Fractional CO2 Research Articles

Dynamic modeling of geological carbon storage in an oil reservoir, Bredasdorp Basin, South Africa

Geological carbon storage provides an efficient technology for the large-scale reduction of atmospheric carbon, and the drive for net-zero emissions may necessitate the future usage of oil reservoirs for CO2 projects (without oil production), hence, dynamic modeling of an oil reservoir for CO2 storage in the Bredasdorp basin, South Africa, was therefore conducted. Injection into the reservoir was for 20 years (2030–2050), and 100 years (2050–2150) to study the CO2–brine–oil interactions, with sensitivities carried out on reservoir boundary conditions. The closed boundary scenario experienced pressure buildup with a target injection rate of 0.5 Mt/year, and a cutback on injection rate progressively until 2050 to not exceed the fracture pressure of the reservoir. The CO2 plume migration was not rapid due to the reduced volume of CO2 injected and the confining pressure. The system was gravity dominated, and gravity stability was not attained at the end of the simulation as fluid interfaces were not yet flat. The open boundary reservoir did not experience a pressure buildup because all boundaries were open, the target injection rate was achieved, and it was a viscous-dominated system. In both cases, the dissolution of CO2 in oil and brine was active, and there was a growing increase of CO2 fraction dissolved in water and oil, a decline in gaseous mobile CO2 phase between 2050 and 2150, and active trapping mechanisms were structural trapping, dissolution in oil and water, and residual trapping. The study showed that boundary condition was very crucial to the success of the project, with direct impacts on injection rate and pressure. This pioneering study has opened a vista on the injection of CO2 into an oil reservoir, and CO2–brine–oil interactions, with sensitivities carried out on reservoir boundary conditions in a closed and an open hydrocarbon system in South Africa.

Impact of different kinds of biomass mixtures on combustion performance, interaction and synergistic effects in cofiring of coal and biomass in steam power plants

Abstract The cofiring of biomass and coal may be one of the most effective methods to improve energy utilization efficiency and reduce greenhouse gas emissions. This study aims to investigate combustion performance, interaction and synergistic effects in the cofiring of coal and three types of biomass. Blended fuel consisting of coal and three types of biomass such as sawdust, rice husk and solid recovery fuel was selected as the research object. Ultimate and proximate analysis and differential thermogravimetric analysis with heating rates of between 10°C and 40°C/minute are used to analyse combustion characteristics. Simulation of combustion in a 600-MWe steam power plant with a Carolina-type boiler is also carried out with the help of computational fluid dynamic (CFD) analysis to see the effect of the interaction and synergy of the mixed fuel on the performance of the steam generator. The effect on the combustion process in the combustion chamber of a steam power plant is also simulated. Based on the analysis of several test results of parameters such as ignition temperature, burnout temperature, calorific value of the fuel mixtures as well as CFD simulation, the results of the study show a strong indication of a positive synergy in mixing some of these biomasses as compared with a fuel mixture consisting only of coal and one type of biomass. Practically no power derating of the boiler occurs until the biomass content in the fuel mixture is ~30% on a mass basis. The reduction in greenhouse gas emissions also appears significant from the results of the CFD simulation of this study, which is characterized by a decrease in the fraction of CO2 in flue gas from 21.5% for coal alone as fuel to 15.9% in the case of cofiring excluding the CO2 attributed to the biomass.

