Monte Carlo simulations to understand 'breathing' phenomenon of metal organic frameworks

Metal Organic Frameworks (MOFs) are a new class of porous materials synthesized from metal clusters connected by organic linkers. One of the promising applications of MOFs is carbon capture from fuel gasses, where CO2 is adsorbed in the pores of the material. In this presentation, we explore framework flexibility as a possible mechanism for selective and reversible CO2 adsorption by means of Monte Carlo simulations. Most MOFs are fairly rigid structures, in the sense that they undergo small changes in volume when external stress is applied. Typical volume changes are of the order of a few percent only. Nevertheless, some MOF materials have an unexpectedly high flexibility and impressively shrink or swell under pressure, temperature or adsorption changes. A well-known example is MIL-53, a structure that shows volume changes of over 40%. In an adsorption experiment, the gas pressure is gradually increased while the amount of adsorbed material in the pores is measured. For MIL-53, the measured adsorption isotherm shows interesting features: when MIL-53 is brought into contact with a gas at increasing pressure, the framework's pores constrict, while at even higher pressures, the pores return to their original geometry. The process, referred to as "breathing", is reversible and shows hysteresis. Based on Monte Carlo runs, we have constructed a mean-field model to gain insight in the thermodynamics of the breathing. The model shows that the behavior is the result of the different factors at play in a (Nmof,μ,P,T) ensemble (constant amount of MOF material, constant gas chemical potential, constant gas pressure, constant temperature), i.e. the entropy, the pressure and the resistance given by the adsorbed particles. We further investigate how the MOFs' flexibility could be exploited to design an efficient pressure swing setup

Cutting the cost of carbon capture: a case for carbon capture and utilization

A significant part of the cost for Carbon Capture and Storage (CCS) is related to the compression of the captured CO2 to its supercritical state, at 150 bar and typically 99% purity. These stringent conditions may however not always be necessary for specific cases of Carbon Capture and Utilization (CCU). In this manuscript, we investigate how much the parasitic energy of an adsorbent-based carbon capture process may be lowered by utilizing CO2 at 1 bar and adapting the final purity requirement for CO2 from 99% to 70% or 50%. We compare different CO2 sources: the flue gases of coal-fired or natural gas-fired power plants and ambient air. We evaluate the carbon capture performance of over 60 nanoporous materials and determine the influence of the initial and final purity on the parasitic energy of the carbon capture process. Moreover, we demonstrate the underlying principles of the parasitic energy minimization in more detail using the commercially available NaX zeolite. Finally, the calculated utilization cost of CO2 is compared with reported prices for CO2 and published costs for CCS

Dairy product consumption in french children in 2010

Dairy food consumption is important for children as it contributes to the intake of key nutrients, especially calcium. The aim of the present paper is to provide an overview of dairy products consumption for French children, according to age, sex and type of dairy products. Adequacy of dairy and calcium intakes in line with French national guidelines "3 portions of dairy products per day" were also evaluated. Data were extracted and analyzed from the CCAF-Comportementet Consommations Alimentairesen France-study. Seven-day questionnaires were administered to free-living individuals from autumn 2009 to summer 2010. Subjects were children (n=1171) aged 3-17 years. Dairy products contributed substantially to the intake of calcium, phosphorus, potassium, zinc, vitamin B2 and vitamin B12. A general decrease in DP consumption has been observed since 2003. This is most notably due to a lower milk intake which is not compensated by increased cheese or fresh dairy products. Most of children (67%), and up to 73% of adolescents (15 - 17 y), did not reach the recommended "3 servings of dairy products per day". Twenty percent of children from the age of 6 and nearly 2/3 of female adolescents did not reach their estimated average requirement for calcium. The overview of French dairy food consumption during childhood, of particular Public Health concern, emphasizes the need to encourage dairy consumption and particularly milk consumption at breakfast in order to maintain a nutrient adequacy in children and adolescents

Carbon capture turned upside down: high-temperature adsorption & low-temperature desorption (HALD)

Carbon capture & sequestration (CCS) could reduce CO2 emissions from large fossil-fuel power plants on the short term, but the high energy penalty of the process hinders its industrial deployment. Moreover, the utility of nanoporous materials, known to be selective for the CO2/N-2 separation, is drastically reduced due to the competitive adsorption with H2O. Taking advantage of the power plant's waste heat to perform CCS while at the same time surmounting the negative effect of H2O is therefore an attractive idea. We propose an upside-down approach for CCS in nanoporous materials, high-temperature adsorption & low-temperature desorption (HALD), that exploits the temperature-dependent competitive adsorption of CO2 and H2O. First, we provide a theoretical background for this entropy-driven behavior and demonstrate under what conditions competitive adsorption can be in favor of CO2 at high temperature and in favor of H2O at low temperature. Then, molecular simulations in all-silica MFI provide a proof of concept. The International Zeolite Association database is subsequently screened for potential candidates and finally, the most promising materials are selected using a post-Pareto search algorithm. The proposed post-Pareto approach is able to select the material that shows an optimal combination of multiple criteria, such as CO2/H2O selectivity, CO2/N-2 selectivity, CO2 uptake and H2O uptake. As a conclusion, this work provides new perspectives to reduce the energy requirement for CCS and to overcome the competitive adsorption of H2O

