Saturation Loading Research Articles

Modelling link failure in the presence of extended hidden terminals over multi-hop wireless ad hoc networks

IEEE 802.11 uses RTS/CTS (request to send/clear to send) reservation mechanism in multi-hop ad hoc networks to prevent collision drops caused by the hidden terminals. Extended hidden nodes impose great challenges to RTS/CTS mechanism by creating additional interferences and route failures. We introduce a Markov model to compute the probability of collision due to hidden and extended hidden nodes present in multi-hop ad hoc network under saturated traffic loads. This model is derived from the well-known Bianchi Markov chain model of IEEE 802.11 Distributed coordination function by introducing additional states in every back-off stage. Our model differentiates the collisions that could happen to RTS/CTS and data packets. We also compute the probability of link failure that occurs when the maximum retry limit is exceeded. The model is tested for varying network sizes with number of nodes 10, 50, 100, 150 and 200. The model validates the throughput, collision probability and link failure probability against the Bianchi model and ns-2.35 simulation result.

A laboratory scale heat pipe condenser with sweating boosted air cooling

Air-cooled condensers (ACCs) in thermal power plants are more competitive than the water-cooled condensers (WCCs) in addressing the global water crisis. The state-of-art ACCs need emerging heat transfer enhancement technologies, so hybrid wet/dry cooled condensers (HCCs) are employed to compensate for the low efficiency of ACCs. We propose a heat pipe air-cooled condenser (HPACC) to overcome the high capital and operating cost of traditional HCCs. HPACC combines the proven heat pipe technology with a novel sweating-boosted air-cooling strategy. Its architecture is similar to the most efficient once-through WCCs, but replacing conventional water tubes with high-performance heat pipes. A laboratory scale HPACC is built by scaling down the prototype of the proposed HPACC. This study evaluates the heat transport and rejection process within an HPACC. The thermal performance of HPACC is characterized under various heat loads and air velocities, and the sweating-boost effects on the HPACC are investigated. Our study shows that a saturated heat load on the HPACC exists under given air-cooling conditions. The minimum overall thermal resistance of HPACC is 4.7439 × 10−2 K/W achieved at an effective heat load of 1606.40 W with an air velocity of 3.0 m/s. Air cooling is further boosted by the sweating process on the fined surface integrated with superwetting copper hydroxyl nitrate wicks (Cu2(OH)3NO3). It demonstrates that HPACC with a sweating-boosted air cooling (HPACC-SB) significantly improves the total effective heat load by 172.17% and reduces the overall thermal resistance by 64.27%. The proposed HPACC is promising in replacing current cooling equipment of thermal power plants. Moreover, substantial water savings will help alleviate the water crisis facing the world.

Relationship Between Muscle Oxygen Saturation and Exercise Load in Patients with Malignant Hematopoietic Disease.

Our previous research confirmed that patients with malignant hematopoietic disease already had a low hemoglobin level before allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, no study has determined whether a correlation exists between exercise load, hemoglobin level, and muscle oxygen saturation (SmO2), during exercise. Therefore, the purpose of this study was to investigate whether near-infrared spectroscopy (NIRS)-derived SmO2 is associated with exercise load, as determined by a dynamometer, before allo-HSCT. This study included 19 male patients who received allo-HSCT in Hyogo College of Medicine Hospital (Japan) between November 2009 and October 2012. Patients performed isometric repeated dorsiflexion at 50% maximum voluntary contraction for 180s to determine exercise load, and SmO2 was evaluated during exercise at the same time using NIRS (BOM-L1TRW, Omega Wave, Inc., Japan). The hemoglobin level was also evaluated before allo-HSCT. Patients with hematopoietic disease before allo-HSCT already had a low hemoglobin level. There was a significant correlation between exercise load and ∆SmO2; however, the hemoglobin level was not correlated with exercise load. In these patients, exercise load might be affected by muscle oxygen consumption rather than by the hemoglobin level. This finding shows that NIRS can used to assess fatigue in patients with malignant hematopoietic disease.

