This paper reports the visual observations of the formation and growth of clathrate hydrate crystals on the surface of a water droplet exposed to a methane þ ethane þ propane gas mixture. The compositions of the methane þ ethane þ propane gas mixtures are (i) 99.47:0.51:0.02, (ii) 94.1:5.8:0.1, and (iii) 90:7:3 molar ratio. The nucleation of the hydrate first occurred at a random point on the water droplet and then the hydrate grew to form a polycrystalline layer covering the droplet. We visually observed the individual crystals that constitute the polycrystalline hydrate layer and classified the morphology of the hydrate crystals depending on the system subcooling ΔT sub and system pressure. It was found that the size of the individual mixed-gas hydrate crystals decreased with the increasing ΔT sub as observed for the simple hydrates each formed with methane, ethane, or propane. The size of the individual crystals decreased with the increasing molar ratio of methane in the gas mixtures. The mixed-gas hydrate crystals exhibited a morphology different from that of the simple methane hydrate. We also measured the lateral growth rates of the hydrate-film propagation. In any of the systems, the rates increased with increasing ΔT sub as observed in other hydrate-forming systems.

This paper reports the visual observations of the clathrate hydrate crystal growth and morphology at the interface of aqueous NaCl solutions and a guest-substance liquid. The hydrate crystal growth was visually characterized in the systems of a wide range of NaCl concentrations from 0.035 to 0.264 in mass fraction. The mass fraction 0.035 was corresponding to that of ordinary seawater, and the salt concentration tested was extended up to the saturation level, i.e., 0.264. Cyclopentane was used as the guest substance. Formation and growth of hydrate crystals at the cyclopentane-NaCl solution interface were observed. We visually analyzed the individual hydrate crystals and classified the morphology of the crystals according to ΔT sub at atmospheric pressure. It was found that the size of the individual hydrate crystals decreased with increasing ΔT sub . The results showed that the morphology of the individual hydrate crystals in any NaCl concentration is roughly similar at a given ΔT sub . We also measured the lateral growth rates of the hydrate-film propagation. The hydrate film growth rate decreased with decreasing ΔT sub in any of the systems and decreased with increasing concentration of NaCl at a given ΔT sub .

Visual observations of the effect of surfactants on clathrate hydrate crystal growth at the interface of water and cyclopentane has been studied. Surfactants used in the present study are sorbitan monooleate (Span 80), naphthenic acid, and polypropylene glycol. The surfactants were each used at a mass fraction of 0.001% and 0.01%. All the surfactants were soluble in cyclopentane. The crystalline morphology and crystal growth behavior of the hydrate at the interface were found to be substantially affected by the addition of all surfactants. The size of the individual hydrate crystals in the surfactant system was larger than those in the pure cyclopentane system. The observations showed a distinct variation in the behavior of cyclopentane hydrate crystal growth depending on the chemical species of the surfactants, their concentration, and ΔT sub , which is defined as the difference between the equilibrium temperature and the experimental temperature. For the system with surfactants, the growing hydrate crystals did not engulf the interface, because the crystal grains that have grown detached from the interface and fallen into the water. From the observations, it is clear that hydrate crystal production increased in comparison to systems without surfactants due to the interface area being preserved. These observations explain the physical mechanism of two surfactant effects, where one is the prevention of hydrate agglomeration (interface area preservation) and the other is the promotion of hydrate production.

Growth rate of a hydrate layer at the guest/liquid-water interface is analyzed considering the conjugate process of the mass-transfer and hydrate crystal growth. Hydrate-layer growth rate data in the literature are often compiled according to the system subcooling (∆T ≡ T eq − T ex , where T eq is the equilibrium dissociation temperature of the hydrate and T ex is the system temperature), suggesting predominant heat transfer limitations. In this paper, we investigate how the existing data on hydrate-layer growth is better correlated to mass transfer of the guest species in liquid water in three-phase equilibrium with bulk guest fluid and hydrate. We have analyzed the conjugate processes of mass-transfer/hydrate-layer-growth following our previous study on the hydrate crystal growth into liquid water saturated with a guest substance. A dimensionless parameter representing the hydrate-layer growth rate is derived from the analysis. This analysis is based on the idea that the growth rate is controlled by the mass transfer of the hydrate-guest substance, dissolved in the bulk of liquid water, to the front of the growing hydrate-layer along the guest/water interface. The variations in the hydrate-layer growth rate observed in the previous studies are related to the dimensionless parameter.

