread function (PSF). The modulations significantly increase the accuracy of the strain tensor measurement and shear modulus reconstruction (demonstrated using an agar phantom).

Supplementation of laying-hen feed with palm tocos and algae astaxanthin for egg yolk nutrient enrichment.

PubMed

Walker, Laurie A; Wang, Tong; Xin, Hongwei; Dolde, David

2012-02-29

Adding supplements to hen feed can increase egg nutritional value. Astaxanthin, tocotrienols, and tocopherols are potent antioxidants that provide health benefits to humans. We hypothesized that the addition of these nutrients to hen feed would result in an increased nutrient content in egg yolk with minimum changes in functional properties. Laying hens (Hy-Line W-36 breed) were fed four diets with different supplementation levels of palm toco concentrate and algae biomass containing astaxanthin for 8 weeks. Egg yolks were analyzed for physical, chemical, and functional properties. The feed with the highest nutrient concentration was also studied for stability of these antioxidants using the Arrhenius approach. No significant differences were observed in functional properties except for emulsification capacity and sensory characteristics among eggs from different diet treatments. Changes in egg yolk color reached the maximum values at day 8. Incorporation of tocopherols and tocotrienols increased until day 8, astaxanthin incorporation increased until day 10, and all decreased thereafter. Feed nutrients resulted in a dose-response relationship of these compounds in the egg yolk. The transfer efficiency ranged from 0 to 9.9% for tocotrienols and tocopherols and from 7.6 to 14.9% for astaxanthin at their peak values. Results of the Arrhenius accelerated stability study showed significant differences in the shelf life of various nutrients, and these results can be used to properly formulate and store the feed materials.

Density-functional theory computer simulations of CZTS{sub 0.25}Se{sub 0.75} alloy phase diagrams

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

Chagarov, E.; Sardashti, K.; Kummel, A. C.

2016-08-14

Density-functional theory simulations of CZTS, CZTSe, and CZTS{sub 0.25}Se{sub 0.75} photovoltaic compounds have been performed to investigate the stability of the CZTS{sub 0.25}Se{sub 0.75} alloy vs. decomposition into CZTS, CZTSe, and other secondary compounds. The Gibbs energy for vibrational contributions was estimated by calculating phonon spectra and thermodynamic properties at finite temperatures. It was demonstrated that the CZTS{sub 0.25}Se{sub 0.75} alloy is stabilized not by enthalpy of formation but primarily by the mixing contributions to the Gibbs energy. The Gibbs energy gains/losses for several decomposition reactions were calculated as a function of temperature with/without intermixing and vibration contributions to themore » Gibbs energy. A set of phase diagrams was built in the multidimensional space of chemical potentials at 300 K and 900 K temperatures to demonstrate alloy stability and boundary compounds at various chemical conditions. It demonstrated for CZTS{sub 0.25}Se{sub 0.75} that the chemical potentials for stability differ between typical processing temperature (∼900 K) and operating temperature (300 K). This implies that as cooling progresses, the flux/concentration of S should be increased in MBE growth to maintain the CZTS{sub 0.25}Se{sub 0.75} in a thermodynamically stable state to minimize phase decomposition.« less

Variation of Soil Aggregation along the Weathering Gradient: Comparison of Grain Size Distribution under Different Disruptive Forces.

PubMed

Wei, Yujie; Wu, Xinliang; Xia, Jinwen; Shen, Xue; Cai, Chongfa

2016-01-01

The formation and stabilization of soil aggregates play a key role in soil functions. To date, few studies have been performed on the variation of soil aggregation with increasing soil weathering degree. Here, soil aggregation and its influencing factors along the weathering gradient were investigated. Six typical zonal soils (derived from similar parent materials) were sampled from temperate to tropical regions. Grain size distribution (GSD) in aggregate fragmentation with increasing disruptive forces (air-dried, water dispersion and chemical dispersion) was determined by laser diffraction particle size analyzer. Different forms of sesquioxides were determined by selective chemical extraction and their contributions to soil aggregation were identified by multiple stepwise regression analysis. The high variability of sesquioxides in different forms appeared with increasing free oxide content (Fed and Ald) from the temperate to tropical soils. The transformation of GSD peak to small size varied with increasing disruptive forces (p<0.05). Although in different weathering degrees, zonal soils showed a similar fragmentation process. Aggregate water stability generally increased with increasing soil weathering (p<0.01), with higher stability in eluvium (A) horizon than in illuvium (B) horizon (p<0.01). Crystalline oxides and amorphous iron oxides (Feo), especially (Fed-Feo) contributed to the formation of air-dried macroaggregates and their stability against slaking (R2 = 55%, p<0.01), while fine particles (<50μm) and Feo (excluding the complex form Fep) played a positive role in the formation of water stable aggregates (R2 = 93%, p<0.01). Additionally, water stable aggregates (including stability, size distribution and specific surface area) were closely related with pH, organic matter, cation exchange capacity (CEC), bulk density (BD), and free oxides (including various forms) (p<0.05). The overall results indicate that soil aggregation conforms to aggregate hierarchy theory to some extent along the weathering gradient and different forms of sesquioxides perform their specific roles in the formation and stabilization of different size aggregates.

Variation of Soil Aggregation along the Weathering Gradient: Comparison of Grain Size Distribution under Different Disruptive Forces

PubMed Central

Wu, Xinliang; Xia, Jinwen; Shen, Xue; Cai, Chongfa

2016-01-01

The formation and stabilization of soil aggregates play a key role in soil functions. To date, few studies have been performed on the variation of soil aggregation with increasing soil weathering degree. Here, soil aggregation and its influencing factors along the weathering gradient were investigated. Six typical zonal soils (derived from similar parent materials) were sampled from temperate to tropical regions. Grain size distribution (GSD) in aggregate fragmentation with increasing disruptive forces (air-dried, water dispersion and chemical dispersion) was determined by laser diffraction particle size analyzer. Different forms of sesquioxides were determined by selective chemical extraction and their contributions to soil aggregation were identified by multiple stepwise regression analysis. The high variability of sesquioxides in different forms appeared with increasing free oxide content (Fed and Ald) from the temperate to tropical soils. The transformation of GSD peak to small size varied with increasing disruptive forces (p<0.05). Although in different weathering degrees, zonal soils showed a similar fragmentation process. Aggregate water stability generally increased with increasing soil weathering (p<0.01), with higher stability in eluvium (A) horizon than in illuvium (B) horizon (p<0.01). Crystalline oxides and amorphous iron oxides (Feo), especially (Fed-Feo) contributed to the formation of air-dried macroaggregates and their stability against slaking (R2 = 55%, p<0.01), while fine particles (<50μm) and Feo (excluding the complex form Fep) played a positive role in the formation of water stable aggregates (R2 = 93%, p<0.01). Additionally, water stable aggregates (including stability, size distribution and specific surface area) were closely related with pH, organic matter, cation exchange capacity (CEC), bulk density (BD), and free oxides (including various forms) (p<0.05). The overall results indicate that soil aggregation conforms to aggregate hierarchy theory to some extent along the weathering gradient and different forms of sesquioxides perform their specific roles in the formation and stabilization of different size aggregates. PMID:27529618

Stabilizing effect of driving and dissipation on quantum metastable states

NASA Astrophysics Data System (ADS)

Valenti, Davide; Carollo, Angelo; Spagnolo, Bernardo

2018-04-01

We investigate how the combined effects of strong Ohmic dissipation and monochromatic driving affect the stability of a quantum system with a metastable state. We find that, by increasing the coupling with the environment, the escape time makes a transition from a regime in which it is substantially controlled by the driving, displaying resonant peaks and dips, to a regime of frequency-independent escape time with a peak followed by a steep falloff. The escape time from the metastable state has a nonmonotonic behavior as a function of the thermal-bath coupling, the temperature, and the frequency of the driving. The quantum noise-enhanced stability phenomenon is observed in the investigated system.

Voltage-gated sodium channels

PubMed Central

Abdelsayed, Mena; Sokolov, Stanislav

2013-01-01

Epilepsy is a brain disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels, Nav1.1 and Nav1.2. The effects of antiepileptic drugs (AEDs) as effective therapies for epilepsy have been characterized by extensive research. Most of the classic AEDs targeting Nav share a common mechanism of action by stabilizing the channel’s fast-inactivated state. In contrast, novel AEDs, such as lacosamide, stabilize the slow-inactivated state in neuronal Nav1.1 and Nav1.7 isoforms. This paper reviews the different mechanisms by which this stabilization occurs to determine new methods for treatment. PMID:23531742

Stability measures in arid ecosystems

NASA Astrophysics Data System (ADS)

Nosshi, M. I.; Brunsell, N. A.; Koerner, S.

2015-12-01

Stability, the capacity of ecosystems to persist in the face of change, has proven its relevance as a fundamental component of ecological theory. Here, we would like to explore meaningful and quantifiable metrics to define stability, with a focus on highly variable arid and semi-arid savanna ecosystems. Recognizing the importance of a characteristic timescale to any definition of stability, our metrics will be focused scales from annual to multi-annual, capturing different aspects of stability. Our three measures of stability, in increasing order of temporal scale, are: (1) Ecosystem resistance, quantified as the degree to which the system maintains its mean state in response to a perturbation (drought), based on inter-annual variability in Normalized Difference Vegetation Index (NDVI). (2) An optimization approach, relevant to arid systems with pulse dynamics, that models vegetation structure and function based on a trade off between the ability to respond to resource availability and avoid stress. (3) Community resilience, measured as species turnover rate (β diversity). Understanding the nature of stability in structurally-diverse arid ecosystems, which are highly variable, yields theoretical insight which has practical implications.

Phytoplankton Diversity Effects on Community Biomass and Stability along Nutrient Gradients in a Eutrophic Lake

PubMed Central

Tian, Wang; Zhang, Huayong; Zhao, Lei; Zhang, Feifan; Huang, Hai

2017-01-01

The relationship between biodiversity and ecosystem functioning is a central issue in ecology, but how this relationship is affected by nutrient stress is still unknown. In this study, we analyzed the phytoplankton diversity effects on community biomass and stability along nutrient gradients in an artificial eutrophic lake. Four nutrient gradients, varying from slightly eutrophic to highly eutrophic states, were designed by adjusting the amount of polluted water that flowed into the lake. Mean phytoplankton biomass, species richness, and Shannon diversity index all showed significant differences among the four nutrient gradients. Phytoplankton community biomass was correlated with diversity (both species richness and Shannon diversity index), varying from positive to negative along the nutrient gradients. The influence of phytoplankton species richness on resource use efficiency (RUE) also changed from positive to negative along the nutrient gradients. However, the influence of phytoplankton Shannon diversity on RUE was not significant. Both phytoplankton species richness and Shannon diversity had a negative influence on community turnover (measured as community dissimilarity), i.e., a positive diversity–stability relationship. Furthermore, phytoplankton spatial stability decreased along the nutrient gradients in the lake. With increasing nutrient concentrations, the variability (standard deviation) of phytoplankton community biomass increased more rapidly than the average total biomass. Results in this study will be helpful in understanding the phytoplankton diversity effects on ecosystem functioning and how these effects are influenced by nutrient conditions in aquatic ecosystems. PMID:28117684

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method

PubMed Central

Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N.

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination. PMID:29301258

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

PubMed

Aldalbahi, Ali; Rahaman, Mostafizur; Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

Inflammatory Stimuli Increase Progesterone Receptor-A Stability and Transrepressive Activity in Myometrial Cells

PubMed Central

Peters, Gregory A.; Yi, Lijuan; Skomorovska-Prokvolit, Yelenna; Patel, Bansari; Amini, Peyvand; Tan, Huiqing

2017-01-01

The steroid hormone progesterone acting via the nuclear progesterone receptor (PR) isoforms, progesterone receptor A (PR-A) and progesterone receptor B (PR-B), is essential for the maintenance of uterine quiescence during pregnancy. Inhibition of PR signaling augments uterine contractility and induces labor. Human parturition is thought to be triggered by modulation of PR signaling in myometrial cells to induce a functional progesterone withdrawal. One mechanism for functional progesterone withdrawal is increased abundance of PR-A, which decreases progesterone responsiveness by inhibiting the transcriptional activity of PR-B. Human parturition also involves tissue-level inflammation within the myometrium. This study examined the control of PR-A abundance and transrepressive activity in myometrial cells and the role of the inflammatory stimuli in the form of interleukin-1β (IL-1β) and lipopolysaccharide (LPS) in these processes. We found that abundance of PR-A was markedly increased by progesterone and by exposure to IL-1β and LPS via posttranslational mechanisms involving increased PR-A protein stability. In contrast, progesterone decreased abundance of PR-B by increasing its rate of degradation. Together, progesterone and proinflammatory stimuli induced a PR-A–dominant state in myometrial cells similar to that observed in term laboring myometrium. IL-1β and LPS also increased the capacity for PR-A to inhibit the transcriptional activity of PR-B. Taken together, our data suggest that proinflammatory stimuli increase the steady-state levels of PR-A and its transrepressive activity in myometrial cells and support the hypothesis that tissue-level inflammation triggers parturition by inducing PR-A–mediated functional progesterone withdrawal. PMID:27886516

The Effects of a Functional Elbow Brace on Medial Joint Stability: A Case Study

PubMed Central

Pincivero, Danny M.; Rijke, Arie M.; Heinrichs, Kristinn; Perrin, David H.

1994-01-01

Medical elbow ligament sprains in athletics can be traumatic and disabling. In this case report, we outline the effect of a prototype functional elbow brace on joint stability in a female collegiate javelin thrower with an ulnar collateral ligament sprain. A valgus force to both elbows was applied using graded stress radiography (Telos GA-II/E stress device) at 0, 5, 10, and 15 kiloPascals (kPa) of pressure. The increase in gap width between the coronoid process and the medial epicondyle was measured from anteroposterior radiographs to determine medial displacement. The brace resulted in less displacement in both injured and noninjured ulnar collateral ligament; injured ulnar collateral ligament demonstrated greater displacement regardless of condition. The brace restored medial stability to the elbow joint by 49%, 38%, and 35% at 5, 10, and 15 kPa of pressure, respectively. The application of the brace may be useful in athletes with ulnar collateral ligament injuries. ImagesFig 1Fig 2 PMID:16558285

The Amino-Terminus of Vav1 Regulates TCR-Induced SLP-76 Microclusters via the Calponin Homology Domain and Non-Catalytic Surfaces within the GEF Module

PubMed Central

Sylvain, Nicholas R.; Nguyen, Ken; Bunnell, Stephen C.

2013-01-01

The guanine nucleotide exchange factor (GEF) Vav1 synergizes with the adapter SLP-76 to support T cell development and activation. Here, we demonstrate that Vav1 controls the stability and movement T cell receptor-induced SLP-76 microclusters. The SH2 domain enables the recruitment of Vav1 into SLP-76 microclusters, whereas the SH3 domains of Vav1 cooperate to enhance microcluster stability and function. Although the amino-terminus of Vav1 is essential for downstream signaling, it possesses novel scaffolding functions that are unaffected by the inactivation of the Vav1 GEF or by the constitutive GEF activation that accompanies the mutation of the regulatory tyrosine residues 142, 160, and 174. In contrast, GEF-inactivating point mutations predicted to perturb the structural integrity of the Vav1 GEF abolish these scaffolding functions. Paradoxically, the excision of catalytic Dbl-homology (DH) / pleckstrin homology (PH) cassette produces a relatively mild scaffolding defect, indicating that the L213A and L278Q point mutations antagonize scaffolding functions mediated by adjacent domains. A deletion mutant lacking the CH domain potently inhibits calcium responses, but also exhibits mild scaffolding defects. We conclude multiple GEF-independent scaffolding functions contained within the amino-terminus of Vav1 contribute to T cell activation by acting synergistically to increase the stability and functionality of SLP-76 microclusters. PMID:21386095

Functionalized Graphene Sheets As Immobilization Matrix for Fenugreek β-Amylase: Enzyme Kinetics and Stability Studies

PubMed Central

Srivastava, Garima; Singh, Kritika; Talat, Mahe; Srivastava, Onkar Nath; Kayastha, Arvind M.

2014-01-01

β-Amylase finds application in food and pharmaceutical industries. Functionalized graphene sheets were customised as a matrix for covalent immobilization of Fenugreek β-amylase using glutaraldehyde as a cross-linker. The factors affecting the process were optimized using Response Surface Methodology based Box-Behnken design of experiment which resulted in 84% immobilization efficiency. Scanning and Transmission Electron Microscopy (SEM, TEM) and Fourier Tansform Infrared (FTIR) spectroscopy were employed for the purpose of characterization of attachment of enzyme on the graphene. The enzyme kinetic studies were carried out for obtaining best catalytic performance and enhanced reusability. Optimum temperature remained unchanged, whereas optimum pH showed shift towards acidic range for immobilized enzyme. Increase in thermal stability of immobilized enzyme and non-toxic nature of functionalized graphene can be exploited for production of maltose in food and pharmaceutical industries. PMID:25412079

Salt potentiates methylamine counteraction system to offset the deleterious effects of urea on protein stability and function.

PubMed

Rahman, Safikur; Rehman, Md Tabish; Singh, Laishram R; Warepam, Marina; Ahmad, Faizan; Dar, Tanveer Ali

2015-01-01

Cellular methylamines are osmolytes (low molecular weight organic compounds) believed to offset the urea's harmful effects on the stability and function of proteins in mammalian kidney and marine invertebrates. Although urea and methylamines are found at 2:1 molar ratio in tissues, their opposing effects on protein structure and function have been questioned on several grounds including failure to counteraction or partial counteraction. Here we investigated the possible involvement of cellular salt, NaCl, in urea-methylamine counteraction on protein stability and function. We found that NaCl mediates methylamine counteracting system from no or partial counteraction to complete counteraction of urea's effect on protein stability and function. These conclusions were drawn from the systematic thermodynamic stability and functional activity measurements of lysozyme and RNase-A. Our results revealed that salts might be involved in protein interaction with charged osmolytes and hence in the urea-methylamine counteraction.

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

Fernandez, Carlos A.; Nune, Satish K.; Annapureddy, Harsha V.

Metal-organic frameworks (MOFs) have proved to be very attractive for applications including gas storage, separation, sensing and catalysis. In particular, CO2 separation from flue gas in post-combustion processes is one of the main focuses of research among the scientific community. One of the major issues that are preventing the successful commercialization of these novel materials (e.g., MgDOBDC and NiDOBDC) is their high affinity towards water that not only compromises gas sorption capacity but also the chemical stability. In this paper, we demonstrate a novel post-synthesis modification approach to modify MOFs towards increasing hydrophobic behavior and chemical stability against moisture withoutmore » compromising CO2 sorption capacity. Our approach consists of incorporating hydrophobic moieties on the external surface of the MOFs via physical adsorption. The rationale behind this concept is to increase the surface hydrophobicity in the porous materials without the need of introducing bulky functionalities inside the pore which compromises the sorption capacity toward other gases. This allows MOF interaction/sorption of CO2 molecules comparable to unmodified MOFs. We herein report preliminary results on three routinely studied MOF materials [MIL-101(Cr), MgDOBDC and NiDOBDC] demonstrating that the polymer-modified MOFs retain CO2 sorption capacity while reducing the water adsorption up to three times, respect to the un-modified materials, via an equilibrium effect. Furthermore, the water stability of the polymer-functionalized MOFs is significantly higher than the water stability of the bare material. Molecular dynamic simulations demonstrated that this equilibrium effect implies a fundamental and permanent change in the water sorption capacity of MOFs. This approach can also be employed to render moisture stability and selectivity to MOFs that find applications in gas separations, catalysis and sensing where water plays a critical role in compromising MOF performance and recyclability.« less

Introduction of a mutation in the shutter region of antithrombin (Phe77 --> Leu) increases affinity for heparin and decreases thermal stability.

PubMed

Quinsey, Noelene S; Fitton, Hazel L; Coughlin, Paul; Whisstock, James C; Dafforn, Timothy R; Carrell, Robin W; Bottomley, Stephen P; Pike, Robert N

2003-09-02

The shutter region of serpins consists of a number of highly conserved residues that are critical for both stability and function. Several variants of antithrombin with substitutions in this region are unstable and predispose the carrier to thrombosis. Although most mutations in the shutter region investigated to date are deleterious with respect to serpin stability and function, the substitution of Phe51 by Leu in alpha(1)-antitrypsin results in enhanced stability. Here, we have investigated the effects of introducing an analogous mutation into antithrombin (Phe 77 to Leu). The mutation did not affect the kinetics of interaction with proteases. Strikingly, however, the thermostability of the protein was markedly decreased, with the serpin displaying a 13 degrees C decrease in melting temperature as compared to wild-type recombinant antithrombin. Further studies revealed that in contrast to wild-type antithrombin, the mutant adopted the latent (inactive) conformation upon mild heating. Previous studies on shutter region mutations that destabilize antithrombin revealed that such variants possess enhanced affinity for both heparin pentasaccharide and full-length heparin. The N135A/F77L mutant had unchanged affinity for heparin pentasaccharide, but the affinity for full-length heparin was increased. We suggest that the Phe77Leu mutation causes conformational changes around the top of the D-helix in antithrombin, in particular, to the arginine 132 and 133 residues that may mediate additional antithrombin/heparin interactions. This paper also demonstrates that there are major differences between the shutter regions of antithrombin and alpha(1)-antitrypsin since a stabilizing mutation in antitrypsin has the converse effect in antithrombin.

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

DOE PAGES

Pramanick, A.; Dmowski, Wojciech; Egami, Takeshi; ...

2018-05-18

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomicmore » displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.« less

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

NASA Astrophysics Data System (ADS)

Pramanick, A.; Dmowski, W.; Egami, T.; Budisuharto, A. Setiadi; Weyland, F.; Novak, N.; Christianson, A. D.; Borreguero, J. M.; Abernathy, D. L.; Jørgensen, M. R. V.

2018-05-01

The formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba (Zr ,Ti )O3 . It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

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

Pramanick, A.; Dmowski, Wojciech; Egami, Takeshi

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomicmore » displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.« less

Functionalized Poly(3,4-ethylenedioxy bithiophene) Films for Tuning Electrochromic and Thermoelectric Properties.

PubMed

Hu, Yongjing; Liu, Xiaofang; Jiang, Fengxing; Zhou, Weiqiang; Liu, Congcong; Duan, Xuemin; Xu, Jingkun

2017-10-05

Conductive thiophene-based polymers have garnered great attention for use in organic electron materials such as electrochromic and thermoelectric materials. However, they suffer from poor electron transport properties and long-term stability, leading to limited development eventually. Here, we proposed a strategy of functionalized thiophene-based polymers with oligo(ethylene glycol) or alkyl side chains and synthesized a series of poly(3,4-ethylenedioxy bithiophene)s (PEDTs) to tune their electrochromic and thermoelectric properties. An alkyl group bearing electronic ability at the thiophene ring effectively achieved a large increase in the electrical conductivity with nearly invariable Seebeck coefficient, resulting in an enhancement by 1 order of magnitude for the thermoelectric power factor. Moreover, the electrochromic properties of functionalized PEDTs gained an effective improvement in the optical contrast and coloration efficiency as well as stability with multicolor changes between neutral and oxidized states. The functionalized PEDTs can be proposed as an alternative strategy to tune the electrochromic and thermoelectric properties for organic polymer materials.

Lactoferrin-Immobilized Surfaces onto Functionalized PLA Assisted by the Gamma-Rays and Nitrogen Plasma to Create Materials with Multifunctional Properties.

PubMed

Stoleru, Elena; Zaharescu, Traian; Hitruc, Elena Gabriela; Vesel, Alenka; Ioanid, Emil G; Coroaba, Adina; Safrany, Agnes; Pricope, Gina; Lungu, Maria; Schick, Christoph; Vasile, Cornelia

2016-11-23

Both cold nitrogen radiofrequency plasma and gamma irradiation have been applied to activate and functionalize the polylactic acid (PLA) surface and the subsequent lactoferrin immobilization. Modified films were comparatively characterized with respect to the procedure of activation and also with unmodified sample by water contact angle measurements, mass loss, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), and chemiluminescence measurements. All modified samples exhibit enhanced surface properties mainly those concerning biocompatibility, antimicrobial, and antioxidant properties, and furthermore, they are biodegradable and environmentally friendly. Lactoferrin deposited layer by covalent coupling using carbodiimide chemistry showed a good stability. It was found that the lactoferrin-modified PLA materials present significantly increased oxidative stability. Gamma-irradiated samples and lactoferrin-functionalized samples show higher antioxidant, antimicrobial, and cell proliferation activity than plasma-activated and lactoferrin-functionalized ones. The multifunctional materials thus obtained could find application as biomaterials or as bioactive packaging films.

Rapid disinhibition by adjustment of PV intrinsic excitability during whisker map plasticity in mouse S1.

PubMed

Gainey, Melanie A; Aman, Joseph W; Feldman, Daniel E

2018-04-20

Rapid plasticity of layer (L) 2/3 inhibitory circuits is an early step in sensory cortical map plasticity, but its cellular basis is unclear. We show that, in mice of either sex, 1 day whisker deprivation drives rapid loss of L4-evoked feedforward inhibition and more modest loss of feedforward excitation in L2/3 pyramidal (PYR) cells, increasing E-I conductance ratio. Rapid disinhibition was due to reduced L4-evoked spiking by L2/3 parvalbumin (PV) interneurons, caused by reduced PV intrinsic excitability. This included elevated PV spike threshold, associated with an increase in low-threshold, voltage activated delayed rectifier (presumed Kv1) and A-type potassium currents. Excitatory synaptic input and unitary inhibitory output of PV cells were unaffected. Functionally, the loss of feedforward inhibition and excitation were precisely coordinated in L2/3 PYR cells, so that peak feedforward synaptic depolarization remained stable. Thus, rapid plasticity of PV intrinsic excitability offsets early weakening of excitatory circuits to homeostatically stabilize synaptic potentials in PYR cells of sensory cortex. SIGNIFICANCE STATEMENT Inhibitory circuits in cerebral cortex are highly plastic, but the cellular mechanisms and functional importance of this plasticity are incompletely understood. We show that brief (1-day) sensory deprivation rapidly weakens parvalbumin (PV) inhibitory circuits by reducing the intrinsic excitability of PV neurons. This involved a rapid increase in voltage-gated potassium conductances that control near-threshold spiking excitability. Functionally, the loss of PV-mediated feedforward inhibition in L2/3 pyramidal cells was precisely balanced with the separate loss of feedforward excitation, resulting in a net homeostatic stabilization of synaptic potentials. Thus, rapid plasticity of PV intrinsic excitability implements network-level homeostasis to stabilize synaptic potentials in sensory cortex. Copyright © 2018 the authors.

Basal buffer systems for a newly glycosylated recombinant human interferon-β with biophysical stability and DoE approaches.

PubMed

Kim, Nam Ah; Song, Kyoung; Lim, Dae Gon; Hada, Shavron; Shin, Young Kee; Shin, Sangmun; Jeong, Seong Hoon

2015-10-12

The purpose of this study was to develop a basal buffer system for a biobetter version of recombinant human interferon-β 1a (rhIFN-β 1a), termed R27T, to optimize its biophysical stability. The protein was pre-screened in solution as a function of pH (2-11) using differential scanning calorimetry (DSC) and dynamic light scattering (DLS). According to the result, its experimental pI and optimal pH range were 5.8 and 3.6-4.4, respectively. Design of experiment (DoE) approach was developed as a practical tool to aid formulation studies as a function of pH (2.9-5.7), buffer (phosphate, acetate, citrate, and histidine), and buffer concentration (20 mM and 50 mM). This method employed a weight-based procedure to interpret complex data sets and to investigate critical key factors representing protein stability. The factors used were Tm, enthalpy, and relative helix contents which were obtained by DSC and Fourier Transform Infrared spectroscopy (FT-IR). Although the weights changed by three responses, objective functions from a set of experimental designs based on four buffers were highest in 20 mM acetate buffer at pH 3.6 among all 19 scenarios tested. Size exclusion chromatography (SEC) was adopted to investigate accelerated storage stability in order to optimize the pH value with susceptible stability since the low pH was not patient-compliant. Interestingly, relative helix contents and storage stability (monomer remaining) increased with pH and was the highest at pH 4.0. On the other hand, relative helix contents and thermodynamic stability decreased at pH 4.2 and 4.4, suggesting protein aggregation issues. Therefore, the optimized basal buffer system for the novel biobetter was proposed to be 20 mM acetate buffer at pH 3.8±0.2. Copyright © 2015 Elsevier B.V. All rights reserved.

Interactions Between Flavonoid-Rich Extracts and Sodium Caseinate Modulate Protein Functionality and Flavonoid Bioaccessibility in Model Food Systems.

PubMed

Elegbede, Jennifer L; Li, Min; Jones, Owen G; Campanella, Osvaldo H; Ferruzzi, Mario G

2018-05-01

With growing interest in formulating new food products with added protein and flavonoid-rich ingredients for health benefits, direct interactions between these ingredient classes becomes critical in so much as they may impact protein functionality, product quality, and flavonoids bioavailability. In this study, sodium caseinate (SCN)-based model products (foams and emulsions) were formulated with grape seed extract (GSE, rich in galloylated flavonoids) and green tea extract (GTE, rich in nongalloylated flavonoids), respectively, to assess changes in functional properties of SCN and impacts on flavonoid bioaccessibility. Experiments with pure flavonoids suggested that galloylated flavonoids reduced air-water interfacial tension of 0.01% SCN dispersions more significantly than nongalloylated flavonoids at high concentrations (>50 μg/mL). This observation was supported by changes in stability of 5% SCN foam, which showed that foam stability was increased at high levels of GSE (≥50 μg/mL, P < 0.05) but was not affected by GTE. However, flavonoid extracts had modest effects on SCN emulsion. In addition, galloylated flavonoids had higher bioaccessibility in both SCN foam and emulsion. These results suggest that SCN-flavonoid binding interactions can modulate protein functionality leading to difference in performance and flavonoid bioaccessibility of protein-based products. As information on the beneficial health effects of flavonoids expands, it is likely that usage of these ingredients in consumer foods will increase. However, the necessary levels to provide such benefits may exceed those that begin to impact functionality of the macronutrients such as proteins. Flavonoid inclusion within protein matrices may modulate protein functionality in a food system and modify critical consumer traits or delivery of these beneficial plant-derived components. The product matrices utilized in this study offer relevant model systems to evaluate how fortification with flavonoid-rich extracts allows for differing effects on formability and stability of the protein-based systems, and on bioaccessibility of fortified flavonoid extracts. © 2018 Institute of Food Technologists®.

Stability of Electrons in the Virtual Cathode Region of an IEC

NASA Astrophysics Data System (ADS)

Kim, Hyng-Jin; Miley, George; Momota, Hiromu

2003-04-01

In the Inertial Electrostatic Confinement (IEC) device, electrons are confined inside a virtual anode that in turn confines ions. Prior stability studies [1, 2] have considered systems in which one species is electrostatically confined by the other, and either or both species are out of local thermal equilibrium. In the present research, electron stability in the virtual cathode region of an ion injected IEC is being studied. The ion density in an IEC is non-uniform due to the radial electrostatic potential, and increases toward the center region. The potential near the virtual cathode is assumed to have a parabolic shape and is determined assuming that the net space charge density is constant in that region. The corresponding ion distribution function is assumed to have the form f = C [sigma] (H W) /L^0.5 and the electron response is taken to be diabatic. Then using a variational principle after linearizing the hydrodynamic equations, stability properties of the electron layer are determined. Results will be presented as a function of injected ion/electron current ratios. 1. L. Chacon and D. C. Barnes, Phys. Plasma 7, 4774 (2000). 2. D. C. Barnes, L. Chacon, and J. M. Finn, Phys. Plasmas 9, 4448 (2002).

Stability and Bifurcation Analysis of a Three-Species Food Chain Model with Delay

NASA Astrophysics Data System (ADS)

Pal, Nikhil; Samanta, Sudip; Biswas, Santanu; Alquran, Marwan; Al-Khaled, Kamel; Chattopadhyay, Joydev

In the present paper, we study the effect of gestation delay on a tri-trophic food chain model with Holling type-II functional response. The essential mathematical features of the proposed model are analyzed with the help of equilibrium analysis, stability analysis, and bifurcation theory. Considering time-delay as the bifurcation parameter, the Hopf-bifurcation analysis is carried out around the coexisting equilibrium. The direction of Hopf-bifurcation and the stability of the bifurcating periodic solutions are determined by applying the normal form theory and center manifold theorem. We observe that if the magnitude of the delay is increased, the system loses stability and shows limit cycle oscillations through Hopf-bifurcation. The system also shows the chaotic dynamics via period-doubling bifurcation for further enhancement of time-delay. Our analytical findings are illustrated through numerical simulations.

Alanine scan of core positions in ubiquitin reveals links between dynamics, stability, and function

PubMed Central

Lee, Shirley Y.; Pullen, Lester; Virgil, Daniel J.; Castañeda, Carlos A.; Abeykoon, Dulith; Bolon, Daniel N. A.; Fushman, David

2014-01-01

Mutations at solvent inaccessible core positions in proteins can impact function through many biophysical mechanisms including alterations to thermodynamic stability and protein dynamics. As these properties of proteins are difficult to investigate, the impacts of core mutations on protein function are poorly understood for most systems. Here, we determined the effects of alanine mutations at all 15 core positions in ubiquitin on function in yeast. The majority (13 of 15) of alanine substitutions supported yeast growth as the sole ubiquitin. The two null mutants (I30A and L43A) were both less stable to temperature-induced unfolding in vitro than wild-type, but were well folded at physiological temperatures. Heteronuclear NMR studies indicated that the L43A mutation reduces temperature stability while retaining a ground-state structure similar to wild-type. This structure enables L43A to bind to common ubiquitin receptors in vitro. Many of the core alanine ubiquitin mutants, including one of the null variants (I30A), exhibited an increased accumulation of high molecular weight species, suggesting that these mutants caused a defect in the processing of ubiquitin-substrate conjugates. In contrast, L43A exhibited a unique accumulation pattern with reduced levels of high molecular weight species and undetectable levels of free ubiquitin. When conjugation to other proteins was blocked, L43A ubiquitin accumulated as free ubiquitin in yeast. Based on these findings we speculate that ubiquitin's stability to unfolding may be required for efficient recycling during proteasome-mediated substrate degradation. PMID:24361330

An in silico algorithm for identifying stabilizing pockets in proteins: test case, the Y220C mutant of the p53 tumor suppressor protein

PubMed Central

Bromley, Dennis; Bauer, Matthias R.; Fersht, Alan R.; Daggett, Valerie

2016-01-01

The p53 tumor suppressor protein performs a critical role in stimulating apoptosis and cell cycle arrest in response to oncogenic stress. The function of p53 can be compromised by mutation, leading to increased risk of cancer; approximately 50% of cancers are associated with mutations in the p53 gene, the majority of which are in the core DNA-binding domain. The Y220C mutation of p53, for example, destabilizes the core domain by 4 kcal/mol, leading to rapid denaturation and aggregation. The associated loss of tumor suppressor functionality is associated with approximately 75 000 new cancer cases every year. Destabilized p53 mutants can be ‘rescued’ and their function restored; binding of a small molecule into a pocket on the surface of mutant p53 can stabilize its wild-type structure and restore its function. Here, we describe an in silico algorithm for identifying potential rescue pockets, including the algorithm's integration with the Dynameomics molecular dynamics data warehouse and the DIVE visual analytics engine. We discuss the results of the application of the method to the Y220C p53 mutant, entailing finding a putative rescue pocket through MD simulations followed by an in silico search for stabilizing ligands that dock into the putative rescue pocket. The top three compounds from this search were tested experimentally and one of them bound in the pocket, as shown by nuclear magnetic resonance, and weakly stabilized the mutant. PMID:27503952

Viscoelastic and Functional Properties of Cod-Bone Gelatin in the Presence of Xylitol and Stevioside

NASA Astrophysics Data System (ADS)

Nian, Linyu; Cao, Ailing; Wang, Jing; Tian, Hongyu; Liu, Yongguo; Gong, Lingxiao; Cai, Luyun; Wang, Yuhao

2018-05-01

The physical, rheological, structural and functional properties of cod bone gelatin (CBG) with various concentrations (0, 2, 4, 6, 10 and 15%) of low-calorie sweeteners (xylitol (X) and stevioside (S)) to form gels were investigated. The gel strength of CBGX increased with increased xylitol due presumably to hydrogen bonds between xylitol and gelatin, but with CBGS the highest gel strength occurred when S concentration was 4%. Viscosity of CBGS samples were higher than CBGX due to S’s high molecular mass. The viscoelasticity (G' and G″), foaming capacity and fat binding capacity of CBGX were higher while foam stability was lower. The emulsion activity and emulsion stability of CBGX were a little lower than CBGS at the same concentration. The structure of X is linear making it easier to form a dense three-dimensional network structure, while the complex cyclic structure of S had more difficulty forming a network structure with cod bone gelatin. Therefore, X may be a better choice for sweetening gelatin gels.

Viscoelastic and Functional Properties of Cod-Bone Gelatin in the Presence of Xylitol and Stevioside.

PubMed

Nian, Linyu; Cao, Ailing; Wang, Jing; Tian, Hongyu; Liu, Yongguo; Gong, Lingxiao; Cai, Luyun; Wang, Yuhao

2018-01-01

The physical, rheological, structural and functional properties of cod bone gelatin (CBG) with various concentrations (0, 2, 4, 6, 10, and 15%) of low-calorie sweeteners [xylitol (X) and stevioside (S)] to form gels were investigated. The gel strength of CBGX increased with increased xylitol due presumably to hydrogen bonds between xylitol and gelatin, but with CBGS the highest gel strength occurred when S concentration was 4%. Viscosity of CBGS samples were higher than CBGX due to S's high molecular mass. The viscoelasticity (G' and G''), foaming capacity and fat binding capacity of CBGX were higher while foam stability was lower. The emulsion activity and emulsion stability of CBGX were a little lower than CBGS at the same concentration. The structure of X is linear making it easier to form a dense three-dimensional network structure, while the complex cyclic structure of S had more difficulty forming a network structure with cod bone gelatin. Therefore, X may be a better choice for sweetening gelatin gels.

Parvalbumin-expressing interneurons coordinate hippocampal network dynamics required for memory consolidation

NASA Astrophysics Data System (ADS)

Ognjanovski, Nicolette; Schaeffer, Samantha; Wu, Jiaxing; Mofakham, Sima; Maruyama, Daniel; Zochowski, Michal; Aton, Sara J.

2017-04-01

Activity in hippocampal area CA1 is essential for consolidating episodic memories, but it is unclear how CA1 activity patterns drive memory formation. We find that in the hours following single-trial contextual fear conditioning (CFC), fast-spiking interneurons (which typically express parvalbumin (PV)) show greater firing coherence with CA1 network oscillations. Post-CFC inhibition of PV+ interneurons blocks fear memory consolidation. This effect is associated with loss of two network changes associated with normal consolidation: (1) augmented sleep-associated delta (0.5-4 Hz), theta (4-12 Hz) and ripple (150-250 Hz) oscillations; and (2) stabilization of CA1 neurons' functional connectivity patterns. Rhythmic activation of PV+ interneurons increases CA1 network coherence and leads to a sustained increase in the strength and stability of functional connections between neurons. Our results suggest that immediately following learning, PV+ interneurons drive CA1 oscillations and reactivation of CA1 ensembles, which directly promotes network plasticity and long-term memory formation.

Enhanced mucosal immune responses against tetanus toxoid using novel delivery system comprised of chitosan-functionalized gold nanoparticles and botanical adjuvant: characterization, immunogenicity, and stability assessment.

PubMed

Barhate, Ganesh; Gautam, Manish; Gairola, Sunil; Jadhav, Suresh; Pokharkar, Varsha

2014-11-01

Approaches based on combined use of delivery systems and adjuvants are being favored to maximize efficient mucosal delivery of antigens. Here, we describe a novel delivery system comprised of chitosan-functionalized gold nanoparticles (CsAuNPs) and saponin-containing botanical adjuvant; Asparagus racemosus extract (ARE) for oral delivery of tetanus toxoid (TT). A significant increase in TT-specific IgG (34.53-fold) and IgA (43.75-fold) was observed when TT-CsAuNPs were formulated with ARE (TT-ARE-CsAuNPs). The local IgA immune responses for TT also showed a significant increase (106.5-fold in intestine washes and 99.74-fold in feces) with ARE-based formulations as compared with plain TT group. No effect of ARE was observed on size, charge, and loading properties of CsAuNPs. Additionally, no effect of ARE and CsAuNPs was observed on antigenicity and secondary structure of TT as determined by fluorescence, circular dichroism, and Fourier transform infrared spectroscopy. The stability studies demonstrated excellent stability profile of formulation at recommended storage conditions. The study establishes the possible role of immunomodulatory adjuvants in particulate delivery systems for mucosal delivery of vaccines. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Linear stability analysis and nonlinear simulation of the channeling effect on viscous fingering instability in miscible displacement

NASA Astrophysics Data System (ADS)

Shahnazari, M. R.; Maleka Ashtiani, I.; Saberi, A.

2018-03-01

In this paper, the effect of channeling on viscous fingering instability of miscible displacement in porous media is studied. In fact, channeling is introduced as a solution to stabilize the viscous fingering instability. In this solution, narrow channels were placed next to the walls, and by considering an exponential function to model the channeling effect, a heterogeneous media is assumed. In linear stability analysis, the governing equations are transferred to Fourier space, and by introducing a novel numerical method, the transferred equations are analyzed. The growth rate based on the wave number diagram has been drawn up in three sections of the medium. It is found that the flow becomes more stable at the center and unstable along the walls when the permeability ratio is increased. Also when the permeability ratio is approximately equal to one, the channeling has no significant effect. In nonlinear simulations, by using stream function and vortices, new equations have been rewritten and it is shown that channeling has a profound effect on the growth of the fingers and mechanisms. In addition to the superposition of velocity vectors and concentration contours, the development of instability is investigated using the mixing length and sweep efficiency diagram. The results show that although channeling reduces instability, it increases the displacement process time.

Impact of treatment with saxagliptin on glycaemic stability and β-cell function in the SAVOR-TIMI 53 study.

PubMed

Leibowitz, G; Cahn, A; Bhatt, D L; Hirshberg, B; Mosenzon, O; Wei, C; Jermendy, G; Sheu, W H-H; Sendon, J L; Im, K; Braunwald, E; Scirica, B M; Raz, I

2015-05-01

To study the effects of saxagliptin, a dipeptidyl peptidase-4 inhibitor, on glycaemic stability and β-cell function in the SAVOR-TIMI 53 trial. We randomized 16,492 patients with type 2 diabetes (T2D) to saxagliptin or placebo, added to current antidiabetic medications, and followed them for a median of 2.1 years. Glycaemic instability was defined by: (i) a glycated haemoglobin (HbA1c) increase of ≥ 0.5% post-randomization; (ii) the initiation of new antidiabetic medications for ≥ 3 months; or (iii) an increase in dose of oral antidiabetic medication or ≥ 25% increase in insulin dose for ≥ 3 months. β-cell function was assessed according to fasting homeostatic model 2 assessment of β-cell function (HOMA-2β) values at baseline and at year 2 in patients not treated with insulin. Compared with placebo, participants treated with saxagliptin had a reduction in the development of glycaemic instability (hazard ratio 0.71; 95% confidence interval 0.68-0.74; p < 0.0001). In participants treated with saxagliptin compared with placebo, the occurrence of an HbA1c increase of ≥ 0.5% was reduced by 35.2%; initiation of insulin was decreased by 31.7% and the increases in doses of an oral antidiabetic drug or insulin were reduced by 19.5 and 23.5%, respectively (all p < 0.0001). At 2 years, HOMA-2β values decreased by 4.9% in participants treated with placebo, compared with an increase of 1.1% in those treated with saxagliptin (p < 0.0001). Saxagliptin improved glycaemia and prevented the reduction in HOMA-2β values. Saxagliptin may reduce the usual decline in β-cell function in T2D, thereby slowing diabetes progression. © 2015 John Wiley & Sons Ltd.

Formulation and process considerations affecting the stability of solid dosage forms formulated with methacrylate copolymers.

PubMed

Petereit, H U; Weisbrod, W

1999-01-01

General considerations concerning the stability of coated dosage forms are discussed, in order to avoid predictable interactions which may cause long-term stability problems. As polymers themselves maintain a high chemical stability and a low reactivity, instability phenomena mainly have to be explained by interactions of low molecular weight substances or physical changes. Possible interactions of functional groups can be predicted easily and insulating subcoates are proper countermeasures. Impurities, remaining in the polymeric material from the manufacturing process, may accelerate the hydrolysis of sensitive drugs. Instabilities of coated dosage forms are mainly based on physical interactions, caused by improper formulations of coating suspensions (i.e. plasticizers or pigments) or the film coating process. Residual moisture or solvents, probably enclosed in the core and migrating over time, may increase the permeability of coatings, due to plasticizing effects. The functionality of coatings from aqueous dispersions is linked to coalescence of latex particles. Thus any incomplete film formation, caused by too high or too low coating temperatures, may result in high permeable coatings. During storage, preferably under stress conditions this process will continue and thus change the release profile. Therefore bed temperatures of 10-20 degrees C above MFT must ensure the formation of homogeneous polymer layers during the coating process. Stability test procedures and packaging materials also need to be adapted to the physicochemical properties of the dosage form, in order to get meaningful results in stability tests.

Stability of urea in solution and pharmaceutical preparations.