Automatic Generation Control of Multi-area Power System with Network Constraints and Communication Delays

Newly proposed power system control methodologies combine economic dispatch (ED) and automatic generation control (AGC) to achieve the steady-state cost-optimal solution under stochastic operation conditions. However, a real power system is subjected to continuous demand disturbance and system constraints due to the input saturation, communication delays and unmeasurable feed-forward load disturbances. Therefore, optimizing the dynamic response under practical conditions is equally important. This paper proposes a state constrained distributed model predictive control (SCDMPC) scheme for the optimal frequency regulation of an interconnected power system under actual operation conditions, which exist due to the governor saturation, generation rate constraints (GRCs), communication delays, and unmeasured feed-forward load disturbances. In addition, it proposes an algorithm to handle the solution infeasibility within the SCDMPC scheme, when the input and state constraints are conflicting. The proposed SCDMPC scheme is then tested with numerical studies on a three-area interconnected network. The results show that the proposed scheme gives better control and cost performance for both steady state and dynamic state in comparison to the traditional distributed model predictive control (MPC) schemes.

A novel extractant bis(2-ethylhexyl) ((2-ethylhexylamino)methyl) phosphine oxide for cerium(IV) extraction and separation from sulfate medium

By introducing the amine group into phosphorus extractant, a novel aminophosphine compound bis(2-ethylhexyl) ((2-ethylhexylamino)methyl) phosphine oxide (DEHAPO, abbreviated as A) was synthesized for the extraction of cerium (IV) (Ce(IV)) from sulfate medium (H2SO4). The influence factors including extractant concentration, H2SO4 concentration and temperature on the Ce(IV) extraction were investigated and discussed. It is found that the extraction ability of Ce(IV), thorium (IV) (Th(IV)) and rare earths (REs(III)) (La, Gd, Yb) decreases in sulphate medium in the following order: Ce(IV) > Th(IV) > REs(III). The extraction process is an exothermic reaction and the thermodynamic parameters were calculated. The extracted complex of Ce(HSO4)2SO4·A in loaded organic solution was identified by the slope methods and further proved by FT-IR spectral analysis. Stripping studies indicate that Ce(IV) can be effectively stripped from the organic phase. The results of separation factors (β) and saturation loading capacity demonstrate that DEHAPO could be used to selectively extract Ce(IV) from sulphate medium with high separation efficiency and good extraction ability.

PSIV-B-31 Late-Breaking: The effects of iron overload on growth performance and iron metabolism in nursery piglets born at different sizes of development

Abstract Either iron excess or iron deficiency may adversely affect growth of pigs. This study assessed the effect of dose of iron supplement on growth and iron metabolism in nursing piglets born small (SGA) or appropriate for gestational age (AGA). Eight SGA piglets (BW=1.18 kg) and 16 AGA piglets (BW=1.73 kg) were enrolled on postnatal day (PD) 1. The SGA piglets orally received high iron supplementation (15 mg/kg·d; SGAH), and AGA piglets orally received either high (15 mg/kg·d; AGAH, n = 6) or low iron supplementation (1 mg/kg·d; AGAL, n = 6) from PD 2 to 21. Body weight was recorded every third day. Blood samples were collected on PD 1, 7, 14, and 21. Liver and duodenal mucosa samples were collected on PD 21 to analyze the mRNA and protein expressions of iron transporters and regulators. All data were analyzed as a randomized complete block design using the PROC MIXED of SAS. The SGA piglets had lower hematocrit and hemoglobin than AGA piglets on PD1 (P < 0.05). The dose of iron supplement did not affect the growth trajectory of nursing piglets. In comparison with AGAL group, high iron increased (P < 0.05) hematocrit, hemoglobin, plasma iron, transferrin saturation, and iron load in duodenal mucosa (DM) and liver on PD 21 regardless of birth BW. High iron reduced the DMT1 and TFRC and increased FTL in DM (P < 0.05). High iron decreased TFRC and increased HAMP in liver (P < 0.05). Hepatic expression of H-ferritin were increased (P < 0.05) by high iron. Despite drastic induction of HAMP in liver, protein expression of ferroportin in DM were unaffected by high iron intake. In conclusion, iron transporters and regulators in liver and gut were coordinately regulated to prevent iron overload, but the hepcidin-ferroportin axis was unresponsive to dietary iron intake.

