Advantage Of CO Research Articles

Decarburization mechanisms of WC–Co during thermal spraying: Insights from controlled carbon loss and microstructure characterization

Decarburization behavior of WC–Co particles in terms of transformation of WC to W2C and W, and formation of η and γ phases and microstructure evolution during plasma spraying have been systematically investigated in this study. The extent of the carbon loss of WC was tailored by either altering cooling conditions of substrate/pre-coating or spraying the particles into the media with different temperatures. It is revealed that loss of carbon of WC was alleviated by protection of Co during the coating formation stage. W2C exhibits epitaxial growth on the WC substrates in perpendicular direction and forms a nearly complete shell around the WC particles. η phase was formed as a result of decarburization and diffusion of associated phases and is located around WC–Co splats with its crystals being in cross shape. The γ phase in rod-like shape with a size of 10–20 nm embeds within the binder Co and is clearly well separated from WC grains. Further decarburization-induced W was detected mainly in Co binder, being apart entirely from WC grains. The main advantage of Co for preventing decarburization in WC–Co particles is not associated with oxidation, but instead the diffusion-controlled carbon loss. These findings would facilitate fabrication of the WC-based cermet coatings with excellent mechanical properties in particular wear resistance for extreme wear applications.

Electrocatalytic response of poly(cobalt tetraaminophthalocyanine)/multi-walled carbon nanotubes-Nafion modified electrode toward sulfadiazine in urine

A highly sensitive amperometric sulfadiazine sensor fabricated by electrochemical deposition of poly(cobalt tetraaminophthalocyanine) (poly(Co(II)TAPc)) on the surface of a multi-walled carbon nanotubes-Nafion (MWCNTs-Nafion) modified electrode is described. This electrode showed a very attractive performance by combining the advantages of Co(II)TAPc, MWCNTs, and Nafion. Compared with the bare glassy carbon electrode (GCE) and the MWCNTs-Nafion modified electrode, the electrocatalytic activity of poly(Co(II)TAPc)-coated MWCNTs-Nafion GCE generated greatly improved electrochemical detections toward sulfadiazine including low oxidation potential, high current responses, and good anti-fouling performance. The oxidation peak currents of sulfadiazine obtained on the new modified electrode increased linearly while increasing the concentration of sulfadiazine from 0.5 to 43.5 μmol/L with the detection limit of 0.17 μmol/L.

Characterisation of Porous Materials by FTIR Spectroscopy of Isotopically Labelled Probe Molecules

In this review, some of the advantages of the use of isotopically labelled molecules for FTIR characterisation of porous materials are summarised. The most important sites determining the properties of these materials are the hydroxyl groups and the incorporated cations. D → H exchange is very useful for characterisation of hydroxyls and here some new possibilities of the technique are shown. The OH → OD isotopic shift factor, i, of isolated hydroxyls is about 0.737-0.738, a value higher than the theoretical one (0.728). These experimental deviations are mainly due to anharmonicity. The anharmonicity slightly decreases when the OH groups participate in weak H-bonding with adsorbed molecules, which should lead to a decrease of i. However, contrary to the expectations, i additionally increases. This is attributed to the lower acidity of the OD groups as compared to the respective OH groups. It is shown that i of hydroxyls that are H-bonded to framework oxygen is also higher as compared to isolated ones. The use of D → H exchange also allows reassignment of some phenomena, as occurrence of Fermi resonance. Another important characteristic of mesoporous materials is the coordination state of guest cations. The number of coordinative vacancies is well determined by the utilisation of CO isotopic mixtures. Here the principles of this technique are considered and the advantages of CO-¹³C¹⁸O isotopic mixtures as compared to CO-13CO are demonstrated. Finally, other applications of labelled molecules for determination of the structures of species formed on porous materials are briefly reviewed. Keywords: Adsorption, CO isotopic mixtures, D → H isotopic exchange, FTIR spectroscopy, Porous materials, Zeolites, POLYCARBONYLS, deuteroxylated, spectrum, hydroxyls

Characterisation of Porous Materials by FTIR Spectroscopy of Isotopically Labelled Probe Molecules