Analysis of CO2 hydrate formation from flue gas mixtures in a bubble column reactor

Gigascale carbon capture and sequestration (CCS) is increasingly seen as essential to meeting the targets of the Paris Agreement. As an alternative to conventional CCS approaches, carbon dioxide (CO2) hydrates have received attention as materials which can enable new approaches to carbon capture as well as carbon sequestration. CO2 hydrates (ice-like materials of CO2 and water) form at medium pressures (<400 psi) and temperatures of >0 °C from a water-CO2 mixture. Bubble column reactors (BCR) have been studied as a preferred way of forming CO2 hydrates. This study uses an inhouse, recently-developed modeling framework to predict performance of a BCR for CO2 hydrate formation from flue gas (CO2/N2), and pure CO2 streams. We highlight and analyze specific aspects of hydrate formation that are important for CO2 sequestration, and for CO2 separation/capture. In particular, two performance parameters are analyzed: i) gas consumption rate for hydrate formation (normalized with reactor volume), and ii) fraction of CO2 that converts to CO2 hydrates in a single pass (conversion factor). The first metric quantifies the overall productivity of a BCR by obtaining the net CO2 that can be sequestered or separated from the flue gas stream. The second metric relates to the efficiency of the system by quantifying the need for recirculation and the quality of the exit stream after a single pass. Extensive parametric analysis is conducted to study the influence of pressure, temperature, CO2 mole fraction at inlet, gas flow rate and reactor geometry on hydrate formation. Across the range of simulations conducted in this study, the highest gas consumption rate per unit reactor volume was 28.9 ton/yr/m3 and the highest conversion factor was 67.8 %. Both parameters increase with increasing pressure, decreasing temperature and increasing inlet mole fraction of CO2. Increasing gas flow rate increases the gas consumption rate (i.e., hydrate formation rate) but reduces the conversion factor. This suggests that the overall productivity of BCRs increases with gas flow rate at the expense of its efficiency. Reduced efficiency increases recirculation-related costs and high flow rate increases compression and cooling costs. For flue gas, increasing the reactor volume by increasing the height or diameter increases conversion factor but significantly reduces the gas consumption rate per unit reactor volume. For pure CO2, increasing the reactor height increases the conversion factor without changing the volumetric gas consumption rate. Decreasing the diameter increases volumetric gas consumption rate without changing the conversion factor. These findings suggest that compact reactors are more suitable for CO2 hydrate slurry production (on a volumetric basis), while larger reactors are suitable for CO2 separation/capture applications. Overall, this study provides a basis for the design and operation of BCRs for CO2 hydrates-based CCS applications.

Coupled wellbore-reservoir modelling to evaluate CO2 injection rate distribution over thick multilayer storage zones

Technical and economic feasibility of Geologic CO2 Storage (GCS) projects requires maximizing the amount of stored CO2 per unit pore space of the storage zone per well. Considering injection through a fully penetrating vertical well in a multi-layer thick aquifer, CO2 would be unevenly distributed over the aquifer thickness, underutilizing the available pore space. In this work, we use coupled wellbore-reservoir modelling to investigate the interplay between the parameters that control CO2 pore-space filling. Flow capacity profile and gravity/buoyancy override are the primary factors controlling CO2 flux into a layered system. In addition, a higher fraction of CO2 would flow into the aquifer top layers due to the difference in the hydrostatic pressure gradient between the well and the aquifer. Also, movement of CO2/brine interface within the wellbore, and temporal change in the average fluid mobility within layers can affect rate profile. Results show that CO2 rate distribution is solely controlled by the flow capacity profile and pressure difference when gravity is insignificant. Conversely, the injected CO2 is biased towards the aquifer top when buoyancy is strong. Higher gravity numbers amplify this behavior. Results also indicate that strong gravity may lead to underutilizing the bottom perforations which can trigger brine backflow and causes CO2-brine interface to rise within the wellbore. Pauses in the injection would amplify backflow which could increase salt precipitation near the wellbore affecting injectivity and rate distribution. Overall, we find that it may not be possible to reproduce the results of the coupled model using decoupled models.

Therapeutic Efficacy of Bovine Basic Fibroblast Growth Factor Combined with Ultrapulsed Fractional CO2 Laser in Acne Scars: Randomized Controlled Trial.