PubMed

Panyachariwat, Nattakan; Steckel, Hartwig

2014-01-01

The stability of urea in solution and pharmaceutical preparations was analyzed as a function of temperature (25°-60°C), pH (3.11-9.67), and initial urea concentration (2.5%-20%). This study was undertaken to (i) obtain more extensive, quantitative information relative to the degradation of urea in both aqueous and non-aqueous solutions and in pharmaceutical preparations, and (ii) test the effects of initial urea concentration, pH, buffer, and temperature values on urea degradation. The stability analysis shows that urea is more stable at the pH range of 4-8 and the stability of urea decreases by increase in temperature for all pH values. Within the experimental range of temperature and initial urea concentration values, the lowest urea degradation was found with lactate buffer pH 6.0. The urea decomposition rate in solution and pharmaceutical preparations shows the dependence of the initial urea concentrations. At higher initial urea concentrations, the rate of degradation is a decreasing function with time. This suggests that the reverse reaction is a factor in the degradation of concentrated urea solution. For non-aqueous solvents, isopropanol showed the best effort in retarding the decomposition of urea. Since the losses in urea is directly influenced by its stability at a given temperature and pH, the stability analysis of urea by the proposed model can be used to prevent the loss and optimize the operating condition for urea-containing pharmaceutical preparations.

Effect of the use of carprofen in dogs undergoing intense rehabilitation after lateral fabellar suture stabilization.

PubMed

Gordon-Evans, Wanda J; Dunning, Diane; Johnson, Ann L; Knap, Kim E

2011-07-01

To determine whether carprofen, a commercially available NSAID, would decrease perceived exertion and signs of pain in dogs and therefore increase muscle mass and hind limb function without decreasing range of motion after lateral fabellar suture stabilization. Randomized, blinded, controlled clinical trial. 35 dogs with cranial cruciate ligament rupture and lateral fabellar suture stabilization followed by rehabilitation. All dogs underwent surgical stabilization of cranial cruciate ligament rupture by placement of a lateral fabellar suture. Dogs received carprofen (2.2 mg/kg [1 mg/lb], PO, q 12 h) for the first 7 days after surgery and underwent concentrated rehabilitation exercises during weeks 3, 5, and 7 after surgery. Eighteen dogs also received carprofen (2.2 mg/kg, PO, q 12 h) during the weeks of concentrated rehabilitation. Outcomes were measured by a single investigator, who was blinded to group assignments, using pressure platform gait analysis, goniometry, thigh circumference, and mean workout speed at a consistent level of exertion. There were no differences between the 2 groups in ground reaction forces, thigh circumference, or exertion (mean workout speed) over time or at any individual time point. However, both groups improved significantly over time for all outcome measures. Providing carprofen to dogs during concentrated rehabilitation after lateral fabellar suture stabilization did not improve hind limb function, range of motion, or thigh circumference, nor did it decrease perceived exertion, compared with control dogs. Carprofen was not a compulsory component of a physical therapy regimen after lateral fabellar suture stabilization.

Adipose-Derived Cell Construct Stabilizes Heart Function and Increases Microvascular Perfusion in an Established Infarct

PubMed Central

Nguyen, Quang T.; Touroo, Jeremy S.; Aird, Allison L.; Chang, Raymond C.; Ng, Chin K.; Hoying, James B.; Williams, Stuart K.

2013-01-01

We have previously shown that myocardial infarction (MI) immediately treated with an epicardial construct containing stromal vascular fraction (SVF) from adipose tissue preserved microvascular function and left ventricle contractile mechanisms. In order to evaluate a more clinically relevant condition, we investigated the cardiac recovery potential of an SVF construct implanted onto an established infarct. SVF cells were isolated from rat adipose tissue, plated on Vicryl, and cultured for 14 days. Fischer-344 rats were separated into MI groups: (a) 6-week MI (MI), (b) 6-week MI treated with an SVF construct at 2 weeks (MI SVF), (c) 6-week MI with Vicryl construct at 2 weeks (MI Vicryl), and (d) MI 2wk (time point of intervention). Emax, an indicator of systolic performance and contractile function, was lower in the MI and MI Vicryl versus MI SVF. Positron emission tomography imaging (18F-fluorodeoxyglucose) revealed a decreased percentage of relative infarct volume in the MI SVF versus MI and MI Vicryl. Total vessel count and percentage of perfusion assessed via immunohistochemistry were both increased in the infarct region of MI SVF versus MI and MI Vicryl. Overall cardiac function, percentage of relative infarct, and percentage of perfusion were similar between MI SVF and MI 2wk; however, total vessel count increased after SVF treatment. These data suggest that SVF treatment of an established infarct stabilizes the heart at the time point of intervention by preventing a worsening of cardiac performance and infarcted volume, and is associated with increased microvessel perfusion in the area of established infarct. PMID:24106337

Molecular simulation study of cavity-generated instabilities in the superheated Lennard-Jones liquid

NASA Astrophysics Data System (ADS)

Torabi, Korosh; Corti, David S.

2010-10-01

Previous equilibrium-based density-functional theory (DFT) analyses of cavity formation in the pure component superheated Lennard-Jones (LJ) liquid [S. Punnathanam and D. S. Corti, J. Chem. Phys. 119, 10224 (2003); M. J. Uline and D. S. Corti, Phys. Rev. Lett. 99, 076102 (2007)] revealed that a thermodynamic limit of stability appears in which no liquidlike density profile can develop for cavity radii greater than some critical size (being a function of temperature and bulk density). The existence of these stability limits was also verified using isothermal-isobaric Monte Carlo (MC) simulations. To test the possible relevance of these limits of stability to a dynamically evolving system, one that may be important for homogeneous bubble nucleation, we perform isothermal-isobaric molecular dynamics (MD) simulations in which cavities of different sizes are placed within the superheated LJ liquid. When the impermeable boundary utilized to generate a cavity is removed, the MD simulations show that the cavity collapses and the overall density of the system remains liquidlike, i.e., the system is stable, when the initial cavity radius is below some certain value. On the other hand, when the initial radius is large enough, the cavity expands and the overall density of the system rapidly decreases toward vaporlike densities, i.e., the system is unstable. Unlike the DFT predictions, however, the transition between stability and instability is not infinitely sharp. The fraction of initial configurations that generate an instability (or a phase separation) increases from zero to unity as the initial cavity radius increases over a relatively narrow range of values, which spans the predicted stability limit obtained from equilibrium MC simulations. The simulation results presented here provide initial evidence that the equilibrium-based stability limits predicted in the previous DFT and MC simulation studies may play some role, yet to be fully determined, in the homogeneous nucleation and growth of embryos within metastable fluids.

THE EFFICACY OF AN EIGHT-WEEK CORE STABILIZATION PROGRAM ON CORE MUSCLE FUNCTION AND ENDURANCE: A RANDOMIZED TRIAL

PubMed Central

Sperier, Aubrey D.; Hopkins, Colleen F.; Griffiths, Bridgette D.; Principe, Molly F.; Schnall, Barri L.; Bell, Johanna C.; Koppenhaver, Shane L.

2016-01-01

ABSTRACT Background Body armor is credited with increased survival rates in soldiers but the additional axial load may negatively impact the biomechanics of the spine resulting in low back pain. Multiple studies have found that lumbar stabilization programs are superior to generalized programs for patients with chronic low back pain. It is not known if such programs produce objective changes in trunk muscle function with wear of body armor. Hypothesis/Purpose An eight-week core stability exercise program would result in a larger improvement in physical endurance and abdominal muscle thickness than a control intervention. The purpose of this study was to assess the effectiveness of an eight-week core stability exercise program on physical endurance and abdominal muscle thickness with and without wear of body armor. Study Design Randomized controlled trial Methods Participants (N = 33) were randomized into either the core strengthening exercise group or the control group. Testing included ultrasound imaging of abdominal muscle thickness in hook-lying and standing with and without body armor and timed measures of endurance. Results There were statistically significant group by time interactions for transversus abdominis muscle contraction thickness during standing, both with (p = 0.018) and without body armor (p = 0.038). The main effect for hold-time during the horizontal side-support (p = 0.016) indicated improvement over time regardless of group. There was a significant group by time interaction (p = 0.014) for horizontal side-support hold-time when compliance with the exercise protocol was set at 85%, indicating more improvement in the core stabilization group than in the control group. Conclusion Performing an eight-week core stabilization exercise program significantly improves transversus abdominis muscle activation in standing and standing with body armor. When compliant with the exercises, such a program may increase trunk strength and muscle endurance. Levels of Evidence Therapy, Level 2b PMID:27525175

PHYSICAL AND CHEMICAL STABILITY ANALYSIS OF COSMETIC MULTI- PLE EMULSIONS LOADED WITH ASCORBYL PALMITATE AND SODIUM ASCORBYL PHOSPHATE SALTS.

PubMed

Khan, Hira; Akhtar, Naveed; Ali, Atif; Khan, Haji M Shoaib; Sohail, Muhammad; Naeem, Muhammad; Nawaz, Zarqa

2016-09-01

Stability of hydrophilic and lipophilic vitamin C derivatives for quenching synergistic antioxidant activities and to treat oxidative related diseases is a major issue. This study was aimed to encapsulate hydrophilic and lipophilic vitamin C derivatives (ascorbyl palmitate and sodium ascorbyl phosphate) as functional ingredients in a newly formulated multiple emulsion of the W//W type to attain the synergistic antioxidant effects and the resultant system's long term physical and chemical stability. Several multiple emulsions using the same concentration of emulsifiers but different concentrations of ascorbyl palmitate and sodium ascorbyl phosphate were developed. Three finally selected multiple emulsions (ME₁, ME₂ and ME₃) were evaluated for physical stability in terms of rheology, microscopy, conductivity, pH, and organoleptic characteristics under different storage conditions for 3 months. Chemical stability was determined by HPLC on Sykam GmbH HPLC system (Germany), equipped with a variable UV detector. Results showed that at accelerated storage conditions all the three multiple emulsions had shear thinning behavior of varying shear stress with no influence of location of functional ingredients in a carrier system. Conductivity values increased and pH values remained within the skin pH range for 3 months. Microscopic analysis showed an increase in globule size with the passage of time, especially at higher temperatures while decreased at low temperatures. Centrifugation test did not cause phase separation till the 45th day, but little effects after 2 months. Chemical stability analysis by HPLC at the end of 3 months showed that ascorbyl palmitate and sodium ascorbyl phosphate were almost stable in all multiple emulsions with no influence of their location in a carrier system. Multiple emulsions were found a stable carrier for hydrophilic and lipophilic vitamin C derivatives to enhance their desired effects. Considering that many topical formulations contain simple vitamin C it is suggested that present study may contribute to the development of more stable formulations with a combination of vitamin C derivatives to enhance their cosmetic benefits.

Functional modulation of a protein folding landscape via side-chain distortion

PubMed Central

Kelch, Brian A.; Salimi, Neema L.; Agard, David A.

2012-01-01

Ultrahigh-resolution (< 1.0 Å) structures have revealed unprecedented and unexpected details of molecular geometry, such as the deformation of aromatic rings from planarity. However, the functional utility of such energetically costly strain is unknown. The 0.83 Å structure of α-lytic protease (αLP) indicated that residues surrounding a conserved Phe side-chain dictate a rotamer which results in a ∼6° distortion along the side-chain, estimated to cost 4 kcal/mol. By contrast, in the closely related protease Streptomyces griseus Protease B (SGPB), the equivalent Phe adopts a different rotamer and is undistorted. Here, we report that the αLP Phe side-chain distortion is both functional and conserved in proteases with large pro regions. Sequence analysis of the αLP serine protease family reveals a bifurcation separating those sequences expected to induce distortion and those that would not, which correlates with the extent of kinetic stability. Structural and folding kinetics analyses of family members suggest that distortion of this side-chain plays a role in increasing kinetic stability within the αLP family members that use a large Pro region. Additionally, structural and kinetic folding studies of mutants demonstrate that strain alters the folding free energy landscape by destabilizing the transition state (TS) relative to the native state (N). Although side-chain distortion comes at a cost of foldability, it suppresses the rate of unfolding, thereby enhancing kinetic stability and increasing protein longevity under harsh extracellular conditions. This ability of a structural distortion to enhance function is unlikely to be unique to αLP family members and may be relevant in other proteins exhibiting side-chain distortions. PMID:22635267

Investigating the effect of gallium curcumin and gallium diacetylcurcumin complexes on the structure, function and oxidative stability of the peroxidase enzyme and their anticancer and antibacterial activities.

PubMed

Jahangoshaei, Parisa; Hassani, Leila; Mohammadi, Fakhrossadat; Hamidi, Akram; Mohammadi, Khosro

2015-10-01

Curcumin has a wide spectrum of biological and pharmacological activities including anti-inflammatory, antioxidant, antiproliferative, antimicrobial and anticancer activities. Complexation of curcumin with metals has gained attention in recent years for improvement of its stability. In this study, the effect of gallium curcumin and gallium diacetylcurcumin on the structure, function and oxidative stability of horseradish peroxidase (HRP) enzyme were evaluated by spectroscopic techniques. In addition to the enzymatic investigation, the cytotoxic effect of the complexes was assessed on bladder, MCF-7 breast cancer and LNCaP prostate carcinoma cell lines by MTT assay. Furthermore, antibacterial activity of the complexes against S. aureus and E. coli was explored by dilution test method. The results showed that the complexes improve activity of HRP and also increase its tolerance against the oxidative condition. After addition of the complexes, affinity of HRP for hydrogen peroxide substrate decreases, while the affinity increases for phenol substrate. Circular dichroism, intrinsic and synchronous fluorescence spectra showed that the enzyme structure around the catalytic heme group becomes less compact and also the distance between the heme group and tryptophan residues increases due to binding of the complexes to HRP. On the whole, it can be concluded that the change in the enzyme structure upon binding to the gallium curcumin and gallium diacetylcurcumin complexes results in an increase in the antioxidant efficiency and activity of the peroxidise enzyme. The result of anticancer and antibacterial activities suggested that the complexes exhibit the potential for cancer treatment, but they have no significant antibacterial activity.

Increased actin polymerization and stabilization interferes with neuronal function and survival in the AMPKγ mutant Loechrig.

PubMed

Cook, Mandy; Bolkan, Bonnie J; Kretzschmar, Doris

2014-01-01

loechrig (loe) mutant flies are characterized by progressive neuronal degeneration, behavioral deficits, and early death. The mutation is due to a P-element insertion in the gene for the γ-subunit of the trimeric AMP-activated protein kinase (AMPK) complex, whereby the insertion affects only one of several alternative transcripts encoding a unique neuronal isoform. AMPK is a cellular energy sensor that regulates a plethora of signaling pathways, including cholesterol and isoprenoid synthesis via its downstream target hydroxy-methylglutaryl (HMG)-CoA reductase. We recently showed that loe interferes with isoprenoid synthesis and increases the prenylation and thereby activation of RhoA. During development, RhoA plays an important role in neuronal outgrowth by activating a signaling cascade that regulates actin dynamics. Here we show that the effect of loe/AMPKγ on RhoA prenylation leads to a hyperactivation of this signaling pathway, causing increased phosphorylation of the actin depolymerizating factor cofilin and accumulation of filamentous actin. Furthermore, our results show that the resulting cytoskeletal changes in loe interfere with neuronal growth and disrupt axonal integrity. Surprisingly, these phenotypes were enhanced by expressing the Slingshot (SSH) phosphatase, which during development promotes actin depolymerization by dephosphorylating cofilin. However, our studies suggest that in the adult SSH promotes actin polymerization, supporting in vitro studies using human SSH1 that suggested that SSH can also stabilize and bundle filamentous actin. Together with the observed increase in SSH levels in the loe mutant, our experiments suggest that in mature neurons SSH may function as a stabilization factor for filamentous actin instead of promoting actin depolymerization.

Calculation of the Relative Chemical Stabilities of Proteins as a Function of Temperature and Redox Chemistry in a Hot Spring

PubMed Central

Dick, Jeffrey M.; Shock, Everett L.

2011-01-01

Uncovering the chemical and physical links between natural environments and microbial communities is becoming increasingly amenable owing to geochemical observations and metagenomic sequencing. At the hot spring known as Bison Pool in Yellowstone National Park, the cooling of the water in the outflow channel is associated with an increase in oxidation potential estimated from multiple field-based measurements. Representative groups of proteins whose sequences were derived from metagenomic data also exhibit an increase in average oxidation state of carbon in the protein molecules with distance from the hot-spring source. The energetic requirements of reactions to form selected proteins used in the model were computed using amino-acid group additivity for the standard molal thermodynamic properties of the proteins, and the relative chemical stabilities of the proteins were investigated by varying temperature, pH and oxidation state, expressed as activity of dissolved hydrogen. The relative stabilities of the proteins were found to track the locations of the sampling sites when the calculations included a function for hydrogen activity that increases with temperature and is higher, or more reducing, than values consistent with measurements of dissolved oxygen, sulfide and oxidation-reduction potential in the field. These findings imply that spatial patterns in the amino acid compositions of proteins can be linked, through energetics of overall chemical reactions representing the formation of the proteins, to the environmental conditions at this hot spring, even if microbial cells maintain considerably different internal conditions. Further applications of the thermodynamic calculations are possible for other natural microbial ecosystems. PMID:21853048

Sensorimotor Functional and Structural Networks after Intracerebral Stem Cell Grafts in the Ischemic Mouse Brain.

PubMed

Green, Claudia; Minassian, Anuka; Vogel, Stefanie; Diedenhofen, Michael; Beyrau, Andreas; Wiedermann, Dirk; Hoehn, Mathias

2018-02-14

Past investigations on stem cell-mediated recovery after stroke have limited their focus on the extent and morphological development of the ischemic lesion itself over time or on the integration capacity of the stem cell graft ex vivo However, an assessment of the long-term functional and structural improvement in vivo is essential to reliably quantify the regenerative capacity of cell implantation after stroke. We induced ischemic stroke in nude mice and implanted human neural stem cells (H9 derived) into the ipsilateral cortex in the acute phase. Functional and structural connectivity changes of the sensorimotor network were noninvasively monitored using magnetic resonance imaging for 3 months after stem cell implantation. A sharp decrease of the functional sensorimotor network extended even to the contralateral hemisphere, persisting for the whole 12 weeks of observation. In mice with stem cell implantation, functional networks were stabilized early on, pointing to a paracrine effect as an early supportive mechanism of the graft. This stabilization required the persistent vitality of the stem cells, monitored by bioluminescence imaging. Thus, we also observed deterioration of the early network stabilization upon vitality loss of the graft after a few weeks. Structural connectivity analysis showed fiber-density increases between the cortex and white matter regions occurring predominantly on the ischemic hemisphere. These fiber-density changes were nearly the same for both study groups. This motivated us to hypothesize that the stem cells can influence, via early paracrine effect, the functional networks, while observed structural changes are mainly stimulated by the ischemic event. SIGNIFICANCE STATEMENT In recent years, research on strokes has made a shift away from a focus on immediate ischemic effects and towards an emphasis on the long-range effects of the lesion on the whole brain. Outcome improvements in stem cell therapies also require the understanding of their influence on the whole-brain networks. Here, we have longitudinally and noninvasively monitored the structural and functional network alterations in the mouse model of focal cerebral ischemia. Structural changes of fiber-density increases are stimulated in the endogenous tissue without further modulation by the stem cells, while functional networks are stabilized by the stem cells via a paracrine effect. These results will help decipher the underlying networks of brain plasticity in response to cerebral lesions and offer clues to unravelling the mystery of how stem cells mediate regeneration. Copyright © 2018 the authors 0270-6474/18/381648-14$15.00/0.

New use for CETSA: monitoring innate immune receptor stability via post-translational modification by OGT.

PubMed

Drake, Walter R; Hou, Ching-Wen; Zachara, Natasha E; Grimes, Catherine Leimkuhler

2018-06-01

O-GlcNAcylation is a dynamic and functionally diverse post-translational modification shown to affect thousands of proteins, including the innate immune receptor nucleotide-binding oligomerization domain-containing protein 2 (Nod2). Mutations of Nod2 (R702W, G908R and 1007 fs) are associated with Crohn's disease and have lower stabilities compared to wild type. Cycloheximide (CHX)-chase half-life assays have been used to show that O-GlcNAcylation increases the stability and response of both wild type and Crohn's variant Nod2, R702W. A more rapid method to assess stability afforded by post-translational modifications is necessary to fully comprehend the correlation between NLR stability and O-GlcNAcylation. Here, a recently developed cellular thermal shift assay (CETSA) that is typically used to demonstrate protein-ligand binding was adapted to detect shifts in protein stabilization upon increasing O-GlcNAcylation levels in Nod2. This assay was used as a method to predict if other Crohn's associated Nod2 variants were O-GlcNAcylated, and also identified the modification on another NLR, Nod1. Classical immunoprecipitations and NF-κB transcriptional assays were used to confirm the presence and effect of this modification on these proteins. The results presented here demonstrate that CETSA is a convenient method that can be used to detect the stability effect of O-GlcNAcylation on O-GlcNAc-transferase (OGT) client proteins and will be a powerful tool in studying post-translational modification.

Relationships between mechanical joint stability and somatosensory function in individuals with chronic ankle instability.

PubMed

Kirby, Jessica L; Houston, Megan N; Gabriner, Michael L; Hoch, Matthew C

2016-08-01

Individuals with chronic ankle instability (CAI) have demonstrated alterations in ankle mechanics and deficits in sensory function. However, relationships between mechanical stability and somatosensory function have not been examined, nor have those between somatosensory function and injury history characteristics. Therefore, the objective of this study was to examine relationships between (1) somatosensory function and mechanical stability and (2) somatosensory function and injury history characteristics. Forty adults with CAI volunteered to participate. In a single testing session, participants completed mechanical and sensory assessments in a counterbalanced order. Dependent variables included anterior/posterior displacement (mm), inversion/eversion rotation (°), SWM index values, JPS absolute error (°), number of previous ankle sprains, and number of "giving way" episodes in the previous 3 months. Spearman's Rho correlations examined the relationships between somatosensory function and (1) mechanical stability and (2) injury history characteristics (p<0.05). No significant correlations were identified between any variables (p>0.11), and all r-values were considered weak. These results revealed somatosensory function was not significantly correlated to mechanical stability or injury history characteristics. This indicates peripheral sensory impairments associated with CAI are likely caused by factors other than mechanical stability and injury history characteristics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of tautomerism on Au-6-mercaptopurine nanocluster stability

NASA Astrophysics Data System (ADS)

Rashidpour, Neda; Kashid, Vikas; Shah, Vaishali

2013-02-01

We have investigated the stability of conjugated nanoparticles of Au-6-Mercaptopurine (6-MP) using ab initio density functional theory. We have studied the conjugation of the 6 tautomers of 6-MP via the different atomic sites with the gold nanoparticles. Our results show that the least stable tautomer has the strongest adsorption with the Au nanoparticles whereas the most stable tautomer has the weakest adsorption. We will discuss our results to explain the experimentally observed increased plasma half life time of the conjugated drug in vitro.

Combustion Stability Assessments of the Black Brant Solid Rocket Motor

NASA Technical Reports Server (NTRS)

Fischbach, Sean

2014-01-01

The Black Brant variation of the Standard Brant developed in the 1960's has been a workhorse motor of the NASA Sounding Rocket Project Office (SRPO) since the 1970's. In March 2012, the Black Brant Mk1 used on mission 36.277 experienced combustion instability during a flight at White Sands Missile Range, the third event in the last four years, the first occurring in November, 2009, the second in April 2010. After the 2010 event the program has been increasing the motor's throat diameter post-delivery with the goal of lowering the chamber pressure and increasing the margin against combustion instability. During the most recent combustion instability event, the vibrations exceeded the qualification levels for the Flight Termination System. The present study utilizes data generated from T-burner testing of multiple Black Brant propellants at the Naval Air Warfare Center at China Lake, to improve the combustion stability predictions for the Black Brant Mk1 and to generate new predictions for the Mk2. Three unique one dimensional (1-D) stability models were generated, representing distinct Black Brant flights, two of which experienced instabilities. The individual models allowed for comparison of stability characteristics between various nozzle configurations. A long standing "rule of thumb" states that increased stability margin is gained by increasing the throat diameter. In contradiction to this experience based rule, the analysis shows that little or no margin is gained from a larger throat diameter. The present analysis demonstrates competing effects resulting from an increased throat diameter accompanying a large response function. As is expected, more acoustic energy was expelled through the nozzle, but conversely more acoustic energy was generated due to larger gas velocities near the propellant surfaces.

Meniscal material properties are minimally affected by matrix stabilization using glutaraldehyde and glycation with ribose.

PubMed

Hunter, Shawn A; Noyes, Frank R; Haridas, Balakrishna; Levy, Martin S; Butler, David L

2005-05-01

Knee meniscus replacement holds promise, but current allografts are susceptible to biodegradation. Matrix stabilization with glutaraldehyde, a crosslinking agent used clinically to fabricate cardiovascular bioprostheses, or with glycation, a process of crosslinking collagen with sugars such as ribose, is a potential means of rendering tissue resistant to such degradation. However, stabilization should not significantly alter meniscal material properties, which could disturb normal function in the knee. Our objective was to evaluate the effects of glutaraldehyde- and glycation-induced matrix stabilization on the material properties of porcine meniscus. Normal untreated meniscus specimens were tested in confined compression at one of three applied stresses (0.069, 0.208, 0.347 MPa), subjected to either a glutaraldehyde or glycation stabilization treatment, and then re-tested to measure changes in tissue aggregate modulus, permeability, and compressive strain at equilibrium. Changes in these properties significantly increased with glutaraldehyde concentration and exposure time to ribose. One glutaraldehyde and three glycation treatments did not alter aggregate modulus or compressive strain at equilibrium compared to controls (p > 0.10). However, all treatments increased permeability by at least 108% compared to controls (p < 0.001). This study reveals a dose-dependent relationship between meniscal material properties and certain stabilization conditions and identifies treatments that minimally affect these properties. Further research is necessary to determine whether these treatments prevent enzymatic degradation before and after surgical implantation in the knee.

Mediating electrostatic binding of 1-butyl-3-methylimidazolium chloride to enzyme surfaces improves conformational stability.

PubMed

Nordwald, Erik M; Kaar, Joel L

2013-08-01

We have recently developed a general approach to improve the utility of enzymes in ionic liquids (ILs) via tuning of the ratio of enzyme-containing positive to negative surface charges. In this work, the impact of enzyme surface charge ratio on the biophysical interaction of 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) with chymotrypsin and lipase was investigated to understand this approach at the molecular level. Results of fluorescence quenching assays indicated that the extent of binding of the [BMIM] cation decreased (7- and 3.5-fold for chymotrypsin and lipase, respectively) as a function of increasing ratio of positive to negative surface charges. Conformational stability assays further showed a close correlation between thermodynamic stabilization and enzyme surface charge ratio as well as [BMIM] binding. As evidence of this correlation, succinylation and acetylation resulted in the stabilization of chymotrypsin in 10% (v/v) [BMIM][Cl] by 17.0 and 6.6 kJ/mol, respectively, while cationization destabilized chymotrypsin by 3.6 kJ/mol. Combined, these results indicate that altering the surface charge ratio mediates the organization of IL molecules, namely, [BMIM] and [Cl], around the enzymes. Preferential exclusion of [Cl], in particular, via lowering of the ratio of positive to negative surface charges, correlated with increased enzyme stability. Accordingly, these results more broadly provide insight into the mechanism of stabilization in ILs via charge modification.

Shortening a loop can increase protein native state entropy.

PubMed

Gavrilov, Yulian; Dagan, Shlomi; Levy, Yaakov

2015-12-01

Protein loops are essential structural elements that influence not only function but also protein stability and folding rates. It was recently reported that shortening a loop in the AcP protein may increase its native state conformational entropy. This effect on the entropy of the folded state can be much larger than the lower entropic penalty of ordering a shorter loop upon folding, and can therefore result in a more pronounced stabilization than predicted by polymer model for loop closure entropy. In this study, which aims at generalizing the effect of loop length shortening on native state dynamics, we use all-atom molecular dynamics simulations to study how gradual shortening a very long or solvent-exposed loop region in four different proteins can affect their stability. For two proteins, AcP and Ubc7, we show an increase in native state entropy in addition to the known effect of the loop length on the unfolded state entropy. However, for two permutants of SH3 domain, shortening a loop results only with the expected change in the entropy of the unfolded state, which nicely reproduces the observed experimental stabilization. Here, we show that an increase in the native state entropy following loop shortening is not unique to the AcP protein, yet nor is it a general rule that applies to all proteins following the truncation of any loop. This modification of the loop length on the folded state and on the unfolded state may result with a greater effect on protein stability. © 2015 Wiley Periodicals, Inc.

Engineering a Cysteine-Free Form of Human Fibroblast Growth Factor-1 for “Second Generation” Therapeutic Application

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

Xia, Xue; Kumru, Ozan S.; Blaber, Sachiko I.

Human fibroblast growth factor-1 (FGF-1) has broad therapeutic potential in regenerative medicine but has undesirable biophysical properties of low thermostability and 3 buried cysteine (Cys) residues (at positions 16, 83, and 117) that interact to promote irreversible protein unfolding under oxidizing conditions. Mutational substitution of such Cys residues eliminates reactive buried thiols but cannot be accomplished simultaneously at all 3 positions without also introducing further substantial instability. The mutational introduction of a novel Cys residue (Ala66Cys) that forms a stabilizing disulfide bond (i.e., cystine) with one of the extant Cys residues (Cys83) effectively eliminates one Cys while increasing overall stability.more » This increase in stability offsets the associated instability of remaining Cys substitution mutations and permits production of a Cys-free form of FGF-1 (Cys16Ser/Ala66Cys/Cys117Ala) with only minor overall instability. The addition of a further stabilizing mutation (Pro134Ala) creates a Cys-free FGF-1 mutant with essentially wild-type biophysical properties. The elimination of buried free thiols in FGF-1 can substantially increase the protein half-life in cell culture. Here, we show that the effective cell survival/mitogenic functional activity of a fully Cys-free form is also substantially increased and is equivalent to wild-type FGF-1 formulated in the presence of heparin sulfate as a stabilizing agent. The results identify this Cys-free FGF-1 mutant as an advantageous “second generation” form of FGF-1 for therapeutic application.« less

Loss of calreticulin function decreases NFκB activity by stabilizing IκB protein.

PubMed

Massaeli, Hamid; Jalali, Shahrzad; Viswanathan, Divya; Mesaeli, Nasrin

2014-11-01

Transcription factor NFκB is activated by several processes including inflammation, endoplasmic-reticulum (ER) stress, increase in Akt signaling and enhanced proteasomal degradation. Calreticulin (CRT) is an ER Ca(2+)-binding chaperone that regulates many cellular processes. Gene-targeted deletion of CRT has been shown to induce ER stress that is accompanied with a significant increase in the proteasome activity. Loss of CRT function increases the resistance of CRT-deficient (crt-/-) cells to UV- and drug-induced apoptosis. Based on these reports we hypothesized that loss of CRT will activate NFκB signaling thus contributing to enhanced resistance to apoptosis. In contrast to our hypothesis, we observed a significant decrease in the basal transcriptional activity of NFκB in CRT-deficient cells. Treatment with lipopolysaccharide failed to increase the transcriptional activity of NFκB in the crt-/- cells to the same level as in the wt cells. Our data illustrate that the mechanism of decreased NFκB activity in CRT-deficient cells is mediated by a significant increase in IκB protein expression. Furthermore, we showed a significant increase in protein phosphatase 2A activity inhibition which resulted in decreased IκBα protein level in CRT-deficient cells. Based on our data we concluded that loss of CRT increases the stability of IκB protein thus reducing NFκB activity. Copyright © 2014 Elsevier B.V. All rights reserved.

How to measure ecosystem stability? An evaluation of the reliability of stability metrics based on remote sensing time series across the major global ecosystems.

PubMed

De Keersmaecker, Wanda; Lhermitte, Stef; Honnay, Olivier; Farifteh, Jamshid; Somers, Ben; Coppin, Pol

2014-07-01

Increasing frequency of extreme climate events is likely to impose increased stress on ecosystems and to jeopardize the services that ecosystems provide. Therefore, it is of major importance to assess the effects of extreme climate events on the temporal stability (i.e., the resistance, the resilience, and the variance) of ecosystem properties. Most time series of ecosystem properties are, however, affected by varying data characteristics, uncertainties, and noise, which complicate the comparison of ecosystem stability metrics (ESMs) between locations. Therefore, there is a strong need for a more comprehensive understanding regarding the reliability of stability metrics and how they can be used to compare ecosystem stability globally. The objective of this study was to evaluate the performance of temporal ESMs based on time series of the Moderate Resolution Imaging Spectroradiometer derived Normalized Difference Vegetation Index of 15 global land-cover types. We provide a framework (i) to assess the reliability of ESMs in function of data characteristics, uncertainties and noise and (ii) to integrate reliability estimates in future global ecosystem stability studies against climate disturbances. The performance of our framework was tested through (i) a global ecosystem comparison and (ii) an comparison of ecosystem stability in response to the 2003 drought. The results show the influence of data quality on the accuracy of ecosystem stability. White noise, biased noise, and trends have a stronger effect on the accuracy of stability metrics than the length of the time series, temporal resolution, or amount of missing values. Moreover, we demonstrate the importance of integrating reliability estimates to interpret stability metrics within confidence limits. Based on these confidence limits, other studies dealing with specific ecosystem types or locations can be put into context, and a more reliable assessment of ecosystem stability against environmental disturbances can be obtained. © 2013 John Wiley & Sons Ltd.

Effect of pyrolysis temperature on the chemical oxidation stability of bamboo biochar.

PubMed

Chen, Dengyu; Yu, Xinzhi; Song, Chao; Pang, Xiaoli; Huang, Jing; Li, Yanjun

2016-10-01

Biochar produced by biomass pyrolysis has the advantage of carbon sequestration. However, some of the carbon atoms in biochar are not very stable. In this study, the effect of pyrolysis temperature on the chemical oxidation stability of bamboo biochar was investigated using the atomic ratios of H/C and O/C, Fourier transform infrared spectroscopy, and potassium dichromate (K2Cr2O7) oxidation spectrophotometric method. The results show that the carbon yield and ratios of H/C and O/C decreased from 71.72%, 0.71, and 0.32 to 38.48%, 0.22, and 0.06, respectively, as the temperature was increased from 300°C to 700°C. Moreover, the main oxygen-containing functional groups gradually decreased, while the degree of aromatization increased accordingly. The biochar showed a better stability at a higher pyrolysis temperature. The proportion of carbon loss, i.e., the amount of oxidized carbon with respect to the total carbon of the biochar, decreased from 16.52% to 6.69% with increasing temperature. Copyright © 2016 Elsevier Ltd. All rights reserved.

Defect-induced instability mechanisms of sputtered amorphous indium tin zinc oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Park, Jinhee; Rim, You Seung; Li, Chao; Wu, Jiechen; Goorsky, Mark; Streit, Dwight

2018-04-01

We report the device performance and stability of sputtered amorphous indium-tin-zinc-oxide (ITZO) thin-film transistors as a function of oxygen ratio [O2/(Ar + O2)] during growth. Increasing the oxygen ratio enhanced the incorporation of oxygen during ITZO film growth and reduced the concentration of deep-level defects associated with oxygen vacancies. Under illumination with no bias stress, device stability and persistent photocurrent were improved with increased oxygen ratio. Bias stress tests of the devices were also performed with and without illumination. While high oxygen ratio growth conditions resulted in decreased deep-level oxygen vacancies in the ITZO material, the same conditions resulted in degradation of the interfacial layer between the ITZO channel and dielectric due to the migration of energetic oxygen ions to the interface. Therefore, when bias stress was applied, increased carrier trap density at the interface led to a decrease in device stability that offsets any improvement in the material itself. In order to take advantage of the improved ITZO material growth at a high oxygen ratio, the interface-related problems must be solved.

First principles study of edge carboxylated graphene quantum dots

NASA Astrophysics Data System (ADS)

Abdelsalam, Hazem; Elhaes, Hanan; Ibrahim, Medhat A.

2018-05-01

The structure stability and electronic properties of edge carboxylated hexagonal and triangular graphene quantum dots are investigated using density functional theory. The calculated binding energies show that the hexagonal clusters with armchair edges have the highest stability among all the quantum dots. The binding energy of carboxylated graphene quantum dots increases by increasing the number of carboxyl groups. Our study shows that the total dipole moment significantly increases by adding COOH with the highest value observed in triangular clusters. The edge states in triangular graphene quantum dots with zigzag edges produce completely different energy spectrum from other dots: (a) the energy gap in triangular zigzag is very small as compared to other clusters and (b) the highest occupied molecular orbital is localized at the edges which is in contrast to other clusters where it is distributed over the cluster surface. The enhanced reactivity and the controllable energy gap by shape and edge termination make graphene quantum dots ideal for various nanodevice applications such as sensors. The infrared spectra are presented to confirm the stability of the quantum dots.

Effects of gamma irradiation on the protein characteristics and functional properties of sesame (Sesamum indicum L.) seeds

NASA Astrophysics Data System (ADS)

Hassan, Amro B.; Mahmoud, Nagat S.; Elmamoun, Khalid; Adiamo, Oladipupo Q.; Mohamed Ahmed, Isam A.

2018-03-01

This study was aimed at investigating the effect of gamma irradiation at various doses (0.5, 1.0, 1.5 and 2.0 kGy) on protein characteristics and functional properties of sesame seeds. Gamma radiation at high doses (>1.0 kGy) significantly (P ≤ 0.05) increased globulin and albumin fractions of sesame protein. Concomitant (P ≤ 0.05) increase of in-vitro protein digestibility was noticed in irradiated sesame flour compared to non-radiated sample. Maximum protein solubility was observed in sesame flour irradiated at 1.0 kGy. SDS-PAGE electrophoretic patterns of total sesame protein were not affected by irradiation process. Significant enhancement (P ≤ 0.05) in emulsification capacity (EC) and emulsion stability (ES) was recorded after irradiation at a dose level of 1.0 and 1.5-2.0 kGy, respectively. Foaming capacity reached a significantly maximum value in sesame flour irradiated at 1.0 kGy while foaming stability was not significantly affected by gamma irradiation. It can be concluded that gamma radiation enhances the protein and functional properties of sesame flour and thus can be employed as an effective method of preserving sesame flour and its products.

Flow-induced conformational changes in gelatin structure and colloidal stabilization.

PubMed

Akbulut, Mustafa; Reddy, Naveen K; Bechtloff, Bernd; Koltzenburg, Sebastian; Vermant, Jan; Prud'homme, Robert K

2008-09-02

Flow can change the rate at which solutes adsorb on surfaces by changing mass transfer to the surface, but moreover, flow can induce changes in the conformation of macromolecules in solution by providing sufficient stresses to perturb the segmental distribution function. However, there are few studies where the effect of flow on macromolecules has been shown to alter the structure of macromolecules adsorbed on surfaces. We have studied how the local energy dissipation alters the adsorption of gelatin onto polystyrene nanoparticles ( r = 85 nm). The change in the nature of the adsorbed layer is manifest in the change in the ability of the nanoparticles to resist aggregation. Circular dichroism spectroscopy was used to assess conformational changes in gelatin, and dynamic light scattering was used to assess the colloid stability. Experiments were conducted in a vortex jet mixer where energy density and mixing times have been quantified; mixing of the gelatin and unstable nanoparticles occurs on the order of milliseconds. The adsorption of the gelatin provides steric stabilization to the nanoparticles. We found that the stability of the gelatin-adsorbed nanoparticles increased with increasing mixing velocities: when the mixing velocities were changed from 0.9 to 550 m/s, the radius of the nanoclusters (aggregates) formed 12 h after the mixing decreased from 2620 to 600 nm. Increasing temperature also gave rise to similar trends in the stability behavior with increasing temperature, leading to increasing colloid stability. Linear flow birefringence studies also suggested that the velocity fields in the mixer are sufficiently strong to produce conformational changes in the gelatin. These results suggest that the energy dissipation produced by mixing can activate conformational changes in gelatin to alter its adsorption on the surfaces of nanoparticles. Understanding how such conformational changes in gelatin can be driven by local fluid mechanics and how these changes are related to the adsorption behavior of gelatin is very important both industrially and scientifically.

In vivo quantitative analysis of Talin turnover in response to force

PubMed Central

Hákonardóttir, Guðlaug Katrín; López-Ceballos, Pablo; Herrera-Reyes, Alejandra Donají; Das, Raibatak; Coombs, Daniel; Tanentzapf, Guy

2015-01-01

Cell adhesion to the extracellular matrix (ECM) allows cells to form and maintain three-dimensional tissue architecture. Cell–ECM adhesions are stabilized upon exposure to mechanical force. In this study, we used quantitative imaging and mathematical modeling to gain mechanistic insight into how integrin-based adhesions respond to increased and decreased mechanical forces. A critical means of regulating integrin-based adhesion is provided by modulating the turnover of integrin and its adhesion complex (integrin adhesion complex [IAC]). The turnover of the IAC component Talin, a known mechanosensor, was analyzed using fluorescence recovery after photobleaching. Experiments were carried out in live, intact flies in genetic backgrounds that increased or decreased the force applied on sites of adhesion. This analysis showed that when force is elevated, the rate of assembly of new adhesions increases such that cell–ECM adhesion is stabilized. Moreover, under conditions of decreased force, the overall rate of turnover, but not the proportion of adhesion complex components undergoing turnover, increases. Using point mutations, we identify the key functional domains of Talin that mediate its response to force. Finally, by fitting a mathematical model to the data, we uncover the mechanisms that mediate the stabilization of ECM-based adhesion during development. PMID:26446844

Stochastic sensitivity of a bistable energy model for visual perception

NASA Astrophysics Data System (ADS)

Pisarchik, Alexander N.; Bashkirtseva, Irina; Ryashko, Lev

2017-01-01

Modern trends in physiology, psychology and cognitive neuroscience suggest that noise is an essential component of brain functionality and self-organization. With adequate noise the brain as a complex dynamical system can easily access different ordered states and improve signal detection for decision-making by preventing deadlocks. Using a stochastic sensitivity function approach, we analyze how sensitive equilibrium points are to Gaussian noise in a bistable energy model often used for qualitative description of visual perception. The probability distribution of noise-induced transitions between two coexisting percepts is calculated at different noise intensity and system stability. Stochastic squeezing of the hysteresis range and its transition from positive (bistable regime) to negative (intermittency regime) are demonstrated as the noise intensity increases. The hysteresis is more sensitive to noise in the system with higher stability.

DNA damage induces down-regulation of Prp19 via impairing Prp19 stability in hepatocellular carcinoma cells.

PubMed

Yin, Jie; Zhang, Yi-An; Liu, Tao-Tao; Zhu, Ji-Min; Shen, Xi-Zhong

2014-01-01

Pre-mRNA processing factor 19 (Prp19) activates pre-mRNA spliceosome and also mediates DNA damage response. Prp19 overexpression in cells with functional p53 leads to decreased apoptosis and increases cell survival after DNA damage. Here we showed that in hepatocellular carcinoma (HCC) cells with inactive p53 or functional p53, Prp19 was down-regulated due to the impaired stability under chemotherapeutic drug treatment. Silencing Prp19 expression enhanced apoptosis of HCC cells with or without chemotherapeutic drug treatment. Furthermore high level of Prp19 may inhibit chemotherapeutic drugs induced apoptosis in hepatocellular carcinoma cells through modulating myeloid leukemia cell differentiation 1 expression. These results indicated that targeting Prp19 may potentiate pro-apoptotic effect of chemotherapeutic agents on HCC.

Thermal stability of DNA quadruplex-duplex hybrids.

PubMed

Lim, Kah Wai; Khong, Zi Jian; Phan, Anh Tuân

2014-01-14

DNA has the capacity to adopt several distinct structural forms, such as duplex and quadruplex helices, which have been implicated in cellular processes and shown to exhibit important functional properties. Quadruplex-duplex hybrids, generated from the juxtaposition of these two structural elements, could find applications in therapeutics and nanotechnology. Here we used NMR and CD spectroscopy to investigate the thermal stability of two classes of quadruplex-duplex hybrids comprising fundamentally distinct modes of duplex and quadruplex connectivity: Construct I involves the coaxial orientation of the duplex and quadruplex helices with continual base stacking across the two components; Construct II involves the orthogonal orientation of the duplex and quadruplex helices with no base stacking between the two components. We have found that for both constructs, the stability of the quadruplex generally increases with the length of the stem-loop incorporated, with respect to quadruplexes comprising nonstructured loops of the same length, which showed a continuous drop in stability with increasing loop length. The stability of these complexes, particularly Construct I, can be substantially influenced by the base-pair steps proximal to the quadruplex-duplex junction. Bulges at the junction are largely detrimental to the adoption of the desired G-quadruplex topology for Construct I but not for Construct II. These findings should facilitate future design and prediction of quadruplex-duplex hybrids.

