| 1. |
- Aleksich, Mariya, et al.
(författare)
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XFEL Microcrystallography of Self-Assembling Silver n-Alkanethiolates
- 2023
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Ingår i: Journal of the American Chemical Society. - 0002-7863. ; 145:31, s. 17042-17055
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Tidskriftsartikel (refereegranskat)abstract
- New synthetic hybrid materials and their increasing complexity have placed growing demands on crystal growth for single-crystal X-ray diffraction analysis. Unfortunately, not all chemical systems are conducive to the isolation of single crystals for traditional characterization. Here, small-molecule serial femtosecond crystallography (smSFX) at atomic resolution (0.833 Å) is employed to characterize microcrystalline silver n-alkanethiolates with various alkyl chain lengths at X-ray free electron laser facilities, resolving long-standing controversies regarding the atomic connectivity and odd-even effects of layer stacking. smSFX provides high-quality crystal structures directly from the powder of the true unknowns, a capability that is particularly useful for systems having notoriously small or defective crystals. We present crystal structures of silver n-butanethiolate (C4), silver n-hexanethiolate (C6), and silver n-nonanethiolate (C9). We show that an odd-even effect originates from the orientation of the terminal methyl group and its role in packing efficiency. We also propose a secondary odd-even effect involving multiple mosaic blocks in the crystals containing even-numbered chains, identified by selected-area electron diffraction measurements. We conclude with a discussion of the merits of the synthetic preparation for the preparation of microdiffraction specimens and compare the long-range order in these crystals to that of self-assembled monolayers.
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| 2. |
- Canton, Sophie E., et al.
(författare)
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Ultrafast Jahn-Teller Photoswitching in Cobalt Single-Ion Magnets
- 2023
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Ingår i: Advanced Science. - 2198-3844. ; 10:21
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Tidskriftsartikel (refereegranskat)abstract
- Single-ion magnets (SIMs) constitute the ultimate size limit in the quest for miniaturizing magnetic materials. Several bottlenecks currently hindering breakthroughs in quantum information and communication technologies could be alleviated by new generations of SIMs displaying multifunctionality. Here, ultrafast optical absorption spectroscopy and X-ray emission spectroscopy are employed to track the photoinduced spin-state switching of the prototypical complex [Co(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) in solution phase. The combined measurements and their analysis supported by density functional theory (DFT), time-dependent-DFT (TD-DFT) and multireference quantum chemistry calculations reveal that the complex undergoes a spin-state transition from a tetragonally elongated doublet state to a tetragonally compressed quartet state on the femtosecond timescale, i.e., it sustains ultrafast Jahn-Teller (JT) photoswitching between two different spin multiplicities. Adding new Co-based complexes as possible contenders in the search for JT photoswitching SIMs will greatly widen the possibilities for implementing magnetic multifunctionality and eventually controlling ultrafast magnetization with optical photons.
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| 3. |
- Chen, Yifeng, et al.
(författare)
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Developing aqueous porous carbons for biogas upgrading
- 2024
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Ingår i: Separation and Purification Technology. - : Elsevier B.V.. - 1383-5866 .- 1873-3794. ; 329
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Tidskriftsartikel (refereegranskat)abstract
- Developing novel sorbents is essential for biogas upgrading. In this study, mixed sorbents of aqueous porous carbons were developed to separate CO2 from the biogas, where the porous carbon with the developed micropore structure was identified as the most desirable constituent. Both thermodynamics and kinetics were studied experimentally, and Henry’s constant (KH) and the liquid-side mass-transfer coefficient (kL) of CO2 in the mixed sorbent as well as the selectivity of CO2/CH4 were obtained accordingly. Furthermore, the CO2 separation performance was evaluated with a proposed index, and the cost of biogas upgrading using the mixed sorbent was estimated and compared. The results showed that the porous carbon with the developed micropore structure led to better performance on KH and kL of CO2 in the mixed sorbent, and the mixed sorbent with 3.03 wt% porous carbon exhibited the best CO2 separation performance, reducing 36.2 % in cost compared to the current technologies.
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| 4. |
- Chen, Yifeng, et al.
(författare)
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Kinetics study and performance evaluation of a hybrid choline-glycine/polyethylene glycol/water absorbent for CO2 separation
- 2023
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Ingår i: Separation and Purification Technology. - : Elsevier B.V.. - 1383-5866 .- 1873-3794. ; 304
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic and kinetic properties of absorbents are beneficial in evaluating their CO2 separation performance. In this study, the kinetic properties of CO2 in a hybrid choline-glycine/polyethylene glycol/water absorbent, including the liquid-side mass-transfer coefficient, enhancement factor, and reaction rate constant, were systematically determined through experimental measurements and data processing. Furthermore, an index referred to as “absorbility” was proposed to combine the kinetic properties determined in this study with the thermodynamic properties obtained in our previous study to evaluate the CO2 separation performance. Additionally, the regeneration performance of the hybrid absorbent was also conducted. The results show that the performance of the hybrid absorbent (30 wt% [Cho][Gly] + 10 wt% PEG200 + 60 wt% H2O) is comparable to that of aqueous monoethanolamine, and is thus promising for CO2 separation, considering its low regeneration temperature and low environmental impact.
