Buffering of Ocean Export Production by Flexible Elemental Stoichiometry of Particulate Organic Matter

NASA Astrophysics Data System (ADS)

Tanioka, Tatsuro; Matsumoto, Katsumi

2017-10-01

One of the most important factors that determine the ocean-atmosphere carbon partitioning is the sinking of particulate organic matter (POM) from the surface ocean to the deep ocean. The amount of carbon (C) removed from the surface ocean by this POM export production depends critically on the elemental ratio in POM of C to nitrogen (N) and phosphorus (P), two essential elements that limit productivity. Recent observations indicate that P:N:C in marine POM varies both spatially and temporally due to chemical, physical, and ecological dynamics. In a new approach to predicting a flexible P:C ratio, we developed a power law model with a stoichiometry sensitivity factor, which is able to relate P:C of POM to ambient phosphate concentration. The new factor is robust, measurable, and biogeochemically meaningful. Using the new stoichiometry sensitivity factor, we present a first-order estimate that P:C plasticity could buffer against a generally expected future reduction in global carbon export production by up to 5% under a future warming scenario compared to a fixed, Redfield P:C. Further, we demonstrate that our new stoichiometry model can be implemented successfully and easily in a global model to reproduce the large-scale P:N:C variability in the ocean.

Modification of Light Emission in Si-Rich Silicon Nitride Films Versus Stoichiometry and Excitation Light Energy

NASA Astrophysics Data System (ADS)

Torchynska, T.; Khomenkova, L.; Slaoui, A.

2018-04-01

Si-rich SiN x films with different stoichiometry were grown on Si substrate by plasma-enhanced chemical vapor deposition. The Si content was varied by changing the NH3/SiH4 gas flow ratio from 0.45 up to 1.0. Conventional furnace annealing at 1100°C for 30 min was applied to produce the Si quantum dots (QDs) in the SiN x films. Spectroscopic ellipsometry was used to determine the refractive index of the SiN x films that allowed estimating the film's stoichiometry. Fourier transform infrared spectroscopy has been also used to confirm the stoichiometry and microstructure. Photoluminescence (PL) spectra of Si-rich SiN x films are complex. A non-monotonous variation of the different PL peaks versus Si excess contents testifies to the competition of different radiative channels. The analysis of PL spectra, measured at the different excitation light energies and variable temperatures, has revealed that the PL bands with the peaks within the range 2.1-3.0 eV are related to the carrier recombination via radiative native defects in the SiN x host. Simultaneously, the PL bands with the peaks at 1.5-2.0 eV are caused by the exciton recombination in the Si QDs of different sizes. The way to control the SiN x emission is discussed.

Modification of Light Emission in Si-Rich Silicon Nitride Films Versus Stoichiometry and Excitation Light Energy

NASA Astrophysics Data System (ADS)

Torchynska, T.; Khomenkova, L.; Slaoui, A.

2018-07-01

Si-rich SiN x films with different stoichiometry were grown on Si substrate by plasma-enhanced chemical vapor deposition. The Si content was varied by changing the NH3/SiH4 gas flow ratio from 0.45 up to 1.0. Conventional furnace annealing at 1100°C for 30 min was applied to produce the Si quantum dots (QDs) in the SiN x films. Spectroscopic ellipsometry was used to determine the refractive index of the SiN x films that allowed estimating the film's stoichiometry. Fourier transform infrared spectroscopy has been also used to confirm the stoichiometry and microstructure. Photoluminescence (PL) spectra of Si-rich SiN x films are complex. A non-monotonous variation of the different PL peaks versus Si excess contents testifies to the competition of different radiative channels. The analysis of PL spectra, measured at the different excitation light energies and variable temperatures, has revealed that the PL bands with the peaks within the range 2.1-3.0 eV are related to the carrier recombination via radiative native defects in the SiN x host. Simultaneously, the PL bands with the peaks at 1.5-2.0 eV are caused by the exciton recombination in the Si QDs of different sizes. The way to control the SiN x emission is discussed.

Correlates of elemental-isotopic composition of stream fishes: the importance of land-use, species identity and body size.

PubMed

Montaña, C G; Schalk, C M

2018-04-01

The isotopic (δ 13 C and δ 15 N) and stoichiometric (C:N:P) compositions of four fish species (Family Centrarchidae: Lepomis auritus, Lepomis cyanellus; Family Cyprinidae: Nocomis leptocephalus, Semotilus atromaculatus) were examined across four North Carolina Piedmont streams arrayed along an urbanization gradient. Both isotopic and stoichiometric composition of fishes appeared to track changes occurring in basal resource availability. Values of δ 13 C of basal resources and consumers were more enriched at the most urbanized streams. Similarly, basal resources and consumers were δ 15 N-enriched at more urbanized streams. Basal resource stoichiometry varied across streams, with periphyton being the most variable. Primary consumers stoichiometry also differed across streams. Intraspecific variation in fish stoichiometry correlated with the degree of urbanization, as the two cyprinids had higher N content and L. cyanellus had higher P content in more urbanized streams, probably due to enrichment of basal resources. Intrinsic factors, specifically species identity and body size also affected stoichiometric variation. Phosphorus (P) content increased significantly with body size in centrarchids, but not in cyprinids. These results suggest that although species identity and body size are important predictors of elemental stoichiometry, the complex nature of altered urban streams may yield imbalances in the elemental composition of consumers via their food resources. © 2018 The Fisheries Society of the British Isles.

Self-reported personality variability across the social network is associated with interpersonal dysfunction.

PubMed

Clifton, Allan; Kuper, Laura E

2011-04-01

We describe 2 studies (n=52 and n=82) examining variability in perceptions of personality using a social network methodology. Undergraduate participants completed self-report measures of personality and interpersonal dysfunction and then subsequently reported on their personalities with each of 30 members of their social networks. Results across the 2 studies found substantial variability in participants' perceived personalities within their social networks. Measures of interpersonal dysfunction were associated with the amount of variability in dyadic ratings of personality, specifically Agreeableness and Openness to Experience. Results suggest that personality variability across interpersonal contexts may be an important individual difference related to social behavior and dysfunction. © 2011 The Authors. Journal of Personality © 2011, Wiley Periodicals, Inc.

Analysis of odorant receptor protein function in the yellow fever mosquito, aedes aegypti

USDA-ARS?s Scientific Manuscript database

Odorant receptors (ORs) in insects are ligand-gated ion channels comprised of two subunits: a variable receptor and an obligatory co-receptor (Orco). This protein receptor complex of unknown stoichiometry interacts with an odor molecule leading to changes in permeability of the sensory dendrite, th...

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Singh, A.; Baer, S. E.; Riebesell, U.; Martiny, A. C.; Lomas, M. W.

2015-06-01

Nitrogen (N) and phosphorus (P) availability determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio in inorganic nutrients is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deep ocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation of stoichiometric relationships. We have analysed elemental stoichiometry in the suspended POM and total (POM + DOM) organic matter (TOM) pools in the upper 100 m, and in the exported POM and sub-euphotic zone (100-500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N : P ratios in the TOM pool were more than twice that in the POM pool. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield Ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield Ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ~ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry with that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that the variation elemental ratios with depth in the euphotic zone was mainly due to different growth rates of cyanobacterial cells. These time-series data have also allowed us to examine the potential role of climate variability on C : N : P stoichiometry. This study strengthens our understanding of elemental stoichiometry in different organic matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry.

C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Singh, A.; Baer, S. E.; Riebesell, U.; Martiny, A. C.; Lomas, M. W.

2015-11-01

Nitrogen (N) and phosphorus (P) availability, in addition to other macro- and micronutrients, determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio of inorganic nutrient pools is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deep-ocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation in stoichiometric relationships. We have analyzed elemental stoichiometry in the suspended POM and total (POM + DOM) organic-matter (TOM) pools in the upper 100 m and in the exported POM and subeuphotic zone (100-500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N and N : P ratios in TOM were at least twice those in the POM, while C : P ratios were up to 5 times higher in TOM compared to those in the POM. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ~ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry to that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that elemental ratios vary with depth in the euphotic zone, mainly due to different growth rates of cyanobacterial cells. We have also examined the role of the Arctic Oscillation on temporal patterns in C : N : P stoichiometry. This study strengthens our understanding of the variability in elemental stoichiometry in different organic-matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry and the net relative flow of elements between pools.

Learning stoichiometry: A comparison of text and multimedia instructional formats

NASA Astrophysics Data System (ADS)

Evans, Karen L.

Even after multiple instructional opportunities, first year college chemistry students are often unable to apply stoichiometry knowledge in equilibrium and acid-base chemistry problem solving. Cognitive research findings suggest that for learning to be meaningful, learners need to actively construct their own knowledge by integrating new information into, and reorganizing, their prior understandings. Scaffolded inquiry in which facts, procedures, and principles are introduced as needed within the context of authentic problem solving may provide the practice and encoding opportunities necessary for construction of a memorable and usable knowledge base. The dynamic and interactive capabilities of online technology may facilitate stoichiometry instruction that promotes this meaningful learning. Entering college freshmen were randomly assigned to either a technology-rich or text-only set of cognitively informed stoichiometry review materials. Analysis of posttest scores revealed a significant but small difference in the performance of the two treatment groups, with the technology-rich group having the advantage. Both SAT and gender, however, explained more of the variability in the scores. Analysis of the posttest scores from the technology-rich treatment group revealed that the degree of interaction with the Virtual Lab simulation was significantly related to posttest performance and subsumed any effect of prior knowledge as measured by SAT scores. Future users of the online course should be encouraged to engage with the problem-solving opportunities provided by the Virtual Lab simulation through either explicit instruction and/or implementation of some level of program control within the course's navigational features.

Final technical report DOE award DE-SC0007206 Improving CESM Efficiency to Study Variable C:N:P Stoichiometry in the Oceans

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

Primeau, Francois William

2016-02-11

This report lists the accomplishments of the project, which includes: (1) analysis of inorganic nutrient concentration data as well as suspended particulate organic matter data in the ocean to demonstrate that the carbon to nitrogen to phosphorus ratios (C:N:P) of biological uptake and export vary on large spatial scales, (2) the development of a new computationally efficient method for simulating biogeochemical tracers in earth system models, (3) the application of the method to help calibrate an improved representation of dissolved organic matter in the ocean that includes variable C:N:P stoichiometry. This research is important because biological uptake of carbon andmore » nutrients in the upper ocean and export by sinking particles and downward mixing of dissolved organic matter helps maintain a vertical gradient in the carbon dioxide concentration in the ocean. This gradient is key to understanding the partitioning of CO2 between the ocean and the atmosphere. The final report lists seven peer reviewed scientific publications, one Ph.D. thesis, one technical report and two papers in preparation.« less

Unnatural amino acid photo-crosslinking of the IKs channel complex demonstrates a KCNE1:KCNQ1 stoichiometry of up to 4:4

PubMed Central

Murray, Christopher I; Westhoff, Maartje; Eldstrom, Jodene; Thompson, Emely; Emes, Robert; Fedida, David

2016-01-01

Cardiac repolarization is determined in part by the slow delayed rectifier current (IKs), through the tetrameric voltage-gated ion channel, KCNQ1, and its β-subunit, KCNE1. The stoichiometry between α and β-subunits has been controversial with studies reporting either a strict 2 KCNE1:4 KCNQ1 or a variable ratio up to 4:4. We used IKs fusion proteins linking KCNE1 to one (EQ), two (EQQ) or four (EQQQQ) KCNQ1 subunits, to reproduce compulsory 4:4, 2:4 or 1:4 stoichiometries. Whole cell and single-channel recordings showed EQQ and EQQQQ to have increasingly hyperpolarized activation, reduced conductance, and shorter first latency of opening compared to EQ - all abolished by the addition of KCNE1. As well, using a UV-crosslinking unnatural amino acid in KCNE1, we found EQQQQ and EQQ crosslinking rates to be progressively slowed compared to KCNQ1, which demonstrates that no intrinsic mechanism limits the association of up to four β-subunits within the IKs complex. DOI: http://dx.doi.org/10.7554/eLife.11815.001 PMID:26802629

Mechanisms for Variation of Cellular P Stoichiometry: Diverse Cellular Phosphorus Allocation Strategies Across Microbial Groups from the Sargasso Sea

NASA Astrophysics Data System (ADS)

Popendorf, K.; Duhamel, S.

2016-02-01

Phosphorus is the least abundant of the three major macronutrients that define the canonical Redfield ratio, but its place in the backbone of nucleic acids and as an energy trafficking molecule lays a lower bound of cellular phosphorus content that is essential for all life. In addition to forming DNA, RNA, and adenosine triphosphate (ATP), significant amounts of cellular phosphorus may also be allocated to the production of phospholipids and polyphosphate. These latter two biochemicals in particular may occur in significant but highly variable amounts across different microbial groups, and the variation in cellular allocation to these biochemicals may be a contributing factor in defining the elemental stoichiometry of microbes. We investigated this variation in cellular phosphorus allocation across the most abundant microbial groups in the P-depleted Sargasso Sea: Prochlorococcus, Synechococcus, and heterotrophic bacteria. By coupling radioisotope tracing of phosphate and ATP with cell sorting flow cytometry and subsequent biochemical extractions, we made novel measurements of the P allocation to DNA, phospholipids, and polyphosphate in individual microbial groups from environmental populations. These results provide new insights into the cellular mechanisms of variation in stoichiometry and different microbial strategies for adaptation to low-P environments.

Stoichiometry of microbial carbon use efficiency in soils

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

Sinsabaugh, Robert L.; Turner, Benjamin L.; Talbot, Jennifer M.

The carbon use efficiency (CUE) of microbial communities partitions the flow of C from primary producers to the atmosphere, decomposer food webs, and soil C stores. CUE, usually defined as the ratio of growth to assimilation, is a critical parameter in ecosystem models, but is seldom measured directly in soils because of the methodological difficulty of measuring in situ rates of microbial growth and respiration. Alternatively, CUE can be estimated indirectly from the elemental stoichiometry of organic matter and microbial biomass, and the ratios of C to nutrient-acquiring ecoenzymatic activities. In this paper, we used this approach to estimate andmore » compare microbial CUE in >2000 soils from a broad range of ecosystems. Mean CUE based on C:N stoichiometry was 0.269 ± 0.110 (mean ± SD). A parallel calculation based on C:P stoichiometry yielded a mean CUE estimate of 0.252 ± 0.125. The mean values and frequency distributions were similar to those from aquatic ecosystems, also calculated from stoichiometric models, and to those calculated from direct measurements of bacterial and fungal growth and respiration. CUE was directly related to microbial biomass C with a scaling exponent of 0.304 (95% CI 0.237–0.371) and inversely related to microbial biomass P with a scaling exponent of -0.234 (95% CI -0.289 to -0.179). Relative to CUE, biomass specific turnover time increased with a scaling exponent of 0.509 (95% CI 0.467–0.551). CUE increased weakly with mean annual temperature. CUE declined with increasing soil pH reaching a minimum at pH 7.0, then increased again as soil pH approached 9.0, a pattern consistent with pH trends in the ratio of fungal : bacteria abundance and growth. Structural equation models that related geographic variables to CUE component variables showed the strongest connections for paths linking latitude and pH to β-glucosidase activity and soil C:N:P ratios. Finally, the integration of stoichiometric and metabolic models provides a quantitative description of the functional organization of soil microbial communities that can improve the representation of CUE in microbial process and ecosystem simulation models.« less

Stoichiometry of microbial carbon use efficiency in soils

DOE PAGES

Sinsabaugh, Robert L.; Turner, Benjamin L.; Talbot, Jennifer M.; ...

2016-03-23

The carbon use efficiency (CUE) of microbial communities partitions the flow of C from primary producers to the atmosphere, decomposer food webs, and soil C stores. CUE, usually defined as the ratio of growth to assimilation, is a critical parameter in ecosystem models, but is seldom measured directly in soils because of the methodological difficulty of measuring in situ rates of microbial growth and respiration. Alternatively, CUE can be estimated indirectly from the elemental stoichiometry of organic matter and microbial biomass, and the ratios of C to nutrient-acquiring ecoenzymatic activities. In this paper, we used this approach to estimate andmore » compare microbial CUE in >2000 soils from a broad range of ecosystems. Mean CUE based on C:N stoichiometry was 0.269 ± 0.110 (mean ± SD). A parallel calculation based on C:P stoichiometry yielded a mean CUE estimate of 0.252 ± 0.125. The mean values and frequency distributions were similar to those from aquatic ecosystems, also calculated from stoichiometric models, and to those calculated from direct measurements of bacterial and fungal growth and respiration. CUE was directly related to microbial biomass C with a scaling exponent of 0.304 (95% CI 0.237–0.371) and inversely related to microbial biomass P with a scaling exponent of -0.234 (95% CI -0.289 to -0.179). Relative to CUE, biomass specific turnover time increased with a scaling exponent of 0.509 (95% CI 0.467–0.551). CUE increased weakly with mean annual temperature. CUE declined with increasing soil pH reaching a minimum at pH 7.0, then increased again as soil pH approached 9.0, a pattern consistent with pH trends in the ratio of fungal : bacteria abundance and growth. Structural equation models that related geographic variables to CUE component variables showed the strongest connections for paths linking latitude and pH to β-glucosidase activity and soil C:N:P ratios. Finally, the integration of stoichiometric and metabolic models provides a quantitative description of the functional organization of soil microbial communities that can improve the representation of CUE in microbial process and ecosystem simulation models.« less

The Kv7.2/Kv7.3 heterotetramer assembles with a random subunit arrangement.

PubMed

Stewart, Andrew P; Gómez-Posada, Juan Camilo; McGeorge, Jessica; Rouhani, Maral J; Villarroel, Alvaro; Murrell-Lagnado, Ruth D; Edwardson, J Michael

2012-04-06

Voltage-gated K(+) channels composed of Kv7.2 and Kv7.3 are the predominant contributors to the M-current, which plays a key role in controlling neuronal activity. Various lines of evidence have indicated that Kv7.2 and Kv7.3 form a heteromeric channel. However, the subunit stoichiometry and arrangement within this putative heteromer are so far unknown. Here, we have addressed this question using atomic force microscopy imaging of complexes between isolated Kv7.2/Kv7.3 channels and antibodies to epitope tags on the two subunits, Myc on Kv7.2 and HA on Kv7.3. Initially, tsA 201 cells were transiently transfected with equal amounts of cDNA for the two subunits. The heteromer was isolated through binding of either tag to immunoaffinity beads and then decorated with antibodies to the other tag. In both cases, the distribution of angles between pairs of bound antibodies had two peaks, at around 90° and around 180°, and in both cases the 90° peak was about double the size of the 180° peak. These results indicate that the Kv7.2/Kv7.3 heteromer generated by cells expressing approximately equal amounts of the two subunits assembles as a tetramer with a predominantly 2:2 subunit stoichiometry and with a random subunit arrangement. When the DNA ratio for the two subunits was varied, copurification experiments indicated that the subunit stoichiometry was variable and not fixed at 2:2. Hence, there are no constraints on either the subunit stoichiometry or the subunit arrangement.

Elevated ozone affects C, N and P ecological stoichiometry and nutrient resorption of two poplar clones.

PubMed

Shang, Bo; Feng, Zhaozhong; Li, Pin; Calatayud, Vicent

2018-03-01

The effects of elevated ozone on C (carbon), N (nitrogen) and P (phosphorus) ecological stoichiometry and nutrient resorption in different organs including leaves, stems and roots were investigated in poplar clones 546 (P. deltoides cv. '55/56' × P. deltoides cv. 'Imperial') and 107 (P. euramericana cv. '74/76') with a different sensitivity to ozone. Plants were exposed to two ozone treatments, NF (non-filtered ambient air) and NF60 (NF with targeted ozone addition of 60 ppb), for 96 days in open top chambers (OTCs). Significant ozone effects on most variables of C, N and P ecological stoichiometry were found except for the C concentration and the N/P in different organs. Elevated ozone increased both N and P concentrations of individual organs while for C/N and C/P ratios a reduction was observed. On these variables, ozone had a greater effect for clone 546 than for clone 107. N concentrations of different leaf positions ranked in the order upper > middle > lower, showing that N was transferred from the lower senescent leaves to the upper ones. This was also indicative of N resorption processes, which increased under elevated ozone. N resorption of clone 546 was 4 times larger than that of clone 107 under ambient air (NF). However, elevated ozone (NF60) had no significant effect on P resorption for both poplar clones, suggesting that their growth was only limited by N, while available P in the soil was enough to sustain growth. Understanding ecological stoichiometric responses under ozone stress is crucial to predict future effects on ecological processes and biogeochemical cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Estimating the Stoichiometry of HIV Neutralization

PubMed Central

Magnus, Carsten; Regoes, Roland R.

2010-01-01

HIV-1 virions infect target cells by first establishing contact between envelope glycoprotein trimers on the virion's surface and CD4 receptors on a target cell, recruiting co-receptors, fusing with the cell membrane and finally releasing the genetic material into the target cell. Specific experimental setups allow the study of the number of trimer-receptor-interactions needed for infection, i.e., the stoichiometry of entry and also the number of antibodies needed to prevent one trimer from engaging successfully in the entry process, i.e., the stoichiometry of (trimer) neutralization. Mathematical models are required to infer the stoichiometric parameters from these experimental data. Recently, we developed mathematical models for the estimations of the stoichiometry of entry [1]. In this article, we show how our models can be extended to investigate the stoichiometry of trimer neutralization. We study how various biological parameters affect the estimate of the stoichiometry of neutralization. We find that the distribution of trimer numbers—which is also an important determinant of the stoichiometry of entry—influences the estimated value of the stoichiometry of neutralization. In contrast, other parameters, which characterize the experimental system, diminish the information we can extract from the data about the stoichiometry of neutralization, and thus reduce our confidence in the estimate. We illustrate the use of our models by re-analyzing previously published data on the neutralization sensitivity [2], which contains measurements of neutralization sensitivity of viruses with different envelope proteins to antibodies with various specificities. Our mathematical framework represents the formal basis for the estimation of the stoichiometry of neutralization. Together with the stoichiometry of entry, the stoichiometry of trimer neutralization will allow one to calculate how many antibodies are required to neutralize a virion or even an entire population of virions. PMID:20333245

Binomial distribution for quantification of protein subunits in biological Nanoassemblies and functional nanomachines

PubMed Central

Fang, Huaming; Zhang, Peng; Huang, Lisa P.; Zhao, Zhengyi; Pi, Fengmei; Montemagno, Carlo; Guo, Peixuan

2014-01-01

Living systems produce ordered structures and nanomachines that inspire the development of biomimetic nanodevices such as chips, MEMS, actuators, sensors, sorters, and apparatuses for single-pore DNA sequencing, disease diagnosis, drug or therapeutic RNA delivery. Determination of the copy numbers of subunits that build these machines is challenging due to small size. Here we report a simple mathematical method to determine the stoichiometry, using phi29 DNA-packaging nanomotor as a model to elucidate the application of a formula ∑M=0Z(ZM)pZ−MqM, where p and q are the percentage of wild-type and inactive mutant in the empirical assay; M is the copy numbers of mutant and Z is the stoichiometry in question. Variable ratios of mutants and wild-type were mixed to inhibit motor function. Empirical data were plotted over the theoretical curves to determine the stoichiometry and the value of K, which is the number of mutant needed in each machine to block the function, all based on the condition that wild-type and mutant are equal in binding affinity. Both Z and K from 1–12 were investigated. The data precisely confirmed that phi29 motor contains six copies (Z) of the motor ATPase gp16, and K = 1. PMID:24650885

Lake nutrient stoichiometry is less predictable than nutrient concentrations at regional and sub-continental scales.

PubMed

Collins, Sarah M; Oliver, Samantha K; Lapierre, Jean-Francois; Stanley, Emily H; Jones, John R; Wagner, Tyler; Soranno, Patricia A

2017-07-01

Production in many ecosystems is co-limited by multiple elements. While a known suite of drivers associated with nutrient sources, nutrient transport, and internal processing controls concentrations of phosphorus (P) and nitrogen (N) in lakes, much less is known about whether the drivers of single nutrient concentrations can also explain spatial or temporal variation in lake N:P stoichiometry. Predicting stoichiometry might be more complex than predicting concentrations of individual elements because some drivers have similar relationships with N and P, leading to a weak relationship with their ratio. Further, the dominant controls on elemental concentrations likely vary across regions, resulting in context dependent relationships between drivers, lake nutrients and their ratios. Here, we examine whether known drivers of N and P concentrations can explain variation in N:P stoichiometry, and whether explaining variation in stoichiometry differs across regions. We examined drivers of N:P in ~2,700 lakes at a sub-continental scale and two large regions nested within the sub-continental study area that have contrasting ecological context, including differences in the dominant type of land cover (agriculture vs. forest). At the sub-continental scale, lake nutrient concentrations were correlated with nutrient loading and lake internal processing, but stoichiometry was only weakly correlated to drivers of lake nutrients. At the regional scale, drivers that explained variation in nutrients and stoichiometry differed between regions. In the Midwestern U.S. region, dominated by agricultural land use, lake depth and the percentage of row crop agriculture were strong predictors of stoichiometry because only phosphorus was related to lake depth and only nitrogen was related to the percentage of row crop agriculture. In contrast, all drivers were related to N and P in similar ways in the Northeastern U.S. region, leading to weak relationships between drivers and stoichiometry. Our results suggest ecological context mediates controls on lake nutrients and stoichiometry. Predicting stoichiometry was generally more difficult than predicting nutrient concentrations, but human activity may decouple N and P, leading to better prediction of N:P stoichiometry in regions with high anthropogenic activity. © 2017 by the Ecological Society of America.

Lake nutrient stoichiometry is less predictable than nutrient concentrations at regional and sub-continental scales

USGS Publications Warehouse

Collins, Sarah M.; Oliver, Samantha K.; Lapierre, Jean-Francois; Stanley, Emily H.; Jones, John R.; Wagner, Tyler; Soranno, Patricia A.

2017-01-01

Production in many ecosystems is co-limited by multiple elements. While a known suite of drivers associated with nutrient sources, nutrient transport, and internal processing controls concentrations of phosphorus (P) and nitrogen (N) in lakes, much less is known about whether the drivers of single nutrient concentrations can also explain spatial or temporal variation in lake N:P stoichiometry. Predicting stoichiometry might be more complex than predicting concentrations of individual elements because some drivers have similar relationships with N and P, leading to a weak relationship with their ratio. Further, the dominant controls on elemental concentrations likely vary across regions, resulting in context dependent relationships between drivers, lake nutrients and their ratios. Here, we examine whether known drivers of N and P concentrations can explain variation in N:P stoichiometry, and whether explaining variation in stoichiometry differs across regions. We examined drivers of N:P in ~2,700 lakes at a sub-continental scale and two large regions nested within the sub-continental study area that have contrasting ecological context, including differences in the dominant type of land cover (agriculture vs. forest). At the sub-continental scale, lake nutrient concentrations were correlated with nutrient loading and lake internal processing, but stoichiometry was only weakly correlated to drivers of lake nutrients. At the regional scale, drivers that explained variation in nutrients and stoichiometry differed between regions. In the Midwestern U.S. region, dominated by agricultural land use, lake depth and the percentage of row crop agriculture were strong predictors of stoichiometry because only phosphorus was related to lake depth and only nitrogen was related to the percentage of row crop agriculture. In contrast, all drivers were related to N and P in similar ways in the Northeastern U.S. region, leading to weak relationships between drivers and stoichiometry. Our results suggest ecological context mediates controls on lake nutrients and stoichiometry. Predicting stoichiometry was generally more difficult than predicting nutrient concentrations, but human activity may decouple N and P, leading to better prediction of N:P stoichiometry in regions with high anthropogenic activity.

Predicting nutrient excretion of aquatic animals with metabolic ecology and ecological stoichiometry: a global synthesis.

PubMed

Vanni, Michael J; McIntyre, Peter B

2016-12-01

The metabolic theory of ecology (MTE) and ecological stoichiometry (ES) are both prominent frameworks for understanding energy and nutrient budgets of organisms. We tested their separate and joint power to predict nitrogen (N) and phosphorus (P) excretion rates of ectothermic aquatic invertebrate and vertebrate animals (10,534 observations worldwide). MTE variables (body size, temperature) performed better than ES variables (trophic guild, vertebrate classification, body N:P) in predicting excretion rates, but the best models included variables from both frameworks. Size scaling coefficients were significantly lower than predicted by MTE (<0.75), were lower for P than N, and varied greatly among species. Contrary to expectations under ES, vertebrates excreted both N and P at higher rates than invertebrates despite having more nutrient-rich bodies, and primary consumers excreted as much nutrients as carnivores despite having nutrient-poor diets. Accounting for body N:P hardly improved upon predictions from treating vertebrate classification categorically. We conclude that basic data on body size, water temperature, trophic guild, and vertebrate classification are sufficient to make general estimates of nutrient excretion rates for any animal taxon or aquatic ecosystem. Nonetheless, dramatic interspecific variation in size-scaling coefficients and counter-intuitive patterns with respect to diet and body composition underscore the need for field data on consumption and egestion rates. Together, MTE and ES provide a powerful conceptual basis for interpreting and predicting nutrient recycling rates of aquatic animals worldwide. © 2016 by the Ecological Society of America.

Static and dynamic optical properties of La 1-xSr xFeO 3-δ: The effects of A-site and oxygen stoichiometry

DOE PAGES

Sergey Y. Smolin; Sfeir, Matthew Y.; Scafetta, Mark D.; ...

2015-12-09

Perovskite oxides are a promising material class for photovoltaic and photocatalytic applications due to their visible band gaps, nanosecond recombination lifetimes, and great chemical diversity. However, there is limited understanding of the link between composition and static and dynamic optical properties, despite the critical role these properties play in the design of light-harvesting devices. To clarify these relationships, we systemically studied the optoelectronic properties in La 1-xSr xFeO 3-δ epitaxial films, uncovering the effects of A-site cation substitution and oxygen stoichiometry. Variable-angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25more » eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy, revealing similar nanosecond photoexcited carrier lifetimes for oxygen deficient and stoichiometric films with the same nominal Fe valence. Furthermore, these results demonstrate that while the static optical absorption is strongly dependent on nominal Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in the recombination kinetics.« less

Experiences Teaching Stoichiometry to Students in Grades 10 and 11

NASA Astrophysics Data System (ADS)

Bridges, Cynthia Denise

Many students have problems learning stoichiometry, a complex mathematical chemistry concept used to determine how much product will be produced or formed from a given quantity of reactants. The problem addressed in this study was teachers' lack of understanding of how to teach stoichiometry in a Midwestern urban school district. The conceptual framework of the study was based upon constructivist theory. A qualitative narrative approach was used to obtain the perceptions of 5 high school chemistry instructors related to their experiences, successful or unsuccessful, in teaching stoichiometry to students in Grades 10 and 11. Data were gathered through face-to-face interviews, which were analyzed via an inductive approach to reveal 6 themes: a difficult subject to teach, presentation of stoichiometry, relevancy, students' reactions, barriers, and gender differences. Findings suggested the need for teachers to be knowledgeable, creative, and resourceful in their subject areas to help their students to learn stoichiometry. Findings also revealed the need for teachers to adapt their instructional strategies and modes of delivery to reflect their students' individual learning styles. Understanding how the participating teachers explained stoichiometry to their students might help other chemistry teachers to examine and adapt their own instructional styles and delivery methods of the concept. This understanding might, in term, help to improve student achievement in stoichiometry in particular and chemistry in general.

Suicidal Ideation and Schizophrenia: Contribution of Appraisal, Stigmatization, and Cognition.

PubMed

Stip, Emmanuel; Caron, Jean; Tousignant, Michel; Lecomte, Yves

2017-10-01

To predict suicidal ideation in people with schizophrenia, certain studies have measured its relationship with the variables of defeat and entrapment. The relationships are positive, but their interactions remain undefined. To further their understanding, this research sought to measure the relationship between suicidal ideation with the variables of loss, entrapment, and humiliation. The convenience sample included 30 patients with schizophrenia spectrum disorders. The study was prospective (3 measurement times) during a 6-month period. Results were analyzed by stepwise multiple regression. The contribution of the 3 variables to the variance of suicidal ideation was not significant at any of the 3 times (T1: 16.2%, P = 0.056; T2: 19.9%, P = 0.117; T3: 11.2%, P = 0.109). Further analyses measured the relationship between the variables of stigmatization, perceived cognitive dysfunction, symptoms, depression, self-esteem, reason to live, spirituality, social provision, and suicidal ideation. Stepwise multiple regression demonstrated that the contribution of the variables of stigmatization and perceived cognitive dysfunction to the variance of suicidal ideation was significant at all 3 times (T1: 41.7.5%, P = 0.000; T2: 35.2%, P = 0.001; T3: 21.5%, P = 0.012). Yet, over time, the individual contribution of the variables changed: T1, stigmatization (β = 0.518; P = 0.002); T2, stigmatization (β = 0.394; P = 0.025) and perceived cognitive dysfunction (β = 0.349; P = 0.046). Then, at T3, only perceived cognitive dysfunction contributed significantly to suicidal ideation (β = 0.438; P = 0.016). The results highlight the importance of the contribution of the variables of perceived cognitive dysfunction and stigmatization in the onset of suicidal ideation in people with schizophrenia spectrum disorders.

Suicidal Ideation and Schizophrenia: Contribution of Appraisal, Stigmatization, and Cognition

PubMed Central

Stip, Emmanuel; Caron, Jean; Tousignant, Michel

2017-01-01

Objective: To predict suicidal ideation in people with schizophrenia, certain studies have measured its relationship with the variables of defeat and entrapment. The relationships are positive, but their interactions remain undefined. To further their understanding, this research sought to measure the relationship between suicidal ideation with the variables of loss, entrapment, and humiliation. Method: The convenience sample included 30 patients with schizophrenia spectrum disorders. The study was prospective (3 measurement times) during a 6-month period. Results were analyzed by stepwise multiple regression. Results: The contribution of the 3 variables to the variance of suicidal ideation was not significant at any of the 3 times (T1: 16.2%, P = 0.056; T2: 19.9%, P = 0.117; T3: 11.2%, P = 0.109). Further analyses measured the relationship between the variables of stigmatization, perceived cognitive dysfunction, symptoms, depression, self-esteem, reason to live, spirituality, social provision, and suicidal ideation. Stepwise multiple regression demonstrated that the contribution of the variables of stigmatization and perceived cognitive dysfunction to the variance of suicidal ideation was significant at all 3 times (T1: 41.7.5%, P = 0.000; T2: 35.2%, P = 0.001; T3: 21.5%, P = 0.012). Yet, over time, the individual contribution of the variables changed: T1, stigmatization (β = 0.518; P = 0.002); T2, stigmatization (β = 0.394; P = 0.025) and perceived cognitive dysfunction (β = 0.349; P = 0.046). Then, at T3, only perceived cognitive dysfunction contributed significantly to suicidal ideation (β = 0.438; P = 0.016). Conclusion: The results highlight the importance of the contribution of the variables of perceived cognitive dysfunction and stigmatization in the onset of suicidal ideation in people with schizophrenia spectrum disorders. PMID:28673099

Childhood Sexual Abuse as a Predictor of Adult Female Sexual Dysfunction: A Study of Couples Seeking Sex Therapy.

ERIC Educational Resources Information Center

Sarwer, David B.; Durlak, Joseph A.

1996-01-01

A study of 359 married women who sought sex therapy with their spouses found a connection between adult female sexual dysfunction and childhood sexual abuse. Abuse involving sexual penetration was specifically associated with adult sexual dysfunction. Future research on additional variables that contribute to sexual dysfunction is urged. (CR)

Supramolecular assemblies of a nitrogen-embedded buckybowl dimer with C60† †Electronic supplementary information (ESI) available. CCDC 1579079 and 1579080. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04453d

PubMed Central

Yokoi, Hiroki; Sakamaki, Daisuke; Seki, Shu

2017-01-01

A directly connected azabuckybowl dimer was synthesized via a palladium-catalysed C–H/C–Br coupling. The electron-donating nature of the pyrrolic nitrogen atoms of the azabuckybowl enabled a strong complexation with pristine C60. In the presence of two equivalents of C60, the azabuckybowl dimer formed crystals with a 1 : 2 stoichiometry. Conversely, in diluted solution, complexes with a 1 : 1 stoichiometry of the dimer and C60 were detected predominantly, and these precipitated upon increasing the concentration of C60. Scanning electron microscopy images of the precipitate showed fibre-like aggregates, indicating the formation of supramolecular assemblies with 1D chain structures. A variable-temperature 1H NMR analysis revealed that the precipitate consists of the dimer and C60 in a 1 : 1 ratio. PMID:29629149

Plant response to nutrient availability across variable bedrock geologies

USGS Publications Warehouse

Castle, S.C.; Neff, J.C.

2009-01-01

We investigated the role of rock-derived mineral nutrient availability on the nutrient dynamics of overlying forest communities (Populus tremuloides and Picea engelmanni-Abies lasiocarpa v. arizonica) across three parent materials (andesite, limestone, and sandstone) in the southern Rocky Mountains of Colorado. Broad geochemical differences were observed between bedrock materials; however, bulk soil chemistries were remarkably similar between the three different sites. In contrast, soil nutrient pools were considerably different, particularly for P, Ca, and Mg concentrations. Despite variations in nutrient stocks and nutrient availability in soils, we observed relatively inflexible foliar concentrations and foliar stoichiometries for both deciduous and coniferous species. Foliar nutrient resorption (P and K) in the deciduous species followed patterns of nutrient content across substrate types, with higher resorption corresponding to lower bedrock concentrations. Work presented here indicates a complex plant response to available soil nutrients, wherein plant nutrient use compensates for variations in supply gradients and results in the maintenance of a narrow range in foliar stoichiometry. ?? 2008 Springer Science+Business Media, LLC.

Heteroleptic metallosupramolecular racks, rectangles, and trigonal prisms: stoichiometry-controlled reversible interconversion.

PubMed

Neogi, Subhadip; Lorenz, Yvonne; Engeser, Marianne; Samanta, Debabrata; Schmittel, Michael

2013-06-17

A simple approach toward preparation of heteroleptic two-dimensional (2D) rectangles and three-dimensional (3D) triangular prisms is described utilizing the HETPYP (HETeroleptic PYridyl and Phenanthroline metal complexes) concept. By mixing metal-loaded linear bisphenanthrolines of varying lengths with diverse (multi)pyridine (py) ligands in a proper ratio, six different self-assembled architectures arise cleanly and spontaneously in the absence of any template. They are characterized by (1)H and DOSY NMR, ESI-FT-ICR mass spectrometry as well as by Job plots and UV-vis titrations. Density functional theory (DFT) computations provide information about each structure. A stoichiometry-controlled supramolecule-to-supramolecule interconversion based on the relative amounts of metal bisphenanthroline and bipyridine forces the rectangular assembly to reorganize to a rack architecture and back to the rectangle, as clearly supported by variable temperature and DOSY NMR as well as dynamic light scattering data. The highly dynamic nature of the assemblies represents a promising starting point for constitutional dynamic materials.

A Predictive Model of Domestic Violence in Multicultural Families Focusing on Perpetrator.

PubMed

Choi, Eun Young; Hyun, Hye Jin

2016-09-01

This study was conducted to assess predictor variables of husbands in multicultural families and examine the relationship among variables after setting up a hypothetical model including influencing factors, so as to provide a framework necessary for developing nursing interventions of domestic violence. The participants were 260 husbands in multicultural families in four cities in Korea. Data were analyzed using SPSS 22.0 and AMOS 20.0. Self-control, social support, family of origin violence experience and stress on cultural adaptation directly affected to dysfunctional communication, and the explanatory power of the variables was 64.7%. Family of origin violence experience in domestic stress on cultural adaptation, and dysfunctional communication were directly related to domestic violence in multicultural families, and the explanatory power of the variables was 64.6%. We found out that all variables in the model had mediation effects to domestic violence through dysfunctional communication. In other words, self-control and social support had complete mediation effects, and family of origin violence experience in domestic violence and stress on cultural adaptation had partial mediation effects. The variables explained in this study should be considered as predictive factors of domestic violence in multicultural families, and used to provide preventive nursing intervention. Our resutls can be taken into account for developing and implementing programs on alleviating dysfunctional communication in multicultural families in Korea. Copyright © 2016. Published by Elsevier B.V.

Phytoplankton plasticity drives large variability in carbon fixation efficiency

NASA Astrophysics Data System (ADS)

Ayata, Sakina-Dorothée.; Lévy, Marina; Aumont, Olivier; Resplandy, Laure; Tagliabue, Alessandro; Sciandra, Antoine; Bernard, Olivier

2014-12-01

Phytoplankton C:N stoichiometry is highly flexible due to physiological plasticity, which could lead to high variations in carbon fixation efficiency (carbon consumption relative to nitrogen). However, the magnitude, as well as the spatial and temporal scales of variability, remains poorly constrained. We used a high-resolution biogeochemical model resolving various scales from small to high, spatially and temporally, in order to quantify and better understand this variability. We find that phytoplankton C:N ratio is highly variable at all spatial and temporal scales (5-12 molC/molN), from mesoscale to regional scale, and is mainly driven by nitrogen supply. Carbon fixation efficiency varies accordingly at all scales (±30%), with higher values under oligotrophic conditions and lower values under eutrophic conditions. Hence, phytoplankton plasticity may act as a buffer by attenuating carbon sequestration variability. Our results have implications for in situ estimations of C:N ratios and for future predictions under high CO2 world.

Plant and soil nutrient stoichiometry along primary ecological successions: Is there any link?

PubMed Central

Di Palo, Francesca

2017-01-01

Ecological stoichiometry suggests that plant Nitrogen (N)-to-Phosphorus (P) ratios respond to changes in both soil N:P stoichiometry and soil N and P availability. Thus we would expect that soil and plant N:P ratios be significantly related along natural gradients of soil development such as those associated with primary ecological successions. Here we explicitly search for linkages between plant and soil N:P stoichiometry along four primary successions distributed across Europe. We measured N and P content in soils and plant compartments (leaf, stem and root) of 72 wild plant species distributed along two sand dune and two glacier successions where soil age ranges from few to thousand years old. Overall we found that soil N:P ratios strongly increased along successional stages, however, plant N:P ratios were neither related to soil N:P stoichiometry nor to changes in soil N and P availability. Instead changes in plant nutrient stoichiometry were “driven” by plant-functional-group identity. Not only N:P ratios differed between legumes, grasses and forbs but each of these plant functional groups maintained N:P ratios relatively constant across pioneer, middle and advanced successional stages. Our evidence is that soil nutrient stoichiometry may not be a good predictor of changes in plant N:P stoichiometry along natural primary ecological successions, which have not reached yet a retrogressive stage. This could be because wild-plants rely on mechanisms of internal nutrient regulation, which make them less dependent to changes in soil nutrient availability under unpredictable environmental conditions. Further studies need to clarify what underlying evolutionary and eco-physiological mechanisms determine changes in nutrient stoichiometry in plant species distributed across natural environmental gradients. PMID:28787437

Calcium phosphate ceramics in drug delivery

NASA Astrophysics Data System (ADS)

Bose, Susmita; Tarafder, Solaiman; Edgington, Joe; Bandyopadhyay, Amit

2011-04-01

Calcium phosphate (CaP) particulates, cements and scaffolds have attracted significant interest as drug delivery vehicles. CaP systems, including both hydroxyapaptite and tricalcium phosphates, possess variable stoichiometry, functionality and dissolution properties which make them suitable for cellular delivery. Their chemical similarity to bone and thus biocompatibility, as well as variable surface charge density contribute to their controlled release properties. Among specific research areas, nanoparticle size, morphology, surface area due to porosity, and chemistry controlled release kinetics are the most active. This article discusses CaP systems in their particulate, cements, and scaffold forms for drug, protein, and growth factor delivery toward orthopedic and dental applications.

Bridging Food Webs, Ecosystem Metabolism, and Biogeochemistry Using Ecological Stoichiometry Theory.

PubMed

Welti, Nina; Striebel, Maren; Ulseth, Amber J; Cross, Wyatt F; DeVilbiss, Stephen; Glibert, Patricia M; Guo, Laodong; Hirst, Andrew G; Hood, Jim; Kominoski, John S; MacNeill, Keeley L; Mehring, Andrew S; Welter, Jill R; Hillebrand, Helmut

2017-01-01

Although aquatic ecologists and biogeochemists are well aware of the crucial importance of ecosystem functions, i.e., how biota drive biogeochemical processes and vice-versa, linking these fields in conceptual models is still uncommon. Attempts to explain the variability in elemental cycling consequently miss an important biological component and thereby impede a comprehensive understanding of the underlying processes governing energy and matter flow and transformation. The fate of multiple chemical elements in ecosystems is strongly linked by biotic demand and uptake; thus, considering elemental stoichiometry is important for both biogeochemical and ecological research. Nonetheless, assessments of ecological stoichiometry (ES) often focus on the elemental content of biota rather than taking a more holistic view by examining both elemental pools and fluxes (e.g., organismal stoichiometry and ecosystem process rates). ES theory holds the promise to be a unifying concept to link across hierarchical scales of patterns and processes in ecology, but this has not been fully achieved. Therefore, we propose connecting the expertise of aquatic ecologists and biogeochemists with ES theory as a common currency to connect food webs, ecosystem metabolism, and biogeochemistry, as they are inherently concatenated by the transfer of carbon, nitrogen, and phosphorous through biotic and abiotic nutrient transformation and fluxes. Several new studies exist that demonstrate the connections between food web ecology, biogeochemistry, and ecosystem metabolism. In addition to a general introduction into the topic, this paper presents examples of how these fields can be combined with a focus on ES. In this review, a series of concepts have guided the discussion: (1) changing biogeochemistry affects trophic interactions and ecosystem processes by altering the elemental ratios of key species and assemblages; (2) changing trophic dynamics influences the transformation and fluxes of matter across environmental boundaries; (3) changing ecosystem metabolism will alter the chemical diversity of the non-living environment. Finally, we propose that using ES to link nutrient cycling, trophic dynamics, and ecosystem metabolism would allow for a more holistic understanding of ecosystem functions in a changing environment.

Learning Stoichiometry: A Comparison of Text and Multimedia Formats

ERIC Educational Resources Information Center

Evans, Karen L.; Yaron, David; Leinhardt, Gaea

2008-01-01

Even after repeated instruction, first year college chemistry students are often unable to apply stoichiometry knowledge to equilibrium and acid-base chemistry problems. The dynamic and interactive capabilities of online technology may facilitate stoichiometry instruction that promotes more meaningful learning. This study compares a…

Stoichiometry of a semi-aquatic plethodontid salamander: Intraspecific variation due to location, size and diet

EPA Science Inventory

Ecological stoichiometry provides a framework to investigate an organism's relationship to nutrient cycles. An organism's stoichiometry is thought to constrain its contribution to nutrient cycles (recycling or storage), and to limit its growth and reproduction. Factors that influ...

Thai Grade 10 and 11 Students' Understanding of Stoichiometry and Related Concepts

ERIC Educational Resources Information Center

Dahsah, Chanyah; Coll, Richard Kevin

2008-01-01

The research reported in this case study explores the understanding of stoichiometry and related concepts of Thai science students in grades 10 and 11 after major national curriculum reforms. Students' conceptions and alternative conceptions were investigated using a questionnaire--the "Stoichiometry Concept Questionnaire" (SCQ) (N =…

Supporting traditional instructional methods with a constructivist approach to learning: Promoting conceputal change and understanding of stoichiometry using e-learning tools

NASA Astrophysics Data System (ADS)

Abayan, Kenneth Munoz

Stoichiometry is a fundamental topic in chemistry that measures a quantifiable relationship between atoms, molecules, etc. Stoichiometry is usually taught using expository teaching methods. Students are passively given information, in the hopes they will retain the transmission of information to be able to solve stoichiometry problems masterfully. Cognitive science research has shown that this kind of instructional teaching method is not very effecting in meaningful learning practice. Instead, students must take ownership of their learning. The students need to actively construct their own knowledge by receiving, interpreting, integrating and reorganizing that information into their own mental schemas. In the absence of active learning practices, tools must be created in such a way to be able to scaffold difficult problems by encoding opportunities necessary to make the construction of knowledge memorable, thereby creating a usable knowledge base. Using an online e-learning tool and its potential to create a dynamic and interactive learning environment may facilitate the learning of stoichiometry. The study entailed requests from volunteer students, IRB consent form, a baseline questionnaire, random assignment of treatment, pre- and post-test assessment, and post assessment survey. These activities were given online. A stoichiometry-based assessment was given in a proctored examination at the University of Texas at Arlington (UTA) campus. The volunteer students who took part in these studies were at least 18 of age and were enrolled in General Chemistry 1441, at the University of Texas at Arlington. Each participant gave their informed consent to use their data in the following study. Students were randomly assigned to one of 4 treatments groups based on teaching methodology, (Dimensional Analysis, Operational Method, Ratios and Proportions) and a control group who just received instruction through lecture only. In this study, an e-learning tool was created to demonstrate several methodologies, on how to solve stoichiometry, which are all supported by chemical education research. Comparisons of student performance based on pre- and post-test assessment, and a stoichiometry-based examination was done to determine if the information provided within the e-learning tool yielded greater learning outcomes compared to the students in the absence of scaffold learning material. The e-learning tool was created to help scaffold the problem solving process necessary to help students (N=394) solve stoichiometry problems. Therein the study investigated possible predictors for success on a stoichiometry based examination, students' conceptual understanding of solving stoichiometry problems, and their explanation of reasoning. It was found that the way the student answered a given stoichiometry question (i.e. whether the student used dimensional analysis, operational method or any other process) was not statistically relevant (p=0.05). More importantly, if the students were able to describe their thought process clearly, these students scored significantly higher on stoichiometry test (mean 84, p<0.05). This finding has major implications in teaching the topic, as lecturers tend to stress and focus on the method rather than the process on how to solve stoichiometry problems.

InP and GaAs characterization with variable stoichiometry obtained by molecular spray

NASA Technical Reports Server (NTRS)

Massies, J.; Linh, N. T.; Olivier, J.; Faulconnier, P.; Poirier, R.

1979-01-01

Both InP and GaAs surfaces were studied in parallel. A molecular spray technique was used to obtain two semiconductor surfaces with different superficial compositions. The structures of these surfaces were examined by electron diffraction. Electron energy loss was measured spectroscopically in order to determine surface electrical characteristics. The results are used to support conclusions relative to the role of surface composition in establishing a Schottky barrier effect in semiconductor devices.

Interactive effects of genotype and food quality on consumer growth rate and elemental content.

PubMed

Prater, Clay; Wagner, Nicole D; Frost, Paul C

2017-05-01

Consumer body stoichiometry is a key trait that links organismal physiology to population and ecosystem-level dynamics. However, as elemental composition has traditionally been considered to be constrained within a species, the ecological and evolutionary factors shaping consumer elemental composition have not been clearly resolved. To this end, we examined the causes and extent of variation in the body phosphorus (P) content and the expression of P-linked traits, mass specific growth rate (MSGR), and P use efficiency (PUE) of the keystone aquatic consumer Daphnia using lake surveys and common garden experiments. While daphnid body %P was relatively constrained in field assemblages sampled across an environmental P gradient, unique genotypes isolated from these lakes showed highly variable phenotypic responses when raised across dietary P gradients in the laboratory. Specifically, we observed substantial inter- and intra-specific variation and differences in daphnid responses within and among our study lakes. While variation in Daphnia body %P was mostly due to plastic phenotypic changes, we documented considerable genetic differences in daphnid MSGR and PUE, and relationships between MSGR and body P content were highly variable among genotypes. Overall, our study found that consumer responses to food quality may differ considerably among genotypes and that relationships between organismal life-history traits and body stoichiometry may be strongly influenced by genetic and environmental variation in natural assemblages. © 2017 by the Ecological Society of America.

Non-Redfieldian Dynamics Explain Seasonal pCO2 Drawdown in the Gulf of Bothnia

NASA Astrophysics Data System (ADS)

Fransner, Filippa; Gustafsson, Erik; Tedesco, Letizia; Vichi, Marcello; Hordoir, Robinson; Roquet, Fabien; Spilling, Kristian; Kuznetsov, Ivan; Eilola, Kari; Mörth, Carl-Magnus; Humborg, Christoph; Nycander, Jonas

2018-01-01

High inputs of nutrients and organic matter make coastal seas places of intense air-sea CO2 exchange. Due to their complexity, the role of coastal seas in the global air-sea CO2 exchange is, however, still uncertain. Here, we investigate the role of phytoplankton stoichiometric flexibility and extracellular DOC production for the seasonal nutrient and CO2 partial pressure (pCO2) dynamics in the Gulf of Bothnia, Northern Baltic Sea. A 3-D ocean biogeochemical-physical model with variable phytoplankton stoichiometry is for the first time implemented in the area and validated against observations. By simulating non-Redfieldian internal phytoplankton stoichiometry, and a relatively large production of extracellular dissolved organic carbon (DOC), the model adequately reproduces observed seasonal cycles in macronutrients and pCO2. The uptake of atmospheric CO2 is underestimated by 50% if instead using the Redfield ratio to determine the carbon assimilation, as in other Baltic Sea models currently in use. The model further suggests, based on the observed drawdown of pCO2, that observational estimates of organic carbon production in the Gulf of Bothnia, derived with the 14C method, may be heavily underestimated. We conclude that stoichiometric variability and uncoupling of carbon and nutrient assimilation have to be considered in order to better understand the carbon cycle in coastal seas.

Quantification of Lysine Acetylation and Succinylation Stoichiometry in Proteins Using Mass Spectrometric Data-Independent Acquisitions (SWATH)

NASA Astrophysics Data System (ADS)

Meyer, Jesse G.; D'Souza, Alexandria K.; Sorensen, Dylan J.; Rardin, Matthew J.; Wolfe, Alan J.; Gibson, Bradford W.; Schilling, Birgit

2016-11-01

Post-translational modification of lysine residues by NƐ-acylation is an important regulator of protein function. Many large-scale protein acylation studies have assessed relative changes of lysine acylation sites after antibody enrichment using mass spectrometry-based proteomics. Although relative acylation fold-changes are important, this does not reveal site occupancy, or stoichiometry, of individual modification sites, which is critical to understand functional consequences. Recently, methods for determining lysine acetylation stoichiometry have been proposed based on ratiometric analysis of endogenous levels to those introduced after quantitative per-acetylation of proteins using stable isotope-labeled acetic anhydride. However, in our hands, we find that these methods can overestimate acetylation stoichiometries because of signal interferences when endogenous levels of acylation are very low, which is especially problematic when using MS1 scans for quantification. In this study, we sought to improve the accuracy of determining acylation stoichiometry using data-independent acquisition (DIA). Specifically, we use SWATH acquisition to comprehensively collect both precursor and fragment ion intensity data. The use of fragment ions for stoichiometry quantification not only reduces interferences but also allows for determination of site-level stoichiometry from peptides with multiple lysine residues. We also demonstrate the novel extension of this method to measurements of succinylation stoichiometry using deuterium-labeled succinic anhydride. Proof of principle SWATH acquisition studies were first performed using bovine serum albumin for both acetylation and succinylation occupancy measurements, followed by the analysis of more complex samples of E. coli cell lysates. Although overall site occupancy was low (<1%), some proteins contained lysines with relatively high acetylation occupancy.

A motor neuron strategy to save time and energy in neurodegeneration: adaptive protein stoichiometry.

PubMed

Zucchi, Elisabetta; Lu, Ching-Hua; Cho, Yunju; Chang, Rakwoo; Adiutori, Rocco; Zubiri, Irene; Ceroni, Mauro; Cereda, Cristina; Pansarasa, Orietta; Greensmith, Linda; Malaspina, Andrea; Petzold, Axel

2018-06-30

Neurofilament proteins (Nf) are a biomarker of disease progression in amyotrophic lateral sclerosis (ALS). This study investigated whether there are major differences in expression from in vivo measurements of neurofilament isoforms, from the light chain, NfL (68 kDa), compared to larger proteins, the medium chain (NfM, 150 kDa) and the heavy (NfH, 200-210 kDa) chains in ALS patients and healthy controls. New immunological methods were combined with Nf subunit stoichiometry calculations and Monte-Carlo simulations of a coarse-grained Nf brush model. Based on a physiological Nf subunit stoichiometry of 7:3:2 (NfL:NfM:NfH) we found an "adaptive" Nf subunit stoichiometry of 24:2.4:1.6 in ALS. Adaptive Nf stoichiometry preserved NfL gyration radius in the Nf brush model. The energy and time requirements for Nf translation were 56±27k ATP (5.6 hours) in control subjects compared to 123±102k (12.3 h) in ALS with "adaptive" Nf stoichiometry (not significant) and increased significantly to 355±330k (35.5 h) with "luxury" Nf subunit stoichiometry (p<0.0001 for each comparison). Longitudinal disease progression related energy consumption was highest with a "luxury" Nf stoichiometry. Therefore, an energy and time saving option for motor neurons is to shift protein expression from larger to smaller (cheaper) subunits, at little or no costs on a protein structural level, to compensate for increased energy demands. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Thai Grade 10 and 11 Students' Conceptual Understanding and Ability to Solve Stoichiometry Problems

ERIC Educational Resources Information Center

Dahsah, Chanyah; Coll, Richard K.

2007-01-01

Stoichiometry and related concepts are an important part of student learning in chemistry. In this interpretive-based inquiry, we investigated Thai Grade 10 and 11 students' conceptual understanding and ability to solve numerical problems for stoichiometry-related concepts. Ninety-seven participants completed a purpose-designed survey instrument…

Different Infectivity of HIV-1 Strains Is Linked to Number of Envelope Trimers Required for Entry

PubMed Central

Brandenberg, Oliver F.; Magnus, Carsten; Rusert, Peter; Regoes, Roland R.; Trkola, Alexandra

2015-01-01

HIV-1 enters target cells by virtue of envelope glycoprotein trimers that are incorporated at low density in the viral membrane. How many trimers are required to interact with target cell receptors to mediate virus entry, the HIV entry stoichiometry, still awaits clarification. Here, we provide estimates of the HIV entry stoichiometry utilizing a combined approach of experimental analyses and mathematical modeling. We demonstrate that divergent HIV strains differ in their stoichiometry of entry and require between 1 to 7 trimers, with most strains depending on 2 to 3 trimers to complete infection. Envelope modifications that perturb trimer structure lead to an increase in the entry stoichiometry, as did naturally occurring antibody or entry inhibitor escape mutations. Highlighting the physiological relevance of our findings, a high entry stoichiometry correlated with low virus infectivity and slow virus entry kinetics. The entry stoichiometry therefore directly influences HIV transmission, as trimer number requirements will dictate the infectivity of virus populations and efficacy of neutralizing antibodies. Thereby our results render consideration of stoichiometric concepts relevant for developing antibody-based vaccines and therapeutics against HIV. PMID:25569556

Pulse-shaping based two-photon FRET stoichiometry

PubMed Central

Flynn, Daniel C.; Bhagwat, Amar R.; Brenner, Meredith H.; Núñez, Marcos F.; Mork, Briana E.; Cai, Dawen; Swanson, Joel A.; Ogilvie, Jennifer P.

2015-01-01

Förster Resonance Energy Transfer (FRET) based measurements that calculate the stoichiometry of intermolecular interactions in living cells have recently been demonstrated, where the technique utilizes selective one-photon excitation of donor and acceptor fluorophores to isolate the pure FRET signal. Here, we present work towards extending this FRET stoichiometry method to employ two-photon excitation using a pulse-shaping methodology. In pulse-shaping, frequency-dependent phases are applied to a broadband femtosecond laser pulse to tailor the two-photon excitation conditions to preferentially excite donor and acceptor fluorophores. We have also generalized the existing stoichiometry theory to account for additional cross-talk terms that are non-vanishing under two-photon excitation conditions. Using the generalized theory we demonstrate two-photon FRET stoichiometry in live COS-7 cells expressing fluorescent proteins mAmetrine as the donor and tdTomato as the acceptor. PMID:25836193

A Novel Code System for Revealing Sources of Students' Difficulties with Stoichiometry

ERIC Educational Resources Information Center

Gulacar, Ozcan; Overton, Tina L.; Bowman, Charles R.; Fynewever, Herb

2013-01-01

A coding scheme is presented and used to evaluate solutions of seventeen students working on twenty five stoichiometry problems in a think-aloud protocol. The stoichiometry problems are evaluated as a series of sub-problems (e.g., empirical formulas, mass percent, or balancing chemical equations), and the coding scheme was used to categorize each…

Quantification of Lysine Acetylation and Succinylation Stoichiometry in Proteins Using Mass Spectrometric Data-Independent Acquisitions (SWATH)

DOE PAGES

Meyer, Jesse G.; D’Souza, Alexandria K.; Sorensen, Dylan J.; ...

2016-09-02

Post-translational modification of lysine residues by N ε-acylation is an important regulator of protein function. Many large-scale protein acylation studies have assessed relative changes of lysine acylation sites after antibody enrichment using mass spectrometry-based proteomics. Although relative acylation fold-changes are important, this does not reveal site occupancy, or stoichiometry, of individual modification sites, which is critical to understand functional consequences. Recently, methods for determining lysine acetylation stoichiometry have been proposed based on ratiometric analysis of endogenous levels to those introduced after quantitative per-acetylation of proteins using stable isotope-labeled acetic anhydride. However, in our hands, we find that these methods canmore » overestimate acetylation stoichiometries because of signal interferences when endogenous levels of acylation are very low, which is especially problematic when using MS1 scans for quantification. In this study, we sought to improve the accuracy of determining acylation stoichiometry using data-independent acquisition (DIA). Specifically, we use SWATH acquisition to comprehensively collect both precursor and fragment ion intensity data. The use of fragment ions for stoichiometry quantification not only reduces interferences but also allows for determination of site-level stoichiometry from peptides with multiple lysine residues. We also demonstrate the novel extension of this method to measurements of succinylation stoichiometry using deuterium-labeled succinic anhydride. Proof of principle SWATH acquisition studies were first performed using bovine serum albumin for both acetylation and succinylation occupancy measurements, followed by the analysis of more complex samples of E. coli cell lysates. Although overall site occupancy was low (<1%), some proteins contained lysines with relatively high acetylation occupancy.« less

Mother and daughter with adolescent-onset severe frontal lobe dysfunction and epilepsy

PubMed Central

dos Passos, Giordani Rodrigues; Fernández, Alonso Cuadrado; Vasques, Adriana Machado; Martins, William Alves; Palmini, André

2016-01-01

ABSTRACT Familial cases of early-onset prominent frontal lobe dysfunction associated with epilepsy have not been reported to date. We report a mother and her only daughter with incapacitating behavioral manifestations of frontal lobe dysfunction and epilepsy of variable severity. The possibility of a hitherto undescribed genetic condition is discussed. PMID:29213461

Effect of stoichiometry on magnetic and transport properties in polycrystalline Y2Ir2O7

NASA Astrophysics Data System (ADS)

Dwivedi, Vinod Kumar; Mukhopadhyay, Soumik

2018-05-01

In this paper we discuss synthesis of polycrystalline Y2Ir2O7 by solid state reaction route. XRD analysis shows deviation from stoichiometry which is also confirmed by SEM-EDX analysis. SEM analysis indicates average particle size ranging from 100 nm to 800 µm. EDX analysis gives clear evidence for deviation of stoichiometry of the product. Magnetic analysis is indicating effect of stoichiometry and showing ferromagnetic interaction unlike antiferromagnetic feature. Electrical resistivity is showing similar behavior as reported earlier and reveals no effect of different size of grains or grain boundaries from room temperature to 125 K.

Response diversity of free-floating plants to nutrient stoichiometry and temperature: growth and resting body formation.

PubMed

McCann, Michael J

2016-01-01

Free-floating plants, like most groups of aquatic primary producers, can become nuisance vegetation under certain conditions. On the other hand, there is substantial optimism for the applied uses of free-floating plants, such as wastewater treatment, biofuel production, and aquaculture. Therefore, understanding the species-specific responses of floating plants to abiotic conditions will inform both management decisions and the beneficial applications of these plants. I measured the responses of three floating plant species common in the northeast United States (Lemna minor, Spirodela polyrhiza, and Wolffia brasiliensis) to nutrient stoichiometry (nitrogen and phosphorus) and temperature in the laboratory. I also used survey data to determine the pattern of species richness of floating plants in the field and its relationship with the dominance of this group. Floating plant species exhibited unique responses to nutrient stoichiometry and temperature in the laboratory, especially under low temperatures (18 °C) and low nutrient conditions (0.5 mg N L(-1), 0.083 mg P L(-1)). The three species displayed an apparent tradeoff with different strategies of growth or dormancy. In the field, water bodies with three or more species of floating plants were not more frequently dominated by this group. The response diversity observed in the lab may not be associated with the dominance of this group in the field because it is masked by environmental variability, has a weak effect, or is only important during transient circumstances. Future research to develop applied uses of floating plants should examine response diversity across a greater range of species or clones and environmental conditions.

Response diversity of free-floating plants to nutrient stoichiometry and temperature: growth and resting body formation

PubMed Central

2016-01-01

Free-floating plants, like most groups of aquatic primary producers, can become nuisance vegetation under certain conditions. On the other hand, there is substantial optimism for the applied uses of free-floating plants, such as wastewater treatment, biofuel production, and aquaculture. Therefore, understanding the species-specific responses of floating plants to abiotic conditions will inform both management decisions and the beneficial applications of these plants. I measured the responses of three floating plant species common in the northeast United States (Lemna minor, Spirodela polyrhiza, and Wolffia brasiliensis) to nutrient stoichiometry (nitrogen and phosphorus) and temperature in the laboratory. I also used survey data to determine the pattern of species richness of floating plants in the field and its relationship with the dominance of this group. Floating plant species exhibited unique responses to nutrient stoichiometry and temperature in the laboratory, especially under low temperatures (18 °C) and low nutrient conditions (0.5 mg N L−1, 0.083 mg P L−1). The three species displayed an apparent tradeoff with different strategies of growth or dormancy. In the field, water bodies with three or more species of floating plants were not more frequently dominated by this group. The response diversity observed in the lab may not be associated with the dominance of this group in the field because it is masked by environmental variability, has a weak effect, or is only important during transient circumstances. Future research to develop applied uses of floating plants should examine response diversity across a greater range of species or clones and environmental conditions. PMID:26989619

Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system.

PubMed

Scharler, U M; Ulanowicz, R E; Fogel, M L; Wooller, M J; Jacobson-Meyers, M E; Lovelock, C E; Feller, I C; Frischer, M; Lee, R; McKee, K; Romero, I C; Schmit, J P; Shearer, C

2015-11-01

Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system

USGS Publications Warehouse

Scharler, U.M.; Ulanowicz, Robert E.; Fogel, M.L.; Wooller, M.J.; Jacobson-Meyers, M.E.; Lovelock, C.E.; Feller, I.C.; Frischer, M.; Lee, R.; Mckee, Karen L.; Romero, I.C.; Schmit, J.P.; Shearer, C.

2015-01-01

Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

Soil moisture and texture primarily control the soil nutrient stoichiometry across the Tibetan grassland.

PubMed

Tian, Liming; Zhao, Lin; Wu, Xiaodong; Fang, Hongbing; Zhao, Yonghua; Hu, Guojie; Yue, Guangyang; Sheng, Yu; Wu, Jichun; Chen, Ji; Wang, Zhiwei; Li, Wangping; Zou, Defu; Ping, Chien-Lu; Shang, Wen; Zhao, Yuguo; Zhang, Ganlin

2018-05-01

Soil nutrient stoichiometry and its environmental controllers play vital roles in understanding soil-plant interaction and nutrient cycling under a changing environment, while they remain poorly understood in alpine grassland due to lack of systematic field investigations. We examined the patterns and controls of soil nutrients stoichiometry for the top 10cm soils across the Tibetan ecosystems. Soil nutrient stoichiometry varied substantially among vegetation types. Alpine swamp meadow had larger topsoil C:N, C:P, N:P, and C:K ratios compared to the alpine meadow, alpine steppe, and alpine desert. In addition, the presence or absence of permafrost did not significantly impact soil nutrient stoichiometry in Tibetan grassland. Moreover, clay and silt contents explained approximately 32.5% of the total variation in soil C:N ratio. Climate, topography, soil properties, and vegetation combined to explain 10.3-13.2% for the stoichiometry of soil C:P, N:P, and C:K. Furthermore, soil C and N were weakly related to P and K in alpine grassland. These results indicated that the nutrient limitation in alpine ecosystem might shifts from N-limited to P-limited or K-limited due to the increase of N deposition and decrease of soil P and K contents under the changing climate conditions and weathering stages. Finally, we suggested that soil moisture and mud content could be good predictors of topsoil nutrient stoichiometry in Tibetan grassland. Copyright © 2017 Elsevier B.V. All rights reserved.

Functional assessment using Constant's Shoulder Scale after modified radical and selective neck dissection.

PubMed

Chepeha, Douglas B; Taylor, Rodney J; Chepeha, Judith C; Teknos, Theodoros N; Bradford, Carol R; Sharma, Pramod K; Terrell, Jeffrey E; Wolf, Gregory T

2002-05-01

Constant's Shoulder Scale is a validated and widely applied instrument for assessment of shoulder function. We used this instrument to assess which treatment and demographic variables contribute to shoulder dysfunction after neck dissection in head and neck cancer patients. A convenience sample of 54 patients with 64 neck dissections and minimum follow-up of 11 months were evaluated. Thirty-two accessory nerve-sparing modified radical (MRND) and 32 selective neck (SND) dissections were performed. Multivariable regression analysis was used to determine the variables that were predictive for shoulder dysfunction. Clinical variables included age, time from surgery, handedness, weight, radiation therapy, neck dissection type, tumor stage, and site. Patients receiving MRND had significantly worse shoulder function than patients with SND (p =.0007). Radiation therapy contributed negatively, whereas weight contributed positively (p =.0001). The critical factors contributing to shoulder dysfunction after neck dissection were weight, radiation therapy, and neck dissection type. Copyright 2002 Wiley Periodicals, Inc.

Dark field microscopic analysis of discrete Au nanostructures: Understanding the correlation of scattering with stoichiometry

NASA Astrophysics Data System (ADS)

Wang, Guoqing; Bu, Tong; Zako, Tamotsu; Watanabe-Tamaki, Ryoko; Tanaka, Takuo; Maeda, Mizuo

2017-09-01

Due to the potential of gold nanoparticle (AuNP)-based trace analysis, the discrimination of small AuNP clusters with different assembling stoichiometry is a subject of fundamental and technological importance. Here we prepare oligomerized AuNPs with controlled stoichiometry through DNA-directed assembly, and demonstrate that AuNP monomers, dimers and trimers can be clearly distinguished using dark field microscopy (DFM). The scattering intensity for of AuNP structures with stoichiometry ranging from 1 to 3 agrees well with our theoretical calculations. This study demonstrates the potential of utilizing the DFM approach in ultra-sensitive detection as well as the use of DNA-directed assembly for plasmonic nano-architectures.

A global analysis of soil microbial biomass carbon, nitrogen and phosphorus in terrestrial ecosystems

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

Xu, Xiaofeng; Thornton, Peter E; Post, Wilfred M

2013-01-01

Soil microbes play a pivotal role in regulating land-atmosphere interactions; the soil microbial biomass carbon (C), nitrogen (N), phosphorus (P) and C:N:P stoichiometry are important regulators for soil biogeochemical processes; however, the current knowledge on magnitude, stoichiometry, storage, and spatial distribution of global soil microbial biomass C, N, and P is limited. In this study, 3087 pairs of data points were retrieved from 281 published papers and further used to summarize the magnitudes and stoichiometries of C, N, and P in soils and soil microbial biomass at global- and biome-levels. Finally, global stock and spatial distribution of microbial biomass Cmore » and N in 0-30 cm and 0-100 cm soil profiles were estimated. The results show that C, N, and P in soils and soil microbial biomass vary substantially across biomes; the fractions of soil nutrient C, N, and P in soil microbial biomass are 1.6% in a 95% confidence interval of (1.5%-1.6%), 2.9% in a 95% confidence interval of (2.8%-3.0%), and 4.4% in a 95% confidence interval of (3.9%-5.0%), respectively. The best estimates of C:N:P stoichiometries for soil nutrients and soil microbial biomass are 153:11:1, and 47:6:1, respectively, at global scale, and they vary in a wide range among biomes. Vertical distribution of soil microbial biomass follows the distribution of roots up to 1 m depth. The global stock of soil microbial biomass C and N were estimated to be 15.2 Pg C and 2.3 Pg N in the 0-30 cm soil profiles, and 21.2 Pg C and 3.2 Pg N in the 0-100 cm soil profiles. We did not estimate P in soil microbial biomass due to data shortage and insignificant correlation with soil total P and climate variables. The spatial patterns of soil microbial biomass C and N were consistent with those of soil organic C and total N, i.e. high density in northern high latitude, and low density in low latitudes and southern hemisphere.« less

Bridging Food Webs, Ecosystem Metabolism, and Biogeochemistry Using Ecological Stoichiometry Theory

PubMed Central

Welti, Nina; Striebel, Maren; Ulseth, Amber J.; Cross, Wyatt F.; DeVilbiss, Stephen; Glibert, Patricia M.; Guo, Laodong; Hirst, Andrew G.; Hood, Jim; Kominoski, John S.; MacNeill, Keeley L.; Mehring, Andrew S.; Welter, Jill R.; Hillebrand, Helmut

2017-01-01

Although aquatic ecologists and biogeochemists are well aware of the crucial importance of ecosystem functions, i.e., how biota drive biogeochemical processes and vice-versa, linking these fields in conceptual models is still uncommon. Attempts to explain the variability in elemental cycling consequently miss an important biological component and thereby impede a comprehensive understanding of the underlying processes governing energy and matter flow and transformation. The fate of multiple chemical elements in ecosystems is strongly linked by biotic demand and uptake; thus, considering elemental stoichiometry is important for both biogeochemical and ecological research. Nonetheless, assessments of ecological stoichiometry (ES) often focus on the elemental content of biota rather than taking a more holistic view by examining both elemental pools and fluxes (e.g., organismal stoichiometry and ecosystem process rates). ES theory holds the promise to be a unifying concept to link across hierarchical scales of patterns and processes in ecology, but this has not been fully achieved. Therefore, we propose connecting the expertise of aquatic ecologists and biogeochemists with ES theory as a common currency to connect food webs, ecosystem metabolism, and biogeochemistry, as they are inherently concatenated by the transfer of carbon, nitrogen, and phosphorous through biotic and abiotic nutrient transformation and fluxes. Several new studies exist that demonstrate the connections between food web ecology, biogeochemistry, and ecosystem metabolism. In addition to a general introduction into the topic, this paper presents examples of how these fields can be combined with a focus on ES. In this review, a series of concepts have guided the discussion: (1) changing biogeochemistry affects trophic interactions and ecosystem processes by altering the elemental ratios of key species and assemblages; (2) changing trophic dynamics influences the transformation and fluxes of matter across environmental boundaries; (3) changing ecosystem metabolism will alter the chemical diversity of the non-living environment. Finally, we propose that using ES to link nutrient cycling, trophic dynamics, and ecosystem metabolism would allow for a more holistic understanding of ecosystem functions in a changing environment. PMID:28747904

Stoichiometry control in quantum dots: a viable analog to impurity doping of bulk materials.

PubMed

Luther, Joseph M; Pietryga, Jeffrey M

2013-03-26

A growing body of research indicates that the stoichiometry of compound semiconductor quantum dots (QDs) may offer control over the materials' optoelectronic properties in ways that could be invaluable in electronic devices. Quantum dots have been characterized as having a stoichiometric bulk-like core with a highly reconstructed surface of a more flexible composition, consisting essentially of ligated, weakly bound ions. As such, many efforts toward stoichiometry-based control over material properties have focused on ligand manipulation. In this issue of ACS Nano, Murray and Kagan's groups instead demonstrate control of the conductive properties of QD arrays by altering the stoichiometry via atomic infusion using a thermal evaporation technique. In this work, PbSe and PbS QD films are made to show controlled n- or p-type behavior, which is key to developing optimized QD-based electronics. In this Perspective, we discuss recent developments and the future outlook in using stoichiometry as a tool to further manipulate QD material properties in this context.

Plant Fertilization Interacts with Life History: Variation in Stoichiometry and Performance in Nettle-Feeding Butterflies

PubMed Central

Audusseau, Hélène; Kolb, Gundula; Janz, Niklas

2015-01-01

Variation in food stoichiometry affects individual performance and population dynamics, but it is also likely that species with different life histories should differ in their sensitivity to food stoichiometry. To address this question, we investigated the ability of the three nettle-feeding butterflies (Aglais urticae, Polygonia c-album, and Aglais io) to respond adaptively to induced variation in plant stoichiometry in terms of larval performance. We hypothesized that variation in larval performance between plant fertilization treatments should be functionally linked to species differences in host plant specificity. We found species-specific differences in larval performance between plant fertilization treatments that could not be explained by nutrient limitation. We showed a clear evidence of a positive correlation between food stoichiometry and development time to pupal stage and pupal mass in A. urticae. The other two species showed a more complex response. Our results partly supported our prediction that host plant specificity affects larval sensitivity to food stoichiometry. However, we suggest that most of the differences observed may instead be explained by differences in voltinism (number of generations per year). We believe that the potential of some species to respond adaptively to variation in plant nutrient content needs further attention in the face of increased eutrophication due to nutrient leakage from human activities. PMID:25932628

Plant fertilization interacts with life history: variation in stoichiometry and performance in nettle-feeding butterflies.

PubMed

Audusseau, Hélène; Kolb, Gundula; Janz, Niklas

2015-01-01

Variation in food stoichiometry affects individual performance and population dynamics, but it is also likely that species with different life histories should differ in their sensitivity to food stoichiometry. To address this question, we investigated the ability of the three nettle-feeding butterflies (Aglais urticae, Polygonia c-album, and Aglais io) to respond adaptively to induced variation in plant stoichiometry in terms of larval performance. We hypothesized that variation in larval performance between plant fertilization treatments should be functionally linked to species differences in host plant specificity. We found species-specific differences in larval performance between plant fertilization treatments that could not be explained by nutrient limitation. We showed a clear evidence of a positive correlation between food stoichiometry and development time to pupal stage and pupal mass in A. urticae. The other two species showed a more complex response. Our results partly supported our prediction that host plant specificity affects larval sensitivity to food stoichiometry. However, we suggest that most of the differences observed may instead be explained by differences in voltinism (number of generations per year). We believe that the potential of some species to respond adaptively to variation in plant nutrient content needs further attention in the face of increased eutrophication due to nutrient leakage from human activities.