In this review, some of the advantages of the use of isotopically labelled molecules for FTIR characterisation of porous materials are summarised. The most important sites determining the properties of these materials are the hydroxyl groups and the incorporated cations. D → H exchange is very useful for characterisation of hydroxyls and here some new possibilities of the technique are shown. The OH → OD isotopic shift factor, i, of isolated hydroxyls is about 0.737-0.738, a value higher than the theoretical one (0.728). These experimental deviations are mainly due to anharmonicity. The anharmonicity slightly decreases when the OH groups participate in weak H-bonding with adsorbed molecules, which should lead to a decrease of i. However, contrary to the expectations, i additionally increases. This is attributed to the lower acidity of the OD groups as compared to the respective OH groups. It is shown that i of hydroxyls that are H-bonded to framework oxygen is also higher as compared to isolated ones. The use of D → H exchange also allows reassignment of some phenomena, as occurrence of Fermi resonance. Another important characteristic of mesoporous materials is the coordination state of guest cations. The number of coordinative vacancies is well determined by the utilisation of CO isotopic mixtures. Here the principles of this technique are considered and the advantages of CO-¹³C¹⁸O isotopic mixtures as compared to CO-13CO are demonstrated. Finally, other applications of labelled molecules for determination of the structures of species formed on porous materials are briefly reviewed. Keywords: Adsorption, CO isotopic mixtures, D → H isotopic exchange, FTIR spectroscopy, Porous materials, Zeolites, POLYCARBONYLS, deuteroxylated, spectrum, hydroxyls

Differences between children and adults with otitis media with effusion treated with CO 2 laser myringotomy

Background The safety and advantages of CO 2 laser myringotomy for otitis media with effusion (OME) are well described. The goal of such treatment is to avoid unnecessary ventilation tube insertion. Comparisons between different age groups treated with this modality are lacking, and prognostic factors for treatment outcomes are not available. Methods We conducted a retrospective cohort study that included 130 children (160 ears) and 96 adults (108 ears) with OME persisting after conservative antibiotic treatment. In eligible patients, we performed laser myringotomy in the affected ear. Follow-up was scheduled every week for 1 month and then every month for 6 months. Results for 233 ears were available for analysis; 24 ears were excluded (19 due to cancer, four due to a cleft palate, and one due to Down syndrome) and 10 patients (11 ears) were lost during follow-up. A logistic regression model was used for analysis, with success of therapy as the binary outcome. Results Adult patients had more unilateral lesions ( p < 0.001) and serous fluid effusions ( p < 0.001) than did the pediatric patients. However, there was no significant difference in the cure rate (children: 58.1%; adults: 64.7%) and positive culture rate (children: 15.1%; adults: 14.3%) between patient groups. Three factors were found to be associated with a poor prognosis: multiple occurrences in children ( p < 0.001), mucoid effusion ( p = 0.04), and a history of ventilation tube use in adults ( p < 0.001). No other variables predicted treatment outcome. Conclusion Our findings suggest that CO 2 laser myringotomy is a useful treatment modality for OME in children and adults, except for children with multiple occurrences and in adults with mucoid effusions and a history of ventilation tube use.

Carbon assimilation and allocation ( 13C labeling) in a boreal perennial grass ( Phalaris arundinacea) subjected to elevated temperature and CO 2 through a growing season

The responses of carbon assimilation and allocation in different plant organs to changed environment depend on the species, their phenology and growth conditions. An integrated experiment was conducted over an entire growing season to understand the effects of elevated growth temperature (ambient + 3.5 °C) and CO 2 (700 μmol mol −1) on the seasonal photosynthetic capacity, carbon accumulation and allocation (four 21-day periods of 13C pulse labeling-to-harvest) in a boreal perennial grass ( Phalaris arundinacea) using controlled environmental chambers. Elevated temperature was found to significantly enhance leaf photosynthesis and total carbon accumulation in biomass during the early stages of the growing season, while it also resulted in earlier senescence and lower carbon storage at the final harvest. CO 2 enrichment significantly stimulated photosynthesis and total carbon accumulation over the growing season. The combination of elevated temperature and CO 2 caused a lower total carbon accumulation in biomass at maturity compared to elevated CO 2 alone, indicating that this boreal crop grown under increased temperature could not take advantage of CO 2 enrichment. Elevated temperature significantly increased 13C assimilation and allocation to the leaves and the stems during the first labeling period, and resulted in 5–6% higher percentage of carbon allocation in the roots during the final two labeling periods. This did not result in increased carbon storage in the roots, but much less carbon accumulation in the shoots during the latter growing periods. Elevated CO 2 caused a higher 13C assimilation in the roots, but did not significantly increase the below-ground 13C allocation percentage. This was because of the higher growth of the shoots under high nitrogen availability and CO 2 enrichment. The response of carbon allocation pattern to the combined elevation of temperature and CO 2 was similar to the responses to elevated temperature alone. We conclude that plant growth and carbon assimilation are clearly controlled by phenology in this boreal crop under the climatic treatments, however, seasonal carbon allocation pattern within the plants was not significantly changed by the treatments.