To observe the therapeutic efficacy of ultrapulsed fractional CO2 laser combined with bovine basic fibroblast growth factor (bFGF) on acne scars, so as to provide clinical evidence for future treatment of acne scars. One hundred and twenty patients with acne scars admitted between October 2021 and August 2022 were selected as the research participants, of which 60 cases treated with bFGF plus ultrapulsed fractional CO2 laser were regarded as the research group (RG) and 60 cases with ultrapulsed fractional CO2 laser therapy alone were set as the control group (CG). The clinical efficacy, Échelle d'évaluation clinique des cicatrices d'acné (ECCA) score, and scar base depth before and after treatment were comparatively analyzed, and changes in skin pore value, texture value and skin barrier function were detected. Finally, the duration of redness, scabbing and erythema after treatment and the incidence of adverse reactions after treatment were counted. A higher overall response rate was determined in RG versus CG (P<0.05). Besides, RG was lower than CG in post-treatment ECCA score, scar base depth, skin pore value, texture value and transepidermal water loss (TEWL), and higher in skin water and epidermal oil content (P<0.05). Moreover, the duration of redness, scabbing and erythema was shorter and the incidence of adverse reactions was lower in RG than in CG after treatment (P<0.05). The combination of bFGF and ultrapulsed fractional CO2 laser is highly effective and safe in the treatment of acne scars, which reserves widespread use in clinical practice.

Efficacy of low energy fractional carbon dioxide laser therapy in management of post-surgical hypertrophic scars

Background: aberrant &amp; accelerated wound-healing process that results in hypertrophic scarring causes extracellular matrix &amp; collagen to deposit abnormally in the dermis. After tissue damage occurs, a defensive reaction called tissue repair occurs. Aim; in this review; we aimed to present the effectiveness of low-energy fractional carbon dioxide laser therapy in treating hypertrophic scars following surgery. Summary: A safe &amp; effective approach for treating hypertrophic burn scars is fractional ablative CO2 laser therapy. Even though more treatment sessions have been necessary for satisfying outcomes, a big improvement can be seen after just one round of therapy. Combination therapy with other modalities can decrease the need for repetition of therapy as efficacy increases. Though, in some studies, combination therapy may shorten the duration of studied case downtime &amp; in others, combination therapy may increase side effects. essential for laser energy setting needs to be adjusted for each hypertrophic scar condition. larger research population &amp; longer follow-up period are recommended.

CO2 rich cushion gas for hydrogen storage in depleted gas reservoirs: Insight on contact angle and surface tension

Hydrogen storage in porous media (aquifers and depleted reservoirs) is an effective means of achieving large-scale inter-seasonal demand for energy. In particular, the depleted gas reservoir provides substantial storage capacity and additional economic incentives due to the preexistence of the storage infrastructure as well as the requisite reservoir integrity. However, the interfacial phenomenon between the injected hydrogen, the native gas (cushion gas), the formation brine, and the host rocks require further investigation for efficient gas containment. In this study, we conducted a comprehensive examination of the application of CO2 as a cushion gas. Our investigation involved performing contact angle and surface tension experiments using the drop shape analyzer (DSA) 100 equipment. We examined various gas mixtures (H2–CO2 – CH4–N2) under different pressure ranges (500–3000 psi), temperature levels (30, 40, 50, 60, 70 °C), and salinities (2, 5, 10, 15, and 20 wt%).Results indicate that the wettability behavior of the studied gas-mixture compositions remains relatively consistent unless there are changes in the initial wetting state of the rock. The contact angles observed ranged from 29 to 51°, independent of reservoir pressure, temperature, and salinity. The contact angle values increased with higher pressure but decreased with higher temperature. Furthermore, the contact angle was lower for a gas mixture with a lower CO2 fraction compared to a gas mixture with a higher CO2 fraction. Conversely, the gas mixture brine surface tension exhibited a decrease with increasing pressure, temperature, and CO2 fraction. However, it increased with increasing salinity for all gas mixtures. Based on the results obtained from the contact angle and surface tension analysis, mixture 4 emerged as the ideal fraction for designing CO2 cushion gas in terms of both hydrogen storage and withdrawal. These findings present precise and valuable input parameters and data that can be utilized in reservoir-scale simulations to optimize geo-storage in depleted natural gas reservoirs.

