Irreversible Loss Rate Research Articles

Circumlimbal suture and laser burns: Comparison between two different chronic glaucoma models.

Glaucoma is a multifactorial optic neuropathy with a high rate of irreversible visual loss, and its pathogenesis is complex and still unclear. Elevated intraocular pressure (IOP) is well recognized as the sole modifiable risk factor for the development of glaucoma in the majority of cases. This study aims to compare 2 different methods of inducing chronic ocular hypertension by circumlimbal suture or by laser burns in degree and lasting time of the IOP, different status of the retina and retinal ganglion cells (RGCs), and changes of the microstructure of neurons. The chronic ocular hypertension models were induced by 2 different ways. One kind of the models was built by unilateral circumlimbal suture (10/0) implantation (suture group), another kind of model was built by laser burns at trabecular meshwork and episcleral veins (laser group). The untreated contralateral eye served as the control group. Changes in IOP were observed and regularly monitored in the 2 groups of rats. HE staining was applied to observe the retinal and optic nerve pathology. Transmission electron microscope (TEM) was used to observe the mitochondrial morphology. RGCs were specifically labeled with Brn3b antibody and counted. The expression of caspase-3 was detected by Western blotting to clarify the apoptosis of RGCs. Compared with the control group, IOP were significantly increased in the suture group and the laser group (both P<0.05). The suture group induced a 1.5-fold elevation of IOP, and sustained for 8 weeks. The laser group induced a 2-fold elevation of IOP for 12 weeks. Both methods could cause RGCs loss (both P<0.05), which were verified by pathology and immune staining of Brn3b. The expressions of caspase-3 were also increased (both P<0.05). The mitochondrial morphology became more fragment, which changed from long shape to round and small one under TEM in 2 models. For comparison, the pathology changes of retinal structure in suture group were not obviously than those in the laser group. Circumlimbal suture can build an effective model of chronic elevated IOP and induce glaucomatous pathologic changes similar to those in the laser photocoagulation, but the pathologic changes are milder than those in laser photocoagulation. Compare with translimbal laser photocoagulation, equipment and skill demand for circumlimbal suture is less.

Decoupling pressure effects in plating and stripping of lithium metal anodes

Lithium metal anodes hold great promise in realizing high-energy-density secondary batteries. However, improper plating and stripping are susceptible to forming lithium dendrites and dead lithium, causing battery capacity degradation. During the full cycle of plating and stripping, mechanical stress intertwines with electrochemical transfer and reactions. The mechanism of pressure effects in plating and stripping behavior remains ambiguous. Therefore, we develop an electro-chemo-mechanical phase-field model to describe the plating/stripping behavior, with key parameters quantifying dendrite and dead lithium formation, revealing that pressure can optimize electroplating morphology and converse stripping pattern. We successfully decouple the pressure effects from plating and stripping, elaborate the impact of plating and stripping pressure on battery capacity decay, and construct a phase diagram of irreversible capacity loss rate for plating and stripping pressure, clarifying the relevance of pressure and capacity loss. Moreover, we summarize and illustrate the dependent relationship between pressure-induced electroplated morphology and stripping patterns. This work demonstrates and decouples a critical pressure mechanism on lithium plating and stripping, providing new insights into the optimization and modulation of pressure management strategies for lithium metal batteries.

Experimental study on the permeability variation of sandstone at cyclic stress: Implication for underground gas storage

Underground gas storage (UGS) of CH4 and H2 is an economical and reliable solution for large-scale energy storage. Cyclic gas injection-withdrawal of UGS can induce periodical stress perturbation in reservoirs, which may significantly influence the permeability of the reservoir. Understanding the effect of cyclic stress on the permeability evolution in reservoirs is important for optimizing the injection-withdrawal strategy. Therefore, the alterations of rock mechanical properties, permeability and its stress sensitivity of a sandstone sample from UGS under cyclic stress were obtained by experiments. Results indicated that the stress-strain curves of the sandstone under cyclic stress was not coincided and formed a hysteresis loop, and with the increasing cycles, the hysteresis loop transformed from sparse to dense. With the increase of cycles, the elastic modulus (E) in the sandstone first increased, then decreased slightly, and finally almost remained constant, while the Poisson's ratio (v) increased at early cycles and then nearly remain unchanged. The evolution of permeability of sandstone can be separated into three stages: rapid decline stage (1-10th cycles), slight decline stage (10-30th cycles), and almost stable and unchanged stage (30-50th cycles), which shows good consistent with the deformation behaviors of sandstone. Correspondingly, the change of compressibility coefficient in the sandstone can also be divided into three stages, including the rapid decline stage (1-10th cycles), slight increase stage (10-30th cycles) and slow decline stage (30-50th cycles), which shows an opposite variation trend with the rock mechanical properties in sandstone. For a certain cyclic stress loading-unloading, the permeability and compression coefficient in the sandstone at minimum stress were larger than those at maximum stress. The irreversible permeability loss rate of the sandstone showed good consistent with the changes of stress sensitivity coefficient caused by cyclic stress.