Effect of water vapor from power station flue gas on CO 2 capture by vacuum swing adsorption with activated carbon

Due to the high absolute humidity of real flue gas, activated carbon, a hydrophobic adsorbent, was used to selectively adsorb CO 2 by vacuum swing adsorption in this study. The objective of this work is to study the feasibility and advantage of CO 2 capture along with simultaneous moisture removal by activated carbon and the effect of H 2O on CO 2 capture from wet flue gas streams. Through experiment and analysis, the “S” shape isotherms of water indicated water was easier to be desorbed from activated carbon. Then a cone shape model was proposed to depict water distribution inside the adsorption bed. As a consequence, water vapor hardly influenced the CO 2 capture performance. Moreover, the process can be operated under a relatively high vacuum pressure and short evacuation time. The preliminary results showed that our one-bed VSA process could yield a good CO 2 recovery of over 80% and a reasonable purity of 43%.

CO2 capture efficiency and energy requirement analysis of power plant using modified calcium-based sorbent looping cycle

This paper examines the average carbonation conversion, CO 2 capture efficiency and energy requirement for post-combustion CO 2 capture system during the modified calcium-based sorbent looping cycle. The limestone modified with acetic acid solution, i.e. calcium acetate is taken as an example of the modified calcium-based sorbents. The modified limestone exhibits much higher average carbonation conversion than the natural sorbent under the same condition. The CO 2 capture efficiency increases with the sorbent flow ratios. Compared with the natural limestone, much less makeup mass flow of the recycled and the fresh sorbent is needed for the system when using the modified limestone at the same CO 2 capture efficiency. Achieving 0.95 of CO 2 capture efficiency without sulfation, 272 kJ/mol CO 2 is required in the calciner for the natural limestone, whereas only 223 kJ/mol CO 2 for the modified sorbent. The modified limestone possesses greater advantages in CO 2 capture efficiency and energy consumption than the natural sorbent. When the sulfation and carbonation of the sorbents take place simultaneously, more energy is required. It is significantly necessary to remove SO 2 from the flue gas before it enters the carbonator in order to reduce energy consumption in the calciner. ► Compared with limestone, much less makeup of the limestone modified with acetic acid is needed. ► Achieving 0.95 of CO 2 capture without sulfation, 49 kJ/mol CO 2 is saved for modified sorbent. ► Modified limestone has greater advantages in CO 2 capture efficiency and energy consumption. ► It is highly necessary to remove SO 2 from the flue gas before carbonation for energy saving.

Carbonated water injection (CWI)–A productive way of using CO2 for oil recovery and CO2 storage