Modeling of the thermal-hydrodynamic and chemical regime of Geyser reservoir (Valley of Geyser, Kamchatka)

The thermal-hydrodynamic and chemical eight-decade history of the Geysers production reservoir in the Valley of Geysers (Kamchatka) shows either linear multiyear trends, seasonal cycles, or stepwise changes synchronized with geological catastrophes. Recent changes, apparently caused by surface meteoric water inflow into the productive Geysers reservoir as a result of caprock erosion from the 2007 catastrophic landslide and 2014 mud-flow, include: (1) seasonality of deep component discharge, (2) a drop in CO2 fraction of the gas content of geysers followed by a decrease in geyser eruption capacity, (3) increases in standard geothermometers (Na/K and SiO2) and (4) increases in the sulfate component. 2D numerical thermal-hydrodynamic (TH) model was developed and applied to explain the seasonal decrease in deep component discharge as an effect of gas phase condensation and upflows capture caused by cold water infiltration from the surface during flood periods. Thermo-hydrodynamic-chemical (THC) models and total chemical discharge/recharge balances were used to explain CO2 sequestration, increased sulfate component, and increased standard geothermometers due to gypsum/calcite transformation in surface water infiltration pathways rather than reservoir heating.

Efficacy of fractional CO2 laser in combination with stromal vascular fraction (SVF) compared with fractional CO2 laser alone in the treatment of burn scars: a randomized controlled clinical trial

BackgroundThe appearance of skin scars is known as one of the main side effects of skin burns. Stromal vascular fraction (SVF), as a rich source of cell populations with tissue regeneration properties, plays an important role in the healing of skin lesions. Fractional CO2 lasers have occupied a special place in treating skin lesions, particularly skin scars, since their introduction. Our study aimed to compare the combination of SVF and fractional CO2 laser with fractional CO2 laser alone in the treatment of burn scars.MethodThis double-blind clinical trial study was conducted on ten patients with burn scars that were treated three times with a fractional CO2 laser at site of burn lesions, and one of the two areas studied was randomly injected with SVF. Two months after completion of the procedure, patients' scars were assessed using the Vancouver scar scale (VSS), biometric criteria, and physician and patient satisfaction ratings.ResultsThe results confirmed a significant improvement in VSS, cutometry, R7 criteria, complete density sonography, and skin density sonography in the fractional CO2 laser-treated group. The VSS criteria, epidermal thickness sonography, complete density sonography, and skin density sonography in the group treated with the combination of fractional CO2 laser and SVF also showed significant improvement. The VSS criteria and melanin index of Mexameter in the group treated with SVF in combination with fractional CO2 laser were significantly better than the group treated with fractional CO2 laser alone. Also, physician and patient satisfaction in the group treated with SVF injection in combination with fractional CO2 laser was significantly higher than the other group.ConclusionThe results confirm the efficacy of SVF injection in combination with fractional CO2 laser in the treatment of burn scars and can be considered as a treatment option for better management of these lesions.Trial registration: The study protocol was retrospectively registered at Iranian Registry of Clinical Trials with code: IRCT20210515051307N1, Registration date: 2021-11-14, URL: https://www.irct.ir/trial/56337.

Efficacy of fractional CO2 laser therapy combined with hyaluronic acid dressing for treating facial atrophic acne scars: a systematic review and meta-analysis of randomized controlled trials.

