| 1. |
- Aminoff, A, et al.
(author)
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Allele-specific regulation of MTTP expression influences the risk of ischemic heart disease.
- 2010
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In: Journal of lipid research. - 0022-2275 .- 1539-7262. ; 51:1, s. 103-11
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Journal article (peer-reviewed)abstract
- Promoter polymorphisms in microsomal triglyceride transfer protein (MTTP) have been associated with decreased plasma lipids but an increased risk for ischemic heart disease (IHD), indicating that MTTP influences the susceptibility for IHD independent of plasma lipids. The objective of this study was to characterize the functional promoter polymorphism in MTTP predisposing to IHD and its underlying mechanism. Use of pyrosequencing technology revealed that presence of the minor alleles of the promoter polymorphisms -493G>T and -164T>C result in lower transcription of MTTP in vivo in the heart, liver, and macrophages. In vitro experiments indicated that the minor -164C allele mediates the lower gene expression and that C/EBP binds to the polymorphic region in an allele-specific manner. Furthermore, homozygous carriers of the -164C were found to have increased risk for IHD as shown in a case-control study including a total of 544 IHD patients and 544 healthy control subjects. We concluded that carriers of the minor -164C allele have lower expression of MTTP in the heart, mediated at least partly by the transcription factor CCAAT/enhancer binding protein, and that reduced concentration of MTTP in the myocardium may contribute to IHD upon ischemic damage.
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| 2. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
-
In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
- Bellani, Sebastiano, et al.
(author)
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Graphene-Based Electrodes in a Vanadium Redox Flow Battery Produced by Rapid Low-Pressure Combined Gas Plasma Treatments
- 2021
-
In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 33:11, s. 4106-4121
-
Journal article (peer-reviewed)abstract
- The development of high-power density vanadium redox flow batteries (VRFBs) with high energy efficiencies (EEs) is crucial for the widespread dissemination of this energy storage technology. In this work, we report the production of novel hierarchical carbonaceous nanomaterials for VRFB electrodes with high catalytic activity toward the vanadium redox reactions (VO2+/VO2+ and V2+/V3+). The electrode materials are produced through a rapid (minute timescale) low-pressure combined gas plasma treatment of graphite felts (GFs) in an inductively coupled radio frequency reactor. By systematically studying the effects of either pure gases (O-2 and N-2) or their combination at different gas plasma pressures, the electrodes are optimized to reduce their kinetic polarization for the VRFB redox reactions. To further enhance the catalytic surface area of the electrodes, single-/fewlayer graphene, produced by highly scalable wet-jet milling exfoliation of graphite, is incorporated into the GFs through an infiltration method in the presence of a polymeric binder. Depending on the thickness of the proton-exchange membrane (Nafion 115 or Nafion XL), our optimized VRFB configurations can efficiently operate within a wide range of charge/discharge current densities, exhibiting energy efficiencies up to 93.9%, 90.8%, 88.3%, 85.6%, 77.6%, and 69.5% at 25, 50, 75, 100, 200, and 300 mA cm(-2), respectively. Our technology is cost-competitive when compared to commercial ones (additional electrode costs < 100 (sic) m(-2)) and shows EEs rivalling the record-high values reported for efficient systems to date. Our work remarks on the importance to study modified plasma conditions or plasma methods alternative to those reported previously (e.g., atmospheric plasmas) to improve further the electrode performances of the current VRFB systems.
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| 4. |
- Beydaghi, Hossein, et al.
(author)
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Functionalized metallic transition metal dichalcogenide (TaS2) for nanocomposite membranes in direct methanol fuel cells
- 2021
-
In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 9:10, s. 6368-6381
-
Journal article (peer-reviewed)abstract
- In this work, we designed a novel nanocomposite proton-exchange membrane (PEM) based on sulfonated poly(ether ether ketone) (SPEEK) and tantalum disulfide functionalized with terminal sulfonate groups (S-TaS2). The PEMs are prepared through a solution-casting method and exploited in direct methanol fuel cells (DMFCs). Two-dimensional S-TaS2 nanoflakes were prepared as a functional additive to produce the novel nanocomposite membrane for DMFCs due to their potential as a fuel barrier and an excellent proton conductor. To optimize the degree of sulfonation (DS) of SPEEK and the weight percentage (wt%) of S-TaS2 nanoflakes in PEMs, we used the central composite design of the response surface method. The optimum PEM was obtained for SPEEK DS of 1.9% and a weight fraction (wt%) of S-TaS2 nanoflakes of 70.2%. The optimized membrane shows a water uptake of 45.72%, a membrane swelling of 9.64%, a proton conductivity of 96.24 mS cm(-1), a methanol permeability of 2.66 x 10(-7) cm(2) s(-1), and a selectivity of 36.18 x 10(4) S s cm(-3). Moreover, SPEEK/S-TaS2 membranes show superior thermal and chemical stabilities compared to those of pristine SPEEK. The DMFC fabricated with the SPEEK/S-TaS2 membrane has reached the maximum power densities of 64.55 mW cm(-2) and 161.18 mW cm(-2) at 30 degrees C and 80 degrees C, respectively, which are similar to 78% higher than the values obtained with the pristine SPEEK membrane. Our results demonstrate that SPEEK/S-TaS2 membranes have a great potential for DMFC applications.
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| 5. |
- Beydaghi, Hossein, et al.