Global analysis of protein folding using massively parallel design, synthesis and testing

PubMed Central

Rocklin, Gabriel J.; Chidyausiku, Tamuka M.; Goreshnik, Inna; Ford, Alex; Houliston, Scott; Lemak, Alexander; Carter, Lauren; Ravichandran, Rashmi; Mulligan, Vikram K.; Chevalier, Aaron; Arrowsmith, Cheryl H.; Baker, David

2017-01-01

Proteins fold into unique native structures stabilized by thousands of weak interactions that collectively overcome the entropic cost of folding. Though these forces are “encoded” in the thousands of known protein structures, “decoding” them is challenging due to the complexity of natural proteins that have evolved for function, not stability. Here we combine computational protein design, next-generation gene synthesis, and a high-throughput protease susceptibility assay to measure folding and stability for over 15,000 de novo designed miniproteins, 1,000 natural proteins, 10,000 point-mutants, and 30,000 negative control sequences, identifying over 2,500 new stable designed proteins in four basic folds. This scale—three orders of magnitude greater than that of previous studies of design or folding—enabled us to systematically examine how sequence determines folding and stability in uncharted protein space. Iteration between design and experiment increased the design success rate from 6% to 47%, produced stable proteins unlike those found in nature for topologies where design was initially unsuccessful, and revealed subtle contributions to stability as designs became increasingly optimized. Our approach achieves the long-standing goal of a tight feedback cycle between computation and experiment, and promises to transform computational protein design into a data-driven science. PMID:28706065

Study on the stability of waterpower-speed control system for hydropower station with air cushion surge chamber

NASA Astrophysics Data System (ADS)

Guo, W. C.; Yang, J. D.; Chen, J. P.; Teng, Y.

2014-03-01

According to the fact that the effects of penstock, unit and governor on stability of water level fluctuation for hydropower station with air cushion surge chamber are neglected in previous researches, in this paper, Thoma assumption is broken through, the complete mathematical model of waterpower-speed control system for hydropower station with air cushion surge chamber is established, and the comprehensive transfer function and linear homogeneous differential equation that characterize the dynamic characteristics of system are derived. The stability domain that characterizes the good or bad of stability quantitatively is drawn by using the stability conditions. The effects of the fluid inertia in water diversion system, the air cushion surge chamber parameters, hydraulic turbine characteristics, generator characteristics, and regulation modes of governor on the stability of waterpower-speed control system are analyzed through stability domain. The main conclusions are as follows: The fluid inertia in water diversion system and hydraulic turbine characteristics have unfavorable effects on the system while generator characteristics have favorable effect. The stability keeps getting better with the increase of chamber height and basal area and the decrease of air pressure and air polytropic exponent. The stability of power regulation mode is obviously better than that of frequency regulation mode.

A thermostable variant of fructose bisphosphate aldolase constructed by directed evolution also shows increased stability in organic solvents.

PubMed

Hao, Jijun; Berry, Alan

2004-09-01

Thermostable variants of the Class II fructose bisphosphate aldolase have been isolated following four rounds of directed evolution using DNA shuffling of the fda genes from Escherichia coli and Edwardsiella ictaluri. Variants from all four generations of evolution have been purified and characterized. The variants show increased thermostability with no loss of catalytic function at room temperature. The temperature at which 50% of the initial enzyme activity is lost after incubation for 10 min (T50) of the most stable variant, 4-43D6, is increased by 11-12 degrees C over the wild-type enzymes and the half-life of activity at 53 degrees C is increased approximately 190-fold. In addition, variant 4-43D6 shows increased stability to treatment with organic solvents. DNA sequencing of the evolved variants has identified the mutations which have been introduced and which lead to increased thermostability, and the role of the mutations introduced is discussed.

Computational Design of Thermostabilizing d-Amino Acid Substitutions

PubMed Central

Rodriguez-Granillo, Agustina; Annavarapu, Srinivas; Zhang, Lei; Koder, Ronald L.; Nanda, Vikas

2012-01-01

Judicious incorporation of d-amino acids in engineered proteins confer many advantages such as preventing degradation by endogenous proteases, and designing novel structures and functions not accessible to homochiral polypeptides. Glycine to d-alanine substitutions at the carboxy-termini can stabilize α-helices by reducing conformational entropy. Beyond alanine, we propose additional side chain effects on the degree of stabilization conferred by d-amino acid substitutions. A detailed, molecular understanding of backbone and side chain interactions is important for developing rational, broadly applicable strategies in using d-amino acids to increase protein thermostability. Insight from structural bioinformatics combined with computational protein design can successfully guide the selection of stabilizing d-amino acid mutations. Substituting a key glycine in the Trp-Cage mini-protein with d-Gln dramatically stabilizes the fold without altering the protein backbone. Stabilities of individual substitutions can be understood in terms of the balance of intramolecular forces at both the α-helix C-terminus and throughout the protein. PMID:21978298

In vitro stabilization of a low-tin bone-imaging agent (99mTc-Sn-HEDP) by ascorbic acid.

PubMed

Tofe, A J; Francis, M D

1976-09-01

The presence of oxidants in the 99mTc-pertechnetate and of oxygen in diagnostic kits containing low concentrations of Sn(II) has a detrimental effect upon in vitro and in vivo stability. Maintaining a nitrogen atmosphere or increasing the Sn(II) concentration inhibits the formation of 99mTcO4-. However, the latter remedy is likely to cause uptake in the reticuloendothelial system and has been associated with false positive or negative brain scans. We used ascorbic acid (an antioxidant) to ensure the in vitro stability with the low-Sn(II) bone agent disodium etidronate. In vitro stability studies by instant thin-layer chromatography, using high-acitivity generators and "instant pertechnetate," yielded less than 2% free pertechnetate at 24 hr after preparation. Distribution studies in guinea pigs show neither altered distribution of the bone agent nor abnormal distribution of ascorbic acid, suggesting its sole function as a noncomplexing stabilizer.

Reciprocal Regulation of ERα and ERβ Stability and Activity by Diptoindonesin G.

PubMed

Zhao, Zibo; Wang, Lu; James, Taryn; Jung, Youngeun; Kim, Ikyon; Tan, Renxiang; Hoffmann, F Michael; Xu, Wei

2015-12-17

ERβ is regarded as a "tumor suppressor" in breast cancer due to its anti-proliferative effects. However, unlike ERα, ERβ has not been developed as a therapeutic target in breast cancer due to loss of ERβ in aggressive cancers. In a small-molecule library screen for ERβ stabilizers, we identified Diptoindonesin G (Dip G), which significantly increases ERβ protein stability while decreasing ERα protein levels. Dip G enhances the transcription and anti-proliferative activities of ERβ, while attenuating the transcription and proliferative effects of ERα. Further investigation revealed that instead of targeting ER, Dip G targets the CHIP E3 ubiquitin ligase shared by ERα and ERβ. Thus, Dip G is a dual-functional moiety that reciprocally controls ERα and ERβ protein stability and activities via an indirect mechanism. The ERβ stabilization effects of Dip G may enable the development of ERβ-targeted therapies for human breast cancers. Copyright © 2015 Elsevier Ltd. All rights reserved.

Salt Potentiates Methylamine Counteraction System to Offset the Deleterious Effects of Urea on Protein Stability and Function

PubMed Central

Singh, Laishram R.; Warepam, Marina; Ahmad, Faizan; Dar, Tanveer Ali

2015-01-01

Cellular methylamines are osmolytes (low molecular weight organic compounds) believed to offset the urea’s harmful effects on the stability and function of proteins in mammalian kidney and marine invertebrates. Although urea and methylamines are found at 2:1 molar ratio in tissues, their opposing effects on protein structure and function have been questioned on several grounds including failure to counteraction or partial counteraction. Here we investigated the possible involvement of cellular salt, NaCl, in urea-methylamine counteraction on protein stability and function. We found that NaCl mediates methylamine counteracting system from no or partial counteraction to complete counteraction of urea’s effect on protein stability and function. These conclusions were drawn from the systematic thermodynamic stability and functional activity measurements of lysozyme and RNase-A. Our results revealed that salts might be involved in protein interaction with charged osmolytes and hence in the urea-methylamine counteraction. PMID:25793733

Voltage-gated sodium channels: pharmaceutical targets via anticonvulsants to treat epileptic syndromes.

PubMed

Abdelsayed, Mena; Sokolov, Stanislav

2013-01-01

Epilepsy is a brain disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels, Nav1.1 and Nav1.2. The effects of antiepileptic drugs (AEDs) as effective therapies for epilepsy have been characterized by extensive research. Most of the classic AEDs targeting Nav share a common mechanism of action by stabilizing the channel's fast-inactivated state. In contrast, novel AEDs, such as lacosamide, stabilize the slow-inactivated state in neuronal Nav1.1 and Nav1.7 isoforms. This paper reviews the different mechanisms by which this stabilization occurs to determine new methods for treatment.

Soil aggregate stability as an indicator for eco-engineering effectiveness?

NASA Astrophysics Data System (ADS)

Graf, Frank

2015-04-01

Eco-engineering aims at stabilising soil and slopes by applying technical and biological measures. Engineering structures are commonly well defined, immediately usable and operative, and their stability effects quantifiable and verifiable. Differently, the use of plants requires more restrictive boundary conditions and the protection potential is rarely easily calculable and develop-ing as a function of growth rate. Although the use of vegetation is widely appreciated and their stabilising effect recognised, there is an increasing demand on sound facts on its efficiency, in particular, in relation to time. Conclusively, a certain necessity has been recognised to monitor, assess and quantify the effectiveness of ecological restora-tion measures in order to facilitate the transfer of technology and knowledge. Recent theoretical models emphasize the im-portance of taking an integrated monitoring approach that considers multiple variables. However, limited financial and time resources often prevent such comprehensive assessments. A solution to this problem may be to use integrated indicators that reflect multiple aspects and, therefore, allow extensive information on ecosystem status to be gathered in a relatively short time. Among various other indicators, such as fractal dimension of soil particle size distribution or microbiological parameters, soil aggregate stability seems the most appropriate indicator with regard to protecting slopes from superficial soil failure as it is critical to both plant growth and soil structure. Soil aggregation processes play a crucial role in re-establishing soil structure and function and, conclusively, for successful and sustainable re-colonisation. Whereas the key role of soil aggregate stability in ecosystem functioning is well known concerning water, gas, and nutrient fluxes, only limited information is available with regard to soil mechanical and geotechnical aspects. Correspondingly, in the last couple of years several studies have been performed in order to bridge this gap addressing partic-ularly the influence of root growth and mycorrhizal fungi on the resistance of soil aggregates against disintegration and linking it to slope stability. As superficial soil failure is often related to heavy rainstorms and, in this regard, mainly due to water satura-tion, recent investigations focused on the pore water pressure, too. Summarising main results of the different studies a positive relationship between soil aggregate stability and traditional soil mechanical shear strength parameters was found, e.g. given certain soil conditions, an increase in aggregate stability may be equated to an increase of the angle of internal friction Φ' and/or cohesion c'. In addition, almost all investigations showed a strong positive correlation between root length per soil volume and soil aggregate stability. In respect of mycorrhizal fungi, results are not yet as clear. On the one hand it was found that the use of unspecific (commercial) inoculum had no or even a negative effect on root growth within the first vegetation period and, correspondingly, on soil aggregate stability. However, the use of specific plant fungi combinations almost ever resulted in an obvious acceleration of root growth immediately with con-comitant gain of soil stability. As far as pore water pressure is concerned we did not yet find an interpretation that is fairly straightforward and not overly prone to controversy. It looks like soil aggregated by mycorrhized plants does have a higher capacity for building up pressure than such permeated by non-mycorrhized roots. Within this scope results of several studies showing these (inter-) relationships and correlations are presented and differences as well as unexpected results discussed.

The horizontal transport of pollutants from a slope wind layer into the valley core as a function of atmospheric stability

NASA Astrophysics Data System (ADS)

Leukauf, Daniel; Gohm, Alexander; Rotach, Mathias W.; Posch, Christian

2016-04-01

Slope winds provide a mechanism for the vertical exchange of air between the valley and the free atmosphere aloft. By this means, heat, moisture and pollutants are exported or imported. However, it the static stability of the valley atmosphere is strong, one part of the up-slope flow is redirected towards the valley center and pollutants are recirculated within the valley. This may limit the venting potential of slope winds severely. The main objective of this study is to quantify the horizontal transport of pollutants from the slope wind layer into the stable valley core and to determine the dependency of this flux as a function of the initial stability of the atmosphere. For this purpose, we conducted large eddy simulations with the Weather Research and Forecasting (WRF) model for a quasi-two-dimensional valley. The valley geometry consists of two slopes with constant slope angle rising to a crest height of 1500 m and a 4 km wide flat valley floor in between. The valley is 20 km long and homogeneous in along-valley direction. Hence, only slope winds but no valley winds can evolve. The surface sensible heat flux is prescribed by a sine function with an amplitude of 125 W m-2. The initial sounding characterized by an atmosphere at rest and by a constant Brunt-Väisälä frequency which is varied between 0.006 s-1 and 0.02 s-1. A passive tracer is released with an arbitrary but constant rate at the valley floor. As expected, the atmospheric stability has a strong impact on the vertical and horizontal transport of tracer mass. A horizontal intrusion forms at the top of the mixed layer due to outflow from the slope wind layer. Tracer mass is transported from the slope towards the center of the valley. The efficiency of this mechanism increases with increasing stability N. For the lowest value of N, about 70% of the tracer mass released at the valley bottom is exported out of the valley. This value drops to about 12% in the case of the strongest stability. Hence, most of the tracer mass, which enters the slope wind layer at the valley bottom, is leaving it again through horizontal fluxes at the height of the intrusion and therefore remains inside the valley.

Safety and efficacy of exercise training in adults with Pompe disease: evalution of endurance, muscle strength and core stability before and after a 12 week training program.

PubMed

van den Berg, Linda E M; Favejee, Marein M; Wens, Stephan C A; Kruijshaar, Michelle E; Praet, Stephan F E; Reuser, Arnold J J; Bussmann, Johannes B J; van Doorn, Pieter A; van der Ploeg, Ans T

2015-07-19

Pompe disease is a proximal myopathy. We investigated whether exercise training is a safe and useful adjuvant therapy for adult Pompe patients, receiving enzyme replacement therapy. Training comprised 36 sessions of standardized aerobic, resistance and core stability exercises over 12 weeks. Before and after, the primary outcome measures safety, endurance (aerobic exercise capacity and distance walked on the 6 min walk test) and muscle strength, and secondary outcome measures core stability, muscle function and body composition, were evaluated. Of 25 patients enrolled, 23 successfully completed the training. Improvements in endurance were shown by increases in maximum workload capacity (110 W before to 122 W after training, [95 % CI of the difference 6 · 0 to 19 · 7]), maximal oxygen uptake capacity (69 · 4 % and 75 · 9 % of normal, [2 · 5 to 10 · 4]), and maximum walking distance (6 min walk test: 492 meters and 508, [-4 · 4 to 27 · 7] ). There were increases in muscle strength of the hip flexors (156 · 4 N to 180 · 7 N [1 · 6 to 13 · 6) and shoulder abductors (143 · 1 N to 150 · 7 N [13 · 2 to 35 · 2]). As an important finding in secondary outcome measures the number of patients who were able to perform the core stability exercises rose, as did the core stability balancing time (p < 0.05, for all four exercises). Functional tests showed small reductions in the time needed to climb four steps (2 · 4 sec to 2 · 1, [- 0 · 54 to -0 · 04 ]) and rise to standing position (5 · 8 sec to 4 · 8, [-2 · 0 to 0 · 0]), while time to run, the quick motor function test results and body composition remained unchanged. Our study shows that a combination of aerobic, strength and core stability exercises is feasible, safe and beneficial to adults with Pompe disease.

Optimization on Fc for Improvement of Stability and Aggregation Resistance.

PubMed

Chen, Xiaobo; Zeng, Fang; Huang, Tao; Cheng, Liang; Liu, Huan; Gong, Rui

2016-01-01

Fc-based therapeutics including therapeutic full-size monoclonal antibodies (mAbs) and Fcfusion proteins represent fastest-growing market in biopharmaceutical industrial. However, one major challenge during development of Fc-based therapeutics is how to maintain their efficacy in clinic use. Many factors may lead to failure in final marketing. For example, the stability and aggregation resistance might not be high enough for bearing the disadvantages during fermentation, purification, formulation, storage, shipment and other steps in manufacture and sale. Low stability and high aggregation tendency lead to decreased bioactivity and increased risk of immunogenicity resulting in serious side effect. Because Fc is one of the major parts in monoclonal antibodies and Fc-fusion proteins, engineering of Fc to increase its stability and reduce or eliminate aggregation due to incorrect association are of great importance and could further extend the potential of Fc-based therapeutics. Lots of studies focus on Fc optimization for better physical and chemical characteristics and function by structured-based computer-aid rational design, high-throughput screening expression system selection and other methods. The identification of optimized Fc mutants increases the clinic potential of currently existed therapeutics mAbs and Fc-fusion proteins, and accelerates the development of new Fc-based therapeutics. Here we provide an overview of the related field, and discuss recent advances and future directions in optimization of Fc-based therapeutics with modified stability and aggregation resistance. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Altered Kinematics and Time to Stabilization During Drop-Jump Landings in Individuals With or Without Functional Ankle Instability

PubMed Central

Wright, Cynthia J.; Arnold, Brent L.; Ross, Scott E.

2016-01-01

Context It has been proposed that altered dynamic-control strategies during functional activity such as jump landings may partially explain recurrent instability in individuals with functional ankle instability (FAI). Objective To capture jump-landing time to stabilization (TTS) and ankle motion using a multisegment foot model among FAI, coper, and healthy control individuals. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants Participants were 23 individuals with a history of at least 1 ankle sprain and at least 2 episodes of giving way in the past year (FAI), 23 individuals with a history of a single ankle sprain and no subsequent episodes of instability (copers), and 23 individuals with no history of ankle sprain or instability in their lifetime (controls). Participants were matched for age, height, and weight (age = 23.3 ± 3.8 years, height = 1.71 ± 0.09 m, weight = 69.0 ± 13.7 kg). Intervention(s) Ten single-legged drop jumps were recorded using a 12-camera Vicon MX motion-capture system and a strain-gauge force plate. Main Outcome Measures Mediolateral (ML) and anteroposterior (AP) TTS in seconds, as well as forefoot and hindfoot sagittal- and frontal-plane angles at jump-landing initial contact and at the point of maximum vertical ground reaction force were calculated. Results For the forefoot and hindfoot in the sagittal plane, group differences were present at initial contact (forefoot: P = .043, hindfoot: P = .004). At the hindfoot, individuals with FAI displayed more dorsiflexion than the control and coper groups. Time to stabilization differed among groups (AP TTS: P < .001; ML TTS: P = .040). Anteroposterior TTS was longer in the coper group than in the FAI or control groups, and ML TTS was longer in the FAI group than in the control group. Conclusions During jump landings, copers showed differences in sagittal-plane control, including less plantar flexion at initial contact and increased AP sway during stabilization, which may contribute to increased dynamic stability. PMID:26794631

A full-scale wind tunnel investigation of a helicopter bearingless main rotor. [Ames 40 by 80 Wind Tunnel

NASA Technical Reports Server (NTRS)

Warmbrodt, W.; Mccloud, J. L., II

1981-01-01

A helicopter bearingless main rotor was tested. Areas of investigation included aeroelastic stability, aerodynamic performance, and rotor loads as a function of collective pitch setting, RPM, airspeed and shaft angle. The rotor/support system was tested with the wind tunnel balance dampers installed and, subsequently, removed. Modifications to the rotor hub were tested. These included a reduction in the rotor control system stiffness and increased flexbeam structural damping. The primary objective of the test was to determine aeroelastic stability of the fundamental flexbeam/blade chordwise bending mode. The rotor was stable for all conditions. Damping of the rotor chordwise bending mode increases with increased collective pitch angle at constant operating conditions. No significant decrease in rotor damping occured due to frequency coalescence between the blade chordwise fundamental bending mode and the support system.

A plastic stabilizer dibutyltin dilaurate induces subchronic neurotoxicity in rats☆

PubMed Central

Jin, Minghua; Song, Peilin; Li, Na; Li, Xuejun; Chen, Jiajun

2012-01-01

Dibutyltin dilaurate functions as a stabilizer for polyvinyl chloride. In this study, experimental rats were intragastrically administered 5, 10, or 20 mg/kg dibutyltin dilaurate to model sub-chronic poisoning. After exposure, our results showed the activities of superoxide dismutase and glutathione peroxidase decreased in rat brain tissue, while the malondialdehyde and nitric oxide content, as well as nitric oxide synthase activity in rat brain tissue increased. The cell cycle in the right parietal cortex was disordered and the rate of apoptosis increased. DNA damage was aggravated in the cerebral cortex, and the ultrastructure of the right parietal cortex tissues was altered. The above changes became more apparent with exposure to increasing doses of dibutyltin dilaurate. Our experimental findings confirmed the neurotoxicity of dibutyltin dilaurate in rat brain tissues, and demonstrated that the poisoning was dose-dependent. PMID:25538742

Surface functionalization of thin-film diamond for highly stable and selective biological interfaces

PubMed Central

Stavis, Courtney; Clare, Tami Lasseter; Butler, James E.; Radadia, Adarsh D.; Carr, Rogan; Zeng, Hongjun; King, William P.; Carlisle, John A.; Aksimentiev, Aleksei; Bashir, Rashid; Hamers, Robert J.

2011-01-01

Carbon is an extremely versatile family of materials with a wide range of mechanical, optical, and mechanical properties, but many similarities in surface chemistry. As one of the most chemically stable materials known, carbon provides an outstanding platform for the development of highly tunable molecular and biomolecular interfaces. Photochemical grafting of alkenes has emerged as an attractive method for functionalizing surfaces of diamond, but many aspects of the surface chemistry and impact on biological recognition processes remain unexplored. Here we report investigations of the interaction of functionalized diamond surfaces with proteins and biological cells using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and fluorescence methods. XPS data show that functionalization of diamond with short ethylene glycol oligomers reduces the nonspecific binding of fibrinogen below the detection limit of XPS, estimated as > 97% reduction over H-terminated diamond. Measurements of different forms of diamond with different roughness are used to explore the influence of roughness on nonspecific binding onto H-terminated and ethylene glycol (EG)-terminated surfaces. Finally, we use XPS to characterize the chemical stability of Escherichia coli K12 antibodies on the surfaces of diamond and amine-functionalized glass. Our results show that antibody-modified diamond surfaces exhibit increased stability in XPS and that this is accompanied by retention of biological activity in cell-capture measurements. Our results demonstrate that surface chemistry on diamond and other carbon-based materials provides an excellent platform for biomolecular interfaces with high stability and high selectivity. PMID:20884854

Inhibition of the bioavailability of heavy metals in sewage sludge biochar by adding two stabilizers.

PubMed

Huang, Zhujian; Lu, Qin; Wang, Jun; Chen, Xian; Mao, Xiaoyun; He, Zhenli

2017-01-01

Agricultural application of sewage sludge (SS) after carbonization is a plausible way for disposal. Despite its benefits of improving soil fertility and C sequestration, heavy metals contained in sewage sludge biochars (SSB) are still a concern. In this study, two types of heavy metal stabilizers were chosen: fulvic acid (FA) and phosphogypsum (with CaSO4, CS, as the main component). The two stabilizers were incorporated into SS prior to 350°C carbonization for 1 h at the rates of 1%, 2%, or 4%. The obtained SSBs were then analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Total and available concentrations of four heavy metals, i.e., Zn, Pb, Cd, and Ni, in the SSBs were determined. In addition, a series of pot soil culture experiments was conducted to investigate the effects of stabilizers incorporation into SSB on heavy metal bioavailability and the uptake by plants (corn as an indicator) and plant biomass yield, with SS and SSB (no stabilizers) as controls. The results showed that incorporation of both FA and CS increased functional groups such as carboxyl, phenol, hydroxyl, amine and quinine groups in the SSBs. The percentage of heavy metals in sulfuric and oxidizable state and residual state of SSBs were significantly increased after carbonization, and hence the mobility of the heavy metals in SSBs was decreased. The introduction of the stabilizers (i.e., FA or CS) significantly lowered the total and available concentrations of Zn, Pb, Cd, and Ni. The reduction in available heavy metal concentration increased with incorporation rate of the stabilizers from 1% to 4%. In the treatments with FA or CS incorporated SSB, less heavy metals were taken up by plants and more plant biomass yields were obtained. The mitigating effects were more pronounced at higher rates of FA or CS stabilizer. These findings provide a way to lower bioavailability of heavy metals in SS or SSB for land application or horticulture as a peat substitute.

Temperature effect on the structural stabilities and electronic properties of X22H28 (X=C, Si and Ge) nanocrystals: A first-principles study

NASA Astrophysics Data System (ADS)

Deng, Xiao-Lin; Zhao, Yu-Jun; Wang, Ya-Ting; Liao, Ji-Hai; Yang, Xiao-Bao

2016-12-01

Based on ab initio molecular dynamic simulations, we have theoretically investigated the structural stabilities and electronic properties of X22H28 (X=C, Si, and Ge) nanocrystals, as a function of temperature with consideration of vibrational entropy effects. To compare the relative stabilities of X22H28 isomers, the vibration free energies are obtained according to the calculated phonon spectrum, where the typical modes are shown to be dominant to the structural stabilities. In addition, there is a significant gap reduction as the temperature increases from 0 K to 300 K, where the decrements are 0.2 /0.5 /0.6eV for C/Si/Ge nanocrystals, respectively. The dependence of energy gap on the variance of bond length is also analyzed according to the corresponding atomic attributions to the HOMO and LUMO levels.

Large-field-of-view, modular, stabilized, adaptive-optics-based scanning laser ophthalmoscope.

PubMed

Burns, Stephen A; Tumbar, Remy; Elsner, Ann E; Ferguson, Daniel; Hammer, Daniel X

2007-05-01

We describe the design and performance of an adaptive optics retinal imager that is optimized for use during dynamic correction for eye movements. The system incorporates a retinal tracker and stabilizer, a wide-field line scan scanning laser ophthalmoscope (SLO), and a high-resolution microelectromechanical-systems-based adaptive optics SLO. The detection system incorporates selection and positioning of confocal apertures, allowing measurement of images arising from different portions of the double pass retinal point-spread function (psf). System performance was excellent. The adaptive optics increased the brightness and contrast for small confocal apertures by more than 2x and decreased the brightness of images obtained with displaced apertures, confirming the ability of the adaptive optics system to improve the psf. The retinal image was stabilized to within 18 microm 90% of the time. Stabilization was sufficient for cross-correlation techniques to automatically align the images.

Theoretical Studies on Structures and Relative Stability for Polynitrohexaazaadamantanes

NASA Astrophysics Data System (ADS)

Xu, Xiao-juan; Xiao, He-ming; Wang, Gui-xiang; Ju, Xue-hai

2006-10-01

The density function theory at the B3LYP/6-31G* level was employed to study the structures, including the total energies (EZPE), the geometries, the oxygen balances (OB100), the dipole moments, of polynitro-hexaazaadamantanes (PNHAAs) and the potential candidates of high energy density compounds (HEDCs). The structural parameters of PNHAAs, such as the the maximum N—NO2 bond length (LBmax), the least N—N Mulliken population (BN—N), the least negative charge on the nitro group (QNO2) and OB100, were studied to predict their relative stability or sensitivity (the easiness for initiating a detonation, high sensitivity means low stability). It was found that the same conclusion was drawn from the four parameters. With the number of nitro groups increasing, the stabilities of these compounds decrease. OB100 failed in identifying the isomers, but the EZPE energy and the dipole moment were considered to give more reliable results for the isomers.

Error trends in SASS winds as functions of atmospheric stability and sea surface temperature

NASA Technical Reports Server (NTRS)

Liu, W. T.

1983-01-01

Wind speed measurements obtained with the scatterometer instrument aboard the Seasat satellite are compared equivalent neutral wind measurements obtained from ship reports in the western N. Atlantic and eastern N. Pacific where the concentration of ship reports are high and the ranges of atmospheric stability and sea surface temperature are large. It is found that at low wind speeds the difference between satellite measurements and surface reports depends on sea surface temperature. At wind speeds higher than 8 m/s the dependence was greatly reduced. The removal of systematic errors due to fluctuations in atmospheric stability reduced the r.m.s. difference from 1.7 m/s to 0.8 m/s. It is suggested that further clarification of the effects of fluctuations in atmospheric stability on Seasat wind speed measurements should increase their reliability in the future.

Physiological stability and renal clearance of ultrasmall zwitterionic gold nanoparticles: Ligand length matters

NASA Astrophysics Data System (ADS)

Ning, Xuhui; Peng, Chuanqi; Li, Eric S.; Xu, Jing; Vinluan, Rodrigo D.; Yu, Mengxiao; Zheng, Jie

2017-05-01

Efficient renal clearance has been observed from ultrasmall zwitterionic glutathione-coated gold nanoparticles (GS-AuNPs), which have broad preclinical applications in cancer diagnosis and kidney functional imaging. However, origin of such efficient renal clearance is still not clear. Herein, we conducted head-to-head comparison on physiological stability and renal clearance of two zwitterionic luminescent AuNPs coated with cysteine and glycine-cysteine (Cys-AuNPs and Gly-Cys-AuNPs), respectively. While both of them exhibited similar surface charges and the same core sizes, additional glycine slightly increased the hydrodynamic diameter of the AuNPs by 0.4 nm but significantly enhanced physiological stability of the AuNPs as well as altered their clearance pathways. These studies indicate that the ligand length, in addition to surface charges and size, also plays a key role in the physiological stability and renal clearance of ultrasmall zwitterionic inorganic NPs.

Innovative Ingredients and Emerging Technologies for Controlling Ice Recrystallization, Texture, and Structure Stability in Frozen Dairy Desserts: A Review.

PubMed

Soukoulis, Christos; Fisk, Ian

2016-11-17

Over the past decade, ice cream manufacturers have developed a strong understanding of the functionality of key ingredients and processing, developing effective explanations for the link between structure forming agents, stability mechanisms, and perceived quality. Increasing demand for products perceived as healthier/more natural with minimal processing has identified a number of new tools to improve quality and storage stability of frozen dairy desserts. Ingredients such as dietary fiber, polysaccharides, prebiotics, alternate sweeteners, fat sources rich in unsaturated fatty acids and ice strucsturing proteins (ISP) have been successfully applied as cryoprotective, texturizing, and structuring agents. Emerging minimal processing technologies including hydrostatic pressure processing, ultrasonic or high pressure assisted freezing, low temperature extrusion and enzymatically induced biopolymers crosslinking have been evaluated for their ability to improve colloidal stability, texture and sensory quality. It is therefore timely for a comprehensive review.

Influence of thermofixation on artificial ACL ligament dimensional and mechanical properties

NASA Astrophysics Data System (ADS)

Ben Abdessalem, S.; Jedda, H.; Skhiri, S.; Karray, S.; Dahmen, J.; Boughamoura, H.

2005-11-01

The anterior cruciate ligament (ACL) is the major articular ligamentous structure of the knee, it functions as a joint stabilizer. When ruptured, the natural ACL ligament can be replaced by a textile synthetic ligament such as a braid, knitted cord, or woven cord. Theses structures are composed of biocompatible materials such as polyester or Gore-Tex filaments. The success of an ACL replacement is widely linked to its mechanical and dimensional properties such as tensile strength, dimensional stability and resistance to abrasion. We introduced an additional treatment in the manufacturing of textile ACL ligaments based on the thermofixation of the textile structure by using textile industry stabilization techniques. Boiling water, saturated vapor and dry heat have been tested to stabilize a braided ligament made of Dacron polyester. The application of these three techniques led to shrinkage and an increase of breaking strength of the textile structure.

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

Thomas, Carla S.; Xu, Liza; Olsen, Bradley D.

Blending the small molecule osmolytes glycerol and trehalose with the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) (mCherry-b-PNIPAM) is demonstrated to improve protein functionality in self-assembled nanostructures. The incorporation of either additive into block copolymers results in functionality retention in the solid state of 80 and 100% for PNIPAM volume fractions of 40 and 55%, respectively. This represents a large improvement over the 50–60% functionality observed in the absence of any additive. Furthermore, glycerol decreases the thermal stability of block copolymer films by 15–20 °C, while trehalose results in an improvement in the thermal stability by 15–20 °C. These resultsmore » suggest that hydrogen bond replacement is responsible for the retention of protein function but suppression or enhancement of thermal motion based on the glass transition of the osmolyte primarily determines thermal stability. While both osmolytes are observed to have a disordering effect on the nanostructure morphology with increasing concentration, this effect is less pronounced in materials with a larger polymer volume fraction. Glycerol preferentially localizes in the protein domains and swells the nanostructures, inducing disordering or a change in morphology depending on the PNIPAM coil fraction. In contrast, trehalose is observed to macrophase separate from the block copolymer, which results in nanodomains becoming more disordered without changing significantly in size.« less

Floral trait variation and integration as a function of sexual deception in Gorteria diffusa

PubMed Central

Ellis, Allan G.; Brockington, Samuel F.; de Jager, Marinus L.; Mellers, Gregory; Walker, Rachel H.; Glover, Beverley J.

2014-01-01

Phenotypic integration, the coordinated covariance of suites of morphological traits, is critical for proper functioning of organisms. Angiosperm flowers are complex structures comprising suites of traits that function together to achieve effective pollen transfer. Floral integration could reflect shared genetic and developmental control of these traits, or could arise through pollinator-imposed stabilizing correlational selection on traits. We sought to expose mechanisms underlying floral trait integration in the sexually deceptive daisy, Gorteria diffusa, by testing the hypothesis that stabilizing selection imposed by male pollinators on floral traits involved in mimicry has resulted in tighter integration. To do this, we quantified patterns of floral trait variance and covariance in morphologically divergent G. diffusa floral forms representing a continuum in the levels of sexual deception. We show that integration of traits functioning in visual attraction of male pollinators increases with pollinator deception, and is stronger than integration of non-mimicry trait modules. Consistent patterns of within-population trait variance and covariance across floral forms suggest that integration has not been built by stabilizing correlational selection on genetically independent traits. Instead pollinator specialization has selected for tightened integration within modules of linked traits. Despite potentially strong constraint on morphological evolution imposed by developmental genetic linkages between traits, we demonstrate substantial divergence in traits across G. diffusa floral forms and show that divergence has often occurred without altering within-population patterns of trait correlations. PMID:25002705

Oridonin stabilizes retinoic acid receptor alpha through ROS-activated NF-κB signaling.

PubMed

Cao, Yang; Wei, Wei; Zhang, Nan; Yu, Qing; Xu, Wen-Bin; Yu, Wen-Jun; Chen, Guo-Qiang; Wu, Ying-Li; Yan, Hua

2015-04-10

Retinoic acid receptor alpha (RARα) plays an essential role in the regulation of many biological processes, such as hematopoietic cell differentiation, while abnormal RARα function contributes to the pathogenesis of certain diseases including cancers, especially acute promyelocytic leukemia (APL). Recently, oridonin, a natural diterpenoid isolated from Rabdosia rubescens, was demonstrated to regulate RARα by increasing its protein level. However, the underlying molecular mechanism for this action has not been fully elucidated. In the APL cell line, NB4, the effect of oridonin on RARα protein was analyzed by western blot and real-time quantitative RT-PCR analyses. Flow cytometry was performed to detect intracellular levels of reactive oxygen species (ROS). The association between nuclear factor-kappa B (NF-κB) signaling and the effect of oridonin was assessed using specific inhibitors, shRNA gene knockdown, and immunofluorescence assays. In addition, primary leukemia cells were treated with oridonin and analyzed by western blot in this study. RARα possesses transcriptional activity in the presence of its ligand, all-trans retinoic acid (ATRA). Oridonin remarkably stabilized the RARα protein, which retained transcriptional activity. Oridonin also moderately increased intracellular ROS levels, while pretreatment with the ROS scavenger, N-acetyl-l-cysteine (NAC), dramatically abrogated RARα stabilization by oridonin. More intriguingly, direct exposure to low concentrations of H2O2 also increased RARα protein but not mRNA levels, suggesting a role for ROS in oridonin stabilization of RARα protein. Further investigations showed that NAC antagonized oridonin-induced activation of NF-κB signaling, while the NF-κB signaling inhibitor, Bay 11-7082, effectively blocked the oridonin increase in RARα protein levels. In line with this, over-expression of IκΒα (A32/36), a super-repressor form of IκΒα, or NF-κB-p65 knockdown inhibited oridonin or H2O2-induced RARα stability. Finally, tumor necrosis factor alpha (TNFα), a classical activator of NF-κB signaling, modulated the stability of RARα protein. Oridonin stabilizes RARα protein by increasing cellular ROS levels, which causes activation of the NF-κB signaling pathway.

Return to Sports and Recurrences After Arthroscopic Anterior Shoulder Stabilization in Martial Arts Athletes

PubMed Central

Ranalletta, Maximiliano; Rossi, Luciano A.; Sirio, Adrian; Dilernia, Fernando Diaz; Bertona, Agustin; Maignon, Gastón D.; Bongiovanni, Santiago L.

2017-01-01

Background: The high demands to the glenohumeral joint and the violent shoulder blows experienced during martial arts (MA) could compromise return to sports and increase the recurrence rate after arthroscopic stabilization for anterior shoulder instability in these athletes. Purpose: To report the functional outcomes, return to sports, and recurrences in a series of MA athletes with anterior shoulder instability treated with arthroscopic stabilization with suture anchors. Study Design: Case series; Level of evidence, 4. Methods: A total of 20 consecutive MA athletes were treated for anterior shoulder instability at a single institution between January 2008 and December 2013. Range of motion (ROM), the Rowe score, a visual analog scale (VAS), and the Athletic Shoulder Outcome Scoring System (ASOSS) were used to assess functional outcomes. Return-to-sport and recurrence rates were also evaluated. Results: The mean age at the time of surgery was 25.4 years (range, 18-35 years), and the mean follow-up was 71 months (range, 36-96 months). No significant difference in preoperative and postoperative shoulder ROM was found. The Rowe, VAS, and ASOSS scores showed statistical improvement after surgery (P < .001). In all, 19 athletes (95%) returned to sports. However, only 60% achieved ≥90% recovery after surgery. The recurrence rate was 20%. Conclusion: In this retrospective study of a consecutive cohort of MA athletes, arthroscopic anterior shoulder stabilization significantly improved functional scores. However, only 60% of the athletes achieved the same level of competition, and there was a 20% recurrence rate. PMID:28932751

Return to Sports and Recurrences After Arthroscopic Anterior Shoulder Stabilization in Martial Arts Athletes.

PubMed

Ranalletta, Maximiliano; Rossi, Luciano A; Sirio, Adrian; Dilernia, Fernando Diaz; Bertona, Agustin; Maignon, Gastón D; Bongiovanni, Santiago L

2017-09-01

The high demands to the glenohumeral joint and the violent shoulder blows experienced during martial arts (MA) could compromise return to sports and increase the recurrence rate after arthroscopic stabilization for anterior shoulder instability in these athletes. To report the functional outcomes, return to sports, and recurrences in a series of MA athletes with anterior shoulder instability treated with arthroscopic stabilization with suture anchors. Case series; Level of evidence, 4. A total of 20 consecutive MA athletes were treated for anterior shoulder instability at a single institution between January 2008 and December 2013. Range of motion (ROM), the Rowe score, a visual analog scale (VAS), and the Athletic Shoulder Outcome Scoring System (ASOSS) were used to assess functional outcomes. Return-to-sport and recurrence rates were also evaluated. The mean age at the time of surgery was 25.4 years (range, 18-35 years), and the mean follow-up was 71 months (range, 36-96 months). No significant difference in preoperative and postoperative shoulder ROM was found. The Rowe, VAS, and ASOSS scores showed statistical improvement after surgery ( P < .001). In all, 19 athletes (95%) returned to sports. However, only 60% achieved ≥90% recovery after surgery. The recurrence rate was 20%. In this retrospective study of a consecutive cohort of MA athletes, arthroscopic anterior shoulder stabilization significantly improved functional scores. However, only 60% of the athletes achieved the same level of competition, and there was a 20% recurrence rate.

Robust enzyme design: bioinformatic tools for improved protein stability.

PubMed

Suplatov, Dmitry; Voevodin, Vladimir; Švedas, Vytas

2015-03-01

The ability of proteins and enzymes to maintain a functionally active conformation under adverse environmental conditions is an important feature of biocatalysts, vaccines, and biopharmaceutical proteins. From an evolutionary perspective, robust stability of proteins improves their biological fitness and allows for further optimization. Viewed from an industrial perspective, enzyme stability is crucial for the practical application of enzymes under the required reaction conditions. In this review, we analyze bioinformatic-driven strategies that are used to predict structural changes that can be applied to wild type proteins in order to produce more stable variants. The most commonly employed techniques can be classified into stochastic approaches, empirical or systematic rational design strategies, and design of chimeric proteins. We conclude that bioinformatic analysis can be efficiently used to study large protein superfamilies systematically as well as to predict particular structural changes which increase enzyme stability. Evolution has created a diversity of protein properties that are encoded in genomic sequences and structural data. Bioinformatics has the power to uncover this evolutionary code and provide a reproducible selection of hotspots - key residues to be mutated in order to produce more stable and functionally diverse proteins and enzymes. Further development of systematic bioinformatic procedures is needed to organize and analyze sequences and structures of proteins within large superfamilies and to link them to function, as well as to provide knowledge-based predictions for experimental evaluation. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Directional, stabilizing, and disruptive trait selection as alternative mechanisms for plant community assembly.

PubMed

Rolhauser, Andrés G; Pucheta, Eduardo

2017-03-01

How plant functional traits (e.g., seed mass) drive species abundance within communities remains an unsolved question. Borrowing concepts from natural selection theory, we propose that trait-abundance relationships can generally correspond to one of three modes of trait selection: directional (a rectilinear relationship, where species at one end of a trait axis are most abundant), stabilizing (an n-shaped relationship), and disruptive (a u-shaped relationship). Stabilizing selection (i.e., the functional convergence of abundant species) would result from positive density-dependent interactions (e.g., facilitation) or due to generalized trade-offs in resource acquisition/use, while disruptive selection (i.e., the divergence of abundant species) would result from negative density-dependent interactions (e.g., competition) or due to environmental heterogeneity. These selection modes can be interpreted as proxies for community-level trait-fitness functions, which establish the degree to which traits are truly "functional". We searched for selection modes in a desert annual-plant community in Argentina (which was divided into winter and summer guilds) to test the hypothesis that the relative importance of disruptive mechanisms (competition, disturbances) decreases with the increase of abiotic stress, a stabilizing agent. Average density was analyzed as a function of eight traits generally linked to resource acquisition and competitive ability (maximum plant height, leaf size, specific leaf area, specific root length), resource retention and stress tolerance (leaf dissection, leaf dry matter content, specific root volume), and regeneration (seed mass) using multiple quadratic-regression models. Trait selection was stabilizing and/or directional when the environment was harshest (winter) and disruptive and/or directional when conditions were milder (summer). Selection patterns differed between guilds for two important traits: plant height and seed mass. These results suggest that abiotic stress may drive within-community functional convergence independently of the trait considered, opposing the view that some traits may be inherently convergent while others divergent. Our quadratic model-based approach provides standardized metrics of both linear and nonlinear selection that may allow simple comparisons among communities subjected to contrasting environmental conditions. These concepts, rooted in natural selection theory, may clarify the functional link between traits and species abundance, and thus help untangle the contributions of deterministic and stochastic processes on community assembly. © 2017 by the Ecological Society of America.

The role of rabbit meat as functional food.

PubMed

Dalle Zotte, Antonella; Szendro, Zsolt

2011-07-01

Increasing consumer knowledge of the link between diet and health has raised the awareness and demand for functional food ingredients. Meat and its derivatives may be considered functional foods to the extent that they contain numerous compounds thought to be functional. This review will attempt to outline the excellent nutritional and dietetic properties of rabbit meat and offer an overview of the studies performed on the strategies adopted to improve the functional value of rabbit meat. Dietary manipulation has been seen to be very effective in increasing the levels of essential FA, EPA, DHA, CLA, branched chain FA, vitamin E, and selenium in rabbit meat. Dietary fortification with vitamin E or natural products such as oregano essential oil, chia seed oil, and Spirulina platensis microalga seem promising in improving the oxidative stability of rabbit meat while also adding functional ingredients. Copyright © 2011 Elsevier Ltd. All rights reserved.

Analysis of feeding function and jaw stability in bedridden elderly.

PubMed

Tamura, Fumiyo; Mizukami, Miki; Ayano, Rika; Mukai, Yoshiharu

2002-01-01

The purpose of this study was to analyze the relationship between jaw stability and the feeding function of 53 bedridden elderly dysphagic patients. Investigations included a questionnaire on daily life activities and meals, oral examinations, functional tests for feeding ability, and assessments of feeding function during the meal. The results of intraoral examination of this patient population for jaw stability revealed that 34.0% of individuals had posterior support for occlusion regardless of whether they had natural teeth or dentures. Thus, the number classified as having mandibular stability (ST) was 18 and that with no mandibular stability (NST) was 35. In a Repetitive Saliva Swallowing Test (RSST), 83.3% of the NST group and 40.0% of the ST group were unable to swallow more than 3 times within 30 seconds. In a water swallowing test, 91.4% of the NST of group was unable to swallow 15 mL of water by a single swallow, while 40.0% of ST group was capable. The results suggest that jaw stabilization by occlusion with the posterior teeth or dental prosthetics is important to feeding function, particularly swallowing.

[Analyses of segment motor function in patients with degenerative lumbar disease on the treatment of WavefleX dynamic stabilization system].