Abstract The main advantage of CO 2 is that at most reservoir conditions it is a supercritical fluid which is likely to develop miscibility with the oil. In reservoirs that miscibility cannot be achieved, CO 2 injection can lead to additional oil recovery by mixing with the oil and favourably modifying the flow properties of the oil. Displacement and recovery of oil by CO 2 injection has been studied and applied in the field extensively in the past three decades. Concerns over the environmental impact of CO 2 have led to a resurgence of interest in CO 2 injection in oil reservoirs. The injection of CO 2 can enhance oil recovery from these reservoirs and at the same time help mitigating the problem of increased CO 2 concentrations in the atmosphere by storing large quantities of CO 2 for a long period of time. CO 2 injection projects so far have been mainly limited geographically to oil fields located in areas where large quantities of CO 2 have been available mainly from natural resources. Various CO 2 injection strategies e.g. cyclic injection, continuous CO 2 flood, alternating (WAG) or simultaneous injection of CO 2 and water have been applied in these fields. With the new global interest in CO 2 injection, many other reservoir settings and scenarios are being considered for CO 2 injection in oil reservoirs. This may require injection strategies other than those conventionally used for CO 2 injection especially for offshore reservoirs or in cases where the supply of CO 2 can be variable or limited. An alternative CO 2 injection strategy is carbonated (CO 2 -enriched) water injection. In carbonated water, CO 2 exists as a dissolved phase as opposed to a free phase eliminating the problems of gravity segregation and poor sweep efficiency, which are characteristics of a typical CO 2 injection project. In fact, both viscosity and density of water increase as a result of the dissolution of CO 2 in water. In terms of CO 2 storage, through carbonated water injection, large volumes of CO 2 can be injected into the reservoir without the risk of leakage of CO 2 through caprock. Using the results of a series of high-pressure flow visualisation experiments, we reveal the underlying physical processes taking place during CWI. The results show that CWI, compared to conventional water injection, improves oil recovery in both secondary (pre-waterflood) and tertiary (post-waterflood) injection modes. Several key mechanisms taking place at the pore level during CWI leading to additional recovery are presented and discussed. Both conventional (light) oil and viscous oil was used in the experiments.

A symbiotic gas exchange between bioreactors enhances microalgal biomass and lipid productivities: taking advantage of complementary nutritional modes

This paper describes the association of two bioreactors: one photoautotrophic and the other heterotrophic, connected by the gas phase and allowing an exchange of O(2) and CO(2) gases between them, benefiting from a symbiotic effect. The association of two bioreactors was proposed with the aim of improving the microalgae oil productivity for biodiesel production. The outlet gas flow from the autotrophic (O(2) enriched) bioreactor was used as the inlet gas flow for the heterotrophic bioreactor. In parallel, the outlet gas flow from another heterotrophic (CO(2) enriched) bioreactor was used as the inlet gas flow for the autotrophic bioreactor. Aside from using the air supplied from the auto- and hetero-trophic bioreactors as controls, one mixotrophic bioreactor was also studied and used as a model, for its claimed advantage of CO(2) and organic carbon being simultaneously assimilated. The microalga Chlorella protothecoides was chosen as a model due to its ability to grow under different nutritional modes (auto, hetero, and mixotrophic), and its ability to attain a high biomass productivity and lipid content, suitable for biodiesel production. The comparison between heterotrophic, autotrophic, and mixotrophic Chlorella protothecoides growth for lipid production revealed that heterotrophic growth achieved the highest biomass productivity and lipid content (>22%), and furthermore showed that these lipids had the most suitable fatty acid profile in order to produce high quality biodiesel. Both associations showed a higher biomass productivity (10-20%), when comparing the two separately operated bioreactors (controls) which occurred on the fourth day. A more remarkable result would have been seen if in actuality the two bioreactors had been inter-connected in a closed loop. The biomass productivity gain would have been 30% and the lipid productivity gain would have been 100%, as seen by comparing the productivities of the symbiotic assemblage with the sum of the two bioreactors operating separately (controls). These results show an advantage of the symbiotic bioreactors association towards a cost-effective microalgal biodiesel production.

Molecular Exchange of CH4and CO2in Coal: Enhanced Coalbed Methane on a Nanoscale†

Coalbed methane (CH 4 ) is an important energy source. With increasing climate change concerns, coalbeds are also considered potential sinks for underground carbon dioxide (CO 2 ) storage. 1,2 Roughly twice the amount of CO 2 can be adsorbed than CH 4 in most bituminous coals. 1 Another advantage of CO 2 injection into coalbeds is the additional production of C H 4. This process is known as CO 2 -enhanced coalbed methane (ECBM) and is very attractive considering the increasing energy demand. Several ECBM pilot programs have been implemented in several parts of the world; 3,4 however, its full potential has yet to be exploited. 5 ECBM field operations can be better managed by an improved understanding of laboratory measurements and coalbed reservoir simulations. 6 Both CH 4 and CO 2 are predominantly stored in the micropores of the coal matrix, 7 which appear as isolated locations. 8 No consensus exists on measuring the total surface area, 9 the heat of adsorption, 1 or the theoretical description of adsorption, 10 partially because coal is difficult to characterize as a result of its heterogeneity 11 and complex response to CO 2 adsorption. 12 In this study, molecular simulations are used to identify energetically favorable adsorption regions, thereby testing the molecular exchange of CH 4 by CO 2 . 13,14 Our goal is to discuss the adsorption distribution at a molecular scale.