The present work aimed to systematically identify the efficacy and safety of fractional carbon dioxide (CO2) laser plus hyaluronic acid (HA) dressing in dealing with facial atrophic acne scars. Randomized controlled trials (RCTs) concerning fractional CO2 laser in combination with HA dressing for treating atrophic acne scars were screened in 8 electronic databases (containing PubMed, Embase, the Cochrane Library, Web of Science, China National Knowledge Internet, Wanfang, Sinomed as well as VIP). Besides, for the purpose of evaluating the risk of bias of the enrolled RCTs, the Cochrane Collaboration tool was adopted. Statistical analysis was completed using Revman5.3 software and Stata 14.0 software. Meanwhile, the quality of evidence was assessed by the GRADE system. Finally, 6 studies involving 623 patients were enrolled. According to the findings in this study, compared with fractional CO2 laser alone, fractional CO2 laser therapy combined with HA dressing reduced the scores of ECCA (échelle d'évaluation clinique des cicatrices d'acné) grading scale (MD=-3.37,95% CI [-5.03, -1.70], P<0.0001), shortened the time of crust formation (MD=-0.42,95% CI [-0.80, -0.04], P=0.03) and the time of crust removal(MD=-1.31,95% CI [-1.67, -0.95], P<0.00001), enhanced patient satisfaction (RR=1.85, 95% CI [1.44, 2.38], P<0.00001). All the reported adverse events including hyperpigmentation, erythema, edema, mild itching, and slight burning pain were controllable. In addition, fractional CO2 laser combined with HA dressing therapy had a lower incidence of hyperpigmentation than fractional CO2 laser alone (RR=0.37, 95% CI [0.23, 0.61], P<0.0001). The level of evidence for outcomes was classified to be low to moderate. According to our findings, fractional CO2 laser combined with HA dressing is efficacious and safe option for facial atrophic acne scars. Nevertheless, more high-quality trials are required for further verification in the future.

Vaginal Laser Treatment for the Genitourinary Syndrome of Menopause in Breast Cancer Survivors: A Narrative Review.

Vulvovaginal atrophy (VVA) is a chronic condition resulting from reduced estrogen levels during menopause. The North American Menopause Society and the International Society for the Study of Women's Sexual Health suggested the term "genitourinary syndrome of menopause" (GSM) to indicate the broader aspects of VVA. Breast cancer treatments, such as chemotherapy and endocrine therapy, can induce early and abrupt menopausal symptoms, including GSM, which negatively affects sexual function and the quality of life of the survivors. Vaginal laser therapy has emerged as a safe and effective option for the management of GSM in breast cancer survivors (BCSs). Two main types of lasers, the non-ablative erbium:YAG laser and fractional microablative CO2 vaginal laser, have been evaluated for GSM treatment. While there are few randomized controlled trials (RCTs) on the subject of BCSs, a wealth of prospective and retrospective studies have highlighted the beneficial effects of vaginal laser therapy on the symptoms of VVA, vaginal health, sexual function, and overall quality of life. More comprehensive research is essential to confirm its enduring effectiveness and safety, with a focus on conducting standardized and meticulously controlled investigations. This study is a narrative review that summarizes clinical trials ranging from the earliest to the most recent ones on laser treatment for GSM in BCSs.

Seasonal and Diurnal Variations in XCO2 Characteristics in China as Observed by OCO‐2/3 Satellites: Effects of Land Cover and Local Meteorology