The effect of resource quantity and resource stoichiometry on microbial carbon-use-efficiency

USGS Publications Warehouse

Kleiblinger, K.M.; Hall, E.K.; Wanek, W.; Szukics, U.; Hämmerle, I.; Ellersdorfer, G.; Böck, S.; Strauss, J.; Sterflinger, K.; Richter, A.; Zechmeister-Boltenstern, S.

2010-01-01

The carbon-use-efficiency (CUE) of microorganisms is an important parameter in determining ecosystem-level carbon (C) cycling; however, little is known about how variance in resources affects microbial CUE. To elucidate how resource quantity and resource stoichiometry affect microbial CUE, we cultured four microorganisms - two fungi (Aspergillus nidulans and Trichoderma harzianum) and two bacteria (Pectobacterium carotovorum and Verrucomicrobium spinosum) - under 12 unique C, nitrogen (N) and phosphorus (P) ratios. Whereas the CUE of A. nidulans was strongly affected by C, bacterial CUE was more strongly affected by mineral nutrients (N and P). Specifically, CUE in P. carotovorum was positively correlated with P, while CUE of V. spinosum primarily depended on N. This resulted in a positive relationship between fungal CUE and resource C : nutrient stoichiometry and a negative relationship between bacterial CUE and resource C : nutrient stoichiometry. The difference in the direction of the relationship between CUE and C : nutrient for fungi vs. bacteria was consistent with differences in biomass stoichiometry and suggested that fungi have a higher C demand than bacteria. These results suggest that the links between biomass stoichiometry, resource demand and CUE may provide a mechanism for commonly observed temporal and spatial patterns in microbial community structure and function in natural habitats.

The Temperature Dependence of Phytoplankton Stoichiometry: Investigating the Roles of Species Sorting and Local Adaptation

PubMed Central

Yvon-Durocher, Gabriel; Schaum, Charlotte-Elisa; Trimmer, Mark

2017-01-01

The elemental composition of phytoplankton (C:N:P stoichiometry) is a critical factor regulating nutrient cycling, primary production and energy transfer through planktonic food webs. Our understanding of the multiple direct and indirect mechanisms through which temperature controls phytoplankton stoichiometry is however incomplete, increasing uncertainty in the impacts of global warming on the biogeochemical functioning of aquatic ecosystems. Here, we use a decade-long warming experiment in outdoor freshwater ponds to investigate how temperature-driven turnover in species composition and shifts in stoichiometric traits within species through local thermal adaptation contribute to the effects of warming on seston stoichiometry. We found that experimental warming increased seston C:P and N:P ratios, while the C:N ratio was unaffected by warming. Temperature was also the dominant driver of seasonal variation in seston stoichiometry, correlating positively with both C:P and N:P ratios. The taxonomic composition of the phytoplankton community differed substantially between the warmed and ambient treatments indicating that warming resulted in differential sorting of species from the regional pool. Furthermore, taxonomic composition also changed markedly over the year within each of the warmed and ambient treatments, highlighting substantial temporal turnover in species. To investigate whether local adaptation also played an important role in shaping the effects of warming on seston stoichiometry, we isolated multiple strains of the cosmopolitan alga, Chlamydomonas reinhardtii from across the warmed and ambient mesocosms. We found that warmed isolates had higher C:P and N:P ratios, shifts that were comparable in direction and magnitude to the effects of warming on seston stoichiometry. Our results suggest that both species sorting and local adaptation are likely to play important roles in shaping the effects of warming on bulk phytoplankton stoichiometry and indicate that major shifts in aquatic biogeochemistry should be expected in a warmer world. PMID:29109703

Temporal changes in soil C-N-P stoichiometry over the past 60 years across subtropical China.

PubMed

Yu, Zaipeng; Wang, Minhuang; Huang, Zhiqun; Lin, Teng-Chiu; Vadeboncoeur, Matthew A; Searle, Eric B; Chen, Han Y H

2018-03-01

Controlled experiments have shown that global changes decouple the biogeochemical cycles of carbon (C), nitrogen (N), and phosphorus (P), resulting in shifting stoichiometry that lies at the core of ecosystem functioning. However, the response of soil stoichiometry to global changes in natural ecosystems with different soil depths, vegetation types, and climate gradients remains poorly understood. Based on 2,736 observations along soil profiles of 0-150 cm depth from 1955 to 2016, we evaluated the temporal changes in soil C-N-P stoichiometry across subtropical China, where soils are P-impoverished, with diverse vegetation, soil, and parent material types and a wide range of climate gradients. We found a significant overall increase in soil total C concentration and a decrease in soil total P concentration, resulting in increasing soil C:P and N:P ratios during the past 60 years across all soil depths. Although average soil N concentration did not change, soil C:N increased in topsoil while decreasing in deeper soil. The temporal trends in soil C-N-P stoichiometry differed among vegetation, soil, parent material types, and spatial climate variations, with significantly increased C:P and N:P ratios for evergreen broadleaf forest and highly weathered Ultisols, and more pronounced temporal changes in soil C:N, N:P, and C:P ratios at low elevations. Our sensitivity analysis suggests that the temporal changes in soil stoichiometry resulted from elevated N deposition, rising atmospheric CO 2 concentration and regional warming. Our findings revealed that the responses of soil C-N-P and stoichiometry to long-term global changes have occurred across the whole soil depth in subtropical China and the magnitudes of the changes in soil stoichiometry are dependent on vegetation types, soil types, and spatial climate variations. © 2017 John Wiley & Sons Ltd.

Vagal Activity During Physiological Sexual Arousal in Women With and Without Sexual Dysfunction.

PubMed

Stanton, Amelia M; Pulverman, Carey S; Meston, Cindy M

2017-01-02

Recently, heart rate variability (HRV) level has been found to be a risk factor for female sexual dysfunction. Low HRV was a significant predictor of female sexual arousal dysfunction and overall sexual dysfunction. Building upon this finding, the present study examined whether differences in vagal activity between sexually functional and sexually dysfunctional women may be driving the association between low HRV and female sexual dysfunction. Specifically, respiratory sinus arrhythmia (RSA) was assessed before, during, and after physiological sexual arousal in 84 women, aged 18 to 47, to examine potential differences in vagal activity between sexually functional and sexually dysfunctional women. Significant differences in vagal activity between these two groups were observed (p =.02). These findings provide additional specificity to the recently established relationship between HRV and female sexual function while also proposing a mechanism to target during treatments for sexual dysfunction.

Is Reaction Time Variability in ADHD Mainly at Low Frequencies?

ERIC Educational Resources Information Center

Karalunas, Sarah L.; Huang-Pollock, Cynthia L.; Nigg, Joel T.

2013-01-01

Background: Intraindividual variability in reaction times (RT variability) has garnered increasing interest as an indicator of cognitive and neurobiological dysfunction in children with attention deficit hyperactivity disorder (ADHD). Recent theory and research has emphasized specific low-frequency patterns of RT variability. However, whether…

Modeling the Hydrodynamics and Water Quality of the Lower Minnesota River Using CE-QUAL-W2: A Report on the Development, Calibration, Verification, and Application of the Model

DTIC Science & Technology

2012-05-01

V3.6, allows P sorption to suspended particles and settling but does not support desorption (Cole and Wells 2008).  The OM groups in CE-QUAL-W2...model developers. Sediment transport, sediment diagenesis, phosphorus sorption , and variable algal stoichiometry were noted as potentially useful...ing Chemicals) and PPCPs ( Pharmaceut ical and Person al care Products) in receiv ing water ecosystems. He is coordinat ing this inte rnat ional

Cellulose synthase stoichiometry in aspen differs from Arabidopsis and Norway spruce.

PubMed

Zhang, Xueyang; Dominguez, Pia Guadalupe; Kumar, Manoj; Bygdell, Joakim; Miroshnichenko, Sergey; Sundberg, Bjorn; Wingsle, Gunnar; Niittyla, Totte

2018-05-14

Cellulose is synthesised at the plasma membrane by cellulose synthase complexes (CSCs) containing cellulose synthases (CESAs). Genetic analysis and CESA isoform quantification indicate that cellulose in the secondary cell walls of Arabidopsis (Arabidopsis thaliana) is synthesised by isoforms CESA4, CESA7 and CESA8 in equimolar amounts. Here, we used quantitative proteomics to investigate whether the CSC model based on Arabidopsis secondary cell wall CESA stoichiometry can be applied to the angiosperm tree aspen (Populus tremula) and the gymnosperm tree Norway spruce (Picea abies). In the developing xylem of aspen the secondary cell wall CESA stoichiometry was 3:2:1 for PtCESA8a/b : PtCESA4 : PtCESA7a/b, while in Norway spruce the stoichiometry was 1:1:1 as previously observed in Arabidopsis. Furthermore, in aspen tension wood the secondary cell wall CESA stoichiometry changed to 8:3:1 for PtCESA8a/b : PtCESA4 : PtCESA7a/b. PtCESA8b represented 73% of the total secondary cell wall CESA pool, and quantitative PCR analysis of CESA transcripts in cryo-sectioned tension wood revealed increased PtCESA8b expression during formation of the cellulose-enriched gelatinous layer while the transcripts of PtCESA4, PtCESA7a/b and PtCESA8a decreased. A wide-angle X-ray scattering analysis showed that the shift in CESA stoichiometry in tension wood coincided with an increase in crystalline cellulose microfibril diameter suggesting that the CSC CESA composition influences microfibril properties. The aspen CESA stoichiometry results raise the possibility of alternative CSC models, and suggest that homomeric PtCESA8b complexes are responsible for cellulose biosynthesis in the gelatinous layer in tension wood. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.

Land-use and soil depth affect resource and microbial stoichiometry in a tropical mountain rainforest region of southern Ecuador.

PubMed

Tischer, Alexander; Potthast, Karin; Hamer, Ute

2014-05-01

Global change phenomena, such as forest disturbance and land-use change, significantly affect elemental balances as well as the structure and function of terrestrial ecosystems. However, the importance of shifts in soil nutrient stoichiometry for the regulation of belowground biota and soil food webs have not been intensively studied for tropical ecosystems. In the present account, we examine the effects of land-use change and soil depth on soil and microbial stoichiometry along a land-use sequence (natural forest, pastures of different ages, secondary succession) in the tropical mountain rainforest region of southern Ecuador. Furthermore, we analyzed (PLFA-method) whether shifts in the microbial community structure were related to alterations in soil and microbial stoichiometry. Soil and microbial stoichiometry were affected by both land-use change and soil depth. After forest disturbance, significant decreases of soil C:N:P ratios at the pastures were followed by increases during secondary succession. Microbial C:N ratios varied slightly in response to land-use change, whereas no fixed microbial C:P and N:P ratios were observed. Shifts in microbial community composition were associated with soil and microbial stoichiometry. Strong positive relationships between PLFA-markers 18:2n6,9c (saprotrophic fungi) and 20:4 (animals) and negative associations between 20:4 and microbial N:P point to land-use change affecting the structure of soil food webs. Significant deviations from global soil and microbial C:N:P ratios indicated a major force of land-use change to alter stoichiometric relationships and to structure biological systems. Our results support the idea that soil biotic communities are stoichiometrically flexible in order to adapt to alterations in resource stoichiometry.

Influences of micro-geomorphology on the stoichiometry of C, N and P in Chenier Island soils and plants in the Yellow River Delta, China

PubMed Central

Yu, Junbao; Liu, Jingtao; Sun, Jingkuan; Yang, Hongjun; Dong, Linshui

2017-01-01

Studies have indicated that consistent or well-constrained (relatively low variability) carbon:nitrogen:phosphorus (C:N:P) ratios exist in large-scale ecosystems, including both marine and terrestrial ecosystems. Little is known about the C, N and P stoichiometric ratios that exist in the soils and plants of Chenier Island in the Yellow River Delta (YRD). We examined the distribution patterns and relationships of C, N and P stoichiometry in the soils and plants of Chenier Island, as well as the potential influences of the island’s micro-geomorphology. Based on a study of four soil profile categories and Phragmites australis and Suaeda heteroptera plant tissues, our results showed that micro-geomorphology could leave a distinct imprint on the soil and plant elemental stoichiometry of Chenier Island; significant variation in the atomic C:N:P ratios (RCNP) existed in soils and plants, indicating that the RCNP values in both the soil and plants are not well constrained at the Chenier Island scale. RCN and RCP in Chenier Island soils were high, whereas the RNP values were comparatively low, indicating that the ecosystems of Chenier Island are nutrient-limited by N and P. However, the RNP values in P. australis and S. heteroptera plant tissues were high, suggesting that the plants of Chenier Island are nutrient-limited by P. Finally, we suggest that soil and plant N:P ratios may be good indicators of the soil and plant nutrient status during soil development and plant growth, which could be a useful reference for restoring the degraded soils of Chenier Island. PMID:29236766

Freshwater bacteria are stoichiometrically flexible with a nutrient composition similar to seston

USGS Publications Warehouse

Cotner, James B.; Hall, Edward K.; Scott, J. Thad; Heldal, Mikal

2010-01-01

Although aquatic bacteria are assumed to be nutrient-rich, they out-compete other foodweb osmotrophs for nitrogen (N) and phosphorus (P) an apparent contradiction to resource ratio theory. This paradox could be resolved if aquatic bacteria were demonstrated to be nutrient-poor relative other portions of the planktonic food web. In a survey of >120 lakes in the upper Midwest of the USA, the nutrient content of bacteria was lower than previously reported and very similar to the Redfield ratio, with a mean biomass composition of 102:12:1 (C:N:P). Individual freshwater bacterial isolates grown under P-limiting and P-replete conditions had even higher C:P and N:P ratios with a mean community biomass composition ratio of 875C:179N:1P suggesting that individual strains can be extremely nutrient-poor, especially with respect to P. Cell-specific measurements of individual cells from one lake confirmed that low P content could be observed at the community level in natural systems with a mean biomass composition of 259C:69N:1P. Variability in bacterial stoichiometry is typically not recognized in the literature as most studies assume constant and nutrient-rich bacterial biomass composition. We present evidence that bacteria can be extremely P-poor in individual systems and in culture, suggesting that bacteria in freshwater ecosystems can either play a role as regenerators or consumers of inorganic nutrients and that this role could switch depending on the relationship between bacterial biomass stoichiometry and resource stoichiometry. This ability to switch roles between nutrient retention and regeneration likely facilitates processing of terrestrial organic matter in lakes and rivers and has important implications for a wide range of bacterially mediated biogeochemical processes.

Urbanization and agriculture increase exports and differentially alter elemental stoichiometry of dissolved organic matter (DOM) from tropical catchments.

PubMed

Gücker, Björn; Silva, Ricky C S; Graeber, Daniel; Monteiro, José A F; Boëchat, Iola G

2016-04-15

Many tropical biomes are threatened by rapid land-use change, but its catchment-wide biogeochemical effects are poorly understood. The few previous studies on DOM in tropical catchments suggest that deforestation and subsequent land use increase stream water dissolved organic carbon (DOC) concentrations, but consistent effects on DOM elemental stoichiometry have not yet been reported. Here, we studied stream water DOC concentrations, catchment DOC exports, and DOM elemental stoichiometry in 20 tropical catchments at the Cerrado-Atlantic rainforest transition, dominated by natural vegetation, pasture, intensive agriculture, and urban land cover. Streams draining pasture could be distinguished from those draining natural catchments by their lower DOC concentrations, with lower DOM C:N and C:P ratios. Catchments with intensive agriculture had higher DOC exports and lower DOM C:P ratios than natural catchments. Finally, with the highest DOC concentrations and exports, as well as the highest DOM C:P and N:P ratios, but the lowest C:N ratios among all land-use types, urbanized catchments had the strongest effects on catchment DOM. Thus, urbanization may have alleviated N limitation of heterotrophic DOM decomposition, but increased P limitation. Land use-especially urbanization-also affected the seasonality of catchment biogeochemistry. While natural catchments exhibited high DOC exports and concentrations, with high DOM C:P ratios in the rainy season only, urbanized catchments had high values in these variables throughout the year. Our results suggest that urbanization and pastoral land use exerted the strongest impacts on DOM biogeochemistry in the investigated tropical catchments and should thus be important targets for management and mitigation efforts. Copyright © 2016 Elsevier B.V. All rights reserved.

Interactions between magnetite and humic substances: redox reactions and dissolution processes.

PubMed

Sundman, Anneli; Byrne, James M; Bauer, Iris; Menguy, Nicolas; Kappler, Andreas

2017-10-19

Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe 3 O 4 ) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry. We followed dissolved and solid-phase Fe(II) and Fe(III) concentrations over time to quantify redox reactions between HS and magnetite. Magnetite redox reactions and dissolution processes with HS varied depending on the initial magnetite and HS properties. The interaction between biogenic magnetite and reduced HS resulted in dissolution of the solid magnetite mineral, as well as an overall reduction of the magnetite. In contrast, a slight oxidation and no dissolution was observed when native and reduced HS interacted with 500 nm magnetite. This variability in the solubility and electron accepting and donating capacity of the different types of magnetite is likely an effect of differences in their reduction potential that is correlated to the magnetite Fe(II)/Fe(III) stoichiometry, particle size, and crystallinity. Our study suggests that redox-active HS play an important role for Fe redox speciation within minerals such as magnetite and thereby influence the reactivity of these Fe minerals and their role in biogeochemical Fe cycling. Furthermore, such processes are also likely to have an effect on the fate of other elements bound to the surface of Fe minerals.

Influences of micro-geomorphology on the stoichiometry of C, N and P in Chenier Island soils and plants in the Yellow River Delta, China.

PubMed

Qu, Fanzhu; Meng, Ling; Yu, Junbao; Liu, Jingtao; Sun, Jingkuan; Yang, Hongjun; Dong, Linshui

2017-01-01

Studies have indicated that consistent or well-constrained (relatively low variability) carbon:nitrogen:phosphorus (C:N:P) ratios exist in large-scale ecosystems, including both marine and terrestrial ecosystems. Little is known about the C, N and P stoichiometric ratios that exist in the soils and plants of Chenier Island in the Yellow River Delta (YRD). We examined the distribution patterns and relationships of C, N and P stoichiometry in the soils and plants of Chenier Island, as well as the potential influences of the island's micro-geomorphology. Based on a study of four soil profile categories and Phragmites australis and Suaeda heteroptera plant tissues, our results showed that micro-geomorphology could leave a distinct imprint on the soil and plant elemental stoichiometry of Chenier Island; significant variation in the atomic C:N:P ratios (RCNP) existed in soils and plants, indicating that the RCNP values in both the soil and plants are not well constrained at the Chenier Island scale. RCN and RCP in Chenier Island soils were high, whereas the RNP values were comparatively low, indicating that the ecosystems of Chenier Island are nutrient-limited by N and P. However, the RNP values in P. australis and S. heteroptera plant tissues were high, suggesting that the plants of Chenier Island are nutrient-limited by P. Finally, we suggest that soil and plant N:P ratios may be good indicators of the soil and plant nutrient status during soil development and plant growth, which could be a useful reference for restoring the degraded soils of Chenier Island.

Role of relative humidity and Cd/Zn stoichiometry in the photo-oxidation process of cadmium yellows (CdS/Cd1-xZnxS) in oil paintings.

PubMed

Monico, Letizia; Chieli, Annalisa; De Meyer, Steven; Cotte, Marine; de Nolf, Wout; Falkenberg, Gerald; Janssens, Koen; Romani, Aldo; Miliani, Costanza

2018-06-06

Cadmium yellows (CdYs) refer to a family of cadmium sulfide pigments which have been widely used by artists since the late 19th c. Despite being considered stable, they are suffering from discoloration in iconic paintings, such as Joy of Life by Matisse, Flowers in a blue vase by Van Gogh and the Scream by Munch, most likely due to the formation of CdSO₄·nH₂O. Questions about what the factors driving the CdYs degradation are and how they affect the overall process are still open. Here, we study a series of oil mock-up paints made of CdYs of different stoichiometry (CdS/Cd₀.₇₆Zn₀.₂₄S) and crystalline structure (hexagonal/cubic) before and after aging at variable relative humidity under exposure to light and in darkness. Synchrotron-based X-ray methods combined with UV-Visible and FTIR spectroscopies show that: (i) Cd₀.₇₆Zn₀.₂₄S is more susceptible to photo-oxidation than CdS; both compounds can act as photocatalysts for the oil oxidation. (ii) The photo-oxidation of CdS/Cd₀.₇₆Zn₀.₂₄S to CdSO₄·nH₂O is triggered by moisture. (iii) The nature of alteration products depends on the aging conditions and Cd/Zn stoichiometry. Based on our findings, we propose a scheme for the mechanism of the photocorrosion process and photocatalytic activity of CdY pigments in the oil binder. Overall, our results form a reliable basis for understanding the degradation of CdS-based paints of artworks and contribute towards developing better ways of preserving them for future generations. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Frontal lobe function in elderly patients with Alzheimer's disease and caregiver burden.

PubMed

Hashimoto, Akiko; Matsuoka, Kiwamu; Yasuno, Fumihiko; Takahashi, Masato; Iida, Junzo; Jikumaru, Kiyoko; Kishimoto, Toshifumi

2017-07-01

Understanding of the relationship between caregiver burden and the degree of behavioural deficits in patients with Alzheimer's disease (AD) is relatively limited. Therefore, it is worthwhile to examine the correlations between the various relevant factors to improve the efficacy of care for patients with AD. The aim of this study was to investigate the specific contributions of frontal lobe dysfunction in AD patients to caregiver burden, while controlling for other predictor variables. Participants included 30 pairs of caregivers and patients with AD. The Zarit Burden Interview and Frontal Assessment Battery were used to measure the caregiver burden and patients' frontal lobe function, respectively. To investigate the effects of frontal lobe dysfunction on caregiver burden, hierarchical regression equations with steps incorporating additional predictor variables were fitted. We also performed a correlation analysis between the individual subdomains of the Zarit Burden Interview and the predictor variables. Our study suggests that the degree of frontal lobe dysfunction in AD patients predicts their caregiver burden, when other factors of daily functional limitations and neuropsychiatric symptoms are controlled. Daily functional limitations and neuropsychiatric symptoms affected caregivers' psychosocial burden, whereas frontal lobe dysfunction affected caregivers' burden due to the increase in the dependency of the patients. Our findings indicate that to ameliorate the disabilities of patients and reduce caregiver burden, there is a need for interventions that focus on psychosocial burdens, as shown in previous studies, as well as on excessive dependency due to frontal lobe dysfunction. © 2017 Japanese Psychogeriatric Society.

Maximizing the efficiency of multienzyme process by stoichiometry optimization.

PubMed

Dvorak, Pavel; Kurumbang, Nagendra P; Bendl, Jaroslav; Brezovsky, Jan; Prokop, Zbynek; Damborsky, Jiri

2014-09-05

Multienzyme processes represent an important area of biocatalysis. Their efficiency can be enhanced by optimization of the stoichiometry of the biocatalysts. Here we present a workflow for maximizing the efficiency of a three-enzyme system catalyzing a five-step chemical conversion. Kinetic models of pathways with wild-type or engineered enzymes were built, and the enzyme stoichiometry of each pathway was optimized. Mathematical modeling and one-pot multienzyme experiments provided detailed insights into pathway dynamics, enabled the selection of a suitable engineered enzyme, and afforded high efficiency while minimizing biocatalyst loadings. Optimizing the stoichiometry in a pathway with an engineered enzyme reduced the total biocatalyst load by an impressive 56 %. Our new workflow represents a broadly applicable strategy for optimizing multienzyme processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Path finding methods accounting for stoichiometry in metabolic networks

PubMed Central

2011-01-01

Graph-based methods have been widely used for the analysis of biological networks. Their application to metabolic networks has been much discussed, in particular noting that an important weakness in such methods is that reaction stoichiometry is neglected. In this study, we show that reaction stoichiometry can be incorporated into path-finding approaches via mixed-integer linear programming. This major advance at the modeling level results in improved prediction of topological and functional properties in metabolic networks. PMID:21619601

Regulation of the sodium bicarbonate cotransporter kNBC1 function: role of Asp(986), Asp(988) and kNBC1-carbonic anhydrase II binding.

PubMed

Gross, Eitan; Pushkin, Alexander; Abuladze, Natalia; Fedotoff, Olga; Kurtz, Ira

2002-11-01

The HCO(3)(-) : Na(+) cotransport stoichiometry of the electrogenic sodium bicarbonate cotransporter kNBC1 determines the reversal potential (E(rev)) and thus the net direction of transport of these ions through the cotransporter. Previously, we showed that phosphorylation of kNBC1-Ser(982) in the carboxy-terminus of kNBC1 (kNBC1-Ct), by cAMP-protein kinase A (PKA), shifts the stoichiometry from 3 : 1 to 2 : 1 and that binding of bicarbonate to the cotransporter is electrostaticaly modulated. These results raise the possibility that phosphorylated kNBC1-Ser(982), or other nearby negatively charged residues shift the stoichiometry by blocking a bicarbonate-binding site. In the current study, we examined the role of the negative charge on Ser(982)-phosphate and three aspartate residues in a D986NDD custer in altering the stoichiometry of kNBC1. mPCT cells expressing kNBC1 mutants were grown on filters and mounted in an Ussing chamber for electrophysiological studies. Enhanced green fluorescence protein (EGFP)-tagged mutant constructs expressed in the same cells were used to determine the phosphorylation status of kNBC1-Ser(982). The data indicate that both kNBC1-Asp(986) and kNBC1-Asp(988), but not kNBC1-Asp(989), are required for the phosphorylation-induced shift in stoichiometry. A homologous motif (D887ADD) in the carboxy-terminus of the anion exchanger AE1 binds to carbonic anhydrase II (CAII). In isothermal titration calorimetry experiments, CAII was found to bind to kNBC1-Ct with a K(D) of 160 +/- 10 nM. Acetazolamide inhibited the short-circuit current through the cotransporter by 65 % when the latter operated in the 3 : 1 mode, but had no effect on the current in the 2 : 1 mode. Acetazolamide did not affect the cotransport stoichiometry or the ability of 8-Br-cAMP to shift the stoichiometry. Although CAII does not affect the transport stoichiometry, it may play an important role in enhancing the flux through the transporter when kNBC1-Ser(982) is unphosphorylated.

Nutrient stoichiometry of temperate trees and effects on the coupled cycles of carbon, nitrogen, and cations in soil

NASA Astrophysics Data System (ADS)

Mueller, K. E.; Oleksyn, J.; Hobbie, S. E.; Reich, P.; Chorover, J. D.; Freeman, K. H.; Eissenstat, D.

2009-12-01

Nutrient stoichiometry of leaf litter (LL) is a potentially important driver of plant effects on soil biogeochemistry; it is also responsive to environmental perturbations and differs among plant functional groups that may have predictable responses to the environment. Thus variation in LL nutrient stoichiometry may provide a predictive framework for the influence of global change on soil. However, this approach depends on several key, but poorly tested assumptions, including: 1) other plant organs follow similar patterns and have similar effects on soil biogeochemistry, and 2) patterns in leaf traits, functional group dominance, and soil properties across large-spatial scales are predictive at smaller scales. To address these assumptions and test the utility of nutrient stoichiometry as a predictive framework for soil change, we synthesize data on tree stoichiometry and soil biogeochemistry from a long-term (> 30 yr) common garden experiment containing replicated, monoculture plots of 14 temperate tree species. LL nutrient stoichiometry alone is insufficient to explain differences in biogeochemical cycling among tree species, in part due to the dissimilarity of leaf and root traits within species. Notably, different elements and plant organs have independent impacts on soil biogeochemistry. LL nitrogen (N) concentration and lignin:N ratios have small or negligible effects on soil carbon (C), N, and cation cycling, while LL-calcium (Ca) drives differences in litter decomposition and soil pH among species in a manner consistent with nutrient requirements of anecic earthworms. However, LL-Ca effects on C and N cycles in soil appear minor compared to the influences of root N and, unexpectedly, green leaf N, which combine to drive differences in soil N dynamics via unique mechanisms consistent with nutrient requirements of soil microbes and the trees. In turn, soil N dynamics are strongly correlated with soil acidity and C stabilization. By taking into account the stoichiometry of each plant organ, of soil microbes and fauna, and the interactions among C, N, and cation cycles, the predictive capacity of tree nutrient stoichiometry for understanding soil change is apparent, albeit complex.

Crystal Structure and Transport Properties of Oxygen-Deficient Perovskite Sr 0.9Y 0.1CoO 3-δ

DOE PAGES

Yang, Tianrang; Mattick, Victoria F.; Chen, Yan; ...

2018-01-29

The present work reports a systematic study on temperature-dependent local crystal structure, oxygen stoichiometry, and electrical/electrochemical properties of an oxygen-deficient Sr 0.9Y 0.1CoO 3-δ (SYC10) perovskite using variable-temperature neutron diffraction (VTND), thermal gravimetric analysis, and electrical/electrochemical methods, respectively. The VTND reveals that the crystal symmetry of SYC10 remains P4/mmm tetragonal up to 900 °C. The tetragonal symmetry reflects the net effects of temperature and oxygen stoichiometry on crystal symmetry. The observed p-type electronic conductivity behavior originates from the charge-ordering between the two distinctive Co-sites. The partial oxide-ion conductivity and diffusivity obtained from oxygen permeation measurements are 2.3 × 10 –2more » S cm –1 and 7.98 × 10–8 cm 2/s at 800 °C in air, respectively. The electrochemical oxygen reduction reaction kinetics of the SYC10 cathode is primarily limited by the charge-transfer process at low temperatures (600–650 °C) and oxide-ion migration from the cathode into the electrolyte at high temperatures (700–800 °C).« less

Thiosulfate oxidation by Thiomicrospira thermophila: metabolic flexibility in response to ambient geochemistry

PubMed Central

Houghton, J.L.; Foustoukos, D.; Flynn, T.M.; Vetriani, C.; Bradley, A.S.; Fike, D.A.

2017-01-01

Summary Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here we present reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise. At pH 8.0, thiosulfate is stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation are extracellular elemental sulfur and sulfate. We were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reports of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway (soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observe in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling. PMID:26914243

Genotype-specific relationships among phosphorus use, growth and abundance in Daphnia pulicaria

PubMed Central

Chowdhury, Priyanka Roy; Baker, Kristina D.; Weider, Lawrence J.; Jeyasingh, Punidan D.

2017-01-01

The framework ecological stoichiometry uses elemental composition of species to make predictions about growth and competitive ability in defined elemental supply conditions. Although intraspecific differences in stoichiometry have been observed, we have yet to understand the mechanisms generating and maintaining such variation. We used variation in phosphorus (P) content within a Daphnia species to test the extent to which %P can explain variation in growth and competition. Further, we measured 33P kinetics (acquisition, assimilation, incorporation and retention) to understand the extent to which such variables improved predictions. Genotypes showed significant variation in P content, 33P kinetics and growth rate. P content alone was a poor predictor of growth rate and competitive ability. While most genotypes exhibited the typical growth penalty under P limitation, a few varied little in growth between P diets. These observations indicate that some genotypes can maintain growth under P-limited conditions by altering P use, suggesting that decomposing P content of an individual into physiological components of P kinetics will improve stoichiometric models. More generally, attention to the interplay between nutrient content and nutrient-use is required to make inferences regarding the success of genotypes in defined conditions of nutrient supply. PMID:29308224

Crystal Structure and Transport Properties of Oxygen-Deficient Perovskite Sr 0.9Y 0.1CoO 3-δ

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

Yang, Tianrang; Mattick, Victoria F.; Chen, Yan

The present work reports a systematic study on temperature-dependent local crystal structure, oxygen stoichiometry, and electrical/electrochemical properties of an oxygen-deficient Sr 0.9Y 0.1CoO 3-δ (SYC10) perovskite using variable-temperature neutron diffraction (VTND), thermal gravimetric analysis, and electrical/electrochemical methods, respectively. The VTND reveals that the crystal symmetry of SYC10 remains P4/mmm tetragonal up to 900 °C. The tetragonal symmetry reflects the net effects of temperature and oxygen stoichiometry on crystal symmetry. The observed p-type electronic conductivity behavior originates from the charge-ordering between the two distinctive Co-sites. The partial oxide-ion conductivity and diffusivity obtained from oxygen permeation measurements are 2.3 × 10 –2more » S cm –1 and 7.98 × 10–8 cm 2/s at 800 °C in air, respectively. The electrochemical oxygen reduction reaction kinetics of the SYC10 cathode is primarily limited by the charge-transfer process at low temperatures (600–650 °C) and oxide-ion migration from the cathode into the electrolyte at high temperatures (700–800 °C).« less

Thiosulfate oxidation by Thiomicrospira thermophila: Metabolic flexibility in response to ambient geochemistry

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

Houghton, J. L.; Foustoukos, D. I.; Flynn, T. M.

Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here the reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise, is presented. At pH 8.0, thiosulfate was stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation were extracellular elemental sulfur and sulfate. Here, we were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reportsmore » of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway ( soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observed in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.« less

Thiosulfate oxidation by Thiomicrospira thermophila: Metabolic flexibility in response to ambient geochemistry

DOE PAGES

Houghton, J. L.; Foustoukos, D. I.; Flynn, T. M.; ...

2016-03-21

Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here the reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise, is presented. At pH 8.0, thiosulfate was stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation were extracellular elemental sulfur and sulfate. Here, we were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reportsmore » of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway ( soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observed in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.« less

Enhanced Respiratory Chain Supercomplex Formation in Response to Exercise in Human Skeletal Muscle.

PubMed

Greggio, Chiara; Jha, Pooja; Kulkarni, Sameer S; Lagarrigue, Sylviane; Broskey, Nicholas T; Boutant, Marie; Wang, Xu; Conde Alonso, Sonia; Ofori, Emmanuel; Auwerx, Johan; Cantó, Carles; Amati, Francesca

2017-02-07

Mitochondrial dysfunction is a hallmark of multiple metabolic complications. Physical activity is known to increase mitochondrial content in skeletal muscle, counteracting age-related decline in muscle function and protecting against metabolic and cardiovascular complications. Here, we investigated the effect of 4 months of exercise training on skeletal muscle mitochondria electron transport chain complexes and supercomplexes in 26 healthy, sedentary older adults. Exercise differentially modulated respiratory complexes. Complex I was the most upregulated complex and not stoichiometrically associated to the other complexes. In contrast to the other complexes, complex I was almost exclusively found assembled in supercomplexes in muscle mitochondria. Overall, supercomplex content was increased after exercise. In particular, complexes I, III, and IV were redistributed to supercomplexes in the form of I+III 2 +IV. Taken together, our results provide the first evidence that exercise affects the stoichiometry of supercomplex formation in humans and thus reveal a novel adaptive mechanism for increased energy demand. Copyright © 2017 Elsevier Inc. All rights reserved.

Linking microbial and ecosystem ecology using ecological stoichiometry: a synthesis of conceptual and empirical approaches

USGS Publications Warehouse

Hall, E.K.; Maixner, F.; Franklin, O.; Daims, H.; Richter, A.; Battin, T.

2011-01-01

Currently, one of the biggest challenges in microbial and ecosystem ecology is to develop conceptual models that organize the growing body of information on environmental microbiology into a clear mechanistic framework with a direct link to ecosystem processes. Doing so will enable development of testable hypotheses to better direct future research and increase understanding of key constraints on biogeochemical networks. Although the understanding of phenotypic and genotypic diversity of microorganisms in the environment is rapidly accumulating, how controls on microbial physiology ultimately affect biogeochemical fluxes remains poorly understood. We propose that insight into constraints on biogeochemical cycles can be achieved by a more rigorous evaluation of microbial community biomass composition within the context of ecological stoichiometry. Multiple recent studies have pointed to microbial biomass stoichiometry as an important determinant of when microorganisms retain or recycle mineral nutrients. We identify the relevant cellular components that most likely drive changes in microbial biomass stoichiometry by defining a conceptual model rooted in ecological stoichiometry. More importantly, we show how X-ray microanalysis (XRMA), nanoscale secondary ion mass spectroscopy (NanoSIMS), Raman microspectroscopy, and in situ hybridization techniques (for example, FISH) can be applied in concert to allow for direct empirical evaluation of the proposed conceptual framework. This approach links an important piece of the ecological literature, ecological stoichiometry, with the molecular front of the microbial revolution, in an attempt to provide new insight into how microbial physiology could constrain ecosystem processes.

The Reactivity and Structure of Size Selected VxO y Clusters on a TiO2 (110)-(1 X 1) Surface of Variable Oxidation State

NASA Astrophysics Data System (ADS)

Neilson, Hunter L.

The Reactivity and Structure of Size Selected VxOy Clusters on a TiO2 (110) Surface of Variable Oxidation State by Hunter L Neilson The selective oxidative dehydrogenation of methanol by vanadium oxide/TiO2 model systems has received a great deal of interest in the surface science community. Previous studies using temperature programmed desorption and reaction (TPD/R) to probe the oxidation of methanol to formaldehyde by vanadia/TiO2 model catalysts have shown that the activity of these systems vary considerably based on the way in which the model system is prepared with formaldehyde desorption temperatures observed anywhere from room temperature to 660 K. The principle reason for this variation is that the preparation of sub-monolayer films of vanadia on TiO2 produces clusters with a multitude of VxOy structures and a mixture of vanadium oxidation states. As a result the stoichiometry of the active vanadium oxide catalyst as well as the oxidation state of vanadium in the active catalyst remain unknown. To better understand this system, our group has probed the reactivity and structure of size-selected Vx, VOy and VxOy clusters on a reduced TiO2 (110) support in ultra-high vacuum (UHV) via TPD/R and scanning tunneling microscopy (STM). Ex situ preparation of these clusters in the gas phase prior to deposition has allowed us to systematically vary the stoichiometry of the vanadia clusters; a layer of control not available via the usual routes to vanadium oxide. The most active catalysts are shown to have (VO3)n stoichiometry in agreement with the theoretical models of the Metiu group. We have shown that both the activity and selectivity of V2O6 and V3O9 cluster catalysts depend sensitively on the oxidation state of the TiO2 (110) support. For example, V2O6 on a reduced surface is selective for the oxidation of methanol to formaldehyde while the selectivity shifts to favor methyl formate as the surface becomes increasingly oxidized. STM studies show that the structure of size-selected V2O6 clusters, upon adsorption to the surface, varies considerably with the oxidation state of the support, in good agreement with our reactivity studies. V 3O9 was shown to catalyze the oxidation of methanol to both formaldehyde and methyl formate on a reduced surface while STM suggests that, unlike V2O6, these clusters are prone to decomposition upon adsorption to the surface. Furthermore, TPD/R of size selected V 2O5 and V2O7 on TiO2 suggests that altering the stoichiometry of the (VO3)n clusters by a single oxygen atom significantly inhibits the activity of these catalysts.

Stoichiometry of Reducing Equivalents and Splitting of Water in the Citric Acid Cycle.

ERIC Educational Resources Information Center

Madeira, Vitor M. C.

1988-01-01

Presents a solution to the problem of finding the source of extra reducing equivalents, and accomplishing the stoichiometry of glucose oxidation reactions. Discusses the citric acid cycle and glycolysis. (CW)

Chewing movements altered in the presence of temporomandibular joint internal derangements.

PubMed

Radke, John C; Kull, Robert S; Sethi, Manminder S

2014-07-01

The objectives were to find specific factors that are mathematically distinct between the chewing timings, movement pattern shapes, variability, and movement velocities of: (1) normal asymptomatic subjects and (2) a group of subjects with verified temporomandibular joint (TMJ) internal derangements. Left- and right-sided chewing movement recordings of 28 subjects (34.5 ± 14.0 years) were randomly selected from a large database of patients exhibiting verified unilateral or bilateral TMJ internal derangements. The chewing movements of an age- and gender-matched control group of 20 asymptomatic subjects (32.5 ± 11.6 years, P>0.60) with verified normal TMJ function were also recorded. Means and standard deviations of the opening, closing, turning point, terminal chewing position, and velocity patterns were calculated. A two-tailed Student's t-test with unequal variances was used to compare the parameters between the two groups (alpha = 0.05). The dysfunctional group functioned significantly slower and with greater variability than the control group. The vertical dimension was consistently smaller in the dysfunctional group (P<0.00001). The terminal chewing position was significantly less precise in the dysfunctional group (vertical: P<0.002 and lateral: P<0.037). The maximum lateral width was significantly less (P<0.0071), and the peak and the average velocities were significantly lower (P<0.00001 for both) in the dysfunctional group. This group of dysfunctional subjects exhibited significantly slower, smaller, and more variable chewing patterns than the control group. The functional pattern of mastication appears to be significantly altered in the presence of an internal derangement of the TMJ.

Differential Nutrient Limitation of Soil Microbial Biomass and Metabolic Quotients (qCO2): Is There a Biological Stoichiometry of Soil Microbes?

PubMed Central

Hartman, Wyatt H.; Richardson, Curtis J.

2013-01-01

Background Variation in microbial metabolism poses one of the greatest current uncertainties in models of global carbon cycling, and is particularly poorly understood in soils. Biological Stoichiometry theory describes biochemical mechanisms linking metabolic rates with variation in the elemental composition of cells and organisms, and has been widely observed in animals, plants, and plankton. However, this theory has not been widely tested in microbes, which are considered to have fixed ratios of major elements in soils. Methodology/Principal Findings To determine whether Biological Stoichiometry underlies patterns of soil microbial metabolism, we compiled published data on microbial biomass carbon (C), nitrogen (N), and phosphorus (P) pools in soils spanning the global range of climate, vegetation, and land use types. We compared element ratios in microbial biomass pools to the metabolic quotient qCO2 (respiration per unit biomass), where soil C mineralization was simultaneously measured in controlled incubations. Although microbial C, N, and P stoichiometry appeared to follow somewhat constrained allometric relationships at the global scale, we found significant variation in the C∶N∶P ratios of soil microbes across land use and habitat types, and size-dependent scaling of microbial C∶N and C∶P (but not N∶P) ratios. Microbial stoichiometry and metabolic quotients were also weakly correlated as suggested by Biological Stoichiometry theory. Importantly, we found that while soil microbial biomass appeared constrained by soil N availability, microbial metabolic rates (qCO2) were most strongly associated with inorganic P availability. Conclusions/Significance Our findings appear consistent with the model of cellular metabolism described by Biological Stoichiometry theory, where biomass is limited by N needed to build proteins, but rates of protein synthesis are limited by the high P demands of ribosomes. Incorporation of these physiological processes may improve models of carbon cycling and understanding of the effects of nutrient availability on soil C turnover across terrestrial and wetland habitats. PMID:23526933

Family functionality: a study of Brazilian institutionalized elderly individuals.

PubMed

de Oliveira, Simone Camargo; Pavarini, Sofia Cristina Iost; Orlandi, Fabiana de Souza; de Mendiondo, Marisa Silvana Zazzeta

2014-01-01

This study presents an analysis of a potential association between family functionality and the variables of gender, length of institutionalization, family composition, depressive symptoms, and cognitive disorders in elderly individuals living in Long-Term Care Facilities (LTCF) in a city in the interior of São Paulo, Brazil. This is a quantitative, cross-sectional study with a descriptive-correlational design. A total of 107 institutionalized elderly individuals were interviewed. Data were analyzed through raw and adjusted Logistic Regression. The results indicate that most elderly individuals experience family dysfunction, 57% present a high level of family dysfunction, 21% present moderate family dysfunction and 22% present good family functionality. There was a statistical association between the Family APGAR and the variables of length of institutionalization, depressive symptoms, family composition and cognitive disorders. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Non-stoichiometry in U 3Si 2

DOE PAGES

Middleburgh, Simon C.; Grimes, Robin W.; Lahoda, Ed J.; ...

2016-10-08

Uranium silicides, in particular U 3Si 2, are being explored as an advanced nuclear fuel with increased accident tolerance as well as competitive economics compared to the baseline UO 2 fuel. Here we use density functional theory calculations and thermochemical analysis to assess the stability of U 3Si 2 with respect to non-stoichiometry reactions in both the hypo- and hyper-stoichiometric regimes. We find that the degree of non-stoichiometry in U 3Si 2 is much smaller than in UO 2 and at most reaches a few percent at high temperature. Non-stoichiometry impacts fuel performance by determining whether the loss of uraniummore » due to fission leads to a non-stoichiometric U 3Si 2±x phase or precipitation of a second U-Si phase. Lastly, we also investigate the U 5Si 4 phase as a candidate for the equilibrium phase diagram.« less

Carbon and nitrogen stoichiometry across stream ecosystems

NASA Astrophysics Data System (ADS)

Wymore, A.; Kaushal, S.; McDowell, W. H.; Kortelainen, P.; Bernhardt, E. S.; Johnes, P.; Dodds, W. K.; Johnson, S.; Brookshire, J.; Spencer, R.; Rodriguez-Cardona, B.; Helton, A. M.; Barnes, R.; Argerich, A.; Haq, S.; Sullivan, P. L.; López-Lloreda, C.; Coble, A. A.; Daley, M.

2017-12-01

Anthropogenic activities are altering carbon and nitrogen concentrations in surface waters globally. The stoichiometry of carbon and nitrogen regulates important watershed biogeochemical cycles; however, controls on carbon and nitrogen ratios in aquatic environments are poorly understood. Here we use a multi-biome and global dataset (tropics to Arctic) of stream water chemistry to assess relationships between dissolved organic carbon (DOC) and nitrate, ammonium and dissolved organic nitrogen (DON), providing a new conceptual framework to consider interactions between DOC and the multiple forms of dissolved nitrogen. We found that across streams the total dissolved nitrogen (TDN) pool is comprised of very little ammonium and as DOC concentrations increase the TDN pool shifts from nitrate to DON dominated. This suggests that in high DOC systems, DON serves as the primary source of nitrogen. At the global scale, DOC and DON are positively correlated (r2 = 0.67) and the average C: N ratio of dissolved organic matter (molar ratio of DOC: DON) across our data set is approximately 31. At the biome and smaller regional scale the relationship between DOC and DON is highly variable (r2 = 0.07 - 0.56) with the strongest relationships found in streams draining the mixed temperate forests of the northeastern United States. DOC: DON relationships also display spatial and temporal variability including latitudinal and seasonal trends, and interactions with land-use. DOC: DON ratios correlated positively with gradients of energy versus nutrient limitation pointing to the ecological role (energy source versus nutrient source) that DON plays with stream ecosystems. Contrary to previous findings we found consistently weak relationships between DON and nitrate which may reflect DON's duality as an energy or nutrient source. Collectively these analyses demonstrate how gradients of DOC drive compositional changes in the TDN pool and reveal a high degree of variability in the C: N ratio (3-100) of stream water dissolved organic matter.

Growth and stoichiometry of a common aquatic detritivore respond to changes in resource stoichiometry.

PubMed

Fuller, Chris L; Evans-White, Michelle A; Entrekin, Sally A

2015-03-01

Consumer growth determines the quantity of nutrients transferred through food webs. The extent to which leaf composition and consumer physiology interact to constrain consumer production is not well understood. For example, detritivore growth, and thus material transfer, could change with detrital elemental composition. Detrital type and associated microbial biofilms can mediate the amount and rate of detritus consumed and used towards growth. Detritivore body stoichiometry or the threshold elemental ratio, the food ratio resulting in optimal growth, may predict taxon-specific growth response to stoichiometrically-altered detritus. Empirical measures of detritivore growth responses across a range of detrital stoichiometry are rare. We fed a common detritivore, Tipula abdominalis, maple or oak leaves that spanned a gradient of carbon:phosphorus (C:P) to examine how leaf identity and C:P interact to influence growth, consumption, assimilation efficiencies, and post-assimilatory processes. Tipula abdominalis growth and consumption varied with leaf type and stoichiometry. Individuals fed oak grew faster and ate more compared to individuals fed maple. Individuals fed maple grew faster and ate more as leaf C:P decreased. All individuals lost most of the material they assimilated through respiration and excretion regardless of leaf type or leaf stoichiometry. Consumption and growth rates of T. abdominalis increased with maple nutrient enrichment, but not oak, indicating leaf-specific nutrient enrichment affected leaf palatability. Slightly non-homeostatic T. abdominalis C:P was maintained by varied consumption, carbon assimilation, and P excretion. Our study underlines the importance of how detritivore consumption and post-assimilatory processing could influence whole-stream material storage and nutrient cycling in detrital-based ecosystems.

Simultaneous regulation of antenna size and photosystem I/II stoichiometry in Arabidopsis thaliana.

PubMed

Jia, Ting; Ito, Hisashi; Tanaka, Ayumi

2016-11-01

The photosystem I/II ratio increased when antenna size was enlarged by transient induction of CAO in chlorophyll b -less mutants, thus indicating simultaneous regulation of antenna size and photosystem I/II stoichiometry. Regulation of antenna size and photosystem I/II stoichiometry is an indispensable strategy for plants to acclimate to changes to light environments. When plants grown in high-light conditions are transferred to low-light conditions, the peripheral antennae of photosystems are enlarged. A change in the photosystem I/II ratio is also observed under the same light conditions. However, our knowledge of the correlation between antenna size modulation and variation in photosystem I/II stoichiometry remains limited. In this study, chlorophyll a oxygenase was transiently induced in Arabidopsis thaliana chlorophyll b-less mutants, ch1-1, to alter the antenna size without changing environmental conditions. In addition to the accumulation of chlorophyll b, the levels of the peripheral antenna complexes of both photosystems gradually increased, and these were assembled to the core antenna of both photosystems. However, the antenna size of photosystem II was greater than that of photosystem I. Immunoblot analysis of core antenna proteins showed that the number of photosystem I increased, but not that of photosystem II, resulting in an increase in the photosystem I/II ratio. These results clearly indicate that antenna size adjustment was coupled with changes in photosystem I/II stoichiometry. Based on these results, the physiological importance of simultaneous regulation of antenna size and photosystem I/II stoichiometry is discussed in relation to acclimation to light conditions.

Impedance of Barrier-Type Oxide Layer on Aluminum

NASA Astrophysics Data System (ADS)

Oh, Han-Jun; Kim, Jung-Gu; Jeong, Yong-Soo; Chi, Choong-Soo

2000-12-01

The impedance characteristics of barrier-type oxide layers on aluminum was studied using impedance spectroscopy. Since anodic films on Al have a variable stoichiometry with a gradual reduction of oxygen deficiency towards the oxide-electrolyte interface, the interpretation of impedance spectra for oxide layers is complex and the impedance of surface layers differs from those of ideal capacitors. This frequency response of the layer with conductance gradients cannot be described by a single resistance-capacitance (RC) element. The oxide layers of Al are properly described by the Young model of dielectric constant with a vertical decay of conductivity.

Links between Life Course Trajectories of Family Dysfunction and Anxiety during Middle Childhood

ERIC Educational Resources Information Center

Pagani, Linda S.; Japel, Christa; Vaillancourt, Tracy; Cote, Sylvana; Tremblay, Richard E.

2008-01-01

Using data from three waves of a large Canadian data set, we examine the relationship between two middle childhood trajectory variables, family dysfunction and anxiety. We draw upon family systems theory and developmental psychopathology, while attempting to expand their boundaries by capitalizing on the strengths within both approaches. Our data…

Career Decision-Making Difficulties, Dysfunctional Thinking and Generalized Self-Efficacy of University Students in Greece

ERIC Educational Resources Information Center

Sidiropoulou-Dimakakou, Despina; Mylonas, Kostas; Argyropoulou, Katerina; Tampouri, Sofia

2012-01-01

The present study aims to examine the relationship of career decision-making difficulties, dysfunctional career thoughts and generalized self-efficacy, as factors involved in the decision-making process for university students. The study also investigates the influence of demographics and individual variables, and examines the predictive power of…

Joint symbolic dynamics as a model-free approach to study interdependence in cardio-respiratory time series.

PubMed

Baumert, Mathias; Brown, Rachael; Duma, Stephen; Broe, G Anthony; Kabir, Muammar M; Macefield, Vaughan G

2012-01-01

Heart rate and respiration display fluctuations that are interlinked by central regulatory mechanisms of the autonomic nervous system (ANS). Joint assessment of respiratory time series along with heart rate variability (HRV) may therefore provide information on ANS dysfunction. The aim of this study was to investigate cardio-respiratory interaction in patients with Parkinson's disease (PD), a neurodegenerative disorder that is associated with progressive ANS dysfunction. Short-term ECG and respiration were recorded in 25 PD patients and 28 healthy controls during rest. To assess ANS dysfunction we analyzed joint symbolic dynamics of heart rate and respiration, cardio-respiratory synchrograms along with heart rate variability. Neither HRV nor cardio-respiratory synchrograms were significantly altered in PD patients. Symbolic analysis, however, identified a significant reduction in cardio-respiratory interactions in PD patients compared to healthy controls (16 ± 3.6 % vs. 20 ± 6.1 %; p= 0.02). In conclusion, joint symbolic analysis of cardio-respiratory dynamics provides a powerful tool to detect early signs of autonomic nervous system dysfunction in Parkinson's disease patients at an early stage of the disease.

The relationship between inotrope exposure, six-hour postoperative physiological variables, hospital mortality and renal dysfunction in patients undergoing cardiac surgery.

PubMed

Shahin, Jason; DeVarennes, Benoit; Tse, Chun Wing; Amarica, Dan-Alexandru; Dial, Sandra

2011-07-07

Acute haemodynamic complications are common after cardiac surgery and optimal perioperative use of inotropic agents, typically guided by haemodynamic variables, remains controversial. The aim of this study was to examine the relationship of inotrope use to hospital mortality and renal dysfunction. A retrospective cohort study of 1,326 cardiac surgery patients was carried out at two university-affiliated ICUs. Multivariable logistic regression analysis and propensity matching were performed to evaluate whether inotrope exposure was independently associated with mortality and renal dysfunction. Patients exposed to inotropes had a higher mortality rate than those not exposed. After adjusting for differences in Parsonnet score, left ventricular ejection fraction, perioperative intraaortic balloon pump use, bypass time, reoperation and cardiac index, inotrope exposure appeared to be independently associated with increased hospital mortality (adjusted odds ratio (OR) 2.3, 95% confidence interval (95% CI) 1.2 to 4.5) and renal dysfunction (adjusted OR 2.7, 95% CI 1.5 to 4.6). A propensity score-matched analysis similarly demonstrated that death and renal dysfunction were significantly more likely to occur in patients exposed to inotropes (P = 0.01). Postoperative inotrope exposure was independently associated with worse outcomes in this cohort study. Further research is needed to better elucidate the appropriate use of inotropes in cardiac surgery.

Fizzy Drinks: Stoichiometry You Can Taste.

ERIC Educational Resources Information Center

Rohrig, Brian

2000-01-01

Presents an activity that is suitable for a high school chemistry or introductory college chemistry lab in which students create their own Fizzie-style carbonated beverage and use stoichiometry to calculate the correct mix of citric acid and baking soda. (Author/ASK)

Decomposition drives convergence of forest litter nutrient stoichiometry following phosphorus addition

USGS Publications Warehouse

van Huysen, Tiff L.; Perakis, Steven; Harmon, Mark E.

2016-01-01

We conclude that litter P concentrations and to some extent soil P may influence litter nutrient dynamics during decomposition, resulting in a convergence of element ratios that reflect the balance of substrate decomposition and microbial nutrient stoichiometry.

Nano-scale stoichiometry analysis of a high temperature superconductor by atom probe tomography

DOE PAGES

Pedrazzini, Stella; London, Andrew J.; Gault, Baptiste; ...

2017-01-31

The functional properties of the high-temperature superconductor Y 1Ba 2Cu 3O 7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y 7.7Ba 15.3Cu 23O 54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of themore » experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) samples in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y 7.9Ba 10.4Cu 24.4O 57.2.« less

Near Surface Stoichiometry in UO 2 : A Density Functional Theory Study

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

Yu, Jianguo; Valderrama, Billy; Henderson, Hunter B.

2015-01-01

The mechanisms of oxygen stoichiometry variation in UO 2at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO 2near surface and defect effects of near surface on stoichiometry in which the system can exchange atoms with the external reservoir. In this study, the near (110) surface relaxation and stoichiometry in UO 2have been studied with density functional theory (DFT) calculations. On the basis of the point-defect model (PDM), a general expression for the near surface stoichiometric variationmore » is derived by using DFT total-energy calculations and atomistic thermodynamics, in an attempt to pin down the mechanisms of oxygen exchange between the gas environment and defected UO 2. By using the derived expression, it is observed that, under poor oxygen conditions, the stoichiometry of near surface is switched from hyperstoichiometric at 300 K with a depth around 3 nm to near-stoichiometric at 1000 K and hypostoichiometric at 2000 K. Furthermore, at very poor oxygen concentrations and high temperatures, our results also suggest that the bulk of the UO 2prefers to be hypostoichiometric, although the surface is near-stoichiometric.« less

Near surface stoichiometry in UO 2: A density functional theory study

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

Yu, Jianguo; Valderrama, Billy; Henderson, Hunter B.

2015-08-01

The mechanisms of oxygen stoichiometry variation in UO 2 at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO 2 near surface and defect effects of near surface on stoichiometry in which the system can exchange atoms with the external reservoir. In this study, the near (110) surface relaxation and stoichiometry in UO 2 have been studied with density functional theory (DFT) calculations. On the basis of the point-defect model (PDM), a general expression for the nearmore » surface stoichiometric variation is derived by using DFT total-energy calculations and atomistic thermodynamics, in an attempt to pin down the mechanisms of oxygen exchange between the gas environment and defected UO 2. By using the derived expression, it is observed that, under poor oxygen conditions, the stoichiometry of near surface is switched from hyperstoichiometric at 300 K with a depth around 3 nm to near-stoichiometric at 1000 K and hypostoichiometric at 2000 K. Furthermore, at very poor oxygen concentrations and high temperatures, our results also suggest that the bulk of the UO 2 prefers to be hypostoichiometric, although the surface is near-stoichiometric.« less

Personal and Environmental Resources Mediate the Positivity-Emotional Dysfunction Relationship.

PubMed

Lehrer, H Matthew; Janus, Katherine C; Gloria, Christian T; Steinhardt, Mary A

2017-03-01

We investigated the relationships among positivity, perceived personal and environmental resources, and emotional dysfunction in adolescent girls. We hypothesized that perceived resources would mediate the relationship between positivity and emotional dysfunction. Participants (N = 510) attending an all-girls public school completed a survey assessing emotional dysfunction (depressive symptoms and perceived stress), positivity (positive/negative emotions), and personal/ environmental resources (resilience, hope, percent adaptive coping, community connectedness, social support, and school connectedness). Perceived resources were combined into one latent variable, and structural equation modeling tested the mediating effect of perceived resources on the relationship between positivity and emotional dysfunction. The model accounted for 63% of the variance in emotional dysfunction. Positivity exerted a significant direct effect on emotional dysfunction (β = -.14, p < .01), but its influence was primarily mediated through perceived resources (indirect effect: β = -.43, p < .001). The impact of positivity on emotional dysfunction is primarily but not entirely mediated by perceived personal and environmental resources. Schools should consider strategies to enhance experiences of positive emotions and/or decrease experiences of negative emotions, in conjunction with encouraging student awareness and development of personal and environmental resources.

Determination of Reaction Stoichiometries by Flow Injection Analysis.

ERIC Educational Resources Information Center

Rios, Angel; And Others

1986-01-01

Describes a method of flow injection analysis intended for calculation of complex-formation and redox reaction stoichiometries based on a closed-loop configuration. The technique is suitable for use in undergraduate laboratories. Information is provided for equipment, materials, procedures, and sample results. (JM)

Lesson from the stoichiometry determination of the cohesin complex: a short protease mediated elution increases the recovery from cross-linked antibody-conjugated beads.

PubMed

Holzmann, Johann; Fuchs, Johannes; Pichler, Peter; Peters, Jan-Michael; Mechtler, Karl

2011-02-04

Affinity purification of proteins using antibodies coupled to beads and subsequent mass spectrometric analysis has become a standard technique for the identification of protein complexes. With the recent transfer of the isotope dilution mass spectrometry principle (IDMS) to the field of proteomics, quantitative analyses-such as the stoichiometry determination of protein complexes-have become achievable. Traditionally proteins were eluted from antibody-conjugated beads using glycine at low pH or using diluted acids such as HCl, TFA, or FA, but elution was often found to be incomplete. Using the cohesin complex and the anaphase promoting complex/cyclosome (APC/C) as examples, we show that a short 15-60 min predigestion with a protease such as LysC (modified on-bead digest termed protease elution) increases the elution efficiency 2- to 3-fold compared to standard acid elution protocols. While longer incubation periods-as performed in standard on-bead digestion-led to partial proteolysis of the cross-linked antibodies, no or only insignificant cleavage was observed after 15-60 min protease mediated elution. Using the protease elution method, we successfully determined the stoichiometry of the cohesin complex by absolute quantification of the four core subunits using LC-SRM analysis and 19 reference peptides generated with the EtEP strategy. Protease elution was 3-fold more efficient compared to HCl elution, but measurements using both elution techniques are in agreement with a 1:1:1:1 stoichiometry. Furthermore, using isoform specific reference peptides, we determined the exact STAG1:STAG2 stoichiometry within the population of cohesin complexes. In summary, we show that the protease elution protocol increases the recovery from affinity beads and is compatible with quantitative measurements such as the stoichiometry determination of protein complexes.

Mood state dependency of dysfunctional attitudes in bipolar affective disorder.

PubMed

Babakhani, Anet; Startup, Mike

2012-01-01

Studies of cognitive styles among euthymic people with bipolar affective disorder (BAD) without use of mood induction techniques to access those cognitive styles give misleading impressions of normality of those cognitions. The aim of this study was to assess dysfunctional attitudes of participants with BAD, and control participants with no previous psychiatric histories, after mood inductions. Sad and happy moods were induced within 49 BAD and 37 controls. Dysfunctional attitudes were measured following mood inductions using the Dysfunctional Attitude Scale-short form (DAS-24), which has three subscales of achievement, interpersonal, and goal attainment. It was hypothesised that within BAD the sad mood induction would help in accessing dysfunctional attitudes in all three domains relative to the happy mood induction. This was supported. It was also hypothesised that the mood inductions would not affect dysfunctional attitudes within controls. This was supported. When diagnosis was entered as a between group variable, achievement dysfunctional attitudes were significantly higher in BAD compared to controls after a happy induction. Both sad and happy moods provoked higher levels of dysfunctional attitudes within BAD. Euphoria may be related to elevated achievement dysfunctional attitudes, raising risk for mania.

The relative availability of inorganic carbon and inorganic nitrogen influences the response of the dinoflagellate Protoceratium reticulatum to elevated CO2.

PubMed

Pierangelini, Mattia; Raven, John A; Giordano, Mario

2017-04-01

This work originates from three facts: (i) changes in CO 2 availability influence metabolic processes in algal cells; (ii) Spatial and temporal variations of nitrogen availability cause repercussions on phytoplankton physiology; (iii) Growth and cell composition are dependent on the stoichiometry of nutritional resources. In this study, we assess whether the impact of rising pCO 2 is influenced by N availability, through the impact that it would have on the C/N stoichiometry, in conditions of N sufficiency. Our experiments used the dinoflagellate Protoceratium reticulatum, which we cultured under three CO 2 regimes (400, 1,000, and 5,000 ppmv, pH of 8.1) and either variable (the NO 3 - concentration was always 2.5 mmol · L -1 ) or constant (NO 3 - concentration varied to maintain the same C i /NO 3 - ratio at all pCO 2 ) C i /NO 3 - ratio. Regardless of N availability, cells had higher specific growth rates, but lower cell dry weight and C and N quotas, at elevated CO 2 . The carbohydrate pool size and the C/N was unaltered in all treatments. The lipid content only decreased at high pCO 2 at constant C i /NO 3 - ratio. In the variable C i /NO 3 - conditions, the relative abundance of Rubisco (and other proteins) also changed; this did not occur at constant C i /NO 3 - . Thus, the biomass quality of P. reticulatum for grazers was affected by the C i /NO 3 - ratio in the environment and not only by the pCO 2 , both with respect to the size of the main organic pools and the composition of the expressed proteome. © 2016 Phycological Society of America.

Non-Redfield, nutrient synergy and flexible internal elemental stoichiometry in a marine bacterium

PubMed Central

Trautwein, Kathleen; Feenders, Christoph; Hulsch, Reiner; Ruppersberg, Hanna S.; Strijkstra, Annemieke; Kant, Mirjam; Vagts, Jannes; Wünsch, Daniel; Michalke, Bernhard; Maczka, Michael; Schulz, Stefan; Hillebrand, Helmut; Blasius, Bernd

2017-01-01

Abstract The stoichiometric constraints of algal growth are well understood, whereas there is less knowledge for heterotrophic bacterioplankton. Growth of the marine bacterium Phaeobacter inhibens DSM 17395, belonging to the globally distributed Roseobacter group, was studied across a wide concentration range of NH4+ and PO43−. The unique dataset covers 415 different concentration pairs, corresponding to 207 different molar N:P ratios (from 10−2 to 105). Maximal growth (by growth rate and biomass yield) was observed within a restricted concentration range at N:P ratios (∼50−120) markedly above Redfield. Experimentally determined growth parameters deviated to a large part from model predictions based on Liebig's law of the minimum, thus implicating synergistic co-limitation due to biochemical dependence of resources. Internal elemental ratios of P. inhibens varied with external nutrient supply within physiological constraints, thus adding to the growing evidence that aquatic bacteria can be flexible in their internal elemental composition. Taken together, the findings reported here revealed that P. inhibens is well adapted to fluctuating availability of inorganic N and P, expected to occur in its natural habitat (e.g. colonized algae, coastal areas). Moreover, this study suggests that elemental variability in bacterioplankton needs to be considered in the ecological stoichiometry of the oceans. PMID:28486660

Non-Redfield, nutrient synergy and flexible internal elemental stoichiometry in a marine bacterium.

PubMed

Trautwein, Kathleen; Feenders, Christoph; Hulsch, Reiner; Ruppersberg, Hanna S; Strijkstra, Annemieke; Kant, Mirjam; Vagts, Jannes; Wünsch, Daniel; Michalke, Bernhard; Maczka, Michael; Schulz, Stefan; Hillebrand, Helmut; Blasius, Bernd; Rabus, Ralf

2017-05-01

The stoichiometric constraints of algal growth are well understood, whereas there is less knowledge for heterotrophic bacterioplankton. Growth of the marine bacterium Phaeobacter inhibens DSM 17395, belonging to the globally distributed Roseobacter group, was studied across a wide concentration range of NH4+ and PO43-. The unique dataset covers 415 different concentration pairs, corresponding to 207 different molar N:P ratios (from 10-2 to 105). Maximal growth (by growth rate and biomass yield) was observed within a restricted concentration range at N:P ratios (∼50-120) markedly above Redfield. Experimentally determined growth parameters deviated to a large part from model predictions based on Liebig's law of the minimum, thus implicating synergistic co-limitation due to biochemical dependence of resources. Internal elemental ratios of P. inhibens varied with external nutrient supply within physiological constraints, thus adding to the growing evidence that aquatic bacteria can be flexible in their internal elemental composition. Taken together, the findings reported here revealed that P. inhibens is well adapted to fluctuating availability of inorganic N and P, expected to occur in its natural habitat (e.g. colonized algae, coastal areas). Moreover, this study suggests that elemental variability in bacterioplankton needs to be considered in the ecological stoichiometry of the oceans. © FEMS 2017.

Oxygen transport in off-stoichiometric uranium dioxide mediated by defect clustering dynamics

DOE PAGES

Yu, Jianguo; Bai, Xian -Ming; El-Azab, Anter; ...

2015-03-05

In this study, oxygen transport is central to many properties of oxides such as stoichiometric changes, phase transformation and ionic conductivity. In this paper, we report a mechanism for oxygen transport in uranium dioxide (UO 2) in which the kinetics is mediated by defect clustering dynamics. In particular, the kinetic Monte Carlo (KMC) method has been used to investigate the kinetics of oxygen transport in UO 2 under the condition of creation and annihilation of oxygen vacancies and interstitials as well as oxygen interstitial clustering, with variable offstoichiometry and temperature conditions. It is found that in hypo-stoichiometric UO 2-x, oxygenmore » transport is well described by the vacancy diffusion mechanism while in hyper-stoichiometric UO 2+x, oxygen interstitial cluster diffusion contributes significantly to oxygen transport kinetics, particularly at high temperatures and high off-stoichiometry levels. It is also found that diinterstitial clusters and single interstitials play dominant roles in oxygen diffusion while other larger clusters have negligible contributions. However, the formation, coalescence and dissociation of these larger clusters indirectly affects the overall oxygen diffusion due to their interactions with mono and di-interstitials, thus providing a explanation of the experimental observation of saturation or even drop of oxygen diffusivity at high off-stoichiometry.« less

Tuning optical absorption and photoexcited recombination dynamics in La1-xSrxFeO3-δ through A-site substitution and oxygen vacancies

NASA Astrophysics Data System (ADS)

Smolin, Sergey; Scafetta, Mark; Choquette, Amber; Sfeir, Matthew; Baxter, Jason; May, Steven

We study optical absorption and recombination dynamics in La1-xSrxFeO3-δ thin films, uncovering the effects of tuning nominal Fe valence via A-site substitution and oxygen stoichiometry. Variable angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy, revealing similar nanosecond photoexcited carrier lifetimes for oxygen deficient and stoichiometric films with the same nominal Fe valence. These results demonstrate that while the static optical absorption is strongly dependent on Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in the recombination kinetics. Nsf: ECCS-1201957, MRI DMR-0922929, MRI DMR-1040166. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

What Is Chemical Stoichiometry?

ERIC Educational Resources Information Center

Smith, William R.; Missen, Ronald W.

1979-01-01

Chemical stoichiometry is discussed free from kinetic or thermodynamic considerations. The means for determining the following are presented: the number of stoichiometric degrees of freedom, the number of components, a permissible set of chemical equations, and a permissible set of components, for a closed system undergoing chemical reaction.…

"Why not stoichiometry" versus "stoichiometry--why not?" Part I: General context.

PubMed

Michałowska-Kaczmarczyk, Anna Maria; Asuero, Agustin G; Michałowski, Tadeusz

2015-01-01

The elementary concepts involved with stoichiometry are considered from different viewpoints. Some examples of approximate calculations made according to the stoichiometric scheme are indicated, and correct resolution of the problems involved is presented. The principles of balancing chemical equations, based on their apparent similarities with algebraic equations, are criticized. The review concerns some peculiarities inherent in chemical reaction notation and its use (and abuse) in stoichiometric calculations that provide inconsistent results for various reasons. This "conventional" approach to stoichiometry is put in context with the generalized approach to electrolytic systems (GATES) established by Michałowski. The article contains a number of proposals that could potentially be taken into account and included in the next edition of the Orange Book. Notation of ions used in this article is not, deliberately, in accordance with actual IUPAC requirements in this respect. This article is intended to be provocative with the hope that some critical debate around the important topics treated should be generated and creatively expanded in the scientific community.

Treatment efficiency and stoichiometry of a high-strength graywater.

PubMed

Morse, Audra; Khatri, Sukrut; Jackson, W Andrew

2007-12-01

The transit mission wastewater may represent a future graywater, in which toilet waste is separated from other household waste streams, and dilution water is minimal. A loading rate study indicated that denitrification is stoichiometrically limited, and nitrification was kinetically limited. Denitrification stoichiometry was developed by deriving hypothetical molecular formulas of organic carbon inputs to be represented by the relative proportions of carbon, hydrogen, oxygen, and nitrogen. The derived stoichiometry was validated against experimental data by adjusting the values of fe and fs and multiplying the total dissolved organic carbon loss across the system by the overall R equation and then comparing the total nitrogen removed in the reaction to experimentally observed total nitrogen removal. The nitrification stoichiometry was similarly validated by multiplying the R equation by the ammonium-nitrogen removed and then comparing the NO(x)-N formed in the equation to actual NO(x)-N production values. The fs values for the denitrifying and nitrifying bacteria were 0.33 and 0.15, respectively.

Stoichiometry patterns in the androdioecious Acer tegmentosum

PubMed Central

Zhang, Xinna; Yao, Jie; Fan, Chunyu; Tan, Lingzhao; Zhang, Chunyu; Wang, Juan; Zhao, Xiuhai; von Gadow, Klaus

2016-01-01

This study evaluates stoichiometry patterns in the androdioecious Acer tegmentosum, a species characterized by a rare reproductive system where males and hermaphrodites coexist. Altogether 31 hermaphrodites and 29 male plants were harvested and samples of leaves, current-year shoots, branches and coarse roots were analyzed to explore gender differences in biomass, C, N and P concentrations of these four components. The nitrogen to phosphorus relationship of each component was examined using SMA estimates. Males had significantly greater amounts of leaf and coarse root dry matter content than hermaphrodites. C, N and P stoichiometry differed significantly between genders, especially in the newly emerging vegetative components (leaves and shoots). Males had higher C/N and C/P ratios in current-year shoots and lower C/P ratios in leaves and branches. Hermaphrodites had higher N/P ratios in the leaves and branches. Males had higher rates of increase in leaf P content than hermaphrodites. This study suggests that stoichiometry patterns may be significantly affected by gender. PMID:27725739

Stoichiometry for α-bungarotoxin block of α7 acetylcholine receptors

NASA Astrophysics Data System (ADS)

Dacosta, Corrie J. B.; Free, Chris R.; Sine, Steven M.

2015-08-01

α-Bungarotoxin (α-Btx) binds to the five agonist binding sites on the homopentameric α7-acetylcholine receptor, yet the number of bound α-Btx molecules required to prevent agonist-induced channel opening remains unknown. To determine the stoichiometry for α-Btx blockade, we generate receptors comprised of wild-type and α-Btx-resistant subunits, tag one of the subunit types with conductance mutations to report subunit stoichiometry, and following incubation with α-Btx, monitor opening of individual receptor channels with defined subunit stoichiometry. We find that a single α-Btx-sensitive subunit confers nearly maximal suppression of channel opening, despite four binding sites remaining unoccupied by α-Btx and accessible to the agonist. Given structural evidence that α-Btx locks the agonist binding site in an inactive conformation, we conclude that the dominant mechanism of antagonism is non-competitive, originating from conformational arrest of the binding sites, and that the five α7 subunits are interdependent and maintain conformational symmetry in the open channel state.

A Method to Determine Lysine Acetylation Stoichiometries

DOE PAGES

Nakayasu, Ernesto S.; Wu, Si; Sydor, Michael A.; ...

2014-01-01

Lysine acetylation is a common protein posttranslational modification that regulates a variety of biological processes. A major bottleneck to fully understanding the functional aspects of lysine acetylation is the difficulty in measuring the proportion of lysine residues that are acetylated. Here we describe a mass spectrometry method using a combination of isotope labeling and detection of a diagnostic fragment ion to determine the stoichiometry of protein lysine acetylation. Using this technique, we determined the modification occupancy for ~750 acetylated peptides from mammalian cell lysates. Furthermore, the acetylation on N-terminal tail of histone H4 was cross-validated by treating cells with sodiummore » butyrate, a potent deacetylase inhibitor, and comparing changes in stoichiometry levels measured by our method with immunoblotting measurements. Of note we observe that acetylation stoichiometry is high in nuclear proteins, but very low in mitochondrial and cytosolic proteins. In summary, our method opens new opportunities to study in detail the relationship of lysine acetylation levels of proteins with their biological functions.« less

Mammalian complex I pumps 4 protons per 2 electrons at high and physiological proton motive force in living cells.

PubMed

Ripple, Maureen O; Kim, Namjoon; Springett, Roger

2013-02-22

Mitochondrial complex I couples electron transfer between matrix NADH and inner-membrane ubiquinone to the pumping of protons against a proton motive force. The accepted proton pumping stoichiometry was 4 protons per 2 electrons transferred (4H(+)/2e(-)) but it has been suggested that stoichiometry may be 3H(+)/2e(-) based on the identification of only 3 proton pumping units in the crystal structure and a revision of the previous experimental data. Measurement of proton pumping stoichiometry is challenging because, even in isolated mitochondria, it is difficult to measure the proton motive force while simultaneously measuring the redox potentials of the NADH/NAD(+) and ubiquinol/ubiquinone pools. Here we employ a new method to quantify the proton motive force in living cells from the redox poise of the bc(1) complex measured using multiwavelength cell spectroscopy and show that the correct stoichiometry for complex I is 4H(+)/2e(-) in mouse and human cells at high and physiological proton motive force.

Stoichiometry of Cd(S,Se) nanocrystals by anomalous small-angle x-ray scattering

NASA Astrophysics Data System (ADS)

Ramos, Aline; Lyon, Olivier; Levelut, Claire

1995-12-01

In Cd(S,Se)-doped glasses the optical properties are strongly dependent on the size of the nanocrystals, but can be also largely modified by changes in the crystal stoichiometry; however, the information on both stoichiometry and size is difficult to obtain in crystals smaller than 10 nm. The intensity scattered at small angles is classically used to get information about nanoparticles sizes. Moreover the variation of amplitude of this intensity with the energy of the x ray—``the anomalous effect''—near the selenium edge is related to stoichiometry. Anomalous small-angle x-ray scattering has been used as a tentative method to get information about stoichiometry in nanocrystals with size lower than 10 nm. Experiments have been performed on samples treated for 2 days at temperatures in the range 540-650 °C. The samples treated at temperatures above 580 °C contain crystals with size larger than 4 nm. For all these samples the anomalous effect has nearly the same amplitude, and we found the stoichiometry x=0.4 for the CdSxSe1-x nanocrystals. This agrees with the previous results obtained by scanning electron microscopy and Raman spectroscopy. The results are also confirmed by measurements of the position of the optical absorption edge and by wide-angle x-ray scattering experiments. For the sample treated at 560 °C, the nanocrystal size is 3 nm and the stoichiometry x=0.6 is deduced from the anomalous effect. For samples treated at lower temperatures the anomalous effect is not observable, indicating an even lower selenium content in the nanocrystals (x≳0.7). We observed differences in the Se content of nanocrystals for different heat treatments of the same initial glass. These results may be very helpful to interpret the change in the optical properties when the temperature of the treatments decreases in the range 560-590 °C. In this temperature range, compositional effects seem to be of the same order of magnitude as the effects of the quantum confinement.

Utility of Time and Frequency Domain Parameters of Heart Rate Variability in the Context of Autonomic Disorders Characterized by Orthostatic Dysfunction.