TiO2 Hollow Spheres With Flower-Like SnO2 Shell as Anodes for Lithium-Ion Batteries

SnO2 is a promising anode material for lithium-ion batteries due to its high theoretical specific capacity and low operation voltage. However, its poor cycling performance hinders its commercial application. In order to improve the cycling stability of SnO2 electrodes, novel flower-like SnO2/TiO2 hollow spheres were prepared by facile hydrothermal method using carbon spheres as templates. Their flower-like shell and mesoporous structure highlighted a large specific surface area and excellent ion migration performance. Their TiO2 hollow sphere matrix and 2D SnO2 nano-flakes ensured good cycle stability. The electrochemical measurements indicated that novel flower-like SnO2/TiO2 hollow spheres delivered a high specific capacity, low irreversible capacity loss and superior rate performance. After 1,000 cycles at current densities of 200 mA g−1, the capacity of the flower-like SnO2/TiO2 hollow spheres was still maintained at 720 mAh g−1. Their rate capacity reached 486 mAh g−1 when the current densities gradually increase to 2,000 mA g−1.

A small-scale experimental study of CO2 enhanced injectivity methods of the high-rank coal

The attenuation of CO2 injectivity has become the biggest technical barrier for the application of CO2 enhanced coalbed methane recovery (CO2-ECBM). Commonly, the intermittent CO2 injection, N2 displacing CO2 and pre-fracturing are the potential CO2 enhanced injectivity methods for coal reservoirs, but their mechanism and effectiveness remain to be clarified. This paper thus conducted small-scale experiments to simulate the working process of these engineering measures by an independently developed experimental device. Results show that the CO2 injectivity of coal is remarkably improved by the intermittent injection mode since the CO2 injection time is increased by folds and the loss of reservoir pressure can be complemented in time. The N2 displacing CO2 method promotes the desorption of CO2 and reduces the swelling strain, with the result that the permeability of coal is improved by 74.82% and 64.95% compared with the methods of the primary subcritical CO2 (SubCO2) and supercritical CO2 (ScCO2) injection. However, the permeability reduces again with the secondary CO2 injection. The permeability of the coal sample after pre-fracturing is averagely improved by 1–2 orders of magnitude, the irreversible permeability loss rate, average stress sensitivity coefficient and the permeability loss rate due to adsorption are averagely reduced by 95.885%, 61.538% and 96.297%, respectively. This indicates that the permeability of coal after pre-fracturing is no longer sensitive to both the effective stress and ScCO2 adsorption, the injectivity is thus improved and stable. The CO2 enhanced injectivity effects of the intermittent CO2 injection, the N2 displacing CO2 and the pre-fracturing are various, which thus can be selected individually or jointly to improve the CO2 injectivity according to the reservoir physical properties and geological conditions. This research deepens the understanding of the functional mechanism of CO2 enhanced injectivity methods and provides some guidance for their selection and application in engineering practices.

Investigation of Seepage Law in Broken Coal and Rock Mass under Different Loading and Unloading Cycles

In order to study the seepage law of broken coal seams affected by multiple mining operations, a cyclic loading and unloading seepage experiment was carried out. For this purpose, the seepage law of broken samples with different coal and rock ratios was analyzed. The results of our study demonstrated that the permeability of the broken samples showed a decreasing trend. After a loading and unloading cycle, the permeability was significantly reduced. The impact of the loading stage on the broken sample was higher than that of the unloading phase. When the proportion of coal particles in the mixed samples of broken coal and rock was 50%, the irreversible permeability loss rate and permeability loss rate of the samples showed the highest values. The irreversible permeability loss rate and permeability loss rate of the broken rock mass were greater than those displayed by the broken coal mass. The stress sensitivity coefficient curves of the 5 types of broken coal and rock masses presented the same changes. The stress sensitivity coefficient curve and the effective stress displayed an exponential relationship.