Does the use of carbon dioxide field flooding during heart valve surgery prevent postoperative cerebrovascular complications?

A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was whether there is any benefit with the use of carbon dioxide (CO(2)) field flooding techniques in heart valve surgery, in order to reduce postoperative neurological complications. Altogether 202 articles were found using the reported search, and six of them were used to answer the clinical question. All but one trial, were prospective, randomised. Four studies reported a significantly lower intracardiac bubble count in the CO(2) group. A significant reduction of p300 peak latencies in the CO(2) group was observed in one study. Otherwise, neurocognitive test batteries did not reveal any advantages of CO(2) field flooding in two studies. Three studies reported on postoperative cerebrovascular complications and the overall rate of stroke, transient ischemic attack (TIA) or prolonged reversible ischemic neurological deficit was 1.2% in the CO(2) group and 2.5% in the control group (P=ns). Although the use of CO(2) field flooding has been observed to be associated with a significantly lower count of intracardiac air bubbles, and improved survival in two small studies, so far there is no evidence of a sustained reduction of cerebrovascular complications with the use of this method.

Hollow fiber contained hydrogel-CA membrane contactor for carbon dioxide removal from the enclosed spaces

Control of CO 2 level within a certain range is one of the most important tasks in life support systems, such as spaceship and submarine. In order to control the membrane liquid evaporation into the gas phase for the hollow fiber contained carbonic anhydrase (CA) and its buffer membrane contactor (buffer-CA HFCLM), a poly(acrylic acid-co-acrylamide) (poly(AA-co-AM)) hydrogel showing biocompatibility is synthesized for the immobilization of CA. The hollow fiber contained hydrogel-CA membrane contactor (hydrogel-CA HFCLM) is then prepared for the comparison of operating stability and CO 2 removal efficiency with that of buffer-CA HFCLM. The results show that the loss of the membrane liquid is alleviated while the water-rich ambience is still retained by holding the water molecule within the network of the hydrogel. The hydrogel-CA HFCLM in combining both advantages of CO 2 facilitated transport using CA and the poly(AA-co-AM) hydrogel as facilitators shows higher CO 2 removal capability, reducing CO 2 from 0.52 vol.% in the inlet feed gas to under 0.09% while the buffer-CA HFCLM only reducing CO 2 to 0.32% under the same operating conditions. Consequently, as a safer and more reliable CO 2 removal system, the hydrogel-CA HFCLM deserves to be further studied.

Environmentally Benign Multiphase Catalysis with Dense Phase Carbon Dioxide.

Abstract Environmental concerns stemming from the use of conventional solvents and from hazardous waste generation have propelled research efforts aimed at developing benign chemical processing techniques that either eliminate or significantly mitigate pollution at the source. This paper provides an overview of heterogeneous and homogeneous catalysis in dense phase CO 2 , considered a green solvent. In addition to solvent replacement, the demonstrated advantages of using dense phase CO 2 include the enhanced miscibility of reactants, such as O 2 and H 2 which eliminate interphase transport limitations, and the chemical inertness of CO 2 . Further, the physicochemical properties of CO 2 -based reaction media can be pressure-tuned to obtain unique fluid properties (e.g. gas-like transport properties, liquid-like solvent power and heat capacities). The advantages of CO 2 -based reaction media for optimizing catalyst activity and product selectivity are highlighted for a variety of reactions including alkylation on solid-acid catalysts, hydrogenation on supported noble metal catalysts and a broad range of homogeneous oxidations with transition metal catalysts and dioxygen as an oxidant. Through these examples, the need is emphasized for a systematic approach to research and development of supercritical carbon dioxide based processes, taking into account conventional multiphase reaction engineering principles, catalytic chemistry and phase behavior.

Advantages of CO 2 in diagnostic hysteroscopy

Advantages of CO 2 in diagnostic hysteroscopy

Laparoscopy: searching for the proper insufflation gas.