PubMed

Wu, Junsong; Du, Junhua; Jiang, Xiangyun; Wang, Quan; Li, Xigong; Du, Jingyu; Lin, Xiangjin

2014-06-17

To explore the changes of range-of-motion (ROM) in patients with degenerative lumbar disease on the treatment of WavefleX dynamic stabilization system and examine the postoperative lumbar regularity and tendency of ROM. Nine patients with degenerative lumbar disease on the treatment of WavefleX dynamic stabilization system were followed up with respect to ROMs at 5 timepoints within 12 months. Records of ROM were made for instrumented segments, adjacent segments and total lumbar. Compared with preoperation, ROMs in non-fusional segments with WavefleX dynamic stabilization system decreased statistical significantly (P < 0.05 or P < 0.01) at different timepoints; ROMs in adjacent segments increased at some levels without wide statistical significance. The exception was single L3/4 at Month 12 (P < 0.05) versus control group simultaneously at the levels of L3/4, L4/5 and L5/S1, ROMs decreased at Months 6 and 12 with wide statistical significance (P < 0.05 or P < 0.01). ROMs in total lumbar had statistical significant decrease (P < 0.01) in both group of non-fusional segments and hybrid group of non-fusion and fusion. The trends of continuous augments were observed during follow-ups. Statistically significant augments were also acquired at 4 timepoints as compared to control group (P < 0.01). The treatment of degenerative lumbar diseases with WavefleX dynamic stabilization system may limit excessive extension/inflexion and preserve some motor functions. Moreover, it can sustain physiological lordosis, decrease and transfer disc load in adjacent segments to prevent early degeneration of adjacent segment. Trends of motor function augment in total lumbar need to be confirmed during future long-term follow-ups.

Influence of the chelator structures on the stability of Re and Tc tricarbonyl complexes with iminodiacetic acid tridentate ligands: a computational study.

PubMed

Hernández-Valdés, Daniel; Rodríguez-Riera, Zalua; Díaz-García, Alicia; Benoist, Eric; Jáuregui-Haza, Ulises

2016-08-01

The development of novel radiopharmaceuticals for nuclear medicine based on M(CO)3 (M = Tc, Re) complexes has attracted great attention. The versatility of this core and the easy production of the fac-[M(CO)3(H2O)3](+) precursor could explain this interest. The main characteristics of these tricarbonyl complexes are the high substitution stability of the three CO ligands and the corresponding lability of the coordinated water molecules, yielding, via easy exchange of a variety of bi- and tridentate ligands, complexes xof very high kinetic stability. Here, a computational study of different tricarbonyl complexes of Re(I) and Tc(I) was performed using density functional theory. The solvent effect was simulated using the polarizable continuum model. These structures were used as a starting point to investigate the relative stabilities of tricarbonyl complexes with various tridentate ligands. These complexes included an iminodiacetic acid unit for tridentate coordination to the fac-[M(CO)3](+) moiety (M = Re, Tc), an aromatic ring system bearing a functional group (-NO2, -NH2, and -Cl) as a linking site model, and a tethering moiety (a methylene, ethylene, propylene butylene, or pentylene bridge) between the linking and coordinating sites. The optimized complexes showed geometries comparable to those inferred from X-ray data. In general, the Re complexes were more stable than the corresponding Tc complexes. Furthermore, using NH2 as the functional group, a medium length carbon chain, and ortho substitution increased complex stability. All of the bonds involving the metal center presented a closed shell interaction with dative or covalent character, and the strength of these bonds decreased in the sequence Tc-CO > Tc-O > Tc-N.

Skeletal and cardiac muscle pericytes: Functions and therapeutic potential

PubMed Central

Murray, Iain R.; Baily, James E.; Chen, William C.W.; Dar, Ayelet; Gonzalez, Zaniah N.; Jensen, Andrew R.; Petrigliano, Frank A.; Deb, Arjun; Henderson, Neil C.

2017-01-01

Pericytes are periendothelial mesenchymal cells residing within the microvasculature. Skeletal muscle and cardiac pericytes are now recognized to fulfill an increasing number of functions in normal tissue homeostasis, including contributing to microvascular function by maintaining vessel stability and regulating capillary flow. In the setting of muscle injury, pericytes contribute to a regenerative microenvironment through release of trophic factors and by modulating local immune responses. In skeletal muscle, pericytes also directly enhance tissue healing by differentiating into myofibers. Conversely, pericytes have also been implicated in the development of disease states, including fibrosis, heterotopic ossication and calcification, atherosclerosis, and tumor angiogenesis. Despite increased recognition of pericyte heterogeneity, it is not yet clear whether specific subsets of pericytes are responsible for individual functions in skeletal and cardiac muscle homeostasis and disease. PMID:27595928

Evolution of the axial system in craniates: morphology and function of the perivertebral musculature

PubMed Central

2011-01-01

The axial musculoskeletal system represents the plesiomorphic locomotor engine of the vertebrate body, playing a central role in locomotion. In craniates, the evolution of the postcranial skeleton is characterized by two major transformations. First, the axial skeleton became increasingly functionally and morphologically regionalized. Second, the axial-based locomotion plesiomorphic for craniates became progressively appendage-based with the evolution of extremities in tetrapods. These changes, together with the transition to land, caused increased complexity in the planes in which axial movements occur and moments act on the body and were accompanied by profound changes in axial muscle function. To increase our understanding of the evolutionary transformations of the structure and function of the perivertebral musculature, this review integrates recent anatomical and physiological data (e.g., muscle fiber types, activation patterns) with gross-anatomical and kinematic findings for pivotal craniate taxa. This information is mapped onto a phylogenetic hypothesis to infer the putative character set of the last common ancestor of the respective taxa and to conjecture patterns of locomotor and muscular evolution. The increasing anatomical and functional complexity in the muscular arrangement during craniate evolution is associated with changes in fiber angulation and fiber-type distribution, i.e., increasing obliqueness in fiber orientation and segregation of fatigue-resistant fibers in deeper muscle regions. The loss of superficial fatigue-resistant fibers may be related to the profound gross anatomical reorganization of the axial musculature during the tetrapod evolution. The plesiomorphic function of the axial musculature -mobilization- is retained in all craniates. Along with the evolution of limbs and the subsequent transition to land, axial muscles additionally function to globally stabilize the trunk against inertial and extrinsic limb muscle forces as well as gravitational forces. Associated with the evolution of sagittal mobility and a parasagittal limb posture, axial muscles in mammals also stabilize the trunk against sagittal components of extrinsic limb muscle action as well as the inertia of the body's center of mass. Thus, the axial system is central to the static and dynamic control of the body posture in all craniates and, in gnathostomes, additionally provides the foundation for the mechanical work of the appendicular system. PMID:21306656

Evolution of Functional Groups during Pyrolysis Oil Upgrading

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

Stankovikj, Filip; Tran, Chi-Cong; Kaliaguine, Serge

In this paper, we examine the evolution of functional groups (carbonyl, carboxyl, phenol, and hydroxyl) during stabilization at 100–200 °C of two typical wood derived pyrolysis oils from BTG and Amaron in a batch reactor over Ru/C catalyst for 4h. An aqueous and an oily phase were obtained. The content of functional groups in both phases were analyzed by GC/MS, 31P-NMR, 1H-NMR, elemental analysis, KF titration, carbonyl groups by Faix, Folin – Ciocalteu method and UV-Fluorescence. The consumption of hydrogen was between 0.007 and 0.016 g/g oil, and 0.001-0.020 g of CH4/g of oil, 0.005-0.016 g of CO2/g oil andmore » 0.03-0.10 g H2O/g oil were formed. The content of carbonyl, hydroxyl, and carboxyl groups in the volatile GC-MS detectable fraction decreased (80, 65, and ~70% respectively), while their behavior in the total oil and hence in the non-volatile fraction was more complex. The carbonyl groups initially decreased having minimum at ~125-150°C and then increased, while the hydroxyl groups had reversed trend. This might be explained by initial hydrogenation of the carbonyl groups to form hydroxyls, followed by continued dehydration reactions at higher temperatures that may increase their content. The 31P-NMR was on the limit of its sensitivity for the carboxylic groups to precisely detect changes in the non-volatile fraction, however the more precise titration method showed that the concentration of carboxylic groups in the non-volatile fraction remains constant with increased stabilization temperature. The UV-Fluorescence results show that repolymerization increases with temperature. ATR-FTIR method coupled with deconvolution of the region between 1490 and 1850 cm-1 showed to be a good tool for following the changes in carbonyl groups and phenols of the stabilized pyrolysis oils. The deconvolution of the IR bands around 1050 and 1260 cm-1 correlated very well with the changes in the 31P-NMR silent O groups (likely ethers). Most of the H2O formation could be explained from the significant reduction of these silent O groups (from 12% in the fresh oils, to 6 to 2% in the stabilized oils) most probably belonging to ethers.« less

Effect of the viscosity of the liquid on the angle of inclination of a wet sandpile*

NASA Astrophysics Data System (ADS)

Samadani, Azadeh; Kudrolli, Arshad

2002-03-01

We study the effect of liquids on the angle of inclination of a wet sandpile in a rotating drum system. In this system, the surface exhibits stick slip motion for slow rotation rates omega, and continuos avalanching above a critical omega. We will focus on the stick-slip regime, where the angle of inclination of the pile oscillates between the maximum angle of stability before an avalanche, and the angle of repose after the avalanche. Both angles are observed to increase and saturate as a function of the volume fraction of the fluid. Furthermore, by changing the viscosity of the fluid using water-glycerol mixtures, we observe that both the maximum angle of stability and the angle of repose increase with the viscosity of the fluid. There are two possible explanations for the increase of the angle of stability of the pile. First, there may be creep motion between the particles giving rise to viscous forces before an avalanche, that are too small to observe visually. The creep motion is also slower than the rate of increase of the surface due to rotation. Second, the average number of liquid bridges between particles may increase with viscosity. We will comment on both possibilities using experimental data and scaling arguments.

Short-range stabilizing potential for computing energies and lifetimes of temporary anions with extrapolation methods.

PubMed

Sommerfeld, Thomas; Ehara, Masahiro

2015-01-21

The energy of a temporary anion can be computed by adding a stabilizing potential to the molecular Hamiltonian, increasing the stabilization until the temporary state is turned into a bound state, and then further increasing the stabilization until enough bound state energies have been collected so that these can be extrapolated back to vanishing stabilization. The lifetime can be obtained from the same data, but only if the extrapolation is done through analytic continuation of the momentum as a function of the square root of a shifted stabilizing parameter. This method is known as analytic continuation of the coupling constant, and it requires--at least in principle--that the bound-state input data are computed with a short-range stabilizing potential. In the context of molecules and ab initio packages, long-range Coulomb stabilizing potentials are, however, far more convenient and have been used in the past with some success, although the error introduced by the long-rang nature of the stabilizing potential remains unknown. Here, we introduce a soft-Voronoi box potential that can serve as a short-range stabilizing potential. The difference between a Coulomb and the new stabilization is analyzed in detail for a one-dimensional model system as well as for the (2)Πu resonance of CO2(-), and in both cases, the extrapolation results are compared to independently computed resonance parameters, from complex scaling for the model, and from complex absorbing potential calculations for CO2(-). It is important to emphasize that for both the model and for CO2(-), all three sets of results have, respectively, been obtained with the same electronic structure method and basis set so that the theoretical description of the continuum can be directly compared. The new soft-Voronoi-box-based extrapolation is then used to study the influence of the size of diffuse and the valence basis sets on the computed resonance parameters.

[Study on mechanism of SOM stabilization of paddy soils under long-term fertilizations].

PubMed

Luo, Lu; Zhou, Ping; Tong, Cheng-Li; Shi, Hui; Wu, Jin-Shui; Huang, Tie-Ping

2013-02-01

Fourier transform infrared spectroscopy (FTIR) was applied to study the structure of soil organic matter (SOM) of paddy soils under long-term different fertilization treatments. The aim was to clarify the different distribution of SOM between different fertilization methods and between topsoil and subsoil, and to explore the stability mechanism of SOM under different fertilization treatments. The results showed that the content of topsoil organic carbon (SOC) was the highest under organic-inorganic fertilizations, with the increment of SOC by 18.5%, 12.9% and 18.4% under high organic manure (HOM), low organic manure (LOM) and straw returning (STW) respectively compared with no fertilization treatment (CK). The long-term fertilizations also changed the chemical structure of SOM. As compared with CK, different fertilization treatments increased the functional group absorbing intensity of chemical resistance compounds (aliphatic, aromaticity), carbohydrate and organo-silicon compounds, which was the most distinctive under treatments of HOM, LOM and STW. For example, the absorbing intensity of alkyl was 0.30, 0.25 and 0.29 under HOM, LOM and STW, respectively. These values were increased by 87% , 56% and 81% as compared with that under CK treatment. The functional group absorbing intensity of SOM in the topsoil was stronger than that in the subsoil, with the most distinctive difference under HOM, LOM and STW treatments. The present research indicated that the enhanced chemical resistance of functional group of SOM may contribute to the high contents of SOC in the paddy soils under long-term organic-inorganic fertilizations, which also suggested a chemical stabilization mechanism of SOM in the paddy soils.

A clinical study to evaluate denture adhesive use in well-fitting dentures.

PubMed

Munoz, Carlos A; Gendreau, Linda; Shanga, Gilbert; Magnuszewski, Tabetha; Fernandez, Patricia; Durocher, John

2012-02-01

The objective of this study was the assessment of retention and stability and functional benefits of denture adhesive applied to well-fitting and well-made dentures. This was a randomized, crossover study to compare two marketed denture adhesives (test cream, Super Poligrip® Free, and test strip, Super Poligrip® Comfort Seal Strips) and an unmarketed cream adhesive (GlaxoSmith Kline Consumer Healthcare) with no adhesive as the negative control. Thirty-six subjects completed the study. One hour after the application of denture adhesive, retention and stability were measured using the Kapur Index and maxillary incisal bite force. Two hours after application, functional tests were used to assess denture movement and peanut particle migration under the denture. Subjects also rated confidence, comfort, satisfaction with dentures, and denture wobble in conjunction with the functional tests. Denture adhesives significantly (p < 0.05) improved retention and stability of well-fitting dentures. Subjects experienced significantly (p < 0.05) fewer dislodgements while eating an apple after adhesive was applied to dentures. Significant (p < 0.05) increases in subjective ratings of confidence and comfort as well as decreases in denture wobble were associated with the use of adhesive. There was significant (p < 0.05) improvement in satisfaction ratings for cream adhesives. A single application of each denture adhesive was well tolerated. The results of this study provide evidence that use of Super Poligrip® denture adhesives can enhance aspects of performance of complete well-fitting dentures as well as provide increased comfort, confidence, and satisfaction with dentures. © 2011 by the American College of Prosthodontists.

Integrated Locomotor Function Tests for Countermeasure Evaluation

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Mulavara, A. P.; Peters, B. T.; Cohen, H. S.; Landsness, E. C.; Black, F. O.

2005-01-01

Following spaceflight crewmembers experience locomotor dysfunction due to inflight adaptive alterations in sensorimotor function. Countermeasures designed to mitigate these postflight gait alterations need to be assessed with a new generation of tests that evaluate the interaction of various sensorimotor sub-systems central to locomotor control. The goal of the present study was to develop new functional tests of locomotor control that could be used to test the efficacy of countermeasures. These tests were designed to simultaneously examine the function of multiple sensorimotor systems underlying the control of locomotion and be operationally relevant to the astronaut population. Traditionally, gaze stabilization has been studied almost exclusively in seated subjects performing target acquisition tasks requiring only the involvement of coordinated eye-head movements. However, activities like walking involve full-body movement and require coordination between lower limbs and the eye-head-trunk complex to achieve stabilized gaze during locomotion. Therefore the first goal of this study was to determine how the multiple, interdependent, full-body sensorimotor gaze stabilization subsystems are functionally coordinated during locomotion. In an earlier study we investigated how alteration in gaze tasking changes full-body locomotor control strategies. Subjects walked on a treadmill and either focused on a central point target or read numeral characters. We measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, shank and foot, accelerations along the vertical axis at the head and the shank, and the vertical forces acting on the support surface. In comparison to the point target fixation condition, the results of the number reading task showed that compensatory head pitch movements increased, peak head acceleration was reduced and knee flexion at heel-strike was increased. In a more recent study we investigated the adaptive remodeling of the full-body gaze control systems following exposure to visual-vestibular conflict. Subjects walked on a treadmill before and after a 30- minute exposure to 0.5X minifying during which self-generated sinusoidal vertical head rotations were performed while seated. Following exposure to visual-vestibular conflict subjects showed a restriction in compensatory head movements, increased knee and ankle flexion after heel-strike and a decrease in the rate of body loading during the rapid weight transfer phase after the heel strike event. Taken together, results from both studies provide evidence that the full body contributes to gaze stabilization during locomotion, and that different functional elements are responsive to changes in visual task constraints and are subject to adaptive alterations following exposure to visual-vestibular conflict. This information provides the basis for the design of a new generation of integrative tests that incorporate the evaluation of multiple neural control systems relevant to astronaut operational performance.

Movement Assessment of Children (MAC): validity, reliability, stability and sensitivity to change in typically developing children.

PubMed

Chandler, L S; Terhorst, L; Rogers, J C; Holm, M B

2016-07-01

The purpose of this study was to establish the validity, reliability, stability and sensitivity to change of the family-centred Movement Assessment of Children (MAC) in typically developing infants/toddlers from 2 months (1 month 16 days) to 2 years (24 months 15 days) of age. Assessment of infant/toddler motor development is critical so that infants and toddlers who are at-risk for developmental delay or whose functional motor development is delayed can be monitored and receive therapy to improve their developmental outcomes. Infants/toddlers are thought to be more responsive during the MAC assessment because parents and siblings participate and elicit responses. Two hundred seventy six children and 405 assessments contributed to the establishment of age-related parameters for typically developing infants and toddlers on the MAC. The MAC assesses three core domains of functional movement (head control, upper extremities and hands, pelvis and lower extremities), and generates a core total score. Four explanatory domains serve to alert examiners to factors that may impact atypical development (general observations, special senses, primitive reflexes/reactions, muscle tone). Construct validity of functional motor development was examined using the relationship between incremental increases in scores and increases in participants' ages. Subsamples were used to establish inter-rater reliability, test-retest reliability, stability and sensitivity to change. Construct validity was established and inter-rater reliability ICCs for the core items and core total ranged from 0.83 to 0.99. Percent agreement for the explanatory items ranged from 0.72 to 0.96. Stability within age grouping was consistent from baseline to 6 months post-baseline, and sensitivity to change from baseline to 6 months was significant for all core items and the total score. The MAC has proven to be a well-constructed assessment of infant and toddler functional motor development. It is a family-centred and efficient tool that can be used to assess and follow-up of infants and toddlers from 2 months to 2 years. © 2016 John Wiley & Sons Ltd.

The decapping activator Edc3 and the Q/N-rich domain of Lsm4 function together to enhance mRNA stability and alter mRNA decay pathway dependence in Saccharomyces cerevisiae.

PubMed

Huch, Susanne; Müller, Maren; Muppavarapu, Mridula; Gommlich, Jessie; Balagopal, Vidya; Nissan, Tracy

2016-10-15

The rate and regulation of mRNA decay are major elements in the proper control of gene expression. Edc3 and Lsm4 are two decapping activator proteins that have previously been shown to function in the assembly of RNA granules termed P bodies. Here, we show that deletion of edc3, when combined with a removal of the glutamine/asparagine rich region of Lsm4 (edc3Δ lsm4ΔC) reduces mRNA stability and alters pathways of mRNA degradation. Multiple tested mRNAs exhibited reduced stability in the edc3Δ lsm4ΔC mutant. The destabilization was linked to an increased dependence on Ccr4-mediated deadenylation and mRNA decapping. Unlike characterized mutations in decapping factors that either are neutral or are able to stabilize mRNA, the combined edc3Δ lsm4ΔC mutant reduced mRNA stability. We characterized the growth and activity of the major mRNA decay systems and translation in double mutant and wild-type yeast. In the edc3Δ lsm4ΔC mutant, we observed alterations in the levels of specific mRNA decay factors as well as nuclear accumulation of the catalytic subunit of the decapping enzyme Dcp2. Hence, we suggest that the effects on mRNA stability in the edc3Δ lsm4ΔC mutant may originate from mRNA decay protein abundance or changes in mRNPs, or alternatively may imply a role for P bodies in mRNA stabilization. © 2016. Published by The Company of Biologists Ltd.

The decapping activator Edc3 and the Q/N-rich domain of Lsm4 function together to enhance mRNA stability and alter mRNA decay pathway dependence in Saccharomyces cerevisiae

PubMed Central

Huch, Susanne; Müller, Maren; Muppavarapu, Mridula; Gommlich, Jessie; Balagopal, Vidya; Nissan, Tracy

2016-01-01

ABSTRACT The rate and regulation of mRNA decay are major elements in the proper control of gene expression. Edc3 and Lsm4 are two decapping activator proteins that have previously been shown to function in the assembly of RNA granules termed P bodies. Here, we show that deletion of edc3, when combined with a removal of the glutamine/asparagine rich region of Lsm4 (edc3Δ lsm4ΔC) reduces mRNA stability and alters pathways of mRNA degradation. Multiple tested mRNAs exhibited reduced stability in the edc3Δ lsm4ΔC mutant. The destabilization was linked to an increased dependence on Ccr4-mediated deadenylation and mRNA decapping. Unlike characterized mutations in decapping factors that either are neutral or are able to stabilize mRNA, the combined edc3Δ lsm4ΔC mutant reduced mRNA stability. We characterized the growth and activity of the major mRNA decay systems and translation in double mutant and wild-type yeast. In the edc3Δ lsm4ΔC mutant, we observed alterations in the levels of specific mRNA decay factors as well as nuclear accumulation of the catalytic subunit of the decapping enzyme Dcp2. Hence, we suggest that the effects on mRNA stability in the edc3Δ lsm4ΔC mutant may originate from mRNA decay protein abundance or changes in mRNPs, or alternatively may imply a role for P bodies in mRNA stabilization. PMID:27543059

Mutations that Allow SIR2 Orthologs to Function in a NAD+-Depleted Environment.

PubMed

Ondracek, Caitlin R; Frappier, Vincent; Ringel, Alison E; Wolberger, Cynthia; Guarente, Leonard

2017-03-07

Sirtuin enzymes depend on NAD + to catalyze protein deacetylation. Therefore, the lowering of NAD + during aging leads to decreased sirtuin activity and may speed up aging processes in laboratory animals and humans. In this study, we used a genetic screen to identify two mutations in the catalytic domain of yeast Sir2 that allow the enzyme to function in an NAD + -depleted environment. These mutant enzymes give rise to a significant increase of yeast replicative lifespan and increase deacetylation by the Sir2 ortholog, SIRT1, in mammalian cells. Our data suggest that these mutations increase the stability of the conserved catalytic sirtuin domain, thereby increasing the catalytic efficiency of the mutant enzymes. Our approach to identifying sirtuin mutants that permit function in NAD + -limited environments may inform the design of small molecules that can maintain sirtuin activity in aging organisms. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

NASA Astrophysics Data System (ADS)

Parlange, M. B.; Katul, G. G.

1995-04-01

Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and latent and sensible heat fluxes were measured above the trees which are up to 9 m in height. Near-neutral wind speed profile measurements allowed the determination of the watershed surface roughness (z0 = 1.4 m) and the momentum displacement height (d0 = 7.0 m). The wind speed measurements obtained under unstable atmospheric stability were analyzed using Monin-Obukhov similarity theory. New stability correction functions proposed based on theory and experiments of Kader-Yaglom as well as the now classic Businger-Dyer type functions were tested. The watershed shear stress values calculated using the surface layer wind speed profiles with the new Monin-Obukhov stability functions were found to be improved in comparison with the values obtained with the Businger-Dyer functions under strongly unstable stability conditions. The Monin-Obukhov model with the Businger-Dyer stability correction function underpredicted the momentum flux by 25% under strongly unstable stability conditions, while the new Kader-Yaglom formulation compared well on average (R2 = 0.77) with the surface eddy correlation measurements for all atmospheric stability conditions. The unstable 100-m drag coefficient was found to be u*2/V1002 = 0.0182.

[Changes in respiratory function tests of healthy miners in accordance with length of service].

PubMed

Shishkin, G S; Ustiuzhaninova, N V; Krasulina, G P

2010-01-01

The study covered respiratory function tests in healthy miners with variable length of service. Findings are that the first year of mining is characterized by slower interchange of gases in respiratory parts of lungs, by induced protective reaction that increases dilution of inspired air. The years from second to fifth demonstrate stabilized changes and external respiratory system fixed in new functional state kept over next 15-18 years. After 20 years of service in mine, the external respiration system becomes overstrained with intensified compensatory pulmonary ventilation and protective reaction.

Enhancing Functional Performance using Sensorimotor Adaptability Training Programs

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Mulavara, A. P.; Peters, B. T.; Brady, R.; Audas, C.; Ruttley, T. M.; Cohen, H. S.

2009-01-01

During the acute phase of adaptation to novel gravitational environments, sensorimotor disturbances have the potential to disrupt the ability of astronauts to perform functional tasks. The goal of this project is to develop a sensorimotor adaptability (SA) training program designed to facilitate recovery of functional capabilities when astronauts transition to different gravitational environments. The project conducted a series of studies that investigated the efficacy of treadmill training combined with a variety of sensory challenges designed to increase adaptability including alterations in visual flow, body loading, and support surface stability.

Rye and Wheat Bran Extracts Isolated with Pressurized Solvents Increase Oxidative Stability and Antioxidant Potential of Beef Meat Hamburgers.

PubMed

Šulniūtė, Vaida; Jaime, Isabel; Rovira, Jordi; Venskutonis, Petras Rimantas

2016-02-01

Rye and wheat bran extracts containing phenolic compounds and demonstrating high DPPH• (2,2-diphenyl-1-picrylhydrazyl), ABTS(•+) (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) scavenging and oxygen radical absorbance capacities (ORAC) were tested in beef hamburgers as possible functional ingredients. Bran extracts significantly increased the indicators of antioxidant potential of meat products and their global antioxidant response (GAR) during physiological in vitro digestion. The extracts also inhibited the formation of oxidation products, hexanal and malondialdehyde, of hamburgers during their storage; however, they did not have significant effect on the growth of microorganisms. Hamburgers with 0.8% wheat bran extract demonstrated the highest antioxidant potential. Some effects of bran extracts on other quality characteristics such as pH, color, formation of metmyoglobin were also observed, however, these effects did not have negative influence on the overall sensory evaluation score of hamburgers. Consequently, the use of bran extracts in meat products may be considered as promising means of increasing oxidative product stability and enriching with functional ingredients which might possess health benefits. © 2016 Institute of Food Technologists®

Probing size-dependent electrokinetics of hematite aggregates

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

Kedra-Królik, Karolina; Rosso, Kevin M.; Zarzycki, Piotr

Aqueous particle suspensions of many kinds are stabilized by the electrostatic potential developed at their surfaces from reaction with water and ions. An important and less well understood aspect of this stabilization is the dependence of the electrostatic surface potential on particle size. Surface electrostatics are typically probed by measuring particle electrophoretic mobilities and quantified in the electrokinetic potential (f), using commercially available Zeta Potential Analyzers (ZPA). Even though ZPAs provide frequency-spectra (histograms) of electrophoretic mobility and hydrodynamic diameter, typically only the maximal-intensity values are reported, despite the information in the remainder of the spectra. Here we propose a mappingmore » procedure that inter-correlates these histograms to extract additional insight, in this case to probe particle size-dependent electrokinetics. Our method is illustrated for a suspension of prototypical iron (III) oxide (hematite, a-Fe2O3). We found that the electrophoretic mobility and f-potential are a linear function of the aggregate size. By analyzing the distribution of surface site types as a function of aggregate size we show that site coordination increases with increasing aggregate diameter. This observation explains why the acidity of the iron oxide particles decreases with increasing particle size.« less

Identification of the molecular genetic basis of the low palmitic acid seed oil trait in soybean mutant line RG3 and association analysis of molecular markers with elevated seed stearic acid and reduced seed palmitic acid

USDA-ARS?s Scientific Manuscript database

The fatty acid composition of vegetable oil is becoming increasingly critical for the ultimate functionality and utilization in foods and industrial products. Partial chemical hydrogenation of soybean oil increases oxidative stability and shelf life but also results in the introduction of trans fats...

Deciphering the Dynamics of Non-Covalent Interactions Affecting Thermal Stability of a Protein: Molecular Dynamics Study on Point Mutant of Thermus thermophilus Isopropylmalate Dehydrogenase.

PubMed

Sharma, Reetu; Sastry, G Narahari

2015-01-01

Thermus thermophilius isopropylmalate dehydrogenase catalyzes oxidative decarboxylation and dehydrogenation of isopropylmalate. Substitution of leucine to alanine at position 172 enhances the thermal stability among the known point mutants. Exploring the dynamic properties of non-covalent interactions such as saltbridges, hydrogen bonds and hydrophobic interactions to explain thermal stability of a protein is interesting in its own right. In this study dynamic changes in the non-covalent interactions are studied to decipher the deterministic features of thermal stability of a protein considering a case study of a point mutant in Thermus thermophilus isopropylmalate dehydrogenase. A total of four molecular dynamic simulations of 0.2 μs were carried out on wild type and mutant's functional dimers at 300 K and 337 K. Higher thermal stability of the mutant as compared to wild type is revealed by root mean square deviation, root mean square fluctuations and Cα-Cα distance with an increase in temperature from 300 K to 337 K. Most of the regions of wild type fluctuate higher than the corresponding regions of mutant with an increase in temperature. Cα-Cα distance analysis suggests that long distance networks are significantly affected in wild type as compared to the mutant. Short lived contacts are higher in wild type, while long lived contacts are lost at 337 K. The mutant forms less hydrogen bonds with water as compared to wild type at 337 K. In contrast to wild type, the mutant shows significant increase in unique saltbridges, hydrogen bonds and hydrophobic contacts at 337 K. The current study indicates that there is a strong inter-dependence of thermal stability on the way in which non-covalent interactions reorganize, and it is rewarding to explore this connection in single mutant studies.

Aggregative stability of fungicidal nanomodifier based on zinc hydrosilicates

NASA Astrophysics Data System (ADS)

Grishina, Anna; Korolev, Evgeniy

2018-03-01

Currently, there is a strong need of high performance multi functional materials in high-rise construction. Obviously, such materials should be characterized by high strength; but for interior rooms biosafety is important as well. The promising direction to obtain both high strength and maintain biosafety in buildings and structures is to manage the structure of mineral binders by means of fungicidal nanomodifier based on zinc hydrosilicates. In the present work the aggregative stability of colloidal solutions of zinc hydrosilicates after one year of storage was studied. It has been established that the concentration of iron (III) hydroxide used to prepare the precursor of zinc hydrosilicates has a significant effect on the long-term aggregative stability: as the concentration of iron (III) hydroxide increases, the resistance of the fungicidal nanomodifier increases. It was found that, despite the minimal concentration of nano-sized zinc hydrosilicates (0.028%), the colloidal solution possesses a low long-term aggregative stability; while in the initial period (not less than 14 days) the colloidal solution of the nanomodifier is aggregatively stable. It is shown that when the ratio in the colloidal solution of the amount of the substance CH3COOH / SiO2 = 0.43 is reached, an increase in the polymerization rate is observed, which is the main cause of low aggregative stability. Colloidal solutions containing zinc hydrosilicates synthesized at a concentration of iron (III) hydroxide used to produce a precursor equal to 0.7% have a long-term aggregative stability and do not significantly change the reduced particle. Such compositions are to be expediently used for the nanomodifying of building composites in order to control their structure formation and to create conditions that impede the development of various mycelial fungi.

Influence of Endo- and Exocyclic Heteroatoms on Stabilities and 1,3-Dipolar Cycloaddition Reactivities of Mesoionic Azomethine Ylides and Imines.

PubMed

Champagne, Pier Alexandre; Houk, K N

2017-10-20

The geometries, stabilities, and 1,3-dipolar cycloaddition reactivities of 24 mesoionic azomethine ylides and imines were investigated using density functional theory calculations at the M06-2X/6-311+G-(d,p)/M06-2X/6-31G-(d) level. The computed structures highlight how the commonly used "aromatic" resonance form should be replaced by two more accurate resonance structures. Stabilities of the dipoles were assessed by various homodesmotic schemes and are consistent with these compounds being nonaromatic. The activation free energies with ethylene or acetylene range from 11.8 to 36.6 kcal/mol. Within each dipole type, the predicted cycloaddition reactivities correlate with the reaction energies and the resonance stabilization energies provided by the various substituents. Endocyclic (X) heteroatoms increase the reactivity of the 1,3-dipoles in the order of O > NH ≅ S, whereas exocyclic (Y) substituents increase it in the order of CH 2 > NH > O > S. Distortion/interaction analysis indicated that the difference in reactivity between differently substituted 1,3-dipoles is driven by distortion, whereas the difference between azomethine ylides and imines is related to lower interaction energies of imines with the dipolarophiles.

Studies of the conformational stability of invasion plasmid antigen B from Shigella

PubMed Central

Choudhari, Shyamal P; Kramer, Ryan; Barta, Michael L; Greenwood, Jamie C; Geisbrecht, Brian V; Joshi, Sangeeta B; Picking, William D; Middaugh, C Russell; Picking, Wendy L

2013-01-01

Shigella spp. are the causative agent of shigellosis, the second leading cause of diarrhea in children of ages 2–5. Despite many years of research, a protective vaccine has been elusive. We recently demonstrated that invasion plasmid antigens B and D (IpaB and IpaD) provide protection against S. flexneri and S. sonnei. These proteins, however, have very different properties which must be recognized and then managed during vaccine formulation. Herein, we employ spectroscopy to assess the stability of IpaB as well as IpgC (invasion protein gene), IpaB's cognate chaperone, and the IpaB/IpgC complex. The resulting data are mathematically summarized into a visual map illustrating the stability of the proteins and their complex as a function of pH and temperature. The IpaB/IpgC complex exhibits thermal stability at higher pH values but, though initially stable, quickly unfolds with increasing temperature when maintained at lower pH. In contrast, IpaB is a much more complex protein exhibiting increased stability at higher pH, but shows initial instability at lower pH values with pH 5 showing a distinct transition. IpgC precipitates at and below pH 5 and is stable above pH 7. Most strikingly, it is clear that complex formation results in stabilization of the two components. This work serves as a basis for the further development of IpaB as a vaccine candidate as well as extends our understanding of the structural stability of the Shigella type III secretion system. PMID:23494968

Asymptotic stability and instability of large-scale systems. [using vector Liapunov functions

NASA Technical Reports Server (NTRS)

Grujic, L. T.; Siljak, D. D.

1973-01-01

The purpose of this paper is to develop new methods for constructing vector Lyapunov functions and broaden the application of Lyapunov's theory to stability analysis of large-scale dynamic systems. The application, so far limited by the assumption that the large-scale systems are composed of exponentially stable subsystems, is extended via the general concept of comparison functions to systems which can be decomposed into asymptotically stable subsystems. Asymptotic stability of the composite system is tested by a simple algebraic criterion. By redefining interconnection functions among the subsystems according to interconnection matrices, the same mathematical machinery can be used to determine connective asymptotic stability of large-scale systems under arbitrary structural perturbations.

Improving electrokinetic microdevice stability by controlling electrolysis bubbles.

PubMed

Lee, Hwi Yong; Barber, Cedrick; Minerick, Adrienne R

2014-07-01

The voltage-operating window for many electrokinetic microdevices is limited by electrolysis gas bubbles that destabilize microfluidic system causing noise and irreproducible responses above ∼3 V DC and less than ∼1 kHz AC at 3 Vpp. Surfactant additives, SDS and Triton X-100, and an integrated semipermeable SnakeSkin® membrane were employed to control and assess electrolysis bubbles from platinum electrodes in a 180 by 70 μm, 10 mm long microchannel. Stabilized current responses at 100 V DC were observed with surfactant additives or SnakeSkin® barriers. Electrolysis bubble behaviors, visualized via video microscopy at the electrode surface and in the microchannels, were found to be influenced by surfactant function and SnakeSkin® barriers. Both SDS and Triton X-100 surfactants promoted smaller bubble diameters and faster bubble detachment from electrode surfaces via increasing gas solubility. In contrast, SnakeSkin® membranes enhanced natural convection and blocked bubbles from entering the microchannels and thus reduced current disturbances in the electric field. This data illustrated that electrode surface behaviors had substantially greater impacts on current stability than microbubbles within microchannels. Thus, physically blocking bubbles from microchannels is less effective than electrode functionalization approaches to stabilize electrokinetic microfluidic systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Distinct effects of tubulin isotype mutations on neurite growth in Caenorhabditis elegans

PubMed Central

Zheng, Chaogu; Diaz-Cuadros, Margarete; Nguyen, Ken C. Q.; Hall, David H.; Chalfie, Martin

2017-01-01

Tubulins, the building block of microtubules (MTs), play a critical role in both supporting and regulating neurite growth. Eukaryotic genomes contain multiple tubulin isotypes, and their missense mutations cause a range of neurodevelopmental defects. Using the Caenorhabditis elegans touch receptor neurons, we analyzed the effects of 67 tubulin missense mutations on neurite growth. Three types of mutations emerged: 1) loss-of-function mutations, which cause mild defects in neurite growth; 2) antimorphic mutations, which map to the GTP binding site and intradimer and interdimer interfaces, significantly reduce MT stability, and cause severe neurite growth defects; and 3) neomorphic mutations, which map to the exterior surface, increase MT stability, and cause ectopic neurite growth. Structure-function analysis reveals a causal relationship between tubulin structure and MT stability. This stability affects neuronal morphogenesis. As part of this analysis, we engineered several disease-associated human tubulin mutations into C. elegans genes and examined their impact on neuronal development at the cellular level. We also discovered an α-tubulin (TBA-7) that appears to destabilize MTs. Loss of TBA-7 led to the formation of hyperstable MTs and the generation of ectopic neurites; the lack of potential sites for polyamination and polyglutamination on TBA-7 may be responsible for this destabilization. PMID:28835377

Predicting stability of DNA duplexes in solutions containing magnesium and monovalent cations.

PubMed

Owczarzy, Richard; Moreira, Bernardo G; You, Yong; Behlke, Mark A; Walder, Joseph A

2008-05-13

Accurate predictions of DNA stability in physiological and enzyme buffers are important for the design of many biological and biochemical assays. We therefore investigated the effects of magnesium, potassium, sodium, Tris ions, and deoxynucleoside triphosphates on melting profiles of duplex DNA oligomers and collected large melting data sets. An empirical correction function was developed that predicts melting temperatures, transition enthalpies, entropies, and free energies in buffers containing magnesium and monovalent cations. The new correction function significantly improves the accuracy of predictions and accounts for ion concentration, G-C base pair content, and length of the oligonucleotides. The competitive effects of potassium and magnesium ions were characterized. If the concentration ratio of [Mg (2+)] (0.5)/[Mon (+)] is less than 0.22 M (-1/2), monovalent ions (K (+), Na (+)) are dominant. Effects of magnesium ions dominate and determine duplex stability at higher ratios. Typical reaction conditions for PCR and DNA sequencing (1.5-5 mM magnesium and 20-100 mM monovalent cations) fall within this range. Conditions were identified where monovalent and divalent cations compete and their stability effects are more complex. When duplexes denature, some of the Mg (2+) ions associated with the DNA are released. The number of released magnesium ions per phosphate charge is sequence dependent and decreases surprisingly with increasing oligonucleotide length.

Impact of self-assembled surfactant structures on rheology of concentrated nanoparticle dispersions.

PubMed

Zaman, A A; Singh, P; Moudgil, B M

2002-07-15

Rheological behavior of surfactant-stabilized colloidal dispersions of silica particles under extreme conditions (low pH, high ionic strength) has been investigated in relation to interparticle forces and stability of the dispersion. The surfactant used as the dispersing agent was C(12)TAB, a cationic surfactant. Stability analysis through turbidity measurements indicated that there is a sharp increase in the stability of the dispersion when the surfactant concentration is in the range of 8 to 10 mM in the system. The state of the dispersion changes from an unstable regime to a stable regime above a critical concentration of C(12)TAB in the system. In the case of interaction forces measured between the silica substrate and AFM tip, no repulsive force was observed up to a surfactant concentration of 8 mM and a transition from no repulsive forces to steric repulsive forces occurred between 8 and 10 mM. Rheological measurements as a function of C(12)TAB concentration indicated a significant decrease in the viscosity and linear viscoelastic functions of the dispersion over the same range of surfactant concentration (8 to 10 mM C(12)TAB), showing a strong correlation between the viscosity behavior, interparticle forces, and structure development in the dispersion.

Design optimization of natural laminar flow bodies in compressible flow

NASA Technical Reports Server (NTRS)

Dodbele, Simha S.

1992-01-01

An optimization method has been developed to design axisymmetric body shapes such as fuselages, nacelles, and external fuel tanks with increased transition Reynolds numbers in subsonic compressible flow. The new design method involves a constraint minimization procedure coupled with analysis of the inviscid and viscous flow regions and linear stability analysis of the compressible boundary-layer. In order to reduce the computer time, Granville's transition criterion is used to predict boundary-layer transition and to calculate the gradients of the objective function, and linear stability theory coupled with the e(exp n)-method is used to calculate the objective function at the end of each design iteration. Use of a method to design an axisymmetric body with extensive natural laminar flow is illustrated through the design of a tiptank of a business jet. For the original tiptank, boundary layer transition is predicted to occur at a transition Reynolds number of 6.04 x 10(exp 6). For the designed body shape, a transition Reynolds number of 7.22 x 10(exp 6) is predicted using compressible linear stability theory coupled with the e(exp n)-method.

Effect of vulcanization temperature and humidity on the properties of RTV silicone rubber

NASA Astrophysics Data System (ADS)

Wu, Xutao; Li, Xiuguang; Hao, Lu; Wen, Xishan; Lan, Lei; Yuan, Xiaoqing; Zhang, Qingping

2017-06-01

In order to study the difference in performance of room temperature vulcanized (RTV) silicone rubber in vulcanization environment with different temperature and humidity, static contact angle method, FTIR and TG is utilized to depict the properties of hydrophobicity, transfer of hydrophobicity, functional groups and thermal stability of RTV silicone rubber. It is found that different vulcanization conditions have effects on the characteristics of RTV silicone rubber, which shows that the hydrophobicity of RTV silicone rubber changes little with the vulcanization temperature but a slight increase with the vulcanization humidity. Temperature and humidity have obvious effects on the hydrophobicity transfer ability of RTV silicone rubber, which is better when vulcanization temperature is 5°C or vulcanization humidity is 95%. From the Fourier transform infrared spectroscopy, it can be concluded that humidity and temperature of vulcanization conditions have great effect on the functional groups of silicone rubber, and vulcanization conditions also have effect on thermal stability of RTV silicone rubber. When vulcanization temperature is 5°C or vulcanization humidity is 15% or 95%, the thermal stability of silicone rubber becomes worse.

Paliperidone for the treatment of schizoaffective disorder.

PubMed

Alphs, Larry; Fu, Dong-Jing; Turkoz, Ibrahim

2016-01-01

Schizoaffective disorder (SCA) is a complex mental illness characterized by psychosis and affective symptoms. Treatment usually involves concomitant therapy with antipsychotics, mood stabilizers, and/or antidepressants. Effective treatment must address acute symptoms, maintain long-term stability, promote recovery, and improve patient functioning. Data from 3 pivotal studies evaluating the acute and maintenance treatment of SCA with paliperidone are reviewed. Two formulations of paliperidone have been studied for these indications: an extended-release oral formulation (NCT00397033, NCT00412373) and long-acting injectable once-monthly paliperidone palmitate (NCT01193153). The reported effects of these formulations on psychotic, depressive, and manic symptoms are discussed. Both formulations were found to be safe and effective for the acute and maintenance treatment of SCA. Of critical importance for this treatment population is that rapid improvement was seen in all major symptoms of SCA, including psychosis, depression, and mania. Mediation analyses suggest that the known antipsychotic effects of paliperidone occur independently of its antidepressant effects. Both formulations of the drug are effective when used as monotherapy or adjunctively with antidepressants or mood stabilizers. Beyond symptom control, both formulations improved patient functioning and increased patient satisfaction.

Synergic combination of the sol–gel method with dip coating for plasmonic devices

PubMed Central

Patrini, Maddalena; Floris, Francesco; Fornasari, Lucia; Pellacani, Paola; Marchesini, Gerardo; Valsesia, Andrea; Artizzu, Flavia; Marongiu, Daniela; Saba, Michele; Marabelli, Franco; Mura, Andrea; Bongiovanni, Giovanni

2015-01-01

Summary Biosensing technologies based on plasmonic nanostructures have recently attracted significant attention due to their small dimensions, low-cost and high sensitivity but are often limited in terms of affinity, selectivity and stability. Consequently, several methods have been employed to functionalize plasmonic surfaces used for detection in order to increase their stability. Herein, a plasmonic surface was modified through a controlled, silica platform, which enables the improvement of the plasmonic-based sensor functionality. The key processing parameters that allow for the fine-tuning of the silica layer thickness on the plasmonic structure were studied. Control of the silica coating thickness was achieved through a combined approach involving sol–gel and dip-coating techniques. The silica films were characterized using spectroscopic ellipsometry, contact angle measurements, atomic force microscopy and dispersive spectroscopy. The effect of the use of silica layers on the optical properties of the plasmonic structures was evaluated. The obtained results show that the silica coating enables surface protection of the plasmonic structures, preserving their stability for an extended time and inducing a suitable reduction of the regeneration time of the chip. PMID:25821692

Theoretical investigations on diamondoids (CnHm, n = 10-41): Nomenclature, structural stabilities, and gap distributions

NASA Astrophysics Data System (ADS)

Wang, Ya-Ting; Zhao, Yu-Jun; Liao, Ji-Hai; Yang, Xiao-Bao

2018-01-01

Combining the congruence check and the first-principles calculations, we have systematically investigated the structural stabilities and gap distributions of possible diamondoids (CnHm) with the carbon numbers (n) from 10 to 41. A simple method for the nomenclature is proposed, which can be used to distinguish and screen the candidates with high efficiency. Different from previous theoretical studies, the possible diamondoids can be enumerated according to our nomenclature, without any pre-determination from experiments. The structural stabilities and electronic properties have been studied by density functional based tight binding and first-principles methods, where a nearly linear correlation is found between the energy gaps obtained by these two methods. According to the formation energy of structures, we have determined the stable configurations as a function of chemical potential. The maximum and minimum energy gaps are found to be dominated by the shape of diamondoids for clusters with a given number of carbon atoms, while the gap decreases in general as the size increases due to the quantum confinement.