BackgroundData on the extent of treat-to-target (T2T) recommendations application in SpA patients across Asia Pacific region is lacking. APLAR SpA Registry aimed to assess the utility of T2T on long term clinical outcomes, and to improve disease management and inform health care policy.ObjectivesTo provide a snapshot of the registry including demographics, disease activity and medication use.MethodsPatients fulfill the CASPAR 2006 for psoriatic arthritis (PsA) and 2009 ASAS criteria for axial spondylitis (AxSpA) were recruited. This cross sectional analysis included the first 188 patients recruited across 7 Asia Pacific regions (Hong Kong, Singapore, Korea, Thailand, India, Qatar & Pakistan).Results83 patients PsA and 115 AxSpA patients were included. They had moderate inflammation (DAPSA: 19.61±14.29, ASDAS: 2.32±1.07). Majority of PsA patients received conventional synthetic disease-modifying drug (csDMARDs, 81%) with relatively low prevalence of biologic DMARDs (bDMARDs) (24%). Most AxSpA patients used NSAIDs (79%) while nearly half of them received bDMARDs (49%). Other details listed in Table 1. Prevalence of bDMARDs use in our registry was lower than that from the USA (Corrona PsA Registry, 59%), Turkey & Canada (PsArt-ID, 40%) and the Netherlands AxSpA registry (56%) (1-3). Regarding T2T, 28% and 44% of PsA patient achieved minimal disease activity (MDA) and Disease Activity in Psoriatic Arthritis low disease activity (DAPSA LDA) respectively. The proportion of patients achieving target in other cohorts were 46% for MDA (PsArt-ID) and 46% for DAPSA LDA (Corrona) (1, 2). 37% and 47% of AxSpA patient achieved Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)<4 and Ankylosing Spondylitis Disease Activity Score (ASDAS) LDA. Proportion of patients achieving ASDAS LDA were similar to the Netherlands registry for patients with ASDAS LDA or BASDAI<4 (Figure 1A)(3). Patient on bDMARD were more likely to achieve treatment target (Figure 1B). There were no significant difference between socio-economic status and disease features between bDMARD user and non-user.Table 1.Demographics, clinical features and disease activity of patientsPsA (n=83)AxSpA (n=115)Age50.012.836.512.4Male n, %4251%8583%Asian n, %83100%10196%Disease duration, years7.17.35.27.6Any sacroiliitis n, %10299%HLA B27, positive n, %9189%Duration of early morning stiffness, min30392529Tender joint count7901Swollen joint count3400No. of dactylitis digit1100PASI4.05.0SPRACC1201BASDAI2.82.0ESR, mm/h31262016CRP, mg/L10151127HAQ-DI0.610.610.390.51DAPSA19.6114.29ASDAS CRP2.321.07Data given in mean SD unless stated. No. of case from Hong Kong 40; Singapore 46; Korea 24; Thailand 20, India 15; Qatar 10; Pakistan 33; HLA - human leucucyte antigen; PASI - psoriasis area and severity index; SPRACC - Spondyloarthritis Research Consortium of Canada Enthesitis Index; BASDAI - Bath Ankylosing Spondylitis Disease Activity Index; ESR - erythrocyte sedimentation rate; CRP - C-reactive protein; HAQ-DI - Health assessment questionnaire disability index; DAPSA - Disease activity in Psoriatic Arthritis; ASDAS - Ankylosing Spondylitis Disease Activity ScoreFigure 1.(A) Achievement of LDA in APLAR SpA registry and other registry and (B) use of bDMARDs among patients in APLAR SpA registry with or without achieving LDAConclusionPatient using bDMARDs were more likely to achieve treatment target. We expect that when T2T is widely applied, better outcomes will be reported in future.References[1]Bakirci, S., et al. (2019). “What are the main barriers to achieve minimal disease activity in psoriatic arthritis in real life?” Clin Exp Rheumatol37(5): 808-812.[2]Beckers, E., et al. (2021). “Treat-to-target in axial spondyloarthritis: an observational study in daily practice.” Rheumatology (Oxford).[3]Ogdie, A., et al. (2021). “Effect of Multidomain Disease Presentations on Patients With Psoriatic Arthritis in the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.” J Rheumatol48(5): 698-706.Disclosure of InterestsIsaac T. Cheng: None declared, Ho SO: None declared, Ying Ying Leung Speakers bureau: received honorarium/ speaker fee from AbbVie, DKSH, Janssen, Novartis and Pfizer., Praveena Chiowchanwisawakit: None declared, Stanley Angkodjojo Speakers bureau: Boehringer Ingelheim Singapore in Nov 2021, Consultant of: Abbvie (Singapore), DKSH (Singapore) in 2021, Muhammad Ahmed Saeed: None declared, Kichul Shin: None declared, Mohit Goyal: None declared, Muhammad Haroon: None declared, Mohammed Hammoudeh Speakers bureau: Have you been paid as a speaker for (pharmaceutical) companies, Grant/research support from: participated in drug companies sponsored trials, Nallasivan Subramanian: None declared, Ho Yin Chung: None declared, James Cheng-Chung Wei: None declared, Mitsumasa Kishimoto Consultant of: MK received consulting fees and/or speaker fees from AbbVie, Amgen, Asahi-Kasei Pharma, Astellas, Ayumi Pharma, BMS, Chugai, Daiichi-Sankyo, Eisai, Eli Lilly, Gilead, Janssen, Kyowa Kirin, Novartis, Ono Pharma, Pfizer, Tanabe-Mitsubishi, and UCB Pharma., Lai-Shan Tam Consultant of: has acted as a consultant for Janssen, Pfizer, Sanofi, AbbVie, Boehringer Ingelheim, and Lilly, Grant/research support from: has received grant/research support from Amgen, Boehringer Ingelheim, Janssen, GSK, Novartis, and Pfizer