Recovery of cerium(IV) in acidic nitrate solutions by solvent extraction with a novel extractant tris(2-ethylhexyl)phosphine oxide

The extraction of cerium(IV) (Ce(IV)) from a nitric acid (HNO3) system using a novel extractant, tris(2-ethylhexyl)phosphine oxide (TEHPO), was studied. The separation factors of Ce(IV)/Th(IV) and Ce(IV)/Ln(III) (La3+, Gd3+ and Lu3+) were found to be in the range of 60–127 and 121–827, respectively, in the HNO3 concentration range of 0.5–5.0 mol/L, showing high selectivity with TEHPO. The experimental results showed that TEHPO can effectively extract Ce(IV) from a HNO3 system quantitatively in a 2:1 form (molar ratio of TEHPO: Ce(IV)), which is unrelated to the experimental conditions, that is, factors such as HNO3 concentration, extractant concentration, and temperature. The loaded Th(IV) could be stripped efficiently using H2O, but Ce(IV) should be stripped using H2O2. The extraction mechanisms of HNO3 and Ce(IV) with TEHPO were determined through the slope analysis method, infrared spectroscopy (FT-IR), and electrospray ionization mass spectrometry (ESI-MS), and the extracted complexes were found to be HNO3·TEHPO and Ce(NO3)4·2TEHPO. Comparison of their extraction performances revealed that TEHPO shows a better interfacial phenomenon and higher extraction ability and saturation loading capacity than those of Cyanex923.

Applying the Concept of a Virtual Competitive Window to Determine the Qualitative Performance of a Wireless Network of the 802.11 Standard

The article presents the results of the application of the concept of a virtual competitive window to determine such qualitative indicators as the bandwidth of the wireless network Wi-Fi, delay transmission of the data packet through the wireless channel, the probability of loss of data packet, jitter. Practical calculations was made for a network operating on the 802.11a specification in RST / CST mode, taking into account the collisions occurring on networks with a large number of active stations. The article considers the ideal network. That is, the one that was neglected by the effects of interference and interference occurring in the real wireless network. The paper examines processes in a wireless network with saturated load as quasi-stationary processes. On the basis of such a concept, the parameter named Virtual Competitive Window was introduced. Our research has allowed us to obtain the calculated relations, which establish the unequivocal connection between the system parameters of the network and the stochastic parameters of the network operation process. The results of the research are useful for improving the settlement ratios for determining the parameters of the quality of the 802.11 wireless network in the mode of competitive access. The above calculations do not take into account the effects of interference and interference occurring in the real wireless network. The calculation takes into account the time spent on transmitting the headings and checking blocks provided by the mentioned protocols, as well as the costs associated with the use of the SNAP protocol. The calculation is made for frames with different loads, namely: 64, 128, 256, 512, 1024, 1500 bytes, for networks in which the number of active stations varies from 2 to 14. To calculate the parameters of the network operation, which are provided for signal speed, are used. 24 Mbps (maximum required speed of the 802.11a specification). The calculations are made for cases where the data is transmitted using the protocols TCP and UDP. Chart of network operation in RTS / CTS mode is presented in the article. Thus, the results of the research are graphical dependencies for maximum bandwidth of the 802.11a wireless network in RTS / CTS mode, 802.11a wireless network bandwidth in RTS / CTS mode with allowance for collisions, the dependence of the average latency of data transmission on the 802.11a network in RTS / CTS mode and jitter change curve in a network with a different number of stations in the payload mode of all frames of 64 bytes. Determined that the transmission delay of the data frame depending on the type of multimedia information (small volumes for voice traffic and large for the transmission of digital data) can vary in very wide ranges from 450 to 1300 microseconds, and jitter from 600 to almost 4000 microseconds (for example, files from payload of 64 bytes). The research is relevant because, under ideal transmission conditions, without taking into account signal processing delays by hardware, the maximum bandwidth of the 802.11a network channel in RTS / CTS mode may vary several times compared to the declared 24 Mbps rate. Ref. 4, fig. 5.

A novel extractant 2-Ethylhexyl Bis(2-ethylhexyl)phosphinate for cerium(IV) and fluorine extraction from nitric acid system

A novel extractant, 2-ethylhexyl Bis(2-ethylhexyl)phosphinate (EHBEHP, abbreviated as B), was synthesized for the extraction of Cerium(IV) (Ce(IV)) and fluorine (F(I)) from nitric acid (HNO3) media. The effects of HNO3 concentration, extractant concentration, F(I) concentration and the temperature on the Ce(IV) and F(I) extraction were studied and discussed. The experimental results show that EHBEHP has a strong ability to extract Ce(IV), while the presence of F(I) decreases the extraction ability of Ce(IV). The extraction process had nothing to do within the studied temperature range. The extraction of HNO3, Ce(IV) and Ce(IV)-F(I) were studied respectively, and the extracted complexes were found to be 2HNO3·EHBEHP, Ce(NO3)4·2EHBEHP and Ce(HF)(NO3)4·EHBEHP, individually. The extraction mechanisms were determined according to slope analysis method. Saturation loading capacity of Ce(IV) and F(I) extracted by 0.867 mol/L EHBEHP in HNO3 system was about 50.98 g/L and 5.67 g/L, respectively. The stripping experiment shows that 95.3% of stripping efficiency of Ce(IV) can be obtained with 2.4% H2O2. The FT-IR of extracted complexes were measured and characterized. EHBEHP shows higher extraction ability and saturation loading capacity compared with DEHEHP.