Covalently functionalized noble metal nanoparticles for molecular imprinted polymer biosensors: Synthesis, characterization, and SERS detection

NASA Astrophysics Data System (ADS)

Volkert, Anna Allyse

This dissertation evaluates how gold nanoparticle structure and local environment influence resulting sensor function when using these nanomaterials for complex sample analysis. Molecular imprinted polymers (MIPs), a class of plastic antibodies, are engineered and incorporated into these nanosensors thereby facilitating the quantitative detection of a variety of small molecules when Raman spectroscopy and surface enhanced Raman scattering (SERS) are used for detection. First, homogeneous seeded growth gold nanosphere synthesis is evaluated as a function of ionic double layer composition and thickness. Systematically increasing the citrate concentration during synthesis improves nanomaterial shape homogeneity; however, further elevations of citrate concentration increase the number of internal and/or external atomic defects in the nanomaterials which leads to decreasing solution-phase stability. Next, spherical gold nanoparticles are modified with self-assembled monolayer (SAM), modeled using interfacial energy calculations, and experimental characterized using transmission electron microscopy, NMR, extinction spectroscopy, zeta potential, X-ray photoelectron spectroscopy, and flocculation studies to assess the morphology, surface chemistry, optical properties, surface charge, SAM packing density, and nanoparticle stability, respectively. The number of molecules on the nanostructures increases with increasing ionic strength (by decreasing the electrostatic interfacial energy between assembled molecules) which subsequently promotes nanoparticle stability. Third, plastic antibodies that recognize three drugs commonly used to treat migraines are engineered. These methacrylate-based MIPs are synthesized, extracted, characterized, and used to quantitatively and directly detect over-the-counter drugs in complex samples using Raman microscopy. These results along with numerical approximation methods to estimate drug binding site densities and dissociation constants with the MIPs serve as a foundation for understanding how modest recognition selectivity of MIPs coupled with shifts in the vibrational energy modes from the drugs upon hydrogen binding to the polymer backbone promote sensitive and selective drug detection in complex samples. Finally, nanomaterial incorporation into MIPs for applications in SERS-based biosensors is evaluated. Importantly, gold nanorod concentration increases the detectability of the same drugs using MIPs as pre-concentration and recognition elements. This combination of materials, theory, and applications forms a solid foundation which should aid in the design and development of MIP nanobiosensors for specific and sensitive detection of small molecules in complex matrices.

Preformulation stability study of the EGFR inhibitor HKI-272 (Neratinib) and mechanism of degradation.

PubMed

Lu, Qinghong; Ku, Mannching Sherry

2012-03-01

The stability in solution of HKI-272 (Neratinib) was studied as a function of pH. The drug is most stable from pH 3 to 4, and degradation rate increases rapidly around pH 6 and appears to approach a maximum asymptotic limit in the range of pH 812. Pseudo first-order reaction kinetics was observed at all pH values. The structure of the major degradation product indicates that it is formed by a cascade of reactions within the dimethylamino crotonamide group of HKI-272. It is assumed that the rate-determining step is the initial isomerization from allyl amine to enamine functionality, followed by hydrolysis and subsequent cyclization to a stable lactam. The maximum change in degradation rate as a function of pH occurs at about pH 6, which corresponds closely to the theoretical pKa value of the dimethylamino group of HKI-272 when accounting for solvent/temperature effects. The observed relationship between pH and degradation rate is discussed, and a self-catalyzed mechanism for the allylamine-enamine isomerization reaction is proposed. The relevance of these findings to other allylamine drugs is discussed in terms of the relative stability of the allylic anion intermediate through which, the isomerization occurs.

Polyoxylglycerides and glycerides: effects of manufacturing parameters on API stability, excipient functionality and processing.

PubMed

Jannin, Vincent; Rodier, Jean-David; Musakhanian, Jasmine

2014-05-15

Lipid-based formulations are a viable option to address modern drug delivery challenges such as increasing the oral bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs), or sustaining the drug release of molecules intended for chronic diseases. Esters of fatty acids and glycerol (glycerides) and polyethylene-glycols (polyoxylglycerides) are two main classes of lipid-based excipients used by oral, dermal, rectal, vaginal or parenteral routes. These lipid-based materials are more and more commonly used in pharmaceutical drug products but there is still a lack of understanding of how the manufacturing processes, processing aids, or additives can impact the chemical stability of APIs within the drug product. In that regard, this review summarizes the key parameters to look at when formulating with lipid-based excipients in order to anticipate a possible impact on drug stability or variation of excipient functionality. The introduction presents the chemistry of natural lipids, fatty acids and their properties in relation to the extraction and refinement processes. Then, the key parameters during the manufacturing process influencing the quality of lipid-based excipients are provided. Finally, their critical characteristics are discussed in relation with their intended functionality and ability to interact with APIs and others excipients within the formulation. Copyright © 2014. Published by Elsevier B.V.

Increased efficacy of VX-809 in different cellular systems results from an early stabilization effect of F508del-CFTR.

PubMed

Farinha, Carlos M; Sousa, Marisa; Canato, Sara; Schmidt, André; Uliyakina, Inna; Amaral, Margarida D

2015-08-01

Cystic fibrosis (CF), the most common recessive autosomal disease among Caucasians, is caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein. The most common mutation, F508del, leads to CFTR impaired plasma membrane trafficking. Therapies modulating CFTR basic defect are emerging, such as VX-809, a corrector of F508del-CFTR traffic which just succeeded in a Phase III clinical trial. We recently showed that VX-809 is additive to two other correctors (VRT-325 and compound 4a). Here, we aimed to determine whether the differential rescuing by these compounds results from cell-specific factors or rather from distinct effects at the early biogenesis and/or processing. The rescuing efficiencies of the above three correctors were first compared in different cellular models (primary respiratory cells, cystic fibrosis bronchial epithelial and baby hamster kidney [BHK] cell lines) by functional approaches: micro-Ussing chamber and iodide efflux. Next, biochemical methods (metabolic labeling, pulse-chase and immunoprecipitation) were used to determine their impact on CFTR biogenesis / processing. Functional analyses revealed that VX-809 has the greatest rescuing efficacy and that the relative efficiencies of the three compounds are essentially maintained in all three cellular models tested. Nevertheless, biochemical data show that VX-809 significantly stabilizes F508del-CFTR immature form, an effect that is not observed for C3 nor C4. VX-809 and C3 also significantly increase accumulation of immature CFTR. Our data suggest that VX-809 increases the stability of F508del-CFTR immature form at an early phase of its biogenesis, thus explaining its increased efficacy when inducing its rescue.

Increased efficacy of VX-809 in different cellular systems results from an early stabilization effect of F508del-CFTR

PubMed Central

Farinha, Carlos M; Sousa, Marisa; Canato, Sara; Schmidt, André; Uliyakina, Inna; Amaral, Margarida D

2015-01-01

Cystic fibrosis (CF), the most common recessive autosomal disease among Caucasians, is caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein. The most common mutation, F508del, leads to CFTR impaired plasma membrane trafficking. Therapies modulating CFTR basic defect are emerging, such as VX-809, a corrector of F508del-CFTR traffic which just succeeded in a Phase III clinical trial. We recently showed that VX-809 is additive to two other correctors (VRT-325 and compound 4a). Here, we aimed to determine whether the differential rescuing by these compounds results from cell-specific factors or rather from distinct effects at the early biogenesis and/or processing. The rescuing efficiencies of the above three correctors were first compared in different cellular models (primary respiratory cells, cystic fibrosis bronchial epithelial and baby hamster kidney [BHK] cell lines) by functional approaches: micro-Ussing chamber and iodide efflux. Next, biochemical methods (metabolic labeling, pulse-chase and immunoprecipitation) were used to determine their impact on CFTR biogenesis / processing. Functional analyses revealed that VX-809 has the greatest rescuing efficacy and that the relative efficiencies of the three compounds are essentially maintained in all three cellular models tested. Nevertheless, biochemical data show that VX-809 significantly stabilizes F508del-CFTR immature form, an effect that is not observed for C3 nor C4. VX-809 and C3 also significantly increase accumulation of immature CFTR. Our data suggest that VX-809 increases the stability of F508del-CFTR immature form at an early phase of its biogenesis, thus explaining its increased efficacy when inducing its rescue. PMID:26171232

PEG 400-Based Phase Change Materials Nano-Enhanced with Functionalized Graphene Nanoplatelets.

PubMed

Marcos, Marco A; Cabaleiro, David; Guimarey, María J G; Comuñas, María J P; Fedele, Laura; Fernández, Josefa; Lugo, Luis

2017-12-29

This study presents new Nano-enhanced Phase Change Materials, NePCMs, formulated as dispersions of functionalized graphene nanoplatelets in a poly(ethylene glycol) with a mass-average molecular mass of 400 g·mol -1 for possible use in Thermal Energy Storage. Morphology, functionalization, purity, molecular mass and thermal stability of the graphene nanomaterial and/or the poly(ethylene glycol) were characterized. Design parameters of NePCMs were defined on the basis of a temporal stability study of nanoplatelet dispersions using dynamic light scattering. Influence of graphene loading on solid-liquid phase change transition temperature, latent heat of fusion, isobaric heat capacity, thermal conductivity, density, isobaric thermal expansivity, thermal diffusivity and dynamic viscosity were also investigated for designed dispersions. Graphene nanoplatelet loading leads to thermal conductivity enhancements up to 23% while the crystallization temperature reduces up to in 4 K. Finally, the heat storage capacities of base fluid and new designed NePCMs were examined by means of the thermophysical properties through Stefan and Rayleigh numbers. Functionalized graphene nanoplatelets leads to a slight increase in the Stefan number.

PEG 400-Based Phase Change Materials Nano-Enhanced with Functionalized Graphene Nanoplatelets

PubMed Central

Marcos, Marco A.; Guimarey, María J. G.; Comuñas, María J. P.

2017-01-01

This study presents new Nano-enhanced Phase Change Materials, NePCMs, formulated as dispersions of functionalized graphene nanoplatelets in a poly(ethylene glycol) with a mass-average molecular mass of 400 g·mol−1 for possible use in Thermal Energy Storage. Morphology, functionalization, purity, molecular mass and thermal stability of the graphene nanomaterial and/or the poly(ethylene glycol) were characterized. Design parameters of NePCMs were defined on the basis of a temporal stability study of nanoplatelet dispersions using dynamic light scattering. Influence of graphene loading on solid-liquid phase change transition temperature, latent heat of fusion, isobaric heat capacity, thermal conductivity, density, isobaric thermal expansivity, thermal diffusivity and dynamic viscosity were also investigated for designed dispersions. Graphene nanoplatelet loading leads to thermal conductivity enhancements up to 23% while the crystallization temperature reduces up to in 4 K. Finally, the heat storage capacities of base fluid and new designed NePCMs were examined by means of the thermophysical properties through Stefan and Rayleigh numbers. Functionalized graphene nanoplatelets leads to a slight increase in the Stefan number. PMID:29286324

Repeated burning of eastern tallgrass prairie increases richness and diversity, stabilizing late successional vegetation.

PubMed

Bowles, Marlin L; Jones, Michael D

2013-03-01

Understanding temporal effects of fire frequency on plant species diversity and vegetation structure is critical for managing tallgrass prairie (TGP), which occupies a mid-continental longitudinal precipitation and productivity gradient. Eastern TGP has contributed little information toward understanding whether vegetation-fire interactions are uniform or change across this biome. We resampled 34 fire-managed mid- and late-successional ungrazed TGP remnants occurring across a dry to wet-mesic moisture gradient in the Chicago region of Illinois, USA. We compared hypotheses that burning acts either as a stabilizing force or causes change in diversity and structure, depending upon fire frequency and successional stage. Based on western TGP, we expected a unimodal species richness distribution across a cover-productivity gradient, variable functional group responses to fire frequency, and a negative relationship between fire frequency and species richness. Species diversity was unimodal across the cover gradient and was more strongly humpbacked in stands with greater fire frequency. In support of a stabilizing hypothesis, temporal similarity of late-successional vegetation had a logarithmic relationship with increasing fire frequency, while richness and evenness remained stable. Temporal similarity within mid-successional stands was not correlated with fire frequency, while richness increased and evenness decreased over time. Functional group responses to fire frequency were variable. Summer forb richness increased under high fire frequency, while C4 grasses, spring forbs, and nitrogen-fixing species decreased with fire exclusion. On mesic and wet-mesic sites, vegetation structure measured by the ratio of woody to graminoid species was negatively correlated with abundance of forbs and with fire frequency. Our findings that species richness responds unimodally to an environmental-productivity gradient, and that fire exclusion increases woody vegetation and leads to loss of C4 and N-fixing species, suggest that these processes are uniform across the TGP biome and not affected by its rainfall-productivity gradient. However, increasing fire frequency in eastern TGP appears to increase richness of summer forbs and stabilize late-successional vegetation in the absence of grazing, and these processes may differ across the longitudinal axis of TGP. Managing species diversity in ungrazed eastern TGP may be dependent upon high fire frequency that removes woody vegetation and prevents biomass accumulation.

Predicting the Functional Roles of Knee Joint Muscles from Internal Joint Moments.

PubMed

Flaxman, Teresa E; Alkjær, Tine; Simonsen, Erik B; Krogsgaard, Michael R; Benoit, Daniel L

2017-03-01

Knee muscles are commonly labeled as flexors or extensors and aptly stabilize the knee against sagittal plane loads. However, how these muscles stabilize the knee against adduction-abduction and rotational loads remains unclear. Our study sought 1) to classify muscle roles as they relate to joint stability by quantifying the relationship between individual muscle activation patterns and internal net joint moments in all three loading planes and 2) to determine whether these roles change with increasing force levels. A standing isometric force matching protocol required subjects to modulate ground reaction forces to elicit various combinations and magnitudes of sagittal, frontal, and transverse internal joint moments. Surface EMG measured activities of 10 lower limb muscles. Partial least squares regressions determined which internal moment(s) were significantly related to the activation of individual muscles. Rectus femoris and tensor fasciae latae were classified as moment actuators for knee extension and hip flexion. Hamstrings were classified as moment actuators for hip extension and knee flexion. Gastrocnemius and hamstring muscles were classified as specific joint stabilizers for knee rotation. Vastii were classified as general joint stabilizers because activation was independent of moment generation. Muscle roles did not change with increasing effort levels. Our findings indicate muscle activation is not dependent on anatomical orientation but perhaps on its role in maintaining knee joint stability in the frontal and transverse loading planes. This is useful for delineating the roles of biarticular knee joint muscles and could have implications in robotics, musculoskeletal modeling, sports sciences, and rehabilitation.

Footwear for the neuropathic patient: offloading and stability.

PubMed

van Deursen, Robert

2008-01-01

Diabetic neuropathy is related to plantar ulceration through a variety of factors of which increased plantar pressures and loss of protective sensation are the most important. Loss of sensation in the lower limbs is also related to postural instability and an increased risk of falling. Ankle and foot proprioception play an important role in postural control and this sensory function is also affected by neuropathy. It is conceivable that footwear, orthotics, casts and braces used for treatment or prevention of plantar ulceration through offloading of the injured or at-risk foot area can exacerbate the postural instability and risk of falling. This has, however, received very limited attention in the literature. There are studies that have demonstrated that footwear adjustments can influence balance and stability in healthy, elderly subjects. The adjustments made to footwear for the diabetic foot are generally more dramatic and, therefore, are expected to have a greater influence on postural stability. Furthermore, casts and braces tend to deviate even more from normal footwear. This may seriously interfere with normal gait and posture and, therefore, stability. So far the evidence suggests that patients wearing such devices demonstrate markedly reduced activity levels. This reduced activity could add to the effect of offloading. This could also be interpreted to indicate problems with stability. This presentation will review the different types of offloading interventions frequently used for ulcer treatment and prevention and will consider the mechanical effect of these interventions on stability.

Supplemental irrigation as an initiative to support water and food security: A global evaluation of the potential to support and increase precipitation-fed wheat production

NASA Astrophysics Data System (ADS)

Smilovic, M.; Gleeson, T. P.; Adamowski, J. F.; Langhorn, C.; Kienzle, S. W.

2016-12-01

Supplemental irrigation is the practice of supporting precipitation-fed agriculture with limited irrigation. Precipitation-fed agriculture dominates the agricultural landscape, but is vulnerable to intraseasonal and interannual variability in precipitation and climate. The interplay between food security, water resources, ecosystem health, energy, and livelihoods necessitates evaluating and integrating initiatives that increase agricultural production while reducing demands on water resources. Supplemental irrigation is the practice of minimally irrigating in an effort to stabilize and increase agricultural production, as well as increase water productivity - the amount of crop produced per unit of water. The potential of supplemental irrigation to support both water and food security has yet to be evaluated at regional and global scales. We evaluate whether supplemental irrigation could stabilize and increase agricultural production of wheat by determining locally-calibrated water use-crop yield relationships, known as crop-water production functions. Crop-water production functions are functions of seasonal water use and crop yield, and previous efforts have largely ignored the effects of the temporal distribution of water use throughout the growing season. We significantly improve upon these efforts and provide an opportunity to evaluate supplemental irrigation that appropriately acknowledges the effects of irrigation scheduling. Integrating agroclimatic and crop data with the crop-water model Aquacrop, we determine the increases in wheat production achieved by maximizing water productivity, sharing limited water between different years, and other irrigation scenarios. The methodology presented and evaluation of supplemental irrigation provides water mangers, policy makers, governments, and non-governmental organizations the tools to appropriately understand and determine the potential of this initiative to support precipitation-fed agriculture.

[Assessment of influence of breath holding and hyperventilation on human postural stability with spectral analysis of stabilographic signal].

PubMed

Malakhov, M V; Makarenkova, E A; Mel'nikov, A A; Vikulov, A D

2014-01-01

The influence of breath holding and voluntary hyperventilation on the classic stabilometric parameters and the frequency characteristic of stabilographic signal were studied. We measured the stabilometric parameters on the force platform ("Ritm", Russia) on the healthy volunteers (n = 107) during quiet breath, voluntary hyperventilation (20 seconds) and maximal inspiratory breath holding (20 seconds). Respiratory frequency, respiratory amplitude and ventilation were estimated with strain gauge. We found that antero-posterior and medio-lateral sway amplitude and velocity as well as sway surface at breath-holding and at quiet breathing were the same, so breath holding didn't influence the postural stability. However the spectral parameters shifted to the high frequency range due to alteration of the respiratory muscles contractions during breath-holding versus quiet breath. Voluntary hyperventilation caused significant increase of all stabilographic indices that implied an impairment of postural stability, which was due to the increase of respiration frequency and amplitude. We also found that the spectral indices moved toward the high-frequency range with more pronounced degree of this shift versus breath holding. Besides, amplitudes of spectral peaks also increased. Perhaps such change of spectral indices was due to distortion of proprioceptive information because of increased excitability of nerve fibers during hyperventilation. Maximal inspiration breath holding causes strain of the postural control mechanisms that is reflected as elevation of postural sway frequency with no postural stability changes. Hyperventilation leads to the most prominent strain of balance function and decrease of steadiness that is manifested as increase of center of pressure oscillations amplitude and frequency.

Ancient thioredoxins evolved to modern-day stability-function requirement by altering native state ensemble.

PubMed

Modi, Tushar; Huihui, Jonathan; Ghosh, Kingshuk; Ozkan, S Banu

2018-06-19

Thioredoxins (THRXs)-small globular proteins that reduce other proteins-are ubiquitous in all forms of life, from Archaea to mammals. Although ancestral thioredoxins share sequential and structural similarity with the modern-day (extant) homologues, they exhibit significantly different functional activity and stability. We investigate this puzzle by comparative studies of their (ancient and modern-day THRXs') native state ensemble, as quantified by the dynamic flexibility index (DFI), a metric for the relative resilience of an amino acid to perturbations in the rest of the protein. Clustering proteins using DFI profiles strongly resemble an alternative classification scheme based on their activity and stability. The DFI profiles of the extant proteins are substantially different around the α3, α4 helices and catalytic regions. Likewise, allosteric coupling of the active site with the rest of the protein is different between ancient and extant THRXs, possibly explaining the decreased catalytic activity at low pH with evolution. At a global level, we note that the population of low-flexibility (called hinges) and high-flexibility sites increases with evolution. The heterogeneity (quantified by the variance) in DFI distribution increases with the decrease in the melting temperature typically associated with the evolution of ancient proteins to their modern-day counterparts.This article is part of a discussion meeting issue 'Allostery and molecular machines'. © 2018 The Author(s).

The physical properties of Li-doped g-C{sub 3}N{sub 4} monolayer sheet investigated by the first-principles

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

Ruan, Linwei; Xu, Gengsheng; Gu, Lina

2015-06-15

Highlights: • Systematically research on Li-doped g-C{sub 3}N{sub 4} monolayer sheets by first-principles calculation. • Optimal dopant concentration for optical absorption is 7.12%. • Thermodynamics stability of the doped substrate g-C{sub 3}N{sub 4} decreased with Li dopant concentration increasing. • The values of work function Φ decreased monotonously with the increasing of Li dopant concentration. - Abstract: The geometric, electronic, optical properties, thermodynamic stability, and work function of Li-doped g-C{sub 3}N{sub 4} monolayer were investigated by the first-principles calculation. It was found that the Li atoms were preferentially substituted the open-hollow sites of g-C{sub 3}N{sub 4}. Interestingly, the “odd” numbermore » of Li doped g-C{sub 3}N{sub 4} showed metallic properties, while the “even” number of Li atoms widened the band gap of g-C{sub 3}N{sub 4}. The HOMO and LUMO distributions reveal that the active sites located at edge N and C atoms for both pristine and the Li-doped g-C{sub 3}N{sub 4}. In addition, thermodynamic analysis showed that the doped Li atoms reduced the thermodynamic stability of g-C{sub 3}N{sub 4} monolayer sheets.« less

Peptidyl Prolyl Isomerase PIN1 Directly Binds to and Stabilizes Hypoxia-Inducible Factor-1α

PubMed Central

Han, Hyeong-jun; Kwon, Nayoung; Choi, Min-A; Jung, Kyung Oh; Piao, Juan-Yu; Ngo, Hoang Kieu Chi; Kim, Su-Jung; Kim, Do-Hee; Chung, June-Key; Cha, Young-Nam; Youn, Hyewon; Choi, Bu Young; Min, Sang-Hyun; Surh, Young-Joon

2016-01-01

Peptidyl prolyl isomerase (PIN1) regulates the functional activity of a subset of phosphoproteins through binding to phosphorylated Ser/Thr-Pro motifs and subsequently isomerization of the phosphorylated bonds. Interestingly, PIN1 is overexpressed in many types of malignancies including breast, prostate, lung and colon cancers. However, its oncogenic functions have not been fully elucidated. Here, we report that PIN1 directly interacts with hypoxia-inducible factor (HIF)-1α in human colon cancer (HCT116) cells. PIN1 binding to HIF-1α occurred in a phosphorylation-dependent manner. We also found that PIN1 interacted with HIF-1α at both exogenous and endogenous levels. Notably, PIN1 binding stabilized the HIF-1α protein, given that their levels were significantly increased under hypoxic conditions. The stabilization of HIF-1α resulted in increased transcriptional activity, consequently upregulating expression of vascular endothelial growth factor, a major contributor to angiogenesis. Silencing of PIN1 or pharmacologic inhibition of its activity abrogated the angiogenesis. By utilizing a bioluminescence imaging technique, we were able to demonstrate that PIN1 inhibition dramatically reduced the tumor volume in a subcutaneous mouse xenograft model and angiogenesis as well as hypoxia-induced transcriptional activity of HIF-1α. These results suggest that PIN1 interacting with HIF-1α is a potential cancer chemopreventive and therapeutic target. PMID:26784107

Network structure and functional properties of transparent hydrogel sanxan produced by Sphingomonas sanxanigenens NX02.

PubMed

Wu, Mengmeng; Shi, Zhong; Huang, Haidong; Qu, Jianmei; Dai, Xiaohui; Tian, Xuefeng; Wei, Weiying; Li, Guoqiang; Ma, Ting

2017-11-15

The micro-network structure and functional properties of sanxan, a novel polysaccharide produced by Sphingomonas sanxanigenens NX02, were investigated. Transparent hydrogel sanxan was a high acyl polymer containing 8.96% acetyl and 4.75% glyceroyl. The micro-network structure of sanxan was mainly cyclic configurations composed of side-by-side intermolecular associations, with many rounded nodes found. Sanxan exhibited predominant gelation behavior at concentrations above 0.1%, which was enhanced by adding cations, especially Ca 2+ . The gel strength of sanxan was much higher than that of low acyl gellan, but slightly lower than that of high acyl gellan. Furthermore, the conformation transition temperature was increased in the presence of added cations. Moreover, sanxan showed excellent emulsifying and emulsion stabilizing properties. Consequently, such excellent functional properties make sanxan a good candidate as a gelling, stabilizing, emulsifying, or suspending agent in food and cosmetics industries, and in medical and pharmaceutical usage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Core Stability Exercise Versus General Exercise for Chronic Low Back Pain.

PubMed

Coulombe, Brian J; Games, Kenneth E; Neil, Elizabeth R; Eberman, Lindsey E

2017-01-01

Reference: Wang XQ, Zheng JJ, Yu ZW, et al. A meta-analysis of core stability exercise versus general exercise for chronic low back pain. PLoS One. 2012;7(12):e52082. Clinical Questions: Is core stability exercise more effective than general exercise in the treatment of patients with nonspecific low back pain (LBP)?  The authors searched the following databases: China Biological Medicine disc, Cochrane Library, Embase, and PubMed from 1970 through 2011. The key medical subject headings searched were chronic pain, exercise, LBP, lumbosacral region, and sciatica.  Randomized controlled trials comparing core stability exercise with general exercise in the treatment of chronic LBP were investigated. Participants were male and female adults with LBP for at least 3 months that was not caused by a specific known condition. A control group receiving general exercise and an experimental group receiving core stability exercise were required for inclusion in the meta-analysis. Core stability was defined as the ability to ensure a stable neutral spine position, but the type of exercise was not specified. Outcome measures of pain intensity, back-specific functional status, quality of life, and work absenteeism were recorded at 3-, 6-, and 12-month intervals.  The study design, participant information, description of interventions in the control and experimental groups, outcome measures, and follow-up period were extracted. The mean difference (MD) and 95% confidence interval (CI) were calculated to evaluate statistical significance. Risk of bias was assessed using the Cochrane Collaboration Recommendations, and all articles were rated as high risk for other bias with no further explanation given.  Five studies involving 414 patients were included. Four studies assessed pain intensity using the visual analog scale or numeric rating scale. In the core stability exercise group, the reduction in pain was significant at 3 months (MD = -1.29, 95% CI = -2.47, -0.11; P = .003) but not at 6 months (MD = -0.50, 95% CI = -1.36, 0.35; P = .26). Functional status was improved at 3 months (MD = -7.14, 95% CI = -11.64, -2.65; P = .002) but not at 6 months (MD = -0.50, 95% CI = 0.36, 0.35; P = .26) or 12 months (MD = -0.32, 95% CI = -0.87, 0.23; P = .25). All of the included studies assessed back-specific functional status: 4 used the Oswestry Disability Index and 1 used the Roland-Morris Disability Questionnaire. Patients in the core stability exercise groups experienced improved functional status versus the general exercise group at 3 months (MD = -7.14, 95% CI = -11.64, -2.65; P = .002); no results were recorded at 6 or 12 months.  In the short term, core stability exercise was more effective than general exercise for decreasing pain and increasing back-specific functional status in patients with LBP.

Efficient CO2 capture by tertiary amine-functionalized ionic liquids through Li+-stabilized zwitterionic adduct formation

PubMed Central

Yang, Zhen-Zhen

2014-01-01

Summary Highly efficient CO2 absorption was realized through formation of zwitterionic adducts, combining synthetic strategies to ionic liquids (ILs) and coordination. The essence of our strategy is to make use of multidentate cation coordination between Li+ and an organic base. Also PEG-functionalized organic bases were employed to enhance the CO2-philicity. The ILs were reacted with CO2 to form the zwitterionic adduct. Coordination effects between various lithium salts and neutral ligands, as well as the CO2 capacity of the chelated ILs obtained were investigated. For example, the CO2 capacity of PEG150MeBu2N increased steadily from 0.10 to 0.66 (mol CO2 absorbed per mol of base) through the formation of zwitterionic adducts being stabilized by Li+. PMID:25246955

Core stability training for injury prevention.

PubMed

Huxel Bliven, Kellie C; Anderson, Barton E

2013-11-01

Enhancing core stability through exercise is common to musculoskeletal injury prevention programs. Definitive evidence demonstrating an association between core instability and injury is lacking; however, multifaceted prevention programs including core stabilization exercises appear to be effective at reducing lower extremity injury rates. PUBMED WAS SEARCHED FOR EPIDEMIOLOGIC, BIOMECHANIC, AND CLINICAL STUDIES OF CORE STABILITY FOR INJURY PREVENTION (KEYWORDS: "core OR trunk" AND "training OR prevention OR exercise OR rehabilitation" AND "risk OR prevalence") published between January 1980 and October 2012. Articles with relevance to core stability risk factors, assessment, and training were reviewed. Relevant sources from articles were also retrieved and reviewed. Stabilizer, mobilizer, and load transfer core muscles assist in understanding injury risk, assessing core muscle function, and developing injury prevention programs. Moderate evidence of alterations in core muscle recruitment and injury risk exists. Assessment tools to identify deficits in volitional muscle contraction, isometric muscle endurance, stabilization, and movement patterns are available. Exercise programs to improve core stability should focus on muscle activation, neuromuscular control, static stabilization, and dynamic stability. Core stabilization relies on instantaneous integration among passive, active, and neural control subsystems. Core muscles are often categorized functionally on the basis of stabilizing or mobilizing roles. Neuromuscular control is critical in coordinating this complex system for dynamic stabilization. Comprehensive assessment and training require a multifaceted approach to address core muscle strength, endurance, and recruitment requirements for functional demands associated with daily activities, exercise, and sport.

Effect of Core Stability Training on Trunk Function, Standing Balance, and Mobility in Stroke Patients.

PubMed

Haruyama, Koshiro; Kawakami, Michiyuki; Otsuka, Tomoyoshi

2017-03-01

Trunk function is important for standing balance, mobility, and functional outcome after stroke, but few studies have evaluated the effects of exercises aimed at improving core stability in stroke patients. To investigate the effectiveness of core stability training on trunk function, standing balance, and mobility in stroke patients. An assessor-blinded, randomized controlled trial was undertaken in a stroke rehabilitation ward, with 32 participants randomly assigned to an experimental group or a control group (n = 16 each). The experimental group received 400 minutes of core stability training in place of conventional programs within total training time, while the control group received only conventional programs. Primary outcome measures were evaluated using the Trunk Impairment Scale (TIS), which reflects trunk function. Secondary outcome measures were evaluated by pelvic tilt active range of motion in the sagittal plane, the Balance Evaluation Systems Test-brief version (Brief-BESTest), Functional Reach test, Timed Up-and-Go test (TUG), and Functional Ambulation Categories (FAC). A general linear repeated-measures model was used to analyze the results. A treatment effect was found for the experimental group on the dynamic balance subscale and total score of the TIS ( P = .002 and P < .001, respectively), pelvic tilt active range of motion ( P < .001), Brief-BESTest ( P < .001), TUG ( P = .008), and FAC ( P = .022). Core stability training has beneficial effects on trunk function, standing balance, and mobility in stroke patients. Our findings might provide support for introducing core stability training in stroke rehabilitation.

To explore the efficacy of community rehabilitation for facilitating daily function among patients with mental illness.

PubMed

Cheng, Jui-Fen; Chen, Chung-Ying; Lin, Mei-Chu; Huang, Xuan-Yi

2018-04-17

To explore the efficacy of community rehabilitation for facilitating daily function among patients with mental illness. A quasi-experimental design was used. Two hundred and sixty-four participants completed a daily living function scale questionnaire and provided disease-related information. Community rehabilitation was shown to be efficient in helping to stabilize mental illness and enhance daily function. Daily function had a significant and positive correlation with disease stability. Community rehabilitation for patients with mental illness can effectively stabilize and prevent disability among those with mental illness. © 2018 Wiley Periodicals, Inc.

Explicit construction of quadratic Lyapunov functions for the small gain, positivity, circle, and Popov theorems and their application to robust stability

NASA Technical Reports Server (NTRS)

Haddad, Wassim M.; Bernstein, Dennis S.

1991-01-01

Lyapunov function proofs of sufficient conditions for asymptotic stability are given for feedback interconnections of bounded real and positive real transfer functions. Two cases are considered: (1) a proper bounded real (resp., positive real) transfer function with a bounded real (resp., positive real) time-varying memoryless nonlinearity; and (2) two strictly proper bounded real (resp., positive real) transfer functions. A similar treatment is given for the circle and Popov theorems. Application of these results to robust stability with time-varying bounded real, positive real, and sector-bounded uncertainty is discussed.

Decreased histone deacetylase 2 impairs Nrf2 activation by oxidative stress

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

Mercado, Nicolas; Thimmulappa, Rajesh; Thomas, Catherine M.R.

2011-03-11

Research highlights: {yields} Nrf2 anti-oxidant function is impaired when HDAC activity is inhibited. {yields} HDAC inhibition decreases Nrf2 protein stability. {yields} HDAC2 is involved in reduced Nrf2 stability and both correlate in COPD samples. {yields} HDAC inhibition increases Nrf2 acetylation. -- Abstract: Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a crucial role in cellular defence against oxidative stress by inducing the expression of multiple anti-oxidant genes. However, where high levels of oxidative stress are observed, such as chronic obstructive pulmonary disease (COPD), Nrf2 activity is reduced, although the molecular mechanism for this defect is uncertain. Here, we show thatmore » down-regulation of histone deacetylase (HDAC) 2 causes Nrf2 instability, resulting in reduced anti-oxidant gene expression and increase sensitivity to oxidative stress. Although Nrf2 protein was clearly stabilized after hydrogen peroxide (H{sub 2}O{sub 2}) stimulation in a bronchial epithelial cell line (BEAS2B), Nrf2 stability was decreased and Nrf2 acetylation increased in the presence of an HDAC inhibitor, trichostatin A (TSA). TSA also reduced Nrf2-regulated heme-oxygenase-1 (HO-1) expression in these cells, and this was confirmed in acute cigarette-smoke exposed mice in vivo. HDAC2 knock-down by RNA interference resulted in reduced H{sub 2}O{sub 2}-induced Nrf2 protein stability and activity in BEAS2B cells, whereas HDAC1 knockdown had no effect. Furthermore, monocyte-derived macrophages obtained from healthy volunteers (non-smokers and smokers) and COPD patients showed a significant correlation between HDAC2 expression and Nrf2 expression (r = 0.92, p < 0.0001). Thus, reduced HDAC2 activity in COPD may account for increased Nrf2 acetylation, reduced Nrf2 stability and impaired anti oxidant defences.« less

Fusion of an oligopeptide to the N terminus of an alkaline α-amylase from Alkalimonas amylolytica simultaneously improves the enzyme's catalytic efficiency, thermal stability, and resistance to oxidation.

PubMed

Yang, Haiquan; Lu, Xinyao; Liu, Long; Li, Jianghua; Shin, Hyun-dong; Chen, Rachel R; Du, Guocheng; Chen, Jian

2013-05-01

In this study, we constructed and expressed six fusion proteins composed of oligopeptides attached to the N terminus of the alkaline α-amylase (AmyK) from Alkalimonas amylolytica. The oligopeptides had various effects on the functional and structural characteristics of AmyK. AmyK-p1, the fusion protein containing peptide 1 (AEAEAKAKAEAEAKAK), exhibited improved specific activity, catalytic efficiency, alkaline stability, thermal stability, and oxidative stability compared with AmyK. Compared with AmyK, the specific activity and catalytic constant (kcat) of AmyK-p1 were increased by 4.1-fold and 3.5-fold, respectively. The following properties were also improved in AmyK-p1 compared with AmyK: kcat/Km increased from 1.8 liter/(g·min) to 9.7 liter/(g·min), stable pH range was extended from 7.0 to 11.0 to 7.0 to 12.0, optimal temperature increased from 50°C to 55°C, and the half-life at 60°C increased by ∼2-fold. Moreover, AmyK-p1 showed improved resistance to oxidation and retained 54% of its activity after incubation with H2O2, compared with 20% activity retained by AmyK. Finally, AmyK-p1 was more compatible than AmyK with the commercial solid detergents tested. The mechanisms responsible for these changes were analyzed by comparing the three-dimensional (3-D) structural models of AmyK and AmyK-p1. The significantly enhanced catalytic efficiency and stability of AmyK-p1 suggests its potential as a detergent ingredient. In addition, the oligopeptide fusion strategy described here may be useful for improving the catalytic efficiency and stability of other industrial enzymes.

Fusion of an Oligopeptide to the N Terminus of an Alkaline α-Amylase from Alkalimonas amylolytica Simultaneously Improves the Enzyme's Catalytic Efficiency, Thermal Stability, and Resistance to Oxidation

PubMed Central

Yang, Haiquan; Lu, Xinyao; Li, Jianghua; Shin, Hyun-dong; Chen, Rachel R.; Du, Guocheng

2013-01-01

In this study, we constructed and expressed six fusion proteins composed of oligopeptides attached to the N terminus of the alkaline α-amylase (AmyK) from Alkalimonas amylolytica. The oligopeptides had various effects on the functional and structural characteristics of AmyK. AmyK-p1, the fusion protein containing peptide 1 (AEAEAKAKAEAEAKAK), exhibited improved specific activity, catalytic efficiency, alkaline stability, thermal stability, and oxidative stability compared with AmyK. Compared with AmyK, the specific activity and catalytic constant (kcat) of AmyK-p1 were increased by 4.1-fold and 3.5-fold, respectively. The following properties were also improved in AmyK-p1 compared with AmyK: kcat/Km increased from 1.8 liter/(g·min) to 9.7 liter/(g·min), stable pH range was extended from 7.0 to 11.0 to 7.0 to 12.0, optimal temperature increased from 50°C to 55°C, and the half-life at 60°C increased by ∼2-fold. Moreover, AmyK-p1 showed improved resistance to oxidation and retained 54% of its activity after incubation with H2O2, compared with 20% activity retained by AmyK. Finally, AmyK-p1 was more compatible than AmyK with the commercial solid detergents tested. The mechanisms responsible for these changes were analyzed by comparing the three-dimensional (3-D) structural models of AmyK and AmyK-p1. The significantly enhanced catalytic efficiency and stability of AmyK-p1 suggests its potential as a detergent ingredient. In addition, the oligopeptide fusion strategy described here may be useful for improving the catalytic efficiency and stability of other industrial enzymes. PMID:23455344

Physiochemical and functional properties of chum salmon (Oncorhynchus keta) skin gelatin extracted at different temperatures.

PubMed

Liu, Yang; Xia, Lining; Jia, Hui; Li, Qi; Jin, Wengang; Dong, Xiuping; Pan, Jinfeng

2017-12-01

Aquatic source gelatins are gaining more attention due to the advantages in safety and religion acceptability compared with mammalian sources. For understanding the effects of extracting temperature on gelatins from chum salmon (Oncorhynchus keta) skins (GCSS), gelatins were extracted at temperatures from 40 to 90°C and the physiochemical properties of GCSS were investigated. GCSS yield increased while imino acids content declined as the increase of temperature. GCSS40, 50 and 60 showed strong β-, α1- and α2-chains but the three faded in GCSS70, 80 and 90, with the presence of low molecular weight fragments. Amides A, I and III were shifted to higher wavenumber in GCSS70, 80 and 90 compared with that of GCSS40, 50 and 60. X-ray diffraction showed lower intensity of peak at 7° in GCSS80 and 90 than in the other GCSS. Gel strength declined while a*, b* and ΔE* value increased as temperature increased. Foam expansion and stability of GCSS40, 50 and 60 were lower than those of GCSS70, 80 and 90. Emulsion activity and stability decreased as temperature increased. Extracting temperature greatly affected yield, molecular composition and functionalities of GCSS. A temperature lower than 50°C is recommended for GCSS extraction. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Improved genetic stability of recombinant yellow fever 17D virus expressing a lentiviral Gag gene fragment.

PubMed

de Santana, Marlon G Veloso; Neves, Patrícia C C; dos Santos, Juliana Ribeiro; Lima, Noemia S; dos Santos, Alexandre A C; Watkins, David I; Galler, Ricardo; Bonaldo, Myrna C

2014-03-01

We have previously designed a method to construct viable recombinant Yellow Fever (YF) 17D viruses expressing heterologous polypeptides including part of the Simian Immunodeficiency Virus (SIV) Gag protein. However, the expressed region, encompassing amino acid residues from 45 to 269, was genetically unstable. In this study, we improved the genetic stability of this recombinant YF 17D virus by introducing mutations in the IRES element localized at the 5' end of the SIV gag gene. The new stable recombinant virus elicited adaptive immune responses similar to those induced by the original recombinant virus. It is, therefore, possible to increase recombinant stability by removing functional motifs from the insert that may have deleterious effects on recombinant YF viral fitness. Copyright © 2014 Elsevier Inc. All rights reserved.

Thermal stability of bioactive enzymatic papers.

PubMed

Khan, Mohidus Samad; Li, Xu; Shen, Wei; Garnier, Gil

2010-01-01

The thermal stability of two enzymes adsorbed on paper, alkaline phosphatase (ALP) and horseradish peroxidase (HRP), was measured using a colorimetric technique quantifying the intensity of the product complex. The enzymes adsorbed on paper retained their functionality and selectivity. Adsorption on paper increased the enzyme thermal stability by 2-3 orders of magnitude compared to the same enzyme in solution. ALP and HRP enzymatic papers had half-lives of 533 h and 239 h at 23 degrees C, respectively. The thermal degradation of adsorbed enzyme was found to follow two sequential first-order reactions, indication of a reaction system. A complex pattern of enzyme was printed on paper using a thermal inkjet printer. Paper and inkjet printing are ideal material and process to manufacture low-cost-high volume bioactive surfaces.

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

DOE PAGES

Fergus, Jeffrey W.

2014-04-12

One of the important applications of yttria stabilized zirconia is as a thermal barrier coating for gas turbine engines. While yttria stabilized zirconia performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatingsmore » are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.« less

Compact and highly stable quantum dots through optimized aqueous phase transfer

NASA Astrophysics Data System (ADS)

Tamang, Sudarsan; Beaune, Grégory; Poillot, Cathy; De Waard, Michel; Texier-Nogues, Isabelle; Reiss, Peter

2011-03-01

A large number of different approaches for the aqueous phase transfer of quantum dots have been proposed. Surface ligand exchange with small hydrophilic thiols, such as L-cysteine, yields the lowest particle hydrodynamic diameter. However, cysteine is prone to dimer formation, which limits colloidal stability. We demonstrate that precise pH control during aqueous phase transfer dramatically increases the colloidal stability of InP/ZnS quantum dots. Various bifunctional thiols have been applied. The formation of disulfides, strongly diminishing the fluorescence QY has been prevented through addition of appropriate reducing agents. Bright InP/ZnS quantum dots with a hydrodynamic diameter <10 nm and long-term stability have been obtained. Finally we present in vitro studies of the quantum dots functionalized with the cell-penetrating peptide maurocalcine.

Stabilization, Rolling, and Addition of Other Extracellular Matrix Proteins to Collagen Hydrogels Improve Regeneration in Chitosan Guides for Long Peripheral Nerve Gaps in Rats.

PubMed

Gonzalez-Perez, Francisco; Cobianchi, Stefano; Heimann, Claudia; Phillips, James B; Udina, Esther; Navarro, Xavier

2017-03-01

Autograft is still the gold standard technique for the repair of long peripheral nerve injuries. The addition of biologically active scaffolds into the lumen of conduits to mimic the endoneurium of peripheral nerves may increase the final outcome of artificial nerve devices. Furthermore, the control of the orientation of the collagen fibers may provide some longitudinal guidance architecture providing a higher level of mesoscale tissue structure. To evaluate the regenerative capabilities of chitosan conduits enriched with extracellular matrix-based scaffolds to bridge a critical gap of 15 mm in the rat sciatic nerve. The right sciatic nerve of female Wistar Hannover rats was repaired with chitosan tubes functionalized with extracellular matrix-based scaffolds fully hydrated or stabilized and rolled to bridge a 15 mm nerve gap. Recovery was evaluated by means of electrophysiology and algesimetry tests and histological analysis 4 months after injury. Stabilized constructs enhanced the success of regeneration compared with fully hydrated scaffolds. Moreover, fibronectin-enriched scaffolds increased muscle reinnervation and number of myelinated fibers compared with laminin-enriched constructs. A mixed combination of collagen and fibronectin may be a promising internal filler for neural conduits for the repair of peripheral nerve injuries, and their stabilization may increase the quality of regeneration over long gaps. Copyright © 2017 by the Congress of Neurological Surgeons

The effect of charge mutations on the stability and aggregation of a human single chain Fv fragment.