Stress sensitivity of formation during multi-cycle gas injection and production in an underground gas storage rebuilt from gas reservoirs

Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability. A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed, and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed. Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles. The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress. The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress. With the increase of cycle number of net stress variation, the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress. The lower the reservoir permeability, the greater the irreversible permeability loss rate, the stronger the cyclic stress sensitivity, and the higher the stress sensitivity index of the reservoir, the stronger the reservoir stress sensitivity. The gas zones with permeability lower than 0.3×10−3 μm2 are not suitable as gas storage regions. Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.

Entropy and exergy analysis and optimization of the VVER nuclear power plant with a capacity of 1000 MW using the firefly optimization algorithm

A light water nuclear Reactor has been exergy analyzed, and the rate of irreversible exergy loss and exergy destruction is calculated for each of its components. The ratio of these losses compared to the total input exergy loss is calculated, which shows that most irreversible losses occur in the reactors, turbines, steam generators, respectively, as well as in the downstream operations. The main aim of this paper is to optimize the power plant using an innovative firefly algorithm and then to propose a novel strategy to improve the overall performance of the plant. As shown in the results, the exergy destruction rate of the plant decreased by 1.18% using the firefly method, and the exergy efficiency of the plant reached 29.3% comparing to the operational amount of 28.99%. Also, the results of the firefly optimization process compared to the Genetic algorithm and gravitational search algorithm to study the accuracy of the model for exergy analysis fitness problems in the power plants and the results of this comparison has shown that the results are nearly similar in the mentioned methods. However, the firefly is faster and more accurate in limited iterations.

Changes in the anisotropic permeability of low-rank coal under varying effective stress in Fukang mining area, China

Fractures are coalbed methane (CBM) migration pathways and key factors in determining coal reservoir permeability. During the depletion of CBM wells, the increase of effective stress with water pumping and gas desorption will affect gas production by changing reservoir permeability. However, the current understanding of the impacts of fracturing in different directions on CBM recovery is inadequate. In this work, we collected 4 types of cubic coal samples (samples cut parallel to face and butt cleats and perpendicular to the bedding plane) from the Fukang mining area in China to investigate the anisotropic characteristics of P-wave velocity, fractures and permeability under varying effective stresses from 3.5 to 8.5 MPa in the laboratory. The results indicate that the permeability exponentially decreased with increasing P-wave velocity. The acoustic wave velocities significantly decreased from direction perpendicular to the bedding plane to the butt cleat direction to the face cleat direction. However, the fracture aperture exhibited the opposite trend. The maximum acoustic wave velocities ratios of the perpendicular bedding plane direction to the parallel bedding plane direction are 1.12, 1.23, 1.05 and 1.15 for sample LY, DH, XG and QM, respectively. However, the ratios of butt cleat direction to face cleat direction are 1.23, 1.21, 1.01 and 1.07. A good coupling effect was detected between the aperture, porosity, connectivity, and permeability. The permeability decreased exponentially as the effective stress increased in the selected coal samples. Under the 3.5–6.5 MPa effective stress conditions, the permeability decreased rapidly, and from 6.5 to 8.5 MPa, the permeability decreased more slowly. Contrary to the permeability loss rate (PLR), the stress sensitivity coefficient and dimensionless permeability parallel to the bedding plane were greater than perpendicular to the bedding plane. The effective stress returned from 8.5 MPa to 3.5 MPa, and the permeability rebounded but did not fully recover. The irreversible permeability loss rate (IPLR) showed that the permeability was restored the least in the direction perpendicular to the bedding plane. The maximum IPLR ratios of the perpendicular to the bedding plane direction to the parallel bedding plane direction are 3.39, 5.34, 1.86 and 23.00 in sample LY, DH, XG and QM, respectively. According to the study of anisotropic fractures and permeability, multi-lateral well is recommended as the appropriate well type to obtain the optimal CBM recovery effect.