AbstractMonitoring the dynamics of atmospheric CO2 is crucial for enhancing comprehension of the carbon cycle. Using column‐averaged dry‐air mole fraction of CO2 (XCO2) data collected by the Orbiting Carbon Observatory (OCO)‐2 and OCO‐3 satellites during 2020–2021, this study explored seasonal and diurnal variations in XCO2 characteristics in typical land cover biomes in China, and investigated their relationships with meteorological drivers. Results showed that XCO2 products retrieved by OCO‐2 and OCO‐3 have good agreement with Total Carbon Column Observing Network measurements, with average deviations of 0.8 and 1.2 ppm, respectively. The satellite observations revealed XCO2 hotpots located mainly in central and eastern China, and areas of low XCO2 values in western China, with a seasonal curve that was highest (lowest) in spring (summer). The largest seasonal cycle amplitude (∼9 ppm) of XCO2 was observed in forest areas, highlighting its key role in carbon exchange. Additionally, XCO2 was found to have a near‐sinusoidal diurnal pattern, characterized by rapid decrease in the early morning as photosynthesis resumed after sunrise, as indicated by the sun‐induced chlorophyll fluorescence (SIF), a peak at around midday, and subsequent decrease as SIF increased after mid‐afternoon. Urban regions had the highest diurnal cycle amplitude (∼6 ppm) among biomes. Statistical analyses revealed seasonal shift and nonlinear variation in the relationships between XCO2 and meteorological variables, suggesting that CO2 uptake is influenced by favorable humidity conditions. These relationships also provide insight into the sensitivity and adaptability of XCO2 to meteorological factors in diverse ecosystems such as savanna and grassland.

Inter-comparison and evaluation of global satellite XCO2 products

ABSTRACT Carbon dioxide (CO2) is one of the main greenhouse gases and has become a major concern as its concentration has been growing in recent years. Satellite remote sensing is an efficient way to monitor CO2 in the atmosphere, and several satellites are already used for CO2 monitoring. It is imperative to investigate the spatial coverage and spatio-temporal trends of satellite products, as well as identify the satellites with higher levels of accuracy. Additionally, examining the disparities between the older and new generations of satellites would be meaningful. Therefore, this paper provides a comprehensive evaluation and inter-comparison for the commonly used satellite column-averaged dry-air mole fraction of CO2 (XCO2) products. Specifically, the temporal trends and monthly coverage of the Greenhouse Gases Observing SATellite (GOSAT), Greenhouse Gases Observing SATellite-2 (GOSAT-2), Orbiting Carbon Observatory-2 (OCO-2), Orbiting Carbon Observatory-3 (OCO-3), and SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) are investigated. The accuracy of these satellite products is evaluated and analyzed based on Total Carbon Column Observing Network (TCCON) data. The results indicate that the XCO2 of all the satellite products show a year-by-year increase, with seasonal periodicity. In terms of overall accuracy, the OCO series satellites exhibit a slightly higher level of accuracy compared to the GOSAT series. The products of the new generation of satellites are less stable than those of the older generation, probably due to the impacts of the inversion algorithm and platforms.

Solubility and interfacial tension models for CO2–brine systems under CO2 geological storage conditions

Thermodynamic properties of the CO2–brine pseudo-binary system are essential for the design of geological carbon storage (GCS) projects, especially those utilizing saline aquifers. The gas–liquid–solid interactions manifest in the interfacial tensions (IFTs) and contact angle determine the injectability, sealing capacity, and storage security of the GCS process. Dissolution of CO2 in the reservoir brine occurs throughout the entire GCS process, leading to enhanced storage capacity but also to acidification of the brine, possibly leading to reservoir or seal damage. Two of the most important thermodynamic properties of the fluids are the mutual solubility and the IFT of the CO2–brine pseudo-binary system. In this work, we report a new correlative model for the IFT between CO2- and water-rich phases over wide ranges of temperature (273 to 473 K) and pressure (up to 100 MPa). The model is parameterized for brines comprising any combinations of sodium, potassium, calcium and magnesium cations with chloride, sulphate and bicarbonate anions up to a total molality of at least 5 mol·kg−1. The independent variables in this new model are reduced temperature, ion molalities and the mole fraction of CO2 dissolved in the aqueous phase. The latter is related to temperature, pressure and ion molalities by an improved model for the mutual solubility. More than 2000 experimental data points were used in the development of the two models. For the IFT of the CO2-H2O binary system, the overall root-mean-square deviation (RMSD) is 0.65mN·m−1 while the absolute average relative deviation (AARD) is 1.8%. In the case of mutual solubility, the RMSD of CO2 mole fraction in the aqueous phase is 0.0003 and the AARD is 5.5% while, in the non-aqueous phase, the RMSD of H2O mole fraction is 0.0035 and the corresponding AARD is 8.7%. Similar results are found for the CO2-brine systems.