PubMed

Austerberry, James I; Dajani, Rana; Panova, Stanislava; Roberts, Dorota; Golovanov, Alexander P; Pluen, Alain; van der Walle, Christopher F; Uddin, Shahid; Warwicker, Jim; Derrick, Jeremy P; Curtis, Robin

2017-06-01

The aggregation propensities for a series of single-chain variable fragment (scFv) mutant proteins containing supercharged sequences, salt bridges and lysine/arginine-enriched motifs were characterised as a function of pH and ionic strength to isolate the electrostatic contributions. Recent improvements in aggregation predictors rely on using knowledge of native-state protein-protein interactions. Consistent with previous findings, electrostatic contributions to native protein-protein interactions correlate with aggregate growth pathway and rates. However, strong reversible self-association observed for selected mutants under native conditions did not correlate with aggregate growth, indicating 'sticky' surfaces that are exposed in the native monomeric state are inaccessible when aggregates grow. We find that even though similar native-state protein-protein interactions occur for the arginine and lysine-enriched mutants, aggregation propensity is increased for the former and decreased for the latter, providing evidence that lysine suppresses interactions between partially folded states under these conditions. The supercharged mutants follow the behaviour observed for basic proteins under acidic conditions; where excess net charge decreases conformational stability and increases nucleation rates, but conversely reduces aggregate growth rates due to increased intermolecular electrostatic repulsion. The results highlight the limitations of using conformational stability and native-state protein-protein interactions as predictors for aggregation propensity and provide guidance on how to engineer stabilizing charged mutations. Copyright © 2017. Published by Elsevier B.V.

Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

PubMed

Zhang, Jiewen; Bell, Leonard N

2017-04-01

Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm 2 for dark conditions, 27 μW/cm 2 for low intensity, and 190 μW/cm 2 for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability. © 2017 Institute of Food Technologists®.

Thermostability in rubredoxin and its relationship to mechanical rigidity

NASA Astrophysics Data System (ADS)

Rader, A. J.

2010-03-01

The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features possibly responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. Experimental evidence exists to both support and contradict this supposition. We computationally investigate the relationship between thermostability and rigidity using rubredoxin as a case study. The mechanical rigidity is calculated using atomic models of homologous rubredoxin structures from the hyperthermophile Pyrococcus furiosus and mesophile Clostridium pasteurianum using the FIRST software. A global increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. Locally, rigidity differences (between mesophilic and thermophilic structures) agree with differences in protection factors.

Effect of echo spacing and readout bandwidth on basic performances of EPI-fMRI acquisition sequences implemented on two 1.5 T MR scanner systems.

PubMed

Giannelli, Marco; Diciotti, Stefano; Tessa, Carlo; Mascalchi, Mario

2010-01-01

Although in EPI-fMRI analyses typical acquisition parameters (TR, TE, matrix, slice thickness, etc.) are generally employed, various readout bandwidth (BW) values are used as a function of gradients characteristics of the MR scanner. Echo spacing (ES) is another fundamental parameter of EPI-fMRI acquisition sequences but the employed ES value is not usually reported in fMRI studies. In the present work, the authors investigated the effect of ES and BW on basic performances of EPI-fMRI sequences in terms of temporal stability and overall image quality of time series acquisition. EPI-fMRI acquisitions of the same water phantom were performed using two clinical MR scanner systems (scanners A and B) with different gradient characteristics and functional designs of radiofrequency coils. For both scanners, the employed ES values ranged from 0.75 to 1.33 ms. The used BW values ranged from 125.0 to 250.0 kHz/64pixels and from 78.1 to 185.2 kHz/64pixels for scanners A and B, respectively. The temporal stability of EPI-fMRI sequence was assessed measuring the signal-to-fluctuation noise ratio (SFNR) and signal drift (DR), while the overall image quality was assessed evaluating the signal-to-noise ratio (SNR(ts)) and nonuniformity (NU(ts)) of the time series acquisition. For both scanners, no significant effect of ES and BW on signal drift was revealed. The SFNR, NU(ts) and SNR(ts) values of scanner A did not significantly vary with ES. On the other hand, the SFNR, NU(ts), and SNR(ts) values of scanner B significantly varied with ES. SFNR (5.8%) and SNR(ts) (5.9%) increased with increasing ES. SFNR (25% scanner A, 32% scanner B) and SNR(ts) (26.2% scanner A, 30.1% scanner B) values of both scanners significantly decreased with increasing BW. NU(ts) values of scanners A and B were less than 3% for all BW and ES values. Nonetheless, scanner A was characterized by a significant upward trend (3% percentage of variation) of time series nonuniformity with increasing BW while NU(ts) of scanner B significantly increased (19% percentage of variation) with increasing ES. Temporal stability (SFNR and DR) and overall image quality (NU(ts) and SNR(ts)) of EPI-fMRI time series can significantly vary with echo spacing and readout bandwidth. The specific pattern of variation may depend on the performance of each single MR scanner system in terms of gradients characteristics, EPI sequence calibrations (eddy currents, shimming, etc.), and functional design of radiofrequency coil. Our results indicate that the employment of low BW improves not only the signal-to-noise ratio of EPI-fMRI time series but also the temporal stability of functional acquisitions. The use of minimum ES values is not entirely advantageous when the MR scanner system is characterized by gradients with low performances and suboptimal EPI sequence calibration. Since differences in basic performances of MR scanner system are potential source of variability for fMRI activation, phantom measurements of SFNR, DR, NU(ts), and SNR(ts) can be executed before subjects acquisitions to monitor the stability of MR scanner performances in clinical group comparison and longitudinal studies.

LMI-based stability analysis of fuzzy-model-based control systems using approximated polynomial membership functions.

PubMed

Narimani, Mohammand; Lam, H K; Dilmaghani, R; Wolfe, Charles

2011-06-01

Relaxed linear-matrix-inequality-based stability conditions for fuzzy-model-based control systems with imperfect premise matching are proposed. First, the derivative of the Lyapunov function, containing the product terms of the fuzzy model and fuzzy controller membership functions, is derived. Then, in the partitioned operating domain of the membership functions, the relations between the state variables and the mentioned product terms are represented by approximated polynomials in each subregion. Next, the stability conditions containing the information of all subsystems and the approximated polynomials are derived. In addition, the concept of the S-procedure is utilized to release the conservativeness caused by considering the whole operating region for approximated polynomials. It is shown that the well-known stability conditions can be special cases of the proposed stability conditions. Simulation examples are given to illustrate the validity of the proposed approach.

The Effect of Small Molecule Additives on the Self-Assembly and Functionality of Protein-Polymer Diblock Copolymers

NASA Astrophysics Data System (ADS)

Thomas, Carla; Xu, Liza; Olsen, Bradley

2013-03-01

Self-assembly of globular protein-polymer block copolymers into well-defined nanostructures provides a route towards the manufacture of protein-based materials which maintains protein fold and function. The model material mCherry-b-poly(N-isopropyl acrylamide) forms self-assembled nanostructures from aqueous solutions via solvent evaporation. To improve retention of protein functionality when dehydrated, small molecules such as trehalose and glycerol are added in solution prior to solvent removal. With as little as 10 wt% additive, improvements in retained functionality of 20-60% are observed in the solid-state as compared to samples in which no additive is present. Higher additive levels (up to 50%) continue to show improvement until approximately 100% of the protein function is retained. These large gains are hypothesized to originate from the ability of the additives to replace hydrogen bonds normally fulfilled by water. The addition of trehalose in the bulk material also improves the thermal stability of the protein by 15-20 °C, while glycerol decreases the thermal stability. Materials containing up to 50% additives remain microphase separated, and, upon incorporation of additives, nanostructure domain spacing tends to increase, accompanied by order-order transitions.

The contribution of fine roots to peatland stability under changing environmental conditions

NASA Astrophysics Data System (ADS)

Malhotra, A.; Brice, D. J.; Childs, J.; Phillips, J.; Hanson, P. J.; Iversen, C. M.

2017-12-01

Fine-root production and traits are closely linked with ecosystem nutrient and water fluxes, and may regulate these fluxes in response to environmental change. Plant strategies can shift to favoring below- over aboveground biomass allocation when nutrients or moisture are limited. Fine-roots traits such as root tissue density (RTD) or specific root length (SRL) can also adapt to the environment, for example, by maximizing the area of soil exploited by decreasing RTD and increasing SRL during dry conditions. Fine-root trait plasticity could contribute to the stability of peatland carbon function in response to environmental change. However, the extent and mechanisms of peatland fine-root plasticity are unknown. We investigated fine-root growth and traits and their link to environmental factors and aboveground dynamics at SPRUCE (Spruce and Peatland Responses Under Changing Environments), a warming and elevated CO2 (eCO2) experiment in an ombrotrophic peatland. In the first growing season of whole ecosystem warming, fine-root production increased with warming and drying. Above- versus belowground allocation strategies varied by plant functional type (PFT). In shrubs, contrary to our expectation, aboveground- to fine-root production allocation ratio increased with dryer conditions, perhaps as a response to a concurrent increase in nutrients. Trait response hypotheses were largely supported, with RTD decreasing and SRL increasing with warming; however, response varied among PFTs. Once eCO2 was turned on in the second growing season, preliminary results suggest interactive effects of warming and eCO2 on total fine-root production: production decreased or increased with warming in ambient or elevated CO2 plots, respectively. Both trait and production responses to warming and eCO2 varied by microtopography and depth. Our results highlight plasticity of fine-root traits and biomass allocation strategies; the extent and mechanism of which varies by PFT. We will summarize our results using a trait-based approach as a first step toward modeling fine-root contributions to peatland carbon stability in response to environmental change.

Case study comparison of functional vs. organic stability approaches for assessing threat potential at closed landfills in the USA.

PubMed

O'Donnell, Sean T; Caldwell, Michael D; Barlaz, Morton A; Morris, Jeremy W F

2018-05-01

Municipal solid waste (MSW) landfills in the USA are regulated under Subtitle D of the Resource Conservation and Recovery Act (RCRA), which includes the requirement to protect human health and the environment (HHE) during the post-closure care (PCC) period. Several approaches have been published for assessment of potential threats to HHE. These approaches can be broadly divided into organic stabilization, which establishes an inert waste mass as the ultimate objective, and functional stability, which considers long-term emissions in the context of minimizing threats to HHE in the absence of active controls. The objective of this research was to conduct a case study evaluation of a closed MSW landfill using long-term data on landfill gas (LFG) production, leachate quality, site geology, and solids decomposition. Evaluations based on both functional and organic stability criteria were compared. The results showed that longer periods of LFG and leachate management would be required using organic stability criteria relative to an approach based on functional stability. These findings highlight the somewhat arbitrary and overly stringent nature of assigning universal stability criteria without due consideration of the landfill's hydrogeologic setting and potential environmental receptors. This supports previous studies that advocated for transition to a passive or inactive control stage based on a performance-based functional stability framework as a defensible mechanism for optimizing and ending regulatory PCC. Copyright © 2018 Elsevier Ltd. All rights reserved.

In Silico Template Selection of Short Antimicrobial Peptide Viscotoxin for Improving Its Antimicrobial Efficiency in Development of Potential Therapeutic Drugs.

PubMed

Senthilkumar, B; Rajasekaran, R

2017-03-01

Rapid increase in antibiotic resistance has posed a worldwide threat, due to increased mortality, morbidity, and expenditure caused by antibiotic-resistant microbes. Recent development of the antimicrobial peptides like viscotoxin (Vt) has been successfully comprehended as a substitute for classical antibiotics. A structurally stable peptide, Vt can enhance antimicrobial property and can be used for various developmental purposes. Thus, structural stability among the antimicrobial peptides, Vt A1 (3C8P), A2 (1JMN), A3 (1ED0), B (1JMP), and C (1ORL) of Viscus album was computationally analyzed. In specific, the static confirmation of VtA3 showed high number of intramolecular interactions, along with an increase in hydrophobicity than others comparatively. Further, conformational sampling was used to analyze various geometrical parameters such as root mean square deviation, root mean square fluctuation, radius of gyration, and ovality which also revealed the structural stability of VtA3. Moreover, the statistically validated contours of surface area, lipophilicity, and distance constraints of disulfide bonds also supported the priority of VtA3 with respect to stability. Finally, the functional activity of peptides was accessed by computing their free energy of membrane association and membrane interactions, which defined VtA3 as functionally stable. Currently, peptide-based antibiotics and nanoparticles have attracted the pharmaceutical industries for their potential therapeutic applications. Thereby, it is proposed that viscotoxin A3 (1ED0) could be used as a preeminent template for scaffolding potentially efficient antimicrobial peptide-based drugs and nanomaterials in future.

Extreme trajectory approach to the problem of determining the degree of stability of a laser surface scanning system

NASA Astrophysics Data System (ADS)

Nikitin, V. N.; Chemodanov, V. B.

2018-02-01

The degree of stability of a laser system for surface scanning with nonlinear multiplicative crosstalks is discussed. To determine its stability, the action functional is introduced, which is defined on the set of virtual (achievable) trajectories. The action functional is a measure of external action, which should be applied to a system to move it along a predetermined trial trajectory in the state space.The degree of stability of the system depends on the minimum value of the action functional which is reached on the extreme trajectory transferring the laser scanning system from equilibrium to the limit of the normal operation range. Numerical methods are proposed for calculating the degree of stability.

Increasing the thermal stability of cellulase C using rules learned from thermophilic proteins: a pilot study.

PubMed

Németh, Attila; Kamondi, Szilárd; Szilágyi, András; Magyar, Csaba; Kovári, Zoltán; Závodszky, Péter

2002-05-02

Some structural features underlying the increased thermostability of enzymes from thermophilic organisms relative to their homologues from mesophiles are known from earlier studies. We used cellulase C from Clostridium thermocellum to test whether thermostability can be increased by mutations designed using rules learned from thermophilic proteins. Cellulase C has a TIM barrel fold with an additional helical subdomain. We designed and produced a number of mutants with the aim to increase its thermostability. Five mutants were designed to create new electrostatic interactions. They all retained catalytic activity but exhibited decreased thermostability relative to the wild-type enzyme. Here, the stabilizing contributions are obviously smaller than the destabilization caused by the introduction of the new side chains. In another mutant, the small helical subdomain was deleted. This mutant lost activity but its melting point was only 3 degrees C lower than that of the wild-type enzyme, which suggests that the subdomain is an independent folding unit and is important for catalytic function. A double mutant was designed to introduce a new disulfide bridge into the enzyme. This mutant is active and has an increased stability (deltaT(m)=3 degrees C, delta(deltaG(u))=1.73 kcal/mol) relative to the wild-type enzyme. Reduction of the disulfide bridge results in destabilization and an altered thermal denaturation behavior. We conclude that rules learned from thermophilic proteins cannot be used in a straightforward way to increase the thermostability of a protein. Creating a crosslink such as a disulfide bond is a relatively sure-fire method but the stabilization may be smaller than calculated due to coupled destabilizing effects.

Ionic Liquids in Electro-active Devices (ILED)

DTIC Science & Technology

2013-12-12

Polyesters: Structure-Property Relationships in Thermal Behavior, Ionic Conductivity , and Morphology , Advanced Functional Materials, (01 2010...and Ionic Conductivities , Macromolecular Chemistry and Physics, (10 2011): . doi: M. Green, C. Schreiner, T. Long. Thermal , Rheological, and Ion...block giving thermal stability and ionic conductivity . Table 1 shows the molecular weight analysis of the triblock copolymers with increasing

Under the radar: advances in murrelet monitoring.

Treesearch

Sally Duncan

2001-01-01

Future choices in managing federal and private forest lands in the Pacific Northwest, particularly for commodity production, are partly dependent on how the threatened marbled murrelet responds to the Northwest Forest Plan. Is the plan functioning for this elusive species, and are populations stabilized or increasing?Because the murrelet forages at sea but...

Structure and Magnetic Properties of Rare Earth Doped Transparent Alumina

NASA Astrophysics Data System (ADS)

Limmer, Krista; Neupane, Mahesh; Chantawansri, Tanya

Recent experimental studies of rare earth (RE) doped alumina suggest that the RE induced novel phase-dependent structural and magnetic properties. Motivated by these efforts, the effects of RE doping of alpha and theta alumina on the local structure, magnetic properties, and phase stability have been examined in this first principles study. Although a direct correlation between the magnetic field dependent materials properties observed experimentally and calculated from first principles is not feasible because of the applied field and the scale, the internal magnetic properties and other properties of the doped materials are evaluated. The RE dopants are shown to increase the substitutional site volume as well as increasingly distort the site structure as a function of ionic radii. Doping both the alpha (stable) and theta (metastable) phases enhanced the relative stability of the theta phase. The energetic doping cost and internal magnetic moment were shown to be a function of the electronic configuration of the RE-dopant, with magnetic moment directly proportional to the number of unpaired electrons and doping cost being inversely related.

Relations between postural stability, gait and falls in elderly persons--preliminary report.

PubMed

Baczkowicz, Dawid; Szczegielniak, Jan; Proszkowiec, Małgorzata

2008-01-01

Balance control in elderly patients is the area of interest of many researchers. The results of their studies suggest that the measurement of shifts in the centre of foot pressure on the support base (COP) can be used as a tool for identification of fall-prone persons. It is interesting whether there are any relations between functional status, gait, posture stability and the risk of falling. The aim of this study was to find the answer to this question. The study involved 20 patients (mean age 78.1+/-11.6). The functional status of the patients was evaluated according to the Barthel Index. Postural stability was assessed with the use of a Neurocom Balance Master platform. Three measurements were taken with visual feedback (eyes open-EO) and three without visual feedback (eyes closed-EC). Balance control was also evaluated with the Berg test and on the basis of the history of episodes of falling in the preceding six months. Gait was evaluated with the six-minute walking test. The parameters recorded by the force platform showed a significant relation to the values obtained in the Berg test (r=-0.60; p<0.001 for EO and r=-0.58; p<0.001 for EC). Similar trends were noted for the relation between EO and distance/velocity as well as functional status (r=-0.63 and -0.68; p<0.001). On the other hand the number of falls showed a significant relation only to the EO test (r=0.4; p<0.05). 1. An evaluation of balance control with a force platform and the Berg test produced convergent results. 2. The incidence of falls was connected with increased body sway. 3. The functional status of the patient and the balance control evaluation according to the Berg test failed to determine the risk of falling. 4. A relation was observed between postural stability, functional status and gait.

Laboratory sample stability. Is it possible to define a consensus stability function? An example of five blood magnitudes.

PubMed

Gómez Rioja, Rubén; Martínez Espartosa, Débora; Segovia, Marta; Ibarz, Mercedes; Llopis, María Antonia; Bauça, Josep Miquel; Marzana, Itziar; Barba, Nuria; Ventura, Monserrat; García Del Pino, Isabel; Puente, Juan José; Caballero, Andrea; Gómez, Carolina; García Álvarez, Ana; Alsina, María Jesús; Álvarez, Virtudes

2018-05-05

The stability limit of an analyte in a biological sample can be defined as the time required until a measured property acquires a bias higher than a defined specification. Many studies assessing stability and presenting recommendations of stability limits are available, but differences among them are frequent. The aim of this study was to classify and to grade a set of bibliographic studies on the stability of five common blood measurands and subsequently generate a consensus stability function. First, a bibliographic search was made for stability studies for five analytes in blood: alanine aminotransferase (ALT), glucose, phosphorus, potassium and prostate specific antigen (PSA). The quality of every study was evaluated using an in-house grading tool. Second, the different conditions of stability were uniformly defined and the percent deviation (PD%) over time for each analyte and condition were scattered while unifying studies with similar conditions. From the 37 articles considered as valid, up to 130 experiments were evaluated and 629 PD% data were included (106 for ALT, 180 for glucose, 113 for phosphorus, 145 for potassium and 85 for PSA). Consensus stability equations were established for glucose, potassium, phosphorus and PSA, but not for ALT. Time is the main variable affecting stability in medical laboratory samples. Bibliographic studies differ in recommedations of stability limits mainly because of different specifications for maximum allowable error. Definition of a consensus stability function in specific conditions can help laboratories define stability limits using their own quality specifications.

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

NASA Astrophysics Data System (ADS)

Amstad, Esther; Textor, Marcus; Reimhult, Erik

2011-07-01

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given. This article was submitted as part of a collection of articles on surface nanotechnology for biological applications. Other papers on this topic can be found in issue 2 of vol. 3 (2011). This issue can be found from the Nanoscale homepage [http://www.rsc.org/nanoscale].

Biodiversity, ecosystem functioning, and classical biological control.

PubMed

Evans, Edward W

Increasing concern over worldwide loss of biodiversity has led ecologists to focus intently on how ecosystem functioning may depend on diversity. In applied entomology, there is longstanding interest in the issue, especially as regards the importance of natural enemy diversity for pest control. Here I review parallels in interest, conceptual framework, and conclusions concerning biodiversity as it affects ecosystem functioning in general and classical biological control in particular. Whereas the former focuses on implications of loss of diversity, the latter focuses on implications of increase in diversity as additional species of natural enemies are introduced to novel communities in new geographic regions for insect pest and weed control. Many field studies now demonstrate that ecosystem functioning, e.g., as reflected in primary productivity, is enhanced and stabilized over time by high diversity as the community increases in its efficiency in exploiting available resources. Similarly, there is growing field support for the generalization that increasing species and functional diversity of natural enemies leads to increasing pest suppression. Nonetheless a central concern of classical biological control in particular, as it seeks to minimize non-target effects, remains as to whether one or a few species of natural enemies can provide sufficient pest control.

Synthesis of highly stable cyanine-dye-doped silica nanoparticle for biological applications

NASA Astrophysics Data System (ADS)

Lian, Ying; Ding, Long-Jiang; Zhang, Wei; Zhang, Xiao-ai; Zhang, Ying-Lu; Lin, Zhen-zhen; Wang, Xu-dong

2018-07-01

Cyanine dyes are widely used in biological labeling and imaging because of their narrow near infrared emission, good brightness and high flexibility in functionalization, which not only enables multiplex analysis and multi-color imaging, but also greatly reduces autofluorescence from biological matter and increases signal-to-noise ratio. Unfortunately, their poor chemical- and photo-stability strongly limits their applications. The incorporation of cyanine dyes in silica nanoparticles provides a solution to the problem. On one hand, the incorporation of cyanine dyes in silica matrix can enhance their chemical- and photo-stability and increase brightness of the nanomaterials. On the other hand, silica matrix provides an optimized condition to host the dye, which helps to maintain their fluorescent properties during application. In addition, the well-established silane technique provides numerous functionalities for diverse applications. However, commercially available cyanine dyes are not very stable at high alkaline conditions, which will gradually lose their fluorescence over time. Our results showed that cyanine dyes are very vulnerable in the reverse micelle system, in which they will lose their fluorescence in less than half an hour. The existence of surfactant could greatly promote degradation of cyanine dyes. Fluorescent silica nanoparticles cannot be obtained at the high alkaline condition with the existence of surfactant. In contrast, the cyanine dyes are relatively stable in Stöber media. Owing to the fast formation of silica particles in Stöber media, the exposure time of cyanine dye in alkaline solution was greatly reduced, and highly fluorescent particles with good morphology and size distribution could be obtained via Stöber approach. However, the increasing water content in the Stöber could reduce the stability of cyanine dyes, which should be avoided. This research here provides a clear guidance on how to successfully synthesize cyanine dye-doped silica nanoparticles with good morphology, size distribution, stability and brightness.

Capsular Management in Hip Arthroscopy: An Anatomic, Biomechanical, and Technical Review

PubMed Central

Kuhns, Benjamin D.; Weber, Alexander E.; Levy, David M.; Bedi, Asheesh; Mather, Richard C.; Salata, Michael J.; Nho, Shane J.

2016-01-01

Hip arthroscopy has become an increasingly utilized surgical technique for the treatment of the young, active patients with hip pain. The clinical outcomes of hip arthroscopy in this patient population have been largely successful; however, there is increasing interest in the contribution of hip capsule in postoperative clinical and functional outcomes. The structure and function of the normal hip capsule will be reviewed. Capsular contributions to hip stability will be discussed in the setting of hip arthroscopy with an emphasis on diagnosis-based considerations. Lastly, clinical outcomes following hip arthroscopy will be discussed as they relate to capsular management. PMID:26973840

[Co-management in geriatric traumatology].

PubMed

Kammerlander, C; Blauth, M; Gosch, M; Böcker, W

2015-09-01

Fragility fractures are becoming more common and are leading to significantly increased morbidity and mortality rates. In order to improve the outcome of these patients, they are increasingly being treated from the beginning interdisciplinarily and interprofessionally as part of co-management models. The main contents of these systems are rapid surgical stabilization for rapid remobilization, treatment with standardized paths and regular communication within the team and a well-functioning discharge management. Furthermore, the organization is a key ingredient in secondary prevention of geriatric traumatology. If this system can be implemented as a whole, this will lead to an improvement of the functional outcomes for the patient as well as to cost savings.

Immediately loaded mini dental implants as overdenture retainers: 1-Year cohort study of implant stability and peri-implant marginal bone level.

PubMed

Šćepanović, Miodrag; Todorović, Aleksandar; Marković, Aleksa; Patrnogić, Vesna; Miličić, Biljana; Moufti, Adel M; Mišić, Tijana

2015-05-01

This 1-year cohort study investigated stability and peri-implant marginal bone level of immediately loaded mini dental implants used to retain overdentures. Each of 30 edentulous patients received 4 mini dental implants (1.8 mm × 13 mm) in the interforaminal mandibular region. The implants were immediately loaded with pre-made overdentures. Outcome measures included implant stability and bone resorption. Implant stability was measured using the Periotest Classic(®) device immediately after placement and on the 3rd and 6th weeks and the 4th, 6th and 12th months postoperatively. The peri-implant marginal bone level (PIBL) was evaluated at the implant's mesial and distal sides from the polished platform to the marginal crest. Radiographs were taken using a tailored film holder to reproducibly position the X-ray tube at the 6th week, 4th and 12th months postoperatively. The primary stability (Periotest value, PTV) measured -0.27 ± 3.41 on a scale of -8 to + 50 (lower PTV reflects higher stability). The secondary stability decreased significantly until week 6 (mean PTV = 7.61 ± 7.05) then increased significantly reaching (PTV = 6.17 ± 6.15) at 12 months. The mean PIBL measured -0.40 mm after 1 year of functional loading, with no statistically significant differences at the various follow-ups (p = 0.218). Mini dental implants placed into the interforaminal region could achieve a favorable primary stability for immediate loading. The follow-up Periotest values fluctuated, apparently reflecting the dynamics of bone remodeling, with the implants remaining clinically stable (98.3%) after 1 year of function. The 1-year bone resorption around immediately loaded MDIs is within the clinically acceptable range for standard implants. Copyright © 2014 Elsevier GmbH. All rights reserved.

Carbon nanotubes for stabilization of nanostructured lipid particles

NASA Astrophysics Data System (ADS)

Gaunt, Nicholas P.; Patil-Sen, Yogita; Baker, Matthew J.; Kulkarni, Chandrashekhar V.

2014-12-01

Carbon nanotubes (CNTs) are increasingly studied for innovative biotechnological applications particularly where they are combined with essential biological materials like lipids. Lipids have been used earlier for enhancing the dispersibility of CNTs in aqueous solutions. Here we report a novel application of CNTs for stabilization of internally self-assembled nanostructured lipid particles of 2-5 μm size. Single-walled (pristine) as well as -OH and -COOH functionalized multi-walled CNTs were employed to produce nanostructured emulsions which stayed stable for months and could be re-dispersed after complete dehydration. Concentrations of CNTs employed for stabilization were very low; moreover CNTs were well-decorated with lipid molecules. These features contribute towards reducing their toxicity and improving biocompatibility for biomedical and pharmaceutical applications. Our approach paves the way for future development of combination therapies employing both CNTs and nanostructured lipid self-assembly together as carriers of different drugs.Carbon nanotubes (CNTs) are increasingly studied for innovative biotechnological applications particularly where they are combined with essential biological materials like lipids. Lipids have been used earlier for enhancing the dispersibility of CNTs in aqueous solutions. Here we report a novel application of CNTs for stabilization of internally self-assembled nanostructured lipid particles of 2-5 μm size. Single-walled (pristine) as well as -OH and -COOH functionalized multi-walled CNTs were employed to produce nanostructured emulsions which stayed stable for months and could be re-dispersed after complete dehydration. Concentrations of CNTs employed for stabilization were very low; moreover CNTs were well-decorated with lipid molecules. These features contribute towards reducing their toxicity and improving biocompatibility for biomedical and pharmaceutical applications. Our approach paves the way for future development of combination therapies employing both CNTs and nanostructured lipid self-assembly together as carriers of different drugs. Electronic supplementary information (ESI) available: Concentration series studies with Raman spectroscopy and small angle X-ray diffraction pattern for dry lipid and dehydrated CNT-lipid particles support the article. See DOI: 10.1039/c4nr05593d

Is There a Role for Oligosaccharides in Seed Longevity? An Assessment of Intracellular Glass Stability1

PubMed Central

Buitink, Julia; Hemminga, Marcus A.; Hoekstra, Folkert A.

2000-01-01

We examined whether oligosaccharides extend seed longevity by increasing the intracellular glass stability. For that purpose, we used a spin probe technique to measure the molecular mobility and glass transition temperature of the cytoplasm of impatiens (Impatiens walleriana) and bell pepper (Capsicum annuum) seeds that were osmo-primed to change oligosaccharide content and longevity. Using saturation transfer electron paramagnetic resonance spectroscopy, we found that the rotational correlation time of the polar spin probe 3-carboxy-proxyl in the cytoplasm decreased, together with longevity, as a function of increasing seed water content, suggesting that longevity may indeed be regulated by cytoplasmic mobility. Osmo-priming of the seeds resulted in considerable decreases in longevity and oligosaccharide content, while the sucrose content increased. No difference in the glass transition temperature was found between control and primed impatiens seeds at the same temperature and water content. Similarly, there was no difference in the rotational motion of the spin probe in the cytoplasm between control and primed impatiens and bell pepper seeds. We therefore conclude that oligosaccharides in seeds do not affect the stability of the intracellular glassy state, and that the reduced longevity after priming is not the result of increased molecular mobility in the cytoplasm. PMID:10759518

Toward understanding the structural heterogeneity and ion pair stability in dicationic ionic liquids.

PubMed

Li, Song; Bañuelos, José Leobardo; Zhang, Pengfei; Feng, Guang; Dai, Sheng; Rother, Gernot; Cummings, Peter T

2014-12-07

The structural and dynamical properties of dicationic ionic liquids (DILs) [Cn(mim)2](Tf2N)2, that is, 3-methylimidazolium dications separated by an alkyl chain and with bis(trifluoromethylsulfonyl)amide as the anion, were investigated by molecular dynamics (MD) simulation in combination with small/wide-angle X-ray scattering (SWAXS) measurements. Enhanced spatial heterogeneity is observed as the DIL chain length is increased, characterized by the changes in the scattering and the increased heterogeneity order parameter (HOP). Temperature variation imposes only slight influences on the local structures of DILs compared to monocationic ionic liquids (MILs). The peaks at 0.9 Å(-1) and 1.4 Å(-1) of the structure function shift towards low Q as the temperature increases, in a similar manner to MILs, and changes in peak positions in response to temperature changes are reflected in HOP variations. However, the prepeak shift with increasing temperature is ∼3 times smaller in DILs compared to MILs, and both MD and SWAXS indicate a DIL-specific prepeak shifting. Furthermore, the high ion pair/ion cage stability in DILs is indicative of high thermal stability and relative insensitivity of structural heterogeneity to temperature variation, which might be caused by the stronger Coulombic interactions in DILs.

Membrane cholesterol effect on the 5-HT2A receptor: Insights into the lipid-induced modulation of an antipsychotic drug target.

PubMed

Ramírez-Anguita, Juan Manuel; Rodríguez-Espigares, Ismael; Guixà-González, Ramon; Bruno, Agostino; Torrens-Fontanals, Mariona; Varela-Rial, Alejandro; Selent, Jana

2018-01-01

The serotonin 5-hydroxytryptamine 2A (5-HT 2A ) receptor is a G-protein-coupled receptor (GPCR) relevant for the treatment of CNS disorders. In this regard, neuronal membrane composition in the brain plays a crucial role in the modulation of the receptor functioning. Since cholesterol is an essential component of neuronal membranes, we have studied its effect on the 5-HT 2A receptor dynamics through all-atom MD simulations. We find that the presence of cholesterol in the membrane increases receptor conformational variability in most receptor segments. Importantly, detailed structural analysis indicates that conformational variability goes along with the destabilization of hydrogen bonding networks not only within the receptor but also between receptor and lipids. In addition to increased conformational variability, we also find receptor segments with reduced variability. Our analysis suggests that this increased stabilization is the result of stabilizing effects of tightly bound cholesterol molecules to the receptor surface. Our finding contributes to a better understanding of membrane-induced alterations of receptor dynamics and points to cholesterol-induced stabilizing and destabilizing effects on the conformational variability of GPCRs. © 2017 International Union of Biochemistry and Molecular Biology, Inc.

Functional properties and in vitro trypsin digestibility of red kidney bean (Phaseolus vulgaris L.) protein isolate: Effect of high-pressure treatment.

PubMed

Yin, Shou-Wei; Tang, Chuan-He; Wen, Qi-Biao; Yang, Xiao-Quan; Li, Lin

2008-10-15

The effects of high-pressure (HP) treatment at 200-600MPa, prior to freeze-drying, on some functional properties and in vitro trypsin digestibility of vicilin-rich red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) were investigated. Surface hydrophobicity and free sulfhydryl (SH) and disulfide bond (SS) contents were also evaluated. HP treatment resulted in gradual unfolding of protein structure, as evidenced by gradual increases in fluorescence strength and SS formation from SH groups, and decrease in denaturation enthalpy change. The protein solubility of KPI was significantly improved at pressures of 400MPa or higher, possibly due to formation of soluble aggregate from insoluble precipitate. HP treatment at 200 and 400MPa significantly increased emulsifying activity index (EAI) and emulsion stability index (ESI); however, EAI was significantly decreased at 600MPa (relative to untreated KPI). The thermal stability of the vicilin component was not affected by HP treatment. Additionally, in vitro trypsin digestibility of KPI was decreased only at a pressure above 200MPa and for long incubation time (e.g., 120min). The data suggest that some physiochemical and functional properties of vicilin-rich kidney proteins can be improved by means of high-pressure treatment. Copyright © 2008 Elsevier Ltd. All rights reserved.

Nonlinear d10-ML2 Transition-Metal Complexes

PubMed Central

Wolters, Lando P; Bickelhaupt, F Matthias

2013-01-01

We have investigated the molecular geometries of a series of dicoordinated d10-transition-metal complexes ML2 (M=Co−, Rh−, Ir−, Ni, Pd, Pt, Cu+, Ag+, Au+; L=NH3, PH3, CO) using relativistic density functional theory (DFT) at ZORA-BLYP/TZ2P. Not all complexes have the expected linear ligand–metal–ligand (L–M–L) angle: this angle varies from 180° to 128.6° as a function of the metal as well as the ligands. Our main objective is to present a detailed explanation why ML2 complexes can become bent. To this end, we have analyzed the bonding mechanism in ML2 as a function of the L–M–L angle using quantitative Kohn–Sham molecular orbital (MO) theory in combination with an energy decomposition analysis (EDA) scheme. The origin of bent L–M–L structures is π backdonation. In situations of strong π backdonation, smaller angles increase the overlap of the ligand’s acceptor orbital with a higher-energy donor orbital on the metal-ligand fragment, and therefore favor π backdonation, resulting in additional stabilization. The angle of the complexes thus depends on the balance between this additional stabilization and increased steric repulsion that occurs as the complexes are bent. PMID:24551547

Recovery of Posture Stability at Different Foot Placements in Patients Who Underwent Minimally Invasive Total Hip Arthroplasty: A One-Year Follow-Up Study.

PubMed

Chang, Chun-Ju; Lin, Na-Ling; Lee, Mel S; Chern, Jen-Suh

2015-01-01

To understand the progression of recovery in postural stability and physical functioning after patients received the minimally invasive total hip arthroplasty (MTHA), we monitor the pain level, functional capacity, and postural stability before and after operation within one year. In total of 23 subjects in our study, we found out that MTHA was effective in relieving pain in first 2 weeks and restoring the hip joint integrity, but the postural stability was influenced especially in tandem stand in both anterior-posterior and medial-lateral directions. The recovery of postural stability and functional capacity in one year duration fluctuated and no consistent improvement tendency was found. We suggested clinicians designing postsurgery rehabilitation program for consistent and progressive long-term recovery of postural stability and fall prevention to optimize surgical results and prevent undesired postoperative consequences.

Global stability of plane Couette flow beyond the energy stability limit

NASA Astrophysics Data System (ADS)

Fuentes, Federico; Goluskin, David

2017-11-01

This talk will present computations verifying that the laminar state of plane Couette flow is nonlinearly stable to all perturbations. The Reynolds numbers up to which this globally stability is verified are larger than those at which stability can be proven by the energy method, which is the typical method for demonstrating nonlinear stability of a fluid flow. This improvement is achieved by constructing Lyapunov functions that are more general than the energy. These functions are not restricted to being quadratic, and they are allowed to depend explicitly on the spectrum of the velocity field in the eigenbasis of the energy stability operator. The optimal choice of such a Lyapunov function is a convex optimization problem, and it can be constructed with computer assistance by solving a semidefinite program. This general method will be described in a companion talk by David Goluskin; the present talk focuses on its application to plane Couette flow.

Decomposition-aggregation stability analysis. [for large scale dynamic systems with application to spinning Skylab control system

NASA Technical Reports Server (NTRS)

Siljak, D. D.; Weissenberger, S.; Cuk, S. M.

1973-01-01

This report presents the development and description of the decomposition aggregation approach to stability investigations of high dimension mathematical models of dynamic systems. The high dimension vector differential equation describing a large dynamic system is decomposed into a number of lower dimension vector differential equations which represent interconnected subsystems. Then a method is described by which the stability properties of each subsystem are aggregated into a single vector Liapunov function, representing the aggregate system model, consisting of subsystem Liapunov functions as components. A linear vector differential inequality is then formed in terms of the vector Liapunov function. The matrix of the model, which reflects the stability properties of the subsystems and the nature of their interconnections, is analyzed to conclude over-all system stability characteristics. The technique is applied in detail to investigate the stability characteristics of a dynamic model of a hypothetical spinning Skylab.

Interfacial Strength and Physical Properties of Functionalized Graphene - Epoxy Nanocomposites

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Heimann, Paula; Scheiman, Daniel; Adamson, Douglas H.; Aksay, Iihan A.; Prud'homme, Robert K.

2006-01-01

The toughness and coefficient of thermal expansion of a series of functionalized graphene sheet - epoxy nanocomposites are investigated. Functionalized graphene sheets are produced by splitting graphite oxide into single graphene sheets through a rapid thermal expansion process. These graphene sheets contain approx. 10% oxygen due to the presence of hydroxide, epoxide, and carboxyl functional groups which assist in chemical bond formation with the epoxy matrix. Intrinsic surface functionality is used to graft alkyl amine chains on the graphene sheets, and the addition of excess hardener insures covalent bonding between the epoxide matrix and graphene sheets. Considerable improvement in the epoxy dimensional stability is obtained. An increase in nanocomposite toughness is observed in some cases.

Modulation of protein stability and aggregation properties by surface charge engineering.

PubMed

Raghunathan, Govindan; Sokalingam, Sriram; Soundrarajan, Nagasundarapandian; Madan, Bharat; Munussami, Ganapathiraman; Lee, Sun-Gu

2013-09-01

An attempt to alter protein surface charges through traditional protein engineering approaches often affects the native protein structure significantly and induces misfolding. This limitation is a major hindrance in modulating protein properties through surface charge variations. In this study, as a strategy to overcome such a limitation, we attempted to co-introduce stabilizing mutations that can neutralize the destabilizing effect of protein surface charge variation. Two sets of rational mutations were designed; one to increase the number of surface charged amino acids and the other to decrease the number of surface charged amino acids by mutating surface polar uncharged amino acids and charged amino acids, respectively. These two sets of mutations were introduced into Green Fluorescent Protein (GFP) together with or without stabilizing mutations. The co-introduction of stabilizing mutations along with mutations for surface charge modification allowed us to obtain functionally active protein variants (s-GFP(+15-17) and s-GFP(+5-6)). When the protein properties such as fluorescent activity, folding rate and kinetic stability were assessed, we found the possibility that the protein stability can be modulated independently of activity and folding by engineering protein surface charges. The aggregation properties of GFP could also be altered through the surface charge engineering.

Computational simulations assessment of mutations impact on streptokinase (SK) from a group G streptococci with enhanced activity - insights into the functional roles of structural dynamics flexibility of SK and stabilization of SK-μplasmin catalytic complex.

PubMed

Kazemi, Faegheh; Arab, Seyed Shahriar; Mohajel, Nasir; Keramati, Malihe; Niknam, Niloofar; Aslani, Mohammad Mehdi; Roohvand, Farzin

2018-05-28

Streptokinase (SK), a plasminogen activator (PA) that converts inactive plasminogen (Pg) to plasmin (Pm), is a protein secreted by groups A, C, and G streptococci (GAS, GCS, and GGS, respectively), with high sequence divergence and functional heterogeneity. While roles of some residual changes in altered SK functionality are shown, the underlying structural mechanisms are less known. Herein, using computational approaches, we analyzed the conformational basis for the increased activity of SK from a GGS (SKG132) isolate with four natural residual substitutions (Ile33Phe, Arg45Gln, Asn228Lys, Phe287Ile) compared to the standard GCS (SKC). Using the crystal structure of SK.Pm catalytic complex as main template SKC.μPm catalytic complex was modeled through homology modeling process and validated by several online validation servers. Subsequently, SKG132.μPm structure was constructed by altering the corresponding residual substitutions. Results of three independent MD simulations showed increased RMSF values for SKG132.μPm, indicating the enhanced structural flexibility compared to SKC.μPm, specially in 170 and 250 loops and three regions: R1 (149-161), R2 (182-215) and R3 (224-229). In parallel, the average number of Hydrogen bonds in 170 loop, R2 and R3 (especially for Asn228Lys) of SKG132 compared to that of the SKC was decreased. Accordingly, residue interaction networks (RINs) analyses indicated that Asn228Lys might induce more level of structural flexibility by generation of free Lys256, while Phe287Ile and Ile33Phe enhanced the stabilization of the SKG132.μPm catalytic complex. These results denoted the potential role of the optimal dynamic state and stabilized catalytic complex for increased PA potencies of SK as a thrombolytic drug.

B-DNA Structure and Stability as Function of Nucleic Acid Composition: Dispersion-Corrected DFT Study of Dinucleoside Monophosphate Single and Double Strands

PubMed Central

Barone, Giampaolo; Fonseca Guerra, Célia; Bickelhaupt, F Matthias

2013-01-01

We have computationally investigated the structure and stability of all 16 combinations of two out of the four natural DNA bases A, T, G and C in a di-2′-deoxyribonucleoside-monophosphate model DNA strand as well as in 10 double-strand model complexes thereof, using dispersion-corrected density functional theory (DFT-D). Optimized geometries with B-DNA conformation were obtained through the inclusion of implicit water solvent and, in the DNA models, of sodium counterions, to neutralize the negative charge of the phosphate groups. The results obtained allowed us to compare the relative stability of isomeric single and double strands. Moreover, the energy of the Watson–Crick pairing of complementary single strands to form double-helical structures was calculated. The latter furnished the following increasing stability trend of the double-helix formation energy: d(TpA)2

Screw joint stability after the application of retorque in implant-supported dentures under simulated masticatory conditions.

PubMed

Farina, Ana Paula; Spazzin, Aloísio Oro; Consani, Rafael Leonardo Xediek; Mesquita, Marcelo Ferraz

2014-06-01

Screws can loosen through mechanisms that have not been clearly established. The purpose of this study was to evaluate the influence of the tightening technique (the application of torque and retorque on the joint stability of titanium and gold prosthetic screws) in implant-supported dentures under different fit levels after 1 year of simulated masticatory function by means of mechanical cycling. Ten mandibular implant-supported dentures were fabricated, and 20 cast models were prepared by using the dentures to create 2 fit levels: passive fit and created misfit. The tightening protocol was evaluated according to 4 distinct profiles: without retorque plus titanium screws, without retorque plus gold screws, retorque plus titanium screws, and retorque plus gold screws. In the retorque application, the screws were tightened to 10 Ncm and retightened to 10 Ncm after 10 minutes. The screw joint stability after 1 year of simulated clinical function was measured with a digital torque meter. Data were analyzed statistically by 2-way ANOVA and Tukey honestly significant difference (HSD) post hoc tests (α=.05). The factors of fit level and tightening technique as well as the interaction between the factors, were statistically significant. The misfit decreases the loosening torque. The retorque application increased joint stability independent of fit level or screw material, which suggests that this procedure should be performed routinely during the tightening of these devices. All tightening techniques revealed reduced loosening torque values that were significantly lower in misfit dentures than in passive fit dentures. However, the retorque application significantly increased the loosening torque when titanium and gold screws were used. Therefore, this procedure should be performed routinely during screw tightening. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Trajectory of frequency stability in typical development.