The Influence of the Platinum Loading and the Ionomer to Carbon Ratio on the Durability of the PEMFC

Cost and durability are the major barriers to the success of the Proton Exchange Membrane Fuel Cells (PEMFCs), and reducing the platinum loading of the catalyst layer could reduce the cost of the device. Thus, in this work, long-term durability tests in constant-current mode were performed using single-cells of 25 cm2 with Membrane Electrode Assemblies (MEAs) prepared with 20% Pt/C (BASF) catalyst and electrodes with platinum loadings of 0.4 and 0.1 mgPt.cm-2. Different ionomer to carbon ratios were also studied with the electrodes containing 0.1 mgPt.cm-2 of catalyst loading. To characterize the electrochemical and structural properties of the MEAs, cyclic voltammograms, electrochemical impedance spectroscopy and field-emission scanning electron microscopy were utilized before and after the long-term durability tests. Concerning the platinum loading, the electrodes prepared with 0.1 mg Pt cm-2 have lost proportionally more electrochemical surface area than the ones prepared with 0.4 mg Pt cm-2 but at the same time, the electrodes with the lowest platinum loading presented lower irreversible performance loss rate when using higher ionomer to carbon ratio. The analyses made by several electrochemical techniques have indicated that the raise of the ohmic and mass transport resistances are the factors that most contribute to the irreversible performance loss, meanwhile the charge transport resistance due to the electrodes flooding is the main responsible for the reversible performance loss. The proportion of ionomer in the catalytic layer was studied and it was possible to infer that the highest ionomer proportion studied has contributed to mitigate the MEA degradation, although it facilitates the occurrence of flooding in the electrodes. Finally, it was observed that the quality of the contact formed between the electrodes and the membrane has remarkable influence on the PEMFCs durability.

Performance study on a single-screw compressor for a portable natural gas liquefaction process

Portable natural gas liquefaction devices are widely used to exploit unconventional natural gas resources and one of key components is a compressor. In this paper, a new natural gas liquefaction process is simulated and optimized and a single-screw compressor with 200 mm diameter is designed to be applied in this process. To verify the performance of the single-screw compressor, an experimental system was set up and performance parameters were studied, including volumetric efficiency, specific power rate, shaft efficiency, irreversible loss rate and cooling efficiency of the lubricating oil. The influence of the lubricating oil on the volumetric efficiency was also observed. Furthermore, the impact of actual compressor performance on the liquefaction process was also analyzed. The results indicate that the performance of the compressor changes greatly when it operates deviating from its design condition. The maximum volumetric efficiency, shaft efficiency, irreversible loss rate and cooling efficiency of the lubricating oil are 0.91, 0.64, 0.56 and 0.22, respectively. The minimum specific power rate is 6.5 kW·(m3·min−1)−1. In addition, the lubricating oil has a good effect of sealing so that the volumetric efficiency can be improved by 10.5%. Considering the actual performance of the single-screw compressor, specific power consumption of the process increases by 43.3%.

Evaluation of reversible and irreversible degradation rates of polymer electrolyte membrane fuel cells tested in automotive conditions

Abstract This work provides single cell durability tests of membrane electrode assemblies in dynamic operation regularly interrupted by recovery procedures for the removal of reversible voltage losses. Degradation rates at different loads in one single test can be determined from these tests. Hence, it is possible to report degradation rates versus current density instead of a single degradation rate value. A clear discrimination between reversible and irreversible voltage loss rates is provided. The irreversible degradation rate can be described by a linear regression of voltage values after the recovery steps. Using voltage values before refresh is less adequate due to possible impacts of reversible effects. The reversible contribution to the voltage decay is dominated by an exponential decay after restart, eventually turning into a linear one. A linear-exponential function is proposed to fit the reversible voltage degradation. Due to this function, the degradation behavior of an automotive fuel cell can be described correctly during the first hours after restart. The fit parameters decay constant, exponential amplitude and linear slope are evaluated. Eventually, the reasons for the voltage recovery during shutdown are analyzed showing that ionomer effects in the catalyst layer and/or membrane seem to be the key factor in this process.

Whole-body and splanchnic amino acid metabolism in sheep during an acute endotoxin challenge.