Exploring new frontiers in modeling complex zeolite-catalyzed reactions using advanced molecular dynamics techniques

We show the potential of advanced molecular dynamics techniques to obtain insight into the complex MTO process by thoroughly studying proton mobility and mapping free energy surfaces of reaction steps at high temperature. The applied methodology can be used to unravel any complex zeolitic process at the nanometer scale level

PHF2 regulates homology-directed DNA repair by controlling the resection of DNA double strand breaks

Post-translational histone modifications and chromatin remodelling play a critical role controlling the integrity of the genome. Here, we identify histone lysine demethylase PHF2 as a novel regulator of the DNA damage response by regulating DNA damage-induced focus formation of 53BP1 and BRCA1, critical factors in the pathway choice for DNA double strand break repair. PHF2 knockdown leads to impaired BRCA1 focus formation and delays the resolution of 53BP1 foci. Moreover, irradiation-induced RPA phosphorylation and focus formation, as well as localization of CtIP, required for DNA end resection, to sites of DNA lesions are affected by depletion of PHF2. These results are indicative of a defective resection of double strand breaks and thereby an impaired homologous recombination upon PHF2 depletion. In accordance with these data, Rad51 focus formation and homology-directed double strand break repair is inhibited in cells depleted for PHF2. Importantly, we demonstrate that PHF2 knockdown decreases CtIP and BRCA1 protein and mRNA levels, an effect that is dependent on the demethylase activity of PHF2. Furthermore, PHF2-depleted cells display genome instability and are mildly sensitive to the inhibition of PARP. Together these results demonstrate that PHF2 promotes DNA repair by homologous recombination by controlling CtIP-dependent resection of double strand breaks.España Ministerio de Ciencia e Innovacion SAF2016-80626-REspaña, Fundación Canaria Instituto de Investigación Sanitaria de Canarias (FIISC) [PIFUN16/18

Effects of Interactive Musical Activities on the Well-being of Children with Urogenital Anomalies during Hospitalization for Surgery

Background: Hospitalizations and surgeries are stressful situations mainly for children. It is extremely important to search for strategies that can help to reduce suffering and stress in children during medical treatments, contributing then to the process of humanization in health care. Due to the therapeutic potential of music, we believe that it could be an alternative to help children to cope better with the situation of anxiety and stress arising from a hospitalization. This research intended to evaluate the effect of interactive musical activities in reducing stress in children hospitalized for urological surgery. Methods: Fifty-four children were invited for the study of which 40 participated. Twenty-two of those were part of the experimental group and 18 of the control group. The experimental group participated in 15 to 30 minutes daily sessions of playful interactive musical activities during hospitalization (~5 days), except on the day of surgery. The Child Stress Scale - ESI, the drawing-and-story procedure for analysis of the feelings towards surgery and salivary cortisol at 8:00 AM and 4:00 PM were used to evaluate the degree of stress in these children. Results: The stress score obtained before and after surgery significantly decreased in both groups, mainly in the experimental group. There was no significant difference in positive and negative feelings towards the surgery in both groups. Salivary cortisol levels between the 2 groups were also similar. Conclusion: A positive effect of musical activities in children’s stress reduction during the hospitalization period was observed, indicating that these procedures can contribute to the well-being of these patients. Keywords: Hospitalized child, Music, Stress, Music therapy, Urogenital abnormalities/surger

Noninvasive Ventilation in Preterm Infants: Factors Influencing Weaning Decisions and the Role of the Silverman-Andersen Score

The factors influencing weaning of preterm infants from noninvasive ventilation (NIV) are poorly defined and the weaning decisions are often driven by subjective judgement rather than objective measures. To standardize quantification of respiratory effort, the Silverman-Andersen Score (SAS) was included in our nursing routine. We investigated the factors that steer the weaning process and whether the inclusion of the SAS would lead to more stringent weaning. Following SAS implementation, we prospectively evaluated 33 neonates born <= 32 + 0 weeks gestational age. Age-, weight- and sex-matched infants born before routine SAS evaluation served as historic control. In 173 of 575 patient days, NIV was not weaned despite little respiratory distress (SAS <= 2), mainly due to bradycardias (60% of days without weaning), occurring alone (40%) or in combination with other factors such as apnea/desaturations. In addition, soft factors that are harder to grasp impact on weaning decisions, whereas the SAS overall played a minor role. Consequently, ventilation times did not differ between the groups. In conclusion, NIV weaning is influenced by various factors that override the absence of respiratory distress limiting the predictive value of the SAS. An awareness of the factors that influence weaning decisions is important as prolonged use of NIV has been associated with adverse outcome. Guidelines are necessary to standardize NIV weaning practice