SMOOTH protocol: A pilot randomised prospective intra-patient single-blinded observational study for examining the mechanistic basis of ablative fractional carbon dioxide laser therapy in treating hypertrophic scarring.

Burn injuries are the fourth most common type of trauma and are associated with substantial morbidity and mortality. The impact of burn injury is clinically significant as burn injuries often give rise to exuberant scarring. Hypertrophic scarring (HTS) is a particular concern as up to 70% of burns patients develop HTS. Laser therapy is used for treating HTS and has shown positive clinical outcomes, although the mechanisms remain unclear limiting approaches to improve its effectiveness. Emerging evidence has shown that fibroblasts and senescent cells are important modifiers of scarring. This study aims to investigate the cellular kinetics in HTS after laser therapy, with a focus on the association of scar reduction with the presence of senescent cells. We will conduct a multicentre, intra-patient, single-blinded, randomised controlled longitudinal pilot study with parallel assignments to achieve this objective. 60 participants will be recruited to receive 3 interventional ablative fractional CO2 laser treatments over a 12-month period. Each participant will have two scars randomly allocated to receive either laser treatment or standard care. Biopsies will be obtained from laser-treated, scarred-no treatment and non-scarred tissues for immune-histological staining to investigate the longitudinal kinetics of p16INK4A+-senescent cells and fibroblast subpopulations (CD90+/Thy1+ and αSMA+). Combined subjective scar assessments including Modified Vancouver Scar Scale, Patient and Observer Scar Assessment Scale and Brisbane Burn Scar Impact Profile; and objective assessment tools including 3D-Vectra-H1 photography, DermaScan® Cortex, Cutometer® and ColoriMeter®DSMIII will be used to evaluate clinical outcomes. These will then be used to investigate the association between senescent cells and scar reduction after laser therapy. This study will also collect blood samples to explore the systemic biomarkers associated with the response to laser therapy. This study will provide an improved understanding of mechanisms potentially mediating scar reduction with laser treatment, which will enable better designs of laser treatment regimens for those living with HTS. ClinicalTrials.gov: NCT04736251.

Central sleep apnea treated by a constant low-dose CO2 supplied by a novel device.

CO2 inhalation has been previously reported as a treatment for central sleep apnea both when associated with heart failure or where the cause is unknown. Here, we evaluated a novel CO2 supply system using a novel open mask capable of comfortably delivering a constantly inspired fraction of CO2 ([Formula: see text]) during sleep. We recruited 18 patients with central sleep apnea (13 patients with cardiac disease, and 5 patients idiopathic) diagnosed by diaphragm electromyogram (EMG) recordings made during overnight full polysomnography (PSG) (night 1). In each case, the optimal [Formula: see text] was determined by an overnight manual titration with PSG (night 2). Titration commenced at 1% CO2 and increased by 0.2% increments until central sleep apnea (CSA) disappeared. Patients were then treated on the third night (night 3) with the lowest therapeutically effective concentration of CO2 derived from night 2. Comparing night 1 and night 3, both apnea-hypopnea index (AHI; 31 ± 14 vs. 6 ± 3 events/h, P < 0.01) and arousal index (22 ± 8 vs. 15 ± 8 events/h, P < 0.01) were significantly improved during CO2 treatment. Sleep efficiency improved from 71 ± 18 to 80 ± 11%, P < 0.05, and sleep latency was shorter (23 ± 18 vs. 10 ± 10 min, P < 0.01). Heart rate was not different between night 1 and night 3. Our data confirm the feasibility of our CO2 delivery system and indicate that individually titrated CO2 supplementation with a novel device including a special open mask can reduce sleep disordered breathing severity and improve sleep quality. Randomized controlled studies should now be undertaken to assess therapeutic benefit for patients with CSA.NEW & NOTEWORTHY A novel device using a special mask was developed and proved that CO2 therapy using the device could eliminate central sleep apnea (CSA) events and improve sleep quality including reducing arousal index in patients with heart failure. The device would become a useful clinical treatment for heart failure patients with CSA.