Supplemented protein or specific amino acids (AA) are proposed to help animals combat infection and inflammation. The current study investigates whole-body and splanchnic tissue metabolism in response to a lipopolysaccharide (LPS) challenge with or without a supplement of six AA (cysteine, glutamine, methionine, proline, serine and threonine). Eight sheep were surgically prepared with vascular catheters across the gut and liver. On two occasions, four sheep were infused through the jugular vein for 20 h with either saline or LPS from Escherichia coli (2 ng/kg body weight per min) in a random order, plus saline infused into the mesenteric vein; the other four sheep were treated with saline or LPS plus saline or six AA infused via the jugular vein into the mesenteric vein. Whole-body AA irreversible loss rate (ILR) and tissue protein metabolism were monitored by infusion of [ring-2H2]phenylalanine. LPS increased (P<0·001) ILR (+17 %), total plasma protein synthesis (+14 %) and lymphocyte protein synthesis (+386 %) but decreased albumin synthesis (-53 %, P=0·001), with no effect of AA infusion. Absorption of dietary AA was not reduced by LPS, except for glutamine. LPS increased the hepatic removal of leucine, lysine, glutamine and proline. Absolute hepatic extraction of supplemented AA increased, but, except for glutamine, this was less than the amount infused. This increased net appearance across the splanchnic bed restored arterial concentrations of five AA to, or above, values for the saline-infused period. Infusion of key AA does not appear to alter the acute period of endotoxaemic response, but it may have benefits for the chronic or recovery phases.

Durability Testing of Polymer Electrolyte Fuel Cells Under Stationary and Automotive Conditions

Our presentation focuses on durability testing and degradation of fuel cells. A major motivation of our work is the lack of common description procedures and determination approaches of voltage losses in durability tests of fuel cell for both stationary and automotive applications; this issue leads to severe difficulties in the comparison of results obtained by different institutions or within different projects, especially if only a single value for the degradation rate is reported. In this context, special attention is devoted to the discrimination between so called reversible and irreversible voltage losses. The first are permanent and determine the maximum lifetime of a fuel cell. The latter strongly depend on the chosen operation conditions and can be recovered by specific procedures. In order so systematically address voltage losses we have performed single cell durability measurements of several hundreds of hours in 25 cm2 lab-scale cells using different test protocols containing regular refresh procedures (soak time) allowing to distinguish between reversible and irreversible losses. Furthermore, operation strategies to minimize reversible degradation without using the time consuming refresh procedures are provided. To test the refresh procedures and analyze their effect on cell performance, parameters such as duration of the soak time steps have been varied. Between these refresh steps the cells were typically operated for 50 to 150 h. As samples conventional 5-layer membrane electrode assemblies were used with PFSA membranes, Pt-based catalysts and hydrophobized carbon fiber substrates with micro porous layers as GDLs. For in-situ diagnosis of the operated cells polarization curves, electrochemical impedance spectra, and cyclic voltammograms were recorded in order to determine the impact of the operation conditions and the refresh procedures on degradation. The interpretation of the degradation of the measured membrane electrode assemblies is supported by post-mortem analysis using physical characterization techniques. Additionally, we provide possible approaches to quantitatively determine irreversible voltage decay rates. For instance, voltage values before or after voltage recovery steps can be used to calculate the irreversible loss rate. The advantages and drawbacks of different approaches are discussed. One clear conclusion is that short time tests in the range of 100 hour are not conclusive since this time is too short to make a reliable discrimination between reversible and irreversible losses; also, the decay rate of reversible loss observed after each refresh step increases substantially upon long time operation independent on the type of the refresh procedure. In summary, in our presentation strategies for determination of fuel cell voltages loss rates are compared, evaluated and assessed according to their suitability to distinguish between reversible and irreversible degradation rates; a description of voltage loss rates is proposed. Moreover, operation strategies to minimize reversible degradation are provided. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for Fuel Cell and Hydrogen Joint Technology Initiative under Grant No. 621216 (SecondAct) and No. 303452 (Impact).

The impact of effective stress and gas slippage on coal permeability under cyclic loading

The determination of the effective stress coefficient of porous media (such as coal) remains a controversial issue. The purpose of this paper is to determine the effective stress coefficient of coal during gas penetration and to investigate the impact of effective stress and gas slippage on coal permeability under cyclic loading conditions. Analyzing the evolution law of coal anisotropic permeability with effective stress allows the deformation characteristics of the coal's internal structure, such as cleat or bedding, to be studied. The effective stress coefficient of long flame coal is obtained through modified permeability models based on experimental data. Test results show that the slippage effect significantly influences the permeability of coal samples, specifically in the range of low pore gas pressure, and that the effect of gas slippage is larger than that of effective stress. Permeability decreases gradually when effective stress increases, but it increases during unloading, and ascending and descending curves show significant irreversibility of permeability. Moreover, PLR (permeability loss rate) and IPLR (irreversible permeability loss rate) results indicate that the influence of effective stress on permeability perpendicular to bedding is greater than that of permeability parallel to bedding and that the ability of the cleat to resist deformation induced by effective stress is weaker than that of bedding. Under identical pressure conditions, the cleat shows more vulnerability and produces larger plastic deformation.