PubMed

Baker, Jacquie; Racosta, Juan M; Balint, Brittany; Kimpinski, Kurt

2018-03-01

The clinical significance of heart rate variability in the context of autonomic dysfunction continues to be a matter of debate. A consensus is lacking on the best heart rate variability measures for clinical purposes. Therefore, the purpose of this study was to investigate the utility of heart rate variability parameters in healthy versus autonomic dysfunction. Healthy young (n = 134), healthy older (n = 32), and patients with mild (postural tachycardia syndrome; n = 25) and severe (neurogenic orthostatic hypotension; n = 34) autonomic dysfunction were included. Time and frequency parameters during baseline, head-up tilt (HUT), and heart rate response to deep breathing (HRDB) were compared. Cardiovagal time parameters were significantly reduced during HUT in healthy young and postural tachycardia syndrome (P < 0.001). Healthy young had significantly higher time parameters during baseline, HUT, and HRDB (P < 0.01). This was reflected by a significantly lower resting heart rate (HR) (61.4 ± 9.0 bpm vs. 76.8 ± 13.6 bpm; P < 0.001) and a smaller [INCREMENT]HR during HUT (32.8 ± 10.5 bpm vs. 44.4 ± 13.3 bpm; P < 0.001). Time parameters increased in young and postural tachycardia syndrome during HRDB, which was characterized by a nonsignificant difference in [INCREMENT]HR between both groups. Time parameters were significantly higher in healthy old versus neurogenic orthostatic hypotension at rest and during HRDB (P < 0.05). During HUT, only the SD of all normal RR intervals remained significantly higher. Heart rate changes corroborated these findings. Resting HR was significantly lower in healthy older (62.6 ± 11.0 bpm vs. 70.7 ± 12.4 bpm), and [INCREMENT]HR during HRDB was significantly higher (15.9 ± 9.2 bpm vs. 3.9 ± 4.2 bpm; P < 0.001). During HUT, [INCREMENT]HR showed no significant differences. Time domain parameters of heart rate variability have a greater utility than frequency parameters in clinical autonomic disorders.

Crystal growth of GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.; Pawlowicz, L. M.; Dabkowski, F.; Li, C. J.

1984-01-01

It is shown that stoichiometry variations in the GaAs melt during growth constitute the most critical parameter regarding defect formations and their interactions; this defect structure determines all relevant characteristics of GaAs. Convection in the melt leads to stoichiometric variations. Growth in axial magnetic fields reduces convection and permits the study of defect structure. In order to control stoichiometry in space and to accommodate expansion during solidification, a partially confined configuration was developed. A triangular prism is employed to contain the growth melt. This configuration permits the presence of the desired vapor phase in contact with the melt for controlling the melt stoichiometry.

Ghanaian Teacher Trainees' Conceptual Understanding of Stoichiometry

ERIC Educational Resources Information Center

Hanson, Ruby

2015-01-01

Chemical stoichiometry is a conceptual framework that encompasses other concepts such as the mole, writing of chemical equations in word and representative form, balancing of equations and the equilibrium concept. The underlying concepts enable students to understand relationships among entities of matter and required amounts for use when…

Ghanaian Teacher Trainees' Conceptual Understanding of Stoichiometry

ERIC Educational Resources Information Center

Hanson, Ruby

2016-01-01

Chemical stoichiometry is a conceptual framework that encompasses other concepts such as the mole, writing of chemical equations in word and representative form, balancing of equations and the equilibrium concept. The underlying concepts enable students to understand relationships among entities of matter and required amounts for use when…

Ecoenzymatic Stoichiometry of Stream Sediments with Comparison to Terrestrial Soils

EPA Science Inventory

In this study, we extend the development of ecoenzymatic stoichiometry to the surface sediments of stream ecosystems using data collected in a nationwide survey. The data set is larger and more comprehensive than those used in our previous studies. The data include the first broa...

Legume Shrubs Are More Nitrogen-Homeostatic than Non-legume Shrubs

PubMed Central

Guo, Yanpei; Yang, Xian; Schöb, Christian; Jiang, Youxu; Tang, Zhiyao

2017-01-01

Legumes are characterized as keeping stable nutrient supply under nutrient-limited conditions. However, few studies examined the legumes' stoichiometric advantages over other plants across various taxa in natural ecosystems. We explored differences in nitrogen (N) and phosphorus (P) stoichiometry of different tissue types (leaf, stem, and root) between N2-fixing legume shrubs and non-N2-fixing shrubs from 299 broadleaved deciduous shrubland sites in northern China. After excluding effects of taxonomy and environmental variables, these two functional groups differed considerably in nutrient regulation. N concentrations and N:P ratios were higher in legume shrubs than in non-N2-fixing shrubs. N concentrations were positively correlated between the plants and soil for non-N2-fixing shrubs, but not for legume shrubs, indicating a stronger stoichiometric homeostasis in legume shrubs than in non-N2-fixing shrubs. N concentrations were positively correlated among three tissue types for non-N2-fixing shrubs, but not between leaves and non-leaf tissues for legume shrubs, demonstrating that N concentrations were more dependent among tissues for non-N2-fixing shrubs than for legume shrubs. N and P concentrations were correlated within all tissues for both functional groups, but the regression slopes were flatter for legume shrubs than non-N2-fixing shrubs, implying that legume shrubs were more P limited than non-N2-fixing shrubs. These results address significant differences in stoichiometry between legume shrubs and non-N2-fixing shrubs, and indicate the influence of symbiotic nitrogen fixation (SNF) on plant stoichiometry. Overall, N2-fixing legume shrubs are higher and more stoichiometrically homeostatic in N concentrations. However, due to excess uptake of N, legumes may suffer from potential P limitation. With their N advantage, legume shrubs could be good nurse plants in restoration sites with degraded soil, but their P supply should be taken care of during management according to our results. PMID:29018468

Legume Shrubs Are More Nitrogen-Homeostatic than Non-legume Shrubs.

PubMed

Guo, Yanpei; Yang, Xian; Schöb, Christian; Jiang, Youxu; Tang, Zhiyao

2017-01-01

Legumes are characterized as keeping stable nutrient supply under nutrient-limited conditions. However, few studies examined the legumes' stoichiometric advantages over other plants across various taxa in natural ecosystems. We explored differences in nitrogen (N) and phosphorus (P) stoichiometry of different tissue types (leaf, stem, and root) between N 2 -fixing legume shrubs and non-N 2 -fixing shrubs from 299 broadleaved deciduous shrubland sites in northern China. After excluding effects of taxonomy and environmental variables, these two functional groups differed considerably in nutrient regulation. N concentrations and N:P ratios were higher in legume shrubs than in non-N 2 -fixing shrubs. N concentrations were positively correlated between the plants and soil for non-N 2 -fixing shrubs, but not for legume shrubs, indicating a stronger stoichiometric homeostasis in legume shrubs than in non-N 2 -fixing shrubs. N concentrations were positively correlated among three tissue types for non-N 2 -fixing shrubs, but not between leaves and non-leaf tissues for legume shrubs, demonstrating that N concentrations were more dependent among tissues for non-N 2 -fixing shrubs than for legume shrubs. N and P concentrations were correlated within all tissues for both functional groups, but the regression slopes were flatter for legume shrubs than non-N 2 -fixing shrubs, implying that legume shrubs were more P limited than non-N 2 -fixing shrubs. These results address significant differences in stoichiometry between legume shrubs and non-N 2 -fixing shrubs, and indicate the influence of symbiotic nitrogen fixation (SNF) on plant stoichiometry. Overall, N 2 -fixing legume shrubs are higher and more stoichiometrically homeostatic in N concentrations. However, due to excess uptake of N, legumes may suffer from potential P limitation. With their N advantage, legume shrubs could be good nurse plants in restoration sites with degraded soil, but their P supply should be taken care of during management according to our results.

An Analysis of Diet Quality, How It Controls Fatty Acid Profiles, Isotope Signatures and Stoichiometry in the Malaria Mosquito Anopheles arabiensis

PubMed Central

Hood-Nowotny, Rebecca; Schwarzinger, Bettina; Schwarzinger, Clemens; Soliban, Sharon; Madakacherry, Odessa; Aigner, Martina; Watzka, Margarete; Gilles, Jeremie

2012-01-01

Background Knowing the underlying mechanisms of mosquito ecology will ensure effective vector management and contribute to the overall goal of malaria control. Mosquito populations show a high degree of population plasticity in response to environmental variability. However, the principle factors controlling population size and fecundity are for the most part unknown. Larval habitat and diet play a crucial role in subsequent mosquito fitness. Developing the most competitive insects for sterile insect technique programmes requires a “production” orientated perspective, to deduce the most effective larval diet formulation; the information gained from this process offers us some insight into the mechanisms and processes taking place in natural native mosquito habitats. Methodology/Principal Findings Fatty acid profiles and de-novo or direct assimilation pathways, of whole-individual mosquitoes reared on a range of larval diets were determined using pyrolysis gas chromatograph/mass spectrometry. We used elemental analysis and isotope ratio mass spectrometry to measure individual-whole-body carbon, nitrogen and phosphorous values and to assess the impact of dietary quality on subsequent population stoichiometry, size, quality and isotopic signature. Diet had the greatest impact on fatty acid (FA) profiles of the mosquitoes, which exhibited a high degree of dietary routing, characteristic of generalist feeders. De-novo synthesis of a number of important FAs was observed. Mosquito C:N stoichiometry was fixed in the teneral stage. Dietary N content had significant influence on mosquito size, and P was shown to be a flexible pool which limited overall population size. Conclusions/Significance Direct routing of FAs was evident but there was ubiquitous de-novo synthesis suggesting mosquito larvae are competent generalist feeders capable of survival on diet with varying characteristics. It was concluded that nitrogen availability in the larval diet controlled teneral mosquito size and that teneral CN ratio is a sex- and species-specific fixed parameter. This finding has significant implications for overall mosquito competitiveness and environmental management. PMID:23133509

Simultaneous shifts in elemental stoichiometry and fatty acids of Emiliania huxleyi in response to environmental changes

NASA Astrophysics Data System (ADS)

Bi, Rong; Ismar, Stefanie M. H.; Sommer, Ulrich; Zhao, Meixun

2018-02-01

Climate-driven changes in environmental conditions have significant and complex effects on marine ecosystems. Variability in phytoplankton elements and biochemicals can be important for global ocean biogeochemistry and ecological functions, while there is currently limited understanding on how elements and biochemicals respond to the changing environments in key coccolithophore species such as Emiliania huxleyi. We investigated responses of elemental stoichiometry and fatty acids (FAs) in a strain of E. huxleyi under three temperatures (12, 18 and 24 °C), three N : P supply ratios (molar ratios 10:1, 24:1 and 63:1) and two pCO2 levels (560 and 2400 µatm). Overall, C : N : P stoichiometry showed the most pronounced response to N : P supply ratios, with high ratios of particulate organic carbon vs. particulate organic nitrogen (POC : PON) and low ratios of PON vs. particulate organic phosphorus (PON : POP) in low-N media, and high POC : POP and PON : POP in low-P media. The ratio of particulate inorganic carbon vs. POC (PIC : POC) and polyunsaturated fatty acid proportions strongly responded to temperature and pCO2, both being lower under high pCO2 and higher with warming. We observed synergistic interactions between warming and nutrient deficiency (and high pCO2) on elemental cellular contents and docosahexaenoic acid (DHA) proportion in most cases, indicating the enhanced effect of warming under nutrient deficiency (and high pCO2). Our results suggest differential sensitivity of elements and FAs to the changes in temperature, nutrient availability and pCO2 in E. huxleyi, which is to some extent unique compared to non-calcifying algal classes. Thus, simultaneous changes of elements and FAs should be considered when predicting future roles of E. huxleyi in the biotic-mediated connection between biogeochemical cycles, ecological functions and climate change.

Changing nutrient stoichiometry affects phytoplankton production, DOP build up and dinitrogen fixation - a mesocosm experiment in the eastern tropical North Atlantic

NASA Astrophysics Data System (ADS)

Meyer, J.; Löscher, C. R.; Neulinger, S. C.; Reichel, A. F.; Loginova, A.; Borchard, C.; Schmitz, R. A.; Hauss, H.; Kiko, R.; Riebesell, U.

2015-07-01

Ocean deoxygenation due to climate change may alter redox-sensitive nutrient cycles in the marine environment. The productive eastern tropical North Atlantic (ETNA) upwelling region may be particularly affected when the relatively moderate oxygen minimum zone (OMZ) deoxygenates further and microbially-driven nitrogen (N) loss processes are promoted. Consequently, water masses with a low N : P ratio could reach the euphotic layer, possibly influencing primary production in those waters. Previous mesocosm studies in the oligotrophic Atlantic Ocean identified N availability as controlling of primary production, while a possible co-limitation of nitrate and phosphate (P) could not be ruled out. To better understand the impact of changing N : P ratios on primary production and on N2 fixation in the ETNA surface ocean, we conducted land-based mesocosm experiments with natural plankton communities and applied a broad range of N : P ratios (2.67-48). Silicate was supplied at 15 μmol L-1 in all mesocosms. We monitored nutrient drawdown, bloom formation, biomass build up and diazotrophic feedback in response to variable nutrient stoichiometry. Our results confirmed N to be limiting to primary production. We found that excess P was channeled through particulate organic matter (POP) into the dissolved organic matter (DOP) pool. In mesocosms with low P availability, DOP was utilized while N2 fixation increased, suggesting a link between those two processes. Interestingly this observation was most pronounced in mesocosms where inorganic N was still available, indicating that bioavailable N does not necessarily has to have a negative impact on N2 fixation. We observed a shift from a mixed cyanobacterial/proteobacterial dominated active diazotrophic community towards diazotrophic diatom symbionts of the Richelia-Rhizosolenia symbiosis. We hypothesize that a potential change in nutrient stoichiometry in the ETNA might lead to a general shift within the diazotrophic community, potentially modifying primary productivity.

Changing nutrient stoichiometry affects phytoplankton production, DOP accumulation and dinitrogen fixation - a mesocosm experiment in the eastern tropical North Atlantic

NASA Astrophysics Data System (ADS)

Meyer, J.; Löscher, C. R.; Neulinger, S. C.; Reichel, A. F.; Loginova, A.; Borchard, C.; Schmitz, R. A.; Hauss, H.; Kiko, R.; Riebesell, U.

2016-02-01

Ocean deoxygenation due to climate change may alter redox-sensitive nutrient cycles in the marine environment. The productive eastern tropical North Atlantic (ETNA) upwelling region may be particularly affected when the relatively moderate oxygen minimum zone (OMZ) deoxygenates further and microbially driven nitrogen (N) loss processes are promoted. Consequently, water masses with a low nitrogen to phosphorus (N : P) ratio could reach the euphotic layer, possibly influencing primary production in those waters. Previous mesocosm studies in the oligotrophic Atlantic Ocean identified nitrate availability as a control of primary production, while a possible co-limitation of nitrate and phosphate could not be ruled out. To better understand the impact of changing N : P ratios on primary production and N2 fixation in the ETNA surface ocean, we conducted land-based mesocosm experiments with natural plankton communities and applied a broad range of N : P ratios (2.67-48). Silicic acid was supplied at 15 µmol L-1 in all mesocosms. We monitored nutrient drawdown, biomass accumulation and nitrogen fixation in response to variable nutrient stoichiometry. Our results confirmed nitrate to be the key factor determining primary production. We found that excess phosphate was channeled through particulate organic matter (POP) into the dissolved organic matter (DOP) pool. In mesocosms with low inorganic phosphate availability, DOP was utilized while N2 fixation increased, suggesting a link between those two processes. Interestingly this observation was most pronounced in mesocosms where nitrate was still available, indicating that bioavailable N does not necessarily suppress N2 fixation. We observed a shift from a mixed cyanobacteria-proteobacteria dominated active diazotrophic community towards a diatom-diazotrophic association of the Richelia-Rhizosolenia symbiosis. We hypothesize that a potential change in nutrient stoichiometry in the ETNA might lead to a general shift within the diazotrophic community, potentially influencing primary productivity and carbon export.

Cognitive complaints and predictors of perceived cognitive dysfunction in adults with major depressive disorder: Findings from the Cognitive Dysfunction in Asians with Depression (CogDAD) study.

PubMed

Srisurapanont, Manit; Mok, Yee Ming; Yang, Yen Kuang; Chan, Herng-Nieng; Della, Constantine D; Zainal, Nor Zuraida; Jambunathan, Stephen; Amir, Nurmiati; Kalita, Pranab

2018-05-01

Several studies have described the presence of perceived cognitive dysfunction amongst Asian patients with major depressive disorder (MDD). To date, no study has been conducted investigating the predictors of perceived cognitive dysfunction amongst Asian MDD patients. This was a post-hoc analysis of the Cognitive Dysfunction in Asian patients with Depression (CogDAD) study. Descriptive statistics were used to describe the most common cognitive complaints by patients. Univariate and multivariate analyses were performed to determine variables associated with perceived cognitive dysfunction (Perceived Deficit Questionnaire-Depression, PDQ-D). The CogDAD study population is comprised of MDD patients with mild-to-moderate depression (Patient Health Questionnaire 9-item [PHQ-9]: 11.3 ± 6.9) who reported perceived cognitive dysfunction (PDQ-D = 22.6 ± 16.2). The most common cognitive complaints were: mind drifting (42.3%), trouble making decision (39.6%) and trouble concentrating (38.0%). Predictors of perceived cognitive dysfunction were: being Southeast Asians (vs. Taiwanese) (p < 0.001), current episode longer than 8 weeks (vs. 1-8 weeks) (p < 0.05), the presence of disability (vs. no disability) (p < 0.05), younger age (p < 0.01), and higher PHQ-9 total scores (p < 0.001). The causal relationship between predictive variables and PDQ-D could not be tested due to the cross-sectional nature of the study. Furthermore, a neuropsychological test was not included in the CogDAD study and use of concomitant medications, including anti-depressants, could have impacted patient's perceived cognitive ability. The present study results suggest a potential role for subjective cognitive assessment in patients with MDD who are young, with long durations of depression or severe depression. Copyright © 2018 Elsevier B.V. All rights reserved.

The relationship between inotrope exposure, six-hour postoperative physiological variables, hospital mortality and renal dysfunction in patients undergoing cardiac surgery

PubMed Central

2011-01-01

Introduction Acute haemodynamic complications are common after cardiac surgery and optimal perioperative use of inotropic agents, typically guided by haemodynamic variables, remains controversial. The aim of this study was to examine the relationship of inotrope use to hospital mortality and renal dysfunction. Material and methods A retrospective cohort study of 1,326 cardiac surgery patients was carried out at two university-affiliated ICUs. Multivariable logistic regression analysis and propensity matching were performed to evaluate whether inotrope exposure was independently associated with mortality and renal dysfunction. Results Patients exposed to inotropes had a higher mortality rate than those not exposed. After adjusting for differences in Parsonnet score, left ventricular ejection fraction, perioperative intraaortic balloon pump use, bypass time, reoperation and cardiac index, inotrope exposure appeared to be independently associated with increased hospital mortality (adjusted odds ratio (OR) 2.3, 95% confidence interval (95% CI) 1.2 to 4.5) and renal dysfunction (adjusted OR 2.7, 95% CI 1.5 to 4.6). A propensity score-matched analysis similarly demonstrated that death and renal dysfunction were significantly more likely to occur in patients exposed to inotropes (P = 0.01). Conclusions Postoperative inotrope exposure was independently associated with worse outcomes in this cohort study. Further research is needed to better elucidate the appropriate use of inotropes in cardiac surgery. PMID:21736726

The impulsivity and sensation-seeking mediators of the psychological consequences of pathological gambling in adolescence.

PubMed

Estevez, Ana; Herrero-Fernández, David; Sarabia, Izaskun; Jauregui, Paula

2015-03-01

Pathological gambling has severe consequences for adolescents and their families and friends. Despite its high prevalence, pathological gambling in adolescents has been insufficiently studied. Sensation seeking and impulsivity are two variables that are related to the appearance and maintenance of pathological gambling. However, few studies have determined the role these variables play in the development of the dysfunctional symptomatology of gambling behavior in adolescents and young adults. The aims of this study were to analyze the consequences of gambling in young adults and adolescents, and to evaluate the roles of sensation seeking and impulsivity in the appearance of dysfunctional symptomatology. The sample consisted of 1,241 young adults and adolescents recruited from scholar centers and free-time groups, as well as 71 subjects from associations that assist pathological gamblers. Pathological gambling, impulsive behavior, dysfunctional symptomatology and sensation seeking were assessed. The results confirmed that young adults and adolescents who gamble pathologically have more dysfunctional symptomatology related to anxiety, depression, hostility, obsessive-compulsive behavior and somatization, as well as sensation seeking, impulsivity and addictive behavior. Moreover, the results showed that sensation seeking did not mediate the appearance of dysfunctional symptomatology and that impulsivity partially mediated the appearance of anxiety, phobic anxiety, depression and psychosis and perfectly mediated somatization, obsessive-compulsive behavior, interpersonal sensitivity, paranoid ideation and hostility. These results have consequences for the development of treatment and prevention programs for adolescent pathological gambling.

Sacral neuromodulation for the treatment of neurogenic lower urinary tract dysfunction caused by multiple sclerosis: a single-centre prospective series.

PubMed

Engeler, Daniel S; Meyer, Daniel; Abt, Dominik; Müller, Stefanie; Schmid, Hans-Peter

2015-10-23

Sacral neuromodulation is well established in the treatment of refractory, non-neurogenic lower urinary tract dysfunction, but its efficacy and safety in patients with lower urinary tract dysfunction of neurological origin is unclear. Only few case series have been reported for multiple sclerosis. We prospectively evaluated the efficacy and safety of sacral neuromodulation in patients with multiple sclerosis. Seventeen patients (13 women, 4 men) treated with sacral neuromodulation for refractory neurogenic lower urinary tract dysfunction caused by multiple sclerosis were prospectively enrolled (2007-2011). Patients had to have stable disease and confirmed neurogenic lower urinary tract dysfunction. Voiding variables, adverse events, and subjective satisfaction were assessed. Sixteen (94 %) patients had a positive test phase with a >70 % improvement. After implantation of the pulse generator (InterStim II), the improvement in voiding variables persisted. At 3 years, the median voided volume had improved significantly from 125 (range 0 to 350) to 265 ml (range 200 to 350) (p < 0.001), the post void residual from 170 (range 0 to 730) to 25 ml (range 0 to 300) (p = 0.01), micturition frequency from 12 (range 6 to 20) to 7 (range 4 to 12) (p = 0.003), and number of incontinence episodes from 3 (range 0 to 10) to 0 (range 0 to 1) (p = 0.006). The median subjective degree of satisfaction was 80 %. Only two patients developed lack of benefit. No major complications occurred. Chronic sacral neuromodulation promises to be an effective and safe treatment of refractory neurogenic lower urinary tract dysfunction in selected patients with multiple sclerosis.

Oxalate Synthesis and Pyrolysis: A Colorful Introduction to Stoichiometry

ERIC Educational Resources Information Center

Vannatta, Michael W.; Richards-Babb, Michelle; Sweeney, Robert J.

2010-01-01

Metal oxalate synthesis and pyrolysis provides an opportunity for students to (i) learn stoichiometry, (ii) experience the consequences of proper stoichiometric calculations and experimental techniques, and (iii) be introduced to the relevance of chemistry by highlighting oxalates in context, for example, usages and health effects. At our…

The Decomposition of Zinc Carbonate: Using Stoichiometry to Choose between Chemical Formulas

ERIC Educational Resources Information Center

DeMeo, Stephen

2004-01-01

The existence of different stoichiometries in two basic zinc carbonates helps to explain their decomposition potential, and to select between the two compound formulas, which better describes zinc carbonate. The accuracy of the experiment makes it a viable means for students to perform various quantitative measurements.

Novel Materials through Non-Hydrolytic Sol-Gel Processing: Negative Thermal Expansion Oxides and Beyond

PubMed Central

Lind, Cora; Gates, Stacy D.; Pedoussaut, Nathalie M.; Baiz, Tamam I.

2010-01-01

Low temperature methods have been applied to the synthesis of many advanced materials. Non-hydrolytic sol-gel (NHSG) processes offer an elegant route to stable and metastable phases at low temperatures. Excellent atomic level homogeneity gives access to polymorphs that are difficult or impossible to obtain by other methods. The NHSG approach is most commonly applied to the preparation of metal oxides, but can be easily extended to metal sulfides. Exploration of experimental variables allows control over product stoichiometry and crystal structure. This paper reviews the application of NHSG chemistry to the synthesis of negative thermal expansion oxides and selected metal sulfides.

Racial differences in sexual dysfunction among postdeployed Iraq and Afghanistan veterans

PubMed Central

Monawar Hosain, G. M.; Latini, David M.; Kauth, Micahel R.; Goltz, Heather Honoré; Helmer, Drew A.

2015-01-01

This study examined the racial/ethnic differences in prevalence and risk factors of sexual dysfunction among postdeployed Iraqi/Afghanistan veterans. A total of 3,962 recently deployed veterans were recruited from Houston Veterans Affairs medical center. The authors examined sociodemographic, medical, mental-health, and lifestyle-related variables. Sexual dysfunction was diagnosed by ICD9-CM code and/or medicines prescribed for sexual dysfunction. Analyses included chi-square, analysis of variance, and multivariate logistic regression. Sexual dysfunction was observed 4.7% in Whites, 7.9% in African Americans, and 6.3% in Hispanics. Age, marital status, smoking, and hypertension were risk factors for Whites, whereas age, marital status, posttraumatic stress disorder and hypertension were significant for African Americans. For Hispanics, only age and posttraumatic stress disorder were significant. This study identified that risk factors of sexual dysfunction varied by race/ethnicity. All postdeployed veterans should be screened; and psychosocial support and educational materials should address race/ethnicity-specific risk factors. PMID:23300201

New approach to control the methanogenic reactor of a two-phase anaerobic digestion system.

PubMed

von Sachs, Jürgen; Meyer, Ulrich; Rys, Paul; Feitkenhauer, Heiko

2003-03-01

A new control strategy for the methanogenic reactor of a two-phase anaerobic digestion system has been developed and successfully tested on the laboratory scale. The control strategy serves the purpose to detect inhibitory effects and to achieve good conversion. The concept is based on the idea that volatile fatty acids (VFA) can be measured in the influent of the methanogenic reactor by means of titration. Thus, information on the output (methane production) and input of the methanogenic reactor is available, and a (carbon) mass balance can be obtained. The control algorithm comprises a proportional/integral structure with the ratio of (a) the methane production rate measured online and (b) a maximum methane production rate expected (derived from the stoichiometry) as a control variable. The manipulated variable is the volumetric feed rate. Results are shown for an experiment with VFA (feed) concentration ramps and for experiments with sodium chloride as inhibitor.

Tadalafil reversal of sexual dysfunction caused by serotonin enhancing medications in women.

PubMed

Ashton, Adam Keller; Weinstein, Wendy

2006-01-01

Sexual dysfunction is a common side effect of many antidepressants, especially those that increase serotonin. Many strategies have been reported to assist patients in minimizing impairment, with variable degrees of success. One of the newer approaches is to augment with phosphodiesterase type-5 inhibitors. Our report using the most recently released agent in this class, tadalafil is the first demonstrating potential benefit in women. We report here of three women who derived benefit from using 20 mg of tadalafil before anticipated sexual activity to reverse medication-induced sexual dysfunction. Tadalafil utility was maintained over time and was well tolerated.

On Swedish women's distressing sexual dysfunctions: some concomitant conditions and life satisfaction.

PubMed

Oberg, Katarina; Sjögren Fugl-Meyer, Kerstin

2005-03-01

To explore the associations between women's distressing sexual dysfunctions and different aspects of life satisfaction together with women's concomitant socio-psychological characteristics. Thus, this descriptive article does not discuss causalities. A nationally representative sample of sexually active Swedish women aged 18-65 years in a heterosexual steady partner relationship participated in 1996 in a combined structured interview/questionnaire investigation. Personal sexual distress caused by low sexual interest, insufficient lubrication, orgasm dysfunction, dyspareunia, and vaginism was classified as manifest and mild. Concomitant conditions explored were perceived health, stability of domestic situation, perception of male partner's sexual functions/dysfunctions per se, and some socio-demographic factors. Satisfaction with life as a whole and with 10 different domains of life were reported by using the LiSat-11 checklist. Main results were that a multitude of the independent variables were univariately associated with manifest and, to a lesser extent, mild distressing sexual dysfunctions. This was particularly true for satisfaction with partner relationship and for male's sexual dysfunctions. By performing multiple logistic regressions, the numbers were markedly reduced. The resulting statistical models still contained sexual partner's sexual dysfunctions and satisfaction with partner relationship as dominant covariants of most distressing sexual dysfunctions. Reported low level of satisfaction with partner relationship and male sexual dysfunctions per se are likely to co-occur with manifest but, to a lesser extent, mild distressing sexual dysfunctions in Swedish women aged 18-65 years.

Teaching Lab Report Writing through Inquiry: A Green Chemistry Stoichiometry Experiment for General Chemistry

ERIC Educational Resources Information Center

Cacciatore, Kristen L.; Sevian, Hannah

2006-01-01

We present an alternative to a traditional first-year chemistry laboratory experiment. This experiment has four key features: students utilize stoichiometry, learn and apply principles of green chemistry, engage in authentic scientific inquiry, and discover why each part of a scientific lab report is necessary. The importance and essential…

Students' Understanding of Conservation of Matter, Stoichiometry and Balancing Equations in Indonesia

ERIC Educational Resources Information Center

Agung, Salamah; Schwartz, Marc S.

2007-01-01

This study examines Indonesian students' understanding of conservation of matter, balancing of equations and stoichiometry. Eight hundred and sixty-seven Grade 12 students from 22 schools across four different cities in two developed provinces in Indonesia participated in the study. Nineteen teachers also participated in order to validate the…

Students' Dilemmas in Reaction Stoichiometry Problem Solving: Deducing the Limiting Reagent in Chemical Reactions

ERIC Educational Resources Information Center

Chandrasegaran, A. L.; Treagust, David F.; Waldrip, Bruce G.; Chandrasegaran, Antonia

2009-01-01

A qualitative case study was conducted to investigate the understanding of the limiting reagent concept and the strategies used by five Year 11 students when solving four reaction stoichiometry problems. Students' written problem-solving strategies were studied using the think-aloud protocol during problem-solving, and retrospective verbalisations…

Thermometric titration of beta-aryl-alpha-mercaptopropenoic acids and determination of the stoichiometry of their metal complexes.

PubMed

Izquierdo, A; Carrasco, J

1981-05-01

Automatic thermometric titration was applied to some beta-aryl-alpha-mercaptopropenoic acids and the stoichiometry of their complexes with several metal ions was investigated. The heats of neutralization of the mercapto-acids with sodium hydroxide and the heats of their reaction with metal ions were calculated.

Validation of a Novel Bioassay for Low-level Perchlorate Determination

DTIC Science & Technology

2014-04-01

was not attractive, since these reduce PMS2 , and it was thought they would interfere with the stoichiometry of NADH and perchlorate in the bioassay...these reduce PMS2 directly, and would interfere with the stoichiometry of NADH and perchlorate in the bioassay. Thus the only approach that could be

Validation of a Novel Bioassay for Low-level Perchlorate Determination

DTIC Science & Technology

2013-05-01

since these reduce PMS2 , and it was thought they would interfere with the stoichiometry of NADH and perchlorate in the bioassay. With regard to the...reduce PMS2 directly, and would interfere with the stoichiometry of NADH and perchlorate in the bioassay. Thus the only approach that could be

The pattern of N/P/Si stoichiometry and ecological nutrient limitation in Ganga River: up- and downstream urban influences

NASA Astrophysics Data System (ADS)

Yadav, Amita; Pandey, Jitendra

2018-06-01

The pattern of N/P/Si stoichiometry, although an important driver regulating river ecology, has received limited research attention for Ganga River. We investigated shifts in N/P/Si stoichiometry and ecological nutrient limitation as influenced by Varanasi urban core along a 37-km-long stretch of Ganga River. We also assessed the trophic status of the river in relation to shifting elemental stoichiometry. Together with point sources, atmospheric deposition coupled surface runoff appeared important factors leading to N/P/Si stoichiometric imbalances along the study stretch. The N/P and Si/P ratios declined downstream from 15.5 to 6.5 and 15.7 to 4.4, respectively, whereas N/Si increased from 1.01 to 1.6. Significant negative correlation of N/Si with biogenic silica to chlorophyll a (Chl a) ratios, and biogenic silica to phycocyanin ratios indicated increased growth of non-siliceous algae downstream signifying N and Si limitation with possible implications on food-web dynamics and feedback processes in the river in long run.

The Stoichiometry of Isoquercitrin Complex with Iron or Copper Is Highly Dependent on Experimental Conditions

PubMed Central

Tvrdý, Václav; Karlíčková, Jana; Migkos, Thomas; Mladěnka, Přemysl

2017-01-01

Interaction of flavonoids with transition metals can be partially responsible for their impact on humans. Stoichiometry of the iron/copper complex with a flavonoid glycoside isoquercitrin, a frequent component of food supplements, was assessed using competitive and non-competitive methods in four (patho)physiologically-relevant pH values (4.5. 5.5, 6.8, and 7.5). Isoquercitrin chelated all tested ions (Fe2+, Fe3+, Cu2+, and Cu+) but its affinity for Cu+ ions proved to be very low. In general, the chelation potency dropped with pH lowering. Metal complexes of 1:1 stoichiometry were mostly formed, however, they were not stable and the stoichiometry changed depending on conditions. Isoquercitrin was able to reduce both Cu2+ and Fe3+ ions at low ratios, but its reducing potential was diminished at higher ratios (isoquercitrin to metal) due to the metal chelation. In conclusion, this study emphasizes the need of using multiple different methods for the assessment of chelation potential in moderately-active metal chelators, like flavonoids. PMID:29084179

Influence of Stoichiometry on the Magnetic Properties of Electrodeposited Thin Films of Iron Chromium Hexacyanide Based Molecular Magnet

NASA Astrophysics Data System (ADS)

Bhatt, Pramod; Yusuf, S. M.; Mukadam, M. D.; Yakhmi, J. V.

2010-12-01

Present paper deals with investigation of magnetic properties of electrochemically prepared crystalline films of Prussian blue analogues (PBAs) based molecular magnet, KjFek[Cr(CN)6]lṡmH2O with varying film stoichiometry. Film stoichiometry has been varied by depositing films at -0.5, -0.6 and -0.8 V at room temperature. It has been observed that the alkali metal ions are introduced into the films just by using suitable electrode voltage, contrary to usual method where alkali metal ions are intentionally introduced into the lattice by using additional compounds of alkali metals as starting materials. Magnetization data show ferromagnetic (parallel spin ordering) nature of all deposited film with the Curie temperature (TC)˜11 K for Fe1.5[Cr(CN)6]ṡ7.5H2O film. Changes in the magnetic properties such as TC, coercivity and saturation magnetization have also been observed with variation in film stoichiometry. The observed changes are mainly attributed to the inclusion of potassium ion, which alters FeII/CrIII ratio, thus magnetic properties.

Mammalian Complex I Pumps 4 Protons per 2 Electrons at High and Physiological Proton Motive Force in Living Cells*

PubMed Central

Ripple, Maureen O.; Kim, Namjoon; Springett, Roger

2013-01-01

Mitochondrial complex I couples electron transfer between matrix NADH and inner-membrane ubiquinone to the pumping of protons against a proton motive force. The accepted proton pumping stoichiometry was 4 protons per 2 electrons transferred (4H+/2e−) but it has been suggested that stoichiometry may be 3H+/2e− based on the identification of only 3 proton pumping units in the crystal structure and a revision of the previous experimental data. Measurement of proton pumping stoichiometry is challenging because, even in isolated mitochondria, it is difficult to measure the proton motive force while simultaneously measuring the redox potentials of the NADH/NAD+ and ubiquinol/ubiquinone pools. Here we employ a new method to quantify the proton motive force in living cells from the redox poise of the bc1 complex measured using multiwavelength cell spectroscopy and show that the correct stoichiometry for complex I is 4H+/2e− in mouse and human cells at high and physiological proton motive force. PMID:23306206

Growth control of oxygen stoichiometry in homoepitaxial SrTiO3 films by pulsed laser epitaxy in high vacuum

PubMed Central

Lee, Ho Nyung; Ambrose Seo, Sung S.; Choi, Woo Seok; Rouleau, Christopher M.

2016-01-01

In many transition metal oxides, oxygen stoichiometry is one of the most critical parameters that plays a key role in determining the structural, physical, optical, and electrochemical properties of the material. However, controlling the growth to obtain high quality single crystal films having the right oxygen stoichiometry, especially in a high vacuum environment, has been viewed as a challenge. In this work, we show that, through proper control of the plume kinetic energy, stoichiometric crystalline films can be synthesized without generating oxygen defects even in high vacuum. We use a model homoepitaxial system of SrTiO3 (STO) thin films on single crystal STO substrates. Physical property measurements indicate that oxygen vacancy generation in high vacuum is strongly influenced by the energetics of the laser plume, and it can be controlled by proper laser beam delivery. Therefore, our finding not only provides essential insight into oxygen stoichiometry control in high vacuum for understanding the fundamental properties of STO-based thin films and heterostructures, but expands the utility of pulsed laser epitaxy of other materials as well. PMID:26823119

Rhabdomyolysis and acute kidney injury in patients with traumatic spinal cord injury

PubMed Central

Galeiras, Rita; Mourelo, Mónica; Pértega, Sonia; Lista, Amanda; Ferreiro, Mª Elena; Salvador, Sebastián; Montoto, Antonio; Rodríguez, Antonio

2016-01-01

Background: Patients with acute traumatic spinal cord injuries (SCIs) exhibit factors that, in other populations, have been associated with rhabdomyolysis. Purpose: The aim of the study is to determine the incidence of rhabdomyolysis in patients with acute traumatic SCI admitted to the Intensive Care Unit (ICU), as well as the development of secondary acute kidney injury and associated factors. Study Design and Setting: This was an observational, retrospective study. Patient Sample: All adult patients admitted to the ICU with acute traumatic SCI who presented rhabdomyolysis, diagnosed through creatine phosphokinase (CPK) levels >500 IU/L. Outcome Measures: Incidence of rhabdomyolysis and subsequent renal dysfunction was calculated. Materials and Methods: Data about demographic variables, comorbidity, rhabdomyolysis risk factors, and variables involving SCI, severity scores, and laboratory parameters were obtained from clinical records. Multivariate logistic regression was used to identify renal injury risk factors. Results: In 2006–2014, 200 patients with acute SCI were admitted to ICU. Of these, 103 had rhabdomyolysis (incidence = 51.5%; 95% confidence interval [CI]: 44.3%–58.7%). The most typical American Spinal Injury Association classification was A (70.3%). The injury severity score was 30.3 ± 12.1 and sequential organ failure assessment (SOFA) score was 5.6 ± 3.3 points. During their stay, 57 patients (55.3%; 95% CI: 45.2%–65.4%) presented renal dysfunction (creatinine ≥1.2 mg/dL). In the multivariate analysis, variables associated with renal dysfunction were creatinine at admission (odds ratio [OR] = 9.20; P = 0.006) and hemodynamic SOFA score the day following admission (OR = 1.33; P = 0.024). Creatinine was a better predictor of renal dysfunction than the peak CPK value during the rhabdomyolysis (area under the receiver operating characteristic curve: 0.91 vs. 0.63, respectively). Conclusions: Rhabdomyolysis is a frequent condition in patients with acute traumatic SCI admitted to the ICU, and renal dysfunction occurs in half of the cases. Creatinine values should be requested starting at the admission while neither the peak CPK values nor the hemodynamic SOFA scores could be used to properly discriminate between patients with and without renal dysfunction. PMID:27688625

Environmental Dysfunctions, Childhood Maltreatment and Women's Intimate Partner Violence Victimization.

PubMed

Cascio, Maria Lo; Guarnaccia, Cinzia; Infurna, Maria Rita; Mancuso, Laura; Parroco, Anna Maria; Giannone, Francesca

2017-06-01

Childhood maltreatment is considered a crucial explanatory variable for intimate partner violence (IPV) in adulthood. However, a developmental multifactorial model for the etiology of IPV is not shared by researchers yet. This study has investigated the role of a wide range of childhood maltreatments and family and social dysfunctions in predicting IPV; furthermore, it tests a model where childhood maltreatment mediates the relationship between environmental dysfunctions and IPV. The sample included 78 women: IPV (38) and non-IPV (40). The Italian version of the Childhood Experience of Care and Abuse (CECA) Interview was used to assess the presence of adverse childhood experiences. The Revised Conflict Tactics Scale (CTS-2) and the IPV History Interview were used to assess IPV in the last year and lifetime, respectively. The results of a multivariate logistic regression model have indicated that only sexual (odds ratio [OR] = 4.24) and psychological (OR = 3.45) abuse significantly predicted IPV; with regard to association between IPV and environmental dysfunctions, only poor social support (OR = 8.91) significantly predicted IPV. The results of a mediation model have shown that childhood psychological and sexual abuse, in association with each other, partially mediate the relationship between poor social support and IPV. The findings from this study pinpoint poor social support as an important predictor of IPV so far neglected in the literature on the developmental antecedents of IPV. They also support the theoretical assumption according to which dysfunctional environmental variables and types of childhood maltreatment interacting with each other may influence development outcomes.

Effects of vildagliptin versus sitagliptin, on cardiac function, heart rate variability and mitochondrial function in obese insulin-resistant rats

PubMed Central

Apaijai, Nattayaporn; Pintana, Hiranya; Chattipakorn, Siriporn C; Chattipakorn, Nipon

2013-01-01

Background and Purpose Long-term high-fat diet (HFD) consumption has been shown to cause insulin resistance, which is characterized by hyperinsulinaemia with metabolic inflexibility. Insulin resistance is associated with cardiac sympathovagal imbalance, cardiac dysfunction and cardiac mitochondrial dysfunction. Dipeptidyl peptidase-4 (DPP-4) inhibitors, vildagliptin and sitagliptin, are oral anti-diabetic drugs often prescribed in patients with cardiovascular disease. Therefore, in this study, we sought to determine the effects of vildagliptin and sitagliptin in a murine model of insulin resistance. Experimental Approach Male Wistar rats weighing 180–200 g, were fed either a normal diet (20% energy from fat) or a HFD (59% energy from fat) for 12 weeks. These rats were then divided into three subgroups to receive vildagliptin (3 mg·kg−1·day−1), sitagliptin (30 mg·kg−1·day−1) or vehicle for another 21 days. Metabolic parameters, oxidative stress, heart rate variability (HRV), cardiac function and cardiac mitochondrial function were determined. Key Results Rats that received HFD developed insulin resistance characterized by increased body weight, plasma insulin, total cholesterol and oxidative stress levels along with a decreased high-density lipoprotein (HDL) level. Moreover, cardiac dysfunction, depressed HRV, cardiac mitochondrial dysfunction and cardiac mitochondrial morphology changes were observed in HFD rats. Both vildagliptin and sitagliptin decreased plasma insulin, total cholesterol and oxidative stress as well as increased HDL level. Furthermore, vildagliptin and sitagliptin attenuated cardiac dysfunction, prevented cardiac mitochondrial dysfunction and completely restored HRV. Conclusions and Implications Both vildagliptin and sitagliptin share similar efficacy in cardioprotection in obese insulin-resistant rats. PMID:23488656

Stoichiometry and estimates of nutrient standing stocks of larval salamanders in Appalachian headwater streams

Treesearch

Joseph R. Milanovich; John C. Maerz; Amy D. Rosemond

2015-01-01

1.Because of their longevity and skeletal phosphorus demand, vertebrates can have distinct influences on the uptake, storage and recycling of nutrients in ecosystems. Quantification of body stoichiometry, combined with estimates of abundance or biomass, can provide insights into the effect of vertebrates on nutrient cycling. 2.We measured the nutrient content and...

Effectiveness of Inquiry-Based Lessons Using Particulate Level Models to Develop High School Students' Understanding of Conceptual Stoichiometry

ERIC Educational Resources Information Center

Kimberlin, Stephanie; Yezierski, Ellen

2016-01-01

Students' inaccurate ideas about what is represented by chemical equations and concepts underlying stoichiometry are well documented; however, there are few classroom-ready instructional solutions to help students build scientifically accurate ideas about these topics central to learning chemistry. An intervention (two inquiry-based activities)…

Amino Acid Complementarity: A Biochemical Exemplar of Stoichiometry for General and Health Sciences Chemistry

ERIC Educational Resources Information Center

Vitz, Ed

2005-01-01

The standard introduction to stoichiometry and simple exemplars can motivate students to learn the stoichiometric studies and the condensation reaction that occurs between amino acids to form the peptide bond. This topic can be integrated into general chemistry courses as an alternative to inclusion of a separate biochemistry course that could be…

Carbon, nitrogen, and phosphorus stoichiometry and eutrophication in River Thames Tributaries, UK

USDA-ARS?s Scientific Manuscript database

Primary productivity in aquatic systems relies on the availability of carbon (C), nitrogen (N) and phosphorus (P), with a preferred stoichiometric ratio of 106 C/16 N/1 P, known as the Redfield ratio. The intent of this paper is to present a methodology to visualize C/N/P stoichiometry and examine ...

Investigating the Effect of Complexity Factors in Stoichiometry Problems Using Logistic Regression and Eye Tracking

ERIC Educational Resources Information Center

Tang, Hui; Kirk, John; Pienta, Norbert J.

2014-01-01

This paper includes two experiments, one investigating complexity factors in stoichiometry word problems, and the other identifying students' problem-solving protocols by using eye-tracking technology. The word problems used in this study had five different complexity factors, which were randomly assigned by a Web-based tool that we developed. The…

Using Audience Response Systems during Interactive Lectures to Promote Active Learning and Conceptual Understanding of Stoichiometry

ERIC Educational Resources Information Center

Cotes, Sandra; Cotuá, José

2014-01-01

This article describes a method of instruction using an active learning strategy for teaching stoichiometry through a process of gradual knowledge building. Students identify their misconceptions and progress through a sequence of questions based on the same chemical equation. An infrared device and software registered as the TurningPoint Audience…

Does diet influence consumer nutrient cycling? Macroinvertebrate and fish excretion in streams

Treesearch

Ryan McManamay; Jackson Webster; H. Valett; C. Dolloff

2011-01-01

Consumer nutrient cycling supplies limiting elements to autotrophic and heterotrophic organisms in aquatic systems. However, the role of consumers in supplying nutrients may change depending on their diet and their own stoichiometry. We evaluated the stoichiometry, N and P excretion, and diets of the dominant macroinvertebrates and fish at 6 stream sites to determine...

Influence of the deposition conditions on radiofrequency magnetron sputtered MoS2 films

NASA Technical Reports Server (NTRS)

Steinmann, Pierre A.; Spalvins, Talivaldis

1990-01-01

By varying the radiofrequency (RF) power, the Ar pressure, and the potential on the substrates, MoS(x) films of various stoichiometry, density, adhesion, and morphology were produced. An increase of RF power increased the deposition rate and density of the MoS2 films as well as improved adhesion. However, the stoichiometry remained constant. An increase of Ar pressure increased the deposition rate but decreased the density, wheras both stoichiometry and adhesion were maximized at around 20 mtorr Ar pressure. Furthermore, a transition from compact film growth to columnar film growth was observed when the pressure was varied from 5 to 15 mtorr. Substoichiometric films were grown when a negative (bias) voltage was applied to the substrates.

Effects of cation stoichiometry on electronic and structural properties of LaNiO{sub 3}

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

Smith, Cole R.; Lang, Andrew C.; Taheri, Mitra L.

2015-07-15

LaNiO{sub 3} films with varying La:Ni ratios were deposited onto SrTiO{sub 3} (001) substrates via molecular beam epitaxy to elucidate the effects of cation off-stoichiometry. The physical properties of La-deficient films are found to differ substantially from those of Ni-deficient films, with La-deficient films exhibiting lower electrical resistivities and smaller c-axis parameters than Ni-deficient films. No evidence of secondary phases is observed; however, transmission electron microscopy reveals an abundance of defects, the nature of which differs in lanthanum- and nickel-deficient films. This work illustrates the nontrivial role that cation stoichiometry can play on the functional properties of complex oxides.

Predicting athletes' functional and dysfunctional emotions: The role of the motivational climate and motivation regulations.

PubMed

Ruiz, Montse C; Haapanen, Saara; Tolvanen, Asko; Robazza, Claudio; Duda, Joan L

2017-08-01

This study examined the relationships between perceptions of the motivational climate, motivation regulations, and the intensity and functionality levels of athletes' pleasant and unpleasant emotional states. Specifically, we examined the hypothesised mediational role of motivation regulations in the climate-emotion relationship. We also tested a sequence in which emotions were assumed to be predicted by the motivational climate dimensions and then served as antecedents to variability in motivation regulations. Participants (N = 494) completed a multi-section questionnaire assessing targeted variables. Structural equation modelling (SEM) revealed that a perceived task-involving climate was a positive predictor of autonomous motivation and of the impact of functional anger, and a negative predictor of the intensity of anxiety and dysfunctional anger. Autonomous motivation was a partial mediator of perceptions of a task-involving climate and the impact of functional anger. An ego-involving climate was a positive predictor of controlled motivation, and of the intensity and impact of functional anger and the intensity of dysfunctional anger. Controlled motivation partially mediated the relationship between an ego-involving climate and the intensity of dysfunctional anger. Good fit to the data also emerged for the motivational climate, emotional states, and motivation regulations sequence. Findings provide support for the consideration of hedonic tone and functionality distinctions in the assessment of athletes' emotional states.

The Role of Dysfunctional Myths in a Decision-Making Process under Bounded Rationality: A Complex Dynamical Systems Perspective.

PubMed

Stamovlasis, Dimitrios; Vaiopoulou, Julie

2017-07-01

The present study examines the factors influencing a decision-making process, with specific focus on the role of dysfunctional myths (DM). DM are thoughts or beliefs that are rather irrational, however influential to people's decisions. In this paper a decision-making process regarding the career choice of university students majoring in natural sciences and education (N=496) is examined by analyzing survey data taken via Career Decision Making Difficulties Questionnaire (CDDQ). The difficulty of making the choice and the certainty about one's decision were the state variables, while the independent variables were factors related to the lack of information or knowledge needed, which actually reflect a bounded rationality. Cusp catastrophe analysis, based on both least squares and maximum likelihood procedures, showed that the nonlinear models predicting the two state variables were superior to linear alternatives. Factors related to lack of knowledge about the steps involved in the process of career decision-making, lack of information about the various occupations, lack of information about self and lack of motivation acted as asymmetry, while dysfunctional myths acted as bifurcation factor for both state variables. The catastrophe model, grounded in empirical data, revealed a unique role for DM and a better interpretation within the context of complexity and the notion of bounded rationality. The analysis opens the nonlinear dynamical systems (NDS) perspective in studying decision-making processes. Theoretical and practical implications are discussed.

Molecular counting by photobleaching in protein complexes with many subunits: best practices and application to the cellulose synthesis complex

PubMed Central

Chen, Yalei; Deffenbaugh, Nathan C.; Anderson, Charles T.; Hancock, William O.

2014-01-01

The constituents of large, multisubunit protein complexes dictate their functions in cells, but determining their precise molecular makeup in vivo is challenging. One example of such a complex is the cellulose synthesis complex (CSC), which in plants synthesizes cellulose, the most abundant biopolymer on Earth. In growing plant cells, CSCs exist in the plasma membrane as six-lobed rosettes that contain at least three different cellulose synthase (CESA) isoforms, but the number and stoichiometry of CESAs in each CSC are unknown. To begin to address this question, we performed quantitative photobleaching of GFP-tagged AtCESA3-containing particles in living Arabidopsis thaliana cells using variable-angle epifluorescence microscopy and developed a set of information-based step detection procedures to estimate the number of GFP molecules in each particle. The step detection algorithms account for changes in signal variance due to changing numbers of fluorophores, and the subsequent analysis avoids common problems associated with fitting multiple Gaussian functions to binned histogram data. The analysis indicates that at least 10 GFP-AtCESA3 molecules can exist in each particle. These procedures can be applied to photobleaching data for any protein complex with large numbers of fluorescently tagged subunits, providing a new analytical tool with which to probe complex composition and stoichiometry. PMID:25232006

Sustaining nutrient supply and carbon export in a seasonally-stratifying shelf sea through inconsistent production and remineralisation stoichiometry

NASA Astrophysics Data System (ADS)

Humphreys, Matthew; Moore, Mark; Achterberg, Eric; Chowdhury, Mohammed; Griffiths, Alex; Hartman, Susan; Hopkins, Joanne; Hull, Tom; Kivimäe, Caroline; Sivyer, Dave; Smilenova, Angelina; Wihsgott, Juliane; Woodward, Malcolm

2017-04-01

Continental shelf seas support 15-20% of global primary productivity despite covering only about 5% of the Earth's ocean surface area. As a result, they may have a significant role in oceanic uptake and storage of carbon dioxide (CO2) from the atmosphere, through the 'continental shelf pump' mechanism. The northwest European continental shelf, in particular the Celtic Sea (50°N 8°W), was the target of extensive biogeochemical sampling from March 2014 to September 2015, as part of the UK Shelf Sea Biogeochemistry research programme (UK-SSB). Here, we use the UK-SSB carbonate chemistry and macronutrient measurements to investigate the biogeochemical seasonality in the temperate, seasonally-stratifying Celtic Sea. During the spring-summer, near-surface biological activity removed dissolved inorganic carbon and nutrients, some of which were then exported into the deeper layer. We calculated vertical inventories of these variables throughout 1.5 seasonal cycles and attempted to correct these for air-sea CO2 exchange, advection and denitrification, thus isolating the combined effect of net community production and remineralisation on the inorganic macronutrient inventories, and revealing fluctuating deviations from Redfield stoichiometry. Here, we discuss the capacity of these stoichiometric inconsistencies to sustain the Celtic Sea nutrient supply, and thus examine whether an effective continental shelf pump for CO2 could operate in this region.

Molecular counting by photobleaching in protein complexes with many subunits: best practices and application to the cellulose synthesis complex

DOE PAGES

Chen, Yalei; Deffenbaugh, Nathan C.; Anderson, Charles T.; ...

2014-09-17

The constituents of large, multisubunit protein complexes dictate their functions in cells, but determining their precise molecular makeup in vivo is challenging. One example of such a complex is the cellulose synthesis complex (CSC), which in plants synthesizes cellulose, the most abundant biopolymer on Earth. In growing plant cells, CSCs exist in the plasma membrane as six-lobed rosettes that contain at least three different cellulose synthase (CESA) isoforms, but the number and stoichiometry of CESAs in each CSC are unknown. To begin to address this question, we performed quantitative photobleaching of GFP-tagged AtCESA3-containing particles in living Arabidopsis thaliana cells usingmore » variable-angle epifluorescence microscopy and developed a set of information-based step detection procedures to estimate the number of GFP molecules in each particle. The step detection algorithms account for changes in signal variance due to changing numbers of fluorophores, and the subsequent analysis avoids common problems associated with fitting multiple Gaussian functions to binned histogram data. The analysis indicates that at least 10 GFP-AtCESA3 molecules can exist in each particle. In conclusion, these procedures can be applied to photobleaching data for any protein complex with large numbers of fluorescently tagged subunits, providing a new analytical tool with which to probe complex composition and stoichiometry.« less

Alien and endangered plants in the Brazilian Cerrado exhibit contrasting relationships with vegetation biomass and N : P stoichiometry.

PubMed

Lannes, Luciola S; Bustamante, Mercedes M C; Edwards, Peter J; Venterink, Harry Olde

2012-11-01

Although endangered and alien invasive plants are commonly assumed to persist under different environmental conditions, surprisingly few studies have investigated whether this is the case. We examined how endangered and alien species are distributed in relation to community biomass and N : P ratio in the above-ground community biomass in savanna vegetation in the Brazilian Cerrado. For 60 plots, we related the occurrence of endangered (Red List) and alien invasive species to plant species richness, vegetation biomass and N : P ratio, and soil variables. Endangered plants occurred mainly in plots with relatively low above-ground biomass and high N : P ratios, whereas alien invasive species occurred in plots with intermediate to high biomass and low N : P ratios. Occurrences of endangered or alien plants were unrelated to extractable N and P concentrations in the soil. These contrasting distributions in the Cerrado imply that alien species only pose a threat to endangered species if they are able to invade sites occupied by these species and increase the above-ground biomass and/or decrease the N : P ratio of the vegetation. We found some evidence that alien species do increase above-ground community biomass in the Cerrado, but their possible effect on N : P stoichiometry requires further study. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Predictive Value of Beat-to-Beat QT Variability Index across the Continuum of Left Ventricular Dysfunction: Competing Risks of Non-cardiac or Cardiovascular Death, and Sudden or Non-Sudden Cardiac Death

PubMed Central

Tereshchenko, Larisa G.; Cygankiewicz, Iwona; McNitt, Scott; Vazquez, Rafael; Bayes-Genis, Antoni; Han, Lichy; Sur, Sanjoli; Couderc, Jean-Philippe; Berger, Ronald D.; de Luna, Antoni Bayes; Zareba, Wojciech

2012-01-01

Background The goal of this study was to determine the predictive value of beat-to-beat QT variability in heart failure (HF) patients across the continuum of left ventricular dysfunction. Methods and Results Beat-to-beat QT variability index (QTVI), heart rate variance (LogHRV), normalized QT variance (QTVN), and coherence between heart rate variability and QT variability have been measured at rest during sinus rhythm in 533 participants of the Muerte Subita en Insuficiencia Cardiaca (MUSIC) HF study (mean age 63.1±11.7; males 70.6%; LVEF >35% in 254 [48%]) and in 181 healthy participants from the Intercity Digital Electrocardiogram Alliance (IDEAL) database. During a median of 3.7 years of follow-up, 116 patients died, 52 from sudden cardiac death (SCD). In multivariate competing risk analyses, the highest QTVI quartile was associated with cardiovascular death [hazard ratio (HR) 1.67(95%CI 1.14-2.47), P=0.009] and in particular with non-sudden cardiac death [HR 2.91(1.69-5.01), P<0.001]. Elevated QTVI separated 97.5% of healthy individuals from subjects at risk for cardiovascular [HR 1.57(1.04-2.35), P=0.031], and non-sudden cardiac death in multivariate competing risk model [HR 2.58(1.13-3.78), P=0.001]. No interaction between QTVI and LVEF was found. QTVI predicted neither non-cardiac death (P=0.546) nor SCD (P=0.945). Decreased heart rate variability (HRV) rather than increased QT variability was the reason for increased QTVI in this study. Conclusions Increased QTVI due to depressed HRV predicts cardiovascular mortality and non-sudden cardiac death, but neither SCD nor excracardiac mortality in HF across the continuum of left ventricular dysfunction. Abnormally augmented QTVI separates 97.5% of healthy individuals from HF patients at risk. PMID:22730411

Assay Development for the Determination of Phosphorylation Stoichiometry using MRM methods with and without Phosphatase Treatment: Application to Breast Cancer Signaling Pathways

PubMed Central

Domanski, Dominik; Murphy, Leigh C.; Borchers, Christoph H.

2010-01-01

We have developed a phosphatase-based phosphopeptide quantitation (PPQ) method for determining phosphorylation stoichiometry in complex biological samples. This PPQ method is based on enzymatic dephosphorylation, combined with specific and accurate peptide identification and quantification by multiple reaction monitoring (MRM) detection with stable-isotope-labeled standard peptides. In contrast with the classical MRM methods for the quantitation of phosphorylation stoichiometry, the PPQ-MRM method needs only one non-phosphorylated SIS (stable isotope-coded standard) and two analyses (one for the untreated and one for the phosphatase-treated sample), from which the expression and modification levels can accurately be determined. From these analyses, the % phosphorylation can be determined. In this manuscript, we compare the PPQ-MRM method with an MRM method without phosphatase, and demonstrate the application of these methods to the detection and quantitation of phosphorylation of the classic phosphorylated breast cancer biomarkers (ERα and HER2), and for phosphorylated RAF and ERK1, which also contain phosphorylation sites with important biological implications. Using synthetic peptides spiked into a complex protein digest, we were able to use our PPQ-MRM method to accurately determine the total phosphorylation stoichiometry on specific peptides, as well as the absolute amount of the peptide and phosphopeptide present. Analyses of samples containing ERα protein revealed that the PPQ-MRM is capable of determining phosphorylation stoichiometry in proteins from cell lines, and is in good agreement with determinations obtained using the direct MRM approach in terms of phosphorylation and total protein amount. PMID:20524616

Characterization, stoichiometry, and stability of salivary protein-tannin complexes by ESI-MS and ESI-MS/MS.

PubMed

Canon, Francis; Paté, Franck; Meudec, Emmanuelle; Marlin, Thérèse; Cheynier, Véronique; Giuliani, Alexandre; Sarni-Manchado, Pascale

2009-12-01

Numerous protein-polyphenol interactions occur in biological and food domains particularly involving proline-rich proteins, which are representative of the intrinsically unstructured protein group (IUP). Noncovalent protein-ligand complexes are readily detected by electrospray ionization mass spectrometry (ESI-MS), which also gives access to ligand binding stoichiometry. Surprisingly, the study of interactions between polyphenolic molecules and proteins is still an area where ESI-MS has poorly benefited, whereas it has been extensively applied to the detection of noncovalent complexes. Electrospray ionization mass spectrometry has been applied to the detection and the characterization of the complexes formed between tannins and a human salivary proline-rich protein (PRP), namely IB5. The study of the complex stability was achieved by low-energy collision-induced dissociation (CID) measurements, which are commonly implemented using triple quadrupole, hybrid quadrupole time-of-flight, or ion trap instruments. Complexes composed of IB5 bound to a model polyphenol EgCG have been detected by ESI-MS and further analyzed by MS/MS. Mild ESI interface conditions allowed us to observe intact noncovalent PRP-tannin complexes with stoichiometries ranging from 1:1 to 1:5. Thus, ESI-MS shows its efficiency for (1) the study of PRP-tannin interactions, (2) the determination of stoichiometry, and (3) the study of complex stability. We were able to establish unambiguously both their stoichiometries and their overall subunit architecture via tandem mass spectrometry and solution disruption experiments. Our results prove that IB5.EgCG complexes are maintained intact in the gas phase.

The stoichiometry of nutrient release by terrestrial herbivores and its ecosystem consequences

NASA Astrophysics Data System (ADS)

Sitters, Judith; Bakker, Elisabeth S.; Veldhuis, Michiel P.; Veen, G. F.; Olde Venterink, Harry; Vanni, Michael J.

2017-04-01

It is widely recognized that the release of nutrients by herbivores via their waste products strongly impacts nutrient availability for autotrophs. The ratios of nitrogen (N) and phosphorus (P) recycled through herbivore release (i.e., waste N:P) are mainly determined by the stoichiometric composition of the herbivore’s food (food N:P) and its body nutrient content (body N:P). Waste N:P can in turn impact autotroph nutrient limitation and productivity. Herbivore-driven nutrient recycling based on stoichiometric principles is dominated by theoretical and experimental research in freshwater systems, in particular interactions between algae and invertebrate herbivores. In terrestrial ecosystems, the impact of herbivores on nutrient cycling and availability is often limited to studying carbon (C ):N and C:P ratios, while the role of terrestrial herbivores in mediating N:P ratios is also likely to influence herbivore-driven nutrient recycling. In this review, we use rules and predictions on the stoichiometry of nutrient release originating from algal-based aquatic systems to identify the factors that determine the stoichiometry of nutrient release by herbivores. We then explore how these rules can be used to understand the stoichiometry of nutrient release by terrestrial herbivores, ranging from invertebrates to mammals, and its impact on plant nutrient limitation and productivity. Future studies should focus on measuring both N and P when investigating herbivore-driven nutrient recycling in terrestrial ecosystems, while also taking the form of waste product (urine or feces) and other pathways by which herbivores change nutrients into account, to be able to quantify the impact of waste stoichiometry on plant communities.

Controlling the stoichiometry and doping of semiconductor materials

DOEpatents

Albin, David; Burst, James; Metzger, Wyatt; Duenow, Joel; Farrell, Stuart; Colegrove, Eric

2016-08-16

Methods for treating a semiconductor material are provided. According to an aspect of the invention, the method includes annealing the semiconductor material in the presence of a compound that includes a first element and a second element. The first element provides an overpressure to achieve a desired stoichiometry of the semiconductor material, and the second element provides a dopant to the semiconductor material.

Using a Laboratory Inquiry with High School Students to Determine the Reaction Stoichiometry of Neutralization by a Thermochemical Approach

ERIC Educational Resources Information Center

Journal of Chemical Education, 2015

2015-01-01

This paper presents the design and practical application of a laboratory inquiry at high school chemistry level for systematic chemistry learning, as exemplified by a thermochemical approach to the reaction stoichiometry of neutralization using Job's method of continuous variation. In the laboratory inquiry, students are requested to propose the…

Determination of the Stoichiometry between α- and γ1 Subunits of the BK Channel Using LRET.

PubMed

Carrasquel-Ursulaez, Willy; Alvarez, Osvaldo; Bezanilla, Francisco; Latorre, Ramon

2018-06-05

Two families of accessory proteins, β and γ, modulate BK channel gating and pharmacology. Notably, in the absence of internal Ca 2+ , the γ1 subunit promotes a large shift of the BK conductance-voltage curve to more negative potentials. However, very little is known about how α- and γ1 subunits interact. In particular, the association stoichiometry between both subunits is unknown. Here, we propose a method to answer this question using lanthanide resonance energy transfer. The method assumes that the kinetics of lanthanide resonance energy transfer-sensitized emission of the donor double-labeled α/γ1 complex is the linear combination of the kinetics of the sensitized emission in single-labeled complexes. We used a lanthanide binding tag engineered either into the α- or the γ1 subunits to bind Tb +3 as the donor. The acceptor (BODIPY) was attached to the BK pore-blocker iberiotoxin. We determined that γ1 associates with the α-subunit with a maximal 1:1 stoichiometry. This method could be applied to determine the stoichiometry of association between proteins within heteromultimeric complexes. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Growth control of oxygen stoichiometry in homoepitaxial SrTiO 3 films by pulsed laser epitaxy in high vacuum

DOE PAGES

Lee, Ho Nyung; Ambrose Seo, Sung S.; Choi, Woo Seok; ...

2016-01-29

In many transition metal oxides, oxygen stoichiometry is one of the most critical parameters that plays a key role in determining the structural, physical, optical, and electrochemical properties of the material. However, controlling the growth to obtain high quality single crystal films having the right oxygen stoichiometry, especially in a high vacuum environment, has been viewed as a challenge. In this work, we show that, through proper control of the plume kinetic energy, stoichiometric crystalline films can be synthesized without generating oxygen defects even in high vacuum. We use a model homoepitaxial system of SrTiO 3 (STO) thin films onmore » single crystal STO substrates. Physical property measurements indicate that oxygen vacancy generation in high vacuum is strongly influenced by the energetics of the laser plume, and it can be controlled by proper laser beam delivery. Thus, our finding not only provides essential insight into oxygen stoichiometry control in high vacuum for understanding the fundamental properties of STO-based thin films and heterostructures, but it expands the utility of pulsed laser epitaxy of other materials as well.₃« less

Nanoscale Stoichiometric Analysis of a High-Temperature Superconductor by Atom Probe Tomography.

PubMed

Pedrazzini, Stella; London, Andrew J; Gault, Baptiste; Saxey, David; Speller, Susannah; Grovenor, Chris R M; Danaie, Mohsen; Moody, Michael P; Edmondson, Philip D; Bagot, Paul A J

2017-04-01

The functional properties of the high-temperature superconductor Y1Ba2Cu3O7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y7.7Ba15.3Cu23O54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of the experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) samples in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y7.9Ba10.4Cu24.4O57.2.

The influence of filament temperature and oxygen concentration on tungsten oxide nanostructures by hot filament metal oxide deposition

NASA Astrophysics Data System (ADS)

Lou, J.; Ye, B. J.; Weng, H. M.; Du, H. J.; Wang, Z. B.; Wang, X. P.

2008-08-01

Tungsten oxide (WOx) nanostructures were prepared by a hot filament chemical vapour deposition system and the temperature of the hot tungsten filaments was changed by steps of degrees. The morphology and average growth rate were indicated by scanning electron microscopy which showed that the morphology was highly related to the filament temperature (Tf) and the distance between the filaments and the polished Si (1 0 0) substrates (df). The influence of Tf on the crystalline nature was studied by x-ray diffraction and Raman spectroscopy. The evolution of stoichiometry and types of defects was indicated by x-ray photoelectron spectroscopy and slow positron implantation spectroscopy. When Tf was up to 1750 °C, tungsten oxide nanostructure was synthesized. A turning point of Tf was found at which the nature of crystallinity and of stoichiometry was the best. As Tf increased to 2100 °C or df decreased, the film crystallinity decreased; correspondingly, the component ratio of stoichiometry WO3 decreased and lots of vacancy agglomerates were present. In order to develop the chemical phase from substoichiometry to stoichiometry, the oxygen gas concentration in the mixture gas during deposition should be raised to an appropriate level.

Coexistence and community structure in a consumer resource model with implicit stoichiometry.

PubMed

Orlando, Paul A; Brown, Joel S; Wise, David H

2012-09-01

We combine stoichiometry theory and optimal foraging theory into the MacArthur consumer-resource model. This generates predictions for diet choice, coexistence, and community structure of heterotroph communities. Tradeoffs in consumer resource-garnering traits influence community outcomes. With scarce resources, consumers forage opportunistically for complementary resources and may coexist via tradeoffs in resource encounter rates. In contrast to single currency models, stoichiometry permits multiple equilibria. These alternative stable states occur when tradeoffs in resource encounter rates are stronger than tradeoffs in elemental conversion efficiencies. With abundant resources consumers exhibit partially selective diets for essential resources and may coexist via tradeoffs in elemental conversion efficiencies. These results differ from single currency models, where adaptive diet selection is either opportunistic or selective. Interestingly, communities composed of efficient consumers share many of the same properties as communities based on substitutable resources. However, communities composed of relatively inefficient consumers behave similarly to plant communities as characterized by Tilman's consumer resource theory. The results of our model indicate that the effects of stoichiometry theory on community ecology are dependent upon both consumer foraging behavior and the nature of resource garnering tradeoffs. Copyright © 2012 Elsevier Inc. All rights reserved.

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

Pedrazzini, Stella; London, Andrew J.; Gault, Baptiste

The functional properties of the high-temperature superconductor Y 1Ba 2Cu 3O 7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y 7.7Ba 15.3Cu 23O 54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of themore » experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) samples in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y 7.9Ba 10.4Cu 24.4O 57.2.« less

Stoichiometric control of DNA-grafted colloid self-assembly

DOE PAGES

Vo, Thi; Venkatasubramanian, Venkat; Kumar, Sanat; ...

2015-04-06

In this study, there has been considerable interest in understanding the self-assembly of DNA-grafted nanoparticles into different crystal structures, e.g., CsCl, AlB₂, and Cr₃Si. Although there are important exceptions, a generally accepted view is that the right stoichiometry of the two building block colloids needs to be mixed to form the desired crystal structure. To incisively probe this issue, we combine experiments and theory on a series of DNA-grafted nanoparticles at varying stoichiometries, including noninteger values. We show that stoichiometry can couple with the geometries of the building blocks to tune the resulting equilibrium crystal morphology. As a concrete example,more » a stoichiometric ratio of 3:1 typically results in the Cr₃Si structure. However, AlB₂ can form when appropriate building blocks are used so that the AlB₂ standard-state free energy is low enough to overcome the entropic preference for Cr₃Si. These situations can also lead to an undesirable phase coexistence between crystal polymorphs. Thus, whereas stoichiometry can be a powerful handle for direct control of lattice formation, care must be taken in its design and selection to avoid polymorph coexistence.« less

Effects of oxygen stoichiometry on the scaling behaviors of YBa2Cu3O(x) grain boundary weak-links

NASA Technical Reports Server (NTRS)

Wu, K. H.; Fu, C. M.; Jeng, W. J.; Juang, J. Y.; Uen, T. M.; Gou, Y. S.

1995-01-01

The effects of oxygen stoichiometry on the transport properties of the pulsed laser deposited YBa2Cu3O(x) bicrystalline grain boundary weak-link junctions were studied. It is found that not only the cross boundary resistive transition foot structure can be manipulated repeatedly with oxygen annealing processes but the junction behaviors are also altered in accordance. In the fully oxygenated state i.e with x = 7.0 in YBa2Cu3O(x) stoichiometry, the junction critical current exhibits a power of 2 scaling behavior with temperature. In contrast, when annealed in the conditions of oxygen-deficient state (e.g with x = 6.9 in YBa2Cu3O(x) stoichiometry) the junction critical current switches to a linear temperature dependence behavior. The results are tentatively attributed to the modification of the structure in the boundary area upon oxygen annealing, which, in turn, will affect the effective dimension of the geometrically constrained weak-link bridges. The detailed discussion on the responsible physical mechanisms as well as the implications of the present results on device applications will be given.

Mechanisms of Autonomic Dysfunction Associated with Extreme Exertional Heat Stroke and Potential Efficacy of Novel Pharmacological Treatments

DTIC Science & Technology

2014-12-01

cardiovascular diseases. At higher doses, these medications have been prescribed to treat high blood pressure in humans and both may have relevance as...HR, and Tc. § Low frequency (LF) systolic blood pressure variability as an index of sympathetic modulation of vascular tone. § LF and high ... blood pressure variability (LFSYS), LF heart rate variability (LFHR), and high frequency heart rate variability (HFHR) in placebo-, clonidine-, and

Incidence and Prevalence of Sexual Dysfunction in Women and Men: A Consensus Statement from the Fourth International Consultation on Sexual Medicine 2015.

PubMed

McCabe, Marita P; Sharlip, Ira D; Lewis, Ron; Atalla, Elham; Balon, Richard; Fisher, Alessandra D; Laumann, Edward; Lee, Sun Won; Segraves, Robert T

2016-02-01

The incidence and prevalence of various sexual dysfunctions in women and men are important to understand to designate priorities for epidemiologic and clinical research. This manuscript was designed to conduct a review of the literature to determine the incidence and prevalence of sexual dysfunction in women and men. Members of Committee 1 of the Fourth International Consultation on Sexual Medicine (2015) searched and reviewed epidemiologic literature on the incidence and prevalence of sexual dysfunctions. Key older studies and most studies published after 2009 were included in the text of this article. The outcome measures were the reports in the various studies of the incidence and prevalence of sexual dysfunction among women and men. There are more studies on incidence and prevalence for men than for women and many more studies on prevalence than incidence for women and men. The data indicate that the most frequent sexual dysfunctions for women are desire and arousal dysfunctions. In addition, there is a large proportion of women who experience multiple sexual dysfunctions. For men, premature ejaculation and erectile dysfunction are the most common sexual dysfunctions, with less comorbidity across sexual dysfunctions for men compared with women. These data need to be treated with caution, because there is a high level of variability across studies caused by methodologic differences in the instruments used to assess presence of sexual dysfunction, ages of samples, nature of samples, methodology used to gather the data, and cultural differences. Future research needs to use well-validated tools to gather data and ensure that the data collection strategy is clearly described. Copyright © 2016 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

The Structure and Composition Statistics of 6A Binary and Ternary Crystalline Materials.

PubMed

Hever, Alon; Oses, Corey; Curtarolo, Stefano; Levy, Ohad; Natan, Amir

2018-01-16

The fundamental principles underlying the arrangement of elements into solid compounds with an enormous variety of crystal structures are still largely unknown. This study presents a general overview of the structure types appearing in an important subset of the solid compounds, i.e., binary and ternary compounds of the 6A column oxides, sulfides and selenides. It contains an analysis of these compounds, including the prevalence of various structure types, their symmetry properties, compositions, stoichiometries and unit cell sizes. It is found that these compound families include preferred stoichiometries and structure types that may reflect both their specific chemistry and research bias in the available empirical data. Identification of nonoverlapping gaps and missing stoichiometries in these structure populations may be used as guidance in the search for new materials.

Effects of stoichiometry, purity, etching and distilling on resistance of MgB 2 pellets and wire segments

NASA Astrophysics Data System (ADS)

Ribeiro, R. A.; Bud'ko, S. L.; Petrovic, C.; Canfield, P. C.

2002-11-01

We present a study of the effects of non-stoichiometry, boron purity, wire diameter and post-synthesis treatment (etching and Mg distilling) on the temperature dependent resistance and resistivity of sintered MgB 2 pellets and wire segments. Whereas the residual resistivity ratio (RRR) varies between RRR≈4 to RRR⩾20 for different boron purity, it is only moderately affected by non-stoichiometry (from 20% Mg deficiency to 20% Mg excess) and is apparently independent of wire diameter and presence of Mg metal traces on the wire surface. The obtained set of data indicates that RRR values in excess of 20 and residual resistivities as low as ρ 0≈0.4 μΩ cm are intrinsic material properties of high purity MgB 2.

Application of ESCA to the determination of stoichiometry in sputtered coatings and interface regions

NASA Technical Reports Server (NTRS)

Wheeler, D. R.

1978-01-01

X-ray photoelectron spectroscopy was used to characterize radiofrequency sputter deposited films of several refractory compounds. Both the bulk film properties such as purity and stoichiometry and the character of the interfacial region between the film and substrate were examined. The materials were CrB2, MoS2, Mo2C, and Mo2B5 deposited on 440C steel. It was found that oxygen from the sputtering target was the primary impurity in all cases. Biasing improves the film purity. The effect of biasing on film stoichiometry is different for each compound. Comparison of the interfacial composition with friction data suggests that adhesion of these films is improved if a region of mixed film and iron oxides can be formed.

The frequency of sexual dysfunctions in male partners of women with vaginismus in a Turkish sample.

PubMed

Dogan, S; Dogan, M

2008-01-01

The aim of this investigation is to determine the sexual history traits, sexual satisfaction level and frequency of sexual dysfunctions in men whose partners have vaginismus. The study included 32 male partners of vaginismic patients, who presented at a psychiatry department. Subjects were evaluated by a semi-structured questionnaire. The questionnaire was developed by researchers for assessing sexually dysfunctional patients and included detailed questions with regard to socio-demographic variables, general medical and sexual history. All participants also received the Golombok Rust Inventory of Sexual Satisfaction (GRISS). According to DSM-IV-TR criteria, 65.6% of the investigated males were diagnosed with one or more sexual dysfunctions. The most common problem was premature ejaculation (50%) and the second one was erectile dysfunction (28%). The transformed GRISS subscale scores provided similar data. It is concluded that the assessment of sexual functions of males who have vaginismic partners should be an integral part of the management procedure of vaginismus for optimal outcome.

Ordinary Stoichiometry of Extraordinary Microbes

NASA Astrophysics Data System (ADS)

Neveu, M.; Poret-Peterson, A. T.; Anbar, A. D.; Elser, J. J.