Effect of CaO and biomass ash on catalytic hydrogasification behavior of coal char

Three rich-alkalis biomasses ashes, wheat straw ash (WSA), sea grape ash (SGA) and Ixeris Chinese ash (ICA) and calcium-based additives, were applied in char hydrogasification. Hydrogasification behavior of coal and biomass ash and saturated loading and loading methods of calcium-based additives were investigated. The loading calcium-based additives has affected on the methane release curves of SFC hydrogasification. The total amount of gaseous products and the CH4 yield were obviously improved with the increase of the CaO loading. Hydrogasification of SF char with the 6% calcium-based loading presented the highest methane yield. SFC hydrogasification was divided into two stages according to the methane release rate curve of the calcium-based additives-loaded samples hydrogasification. The carbon and hydrogen reaction occurred in the second stage of coal hydrogasification. The calcium-based additives have effects on catalytic performance of three rich-alkalis biomass ashes for hydrogasification characteristics of Shenfu coal char. Loading methods of calcium-based additives and component of biomass ashes affected on the total CH4 yield and the total amount of gaseous products of samples. Calcium-based additives emerged obviously synergistic reaction with WSA or SGA during char hydrogasification. Calcium-based additives reacted with Si of biomass ashes and produce more stable calcium silicate in the early stage of reaction. The promotion of biomass ashes on char hydrogasification mainly was attributed to the fixation of Si and Cl by CaO.

Timber-framed building damage from tephra fall and lahar: 2015 Calbuco eruption, Chile

Assessing the damage to buildings from volcanic eruptions is an important aspect of volcanic risk assessment and management. However, there is a limited empirical evidence base to draw upon when describing the relation between volcanic hazard intensity and resulting physical damage. The 2015 subplinian eruption of Calbuco volcano, Chile, caused damage to buildings near the volcano because of tephra fall and lahars. Chilean authorities conducted a damage assessment of 961 properties (990 buildings) to inform an assistance programme for property owners affected by the eruption. Property assessments typically contained observations and classification of damage to a house, and in some instances accessory buildings such as sheds, garages, and exterior storage rooms. In this study we used this unique damage data set to adapt damage state frameworks for tephra fall and lahar for classifying and analysing damage observations. We developed data quality indicators to provide transparency for how we accounted for data quality issues. We assigned a tephra and/or lahar damage state to 571 buildings (530 houses and 41 accessory buildings). The 419 buildings for which we did not assign a damage state either had too little information or fell outside of tephra and/or lahar hazard zones. The minimum tephra thickness isopach band that caused complete collapse was 10 to 15 cm (dry deposit loading ~1 to 1.6 kN m−2, saturated deposit loading 1.6 to 2.4 kN m−2), but most commonly (55% of tephra exposed DS5 houses n = 11), this occurred at 15 to 30 cm (dry deposit loading ~1.5 to 3.3 kN m−2, saturated deposit loading 2.4 to 4.8 kN m−2). Lahar damage was typically described as complete (DS5), with 26 houses being swept away or destroyed around the Blanco South River. Our results add to the limited evidence base of post-eruption tephra and lahar impacts to buildings and contribute to volcanic risk and impact assessment.