Dietary Amino Acid Deficiency Reduces the Utilization of Amino Acids for Growth in Growing Pigs after a Period of Poor Health

Background: During immune system activation, partitioning of amino acids (AAs) changes between protein gain and use by the immune system.Objective: We determined the effects of health status and dietary AA deficiency on nitrogen retention and AA utilization in pigs.Methods: Barrows (55 d of age) were obtained from good health (GH, n = 14) or poor health (PH, n = 14) status farms and allocated to a diet either adequate in essential amino acids (Adq) or 25% deficient in Met + Cys, Thr, and Trp (Def). Nitrogen balance was measured and AA irreversible loss rates (ILRs) were measured after an intravenous bolus of U-13C–labeled L-AAs.Results: On arrival at the experimental facilities, the PH pigs had 14% lower serum albumin and 50% greater serum haptoglobin and blood leukocyte counts than the GH pigs (P < 0.01), but the PH pigs showed signs of recovery during the trial. Total tract nitrogen digestibility was 3 percentage points lower in the PH pigs (P < 0.01). The PH-Adq pigs had compensatory body weight gain after arrival, coinciding with 7% greater nitrogen retention (P < 0.01) in the PH pigs than in the GH pigs. The PH pigs had a 24% greater ILR for Lys. Health status × diet interactions for Lys (P = 0.07), Val (P = 0.03), and Leu (P = 0.10) pool sizes and a greater urea pool size in the PH pigs (P = 0.01) support the observation that the increase in the ILR of Lys in the PH pigs was related to oxidation when feeding the Def diet, but to synthesis when feeding the Adq diet. Feeding Def diets increased monocyte counts by 30% (P < 0.01).Conclusions: This study illustrates how the competition for AAs between protein synthesis associated with immune system activation and body protein deposition is greater when the dietary supply of Met + Cys, Thr, and Trp is limited in pigs during and after a period of poor health.

Responses in whole-body amino acid kinetics to an acute, sub-clinical endotoxin challenge in lambs.

Some effects of parasitism, endotoxaemia or sepsis can be mitigated by provision of extra protein. Supplemented protein may encompass a metabolic requirement for specific amino acids (AA). The current study investigates a method to identify and quantify the amounts of AA required during inflammation induced by an endotoxin challenge. One of each pair of six twin sheep was infused in the jugular vein for 20 h with either saline (control) or lipopolysaccharide (LPS, 2 ng/kg body weight per min) from Escherichia coli. Between 12 and 20 h a mixture of stable isotope-labelled AA was infused to measure irreversible loss rates. From 16 to 20 h all sheep were supplemented with a mixture of unlabelled AA infused intravenously. Blood samples were taken before the start of infusions, and then continuously over intervals between 14 and 20 h. At 20 h the sheep were euthanised, and liver and kidney samples were taken for measurement of serine-threonine dehydratase (SDH) activity. LPS infusion decreased plasma concentrations of most AA (P<0·05; P<0·10 for leucine and tryptophan), except for phenylalanine (which increased P=0·022) and tyrosine. On the basis of the incremental response to the supplemental AA, arginine, aspartate, cysteine, glutamate, lysine (tendency only), glycine, methionine, proline, serine and threonine were important in the metabolic response to the endotoxaemia. The AA infusion between 16 and 20 h restored the plasma concentrations in the LPS-treated sheep for the majority of AA, except for glutamine, isoleucine, methionine, serine and valine. LPS treatment increased (P<0·02) SDH activity in both liver and kidney. The approach allows quantification of key AA required during challenge situations.

Induced lung inflammation and dietary protein supply affect nitrogen retention and amino acid metabolism in growing pigs.