Emission and in-cylinder combustion characteristics of a spark ignition engine operated on binary mixtures of gas and liquid fuels

In this study, three different gas fuels such as hydrogen, propane, methane and six different liquid fuels such as, benzene, gasoline, toluene, hexane, methanol and ethanol have been combined and combustion characteristics have been simulated for a spark ignition engine (SIE). Variation of in-cylinder temperature, in-cylinder pressure, CO, CO2 and NO has been investigated. The gas fuel ratios in the mixtures were changed between 0 and 100% by mass. It was investigated that how the addition of gaseous fuels to liquid fuels at different ratios affects the combustion characteristics and emission formation. The gas fuel ratios considerably affected emission and combustion specifications of the engine. Increasing liquefied gas fuel ratio in the mixture leads to decrement in the temperature of charge. The maximum pressure first increases with increasing gas fuel ratio and then start to minimize after maximum pressure. The maximum peak pressure values are observed at 50% gasoline and 50% methane, 75% gasoline and 25% propane, 50% gasoline-50% hydrogen as 48.1 bar, 46 bar and 62.4 bar for different gas fuel mixtures. The minimum peak pressure value is displayed at 100% methanol as 44.06 bar. The maximum temperature value is observed at 100% benzene as 2582 K and its minimum value seems at 100% hydrogen as 2059 K. The maximum mass fractions of CO, CO2, NO are observed at 100% benzene as 0.0271, 0.161, 0.0076, the minimum mass fraction of CO2 is observed at 100% methane as 0.095. The minimum mass fraction of CO is observed at 100% methanol as 0.01243. The minimum mass fraction of NO is observed at 100% hydrogen as 0.00085. The fuels are ranked using a multi-criteria decision-making algorithm called AHP after evaluating the values of all performance criteria and their respective sub-criteria, including in-cylinder pressure, in-cylinder temperature, NO, CO2 and CO to get preference rank between fuels.

A retrieval of xCO2 from ground-based mid-infrared NDACC solar absorption spectra and comparison to TCCON

Abstract. Two global networks of ground-based Fourier transform spectrometers are measuring abundances of atmospheric trace gases that absorb in the near infrared and mid-infrared: the Network for the Detection of Atmospheric Composition Change (NDACC) and the Total Carbon Column Observing Network (TCCON). The first lacks a CO2 product; therefore, this study focuses on developing an xCO2 retrieval method for NDACC from a spectral window in the 4800 cm−1 region. This retrieval will allow extending ground-based measurements back in time, which we will demonstrate with historical data available from Ny-Ålesund, Svalbard. At this site, both TCCON and NDACC measurements are routinely performed, which is an advantage for collocated comparisons. The results are compared with collocated TCCON measurements of column-averaged dry-air mole fractions of CO2 (denoted by xCO2) in Ny-Ålesund, Svalbard, and only TCCON in Burgos, Philippines. We found that it is possible to retrieve xCO2 from NDACC spectra with a precision of 0.2 %. The comparison between the new retrieval and TCCON showed that the sensitivity of the new retrieval is high in the troposphere and lower in the upper stratosphere, similar to TCCON, as seen in the averaging kernels, and that the seasonality is well captured as seen in the retrieved time series. Additionally, we have included a retrieval strategy suggestion to improve the quality of the xCO2 product.

Assessment of Safety and Efficacy: Fractional CO2 Laser Treatment for Acne Scars

Assessment of Safety and Efficacy: Fractional CO2 Laser Treatment for Acne Scars

40725 Fractional CO2 laser for active acne treatment: A Case Series

40725 Fractional CO2 laser for active acne treatment: A Case Series