Efficient preparation and molecular dynamic (MD) simulations of Gemini surfactant modified layered montmorillonite to potentially remove emerging organic contaminants from wastewater

A novel Gemini surfactant, Propyl bis (hexadecyl dimethyl ammonium) chloride (16-3-16), was utilized to modify Ca-montmorillonite (Ca-Mt) to obtain organo-montmorillonite (G-Mt). The structure and morphology of G-Mt were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FT-IR), Scanning electron microscope (SEM), Energy Dispersive Spectrometer (EDS), Thermogravimetric analysis (TGA), N2 adsorption/desorption isotherms (BET) and Zeta potential. G-Mt was used to adsorb a class of emerging contaminants (ECS) such as 1-Hydroxybenzotriazole (HOBT), 1H-Benzotriazole (BTA) and 5-Methyl-1H-benzotriazole (TTA) from wastewater. Molecular dynamic (MD) simulations were performed to reveal the arrangement of 16-3-16 in the interlayer gallery of Ca-Mt. Furthermore, the adsorption properties of G-Mt were observed under different experimental conditions. The results showed that the saturation loading of 16-3-16 on Ca-Mt was 1.0 CEC and the maximum adsorption capacities at equilibrium were 25.93 mg/g, 18.31 mg/g and 16.24 mg/g for HOBT, BTA, and TTA, respectively. However, the adsorption capacities of three contaminants on Ca-Mt were only 2.37 mg/g, 1.28 mg/g, and 1.06 mg/g. The optimum removal of HOBT, BTA and TTA occurred at pH 4, 9, 9 respectively. The adsorption processes of three contaminants fitted well with the Langmuir isotherm model and the pseudo-second-order model. Thermodynamic results indicated that the adsorption processes of HOBT, BTA, and TTA on G-Mt were spontaneous and endothermic. These researches are expected to provide a sixpenny and efficient method to treat emerging contaminants in wastewater.

Hydrothermal Synthesis of Graphene Quantum Dots Supported on Three-Dimensional Graphene for Supercapacitors.

Incorporation of new functional components into a three-dimensional graphene (3DG) framework improves the performance of supercapacitors based on 3DG as electrodes by tailoring the framework’s structure and properties. In this work, graphene quantum dots (GQDs) were incorporated into 3DG via one-step hydrothermal treatment of GQDs and graphene oxide (GO). By simply adjusting the GQDs/GO feeding ratio by weight, various GQDs/3DG composites were formed. The maximum feeding ratio was 80%, and the prepared composites possessed saturated GQDs loading on the 3DG framework, whereas composites obtained with a GQDs/GO feeding ratio of 40% as electrodes exhibited optimal specific capacitance of 242 F·g−1 for supercapacitors, an increase of 22% compared with that of pure 3DG electrodes (198 F·g−1). This improved performance was mainly due to better electrical conductivity and larger surface area for GQDs/3DG composites with moderate GQDs content. The fabricated GQDs/3DG composites as electrodes for supercapacitors revealed high electrochemical stability. Their capacitance kept 93% of the initial value after 10,000 charge-discharge cycles.

Adsorption and Diffusion of Benzene in Mg-MOF-74 with Open Metal Sites.

We performed molecular simulations to investigate the adsorption and diffusion of benzene in metal-organic framework Mg-MOF-74. At 300 K and 20 Pa, the saturated loading of benzene reaches 8.2 mmol/g, almost twice of (12,12) single-walled carbon nanotube with a similar pore size, and 93% of the benzene molecules in Mg-MOF-74 can desorb at 390 K. The energy analysis indicates that the van der Waals contribution still dominates 70-80% of the total fluid-wall interaction energy compared with the Coulombic contribution. We further analyzed the structure of benzene confined in Mg-MOF-74 by the molecular snapshots, pair correlation functions, orientational order parameters, and local density profiles. It is found that low temperature and high pressure make the structure of adsorbed benzene more similar to that of the liquid benzene. Moreover, the benzene molecules in the contact adsorption layer lie flat on the surface of adsorbent, whereas those molecules near the pore center have no particular orientations. Due to the existence of open metal sites, the structures of adsorbed benzene are more compact and ordered than those of bulk liquid benzene. Consequently, the self-diffusion coefficient of saturated benzene in Mg-MOF-74 at 300 K is significantly lower than that of bulk liquid benzene and confined liquid benzene in slit pores and disordered carbons by 4-5 orders of magnitude. We investigated the separation and diffusion of benzene/cyclohexane in the mixture in Mg-MOF-74 and found that the pores almost completely adsorbed benzene, although its self-diffusion coefficient was slightly lower than that of cyclohexane.

Enhanced design and formulation of nanoparticles for anti-biofilm drug delivery.