PubMed

Frohlich, Joel; Irimia, Andrei; Jeste, Shafali S

2015-03-01

This work explores a feature of brain dynamics, metastability, by which transients are observed in functional brain data. Metastability is a balance between static (stable) and dynamic (unstable) tendencies in electrophysiological brain activity. Furthermore, metastability is a theoretical mechanism underlying the rapid synchronization of cell assemblies that serve as neural substrates for cognitive states, and it has been associated with cognitive flexibility. While much previous research has sought to characterize metastability in the adult human brain, few studies have examined metastability in early development, in part because of the challenges of acquiring adequate, noise free continuous data in young children. To accomplish this endeavor, we studied a new method for characterizing the stability of EEG frequency in early childhood, as inspired by prior approaches for describing cortical phase resets in the scalp EEG of healthy adults. Specifically, we quantified the variance of the rate of change of the signal phase (i.e., frequency) as a proxy for phase resets (signal instability), given that phase resets occur almost simultaneously across large portions of the scalp. We tested our method in a cohort of 39 preschool age children (age =53 ± 13.6 months). We found that our outcome variable of interest, frequency variance, was a promising marker of signal stability, as it increased with the number of phase resets in surrogate (artificial) signals. In our cohort of children, frequency variance decreased cross-sectionally with age (r = -0.47, p = 0.0028). EEG signal stability, as quantified by frequency variance, increases with age in preschool age children. Future studies will relate this biomarker with the development of executive function and cognitive flexibility in children, with the overarching goal of understanding metastability in atypical development.

Floral trait variation and integration as a function of sexual deception in Gorteria diffusa.

PubMed

Ellis, Allan G; Brockington, Samuel F; de Jager, Marinus L; Mellers, Gregory; Walker, Rachel H; Glover, Beverley J

2014-08-19

Phenotypic integration, the coordinated covariance of suites of morphological traits, is critical for proper functioning of organisms. Angiosperm flowers are complex structures comprising suites of traits that function together to achieve effective pollen transfer. Floral integration could reflect shared genetic and developmental control of these traits, or could arise through pollinator-imposed stabilizing correlational selection on traits. We sought to expose mechanisms underlying floral trait integration in the sexually deceptive daisy, Gorteria diffusa, by testing the hypothesis that stabilizing selection imposed by male pollinators on floral traits involved in mimicry has resulted in tighter integration. To do this, we quantified patterns of floral trait variance and covariance in morphologically divergent G. diffusa floral forms representing a continuum in the levels of sexual deception. We show that integration of traits functioning in visual attraction of male pollinators increases with pollinator deception, and is stronger than integration of non-mimicry trait modules. Consistent patterns of within-population trait variance and covariance across floral forms suggest that integration has not been built by stabilizing correlational selection on genetically independent traits. Instead pollinator specialization has selected for tightened integration within modules of linked traits. Despite potentially strong constraint on morphological evolution imposed by developmental genetic linkages between traits, we demonstrate substantial divergence in traits across G. diffusa floral forms and show that divergence has often occurred without altering within-population patterns of trait correlations. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Effect of polyoxyethylene sorbitan esters and sodium caseinate on physicochemical properties of palm-based functional lipid nanodispersions.

PubMed

Cheong, Jean Ne; Mirhosseini, Hamed; Tan, Chin Ping

2010-06-01

The main objective of the present study was to investigate the effect of polyoxyethylene sorbitan esters and sodium caseinate on physicochemical properties of palm-based functional lipid nanodispersions prepared by the emulsification-evaporation technique. The results indicated that the average droplet size increased significantly (P < 0.05) by increasing the chain length of fatty acids and also by increasing the hydrophile-lipophile balance value. Among the prepared nanodispersions, the nanoemulsion containing Polysorbate 20 showed the smallest average droplet size (202 nm) and narrowest size distribution for tocopherol-tocotrienol nanodispersions, while sodium caseinate-stabilized nanodispersions containing carotenoids had the largest average droplet size (386 nm), thus indicating a greater emulsifying role for Polysorbate 20 compared with sodium caseinate.

Zinc complexation in chloride-rich hydrothermal fluids (25-600 °C): A thermodynamic model derived from ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

Mei, Yuan; Sherman, David M.; Liu, Weihua; Etschmann, Barbara; Testemale, Denis; Brugger, Joël

2015-02-01

The solubility of zinc minerals in hydrothermal fluids is enhanced by chloride complexation of Zn2+. Thermodynamic models of these complexation reactions are central to models of Zn transport and ore formation. However, existing thermodynamic models, derived from solubility measurements, are inconsistent with spectroscopic measurements of Zn speciation. Here, we used ab initio molecular dynamics simulations (with the PBE exchange-correlation functional) to predict the speciation of Zn-Cl complexes from 25 to 600 °C. We also obtained in situ XAS measurements of Zn-Cl solutions at 30-600 °C. Qualitatively, the simulations reproduced the main features derived from in situ XANES and EXAFS measurements: octahedral to tetrahedral transition with increasing temperature and salinity, stability of ZnCl42- at high chloride concentration up to ⩾500 °C, and increasing stability of the trigonal planar [ZnCl3]- complex at high temperature. Having confirmed the dominant species, we directly determined the stability constants for the Zn-Cl complexes using thermodynamic integration along constrained Zn-Cl distances in a series of MD simulations. We corrected our stability constants to infinite dilution using the b-dot model for the activity coefficients of the solute species. In order to compare the ab initio results with experiments, we need to re-model the existing solubility data using the species we identified in our MD simulations. The stability constants derived from refitting published experimental data are in reasonable agreement with those we obtained using ab initio MD simulations. Our new thermodynamic model accurately predicts the experimentally observed changes in ZnO(s) and ZnCO3(s) solubility as a function of chloride concentration from 200 (Psat) to 600 °C (2000 bar). This study demonstrates that metal speciation and geologically useful stability constants can be derived for species in hydrothermal fluids from ab initio MD simulations even at the generalized gradient approximation for exchange-correlation. We caution, however, that simulations are mostly reliable at high T where ligand exchange is fast enough to yield thermodynamic averages over the timescales of the simulations.

Highly stabilized, polymer-lipid membranes prepared on silica microparticles as stationary phases for capillary chromatography

PubMed Central

Gallagher, Elyssia S.; Adem, Seid M.; Baker, Christopher A.; Ratnayaka, Saliya N.; Jones, Ian W.; Hall, Henry K.; Saavedra, S. Scott; Aspinwall, Craig A.

2015-01-01

The ability to rapidly screen complex libraries of pharmacological modulators is paramount to modern drug discovery efforts. This task is particularly challenging for agents that interact with lipid bilayers or membrane proteins due to the limited chemical, physical, and temporal stability of conventional lipid-based chromatographic stationary phases. Here, we describe the preparation and characterization of a novel stationary phase material composed of highly stable, polymeric-phospholipid bilayers self-assembled onto silica microparticles. Polymer lipid membranes were prepared by photochemical or redox initiated polymerization of 1,2-bis[10-(2′,4′-hexadieoyloxy)decanoyl]-sn-glycero-2-phosphocholine (bis-SorbPC), a synthetic, polymerizable lipid. The resulting polymerized bis-SorbPC (poly(bis-SorbPC)) stationary phases exhibited enhanced stability compared to particles coated with 1,2-dioleoyl-sn-glycero-phosphocholine (unpolymerized) phospholipid bilayers when exposed to chemical (50mM triton X-100 or 50% acetonitrile) and physical (15 min sonication) insults after 30 days of storage. Further, poly(bis-SorbPC)-coated particles survived slurry packing into fused silica capillaries, compared to unpolymerized lipid membranes, where the lipid bilayer was destroyed during packing. Frontal chromatographic analyses of the lipophilic small molecules acetylsalicylic acid, benzoic acid, and salicylic acid showed > 44% increase in retention times (P < 0.0001) for all analytes on poly(bis-SorbPC)-functionalized stationary phase compared to bare silica microspheres, suggesting a lipophilic retention mechanism. Phospholipid membrane-functionalized stationary phases that withstand the chemical and physical rigors of capillary LC conditions can substantially increase the efficacy of lipid membrane affinity chromatography, and represents a key advance towards the development of robust membrane protein-functionalized chromatographic stationary phases. PMID:25670414

Phosphorus allotropes: Stability of black versus red phosphorus re-examined by means of the van der Waals inclusive density functional method

NASA Astrophysics Data System (ADS)

Aykol, Muratahan; Doak, Jeff W.; Wolverton, C.

2017-06-01

We evaluate the energetic stabilities of white, red, and black allotropes of phosphorus using density functional theory (DFT) and hybrid functional methods, van der Waals (vdW) corrections (DFT+vdW and hybrid+vdW), vdW density functionals, and random phase approximation (RPA). We find that stability of black phosphorus over red-V (i.e., the violet form) is not ubiquitous among these methods, and the calculated enthalpies for the reaction phosphorus (red-V)→phosphorus (black) are scattered between -20 and 40 meV/atom. With local density and generalized gradient approximations, and hybrid functionals, mean absolute errors (MAEs) in densities of P allotropes relative to experiments are found to be around 10%-25%, whereas with vdW-inclusive methods, MAEs in densities drop below ˜5 %. While the inconsistency among the density functional methods could not shed light on the stability puzzle of black versus red phosphorus, comparison of their accuracy in predicting densities and the supplementary RPA results on relative stabilities indicate that opposite to the common belief, black and red phosphorus are almost degenerate, or the red-V (violet) form of phosphorus might even be the ground state.

Generalized decompositions of dynamic systems and vector Lyapunov functions

NASA Astrophysics Data System (ADS)

Ikeda, M.; Siljak, D. D.

1981-10-01

The notion of decomposition is generalized to provide more freedom in constructing vector Lyapunov functions for stability analysis of nonlinear dynamic systems. A generalized decomposition is defined as a disjoint decomposition of a system which is obtained by expanding the state-space of a given system. An inclusion principle is formulated for the solutions of the expansion to include the solutions of the original system, so that stability of the expansion implies stability of the original system. Stability of the expansion can then be established by standard disjoint decompositions and vector Lyapunov functions. The applicability of the new approach is demonstrated using the Lotka-Volterra equations.

Long term in vitro stability of fully integrated wireless neural interfaces based on Utah slant electrode array

NASA Astrophysics Data System (ADS)

Sharma, Asha; Rieth, Loren; Tathireddy, Prashant; Harrison, Reid; Solzbacher, Florian

2010-02-01

We herein report in vitro functional stability and recording longevity of a fully integrated wireless neural interface (INI). The INI uses biocompatible Parylene-C as an encapsulation layer, and was immersed in phosphate buffered saline (PBS) for a period of over 150 days. The full functionality (wireless radio-frequency power, command, and signal transmission) and the ability of INI to record artificial action potentials even after 150 days of PBS soaking without any change in signal/noise amplitude constitutes a major milestone in long term stability, and evaluate the encapsulation reliability, functional stability, and potential usefulness for future chronic implants.

Thermal Stability of Nanocrystalline Copper for Potential Use in Printed Wiring Board Applications

NASA Astrophysics Data System (ADS)

Woo, Patrick Kai Fai

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultra-fine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25-230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40?C to 400?C. During isothermal annealing experiments samples were annealed at 23?C, 100?C and 300?C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of copper is greatly related to changes in driving and dragging forces, which in turn, are strongly depended on parameters such as annealing temperature and time, total sulfur impurity content and the distribution of the impurities within the material. It was shown that a simple increase in the sulfur impurity level does not necessarily improve the thermal stability of nanocrystalline copper.

Two choices for the functionalization of silica nanoparticles with gallic acid: characterization of the nanomaterials and their antimicrobial activity against Paenibacillus larvae

NASA Astrophysics Data System (ADS)

Vico, Tamara A.; Arce, Valeria B.; Fangio, María F.; Gende, Liesel B.; Bertran, Celso A.; Mártire, Daniel O.; Churio, María S.

2016-11-01

Silica nanoparticles attached to gallic acid were synthesized from 7-nm diameter fumed silica particles by different functionalization methods involving the condensation of hydroxyl or carboxyl groups. The particles were characterized by thermal analyses and UV-vis, FTIR, NMR, and EPR spectroscopies. In comparison to free gallic acid, enhanced stability and increased antimicrobial activity against Paenibacillus larvae were found for the functionalized nanoparticles. Thus, both derivatization strategies result in improved properties of the natural polyphenol as antimicrobial agent for the treatment of honeybee pathologies.

Self-assembly and reactive molding techniques for controlling the interface and dispersion of the particulate phase in nanocomposites

NASA Astrophysics Data System (ADS)

Pranger, Lawrence A.

This research explored the processing and properties of PNCs using a polyfurfural alcohol (PFA) matrix. The precursor for PFA, furfuryl alcohol (FA) is sourced from feedstocks rich in hemicellulose, such as corn cobs, oat hulls and wood. To exploit FA as a polymerizable solvent, cellulose whiskers (CW) and montmorillonite clay (MMT) were used as the nanoparticle phase. Results from PNC processing show that CW and MMT can be dispersed in the PFA matrix by means of insitu polymerization, without the use of surfactants or dilution in solvents. Both CW and MMT nanoparticles catalyze the polymerization of furfuryl alcohol (FA). Moreover, the insitu intercalative polymerization of FA in the interlayer galleries of MMT leads to the complete exfoliation of the MMT in the PFA matrix. CW and MMT both function as effective matrix modifiers, increasing the thermal stability of PFA nanocomposites compared to pure PFA polymer. The increased thermal stability is seen as significant increases in the onset of degradation and in residual weight at high temperature. This research also explored the surface functionalization of Cu, Ni and Pt substrates by self-assembly of a range of difunctional linker molecules. Characterization by XPS and PM-IRRAS indicate that diisocyanides and dicarboxylic acids both form chemically "sticky" surfaces after self-assembly on Cu and Ni. Sticky surfaces may provide a means of increasing nanoparticle dispersion in metal nanocluster filled PNCs, by increasing their interaction with the matrix polymer. Another potential application for sticky surfaces on Cu is in the ongoing miniaturization of circuit boards. The functionalization of Cu bond pad substrates with linker molecules may provide an alternate means of bonding components to their bond pads, with higher placement accuracy compared to solder bumps.

Kinematic effect of Nintendo WiiTM sports program exercise on obstacle gait in elderly women with falling risk

PubMed Central

Jung, Dae-In; Ko, Dae-Sik; Jeong, Mi-Ae

2015-01-01

[Purpose] This study evaluated the changes in balance ability and obstacle gait after lumbar stabilization exercise and Nintendo WiiTM Sports in elderly at risk for falls. [Subjects and Methods] Twenty-four elderly women with at risk for falls were randomly divided into the control, lumbar stabilization exercise, and Nintendo Wii Sports groups. Static balance was measured by the Berg Balance Scale and functional reach test, dynamic balance by the timed up-and-go test, and obstacle negotiation function by crossing velocity and maximum vertical heel clearance. [Results] Both the lumbar stabilization exercise and Nintendo Wii Sports groups showed significant improvements in obstacle negotiation function after the exercise compared to the control group. Berg Balance Scale and functional reach test scores were greater in the lumbar stabilization exercise group, while the timed up-and-go test time was significantly better in the Nintendo Wii Sports groups. [Conclusion] Lumbar stabilization exercises and Nintendo Wii Sports improve falling related balance and obstacle negotiation function in elderly women at risk for falls. PMID:26157228

Kinematic effect of Nintendo Wii(TM) sports program exercise on obstacle gait in elderly women with falling risk.

PubMed

Jung, Dae-In; Ko, Dae-Sik; Jeong, Mi-Ae

2015-05-01

[Purpose] This study evaluated the changes in balance ability and obstacle gait after lumbar stabilization exercise and Nintendo Wii(TM) Sports in elderly at risk for falls. [Subjects and Methods] Twenty-four elderly women with at risk for falls were randomly divided into the control, lumbar stabilization exercise, and Nintendo Wii Sports groups. Static balance was measured by the Berg Balance Scale and functional reach test, dynamic balance by the timed up-and-go test, and obstacle negotiation function by crossing velocity and maximum vertical heel clearance. [Results] Both the lumbar stabilization exercise and Nintendo Wii Sports groups showed significant improvements in obstacle negotiation function after the exercise compared to the control group. Berg Balance Scale and functional reach test scores were greater in the lumbar stabilization exercise group, while the timed up-and-go test time was significantly better in the Nintendo Wii Sports groups. [Conclusion] Lumbar stabilization exercises and Nintendo Wii Sports improve falling related balance and obstacle negotiation function in elderly women at risk for falls.

What do Boletus, Chanterelle and Co. have in common with Eco engineering?

NASA Astrophysics Data System (ADS)

Graf, F.; Burri, K.; Böll, A.

2009-04-01

A major goal of eco engineering is its contribution to slope stability. The carefully selected plant and technical construction material are an indispensable requirement but not necessarily sufficient in view of long-term success. For that purpose, plant growth and the development of a functional vegetation cover are essential. However, particularly under extreme climatic and environmental conditions even pioneer plants reach their limits in bridging the gap between their proper needs and the effective yield of the soil degraded by erosion or sliding processes. Besides the conventional solutions that are the application of artificial fertiliser and soil conditioners, a competitive option is to be found in the "Kingdom of Fungi". Under natural conditions, as good as every plant species used in eco engineering lives in a symbiotic relationship with fungi, called mycorrhiza with Boletus and Chanterelle as two prominent representatives. Within these partnerships, the fungi take charge of the host's water and nutrient supply; considerably increasing its efficiency compared to non-mycorrhized roots. Consequently, plant growth, in particular root performance, and survival are significantly improved as is shown in a restoration experiment on an alpine ski slope in the Swiss mountains and has been demonstrated many times elsewhere. In addition to this indirect contribution to the restoration and re-stabilisation process, the mycorrhizal fungi provide more direct functions related to the development of a stable soil structure starting from a severely degraded soil material. The mycelia producing fungi assemble and stabilise micro- and macro-aggregates out of smallest organic and inorganic soil particles. The formation and stabilisation of the soil structure proceed at different spatial scales directly by electrostatic charge, adhesive and enmeshment mechanisms. Numerous investigations prove that, on the one hand, the sole application of mycorrhizal fungi to loose soil material may result in an increase of aggregate stability but, on the other hand, demonstrate its species specific dependency. Furthermore, mycorrhizal fungi support the soil aggregate stability by serving as a distribution vector for associated micro-organisms, mainly bacteria and archaea, some of them soil stabilising alike. A positive correlation was found between soil aggregate stability and dry unit weight, based on laboratory as well as field samples. Such a correlation is known for the shear strength parameters - particularly for the angle of internal friction Φ' - of the Mohr-Coulomb failure criterion on which most of the conventionally used models for soil and slope stability calculations are based. Moreover, evidence was provided that the aggregate stability of soil at low dry unit weight (~15.5 kN/m3) added with plants and mycorrhizal fungi corresponds to that of untreated soil material at high dry unit weight (~19.5 kN/m3) a feature found for the angle of internal friction Φ' too. Conclusively, based on these relationships, effects of plants and mycorrhizal fungi on soil stability may be interpreted as a virtual increase in dry unit weight and a real increase in the angle of internal friction Φ', respectively. The effect of plants and fungi on soil stability is, however, not restricted to withstand erosion and sliding processes induced by water. Recent experiments in a wind tunnel reveal the potential of this symbiosis related to wind erosion and, therefore, in view of combating desertification. Experiments with differently dense planted soil confirmed the negative correlation with the amount of sediment transport and health threatening fine dust (PM10) emission. The "mycorrhiza network" including and connecting plants, soil aggregate stability, and the angle of internal friction Φ' is of special meaning in view of soil stabilisation and the development of degraded soil. Carefully selected fungus-plant combinations shorten the delicate phase of re-colonisation and the development of a functional vegetation cover at simultaneous amelioration of the site specific conditions - representing the essential requirements for long-term success of eco engineering measures.

The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence

PubMed Central

Geisberger, Roland; Rada, Cristina; Neuberger, Michael S.

2009-01-01

The carboxyterminal region of activation-induced deaminase (AID) is required for its function in Ig class switch recombination (CSR) and also contains a nuclear-export sequence (NES). Here, based on an extensive fine-structure mutation analysis of the AID NES, as well as from AID chimeras bearing heterologous NESs, we show that while a functional NES is indeed essential for CSR, it is not sufficient. The precise nature of the NES is critical both for AID stabilization and CSR function: minor changes in the NES can perturb stabilization and CSR without jeopardizing nuclear export. The results indicate that the AID NES fulfills a function beyond simply providing a signal for nuclear export and suggest the possibility that the quality of exportin-binding may be critical to the stabilization of AID and its activity in CSR. PMID:19351893

Enhanced stability of monomer fold correlates with extreme drug resistance of HIV-1 protease.

PubMed

Louis, John M; Tözsér, József; Roche, Julien; Matúz, Krisztina; Aniana, Annie; Sayer, Jane M

2013-10-29

During treatment, mutations in HIV-1 protease (PR) are selected rapidly that confer resistance by decreasing affinity to clinical protease inhibitors (PIs). As these unique drug resistance mutations can compromise the fitness of the virus to replicate, mutations that restore conformational stability and activity while retaining drug resistance are selected on further evolution. Here we identify several compensating mechanisms by which an extreme drug-resistant mutant bearing 20 mutations (PR20) with >5-fold increased Kd and >4000-fold decreased affinity to the PI darunavir functions. (1) PR20 cleaves, albeit poorly, Gag polyprotein substrates essential for viral maturation. (2) PR20 dimer, which exhibits distinctly enhanced thermal stability, has highly attenuated autoproteolysis, thus likely prolonging its lifetime in vivo. (3) The enhanced stability of PR20 results from stabilization of the monomer fold. Both monomeric PR20(T26A) and dimeric PR20 exhibit Tm values 6-7.5 °C higher than those for their PR counterparts. Two specific mutations in PR20, L33F and L63P at sites of autoproteolysis, increase the Tm of monomeric PR(T26A) by ~8 °C, similar to PR20(T26A). However, without other compensatory mutations as seen in PR20, L33F and L63P substitutions, together, neither restrict autoproteolysis nor significantly reduce binding affinity to darunavir. To determine whether dimer stability contributes to binding affinity for inhibitors, we examined single-chain dimers of PR and PR(D25N) in which the corresponding identical monomer units were covalently linked by GGSSG sequence. Linking of the subunits did not appreciably change the ΔTm on inhibitor binding; thus stabilization by tethering appears to have little direct effect on enhancing inhibitor affinity.

Electrochemical investigation of functionalized graphene aerogel with different amount of p-phenylenediamine as an advanced electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Gholipour-Ranjbar, Habib; Ganjali, Mohammad Reza; Norouzi, Parviz; Naderi, Hamid Reza

2016-07-01

Graphene aerogel has attracted great attention as a new and efficient electrode material for supercapacitors. It can be expected that functionalization of graphene aerogels can further improve their capability. In this study, graphene aerogel functionalized with different amount of p-phenylenediamine (PPD) and the effect of PPD amount on the supercapacitive performance of functionalized graphene aerogel (FGA) was investigated. Structural characterizations showed that PPD molecules initiated graphene aerogel sheets assembly into three-dimensional structures and also increasing PPD amount led to increase in surface area. Electrochemical investigations proved that the FGA with larger pore size showed enhanced supercapacitive performance compared with the FGA with smaller pore size. The optimized FGA-based electrode exhibited outstanding specific capacitance (SC) of 385 F g-1 at a discharge current density of 1 A g-1, good rate capability (215 F g-1 at 20 A g-1), and exceptionally high cyclic stability by displaying 25% increase in SC after 5000 cycle.

A comparison of water-based and land-based core stability exercises in patients with lumbar disc herniation: a pilot study.

PubMed

Bayraktar, Deniz; Guclu-Gunduz, Arzu; Lambeck, Johan; Yazici, Gokhan; Aykol, Sukru; Demirci, Harun

2016-01-01

To determine and compare the effects of core stability exercise programs performed in two different environments in lumbar disc herniation (LDH) patients. Thirty-one patients who were diagnosed with LDH and were experiencing pain or functional disability for at least 3 months were randomly divided into two groups as land-based exercises or water specific therapy. Also, 15 age-sex-matched healthy individuals were recruited as healthy controls. Both groups underwent an 8-week (3 times/week) core stabilization exercise program. Primary outcomes were pain, trunk muscle static endurance and perceived disability level. The secondary outcome was health-related quality of life. Level of static endurance of trunk muscles was found to be lower in the patients compared to the controls at baseline (p < 0.05). Both treatment groups showed significant improvements in all outcomes (p < 0.05) after 8-week intervention. When two treatment groups were compared, no differences were found in the amount of change after the intervention (p > 0.05). After the treatment, static endurance of trunk muscles of the LDH patients became similar to controls (p > 0.05). According to these results, core stabilization exercise training performed on land or in water both could be beneficial in LDH patients and there is no difference between the environments. An 8-week core stabilization program performed in water or on land decrease pain level and improve functional status in LDH patients. Both programs seem beneficial to increase health-related quality of life and static endurance of trunk muscles. Core stability exercises could be performed in water as well, no differences were found between methods due to environment.

Surface functionalization of titanium dioxide nanoparticles: Photo-stability and reactive oxygen species (ROS) generation

NASA Astrophysics Data System (ADS)

Louis, Kacie M.

Metal oxide nanoparticles are becoming increasingly prevalent in society for applications of sunscreens, cosmetics, paints, biomedical imaging, and photovoltaics. Due to the increased surface area to volume ratio of nanoparticles compared to bulk materials, it is important to know the health and safety impacts of these materials. One mechanism of toxicity of nominally "safe" materials such as TiO 2 is through the photocatalytic generation of reactive oxygen species (ROS). ROS production and ligand degradation can affect the bioavailability of these particles in aqueous organisms. We have investigated ROS generation by functionalized TiO2 nanoparticles and its influence on aggregation and bioavailability and toxicity to zebrafish embryos/larvae. For these studies we investigated anatase TiO2 nanoparticles. For application purposes and solution stability, the TiO2 nanoparticles were functionalized with a variety of ligands such as citrate, 3,4-dihydroxybenzaldehyde, and ascorbate. We quantitatively examined the amount of ROS produced in aqueous solution using fluorescent probes and see that more ROS is produced under UV light than in the dark control. Our measurements show that TiO2 toxicity reaches a maximum for nanoparticles with smaller diameters, and is correlated with surface area dependent changes in ROS generation. In an effort to reduce toxicity through control of the surface and surface ligands, we synthesized anatase nanoparticles of different sizes, functionalized them with different ligands, and examined the resulting ROS generation and ligand stability. Using a modular ligand containing a hydrophobic inner region and a hydrophilic outer region, we synthesized water-stable nanoparticles, via two different chemical reactions, having much-reduced ROS generation and thus reduced toxicity. These results suggest new strategies for making safer nanoparticles while still retaining their desired properties. We also examine the degradation of the different ligands on the surface of the particles using XPS and FTIR. The combination of ROS production and ligand degradation can affect the bioavailability of these particles in aqueous species.

Interplay between population firing stability and single neuron dynamics in hippocampal networks

PubMed Central

Slomowitz, Edden; Styr, Boaz; Vertkin, Irena; Milshtein-Parush, Hila; Nelken, Israel; Slutsky, Michael; Slutsky, Inna

2015-01-01

Neuronal circuits' ability to maintain the delicate balance between stability and flexibility in changing environments is critical for normal neuronal functioning. However, to what extent individual neurons and neuronal populations maintain internal firing properties remains largely unknown. In this study, we show that distributions of spontaneous population firing rates and synchrony are subject to accurate homeostatic control following increase of synaptic inhibition in cultured hippocampal networks. Reduction in firing rate triggered synaptic and intrinsic adaptive responses operating as global homeostatic mechanisms to maintain firing macro-stability, without achieving local homeostasis at the single-neuron level. Adaptive mechanisms, while stabilizing population firing properties, reduced short-term facilitation essential for synaptic discrimination of input patterns. Thus, invariant ongoing population dynamics emerge from intrinsically unstable activity patterns of individual neurons and synapses. The observed differences in the precision of homeostatic control at different spatial scales challenge cell-autonomous theory of network homeostasis and suggest the existence of network-wide regulation rules. DOI: http://dx.doi.org/10.7554/eLife.04378.001 PMID:25556699

On the nonlinear stability of viscous modes within the Rayleigh problem on an infinite flat plate

NASA Technical Reports Server (NTRS)

Webb, J. C.; Otto, S. R.; Lilley, G. M.

1994-01-01

The stability has been investigated of the unsteady flow past an infinite flat plate when it is moved impulsively from rest, in its own plane. For small times the instantaneous stability of the flow depends on the linearized equations of motion which reduce in this problem to the Orr-Sommerfeld equation. It is known that the flow for certain values of Reynolds number, frequency and wave number is unstable to Tollmien-Schlichting waves, as in the case of the Blasius boundary layer flow past a flat plate. With increase in time, the unstable waves only undergo growth for a finite time interval, and this growth rate is itself a function of time. The influence of finite amplitude effects is studied by solving the full Navier-Stokes equations. It is found that the stability characteristics are markedly changed both by the consideration of the time evolution of the flow, and by the introduction of finite amplitude effects.

Materials Screening for the Discovery of New Half-Heuslers: Machine Learning versus ab Initio Methods.

PubMed

Legrain, Fleur; Carrete, Jesús; van Roekeghem, Ambroise; Madsen, Georg K H; Mingo, Natalio

2018-01-18

Machine learning (ML) is increasingly becoming a helpful tool in the search for novel functional compounds. Here we use classification via random forests to predict the stability of half-Heusler (HH) compounds, using only experimentally reported compounds as a training set. Cross-validation yields an excellent agreement between the fraction of compounds classified as stable and the actual fraction of truly stable compounds in the ICSD. The ML model is then employed to screen 71 178 different 1:1:1 compositions, yielding 481 likely stable candidates. The predicted stability of HH compounds from three previous high-throughput ab initio studies is critically analyzed from the perspective of the alternative ML approach. The incomplete consistency among the three separate ab initio studies and between them and the ML predictions suggests that additional factors beyond those considered by ab initio phase stability calculations might be determinant to the stability of the compounds. Such factors can include configurational entropies and quasiharmonic contributions.

Yeast mannoproteins improve thermal stability of anthocyanins at pH 7.0.

PubMed

Wu, Jine; Guan, Yongguang; Zhong, Qixin

2015-04-01

Anthocyanins are food colourants with strong antioxidant activities, but poor thermal stability limits their application in neutral foods. In the present study, impacts of yeast mannoproteins on the thermal stability of anthocyanins were studied at pH 7.0. The degradation of anthocyanins at 80 and 126 °C followed first order kinetics, and the addition of mannoproteins reduced the degradation rate constant and increased the half-life by 4 to 5-fold. After heating at 80 and 126 °C for 30 min, mannoproteins improved the colour stability of anthocyanins by 4 to 5-fold and maintained the antioxidant capacity of anthocyanins. Visible light absorption, fluorescence spectroscopy, and zeta-potential results suggest that anthocyanins bound with the protein moiety of mannoproteins by hydrophobic interactions, and that the inclusion of anthocyanins in complexes effectively reduced the thermal degradation at pH 7.0. Therefore, mannoproteins may expand the application of anthocyanins as natural colours or functional ingredients. Copyright © 2014 Elsevier Ltd. All rights reserved.

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

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

Zhou, Hua; Uysal, Ahmet; Anjos, Daniela M.

2015-09-01

The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminalmore » hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.« less

Probing the pH sensitivity of R-phycoerythrin: investigations of active conformational and functional variation.

PubMed

Liu, Lu-Ning; Su, Hai-Nan; Yan, Shi-Gan; Shao, Si-Mi; Xie, Bin-Bin; Chen, Xiu-Lan; Zhang, Xi-Ying; Zhou, Bai-Cheng; Zhang, Yu-Zhong

2009-07-01

Crystal structures of phycobiliproteins have provided valuable information regarding the conformations and amino acid organizations of peptides and chromophores, and enable us to investigate their structural and functional relationships with respect to environmental variations. In this work, we explored the pH-induced conformational and functional dynamics of R-phycoerythrin (R-PE) by means of absorption, fluorescence and circular dichroism spectra, together with analysis of its crystal structure. R-PE presents stronger functional stability in the pH range of 3.5-10 compared to the structural stability. Beyond this range, pronounced functional and structural changes occur. Crystal structure analysis shows that the tertiary structure of R-PE is fixed by several key anchoring points of the protein. With this specific association, the fundamental structure of R-PE is stabilized to present physiological spectroscopic properties, while local variations in protein peptides are also allowed in response to environmental disturbances. The functional stability and relative structural sensitivity of R-PE allow environmental adaptation.

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

DOE PAGES

Zhou, Hua; Uysal, Ahmet; Anjos, Daniela M.; ...

2015-09-01

For the noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The fi ndings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. Moreover, the structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogenmore » bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. Finally, these results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.« less

The system of high accuracy UV spectral radiation system

NASA Astrophysics Data System (ADS)

Lin, Guan-yu; Yu, Lei; Xu, Dian; Cao, Dian-sheng; Yu, Yu-Xiang

2016-10-01

UV spectral radiation detecting and visible observation telescope is designed by the coaxial optical. In order to decrease due to the incident light polarization effect, and improve the detection precision, polarizer need to be used in the light path. Four pieces of quartz of high Precision UV radiation depolarizer retarder stack together is placed in front of Seya namioka dispersion unit. The coherent detection principle of modulation of light signal and the reference signal multiplied processing, increase the phase sensitive detector can be adjustment function, ensure the UV spectral radiation detection stability. A lock-in amplifier is used in the electrical system to advance the accuracy of measurement. To ensure the precision measurement detected, the phase-sensitive detector function can be adjustable. the output value is not more than 10mV before each measurement, so it can be ensured that the stability of the measured radiation spectrum is less than 1 percent.

Synthesis of Cross-Linked Polymeric Micelle pH Nanosensors: An Investigation of Design Flexibility.

PubMed

Kumar, E K Pramod; Jølck, Rasmus I; Andresen, Thomas L

2015-09-01

The design flexibility that polymeric micelles offer in the fabrication of optical nanosensors for ratiometric pH measurements is investigated. pH nanosensors based on polymeric micelles are synthesized either by a mixed-micellization approach or by a postmicelle modification strategy. In the mixed-micellization approach, self-assembly of functionalized unimers followed by shell cross-linking by copper-catalyzed azide-alkyne cycloaddition (CuAAC) results in stabilized cRGD-functionalized micelle pH nanosensors. In the postmicelle modification strategy, simultaneous cross-linking and fluorophore conjugation at the micelle shell using CuAAC results in a stabilized micelle pH nanosensor. Compared to the postmicelle modification strategy, the mixed-micellization approach increases the control of the overall composition of the nanosensors. Both approaches provide stable nanosensors with similar pKa profiles and thereby nanosensors with similar pH sensitivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical properties of boron-group (V) hexagonal nanowires: DFT investigation

NASA Astrophysics Data System (ADS)

Santhibhushan, B.; Soni, Mahesh; Srivastava, Anurag

2017-07-01

The paper presents structural, electronic and optical properties of boron-group V hexagonal nanowires (h-NW) within the framework of density functional theory. The h-NW of boron-group V compounds with an analogous diameter of 12 Å have been designed in (1 1 1) plane. Stability analysis performed through formation energies reveal that, the stability of these structures decreases with increasing atomic number of the group V element. The band nature predicts that these nanowires are good electrical conductors. Optical behaviour of the nanowires has been analysed through absorption coefficient, reflectivity, refractive index, optical conductivity and electron energy loss spectrum (EELS), that are computed from the frequency-dependent complex dielectric function. The analysis reveals high reactivity of BP and BAs h-NWs to the incident light especially in the IR and visible ranges, and the optical transparency of BN h-NW in the visible and UV ranges.

The role of interventional radiology in abdominopelvic trauma

PubMed Central

Ierardi, Anna Maria; Duka, Ejona; Lucchina, Natalie; Floridi, Chiara; De Martino, Alessandro; Donat, Daniela; Fontana, Federico

2016-01-01

The management of trauma patients has evolved in recent decades owing to increasing availability of advanced imaging modalities such as CT. Nowadays, CT has replaced the diagnostic function of angiography. The latter is considered when a therapeutic option is hypothesized. Arterial embolization is a life-saving procedure in abdominopelvic haemorrhagic patients, reducing relevant mortality rates and ensuring haemodynamic stabilization of the patient. Percutaneous transarterial embolization has been shown to be effective for controlling ongoing bleeding for patients with high-grade abdominopelvic injuries, thereby reducing the failure rate of non-operative management, preserving maximal organ function. Surgery is not always the optimal solution for stabilization of a patient with polytrauma. Mini-invasivity and repeatability may be considered as relevant advantages. We review technical considerations, efficacy and complication rates of hepatic, splenic, renal and pelvic embolization to extrapolate current evidence about transarterial embolization in traumatic patients. PMID:26642310

Evolution of anisotropy in bcc Fe distorted by interstitial boron

NASA Astrophysics Data System (ADS)

Gölden, Dominik; Zhang, Hongbin; Radulov, Iliya; Dirba, Imants; Komissinskiy, Philipp; Hildebrandt, Erwin; Alff, Lambert

2018-01-01

The evolution of magnetic anisotropy in bcc Fe as a function of interstitial boron atoms was investigated in thin films grown by molecular beam epitaxy. The thermodynamic nonequilibrium conditions during film growth allowed one to stabilize an interstitial boron content of about 14 at .% accompanied by lattice tetragonalization. The c /a ratio scaled linearly with the boron content up to a maximum value of 1.05 at 300 °C substrate growth temperature, with a room-temperature magnetization of. In contrast to nitrogen interstitials, the magnetic easy axis remained in-plane with an anisotropy of approximately -5.1 ×106erg /cm3 . Density functional theory calculations using the measured lattice parameters confirm this value and show that boron local ordering indeed favors in-plane magnetization. Given the increased temperature stability of boron interstitials as compared to nitrogen interstitials, this study will help to find possible ways to manipulate boron interstitials into a more favorable local order.

Oral Rehabilitation With Orthognathic Surgery After Dental Implant Placement for Class III Malocclusion With Skeletal Asymmetry and Posterior Bite Collapse.

PubMed

Ohba, Seigo; Nakatani, Yuya; Kawasaki, Takako; Tajima, Nobutaka; Tobita, Takayoshi; Yoshida, Noriaki; Sawase, Takashi; Asahina, Izumi

2015-08-01

Increasing numbers of older patients are seeking orthognathic surgery to treat jaw deformity. However, orthodontic and orthognathic surgical treatment is difficult in cases without occlusal vertical stop. A 55-year-old man presented with Class III malocclusion and mandibular protrusion including esthetic problems and posterior bite collapse. He underwent dental implant treatment to reconstruct an occlusal vertical stop before orthognathic surgery. His occlusal function and esthetic problems improved after surgery, and his skeletal and occlusal stability has been maintained for 6 years. Dental implant placement at appropriate positions could help to determine the position of the proximal segment at orthognathic surgery and could shorten the time required to restore esthetic and occlusal function. This case demonstrates how skeletal and dental stability can be maintained long after surgery in a patient with jaw deformity and posterior bite collapse.

Inhibition of the bioavailability of heavy metals in sewage sludge biochar by adding two stabilizers

PubMed Central

Huang, Zhujian; Lu, Qin; Wang, Jun; Chen, Xian; He, Zhenli

2017-01-01

Agricultural application of sewage sludge (SS) after carbonization is a plausible way for disposal. Despite its benefits of improving soil fertility and C sequestration, heavy metals contained in sewage sludge biochars (SSB) are still a concern. In this study, two types of heavy metal stabilizers were chosen: fulvic acid (FA) and phosphogypsum (with CaSO4, CS, as the main component). The two stabilizers were incorporated into SS prior to 350°C carbonization for 1 h at the rates of 1%, 2%, or 4%. The obtained SSBs were then analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Total and available concentrations of four heavy metals, i.e., Zn, Pb, Cd, and Ni, in the SSBs were determined. In addition, a series of pot soil culture experiments was conducted to investigate the effects of stabilizers incorporation into SSB on heavy metal bioavailability and the uptake by plants (corn as an indicator) and plant biomass yield, with SS and SSB (no stabilizers) as controls. The results showed that incorporation of both FA and CS increased functional groups such as carboxyl, phenol, hydroxyl, amine and quinine groups in the SSBs. The percentage of heavy metals in sulfuric and oxidizable state and residual state of SSBs were significantly increased after carbonization, and hence the mobility of the heavy metals in SSBs was decreased. The introduction of the stabilizers (i.e., FA or CS) significantly lowered the total and available concentrations of Zn, Pb, Cd, and Ni. The reduction in available heavy metal concentration increased with incorporation rate of the stabilizers from 1% to 4%. In the treatments with FA or CS incorporated SSB, less heavy metals were taken up by plants and more plant biomass yields were obtained. The mitigating effects were more pronounced at higher rates of FA or CS stabilizer. These findings provide a way to lower bioavailability of heavy metals in SS or SSB for land application or horticulture as a peat substitute. PMID:28832651

Finite-time output feedback stabilization of high-order uncertain nonlinear systems

NASA Astrophysics Data System (ADS)

Jiang, Meng-Meng; Xie, Xue-Jun; Zhang, Kemei

2018-06-01

This paper studies the problem of finite-time output feedback stabilization for a class of high-order nonlinear systems with the unknown output function and control coefficients. Under the weaker assumption that output function is only continuous, by using homogeneous domination method together with adding a power integrator method, introducing a new analysis method, the maximal open sector Ω of output function is given. As long as output function belongs to any closed sector included in Ω, an output feedback controller can be developed to guarantee global finite-time stability of the closed-loop system.

Effects of functional electrical stimulation assisted rowing on aerobic fitness and shoulder pain in manual wheelchair users with spinal cord injury.

PubMed

Wilbanks, Susan R; Rogers, Rebecca; Pool, Sean; Bickel, C Scott

2016-11-01

Test the effectiveness of a 6-week functional electrical stimulation (FES)-assisted rowing intervention to increase aerobic fitness and decrease shoulder pain in manual wheelchair users with spinal cord injury (SCI) Methods: Ten adults with SCI (47 ± 12 years, 86 ± 19.7 kg, 175.5 ± 13.2 cm) 18 ± 14 years since injury, AIS classification A-C who had pain in one or both shoulders for >6 months took part in a pre-test, post-test experiment in our human performance laboratory. Participants took part in 30 minutes of FES-assisted rowing, 3 days/week × 6 weeks. Participants were evaluated for VO 2 peak (FES-row and arm bike), distance rowed, arm power output, Wheelchair User Shoulder Pain Index (WUSPI), upper extremity isokinetic strength, scapular stabilization, participation (LIFE-H), quality of life (QOL-SCI), qualitative exit interview. Participants increased distance rowed by 257 ± 266 m and increased arm power output by 6.7 ± 7.9 W. An 8% increase in VO 2 peak and 10.5 ± 4.4 point decrease in shoulder pain were observed (all P < 0.05). There were no changes in upper extremity strength, scapular stabilization, or survey-based measures of participation or quality of life. Qualitative interviewing indicated overall enjoyment of the intervention and improvement in perceived quality of life. FES-assisted rowing is effective to increase aerobic fitness and decrease shoulder pain in manual wheelchair users with SCI. Further research is necessary to determine if rowing without FES can provide similar benefits, and to determine mechanisms driving improvements in shoulder pain, as no changes in measures of upper extremity strength or scapular stabilization were observed.

The influence of disulfide bonds on the mechanical stability of proteins is context dependent.

PubMed

Manteca, Aitor; Alonso-Caballero, Álvaro; Fertin, Marie; Poly, Simon; De Sancho, David; Perez-Jimenez, Raul

2017-08-11

Disulfide bonds play a crucial role in proteins, modulating their stability and constraining their conformational dynamics. A particularly important case is that of proteins that need to withstand forces arising from their normal biological function and that are often disulfide bonded. However, the influence of disulfides on the overall mechanical stability of proteins is poorly understood. Here, we used single-molecule force spectroscopy (smFS) to study the role of disulfide bonds in different mechanical proteins in terms of their unfolding forces. For this purpose, we chose the pilus protein FimG from Gram-negative bacteria and a disulfide-bonded variant of the I91 human cardiac titin polyprotein. Our results show that disulfide bonds can alter the mechanical stability of proteins in different ways depending on the properties of the system. Specifically, disulfide-bonded FimG undergoes a 30% increase in its mechanical stability compared with its reduced counterpart, whereas the unfolding force of I91 domains experiences a decrease of 15% relative to the WT form. Using a coarse-grained simulation model, we rationalized that the increase in mechanical stability of FimG is due to a shift in the mechanical unfolding pathway. The simple topology-based explanation suggests a neutral effect in the case of titin. In summary, our results indicate that disulfide bonds in proteins act in a context-dependent manner rather than simply as mechanical lockers, underscoring the importance of considering disulfide bonds both computationally and experimentally when studying the mechanical properties of proteins. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Dispersion stability of a ceramic glaze achieved through ionic surfactant adsorption.