2013-12-01

Life on Earth seems to be composed of the same chemical elements in relatively conserved stoichiometric proportions. However, this observation is largely based on observations of biota from habitats spanning a moderate range of temperature and chemical composition (e.g., temperate lakes, forests, grasslands, oceanic phytoplankton). Whether this stoichiometry is conserved in settings that differ radically from such "normal" planetary settings may provide insight into the habitability of environments with radically different stoichiometries, and into possible stoichiometries for putative life beyond Earth. Here we report the first measurements of elemental stoichiometries of microbial extremophiles from hot springs of Yellowstone National Park (YNP). These phototrophic and chemotrophic microbes were collected in locations spanning large ranges of temperature (ambient to boiling) and pH (1 to 9). Microbial biomass was carefully extracted from hot spring sediment substrata following a procedure adapted from [1], which conserves cellular elemental abundances [2]. Their C and N contents were determined by Elemental Analysis Isotope Ratio Mass Spectrometry, and their P and trace element (Mg, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and non-biogenic Al and Ti) contents were measured by Inductively Coupled Plasma Mass Spectrometry. Residual mineral contamination was an issue in some samples with low measured C and N; we eliminated these from our results. Even in the remaining samples, contamination sometimes prevented accurate determinations of cellular Mg, Ca, Mn, and Fe abundances; however, the cellular Ni, Cu, Zn, and Mo contents were several-fold above contamination level. Although hot spring water and sediment elemental abundances varied by orders of magnitude, the data showed that the extremophiles have a major and trace element stoichiometry similar to those previously measured in "normal" microbial biomass [3-6]. For example, biomass C:N:P ratios resembled those commonly observed in temperate lakes (e.g., C:P ratios of 260 to 1600 and N:P ratios of 35 to 200) while cellular C:Fe ratios were of a similar magnitude to those of marine phytoplankton. Exceptions were Al and Ti, much higher than previously measured, likely because of contamination from residual sediment. Moreover, the low phosphorus contents (high C:P and N:P ratios) are suggestive of limited P supply. Chemotrophs and phototrophs had similar elemental compositions to one another, although Mg, Mn, Ni, and Zn abundances were higher and nearly constant in phototrophs, due to their importance in phototrophic metabolism. Despite the tremendous physical and chemical diversity of YNP environments, the stoichiometry of life in these settings is surprisingly ordinary. Thus, our study supports the view that the biological stoichiometry of life is heavily constrained by the elemental composition of core biomolecules, and that even life in extreme environments must operate within these constraints. In the frame of life detection in exotic locales, these results suggest a general elemental biosignature for life as we know it. References: [1] Amalfitano and Fazi. 2008. J. Microbiol. Meth. 75:237 [2] Neveu et al. L&O: Meth., in review [3] Ho et al. 2003. J. Phycol. 39:1145 [4] Nuester et al. 2012. Front. Microbiol. 3:150 [5] Sterner and Elser. 2002. Ecological Stoichiometry. Princeton U. Press [6] Twining et al. 2011. Deep-Sea Res. II 58:325

Mild Cognitive Dysfunction: An Epidemiological Perspective with an Emphasis on African Americans

PubMed Central

Unverzagt, Frederick W.; Gao, Sujuan; Lane, Kathleen A.; Callahan, Christopher; Ogunniyi, Adesola; Baiyewu, Olusegun; Gureje, Oye; Hall, Kathleen S.; Hendrie, Hugh C.

2009-01-01

In this review, we begin with a historical accounting of the evolution of the concept of mild cognitive dysfunction including nomenclature and criteria from Kral to Petersen. A critical analysis of the main elements relating to assessment and diagnosis of mild cognitive dysfunction are described. Methodological limitations in design, measurement, and characterization, especially as they relate to older African Americans, are identified. Data from a 15-year longitudinal study of community-dwelling, African Americans in Indianapolis indicate 23% prevalence of all-cause mild cognitive dysfunction with approximately 25% progressing to dementia in 2 years and another 25% reverting to normal in the same interval. Factors contributing to this longitudinal variability in outcome are reviewed including the role of medical health factors. We close with suggestions for next steps in the epidemiological research of mild cognitive impairment. PMID:18004008

Treatment of Chronic Inflammatory Demyelinating Polyneuropathy: From Molecular Bases to Practical Considerations

PubMed Central

Ripellino, Paolo; Fleetwood, Thomas; Cantello, Roberto; Comi, Cristoforo

2014-01-01

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an autoimmune disease of the peripheral nervous system, in which both cellular and humoral immune responses are involved. The disease is clinically heterogeneous with some patients displaying pure motor form and others also showing a variable degree of sensory dysfunction; disease evolution may also differ from patient to patient, since monophasic, progressive, and relapsing forms are reported. Underlying such clinical variability there is probably a broad spectrum of molecular dysfunctions that are and will be the target of therapeutic strategies. In this review we first explore the biological bases of current treatments and subsequently we focus on the practical management that must also take into account pharmacoeconomic issues. PMID:24527207

Determinants of tobacco use by students

PubMed Central

Vargas, Lorena Silva; Lucchese, Roselma; da Silva, Andrécia Cósmem; Guimarães, Rafael Alves; Vera, Ivânia; de Castro, Paulo Alexandre

2017-01-01

ABSTRACT OBJECTIVE Estimate the prevalence and determinants of tobacco use by students. METHODS This cross-sectional study, carried out between 2013 and 2014, evaluates 701 public school students between 10 and 79 years of age living in a city in the countryside of the State of Goias, Midwest of Brazil. A structured questionnaire collected the data and the predictor variables were demographic data, family nucleus, religion, physical activity practice, family functionality and parental smoking. Two multivariable models were implemented, the first for occasional tobacco use and the second for regular use, acquiring the measure of prevalence ratio (PR) and their respective 95%CI. Variables with p < 0.10 were included in Poisson regression models with robust variance to obtain the adjusted PR (adPR) and 95%CI. The Wald Chi-Squared test examined the differences between proportions, and values with p < 0.05 were statistically significant. RESULTS The prevalence of occasional and regular tobacco use were 33.4% (95%CI 29.8–36.9) and 6.7% (95%CI 5.0–8.8), respectively. The factors associated with occasional tobacco consumption were age of 15 to 17 years (adPR = 1.98) and above 18 years (adPR = 3.87), male gender (adPR = 1.23), moderate family dysfunction (adPR = 1.30), high family dysfunction (adPR = 1.97) and parental smoking (adPR = 1.60). In regards to regular consumption of tobacco, age above 18 years (adPR = 4.63), lack of religion (adPR = 2.08), high family dysfunction (adPR = 2.35) and parental smoking (adPR = 2.89) remained associated. CONCLUSIONS Students exhibit a high prevalence of occasional and regular tobacco use. This consumption relates to sociodemographic variables and family dysfunction. PMID:28492760

Isolating the Role of Psychological Dysfunction in Smoking Cessation Failure: Relations of Personality and Psychopathology to Attaining Smoking Cessation Milestones

PubMed Central

Leventhal, Adam M.; Japuntich, Sandra J.; Piper, Megan E.; Jorenby, Douglas E.; Schlam, Tanya R.; Baker, Timothy B.

2012-01-01

Research exploring psychological dysfunction as a predictor of smoking cessation success may be limited by nonoptimal predictor variables (i.e., categorical psychodiagnostic measures vs. continuous personality-based manifestations of dysfunction) and imprecise outcomes (i.e., summative point prevalence abstinence vs. constituent cessation milestone measures). Accordingly, this study evaluated the unique and overlapping relations of broad-spectrum personality traits (positive emotionality, negative emotionality, and constraint) and past-year psychopathology (anxiety, mood, and substance use disorder) to point prevalence abstinence and three smoking cessation milestones: (1) initiating abstinence; (2) first lapse; and (3) transition from lapse to relapse. Participants were daily smokers (N=1365) enrolled in a smoking cessation treatment study. In single predictor regression models, each manifestation of internalizing dysfunction (lower positive emotionality, higher negative emotionality, and anxiety and mood disorder) predicted failure at one or more cessation milestone. In simultaneous predictor models, lower positive and higher negative emotionality significantly predicted failure to achieve milestones after controlling for psychopathology. Psychopathology did not predict any outcome when controlling for personality. Negative emotionality showed the most robust and consistent effects, significantly predicting failure to initiate abstinence, earlier lapse, and lower point prevalence abstinence rates. Substance use disorder and constraint did not predict cessation outcomes, and no single variable predicted lapse-to-relapse transition. These findings suggest that personality-related manifestations of internalizing dysfunction are more accurate markers of affective sources of relapse risk than mood and anxiety disorders. Further, individuals with high trait negative emotionality may require intensive intervention to promote the initiation and early maintenance of abstinence. PMID:22642858

The elemental stoichiometry (C, Si, N, P) of the Hebrides Shelf and its role in carbon export

NASA Astrophysics Data System (ADS)

Painter, Stuart C.; Hartman, Susan E.; Kivimäe, Caroline; Salt, Lesley A.; Clargo, Nicola M.; Daniels, Chris J.; Bozec, Yann; Daniels, Lucie; Allen, Stephanie; Hemsley, Victoria S.; Moschonas, Grigorios; Davidson, Keith

2017-12-01

A detailed analysis of the internal stoichiometry of a temperate latitude shelf sea system is presented which reveals strong vertical and horizontal gradients in dissolved nutrient and particulate concentrations and in the elemental stoichiometry of those pools. Such gradients have implications for carbon and nutrient export from coastal waters to the open ocean. The mixed layer inorganic nutrient stoichiometry shifted from balanced N:P in winter, to elevated N:P in spring and to depleted N:P in summer, relative to the Redfield ratio. This pattern suggests increased likelihood of P limitation of fast growing phytoplankton species in spring and of N limitation of slower growing species in summer. However, as only silicate concentrations were below potentially limiting concentrations during summer and autumn the stoichiometric shifts in inorganic nutrient N:P are considered due to phytoplankton nutrient preference patterns rather than nutrient exhaustion. Elevated particulate stoichiometries corroborate non-Redfield optima underlying organic matter synthesis and nutrient uptake. Seasonal variation in the stoichiometry of the inorganic and organic nutrient pools has the potential to influence the efficiency of nutrient export. In summer, when organic nutrient concentrations were at their highest and inorganic nutrient concentrations were at their lowest, the organic nutrient pool was comparatively C poor whilst the inorganic nutrient pool was comparatively C rich. The cross-shelf export of these pools at this time would be associated with different efficiencies regardless of the total magnitude of exchange. In autumn the elemental stoichiometries increased with depth in all pools revealing widespread carbon enrichment of shelf bottom waters with P more intensely recycled than N, N more intensely recycled than C, and Si weakly remineralized relative to C. Offshelf carbon fluxes were most efficient via the inorganic nutrient pool, intermediate for the organic nutrient pool and least efficient for the particulate pool. N loss from the shelf however was most efficient via the dissolved organic nutrient pool. Mass balance calculations suggest that 28% of PO43-, 34% of NO3- and 73% of Si drawdown from the mixed layer fails to reappear in the benthic water column thereby indicating the proportion of the nutrient pools that must be resupplied from the ocean each year to maintain shelf wide productivity. Loss to the neighbouring ocean, the sediments, transference to the dissolved organic nutrient pool and higher trophic levels are considered the most likely fate for these missing nutrients.

Determination of Al Content in Commercial Samples through Stoichiometry: A Simple Experiment for an Advanced High-School Chemistry Olympiad Preparatory Course

ERIC Educational Resources Information Center

de Lima, Kassio M. G.; da Silva, Amison R. L.; de Souza, Joao P. F.; das Neves, Luiz S.; Gasparotto, Luiz H. S.

2014-01-01

Stoichiometry has always been a puzzling subject. This may be partially due to the way it is introduced to students, with stoichiometric coefficients usually provided in the reaction. If the stoichiometric coefficients are not given, students find it very difficult to solve problems. This article describes a simple 4-h laboratory experiment for…

Warming reinforces nonconsumptive predator effects on prey growth, physiology, and body stoichiometry.

PubMed

Janssens, Lizanne; Van Dievel, Marie; Stoks, Robby

2015-12-01

While nonconsumptive effects of predators may strongly affect prey populations, little is known how future warming will modulate these effects. Such information would be especially relevant with regard to prey physiology and resulting changes in prey stoichiometry. We investigated in Enallagma cyathigerum damselfly larvae the effects of a 4°C warming (20°C vs. 24°C) and predation risk on growth rate, physiology and body stoichiometry, for the first time including all key mechanisms suggested by the general stress paradigm (GSP) on how stressors shape changes in body stoichiometry. Growth rate and energy storage were higher at 24°C. Based on thermodynamic principles and the growth rate hypothesis, we could demonstrate predictable reductions in body C:P under warming and link these to the increase in P-rich RNA; the associated warming-induced decrease in C:N may be explained by the increased synthesis of N-rich proteins. Yet, under predation risk, growth rate instead decreased with warming and the warming-induced decreases in C:N and C:P disappeared. As predicted by the GSP, larvae increased body C:N and C:P at 24°C under predation risk. Notably, we did not detect the assumed GSP-mechanisms driving these changes: despite an increased metabolic rate there was neither an increase of C-rich biomolecules (instead fat and sugar contents decreased under predation risk), nor a decrease of N-rich proteins. We hypothesize that the higher C:N and N:P under predation risk are caused by a higher investment in morphological defense. This may also explain the stronger predator-induced increase in C:N under warming. The expected higher C:P under predation risk was only present under warming and matched the observed growth reduction and associated reduction in P-rich RNA. Our integrated mechanistic approach unraveled novel pathways of how warming and predation risk shape body stoichiometry. Key findings that (1) warming effects on elemental stoichiometry were predictable and only present in the absence of predation risk and that (2) warming reinforced the predator-induced effects on C:N:P, are pivotal in understanding how nonconsumptive predator effects under global warming will shape prey populations.

Marine phytoplankton stoichiometry mediates nonlinear interactions between nutrient supply, temperature, and atmospheric CO2

NASA Astrophysics Data System (ADS)

Moreno, Allison R.; Hagstrom, George I.; Primeau, Francois W.; Levin, Simon A.; Martiny, Adam C.

2018-05-01

Marine phytoplankton stoichiometry links nutrient supply to marine carbon export. Deviations of phytoplankton stoichiometry from Redfield proportions (106C : 1P) could therefore have a significant impact on carbon cycling, and understanding which environmental factors drive these deviations may reveal new mechanisms regulating the carbon cycle. To explore the links between environmental conditions, stoichiometry, and carbon cycling, we compared four different models of phytoplankton C : P: a fixed Redfield model, a model with C : P given as a function of surface phosphorus concentration (P), a model with C P given as a function of temperature, and a new multi-environmental model that predicts C : P as a function of light, temperature, and P. These stoichiometric models were embedded into a five-box ocean circulation model, which resolves the three major ocean biomes (high-latitude, subtropical gyres, and tropical upwelling regions). Contrary to the expectation of a monotonic relationship between surface nutrient drawdown and carbon export, we found that lateral nutrient transport from lower C : P tropical waters to high C : P subtropical waters could cause carbon export to decrease with increased tropical nutrient utilization. It has been hypothesized that a positive feedback between temperature and pCO2, atm will play an important role in anthropogenic climate change, with changes in the biological pump playing at most a secondary role. Here we show that environmentally driven shifts in stoichiometry make the biological pump more influential, and may reverse the expected positive relationship between temperature and pCO2, atm. In the temperature-only model, changes in tropical temperature have more impact on the Δ pCO2, atm (˜ 41 ppm) compared to subtropical temperature changes (˜ 4.5 ppm). Our multi-environmental model predicted a decline in pCO2, atm of ˜ 46 ppm when temperature spanned a change of 10 °C. Thus, we find that variation in marine phytoplankton stoichiometry and its environmental controlling factors can lead to nonlinear controls on pCO2, atm, suggesting the need for further studies of ocean C : P and the impact on ocean carbon cycling.

Resource stoichiometry and availability modulate species richness and biomass of tropical litter macro-invertebrates.

PubMed

Jochum, Malte; Barnes, Andrew D; Weigelt, Patrick; Ott, David; Rembold, Katja; Farajallah, Achmad; Brose, Ulrich

2017-09-01

High biodiversity and biomass of soil communities are crucial for litter decomposition in terrestrial ecosystems such as tropical forests. However, the leaf litter that these communities consume is of particularly poor quality as indicated by elemental stoichiometry. The impact of resource quantity, quality and other habitat parameters on species richness and biomass of consumer communities is often studied in isolation, although much can be learned from simultaneously studying both community characteristics. Using a dataset of 780 macro-invertebrate consumer species across 32 sites in tropical lowland rain forest and agricultural systems on Sumatra, Indonesia, we investigated the effects of basal resource stoichiometry (C:X ratios of N, P, K, Ca, Mg, Na, S in local leaf litter), litter mass (basal resource quantity and habitat space), plant species richness (surrogate for litter habitat heterogeneity), and soil pH (acidity) on consumer species richness and biomass across different consumer groups (i.e. 3 feeding guilds and 10 selected taxonomic groups). In order to distinguish the most important predictors of consumer species richness and biomass, we applied a standardised model averaging approach investigating the effects of basal resource stoichiometry, litter mass, plant species richness and soil pH on both consumer community characteristics. This standardised approach enabled us to identify differences and similarities in the magnitude and importance of such effects on consumer species richness and biomass. Across consumer groups, we found litter mass to be the most important predictor of both species richness and biomass. Resource stoichiometry had a more pronounced impact on consumer species richness than on their biomass. As expected, taxonomic groups differed in which resource and habitat parameters (basal resource stoichiometry, litter mass, plant species richness and pH) were most important for modulating their community characteristics. The importance of litter mass for both species richness and biomass indicates that these tropical consumers strongly depend on habitat space and resource availability. Our study supports previous theoretical work indicating that consumer species richness is jointly influenced by resource availability and the balanced supply of multiple chemical elements in their resources. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

The Activation of Incompetence Schemas in Response to Negative Sexual Events in Heterosexual and Lesbian Women: The Moderator Role of Personality Traits and Dysfunctional Sexual Beliefs.

PubMed

Peixoto, Maria Manuela; Nobre, Pedro

2017-01-01

Personality traits and dysfunctional sexual beliefs have been described as vulnerability factors for sexual dysfunction in women, and have also been proposed as dispositional variables for the activation of incompetence schemas in response to negative sexual events. However, no study has tested the role of personality traits and dysfunctional sexual beliefs in the activation of incompetence schemas. The current study aimed to assess the moderator role of neuroticism, extraversion, and dysfunctional sexual beliefs in the association between frequency of unsuccessful sexual episodes and activation of incompetence schemas in heterosexual and lesbian women. An online survey was completed by 1,121 women (831 heterosexual; 290 lesbian). Participants completed the NEO Five-Factor Inventory (NEO-FFI), the Sexual Dysfunctional Beliefs Questionnaire-Female Version (SDBQ), and the Questionnaire of Cognitive Schemas Activated in Sexual Context (QCSASC). Findings indicate that neuroticism moderates the association between frequency of negative sexual events and activation of incompetence schemas in heterosexual women. Moreover, several sexual beliefs also act as moderators of the relationship between negative sexual episodes and the activation of cognitive schemas in both heterosexual and lesbian women. Overall, findings support the cognitive-emotional model of sexual dysfunctions, emphasizing the role of personality traits and dysfunctional sexual beliefs as facilitators of the activation of incompetence schemas in response to negative events in women.

Alcohol-related dysfunction in working-age men in Izhevsk, Russia: an application of structural equation models to study the association with education.

PubMed

Cook, Sarah; Leon, David A; Kiryanov, Nikolay; Ploubidis, George B; De Stavola, Bianca L

2013-01-01

Acute alcohol-related dysfunctional behaviours, such as hangover, are predictive of poor health and mortality. Although much is known about the association of education with alcohol consumption, little is known about its association with these dysfunctional behaviours. The study population was 1,705 male drinkers aged 25-54 years resident in the city of Izhevsk, Russia who participated in a cross-sectional survey (2003-6). Structural equation modelling was used to examine the relationships between education, beverage and non-beverage alcohol intake, drinking patterns, and acute alcohol-related dysfunction score among these drinkers. Dysfunction was related to all other drinking variables, with the strongest predictors being spirit intake, non-beverage alcohol consumption and drinking patterns. There was a strong relationship between education and acute dysfunction which was not explained by adjusting for alcohol intake and drinking patterns (mean adjusted dysfunction score 0.35 SD (95% CI 0.10, 0.61) lower in men with higher versus secondary education). Although by definition one or more aspects of alcohol consumption should explain the educational differences in alcohol-related dysfunction, detailed information on drinking only partly accounted for the observed patterns. Thus beyond their intrinsic interest, these results illustrate the challenges in constructing statistical models that convincingly identify the pathways that link educational differences to health-related outcomes.

Classifying Patients with Chronic Pelvic Pain into Levels of Biopsychosocial Dysfunction Using Latent Class Modeling of Patient Reported Outcome Measures

PubMed Central

Fenton, Bradford W.; Grey, Scott F.; Tossone, Krystel; McCarroll, Michele; Von Gruenigen, Vivian E.

2015-01-01

Chronic pelvic pain affects multiple aspects of a patient's physical, social, and emotional functioning. Latent class analysis (LCA) of Patient Reported Outcome Measures Information System (PROMIS) domains has the potential to improve clinical insight into these patients' pain. Based on the 11 PROMIS domains applied to n=613 patients referred for evaluation in a chronic pelvic pain specialty center, exploratory factor analysis (EFA) was used to identify unidimensional superdomains. Latent profile analysis (LPA) was performed to identify the number of homogeneous classes present and to further define the pain classification system. The EFA combined the 11 PROMIS domains into four unidimensional superdomains of biopsychosocial dysfunction: Pain, Negative Affect, Fatigue, and Social Function. Based on multiple fit criteria, a latent class model revealed four distinct classes of CPP: No dysfunction (3.2%); Low Dysfunction (17.8%); Moderate Dysfunction (53.2%); and High Dysfunction (25.8%). This study is the first description of a novel approach to the complex disease process such as chronic pelvic pain and was validated by demographic, medical, and psychosocial variables. In addition to an essentially normal class, three classes of increasing biopsychosocial dysfunction were identified. The LCA approach has the potential for application to other complex multifactorial disease processes. PMID:26355825

Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea

PubMed Central

2016-01-01

Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA), a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp.) collected from different sites of the Catalan coast (NW Mediterranean Sea). As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20–23). The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical cycles. PMID:27111067

Unexpected stasis in a changing world: Lake nutrient and chlorophyll trends since 1990

USGS Publications Warehouse

Oliver, Samantha K.; Collins, Sarah M.; Soranno, Patricia A.; Wagner, Tyler; Stanley, Emily H.; Jones, John R.; Stow, Craig A.; Lottig, Noah R.

2017-01-01

The United States (U.S.) has faced major environmental changes in recent decades, including agricultural intensification and urban expansion, as well as changes in atmospheric deposition and climate—all of which may influence eutrophication of freshwaters. However, it is unclear whether or how water quality in lakes across diverse ecological settings has responded to environmental change. We quantified water quality trends in 2913 lakes using nutrient and chlorophyll (Chl) observations from the Lake Multi-Scaled Geospatial and Temporal Database of the Northeast U.S. (LAGOS-NE), a collection of preexisting lake data mostly from state agencies. LAGOS-NE was used to quantify whether lake water quality has changed from 1990 to 2013, and whether lake-specific or regional geophysical factors were related to the observed changes. We modeled change through time using hierarchical linear models for total nitrogen (TN), total phosphorus (TP), stoichiometry (TN:TP), and Chl. Both the slopes (percent change per year) and intercepts (value in 1990) were allowed to vary by lake and region. Across all lakes, TN declined at a rate of 1.1% year−1, while TP, TN:TP, and Chl did not change. A minority (7%–16%) of individual lakes had changing nutrients, stoichiometry, or Chl. Of those lakes that changed, we found differences in the geospatial variables that were most related to the observed change in the response variables. For example, TN and TN:TP trends were related to region-level drivers associated with atmospheric deposition of N; TP trends were related to both lake and region-level drivers associated with climate and land use; and Chl trends were found in regions with high air temperature at the beginning of the study period. We conclude that despite large environmental change and management efforts over recent decades, water quality of lakes in the Midwest and Northeast U.S. has not overwhelmingly degraded or improved.

Climate-driven changes in riverine inputs affecting the stoichiometry of Earth's largest lake

NASA Astrophysics Data System (ADS)

Sterner, R.; Small, G. E.

2014-12-01

Lake Superior, Earth's largest lake by area, has seen a steady increase in nitrate levels over the past century, while phosphorus remains exceedingly low, resulting in an increasingly imbalanced stoichiometry. Although its ratio of watershed area:lake area is relatively small, rivers emptying into Lake Superior could be important drivers of long-term changes in lake stoichiometry. To better assess how the Lake Superior watershed affects its stoichiometry, we examined the chemistry of two of its largest tributaries, the Saint Louis River and the Nipigon River, at their confluences with Lake Superior. Both of these rivers have high dissolved organic carbon (DOC) but low nitrate (NO3) concentrations relative to the lake. Using simple mixing models, we found these nearshore confluences to create sinks of lake NO3 as a result of relatively high rates of denitrification. Climate change is altering the amounts and patterns of delivery of materials from land to lakes and we also examined the plume from a June, 2012 100-year flood in the Saint Louis River. Three days after this historic rain event, we found elevated chlorophyll levels throughout the plume, up to 5-fold higher than in the open lake. Combining our samples with satellite imagery, we conservatively estimate that this plume contained 598,000 kg of phosphorus in dissolved and particulate form, or 40% of the average annual P input to the lake. If storm events such as this occur with increasing frequency as predicted in climate change scenarios, the lake's productivity may increase and stoichiometry could become more balanced, through greater P input and increased N retention due to sedimentation and denitrification.

Influence of surface and finite size effects on the structural and magnetic properties of nanocrystalline lanthanum strontium perovskite manganites

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

Žvátora, Pavel; Veverka, Miroslav; Veverka, Pavel

2013-08-15

Syntheses of nanocrystalline perovskite phases of the general formula La{sub 1−x}Sr{sub x}MnO{sub 3+δ} were carried out employing sol–gel technique followed by thermal treatment at 700–900 °C under oxygen flow. The prepared samples exhibit a rhombohedral structure with space group R3{sup ¯}c in the whole investigated range of composition 0.20≤x≤0.45. The studies were aimed at the chemical composition including oxygen stoichiometry and extrinsic properties, i.e. size of the particles, both influencing the resulting structural and magnetic properties. The oxygen stoichiometry was determined by chemical analysis revealing oxygen excess in most of the studied phases. The excess was particularly high for themore » samples with the smallest crystallites (12–28 nm) while comparative bulk materials showed moderate non-stoichiometry. These differences are tentatively attributed to the surface effects in view of the volume fraction occupied by the upper layer whose atomic composition does not comply with the ideal bulk stoichiometry. - Graphical abstract: Evolution of the particle size with annealing temperature in the nanocrystalline La{sub 0.70}Sr{sub 0.30}MnO{sub 3+δ} phase. Display Omitted - Highlights: • The magnetic behaviour of nanocrystalline La{sub 1−x}Sr{sub x}MnO{sub 3+δ} phases was analyzed on the basis of their crystal structure, chemical composition and size of the particles. • Their Curie temperature and magnetization are markedly affected by finite size and surface effects. • The oxygen excess observed in the La{sub 1−x}Sr{sub x}MnO{sub 3+δ} nanoparticles might be generated by the surface layer with deviated oxygen stoichiometry.« less

Characterization of Ternary NiTiPt High-Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Rios, Orlando; Noebe, Ronald; Biles, Tiffany; Garg, Anita; Palczer, Anna; Scheiman, Daniel; Seifert, Hans Jurgen; Kaufman, Michael

2005-01-01

Pt additions substituted for Ni in NiTi alloys are known to increase the transformation temperature of the alloy but only at fairly high Pt levels. However, until now only ternary compositions with a very specific stoichiometry, Ni50-xPtxTi50, have been investigated and then only to very limited extent. In order to learn about this potential high-temperature shape memory alloy system, a series of over twenty alloys along and on either side of a line of constant stoichiometry between NiTi and TiPt were arc melted, homogenized, and characterized in terms of their microstructure, transformation temperatures, and hardness. The resulting microstructures were examined by scanning electron microscopy and the phase compositions quantified by energy dispersive spectroscopy."Stoichiometric" compositions along a line of constant stoichiometry between NiTi to TiPt were essentially single phase but by any deviations from a stoichiometry of (Ni,Pt)50Ti50 resulted in the presence of at least two different intermetallic phases, depending on the overall composition of the alloy. Essentially all alloys, whether single or two-phase, still under went a martensitic transformation. It was found that the transformation temperatures were depressed with initial Pt additions but at levels greater than 10 at.% the transformation temperature increased linearly with Pt content. Also, the transformation temperatures were relatively insensitive to alloy stoichiometry within the range of alloys examined. Finally, the dependence of hardness on Pt content for a series of Ni50-xPtxTi50 alloys showed solution softening at low Pt levels, while hardening was observed in ternary alloys containing more than about 10 at.% Pt. On either side of these "stoichiometric" compositions, hardness was also found to increase significantly.

Respiratory Complex I in Bos taurus and Paracoccus denitrificans Pumps Four Protons across the Membrane for Every NADH Oxidized.

PubMed

Jones, Andrew J Y; Blaza, James N; Varghese, Febin; Hirst, Judy

2017-03-24

Respiratory complex I couples electron transfer between NADH and ubiquinone to proton translocation across an energy-transducing membrane to support the proton-motive force that drives ATP synthesis. The proton-pumping stoichiometry of complex I ( i.e. the number of protons pumped for each two electrons transferred) underpins all mechanistic proposals. However, it remains controversial and has not been determined for any of the bacterial enzymes that are exploited as model systems for the mammalian enzyme. Here, we describe a simple method for determining the proton-pumping stoichiometry of complex I in inverted membrane vesicles under steady-state ADP-phosphorylating conditions. Our method exploits the rate of ATP synthesis, driven by oxidation of NADH or succinate with different sections of the respiratory chain engaged in catalysis as a proxy for the rate of proton translocation and determines the stoichiometry of complex I by reference to the known stoichiometries of complexes III and IV. Using vesicles prepared from mammalian mitochondria (from Bos taurus ) and from the bacterium Paracoccus denitrificans , we show that four protons are pumped for every two electrons transferred in both cases. By confirming the four-proton stoichiometry for mammalian complex I and, for the first time, demonstrating the same value for a bacterial complex, we establish the utility of P. denitrificans complex I as a model system for the mammalian enzyme. P. denitrificans is the first system described in which mutagenesis in any complex I core subunit may be combined with quantitative proton-pumping measurements for mechanistic studies. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Prefrontal system dysfunction and credit card debt.

PubMed

Spinella, Marcello; Yang, Bijou; Lester, David

2004-10-01

Credit card use often involves a disadvantageous allocation of finances because they allow for spending beyond means and buying on impulse. Accordingly they are associated with increased bankruptcy, anxiety, stress, and health problems. Mounting evidence from functional neuroimaging and clinical studies implicates prefrontal-subcortical systems in processing financial information. This study examined the relationship of credit card debt and executive functions using the Frontal System Behavior Scale (FRSBE). After removing the influences of demographic variables (age, sex, education, and income), credit card debt was associated with the Executive Dysfunction scale, but not the Apathy or Disinhibition scales. This suggests that processes of conceptualizing and organizing finances are most relevant to credit card debt, and implicates dorsolateral prefrontal dysfunction.

Emotional distress and dysfunctional illness perception are associated with low mental and physical quality of life in Chinese breast cancer patients.

PubMed

Tang, Lili; Fritzsche, Kurt; Leonhart, Rainer; Pang, Ying; Li, Jinjiang; Song, Lili; Fischer, Irmela; Koch, Maike; Wuensch, Alexander; Mewes, Ricarda; Schaefert, Rainer

2017-12-01

To evaluate the relationship between quality of life (QOL) and physical as well as psychological variables in Chinese breast cancer patients. This multicenter cross-sectional study enrolled 254 Chinese breast cancer patients in different stages and treatment phases. They answered standard instruments assessing QOL (EORTC), somatic symptom severity (PHQ-15), depression (PHQ-9), anxiety (GAD-7), health-related anxiety (WI-7), illness perception (BIPQ), and sense of coherence (SOC-9). Canonical correlation was applied to identify the strongest correlates between the physical, emotional and social QOL scales and the physical and psychological variables. In our sample, a low global QOL was significantly associated with the following physical and psychological variables: symptom-related disability (Karnofsky Index) (r = .211, p < .01), somatic symptom severity (r = -.391, p < .001), depression (r = -.488, p < .001), anxiety (r = -.439, p < .001), health-related anxiety (r = -.398, p < .001), dysfunctional illness perception (r = -.411, p < .001), and sense of coherence (r = .371, p < .001). In the canonical correlation analysis, high somatic symptom severity, depression, anxiety, dysfunctional illness perception, and low sense of coherence showed the strongest correlations with low physical, emotional and social functioning. The first three significant canonical correlations between these two sets of variables were .78, .56, and .45. QOL in Chinese breast cancer patients is strongly associated with psychological factors. Our results suggest that Chinese physicians and nurses should incorporate these factors into their care for women with breast cancer to improve patients' QOL.

Predictive factors of health-related quality of life in patients with polycystic ovary syndrome: a structural equation modeling approach.

PubMed

Bazarganipour, Fatemeh; Ziaei, Saeide; Montazeri, Ali; Foroozanfard, Fatemeh; Kazemnejad, Anoshirvan; Faghihzadeh, Soghrat

2013-11-01

To determine association between health-related quality of life (HRQOL) and psychosexual variables in patients with polycystic ovary syndrome (PCOS). Cross-sectional study. Two private gynecology clinics. A sample of 300 women with PCOS were entered into the study and were subdivided into three groups: hyperandrogenism (HA) and PCO morphology; menstrual dysfunction and PCO morphology; menstrual dysfunction and HA and/or PCO morphology. Then each patient completed the following questionnaires: the Hospital Anxiety and Depression Scale, the Body Image Concern Inventory, the Rosenberg Self-Esteem Scale, the Short-Form Health Survey, and the Female Sexual Function Index. None. Both direct and indirect relationships among clinical symptoms, psychologic status, self-esteem, body image, and sexual function as independent predictors of HRQOL were examined with the use of structural equation modeling analysis. The clinical variables and psychologic distress had the strongest indirect relationships with HRQOL in the HA phenotype. The highest effect of PCOS symptoms on HRQOL impairment in patients with menstrual irregularities along with HA and patients with menstrual irregularities along with polycystic ovaries was exerted by clinical variables, poor perception of self-worth, negative body image, and sexual dysfunction. In patients with various phenotypes of PCOS, the effects of mediating variables on HRQOL are different. In patients with PCOS, the findings suggest that mediating factors, especially psychologic distress, self-esteem, body image, and sexual function, play an important role and should be taken into consideration and adequately treated if present. Copyright © 2013 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Stoichiometry-Controlled Inversion of Supramolecular Chirality in Nanostructures Co-assembled with Bipyridines.

PubMed

Wang, Fang; Feng, Chuan-Liang

2018-02-01

To control supramolecular chirality of the co-assembled nanostructures, one of the remaining issues is how stoichiometry of the different molecules involved in co-assembly influence chiral transformation. Through co-assembly of achiral 1,4-bis(pyrid-4-yl)benzene and chiral phenylalanine-glycine derivative hydrogelators, stoichiometry is found to be an effective tool for controlling supramolecular chirality inversion processes. This inversion is mainly mediated by a delicate balance between intermolecular hydrogen bonding interactions and π-π stacking of the two components, which may subtly change the stacking of the molecules, in turn, the self-assembled nanostructures. This study exemplifies a simplistic way to invert the handedness of chiral nanostructures and provide fundamental understanding of the inherent principles of supramolecular chirality. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonstoichiometric defects in GaAs and the EL2 bandwagon

NASA Astrophysics Data System (ADS)

Lagowski, J.; Gatos, H. C.

1985-09-01

In the present paper, an attempt is made to formulate a common framework for a discussion of nonstoichiometric defects, especially EL2 and dislocations. An outline is provided of the most important settled and unsettled issues, taking into account not only fundamental interests, but also urgent needs in advancing IC technology. Attention is given to stoichiometry-controlled compensation, the expected role of melt stoichiometry in electrical conductivity for the basic atomic disorders, defect equilibria-dislocations and EL2, and current issues pertaining to the identification of EL2. It is concluded that nonstoichiometric defects play a critical role in the electronic properties of GaAs and its electronic applications. Very significant progress has been recently made in learning how to adjust melt stoichiometry in order to maximize its beneficial effects and minimize its detrimental ones.

Nonstoichiometric defects in GaAs and the EL2 bandwagon

NASA Technical Reports Server (NTRS)

Lagowski, J.; Gatos, H. C.

1985-01-01

In the present paper, an attempt is made to formulate a common framework for a discussion of nonstoichiometric defects, especially EL2 and dislocations. An outline is provided of the most important settled and unsettled issues, taking into account not only fundamental interests, but also urgent needs in advancing IC technology. Attention is given to stoichiometry-controlled compensation, the expected role of melt stoichiometry in electrical conductivity for the basic atomic disorders, defect equilibria-dislocations and EL2, and current issues pertaining to the identification of EL2. It is concluded that nonstoichiometric defects play a critical role in the electronic properties of GaAs and its electronic applications. Very significant progress has been recently made in learning how to adjust melt stoichiometry in order to maximize its beneficial effects and minimize its detrimental ones.

Global dynamics in a stoichiometric food chain model with two limiting nutrients.

PubMed

Chen, Ming; Fan, Meng; Kuang, Yang

2017-07-01

Ecological stoichiometry studies the balance of energy and multiple chemical elements in ecological interactions to establish how the nutrient content affect food-web dynamics and nutrient cycling in ecosystems. In this study, we formulate a food chain with two limiting nutrients in the form of a stoichiometric population model. A comprehensive global analysis of the rich dynamics of the targeted model is explored both analytically and numerically. Chaotic dynamic is observed in this simple stoichiometric food chain model and is compared with traditional model without stoichiometry. The detailed comparison reveals that stoichiometry can reduce the parameter space for chaotic dynamics. Our findings also show that decreasing producer production efficiency may have only a small effect on the consumer growth but a more profound impact on the top predator growth. Copyright © 2017 Elsevier Inc. All rights reserved.

Vickers indentation hardness of stoichiometric and reduced single crystal TiO2 (rutile) from 25 to 800 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Deadmore, Daniel L.

1993-01-01

The indentation microhardness of stoichiometric and reduced single crystal rutile (TiO2) from 25 to 800 C is presented in this paper. The results serve two main purposes. One is to assess the effect of rutile's stoichiometry on its hardness. The other is to test recently suggested theory on solid lubrication with sub Stoichiometric rutile in an effort to better understand shear controlled phenomenon. Microhardness was measured using a Vickers diamond indentor on both vacuum and hydrogen reduced single crystal rutile from 25 to 800 C. The results indicate that stoichiometry and temperature have a pronounced effect on rutile's hardness. The measured effects lend support to theory on solid lubrication by enhanced crystallographic slip and suggest that solid lubricant materials may be produced by careful atomic level tailoring (stoichiometry control).

Erectile dysfunction is a strong predictor of poor quality of life in men with Type 2 diabetes mellitus.

PubMed

Malavige, L S; Jayaratne, S D; Kathriarachchi, S T; Sivayogan, S; Ranasinghe, P; Levy, J C

2014-06-01

To identify predictors of poor quality of life among men with diabetes from a comprehensive set of sexual, clinical, socio-economic and lifestyle variables. This was a cross-sectional observational-study of 253 men with Type 2 diabetes, randomly selected from a clinic in Colombo, Sri Lanka. Erectile dysfunction was assessed using the five-item International Index of Erectile Function and quality of life was assessed using the Sri Lankan version of the 36-item short form health survey questionnaire and the disease-specific Psychological Impact of Erectile Dysfunction scale. The presence of premature ejaculation, reduced libido, socio-demographic and lifestyle data was obtained using an interviewer-administered questionnaire. Significant predictors of quality of life were identified by stepwise multivariate linear regression models for short form-36 subscales, summary scales and two scales of Psychological Impact of Erectile Dysfunction. Significant predictors on the physical summary scale of the 36-item short form were erectile dysfunction (β = 7.93, 95% CI 3.70-12.17, P < 0.001) and reduced libido (β = 5.20, 95% CI 0.82-9.59, P < 0.05). Predictors on the mental health summary scale of the 36-item short form were erectile dysfunction (β = 5.82, 95% CI 2.26-9.37, P < 0.01), BMI > 27.5 kg/m(2) (β = 9.12, 95% CI 1.38-17.44, P < 0.05), ischaemic heart disease (β = 6.39, 95% CI 0.74-12.04, P < 0.05) and insulin therapy (β = 5.28, 95% CI 0.34-10.22, P < 0.05). Significant predictors in the sexual experience scale of the Psychological Impact of Erectile Dysfunction were erectile dysfunction (β = 6.57, 95% CI 4.63-8.51, P < 0.001), reduced libido (β =4.33, 95% CI 2.34-6.32, P < 0.001) and postural hypotension (β = 3.99, 95% CI 0.13-7.85, P < 0.05). Predictors on the emotional life scale of the Psychological Impact of Erectile Dysfunction were erectile dysfunction (β = 2.96, 95% CI 1.37-4.58, P < 0.001), reduced libido 2.75 (β = 2.75, 95% CI 1.12-4.40, P < 0.01), younger age (β = 1.05, 95% CI 0.35-1.75, P < 0.01) and postural hypotension (β = 3.39, 95% CI 0.35-6.45, P < 0.05). Erectile dysfunction was a strong predictor of poor generic and disease-specific quality of life among other sexual and clinical variables in men with diabetes. © 2014 The Authors. Diabetic Medicine © 2014 Diabetes UK.

A mass balance model to estimate the rate of composting, methane oxidation and anaerobic digestion in soil covers and shallow waste layers.

PubMed

Rafiee, Reza; Obersky, Lizanne; Xie, Sihuang; Clarke, William P

2017-05-01

Although CH 4 oxidation in landfill soil covers is widely studied, the extent of composting and CH 4 oxidation in underlying waste layers has been speculated but not measured. The objective of this study was to develop and validate a mass balance model to estimate the simultaneous rates of anaerobic digestion (r AD ), CH 4 oxidation (r OX ) and composting (r COM ) in environments where O 2 penetration is variable and zones of aerobic and anaerobic activity are intermingled. The modelled domain could include, as an example, a soil cover and the underlying shallow waste to a nominated depth. The proposed model was demonstrated on a blend of biogas from three separate known sources of gas representing the three reaction processes: (i) a bottle of laboratory grade 50:50% CH 4 :CO 2 gas representing anaerobic digestion biogas; (ii) an aerated 250mL bottle containing food waste that represented composting activity; and (iii) an aerated 250mL bottle containing non-degradable graphite granules inoculated with methanotrophs and incubated with CH 4 and O 2 to represent methanotrophic activity. CO 2 , CH 4 , O 2 and the stable isotope 13 C-CO 2 were chosen as the components for the mass balance model. The three reaction rates, r (=r AD , r OX , r COM ) were calculated as fitting parameters to the overdetermined set of 4mass balance equations with the net flux of these components from the bottles q (= [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] ) as inputs to the model. The coefficient of determination (r 2 ) for observed versus modelled values of r were 1.00, 0.97, 0.98 when the stoichiometry of each reaction was based on gas yields measured in the individual bottles and q was calculated by summing yields from the three bottles. r 2 deteriorated to 0.95, 0.96, 0.87 when using an average stoichiometry from 11 incubations of each of the composting and methane oxidation processes. The significant deterioration in the estimation of r COM showed that this output is highly sensitive to the evaluated stoichiometry coefficients for the reactions. r 2 deteriorated further to 0.86, 0.77, 0.74 when using the average stoichiometry and experimental measurement of the composition and volume of the blended biogas to determine q. This was primarily attributed to average errors of 8%, 7%, 11% and 14% in the measurement of [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] relative to the measurement of the same quantities from the individual bottles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thyroid dysfunctions of prematurity and their impacts on neurodevelopmental outcome.

PubMed

Chung, Mi Lim; Yoo, Han Wok; Kim, Ki-Soo; Lee, Byong Sop; Pi, Soo-Young; Lim, Gina; Kim, Ellen Ai-Rhan

2013-01-01

Thyroid dysfunction is very common and is associated with neurodevelopmental impairments in preterm infants. This study was conducted to determine the incidence and natural course of various thyroid dysfunctions and their impacts on neurodevelopmental outcomes among premature infants. A total of 177 infants were enrolled who were born at <34 weeks or whose birth weight was <1500 g and who underwent repeat thyroid function tests. We analyzed how various thyroid dysfunctions affected neurodevelopmental outcomes at 18 months of corrected age. Thyroid dysfunction was noted in 88 infants. Hypothyroxinemia was observed in 23 infants, and their thyroid function was influenced by variable clinical factors. Free T4 levels were all normalized without thyroxine medication, and neurodevelopmental outcomes were not affected. In contrast, hyperthyrotropinemia was not associated with other clinical factors. Among 58 subjects who had hyperthyrotropinemia, only 31 infants showed normal thyroid-stimulating hormone (TSH) levels at follow-up tests. The remaining 27 infants had persistently high TSH levels, which significantly and poorly influenced the neurodevelopmental outcomes. Thyroid dysfunction is common among preterm infants. With the exception of persistent hyperthyrotropinemia, it generally does not affect neurodevelopmental outcomes. However, the beneficial effects of thyroid hormone therapy in patients with persistent hyperthyrotropinemia merits further study.

Computational Modeling of Pathophysiologic Responses to Exercise in Fontan Patients

PubMed Central

Kung, Ethan; Perry, James C.; Davis, Christopher; Migliavacca, Francesco; Pennati, Giancarlo; Giardini, Alessandro; Hsia, Tain-Yen; Marsden, Alison

2014-01-01

Reduced exercise capacity is nearly universal among Fontan patients. Although many factors have emerged as possible contributors, the degree to which each impacts the overall hemodynamics is largely unknown. Computational modeling provides a means to test hypotheses of causes of exercise intolerance via precisely controlled virtual experiments and measurements. We quantified the physiological impacts of commonly encountered, clinically relevant dysfunctions introduced to the exercising Fontan system via a previously developed lumped-parameter model of Fontan exercise. Elevated pulmonary arterial pressure was observed in all cases of dysfunction, correlated with lowered cardiac output, and often mediated by elevated atrial pressure. Pulmonary vascular resistance was not the most significant factor affecting exercise performance as measured by cardiac output. In the absence of other dysfunctions, atrioventricular valve insufficiency alone had significant physiological impact, especially under exercise demands. The impact of isolated dysfunctions can be linearly summed to approximate the combined impact of several dysfunctions occurring in the same system. A single dominant cause of exercise intolerance was not identified, though several hypothesized dysfunctions each led to variable decreases in performance. Computational predictions of performance improvement associated with various interventions should be weighed against procedural risks and potential complications, contributing to improvements in routine patient management protocol. PMID:25260878

Development of Analytical Thinking Ability and Attitudes towards Science Learning of Grade-11 Students through Science Technology Engineering and Mathematics (STEM Education) in the Study of Stoichiometry

ERIC Educational Resources Information Center

Chonkaew, Patcharee; Sukhummek, Boonnak; Faikhamta, Chatree

2016-01-01

The purpose of this study was to investigate the analytical thinking abilities and attitudes towards science learning of grade-11 students through science, technology, engineering, and mathematics (STEM) education integrated with a problem-based learning in the study of stoichiometry. The research tools consisted of a pre- and post-analytical…

Effects of oxygen stoichiometry on the scaling behaviors of YBa{sub 2}Cu{sub 3}O{sub x} grain boundary weak-links

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

Wu, K.H.; Fu, C.M.; Jeng, W.J.

1994-12-31

The effects of oxygen stoichiometry on the transport properties of the pulsed laser deposited YBa{sub 2}Cu{sub 3}O{sub x} bicrystalline grain boundary weak-link junctions were studied. It is found that not only the cross boundary resistive transition foot structure can be manipulated repeatedly with oxygen annealling processes but the junction behaviors are also altered in accordance. In the fully oxygenated state i.e. with x=7.0 in YBa{sub 2}Cu{sub 3}O{sub x} stoichiometry, the junction critical current exhibits a power of 2 scaling behavior with temperature. In contrast, when annealed in the conditions of oxygen-deficient state (e.g. with x=6.9 in YBa{sub 2}Cu{sub 3}O{sub x}more » stoichiometry) the junction critical current switches to a linear temperature dependence behavior. The results are tentatively attributed to the modification of the structure in the boundary area upon oxygen annealing, which, in turn, will affect the effective dimension of the geometrically constrained weak-link bridges. The detailed discussion on the responsible physical mechanisms as well as the implications of the present results on device applications will be given.« less

Shifts in leaf N:P stoichiometry during rehabilitation in highly alkaline bauxite processing residue sand

PubMed Central

Goloran, Johnvie B.; Chen, Chengrong; Phillips, Ian R.; Elser, James J.

2015-01-01

Large quantities of sodic and alkaline bauxite residue are produced globally as a by-product from alumina refineries. Ecological stoichiometry of key elements [nitrogen (N) and phosphorus (P)] plays a critical role in establishing vegetation cover in bauxite residue sand (BRS). Here we examined how changes in soil chemical properties over time in rehabilitated sodic and alkaline BRS affected leaf N to P stoichiometry of native species used for rehabilitation. Both Ca and soil pH influenced the shifts in leaf N:P ratios of the study species as supported by consistently significant positive relationships (P < 0.001) between these soil indices and leaf N:P ratios. Shifts from N to P limitation were evident for N-fixing species, while N limitation was consistently experienced by non-N-fixing plant species. In older rehabilitated BRS embankments, soil and plant indices (Ca, Na, pH, EC, ESP and leaf N:P ratios) tended to align with those of the natural ecosystem, suggesting improved rehabilitation performance. These findings highlight that leaf N:P stoichiometry can effectively provide a meaningful assessment on understanding nutrient limitation and productivity of native species used for vegetating highly sodic and alkaline BRS, and is a crucial indicator for assessing ecological rehabilitation performance. PMID:26443331

Shifts in leaf N:P stoichiometry during rehabilitation in highly alkaline bauxite processing residue sand.

PubMed

Goloran, Johnvie B; Chen, Chengrong; Phillips, Ian R; Elser, James J

2015-10-07

Large quantities of sodic and alkaline bauxite residue are produced globally as a by-product from alumina refineries. Ecological stoichiometry of key elements [nitrogen (N) and phosphorus (P)] plays a critical role in establishing vegetation cover in bauxite residue sand (BRS). Here we examined how changes in soil chemical properties over time in rehabilitated sodic and alkaline BRS affected leaf N to P stoichiometry of native species used for rehabilitation. Both Ca and soil pH influenced the shifts in leaf N:P ratios of the study species as supported by consistently significant positive relationships (P < 0.001) between these soil indices and leaf N:P ratios. Shifts from N to P limitation were evident for N-fixing species, while N limitation was consistently experienced by non-N-fixing plant species. In older rehabilitated BRS embankments, soil and plant indices (Ca, Na, pH, EC, ESP and leaf N:P ratios) tended to align with those of the natural ecosystem, suggesting improved rehabilitation performance. These findings highlight that leaf N:P stoichiometry can effectively provide a meaningful assessment on understanding nutrient limitation and productivity of native species used for vegetating highly sodic and alkaline BRS, and is a crucial indicator for assessing ecological rehabilitation performance.

Elemental stoichiometry and compositions of weevil larvae and two acorn hosts under natural phosphorus variation

NASA Astrophysics Data System (ADS)

Ji, Huawei; Du, Baoming; Liu, Chunjiang

2017-04-01

To understand how different trophic organisms in a parasite food chain adapt to the differences in soil nutrient conditions, we investigated stoichiometric variation and homeostasis of multiple elements in two acorn trees, Quercus variabilis and Quercus acutissima, and their parasite weevil larvae (Curculio davidi Fairmaire) at phosphorus (P)-deficient and P-rich sites in subtropical China where P-rich ores are scattered among dominant P-deficient soils. Results showed that elemental stoichiometry and compositions of both acorns and weevil larvae differed significantly between P-deficient and P-rich sites (p < 0.05), with the largest contribution of acorn and weevil larva P in distinguishing the stoichiometric compositions between the two site types. The two acorn species were statistically separated by their acorn elemental stoichiometry and compositions (p < 0.05), but no difference was observed on weevil larvae between the two acorn species. P was one of the few elements that were non strict homeostasis in both acorns and weevil larvae. These findings highlight the importance of both environmental influence in elemental stoichiometry and composition and physiological regulations of nutritional needs in organisms and provide possible stoichiometric responses of both plants and animals to P loading, a worldwide issue from excess release of P into the environment.

Climate change effects on macrofaunal litter decomposition: the interplay of temperature, body masses and stoichiometry.

PubMed

Ott, David; Rall, Björn C; Brose, Ulrich

2012-11-05

Macrofauna invertebrates of forest floors provide important functions in the decomposition process of soil organic matter, which is affected by the nutrient stoichiometry of the leaf litter. Climate change effects on forest ecosystems include warming and decreasing litter quality (e.g. higher C : nutrient ratios) induced by higher atmospheric CO(2) concentrations. While litter-bag experiments unravelled separate effects, a mechanistic understanding of how interactions between temperature and litter stoichiometry are driving decomposition rates is lacking. In a laboratory experiment, we filled this void by quantifying decomposer consumption rates analogous to predator-prey functional responses that include the mechanistic parameters handling time and attack rate. Systematically, we varied the body masses of isopods, the environmental temperature and the resource between poor (hornbeam) and good quality (ash). We found that attack rates increased and handling times decreased (i) with body masses and (ii) temperature. Interestingly, these relationships interacted with litter quality: small isopods possibly avoided the poorer resource, whereas large isopods exhibited increased, compensatory feeding of the poorer resource, which may be explained by their higher metabolic demands. The combination of metabolic theory and ecological stoichiometry provided critically important mechanistic insights into how warming and varying litter quality may modify macrofaunal decomposition rates.

Sexual dysfunctions in MS in relation to neuropsychiatric aspects and its psychological treatment: A scoping review

PubMed Central

Rose, Anita; van de Vis, Wim; Engelbrecht, Jannie; Pirard, Michelle; Lau, Stefanie; Heesen, Christoph; Köpke, Sascha

2018-01-01

Objective Sexual dysfunction in multiple sclerosis (MS) is a significant, but often underestimated and overlooked suffering. Interventions to treat sexual dysfunction in MS are rare. The relation between sexual dysfunction in MS and psychological as well as neuropsychological aspects is evident. However, this field of research remains markedly underdeveloped in this severe chronic illness. The aim of this scoping review is to describe the relevant knowledge in this area and to identify psychological interventions to treat sexual dysfunctions in MS. Methods A scoping review was conducted to answer the following questions: (1) Which psychological and neuropsychological factors impact on sexual dysfunction in MS and vice versa? (2) What kind of psychological interventions aiming to improve sexual dysfunctions in MS are available? A comprehensive search and review of MEDLINE, PsycINFO, and CINAHL was completed by using a recent methodological framework for scoping reviews. Results 23 publications covering a total of 13,259 people with MS and 532 healthy controls were identified. Sexual dysfunction was found to be very common in MS and there is an obvious relation to psychological disorders as e.g. depression and anxiety and also to psychological aspects as partner relationship and quality of life. The relation between sexual dysfunction in MS and neuropsychological impairment has only rarely been studied and no clear results were found. Only two studies were identified, assessing the effectiveness of psychological intervention studies on sexual dysfunction in people with MS, and a third study presenting a secondary analysis of a study targeting depression. All three studies reported significant improvements in sexual dysfunction as well as partly in psychological variables. Conclusions There is a pressing need for the development and adequate evaluation of psychological interventions for sexual dysfunctions in MS. In addition, sexual dysfunction and its impact on psychological wellbeing should be more focussed in clinical care. Registration This review is registered with PROSPERO; Registration number: CRD42016033066. PMID:29486006

Sexual dysfunctions in MS in relation to neuropsychiatric aspects and its psychological treatment: A scoping review.

PubMed

Pöttgen, Jana; Rose, Anita; van de Vis, Wim; Engelbrecht, Jannie; Pirard, Michelle; Lau, Stefanie; Heesen, Christoph; Köpke, Sascha

2018-01-01

Sexual dysfunction in multiple sclerosis (MS) is a significant, but often underestimated and overlooked suffering. Interventions to treat sexual dysfunction in MS are rare. The relation between sexual dysfunction in MS and psychological as well as neuropsychological aspects is evident. However, this field of research remains markedly underdeveloped in this severe chronic illness. The aim of this scoping review is to describe the relevant knowledge in this area and to identify psychological interventions to treat sexual dysfunctions in MS. A scoping review was conducted to answer the following questions: (1) Which psychological and neuropsychological factors impact on sexual dysfunction in MS and vice versa? (2) What kind of psychological interventions aiming to improve sexual dysfunctions in MS are available? A comprehensive search and review of MEDLINE, PsycINFO, and CINAHL was completed by using a recent methodological framework for scoping reviews. 23 publications covering a total of 13,259 people with MS and 532 healthy controls were identified. Sexual dysfunction was found to be very common in MS and there is an obvious relation to psychological disorders as e.g. depression and anxiety and also to psychological aspects as partner relationship and quality of life. The relation between sexual dysfunction in MS and neuropsychological impairment has only rarely been studied and no clear results were found. Only two studies were identified, assessing the effectiveness of psychological intervention studies on sexual dysfunction in people with MS, and a third study presenting a secondary analysis of a study targeting depression. All three studies reported significant improvements in sexual dysfunction as well as partly in psychological variables. There is a pressing need for the development and adequate evaluation of psychological interventions for sexual dysfunctions in MS. In addition, sexual dysfunction and its impact on psychological wellbeing should be more focussed in clinical care. This review is registered with PROSPERO; Registration number: CRD42016033066.

Heart rate variability in patients with systemic lupus erythematosus: a systematic review and methodological considerations.

PubMed

Matusik, P S; Matusik, P T; Stein, P K

2018-07-01

Aim The aim of this review was to summarize current knowledge about the scientific findings and potential clinical utility of heart rate variability measures in patients with systemic lupus erythematosus. Methods PubMed, Embase and Scopus databases were searched for the terms associated with systemic lupus erythematosus and heart rate variability, including controlled vocabulary, when appropriate. Articles published in English and available in full text were considered. Finally, 11 publications were selected, according to the systematic review protocol and were analyzed. Results In general, heart rate variability, measured in the time and frequency domains, was reported to be decreased in patients with systemic lupus erythematosus compared with controls. In some systemic lupus erythematosus studies, heart rate variability was found to correlate with inflammatory markers and albumin levels. A novel heart rate variability measure, heart rate turbulence onset, was shown to be increased, while heart rate turbulence slope was decreased in systemic lupus erythematosus patients. Reports of associations of changes in heart rate variability parameters with increasing systemic lupus erythematosus activity were inconsistent, showing decreasing heart rate variability or no relationship. However, the low/high frequency ratio was, in some studies, reported to increase with increasing disease activity or to be inversely correlated with albumin levels. Conclusions Patients with systemic lupus erythematosus have abnormal heart rate variability, which reflects cardiac autonomic dysfunction and may be related to inflammatory cytokines but not necessarily to disease activity. Thus measurement of heart rate variability could be a useful clinical tool for monitoring autonomic dysfunction in systemic lupus erythematosus, and may potentially provide prognostic information.

Cumulative risk effect of household dysfunction for child maltreatment after intensive intervention of the child protection system in Japan: a longitudinal analysis.

PubMed

Ohashi, Hirotsuna; Wada, Ichiro; Yamaoka, Yui; Nakajima-Yamaguchi, Ryoko; Ogai, Yasukazu; Morita, Nobuaki

2018-04-20

Building an effective casework system for child maltreatment is a global issue. We estimated the effect of household dysfunction (i.e., interparental violence, caregiver mental health problems, and caregiver substance abuse) on child maltreatment to understand how to advance the current framework of child welfare. The sample comprised 759 children (1- to 17-year-old; mean age was 10.6; 404 boys and 355 girls) placed in temporary custody units (one of the strongest intervention of the Japanese child protection system). Caseworkers from 180 units across 43 prefectures completed questionnaires on children and their family and were asked whether a child maltreatment report had been made after cancelation of custody in a 15-month follow-up period. The relations of household dysfunction and maltreatment reports were assessed using the Cox proportional hazard model. About half (48.4%) of the children had been placed in the unit because of maltreatment, and 88.3% had a history of victimization. Seventy-six cases had maltreatment reports after cancelation. We entered household dysfunction variables individually into the model, and each had a significant relationship with maltreatment reports (hazard ratios for interparental violence, caregiver mental health problem, and substance abuse were 1.69, 1.69, and 2.19, respectively) after covariate adjustment. When treating these three variables as cumulative risk score model of household dysfunction, the hazard ratio increased with increasing number of score (1.96 for score two; 2.35 for score three; score 0 as reference). Greater household dysfunction score is a risk of maltreatment after intensive intervention. It is imperative to construct systems facilitating cooperation between child and adult service sectors and to deliver seamless services to children and families. Our findings provide child protect services with risk-stratified interventions for children at victimization risk and promote adult-focused services to be proactive in prevention or intervention for adults with perpetration risk.

Impact of Pubertal Development and Physical Activity on Heart Rate Variability in Overweight and Obese Children in Taiwan

ERIC Educational Resources Information Center

Chen, Su-Ru; Chiu, Hung-Wen; Lee, Yann-Jinn; Sheen, Tzong-Chi; Jeng, Chii

2012-01-01

Child obesity is frequently associated with dysfunction of autonomic nervous system. Children in pubertal development were suggested to be vulnerable to autonomic nervous system problems such as decrease of heart rate variability from dysregulation of metabolic control. This study explored the influence of pubertal development on autonomic nervous…

Right ventricular systolic dysfunction and vena cava dilatation precede alteration of renal function in adult patients undergoing cardiac surgery: An observational study.

PubMed

Guinot, Pierre Grégoire; Abou-Arab, Osama; Longrois, Dan; Dupont, Herve

2015-08-01

Several authors have suggested that right ventricular dysfunction (RVd) may contribute to renal dysfunction in nonsurgical patients. We tested the hypothesis that RVd diagnosed immediately after cardiac surgery may be associated with subsequent development of renal dysfunction and tried to identify the possible mechanisms. A single-centre, prospective observational study. Amiens University Hospital, France. All adult patients undergoing cardiac surgery were considered eligible for participation. Patients who had undergone pulmonary or tricuspid valve surgery, repeat surgery or who underwent immediate postoperative renal replacement therapy were excluded. Data from 74 patients were analysed. Left ventricular and right ventricular function were assessed before surgery and on admission to ICU by transthoracic echocardiography (TTE): left ventricular and right ventricular ejection fractions (LVEF/RVEF), tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (Sr(t)) and right ventricular dilatation. RVd was defined as values in the lowest quartile of at least two echocardiographic variables. Renal dysfunction was defined as an increase in serum creatinine concentration (sCr) on postoperative day 1. All right ventricular TTE variables decreased (P < 0.05) after surgery: RVEF from 50% (49 to 60) to 40% (35 to 50); TAPSE from 22.3 mm (19.4 to 25.3) to 12.2 mm (8.8 to 14.8); and Sr(t) from 15.0 cm s(-1) (12.0 to 18.0) to 8.1 cm s(-1) (6.3 to 9.2). Fourteen (19%) patients had right ventricular dilatation and RVd was present in 23 (31%) patients. Forty patients had a positive variation in sCr. In multivariate analysis, patients with RVd had an odds ratio (OR) of 12.7 [95% confidence interval (95% CI) 2.6 to 63.4, P = 0.02] for development of renal dysfunction. Renal dysfunction was associated with increased central venous pressure but was not associated with cardiac index (CI). These results suggest that early postoperative RVd is associated with a subsequent increase of sCr and that the mechanism involved is congestion (vena cava dilatation/elevated CVP) rather than decreased CI.

Function and dysfunction of CNG channels: insights from channelopathies and mouse models.

PubMed

Biel, Martin; Michalakis, Stylianos

2007-06-01

Channels directly gated by cyclic nucleotides (CNG channels) are important cellular switches that mediate influx of Na+ and Ca2+ in response to increases in the intracellular concentration of cAMP and cGMP. In photoreceptors and olfactory receptor neurons, these channels serve as final targets for cGMP and cAMP signaling pathways that are initiated by the absorption of photons and the binding of odorants, respectively. CNG channels have been also found in other types of neurons and in non-excitable cells. However, in most of these cells, the physiological role of CNG channels has yet to be determined. CNG channels have a complex heteromeric structure. The properties of individual subunits that assemble in specific stoichiometries to the native channels have been extensively investigated in heterologous expression systems. Recently, mutations in human CNG channel genes leading to inherited diseases (so-called channelopathies) have been functionally characterized. Moreover, mouse knockout models were generated to define the role of CNG channel proteins in vivo. In this review, we will summarize recent insights into the physiological and pathophysiological role of CNG channel proteins that have emerged from genetic studies in mice and humans.

Temporal variability of foliar nutrients: responses to nitrogen deposition and prescribed fire in a temperate steppe

USGS Publications Warehouse

Lü, Xiao-Tao; Reed, Sasha C.; Hou, Shuang-Li; Hu, Yan-Yu; Wei, Hai-Wei; Lü, Fu-Mei; Cui, Qiang; Han, Xing Guo

2017-01-01

Plant nutrient concentrations and stoichiometry drive fundamental ecosystem processes, with important implications for primary production, diversity, and ecosystem sustainability. While a range of evidence exists regarding how plant nutrients vary across spatial scales, our understanding of their temporal variation remains less well understood. Nevertheless, we know nutrients regulate plant function across time, and that important temporal controls could strongly interact with environmental change. Here, we report results from a 3-year assessment of inter-annual changes of foliar nitrogen (N) and phosphorus (P) concentrations and stoichiometry in three dominant grasses in response to N deposition and prescribed fire in a temperate steppe of northern China. Foliar N and P concentrations and their ratios varied greatly among years, with this temporal variation strongly related to inter-annual variation in precipitation. Nitrogen deposition significantly increased foliar N concentrations and N:P ratios in all species, while fire significantly altered foliar N and P concentrations but had no significant impacts on N:P ratios. Generally, N addition enhanced the temporal stability of foliar N and decreased that of foliar P and of N:P ratios. Our results indicate that plant nutrient status and response to environmental change are temporally dynamic and that there are differential effects on the interactions between environmental change drivers and timing for different nutrients. These responses have important implications for consideration of global change effects on plant community structure and function, management strategies, and the modeling of biogeochemical cycles under global change scenarios.

Longitudinal effects of dysfunctional perfectionism and avoidant personality style on postpartum mental disorders: Pathways through antepartum depression and anxiety.

PubMed

Oddo-Sommerfeld, Silvia; Hain, Sarah; Louwen, Frank; Schermelleh-Engel, Karin

2016-02-01

There is first evidence that some personality characteristics raise the risk of postpartum depression (PPD). The present longitudinal study investigates whether dysfunctional perfectionism and avoidant personality style predict PPD, postpartum anxiety (PPA) and bonding impairment (BI) directly or indirectly through antepartum anxiety (APA) and antepartum depression (APD). Pregnant women were recruited in two obstetric departments in Germany. The assessment occurred at two measurement time points: In the third trimester of pregnancy (N=297) and twelve weeks postpartum (N=266). Six questionnaires were administered during pregnancy: perfectionism, personality styles, anxiety, and depression. Postpartum, data on PPA, PPD and BI were collected. We conducted two path analyses in order to examine direct and indirect effects of the two personality characteristics on postpartum disorders. Testing for direct effects of dysfunctional perfectionism and avoidant personality style on PPD, PPA, and BI did not yield significant results. Instead, significant indirect effects were found: PPD, PPA, and BI were influenced indirectly by dysfunctional perfectionism and avoidant personality style via APD and APA. This model explained high portions of the variance of PPD, PPA, and impaired bonding. Each of the two personality characteristics explained a unique part of the outcome measures. The influence on BI was mediated by PPD. APD affected PPD and PPA more strongly than APA. Path models with manifest (observed) variables may lead to measurement errors. Self-rating questionnaires may raise the problem of social desirability. Dysfunctional perfectionism and avoidant personality style are significant risk factors for PPD, PPA, and BI. Screenings of both variables, as well as of APA and APD, which mediated the effect of personality traits on postpartum syndromes, are necessary. Copyright © 2015 Elsevier B.V. All rights reserved.

The Evaluation of Relationship between Sexual Self-concept and Sexual Dysfunction in Individuals Undergoing Methadone Maintenance Treatment

PubMed Central

Rajabizadeh, Ghodratolah; Yazdanpanah, Fatemeh; Ramezani, Mohammad Arash

2017-01-01

Background The present study was conducted with the aim of designing a causal model for the evaluation of sexual dysfunctions based on the variables of methadone dosage and sexual self-concept among individuals undergoing methadone maintenance treatment (MMT). Methods The study population of the present study consisted of married men of 20 to 45 years of age with sexual ýrelations and undergoing MMT for a minimum of 8 weeks referring to all MMT clinics of Kerman, Iran, in ýý2015-2016. ýThe subjects were selected through multi-stage cluster sampling (n = 250). Data were collected using the General Health Questionnaire (GHQ-28), Multi-Dimensional Sexual Self-concept Questionnaire (MSSQ), and Internal Index for Erectile Function (IIEF). Data were analyzed using path analysis method and Pearson correlation coefficient. The suggested model was evaluated using structural equation model (SEM), and indirect relationships were assessed using Bootstrap method. Findings The suggested model showed acceptable fitness with the data, and all routes, except methadone use route, to sexual function were significant. The result of the multiple ýindirect route showed that sexual function had a significant relationship with methadone use through ýsexual self-concept. In total, 60% of variance in sexual dysfunction was explained using the variables of the suggested model. Conclusion Further studies are suggested to be conducted regarding psychological factors effective on the sexual dysfunctions among individuals undergoing MMT, such as sexual self-concept. Moreover, more detailed evaluation of each subscale of positive and negative sexual self-concept is recommended to assess the psychological causes of sexual dysfunctions in these individuals and design psychological, behavioral, and cognitive-behavioral treatment interventions for them. PMID:29299211

Vildagliptin and caloric restriction for cardioprotection in pre-diabetic rats.

PubMed

Tanajak, Pongpan; Pintana, Hiranya; Siri-Angkul, Natthaphat; Khamseekaew, Juthamas; Apaijai, Nattayaporn; Chattipakorn, Siriporn C; Chattipakorn, Nipon

2017-02-01

Long-term high-fat diet (HFD) consumption causes cardiac dysfunction. Although calorie restriction (CR) has been shown to be useful in obesity, we hypothesized that combined CR with dipeptidyl peptidase-4 (DPP-4) inhibitor provides greater efficacy than monotherapy in attenuating cardiac dysfunction and metabolic impairment in HFD-induced obese-insulin resistant rats. Thirty male Wistar rats were divided into 2 groups to be fed on either a normal diet (ND, n = 6) or a HFD (n = 24) for 12 weeks. Then, HFD rats were divided into 4 subgroups (n = 6/subgroup) to receive just the vehicle, CR diet (60% of mean energy intake and changed to ND), vildagliptin (3 mg/kg/day) or combined CR and vildagliptin for 4 weeks. Metabolic parameters, heart rate variability (HRV), cardiac mitochondrial function, left ventricular (LV) and fibroblast growth factor (FGF) 21 signaling pathway were determined. Rats on a HFD developed insulin and FGF21 resistance, oxidative stress, cardiac mitochondrial dysfunction and impaired LV function. Rats on CR alone showed both decreased body weight and visceral fat accumulation, whereas vildagliptin did not alter these parameters. Rats in CR, vildagliptin and CR plus vildagliptin subgroups had improved insulin sensitivity and oxidative stress. However, vildagliptin improved heart rate variability (HRV), cardiac mitochondrial function and LV function better than the CR. Chronic HFD consumption leads to obese-insulin resistance and FGF21 resistance. Although CR is effective in improving metabolic regulation, vildagliptin provides greater efficacy in preventing cardiac dysfunction by improving anti-apoptosis and FGF21 signaling pathways and attenuating cardiac mitochondrial dysfunction in obese-insulin-resistant rats. © 2017 Society for Endocrinology.

The Evaluation of Relationship between Sexual Self-concept and Sexual Dysfunction in Individuals Undergoing Methadone Maintenance Treatment.

PubMed

Rajabizadeh, Ghodratolah; Yazdanpanah, Fatemeh; Ramezani, Mohammad Arash

2017-04-01

The present study was conducted with the aim of designing a causal model for the evaluation of sexual dysfunctions based on the variables of methadone dosage and sexual self-concept among individuals undergoing methadone maintenance treatment (MMT). The study population of the present study consisted of married men of 20 to 45 years of age with sexual ýrelations and undergoing MMT for a minimum of 8 weeks referring to all MMT clinics of Kerman, Iran, in ýý2015-2016. ýThe subjects were selected through multi-stage cluster sampling (n = 250). Data were collected using the General Health Questionnaire (GHQ-28), Multi-Dimensional Sexual Self-concept Questionnaire (MSSQ), and Internal Index for Erectile Function (IIEF). Data were analyzed using path analysis method and Pearson correlation coefficient. The suggested model was evaluated using structural equation model (SEM), and indirect relationships were assessed using Bootstrap method. The suggested model showed acceptable fitness with the data, and all routes, except methadone use route, to sexual function were significant. The result of the multiple ýindirect route showed that sexual function had a significant relationship with methadone use through ýsexual self-concept. In total, 60% of variance in sexual dysfunction was explained using the variables of the suggested model. Further studies are suggested to be conducted regarding psychological factors effective on the sexual dysfunctions among individuals undergoing MMT, such as sexual self-concept. Moreover, more detailed evaluation of each subscale of positive and negative sexual self-concept is recommended to assess the psychological causes of sexual dysfunctions in these individuals and design psychological, behavioral, and cognitive-behavioral treatment interventions for them.

Chronic renal failure and sexual functioning: clinical status versus objectively assessed sexual response.

PubMed

Toorians, A W; Janssen, E; Laan, E; Gooren, L J; Giltay, E J; Oe, P L; Donker, A J; Everaerd, W

1997-12-01

Sexual dysfunctions are common among patients with chronic renal failure. The prevalence was assessed in a population of 281 patients (20-60 years), and it was attempted to determine whether their mode of treatment (haemodialysis, peritoneal dialysis, or kidney transplantation), or biochemical and endocrine variables and neuropathy affect sexual functioning. Patients with rheumatoid arthritis served as a comparison group. Assessment included clinical history, physical and laboratory examinations, questionnaires measuring erotosexual dysfunctions, and a psychophysiological test procedure. The latter is a laboratory method which measures, in a waking state, subjective and physiological sexual arousal. Men on haemodialysis or peritoneal dialysis suffered significantly more often from 'Hypoactive Sexual Desire Disorder', 'Sexual Aversion Disorder' and 'Inhibited Male Orgasm' than men with kidney transplantation or rheumatoid arthritis. Interestingly, the prevalence of 'Male Erectile Disorder' did not differ significantly between the four groups and ranged between 17 and 43%. Of the women, transplanted patients suffered significantly less from 'Hypoactive Sexual Desire Disorder' than the other three groups; the prevalence of other sexual dysfunctions did not differ between the groups. Although 'Male Erectile Disorder' and 'Female Sexual Arousal Disorder' had a relatively high prevalence there were no differences in the four groups of patients in genital responses during psychophysiological testing. Genital responses during psychophysiological assessment had no relationship to the duration of renal replacement treatment, biochemical/endocrine variables, or the presence/ absence of neuropathy. The prevalence of sexual dysfunction was high. Sexual dysfunction in men on haemodialysis or peritoneal dialysis was not so much due to erectile failure but largely to loss of sexual interest, subjectively ascribed to fatigue. The latter was also found in women on haemodialysis or peritoneal dialysis.

Bridging disparate symptoms of schizophrenia: a triple network dysfunction theory

PubMed Central

Nekovarova, Tereza; Fajnerova, Iveta; Horacek, Jiri; Spaniel, Filip

2014-01-01

Schizophrenia is a complex neuropsychiatric disorder with variable symptomatology, traditionally divided into positive and negative symptoms, and cognitive deficits. However, the etiology of this disorder has yet to be fully understood. Recent findings suggest that alteration of the basic sense of self-awareness may be an essential distortion of schizophrenia spectrum disorders. In addition, extensive research of social and mentalizing abilities has stressed the role of distortion of social skills in schizophrenia.This article aims to propose and support a concept of a triple brain network model of the dysfunctional switching between default mode and central executive network (CEN) related to the aberrant activity of the salience network. This model could represent a unitary mechanism of a wide array of symptom domains present in schizophrenia including the deficit of self (self-awareness and self-representation) and theory of mind (ToM) dysfunctions along with the traditional positive, negative and cognitive domains. We review previous studies which document the dysfunctions of self and ToM in schizophrenia together with neuroimaging data that support the triple brain network model as a common neuronal substrate of this dysfunction. PMID:24910597

Minimizing Hemodialysis Catheter Dysfunction: An Ounce of Prevention

PubMed Central

Lee, Timmy; Lok, Charmaine; Vazquez, Miguel; Moist, Louise; Maya, Ivan; Mokrzycki, Michele

2012-01-01

The maintenance of tunneled catheter (TC) patency is critical for the provision of adequate hemodialysis in patients who are TC-dependent. TC dysfunction results in the need for costly and inconvenient interventions, and reduced quality of life. Since the introduction of TCs in the late 1980s, heparin catheter lock has been the standard prophylactic regimen for the prevention of TC dysfunction. More recently, alternative catheter locking agents have emerged, and in some cases have shown to be superior to heparin lock with respect to improving TC patency and reducing TC-associated infections. These include citrate, tissue plasminogen activator, and a novel agent containing sodium citrate, methylene blue, methylparaben, and propylparaben. In addition, prophylaxis using oral anticoagulants/antiplatelet agents, including warfarin, aspirin, ticlodipine, as well as the use of modified heparin-coated catheters have also been studied for the prevention of TC dysfunction with variable results. The use of oral anticoagulants and/or antiplatelet agents as primary or secondary prevention of TC dysfunction must be weighed against their potential adverse effects, and should be individualized for each patient. PMID:22518310

Integrating a Smartphone and Molecular Modeling for Determining the Binding Constant and Stoichiometry Ratio of the Iron(II)-Phenanthroline Complex: An Activity for Analytical and Physical Chemistry Laboratories

ERIC Educational Resources Information Center

de Morais, Camilo de L. M.; Silva, Se´rgio R. B.; Vieira, Davi S.; Lima, Ka´ssio M. G.

2016-01-01

The binding constant and stoichiometry ratio for the formation of iron(II)-(1,10-phenanthroline) or iron(II)-o-phenanthroline complexes has been determined by a combination of a low-cost analytical method using a smartphone and a molecular modeling method as a laboratory experiment designed for analytical and physical chemistry courses. Intensity…

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

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

Wicklein, S.; Koehl, A.; Dittmann, R.