Biofilms are surface-bound, structured microbial communities underpinning persistent bacterial infections. Biofilms often create acidic pH microenvironments, providing opportunities to leverage responsive drug delivery systems to improve antibacterial efficacy. Here, the antibacterial efficacy of novel formulations containing pH-responsive polymer nanoparticle carriers (NPCs) and farnesol, a hydrophobic antibacterial drug, were investigated. Multiple farnesol-loaded NPCs, which varied in overall molecular weight and corona-to-core molecular weight ratios (CCRs), were tested using standard and saturated drug loading conditions. NPCs loaded at saturated conditions exhibited ∼300% greater drug loading capacity over standard conditions. Furthermore, saturated loading conditions sustained zero-ordered drug release over 48 hours, which was 3-fold longer than using standard farnesol loading. Anti-biofilm activity of saturated NPC loading was markedly amplified using Streptococcus mutans as a biofilm-forming model organism. Specifically, reductions of ∼2-4 log colony forming unit (CFU) were obtained using microplate and saliva-coated hydroxyapatite biofilm assays. Mechanistically, the new formulation reduced total biomass by disrupting insoluble glucan formation and increased NPC-cell membrane localization. Finally, thonzonium bromide, a highly potent, FDA-approved antibacterial drug with similar alkyl chain structure to farnesol, was also loaded into NPCs and used to treat S. mutans biofilms. Similar to farnesol-loaded NPCs, thonzonium bromide-loaded NPCs increased drug loading capacity ≥2.5-fold, demonstrated nearly zero-order release kinetics over 96 hours, and reduced biofilm cell viability by ∼6 log CFU. This work provides foundational insights that may lead to clinical translation of novel topical biofilm-targeting therapies, such as those for oral diseases.

A Grid-Based Method for Distribution Network Planning in Urban Areas

This paper proposes a grid-based method for distribution network planning. Firstly, based on the analysis of the economic and social development targets and distribution network status in the region, the central area is meshed and classified according to the relevant principles and objectives of distribution network planning as well as the nature and development depth of the land. Load forecasting based on grid layout is carried out to determine the saturated load corresponding to the current planning of the area. Finally, according to the current grid, load forecasting results and planning targets, the target grid and transition grid of the planning grid are determined. The above method is applied to the grid planning of a distribution network in Hangzhou China. The planning index is greatly improved, the target network frame of the distribution network is strong, the power supply range is clear, and the power supply reliability is high, which verifies the effectiveness of the method.

Combined Effect of Loading Rate and Water Content on Mechanical Behavior of Natural Stones

Uniaxial compressive strength (UCS) is considered to be the most widely used mechanical property to detect and classify rocks. However, tests are generally performed under dry conditions and standard loading rates. On the other hand, in the land environment neither the saturation degree of rocks is zero nor the loading rate is constant. In this study, three different sedimentary rocks in the Eastern Anatolia Region (Turkey) were used for determination of the effects of saturation degree on mechanical properties and combined effects of saturation degree and loading rates on UCS. For this purpose, point load strength, Schmidt and Shore hardness, ultrasonic wave velocity, and Brazilian tensile strength tests were carried out on oven-dried, 35, 70, 100% saturated specimens, and UCS tests were carried out in 0, 35, 70 and 100% saturation degrees and 0.50, 0.75 and 1.00 kN/s loading rates. Test results showed that increasing water content led to decreasing mechanical properties up to 40-50%, respectively, from dry to saturated conditions. Water absorption had an important effect on Brazilian and point load strength. Internal pressure caused by water effected tensile stress more. It was seen that saturation and loading rate increased with the UCS-increasing saturation rate and caused a buffer effect in low porosity rocks.

Positron annihilation characteristics and catalytic performances of poly (vinyl alcohol) intercalated montmorillonite supported Pd0 nanoparticles composites