PubMed

Panya, Preecha; Arquero, Orn-anong; Franks, George V; Wanless, Erica J

2004-11-01

The adsorption of cetylpyridinium chloride (CPC) and sodium dodecylbenzenesulfonate (SDBS) onto a ceramic glaze mixture composed of limestone, feldspar, quartz, and kaolin has been investigated. Both adsorption isotherms and the average particle zeta potential have been studied in order to understand the suspension stability as a function of pH, ionic strength, and surfactant concentration. The adsorption of small amounts of cationic CPC onto the primarily negatively charged surfaces of the particles at pH 7 and 9 results in strong attraction and flocculation due to hydrophobic interactions. At higher surfactant concentrations a zeta potential of more than +60 mV results from the bilayered adsorbed surfactant, providing stability at salt concentrations < or = 0.01 M. At 0.1 M salt poor stability results despite substantial zeta potential values. Three mechanisms for SDBS adsorption have been identified. When anionic SDBS monomers either adsorb by electrostatic interactions with the few positive surface sites at high pH or adsorb onto like charged negative surface sites due to dispersion or hydrophobic interactions, the magnitude of the negative zeta potential increases slightly. At pH 9 this increase is enough to promote stability with an average zeta potential of more than -55 mV, whereas at pH 7 the zeta potential is lower at about -45 mV. The stability of suspensions at pH 7 is additionally due to steric repulsion caused by the adsorption of thick layers of neutrally charged Ca(DBS)2 complexes created when the surfactant interacts with dissolved calcium ions from the calcium carbonate component.

Fluorescence and electron paramagnetic resonance studies of norfloxacin and N-donor mixed-ligand ternary copper(II) complexes: Stability and interaction with SDS micelles

NASA Astrophysics Data System (ADS)

Vignoli Muniz, Gabriel S.; Incio, Jimmy Llontop; Alves, Odivaldo C.; Krambrock, Klaus; Teixeira, Letícia R.; Louro, Sonia R. W.

2018-01-01

The stability of ternary copper(II) complexes of a heterocyclic ligand, L (L being 2,2‧-bipyridine (bipy) or 1,10-phenanthroline (phen)) and the fluorescent antibacterial agent norfloxacin (NFX) as the second ligand was studied at pH 7.4 and different ionic strengths. Fluorescence quenching upon titration of NFX with the binary complexes allowed to obtain stability constants for NFX binding, Kb, as a function of ionic strength. The Kb values vary by more than two orders of magnitude when buffer concentration varies from 0.5 to 100 mM. It was observed that previously synthesized ternary complexes dissociate in buffer according with the obtained stability constants. This shows that equimolar solutions of NFX and binary complexes are equivalent to solutions of synthesized ternary complexes. The interaction of the ternary copper complexes with anionic SDS (sodium dodecyl sulfate) micelles was studied by fluorescence and electron paramagnetic resonance (EPR). Titration of NFX-loaded SDS micelles with the complexes Cu:L allowed to determine the stability constants inside the micelles. Fluorescence quenching demonstrated that SDS micelles increase the stability constants by factors around 50. EPR spectra gave details of the copper(II) local environment, and demonstrated that the structure of the ternary complexes inside SDS micelles is different from that in buffer. Mononuclear ternary complexes formed inside the micelles, while in buffer most ternary complexes are binuclear. The results show that anionic membrane interfaces increase formation of copper fluoroquinolone complexes, which can influence bioavailability, membrane diffusion, and mechanism of action of the antibiotics.

Functional stability of cerebral circulatory system

NASA Technical Reports Server (NTRS)

Moskalenko, Y. Y.

1980-01-01

The functional stability of the cerebral circulation system seems to be based on the active mechanisms and on those stemming from specific of the biophysical structure of the system under study. This latter parameter has some relevant criteria for its quantitative estimation. The data obtained suggest that the essential part of the mechanism for active responses of cerebral vessels which maintains the functional stability of this portion of the vascular system, consists of a neurogenic component involving central nervous structures localized, for instance, in the medulla oblongata.

Application of Two-Parameter Stabilizing Functions in Solving a Convolution-Type Integral Equation by Regularization Method

NASA Astrophysics Data System (ADS)

Maslakov, M. L.

2018-04-01

This paper examines the solution of convolution-type integral equations of the first kind by applying the Tikhonov regularization method with two-parameter stabilizing functions. The class of stabilizing functions is expanded in order to improve the accuracy of the resulting solution. The features of the problem formulation for identification and adaptive signal correction are described. A method for choosing regularization parameters in problems of identification and adaptive signal correction is suggested.

Postural stability in patients with knee osteoarthritis: comparison with controls and evaluation of relationships between postural stability scores and International Classification of Functioning, Disability and Health components.

PubMed

Hsieh, Ru-Lan; Lee, Wen-Chung; Lo, Min-Tzu; Liao, Wei-Cheng

2013-02-01

To assess the differences in postural stability between patients with knee osteoarthritis and controls without knee osteoarthritis, and to evaluate possible relations between postural stability scores and International Classification of Functioning, Disability and Health (ICF) components. An age-matched, case-controlled trial with a cross-sectional design. A teaching hospital. Patients with knee osteoarthritis (n=73) and age-matched controls (n=60). Data on patients' postural stability and additional health-related variables were collected using various instruments. These included the Hospital Anxiety and Depression Scale, the Multidimensional Fatigue Inventory, the World Health Organization Quality of Life Brief Version, the physical function test (chair-rising time), the Chinese version of the Western Ontario and McMaster Universities Osteoarthritis Index, the Chinese version of the Knee Injury and Osteoarthritis Outcome Score, and the Biodex Stability System. A comparison of postural stability in patients with knee osteoarthritis versus that of controls was performed. The relation between postural stability scores for patients with knee osteoarthritis and ICF components was evaluated. Pearson correlation tests were used to determine the variables that correlated with postural stability among these patients. Patients with knee osteoarthritis displayed lower overall postural stability than controls (scores of 0.7 vs. 0.5, P=.006) and scored lower on the environmental domain of the World Health Organization Quality of Life Brief Version (62.2 vs 66.8, P=.014). For patients with knee osteoarthritis, postural stability was weakly associated with the ICF components of body functions and structures, including pain (r=.33-.34, P=.004), physical fatigue (r=.28, P=.016), and reduced motivation (r=.30, P=.011). Weak to moderate associations between postural stability and the ICF components of activities and participation were found; the relevant ICF variables included reduced activity (r=.38, P=.001), physical domain and function (r=.34-.48, P=.001 to P<.004), activities of daily living (r=.51, P<.001), and sports and recreation (r=.35, P=.003). A moderate association between postural stability and the ICF components of personal and environmental factors was observed, including age (r=.52, P<.001) and quality of life (r=0.4, P=.001). Patients with knee osteoarthritis displayed lower postural stability and achieved lower scores in the environmental domain of quality-of-life measures than did controls. The postural stability of patients with knee osteoarthritis was weakly to moderately associated with the following ICF components: body functions and structures, activities and participation, and personal and environmental factors. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Theoretical analyses of Baroclinic flows

NASA Technical Reports Server (NTRS)

Antar, B.

1982-01-01

A stability analysis of a thin horizontal rotating fluid layer which is subjected to arbitrary horizontal and vertical temperature gradients is presented. The basic state is a nonlinear Hadley cell which contains both Ekman and thermal boundary layers; it is given in closed form. The stability analysis is based on the linearized Navier-Stokes equations, and zonally symmetric perturbations in the form of waves propagating in the meridional direction are considered. Numerical methods were used for the stability problem. It was found that the instability sets in when the Richardson number is close to unity and that the critical Richardson number is a non-monotonic function of the Prandtl number. Further, it was found that the critical Richardson number decreases with increasing Ekman number until a critical value of the Ekman number is reached beyond which the fluid is stable.

Towards novel multiferroic and magnetoelectric materials: dipole stability in tetragonal tungsten bronzes

PubMed Central

Rotaru, Andrei; Miller, Andrew J.; Arnold, Donna C.; Morrison, Finlay D.

2014-01-01

We discuss the strategy for development of novel functional materials with the tetragonal tungsten bronze structure. From the starting composition Ba6GaNb9O30, the effect of A- and B-site substitutions on the dielectric properties is used to develop an understanding of the origin and stability of the dipolar response in these compounds. Both tetragonal strain induced by large B-site cations and local strain variations created by isovalent A-site substitutions enhance dipole stability but result in a dilute, weakly correlated dipolar response and canonical relaxor behaviour. Decreasing cation size at the perovskite A2-site increases the dipolar displacements in the surrounding octahedra, but insufficiently to result in dipole ordering. Mechanisms introducing small A-site lanthanide cations and incorporation of A-site vacancies to induce ferroelectricity and magnetism are presented. PMID:24421377

Effect of van der Waals interactions on the stability of SiC polytypes

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

Kawanishi, Sakiko, E-mail: s-kawa@tagen.tohoku.ac.jp; Mizoguchi, Teruyasu

2016-05-07

Density functional theory calculations with a correction of the long-range dispersion force, namely, the van der Waals (vdW) force, are performed for SiC polytypes. The lattice parameters are in good agreement with those obtained from the experiments. Furthermore, the stability of the polytypes in the experiments, which show 3C-SiC as the most stable, is reproduced by the present calculations. The effects of the vdW force on the electronic structure and the stability of polytypes are discussed. We observe that the vdW interaction is more sensitive to the cubic site than the hexagonal site. Thus, the influence of the vdW forcemore » increases with decreasing the hexagonality of the polytype, which results in the confirmation that the most stable polytype is 3C-SiC.« less

Coexistence and local μ-stability of multiple equilibrium points for memristive neural networks with nonmonotonic piecewise linear activation functions and unbounded time-varying delays.

PubMed

Nie, Xiaobing; Zheng, Wei Xing; Cao, Jinde

2016-12-01

In this paper, the coexistence and dynamical behaviors of multiple equilibrium points are discussed for a class of memristive neural networks (MNNs) with unbounded time-varying delays and nonmonotonic piecewise linear activation functions. By means of the fixed point theorem, nonsmooth analysis theory and rigorous mathematical analysis, it is proven that under some conditions, such n-neuron MNNs can have 5 n equilibrium points located in ℜ n , and 3 n of them are locally μ-stable. As a direct application, some criteria are also obtained on the multiple exponential stability, multiple power stability, multiple log-stability and multiple log-log-stability. All these results reveal that the addressed neural networks with activation functions introduced in this paper can generate greater storage capacity than the ones with Mexican-hat-type activation function. Numerical simulations are presented to substantiate the theoretical results. Copyright © 2016 Elsevier Ltd. All rights reserved.

The interaction of the soybean seed high oleic acid oil trait with other fatty acid modifications

USDA-ARS?s Scientific Manuscript database

Oil value is determined by the functional qualities imparted from the fatty acid profile. Soybean oil historically had excellent utilization in both food and industrial uses, but the need to increase the stability of the oil without negative health consequences has led to a significant decline in s...

Academic Functioning and Mental Health in Adolescence: Patterns, Progressions, and Routes from Childhood.

ERIC Educational Resources Information Center

Roeser, Robert W.; Eccles, Jacquelynne S.; Freedman-Doan, Carol

1999-01-01

Examined patterns of academic functioning and mental health in middle school students and the relation of such patterns to their prior and subsequent functioning. Found variegated patterns of academic and emotional functioning at eighth grade and stability in these patterns across the high school transition. Found some long-term stability among…

Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil.

PubMed

Wu, Mengxiong; Feng, Qibo; Sun, Xue; Wang, Hailong; Gielen, Gerty; Wu, Weixiang

2015-05-05

Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using (13)C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems.

Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil

PubMed Central

Wu, Mengxiong; Feng, Qibo; Sun, Xue; Wang, Hailong; Gielen, Gerty; Wu, Weixiang

2015-01-01

Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using 13C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems. PMID:25944542

Far-infrared spectral studies of phase changes in water ice induced by proton irradiation

NASA Technical Reports Server (NTRS)

Moore, Marla H.; Hudson, Reggie L.

1992-01-01

Changes in the FIR spectrum of crystalline and amorphous water ice as a function of temperature are reported. The dramatic differences between the spectra of these ices in the FIR are used to examine the effect of proton irradiation on the stability of the crystalline and amorphous ice phases from 13 to 77 K. In particular, the spectra near 13 K show interconversion between the amorphous and crystalline ice phases beginning at doses near 2 eV/molecule and continuing cyclically with increased dose. The results are used to estimate the stability of irradiated ices in astronomical environments.

Hydroxide Degradation Pathways for Substituted Benzyltrimethyl Ammonium: A DFT Study

DOE PAGES

Long, Hai; Pivovar, Bryan S.

2014-11-01

The stability of cations used in the alkaline exchange membranes has been a major challenge. In this paper, degradation energy barriers were investigated by density functional theory for substituted benzyltrimethyl ammonium (BTMA+) cations. Findings show that electron-donating substituent groups at meta-position(s) of the benzyl ring could result in increased degradation barriers. However, after investigating more than thirty substituted BTMA+ cations, the largest improvement in degradation barrier found was only 6.7 kJ/mol. This suggests a modest (8×) improvement in stability for this type of approach may be possible, but for anything greater other approaches will need to be pursued.

Predicting unfolding thermodynamics and stable intermediates for alanine-rich helical peptides with the aid of coarse-grained molecular simulation.

PubMed

Calero-Rubio, Cesar; Paik, Bradford; Jia, Xinqiao; Kiick, Kristi L; Roberts, Christopher J

2016-10-01

This report focuses on the molecular-level processes and thermodynamics of unfolding of a series of helical peptides using a coarse-grained (CG) molecular model. The CG model was refined to capture thermodynamics and structural changes as a function of temperature for a set of published peptide sequences. Circular dichroism spectroscopy (CD) was used to experimentally monitor the temperature-dependent conformational changes and stability of published peptides and new sequences introduced here. The model predictions were quantitatively or semi-quantitatively accurate in all cases. The simulations and CD results showed that, as expected, in most cases the unfolding of helical peptides is well described by a simply 2-state model, and conformational stability increased with increased length of the helices. A notable exception in a 19-residue helix was when two Ala residues were each replaced with Phe. This stabilized a partly unfolded intermediate state via hydrophobic contacts, and also promoted aggregates at higher peptide concentrations. Copyright © 2016 Elsevier B.V. All rights reserved.

Gum tragacanth stabilized green gold nanoparticles as cargos for Naringin loading: A morphological investigation through AFM.

PubMed

Rao, Komal; Imran, Muhammad; Jabri, Tooba; Ali, Imdad; Perveen, Samina; Shafiullah; Ahmed, Shakil; Shah, Muhammad Raza

2017-10-15

Gold nanoparticles (AuNPs) have attracted greater scientific interests for the construction of drugs loading cargos due to their biocompatibility, safety and facile surface modifications. This study deals with the fabrication of gum tragacanth (GT) green AuNPs as carrier for Naringin, a less water soluble therapeutic molecule. The optimized AuNPs were characterized through UV-vis spectroscopy, FT-IR and atomic force microscope (AFM). Naringin loaded nanoparticles were investigated for their bactericidal potentials using Tetrazolium Microplate assay. Morphological studies conducted via AFM revealed spherical shape for AuNPs with nano-range size and stabilized by GT multi-functional groups. The AuNPs acted as carrier for increased amount of Naringin. Upon loading in AuNPs, Naringin An increased in the bactericidal potentials of Naringin was observed after loading on AuNPs against various tested bacterial strains. This was further authenticated by the surface morphological analysis, showing enhanced membrane destabilizing effects of loaded Naringin. The results suggest that GT stabilized green AuNPs can act as effective delivery vehicles for enhancing bactericidal potentials of Naringin. Copyright © 2017 Elsevier Ltd. All rights reserved.

Human hemoglobin structural and functional alterations and heme degradation upon interaction with benzene: A spectroscopic study.

PubMed

Hosseinzadeh, Reza; Moosavi-Movahedi, Ali Akbar

2016-03-15

Here, the effect of benzene on hemoglobin structure, stability and heme prosthetic group integrity was studied by different methods. These included UV-vis absorption spectrophotometry, normal and synchronous fluorescence techniques, and differential scanning calorimetry (DSC). Our results indicated that benzene has high hemolytic potential even at low concentrations. The UV-vis spectroscopic results demonstrated that benzene altered both the globin chain and the heme prosthetic group of hemoglobin increasing met- and deoxy-Hb, while decreasing oxy-Hb. However, with increasing benzene the concentration of all species decreased due to heme destruction. The spectrophotometric results show that benzene has a high potential for penetrating the hydrophobic pocket of hemoglobin. These results were consistent with the molecular docking simulation results of benzene-hHb. Aggregation and thermal denaturation studies show that the increased benzene concentration induced hemoglobin aggregation with a decrease in stability, which is consistent with the DSC results. Conventional fluorescence spectroscopy revealed that the heme degradation species were produced in the presence of benzene. The results of constant wavelength synchronous fluorescence spectroscopy (CWSFS) indicated that at least five heme-degraded species were produced. Together, our results indicated that benzene has adverse effects on hemoglobin structure and function, and heme degradation. Copyright © 2015 Elsevier B.V. All rights reserved.

Control of locomotor stability in stabilizing and destabilizing environments.

PubMed

Wu, Mengnan/Mary; Brown, Geoffrey; Gordon, Keith E

2017-06-01

To develop effective interventions targeting locomotor stability, it is crucial to understand how people control and modify gait in response to changes in stabilization requirements. Our purpose was to examine how individuals with and without incomplete spinal cord injury (iSCI) control lateral stability in haptic walking environments that increase or decrease stabilization demands. We hypothesized that people would adapt to walking in a predictable, stabilizing viscous force field and unpredictable destabilizing force field by increasing and decreasing feedforward control of lateral stability, respectively. Adaptations in feedforward control were measured using after-effects when fields were removed. Both groups significantly (p<0.05) decreased step width in the stabilizing field. When the stabilizing field was removed, narrower steps persisted in both groups and subjects with iSCI significantly increased movement variability (p<0.05). The after-effect of walking in the stabilizing field was a suppression of ongoing general stabilization mechanisms. In the destabilizing field, subjects with iSCI took faster steps and increased lateral margins of stability (p<0.05). Step frequency increases persisted when the destabilizing field was removed (p<0.05), suggesting that subjects with iSCI made feedforward adaptions to increase control of lateral stability. In contrast, in the destabilizing field, non-impaired subjects increased movement variability (p<0.05) and did not change step width, step frequency, or lateral margin of stability (p>0.05). When the destabilizing field was removed, increases in movement variability persisted (p<0.05), suggesting that non-impaired subjects made feedforward decreases in resistance to perturbations. Published by Elsevier B.V.

Acetylation and characterization of banana (Musa paradisiaca) starch.

PubMed

Bello-Pérez, L A; Contreras-Ramos, S M; Jìmenez-Aparicio, A; Paredes-López, O

2000-01-01

Banana native starch was acetylated and some of its functional properties were evaluated and compared to corn starch. In general, acetylated banana starch presented higher values in ash, protein and fat than corn acetylated starch. The modified starches had minor tendency to retrogradation assessed as % transmittance of starch pastes. At high temperature acetylated starches presented a water retention capacity similar to their native counterpart. The acetylation considerably increased the solubility of starches, and a similar behavior was found for swelling power. When freeze-thaw stability was studied, acetyl banana starch drained approximately 60% of water in the first and second cycles, but in the third and fourth cycles the percentage of separated water was low. However, acetyl corn starch showed lower freeze-thaw stability than the untreated sample. The modification increased the viscosity of banana starch pastes.

Effect of controlled adverse chamber environment exposure on tear functions in silicon hydrogel and hydrogel soft contact lens wearers.

PubMed

Kojima, Takashi; Matsumoto, Yukihiro; Ibrahim, Osama M A; Wakamatsu, Tais Hitomi; Uchino, Miki; Fukagawa, Kazumi; Ogawa, Junko; Dogru, Murat; Negishi, Kazuno; Tsubota, Kazuo

2011-11-11

To prospectively evaluate the effect of controlled adverse chamber environment (CACE) exposure on tear function, including tear osmolarity, in subjects wearing narafilcon A versus those wearing etafilcon A soft contact lens (SCL). Thirty-one healthy subjects with no history of contact lens wear (13 women, 18 men; average age, 30.5 ± 6.5 years) were randomly divided into age- and sex-matched groups (15 subjects wearing narafilcon A SCL; 16 subjects wearing etafilcon A SCL) and entered a CACE for 20 minutes. All subjects underwent tear osmolarity, tear evaporation rate, strip meniscometry, tear film breakup time, fluorescein vital staining, and functional visual acuity measurement before and after exposure to the controlled adverse chamber. The mean blink rate increased with significant deteriorations in the mean symptom VAS scores, mean tear osmolarity, tear evaporation rate, strip meniscometry score, and tear stability with CACE exposure along with a decrease in visual maintenance ratio in functional visual acuity testing in etafilcon A wearers. The mean symptom VAS scores, mean tear evaporation rate, tear stability, blink rates, and visual maintenance ratios did not change significantly in narafilcon A wearers after CACE exposure. This study suggested marked tear instability, higher tear osmolarity, and increased tear evaporation with marked dry eye and visual symptomatology in nonadapted hydrogel SCL wearers, suggesting that silicone hydrogel SCLs may be suitable for persons who live and work in cool, low-humidity, and windy environments, as tested in this study.

Colour-stability and gloss-retention of silorane and dimethacrylate composites with accelerated aging.

PubMed

Furuse, Adilson Y; Gordon, Kathryn; Rodrigues, Flávia P; Silikas, Nick; Watts, David C

2008-11-01

To evaluate the colour-stability and gloss-retention of silorane versus dimethacrylate composites exposed to accelerated aging from daylight radiation. Five disc-shaped specimens of photo-cured resin-composites were prepared and manually polished for each material (Filtek Silorane, Herculite XRV, Tetric Evoceram and QuiXfil). Colour and gloss were evaluated before and after periods (baseline, 24, 72, 120 and 192 h) of accelerated photo-aging in xenon light following ISO 7491:2000. Colour measurements were performed with a colourimeter according to the CIE-Lab colour-space. The colour change (DeltaE) for each time was calculated. The surface gloss was measured using a glossmeter. Results were evaluated using one-way ANOVA and Tukey tests (alpha=0.05). Correlations between logtime, DeltaE and gloss were evaluated using Pearson's correlation (alpha=0.05). Materials generally decreased in L and a and increased in b. The strong exception was Filtek Silorane which maintained a and b. DeltaE was found to be a positive linear function of logtime for all materials. Materials varied in the magnitude and rate of increase of DeltaE with logtime: QuiXfil>Tetric EvoCeram>(Filtek Silorane>or=Herculite XRV). DeltaE remained<3.3 for Filtek Silorane and Herculite XRV. Gloss was found to be a negative linear function of logtime. Gloss was maximal in the sequence: Filtek Silorane approximately Tetric EvoCeram>Herculite XRV>QuiXfil. Silorane gave the best overall performance in stability over time, compared to a set of representative dimethacrylate composites.

Phosphorylation-related modification at the dimer interface of 14-3-3ω dramatically alters monomer interaction dynamics.

PubMed

Denison, Fiona C; Gökirmak, Tufan; Ferl, Robert J

2014-01-01

14-3-3 proteins are generally believed to function as dimers in a broad range of eukaryotic signaling pathways. The consequences of altering dimer stability are not fully understood. Phosphorylation at Ser58 in the dimer interface of mammalian 14-3-3 isoforms has been reported to destabilise dimers. An equivalent residue, Ser62, is present across most Arabidopsis isoforms but the effects of phosphorylation have not been studied in plants. Here, we assessed the effects of phosphorylation at the dimer interface of Arabidopsis 14-3-3ω. Protein kinase A phosphorylated 14-3-3ω at Ser62 and also at a previously unreported residue, Ser67, resulting in a monomer-sized band on native-PAGE. Phosphorylation at Ser62 alone, or with additional Ser67 phosphorylation, was investigated using phosphomimetic versions of 14-3-3ω. In electrophoretic and chromatographic analyses, these mutants showed mobilities intermediate between dimers and monomers. Mobility was increased by detergents, by reducing protein concentration, or by increasing pH or temperature. Urea gradient gels showed complex structural transitions associated with alterations of dimer stability, including a previously unreported 14-3-3 aggregation phenomenon. Overall, our analyses showed that dimer interface modifications such as phosphorylation reduce dimer stability, dramatically affecting the monomer-dimer equilibrium and denaturation trajectory. These findings may have dramatic implications for 14-3-3 structure and function in vivo. Copyright © 2013 Elsevier Inc. All rights reserved.

Dynamic Stabilization of Expressed Proteins in Engineered Diatom Biosilica Matrices.

PubMed

Xiong, Yijia; Ford, Nicole R; Hecht, Karen A; Roesijadi, Guritno; Squier, Thomas C

2016-05-18

Self-assembly of recombinant proteins within the biosilica of living diatoms represents a means to construct functional materials in a reproducible and scalable manner that will enable applications that harness the inherent specificities of proteins to sense and respond to environmental cues. Here we describe the use of a silaffin-derived lysine-rich 39-amino-acid targeting sequence (Sil3T8) that directs a single chain fragment variable (scFv) antibody or an enhanced green fluorescent protein (EGFP) to assemble within the biosilica frustule, resulting in abundance of >200 000 proteins per frustule. Using either a fluorescent ligand bound to the scFv or the intrinsic fluorescence of EGFP, we monitored protein conformational dynamics, accessibility to external quenchers, binding affinity, and conformational stability. Like proteins in solution, proteins within isolated frustules undergo isotropic rotational motion, but with 2-fold increases in rotational correlation times that are indicative of weak macromolecular associations within the biosilica. Solvent accessibilities and high-affinity (pM) binding are comparable to those in solution. In contrast to solution conditions, scFv antibodies within the biosilica matrix retain their binding affinity in the presence of chaotropic agents (i.e., 8 M urea). Together, these results argue that dramatic increases in protein conformational stability within the biosilica matrices arise through molecular crowding, acting to retain native protein folds and associated functionality with the potential to allow the utility of engineered proteins under a range of harsh environmental conditions associated with environmental sensing and industrial catalytic transformations.

Organism-Sediment Interactions Govern Post-Hypoxia Recovery of Ecosystem Functioning

PubMed Central

Van Colen, Carl; Rossi, Francesca; Montserrat, Francesc; Andersson, Maria G. I.; Gribsholt, Britta; Herman, Peter M. J.; Degraer, Steven; Vincx, Magda; Ysebaert, Tom; Middelburg, Jack J.

2012-01-01

Hypoxia represents one of the major causes of biodiversity and ecosystem functioning loss for coastal waters. Since eutrophication-induced hypoxic events are becoming increasingly frequent and intense, understanding the response of ecosystems to hypoxia is of primary importance to understand and predict the stability of ecosystem functioning. Such ecological stability may greatly depend on the recovery patterns of communities and the return time of the system properties associated to these patterns. Here, we have examined how the reassembly of a benthic community contributed to the recovery of ecosystem functioning following experimentally-induced hypoxia in a tidal flat. We demonstrate that organism-sediment interactions that depend on organism size and relate to mobility traits and sediment reworking capacities are generally more important than recovering species richness to set the return time of the measured sediment processes and properties. Specifically, increasing macrofauna bioturbation potential during community reassembly significantly contributed to the recovery of sediment processes and properties such as denitrification, bedload sediment transport, primary production and deep pore water ammonium concentration. Such bioturbation potential was due to the replacement of the small-sized organisms that recolonised at early stages by large-sized bioturbating organisms, which had a disproportionately stronger influence on sediment. This study suggests that the complete recovery of organism-sediment interactions is a necessary condition for ecosystem functioning recovery, and that such process requires long periods after disturbance due to the slow growth of juveniles into adult stages involved in these interactions. Consequently, repeated episodes of disturbance at intervals smaller than the time needed for the system to fully recover organism-sediment interactions may greatly impair the resilience of ecosystem functioning. PMID:23185440

Adaptation to low body temperature influences pulmonary surfactant composition thereby increasing fluidity while maintaining appropriately ordered membrane structure and surface activity.

PubMed

Suri, Lakshmi N M; McCaig, Lynda; Picardi, Maria V; Ospina, Olga L; Veldhuizen, Ruud A W; Staples, James F; Possmayer, Fred; Yao, Li-Juan; Perez-Gil, Jesus; Orgeig, Sandra

2012-07-01

The interfacial surface tension of the lung is regulated by phospholipid-rich pulmonary surfactant films. Small changes in temperature affect surfactant structure and function in vitro. We compared the compositional, thermodynamic and functional properties of surfactant from hibernating and summer-active 13-lined ground squirrels (Ictidomys tridecemlineatus) with porcine surfactant to understand structure-function relationships in surfactant membranes and films. Hibernating squirrels had more surfactant large aggregates with more fluid monounsaturated molecular species than summer-active animals. The latter had more unsaturated species than porcine surfactant. Cold-adapted surfactant membranes displayed gel-to-fluid transitions at lower phase transition temperatures with reduced enthalpy. Both hibernating and summer-active squirrel surfactants exhibited lower enthalpy than porcine surfactant. LAURDAN fluorescence and DPH anisotropy revealed that surfactant bilayers from both groups of squirrels possessed similar ordered phase characteristics at low temperatures. While ground squirrel surfactants functioned well during dynamic cycling at 3, 25, and 37 degrees C, porcine surfactant demonstrated poorer activity at 3 degrees C but was superior at 37 degrees C. Consequently the surfactant composition of ground squirrels confers a greater thermal flexibility relative to homeothermic mammals, while retaining tight lipid packing at low body temperatures. This may represent the most critical feature contributing to sustained stability of the respiratory interface at low lung volumes. Thus, while less effective than porcine surfactant at 37 degrees C, summer-active surfactant functions adequately at both 37 degrees C and 3 degrees C allowing these animals to enter hibernation. Here further compositional alterations occur which improve function at low temperatures by maintaining adequate stability at low lung volumes and when temperature increases during arousal from hibernation.

Changes in hepatic levels of tyrosine aminotransferase messenger RNA during induction by hydrocortisone. [Xenopus laevis

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

Nickol, J.M.; Lee, K.L.; Kenney, F.T.

Messenger RNA specific for tyrosine aminotransferase was quantitated by microinjection into oocytes of Xenopus laevis. The heterologously translated enzyme was identified by specific immunoprecipitation and found to be identical with authentic aminotransferase by several criteria. The level of functional message present in rat liver increases during hydrocortisone induction, and this increase is directly proportional to the increased rate of synthesis of the enzyme. Kinetic analysis of the changes in tyrosine aminotransferase mRNA levels during induction and withdrawal indicates that the steroid does not affect the stability of the message, which has a half-life of approximately 1.2 h. Hydrocortisone, therefore, actsmore » to increase the rate of synthesis of the specific messenger by stimulating either its transcription or processing to functional mRNA.« less

Axial allometry in a neutrally buoyant environment: effects of the terrestrial-aquatic transition on vertebral scaling.

PubMed

Jones, K E; Pierce, S E

2016-03-01

Ecological diversification into new environments presents new mechanical challenges for locomotion. An extreme example of this is the transition from a terrestrial to an aquatic lifestyle. Here, we examine the implications of life in a neutrally buoyant environment on adaptations of the axial skeleton to evolutionary increases in body size. On land, mammals must use their thoracolumbar vertebral column for body support against gravity and thus exhibit increasing stabilization of the trunk as body size increases. Conversely, in water, the role of the axial skeleton in body support is reduced, and, in aquatic mammals, the vertebral column functions primarily in locomotion. Therefore, we hypothesize that the allometric stabilization associated with increasing body size in terrestrial mammals will be minimized in secondarily aquatic mammals. We test this by comparing the scaling exponent (slope) of vertebral measures from 57 terrestrial species (23 felids, 34 bovids) to 23 semi-aquatic species (pinnipeds), using phylogenetically corrected regressions. Terrestrial taxa meet predictions of allometric stabilization, with posterior vertebral column (lumbar region) shortening, increased vertebral height compared to width, and shorter, more disc-shaped centra. In contrast, pinniped vertebral proportions (e.g. length, width, height) scale with isometry, and in some cases, centra even become more spool-shaped with increasing size, suggesting increased flexibility. Our results demonstrate that evolution of a secondarily aquatic lifestyle has modified the mechanical constraints associated with evolutionary increases in body size, relative to terrestrial taxa. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Preparation of lactic acid bacteria fermented wheat-yoghurt mixtures.

PubMed

Magala, Michal; Kohajdová, Zlatica; Karovičová, Jolana

2013-01-01

Tarhana, a wheat-yoghurt fermented mixture, is considered as a good source of saccharides, proteins, some vitamins and minerals. Moreover, their preparation is inexpensive and lactic acid fermentation offers benefits like product preservation, enhancement of nutritive value and sensory properties improvement. The aim of this work was to evaluate changes of some chemical parameters during fermentation of tarhana, when the level of salt and amount of yoghurt used were varied. Some functional and sensory characteristics of the fi nal product were also determined. Chemical analysis included determination of pH, titrable acidity, content of reducing saccharides, lactic, acetic and citric acid. Measured functional properties of tarhana powder were foaming capacity, foam stability, water absorption capacity, oil absorption capacity and emulsifying activity. Tarhana soups samples were evaluated for their sensory characteristics (colour, odor, taste, consistency and overall acceptability). Fermentation of tarhana by lactic acid bacteria and yeasts led to decrease in pH, content of reducing saccharides and citric acid, while titrable acidity and concentration of lactic and acetic acid increased. Determination of functional properties of tarhana powder showed, that salt absence and increased amount of yoghurt in tarhana recipe reduced foaming capacity and oil absorption capacity, whereas foam stability and water absorption capacity were improved. Sensory evaluation of tarhana soups showed that variations in tarhana recipe adversly affected sensory parameters of fi nal products. Variations in tarhana recipe (salt absence, increased proportion of yoghurt) led to changes in some chemical parameters (pH, titrable acidity, reducing saccharides, content of lactic, acetic and citric acid). Functional properties were also affected with changed tarhana recipe. Sensory characteristics determination showed, that standard tarhana fermented for 144 h had the highest overall acceptability.

International comparative evaluation of knee replacement with fixed or mobile-bearing posterior-stabilized prostheses.

PubMed

Graves, Stephen; Sedrakyan, Art; Baste, Valborg; Gioe, Terence J; Namba, Robert; Martínez Cruz, Olga; Stea, Susanna; Paxton, Elizabeth; Banerjee, Samprit; Isaacs, Abby J; Robertsson, Otto

2014-12-17

Posterior-stabilized total knee prostheses were introduced to address instability secondary to loss of posterior cruciate ligament function, and they have either fixed or mobile bearings. Mobile bearings were developed to improve the function and longevity of total knee prostheses. In this study, the International Consortium of Orthopaedic Registries used a distributed health data network to study a large cohort of posterior-stabilized prostheses to determine if the outcome of a posterior-stabilized total knee prosthesis differs depending on whether it has a fixed or mobile-bearing design. Aggregated registry data were collected with a distributed health data network that was developed by the International Consortium of Orthopaedic Registries to reduce barriers to participation (e.g., security, proprietary, legal, and privacy issues) that have the potential to occur with the alternate centralized data warehouse approach. A distributed health data network is a decentralized model that allows secure storage and analysis of data from different registries. Each registry provided data on mobile and fixed-bearing posterior-stabilized prostheses implanted between 2001 and 2010. Only prostheses associated with primary total knee arthroplasties performed for the treatment of osteoarthritis were included. Prostheses with all types of fixation were included except for those with the rarely used reverse hybrid (cementless tibial and cemented femoral components) fixation. The use of patellar resurfacing was reported. The outcome of interest was time to first revision (for any reason). Multivariate meta-analysis was performed with linear mixed models with survival probability as the unit of analysis. This study includes 137,616 posterior-stabilized knee prostheses; 62% were in female patients, and 17.6% had a mobile bearing. The results of the fixed-effects model indicate that in the first year the mobile-bearing posterior-stabilized prostheses had a significantly higher hazard ratio (1.86) than did the fixed-bearing posterior-stabilized prostheses (95% confidence interval, 1.28 to 2.7; p = 0.001). For all other time intervals, the mobile-bearing posterior-stabilized prostheses had higher hazard ratios; however, these differences were not significant. Mobile-bearing posterior-stabilized prostheses had an increased rate of revision compared with fixed-bearing posterior-stabilized prostheses. This difference was evident in the first year. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.

Coloring attributes of betalains: a key emphasis on stability and future applications.

PubMed

Martins, Natália; Roriz, Custódio Lobo; Morales, Patricia; Barros, Lillian; Ferreira, Isabel C F R

2017-04-19

Organoleptic characteristics largely determine food acceptance, selection, and subsequent consumption. Therefore, food colorants are extremely important in the food industry. However, based on the latest findings related to the side effects and toxicity issues of some synthetic colorants, consumers worldwide have shown increasing interest in natural alternatives. Betalains are good examples of natural colorants and therefore the present study reviews the main sources of these pigments, their structural elucidation and biosynthetic pathways, their chemical instability to different environmental factors, as well as their potential uses at the industrial level and also for pharmaceutical and cosmetic purposes, due to their ability to act as functional ingredients and health enhancers/promoters. Betalain natural pigments represent a promising and safe alternative to synthetic dyes, but their chemical instability has limited their widespread use. Temperature, pH, water activity, oxygen, light, chelating agents, the presence of other compounds, pigment concentration, storage, and processing conditions are the most important factors affecting their stability. It is, therefore, very important to establish optimum processing conditions to maximize the stability of betalains and their extraction yields, focusing on their effective use as natural food colorants, functional ingredients and value-added food products.

Final Report: “Energetics of Nanomaterials”

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

Woodfield, Brian F.; navrotsky, alexandra; Ross, Nancy

2016-08-30

Nanomaterials, solids with very small particle size, form the basis of new technologies that are revolutionizing fields such as energy, lighting, electronics, medical diagnostics, and drug delivery. These nanoparticles are different from conventional bulk materials in many ways we do not yet fully understand. This project focused on their structure and thermodynamics and emphasized the role of water in nanoparticle surfaces. Using a unique and synergistic combination of high-tech techniques—namely oxide melt solution calorimetry, cryogenic heat capacity measurements, and inelastic neutron scattering—this work has identified differences in structure, thermodynamic stability, and water behavior on nanoparticles as a function of compositionmore » and particle size. The systematics obtained increase the fundamental understanding needed to synthesize, retain, and apply these technologically important nanomaterials and to predict and tailor new materials for enhanced functionality, eventually leading to a more sustainable way of life. Highlights are reported on the following topics: surface energies, thermochemistry of nanoparticles, and changes in stability at the nanoscale; heat capacity models and the gapped phonon spectrum; control of pore structure, acid sites, and thermal stability in synthetic γ-aluminas; the lattice contribution is the same for bulk and nanomaterials; and inelastic neutron scattering studies of water on nanoparticle surfaces.« less

Final Report: "Energetics of Nanomaterials

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

Navrotsky, Alexandra; Ross, Nancy; Woodfield, Brian

2015-02-14

Nanomaterials, solids with very small particle size, form the basis of new technologies that are revolutionizing fields such as energy, lighting, electronics, medical diagnostics, and drug delivery. These nanoparticles are different from conventional bulk materials in many ways we do not yet fully understand. This project focused on their structure and thermodynamics and emphasized the role of water in nanoparticle surfaces. Using a unique and synergistic combination of high-tech techniques—namely oxide melt solution calorimetry, cryogenic heat capacity measurements, and inelastic neutron scattering—this work has identified differences in structure, thermodynamic stability, and water behavior on nanoparticles as a function of compositionmore » and particle size. The systematics obtained increase the fundamental understanding needed to synthesize, retain, and apply these technologically important nanomaterials and to predict and tailor new materials for enhanced functionality, eventually leading to a more sustainable way of life. Highlights are reported on the following topics: surface energies, thermochemistry of nanoparticles, and changes in stability at the nanoscale; heat capacity models and the gapped phonon spectrum; control of pore structure, acid sites, and thermal stability in synthetic γ-aluminas; the lattice contribution is the same for bulk and nanomaterials; and inelastic neutron scattering studies of water on nanoparticle surfaces.« less

Supramolecular PEGylation of biopharmaceuticals

PubMed Central

Webber, Matthew J.; Vinciguerra, Brittany; Cortinas, Abel B.; Thapa, Lavanya S.; Jhunjhunwala, Siddharth; Isaacs, Lyle; Langer, Robert; Anderson, Daniel G.

2016-01-01

The covalent modification of therapeutic biomolecules has been broadly explored, leading to a number of clinically approved modified protein drugs. These modifications are typically intended to address challenges arising in biopharmaceutical practice by promoting improved stability and shelf life of therapeutic proteins in formulation, or modifying pharmacokinetics in the body. Toward these objectives, covalent modification with poly(ethylene glycol) (PEG) has been a common direction. Here, a platform approach to biopharmaceutical modification is described that relies on noncovalent, supramolecular host–guest interactions to endow proteins with prosthetic functionality. Specifically, a series of cucurbit[7]uril (CB[7])–PEG conjugates are shown to substantially increase the stability of three distinct protein drugs in formulation. Leveraging the known and high-affinity interaction between CB[7] and an N-terminal aromatic residue on one specific protein drug, insulin, further results in altering of its pharmacological properties in vivo by extending activity in a manner dependent on molecular weight of the attached PEG chain. Supramolecular modification of therapeutic proteins affords a noncovalent route to modify its properties, improving protein stability and activity as a formulation excipient. Furthermore, this offers a modular approach to append functionality to biopharmaceuticals by noncovalent modification with other molecules or polymers, for applications in formulation or therapy. PMID:27911829

The role of nitrogen doping in ALD Ta2O5 and its influence on multilevel cell switching in RRAM

NASA Astrophysics Data System (ADS)

Sedghi, N.; Li, H.; Brunell, I. F.; Dawson, K.; Potter, R. J.; Guo, Y.; Gibbon, J. T.; Dhanak, V. R.; Zhang, W. D.; Zhang, J. F.; Robertson, J.; Hall, S.; Chalker, P. R.

2017-03-01

The role of nitrogen doping on the stability and memory window of resistive state switching in N-doped Ta2O5 deposited by atomic layer deposition is elucidated. Nitrogen incorporation increases the stability of resistive memory states which is attributed to neutralization of electronic defect levels associated with oxygen vacancies. The density functional simulations with the screened exchange hybrid functional approximation show that the incorporation of nitrogen dopant atoms in the oxide network removes the O vacancy midgap defect states, thus nullifying excess defects and eliminating alternative conductive paths. By effectively reducing the density of vacancy-induced defect states through N doping, 3-bit multilevel cell switching is demonstrated, consisting of eight distinctive resistive memory states achieved by either controlling the set current compliance or the maximum voltage during reset. Nitrogen doping has a threefold effect: widening the switching memory window to accommodate the more intermediate states, improving the stability of states, and providing a gradual reset for multi-level cell switching during reset. The N-doped Ta2O5 devices have relatively small set and reset voltages (< 1 V) with reduced variability due to doping.

Tailoring structure and technological properties of plant proteins using high hydrostatic pressure.

PubMed

Queirós, Rui P; Saraiva, Jorge A; da Silva, José A Lopes

2018-06-13

The demand for proteins is rising and alternatives to meat proteins are necessary since animal husbandry is expensive and intensive to the environment. Plant proteins appear as an alternative; however, their techno-functional properties need improvement. High-pressure processing (HPP) is a non-thermal technology that has several applications including the modification of proteins. The application of pressure allows modifying proteins' structure hence allowing to change several of their properties, such as hydration, hydrophobicity, and hydrophilicity. These properties may influence the solubility of proteins and their ability to stabilize emulsions or foams, create aggregates or gels, and their general role in stability and texture of food commodities. Commonly HPP decreases the proteins' solubility yet increasing their surface hydrophobicity exposing sulfhydryl groups, which promotes aggregation or gelation or enhance their ability to stabilize emulsions/foams. However, these effects are not verifiable for all the proteins and are immensely dependent on the type and concentration of the protein, environmental conditions (pH, ionic strength, and co-solutes), and HPP conditions. This review collects and critically discusses the available information on how HPP affects the structure of plant proteins and how their techno-functional properties can be tailored using this approach.

A Systematic Review of Clinical Functional Outcomes After Medial Stabilized Versus Non-Medial Stabilized Total Knee Joint Replacement

PubMed Central

Young, Tony; Dowsey, Michelle M.; Pandy, Marcus; Choong, Peter F.

2018-01-01

Background Medial stabilized total knee joint replacement (TKJR) construct is designed to closely replicate the kinematics of the knee. Little is known regarding comparison of clinical functional outcomes of patients utilising validated patient reported outcome measures (PROM) after medial stabilized TKJR and other construct designs. Purpose To perform a systematic review of the available literature related to the assessment of clinical functional outcomes following a TKJR employing a medial stabilized construct design. Methods The review was performed with a Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) algorithm. The literature search was performed using variouscombinations of keywords. The statistical analysis was completed using Review Manager (RevMan), Version 5.3. Results In the nineteen unique studies identified, there were 2,448 medial stabilized TKJRs implanted in 2,195 participants, there were 1,777 TKJRs with non-medial stabilized design constructs implanted in 1,734 subjects. The final mean Knee Society Score (KSS) value in the medial stabilized group was 89.92 compared to 90.76 in the non-medial stabilized group, with the final KSS mean value difference between the two groups was statistically significant and favored the non-medial stabilized group (SMD 0.21; 95% CI: 0.01 to 0.41; p = 004). The mean difference in the final WOMAC values between the two groups was also statistically significant and favored the medial stabilized group (SMD: −0.27; 95% CI: −0.47 to −0.07; p = 0.009). Moderate to high values (I2) of heterogeneity were observed during the statistical comparison of these functional outcomes. Conclusion Based on the small number of studies with appropriate statistical analysis, we are unable to reach a clear conclusion in the clinical performance of medial stabilized knee replacement construct. Level of Evidence Level II PMID:29696144