2012-09-24

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime ofmore » Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.« less

How to Say How Much: Amounts and Stoichiometry

NASA Astrophysics Data System (ADS)

Ault, Addison

2001-10-01

This paper presents a concise and consistent pictorial representation of the ways by which chemists describe an amount of material and of the conversion factors by which these statements of amount can be translated into one another. The expressions of amounts are mole, grams, milliliters of a pure liquid, liters of solution, liters of a gas at standard and nonstandard conditions, and number of particles. The paper then presents a visual representation or "map" for the solution of the typical stoichiometry problems discussed in general chemistry. You use the map for mole-to-mole and gram-to-gram calculations (or any combination of these), and for limiting reagent and percent yield problems. You can extend the method to reactions that involve solutions or gases and to titration problems. All stoichiometry problems are presented as variations on a central theme, and all problems are reduced to the same types of elementary steps.

Electrophysiological and biochemical evidence that DEG/ENaC cation channels are composed of nine subunits.

PubMed

Snyder, P M; Cheng, C; Prince, L S; Rogers, J C; Welsh, M J

1998-01-09

Members of the DEG/ENaC protein family form ion channels with diverse functions. DEG/ENaC subunits associate as hetero- and homomultimers to generate channels; however the stoichiometry of these complexes is unknown. To determine the subunit stoichiometry of the human epithelial Na+ channel (hENaC), we expressed the three wild-type hENaC subunits (alpha, beta, and gamma) with subunits containing mutations that alter channel inhibition by methanethiosulfonates. The data indicate that hENaC contains three alpha, three beta, and three gamma subunits. Sucrose gradient sedimentation of alphahENaC translated in vitro, as well as alpha-, beta-, and gammahENaC coexpressed in cells, was consistent with complexes containing nine subunits. FaNaCh and BNC1, two related DEG/ENaC channels, produced complexes of similar mass. Our results suggest a novel nine-subunit stoichiometry for the DEG/ENaC family of ion channels.

Properties of CsI, CsBr and GaAs thin films grown by pulsed laser deposition

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

Brendel, V M; Garnov, S V; Yagafarov, T F

2014-09-30

CsI, CsBr and GaAs thin films have been grown by pulsed laser deposition on glass substrates. The morphology and structure of the films have been studied using X-ray diffraction and scanning electron microscopy. The CsI and CsBr films were identical in stoichiometry to the respective targets and had a polycrystalline structure. Increasing the substrate temperature led to an increase in the density of the films. All the GaAs films differed in stoichiometry from the target. An explanation was proposed for this fact. The present results demonstrate that, when the congruent transport condition is not fulfilled, films identical in stoichiometry tomore » targets can be grown by pulsed laser deposition in the case of materials with a low melting point and thermal conductivity. (interaction of laser radiation with matter)« less

Influence of Coformer Stoichiometric Ratio on Pharmaceutical Cocrystal Dissolution: Three Cocrystals of Carbamazepine/4-Aminobenzoic Acid.

PubMed

Li, Zi; Matzger, Adam J

2016-03-07

Cocrystallization is a technique to optimize solid forms that shows great potential to improve the solubility of active pharmaceutical ingredients (APIs). In some systems, an API can form cocrystals in multiple stoichiometries with the same coformer. However, it remains unclear how coformer stoichiometry influences solubility. This paper investigates the pharmaceutical:coformer pair carbamazepine (CBZ)/p-aminobenzoic acid (PABA); both CBZ/PABA 1:1 and 2:1 cocrystals are known, and a novel 4:1 CBZ/PABA cocrystal is reported here. The 4:1 cocrystal is structurally characterized, and phase stability data suggest that it is a thermodynamically unstable form. Dissolution experiments show that there is no correlation between the cocrystal stoichiometry and dissolution rate in this system. On the other hand, with the relatively weak intermolecular interactions, metastable forms can be beneficial to dissolution rate, which suggests that more effort should be devoted to cocrystal production with kinetic growth methods.

Stoichiometry of Silicon Dioxide Films Obtained by Ion-Beam Sputtering

NASA Astrophysics Data System (ADS)

Telesh, E. V.; Dostanko, A. P.; Gurevich, O. V.

2018-03-01

The composition of SiOx films produced by ion-beam sputtering (IBS) of silicon and quartz targets were studied by infrared spectrometry. Films with thicknesses of 150-390 nm were formed on silicon substrates. It was found that increase in the partial pressure of oxygen in the working gas, increase in the temperature of the substrate, and the presence of a positive potential on the target during reactive IBS of silicon shifted the main absorption band νas into the high-frequency region and increased the composition index from 1.41 to 1.85. During IBS of a quartz target the stoichiometry of the films deteriorates with increase of the energy of the sputtering argon ions. This may be due to increase of the deposition rate. Increase in the current of the thermionic compensator, increase of the substrate temperature, and addition of oxygen led to the formation of SiOx films with improved stoichiometry.

Interobserver and Intraobserver Agreement on Qualitative Assessments of Right Ventricular Dysfunction With Echocardiography in Patients With Pulmonary Embolism.

PubMed

Weekes, Anthony J; Oh, Laura; Thacker, Gregory; Johnson, Angela K; Runyon, Michael; Rose, Geoffrey; Johnson, Thomas; Templin, Megan; Norton, H James

2016-10-01

To evaluate observer agreement using qualitative goal-directed echocardiographic criteria for right ventricular (RV) dysfunction prognostication in submassive pulmonary embolism (PE). Two emergency physicians and 2 cardiologists independently reviewed 31 packets of goal-directed echocardiographic video clips consisting of at least 3 windows obtained by emergency physicians from normotensive patients with PE. Nine packets were repeated to assess for intraobserver agreement. Right ventricular dysfunction criteria on goal-directed echocardiography were as follows: RV enlargement was present, with a right-to-left ventricular basal diameter ratio of 1.0 or higher and blunting of the apex of the RV in 2 or more different windows; RV systolic dysfunction was present if the tricuspid annulus moved toward the apex 10 mm or less and there was RV free wall hypokinesis; and septal deviation was present with any flattening or deviation of the ventricular septum toward the left ventricle. Among the 4 participants, there was 83.9% agreement on the presence or absence of RV enlargement (κ = 0.84), 74.2% agreement on the presence or absence of RV systolic dysfunction (κ = 0.69), and 71.0% agreement on the presence or absence of septal deviation (κ = 0.59). Intraobserver agreement was 100% for each RV dysfunction variable for each observer (κ = 1.0). Agreement was substantial for both severe RV enlargement and RV systolic dysfunction and moderate for septal deviation. Right ventricular dysfunction assessment with qualitative goal-directed echocardiographic criteria is reproducible for PE risk stratification.

Early and simple detection of diastolic dysfunction during weaning from mechanical ventilation

PubMed Central

2012-01-01

Weaning from mechanical ventilation imposes additional work on the cardiovascular system and can provoke or unmask left ventricular diastolic dysfunction with consecutive pulmonary edema or systolic dysfunction with inadequate increase of cardiac output and unsuccessful weaning. Echocardiography, which is increasingly used for hemodynamic assessment of critically ill patients, allows differentiation between systolic and diastolic failure. For various reasons, transthoracic echocardiographic assessment was limited to patients with good echo visibility and to those with sinus rhythm without excessive tachycardia. In these patients, often selected after unsuccessful weaning, echocardiographic findings were predictive for weaning failure of cardiac origin. In some studies, patients with various degrees of systolic dysfunction were included, making evaluation of the diastolic dysfunction to the weaning failure even more difficult. The recent study by Moschietto and coworkers included unselected patients and used very simple diastolic variables for assessment of diastolic function. They also included patients with atrial fibrillation and repeated echocardiographic examination only 10 minutes after starting a spontaneous breathing trial. The main finding was that weaning failure was not associated with systolic dysfunction but with diastolic dysfunction. By measuring simple and robust parameters for detection of diastolic dysfunction, the study was able to predict weaning failure in patients with sinus rhythm and atrial fibrillation as early as 10 minutes after beginning a spontaneous breathing trial. Further studies are necessary to determine whether appropriate treatment tailored according to the echocardiographic findings will result in successful weaning. PMID:22770365

Early and simple detection of diastolic dysfunction during weaning from mechanical ventilation.

PubMed

Voga, Gorazd

2012-07-06

Weaning from mechanical ventilation imposes additional work on the cardiovascular system and can provoke or unmask left ventricular diastolic dysfunction with consecutive pulmonary edema or systolic dysfunction with inadequate increase of cardiac output and unsuccessful weaning. Echocardiography, which is increasingly used for hemodynamic assessment of critically ill patients, allows differentiation between systolic and diastolic failure. For various reasons, transthoracic echocardiographic assessment was limited to patients with good echo visibility and to those with sinus rhythm without excessive tachycardia. In these patients, often selected after unsuccessful weaning, echocardiographic findings were predictive for weaning failure of cardiac origin. In some studies, patients with various degrees of systolic dysfunction were included, making evaluation of the diastolic dysfunction to the weaning failure even more difficult. The recent study by Moschietto and coworkers included unselected patients and used very simple diastolic variables for assessment of diastolic function. They also included patients with atrial fibrillation and repeated echocardiographic examination only 10 minutes after starting a spontaneous breathing trial. The main finding was that weaning failure was not associated with systolic dysfunction but with diastolic dysfunction. By measuring simple and robust parameters for detection of diastolic dysfunction, the study was able to predict weaning failure in patients with sinus rhythm and atrial fibrillation as early as 10 minutes after beginning a spontaneous breathing trial. Further studies are necessary to determine whether appropriate treatment tailored according to the echocardiographic findings will result in successful weaning.

The distribution of patients who seek treatment for the complaint of ejaculating prematurely according to the four premature ejaculation syndromes.

PubMed

Serefoglu, Ege Can; Cimen, Haci Ibrahim; Atmaca, Ali Fuat; Balbay, M Derya

2010-02-01

In addition to "lifelong" and "acquired" premature ejaculation (PE) syndromes, two more PE syndromes have recently been proposed: "Natural variable PE" and "premature-like ejaculatory dysfunction." The purpose of this study was to analyze the prevalence of the four PE syndromes among patients who were admitted to a urology outpatient clinic with the complaint of ejaculating prematurely. Between July 2008 and March 2009, patients admitted to a urology outpatient clinic with a self-reported complaint of PE were enrolled into the study. After taking a careful medical and sexual history, patients were classified as "lifelong,"acquired,"natural variable," PE or "premature-like ejaculatory dysfunction." In addition to medical and sexual history, self-estimated intravaginal ejaculatory latency times (IELTs) of patients were used in the classification of patients. A total of 261 potent men with a mean age of 36.39 +/- 10.45 years (range 20-70) were recruited into the study. The majority of the men was diagnosed as having lifelong PE (62.5%); the remaining men were diagnosed as having acquired (16.1%), natural variable PE (14.5%), or premature-like ejaculatory disorder (6.9%). The mean age of patients with acquired PE was significantly higher than the other groups (P = 0.001). No significant difference was observed for educational status or income level of patients in the different PE groups (P = 0.983 and P = 0.151, respectively). The mean self-estimated IELT for all subjects was 65.16 +/- 83.75 seconds (2-420 seconds). Patients with lifelong PE had significantly lower mean self-reported IELT, whereas the patients with premature-like ejaculatory dysfunction had the highest mean IELT (P = 0.001): (i) life-long PE: 20.47 +/- 28.90 seconds (2-120 seconds); (ii) aquired PE: 57.91 +/- 38.72 seconds (90-180 seconds); (iii) natural variable PE: 144.17 +/- 22.47 seconds (120-180 seconds); and (iv) premature-like ejaculatory dysfunction: 286.67 +/- 69.96 seconds (180-420 seconds). The majority of patients who seek treatment for the complaint of ejaculating prematurely describes lifelong PE. Further population-based studies are required to determine the actual prevalences of these four PE syndromes.

Treatment of sexual dysfunctions in male-only groups: predicting outcome.

PubMed

Dekker, J; Dronkers, J; Staffeleu, J

1985-01-01

Forty men complaining of sexual dysfunctions were treated in male-only groups, using RET, masturbation exercises and social skills training. Sexual functioning improved and social anxiety decreased. Combining these data with previously reported data on 21 men, we tried to predict treatment outcome. Sexual functioning of men with a steady partner and men with varying partners improved; in men without partner(s) no effect could be demonstrated, probably due to a methodological artifact. Inhibited sexual desire was associated with a poor outcome. Several other variables (among them type of dysfunction, social anxiety, age, educational level) did not predict improvement of sexual functioning. This method seems to provide adequate treatment for various complaints of men with quite different backgrounds.

Sex differences in baroreflex sensitivity, heart rate variability, and end organ damage in the TGR(mRen2)27 rat.

PubMed

Johnson, Megan S; DeMarco, Vincent G; Heesch, Cheryl M; Whaley-Connell, Adam T; Schneider, Rebecca I; Rehmer, Nathan T; Tilmon, Roger D; Ferrario, Carlos M; Sowers, James R

2011-10-01

The aim of this investigation was to evaluate sex differences in baroreflex and heart rate variability (HRV) dysfunction and indexes of end-organ damage in the TG(mRen2)27 (Ren2) rat, a model of renin overexpression and tissue renin-angiotensin-aldosterone system overactivation. Blood pressure (via telemetric monitoring), blood pressure variability [BPV; SD of systolic blood pressure (SBP)], spontaneous baroreflex sensitivity, HRV [HRV Triangular Index (HRV-TI), standard deviation of the average NN interval (SDNN), low and high frequency power (LF and HF, respectively), and Poincaré plot analysis (SD1, SD2)], and cardiovascular function (pressure-volume loop analysis and proteinuria) were evaluated in male and female 10-wk-old Ren2 and Sprague Dawley rats. The severity of hypertension was greater in Ren2 males (R2-M) than in Ren2 females (R2-F). Increased BPV, suppression of baroreflex gain, decreased HRV, and associated end-organ damage manifested as cardiac dysfunction, myocardial remodeling, elevated proteinuria, and tissue oxidative stress were more pronounced in R2-M compared with R2-F. During the dark cycle, HRV-TI and SDNN were negatively correlated with SBP within R2-M and positively correlated within R2-F; within R2-M, these indexes were also negatively correlated with end-organ damage [left ventricular hypertrophy (LVH)]. Furthermore, within R2-M only, LVH was strongly correlated with indexes of HRV representing predominantly vagal (HF, SD1), but not sympathetic (LF, SD2), variability. These data demonstrated relative protection in females from autonomic dysfunction and end-organ damage associated with elevated blood pressure in the Ren2 model of hypertension.

Impact of Temperature and Nutrients on Carbon: Nutrient Tissue Stoichiometry of Submerged Aquatic Plants: An Experiment and Meta-Analysis.

PubMed

Velthuis, Mandy; van Deelen, Emma; van Donk, Ellen; Zhang, Peiyu; Bakker, Elisabeth S

2017-01-01

Human activity is currently changing our environment rapidly, with predicted temperature increases of 1-5°C over the coming century and increased nitrogen and phosphorus inputs in aquatic ecosystems. In the shallow parts of these ecosystems, submerged aquatic plants enhance water clarity by resource competition with phytoplankton, provide habitat, and serve as a food source for other organisms. The carbon:nutrient stoichiometry of submerged aquatic plants can be affected by changes in both temperature and nutrient availability. We hypothesized that elevated temperature leads to higher carbon:nutrient ratios through enhanced nutrient-use efficiency, while nutrient addition leads to lower carbon:nutrient ratios by the luxurious uptake of nutrients. We addressed these hypotheses with an experimental and a meta-analytical approach. We performed a full-factorial microcosm experiment with the freshwater plant Elodea nuttallii grown at 10, 15, 20, and 25°C on sediment consisting of pond soil/sand mixtures with 100, 50, 25, and 12.5% pond soil. To address the effect of climatic warming and nutrient addition on the carbon:nutrient stoichiometry of submerged freshwater and marine plants we performed a meta-analysis on experimental studies that elevated temperature and/or added nutrients (nitrogen and phosphorus). In the microcosm experiment, C:N ratios of Elodea nuttallii decreased with increasing temperature, and this effect was most pronounced at intermediate nutrient availability. Furthermore, higher nutrient availability led to decreased aboveground C:P ratios. In the meta-analysis, nutrient addition led to a 25, 22, and 16% reduction in aboveground C:N and C:P ratios and belowground C:N ratios, accompanied with increased N content. No consistent effect of elevated temperature on plant stoichiometry could be observed, as very few studies were found on this topic and contrasting results were reported. We conclude that while nutrient addition consistently leads to decreased carbon:nutrient ratios, elevated temperature does not change submerged aquatic plant carbon:nutrient stoichiometry in a consistent manner. This effect is rather dependent on nutrient availability and may be species-specific. As changes in the carbon:nutrient stoichiometry of submerged aquatic plants can impact the transfer of energy to higher trophic levels, these results suggest that eutrophication may enhance plant consumption and decomposition, which could in turn have consequences for carbon sequestration.

[Mediating role of emotional regulation between impulsive behavior in gambling, Internet and videogame abuse, and dysfunctional symptomatology in young adults and adolescents].

PubMed

Estévez Gutiérrez, Ana; Herrero Fernández, David; Sarabia Gonzalvo, Izaskun; Jáuregui Bilbao, Paula

2014-01-01

The way emotions are regulated might affect the engagement on risk behaviors in adolescents and young adults. Therefore, studying the relationship between these variables could be of great importance. Some of the less studied risky behaviors are pathological gambling, and Internet and videogame abuse. This research aims to analyze the existing relationship between such risky behaviors, emotion regulation, and dysfunctional psychological symptomatology (depression, anxiety, phobic anxiety, somatization, obsessive-–compulsive behavior, interpersonal sensitivity, hostility, paranoid ideation, and psychoticism). In addition, it also looks to assess whether emotional regulation plays a mediating role between pathological gambling, and Internet and videogame abuse, and psychological symptomatology. The sample was composed of 1312 young adults and adolescents, aged between 12 and 30, recruited from scholar centers, universities and free time groups, and from associations and centers associated with FEJAR (Spanish Federation of Rehabilitated Gamblers). Participants completed measurements of impulsive behavior, emotion regulation, and dysfunctional symptomatology. Results showed that there is generally a positive and significant relation between these variables. Moreover, it has been pointed out that emotion regulation mediates the association between impulsive behavior and dysfunctional symptomatology among those young adults and adolescents who engage in these impulsive behaviors, except for the relation between videogame abuse and depressive symptomatology. Training in emotional regulation skills could be useful in dealing with and treating this type of behaviors in adolescents and young adults.

Fatigue, emotional functioning, and executive dysfunction in pediatric multiple sclerosis.

PubMed

Holland, Alice Ann; Graves, Donna; Greenberg, Benjamin M; Harder, Lana L

2014-01-01

Fatigue, depression, anxiety, and executive dysfunction are associated with multiple sclerosis (MS) in adults. Existing research suggests similar problems in pediatric MS, but relationships between these variables have not been investigated. This study investigates the associations between executive functioning and fatigue, emotional functioning, age of onset, and disease duration in pediatric MS. Twenty-six MS or Clinically Isolated Syndrome (CIS) patients, ages 7 to 18, were evaluated through a multidisciplinary demyelinating diseases clinic. Participants completed neuropsychological screening including Verbal Fluency, Digit Span, and Trail-Making Test. Parents completed rating forms of behavioral, emotional, and executive functioning. Patients and parents completed questionnaires related to the patient's quality of life and fatigue. Pearson's correlation coefficients were calculated to investigate relationships between fatigue, emotional functioning, and executive functioning, as well as to examine correlations between parent and child reports of fatigue. Rates of parent-reported anxiety, depression, fatigue, and executive dysfunction varied widely. Means were below average on the Trail-Making Test and average on Verbal Fluency and Digit Span, though scores varied widely. Various fatigue and emotional functioning indices-but not age of onset or disease duration-significantly correlated with various performance-based measures of executive functioning. Results indicate pediatric MS is associated with some degree of fatigue, emotional difficulties, and executive dysfunction, the latter of which is associated with the two former. Notably, age of onset and disease duration did not significantly correlate with executive functioning. Results advance understanding of psychological and clinical variables related to neurocognitive outcomes in pediatric MS.

Growth of III-V films by control of MBE growth front stoichiometry

NASA Technical Reports Server (NTRS)

Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)

1992-01-01

For the growth of strain-layer materials and high quality single and multiple quantum wells, the instantaneous control of growth front stoichiometry is critical. The process of the invention adjusts the offset or phase of molecular beam epitaxy (MBE) control shutters to program the instantaneous arrival or flux rate of In and As4 reactants to grow InAs. The interrupted growth of first In, then As4, is also a key feature.

Effect of stoichiometry and Cu-substitution on the phase structure and hydrogen storage properties of Ml-Mg-Ni-based alloys

NASA Astrophysics Data System (ADS)

Li, Yuan; Tao, Yang; Huo, Quan

2015-01-01

To improve the electrochemical properties of rare-earth-Mg-Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the alloys were studied. Nonsubstituted Ml0.80Mg0.20(Ni2.90Co0.50-Mn0.30Al0.30) x ( x = 0.68, 0.70, 0.72, 0.74, 0.76) alloys and Cu-substituted Ml0.80Mg0.20(Ni2.90Co0.50- y Cu y Mn0.30Al0.30)0.70 ( y = 0, 0.10, 0.30, 0.50) alloys were prepared by induction melting. Phase structure analysis shows that the nonsubstituted alloys consist of a LaNi5 phase, a LaNi3 phase, and a minor La2Ni7 phase; in addition, in the case of Cu-substitution, the Nd2Ni7 phase appears and the LaNi3 phase vanishes. Thermodynamic tests show that the enthalpy change in the dehydriding process decreases, indicating that hydride stability decreases with increasing stoichiometry and increasing Cu content. The maximum discharge capacity, kinetic properties, and cycling stability of the alloy electrodes all increase and then decrease with increasing stoichiometry or increasing Cu content. Furthermore, Cu substitution for Co ameliorates the discharge capacity, kinetics, and cycling stability of the alloy electrodes.

Influence of Magnetite Stoichiometry on the Binding of Emerging Organic Contaminants.

PubMed

Cheng, Wei; Marsac, Rémi; Hanna, Khalil

2018-01-16

While the magnetite stoichiometry (i.e., Fe(II)/Fe(III) ratio) has been extensively studied for the reductive transformation of chlorinated or nitroaromatic compounds, no work exists examining the influence of stoichiometry of magnetite on its binding properties. This study, for the first time, demonstrates that the stoichiometry strongly affects the capacity of magnetite to bind not only quinolone antibiotics such as nalidixic acid (NA) and flumequine (FLU), but also salicylic acid (SA), natural organic matter (humic acid, HA), and dissolved silicates. Fe(II)-amendment of nonstoichiometric magnetite (Fe(II)/Fe(III) = 0.40) led to similar sorbed amounts of NA, FLU, SA, silicates or HA as compared to the stoichiometric magnetite (i.e., Fe(II)/Fe(III) = 0.50). At any pH between 6 and 10, all magnetites exhibiting similar Fe(II)/Fe(III) ratio in the solid phase showed similar adsorption properties for NA or FLU. This enhancement in binding capability of magnetite for NA is still observed in the presence of environmentally relevant ligands (e.g., 10 mg L -1 of HA or 100 μM of silicates). Using surface complexation modeling, it was shown that the NA-magnetite complexation constant does not vary with Fe(II)/Fe(III) between 0.24 and 0.40, but increases by 8 orders of magnitude when Fe(II)/Fe(III) increases from 0.40 to 0.50.

Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films

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

Beebe, Melissa R., E-mail: mrbeebe@email.wm.edu; Beringer, Douglas B.; Burton, Matthew C.

2016-03-15

The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films tomore » exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB{sub 2} thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature T{sub C}, the authors are the first to report on the correlation between stoichiometry and the lower critical field H{sub C1}.« less

Discovery of a new method for potent drug development using power function of stoichiometry ofhomomeric biocomplexes or biological nanomotors

PubMed Central

Pi, Fengmei; Vieweger, Mario; Zhao, Zhengyi; Wang, Shaoying; Guo, Peixuan

2015-01-01

Introduction Multidrug resistance and the appearance of incurable diseases inspire the quest for potent therapeutics. Areas Covered We review a new methodology in designing potent drugs by targeting multi-subunit homomeric biological motors, machines, or complexes with Z>1 and K=1, where Z is the stoichiometry of the target, and K is the number of drugged subunits required to block the function of the complex. The condition is similar to a series, electrical circuit of Christmas decorations; failure of one light bulb causes the entire lighting system to lose power. In most multisubunit, homomeric biological systems, a sequential coordination or cooperative action mechanism is utilized, thus K equals 1. Drug inhibition depends on the ratio of drugged to nondrugged complexes. When K=1, and Z>1, the inhibition effect follows a power law with respect to Z, leading to enhanced drug potency. The hypothesis that the potency of drug inhibition depends on the stoichiometry of the targeted biological complexes was recently quantified by Yang-Hui's Triangle (or binomial distribution), and proved using a highly sensitive in vitro phi29 viral DNA packaging system. Examples of targeting homomeric bio-complexes with high stoichiometry for potent drug discovery are discussed. Expert Opinion Biomotors with multiple subunits are widespread in viruses, bacteria, and cells, making this approach generally applicable in the development of inhibition drugs with high efficiency. PMID:26307193

Magnesium Fertilizer-Induced Increase of Symbiotic Microorganisms Improves Forage Growth and Quality.

PubMed

Chen, Jihui; Li, Yanpeng; Wen, Shilin; Rosanoff, Andrea; Yang, Gaowen; Sun, Xiao

2017-04-26

Magnesium (Mg) plays important roles in photosynthesis and protein synthesis; however, latent Mg deficiencies are common phenomena that can influence food quality. Nevertheless, the effects of Mg fertilizer additions on plant carbon (C):nitrogen (N):phosphorus (P) stoichiometry, an important index of food quality, are unclear and the underlying mechanisms unexplored. We conducted a greenhouse experiment using low-Mg in situ soil without and with a gradient of Mg additions to investigate the effect of Mg fertilizer on growth and stoichiometry of maize and soybean and also measure these plants' main symbiotic microorganisms: arbuscular mycorrhizal fungi (AMF) and rhizobium, respectively. Our results showed that Mg addition significantly improved both plant species' growth and also increased N and P concentrations in soybean and maize, respectively, resulting in low C:N ratio and high N:P ratio in soybean and low C:P and N:P ratios in maize. These results presumably stemmed from the increase of nutrients supplied by activation-enhanced plant symbiotic microorganisms, an explanation supported by statistically significant positive correlations between plant stoichiometry and plants' symbiotic microorganisms' increased growth with Mg addition. We conclude that Mg supply can improve plant growth and alter plant stoichiometry via enhanced activity of plant symbiotic microorganisms. Possible mechanisms underlying this positive plant-soil feedback include an enhanced photosynthetic product flow to roots caused by adequate Mg supply.

Metal binding stoichiometry and isotherm choice in biosorption

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

Schiewer, S.; Wong, M.H.

1999-11-01

Seaweeds that possess a high metal binding capacity may be used as biosorbents for the removal of toxic heavy metals from wastewater. The binding of Cu and Ni by three brown algae (Sargassum, Colpomenia, Petalonia) and one green alga (Ulva) was investigated at pH 4.0 and pH 3.0. The greater binding strength of Cu is reflected in a binding constant that is about 10 times as high as that of Ni. The extent of metal binding followed the order Petalonia {approximately} Sargassum > Colpomenia > Ulva. This was caused by a decreasing number of binding sites and by much lowermore » metal binding constants for Ulva as compared to the brown algae. Three different stoichiometric assumptions are compared for describing the metal binding, which assume either that each metal ion M binds to one binding site B forming a BM complex or that a divalent metal ion M binds to two monovalent sites B forming BM{sub 0.5} or B{sub 2}M complexes, respectively. Stoichiometry plots are proposed as tools to discern the relevant binding stoichiometry. The pH effect in metal binding and the change in proton binding were well predicted for the B{sub 2}M or BM{sub 0.5} stoichiometries with the former being better for Cu and the latter preferable for Ni. Overall, the BM{sub 0.5} model is recommended because it avoids iterations.« less

A biopsychosocial approach to women’s sexual function and dysfunction at midlife: A narrative review

PubMed Central

Thomas, Holly N.; Thurston, Rebecca C.

2016-01-01

A satisfying sex life is an important component of overall well-being, but sexual dysfunction is common, especially in midlife women. The aim of this review is (a) to define sexual function and dysfunction, (b) to present theoretical models of female sexual response, (c) to examine longitudinal studies of how sexual function changes during midlife, and (d) to review treatment options. Four types of female sexual dysfunction are currently recognized: Female Orgasmic Disorder, Female Sexual Interest/Arousal Disorder, Genito-Pelvic Pain/Penetration Disorder, and Substance/Medication-Induced Sexual Dysfunction. However, optimal sexual function transcends the simple absence of dysfunction. A biopsychosocial approach that simultaneously considers physical, psychological, sociocultural, and interpersonal factors is necessary to guide research and clinical care regarding women’s sexual function. Most longitudinal studies reveal an association between advancing menopause status and worsening sexual function. Psychosocial variables, such as availability of a partner, relationship quality, and psychological functioning, also play an integral role. Future directions for research should include deepening our understanding of how sexual function changes with aging and developing safe and effective approaches to optimizing women’s sexual function with aging. Overall, holistic, biopsychosocial approaches to women’s sexual function are necessary to fully understand and treat this key component of midlife women’s well-being. PMID:27013288

A biopsychosocial approach to women's sexual function and dysfunction at midlife: A narrative review.

PubMed

Thomas, Holly N; Thurston, Rebecca C

2016-05-01

A satisfying sex life is an important component of overall well-being, but sexual dysfunction is common, especially in midlife women. The aim of this review is (a) to define sexual function and dysfunction, (b) to present theoretical models of female sexual response, (c) to examine longitudinal studies of how sexual function changes during midlife, and (d) to review treatment options. Four types of female sexual dysfunction are currently recognized: Female Orgasmic Disorder, Female Sexual Interest/Arousal Disorder, Genito-Pelvic Pain/Penetration Disorder, and Substance/Medication-Induced Sexual Dysfunction. However, optimal sexual function transcends the simple absence of dysfunction. A biopsychosocial approach that simultaneously considers physical, psychological, sociocultural, and interpersonal factors is necessary to guide research and clinical care regarding women's sexual function. Most longitudinal studies reveal an association between advancing menopause status and worsening sexual function. Psychosocial variables, such as availability of a partner, relationship quality, and psychological functioning, also play an integral role. Future directions for research should include deepening our understanding of how sexual function changes with aging and developing safe and effective approaches to optimizing women's sexual function with aging. Overall, holistic, biopsychosocial approaches to women's sexual function are necessary to fully understand and treat this key component of midlife women's well-being. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Calcium-dependent stoichiometries of the KCa2.2 (SK) intracellular domain/calmodulin complex in solution

PubMed Central

Halling, D. Brent; Kenrick, Sophia A.; Riggs, Austen F.

2014-01-01

Ca2+ activates SK Ca2+-activated K+ channels through the protein Ca2+ sensor, calmodulin (CaM). To understand how SK channels operate, it is necessary to determine how Ca2+ regulates CaM binding to its target on SK. Tagless, recombinant SK peptide (SKp), was purified for binding studies with CaM at low and high Ca2+ concentrations. Composition gradient multi-angle light scattering accurately measures the molar mass, stoichiometry, and affinity of protein complexes. In 2 mM Ca2+, SKp and CaM bind with three different stoichiometries that depend on the molar ratio of SKp:CaM in solution. These complexes include 28 kD 1SKp/1CaM, 39 kD 2SKp/1CaM, and 44 kD 1SKp/2CaM. A 2SKp/2CaM complex, observed in prior crystallographic studies, is absent. At <5 nM Ca2+, 1SKp/1CaM and 2SKp/1CaM were observed; however, 1SKp/2CaM was absent. Analytical ultracentrifugation was used to characterize the physical properties of the three SKp/CaM stoichiometries. In high Ca2+, the sedimentation coefficient is smaller for a 1SKp:1CaM solution than it is for either 2SKp:1CaM or 1SKp:2CaM. At low Ca2+ and at >100 µM protein concentrations, a molar excess of SKp over CaM causes aggregation. Aggregation is not observed in Ca2+ or with CaM in molar excess. In low Ca2+ both 1SKp:1CaM and 1SKp:2CaM solutions have similar sedimentation coefficients, which is consistent with the absence of a 1SKp/2CaM complex in low Ca2+. These results suggest that complexes with stoichiometries other than 2SKp/2CaM are important in gating. PMID:24420768

Calcium-dependent stoichiometries of the KCa2.2 (SK) intracellular domain/calmodulin complex in solution.

PubMed

Halling, D Brent; Kenrick, Sophia A; Riggs, Austen F; Aldrich, Richard W

2014-02-01

Ca(2+) activates SK Ca(2+)-activated K(+) channels through the protein Ca(2+) sensor, calmodulin (CaM). To understand how SK channels operate, it is necessary to determine how Ca(2+) regulates CaM binding to its target on SK. Tagless, recombinant SK peptide (SKp), was purified for binding studies with CaM at low and high Ca(2+) concentrations. Composition gradient multi-angle light scattering accurately measures the molar mass, stoichiometry, and affinity of protein complexes. In 2 mM Ca(2+), SKp and CaM bind with three different stoichiometries that depend on the molar ratio of SKp:CaM in solution. These complexes include 28 kD 1SKp/1CaM, 39 kD 2SKp/1CaM, and 44 kD 1SKp/2CaM. A 2SKp/2CaM complex, observed in prior crystallographic studies, is absent. At <5 nM Ca(2+), 1SKp/1CaM and 2SKp/1CaM were observed; however, 1SKp/2CaM was absent. Analytical ultracentrifugation was used to characterize the physical properties of the three SKp/CaM stoichiometries. In high Ca(2+), the sedimentation coefficient is smaller for a 1SKp:1CaM solution than it is for either 2SKp:1CaM or 1SKp:2CaM. At low Ca(2+) and at >100 µM protein concentrations, a molar excess of SKp over CaM causes aggregation. Aggregation is not observed in Ca(2+) or with CaM in molar excess. In low Ca(2+) both 1SKp:1CaM and 1SKp:2CaM solutions have similar sedimentation coefficients, which is consistent with the absence of a 1SKp/2CaM complex in low Ca(2+). These results suggest that complexes with stoichiometries other than 2SKp/2CaM are important in gating.

Effects of three global change drivers on terrestrial C:N:P stoichiometry: a global synthesis.

PubMed

Yue, Kai; Fornara, Dario A; Yang, Wanqin; Peng, Yan; Li, Zhijie; Wu, Fuzhong; Peng, Changhui

2017-06-01

Over the last few decades, there has been an increasing number of controlled-manipulative experiments to investigate how plants and soils might respond to global change. These experiments typically examined the effects of each of three global change drivers [i.e., nitrogen (N) deposition, warming, and elevated CO 2 ] on primary productivity and on the biogeochemistry of carbon (C), N, and phosphorus (P) across different terrestrial ecosystems. Here, we capitalize on this large amount of information by performing a comprehensive meta-analysis (>2000 case studies worldwide) to address how C:N:P stoichiometry of plants, soils, and soil microbial biomass might respond to individual vs. combined effects of the three global change drivers. Our results show that (i) individual effects of N addition and elevated CO 2 on C:N:P stoichiometry are stronger than warming, (ii) combined effects of pairs of global change drivers (e.g., N addition + elevated CO 2 , warming + elevated CO 2 ) on C:N:P stoichiometry were generally weaker than the individual effects of each of these drivers, (iii) additive interactions (i.e., when combined effects are equal to or not significantly different from the sum of individual effects) were more common than synergistic or antagonistic interactions, (iv) C:N:P stoichiometry of soil and soil microbial biomass shows high homeostasis under global change manipulations, and (v) C:N:P responses to global change are strongly affected by ecosystem type, local climate, and experimental conditions. Our study is one of the first to compare individual vs. combined effects of the three global change drivers on terrestrial C:N:P ratios using a large set of data. To further improve our understanding of how ecosystems might respond to future global change, long-term ecosystem-scale studies testing multifactor effects on plants and soils are urgently required across different world regions. © 2017 John Wiley & Sons Ltd.

Steady states and stability in metabolic networks without regulation.

PubMed

Ivanov, Oleksandr; van der Schaft, Arjan; Weissing, Franz J

2016-07-21

Metabolic networks are often extremely complex. Despite intensive efforts many details of these networks, e.g., exact kinetic rates and parameters of metabolic reactions, are not known, making it difficult to derive their properties. Considerable effort has been made to develop theory about properties of steady states in metabolic networks that are valid for any values of parameters. General results on uniqueness of steady states and their stability have been derived with specific assumptions on reaction kinetics, stoichiometry and network topology. For example, deep results have been obtained under the assumptions of mass-action reaction kinetics, continuous flow stirred tank reactors (CFSTR), concordant reaction networks and others. Nevertheless, a general theory about properties of steady states in metabolic networks is still missing. Here we make a step further in the quest for such a theory. Specifically, we study properties of steady states in metabolic networks with monotonic kinetics in relation to their stoichiometry (simple and general) and the number of metabolites participating in every reaction (single or many). Our approach is based on the investigation of properties of the Jacobian matrix. We show that stoichiometry, network topology, and the number of metabolites that participate in every reaction have a large influence on the number of steady states and their stability in metabolic networks. Specifically, metabolic networks with single-substrate-single-product reactions have disconnected steady states, whereas in metabolic networks with multiple-substrates-multiple-product reactions manifolds of steady states arise. Metabolic networks with simple stoichiometry have either a unique globally asymptotically stable steady state or asymptotically stable manifolds of steady states. In metabolic networks with general stoichiometry the steady states are not always stable and we provide conditions for their stability. In order to demonstrate the biological relevance we illustrate the results on the examples of the TCA cycle, the mevalonate pathway and the Calvin cycle. Copyright © 2016 Elsevier Ltd. All rights reserved.

Propylene oxidation mechanisms and intermediates using in situ soft X-ray fluorescence methods on the Pt(111) surface

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

Gabelnick, A.M.; Capitano, A.T.; Kane, S.M.

2000-01-12

The oxidation of propylene preabsorbed on the Pt(111) surface has been characterized in oxygen pressures up to 0.02 Torr using fluorescence yield near-edge spectroscopy (FYNES) and temperature-programmed fluorescence yield near-edge spectroscopy (TP-FYNES) above the carbon K edge. During oxidation of adsorbed propylene, a stable intermediate was observed and characterized using these soft X-ray methods. A general in situ method for determining the stoichiometry of carbon-containing reaction intermediate species has been developed and demonstrated for the first time. Total carbon concentration measured during temperature-programmed reaction studies clearly indicates a reaction intermediate is formed in the 300 K temperature range with amore » surface concentration of 0.55 x 10{sup 15} carbon atoms/cm{sup 2}. By comparing the intensity of the C-H {sigma}* resonance at the magic angle with the intensity in the carbon continuum, the stoichiometry of this intermediate can be determined unambiguously. Based on calibration with molecular propylene (C{sub 3}H{sub 6}) and propylidyne (C{sub 3}H{sub 5}), the intermediate has a C{sub 3}H{sub 5} stoichiometry for oxygen pressures up to 0.02 Torr. A set of normal and glancing angle FYNES spectra above the carbon K edge was used to characterize the bonding and structure of this intermediate. Spectra of known coverages of adsorbed propylene and propylidyne served as standards. The spectra of di-{sigma} propylene, propylidyne, and the intermediate were curve fit as a group with consistent energies and widths of all primary features. Based on this procedure, the intermediate is 1,1,2-tri-{sigma} 1-methylvinyl. The stoichiometry and temperature stability range of the 1-methylvinyl intermediate formed in oxygen pressures up to 0.02 Torr is identical with the stoichiometry and stability of the same intermediate formed during oxidation of preadsorbed propylene by excess coadsorbed atomic oxygen.« less

Autonomic Dysfunction Predicts Clinical Outcomes After Acute Ischemic Stroke: A Prospective Observational Study.

PubMed

Xiong, Li; Tian, Ge; Leung, Howan; Soo, Yannie O Y; Chen, Xiangyan; Ip, Vincent H L; Mok, Vincent C T; Chu, Winnie C W; Wong, Ka Sing; Leung, Thomas W H

2018-01-01

Central autonomic dysfunction increases stroke morbidity and mortality. We aimed to investigate whether poststroke autonomic dysfunction graded by Ewing battery can predict clinical outcome. In this prospective observational study, we assessed autonomic function of ischemic stroke patients within 7 days from symptom onset by Ewing battery. On the basis of the magnitude of autonomic dysfunction, we stratified patients into significant (definite, severe, or atypical) or minor (normal or early) autonomic function impairment groups and correlated the impairment with the 3-month modified Rankin Scale score (good outcome: modified Rankin Scale score 0≈2; poor outcome: modified Rankin Scale score 3≈6). Among the 150 patients enrolled (mean age, 66.4±9.9 years; 70.7% males), minor autonomic dysfunction was identified in 36 patients (24.0%), and significant autonomic dysfunction was identified in 114 patients (76.0%) based on Ewing battery. In 3 months, a poor functional outcome was found in 32.5% of significant group patients compared with 13.9% in the minor group ( P =0.031). Crude odds ratios of the magnitude of autonomic dysfunction and 3-month unfavorable functional outcome after acute ischemic stroke were 2.979 (95% confidence interval, 1.071-8.284; P =0.036). After adjusting for confounding variables with statistical significance between the 2 functional outcome subgroups identified in univariate analysis (including sex and National Institutes of Health Stroke Scale score on admission), the magnitude of autonomic dysfunction still independently predicted an unfavorable outcome, with an odds ratio of 3.263 (95% confidence interval, 1.141-9.335; P =0.027). Autonomic dysfunction gauged by Ewing battery predicts poor functional outcome after acute ischemic stroke. © 2017 American Heart Association, Inc.

The impact of duration of organ dysfunction on the outcome of patients with severe sepsis and septic shock.

PubMed

Freitas, Flávio G R; Salomão, Reinaldo; Tereran, Nathalia; Mazza, Bruno Franco; Assunção, Murillo; Jackiu, Mirian; Fernandes, Haggeas; Machado, Flávia Ribeiro

2008-08-01

This study aimed to assess the impact of the duration of organ dysfunction on the outcome of patients with severe sepsis or septic shock. Clinical data were collected from hospital charts of patients with severe sepsis and septic shock admitted to a mixed intensive care unit from November 2003 to February 2004. The duration of organ dysfunction prior to diagnosis was correlated with mortality. Results were considered significant if p<0.05. Fifty-six patients were enrolled. Mean age was 55.6+/-20.7 years, mean APACHE II score was 20.6+/-6.9, and mean SOFA score was 7.9+/-3.7. Thirty-six patients (64.3%) had septic shock. The mean duration of organ dysfunction was 1.9+/-1.9 days. Within the univariate analysis, the variables correlated with hospital mortality were: age (p=0.015), APACHE II (p=0.008), onset outside the intensive care unit (p=0.05), blood glucose control (p=0.05) and duration of organ dysfunction (p=0.0004). In the multivariate analysis, only a duration of organ dysfunction persisting longer than 48 hours correlated with mortality (p=0.004, OR: 8.73 (2.37-32.14)), whereas the APACHE II score remained only a slightly significant factor (p=0.049, OR: 1.11 (1.00-1.23)). Patients who received therapeutic interventions within the first 48 hours after the onset of organ dysfunction exhibited lower mortality (32.1% vs. 82.1%, p=0.0001). These findings suggest that the diagnosis of organ dysfunction is not being made in a timely manner. The time elapsed between the onset of organ dysfunction and initiation of therapeutic intervention can be quite long, and this represents an important determinant of survival in cases of severe sepsis and septic shock.

On categorization and quantification of women's sexual dysfunctions: an epidemiological approach.

PubMed

Oberg, K; Fugl-Meyer, A R; Fugl-Meyer, K S

2004-06-01

The objectives of this study are to compare the two definitions of female sexual dysfunction, namely dysfunction per se (A category) and personal distress caused by dysfunction (B category), and to gauge their associations with some sociodemographic aspects and level of sexual well-being. The subjects were a nationally representative sample of sexually active Swedish women (n: 1056) aged 18-65 y, who participated in a combined structured interview/questionnaire investigation. The functions analysed were: self-reported sexual desire, interest, lubrication, orgasm, genital pain and vaginism, which were subclassified for the A and B categories into no, mild (sporadically occurring) and manifest dysfunction. Sexual well-being was reported along a six-grade scale ranging from very satisfied to very dissatisfied. The sociodemographic items registered were: education, occupation, financial situation, social group, immigrant status, location of domicile and church-going. Aggregated mild and manifest dysfunction per se of sexual interest, orgasm and vaginal lubrication were reported by about 60-90%. More than one-third had dyspareunia, but few reported vaginism. Mild dysfunctions were clearly more common than manifest dysfunctions. Not fully 45% of those with manifest low interest and orgasm perceived these dysfunctions as manifestly distressing, while in 60-70% lubricational insufficiency of dyspareunia led to manifest distress. Age and the included sociodemographic variables had marginal or no influence on sexual functions. A four-factor sexual function pattern was identified, closely linking A and B categories in a pairwise manner. Three factors, labelled sexual desire, orgasm and genital function were powerful classifiers (discriminant analysis) of level of sexual well-being. Hence, it is a matter of taste whether to use the A or the B category. Together, they can explain the gross level of satisfaction with sexual life to an adequate extent.

Attachment to parents and peers as a risk factor for adolescent depressive disorders: the mediating role of emotion regulation.

PubMed

Kullik, Angelika; Petermann, Franz

2013-08-01

This study examined emotion regulation as a mediator in the relationship of attachment and depression in adolescents. Participants (N girls = 127; M age = 14.50; N boys = 121; M age = 14.31) completed self-report questionnaires of attachment to parents and peers, emotion regulation and depression. Models with dysfunctional emotion regulation as a mediation variable were tested via hierarchical multiple regression analyses and bootstrapping procedure. Results revealed significant relations between attachment to parents and peers, dysfunctional emotion regulation and depression. For girls, internal-dysfunctional emotion regulation was a mediator in the relation of attachment to parents and depression and partly mediated the association of attachment to peers. For boys, internal- and external-dysfunctional emotion regulation acted as partly mediators in association of attachment to parents and depression. Results indicate important mechanisms that contribute to the refinement of conceptual models and provide indications for gender specific prevention and intervention for depressive disorders.

Detonation Shock Dynamics Calibration for Non-Ideal HE: ANFO

NASA Astrophysics Data System (ADS)

Short, Mark; Salyer, Terry

2009-06-01

The detonation of ammonium nitrate (AN) and fuel-oil (FO) mixtures (ANFO) is significantly influenced by the properties of the AN (porosity, particle size, coating) and fuel-oil stoichiometry. We report on a new series of rate-stick experiments in cardboard confinement that highlight detonation front speed and curvature dependence on AN/FO stoichiometry and AN particle properties. Standard detonation velocity-curvature calibrations to the experimental data will be presented, as well as higher-order time-dependent detonation shock dynamics calibrations.

Structural investigation of the β-cyclodextrin complexes with chiral bicyclic monoterpenes - Influence of the functionality group on the host-guest stoichiometry

NASA Astrophysics Data System (ADS)

Ceborska, Magdalena

2017-10-01

The crystal structures of the complexes of β-cyclodextrin with (+)- and (-)-camphors are presented. The comparison of the obtained crystal structures with available data for other complexes of β-cyclodextrin with chiral bicyclic monoterpenes (hydrocarbon (+)-fenchene and alcohols: (-)-isopinocampheol, and (+)-, and (-)-borneols) obtained from Cambridge Structural Database (CSD) shows the trend of alcohols to form dimeric complexes of 2:3 stoichiometry, while hydrocarbons and ketones prefer to form 2:2 host-guest inclusion complexes.

Composition of RF-sputtered refractory compounds determined by X-ray photoelectron spectroscopy

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Brainard, W. A.

1978-01-01

RF-sputtered coatings of CrB2, MoSi2, Mo2C, TiC, and MoS2 were examined by X-ray photoelectron spectroscopy (XPS). Data on stoichiometry, impurity content, and chemical bonding were obtained. The influences of sputtering target history, deposition time, RF power level, and substrate bias were studied. Significant deviations from stoichiometry and high oxide levels were related to target outgassing. The effect of substrate bias depended on the particular coating material studied.

Haloacetonitriles are low K1 inhibitors of bacterial dichloromethane dehalogenases.

PubMed

Logan, M S; Blocki, F A; Stimpfl, K J; Wackett, L P

1993-12-15

Distinct dichloromethane dehalogenases from Methylobacterium sp. strain DM4 and Methylophilus DM11 were inhibited by low concentrations of haloacetonitriles. Chloroacetonitrile (ClCH2CN) showed maximal inhibition at a stoichiometry of 1 mol inhibitor:1 mol holoenzyme for both enzymes. This stoichiometry is suggestive of one active site per holoenzyme or extreme negative cooperativity amongst the subunits. Radiolabelled ClCH2CN dissociated completely or partially from the two dehalogenases, respectively, during chromatography. This suggested ClCH2CN was bound non-covalently.

Stoichiometry of maltodextrin-binding sites in LamB, an outer membrane protein from Escherichia coli.

PubMed Central

Gehring, K; Cheng, C H; Nikaido, H; Jap, B K

1991-01-01

We have directly measured the stoichiometry of maltodextrin-binding sites in LamB. Scatchard plots and computer fitting of flow dialysis (rate-of-dialysis) experiments clearly establish three independent binding sites per LamB trimer, with a dissociation constant of approximately 60 microM for maltoheptaose. The current model for LamB's function as a specific pore is discussed with respect to the symmetry in LamB's kinetic properties and the implications of our results. Images PMID:2001992

Optimization of Strontium Titanate (SrTiO3) Thin Films Fabricated by Metal Organic Chemical Vapor Deposition (MOCVD) for Microwave-Tunable Devices

DTIC Science & Technology

2015-12-01

induced (non)stoichiometry on the structure, dielectric response, and thermal conductivity of SrTiO3 thin films. Chemistry of Materials. 2012;24:331...must be below a few percent. The external sources of loss, such as conductor interface losses and various losses that inevitably arise from device...epitaxy • Excellent control of film stoichiometry and thickness • Large area uniformity and potential for complex structure coating • Optimized

Determinants of harsh parenting in Mexico.

PubMed

Frías-Armenta, M; McCloskey, L A

1998-04-01

This paper presents a structural model of the determinants of harsh parenting among Mexican mothers. One hundred five mothers (46 from the community; 59 referred to agencies for child maltreatment) were recruited from Sonora (Northern) Mexico and interviewed. In this model the use of physical punishment was explained by (1) authoritarian parenting style (mothers' beliefs concerning the effective use of physical punishment and mothers' lack of disciplinary skills) and (2) family dysfunction (a latent variable constructed from reports of interspousal violence and the parents' use of alcohol and drugs). In addition, the indirect effects of demographic and historical variables on harsh parenting was included. The findings show that the most important factor influencing the use of physical punishment in these families was authoritarian parenting style, exerting a significant direct effect on the mothers' reports of their use of harsh punishment. Family dysfunction had an indirect effect through parenting style. Some sociodemographic variables also indirectly influenced the use of beliefs maternal punishment It is concluded that cultural beliefs play a major role in parenting within the framework of Mexican family relations.

Immune dysfunction in cirrhosis.

PubMed

Sipeki, Nora; Antal-Szalmas, Peter; Lakatos, Peter L; Papp, Maria

2014-03-14

Innate and adaptive immune dysfunction, also referred to as cirrhosis-associated immune dysfunction syndrome, is a major component of cirrhosis, and plays a pivotal role in the pathogenesis of both the acute and chronic worsening of liver function. During the evolution of the disease, acute decompensation events associated with organ failure(s), so-called acute-on chronic liver failure, and chronic decompensation with progression of liver fibrosis and also development of disease specific complications, comprise distinct clinical entities with different immunopathology mechanisms. Enhanced bacterial translocation associated with systemic endotoxemia and increased occurrence of systemic bacterial infections have substantial impacts on both clinical situations. Acute and chronic exposure to bacteria and/or their products, however, can result in variable clinical consequences. The immune status of patients is not constant during the illness; consequently, alterations of the balance between pro- and anti-inflammatory processes result in very different dynamic courses. In this review we give a detailed overview of acquired immune dysfunction and its consequences for cirrhosis. We demonstrate the substantial influence of inherited innate immune dysfunction on acute and chronic inflammatory processes in cirrhosis caused by the pre-existing acquired immune dysfunction with limited compensatory mechanisms. Moreover, we highlight the current facts and future perspectives of how the assessment of immune dysfunction can assist clinicians in everyday practical decision-making when establishing treatment and care strategies for the patients with end-stage liver disease. Early and efficient recognition of inappropriate performance of the immune system is essential for overcoming complications, delaying progression and reducing mortality.

Rapid-onset obesity, hypoventilation, hypothalamic dysfunction, autonomic dysregulation and neuroendocrine tumor syndrome with a homogenous enlargement of the pituitary gland: a case report.

PubMed

Aljabban, Lama; Kassab, Lina; Bakoura, Nour Alhuda; Alsalka, Mohammad Fayez; Maksoud, Ismaeil

2016-11-22

Rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation syndrome is a rare pediatric disorder with a variable sequence of clinical presentations, undefined etiology, and high risk of mortality. Our patient presented an unusual course of the disease accompanied by a homogenous mild enlargement of her pituitary gland with an intact pituitary-endocrine axis which, to the best of our knowledge, represents a new finding in rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation syndrome. We present a documented case of a 4 years and 8-month-old Syrian Arabic girl with a distinctive course of signs and symptoms of rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation syndrome accompanied by mature ganglioneuroma in her chest, a homogenous mild enlargement of her pituitary gland, generalized cortical brain atrophy, and seizures. Three months after her first marked symptoms were noted she had a sudden progression of severe respiratory distress that ended with her death. The findings of this case could increase our understanding of the pathogenetic mechanisms of rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation, and place more emphases on pediatricians to consider rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation syndrome whenever early rapid onset of obesity, associated with any malfunction, is observed in children. This knowledge could be lifesaving for children with rapid-onset obesity with hypoventilation, hypothalamic dysfunction, and autonomic dysregulation syndrome.

Immune dysfunction in cirrhosis

PubMed Central

Sipeki, Nora; Antal-Szalmas, Peter; Lakatos, Peter L; Papp, Maria

2014-01-01

Innate and adaptive immune dysfunction, also referred to as cirrhosis-associated immune dysfunction syndrome, is a major component of cirrhosis, and plays a pivotal role in the pathogenesis of both the acute and chronic worsening of liver function. During the evolution of the disease, acute decompensation events associated with organ failure(s), so-called acute-on chronic liver failure, and chronic decompensation with progression of liver fibrosis and also development of disease specific complications, comprise distinct clinical entities with different immunopathology mechanisms. Enhanced bacterial translocation associated with systemic endotoxemia and increased occurrence of systemic bacterial infections have substantial impacts on both clinical situations. Acute and chronic exposure to bacteria and/or their products, however, can result in variable clinical consequences. The immune status of patients is not constant during the illness; consequently, alterations of the balance between pro- and anti-inflammatory processes result in very different dynamic courses. In this review we give a detailed overview of acquired immune dysfunction and its consequences for cirrhosis. We demonstrate the substantial influence of inherited innate immune dysfunction on acute and chronic inflammatory processes in cirrhosis caused by the pre-existing acquired immune dysfunction with limited compensatory mechanisms. Moreover, we highlight the current facts and future perspectives of how the assessment of immune dysfunction can assist clinicians in everyday practical decision-making when establishing treatment and care strategies for the patients with end-stage liver disease. Early and efficient recognition of inappropriate performance of the immune system is essential for overcoming complications, delaying progression and reducing mortality. PMID:24627592

Plant rhizosphere species-specific stoichiometry and regulation of extracellular enzyme and microbial community structure

NASA Astrophysics Data System (ADS)

Bell, C. W.; Calderon, F.; Pendall, E.; Wallenstein, M. D.

2012-12-01

Plant communities affect the activity and composition of soil microbial communities through alteration of the soil environment during root growth; substrate availability through root exudation; nutrient availability through plant uptake; and moisture regimes through transpiration. As a result, positive feedbacks in soil properties can result from alterations in microbial community composition and function in the rhizosphere zone. At the ecosystem-scale, many properties of soil microbial communities can vary between forest stands dominated by different species, including community composition and stoichiometry. However, the influence of smaller individual plants on grassland soils and microbial communities is less well documented. There is evidence to suggest that some plants can modify their soil environment in a manner that favors their persistence. For example, when Bromus tectorum plants invade, soil microbial communities tend to have higher N mineralization rates (in the rhizosphere zone) relative to native plants. If tight linkages between individual plant species and microbial communities inhabiting the rhizosphere exist, we hypothesized that any differences among plant species specific rhizosphere zones could be observed by shifts in: 1) soil -rhizosphere microbial community structure, 2) enzymatic C:N:P acquisition activities, 3) alterations in the soil C chemistry composition in the rhizosphere, and 4) plant - soil - microbial C:N:P elemental stoichiometry. We selected and grew 4 different C3 grasses species including three species native to the Shortgrass Steppe region (Pascopyrum smithii, Koeleria macrantha, and Vulpia octoflora) and one exotic invasive plant species (B. tectorum) in root-boxes that are designed to allow for easy access to the rhizosphere. The field soil was homogenized using a 4mm sieve and mixed 1:1 with sterile sand and seeded as monocultures (24 replicate root - boxes for each species). Plant and soil samples (along with no - plant control soil samples) were collected on day 28, 78, and 148 (N = 4 /sample period/species). Microbial community structure was quantified using the barcoded pyrosequencing protocols. We measured the potential activity of seven hydrolytic soil enzymes to represent the degradation of C, N, and P-rich substrates. Soil microbial C:N biomass responses to specific plant rhizospheres (MBC and MBN) were measured using the chloroform fumigation extraction method followed by DOC & N analysis. Fourier Transform Infrared Spectroscopy was used to assess differences in plant and soil C chemistry. We found that species specific rhizospheres are characteristic of very different soil chemical, edaphic, and microbial properties. These plant species act as gateways that introduce variability into soil C, N, and P ecosystem functional dynamics directly facilitated by rhizosphere - microbe associations. Our results suggest that nutrient stoichiometry within plant species' rhizospheres is a useful tool for identifying intra-ecosystem functional patterns. By identifying what and how specific species rhizospheres differ among the overall plant community, we can better predict how below-ground microbial community function and subsequent ecosystem processes can be influenced by alterations in plant community shifts based on the rhizosphere effects.

Diastolic Dysfunction Following Anthracycline-Based Chemotherapy in Breast Cancer Patients: Incidence and Predictors

PubMed Central

González, Iria; Del Castillo, Silvia; Muñiz, Javier; Morales, Luis J.; Moreno, Fernando; Jiménez, Rosa; Cristóbal, Carmen; Graupner, Catherine; Talavera, Pedro; Curcio, Alejandro; Martínez, Paula; Guerra, Juan A.; Alonso, Joaquín J.

2015-01-01

Introduction. Cardiotoxicity represents a major limitation for the use of anthracyclines or trastuzumab in breast cancer patients. Data from longitudinal studies of diastolic dysfunction (DD) in this group of patients are scarce. The objective of the present study was to assess the incidence, evolution, and predictors of DD in patients with breast cancer treated with anthracyclines. Methods. This analytical, observational cohort study comprised 100 consecutive patients receiving anthracycline-based chemotherapy (CHT) for breast cancer. All patients underwent clinical evaluation, echocardiogram, and measurement of cardiac biomarkers at baseline, end of anthracycline-based CHT, and at 3 months and 9 months after anthracycline-based CHT was completed. Fifteen patients receiving trastuzumab were followed with two additional visits at 6 and 12 months after the last dose of anthracycline-based CHT. A multivariate analysis was performed to find variables related to the development of DD. Fifteen of the 100 patients had baseline DD and were excluded from this analysis. Results. At the end of follow-up (median: 12 months, interquartile range: 11.1–12.8), 49 patients (57.6%) developed DD. DD was persistent in 36 (73%) but reversible in the remaining 13 patients (27%). Four patients developed cardiotoxicity (three patients had left ventricular systolic dysfunction and one suffered a sudden cardiac death). None of the patients with normal diastolic function developed systolic dysfunction during follow-up. In the logistic regression model, body mass index (BMI) and age were independently related to the development of DD, with the following odds ratio values: BMI: 1.19 (95% confidence interval [CI]: 1.04–1.36), and age: 1.12 (95% CI: 1.03–1.19). Neither cardiac biomarkers nor remaining clinical variables were predictors of DD. Conclusion. Development of diastolic dysfunction after treatment with anthracycline or anthracycline- plus trastuzumab chemotherapy is common. BMI and age were independently associated with DD following anthracycline chemotherapy. Implications for Practice: This study characterizes the incidence of diastolic dysfunction in a cohort of patients undergoing anthracycline treatment. The incidence of diastolic dysfunction during follow-up was 57% and persisted at the last follow-up visit in 73% of patients. Age and body mass index were found to be independent predictors of anthracycline-related diastolic dysfunction. These findings may help identify patients at higher risk for developing a clinically relevant anthracycline cardiotoxicity from those at lower risk and to differentiate monitoring programs for breast cancer patients according to their risk. PMID:26185196

Interplay between structure, stoichiometry, and electron transfer dynamics in SILAR-based quantum dot-sensitized oxides.

PubMed

Wang, Hai; Barceló, Irene; Lana-Villarreal, Teresa; Gómez, Roberto; Bonn, Mischa; Cánovas, Enrique

2014-10-08

We quantify the rate and efficiency of picosecond electron transfer (ET) from PbS nanocrystals, grown by successive ionic layer adsorption and reaction (SILAR), into a mesoporous SnO2 support. Successive SILAR deposition steps allow for stoichiometry- and size-variation of the QDs, characterized using transmission electron microscopy. Whereas for sulfur-rich (p-type) QD surfaces substantial electron trapping at the QD surface occurs, for lead-rich (n-type) QD surfaces, the QD trapping channel is suppressed and the ET efficiency is boosted. The ET efficiency increase achieved by lead-rich QD surfaces is found to be QD-size dependent, increasing linearly with QD surface area. On the other hand, ET rates are found to be independent of both QD size and surface stoichiometry, suggesting that the donor-acceptor energetics (constituting the driving force for ET) are fixed due to Fermi level pinning at the QD/oxide interface. Implications of our results for QD-sensitized solar cell design are discussed.

Characterization of Oxygen Defect Clusters in UO2+ x Using Neutron Scattering and PDF Analysis.

PubMed

Ma, Yue; Garcia, Philippe; Lechelle, Jacques; Miard, Audrey; Desgranges, Lionel; Baldinozzi, Gianguido; Simeone, David; Fischer, Henry E

2018-06-18

In hyper-stoichiometric uranium oxide, both neutron diffraction work and, more recently, theoretical analyses report the existence of clusters such as the 2:2:2 cluster, comprising two anion vacancies and two types of anion interstitials. However, little is known about whether there exists a region of low deviation-from-stoichiometry in which defects remain isolated, or indeed whether at high deviation-from-stoichiometry defect clusters prevail that contain more excess oxygen atoms than the di-interstitial cluster. In this study, we report pair distribution function (PDF) analyses of UO 2 and UO 2+ x ( x ≈ 0.007 and x ≈ 0.16) samples obtained from high-temperature in situ neutron scattering experiments. PDF refinement for the lower deviation from stoichiometry sample suggests the system is too dilute to differentiate between isolated defects and di-interstitial clusters. For the UO 2.16 sample, several defect structures are tested, and it is found that the data are best represented assuming the presence of center-occupied cuboctahedra.

Virus Neutralisation: New Insights from Kinetic Neutralisation Curves

PubMed Central

Magnus, Carsten

2013-01-01

Antibodies binding to the surface of virions can lead to virus neutralisation. Different theories have been proposed to determine the number of antibodies that must bind to a virion for neutralisation. Early models are based on chemical binding kinetics. Applying these models lead to very low estimates of the number of antibodies needed for neutralisation. In contrast, according to the more conceptual approach of stoichiometries in virology a much higher number of antibodies is required for virus neutralisation by antibodies. Here, we combine chemical binding kinetics with (virological) stoichiometries to better explain virus neutralisation by antibody binding. This framework is in agreement with published data on the neutralisation of the human immunodeficiency virus. Knowing antibody reaction constants, our model allows us to estimate stoichiometrical parameters from kinetic neutralisation curves. In addition, we can identify important parameters that will make further analysis of kinetic neutralisation curves more valuable in the context of estimating stoichiometries. Our model gives a more subtle explanation of kinetic neutralisation curves in terms of single-hit and multi-hit kinetics. PMID:23468602

Influence of Coformer Stoichiometric Ratio on Pharmaceutical Cocrystal Dissolution: Three Cocrystals of Carbamazepine/4-Aminobenzoic Acid

PubMed Central

Li, Zi; Matzger, Adam J.

2016-01-01

Cocrystallization is a technique to optimize solid forms that shows great potential to improve the solubility of active pharmaceutical ingredients (APIs). In some systems, an API can form cocrystals in multiple stoichiometries with the same coformer. However, it remains unclear how coformer stoichiometry influences solubility. This paper investigates the pharmaceutical:coformer pair carbamazepine (CBZ)/p-aminobenzoic acid (PABA); both CBZ/PABA 1:1 and 2:1 cocrystals are known, and a novel 4:1 CBZ/PABA cocrystal is reported here. The 4:1 cocrystal is structurally characterized, and phase stability data suggest that it is a thermodynamically unstable form. Dissolution experiments show that there is no correlation between the cocrystal stoichiometry and dissolution rate in this system. On the other hand, with the relatively weak intermolecular interactions, metastable forms can be beneficial to dissolution rate, which suggests that more effort should be devoted to cocrystal production with kinetic growth methods. PMID:26837376

Growth of electronically distinct manganite thin films by modulating cation stoichiometry

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

Ryu, Sangkyun; Lee, Joonhyuk; Ahn, Eunyoung

Nd 1-xSr xMnO 3 (NSMO) is a well-known manganite due to close connection between structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that abrupt change of electronic and magnetic properties can be achieved by subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 150 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in lessmore » hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.« less

Growth of electronically distinct manganite thin films by modulating cation stoichiometry

DOE PAGES

Ryu, Sangkyun; Lee, Joonhyuk; Ahn, Eunyoung; ...

2017-06-26

Nd 1-xSr xMnO 3 (NSMO) is a well-known manganite due to close connection between structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that abrupt change of electronic and magnetic properties can be achieved by subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 150 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in lessmore » hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.« less

3D Microstructural Characterization of Uranium Oxide as a Surrogate Nuclear Fuel: Effect of Oxygen Stoichiometry on Grain Boundary Distributions

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

Rudman, K.; Dickerson, P.; Byler, Darrin David

The initial microstructure of an oxide fuel can play a key role in its performance. At low burn-ups, the diffusion of fission products can depend strongly on grain size and grain boundary (GB) characteristics, which in turn depend on processing conditions and oxygen stoichiometry. Serial sectioning techniques using Focused Ion Beam were developed to obtain Electron Backscatter Diffraction (EBSD) data for depleted UO2 pellets that were processed to obtain 3 different oxygen stoichiometries. The EBSD data were used to create 3D microstructure reconstructions and to gather statistical information on the grain and GB crystallography, with emphasis on identifying the charactermore » (twist, tilt, mixed) for GBs that meet the Coincident Site Lattice (CSL) criterion as well as GBs with the most common misorientation angles. Data on dihedral angles at triple points were also collected. The results were compared across different samples to understand effects of oxygen content on microstructure evolution.« less

Simulated terrestrial runoff triggered a phytoplankton succession and changed seston stoichiometry in coastal lagoon mesocosms.

PubMed

Deininger, A; Faithfull, C L; Lange, K; Bayer, T; Vidussi, F; Liess, A

2016-08-01

Climate change scenarios predict intensified terrestrial storm runoff, providing coastal ecosystems with large nutrient pulses and increased turbidity, with unknown consequences for the phytoplankton community. We conducted a 12-day mesocosm experiment in the Mediterranean Thau Lagoon (France), adding soil (simulated runoff) and fish (different food webs) in a 2 × 2 full factorial design and monitored phytoplankton composition, shade adaptation and stoichiometry. Diatoms (Chaetoceros) increased four-fold immediately after soil addition, prymnesiophytes and dinoflagellates peaked after six- and 12 days, respectively. Soil induced no phytoplankton shade adaptation. Fish reduced the positive soil effect on dinoflagellates (Scripsiella, Glenodinium), and diatom abundance in general. Phytoplankton community composition drove seston stoichiometry. In conclusion, pulsed terrestrial runoff can cause rapid, low quality (high carbon: nutrient) diatom blooms. However, bloom duration may be short and reduced in magnitude by fish. Thus, climate change may shift shallow coastal ecosystems towards famine or feast dynamics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Plant–herbivore–decomposer stoichiometric mismatches and nutrient cycling in ecosystems

PubMed Central

Cherif, Mehdi; Loreau, Michel

2013-01-01

Plant stoichiometry is thought to have a major influence on how herbivores affect nutrient availability in ecosystems. Most conceptual models predict that plants with high nutrient contents increase nutrient excretion by herbivores, in turn raising nutrient availability. To test this hypothesis, we built a stoichiometrically explicit model that includes a simple but thorough description of the processes of herbivory and decomposition. Our results challenge traditional views of herbivore impacts on nutrient availability in many ways. They show that the relationship between plant nutrient content and the impact of herbivores predicted by conceptual models holds only at high plant nutrient contents. At low plant nutrient contents, the impact of herbivores is mediated by the mineralization/immobilization of nutrients by decomposers and by the type of resource limiting the growth of decomposers. Both parameters are functions of the mismatch between plant and decomposer stoichiometries. Our work provides new predictions about the impacts of herbivores on ecosystem fertility that depend on critical interactions between plant, herbivore and decomposer stoichiometries in ecosystems. PMID:23303537

Predictors of emotional problems and physical aggression among children of Hong Kong Chinese, Mainland Chinese and Filipino immigrants to Canada.

PubMed

Beiser, Morton; Hamilton, Hayley; Rummens, Joanna Anneke; Oxman-Martinez, Jacqueline; Ogilvie, Linda; Humphrey, Chuck; Armstrong, Robert

2010-10-01

Data from the New Canadian Children and Youth Study (NCCYS), a national study of immigrant children and youth in Canada, are used to examine the mental health salience of putatively universal determinants, as well as of immigration-specific factors. Universal factors (UF) include age, gender, family and neighbourhood characteristics. Migration-specific (MS) factors include ethnic background, acculturative stress, prejudice, and the impact of region of resettlement within Canada. In a sample of children from Hong Kong, the Philippines and Mainland China, the study examined the determinants of emotional problems (EP), and physical aggression (PA). A two-step regression analysis entered UF on step 1, and MS variables on step 2. Universal factors accounted for 12.1% of EP variance. Addition of MS variables increased explained variance to 15.6%. Significant UF predictors: parental depression, family dysfunction, and parent's education. Significant MS variables: country of origin, region of resettlement, resettlement stress, prejudice, and limited linguistic fluency. UF accounted for 6.3% of variance in PA scores. Adding migration-specific variables increased variance explained to 9.1%. UF: age, gender, parent's depression, family dysfunction. MS: country of origin, region of resettlement, resettlement stress, and parent's perception of prejudice. Net of the effect of factors affecting the mental health of most, if not all children, migration-specific variables contribute to understanding immigrant children's mental health.

Prevalence and correlates of self-reported sexual dysfunction in CKD: a meta-analysis of observational studies.

PubMed

Navaneethan, Sankar D; Vecchio, Mariacristina; Johnson, David W; Saglimbene, Valeria; Graziano, Giusi; Pellegrini, Fabio; Lucisano, Giuseppe; Craig, Jonathan C; Ruospo, Marinella; Gentile, Giorgio; Manfreda, Valeria Maria; Querques, Marialuisa; Stroumza, Paul; Torok, Marietta; Celia, Eduardo; Gelfman, Ruben; Ferrari, Juan Nin; Bednarek-Skublewska, Anna; Dulawa, Jan; Bonifati, Carmen; Hegbrant, Jörgen; Wollheim, Charlotta; Jannini, Emmanuele A; Strippoli, Giovanni F M

2010-10-01

Sexual dysfunction is an under-recognized problem in men and women with chronic kidney disease (CKD). The prevalence, correlates, and predictors of this condition in patients with CKD have not been evaluated comprehensively. Systematic review and meta-analysis. Patients treated using dialysis (dialysis patients), patients treated using transplant (transplant recipients), and patients with CKD not treated using dialysis or transplant (nondialysis nontransplant patients with CKD). Observational studies conducted in patients with CKD only or including a control group without CKD. Type of study population. Sexual dysfunction in men and women with CKD using validated tools, such as the International Index of Erectile Function, the Female Sexual Function Index (FSFI), or other measures as reported by study investigators. 50 studies (8,343 patients) of variable size (range, 16-1,023 patients) were included in this review. Almost all studies explored sexual dysfunction in men and specifically erectile dysfunction. The summary estimate of erectile dysfunction in men with CKD was 70% (95% CI, 62%-77%; 21 studies, 4,389 patients). Differences in reported prevalence rates of erectile dysfunction between different studies were attributable primarily to age, study populations, and type of study tool used to assess the presence of erectile dysfunction. In women, the reported prevalence of sexual dysfunction was assessed in only 306 patients from 2 studies and ranged from 30%-80%. Compared with the general population, women with CKD had a significantly lower overall FSFI score (8 studies or subgroups, 407 patients; mean difference, -9.28; 95% CI, -12.92 to -5.64). Increasing age, diabetes mellitus, and depression consistently were found to correlate with sexual dysfunction in 20 individual studies of patients with CKD using different methods. Suboptimal and lack of uniform assessment of outcome measures. Sexual dysfunction is highly prevalent in both men and women with CKD, especially among those on dialysis. Larger studies enrolling different ethnic groups, using validated study tools, and analyzing the influence of various factors on the development of sexual dysfunction are needed. Copyright © 2010 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Prevalence and determinants of erectile dysfunction among diabetic patients attending in hospitals of central and northwestern zone of Tigray, northern Ethiopia: a cross-sectional study.

PubMed

Seid, Awole; Gerensea, Hadgu; Tarko, Shambel; Zenebe, Yosef; Mezemir, Rahel

2017-03-15

The prevalence of erectile dysfunction among diabetic men varies between 35-90%. Although erectile dysfunction is widespread among men with diabetes, the condition often remains undiagnosed and demands appropriate assessment and prompt treatment. Erectile dysfunction can affect all aspects of a patient's life including physical, emotional, social, sexual, and relationships. The main aim of this study is to determine the prevalence and determinants of erectile dysfunction among diabetic patients attending hospitals in the Central and Northwest zone of Tigray, Ethiopia. A hospital based cross-sectional study was conducted on 249 male diabetic patients attending five hospitals in the Central and Northwestern Zone of Tigray, Ethiopia using systematic random sampling. The data was collected from January 1 - February 30, 2016 and was entered and analyzed using SPSS version 20. Correlation and multivariate logistic regression was employed to test associations between independent and outcome variables. The mean age of study participants was 43.39 years and the mean duration of diabetes diagnosis was 6.22 years. The overall prevalence of erectile dysfunction was 69.9%, with 32.9% suffering from mild, 31.7% moderate, and 5.2% severe erectile dysfunction. Multivariate logistic regression revealed that erective dysfunction was significantly predicted by old age (Adjusted Odds Ratio [AOR] =15.013, CI:3.212-70.166), longer duration of diabetes (AOR = 3.77, CI:1.291-11.051), and lower monthly income (AOR = 0.285, CI:0.132-0.615). No association was found with body mass index, co-morbidity, glycemic control, and alcohol consumption. The prevalence of erective dysfunction in this study population was very high. Age, income, and duration of diabetes were the independent predictors of erectile dysfunction. Nearly all of the patients in the sample (97%) had not been screened or treated for erectile dysfunction. Assessment and management of erectile dysfunction in the diabetic clinic should be part of routine medical care during follow-up visits with diabetic patients. Healthcare providers should put an emphasis on screening and treating older patients and those who had a diabetes diagnosis for a longer duration.

Relationship between dysfunctional breathing patterns and ability to achieve target heart rate variability with features of "coherence" during biofeedback.

PubMed

Courtney, Rosalba; Cohen, Marc; van Dixhoorn, Jan

2011-01-01

Heart rate variability (HRV) biofeedback is a self-regulation strategy used to improve conditions including asthma, stress, hypertension, and chronic obstructive pulmonary disease. Respiratory muscle function affects hemodynamic influences on respiratory sinus arrhythmia (RSA), and HRV and HRV-biofeedback protocols often include slow abdominal breathing to achieve physiologically optimal patterns of HRV with power spectral distribution concentrated around the 0.1-Hz frequency and large amplitude. It is likely that optimal balanced breathing patterns and ability to entrain heart rhythms to breathing reflect physiological efficiency and resilience and that individuals with dysfunctional breathing patterns may have difficulty voluntarily modulating HRV and RSA. The relationship between breathing movement patterns and HRV, however, has not been investigated. This study examines how individuals' habitual breathing patterns correspond with their ability to optimize HRV and RSA. Breathing pattern was assessed using the Manual Assessment of Respiratory Motion (MARM) and the Hi Lo manual palpation techniques in 83 people with possible dysfunctional breathing before they attempted HRV biofeedback. Mean respiratory rate was also assessed. Subsequently, participants applied a brief 5-minute biofeedback protocol, involving breathing and positive emotional focus, to achieve HRV patterns proposed to reflect physiological "coherence" and entrainment of heart rhythm oscillations to other oscillating body systems. Thoracic-dominant breathing was associated with decreased coherence of HRV (r = -.463, P = .0001). Individuals with paradoxical breathing had the lowest HRV coherence (t(8) = 10.7, P = .001), and the negative relationship between coherence of HRV and extent of thoracic breathing was strongest in this group (r = -.768, P = .03). Dysfunctional breathing patterns are associated with decreased ability to achieve HRV patterns that reflect cardiorespiratory efficiency and autonomic nervous system balance. This suggests that dysfunctional breathing patterns are not only biomechanically inefficient but also reflect decreased physiological resilience. Breathing assessment using simple manual techniques such as the MARM and Hi Lo may be useful in HRV biofeedback to identify if poor responders require more emphasis on correction of dysfunctional breathing.