The microstructure of poly (vinyl alcohol)/ montmorillonite (PVA/MMT) matrices and Pd@PVA/MMT catalytic composite was characterized by positron annihilation spectroscopy (PAS) and other techniques, such as high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), and X-ray photo electron spectroscopy (XPS). XRD and HR-TEM results showed that 20% was the saturation loading percentage of PVA intercalation into MMT. Ortho-positronium (o-Ps) annihilations were mainly distributed in the interlayer spacing of MMT and/or open spaces (free volume) of PVA. Below the saturation loading percentage of PVA (≤ 20%), it was found that the o-Ps annihilation lifetime became shorter after the intercalation of PVA chains into MMT layers. With further addition of PVA, the o-Ps annihilation lifetime became longer after the formation of exfoliated structure. The 20%-PVA/MMT matrix has been selected as the platform to further immobilize Pd specie for preparing novel 0.2%-Pd@20%-PVA/MMT catalytic composite. The effects of Pd immobilization on the microstructure of PVA/MMT matrices were also sensitively detected by PAS. The mean size of the micro-defects (from Tao-Eldrup model) increased from 0.28 nm (20%-PVA/MMT) to 0.29 nm (0.2%-Pd2+@20%-PVA/MMT or 0.2%-Pd0@20%-PVA/MMT), respectively. This increase in the size of the micro-defects of 20%-PVA/MMT matrix after Pd immobilization was mainly due to the replacement of the inter-molecular hydrogen bodings of PVA chains by the interactions formed between the PVA chains and Pd species. The prepared 0.2%-Pd0@20%-PVA/MMT catalytic composite showed excellent catalytic efficiency and recyclability in both Heck-type and Sonogashira-type coupling reactions. The correlations between the microstructure and performance of the 0.2%-Pd0@20%-PVA/MMT composite were thoroughly discussed.

Effects of piperazine concentration and operating conditions on the solubility of CO2 in AMP solution at low CO2 partial pressure

ABSTRACTIn this study, new equilibrium solubility data for carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol and piperazine (PZ) are provided. The two famous Deshmukh–Mather and Kent Eisenberg thermodynamic models are utilized to predict the CO2 absorption. The experimental data show that the solubility of CO2 decreases as the temperature increases. Our data suggest that the addition of PZ has different effects on CO2 absorption under different partial pressure of the CO2 in the gas stream. For high partial pressure, the addition of PZ promotes the absorption performance. However, at low CO2 partial pressure, PZ addition results in less saturated CO2 loading. The Deshmukh–Mather model can provide an accurate prediction of the experimental data at high partial pressure of CO2 (i.e. AAD = 3.4%) whereas the modified Kent–Eisenberg model can capture the inverse effects of the PZ at low partial pressure and provides a relatively good approximation of experimental data at low partial pressure (i.e. AAD = 10%).

Tuning the bioactivity of bone morphogenetic protein-2 with surface immobilization strategies

Bone morphogenetic protein-2 (BMP-2) involved therapy is of great potential for bone regeneration. However, its clinical application is restricted due to the undesirable bioactivity and relevant complications in vivo. Immobilization of recombinant BMP-2 (rhBMP-2) is an efficient strategy to mimic natural microenvironment and retain its bioactivity. Herein, we present evidences indicating that osteoinductive capacity of rhBMP-2 can be regulated via variant immobilizing approaches. Three representative superficial immobilizing models were employed to fabricate rhBMP-2-immobilized surfaces including physical adsorption (Au/rhBMP-2), covalent grafting (rhBMP-2-SAM-Au) and heparin binding (Hep-SAM-Au/rhBMP-2) (SAM: self-assembled monolayer). Loading capacity, releasing behavior, osteogenic differentiation and signaling pathways involved, as well as the cellular recognition of rhBMP-2 under various immobilization modes were systematically investigated. As a result, disparate immobilizing approaches not only have effects on loading capacity, but also lead to disparity of osteoinduction at the same dosage. Notably, heparin could reinforce the recognition between rhBMP-2 and its receptors (BMPRs) whereas weaken its binding to its antagonist Noggin. Owing to this “selective” binding feature, the favorable osteoinduction and maximum ectopic bone formation can be achieved with the heparin-binding approach. In particular, manipulation of orientation-mediated BMP-2-cell recognition efficiency may be a potential target to design more therapeutic efficient rhBMP-2 delivery system. Statement of SignificanceBone morphogenetic protein-2 (BMP-2) is crucial in bone regeneration. However, its clinical application is challenged due to its shorten half-life and supra-physiological dose associated complications. In this study, three representative superficial immobilizing patterns were fabricated through physical adsorption, covalent grafting and electrostatic interaction with heparin respectively. We provided evidences indicating an dose-dependent osteoinductive capacity of immobilized BMP-2. Further, a possible mechanism of rhBMP-2-cell recognition at the interface was presented, highlighting the superior effect of heparin on rhBMP-2 bioactivity. Finally, We proposed a dual mechanism of tuning the bioactivity of immobilized rhBMP-2 through surface immobilization approaches: regulation of the saturated loading capacity and orientation-mediated rhBMP-2-cell recognition. These results provide novel insights into designing criterion of efficient delivery vehicle for rhBMP-2.