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| 5. |
- Daon, J., et al.
(författare)
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Chemically enhanced carbon nanotubes based Thermal Interface Materials
- 2015
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Ingår i: THERMINIC 2015 - 21st International Workshop on Thermal Investigations of ICs and Systems 2015. - 9781467397056
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Konferensbidrag (refereegranskat)abstract
- With progress in microelectronics the component density on a device increases drastically. As a consequence the power density reaches levels that challenge device reliability. New heat dissipation strategies are needed to efficiently drain heat. Thermal Interface Materials (TIMs) are usually used to transfer heat across interfaces, for example between a device and its packaging. Vertically Aligned Carbon Nanotubes (VACNTs) can be used to play this role. Indeed, carbon nanotubes are among the best thermal conductors (similar to 3.000 W/mK) and in the form of VACNT mats, show interesting mechanical properties. On one side, VACNTs are in contact with their growth substrate and there is a low thermal resistance. On the other side, good contact must be created between the opposite substrate and the VACNTs in order to decrease the contact thermal resistance. A thin-film deposition of an amorphous material can be used to play this role. This paper reports a chemically enhanced carbon nanotube based TIM with creation of chemical bonds between the polymer and VACNTs. We show that these covalent bonds enhance the thermal transfer from VACNTs to a copper substrate and can dramatically decrease local resistances. Implementation processes and thermal characterizations of TIMs are studied and reported.
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| 6. |
- Daon, J., et al.
(författare)
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Electrically conductive thermal interface materials based on vertically aligned carbon nanotubes mats
- 2014
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Ingår i: IEEE 20th International Workshop on Thermal Investigation of ICs and Systems (Therminic). Greenwich, London, United Kingdom, 24-26 September 2014. - 9781479954155
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Konferensbidrag (refereegranskat)abstract
- In power microelectronics, the trends towards miniaturization and higher performances result in higher power densities and more heat to be dissipated. In most electronic assembly, thermal interface materials (TIM) help provide a path for heat dissipation but still represent a bottleneck in the total thermal resistance of the system. VA-CNTs mats are typically grown on HR silicon substrate with Al2O3 diffusion barrier layer using Thermal CVD process. In many cases, 'die attach' thermal interface materials need to be electrically conductive and the growth of dense VA-CNT mats on an electrically conductive substrate remains a challenge. This paper presents the growth of dense VA-CNT mats on doped silicon with Al2O3 and TiN diffusion barrier layer. Processes, thermal and electrical characterization of VA-CNTs based thermal interface materials are studied and reported.
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| 7. |
- Fan, X., et al.
(författare)
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Reliability of carbon nanotube bumps for chip on glass application
- 2014
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Ingår i: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962753-
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Konferensbidrag (refereegranskat)abstract
- Carbon nanotubes (CNTs) are an ideal candidate material for electronic interconnects due to their extraordinary thermal, electrical and mechanical properties. In this study, densified CNT bumps utilizing the paper-mediated controlled method were applied as the interconnection for chip on glass (COG) applications, and the silicon chip with patterned CNT bumps was then flipped and bonded onto a glass substrate using anisotropic conductive adhesive (ACA) at a bonding pressure of 127.4 Mpa, 170°C for 8 seconds. The electrical properties of the COG were evaluated with the contact resistance of each bump measured using the four-point probe method. Three different structure traces, marked as Trace A, Trace B, and Trace C, were tested, respectively. Thermal cycling (-40 to 85°C, 800 cycles) and damp heat tests (85°C/85% RH, 1000 hours) were also conducted to evaluate the reliability of the CNT-COG structure. The average contact resistance of the samples was recorded during these tests, in which there was no obvious electrical failure observed after both the thermal cycling and damp heat tests. The results of these tests indicated that the COG has good reliability and the CNT bumps have promising potential applications in COG.
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| 8. |
- Han, Xiaolei, et al.