Structure and Stoichiometry of MgxZny in Hot-Dipped Zn-Mg-Al Coating Layer on Interstitial-Free Steel

NASA Astrophysics Data System (ADS)

Kim, Jaenam; Lee, Chongsoo; Jin, Youngsool

2018-03-01

Correlations of stoichiometry and phase structure of MgxZny in hot-dipped Zn-Mg-Al coating layer which were modified by additive element have been established on the bases of diffraction and phase transformation principles. X-ray diffraction (XRD) results showed that MgxZny in the Zn-Mg-Al coating layers consist of Mg2Zn11 and MgZn2. The additive elements had a significant effect on the phase fraction of Mg2Zn11 while the Mg/Al ratio had a negligible effect. Transmission electron microscope (TEM) assisted selected area electron diffraction (SAED) results of small areas MgxZny were indexed dominantly as MgZn2 which have different Mg/Zn stoichiometry between 0.10 and 0.18. It is assumed that the MgxZny have deviated stoichiometry of the phase structure with additive element. The deviated Mg2Zn11 phase structure was interpreted as base-centered orthorhombic by applying two theoretical validity: a structure factor rule explained why the base-centered orthorhombic Mg2Zn11 has less reciprocal lattice reflections in the SAED compared to hexagonal MgZn2, and a phase transformation model elucidated its reasonable lattice point sharing of the corresponding unit cell during hexagonal MgZn2 (a, b = 0.5252 nm, c = 0.8577 nm) transform to intermediate tetragonal and final base-centered orthorhombic Mg2Zn11 (a = 0.8575 nm, b = 0.8874 nm, c = 0.8771 nm) in the equilibrium state.

The c-ring stoichiometry of ATP synthase is adapted to cell physiological requirements of alkaliphilic Bacillus pseudofirmus OF4

PubMed Central

Preiss, Laura; Klyszejko, Adriana L.; Hicks, David B.; Liu, Jun; Fackelmayer, Oliver J.; Yildiz, Özkan; Krulwich, Terry A.; Meier, Thomas

2013-01-01

The c-rings of ATP synthases consist of individual c-subunits, all of which harbor a conserved motif of repetitive glycine residues (GxGxGxG) important for tight transmembrane α-helix packing. The c-ring stoichiometry determines the number of ions transferred during enzyme operation and has a direct impact on the ion-to-ATP ratio, a cornerstone parameter of cell bioenergetics. In the extreme alkaliphile Bacillus pseudofirmus OF4, the glycine motif is replaced by AxAxAxA. We performed a structural study on two mutants with alanine-to-glycine changes using atomic force microscopy and X-ray crystallography, and found that mutants form smaller c12 rings compared with the WT c13. The molar growth yields of B. pseudofirmus OF4 cells on malate further revealed that the c12 mutants have a considerably reduced capacity to grow on limiting malate at high pH. Our results demonstrate that the mutant ATP synthases with either c12 or c13 can support ATP synthesis, and also underscore the critical importance of an alanine motif with c13 ring stoichiometry for optimal growth at pH >10. The data indicate a direct connection between the precisely adapted ATP synthase c-ring stoichiometry and its ion-to-ATP ratio on cell physiology, and also demonstrate the bioenergetic challenges and evolutionary adaptation strategies of extremophiles. PMID:23613590

Avidin-biotin-PEG-CPA complexes as potential EPR-directed therapeutic protein carriers: preparation and characterization.

PubMed

Ke, Shan; Wright, John C; Kwon, Glen S

2007-01-01

Bovine carboxypeptidase A (CPA) conjugated with biotinylated poly(ethylene glycol) (PEG) has been synthesized and characterized in terms of stoichiometry and half-life of the avidin-biotin-PEG(s)-CPA complex. The half-lives for dissociation are 3.34 days for the avidin-biotin-PEG(3400)-CPA 1:1 complex, 3.65 days for the avidin-biotin-PEG(5000)-CPA 1:1 complex, 3.91 days for the avidin-biotin-PEG(3400)-CPA-PEG(2000) 1:1 complex, and 2.74 days for the avidin-biotin-PEG(5000)-CPA-PEG(2000) 1:1 complex. The slow dissociation demonstrates the stability of complexes using a PEGylated biotin terminus as a linker with avidin. The stoichiometry of the biotin-PEGylated CPA with avidin was determined by the 2,6-ANS method, and the results are consistent with measurements of the stoichiometry using size exclusion chromatography. The stoichiometries are 1:2 for the avidin-biotin-PEG(3400)-CPA complex and the avidin-biotin-PEG(3400)-CPA-PEG(2000) complex, 1:1 for the avidin-biotin-PEG(5000)-CPA complex, and 1:4 for the avidin-biotin-PEG(5000)-CPA-PEG(2000) complex. These findings stress both the importance of the length of a PEG chain as an appropriate spacer between the biotin terminus and a functional group, and the great potential of the avidin-biotin-PEGylated-protein complex as a therapeutic protein delivery system for solid tumor prodrug targeting.

Selectivity and stoichiometry boosting of beta-cyclodextrin in cationic/anionic surfactant systems: when host-guest equilibrium meets biased aggregation equilibrium.

PubMed

Jiang, Lingxiang; Yu, Caifang; Deng, Manli; Jin, Changwen; Wang, Yilin; Yan, Yun; Huang, Jianbin

2010-02-18

Cationic surfactant/anionic surfactant/beta-CD ternary aqueous systems provide a platform for the coexistence of the host-guest (beta-CD/surfactant) equilibrium and the biased aggregation (monomeric/aggregated surfactants) equilibrium. We report here that the interplay between the two equilibria dominates the systems as follows. (1) The biased aggregation equilibrium imposes an apparent selectivity on the host-guest equilibrium, namely, beta-CD has to always selectively bind the major surfactant (molar fraction > 0.5) even if binding constants of beta-CD to the pair of surfactants are quite similar. (2) In return, the host-guest equilibrium amplifies the bias of the aggregation equilibrium, that is, the selective binding partly removes the major surfactant from the aggregates and leaves the aggregate composition approaching the electroneutral mixing stoichiometry. (3) This composition variation enhances electrostatic attractions between oppositely charged surfactant head groups, thus resulting in less-curved aggregates. In particular, the present apparent host-guest selectivity is of remarkably high values, and the selectivity stems from the bias of the aggregation equilibrium rather than the difference in binding constants. Moreover, beta-CD is defined as a "stoichiometry booster" for the whole class of cationic/anionic surfactant systems, which provides an additional degree of freedom to directly adjust aggregate compositions of the systems. The stoichiometry boosting of the compositions can in turn affect or even determine microstructures and macroproperties of the systems.

Latitudinal patterns of leaf N, P stoichiometry and nutrient resorption of Metasequoia glyptostroboides along the eastern coastline of China.

PubMed

Zhang, Hui; Guo, Weihong; Yu, Mukui; Wang, G Geoff; Wu, Tonggui

2018-03-15

Latitudinal patterns of leaf stoichiometry and nutrient resorption were not consistent among published studies, likely due to confounding effects from taxonomy (e.g., plant distribution and community composition), and environment, which is also influenced by altitude and longitude. Thus, the latitudinal patterns and environmental mechanism could be best revealed by testing a given species along a latitude gradient with similar altitude and longitude. We determined nitrogen (N) and phosphorus (P) concentrations of green (leaf) and senesced leaves (litter) from eight Metasequoia glyptostroboides forests along the eastern coastline of China, with similar altitude and longitude. Leaf N, P concentrations increased along latitude, mainly driven by mean annual temperature (MAT), mean annual precipitation (MAP), annual evaporation (AE), aridity index (AI), and annual total solar radiation (ATSR); While leaf N:P ratio was stable with no latitudinal pattern. Nitrogen resorption efficiency (NRE) increased along latitude, and was also mainly influenced by MAT, MAP, AE, and AI. Phosphorus resorption efficiency (PRE) first increased and then decreased with latitude, which was impacted by soil available P. These results indicated that only climate (such as heat, water, and light) controlled the shift in leaf stoichiometry and NRE, while soil nutrient was likely responsible for the shift in PRE along eastern China. Our findings also suggested that leaf N, P stoichiometry and NRE displayed similar latitudinal patterns at regional scale when studied for a given species (this study) or multi-species (previous studies). Copyright © 2017. Published by Elsevier B.V.

Carbon and nutrient use efficiencies optimally balance stoichiometric imbalances

NASA Astrophysics Data System (ADS)

Manzoni, Stefano; Čapek, Petr; Lindahl, Björn; Mooshammer, Maria; Richter, Andreas; Šantrůčková, Hana

2016-04-01

Decomposer organisms face large stoichiometric imbalances because their food is generally poor in nutrients compared to the decomposer cellular composition. The presence of excess carbon (C) requires adaptations to utilize nutrients effectively while disposing of or investing excess C. As food composition changes, these adaptations lead to variable C- and nutrient-use efficiencies (defined as the ratios of C and nutrients used for growth over the amounts consumed). For organisms to be ecologically competitive, these changes in efficiencies with resource stoichiometry have to balance advantages and disadvantages in an optimal way. We hypothesize that efficiencies are varied so that community growth rate is optimized along stoichiometric gradients of their resources. Building from previous theories, we predict that maximum growth is achieved when C and nutrients are co-limiting, so that the maximum C-use efficiency is reached, and nutrient release is minimized. This optimality principle is expected to be applicable across terrestrial-aquatic borders, to various elements, and at different trophic levels. While the growth rate maximization hypothesis has been evaluated for consumers and predators, in this contribution we test it for terrestrial and aquatic decomposers degrading resources across wide stoichiometry gradients. The optimality hypothesis predicts constant efficiencies at low substrate C:N and C:P, whereas above a stoichiometric threshold, C-use efficiency declines and nitrogen- and phosphorus-use efficiencies increase up to one. Thus, high resource C:N and C:P lead to low C-use efficiency, but effective retention of nitrogen and phosphorus. Predictions are broadly consistent with efficiency trends in decomposer communities across terrestrial and aquatic ecosystems.

Modeling Non-Steady Isotopologue and Isotopomer Speciation and Fractionation during Denitrification in Soils

NASA Astrophysics Data System (ADS)

Maggi, F.; Riley, W. J.

2009-12-01

The composition and location of 15N atoms on N2O isotopomers and isotopologues during isotope speciation has been used to characterize soil biological N cycling and N2O surface emissions. Although there exist few experimental observations, no attempt has been made to model N2O isotopomer speciation. The mathematical treatment of biological kinetic reactions in isotopic applications normally makes use of first-order and quasi steady-state complexation assumptions without taking into account changes in enzyme concentration, reaction stoichiometry, and isotopologue and isotopomer speciation. When multiatomic isotopically-labeled reactants are used in a multi-molecurar reaction, these assumptions may fail since they always lead to a constant fractionation factor and cannot describe speciation of isotopologues and isotopomers. We have developed a mathematical framework that is capable of describing isotopologue and isotopmer speciation and fractionation under the assumption of non-steady complexation during biological kinetic reactions that overcome the limitations mentioned above. This framework was applied to a case study of non-steady (variable and inverse) isotopic effects observed during N2O production and consumption in soils. Our mathematical treatment has led to generalized kinetic equations which replicate experimental observations with high accuracy and help interpret non-steady isotopic effects and isotopologue and isotopomer speciation. The kinetic equations introduced and applied here have general validity in describing isotopic effects in any biochemical reactions by considering: changing enzyme concentrations, mass and isotope conservation, and reaction stoichiometry. The equations also describe speciation of any isotopologue and isotopomer product from any isotopologue and isotopmer reactant.

Iron Uptake in a Shelf Sea: Seasonality and Stoichiometry

NASA Astrophysics Data System (ADS)

Daniels, C. J.; Poulton, A. J.; Moore, M. M.; Birchill, A.; Mayers, K.; Lohan, M. C.

2016-02-01

Primary production by phytoplankton in shelf seas represents a significant contribution to global carbon cycling. Trace metals, such as Iron (Fe), are essential micronutrients for phytoplankton growth, and may ultimately limit primary production. The uptake of iron within natural phytoplankton communities is poorly understood. Using carrier free 55Fe, we are able to obtain novel estimates of biological uptake of Fe using trace level Fe additions that do not perturb the system. Here we present results from a study measuring the uptake of carrier free Iron (55Fe), in parallel with measurements of Carbon (14C) and Phosphorus (33P) uptake; samples were collected from the Celtic sea in spring (April 2015) and summer (July 2015), on-shelf and off-shelf, and in 2 size fractions (Total, >2µm), thus producing a novel dataset of the seasonality of macronutrient and micronutrient uptake by phytoplankton within a shelf sea. Primary production ranged from 1.0 - 2.2 mmol C m-3 d-1 in April and 0.2 - 1.5 mmol C m-3 d-1 in July, with a corresponding higher biomass in April (0.7 - 3.24 mg Chl m-3) than July (0.3 - 1.6 mg Chl m-3). Significant rates of Fe uptake were measured in all samples (e.g. 21 nmol m-3 d-1, on-shelf, April), with variable stoichiometry (e.g. Fe/C of 16 µmol/mol, and Fe/P of 0.4 mmol/mol, on-shelf, April). The results will be presented and examined in the context of the available nutrient pools, the phytoplankton community structure and the impact on biogeochemical cycling.

Linking Inflammation, Cardiorespiratory Variability, and Neural Control in Acute Inflammation via Computational Modeling

PubMed Central

Dick, Thomas E.; Molkov, Yaroslav I.; Nieman, Gary; Hsieh, Yee-Hsee; Jacono, Frank J.; Doyle, John; Scheff, Jeremy D.; Calvano, Steve E.; Androulakis, Ioannis P.; An, Gary; Vodovotz, Yoram

2012-01-01

Acute inflammation leads to organ failure by engaging catastrophic feedback loops in which stressed tissue evokes an inflammatory response and, in turn, inflammation damages tissue. Manifestations of this maladaptive inflammatory response include cardio-respiratory dysfunction that may be reflected in reduced heart rate and ventilatory pattern variabilities. We have developed signal-processing algorithms that quantify non-linear deterministic characteristics of variability in biologic signals. Now, coalescing under the aegis of the NIH Computational Biology Program and the Society for Complexity in Acute Illness, two research teams performed iterative experiments and computational modeling on inflammation and cardio-pulmonary dysfunction in sepsis as well as on neural control of respiration and ventilatory pattern variability. These teams, with additional collaborators, have recently formed a multi-institutional, interdisciplinary consortium, whose goal is to delineate the fundamental interrelationship between the inflammatory response and physiologic variability. Multi-scale mathematical modeling and complementary physiological experiments will provide insight into autonomic neural mechanisms that may modulate the inflammatory response to sepsis and simultaneously reduce heart rate and ventilatory pattern variabilities associated with sepsis. This approach integrates computational models of neural control of breathing and cardio-respiratory coupling with models that combine inflammation, cardiovascular function, and heart rate variability. The resulting integrated model will provide mechanistic explanations for the phenomena of respiratory sinus-arrhythmia and cardio-ventilatory coupling observed under normal conditions, and the loss of these properties during sepsis. This approach holds the potential of modeling cross-scale physiological interactions to improve both basic knowledge and clinical management of acute inflammatory diseases such as sepsis and trauma. PMID:22783197

Ambulatory ECG and analysis of heart rate variability in Parkinson's disease.

PubMed

Haapaniemi, T H; Pursiainen, V; Korpelainen, J T; Huikuri, H V; Sotaniemi, K A; Myllylä, V V

2001-03-01

Cardiovascular reflex tests have shown both sympathetic and parasympathetic failure in Parkinson's disease. These tests, however, describe the autonomic responses during a restricted time period and have great individual variability, providing a limited view of the autonomic cardiac control mechanisms. Thus, they do not reflect tonic autonomic regulation. The aim was to examine tonic autonomic cardiovascular regulation in untreated patients with Parkinson's disease. 24 Hour ambulatory ECG was recorded in 54 untreated patients with Parkinson's disease and 47 age matched healthy subjects. In addition to the traditional spectral (very low frequency, VLF; low frequency, LF; high frequency, HF) and non-spectral components of heart rate variability, instantaneous beat to beat variability (SD1) and long term continuous variability (SD2) derived from Poincaré plots, and the slope of the power law relation were analysed. All spectral components (p<0.01) and the slope of the power-law relation (p<0.01) were lower in the patients with Parkinson's disease than in the control subjects. The Unified Parkinson's disease rating scale total and motor scores had a negative correlation with VLF and LF power spectrum values and the power law relation slopes. Patients with mild hypokinesia had higher HF values than patients with more severe hypokinesia. Tremor and rigidity were not associated with the HR variability parameters. Parkinson's disease causes dysfunction of the diurnal autonomic cardiovascular regulation as demonstrated by the spectral measures of heart rate variability and the slope of the power law relation. This dysfunction seems to be more profound in patients with more severe Parkinson's disease.

Linking Inflammation, Cardiorespiratory Variability, and Neural Control in Acute Inflammation via Computational Modeling.

PubMed

Dick, Thomas E; Molkov, Yaroslav I; Nieman, Gary; Hsieh, Yee-Hsee; Jacono, Frank J; Doyle, John; Scheff, Jeremy D; Calvano, Steve E; Androulakis, Ioannis P; An, Gary; Vodovotz, Yoram

2012-01-01

Acute inflammation leads to organ failure by engaging catastrophic feedback loops in which stressed tissue evokes an inflammatory response and, in turn, inflammation damages tissue. Manifestations of this maladaptive inflammatory response include cardio-respiratory dysfunction that may be reflected in reduced heart rate and ventilatory pattern variabilities. We have developed signal-processing algorithms that quantify non-linear deterministic characteristics of variability in biologic signals. Now, coalescing under the aegis of the NIH Computational Biology Program and the Society for Complexity in Acute Illness, two research teams performed iterative experiments and computational modeling on inflammation and cardio-pulmonary dysfunction in sepsis as well as on neural control of respiration and ventilatory pattern variability. These teams, with additional collaborators, have recently formed a multi-institutional, interdisciplinary consortium, whose goal is to delineate the fundamental interrelationship between the inflammatory response and physiologic variability. Multi-scale mathematical modeling and complementary physiological experiments will provide insight into autonomic neural mechanisms that may modulate the inflammatory response to sepsis and simultaneously reduce heart rate and ventilatory pattern variabilities associated with sepsis. This approach integrates computational models of neural control of breathing and cardio-respiratory coupling with models that combine inflammation, cardiovascular function, and heart rate variability. The resulting integrated model will provide mechanistic explanations for the phenomena of respiratory sinus-arrhythmia and cardio-ventilatory coupling observed under normal conditions, and the loss of these properties during sepsis. This approach holds the potential of modeling cross-scale physiological interactions to improve both basic knowledge and clinical management of acute inflammatory diseases such as sepsis and trauma.

Looming Threats and Animacy: Reduced Responsiveness in Youth with Disrupted Behavior Disorders.

PubMed

White, Stuart F; Thornton, Laura C; Leshin, Joseph; Clanton, Roberta; Sinclair, Stephen; Coker-Appiah, Dionne; Meffert, Harma; Hwang, Soonjo; Blair, James R

2018-05-01

Theoretical models have implicated amygdala dysfunction in the development of Disruptive Behavior Disorders (DBDs; Conduct Disorder/Oppositional Defiant Disorder). Amygdala dysfunction impacts valence evaluation/response selection and emotion attention in youth with DBDs, particularly in those with elevated callous-unemotional (CU) traits. However, amygdala responsiveness during social cognition and the responsiveness of the acute threat circuitry (amygdala/periaqueductal gray) in youth with DBDs have been less well-examined, particularly with reference to CU traits. 31 youth with DBDs and 27 typically developing youth (IQ, age and gender-matched) completed a threat paradigm during fMRI where animate and inanimate, threatening and neutral stimuli appeared to loom towards or recede from participants. Reduced responsiveness to threat variables, including visual threats and encroaching stimuli, was observed within acute threat circuitry and temporal, lateral frontal and parietal cortices in youth with DBDs. This reduced responsiveness, at least with respect to the looming variable, was modulated by CU traits. Reduced responsiveness to animacy information was also observed within temporal, lateral frontal and parietal cortices, but not within amygdala. Reduced responsiveness to animacy information as a function of CU traits was observed in PCC, though not within the amygdala. Reduced threat responsiveness may contribute to risk taking and impulsivity in youth with DBDs, particularly those with high levels of CU traits. Future work will need to examine the degree to which this reduced response to animacy is independent of amygdala dysfunction in youth with DBDs and what role PCC might play in the dysfunctional social cognition observed in youth with high levels of CU traits.

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency.

PubMed

Patterson, Emily J; Wilk, Melissa; Langlo, Christopher S; Kasilian, Melissa; Ring, Michael; Hufnagel, Robert B; Dubis, Adam M; Tee, James J; Kalitzeos, Angelos; Gardner, Jessica C; Ahmed, Zubair M; Sisk, Robert A; Larsen, Michael; Sjoberg, Stacy; Connor, Thomas B; Dubra, Alfredo; Neitz, Jay; Hardcastle, Alison J; Neitz, Maureen; Michaelides, Michel; Carroll, Joseph

2016-07-01

Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction. We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family. There were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array. Our findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus.

Reversible autonomic dysfunction in hyperthyroid patients affects gastric myoelectrical activity and emptying.

PubMed

Barczyński, M; Thor, P

2001-08-01

The autonomic nervous system (ANS) function in hyperthyroidism has been so far investigated mainly from the cardiovascular point of view. The aim of this study is to show that the ANS dysfunction in hyperthyroidism is also expressed in gastric myoelectrical activity disturbances and gastric emptying disorders and to search for a correlation between the severity of clinical manifestation and free thyroid hormone levels and the degree of the ANS dysfunction. The analyzed group included 50 recently diagnosed patients with hyperthyroidism who were examined twice: before and after 3 months of thyrostatic treatment. Results were compared with those of a sex-, age- and BMI-matched control group of 50 healthy volunteers. The study included: heart rate variability analysis in time and frequency domain, at rest and during a deep-breathing test, surface electrogastrography in preprandial and postprandial periods measured simultaneously with the ultrasound assessment of gastric emptying time by Bolondi method. In patients with hyperthyroidism in comparison with the control group, the following significant differences were observed: a sharp reduction of the high-frequency component and a decrease of heart rate variability, a high incidence of dysrhythmia with dominant bradyarrhythmia, and a delay of gastric emptying. The degree of disorders related to the degree of clinical manifestation of hyperthyroidism's symptoms and free triiodothyronine serum concentration both. All the disorders were functional and disappeared in a stable euthyroidism. To conclude, the ANS dysfunction in hyperthyroidism results not only in withdrawal of vagal inhibitory effect on sinoatrial node, but in impaired mutual neuro-hormonal regulation (decrease of vagal influence) of gastric myoelectrical activity followed by delay of gastric emptying.

A common pronociceptive pain modulation profile typifying subgroups of chronic pelvic pain syndromes is interrelated with enhanced clinical pain.

PubMed

Grinberg, Keren; Granot, Michal; Lowenstein, Lior; Abramov, Liora; Weissman-Fogel, Irit

2017-06-01

Provoked vestibulodynia (PVD) and painful bladder syndrome (PBS), subgroups of chronic pelvic pain syndromes (CPPS), are considered to share common biophysiological peripheral mechanisms. In addition, indications of a pronociceptive pain profile coexisting with psychological vulnerability suggest common dysfunctional pain processing and pain modulation in these 2 subgroups of CPPS. We therefore aimed at comparing the pain profile and psychological traits of patients with PVD and PBS to see whether the pain profile contributes to intersubject variability of clinical pain symptoms. Patients with PVD (n = 18) and PBS (n = 21) were compared with healthy controls (n = 20) in their responses to (1) pain psychophysical tests applied to both referred (suprapubis) and remote (hand) body areas and (2) pain-related psychological factors (pain catastrophizing, depression, anxiety, and somatization). We found a similar pronociceptive pain profile in the 2 subgroups of CPPS-enhanced facilitation (ie, hyperalgesia in the referred body area [P < 0.001]) and inefficient inhibition (ie, reduced conditioned pain modulation [P < 0.001] that were associated with both enhanced pain ratings evoked during trigger point examination [P < 0.037]) and higher Brief Pain Inventory ratings (P = 0.002). The latter was also correlated with pain catastrophizing (r = 0.504, P = 0.001) and depression symptoms (r = 0.361, P = 0.024). The findings suggest common mechanisms underlying a dysfunctional nociceptive system in both PVD and PBS. The intersubject variability in the level of dysfunction and its association with disease severity recommends a personalized pain treatment that may alleviate daily pain and dysfunction in patients with CPPS.

Watershed vs. within-lake drivers of nitrogen: phosphorus dynamics in shallow lakes.

PubMed

Ginger, Luke J; Zimmer, Kyle D; Herwig, Brian R; Hanson, Mark A; Hobbs, William O; Small, Gaston E; Cotner, James B

2017-10-01

Research on lake eutrophication often identifies variables affecting amounts of phosphorus (P) and nitrogen (N) in lakes, but understanding factors influencing N:P ratios is important given its influence on species composition and toxin production by cyanobacteria. We sampled 80 shallow lakes in Minnesota (USA) for three years to assess effects of watershed size, proportion of watershed as both row crop and natural area, fish biomass, and lake alternative state (turbid vs. clear) on total N : total P (TN : TP), ammonium, total dissolved phosphorus (TDP), and seston stoichiometry. We also examined N:P stoichiometry in 20 additional lakes that shifted states during the study. Last, we assessed the importance of denitrification by measuring denitrification rates in sediment cores from a subset of 34 lakes, and by measuring seston δ 15 N in four additional experimental lakes before and after they were experimentally manipulated from turbid to clear states. Results showed alternative state had the largest influence on overall N:P stoichiometry in these systems, as it had the strongest relationship with TN : TP, seston C:N:P, ammonium, and TDP. Turbid lakes had higher N at given levels of P than clear lakes, with TN and ammonium 2-fold and 1.4-fold higher in turbid lakes, respectively. In lakes that shifted states, TN was 3-fold higher in turbid lakes, while TP was only 2-fold higher, supporting the notion N is more responsive to state shifts than is P. Seston δ 15 N increased after lakes shifted to clear states, suggesting higher denitrification rates may be important for reducing N levels in clear states, and potential denitrification rates in sediment cores were among the highest recorded in the literature. Overall, our results indicate lake state was a primary driver of N:P dynamics in shallow lakes, and lakes in clear states had much lower N at a given level of P relative to turbid lakes, likely due to higher denitrification rates. Shallow lakes are often managed for the clear-water state due to increased value as wildlife habitat. However, our results indicate lake state also influences N biogeochemistry, such that managing shallow lakes for the clear-water state may also mitigate excess N levels at a landscape scale. © 2017 by the Ecological Society of America.

Chronic periodontitis is associated with erectile dysfunction. A case-control study in european population.

PubMed

Martín, Amada; Bravo, Manuel; Arrabal, Miguel; Magán-Fernández, Antonio; Mesa, Francisco

2018-07-01

To determine the association between chronic periodontitis and erectile dysfunction adjusting for biochemical markers and other comorbidities. A case-control study was conducted on 158 male patients; 80 cases with erectile dysfunction according to the International Index of Erectile Function and 78 controls. Sociodemographic data were gathered, and a periodontal examination was performed. Testosterone, lipid profile, C-reactive protein and glycaemic parameters were assessed. All variables were compared between groups, and multivariate logistic regression analyses were performed. 74% of the cases were diagnosed with chronic periodontitis. Number of sites with pocket probing depth 4-6 mm (p = 0.05) and number of sites with clinical attachment loss >3 mm (p < 0.01) were higher in the cases. Triglycerides (p < 0.01), C-reactive protein (p = 0.02) and glycosylated haemoglobin (p = 0.04) were also higher in the cases. Logistic regression showed that patients with chronic periodontitis were more likely to have erectile dysfunction (OR=2.17; 95% CI (1.06-4.43); p = 0.03) independently of other confounders. Patients with erectile dysfunction showed worse periodontal condition. Chronic periodontitis seems to play a key role as a risk factor in the pathogenesis of erectile dysfunction independently of other morbidities. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of a Physical Activity Program on Markers of Endothelial Dysfunction, Oxidative Stress, and Metabolic Status in Adolescents with Metabolic Syndrome

PubMed Central

Camarillo-Romero, Eneida; Dominguez-Garcia, Ma Victoria; Amaya-Chavez, Araceli; Camarillo-Romero, Maria del Socorro; Talavera-Piña, Juan; Huitron-Bravo, Gerardo; Majluf-Cruz, Abraham

2012-01-01

The metabolic syndrome (MetS) is a precursor of diabetes. Physical activity (PA) improves endothelial dysfunction and may benefit patients with MetS. Aims. To evaluate the effect of a physical activity (PA) program on markers of endothelial dysfunction and oxidative stress in adolescents with (MetS). Methods. We carried out a cohort study of 38 adolescents with and without MetS (18 females and 20 males). All participants completed a 3-month PA program. All variables of the MetS as well as markers of endothelial dysfunction and oxidative stress tests were evaluated. Results. Females with and without MetS showed significant differences for almost all components of the MetS, whereas males were significantly different in half of the components. After the PA program, components of the MetS were not different from baseline values except for HDL-C levels. Some baseline endothelial dysfunction markers were significantly different among adolescents with and without MetS; however, after the PA program, most of these markers significantly improved in subjects with and without MetS. Conclusion. PA improves the markers of endothelial dysfunction in adolescents with MetS although other changes in the components of the MetS were not observed. Perhaps the benefits of PA on all components of MetS would appear after a PA program with a longer duration. PMID:22888450

Contribution of autonomic dysfunction to abnormal exercise blood pressure in type 2 diabetes mellitus.

PubMed

Weston, Kassia S; Sacre, Julian W; Jellis, Christine L; Coombes, Jeff S

2013-01-01

The purpose of this study was to compare the presence and severity of autonomic dysfunction in type 2 diabetes mellitus patients, with and without exaggerated blood pressure responses to exercise. We performed a cross-sectional analysis of 98 patients with type 2 diabetes mellitus (aged 59±9). Both time (standard deviation of RR intervals, root-mean-square of successive RR interval differences) and frequency (total spectral power, high frequency, low frequency, very low frequency) domains of heart rate variability were analysed in a 5 min recording at rest and 20 min after a maximal treadmill test. An exaggerated blood pressure response to exercise was identified by peak blood pressure ≥190/105 mmHg (women) or ≥210/105 mmHg (men). Each group of either exaggerated exercise blood pressure response or normal blood pressure response consisted of 49 patients. At rest there were no significant differences between groups for all time and frequency domain parameters of heart rate variability. Post-exercise, there was a significant (p<0.05) reduction in the SDNN, RMSSD and TP in the exaggerated exercise blood pressure group. Independent correlates (p<0.01) of exercise systolic blood pressure included post-exercise TP, resting systolic blood pressure, cardiac autonomic neuropathy and beta-blockers (beta=-0.28, adj. R² = 0.32, p<0.001). Reduced post-exercise heart rate variability in patients with type 2 diabetes mellitus, with an exaggerated exercise blood pressure response suggests preclinical autonomic dysfunction characterized by impaired vagal modulation. Copyright © 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Heart Rate Variability Indexes in Dementia: A Systematic Review with a Quantitative Analysis.

PubMed

da Silva, Vanessa Pereira; Ramalho Oliveira, Bruno Ribeiro; Tavares Mello, Roger Gomes; Moraes, Helena; Deslandes, Andrea Camaz; Laks, Jerson

2018-01-01

Decreased heart rate variability (HRV) indexes indicate low vagal activity and may be associated with development of dementia. The neurodegenerative process is associated with the cardiovascular autonomic control. The aim of this systematic review was to investigate the effect size (ES) magnitude of the HRV indexes in the evaluation of autonomic dysfunction in older persons with dementia. PubMed (Medline), Web of Science, Scopus, Scielo, Lilacs, and APA Psycnet were consulted. Complete original articles published in English or Portuguese, investigating the association between autonomic dysfunction and dementia, using the HRV indexes were included. The search identified 97 potentially relevant articles. After screening the full text, eight articles were included in the qualitative analysis and six were included in the quantitative analysis. Almost all indexes showed a negative ES for all types of dementia and mild cognitive impairment. The most common frequency band of the power spectrum density function was the high frequency, which was reported by six studies. The meta-analysis of high frequency power in Alzheimer's disease group showed high heterogeneity and inconsistent results. The negative effect size suggests an autonomic dysfunction in all types of dementia as well as mild cognitive impairment. However, further analysis is necessary to support these results. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Cervical spine dysfunctions in patients with chronic subjective tinnitus.

PubMed

Michiels, Sarah; De Hertogh, Willem; Truijen, Steven; Van de Heyning, Paul

2015-04-01

To assess, characterize, and quantify cervical spine dysfunction in patients with cervicogenic somatic tinnitus (CST) compared to patients suffering from other forms of chronic subjective non-pulsatile tinnitus. Cross-sectional study. Tertiary referral center. Consecutive adult patients suffering from chronic subjective non-pulsatile tinnitus were included. Ménière's disease, middle ear pathology, intracranial pathology, cervical spine surgery, whiplash trauma, temporomandibular dysfunction. Assessment comprises medical history, ENT examination with micro-otoscopy, audiometry, tinnitus assessment, temporomandibular and cervical spine investigation, and brain MRI. Patients were classified into CST and non-CST population. Cervical spine dysfunction was investigated using the Neck Bournemouth Questionnaire (NBQ) and clinical tests of the cervical spine, containing range of motion, pain provocation (adapted Spurling test, AST), and muscle tests (tenderness via trigger points, strength and endurance of deep neck flexors). Between-group analysis was performed. The prevalence of cervical spine dysfunction was described for the total group and for CST and non-CST groups. In total, 87 patients were included, of which 37 (43%) were diagnosed with CST. In comparison with the non-CST group, the CST group demonstrated a significantly higher prevalence of cervical spine dysfunction. In the CST group, 68% had a positive manual rotation test, 47% a positive AST, 49% a positive score on both, and 81% had positive trigger points. In the non-CST group, these percentages were 36, 18, 10, and 50%, respectively. Furthermore, 79% of the CST group had a positive NBQ versus 40% in the non-CST group. Significant differences between the both groups were found for all the aforementioned variables (all p < 0.005). Although a higher prevalence of neck dysfunction was found in the CST group, neck dysfunction is often in non-CST patients.

Dysfunction of autonomic nervous system in childhood obesity: a cross-sectional study.

PubMed

Baum, Petra; Petroff, David; Classen, Joseph; Kiess, Wieland; Blüher, Susann

2013-01-01

To assess the distribution of autonomic nervous system (ANS) dysfunction in overweight and obese children. Parasympathetic and sympathetic ANS function was assessed in children and adolescents with no evidence of impaired glucose metabolism by analysis of heart rate variability (low frequency power ln(LF), high frequency power, ln(HF); ln(LF/HF) ratio, ratio of longest RR interval during expiration to shortest interval during inspiration (E/I ratio), root mean square of successive differences (RMSSD); sympathetic skin response (SSR); and quantitative pupillography (pupil diameter in darkness, light reflex amplitude, latency, constriction velocity, re-dilation velocity). The relationship of each ANS variable to the standard deviation score of body mass index (BMI-SDS) was assessed in a linear model considering age, gender and pubertal stage as co-variates and employing an F-statistic to compare the fit of nested models. Group comparisons between normal weight and obese children as well as an analysis of dependence on insulin resistance (as indexed by the Homeostasis Model Assessment of Insulin Resistance, HOMA-IR) were performed for parameters shown to correlate with BMI-SDS. Statistical significance was set at 5%. Measurements were performed in 149 individuals (mean age 12.0 y; 90 obese 45 boys; 59 normal weight, 34 boys). E/I ratio (p = 0.003), ln(HF) (p = 0.03), pupil diameter in darkness (p = 0.01) were negatively correlated with BMI-SDS, whereas ln(LF/HF) was positively correlated (p = 0.05). Early re-dilation velocity was in trend negatively correlated to BMI-SDS (p = 0.08). None of the parameters that depended significantly on BMI-SDS was found to be significantly correlated with HOMA-IR. These findings demonstrate extended ANS dysfunction in obese children and adolescents, affecting several organ systems. Both parasympathetic activity and sympathetic activity are reduced. The conspicuous pattern of ANS dysfunction raises the possibility that obesity may give rise to dysfunction of the peripheral autonomic nerves resembling that observed in normal-weight diabetic children and adolescents.

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

Degtyarenko, N. N.; Mazur, E. A., E-mail: eugen-mazur@mail.ru

The structural, electronic, phonon, and other characteristics of the normal phases of phosphorus hydrides with stoichiometry PH{sub k} are analyzed. The properties of the initial substance, namely, diphosphine are calculated. In contrast to phosphorus hydrides with stoichiometry PH{sub 3}, a quasi-two-dimensional phosphorus-stabilized lattice of metallic hydrogen can be formed in this substance during hydrostatic compression at a high pressure. The formed structure with H–P–H elements is shown to be locally stable in phonon spectrum, i.e., to be metastable. The properties of diphosphine are compared with the properties of similar structures of sulfur hydrides.

Rare earth chalcogenide stoichiometry determination. [of thermoelectric properties

NASA Technical Reports Server (NTRS)

Lockwood, R. A.

1983-01-01

Rare earth chalcogenides, and particularly lanthanum sulfide, are currently explored as candidate materials for thermoelectric applications. Since the electrical properties of LaS(x) are largely determined by its stoichiometry, a simple and accurate method has been developed for determining the value of x. The procedure involves dissolving a weighted sample in acid and measuring the amount of hydrogen evolved by the lanthanum that is in excess of the 1.500 ratio of S/La. The analytical error in the determination of x in LaS(x) is about 0.001.

The Effects of Stoichiometry on the Mechanical Properties of Icosahedral Boron Carbide Under Loading

DTIC Science & Technology

2012-11-19

ranging from 10% to 20% C using glancing incidence x - ray diffraction and similar experimental studies of structure as a function of stoichiometry were...blue) positions. it has been suggested that x - ray diffraction analysis of a series of boron-rich materials indicates a distinct change in the c lattice...Angstroms, angles in degrees, volume in cubic Angstroms). Structure Formula % C a b c α β γ Volume Experiment37 B5.6C 15.2 5.19 5.19 5.19 65.18 65.18

Determination of stoichiometry and concentration of trace elements in thin BaxSr1-xTiO3 perovskite layers.

PubMed

Becker, J S; Boulyga, S F

2001-07-01

This paper describes an analytical procedure for determining the stoichiometry of BaxSr1-xTiO3 perovskite layers using inductively coupled plasma mass spectrometry (ICP-MS). The analytical results of mass spectrometry measurements are compared to those of X-ray fluorescence analysis (XRF). The performance and the limits of solid-state mass spectrometry analytical methods for the surface analysis of thin BaxSr1-xTiO3 perovskite layers sputtered neutral mass spectrometry (SNMS)--are investigated and discussed.

Microbial C:P stoichiometry is shaped by redox conditions along an elevation gradient in humid tropical rainforests

NASA Astrophysics Data System (ADS)

Lin, Y.; Gross, A.; Silver, W. L.

2017-12-01

Elemental stoichiometry of microorganisms is intimately related to ecosystem carbon and nutrient fluxes and is ultimately controlled by the chemical (plant tissue, soil, redox) and physical (temperature, moisture, aeration) environment. Previous meta-analyses have shown that the C:P ratio of soil microbial biomass exhibits significant variations among and within biomes. Little is known about the underlying causes of this variability. We examined soil microbial C:P ratios along an elevation gradient in the Luquillo Experimental Forest in Puerto Rico. We analyzed soils from mixed forest paired with monodominant palm forest every 100 m from 300 m to 1000 m a.s.l.. Mean annual precipitation increased with increasing elevation, resulting in stronger reducing conditions and accumulation of soil Fe(II) at higher elevations. The mean value and variability of soil microbial C:P ratios generally increased with increasing elevation except at 1000 m. At high elevations (600-900 m), the average value of microbial C:P ratio (108±10:1) was significantly higher than the global average ( 55:1). We also found that soil organic P increased with increasing elevation, suggesting that an inhibition of organic P mineralization, not decreased soil P availability, may cause the high microbial C:P ratio. The soil microbial C:P ratio was positively correlated with soil HCl-extractable Fe(II), suggesting that reducing conditions may be responsible for the elevational changes observed. In a follow-up experiment, soils from mixed forests at four elevation levels (300, 500, 700, and 1000 m) were incubated under aerobic and anaerobic conditions for two weeks. We found that anaerobic incubation consistently increased the soil microbial C:P ratio relative to the aerobic incubation. Overall, our results indicate that redox conditions can shift the elemental composition of microbial biomass. The high microbial C:P ratios induced under anoxic conditions may reflect inhibition of microbial P mineralization and/or immobilization under reducing conditions. These results will help us to better understand the patterns of nutrient cycling and microbial activity across macro-scale environmental gradients.

Quantitative Evaluation of Protein Heterogeneity within Herpes Simplex Virus 1 Particles.

PubMed

El Bilali, Nabil; Duron, Johanne; Gingras, Diane; Lippé, Roger

2017-05-15

Several virulence genes have been identified thus far in the herpes simplex virus 1 genome. It is also generally accepted that protein heterogeneity among virions further impacts viral fitness. However, linking this variability directly with infectivity has been challenging at the individual viral particle level. To address this issue, we resorted to flow cytometry (flow virometry), a powerful approach we recently employed to analyze individual viral particles, to identify which tegument proteins vary and directly address if such variability is biologically relevant. We found that the stoichiometry of the U L 37, ICP0, and VP11/12 tegument proteins in virions is more stable than the VP16 and VP22 tegument proteins, which varied significantly among viral particles. Most interestingly, viruses sorted for their high VP16 or VP22 content yielded modest but reproducible increases in infectivity compared to their corresponding counterparts containing low VP16 or VP22 content. These findings were corroborated for VP16 in short interfering RNA experiments but proved intriguingly more complex for VP22. An analysis by quantitative Western blotting revealed substantial alterations of virion composition upon manipulation of individual tegument proteins and suggests that VP22 protein levels acted indirectly on viral fitness. These findings reaffirm the interdependence of the virion components and corroborate that viral fitness is influenced not only by the genome of viruses but also by the stoichiometry of proteins within each virion. IMPORTANCE The ability of viruses to spread in animals has been mapped to several viral genes, but other factors are clearly involved, including virion heterogeneity. To directly probe whether the latter influences viral fitness, we analyzed the protein content of individual herpes simplex virus 1 particles using an innovative flow cytometry approach. The data confirm that some viral proteins are incorporated in more controlled amounts, while others vary substantially. Interestingly, this correlates with the VP16 trans -activating viral protein and indirectly with VP22, a second virion component whose modulation profoundly alters virion composition. This reaffirms that not only the presence but also the amount of specific tegument proteins is an important determinant of viral fitness. Copyright © 2017 American Society for Microbiology.

Quantitative Evaluation of Protein Heterogeneity within Herpes Simplex Virus 1 Particles

PubMed Central

El Bilali, Nabil; Duron, Johanne; Gingras, Diane

2017-01-01

ABSTRACT Several virulence genes have been identified thus far in the herpes simplex virus 1 genome. It is also generally accepted that protein heterogeneity among virions further impacts viral fitness. However, linking this variability directly with infectivity has been challenging at the individual viral particle level. To address this issue, we resorted to flow cytometry (flow virometry), a powerful approach we recently employed to analyze individual viral particles, to identify which tegument proteins vary and directly address if such variability is biologically relevant. We found that the stoichiometry of the UL37, ICP0, and VP11/12 tegument proteins in virions is more stable than the VP16 and VP22 tegument proteins, which varied significantly among viral particles. Most interestingly, viruses sorted for their high VP16 or VP22 content yielded modest but reproducible increases in infectivity compared to their corresponding counterparts containing low VP16 or VP22 content. These findings were corroborated for VP16 in short interfering RNA experiments but proved intriguingly more complex for VP22. An analysis by quantitative Western blotting revealed substantial alterations of virion composition upon manipulation of individual tegument proteins and suggests that VP22 protein levels acted indirectly on viral fitness. These findings reaffirm the interdependence of the virion components and corroborate that viral fitness is influenced not only by the genome of viruses but also by the stoichiometry of proteins within each virion. IMPORTANCE The ability of viruses to spread in animals has been mapped to several viral genes, but other factors are clearly involved, including virion heterogeneity. To directly probe whether the latter influences viral fitness, we analyzed the protein content of individual herpes simplex virus 1 particles using an innovative flow cytometry approach. The data confirm that some viral proteins are incorporated in more controlled amounts, while others vary substantially. Interestingly, this correlates with the VP16 trans-activating viral protein and indirectly with VP22, a second virion component whose modulation profoundly alters virion composition. This reaffirms that not only the presence but also the amount of specific tegument proteins is an important determinant of viral fitness. PMID:28275191

Corneal endothelial dysfunction in Pearson syndrome.

PubMed

Kasbekar, Shivani A; Gonzalez-Martin, Jose A; Shafiq, Ayad E; Chandna, Arvind; Willoughby, Colin E

2013-01-01

Mitochondrial disorders are associated with well recognized ocular manifestations. Pearson syndrome is an often fatal, multisystem, mitochondrial disorder that causes variable bone marrow, hepatic, renal and pancreatic exocrine dysfunction. Phenotypic progression of ocular disease in a 12-year-old male with Pearson syndrome is described. This case illustrates phenotypic drift from Pearson syndrome to Kearns-Sayre syndrome given the patient's longevity. Persistent corneal endothelial failure was noted in addition to ptosis, chronic external ophthalmoplegia and mid-peripheral pigmentary retinopathy. We propose that corneal edema resulting from corneal endothelial metabolic pump failure occurs within a spectrum of mitochondrial disorders.

Physical examination tests for hip dysfunction and injury.

PubMed

Reiman, Michael P; Mather, Richard C; Cook, Chad E

2015-03-01

Physical examination tests for hip dysfunction and injury of the strongest diagnostic accuracy were identified in a recent systematic review with meta-analysis in BJSM. These tests are described in this article. A detailed description of the various different tests is given, with photographs for each test procedure. Diagnostic interpretation of each test requires careful consideration, with special attention to specific variables such as test performance and patient population. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

[Treatment of functional somatic syndrome with abdominal pain].

PubMed

Abe, Tetsuya; Kanbara, Kenji; Mizuno, Yasuyuki; Fukunaga, Mikihiko

2009-09-01

Functional somatic syndrome (FSS) with abdominal pain include functional gastrointestinal disorder, chronic pancreatitis, chronic pelvic pain syndrome, which generally contain autonomic dysfunction. Regarding the treatment of FSS, it is important to know about FSS for a therapist at first. Secondly, the therapist should find out physical dysfunction of patients positively, and confirm objectively the hypotheses about both peripheral and central pathophysiological mechanisms as much as possible. Heart rate variability is an easy method, and useful to assess autonomic function. After grasping the patient's explanatory model about the illness, the therapist showes the most acceptable treatment for the patient at last.

Subclinical Hypothyroidism is not a Risk Factor for Female Sexual Dysfunction in Korean Middle-Aged Women.

PubMed

Hong, Hyeri; Lee, Hee Jun; Kim, Sun Min; Jeon, Myung Jae; Shin, Dong Wook; Choi, Ho-Chun; Lee, Hyejin; Yun, Jae Moon; Cho, Belong; Lee, Seung Mi

2015-07-01

Previous studies have suggested that subclinical hypothyroidism is associated with the risk of anxiety or depression and can affect quality of life. However, there is a paucity of information regarding the relationship between subclinical hypothyroidism and female sexual dysfunction. The study population consisted of sexually active middle-aged women (≥40 years old) who visited the center for health promotion and optimal aging at Seoul National University Hospital for a health check-up between 2010 and 2011. Sexual function was evaluated by the female sexual function index (FSFI) questionnaire, and female sexual dysfunction was defined as a FSFI score of ≤26.55. FSFI scores and female sexual dysfunction frequencies were compared between cases with subclinical hypothyroidism and healthy controls. Nonparametric methods were used for statistical analysis. A total of 1086 women were included, and the frequency of subclinical hypothyroidism and female sexual dysfunction was 138 (12.7%) and 741 (68.2%), respectively. The total FSFI score and the scores in each domain were not different between the two groups (median total FSFI score (interquartile range): 23.8 (20.2-27.5) for normal thyroid status vs. 24.4 (20.6-27.6) for subclinical hypothyroidism, p=n.s.). The frequency of female sexual dysfunction was not different between the two groups, either (68.4% for normal thyroid status vs. 67.4% for subclinical hypothyroidism, p=n.s.). These findings were consistent even after adjustment for confounding variables. Subclinical hypothyroidism is not a risk factor for sexual dysfunction in middle-aged women.

Vaginismus and accompanying sexual dysfunctions in a Turkish clinical sample.

PubMed

Dogan, Sultan

2009-01-01

Although vaginismus is a common sexual dysfunction in Turkey, there are only limited data about sexual behavior characteristics and comorbidity with other sexual dysfunctions in vaginismic patients. To investigate the frequency of female sexual dysfunctions (FSDs) in a Turkish clinical sample and to determine the comorbidity of other FSDs in women diagnosed with lifelong vaginismus. The study included 54 female patients who presented to a psychiatry department with sexual problems/complaints. The subjects were evaluated using a semi-structured questionnaire. The questionnaire was developed by the researchers in order to assess sexually dysfunctional patients and included detailed questions about socio-demographic variables, and general medical and sexual history. All participants were also assessed using the Golombok Rust Inventory of Sexual Satisfaction. The most common primary FSD in our sample was vaginismus (75.9%), followed by hypoactive sexual desire (9.2%). Regarding comorbidity, in 36 female patients with lifelong vaginismus, we found dyspareunia in 17 women (47.2%), orgasmic disorder in eight women (22.2%), and sexual desire disorder in six women (16.6%) as a second sexual dysfunction, based on the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition, Text Revision criteria. With respect to FSDs within the Turkish clinical population, vaginismic patients constitute the largest group and cultural factors may play a role in the occurrence of this condition. Additionally, our data indicated that there was a strong correlation between vaginismus and dyspareunia. There was also a high frequency of hypoactive desire and orgasm disorder in vaginismic patients. These results suggest that multidimensional assessment of sexual dysfunction in female patients is of great importance.

Sequential nutrient uptake as a potential mechanism for phytoplankton to maintain high primary productivity and balanced nutrient stoichiometry

NASA Astrophysics Data System (ADS)

Yin, Kedong; Liu, Hao; Harrison, Paul J.

2017-05-01

We hypothesize that phytoplankton have the sequential nutrient uptake strategy to maintain nutrient stoichiometry and high primary productivity in the water column. According to this hypothesis, phytoplankton take up the most limiting nutrient first until depletion, continue to draw down non-limiting nutrients and then take up the most limiting nutrient rapidly when it is available. These processes would result in the variation of ambient nutrient ratios in the water column around the Redfield ratio. We used high-resolution continuous vertical profiles of nutrients, nutrient ratios and on-board ship incubation experiments to test this hypothesis in the Strait of Georgia. At the surface in summer, ambient NO3- was depleted with excess PO43- and SiO4- remaining, and as a result, both N : P and N : Si ratios were low. The two ratios increased to about 10 : 1 and 0. 45 : 1, respectively, at 20 m. Time series of vertical profiles showed that the leftover PO43- continued to be removed, resulting in additional phosphorus storage by phytoplankton. The N : P ratios at the nutricline in vertical profiles responded differently to mixing events. Field incubation of seawater samples also demonstrated the sequential uptake of NO3- (the most limiting nutrient) and then PO43- and SiO4- (the non-limiting nutrients). This sequential uptake strategy allows phytoplankton to acquire additional cellular phosphorus and silicon when they are available and wait for nitrogen to become available through frequent mixing of NO3- (or pulsed regenerated NH4). Thus, phytoplankton are able to maintain high productivity and balance nutrient stoichiometry by taking advantage of vigorous mixing regimes with the capacity of the stoichiometric plasticity. To our knowledge, this is the first study to show the in situ dynamics of continuous vertical profiles of N : P and N : Si ratios, which can provide insight into the in situ dynamics of nutrient stoichiometry in the water column and the inference of the transient status of phytoplankton nutrient stoichiometry in the coastal ocean.

Analysis of the Subunit Stoichiometries in Viral Entry

PubMed Central

Magnus, Carsten; Regoes, Roland R.

2012-01-01

Virions of the Human Immunodeficiency Virus (HIV) infect cells by first attaching with their surface spikes to the CD4 receptor on target cells. This leads to conformational changes in the viral spikes, enabling the virus to engage a coreceptor, commonly CCR5 or CXCR4, and consecutively to insert the fusion peptide into the cellular membrane. Finally, the viral and the cellular membranes fuse. The HIV spike is a trimer consisting of three identical heterodimers composed of the gp120 and gp41 envelope proteins. Each of the gp120 proteins in the trimer is capable of attaching to the CD4 receptor and the coreceptor, and each of the three gp41 units harbors a fusion domain. It is still under debate how many of the envelope subunits within a given trimer have to bind to the CD4 receptors and to the coreceptors, and how many gp41 protein fusion domains are required for fusion. These numbers are referred to as subunit stoichiometries. We present a mathematical framework for estimating these parameters individually by analyzing infectivity assays with pseudotyped viruses. We find that the number of spikes that are engaged in mediating cell entry and the distribution of the spike number play important roles for the estimation of the subunit stoichiometries. Our model framework also shows why it is important to subdivide the question of the number of functional subunits within one trimer into the three different subunit stoichiometries. In a second step, we extend our models to study whether the subunits within one trimer cooperate during receptor binding and fusion. As an example for how our models can be applied, we reanalyze a data set on subunit stoichiometries. We find that two envelope proteins have to engage with CD4-receptors and coreceptors and that two fusion proteins must be revealed within one trimer for viral entry. Our study is motivated by the mechanism of HIV entry but the experimental technique and the model framework can be extended to other viral systems as well. PMID:22479399

Seasonal variations in carbon, nitrogen and phosphorus concentrations and C:N:P stoichiometry in different organs of a Larix principis-rupprechtii Mayr. plantation in the Qinling Mountains, China

PubMed Central

Li, Hailiang; C. Crabbe, M. James; Wang, Weiling; Ma, Lihui; Niu, Ruilong; Gao, Xing; Li, Xingxing; Zhang, Pei; Ma, Xin; Chen, Haikui

2017-01-01

Understanding how concentrations of elements and their stoichiometry change with plant growth and age is critical for predicting plant community responses to environmental change. We used long-term field experiments to explore how the leaf, stem and root carbon (C), nitrogen (N) and phosphorous (P) concentrations and their stoichiometry changed with growth and stand age in a L. principis-rupprechtii Mayr. plantation from 2012–2015 in the Qinling Mountains, China. Our results showed that the C, N and P concentrations and stoichiometric ratios in different tissues of larch stands were affected by stand age, organ type and sampling month and displayed multiple correlations with increased stand age in different growing seasons. Generally, leaf C and N concentrations were greatest in the fast-growing season, but leaf P concentrations were greatest in the early growing season. However, no clear seasonal tendencies in the stem and root C, N and P concentrations were observed with growth. In contrast to N and P, few differences were found in organ-specific C concentrations. Leaf N:P was greatest in the fast-growing season, while C:N and C:P were greatest in the late-growing season. No clear variations were observed in stem and root C:N, C:P and N:P throughout the entire growing season, but leaf N:P was less than 14, suggesting that the growth of larch stands was limited by N in our study region. Compared to global plant element concentrations and stoichiometry, the leaves of larch stands had higher C, P, C:N and C:P but lower N and N:P, and the roots had greater P and C:N but lower N, C:P and N:P. Our study provides baseline information for describing the changes in nutritional elements with plant growth, which will facilitates plantation forest management and restoration, and makes a valuable contribution to the global data pool on leaf nutrition and stoichiometry. PMID:28938020

Emotional maltreatment and disordered eating in adolescents: testing the mediating role of emotion regulation.

PubMed

Mills, Pamela; Newman, Emily Frances; Cossar, Jill; Murray, George

2015-01-01

The present study aimed to determine if emotion regulation mediates the relationship between emotional maltreatment and disordered eating behavior in adolescents. Participants were 222 secondary school pupils (aged 14-18 years) from a state high school in the UK. Standardized questionnaire measures were used to gather self-report data on emotional abuse and emotional neglect, functional and dysfunctional emotion regulation strategies and disordered eating behavior. Results showed that disordered eating was associated with emotional abuse, dysfunctional emotion regulation and being female. Multiple mediation analysis found an indirect relationship between emotional abuse and disordered eating through dysfunctional emotion regulation. Interestingly, emotional neglect predicted lower levels of functional emotion regulation. The findings support previous research showing emotion regulation to mediate the relationship between childhood abuse and disordered eating in adults and a differential effect of abuse and neglect on emotion regulation. Longitudinal studies are required to confirm the direction of relationships; however these data suggest that dysfunctional emotion regulation is a significant variable in the development of disordered eating and may be a useful target for intervention. Copyright © 2014. Published by Elsevier Ltd.

Association between in-hospital mortality and renal dysfunction in 186,219 patients hospitalized for acute stroke in the Emilia-Romagna region of Italy.

PubMed

Fabbian, Fabio; Gallerani, Massimo; Pala, Marco; De Giorgi, Alfredo; Salmi, Raffaella; Dentali, Francesco; Ageno, Walter; Manfredini, Roberto

2014-11-01

Using a regional Italian database, we evaluated the relationship between renal dysfunction and in-hospital mortality (IHM) in patients with acute stroke (ischemic/hemorrhagic). Patients were classified on the basis of renal damage: without renal dysfunction, with chronic kidney disease (CKD), and with end-stage renal disease (ESRD). Of a total of 186,219 patients with a first episode of stroke, 1626 (0.9%) had CKD and 819 (0.4%) had ESRD. Stroke-related IHM (total cases) was independently associated with CKD, ESRD, atrial fibrillation (AF), age, and Charlson comorbidity index (CCI). In patients with ischemic stroke (n=154,026), IHM remained independently associated with CKD, ESRD, AF, and CCI. In patients with hemorrhagic stroke (n=32,189), variables that were independently associated with IHM were CKD, ESRD, and AF. Renal dysfunction is associated with IHM related to stroke, both ischemic and hemorrhagic, with even higher odds ratios than those of other established risk factors, such as age, comorbidities, and AF. © The Author(s) 2013.

Endometrial blood flow measured by xenon 133 clearance in women with normal menstrual cycles and dysfunctional uterine bleeding

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

Fraser, I.S.; McCarron, G.; Hutton, B.

Endometrial blood flow was measured through the menstrual cycle in nonpregnant women (28 studies of 17 women with normal menstrual cycles and 32 studies of 20 women with dysfunctional uterine bleeding) with use of a clearance technique in which 100 to 400 microCi of the gamma-emitting isotope, xenon 133 in saline solution was instilled into the uterine cavity. The mean (+/- SEM) endometrial blood flow in normal cycles was 27.7 +/- 2.6 ml/100 gm/min, with a significant elevation in the middle to late follicular phase, followed by a substantial fall and a secondary slow luteal phase rise that was maintainedmore » until the onset of menstruation. There was a significant correlation between plasma estradiol levels and endometrial blood flow in the follicular but not the luteal phase. Blood flow patterns in women with ovulatory dysfunctional bleeding were similar to normal, except for a significantly lower middle follicular rate. Women with anovulatory dysfunctional bleeding exhibited exceedingly variable flow rates.« less

Relationships between symptomatology and SES-related factors in hyperkinetic/MBD boys.

PubMed

Paternite, C E; Loney, J; Langhorne, J E

1976-04-01

Relationships among symptomatology, socioeconomic status, and parenting styles were examined for 113 hyperkinetic/minimal brain dysfunction boys from intact families. Primary symptoms (e.g. hyperactivity) did not vary as a function of SES, but SES-related differences emerged for secondary symptoms (e.g., aggressive behavior, self-esteem deficits) and for parenting variables. Parenting variables were found to be better predictors of secondary symptoms than was SES. Implications for further research are offered.

Foot segmental motion and coupling in stage II and III tibialis posterior tendon dysfunction.

PubMed

Van de Velde, Maarten; Matricali, Giovanni Arnoldo; Wuite, Sander; Roels, Charlotte; Staes, Filip; Deschamps, Kevin

2017-06-01

Classification systems developed in the field of posterior tibialis tendon dysfunction omit to include dynamic measurements. Since this may negatively affect the selection of the most appropriate treatment modality, studies on foot kinematics are highly recommended. Previous research characterised the foot kinematics in patients with posterior tibialis tendon dysfunction. However, none of the studies analysed foot segmental motion synchrony during stance phase, nor compared the kinematic behaviour of the foot in presence of different posterior tibialis tendon dysfunction stages. Therefore, we aimed at comparing foot segmental motion and coupling in patients with posterior tibialis tendon dysfunction grade 2 and 3 to those of asymptomatic subjects. Foot segmental motion of 11 patients suffering from posterior tibialis tendon dysfunction stage 2, 4 patients with posterior tibialis tendon dysfunction stage 3 and 15 asymptomatic subjects was objectively quantified with the Rizzoli foot model using an instrumented walkway and a 3D passive motion capture system. Dependent variables were the range of motion occurring at the different inter-segment angles during subphases of stance and swing phase as well as the cross-correlation coefficient between a number of segments. Significant differences in range of motion were predominantly found during the forefoot push off phase and swing phase. In general, both patient cohorts demonstrated a reduced range of motion compared to the control group. This hypomobility occurred predominantly in the rearfoot and midfoot (p<0.01). Significant differences between both posterior tibialis tendon dysfunction patient cohorts were not revealed. Cross-correlation coefficients highlighted a loss of joint coupling between rearfoot and tibia as well as between rearfoot and forefoot in both posterior tibialis tendon dysfunction groups. The current evidence reveals considerable mechanical alterations in the foot which should be considered in the decision making process since it may help explaining the success and failure of certain conservative and surgical interventions. Copyright © 2017 Elsevier Ltd. All rights reserved.

The stoichiometry of the TMEM16A ion channel determined in intact plasma membranes of COS-7 cells using liquid-phase electron microscopy.

PubMed

Peckys, Diana B; Stoerger, Christof; Latta, Lorenz; Wissenbach, Ulrich; Flockerzi, Veit; de Jonge, Niels

2017-08-01

TMEM16A is a membrane protein forming a calcium-activated chloride channel. A homodimeric stoichiometry of the TMEM16 family of proteins has been reported but an important question is whether the protein resides always in a dimeric configuration in the plasma membrane or whether monomers of the protein are also present in its native state within in the intact plasma membrane. We have determined the stoichiometry of the human (h)TMEM16A within whole COS-7 cells in liquid. For the purpose of detecting TMEM16A subunits, single proteins were tagged by the streptavidin-binding peptide within extracellular loops accessible by streptavidin coated quantum dot (QD) nanoparticles. The labeled proteins were then imaged using correlative light microscopy and environmental scanning electron microscopy (ESEM) using scanning transmission electron microscopy (STEM) detection. The locations of 19,583 individual proteins were determined of which a statistical analysis using the pair correlation function revealed the presence of a dimeric conformation of the protein. The amounts of detected label pairs and single labels were compared between experiments in which the TMEM16A SBP-tag position was varied, and experiments in which tagged and non-tagged TMEM16A proteins were present. It followed that hTMEM16A resides in the plasma membrane as dimer only and is not present as monomer. This strategy may help to elucidate the stoichiometry of other membrane protein species within the context of the intact plasma membrane in future. Copyright © 2017 Elsevier Inc. All rights reserved.

Stoichiometry as key to ferroelectricity in compressively strained SrTiO{sub 3} films

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

Haislmaier, R. C.; Engel-Herbert, R.; Gopalan, V.

2016-07-18

While strain is a powerful tuning parameter for inducing ferroelectricity in thin film oxides, the role of stoichiometry control is critical, but far less explored. A series of compressively strained SrTiO{sub 3} films on (001) (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} substrates were grown by hybrid molecular beam epitaxy where the Ti cation was supplied using a metal-organic titanium tetraisopropoxide molecule that helps systematically and precisely control Sr:Ti stoichiometry in the resulting films. A stoichiometric growth window is located through X-ray diffraction and in-situ reflection high-energy electron diffraction measurements, which show a minimum out-of-plane lattice parameter as well as constantmore » growth rate within the stoichiometric growth window range. Using temperature dependent optical second harmonic generation (SHG) characterization, a ferroelectric-to-paraelectric transition at T ∼ 180 K is observed for a stoichiometric SrTiO{sub 3} film, as well as a higher temperature structural transition at T ∼ 385 K. Using SHG polarimetry modeling, the polar point group symmetry is determined to be tetragonal 4mm with the polarization pointing out-of-plane of the film. The SHG coefficients, d{sub 31}/d{sub 15}=3 and d{sub 33}/d{sub 15}=21, were determined at 298 K. The ferroelectric transition disappears in films grown outside the growth window, thus proving the critical role of stoichiometry control in realizing strain-induced ferroelectricity.« less

EM structure of a helicase-loader complex depicting a 6:2 binding sub-stoichiometry from Geobacillus kaustophilus HTA426

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

Lin, Yen-Chen; Naveen, Vankadari; Molecular Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan

During DNA replication, bacterial helicase is recruited as a complex in association with loader proteins to unwind the parental duplex. Previous structural studies have reported saturated 6:6 helicase-loader complexes with different conformations. However, structural information on the sub-stoichiometric conformations of these previously-documented helicase-loader complexes remains elusive. Here, with the aid of single particle electron-microscopy (EM) image reconstruction, we present the Geobacillus kaustophilus HTA426 helicase-loader (DnaC-DnaI) complex with a 6:2 binding stoichiometry in the presence of ATPγS. In the 19 Å resolution EM map, the undistorted and unopened helicase ring holds a robust loader density above the C-terminal RecA-like domain. Meanwhile, themore » path of the central DNA binding channel appears to be obstructed by the reconstructed loader density, implying its potential role as a checkpoint conformation to prevent the loading of immature complex onto DNA. Our data also reveals that the bound nucleotides and the consequently induced conformational changes in the helicase hexamer are essential for active association with loader proteins. These observations provide fundamental insights into the formation of the helicase-loader complex in bacteria that regulates the DNA replication process. - Highlights: • Helicase-loader complex structure with 6:2 sub-stoichiometry is resolved by EM. • Helicase hexamer in 6:2 sub-stoichiometry is constricted and un-opened. • 6:2 binding ratio of helicase-loader complex could act as a DNA loading checkpoint. • Nucleotides stabilize helicase-loader complex at low protein concentrations.« less

Warming rate drives microbial limitation and enzyme expression during peat decomposition

NASA Astrophysics Data System (ADS)

Inglett, P.; Sihi, D.; Inglett, K. S.

2015-12-01

Recent developments of enzyme-based decomposition models highlight the importance of enzyme kinetics with warming, but most modeling exercises are based on studies with a step-wise warming. This approach may mask the effect of temperature in controlling in-situ activities as in most ecosystems soil temperature change more gradually than air temperature. We conducted an experiment to test the effects of contrasting warming rates on the kinetics of C, N, and P degradation enzymes in subtropical peat soils. We also wanted to evaluate if the stoichiometry of enzyme kinetics shifts under contrasting warming rates and if so, how does it relate to the stoichiometry in microbial biomass. Contrasting warming rates altered microbial biomass stoichiometry leading to differing patterns of enzyme expression and microbial nutrient limitation. Activity (higher Vmax) and efficiency (lower Km) of C acquisition enzymes were greater in the step treatment; however, expressions of nutrient (N and P) acquiring enzymes were enhanced in the ramp treatment at the end of the experiment. In the step treatment, there was a typical pattern of an initial peak in the Vmax and drop in the Km for all enzyme groups followed by later adjustments. On the other hand, a consistent increase in Vmax and decline in Km of all enzyme groups were observed in the slow warming treatment. These changes were sufficient to alter microbial identity (as indicated by enzyme Km and biomass stoichiometry) with two apparently stable endpoints under contrasting warming rates. This observation resembles the concept of alternate stable states and highlights a need for improved representation of warming in models.

Peri-operative kidney injury and long-term chronic kidney disease following orthotopic heart transplantation in children.

PubMed

Hoskote, Aparna; Burch, Michael

2015-06-01

Significant advances in cardiac intensive care including extracorporeal life support have enabled children with complex congenital heart disease and end-stage heart failure to be supported while awaiting transplantation. With an increasing number of survivors after heart transplantation in children, the complications from long-term immunosuppression, including renal insufficiency, are becoming more apparent. Severe renal dysfunction after heart transplant is defined by a serum creatinine level >2.5 mg/dL (221 μmol/L), and/or need for dialysis or renal transplant. The degree of renal dysfunction is variable and is progressive over time. About 3-10 % of heart transplant recipients will go on to develop severe renal dysfunction within the first 10 years post-transplantation. Multiple risk factors for chronic kidney disease post-transplant have been identified, which include pre-transplant worsening renal function, recipient demographics and morbidity, peri-transplant haemodynamics and long-term exposure to calcineurin inhibitors. Renal insufficiency increases the risk of post-transplant morbidity and mortality. Hence, screening for renal dysfunction pre-, peri- and post-transplantation is important. Early and timely detection of renal insufficiency may help minimize renal insults, and allow prompt implementation of renoprotective strategies. Close monitoring and pre-emptive management of renal dysfunction is an integral aspect of peri-transplant and subsequent post-transplant long-term care.

Relationship Between Self-reported Apathy and Executive Dysfunction in Nondemented Patients With Parkinson Disease

PubMed Central

Zgaljardic, Dennis J.; Borod, Joan C.; Foldi, Nancy S.; Rocco, Mary; Mattis, Paul J.; Gordon, Mark F.; Feigin, Andrew S.; Eidelberg, David

2015-01-01

Objective The prevalence of apathy was assessed across select cognitive and psychiatric variables in 32 nondemented patients with Parkinson disease (PD) and 29 demographically matched healthy control participants. Background Apathy is common in PD, although differentiating apathy from motor, cognitive, and/or other neuropsychiatric symptoms can be challenging. Previous studies have reported a positive relationship between apathy and cognitive impairment, particularly executive dysfunction. Method Patients were categorized according to apathy symptom severity. Stringent criteria were used to exclude patients with dementia. Results Approximately 44% of patients endorsed significant levels of apathy. Those patients performed worse than patients with nonsignificant levels of apathy on select measures of verbal fluency and on a measure of verbal and nonverbal conceptualization. Further, they reported a greater number of symptoms related to depression and behavioral disturbance than did those patients with nonsignificant levels of apathy. Apathy was significantly related to self-report of depression and executive dysfunction. Performance on cognitive tasks assessing verbal fluency, working memory, and verbal abstraction and also on a self-report measure of executive dysfunction was shown to significantly predict increasing levels of apathy. Conclusions Our findings suggest that apathy in nondemented patients with PD seems to be strongly associated with executive dysfunction. PMID:17846518

Patterns of language and auditory dysfunction in 6-year-old children with epilepsy.

PubMed

Selassie, Gunilla Rejnö-Habte; Olsson, Ingrid; Jennische, Margareta

2009-01-01

In a previous study we reported difficulty with expressive language and visuoperceptual ability in preschool children with epilepsy and otherwise normal development. The present study analysed speech and language dysfunction for each individual in relation to epilepsy variables, ear preference, and intelligence in these children and described their auditory function. Twenty 6-year-old children with epilepsy (14 females, 6 males; mean age 6:5 y, range 6 y-6 y 11 mo) and 30 reference children without epilepsy (18 females, 12 males; mean age 6:5 y, range 6 y-6 y 11 mo) were assessed for language and auditory ability. Low scores for the children with epilepsy were analysed with respect to speech-language domains, type of epilepsy, site of epileptiform activity, intelligence, and language laterality. Auditory attention, perception, discrimination, and ear preference were measured with a dichotic listening test, and group comparisons were performed. Children with left-sided partial epilepsy had extensive language dysfunction. Most children with partial epilepsy had phonological dysfunction. Language dysfunction was also found in children with generalized and unclassified epilepsies. The children with epilepsy performed significantly worse than the reference children in auditory attention, perception of vowels and discrimination of consonants for the right ear and had more left ear advantage for vowels, indicating undeveloped language laterality.

Brain structural network topological alterations of the left prefrontal and limbic cortex in psychogenic erectile dysfunction.

PubMed

Chen, Jianhuai; Chen, Yun; Gao, Qingqiang; Chen, Guotao; Dai, Yutian; Yao, Zhijian; Lu, Qing

2018-05-01

Despite increasing understanding of the cerebral functional changes and structural abnormalities in erectile dysfunction, alterations in the topological organization of brain networks underlying psychogenic erectile dysfunction remain unclear. Here, based on the diffusion tensor image data of 25 patients and 26 healthy controls, we investigated the topological organization of brain structural networks and its correlations with the clinical variables using the graph theoretical analysis. Patients displayed a preserved overall small-world organization and exhibited a less connectivity strength in the left inferior frontal gyrus, amygdale and the right inferior temporal gyrus. Moreover, an abnormal hub pattern was observed in patients, which might disturb the information interactions of the remaining brain network. Additionally, the clustering coefficient of the left hippocampus was positively correlated with the duration of patients and the normalized betweenness centrality of the right anterior cingulate gyrus and the left calcarine fissure were negatively correlated with the sum scores of the 17-item Hamilton Depression Rating Scale. These findings suggested that the damaged white matter and the abnormal hub distribution of the left prefrontal and limbic cortex might contribute to the pathogenesis of psychogenic erectile dysfunction and provided new insights into the understanding of the pathophysiological mechanisms of psychogenic erectile dysfunction.

Motor Activity and Intra-Individual Variability According to Sleep-wake States in Preschool-aged Children with Iron-Deficiency Anemia in Infancy

PubMed Central

Angulo-Barroso, R.M.; Peirano, P.; Algarin, C.; Kaciroti, N.; Lozoff, B.

2013-01-01

Background A chronic or acute insult may affect the regulatory processes that guide motor and behavioral performance, leading to increased intra-individual variability (IIV). Increased variability is often interpreted as an indication of regulatory dysfunction. Iron plays an important role in the regulatory processes of the nervous system and affects motor activity. To our knowledge, no study has examined the long-lasting patterns and IIV of motor activity following iron-deficiency anemia in human infants. Aims This study compared 48-hour motor activity and variability in preschool-aged children with or without iron-deficiency anemia (IDA) in infancy. Methods Motor activity was recorded through actigraphs during two week-days in 47 4-year-old Chilean children (23 former IDA and 24 non-anemic in infancy). All were given oral iron as infants. Sleep-wake states were identified by means of automated software. The frequency of movement units per minute was determined for each waking/sleep state during the individual day and night periods; data were examined in blocks of 15 minutes. Analyses of mean frequency and duration and intra-individual variability were conducted using multivariate mixed models. Results For daytime sleep, former IDA children were more active without a difference in the total duration. They also spent less time awake throughout the individual day period. Motor activity intra-individual variability was higher in former IDA children. Conclusions The findings suggest that IDA in infancy sets the stage for long lasting dysfunction in the neural processes regulating sleep-wake states and spontaneous motor activity patterns. PMID:24041817

Motor activity and intra-individual variability according to sleep-wake states in preschool-aged children with iron-deficiency anemia in infancy.

PubMed

Angulo-Barroso, R M; Peirano, P; Algarin, C; Kaciroti, N; Lozoff, B

2013-12-01

A chronic or acute insult may affect the regulatory processes that guide motor and behavioral performance, leading to increased intra-individual variability (IIV). Increased variability is often interpreted as an indication of regulatory dysfunction. Iron plays an important role in the regulatory processes of the nervous system and affects motor activity. To our knowledge, no study has examined the long-lasting patterns and IIV of motor activity following iron-deficiency anemia in human infants. This study compared 48-h motor activity and variability in preschool-aged children with or without iron-deficiency anemia (IDA) in infancy. Motor activity was recorded through actigraphs during two week-days in 47 4-year-old Chilean children (23 former IDA and 24 non-anemic in infancy). All were given oral iron as infants. Sleep-wake states were identified by means of automated software. The frequency of movement units per minute was determined for each waking/sleep state during the individual day and night periods; data were examined in blocks of 15 min. Analyses of mean frequency and duration and intra-individual variability were conducted using multivariate mixed models. For daytime sleep, former IDA children were more active without a difference in the total duration. They also spent less time awake throughout the individual day period. Motor activity intra-individual variability was higher in former IDA children. The findings suggest that IDA in infancy sets the stage for long lasting dysfunction in the neural processes regulating sleep-wake states and spontaneous motor activity patterns. © 2013.

Heart rate variability measure in breast cancer patients and survivors: A systematic review.

PubMed

Arab, Claudia; Dias, Daniel Penteado Martins; Barbosa, Renata Thaís de Almeida; Carvalho, Tatiana Dias de; Valenti, Vitor Engrácia; Crocetta, Tânia Brusque; Ferreira, Marcelo; Abreu, Luiz Carlos de; Ferreira, Celso

2016-06-01

In the current study, we aimed to review literature findings showing the clinical importance of cardiac autonomic modulation assessed by heart rate variability analysis in breast cancer (BC) patients and survivors. We conducted a systematic review according to The PRISMA Statement in Medline, Scopus and Web of Science (_-2015) databases. The search was limited to articles in English language, published in peer-reviewed journals, and with adult age samples only (e.g., women, patients, or survivors, diagnosed with BC in any stage). We included observational studies and randomized trials. Detailed heart rate variability analysis (instruments, data collection protocol, and analysis methods) was required. Search terms included autonomic nervous system, heart rate variability, sympathetic and parasympathetic nervous system, autonomic dysfunction, vagal nervous and breast neoplasms, breast cancer and breast tumor. Twelve studies were included in this review. The clinical importance of cardiac autonomic modulation assessed by heart rate variability analysis in BC patients and survivors is demonstrated by association with effects of BC surgery, and treatments, and the adverse effects of surgery and treatments on survivors (e.g., cardiotoxicity, fatigue, and stress). The strength of evidence of included studies is low: small samples size and heterogeneity, presence of confounders, and observational studies design. The heart rate variability analysis could be used as a complementary non-invasive tool for the early diagnosis and better prognosis of autonomic dysfunction, and survival in BC patients. There are many potential clinical applications of heart rate variability analysis in BC patients, and the employment of such approaches could lead to lower impairment of autonomic function in this individuals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pressure-Stabilized Tin Selenide Phase with an Unexpected Stoichiometry and a Predicted Superconducting State at Low Temperatures

NASA Astrophysics Data System (ADS)

Yu, Hulei; Lao, Wenxin; Wang, Lijuan; Li, Kuo; Chen, Yue

2017-03-01

Tin-selenium binary compounds are important semiconductors that have attracted much interest for thermoelectric and photovoltaic applications. As tin has a +2 or +4 oxidation state and selenium has an oxidation number of -2 , only SnSe and SnSe2 have been observed. In this work, we show that the chemical bonding between tin and selenium becomes counterintuitive under pressures. Combining evolutionary algorithms and density functional theory, a novel cubic tin-selenium compound with an unexpected stoichiometry 3 ∶4 has been predicted and further synthesized in laser-heated diamond anvil cell experiments. Different from the conventional SnSe and SnSe2 semiconductors, Sn3 Se4 is predicted to be metallic and exhibit a superconducting transition at low temperatures. Based on electron density and Bader charge analysis, we show that Sn3 Se4 has a mixed nature of chemical bonds. The successful synthesis of Sn3 Se4 paves the way for the discovery of other IV-VI compounds with nonconventional stoichiometries and novel properties.