It is hypothesised that during immune system activation, there is a competition for amino acids (AA) between body protein deposition and immune system functioning. The aim of the present study was to quantify the effect of immune system activation on N retention and AA metabolism in growing pigs, depending on dietary protein supply. A total of sixteen barrows received an adequate (Ad) or restricted (Res) amount of dietary protein, and were challenged at day 0 with intravenous complete Freund's adjuvant (CFA). At days -5, 3 and 8, an irreversible loss rate (ILR) of eight AA was determined. CFA successfully activated the immune system, as indicated by a 2- to 4-fold increase in serum concentrations of acute-phase proteins (APP). Pre-challenge C-reactive protein concentrations were lower (P<0·05) and pre- and post-challenge albumin tended to be lower in Res-pigs. These findings indicate that a restricted protein supply can limit the acute-phase response. CFA increased urinary N losses (P=0·04) and tended to reduce N retention in Ad-pigs, but not in Res-pigs (P=0·07). The ILR for Val was lower (P=0·05) at day 8 than at day 3 in the post-challenge period. The ILR of most AA, except for Trp, were strongly affected by dietary protein supply and positively correlated with N retention. The correlations between the ILR and APP indices were absent or negative, indicating that changes in AA utilisation for APP synthesis were either not substantial or more likely outweighed by a decrease in muscle protein synthesis during immune system activation in growing pigs.

Analysis of a compartmental model of amyloid beta production, irreversible loss and exchange in humans

Amyloid beta (Aβ) peptides, and in particular Aβ42, are found in senile plaques associated with Alzheimer's disease. A compartmental model of Aβ production, exchange and irreversible loss was recently developed to explain the kinetics of isotope-labeling of Aβ peptides collected in cerebrospinal fluid (CSF) following infusion of stable isotope-labeled leucine in humans. The compartmental model allowed calculation of the rates of production, irreversible loss (or turnover) and short-term exchange of Aβ peptides. Exchange of Aβ42 was particularly pronounced in amyloid plaque-bearing participants. In the current work, we describe in much greater detail the characteristics of the compartmental model to two distinct audiences: physician-scientists and biokineticists. For physician-scientists, we describe through examples the types of questions the model can and cannot answer, as well as correct some misunderstandings of previous kinetic analyses applied to this type of isotope labeling data. For biokineticists, we perform a system identifiability analysis and a sensitivity analysis of the kinetic model to explore the global and local properties of the model. Combined, these analyses motivate simplifications from a more comprehensive physiological model to the final model that was previously presented. The analyses clearly demonstrate that the current dataset and compartmental model allow determination with confidence a single ‘turnover’ parameter, a single ‘exchange’ parameter and a single ‘delay’ parameter. When combined with CSF concentration data for the Aβ peptides, production rates may also be obtained.

Pr6O11-Coated High Capacity Layered Li[Li0.17Ni0.17Co0.10Mn0.56]O2 as a Cathode Material for Lithium Ion Batteries

A Li-rich layered oxide Li[Li0.17Ni0.17Co0.10Mn0.56]O2 is synthesized and coated with Pr6O11 by a chemical deposition method. The pristine and the Pr6O11-coated Li[Li0.17Ni0.17Co0.10Mn0.56]O2 cathodes are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge-discharge measurements. After coating of Pr6O11, the bulk crystallographic structure, morphology and grain size of the layered Li[Li0.17Ni0.17Co0.10Mn0.56]O2 are not essentially changed. Compared to the pristine Li[Li0.17Ni0.17Co0.10Mn0.56]O2 cathode, the Pr6O11-coated Li[Li0.17Ni0.17Co0.10Mn0.56]O2 cathodes coated with suitable thickness exhibit higher discharge capacity with lower irreversible capacity loss, better cyclability and higher rate capability. Especially, 5 wt% Pr6O11-coated sample displays the highest capacity (277.9 mAh g−1 at 0.05 C rate), the best rate capability (196.2 mAh g−1 at 1C rate) and the best cyclability (capacity retention of 91.2% in 50 cycles). Of particular concern is the polarization behavior of Pr6O11-coated cathodes coated with suitable thickness. Impedance analysis demonstrates that the rate capability of Pr6O11-coated cathodes are mainly affected by the lithium ion diffusion resistance through the surface layer (solid-electrolyte interfacial (SEI) layer and Pr6O11 coating), while influences of the faradaic charge transfer resistance is negligible. This work shows a promising approach to improve the electrochemical performance of Li-rich layered oxides by surface modification of semiconductor materials.