Although many aspects of laparoscopic surgery have been determined, the question of which insufflation gas is the best arises repeatedly. The aim of this study was to review the findings on the major gases used today in order to provide information and guidelines for the laparoscopic surgeon. We reviewed the literature for clinical and laboratory studies on the currently used laparoscopic insufflation gases: carbon dioxide (CO(2)), nitrous oxide (N(2)O), helium (He), air, nitrogen (N(2)), and argon (Ar). The following parameters were evaluated: acid-base changes, hemodynamic and respiratory sequelae, hepatic and renal blood flow changes, increase in intracranial pressure, outcome of venous emboli, and port-site tumor growth. The major advantage of CO(2) is its rapid dissolution in the event of venous emboli. Hemodynamic and acid-base changes with CO(2) insufflation usually are mild and clinically negligible for most patients. Although N(2)O is advantageous for procedures requiring local/regional anesthesia, it does not suppress combustion. Findings show that Ar may have unwanted hemodynamic effects, especially on hepatic blood flow. There are almost no hemodynamic or acid-base sequelae with the use of He, air, and N(2), but they dissolve slowly and carry a potential risk of lethal venous emboli. Clearly, CO(2) maintains its role as the primary insufflation gas in laparoscopy, but N(2)O has a role in some cases of depressed pulmonary function or in local/regional anesthesia cases. Other gases have no significant advantage over CO(2) or N(2)O and should be used only in protocol studies. The relation of port-site metastasis to a specific type of gas requires further research.

Advantages of CO 2 OtoScan laser vs. conventional CO 2 laser for office-based LAM

Advantages of CO 2 OtoScan laser vs. conventional CO 2 laser for office-based LAM

The Advantage of CO2-Treated Dental Necks, in Comparison with a Standard Method: Results of an in Vivo Study

Various methods are used for treatment of hypersensitive dental necks. They all aim to seal exposed dentinal tubules, which are open toward the oral cavity and transmit stimuli to the sensitive nerve endings of the tooth pulp. The main sealing materials are fluoride preparations, strontium chloride, and hydroxyapatite. However, these materials must be applied periodically to achieve permanent freedom from pain. Since the introduction of laser technology into dentistry, efforts have been made to treat dentine hypersensitivity with the laser. An in vitro study revealed that CO2 laser irradiation results in almost complete closure of the dentinal tubules in the dental neck region. In the present in vivo study, the efficacy of laser treatment was examined in 72 patients with dentine hypersensitivity and 72 control patients over a period of 12 weeks. When success was defined as complete freedom from pain, the success rate in the laser group was 94.5%; when marked pain relief was included in the definition of treatment success, 98.6% of the patients were treated successfully. Treatment of the control group with conventional dental neck fluoridation resulted in no marked improvement. Laser Doppler measurements of pulpal blood flow immediately before and after treatment revealed no effects of laser irradiation on pulpal blood flow. Dentine samples were obtained from the dental necks 6 weeks after laser treatment and examined with atomic absorption spectroscopy (AAS). Tin was present in the samples, which suggests that the combined laser treatment and fluoridation result in permanent integration of fluoride in the dentine surface.

EVALUATION OF SOLUTIONS FOR SMALL INTESTINAL PRESERVATION

A number of organ preservation solutions have been formulated to slow the inevitable progression of ischemic injury, thus prolonging the storage time between removal and implantation. As adenine nucleotide content has been shown to correlate with the functional recovery of transplanted livers and hearts, this study investigated the effects of 24 hr of storage in three preservation solutions, saline (SA), Euro-Collins (CO), and University of Wisconsin (UW) on adenine and nicotinamide adenine nucleotides and inosine content of the rat small intestine. Significant biochemical differences were found between segments as early as after the initial perfusion when the inosine content was higher in UW-perfused than CO- or SA-perfused segments. After 2 hr of storage in CO solution and after 6 and 24 hr in both CO and UW solutions, the ATP content was higher than in SA-stored segments. In addition to inosine, which was significantly higher at all time points for UW-stored segments, the AMP and total adenine nucleotide content of UW-stored segments at 24 hr was significantly higher than SA- or CO-stored segments. After 24 hr of storage, those segments stored in UW were able to utilize significantly more oxygen than SA-stored. These data provide biochemical evidence supporting the advantages of CO and UW storage solutions over SA for preservation of small intestine segments.