Pressure-Stabilized Tin Selenide Phase with an Unexpected Stoichiometry and a Predicted Superconducting State at Low Temperatures.

PubMed

Yu, Hulei; Lao, Wenxin; Wang, Lijuan; Li, Kuo; Chen, Yue

2017-03-31

Tin-selenium binary compounds are important semiconductors that have attracted much interest for thermoelectric and photovoltaic applications. As tin has a +2 or +4 oxidation state and selenium has an oxidation number of -2, only SnSe and SnSe_{2} have been observed. In this work, we show that the chemical bonding between tin and selenium becomes counterintuitive under pressures. Combining evolutionary algorithms and density functional theory, a novel cubic tin-selenium compound with an unexpected stoichiometry 3∶4 has been predicted and further synthesized in laser-heated diamond anvil cell experiments. Different from the conventional SnSe and SnSe_{2} semiconductors, Sn_{3}Se_{4} is predicted to be metallic and exhibit a superconducting transition at low temperatures. Based on electron density and Bader charge analysis, we show that Sn_{3}Se_{4} has a mixed nature of chemical bonds. The successful synthesis of Sn_{3}Se_{4} paves the way for the discovery of other IV-VI compounds with nonconventional stoichiometries and novel properties.

Mechanism of anion selectivity and stoichiometry of the Na+/I- symporter (NIS).

PubMed

Paroder-Belenitsky, Monika; Maestas, Matthew J; Dohán, Orsolya; Nicola, Juan Pablo; Reyna-Neyra, Andrea; Follenzi, Antonia; Dadachova, Ekaterina; Eskandari, Sepehr; Amzel, L Mario; Carrasco, Nancy

2011-11-01

I(-) uptake in the thyroid, the first step in thyroid hormone biosynthesis, is mediated by the Na(+)/I(-) symporter (NIS) with an electrogenic 2Na(+):1I(-) stoichiometry. We have obtained mechanistic information on NIS by characterizing the congenital I(-) transport defect-causing NIS mutant G93R. This mutant is targeted to the plasma membrane but is inactive. Substitutions at position 93 show that the longer the side chain of the neutral residue at this position, the higher the K(m) for the anion substrates. Unlike WT NIS, which mediates symport of Na(+) and the environmental pollutant perchlorate electroneutrally, G93T/N/Q/E/D NIS, strikingly, do it electrogenically with a 21 stoichiometry. Furthermore, G93E/Q NIS discriminate between anion substrates, a discovery with potential clinical relevance. A 3D homology model of NIS based on the structure of the bacterial Na(+)/galactose transporter identifies G93 as a critical player in the mechanism of the transporter: the changes from an outwardly to an inwardly open conformation during the transport cycle use G93 as a pivot.

Mechanism of anion selectivity and stoichiometry of the Na+/I- symporter (NIS)

PubMed Central

Paroder-Belenitsky, Monika; Maestas, Matthew J.; Dohán, Orsolya; Nicola, Juan Pablo; Reyna-Neyra, Andrea; Follenzi, Antonia; Dadachova, Ekaterina; Eskandari, Sepehr; Amzel, L. Mario; Carrasco, Nancy

2011-01-01

I- uptake in the thyroid, the first step in thyroid hormone biosynthesis, is mediated by the Na+/I- symporter (NIS) with an electrogenic 2Na+ : 1I- stoichiometry. We have obtained mechanistic information on NIS by characterizing the congenital I- transport defect-causing NIS mutant G93R. This mutant is targeted to the plasma membrane but is inactive. Substitutions at position 93 show that the longer the side chain of the neutral residue at this position, the higher the Km for the anion substrates. Unlike WT NIS, which mediates symport of Na+ and the environmental pollutant perchlorate electroneutrally, G93T/N/Q/E/D NIS, strikingly, do it electrogenically with a 2∶1 stoichiometry. Furthermore, G93E/Q NIS discriminate between anion substrates, a discovery with potential clinical relevance. A 3D homology model of NIS based on the structure of the bacterial Na+/galactose transporter identifies G93 as a critical player in the mechanism of the transporter: the changes from an outwardly to an inwardly open conformation during the transport cycle use G93 as a pivot. PMID:22011571

Oxygen stoichiometry, phase stability, and thermodynamic behavior of the lead-doped Bi-2223 and Ag/Bi-2223 systems

NASA Astrophysics Data System (ADS)

Tetenbaum, M.; Hash, M.; Tani, B. S.; Luo, J. S.; Maroni, V. A.

1995-02-01

Electromotive-force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made in the lead-doped Bi-2223 superconducting system in the temperature range 700-815°C by means of an oxygen titration technique that employs an yttria-stabilized zirconia electrolyte. The results of our studies indicate that processing or annealing lead-doped Bi-2223 at temperatures ranging from 750 to 815°C and at oxygen partial pressures ranging from ∼ 0.02 to 0.2 atm should preserve Bi-2223 as essentially single-phase material. Thermodynamic assessments of the partial molar quantities ΔS¯( O2) andΔH¯( O2) indicate that the plateau regions in the plot of oxygen partial pressure versus oxygen stoichiometry ( x) can be represented by the diphasic CuOCu 2O system. In accord with the EMF measurements, it was found that lead-doped Bi-2223 in a silver sheath is stable at 815°C for oxygen partial pressures between 0.02 and 0.13 atm.

Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe.

PubMed

Jiroušek, Martin; Hájek, Michal; Bragazza, Luca

2011-02-01

We investigated the variation of N:P and N:K ratio in ombrotrophic Sphagnum plants along a gradient of atmospheric N deposition from 1 to 2.5 g m(-2) year(-1) in Central-East Europe. The N:P and N:K ratio in Sphagnum capitula increased significantly along the N deposition gradient. Sphagnum species from the Cuspidata section were characterised by significantly lower ratios at low N deposition. When we compared the observed N:P ratios in Sphagnum plants with the values reported in a previous European-wide study, we found a correspondence in nutrient stoichiometry only for a few bogs: higher P concentration in Sphagnum capitula caused a lower N:P ratio in most of the study bogs so that Sphagnum plants still seem N-limited despite their N saturation. Interaction between summer water table decrease and aerial liming of surrounding forests is proposed as an explanation for this discrepancy. Local forestry practice interacting with climate thus alter N:P stoichiometry of Sphagnum along the N deposition gradient. Copyright © 2010 Elsevier Ltd. All rights reserved.

Complex Stoichiometry reordering of PTCDA on Ag(111) upon K Intercalation

NASA Astrophysics Data System (ADS)

Brivio, G. P.; Baby, A.; Zwick, C.; Gruenewald, M.; Forker, R.; Fritz, T.; Fratesi, G.; Hofmann, O. T.; Zojer, E.

Alkali metal atoms are a simple yet efficient n-type dopant of organic semiconductors. However, the molecular crystal structures need be controlled and well understood in order to optimize the electronic properties (charge carrier density and mobility) of the target material. Here, we report that potassium intercalation into PTCDA monolayer domains on a Ag(111) substrate induces distinct stoichiometry-dependent structural reordering processes, resulting in highly ordered and large KxPTCDA domains. The emerging structures are analyzed by low temperature scanning tunneling microscopy (STM), scanning tunneling hydrogen microscopy (STHM), and low-energy electron diffraction (LEED) as a function of the stoichiometry and by density functional theory (DFT) calculations. Large stable monolayer domains are found for x=2,4. The epitaxy types for all intercalated stages are determined as point-on-line. The K atoms adsorb in the vicinity of the oxygen atoms of the PTCDA molecules, and their positions are determined with sub-Angstrom precision. This is a crucial prerequisite for the prospective assessment of the electronic properties of such composite films, as they depend on the mutual alignment between donor atoms and acceptor molecules.

Irradiation-induced effects of proton irradiation on zirconium carbides with different stoichiometries

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

Y. Huang; B.R. Maier; T.R. Allen

2014-10-01

Zirconium carbide (ZrC) is being considered for utilization in deep burn TRISO fuel particles for hightemperature, gas-cooled reactors. Zirconium carbide has a cubic B1 type crystal structure along with a very high melting point (3420 ?C), exceptional hardness and good thermal and electrical conductivities. Understanding the ZrC irradiation response is crucial for establishing ZrC as an alternative component in TRISO fuel. Until now, very few studies on irradiation effects on ZrC have been released and fundamental aspects of defect evolution and kinetics are not well understood although some atomistic simulations and phenomenological studies have been performed. This work was carriedmore » out to understand the damage evolution in float-zone refined ZrC with different stoichiometries. Proton irradiations at 800 ?C up to doses of 3 dpa were performed on ZrCx (where x ranges from 0.9 to 1.2) to investigate the damage evolution. The irradiation-induced defects, such as density of dislocation loops, at different stoichiometries and doses which were characterized by transmission electron microscopy (TEM) is presented and discussed.« less

Stoichiometry and kinetics of the anaerobic ammonium oxidation (Anammox) with trace hydrazine addition.

PubMed

Yao, Zongbao; Lu, Peili; Zhang, Daijun; Wan, Xinyu; Li, Yulian; Peng, Shuchan

2015-12-01

Purpose of this study is to investigate the stoichiometry and kinetics of anaerobic ammonium oxidation (Anammox) with trace hydrazine addition. The stoichiometry was established based on the electron balance of Anammox process with trace N2H4 addition. The stoichiometric coefficients were determined by the proton consumption and the changes in substrates and products. It was found that trace N2H4 addition can increase the yield of Anammox bacteria (AnAOB) and reduce NO3(-) yield, which enhances the Anammox. Subsequently, kinetic model of Anammox with trace N2H4 addition was developed, and the parameters of the anaerobic degradation model of N2H4 were obtained for the first time. The maximum specific substrate utilization rate, half-saturation constant and inhibition constant of N2H4 were 25.09mgN/g VSS/d, 10.42mgN/L and 1393.88mgN/L, respectively. These kinetic parameters might provide important information for the engineering applications of Anammox with trace N2H4 addition. Copyright © 2015 Elsevier Ltd. All rights reserved.

Uncovering the stoichiometry of Pyrococcus furiosus RNase P, a multi-subunit catalytic ribonucleoprotein complex, by surface-induced dissociation and ion mobility mass spectrometry.

PubMed

Ma, Xin; Lai, Lien B; Lai, Stella M; Tanimoto, Akiko; Foster, Mark P; Wysocki, Vicki H; Gopalan, Venkat

2014-10-20

We demonstrate that surface-induced dissociation (SID) coupled with ion mobility mass spectrometry (IM-MS) is a powerful tool for determining the stoichiometry of a multi-subunit ribonucleoprotein (RNP) complex assembled in a solution containing Mg(2+). We investigated Pyrococcus furiosus (Pfu) RNase P, an archaeal RNP that catalyzes tRNA 5' maturation. Previous step-wise, Mg(2+)-dependent reconstitutions of Pfu RNase P with its catalytic RNA subunit and two interacting protein cofactor pairs (RPP21⋅RPP29 and POP5⋅RPP30) revealed functional RNP intermediates en route to the RNase P enzyme, but provided no information on subunit stoichiometry. Our native MS studies with the proteins showed RPP21⋅RPP29 and (POP5⋅RPP30)2 complexes, but indicated a 1:1 composition for all subunits when either one or both protein complexes bind the cognate RNA. These results highlight the utility of SID and IM-MS in resolving conformational heterogeneity and yielding insights on RNP assembly. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Raman spectroscopic studies of defect structures and phase transition in hyper-stoichiometric UO(2+x).

PubMed

He, Heming; Shoesmith, David

2010-07-28

A method to determine the defect structures in hyper-stoichiometric UO(2+x) using a combination of XRD and Raman spectroscopy has been developed. A sequence of phase transitions, from cubic to tetragonal symmetry, occurs with increasing degree of non-stoichiometry. This sequence proceeds from a cubic phase through an intermediate t''-type tetragonal (axial ratio c/a = 1) phase to a final t-type tetragonal (c/a not = 1) phase. Four distinct structural defect regions can be identified in the stoichiometry range, UO(2) to U(3)O(7): (i) a random point defect structure (x (in UO(2+x)) < or = 0.05); (ii) a non-stoichiometry region (0.05 < or = x < or = 0.15) over which point defects are gradually eliminated and replaced by the Willis 2:2:2 cluster; (iii) a mixture of Willis and cuboctahedral clusters (0.15 < or = x < or = 0.23); (iv) the cuboctahedral cluster (x > or = 0.23). The geometry and steric arrangement of these defects is primarily determined by the concentration of the excess-oxygen interstitials.

Characterization of Cardiopulmonary Exercise Testing Variables in Patients with Endomyocardial Fibrosis after Endocardial Resection

PubMed Central

Sayegh, Ana Luiza C.; dos Santos, Marcelo R.; de Oliveira, Patricia; Fernandes, Fábio; Rondon, Eduardo; de Souza, Francis R.; Salemi, Vera M. C.; Alves, Maria Janieire de N. N.; Mady, Charles

2017-01-01

Background Endomyocardial fibrosis (EMF) is a rare disease, characterized by diastolic dysfunction which leads to reduced peak oxygen consumption (VO2). Cardiopulmonary exercise testing (CPET) has been proved to be a fundamental tool to identify central and peripheral alterations. However, most studies prioritize peak VO2 as the main variable, leaving aside other important CPET variables that can specify the severity of the disease and guide the clinical treatment. Objective The aim of this study was to evaluate central and peripheral limitations in symptomatic patients with EMF by different CPET variables. Methods Twenty-six EMF patients (functional class III, NYHA) were compared with 15 healthy subjects (HS). Functional capacity was evaluated using CPET and diastolic and systolic functions were evaluated by echocardiography. Results Age and gender were similar between EMF patients and HS. Left ventricular ejection fraction was normal in EMF patients, but decreased compared to HS. Peak heart rate, peak workload, peak VO2, peak oxygen (O2) pulse and peak pulmonary ventilation (VE) were decreased in EMF compared to HS. Also, EMF patients showed increased Δ heart rate /Δ oxygen uptake and Δ oxygen uptake /Δ work rate compared to HS. Conclusion Determination of the aerobic capacity by noninvasive respiratory gas exchange during incremental exercise provides additional information about the exercise tolerance in patients with EMF. The analysis of different CPET variables is necessary to help us understand more about the central and peripheral alterations cause by both diastolic dysfunction and restrictive pattern. PMID:29364349

Friction Properties of Surface-Fluorinated Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Wal, R. L. Vander; Miyoshi, K.; Street, K. W.; Tomasek, A. J.; Peng, H.; Liu, Y.; Margrave, J. L.; Khabashesku, V. N.

2005-01-01

Surface modification of the tubular or sphere-shaped carbon nanoparticles through chemical treatment, e.g., fluorination, is expected to significantly affect their friction properties. In this study, a direct fluorination of the graphene-built tubular (single-walled carbon nanotubes) structures has been carried out to obtain a series of fluorinated nanotubes (fluoronanotubes) with variable C(n)F (n =2-20) stoichiometries. The friction coefficients for fluoronanotubes, as well as pristine and chemically cut nanotubes, were found to reach values as low as 0.002-0.07, according to evaluation tests run in contact with sapphire in air of about 40% relative humidity on a ball-on-disk tribometer which provided an unidirectional sliding friction motion. These preliminary results demonstrate ultra-low friction properties and show a promise in applications of surface modified nanocarbons as a solid lubricant.

Technical and economical optimization of a full-scale poultry manure treatment process: total ammonia nitrogen balance.

PubMed

Alejo-Alvarez, Luz; Guzmán-Fierro, Víctor; Fernández, Katherina; Roeckel, Marlene

2016-11-01

A full-scale process for the treatment of 80 tons per day of poultry manure was designed and optimized. A total ammonia nitrogen (TAN) balance was performed at steady state, considering the stoichiometry and the kinetic data from the anaerobic digestion and the anaerobic ammonia oxidation. The equipment, reactor design, investment costs, and operational costs were considered. The volume and cost objective functions optimized the process in terms of three variables: the water recycle ratio, the protein conversion during AD, and the TAN conversion in the process. The processes were compared with and without water recycle; savings of 70% and 43% in the annual fresh water consumption and the heating costs, respectively, were achieved. The optimal process complies with the Chilean environmental legislation limit of 0.05 g total nitrogen/L.

Tin sulfides and tin selenides at ambient and high pressure conditions

NASA Astrophysics Data System (ADS)

Nguyen Cong, Kien; Gonzalez, Joseph; Steele, Brad; Oleynik, Ivan

The application of high pressure promotes unusual chemical bonding in condensed phase resulting in the synthesis of novel materials, which may be recoverable in metastable states at ambient conditions. First-principles evolutionary crystal structure search is performed to explore novel tin sulfide (SnxSy) and tin selenide (SnxSy) crystals with the goal to discover novel photovoltaic and thermoelectric materials. Variable stoichiometry searches at various pressures are performed and the phase diagrams are constructed in the range of pressures 0-100 GPa, which include both the thermodynamically stable and lowest enthalpy metastable structures. Several new structures are identified and their dynamical stability is investigated. To help experimental synthesis of these novel compounds, Raman spectra and XRD patterns are also calculated. These new materials are also investigated to identify those with promising photovoltaic and thermoelectric properties.

Nomogram and Validity of a Model for Predicting Malnutrition in Patients on Liver Transplant Lists.

PubMed

García-Rodríguez, María Teresa; Pértega-Díaz, Sonia; López-Calviño, Beatriz; Piñón-Villar, María Del Carmen; Otero-Ferreiro, Alejandra; Suárez-López, Francisco; Gómez-Gutiérrez, Manuel; Seoane-Pillado, María Teresa; Pita-Fernández, Salvador

2018-04-25

Malnutrition is associated with increased morbimortality in liver transplant patients, and it is important to identify factors related to nutritional status in these patients. Determine variables associated with malnutrition and create a nomogram in liver transplant candidates. Cross-sectional study (n = 110). demographic variables, imbalances due to the disease, transplant aetiology and analytical parameters. Physical examination was performed and degree of hepatic dysfunction calculated. Nutritional status was assessed: Controlling Nutritional Status, Spanish Society of Parenteral and Enteral Nutrition criteria, Nutritional Risk Index, Prognostic Nutritional Index or Onodera Index and The Subjective Global Assessment. Logistic regression analysis was performed. A predictive nomogram (discrimination and calibration analysis) was generated. Malnourishment was defined according to at least 4 or more of the methods studied. Patients with ascites, encephalopathy and portal hypertension presented malnourishment more frequently. Malnutrition was associated with greater liver dysfunction and lower grip strength. Variables independently associated with malnourishment were encephalopathy and lower albumin values. A nomogram was created to predict malnourishment, with good discriminatory power and calibration. A score was developed for evaluating malnutrition risk. This would provide a tool that makes it possible to quickly and easily identify the risk of malnutrition in liver transplant candidates.

Cardiac autonomic denervation in Parkinson's disease is linked to REM sleep behavior disorder.

PubMed

Postuma, Ronald B; Montplaisir, Jacques; Lanfranchi, Paola; Blais, Hélène; Rompré, Sylvie; Colombo, Roberto; Gagnon, Jean-François

2011-07-01

Recent studies have suggested a close connection between autonomic dysfunction and rapid eye movement sleep behavior disorder, which differs in nature from other early-stage markers of Parkinson's disease. In this study we examined the relationship between rapid eye movement sleep behavior disorder and autonomic dysfunction in Parkinson's disease as measured by cardiac beat-to-beat variability. In 53 patients with Parkinson's disease and 36 controls, electrocardiographic trace from a polysomnogram was assessed for measures of beat-to-beat RR variability including RR-standard deviation and frequency domains (low- and high-frequency components). Results were compared between patients with Parkinson's disease and controls, and between patients with Parkinson's disease with and without rapid eye movement sleep behavior disorder. On numerous cardiac autonomic measures, patients with Parkinson's disease showed clear abnormalities compared with controls. However, these abnormalities were confined only to those patients with associated rapid eye movement sleep behavior; those without were not different than controls. As with other clinical autonomic variables, cardiac autonomic denervation is predominantly associated not with Parkinson's disease itself, but with the presence of rapid eye movement sleep behavior disorder. Copyright © 2011 Movement Disorder Society.

Cardiovascular disease and cognitive dysfunction in systemic lupus erythematosus.

PubMed

Murray, Sara G; Yazdany, Jinoos; Kaiser, Rachel; Criswell, Lindsey A; Trupin, Laura; Yelin, Edward H; Katz, Patricia P; Julian, Laura J

2012-09-01

Cognitive dysfunction and cardiovascular disease are common and debilitating manifestations of systemic lupus erythematosus (SLE). In this study, we evaluated the relationship between cardiovascular events, traditional cardiovascular risk factors, and SLE-specific risk factors as predictors of cognitive dysfunction in a large cohort of participants with SLE. Subjects included 694 participants from the Lupus Outcomes Study (LOS), a longitudinal study of SLE outcomes based on an annual telephone survey querying demographic and clinical variables. The Hopkins Verbal Learning Test-Revised and the Controlled Oral Word Association Test were administered to assess cognitive function. Multiple logistic regression was used to identify cardiovascular events (myocardial infarction, stroke), traditional cardiovascular risk factors (hypertension, hyperlipidemia, diabetes mellitus, obesity, smoking), and SLE-specific risk factors (antiphospholipid antibodies [aPL], disease activity, disease duration) associated with cognitive impairment in year 7 of the LOS. The prevalence of cognitive impairment as measured by verbal memory and verbal fluency metrics was 15%. In adjusted multiple logistic regression analyses, aPL (odds ratio [OR] 2.10, 95% confidence interval [95% CI] 1.3-3.41), hypertension (OR 2.06, 95% CI 1.19-3.56), and a history of stroke (OR 2.27, 95% CI 1.16-4.43) were significantly associated with cognitive dysfunction. In additional analyses evaluating the association between these predictors and severity of cognitive impairment, stroke was significantly more prevalent in participants with severe impairment when compared to those with mild or moderate impairment (P = 0.036). These results suggest that the presence of aPL, hypertension, and stroke are key variables associated with cognitive impairment, which may aid in identification of patients at greatest risk. Copyright © 2012 by the American College of Rheumatology.

Cholinergic autonomic dysfunction in veterans with Gulf War illness: confirmation in a population-based sample.

PubMed

Haley, Robert W; Charuvastra, Elizabeth; Shell, William E; Buhner, David M; Marshall, W Wesley; Biggs, Melanie M; Hopkins, Steve C; Wolfe, Gil I; Vernino, Steven

2013-02-01

The authors of prior small studies raised the hypothesis that symptoms in veterans of the 1991 Gulf War, such as chronic diarrhea, dizziness, fatigue, and sexual dysfunction, are due to cholinergic autonomic dysfunction. To perform a confirmatory test of this prestated hypothesis in a larger, representative sample of Gulf War veterans. Nested case-control study. Clinical and Translational Research Center, University of Texas Southwestern Medical Center, Dallas. Representative samples of Gulf War veterans meeting a validated case definition of Gulf War illness with 3 variants (called syndromes 1-3) and a control group, all selected randomly from the US Military Health Survey. Validated domain scales from the Autonomic Symptom Profile questionnaire, the Composite Autonomic Severity Score, and high-frequency heart rate variability from a 24-hour electrocardiogram. The Autonomic Symptom Profile scales were significantly elevated in all 3 syndrome groups (P< .001), primarily due to elevation of the orthostatic intolerance, secretomotor, upper gastrointestinal dysmotility, sleep dysfunction, urinary, and autonomic diarrhea symptom domains. The Composite Autonomic Severity Score was also higher in the 3 syndrome groups (P= .045), especially in syndrome 2, primarily due to a significant reduction in sudomotor function as measured by the Quantitative Sudomotor Axon Reflex Test, most significantly in the foot; the score was intermediate in the ankle and upper leg and was nonsignificant in the arm, indicating a peripheral nerve length-related deficit. The normal increase in high-frequency heart rate variability at night was absent or blunted in all 3 syndrome groups (P< .001). Autonomic symptoms are associated with objective, predominantly cholinergic autonomic deficits in the population of Gulf War veterans.

Investigation on dysfunctional beliefs and attitudes about sleep in Chinese college students.

PubMed

Jin, Lairun; Zhou, Jun; Peng, Hui; Ding, Shushu; Yuan, Hui

2018-01-01

The aims of this study were to evaluate a subset of sleep-related cognitions and to examine whether dysfunctional beliefs and attitudes about sleep were associated with sleep quality in college students. A total of 1,333 college students were enrolled in this study by randomized cluster sampling. A brief version of Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS-16) was administered to college students at several colleges. Sleep quality was also assessed using the Pittsburgh Sleep Quality Index (PSQI). The DBAS-16 scores were analyzed across different demographic variables, corresponding subscales of 7-item PSQI, and relevant sleep behavior variables. A total of 343 participants were poor sleepers, while 990 were good sleepers, as defined by PSQI. The DBAS-16 scores were lower in poor sleepers than in good sleepers (46.32 ± 7.851 vs 49.87 ± 8.349, p < 0.001), and DBAS-16 scores were lower in females and nonmedical students when compared with those in males and medical students, respectively (48.20 ± 8.711 vs 49.73 ± 7.923, p = 0.001; 48.56 ± 8.406 vs 49.88 ± 8.208, p = 0.009, respectively). The total score for sleep quality, as measured by PSQI, was negatively correlated with the DBAS-16 total score ( r = -0.197, p < 0.01). There were significant differences in PSQI scores between individuals with attitudes and those without attitudes about sleep with respect to good sleep habits ( p < 0.001), self-relaxation ( p = 0.001), physical exercise ( p < 0.001), taking sleeping pills ( p = 0.004), and taking no action ( p < 0.001). Dysfunctional beliefs about sleep are associated with sleep quality and should be discouraged, especially for females and nonmedical college students.

Predictors of functional dependency after stroke in Nigeria.

PubMed

Ojagbemi, Akin; Owolabi, Mayowa

2013-11-01

The factors impacting poststroke functional dependency have not been adequately explored in sub-Saharan Africa. This study examined the risk factors for functional dependency in a group of Nigerian African stroke survivors. One hundred twenty-eight stroke survivors attending a tertiary general hospital in southwestern Nigeria were consecutively recruited and assessed for functional dependency using the modified Rankin Scale (mRS). Stroke was diagnosed according to the World Health Organization criteria. Candidate independent variables assessed included the demographic and clinical characteristics of survivors, cognitive dysfunction, and a diagnosis of major depressive disorder. Variables with significant relationship to functional dependency were entered into a logistic regression model to identify factors that were predictive of functional dependency among the stroke survivors. In all, 60.9% of the stroke survivors were functionally dependent (mRS scores≥3), with mean±SD mRS scores of 2.71±1.01. Female sex (P=.003; odds ratio [OR] 3.08; 95% confidence interval [CI] 1.47-6.44), global cognitive dysfunction (P=.002; OR 5.04; 95% CI 1.79-14.16), and major depressive disorder (P<.0001; OR 3.06; 95% CI 1.92-4.87) were strongly associated with functional dependency in univariate analysis. Major depressive disorder was an independent predictor of functional dependency in multivariate analysis (P<.0001; OR 6.89; 95% CI 2.55-18.6; R2=0.19). Depression, female sex, and cognitive dysfunction were strongly associated with poorer functioning after stroke. Interventions aimed at depression and cognitive dysfunction after stroke may improve functional independence in stroke survivors. Copyright © 2013 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

PubMed Central

Patterson, Emily J.; Wilk, Melissa; Langlo, Christopher S.; Kasilian, Melissa; Ring, Michael; Hufnagel, Robert B.; Dubis, Adam M.; Tee, James J.; Kalitzeos, Angelos; Gardner, Jessica C.; Ahmed, Zubair M.; Sisk, Robert A.; Larsen, Michael; Sjoberg, Stacy; Connor, Thomas B.; Dubra, Alfredo; Neitz, Jay; Hardcastle, Alison J.; Neitz, Maureen; Michaelides, Michel; Carroll, Joseph

2016-01-01

Purpose Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction. Methods We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family. Results There were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array. Conclusions Our findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus. PMID:27447086

Bilateral Cavernous Nerve Crush Injury in the Rat Model: A Comparative Review of Pharmacologic Interventions.

PubMed

Haney, Nora M; Nguyen, Hoang M T; Honda, Matthew; Abdel-Mageed, Asim B; Hellstrom, Wayne J G

2018-04-01

It is common for men to develop erectile dysfunction after radical prostatectomy. The anatomy of the rat allows the cavernous nerve (CN) to be identified, dissected, and injured in a controlled fashion. Therefore, bilateral CN injury (BCNI) in the rat model is routinely used to study post-prostatectomy erectile dysfunction. To compare and contrast the available literature on pharmacologic intervention after BCNI in the rat. A literature search was performed on PubMed for cavernous nerve and injury and erectile dysfunction and rat. Only articles with BCNI and pharmacologic intervention that could be grouped into categories of immune modulation, growth factor therapy, receptor kinase inhibition, phosphodiesterase type 5 inhibition, and anti-inflammatory and antifibrotic interventions were included. To assess outcomes of pharmaceutical intervention on erectile function recovery after BCNI in the rat model. The ratio of maximum intracavernous pressure to mean arterial pressure was the main outcome measure chosen for this analysis. All interventions improved erectile function recovery after BCNI based on the ratio of maximum intracavernous pressure to mean arterial pressure results. Additional end-point analysis examined the corpus cavernosa and/or the major pelvic ganglion and CN. There was extreme heterogeneity within the literature, making accurate comparisons between crush injury and therapeutic interventions difficult. BCNI in the rat is the accepted animal model used to study nerve-sparing post-prostatectomy erectile dysfunction. However, an important limitation is extreme variability. Efforts should be made to decrease this variability and increase the translational utility toward clinical trials in humans. Haney NM, Nguyen HMT, Honda M, et al. Bilateral Cavernous Nerve Crush Injury in the Rat Model: A Comparative Review of Pharmacologic Interventions. Sex Med Rev 2018;6:234-241. Copyright © 2017 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Phaeochromocytoma in a 86-year-old patient presenting with reversible myocardial dysfunction.

PubMed

Szwench, Elżbieta; P Czkowska, Mariola; Marczewski, Krzysztof; Klisiewicz, Anna; Micha Owska, Ilona; Ciuba, Iwona; Januszewicz, Magdalena; Prejbisz, Aleksander; Hoffman, Piotr; Januszewicz, Andrzej

2011-12-01

BACKGROUND. Phaeochromocytomas and paragangliomas are rare, mostly benign catecholamine-producing tumours of chromaffin cells of the adrenal medulla or of extra-adrenal paraganglia. Phaeochromocytoma may occur at any age, the greatest frequency being in the fourth and fifth decades. Only on extremely rare occasions does the tumour develop in the very old patients. METHODS. We are describing an 86-year-old patient with phaeochromocytoma, presenting with reversible myocardial dysfunction. RESULTS. This very old patient with phaeochromocytoma had hypertension characterized by labile blood pressure values and increased daytime blood pressure variability. This patient exhibited reversible myocardial dysfunction suggestive for "catecholaminergic cardiomyopathy", as the complication of phaeochromocytoma. After surgical removal of the tumour, recovery of left ventricular function was documented by echocardiography showing normalization of systolic function and improvement of diastolic function. CONCLUSION. Phaeochromocytomas are rare forms of secondary hypertension, but should be considered in the differential diagnosis, regardless of age, even in very old patients.

Laryngotracheal separation in neonatal brainstem dysfunction.

PubMed

Patron, G Cariou; Teissier, N; Malard, O; Van Den Abbeele, T

2010-03-01

Neonatal brainstem dysfunction (NBD) associates four symptoms of variable presence and intensity: suction-swallowing dysfunction, abnormal laryngeal sensitivity and motility, gastroesophageal reflux, and cardiac vagal overactivity. We report three cases of severe NBD with chronic aspiration which required surgical management. Successive failures and clinical deterioration led us to perform laryngotracheal separation. The surgical procedure consisted in suturing the distal segment of the trachea to the cervical skin after complete closure of the larynx. After surgery, these children did not present any pulmonary infection and were allowed oral nutrition. However, oral communication was no longer possible. Although it is a theoretically reversible procedure, the decision is ethically difficult in children free of mental deficiency, because of the vocal loss and the unpredictable NBD outcome. Laryngotracheal separation may be recommended after multidisciplinary decision for severe chronic aspiration in the particular case of children presenting with NBD. Copyright © 2010. Published by Elsevier Masson SAS.

Operant treatment of orofacial dysfunction in neuromuscular disorders.

PubMed Central

Parker, L H; Cataldo, M F; Bourland, G; Emurian, C S; Corbin, R J; Page, J M

1984-01-01

The popularity and reported success of biofeedback treatment for neuromuscular disorders has occurred despite a lack of research identifying the critical variables responsible for therapeutic gain. In this study, we assessed the degree to which severe neurological dysfunction could be improved by using one of the components present in all biofeedback treatment, contingency management. Three cases of orofacial dysfunction were treated by reinforcing specific improvements reliably detectable without the use of biofeedback equipment. The results showed that contingency management procedures alone were sufficient to improve overt motor responses but, unlike biofeedback treatment, did not produce decreases in the hypertonic muscle groups associated with the trained motor behavior. The findings suggest that sophisticated, expensive biofeedback equipment may not be necessary in treating some neuromuscular disorders and that important clinical gains may be achieved by redesigning the patient's daily environment to be contingently therapeutic, rather than only accommodating the disabilities of the physically handicapped. PMID:6526764

Psychological and psychosexual aspects of vulvar vestibulitis.

PubMed Central

Nunns, D; Mandal, D

1997-01-01

AIMS: To objectively assess the psychological and psychosexual morbidity of patients with vulvar vestibulitis. METHODS: 30 patients with variable degrees of vulvar vestibulitis were recruited from a vulval clinic. Each patient underwent a detailed history and clinical examination. Friedrich's criteria were used for the diagnosis of vulvar vestibulitis. Standardised questionnaires to assess psychological and psychosexual function were completed by the patient before review. These questionnaires were the STAI and a modified psychosexual questionnaire introduced by Campion. RESULTS: Patients experienced considerable psychological dysfunction compared with controls. All aspects of psychosexual dysfunction were affected. CONCLUSIONS: When managing patients, psychosexual and psychological issues must be considered in addition to other conventional types of therapy. Vulvar vestibulitis may be a risk factor for developing psychosexual complications including vaginismus, low libido, and orgasmic dysfunction. Consideration of these factors must be an integral part of the management of patients with all chronic vulval conditions. PMID:9582478

Longitudinal assessment of excessive daytime sleepiness in early Parkinson's disease.

PubMed

Amara, Amy W; Chahine, Lama M; Caspell-Garcia, Chelsea; Long, Jeffrey D; Coffey, Christopher; Högl, Birgit; Videnovic, Aleksandar; Iranzo, Alex; Mayer, Geert; Foldvary-Schaefer, Nancy; Postuma, Ron; Oertel, Wolfgang; Lasch, Shirley; Marek, Ken; Simuni, Tanya

2017-08-01

Excessive daytime sleepiness (EDS) is common and disabling in Parkinson's disease (PD). Predictors of EDS are unclear, and data on biological correlates of EDS in PD are limited. We investigated clinical, imaging and biological variables associated with longitudinal changes in sleepiness in early PD. The Parkinson's Progression Markers Initiative is a prospective cohort study evaluating progression markers in participants with PD who are unmedicated at baseline (n=423) and healthy controls (HC; n=196). EDS was measured with the Epworth Sleepiness Scale (ESS). Clinical, biological and imaging variables were assessed for associations with EDS for up to 3 years. A machine learning approach (random survival forests) was used to investigate baseline predictors of incident EDS. ESS increased in PD from baseline to year 3 (mean±SD 5.8±3.5 to 7.55±4.6, p<0.0001), with no change in HC. Longitudinally, EDS in PD was associated with non-tremor dominant phenotype, autonomic dysfunction, depression, anxiety and probable behaviour disorder, but not cognitive dysfunction or motor severity. Dopaminergic therapy was associated with EDS at years 2 and 3, as dose increased. EDS was also associated with presynaptic dopaminergic dysfunction, whereas biofluid markers at year 1 showed no significant associations with EDS. A predictive index for EDS was generated, which included seven baseline characteristics, including non-motor symptoms and cerebrospinal fluid phosphorylated-tau/total-tau ratio. In early PD, EDS increases significantly over time and is associated with several clinical variables. The influence of dopaminergic therapy on EDS is dose dependent. Further longitudinal analyses will better characterise associations with imaging and biomarkers. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

The integration of depressive behaviors and cardiac dysfunction during an operational measure of depression: investigating the role of negative social experiences in an animal model.

PubMed

Grippo, Angela J; Moffitt, Julia A; Sgoifo, Andrea; Jepson, Amanda J; Bates, Suzanne L; Chandler, Danielle L; McNeal, Neal; Preihs, Kristin

2012-01-01

There is a bidirectional association between depression and cardiovascular disease. The neurobiological mechanisms underlying this association may involve an inability to cope with disrupted social bonds. This study investigated in an animal model the integration of depressive behaviors and cardiac dysfunction after a disrupted social bond and during an operational measure of depression, relative to the protective effects of intact social bonds. Depressive behaviors in the forced swim test and continuous electrocardiographic parameters were measured in 14 adult, female socially monogamous prairie voles (rodents), after 4 weeks of social pairing or isolation. After social isolation, animals exhibited (all values are mean ± standard error of the mean; isolated versus paired, respectively) increased heart rate (416 ± 14 versus 370 ± 14 bpm, p < .05) and reduced heart rate variability (3.3 ± 0.2 versus 3.9 ± 0.2 ln(ms(2))). During the forced swim test, isolated animals exhibited greater helpless behavior (immobility = 106 ± 11 versus 63 ± 11 seconds, p < .05), increased heart rate (530 ± 22 versus 447 ± 15 bpm, p < .05), reduced heart rate variability (1.8 ± 0.4 versus 2.7 ± 0.2 ln(ms(2)), p < .05), and increased arrhythmias (arrhythmic burden score = 181 ± 46 versus 28 ± 12, p < .05). The display of depressive behaviors during an operational measure of depression is coupled with increased heart rate, reduced heart rate variability, and increased arrhythmias, indicative of dysfunctional behavioral and physiological stress coping abilities as a function of social isolation. In contrast, social pairing with a sibling is behaviorally protective and cardioprotective. The present results can provide insight into a possible social mechanism underlying the association between depression and cardiovascular disease in humans.

Increased intra-individual reaction time variability in cocaine-dependent subjects: role of cocaine-related cues.

PubMed

Liu, Shijing; Lane, Scott D; Schmitz, Joy M; Green, Charles E; Cunningham, Kathryn A; Moeller, F Gerard

2012-02-01

Neuroimaging data suggest that impaired performance on response inhibition and information processing tests in cocaine-dependent subjects is related to prefrontal and frontal cortical dysfunction and that dysfunction in these brain areas may underlie some aspects of cocaine addiction. In subjects with attention-deficit hyperactivity disorder and other psychiatric disorders, the Intra-Individual Reaction Time Variability (IIRTV) has been associated with frontal cortical dysfunction. In the present study, we evaluated IIRTV parameters in cocaine-dependent subjects vs. controls using a cocaine Stroop task. Fifty control and 123 cocaine-dependent subjects compiled from three studies completed a cocaine Stroop task. Standard deviation (SD) and coefficient of variation (CV) for reaction times (RT) were calculated for both trials with neutral and trials with cocaine-related words. The parameters mu, sigma, and tau were calculated using an ex-Gaussian analysis employed to characterize variability in RTs. The ex-Gaussian analysis divides the RTs into normal (mu, sigma) and exponential (tau) components. Using robust regression analysis, cocaine-dependent subjects showed greater SD, CV and Tau on trials with cocaine-related words compared to controls (p<0.05). However, in trials with neutral words, there was no evidence of group differences in any IIRTV parameters (p>0.05). The Wilcoxon matched-pairs signed-rank test showed that for cocaine-dependent subjects, both SD and tau were larger in trials with cocaine-related words than in trials with neutral words (p<0.05). The observation that only cocaine-related words increased IIRTV in cocaine-dependent subjects suggests that cocaine-related stimuli might disrupt information processing subserved by prefrontal and frontal cortical circuits. Copyright © 2011 Elsevier Ltd. All rights reserved.

Behavioral and Nondirective Guided Self-Help for Parents of Children with Externalizing Behavior: Mediating Mechanisms in a Head-To-Head Comparison.

PubMed

Katzmann, Josepha; Hautmann, Christopher; Greimel, Lisa; Imort, Stephanie; Pinior, Julia; Scholz, Kristin; Döpfner, Manfred

2017-05-01

Parent training (PT) delivered as a guided self-help intervention may be a cost- and time-effective intervention in the treatment of children with externalizing disorders. In face-to-face PT, parenting strategies have repeatedly been identified as mediating mechanisms for the decrease of children's problem behavior. Few studies have examined possible mediating effects in guided self-help interventions for parents. The present study aimed to investigate possible mediating variables of a behaviorally oriented guided self-help program for parents of children with externalizing problems compared to a nondirective intervention in a clinical sample. A sample of 110 parents of children with externalizing disorders (80 % boys) were randomized to either a behaviorally oriented or a nondirective guided self-help program. Four putative mediating variables were examined simultaneously in a multiple mediation model using structural equation modelling. The outcomes were child symptoms of ADHD and ODD as well as child externalizing problems, assessed at posttreatment. Analyses showed a significant indirect effect for dysfunctional parental attributions in favor of the group receiving the behavioral program, and significant effects of the behavioral program on positive and negative parenting and parental self-efficacy, compared to the nondirective intervention. Our results indicate that a decrease of dysfunctional parental attributions leads to a decrease of child externalizing problems when parents take part in a behaviorally oriented guided self-help program. However, none of the putative mediating variables could explain the decrease in child externalizing behavior problems in the nondirective group. A change in dysfunctional parental attributions should be considered as a possible mediator in the context of PT.

[Logistic regression model of noninvasive prediction for portal hypertensive gastropathy in patients with hepatitis B associated cirrhosis].

PubMed

Wang, Qingliang; Li, Xiaojie; Hu, Kunpeng; Zhao, Kun; Yang, Peisheng; Liu, Bo

2015-05-12

To explore the risk factors of portal hypertensive gastropathy (PHG) in patients with hepatitis B associated cirrhosis and establish a Logistic regression model of noninvasive prediction. The clinical data of 234 hospitalized patients with hepatitis B associated cirrhosis from March 2012 to March 2014 were analyzed retrospectively. The dependent variable was the occurrence of PHG while the independent variables were screened by binary Logistic analysis. Multivariate Logistic regression was used for further analysis of significant noninvasive independent variables. Logistic regression model was established and odds ratio was calculated for each factor. The accuracy, sensitivity and specificity of model were evaluated by the curve of receiver operating characteristic (ROC). According to univariate Logistic regression, the risk factors included hepatic dysfunction, albumin (ALB), bilirubin (TB), prothrombin time (PT), platelet (PLT), white blood cell (WBC), portal vein diameter, spleen index, splenic vein diameter, diameter ratio, PLT to spleen volume ratio, esophageal varices (EV) and gastric varices (GV). Multivariate analysis showed that hepatic dysfunction (X1), TB (X2), PLT (X3) and splenic vein diameter (X4) were the major occurring factors for PHG. The established regression model was Logit P=-2.667+2.186X1-2.167X2+0.725X3+0.976X4. The accuracy of model for PHG was 79.1% with a sensitivity of 77.2% and a specificity of 80.8%. Hepatic dysfunction, TB, PLT and splenic vein diameter are risk factors for PHG and the noninvasive predicted Logistic regression model was Logit P=-2.667+2.186X1-2.167X2+0.725X3+0.976X4.

Preservation of olfaction in surgery of olfactory groove meningiomas.

PubMed

Jang, Woo-Youl; Jung, Shin; Jung, Tae-Young; Moon, Kyung-Sub; Kim, In-Young

2013-08-01

Olfaction is commonly considered as secondary among the sensory functions, perhaps reflecting a lack of interest in sparing olfaction after surgery for the olfactory groove meningiomas (OGM). However, considering the repercussions of olfaction for the quality of life, the assessment of post-operative olfaction should be necessary. We retrospectively reviewed the olfactory outcome in patients with OGM and investigated the factors associated with sparing the post-operative olfaction. Between 1993 and 2012, 40 patients with OGM underwent surgical resection and estimated the olfactory function using the Korean version of "Sniffin'Sticks" test (KVSS). Variable factors, such as tumor size, degree of preoperative edema, tumor consistency, preoperative olfactory function, surgical approaches, patient's age, and gender were analyzed with attention to the post-operative olfactory function. Anatomical and functional preservation of olfactory structures were achieved in 26 patients (65%) and 22 patients (55%), respectively. Among the variable factors, size of tumor was significant related to the preservation of post-operative olfaction. (78.6% in size<4 cm and 42.3% in size>4 cm, p=0.035). Sparing the olfaction was significantly better in patients without preoperative olfactory dysfunction (84.6%) compared with ones with preoperative olfactory dysfunction (40.7%, p=0.016). The frontolateral approach achieved much more excellent post-operative olfactory function (71.4%) than the bifrontal approach (36.8%, p=0.032). If the tumor was smaller than 4 cm and the patients did not present olfactory dysfunction preoperatively, the possibility of sparing the post-operative olfaction was high. Among the variable surgical approaches, frontolateral route may be preferable sparing the post-operative olfaction. Copyright © 2012 Elsevier B.V. All rights reserved.

The impact of major depression on heart rate variability and endothelial dysfunction in patients with stable coronary artery disease.

PubMed

Aydin Sunbul, Esra; Sunbul, Murat; Gulec, Huseyin

Depression is an independent risk factor in cardiovascular diseases. Changes in the cardiac autonomic functions and pro-inflammatory processes are potential biological factors. Endothelial dysfunction plays an important role in the etiopathogenesis of atherosclerosis. Our objective was to evaluate the impact of major depression on heart rate variability and endothelial dysfunction in patients with stable CAD. The study group included 65 CAD patients with a diagnosis of major depression and 54 CAD patients without major depression. All study population underwent transthoracic echocardiography, measurement of flow mediated dilatation (FMD) and 24-h holter recording for heart rate variability (HRV). Blood samples were drawn to determine the inflammatory parameters. Severity of depressive episode was assessed by Montgomery-Asberg Depression Scale (MADRS). The distribution of age and sex was similar in the patient and control groups (P=0.715, 0.354, respectively). There was no significant difference in medications used between the groups. Echocardiographic parameters were similar between the groups. Inflammatory parameters were also similar between the groups. HRV parameters were significantly lower in the patient group than controls. The absolute FMD value and percentage FMD were significantly lower in the patient group than controls (P<0.001). The MADRS score correlated with pNN50 in both groups (P<0.05), and with FMD in the control group (P<0.001), even after adjusting for age and gender (P<0.001). MADRS score was an independent predictor of pNN50 level, percentage and absolute FMD values regardless of age and gender. Clinician should pay more attention for evaluation of depressive patients with CAD. Copyright © 2016 Elsevier Inc. All rights reserved.

Study of Substitution of Zn FOR Cu in YBa2Cu3O7 System

NASA Astrophysics Data System (ADS)

Sharma, P. K.; Samariya, A.; Dhawan, M. S.; Singhal, R. K.

The polycrystalline YBa2(Cu1-XZnX)3O7-δ samples (x=0.0 to 0.06) were synthesized and studied using X Ray diffraction, titration, resistivity, magnetization and X ray photoelectron spectroscopy (XPS). Results show that O2 stoichiometry (δ) changes on Zn substitution which affects their normal state resistivity as well as the TC. Zn also induces local magnetic moment as evidenced from magnetization results. A combination of change in O2 stoichiometry and magnetic pair breaking is found to be responsible for a rapid suppression of superconductivity.

Report on a NASA astrobiology institute-funded workshop without walls: stellar stoichiometry.

PubMed

Desch, Steven J; Young, Patrick A; Anbar, Ariel D; Hinkel, Natalie; Pagano, Michael; Truitt, Amanda; Turnbull, Margaret

2014-04-01

We report on the NASA Astrobiology Institute-funded Workshop Without Walls entitled "Stellar Stoichiometry," hosted by the "Follow the Elements" team at Arizona State University in April 2013. We describe several innovative practices we adopted that made effective use of the Workshop Without Walls videoconferencing format, including use of information technologies, assignment of scientific tasks before the workshop, and placement of graduate students in positions of authority. A companion article will describe the scientific results arising from the workshop. Our intention here is to suggest best practices for future Workshops Without Walls.

Four-Stranded Dna Formed by Isoguanine Quartets: Complex Stoichiometry, Thermal Stability and Resistance Against Exonucleases

NASA Astrophysics Data System (ADS)

Seela, Frank; Wei, Changfu; Melenewski, Alexander

1997-12-01

Single stranded DNA-fragments containing short runs of isoguanine such as d(T_4iG_4T_4) (5) or d(iG_4T_4) (6) form quartet structures by self-assembly of the isoguanine residues. The stoichiometry of the complexes is deduced from mixed aggregates formed between d(T_4iG_4T_4) and d(iG_4T_4). The iG_d-tetrads are more stable with regard to their thermal denaturation and to their resistance against enzymatic phosphodiester hydrolysis than those formed by dG.

Stoichiometry of the Cre recombinase bound to the lox recombining site.

PubMed Central

Mack, A; Sauer, B; Abremski, K; Hoess, R

1992-01-01

The site-specific recombinase Cre from bacteriophage P1 binds and carries out recombination at a 34 bp lox site. The lox site consists of two 13 bp inverted repeats, separated by an 8 bp spacer region. Both the palindromic nature of the site and the results of footprinting and band shift experiments suggest that a minimum of two Cre molecules bind to a lox site. We report here experiments that demonstrate the absolute stoichiometry of the Cre-lox complex to be one molecule of Cre bound per inverted repeat, or two molecules per lox site. Images PMID:1408747

Clinical importance of the drug interaction between statins and CYP3A4 inhibitors: a retrospective cohort study in The Health Improvement Network

PubMed Central

Rowan, Christopher G.; Brunelli, Steven M.; Munson, Jeffrey; Flory, James; Reese, Peter P.; Hennessy, Sean; Lewis, James; Mines, Daniel; Barrett, Jeffrey S.; Bilker, Warren; Strom, Brian L.

2014-01-01

Objective To compare the relative hazard of muscle toxicity, renal dysfunction, and hepatic dysfunction associated with the drug interaction between statins and concomitant medications that inhibit the CYP3A4 isoenzyme. Background Although statins provide important clinical benefits related to mitigating the risk of cardiovascular events, this class of medications also has the potential for severe adverse reactions. The risk for adverse events may be potentiated by concomitant use of medications that interfere with statin metabolism. Methods Data from The Health Improvement Network (THIN) from 1990 to 2008 were used to conduct a retrospective cohort study. Cohorts were created to evaluate each outcome (muscle toxicity, renal dysfunction, and hepatic dysfunction) independently. Each cohort included new statin initiators and compared the relative hazard of the outcome. The interaction ratio (I*R) was the primary contrast of interest. The I*R represents the relative effect of each statin type (statin 3A4 substrate vs. statin non-3A4 substrate) with a CYP3A4 inhibitor, independent of the effect of the statin type without a CYP3A4 inhibitor. We adjusted for confounding variables using the multinomial propensity score. Results The median follow-up time per cohort was 1.5 years. There were 7889 muscle toxicity events among 362 809 patients and 792 665 person-years. The adjusted muscle toxicity I*R was 1.22 (95% confidence interval [CI] = 0.90–1.66). There were 1449 renal dysfunction events among 272,099 patients and 574 584 person-years. The adjusted renal dysfunction I*R was 0.91 (95%CI = 0.58–1.44). There were 1434 hepatic dysfunction events among 367 612 patients and 815 945 person-years. The adjusted hepatic dysfunction I*R was 0.78 (95%CI = 0.45–1.31). Conclusions Overall, this study found no difference in the relative hazard of muscle toxicity, renal dysfunction, or hepatic dysfunction for patients prescribed a statin 3A4 substrate versus a statin non-3A4 substrate with CYP3A4 inhibitor concomitancy. PMID:22422642

Mitochondrial dysfunction in autism spectrum disorders: a systematic review and meta-analysis

PubMed Central

Rossignol, D A; Frye, R E

2012-01-01

A comprehensive literature search was performed to collate evidence of mitochondrial dysfunction in autism spectrum disorders (ASDs) with two primary objectives. First, features of mitochondrial dysfunction in the general population of children with ASD were identified. Second, characteristics of mitochondrial dysfunction in children with ASD and concomitant mitochondrial disease (MD) were compared with published literature of two general populations: ASD children without MD, and non-ASD children with MD. The prevalence of MD in the general population of ASD was 5.0% (95% confidence interval 3.2, 6.9%), much higher than found in the general population (∼0.01%). The prevalence of abnormal biomarker values of mitochondrial dysfunction was high in ASD, much higher than the prevalence of MD. Variances and mean values of many mitochondrial biomarkers (lactate, pyruvate, carnitine and ubiquinone) were significantly different between ASD and controls. Some markers correlated with ASD severity. Neuroimaging, in vitro and post-mortem brain studies were consistent with an elevated prevalence of mitochondrial dysfunction in ASD. Taken together, these findings suggest children with ASD have a spectrum of mitochondrial dysfunction of differing severity. Eighteen publications representing a total of 112 children with ASD and MD (ASD/MD) were identified. The prevalence of developmental regression (52%), seizures (41%), motor delay (51%), gastrointestinal abnormalities (74%), female gender (39%), and elevated lactate (78%) and pyruvate (45%) was significantly higher in ASD/MD compared with the general ASD population. The prevalence of many of these abnormalities was similar to the general population of children with MD, suggesting that ASD/MD represents a distinct subgroup of children with MD. Most ASD/MD cases (79%) were not associated with genetic abnormalities, raising the possibility of secondary mitochondrial dysfunction. Treatment studies for ASD/MD were limited, although improvements were noted in some studies with carnitine, co-enzyme Q10 and B-vitamins. Many studies suffered from limitations, including small sample sizes, referral or publication biases, and variability in protocols for selecting children for MD workup, collecting mitochondrial biomarkers and defining MD. Overall, this evidence supports the notion that mitochondrial dysfunction is associated with ASD. Additional studies are needed to further define the role of mitochondrial dysfunction in ASD. PMID:21263444

Population pharmacokinetics of oxycodone in patients with cancer-related pain.

PubMed

Komatsu, Toshiaki; Kokubun, Hideya; Suzuki, Ai; Takayanagi, Risa; Yamada, Yasuhiko; Matoba, Motohiro; Yago, Kazuo

2012-09-01

Oxycodone is an opioid widely prescribed to cancer patients for pain relief. However, the pharmacokinetics of oxycodone has not been sufficiently examined. Therefore the aim of this work was to study population pharmacokinetics of oxycodone in patients with cancer pain. The authors analyzed 108 serum oxycodone samples of 33 individuals with nonlinear mixed-effects model (NONMEM). Population pharmacokinetics was calculated using the one-compartment model of clearance, volume of distribution, bioavailability, absorption constant rate, and lag time. An exponential error model was used to determine interindividual variability and a relative error model was applied to assess residual variability. Population pharmacokinetics of oxycodone at the end point were as follows: CL(L/h) = 10.7 × [1 + (2 - Child-Pugh Classification)] (Class: A = 0, B = 1, C = 2); V(d) (L) = 193; k(a) (h(-1)) = 0.336; T(lag) (h) = 0.859; F (%) = 63.9. Interindividual variability was CL: 30.5%, V(d): 44.6%, and F: 37.0%, and residual variability was 16.2%. As the total clearance in patients with liver dysfunction (Child-Pugh class B) was reduced to 33.3%, serum concentration of oxycodone increased by 1.5. Therefore, it became clear that dose adjustments are essential when treating patients with liver dysfunction. These findings suggest that population parameters are useful for evaluating pharmacokinetics of oxycodone in patients with cancer pain.

Stoichiometry of hydrological C, N, and P losses across climate and geology: An environmental matrix approach across New Zealand primary forests

NASA Astrophysics Data System (ADS)

McGroddy, M. E.; Baisden, W. T.; Hedin, L. O.

2008-03-01

Hydrologic losses can play a key role in regulating ecosystem nutrient balances, particularly in regions where baseline nutrient cycles are not augmented by industrial deposition. We used first-order streams to integrate hydrologic losses at the watershed scale across unpolluted old-growth forests in New Zealand. We employed a matrix approach to resolve how stream water concentrations of dissolved organic carbon (DOC), organic and inorganic nitrogen (DON and DIN), and organic and inorganic phosphorus (DOP and DIP) varied as a function of landscape differences in climate and geology. We found stream water total dissolved nitrogen (TDN) to be dominated by organic forms (medians for DON, 81.3%, nitrate-N, 12.6%, and ammonium-N, 3.9%). The median stream water DOC:TDN:TDP molar ratio of 1050:21:1 favored C slightly over N and P when compared to typical temperate forest foliage ratios. Using the full set of variables in a multiple regression approach explained approximately half of the variability in DON, DOC, and TDP concentrations. Building on this approach we combined a simplified set of variables with a simple water balance model in a regression designed to predict DON export at larger spatial scales. Incorporating the effects of climate and geologic variables on nutrient exports will greatly aid the development of integrated Earth-climate biogeochemical models which are able to take into account multiple element dynamics and complex natural landscapes.

Heart Rate Variability in Patients with Acute Ischemic Stroke at Different Stages of Renal Dysfunction: A Cross-sectional Observational Study.

PubMed

Wei, Lin; Zhao, Wen-Bo; Ye, Huan-Wen; Chen, Yan-Hua; Zhang, Xiao-Pei; Huang, Yan; Cai, Ye-Feng; Chen, Quan-Fu; Pan, Su-Yue

2017-03-20

Renal function is associated with mortality and functional disabilities in stroke patients, and impaired autonomic function is common in stroke, but little is known regarding its effects on stroke patients with renal dysfunction. This study sought to evaluate the association between autonomic function and stroke in patients with renal dysfunction. This study comprised 232 patients with acute ischemic stroke consecutively enrolled from February 2013 to November 2014 at Guangdong Provincial Hospital of Chinese Medicine in China. All patients recruited underwent laboratory evaluation and 24 h Holter electrocardiography (ECG). Autonomic function was measured based on the heart rate variability (HRV) using 24 h Holter ECG. Renal damage was assessed through the estimated glomerular filtration rate (eGFR), and stroke severity was rated according to the National Institutes of Health Stroke Scale (NIHSS). The Barthel index and modified Rankin score were also determined following admission. All the clinical covariates that could potentially affect autonomic outcome variables were adjusted with linear regression. In the patients with a mild or moderate decreased eGFR, the values for the standard deviation of the averaged normal-to-normal RR interval (SDANN) index (P = 0.022), very low frequency (VLF) (P = 0.043), low frequency (LF) (P = 0.023), and ratio of low-to-high frequency power (LF/HF) (P = 0.001) were significantly lower than those in the patients with a normal eGFR. A multinomial linear regression indicated that eGFR (t = 2.47, P = 0.014), gender (t = -3.60, P < 0.001), and a history of hypertension (t = -2.65, P = 0.008) were the risk factors of LF/HF; the NIHSS score (SDANN index: t = -3.83, P < 0.001; VLF: t = -3.07, P = 0.002; LF: t = -2.79, P = 0.006) and a history of diabetes (SDANN index: t = -3.58, P < 0.001; VLF: t = -2.54, P = 0.012; LF: t = -2.87, P = 0.004) were independent factors for the SDANN index, VLF, and LF; the Oxfordshire Community Stroke Project (t = -2.38, P = 0.018) was related to the SDANN index. Autonomic dysfunction is aggravated with the progression of eGFR stage in patients with acute ischemic stroke; the eGFR is an independent factor of LF/HF in the adjusted models. Stroke severity and a history of diabetes are more significantly associated with HRV in patients with acute ischemic stroke at different stages of renal dysfunction.

Influence of chronic alcoholism and oestrogen deficiency on the variation of stoichiometry of hydroxyapatite within alveolar bone crest of rats.

PubMed

Marchini, Adriana M P S; Deco, Camila P; Lodi, Karina B; Marchini, Leonardo; Santo, Ana M E; Rocha, Rosilene F

2012-10-01

Previous findings suggest that chronic alcoholism and oestrogenic deficiency may affect bones in general (including alveolar bone) and increase individuals' susceptibility to the development of periodontal disease. The aim of this study was to assess possible alterations in the chemical composition of alveolar bone in rats subjected to chronic alcoholism, oestrogen deficiency or both. Fifty-four rats were initially divided into two groups: ovariectomized (Ovx), and Sham operated (Sham). A month after surgery, the groups were sub-divided and received the following dietary intervention for eight weeks: 20% alcohol, isocaloric diet and ad libitum diet. Samples of the mandible, in the alveolar bone crest region, were analyzed to verify possible changes in the stoichiometric composition of bone hydroxyapatite, by measuring the relationship between the concentration of calcium and phosphorus (Ca/P ratios), using micro X-ray fluorescence spectrometry. The ad libitum groups presented the highest average values of Ca/P ratios, while the groups with dietary restrictions presented the smallest average values. The Ovx ad libitum group presented the highest values of Ca/P ratios (2.03 ± 0.04). However, these values were not considered statistically different (p>0.05) from the Sham ad libitum group (2.01 ± 0.01). The Ovx alcohol group presented lower values for Ca/P ratios (1.92 ± 0.06), being the only group statistically different (p<0.001) from the Sham ad libitum group. Potential confounding variables are discussed. Ovariectomy associated with alcohol consumption at 20% significantly changed the stoichiometry composition of hydroxyapatite in the alveolar bone crest, leading to a reduction in Ca/P ratios. Copyright © 2012 Elsevier Ltd. All rights reserved.

Gas-Phase Analysis of the Complex of Fibroblast GrowthFactor 1 with Heparan Sulfate: A Traveling Wave Ion Mobility Spectrometry (TWIMS) and Molecular Modeling Study

NASA Astrophysics Data System (ADS)

Zhao, Yuejie; Singh, Arunima; Xu, Yongmei; Zong, Chengli; Zhang, Fuming; Boons, Geert-Jan; Liu, Jian; Linhardt, Robert J.; Woods, Robert J.; Amster, I. Jonathan

2017-01-01

Fibroblast growth factors (FGFs) regulate several cellular developmental processes by interacting with cell surface heparan proteoglycans and transmembrane cell surface receptors (FGFR). The interaction of FGF with heparan sulfate (HS) is known to induce protein oligomerization, increase the affinity of FGF towards its receptor FGFR, promoting the formation of the HS-FGF-FGFR signaling complex. Although the role of HS in the signaling pathways is well recognized, the details of FGF oligomerization and formation of the ternary signaling complex are still not clear, with several conflicting models proposed in literature. Here, we examine the effect of size and sulfation pattern of HS upon FGF1 oligomerization, binding stoichiometry and conformational stability, through a combination of ion mobility (IM) and theoretical modeling approaches. Ion mobility-mass spectrometry (IMMS) of FGF1 in the presence of several HS fragments ranging from tetrasaccharide (dp4) to dodecasaccharide (dp12) in length was performed. A comparison of the binding stoichiometry of variably sulfated dp4 HS to FGF1 confirmed the significance of the previously known high-affinity binding motif in FGF1 dimerization, and demonstrated that certain tetrasaccharide-length fragments are also capable of inducing dimerization of FGF1. The degree of oligomerization was found to increase in the presence of dp12 HS, and a general lack of specificity for longer HS was observed. Additionally, collision cross-sections (CCSs) of several FGF1-HS complexes were calculated, and were found to be in close agreement with experimental results. Based on the (CCSs) a number of plausible binding modes of 2:1 and 3:1 FGF1-HS are proposed.

Emissions from the combustion of eucalypt and pine chips in a fluidized bed reactor.

PubMed

Vicente, E D; Tarelho, L A C; Teixeira, E R; Duarte, M; Nunes, T; Colombi, C; Gianelle, V; da Rocha, G O; Sanchez de la Campa, A; Alves, C A

2016-04-01

Interest in renewable energy sources has increased in recent years due to environmental concerns about global warming and air pollution, reduced costs and improved efficiency of technologies. Under the European Union (EU) energy directive, biomass is a suitable renewable source. The aim of this study was to experimentally quantify and characterize the emission of particulate matter (PM2.5) resulting from the combustion of two biomass fuels (chipped residual biomass from pine and eucalypt), in a pilot-scale bubbling fluidized bed (BFB) combustor under distinct operating conditions. The variables evaluated were the stoichiometry and, in the case of eucalypt, the leaching of the fuel. The CO and PM2.5 emission factors were lower when the stoichiometry used in the experiments was higher (0.33±0.1 g CO/kg and 16.8±1.0 mg PM2.5/kg, dry gases). The treatment of the fuel by leaching before its combustion has shown to promote higher PM2.5 emissions (55.2±2.5 mg/kg, as burned). Organic and elemental carbon represented 3.1 to 30 wt.% of the particle mass, while carbonate (CO3(2-)) accounted for between 2.3 and 8.5 wt.%. The particulate mass was mainly composed of inorganic matter (71% to 86% of the PM2.5 mass). Compared to residential stoves, BFB combustion generated very high mass fractions of inorganic elements. Chloride was the water soluble ion in higher concentration in the PM2.5 emitted by the combustion of eucalypt, while calcium was the dominant water soluble ion in the case of pine. Copyright © 2015. Published by Elsevier B.V.

The effect of cation:anion ratio in solution on the mechanism of barite growth at constant supersaturation: Role of the desolvation process on the growth kinetics

NASA Astrophysics Data System (ADS)

Kowacz, M.; Putnis, C. V.; Putnis, A.

2007-11-01

The mechanism of barite growth has been investigated in a fluid cell of an Atomic Force Microscope by passing solutions of constant supersaturation ( Ω) but variable ion activity ratio ( r=a/a) over a barite substrate.The observed dependence of step-spreading velocity on solution stoichiometry can be explained by considering non-equivalent attachment frequency factors for the cation and anion. We show that the potential for two-dimensional nucleation changes under a constant thermodynamic driving force due to the kinetics of barium integration into the surface, and that the growth mode changes from preexisting step advancement to island spreading as the cation/anion activity ratio increases. Scanning electron microscopy studies of crystals grown in bulk solutions support our findings that matching the ion ratio in the fluid to that of the crystal lattice does not result in maximum growth and nucleation rates. Significantly more rapid rates correspond to solution stoichiometries where [Ba 2+] is in excess with respect to [ SO42-]. Experiments performed in dilute aqueous solutions of methanol show that even 0.02 molar fraction of organic cosolvent in the growth solution significantly accelerates step growth velocity and nucleation rates (while keeping Ω the same as in the reference solution in water). Our observations suggest that the effect of methanol on barite growth results first of all from reduction of the barrier that prevents the Ba 2+ from reaching the surface and corroborate the hypothesis that desolvation of the cation and of the surface is the rate limiting kinetic process for two-dimensional nucleation and for crystal growth.

Immune dysfunction prior to Staphylococcus aureus bacteremia is a determinant of long-term mortality.

PubMed

Greenberg, Jared A; David, Michael Z; Hall, Jesse B; Kress, John P

2014-01-01

The clinical implications for patients who survive serious infections are not well understood. It has been hypothesized that the excess mortality for survivors of sepsis observed in epidemiological studies is due to increased vulnerability to subsequent infections. We undertook this study to identify characteristics of patients who are at high risk for death after surviving a common type of blood-stream infection. At a single academic medical center, 237 patients with Staphylococcus aureus bacteremia admitted during a three-year period were retrospectively identified. The primary outcomes were 30-day and 31 to 90-day mortality after the first positive blood culture. The primary predictor variable of interest was clinical immune dysfunction prior to bacteremia. The 30-day mortality was not significantly different for patients with and without prior immune dysfunction. However, during days 31 to 90, 11 patients (20%) with prior immune dysfunction compared to 10 patients (8.6%) without prior immune dysfunction died (OR 2.59, 95% CI 1.03-6.53, p = 0.04). In a Cox-proportional hazard model controlling for age, there was a significant association between prior immune dysfunction and greater 31 to 90 day mortality (HR 2.44, 95% CI 1.01-5.90, p = 0.05) and a non-significant trend towards occurrence of subsequent infections and greater 31 to 90 day mortality (HR 2.12, 95% CI 0.89-5.07, p = 0.09). Patients with prior immune dysfunction are at high risk for death 31 to 90 days, but not <30 days, after S. aureus bacteremia. Further investigation is needed to determine if this finding is due to poor prognosis of chronic disease or increased vulnerability to subsequent infections.

Uric acid is a strong independent predictor of renal dysfunction in patients with rheumatoid arthritis.

PubMed

Daoussis, Dimitrios; Panoulas, Vasileios; Toms, Tracey; John, Holly; Antonopoulos, Ioannis; Nightingale, Peter; Douglas, Karen M J; Klocke, Rainer; Kitas, George D

2009-01-01

Recent evidence suggests that uric acid (UA), regardless of crystal deposition, may play a direct pathogenic role in renal disease. We have shown that UA is an independent predictor of hypertension and cardiovascular disease (CVD), and that CVD risk factors associate with renal dysfunction, in patients with rheumatoid arthritis (RA). In this study we investigated whether UA associates with renal dysfunction in patients with RA and whether such an association is independent or mediated through other comorbidities or risk factors for renal impairment. Renal function was assessed in 350 consecutive RA patients by estimated glomerular filtration rate (GFR) using the six-variable Modification of Diet in Renal Disease equation. Risk factors for renal dysfunction were recorded or measured in all participants. Linear regression was used to test the independence of the association between GFR and UA. Univariable analysis revealed significant associations between GFR and age, systolic blood pressure, total cholesterol, triglycerides, RA duration and UA. UA had the most powerful association with renal dysfunction (r = -0.45, P < 0.001). A basic model was created, incorporating all of the above parameters along with body mass index and gender. UA ranked as the first correlate of GFR (P < 0.001) followed by age. Adjustments for the use of medications (diuretics, low-dose aspirin, cyclooxygenase II inhibitors and nonsteroidal anti-inflammatory drugs) and further adjustment for markers of inflammation and insulin resistance did not change the results. UA is a strong correlate of renal dysfunction in RA patients. Further studies are needed to address the exact causes and clinical implications of this new finding. RA patients with elevated UA may require screening for renal dysfunction and appropriate management.

Innate Immune Signalling Genetics of Pain, Cognitive Dysfunction and Sickness Symptoms in Cancer Pain Patients Treated with Transdermal Fentanyl

PubMed Central

Barratt, Daniel T.; Klepstad, Pål; Dale, Ola; Kaasa, Stein; Somogyi, Andrew A.

2015-01-01

Common adverse symptoms of cancer and chemotherapy are a major health burden; chief among these is pain, with opioids including transdermal fentanyl the mainstay of treatment. Innate immune activation has been implicated generally in pain, opioid analgesia, cognitive dysfunction, and sickness type symptoms reported by cancer patients. We aimed to determine if genetic polymorphisms in neuroimmune activation pathways alter the serum fentanyl concentration-response relationships for pain control, cognitive dysfunction, and other adverse symptoms, in cancer pain patients. Cancer pain patients (468) receiving transdermal fentanyl were genotyped for 31 single nucleotide polymorphisms in 19 genes: CASP1, BDNF, CRP, LY96, IL6, IL1B, TGFB1, TNF, IL10, IL2, TLR2, TLR4, MYD88, IL6R, OPRM1, ARRB2, COMT, STAT6 and ABCB1. Lasso and backward stepwise generalised linear regression were used to identify non-genetic and genetic predictors, respectively, of pain control (average Brief Pain Inventory < 4), cognitive dysfunction (Mini-Mental State Examination ≤ 23), sickness response and opioid adverse event complaint. Serum fentanyl concentrations did not predict between-patient variability in these outcomes, nor did genetic factors predict pain control, sickness response or opioid adverse event complaint. Carriers of the MYD88 rs6853 variant were half as likely to have cognitive dysfunction (11/111) than wild-type patients (69/325), with a relative risk of 0.45 (95% CI: 0.27 to 0.76) when accounting for major non-genetic predictors (age, Karnofsky functional score). This supports the involvement of innate immune signalling in cognitive dysfunction, and identifies MyD88 signalling pathways as a potential focus for predicting and reducing the burden of cognitive dysfunction in cancer pain patients. PMID:26332828

Combined circumferential and longitudinal left ventricular systolic dysfunction in patients with asymptomatic aortic stenosis.

PubMed

Cioffi, Giovanni; Mazzone, Carmine; Barbati, Giulia; Rossi, Andrea; Nistri, Stefano; Ognibeni, Federica; Tarantini, Luigi; Di Lenarda, Andrea; Faggiano, Pompilio; Pulignano, Giovanni; Stefenelli, Carlo; de Simone, Giovanni; Devereux, Richard B

2015-07-01

Early detection of left ventricular (LV) systolic dysfunction is pivotal in the management of patients with aortic stenosis (AS). LV circumferential and/or longitudinal shortening may be impaired in these patients despite LV ejection fraction is preserved. We focused on prevalence and factors associated with combined impairment of circumferential and longitudinal shortening (C&L) in asymptomatic AS patients. Echocardiographic and clinical data from 200 patients with asymptomatic AS of any degree without history of heart failure and normal LV ejection fraction were analyzed. C&L were evaluated by mid-wall shortening (MS) and tissue Doppler mitral annular peak systolic velocity (S'), and classified low if <16.5% and if <8.5 cm/sec, respectively (10th percentiles of controls). Combined C&L dysfunction was detected in 72 patients (36%). The variables associated with this condition were higher LV mass (OR 1.02 [CI 1.01-1.04], P = 0.03), concentric LV geometry (OR 4.30 [CI 1.79-10.34], P = 0.001), increasing pulmonary artery wedge pressure (by E/e' ratio; OR 1.11 [CI 1.04-1.19], P = 0.001). The relation of MS and peak S' was linear and slightly significant in the whole population (r = 0.23; F statistic=0.001), absent in patients with C&L dysfunction (r = 0.04; F = ns), negative (linear model) in the subgroup of patients without C&L dysfunction (r = -0.22; F = 0.02). C&L dysfunction is present in more than one-third of patients with asymptomatic AS and is associated with concentric LV geometry and higher degree of diastolic dysfunction. The relation between MS and peak S' largely varies in the subgroups with different C&L function. © 2014, Wiley Periodicals, Inc.

Bladder sensation measures and overactive bladder.

PubMed

Rapp, David E; Neil, Nancy J; Govier, Fred E; Kobashi, Kathleen C

2009-09-01

We performed a prospective multicomponent study to determine whether subjective and objective bladder sensation instruments may provide data on sensory dysfunction in patients with overactive bladder. We evaluated 70 prospectively enrolled patients with urodynamics and questionnaires on validated urgency (Urgency Perception Score), general overactive bladder (Urogenital Distress Inventory) and quality of life (Incontinence Impact Questionnaire). We first sought a correlation between sensory specific (Urgency Perception Score) and quality of life questionnaire scores. We then assessed a correlation between sensory questionnaire scores and urodynamic variables, exploring the hypothesis that certain urodynamic parameters may be bladder sensation measures. We evaluated 2 urodynamic derivatives (first sensation ratio and bladder urgency velocity) to increase sensory finding discrimination. We noted a moderate correlation between the Urgency Perception Score (0.56) and the Urogenital Distress Inventory (0.74) vs the Incontinence Impact Questionnaire (each p <0.01). A weak negative correlation was seen between Urgency Perception Score and bladder capacity (-0.25, p <0.05). No correlation was noted for the other urodynamics parameters. First sensation ratio and bladder urgency velocity statistically significantly correlated with the Urgency Perception Score despite the lesser or absent correlation associated with the individual components of these derivatives. Bladder sensation questionnaires may be valuable to identify patients with sensory dysfunction and provide additional data not obtained in generalized symptom questionnaires. Urodynamic variables correlated with bladder sensation questionnaire scores and may be an objective method to assess sensory dysfunction.

Behavioral Marital Bibliotherapy: An Initial Investigation of Therapeutic Efficacy.

ERIC Educational Resources Information Center

Bornstein, Philip H.; And Others

1984-01-01

Reports an attempt to validate a self-help behavioral marital bibliotherapy program. Evaluated five clinical distressed couples via a multiple baseline analysis. Treatment involved reading and exercises covering communications, problem solving, and sexual dysfunction. Results were highly variable and reflected minimal change. (BH)

Diagnosis of Swallowing Disorders: How We Interpret Pharyngeal Manometry.

PubMed

Cock, Charles; Omari, Taher

2017-03-01

We provide an overview of the clinical application of novel pharyngeal high-resolution impedance manometry (HRIM) with pressure flow analysis (PFA) in our hands with example cases. In our Centre, we base our interpretation of HRIM recordings upon a qualitative assessment of pressure-impedance waveforms during individual swallows, as well as a quantitative assessment of averaged PFA swallow function variables. We provide a description of two global swallowing efficacy measures, the swallow risk index (SRI), reflecting global swallowing dysfunction (higher SRI = greater aspiration risk) and the post-swallow impedance ratio (PSIR) detecting significant post-swallow bolus residue. We describe a further eight swallow function variables specific to the hypopharynx and upper esophageal sphincter (UES), assessing hypo-pharyngeal distension pressure, contractility, bolus presence and flow timing, and UES basal tone, relaxation, opening and contractility. Pharyngeal HRIM has now come of age, being applicable for routine clinical practice to assess the biomechanics of oropharyngeal swallowing dysfunction. In the future, it may guide treatment strategies and allow more objective longitudinal follow-up on clinical outcomes.

Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

2007-01-01

High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

Development of Potent Antiviral Drugs Inspired by Viral Hexameric DNA-Packaging Motors with Revolving Mechanism

PubMed Central

Pi, Fengmei; Zhao, Zhengyi; Chelikani, Venkata; Yoder, Kristine; Kvaratskhelia, Mamuka

2016-01-01

The intracellular parasitic nature of viruses and the emergence of antiviral drug resistance necessitate the development of new potent antiviral drugs. Recently, a method for developing potent inhibitory drugs by targeting biological machines with high stoichiometry and a sequential-action mechanism was described. Inspired by this finding, we reviewed the development of antiviral drugs targeting viral DNA-packaging motors. Inhibiting multisubunit targets with sequential actions resembles breaking one bulb in a series of Christmas lights, which turns off the entire string. Indeed, studies on viral DNA packaging might lead to the development of new antiviral drugs. Recent elucidation of the mechanism of the viral double-stranded DNA (dsDNA)-packaging motor with sequential one-way revolving motion will promote the development of potent antiviral drugs with high specificity and efficiency. Traditionally, biomotors have been classified into two categories: linear and rotation motors. Recently discovered was a third type of biomotor, including the viral DNA-packaging motor, beside the bacterial DNA translocases, that uses a revolving mechanism without rotation. By analogy, rotation resembles the Earth's rotation on its own axis, while revolving resembles the Earth's revolving around the Sun (see animations at http://rnanano.osu.edu/movie.html). Herein, we review the structures of viral dsDNA-packaging motors, the stoichiometries of motor components, and the motion mechanisms of the motors. All viral dsDNA-packaging motors, including those of dsDNA/dsRNA bacteriophages, adenoviruses, poxviruses, herpesviruses, mimiviruses, megaviruses, pandoraviruses, and pithoviruses, contain a high-stoichiometry machine composed of multiple components that work cooperatively and sequentially. Thus, it is an ideal target for potent drug development based on the power function of the stoichiometries of target complexes that work sequentially. PMID:27356896

Attenuation of nicotine taking and seeking in rats by the stoichiometry-selective alpha4beta2 nicotinic acetylcholine receptor positive allosteric modulator NS9283.

PubMed

Maurer, John J; Sandager-Nielsen, Karin; Schmidt, Heath D

2017-02-01

The rewarding and reinforcing effects of nicotine are produced, in large part, by activation of neuronal α4β2* nicotinic acetylcholine receptors (nAChRs), pentameric protein complexes comprised of different stoichiometries of α4 and β2 subunits. However, little is known about the functional role of distinct subtypes of α4β2* nAChRs in nicotine addiction. NS9283 represents a new class of stoichiometry-selective positive allosteric modulators (PAMs) that selectively bind to α4β2 nAChRs containing three α4 and two β2 subunits (3(α4)2(β2) nAChRs). The present experiments were designed to determine the effects of NS9283 on nicotine self-administration and the reinstatement of nicotine-seeking behavior, an animal model of smoking relapse. Parallel studies of sucrose self-administration and reinstatement were conducted in separate cohorts of rats to determine if the effects of NS9283 generalized to other reinforced behaviors. Acute and repeated administration of NS9283 dose-dependently reduced nicotine self-administration and reinstatement in male Sprague Dawley rats. These effects were reinforcer specific as no effects of NS9283 on sucrose self-administration and reinstatement were noted. NS9283 also failed to substitute for nicotine in supporting self-administration behavior suggesting that, at the doses tested, NS9283 alone is not reinforcing. Taken together, these results provide compelling evidence that stoichiometry-selective PAMs of 3(α4)2(β2) nAChRs attenuate nicotine taking and seeking in rats and suggest that targeting 3(α4)2(β2) nAChRs may represent a promising therapeutic strategy for preventing smoking relapse.

Role of an extracellular loop in determining the stoichiometry of Na+–HCO3− cotransporters

PubMed Central

Chen, Li-Ming; Liu, Ying; Boron, Walter F

2011-01-01

The Na+–HCO3− cotransporters (NBCs) of the solute carrier 4 family (SLC4) are critical for regulating pH in cells as well as in fluids such as blood and cerebrospinal fluid. Moreover, mutations and gene disruptions in NBC are linked to a wide range of pathologies. NBCe1 (SLC4A4) is electrogenic because it has an apparent Na+:HCO3− stoichiometry of 1:2 or 1:3, whereas NBCn1 (SLC4A7) is electroneutral because it has an apparent stoichiometry of 1:1. Because stoichiometry influences the effect of transport on membrane potential and vice versa, a central question is what structural features underlie electrogenicity versus electroneutrality. A previous study on rat NBCe1/n1 chimeras demonstrated that the structural elements determining the electrogenicity of NBCe1-A are located within the transmembrane domain, excluding the large third extracellular loop. In the present study we generated a series of chimeras of human NBCe1-A and human NBCn1-A. We found that replacing merely the predicted fourth extracellular loop (EL4) – containing 32 amino acid residues that include 7 prolines – of human NBCe1-A with EL4 of NBCn1-A creates an electroneutral NBC. The opposite switch converts an electroneutral construct to one with electrogenic properties. The introduction of an N-glycosylation site into EL4 confirms that at least a part of it is exposed to the extracellular fluid. We hypothesize that putative EL4 either contributes to the substrate-binding vestibule or indirectly influences substrate binding by interacting with one or more transmembrane segments, thereby controlling the nature of transport. PMID:21224233

PIP Water Transport and Its pH Dependence Are Regulated by Tetramer Stoichiometry.

PubMed

Jozefkowicz, Cintia; Sigaut, Lorena; Scochera, Florencia; Soto, Gabriela; Ayub, Nicolás; Pietrasanta, Lía Isabel; Amodeo, Gabriela; González Flecha, F Luis; Alleva, Karina

2016-03-29

Many plasma membrane channels form oligomeric assemblies, and heterooligomerization has been described as a distinctive feature of some protein families. In the particular case of plant plasma membrane aquaporins (PIPs), PIP1 and PIP2 monomers interact to form heterotetramers. However, the biological properties of the different heterotetrameric configurations formed by PIP1 and PIP2 subunits have not been addressed yet. Upon coexpression of tandem PIP2-PIP1 dimers in Xenopus oocytes, we can address, for the first time to our knowledge, the functional properties of single heterotetrameric species having 2:2 stoichiometry. We have also coexpressed PIP2-PIP1 dimers with PIP1 and PIP2 monomers to experimentally investigate the localization and biological activity of each tetrameric assembly. Our results show that PIP2-PIP1 heterotetramers can assemble with 3:1, 1:3, or 2:2 stoichiometry, depending on PIP1 and PIP2 relative expression in the cell. All PIP2-PIP1 heterotetrameric species localize at the plasma membrane and present the same water transport capacity. Furthermore, the contribution of any heterotetrameric assembly to the total water transport through the plasma membrane doubles the contribution of PIP2 homotetramers. Our results also indicate that plasma membrane water transport can be modulated by the coexistence of different tetrameric species and by intracellular pH. Moreover, all the tetrameric species present similar cooperativity behavior for proton sensing. These findings throw light on the functional properties of PIP tetramers, showing that they have flexible stoichiometry dependent on the quantity of PIP1 and PIP2 molecules available. This represents, to our knowledge, a novel regulatory mechanism to adjust water transport across the plasma membrane. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Measuring the binding stoichiometry of HIV-1 Gag to very-low-density oligonucleotide surfaces using surface plasmon resonance spectroscopy.

PubMed

Stephen, Andrew G; Datta, Siddhartha A K; Worthy, Karen M; Bindu, Lakshman; Fivash, Matthew J; Turner, Kevin B; Fabris, Daniele; Rein, Alan; Fisher, Robert J

2007-09-01

The interaction of the HIV Gag polyprotein with nucleic acid is a critical step in the assembly of viral particles. The Gag polyprotein is composed of the matrix (MA), capsid (CA), and nucleocapsid (NC) domains. The NC domain is required for nucleic acid interactions, and the CA domain is required for Gag-Gag interactions. Previously, we have investigated the binding of the NC protein to d(TG)(n) oligonucleotides using surface plasmon resonance (SPR) spectroscopy. We found a single NC protein is able to bind to more than one immobilized oligonucleotide, provided that the oligonucleotides are close enough together. As NC is believed to be the nucleic acid binding domain of Gag, we might expect Gag to show the same complex behavior. We wished to analyze the stoichiometry of Gag binding to oligonucleotides without this complication due to tertiary complex formation. We have therefore analyzed Gag binding to extremely low oligonucleotide density on SPR chips. Such low densities of oligonucleotides are difficult to accurately quantitate. We have determined by Fourier transform ion cyclotron (FTICR) mass spectrometry that four molecules of NC bind to d(TG)(10) (a 20-base oligonucleotide). We developed a method of calibrating low-density surfaces using NC calibration injections. Knowing the maximal response and the stoichiometry of binding, we can precisely determine the amount of oligonucleotide immobilized at these very-low-density surfaces (<1 Response Unit). Using this approach, we have measured the binding of Gag to d(TG)(10). Gag binds to a 20-mer with a stoichiometry of greater than 4. This suggests that once Gag is bound to the immobilized oligonucleotide, additional Gag molecules can bind to this complex.

Nightmares and Dysfunctional Beliefs about Sleep Mediate the Effect of Insomnia Symptoms on Suicidal Ideation

PubMed Central

McCall, W. Vaughn; Batson, Nicholas; Webster, Megan; Case, L. Douglas; Joshi, Indu; Derreberry, Todd; McDonough, Adam; Farris, Suzan R.

2013-01-01

Study Objectives: Many studies have reported a positive association between sleep problems and suicidal ideation. Some prospective studies in the elderly have shown that insomnia is a risk factor for suicide death after controlling for other depressive symptoms. However, hypotheses to explain how this risk is mediated have not previously been assessed. We tested the hypothesis that insomnia symptoms are related to suicidal ideation through mediation by dysfunctional beliefs and attitudes about sleep and/or nightmares. Methods: We measured symptoms of depression, hopelessness, insomnia severity, dysfunctional beliefs and attitudes about sleep, nightmares, and suicidal ideation intensity on a convenience sample of 50 patients with depressive disorders, including 23 outpatients, 16 inpatients, and 11 suicidal ED patients. Mediation analysis was used to assess the indirect effects of insomnia symptoms on suicidal ideation through dysfunctional beliefs about sleep and through nightmares. Results: Our findings again confirmed a positive association between insomnia symptoms and the intensity of suicidal ideas in depressed patients (b = 0.64, 95% CI = [0.14, 1.15]). However, we extended and clarified our earlier findings by now showing that dysfunctional beliefs and attitudes about sleep as well as nightmares may mediate the association between insomnia symptoms and suicidal ideation. The indirect effects of insomnia symptoms through dysfunctional beliefs about sleep and through nightmares were 0.38 (-0.03, 0.97) and 0.35 (0.05, 0.75), respectively. Conclusions: Nightmares as well as dysfunctional beliefs and attitudes about sleep each are positively and independently related to the intensity of suicidal ideation, and the effect of insomnia symptoms appears to be mediated through these two variables. Citation: McCall WV; Batson N; Webster M; Case LD; Joshi I; Derreberry T; McDonough A; Farris SR. Nightmares and dysfunctional beliefs about sleep mediate the effect of insomnia symptoms on suicidal ideation. J Clin Sleep Med 2013;9(2):135–140. PMID:23372466

Intermittent noise stress causes baroreflex desensitization and decreased heart rate variability in Wistar Kyoto rats exposed to ozone

EPA Science Inventory

This study shows that intermittent noise stress worsens the cardiopulmonary response of rats to ozone. It increases electrical disturbances and causes dysfunction the homeostatic regulation of the heart and vasculature. Although the acute cardiovascular health impacts o...

A single exposure to acrolein causes arrhythmogenesis, cardiac electrical dysfunction and decreased heart rate variability in hypertensive rats

EPA Science Inventory

Epidemiological studies demonstrate an association between cardiovascular morbidity, arrhythmias, and exposure to air toxicants such as acrolein. We hypothesized that a single exposure to acrolein would increase arrhythmias and cause changes in the electrocardiogram (ECG) of hype...

Milrinone ameliorates cardiac mechanical dysfunction after hypothermia in an intact rat model.

PubMed

Dietrichs, Erik Sveberg; Kondratiev, Timofei; Tveita, Torkjel

2014-12-01

Rewarming from hypothermia is often complicated by cardiac dysfunction, characterized by substantial reduction in stroke volume. Previously we have reported that inotropic agents, working via cardiac β-receptor agonism may exert serious side effects when applied to treat cardiac contractile dysfunction during rewarming. In this study we tested whether Milrinone, a phosphodiesterase III inhibitor, is able to ameliorate such dysfunction when given during rewarming. A rat model designed for circulatory studies during experimental hypothermia with cooling to a core temperature of 15°C, stable hypothermia at this temperature for 3h and subsequent rewarming was used, with a total of 3 groups: (1) a normothermic group receiving Milrinone, (2) a hypothermic group receiving Milrinone the last hour of hypothermia and during rewarming, and (3) a hypothermic saline control group. Hemodynamic function was monitored using a conductance catheter introduced to the left ventricle. After rewarming from 15°C, stroke volume and cardiac output returned to within baseline values in Milrinone treated animals, while these variables were significantly reduced in saline controls. Milrinone ameliorated cardiac dysfunction during rewarming from 15°C. The present results suggest that at low core temperatures and during rewarming from such temperatures, pharmacologic efforts to support cardiovascular function is better achieved by substances preventing cyclic AMP breakdown rather than increasing its formation via β-receptor stimulation. Copyright © 2014 Elsevier Inc. All rights reserved.

Attachment, dysfunctional attitudes, self-esteem, and association to depressive symptoms in patients with mood disorders.

PubMed

Fuhr, Kristina; Reitenbach, Ivanina; Kraemer, Jan; Hautzinger, Martin; Meyer, Thomas D

2017-04-01

Cognitive factors might be the link between early attachment experiences and later depression. Similar cognitive vulnerability factors are discussed as relevant for both unipolar and bipolar disorders. The goals of the study were to test if there are any differences concerning attachment style and cognitive factors between remitted unipolar and bipolar patients compared to controls, and to test if the association between attachment style and depressive symptoms is mediated by cognitive factors. A path model was tested in 182 participants (61 with remitted unipolar and 61 with remitted bipolar disorder, and 60 healthy subjects) in which adult attachment insecurity was hypothesized to affect subsyndromal depressive symptoms through the partial mediation of dysfunctional attitudes and self-esteem. No differences between patients with remitted unipolar and bipolar disorders concerning attachment style, dysfunctional attitudes, self-esteem, and subsyndromal depressive symptoms were found, but both groups reported a more dysfunctional pattern than healthy controls. The path models confirmed that the relationship between attachment style and depressive symptoms was mediated by the cognitive variables 'dysfunctional attitudes' and 'self-esteem'. With the cross-sectional nature of the study, results cannot explain causal development over time. The results emphasize the relevance of a more elaborate understanding of cognitive and interpersonal factors in mood disorders. It is important to address cognitive biases and interpersonal experiences in treatment of mood disorders. Copyright © 2017 Elsevier B.V. All rights reserved.

From neurocognition to community participation in serious mental illness: the intermediary role of dysfunctional attitudes and motivation.

PubMed

Thomas, E C; Luther, L; Zullo, L; Beck, A T; Grant, P M

2017-04-01

Evidence for a relationship between neurocognition and functional outcome in important areas of community living is robust in serious mental illness research. Dysfunctional attitudes (defeatist performance beliefs and asocial beliefs) have been identified as intervening variables in this causal chain. This study seeks to expand upon previous research by longitudinally testing the link between neurocognition and community participation (i.e. time in community-based activity) through dysfunctional attitudes and motivation. Adult outpatients with serious mental illness (N = 175) participated, completing follow-up assessments approximately 6 months after initial assessment. Path analysis tested relationships between baseline neurocognition, emotion perception, functional skills, dysfunctional attitudes, motivation, and outcome (i.e. community participation) at baseline and follow-up. Path models demonstrated two pathways to community participation. The first linked neurocognition and community participation through functional skills, defeatist performance beliefs, and motivation. A second pathway linked asocial beliefs and community participation, via a direct path passing through motivation. Model fit was excellent for models predicting overall community participation at baseline and, importantly, at follow-up. The existence of multiple pathways to community participation in a longitudinal model supports the utility of multi-modal interventions for serious mental illness (i.e. treatment packages that build upon individuals' strengths while addressing the array of obstacles to recovery) that feature dysfunctional attitudes and motivation as treatment targets.

Wavelet and receiver operating characteristic analysis of heart rate variability

NASA Astrophysics Data System (ADS)

McCaffery, G.; Griffith, T. M.; Naka, K.; Frennaux, M. P.; Matthai, C. C.

2002-02-01

Multiresolution wavelet analysis has been used to study the heart rate variability in two classes of patients with different pathological conditions. The scale dependent measure of Thurner et al. was found to be statistically significant in discriminating patients suffering from hypercardiomyopathy from a control set of normal subjects. We have performed Receiver Operating Characteristc (ROC) analysis and found the ROC area to be a useful measure by which to label the significance of the discrimination, as well as to describe the severity of heart dysfunction.

Resolution of erectile dysfunction after an andrological visit in a selected population of patients affected by psychogenic erectile dysfunction.

PubMed

Cavallini, Giorgio

2017-01-01

The aim of this study was to ascertain whether some patients with psychogenic erectile dysfunction (PED) who chose psychotherapy spontaneously improved their sexual function immediately after diagnosis. Two hundred eighty-five patients with PED were retrospectively studied. Complete resolution of PED was analyzed regarding age, primary or secondary PED, marital status, domestic status, prevailing attitude of the female partner to the dysfunction, duration of their partnership, social status, duration of PED, International Index of Erectile Function score, and prevailing attitude of the patient after a diagnosis of PED. The data were analyzed using post-hoc tests. PED was resolved in 32.3% of the patients immediately after diagnosis. These patients were older, more frequently affected by secondary ED, more frequently living with their partner, and more frequently resigned or happy with the diagnosis of PED than the patients who did not resolve their PED. A nonchalant or cooperative female attitude to PED improved the possibility of PED resolution. The other variables did not influence PED resolution. Our data showed that a clear-cut diagnosis of psychogenic erectile deficiency and some psychosocial factors were critical for the management of some patients with PED.

The evaluation of bulbar dysfunction in amyotrophic lateral sclerosis: survey of clinical practice patterns in the United States.

PubMed

Plowman, Emily K; Tabor, Lauren C; Wymer, James; Pattee, Gary

2017-08-01

Speech and swallowing impairments are highly prevalent in individuals with amyotrophic lateral sclerosis (ALS) and contribute to reduced quality of life, malnutrition, aspiration, pneumonia and death. Established practice parameters for bulbar dysfunction in ALS do not currently exist. The aim of this study was to identify current practice patterns for the evaluation of speech and swallowing function within participating Northeast ALS clinics in the United States. A 15-item survey was emailed to all registered NEALS centres. Thirty-eight sites completed the survey. The majority (92%) offered Speech-Language Pathology, augmentative and alternative communication (71%), and dietician (92%) health care services. The ALS Functional Rating Scale-Revised and body weight represented the only parameters routinely collected in greater then 90% of responding sites. Referral for modified barium swallow study was routinely utilised in only 27% of sites and the use of percutaneous gastrostomy tubes in ALS patient care was found to vary considerably. This survey reveals significant variability and inconsistency in the management of bulbar dysfunction in ALS across NEALS sites. We conclude that a great need exists for the development of bulbar practice guidelines in ALS clinical care to accurately detect and monitor bulbar dysfunction.

Is Internet Pornography Causing Sexual Dysfunctions? A Review with Clinical Reports.

PubMed

Park, Brian Y; Wilson, Gary; Berger, Jonathan; Christman, Matthew; Reina, Bryn; Bishop, Frank; Klam, Warren P; Doan, Andrew P

2016-08-05

Traditional factors that once explained men's sexual difficulties appear insufficient to account for the sharp rise in erectile dysfunction, delayed ejaculation, decreased sexual satisfaction, and diminished libido during partnered sex in men under 40. This review (1) considers data from multiple domains, e.g., clinical, biological (addiction/urology), psychological (sexual conditioning), sociological; and (2) presents a series of clinical reports, all with the aim of proposing a possible direction for future research of this phenomenon. Alterations to the brain's motivational system are explored as a possible etiology underlying pornography-related sexual dysfunctions. This review also considers evidence that Internet pornography's unique properties (limitless novelty, potential for easy escalation to more extreme material, video format, etc.) may be potent enough to condition sexual arousal to aspects of Internet pornography use that do not readily transition to real-life partners, such that sex with desired partners may not register as meeting expectations and arousal declines. Clinical reports suggest that terminating Internet pornography use is sometimes sufficient to reverse negative effects, underscoring the need for extensive investigation using methodologies that have subjects remove the variable of Internet pornography use. In the interim, a simple diagnostic protocol for assessing patients with porn-induced sexual dysfunction is put forth.

Objective Cognitive Functioning in Self-reported Habitual Short Sleepers not Reporting Daytime Dysfunction: Examination of Impulsivity via Delay Discounting.

PubMed

Curtis, Brian J; Williams, Paula G; Anderson, Jeffrey S

2018-05-30

1) Examine performance on an objective measure of reward-related cognitive impulsivity (delay discounting) among self-reported habitual short sleepers and medium (i.e., recommended 7-9 hours) length sleepers either reporting or not reporting daytime dysfunction; 2) Inform the debate regarding what type and duration of short sleep (e.g., 21 to 24 hours of total sleep deprivation, self-reported habitual short sleep duration) meaningfully influences cognitive impulsivity; 3) Compare the predictive utility of sleep duration and perceived dysfunction to other factors previously shown to influence cognitive impulsivity via delay discounting performance (age, income, education, and fluid intelligence). We analyzed data from 1,190 adults from the Human Connectome Project database. Participants were grouped on whether they reported habitual short (≤ 6 hours) vs. medium length (7-9 hours) sleep duration and whether they perceived daytime dysfunction using the Pittsburgh Sleep Quality Index. All short sleepers exhibited increased delay discounting compared to all medium length sleepers, regardless of perceived dysfunction. Of the variables examined, self-reported sleep duration was the strongest predictor of delay discounting behavior between groups and across all 1,190 participants. Individuals who report habitual short sleep are likely to exhibit increased reward-related cognitive impulsivity regardless of perceived sleep-related daytime impairment. Therefore, there is reason to suspect that these individuals exhibit more daytime dysfunction, in the form of reward-related cognitive impulsivity, than they may assume. Current findings suggest that assessment of sleep duration over the prior month has meaningful predictive utility for human reward-related impulsivity.

Stroke patients who regain urinary continence in the first week after acute first-ever stroke have better prognosis than patients with persistent lower urinary tract dysfunction.

PubMed

Rotar, Melita; Blagus, Rok; Jeromel, Miran; Skrbec, Miha; Tršinar, Bojan; Vodušek, David B

2011-09-01

Urinary incontinence (UI) is a predictor of greater mortality and poor functional recovery; however published studies failed to evaluate lower urinary tract (LUT) function immediately after stroke. The aim of our study was to evaluate the course of LUT function in the first week after stroke, and its impact on prognosis. We included 100 consecutively admitted patients suffering first-ever stroke and evaluated them within 72 hours after stroke, after 7 days, 6 months, and 12 months. For LUT function assessment we used ultrasound measurement. The patients were divided into three groups: (i) patients who remained continent after stroke, (ii) patients who had LUT dysfunction in the acute phase but regained continence in the first week, and (iii) patients who did not regain normal LUT control in the first week. We assessed the influence of variables on death using the multiple logistic regression model. Immediately after stroke 58 patients had LUT dysfunction. The odds of dying in group with LUT dysfunction were significantly larger than odds in group without LUT dysfunction. Odds for death for patients who regained LUT function in 1 week after stroke were comparable to patients without LUT dysfunction. We confirmed that post-stroke UI is a predictor of greater mortality at 1 week, 6 months and 12 months after stroke. However, patients who regain normal bladder control in the first week have a comparable prognosis as the patients who do not have micturition disturbances following stroke. Copyright © 2011 Wiley-Liss, Inc.

Reasoning strategies used by students to solve stoichiometry problems and its relationship to alternative conceptions, prior knowledge, and cognitive variables

NASA Astrophysics Data System (ADS)

de Astudillo, Luisa Rojas; Niaz, Mansoor

1996-06-01

Achievement in science depends on a series of factors that characterize the cognitive abilities of the students and the complex interactions between these factors and the environment that intervenes in the formation of students' background. The objective of this study is to: a) investigate reasoning strategies students use in solving stoichiometric problems; b) explore the relation between these strategies and alternative conceptions, prior knowledge and cognitive variables; and c) interpret the results within an epistemological framework. Results obtained show how stoichiometric relations produce conflicting situations for students, leading to conceptual misunderstanding of concepts, such as mass, atoms and moles. The wide variety of strategies used by students attest to the presence of competing and conflicting frameworks (progressive transitions, cf. Lakatos, 1970), leading to greater conceptual understanding. It is concluded that the methodology developed in this study (based on a series of closely related probing questions, generally requiring no calculations, that elicit student conceptual understanding to varying degrees within an intact classroom context) was influential in improving student performance. This improvement in performance, however, does not necessarily affect students' hard core of beliefs.

X-ray photoelectron spectroscopy study of radiofrequency sputtered chromium bromide, molybdenum disilicide, and molybdenum disulfide coatings and their friction properties

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Brainard, W. A.

1977-01-01

Radiofrequency sputtered coatings of CRB2, MOSI2, and MOS2 were examined by X-ray photoelectron spectroscopy. The effects of sputtering target history, deposition time, RF power level, and substrate bias on film composition were studied. Friction tests were run on RF sputtered surfaces of 440-C steel to correlate XPS data with lubricating properties. Significant deviations from stoichiometry and high oxide levels for all three compounds were related to target outgassing. The effect of biasing on these two factors depended on the compound. Improved stoichiometry correlated well with good friction and wear properties.

Fundamental study of ash formation and deposition: Effect of reducing stoichiometry. Final report, April 1, 1993--June 30, 1995

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

Bool, L.E. III; Helble, J.J.; Shah, N.

1995-09-01

The technical objectives of this project are: (1) To identify the partitioning of inorganic coal constituents among vapor, submicron fume, and fly ash products generated during the combustion of pulverized coal under a variety of combustion conditions. Fuel lean and fuel rich combustion conditions are considered. (2) To identify and quantify the fundamental processes by which the transformations of minerals and organically-associated inorganic species occur. Emphasis is placed on identifying any changes that occur as a result of combustion under sub-stoichiometric combustion conditions. (3) To incorporate the effects of combustion stoichiometry into an Engineering Model for Ash Formation.

Sharp chemical interface in epitaxial Fe{sub 3}O{sub 4} thin films

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

Gálvez, S.; Rubio-Zuazo, J., E-mail: rubio@esrf.fr; Salas-Colera, E.

Chemically sharp interface was obtained on single phase single oriented Fe{sub 3}O{sub 4} (001) thin film (7 nm) grown on NiO (001) substrate using oxygen assisted molecular beam epitaxy. Refinement of the atomic structure, stoichiometry, and oxygen vacancies were determined by soft and hard x-ray photoelectron spectroscopy, low energy electron diffraction and synchrotron based X-ray reflectivity, and X-ray diffraction. Our results demonstrate an epitaxial growth of the magnetite layer, perfect iron stoichiometry, absence of oxygen vacancies, and the existence of an intermixing free interface. Consistent magnetic and electrical characterizations are also shown.

Gallium vacancies and the growth stoichiometry of GaN studied by positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Saarinen, K.; Seppälä, P.; Oila, J.; Hautojärvi, P.; Corbel, C.; Briot, O.; Aulombard, R. L.

1998-11-01

We have applied positron spectroscopy to study the formation of vacancy defects in undoped n-type metal organic chemical vapor deposition grown GaN, where the stoichiometry was varied. Ga vacancies are found in all samples. Their concentration increases from 1016 to 1019cm-3 when the V/III molar ratio increases from 1000 to 10 000. In nitrogen rich conditions Ga lattice sites are thus left empty and Ga vacancies are abundantly formed. The creation of Ga vacancies is accompanied by the decrease of free electron concentration from 1020 to 1016cm-3, demonstrating their role as compensating centers.

Effect of Reaction Period on Stoichiometry, Phase Purity, and Morphology of Hydrothermally Synthesized Cu2NiSnS4 Nanopowder

NASA Astrophysics Data System (ADS)

Babu, G. Sahaya Dennish; Shajan, X. Sahaya; Alwin, S.; Ramasubbu, V.; Balerao, Gopal M.

2018-01-01

The effect of reaction period on the phase purity, morphology, and stoichiometry of Cu2NiSnS4 (CNTS) nanopowder prepared by hydrothermal method has been investigated. Polyvinylpyrrolidone (PVP) and thioglycolic acid were used as capping agent and sulfur source, respectively. The presence of cubic stannite crystal structure and its phase purity were confirmed by powder x-ray diffraction analysis and Raman spectroscopy. Furthermore, the morphological, crystallographic, and optical features of the prepared CNTS nanopowder were characterized by field-emission scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible (UV-Vis) spectrophotometry. The elemental ratios of Cu/(Ni + Sn) and Ni/Sn showed that the stoichiometry of CNTS was maintained for the compounds synthesized at 230°C with reaction period of 24 h. The occurrence of Cu+, Ni2+, Sn4+, and S2- was evaluated by x-ray photoelectron spectroscopy. The prepared material was used as counter electrode in a dye-sensitized solar cell (DSSC) as an alternative to platinum (Pt), resulting in conversion efficiency of 0.92%. These results indicate that CNTS is a prospective material to replace conventional Pt-based counter electrodes in DSSCs.

Different urea stoichiometries between the dissociation and denaturation of tobacco mosaic virus as probed by hydrostatic pressure.

PubMed

Santos, Jose L R; Aparicio, Ricardo; Joekes, Inés; Silva, Jerson L; Bispo, Jose A C; Bonafe, Carlos F S

2008-05-01

Viruses are very efficient self-assembly structures, but little is understood about the thermodynamics governing their directed assembly. At higher levels of pressure or when pressure is combined with urea, denaturation occurs. For a better understanding of such processes, we investigated the apparent thermodynamic parameters of dissociation and denaturation by assuming a steady-state condition. These processes can be measured considering the decrease of light scattering of a viral solution due to the dissociation process, and the red shift of the fluorescence emission spectra, that occurs with the denaturation process. We determined the apparent urea stoichiometry considering the equilibrium reaction of TMV dissociation and subunit denaturation, which furnished, respectively, 1.53 and 11.1 mol of urea/mol of TMV subunit. The denaturation and dissociation conditions were arrived in a near reversible pathway, allowing the determination of thermodynamic parameters. Gel filtration HPLC, electron microscopy and circular dichroism confirmed the dissociation and denaturation processes. Based on spectroscopic results from earlier papers, the calculation of the apparent urea stoichiometry of dissociation and denaturation of several other viruses resulted in similar values, suggesting a similar virus-urea interaction among these systems.

The influence of hydrogenation and oxygen vacancies on molybdenum oxides work function and gap states for application in organic optoelectronics.

PubMed

Vasilopoulou, Maria; Douvas, Antonios M; Georgiadou, Dimitra G; Palilis, Leonidas C; Kennou, Stella; Sygellou, Labrini; Soultati, Anastasia; Kostis, Ioannis; Papadimitropoulos, Giorgos; Davazoglou, Dimitris; Argitis, Panagiotis

2012-10-03

Molybdenum oxide is used as a low-resistance anode interfacial layer in applications such as organic light emitting diodes and organic photovoltaics. However, little is known about the correlation between its stoichiometry and electronic properties, such as work function and occupied gap states. In addition, despite the fact that the knowledge of the exact oxide stoichiometry is of paramount importance, few studies have appeared in the literature discussing how this stoichiometry can be controlled to permit the desirable modification of the oxide's electronic structure. This work aims to investigate the beneficial role of hydrogenation (the incorporation of hydrogen within the oxide lattice) versus oxygen vacancy formation in tuning the electronic structure of molybdenum oxides while maintaining their high work function. A large improvement in the operational characteristics of both polymer light emitting devices and bulk heterojunction solar cells incorporating hydrogenated Mo oxides as hole injection/extraction layers was achieved as a result of favorable energy level alignment at the metal oxide/organic interface and enhanced charge transport through the formation of a large density of gap states near the Fermi level.

Intrinsic point defects in off-stoichiometric Cu2ZnSnSe4: A neutron diffraction study

NASA Astrophysics Data System (ADS)

Gurieva, Galina; Valle Rios, Laura Elisa; Franz, Alexandra; Whitfield, Pamela; Schorr, Susan

2018-04-01

This work is an experimental study of intrinsic point defects in off-stoichiometric kesterite type CZTSe by means of neutron powder diffraction. We revealed the existence of copper vacancies (VCu), various cation anti site defects (CuZn, ZnCu, ZnSn, SnZn, and CuZn), as well as interstitials (Cui, Zni) in a wide range of off-stoichiometric polycrystalline powder samples synthesized by the solid state reaction. The results show that the point defects present in off-stoichiometric CZTSe agree with the off-stoichiometry type model, assuming certain cation substitutions accounting for charge balance. In addition to the known off-stoichiometry types A-H, new types (I-L) have been introduced. For the very first time, a correlation between the chemical composition of the CZTSe kesterite type phase and the occurring intrinsic point defects is presented. In addition to the off-stoichiometry type specific defects, the Cu/Zn disorder is always present in the CZTSe phase. In Cu-poor/Zn-rich CZTSe, a composition considered as the one that delivers the best photovoltaic performance, mainly copper vacancies, ZnCu and ZnSn anti sites are present. Also, this compositional region shows the lowest degree of Cu/Zn disorder.

Deposition of nanocomposite Cu-TiO2 using heterogeneous colliding plasmas

NASA Astrophysics Data System (ADS)

Pandey, Pramod K.; Thareja, Raj K.; Singh, Ravi Pratap; Costello, John T.

2018-03-01

The formation of CuTiO2 nanocomposites has been observed in an experiment in which laser plasma plumes of Cu and Ti collide and stagnate in an oxygen atmosphere. The inherent advantage of this technique lies in its simplicity and flexibility where laser, target composition and geometry along with ambient atmosphere are all controllable parameters through which the stoichiometry of the deposited nanocomposites may be selected. The experiment has been performed at three oxygen ambient pressures 10-4, 10-2, 100 mbar and we observe its effect on stoichiometry, and morphology of the deposited nanocomposites. Here, we show how the stoichiometry of deposited nanocomposites can be readily controlled by changing just one parameter, namely the ambient oxygen pressure. The different peaks of photoluminescence spectra λ =390{ nm}( {E=3.18{ eV}} ) corresponding to the anatase phase of TiO2, along with the peaks at λ = 483 nm ( E = 2.56 eV) and 582 nm ( E = 2.13 eV) of deposited nanocomposites, shows the doping/blending effect on the band gaps which may potentially be of value in solar cell technology. The technique can, in principle, be extended to include nanocomposites of other materials making it potentially more widely applicable.

Stoichiometry, Metabolism and Nutrient Limitation Across the Periodic Table in Natural Flowing-Water Chemostats

NASA Astrophysics Data System (ADS)

Cohen, M. J.; Nifong, R. L.; Kurz, M. J.; Cropper, W. P.; Martin, J. B.

2014-12-01

Relative supplies of macro and micronutrients (C,N,P, various metals), along with light and water, controls ecosystem metabolism, trophic energy transfer and community structure. Here we test the hypothesis, using measurements from 41 spring-fed rivers in Florida, that tissue stoichiometry indicates autotroph nutrient limitation status. Low variation in discharge, temperature and chemical composition within springs, but large variation across springs creates an ideal setting to assess the relationship between limitation and resource supply. Molar N:P ranges from 0.4 to 90, subjecting autotrophs to dramatically different nutrient supply. Over this gradient, species-specific autotroph tissue C:N:P ratios are strictly homeostatic, and with no evidence that nutrient supply affects species composition. Expanding to include 19 metals and micronutrients revealed autotrophs are more plastic in response to micronutrient variation, particularly for iron and manganese whose supply fluxes are small compared to biotic demand. Using a Droop model modified to reflect springs conditions (benthic production, light limitation, high hydraulic turnover), we show that tissue stoichiometry transitions from homeostatic to plastic with the onset of nutrient limitation, providing a potentially powerful new tool for predicting nutrient limitation and thus eutrophication in flowing waters.

The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae.

PubMed

Reef, Ruth; Pandolfi, John M; Lovelock, Catherine E

2012-08-01

The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae from three lineages, Caulerpa serrulata (Chlorophyta), Laurencia intricata (Rhodophyta), and Sargassum polyphyllum (Phaeophyceae) were grown enriched with nitrogen or phosphorous and under control conditions at Heron Island on the Great Barrier Reef, Australia. Growth rate, photosynthesis, nucleic acid composition, and elemental stoichiometry were measured. Nutrient enrichment had positive effects on photosynthetic rates and on investment in RNA. However, growth rate was not correlated with either photosynthetic rates or RNA content; thus, we did not find support for the GRH in tropical macroalgae. Macroalgae, especially L. intricata, accumulated P to very high levels (>0.6% of dry weight). The growth rate response to tissue P concentrations was unimodal. Above 0.21%, P accumulation had negative effects on growth. Nitrogen was not stored, but evidence of futile cycling was observed. The capacity to store large amounts of P is probably an adaptation to the low and patchy nutrient environment of the tropical oceans.

The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae

PubMed Central

Reef, Ruth; Pandolfi, John M; Lovelock, Catherine E

2012-01-01

The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae from three lineages, Caulerpa serrulata (Chlorophyta), Laurencia intricata (Rhodophyta), and Sargassum polyphyllum (Phaeophyceae) were grown enriched with nitrogen or phosphorous and under control conditions at Heron Island on the Great Barrier Reef, Australia. Growth rate, photosynthesis, nucleic acid composition, and elemental stoichiometry were measured. Nutrient enrichment had positive effects on photosynthetic rates and on investment in RNA. However, growth rate was not correlated with either photosynthetic rates or RNA content; thus, we did not find support for the GRH in tropical macroalgae. Macroalgae, especially L. intricata, accumulated P to very high levels (>0.6% of dry weight). The growth rate response to tissue P concentrations was unimodal. Above 0.21%, P accumulation had negative effects on growth. Nitrogen was not stored, but evidence of futile cycling was observed. The capacity to store large amounts of P is probably an adaptation to the low and patchy nutrient environment of the tropical oceans. PMID:22957199

Characterization of brightness and stoichiometry of bright particles by flow-fluorescence fluctuation spectroscopy.

PubMed

Johnson, Jolene; Chen, Yan; Mueller, Joachim D

2010-11-03

Characterization of bright particles at low concentrations by fluorescence fluctuation spectroscopy (FFS) is challenging, because the event rate of particle detection is low and fluorescence background contributes significantly to the measured signal. It is straightforward to increase the event rate by flow, but the high background continues to be problematic for fluorescence correlation spectroscopy. Here, we characterize the use of photon-counting histogram analysis in the presence of flow. We demonstrate that a photon-counting histogram efficiently separates the particle signal from the background and faithfully determines the brightness and concentration of particles independent of flow speed, as long as undersampling is avoided. Brightness provides a measure of the number of fluorescently labeled proteins within a complex and has been used to determine stoichiometry of protein complexes in vivo and in vitro. We apply flow-FFS to determine the stoichiometry of the group specific antigen protein within viral-like particles of the human immunodeficiency virus type-1 from the brightness. Our results demonstrate that flow-FFS is a sensitive method for the characterization of complex macromolecular particles at low concentrations. Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Fault detection and isolation of high temperature proton exchange membrane fuel cell stack under the influence of degradation

NASA Astrophysics Data System (ADS)

Jeppesen, Christian; Araya, Samuel Simon; Sahlin, Simon Lennart; Thomas, Sobi; Andreasen, Søren Juhl; Kær, Søren Knudsen

2017-08-01

This study proposes a data-drive impedance-based methodology for fault detection and isolation of low and high cathode stoichiometry, high CO concentration in the anode gas, high methanol vapour concentrations in the anode gas and low anode stoichiometry, for high temperature PEM fuel cells. The fault detection and isolation algorithm is based on an artificial neural network classifier, which uses three extracted features as input. Two of the proposed features are based on angles in the impedance spectrum, and are therefore relative to specific points, and shown to be independent of degradation, contrary to other available feature extraction methods in the literature. The experimental data is based on a 35 day experiment, where 2010 unique electrochemical impedance spectroscopy measurements were recorded. The test of the algorithm resulted in a good detectability of the faults, except for high methanol vapour concentration in the anode gas fault, which was found to be difficult to distinguish from a normal operational data. The achieved accuracy for faults related to CO pollution, anode- and cathode stoichiometry is 100% success rate. Overall global accuracy on the test data is 94.6%.

Invasive aquarium fish transform ecosystem nutrient dynamics

PubMed Central

Capps, Krista A.; Flecker, Alexander S.

2013-01-01

Trade of ornamental aquatic species is a multi-billion dollar industry responsible for the introduction of myriad fishes into novel ecosystems. Although aquarium invaders have the potential to alter ecosystem function, regulation of the trade is minimal and little is known about the ecosystem-level consequences of invasion for all but a small number of aquarium species. Here, we demonstrate how ecological stoichiometry can be used as a framework to identify aquarium invaders with the potential to modify ecosystem processes. We show that explosive growth of an introduced population of stoichiometrically unique, phosphorus (P)-rich catfish in a river in southern Mexico significantly transformed stream nutrient dynamics by altering nutrient storage and remineralization rates. Notably, changes varied between elements; the P-rich fish acted as net sinks of P and net remineralizers of nitrogen. Results from this study suggest species-specific stoichiometry may be insightful for understanding how invasive species modify nutrient dynamics when their population densities and elemental composition differ substantially from native organisms. Risk analysis for potential aquarium imports should consider species traits such as body stoichiometry, which may increase the likelihood that an invasion will alter the structure and function of ecosystems. PMID:23966642

Stoichiometry of ferns in Hawaii: implications for nutrient cycling.

PubMed

Amatangelo, Kathryn L; Vitousek, Peter M

2008-10-01

We asked if element concentrations in ferns differ systematically from those in woody dicots in ways that could influence ecosystem properties and processes. Phylogenetically, ferns are deeply separated from angiosperms; for our analyses we additionally separated leptosporangiate ferns into polypod ferns, a monophyletic clade of ferns which radiated after the rise of angiosperms, and all other leptosporangiate (non-polypod) ferns. We sampled both non-polypod and polypod ferns on a natural fertility gradient and within fertilized and unfertilized plots in Hawaii, and compared our data with shrub and tree samples collected previously in the same plots. Non-polypod ferns in particular had low Ca concentrations under all conditions and less plasticity in their N and P stoichiometry than did polypod ferns or dicots. Polypod ferns were particularly rich in N and P, with low N:P ratios, and their stoichiometry varied substantially in response to differences in nutrient availability. Distinguishing between these two groups has the potential to be useful both in and out of Hawaii, as they have distinct properties which can affect ecosystem function. These differences could contribute to the widespread abundance of polypod ferns in an angiosperm-dominated world, and to patterns of nutrient cycling and limitation in sites where ferns are abundant.

Approximate stoichiometry for rich hydrocarbon mixtures

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

Beans, E.W.

1993-03-01

The stoichiometry of lean mixtures can readily and accurately be determined from the assumption that all the carbon oxidizes to carbon dioxide and all the hydrogen oxidizes to water. This assumption is valid up to an equivalence ratio ([sigma]) of 0.8 and can be used with little error up to [sigma] = 1. The composition of the products of a hydrocarbon burnt in air under the foregoing assumption can be obtained from simple carbon, hydrogen, oxygen and nitrogen balances. Given the composition, one can determine the energy released and/or the adiabatic flame temperature. For rich mixtures, the foregoing assumption, ofmore » course, is not valid. Hence, there is no easy way to determine the stoichiometry of the products of a rich mixture. The objective of this note is to present an equation' which will allow one to readily determine the composition of the products of rich hydrocarbon mixtures. The equation is based on equilibrium composition calculations and some assumptions regarding the characteristics of hydrocarbons. The equation gives approximate results. However, the results are sufficiently accurate for many situations. If more accuracy is wanted, one should use an equilibrium combustion program like the one by Gordon and McBride.« less

Thermal adaptation and phosphorus shape thermal performance in an assemblage of rainforest ants.

PubMed

Kaspari, Michael; Clay, Natalie A; Lucas, Jane; Revzen, Shai; Kay, Adam; Yanoviak, Stephen P

2016-04-01

We studied the Thermal Performance Curves (TPCs) of 87 species of rainforest ants and found support for both the Thermal Adaptation and Phosphorus-Tolerance hypotheses. TPCs relate a fitness proxy (here, worker speed) to environmental temperature. Thermal Adaptation posits that thermal generalists (ants with flatter, broader TPCs) are favored in the hotter, more variable tropical canopy compared to the cooler, less variable litter below. As predicted, species nesting in the forest canopy 1) had running speeds less sensitive to temperature; 2) ran over a greater range of temperatures; and 3) ran at lower maximum speeds. Tradeoffs between tolerance and maximum performance are often invoked for constraining the evolution of thermal generalists. There was no evidence that ant species traded off thermal tolerance for maximum speed, however. Phosphorus-Tolerance is a second mechanism for generating ectotherms able to tolerate thermal extremes. It posits that ants active at high temperatures invest in P-rich machinery to buffer their metabolism against thermal extremes. Phosphorus content in ant tissue varied three-fold, and as predicted, temperature sensitivity was lower and thermal range was higher in P-rich species. Combined, we show how the vertical distribution of hot and variable vs. cooler and stable microclimates in a single forest contribute to a diversity of TPCs and suggest that a widely varying P stoichiometry among these ants may drive some of these differences.

Comparing the Ecological Stoichiometry in Green and Brown Food Webs - A Review and Meta-analysis of Freshwater Food Webs.

PubMed

Evans-White, Michelle A; Halvorson, Halvor M

2017-01-01

The framework of ecological stoichiometry was developed primarily within the context of "green" autotroph-based food webs. While stoichiometric principles also apply in "brown" detritus-based systems, these systems have been historically understudied and differ from green ones in several important aspects including carbon (C) quality and the nutrient [nitrogen (N) and phosphorus (P)] contents of food resources for consumers. In this paper, we review work over the last decade that has advanced the application of ecological stoichiometry from green to brown food webs, focusing on freshwater ecosystems. We first review three focal areas where green and brown food webs differ: (1) bottom-up controls by light and nutrient availability, (2) stoichiometric constraints on consumer growth and nutritional regulation, and (3) patterns in consumer-driven nutrient dynamics. Our review highlights the need for further study of how light and nutrient availability affect autotroph-heterotroph interactions on detritus and the subsequent effects on consumer feeding and growth. To complement this conceptual review, we formally quantified differences in stoichiometric principles between green and brown food webs using a meta-analysis across feeding studies of freshwater benthic invertebrates. From 257 datasets collated across 46 publications and several unpublished studies, we compared effect sizes (Pearson's r) of resource N:C and P:C on growth, consumption, excretion, and egestion between herbivorous and detritivorous consumers. The meta-analysis revealed that both herbivore and detritivore growth are limited by resource N:C and P:C contents, but effect sizes only among detritivores were significantly above zero. Consumption effect sizes were negative among herbivores but positive for detritivores in the case of both N:C and P:C, indicating distinct compensatory feeding responses across resource stoichiometry gradients. Herbivore P excretion rates responded significantly positively to resource P:C, whereas detritivore N and P excretion did not respond; detritivore N and P egestion responded positively to resource N:C and P:C, respectively. Our meta-analysis highlights resource N and P contents as broadly limiting in brown and green benthic food webs, but indicates contrasting mechanisms of limitation owing to differing consumer regulation. We suggest that green and brown food webs share fundamental stoichiometric principles, while identifying specific differences toward applying ecological stoichiometry across ecosystems.

Comparing the Ecological Stoichiometry in Green and Brown Food Webs – A Review and Meta-analysis of Freshwater Food Webs

PubMed Central

Evans-White, Michelle A.; Halvorson, Halvor M.

2017-01-01

The framework of ecological stoichiometry was developed primarily within the context of “green” autotroph-based food webs. While stoichiometric principles also apply in “brown” detritus-based systems, these systems have been historically understudied and differ from green ones in several important aspects including carbon (C) quality and the nutrient [nitrogen (N) and phosphorus (P)] contents of food resources for consumers. In this paper, we review work over the last decade that has advanced the application of ecological stoichiometry from green to brown food webs, focusing on freshwater ecosystems. We first review three focal areas where green and brown food webs differ: (1) bottom–up controls by light and nutrient availability, (2) stoichiometric constraints on consumer growth and nutritional regulation, and (3) patterns in consumer-driven nutrient dynamics. Our review highlights the need for further study of how light and nutrient availability affect autotroph–heterotroph interactions on detritus and the subsequent effects on consumer feeding and growth. To complement this conceptual review, we formally quantified differences in stoichiometric principles between green and brown food webs using a meta-analysis across feeding studies of freshwater benthic invertebrates. From 257 datasets collated across 46 publications and several unpublished studies, we compared effect sizes (Pearson’s r) of resource N:C and P:C on growth, consumption, excretion, and egestion between herbivorous and detritivorous consumers. The meta-analysis revealed that both herbivore and detritivore growth are limited by resource N:C and P:C contents, but effect sizes only among detritivores were significantly above zero. Consumption effect sizes were negative among herbivores but positive for detritivores in the case of both N:C and P:C, indicating distinct compensatory feeding responses across resource stoichiometry gradients. Herbivore P excretion rates responded significantly positively to resource P:C, whereas detritivore N and P excretion did not respond; detritivore N and P egestion responded positively to resource N:C and P:C, respectively. Our meta-analysis highlights resource N and P contents as broadly limiting in brown and green benthic food webs, but indicates contrasting mechanisms of limitation owing to differing consumer regulation. We suggest that green and brown food webs share fundamental stoichiometric principles, while identifying specific differences toward applying ecological stoichiometry across ecosystems. PMID:28706509

Energy storage and fecundity explain deviations from ecological stoichiometry predictions under global warming and size-selective predation.

PubMed

Zhang, Chao; Jansen, Mieke; De Meester, Luc; Stoks, Robby

2016-11-01

A key challenge for ecologists is to predict how single and joint effects of global warming and predation risk translate from the individual level up to ecosystem functions. Recently, stoichiometric theory linked these levels through changes in body stoichiometry, predicting that both higher temperatures and predation risk induce shifts in energy storage (increases in C-rich carbohydrates and reductions in N-rich proteins) and body stoichiometry (increases in C : N and C : P). This promising theory, however, is rarely tested and assumes that prey will divert energy away from reproduction under predation risk, while under size-selective predation, prey instead increase fecundity. We exposed the water flea Daphnia magna to 4 °C warming and fish predation risk to test whether C-rich carbohydrates increase and N-rich proteins decrease, and as a result, C : N and C : P increase under warming and predation risk. Unexpectedly, warming decreased body C : N, which was driven by reductions in C-rich fat and sugar contents while the protein content did not change. This reflected a trade-off where the accelerated intrinsic growth rate under warming occurred at the cost of a reduced energy storage. Warming reduced C : N less and only increased C : P and N : P in the fish-period Daphnia. These evolved stoichiometric responses to warming were largely driven by stronger warming-induced reductions in P than in C and N and could be explained by the better ability to deal with warming in the fish-period Daphnia. In contrast to theory predictions, body C : N decreased under predation risk due to a strong increase in the N-rich protein content that offsets the increase in C-rich fat content. The higher investment in fecundity (more N-rich eggs) under predation risk contributed to this stronger increase in protein content. Similarly, the lower body C : N of pre-fish Daphnia also matched their higher fecundity. Warming and predation risk independently shaped body stoichiometry, largely by changing levels of energy storage molecules. Our results highlight that two widespread patterns, the trade-off between rapid development and energy storage and the increased investment in reproduction under size-selective predation, cause predictable deviations from current ecological stoichiometry theory. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

DWPF SIMULANT CPC STUDIES FOR SB7B

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

Koopman, D.

2011-11-01

Lab-scale DWPF simulations of Sludge Batch 7b (SB7b) processing were performed. Testing was performed at the Savannah River National Laboratory - Aiken County Technology Laboratory (SRNL-ACTL). The primary goal of the simulations was to define a likely operating window for acid stoichiometry for the DWPF Sludge Receipt and Adjustment Tank (SRAT). In addition, the testing established conditions for the SRNL Shielded Cells qualification simulation of SB7b-Tank 40 blend, supported validation of the current glass redox model, and validated the coupled process flowsheet at the nominal acid stoichiometry. An acid window of 105-140% by the Koopman minimum acid (KMA) equation (107-142%more » DWPF Hsu equation) worked for the sludge-only flowsheet. Nitrite was present in the SRAT product for the 105% KMA run at 366 mg/kg, while SME cycle hydrogen reached 94% of the DWPF Slurry Mix Evaporator (SME) cycle limit in the 140% KMA run. The window was determined for sludge with added caustic (0.28M additional base, or roughly 12,000 gallons 50% NaOH to 820,000 gallons waste slurry). A suitable processing window appears to be 107-130% DWPF acid equation for sludge-only processing allowing some conservatism for the mapping of lab-scale simulant data to full-scale real waste processing including potentially non-conservative noble metal and mercury concentrations. This window should be usable with or without the addition of up to 7,000 gallons of caustic to the batch. The window could potentially be wider if caustic is not added to SB7b. It is recommended that DWPF begin processing SB7b at 115% stoichiometry using the current DWPF equation. The factor could be increased if necessary, but changes should be made with caution and in small increments. DWPF should not concentrate past 48 wt.% total solids in the SME cycle if moderate hydrogen generation is occurring simultaneously. The coupled flowsheet simulation made more hydrogen in the SRAT and SME cycles than the sludge-only run with the same acid stoichiometric factor. The slow acid addition in MCU seemed to alter the reactions that consumed the small excess acid present such that hydrogen generation was promoted relative to sludge-only processing. The coupled test reached higher wt.% total solids, and this likely contributed to the SME cycle hydrogen limit being exceeded at 110% KMA. It is clear from the trends in the SME processing GC data, however, that the frit slurry formic acid contributed to driving the hydrogen generation rate above the SME cycle limit. Hydrogen generation rates after the second frit addition generally exceeded those after the first frit addition. SRAT formate loss increased with increasing acid stoichiometry (15% to 35%). A substantial nitrate gain which was observed to have occurred after acid addition (and nitrite destruction) was reversed to a net nitrate loss in runs with higher acid stoichiometry (nitrate in SRAT product less than sum of sludge nitrate and added nitric acid). Increased ammonium ion formation was also indicated in the runs with nitrate loss. Oxalate loss on the order 20% was indicated in three of the four acid stoichiometry runs and in the coupled flowsheet run. The minimum acid stoichiometry run had no indicated loss. The losses were of the same order as the official analytical uncertainty of the oxalate concentration measurement, but were not randomly distributed about zero loss, so some actual loss was likely occurring. Based on the entire set of SB7b test data, it is recommended that DWPF avoid concentrating additional sludge solids in single SRAT batches to limit the concentrations of noble metals to SB7a processing levels (on a grams noble metal per SRAT batch basis). It is also recommended that DWPF drop the formic acid addition that accompanies the process frit 418 additions, since SME cycle data showed considerable catalytic activity for hydrogen generation from this additional acid (about 5% increase in stoichiometry occurred from the frit formic acid). Frit 418 also does not appear to need formic acid addition to prevent gel formation in the frit slurry. Simulant processing was successful using 100 ppm of 747 antifoam added prior to nitric acid instead of 200 ppm. This is a potential area for DWPF to cut antifoam usage in any future test program. An additional 100 ppm was added before formic acid addition. Foaming during formic acid addition was not observed. No build-up of oily or waxy material was observed in the off-gas equipment. Lab-scale mercury stripping behavior was similar to SB6 and SB7a. More mercury was unaccounted for as the acid stoichiometry increased.« less

Variable electron correlation in high-quality MBE- and PLD-grown SrRuO3 thin films.

NASA Astrophysics Data System (ADS)

Siemons, Wolter; Koster, Gertjan; Yamamoto, Hideki; Vailionis, Arturas; Geballe, Theodore; Blank, Dave; Beasley, Malcolm

2007-03-01

We show that systematic variations in the degree of correlation can occur within SrRuO3 as a function of disorder/off-stoichiometry. In particular, we find that one source of disorder can be controlled in SrRuO3 thin films by varying the deposition conditions or the deposition technique. Specifically, we clearly demonstrate that variation of vacancies on the ruthenium site gives rise to a variation in correlated behavior as seen in the photoemission spectra (XPS and UPS),. Moreover, the transport properties of our samples are clearly linked to their photoemission spectra, and independently the crystal unit cell parameters. SrRuO3 appears to be a system where these effects can be studied in a more systematic fashion, usually not easily accessible, but we suspect that the underlying physics is generic in complex oxidesWork supported by the DoE BES and EPRI.

Opposite metabolic responses of shoots and roots to drought

NASA Astrophysics Data System (ADS)

Gargallo-Garriga, Albert; Sardans, Jordi; Pérez-Trujillo, Míriam; Rivas-Ubach, Albert; Oravec, Michal; Vecerova, Kristyna; Urban, Otmar; Jentsch, Anke; Kreyling, Juergen; Beierkuhnlein, Carl; Parella, Teodor; Peñuelas, Josep

2014-10-01

Shoots and roots are autotrophic and heterotrophic organs of plants with different physiological functions. Do they have different metabolomes? Do their metabolisms respond differently to environmental changes such as drought? We used metabolomics and elemental analyses to answer these questions. First, we show that shoots and roots have different metabolomes and nutrient and elemental stoichiometries. Second, we show that the shoot metabolome is much more variable among species and seasons than is the root metabolome. Third, we show that the metabolic response of shoots to drought contrasts with that of roots; shoots decrease their growth metabolism (lower concentrations of sugars, amino acids, nucleosides, N, P, and K), and roots increase it in a mirrored response. Shoots are metabolically deactivated during drought to reduce the consumption of water and nutrients, whereas roots are metabolically activated to enhance the uptake of water and nutrients, together buffering the effects of drought, at least at the short term.

Global controls on carbon storage in mangrove soils

NASA Astrophysics Data System (ADS)

Rovai, André S.; Twilley, Robert R.; Castañeda-Moya, Edward; Riul, Pablo; Cifuentes-Jara, Miguel; Manrow-Villalobos, Marilyn; Horta, Paulo A.; Simonassi, José C.; Fonseca, Alessandra L.; Pagliosa, Paulo R.

2018-06-01

Global-scale variation in mangrove ecosystem properties has been explained using a conceptual framework linking geomorphological processes to distinct coastal environmental settings (CES) for nearly 50 years. However, these assumptions have not been empirically tested at the global scale. Here, we show that CES account for global variability in mangrove soil C:N:P stoichiometry and soil organic carbon (SOC) stocks. Using this ecogeomorphology framework, we developed a global model that captures variation in mangrove SOC stocks compatible with distinct CES. We show that mangrove SOC stocks have been underestimated by up to 50% (a difference of roughly 200 Mg ha-1) in carbonate settings and overestimated by up to 86% (around 400 Mg ha-1) in deltaic coastlines. Moreover, we provide information for 57 nations that currently lack SOC data, enabling these and other countries to develop or evaluate their blue carbon inventories.

Parents Who Abuse: What Are They Thinking?

ERIC Educational Resources Information Center

Seng, Alexandra C.; Prinz, Ronald J.

2008-01-01

Child abuse is a major social concern around the world. Important to tackling the problem is an understanding of the mechanisms contributing to abusive parenting. This article brings together research on the cognitive variables associated with abusive or high-risk parenting. Considered are dysfunctional child-centered and parent-centered…

A Review of the Long-Term Effects of Child Sexual Abuse.

ERIC Educational Resources Information Center

Beitchman, Joseph H.; And Others

1992-01-01

Evidence suggests that sexual abuse has serious long-term effects; but specific effects, independent of force, threatened force, or family variables such as parental psychopathology, are not yet clarified. Effects among adults in terms of their relationship to sexual dysfunction, depression, anxiety, fear, multiple or borderline personality…

Between Stressors and Outcomes: Can We Simplify Caregiving Process Variables?

ERIC Educational Resources Information Center

Braithwaite, Valerie

1996-01-01

Examines Lawton, Kleban, Moss, Rovine, and Glickman's (1989) caregiving appraisal through a principal components analysis and varimax rotation of a data set based on in-depth quantitative interviews with 144 caregivers. Five caregiving appraisal dimensions are identified: task load caregiving, dysfunctional caregiving, intimacy and love, social…

Family Dysfunction and Teenage Suicide Attempts.

ERIC Educational Resources Information Center

Koopmans, Matthijs

One of the most persistent findings in the literature on suicidal behavior in adolescence is its association with the characteristics of the adolescent's family. Although empirical work clearly indicates that the family is a critical variable to consider in the study of teenage suicidal behavior, it is less clear how particular family features…

Transient receptor potential cation channel A1 (TRPA1) mediates changes in heart rate variability following a single exposure to acrolein in mice

EPA Science Inventory

The data show that a single exposure to acrolein causes autonomic imbalance in mice through the TRPA1 sensor and subsequent cardiac dysfunction. Human and animal studies have shown that short-term air pollution exposure causes...

The Social Misperception Syndrome in Children with Learning Disabilities: Social Causes versus Neurological Variables.

ERIC Educational Resources Information Center

Spafford, Carol Sullivan; Grosser, George S.

1993-01-01

This article synthesizes the research defining social problems of some children with learning disabilities, especially the role of communication skills deficits. Traditional emphases on family dysfunction, school failure, or personality disturbances are seen to be negated by research which suggests that neural aberrations trigger deficient…

Detecting Virus Exposure During the Pre Symptomatic Incubation Period Using Physiological Data (with Supplementary Materials)

DTIC Science & Technology

2016-06-30

processed the data to reduce short-term variability and normalize diurnal variations , then provided these to a supervised random forest...complementary hypothesis concerning the pathogenesis of multiple organ dysfunction syndrome. Crit Care Med 24: 1107-1116. 61. Goldberger AL, Peng CK

Topographic analysis of individual activation patterns in medial frontal cortex in schizophrenia

PubMed Central

Stern, Emily R.; Welsh, Robert C.; Fitzgerald, Kate D.; Taylor, Stephan F.

2009-01-01

Individual variability in the location of neural activations poses a unique problem for neuroimaging studies employing group averaging techniques to investigate the neural bases of cognitive and emotional functions. This may be especially challenging for studies examining patient groups, which often have limited sample sizes and increased intersubject variability. In particular, medial frontal cortex (MFC) dysfunction is thought to underlie performance monitoring dysfunction among patients with previous studies using group averaging to have yielded conflicting results. schizophrenia, yet compare schizophrenic patients to controls To examine individual activations in MFC associated with two aspects of performance monitoring, interference and error processing, functional magnetic resonance imaging (fMRI) data were acquired while 17 patients with schizophrenia and 21 healthy controls performed an event-related version of the multi-source interference task. Comparisons of averaged data revealed few differences between the groups. By contrast, topographic analysis of individual activations for errors showed that control subjects exhibited activations spanning across both posterior and anterior regions of MFC while patients primarily activated posterior MFC, possibly reflecting an impaired emotional response to errors in schizophrenia. This discrepancy between topographic and group-averaged results may be due to the significant dispersion among individual activations, particularly among healthy controls, highlighting the importance of considering intersubject variability when interpreting the medial frontal response to error commission. PMID:18819107

Severe myopathy in mice lacking the MEF2/SRF-dependent gene leiomodin-3

PubMed Central

Cenik, Bercin K.; Garg, Ankit; McAnally, John R.; Shelton, John M.; Richardson, James A.; Bassel-Duby, Rhonda; Olson, Eric N.; Liu, Ning

2015-01-01

Maintenance of skeletal muscle structure and function requires a precise stoichiometry of sarcomeric proteins for proper assembly of the contractile apparatus. Absence of components of the sarcomeric thin filaments causes nemaline myopathy, a lethal congenital muscle disorder associated with aberrant myofiber structure and contractility. Previously, we reported that deficiency of the kelch-like family member 40 (KLHL40) in mice results in nemaline myopathy and destabilization of leiomodin-3 (LMOD3). LMOD3 belongs to a family of tropomodulin-related proteins that promote actin nucleation. Here, we show that deficiency of LMOD3 in mice causes nemaline myopathy. In skeletal muscle, transcription of Lmod3 was controlled by the transcription factors SRF and MEF2. Myocardin-related transcription factors (MRTFs), which function as SRF coactivators, serve as sensors of actin polymerization and are sequestered in the cytoplasm by actin monomers. Conversely, conditions that favor actin polymerization de-repress MRTFs and activate SRF-dependent genes. We demonstrated that the actin nucleator LMOD3, together with its stabilizing partner KLHL40, enhances MRTF-SRF activity. In turn, SRF cooperated with MEF2 to sustain the expression of LMOD3 and other components of the contractile apparatus, thereby establishing a regulatory circuit to maintain skeletal muscle function. These findings provide insight into the molecular basis of the sarcomere assembly and muscle dysfunction associated with nemaline myopathy. PMID:25774500

Direct and Indirect Effects of PM on the Cardiovascular System

PubMed Central

Nelin, Timothy D.; Joseph, Allan M.; Gorr, Matthew W.; Wold, Loren E.

2011-01-01

Human exposure to particulate matter (PM) elicits a variety of responses on the cardiovascular system through both direct and indirect pathways. Indirect effects of PM on the cardiovascular system are mediated through the autonomic nervous system, which controls heart rate variability, and inflammatory responses, which augment acute cardiovascular events and atherosclerosis. Recent research demonstrates that PM also affects the cardiovascular system directly by entry into the systemic circulation. This process causes myocardial dysfunction through mechanisms of reactive oxygen species production, calcium ion interference, and vascular dysfunction. In this review, we will present key evidence in both the direct and indirect pathways, suggest clinical applications of the current literature, and recommend directions for future research. PMID:22119171

Comparing Sildenafil alone vs. Sildenafil plus brief couple sex therapy on erectile dysfunction and couples' sexual and marital quality of life: a pilot study.

PubMed

Aubin, Sylvie; Heiman, Julia R; Berger, Richard E; Murallo, A V; Yung-Wen, Liu

2009-01-01

Treatment options for managing erectile dysfunction (ED) include medical and psychological interventions. The present study examined the effectiveness of a drug-only vs. combined treatment approach on erectile function as well as other domains of sexual function and cognition, couple intimacy and adaptation, and treatment satisfaction. Couples with ED were randomly assigned to either Viagra-only (VO) or Viagra plus sex therapy (VST). Sexual and relationship variables were measured at specific time points. Despite limitations, study findings extend previous conclusions and provide empirical support for the effectiveness and satisfaction with the combined treatment approach for treating men with ED of mixed etiology.

[Weight loss in overweight or obese patients and family functioning].

PubMed

Jaramillo-Sánchez, Rosalba; Espinosa-de Santillana, Irene; Espíndola-Jaramillo, Ilia Angélica

2012-01-01

to determine the association between weight loss and family functioning. a cohort of 168 persons with overweight or obesity from 20-49 years, either sex, with no comorbidity was studied at the nutrition department. A sociodemographic data was obtained and FACES III instrument to measure family functioning was applied. At the third month a new assessment of the body mass index was measured. Descriptive statistical analysis and relative risk were done. obesity presented in 50.6 %, 59.53 % of them did not lose weight. Family dysfunction was present in 56.6 % of which 50 % did not lose weight. From 43.4 % of functional families, 9.52 % did not lose weight (p = 0.001). The probability or risk of not losing weight was to belong to a dysfunctional family is 4.03 % (CI = 2.60-6.25). A significant association was found between the variables: weight loss and family functioning. Belonging to a dysfunctional family may be a risk factor for not losing weight.

Dysfunctional beliefs in group and individual cognitive behavioral therapy for obsessive compulsive disorder.

PubMed

Jónsson, Hjalti; Hougaard, Esben; Bennedsen, Birgit E

2011-05-01

The primary aim of the study was to investigate dysfunctional beliefs in the form of inflated responsibility (IR) and thought action fusion (TAF) as predictive and mediating variables in individual (n=33) and group (n=37) cognitive behavioral therapy (CBT) for obsessive compulsive disorder (OCD). IR and TAF declined significantly during CBT, and the decline was positively associated with change in OCD symptoms. However, when controlling for change in depressive symptoms, only change in IR remained significantly associated with OCD symptom change. The moral subtype of TAF predicted poorer treatment outcome, but only in group CBT. Both treatments produced a similar amount of change in the dysfunctional beliefs. The results provide some, preliminary evidence that IR, but not TAF, may be specifically involved in the change mechanisms of both individual and group CBT for OCD, although the design of the study with pre- and post-therapy measurements only does not allow for a causal mediator analysis. Copyright © 2010 Elsevier Ltd. All rights reserved.

Unequal access and unmet need: neurotic disorders and the use of primary care services.

PubMed

Bebbington, P; Meltzer, H; Brugha, T; Farrell, M; Jenkins, R; Ceresa, C; Lewis, G

2003-01-01

In this paper we use data from the National Survey of Psychiatric Morbidity to examine how many people with neurotic disorders receive professional evaluation, and how this is affected by clinical and sociodemographic differences. We hypothesized that psychiatric symptoms and attendant dysfunctions would both have an effect on contacting, and that key demographic variables would not. The household component of the British National Surveys of Psychiatric Morbidity was based on a random sample of >10,000 subjects. Lay interviewers using the CIS-R established psychiatric symptoms and ICD-10 diagnosis. Social dysfunction was tapped by asking about difficulties in performing seven types of everyday activity. We examined symptom score, ADL deficit score, and demographic variables in relation to contact with primary care physicians for psychiatric symptoms. The major determinant of contacting a primary care physician was severity, mainly due to the level of psychiatric symptoms, but with an independent contribution from social dysfunction. There were also significant contributions from sex, marital status, age, employment status, and whether the subject had a physical condition as well. The major influence on whether people seek the help of their family doctors for mental health problems is the severity of disorder. Although there are some social inequalities in access to family doctors, these are less important. The most salient finding from our study is that even people suffering from high levels of psychiatric symptoms very often do not have contact with professionals who might help them.

Pharmacokinetic variations in cancer patients with liver dysfunction: applications and challenges of pharmacometabolomics.

PubMed

Aboel Dahab, Ali; El-Hag, Dhia; Moutamed, Gamal M; Aboel Dahab, Sarah; Abuknesha, Ramadan; Smith, Norman W

2016-09-01

In cancer patients, pharmacokinetic variations between individuals and within individuals due to impairments in organs' function and other reasons such as genetic polymorphisms represent a major problem in disease management, which can result in unpredictable toxicity and variable antineoplastic effects. Addressing pharmacokinetic variations in cancer patients with liver dysfunction and their implications on anticancer and analgesic drugs, in addition to the use of advanced analytical techniques such as metabolomics and pharmacometabolomics, to monitor altered kinetic and discover metabolic biomarkers during therapeutic intervention will help in understanding and reducing pharmacokinetic variations of drugs in cancer patients as a step forward towards personalised medicine. Reviewing published literature addressing and/or related to complications resulting from altered pharmacokinetics (PKs) in cancer patients with liver dysfunction, anticancer and analgesic drugs, evaluating recent advances of pharmacokinetic detection using metabolomics/pharmacometabolomics and the challenges that are currently facing these techniques. The current situation presents a pressing need to reduce pharmacokinetic variations of drugs in cancer patients. Although most of the omics technologies are not entirely focussed on the study of pharmacokinetic variations and some studies are met with uncertainty, the use of pharmacometabolomics combined with other omics technology such as pharmacogenomics can provide clues to personalised cancer treatments by providing useful information about the cancer patient's response to medical interventions via identification of patients' dependent variables, understanding of correlations between individuals and population PKs, and therapy outcomes to achieve optimum therapeutic effects with minimum toxicity. We also propose an approach for PKs' evaluation using pharmacometabolomics.

Subclinical thyroid dysfunction and psychiatric disorders: cross-sectional results from the Brazilian Study of Adult Health (ELSA-Brasil).

PubMed

Benseñor, Isabela M; Nunes, Maria Angélica; Sander Diniz, Maria de Fátima; Santos, Itamar S; Brunoni, André R; Lotufo, Paulo A

2016-02-01

To evaluate the association between subclinical thyroid dysfunction and psychiatric disorders using baseline data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Cross-sectional study. The study included 12 437 participants from the ELSA-Brasil with normal thyroid function (92·8%), 193 (1·4%) with subclinical hyperthyroidism and 784 (5·8%) with subclinical hypothyroidism, totalling 13 414 participants (50·6% of women). The mental health diagnoses of participants were assessed by trained raters using the Clinical Interview Schedule - Revised (CIS-R) and grouped according to the International Classification of Diseases 10 (ICD-10). Thyroid dysfunction was assessed using TSH and FT4 as well as routine use of thyroid hormones or antithyroid medications. Logistic models were presented using psychiatric disorders as the dependent variable and subclinical thyroid disorders as the independent variable. All logistic models were corrected for multiple comparisons using Bonferroni correction. After multivariate adjustment for possible confounders, we found a direct association between subclinical hyperthyroidism and panic disorder odds ratio [OR], 2·55; 95% confidence Interval (95% CI), 1·09-5·94; and an inverse association between subclinical hypothyroidism and generalized anxiety disorder (OR, 0·75; 95% CI, 0·59-0·96). However, both lost significance after correction for multiple comparisons. Subclinical hyperthyroidism was positively associated with panic disorder and negatively associated with anxiety disorder, although not significant after adjustment for multiple comparisons. © 2015 John Wiley & Sons Ltd.

Human Movement Variability, Nonlinear Dynamics, and Pathology: Is There A Connection?

PubMed Central

Stergiou, Nicholas; Decker, Leslie M.

2011-01-01

Fields studying movement generation, including robotics, psychology, cognitive science and neuroscience utilize concepts and tools related to the pervasiveness of variability in biological systems. The concept of variability and the measures for nonlinear dynamics used to evaluate this concept open new vistas for research in movement dysfunction of many types. This review describes innovations in the exploration of variability and their potential importance in understanding human movement. Far from being a source of error, evidence supports the presence of an optimal state of variability for healthy and functional movement. This variability has a particular organization and is characterized by a chaotic structure. Deviations from this state can lead to biological systems that are either overly rigid and robotic or noisy and unstable. Both situations result in systems that are less adaptable to perturbations, such as those associated with unhealthy pathological states or absence of skillfulness. PMID:21802756

International pediatric sepsis consensus conference: definitions for sepsis and organ dysfunction in pediatrics.

PubMed

Goldstein, Brahm; Giroir, Brett; Randolph, Adrienne

2005-01-01

Although general definitions of the sepsis continuum have been published for adults, no such work has been done for the pediatric population. Physiologic and laboratory variables used to define the systemic inflammatory response syndrome (SIRS) and organ dysfunction require modification for the developmental stages of children. An international panel of 20 experts in sepsis and clinical research from five countries (Canada, France, Netherlands, United Kingdom, and United States) was convened to modify the published adult consensus definitions of infection, sepsis, severe sepsis, septic shock, and organ dysfunction for children. Consensus conference. This document describes the issues surrounding consensus on four major questions addressed at the meeting: a) How should the pediatric age groups affected by sepsis be delineated? b) What are the specific definitions of pediatric SIRS, infection, sepsis, severe sepsis, and septic shock? c) What are the specific definitions of pediatric organ failure and the validity of pediatric organ failure scores? d) What are the appropriate study populations and study end points required to successfully conduct clinical trials in pediatric sepsis? Five subgroups first met separately and then together to evaluate the following areas: signs and symptoms of sepsis, cell markers, cytokines, microbiological data, and coagulation variables. All conference participants approved the final draft of the proceedings of the meeting. Conference attendees modified the current criteria used to define SIRS and sepsis in adults to incorporate pediatric physiologic variables appropriate for the following subcategories of children: newborn, neonate, infant, child, and adolescent. In addition, the SIRS definition was modified so that either criteria for fever or white blood count had to be met. We also defined various organ dysfunction categories, severe sepsis, and septic shock specifically for children. Although no firm conclusion was made regarding a single appropriate study end point, a novel nonmortality end point, organ failure-free days, was considered optimal for pediatric clinical trials given the relatively low incidence of mortality in pediatric sepsis compared with adult populations. We modified the adult SIRS criteria for children. In addition, we revised definitions of severe sepsis and septic shock for the pediatric population. Our goal is for these first-generation pediatric definitions and criteria to facilitate the performance of successful clinical studies in children with sepsis.

The friction and wear properties of sputtered hard refractory compounds

NASA Technical Reports Server (NTRS)

Brainard, W. A.

1978-01-01

Several refractory silicide, boride, and carbide coatings were examined. The coatings were applied to type 440C steel surfaces by radio-frequency sputtering. The friction and wear properties of the coatings were found to be related to stoichiometry and impurity content of the bulk coating as well as the degree of interfacial adherence between coating and substrate. Bulk coating stoichiometry could to a large extent be controlled by the application of a negative bias voltage during deposition. Adherence was promoted by the formation of an oxidized layer at the interface. Deliberate preoxidizing of the 440C produced enhanced adherence for many compounds which are related to the formation of a mixed oxide transition region.

Low NO sub x heavy fuel combustor concept program

NASA Technical Reports Server (NTRS)

Russell, P.; Beal, G.; Hinton, B.

1981-01-01

A gas turbine technology program to improve and optimize the staged rich lean low NOx combustor concept is described. Subscale combustor tests to develop the design information for optimization of the fuel preparation, rich burn, quick air quench, and lean burn steps of the combustion process were run. The program provides information for the design of high pressure full scale gas turbine combustors capable of providing environmentally clean combustion of minimally of minimally processed and synthetic fuels. It is concluded that liquid fuel atomization and mixing, rich zone stoichiometry, rich zone liner cooling, rich zone residence time, and quench zone stoichiometry are important considerations in the design and scale up of the rich lean combustor.

Copper(II) ions and the Alzheimer's amyloid-β peptide: Affinity and stoichiometry of binding

NASA Astrophysics Data System (ADS)

Tõugu, Vello; Friedemann, Merlin; Tiiman, Ann; Palumaa, Peep

2014-10-01

Deposition of amyloid beta (Aβ) peptides into amyloid plaques is the hallmark of Alzheimer's disease. According to the amyloid cascade hypothesis this deposition is an early event and primary cause of the disease, however, the mechanisms that cause this deposition remain elusive. An increasing amount of evidence shows that the interactions of biometals can contribute to the fibrillization and amyloid formation by amyloidogenic peptides. From different anions the copper ions deserve the most attention since it can contribute not only toamyloid formation but also to its toxicity due to the generation of ROS. In this thesis we focus on the affinity and stoichiometry of copper(II) binding to the Aβ molecule.

Heat Treatments of ZnSe Starting Materials for Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Palosz, W.; Feth, S.; Lehoczky, S. L.

1998-01-01

The effect of different heat treatments on stoichiometry and residual gas pressure in ZnSe physical vapor transport system was investigated. The dependence of the amount and composition of the residual gas on various heat treatment procedures is reported. Heat treatment of ZnSe starting materials by baking under the condition of dynamic vacuum to adjust its stoichiometry was performed and the effectiveness of the treatment was confirmed by the measurements of the partial pressure of Se2, P(sub Se2), in equilibrium with the heat treated samples. Optimum heat treatment procedures on the ZnSe starting material for the physical vapor transport process are discussed and verified experimentally.