(författare)
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Accelerometer-assessed sedentary behaviour among Chinese rural older adults : Patterns and associations with physical function
- 2022
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Ingår i: Journal of Sports Sciences. - : Informa UK Limited. - 0264-0414 .- 1466-447X. ; 40:17, s. 1940-1949
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Tidskriftsartikel (refereegranskat)abstract
- Sedentary behaviour is associated with a range of adverse health conditions. Population-based studies have rarely examined the distribution and associated factors of accelerometer-measured sedentary behaviour patterns in rural-dwelling older adults. This population-based study included 2096 rural-dwelling older adults (age ≥60 years; 59.0% women) derived from baseline participants of the MIND-China Study. Total sedentary time and patterns (e.g., uninterrupted bouts and breaks) were derived from the hip-worn accelerometers for 7 days. Physical function was assessed using the Short Physical Performance Battery test. Data were analysed using general linear models. Overall, participants spent 58.8% of daily waking time in sedentary behaviour, with nearly half of sedentary time being accumulated through sedentary bouts of 30+ minutes. Men spent more total and accumulated sedentary time than women in each sedentary bout duration, while women had more daily 1+ minute sedentary bouts than men (all P < 0.001). Controlling for moderate-to-vigorous physical activity and other confounders, more prolonged sedentary time and fewer breaks were significantly associated with poor physical function, balance, lower limb strength, and walking speed (all P < 0.001). In older adults living in rural communities, prolonged sedentary behaviour and less frequent breaks are associated with poor physical function.
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| 9. |
- Han, Xiaolei, et al.
(författare)
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Association of Cardiovascular Health Metrics with Dementia in Rural Chinese Older Adults : A Population-Based Study
- 2022
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Ingår i: Clinical Interventions in Aging. - 1176-9092 .- 1178-1998. ; 17, s. 947-956
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: We explore the associations of individual and composite cardiovascular health metrics with all-cause dementia, Alzheimer’s disease, and vascular dementia among rural-dwelling older adults and the potential age variations in their associations.Patients and Methods: This community-based cross-sectional study included 4980 older adults (age ≥ 65 years; 57.23% women) from the baseline examination of MIND-China. In March–September 2018, data were collected via face-to-face interviews, clinical examinations, and laboratory test. We defined six cardiovascular health metrics according to the modified American Heart Association’s recommendations. We diagnosed dementia and its subtypes following the international criteria. Data were analyzed using logistic regression models.Results: Of all the participants, 250 were diagnosed with dementia, including 165 with Alzheimer’s disease and 75 with vascular dementia. Ideal composite global cardiovascular health metrics (vs poor composite metrics) were associated with a multi-adjusted odds ratio (95% confidence interval) of 0.62 (0.42– 0.93) for dementia, 0.88 (0.52– 1.48) for Alzheimer’s disease, and 0.31 (0.16– 0.60) for vascular dementia. Moreover, ideal biological cardiovascular health metrics were associated with multi-adjusted odds ratio of 0.52 (0.28– 0.95) for dementia and 0.21 (0.06– 0.77) for vascular dementia in young–old adults (65– 74 years), whereas ideal behavioral cardiovascular health metrics were associated with multi-adjusted odds ratio of 0.48 (0.26– 0.89) for dementia and 0.16 (0.06– 0.43) for vascular dementia in old–old adults (≥ 75 years).Conclusion: Our results suggest that ideal cardiovascular health metrics are cross-sectionally associated with a low likelihood of dementia and vascular dementia among rural-dwelling older Chinese adults. The associations vary with age, components of cardiovascular health metrics, and dementia subtypes.
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| 10. |
- Han, Xiaolei, et al.
(författare)
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Sex disparities in cardiovascular health metrics among rural-dwelling older adults in China : a population-based study
- 2021
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Ingår i: BMC Geriatrics. - : Springer Science and Business Media LLC. - 1471-2318. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cardiovascular health (CVH) metrics among Chinese older adults are poorly understood. We investigated sex disparities in CVH metrics and their management among rural-dwelling older adults in China.Methods: This community-based study included 5026 participants (age >= 65years; 57.2% women) in the baseline survey of a multimodal intervention study in rural China. In March-September 2018, data were collected through face-to-face interviews, clinical examinations, and laboratory tests. We defined six CVH metrics (three behavioral factors-smoking, body mass index, and physical activity; three biological factors-blood pressure, total cholesterol, and blood glucose) following the modified American Heart Association's recommendations. We performed descriptive analysis separately for men and women.Results: Of all participants, only 0.8% achieved ideal levels in all six CVH metrics. Men were more likely than women to have ideal levels in all CVH metrics but smoking. Women had higher prevalence of ideal global (9.7% vs. 7.8%) and behavioral (18.3% vs. 9.5%) CVH metrics (p<0.001), whereas men had higher prevalence of ideal biological CVH metrics (5.4% vs. 3.5%, p<0.001). The prevalence of ideal global and behavioral CVH metrics increased with age in both women and men (p for trend<0.001). Women were more likely to be aware of their hypertension and diabetes, and to receive antihypertensive treatment, while men were more likely to achieve the goal of high cholesterol treatment (p<0.05).Conclusions: The CVH metrics among older adults living in the rural communities in China are characterized by an extremely low proportion of optimal global CVH metrics and distinct sex differences, alongside poor management of major biological risk factors.
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