(author)
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Sulfonated NbS2-based proton-exchange membranes for vanadium redox flow batteries
- 2022
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 14:16, s. 6152-6161
-
Journal article (peer-reviewed)abstract
- In this work, novel proton-exchange membranes (PEMs) based on sulfonated poly(ether ether ketone) (SPEEK) and two-dimensional (2D) sulfonated niobium disulphide (S-NbS2) nanoflakes are synthesized by a solution-casting method and used in vanadium redox flow batteries (VRFBs). The NbS2 nanoflakes are produced by liquid-phase exfoliation of their bulk counterpart and chemically functionalized with terminal sulfonate groups to improve dimensional and chemical stabilities, proton conductivity (sigma) and fuel barrier properties of the as-produced membranes. The addition of S-NbS2 nanoflakes to SPEEK decreases the vanadium ion permeability from 5.42 x 10(-7) to 2.34 x 10(-7) cm(2) min(-1). Meanwhile, it increases the membrane sigma and selectivity up to 94.35 mS cm(-2) and 40.32 x 10(4) S min cm(-3), respectively. The cell assembled with the optimized membrane incorporating 2.5 wt% of S-NbS2 nanoflakes (SPEEK:2.5% S-NbS2) exhibits high efficiency metrics, i.e., coulombic efficiency between 98.7 and 99.0%, voltage efficiency between 90.2 and 73.2% and energy efficiency between 89.3 and 72.8% within the current density range of 100-300 mA cm(-2), delivering a maximum power density of 0.83 W cm(-2) at a current density of 870 mA cm(-2). The SPEEK:2.5% S-NbS2 membrane-based VRFBs show a stable behavior over 200 cycles at 200 mA cm(-2). This study opens up an effective avenue for the production of advanced SPEEK-based membranes for VRFBs.
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| 6. |
- Bianca, Gabriele, et al.
(author)
-
Liquid-Phase Exfoliated GeSe Nanoflakes for Photoelectrochemical-Type Photodetectors and Photoelectrochemical Water Splitting
- 2020
-
In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:43, s. 48598-48613
-
Journal article (peer-reviewed)abstract
- Photoelectrochemical (PEC) systems represent powerful tools to convert electromagnetic radiation into chemical fuels and electricity. In this context, two-dimensional (2D) materials are attracting enormous interest as potential advanced photo(electro)catalysts and, recently, 2D group-IVA metal monochalcogenides have been theoretically predicted to be water splitting photocatalysts. In this work, we use density functional theory calculations to theoretically investigate the photocatalytic activity of single-/few-layer GeSe nanoflakes for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in pH conditions ranging from 0 to 14. Our simulations show that GeSe nanoflakes with different thickness can be mixed in the form of nanoporous films to act as nanoscale tandem systems, in which the flakes, depending on their thickness, can operate as HER- and/or OER photocatalysts. On the basis of theoretical predictions, we report the first experimental characterization of the photo(electro)catalytic activity of single-/few-layer GeSe flakes in different aqueous media, ranging from acidic to alkaline solutions: 0.5 M H2SO4 (pH 0.3), 1 M KCl (pH 6.5), and 1 M KOH (pH 14). The films of the GeSe nanoflakes are fabricated by spray coating GeSe nanoflakes dispersion in 2-propanol obtained through liquid-phase exfoliation of synthesized orthorhombic (Pnma) GeSe bulk crystals. The PEC properties of the GeSe nanoflakes are used to design PEC-type photodetectors, reaching a responsivity of up to 0.32 AW(-1) (external quantum efficiency of 86.3%) under 455 nm excitation wavelength in acidic electrolyte. The obtained performances are superior to those of several self-powered and low-voltage solution-processed photodetectors, approaching that of self-powered commercial UV-Vis photodetectors. The obtained results inspire the use of 2D GeSe in proof-of-concept water photoelectrolysis cells.
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| 7. |
- Chatzimanolis, Konstantinos, et al.
(author)
-
Inverted perovskite solar cells with enhanced lifetime and thermal stability enabled by a metallic tantalum disulfide buffer layer
- 2021
-
In: Nanoscale Advances. - : Royal Society of Chemistry. - 2516-0230. ; 3:11, s. 3124-3135
-
Journal article (peer-reviewed)abstract
- Perovskite solar cells (PSCs) have proved their potential for delivering high power conversion efficiencies (PCE) alongside low fabrication cost and high versatility. The stability and the PCE of PSCs can readily be improved by implementing engineering approaches that entail the incorporation of two-dimensional (2D) materials across the device's layered configuration. In this work, two-dimensional (2D) 6R-TaS2 flakes were exfoliated and incorporated as a buffer layer in inverted PSCs, enhancing the device's PCE, lifetime and thermal stability. A thin buffer layer of 6R-TaS2 flakes was formed on top of the electron transport layer to facilitate electron extraction, thus improving the overall device performance. The optimized devices reach a PCE of 18.45%, representing a 12% improvement compared to the reference cell. The lifetime stability measurements of the devices under ISOS-L2, ISOS-D1, ISOS-D1I and ISOS-D2I protocols revealed that the TaS2 buffer layer retards the intrinsic, thermally activated degradation processes of the PSCs. Notably, the devices retain more than the 80% of their initial PCE over 330 h under continuous 1 Sun illumination at 65 degrees C.
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| 8. |
- Eeg-Olofsson, Katarina, 1968, et al.
(author)
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Risk of cardiovascular disease and mortality in overweight and obese patients with type 2 diabetes: an observational study in 13,087 patients.
- 2009
-
In: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 52:1, s. 65-73
-
Journal article (peer-reviewed)abstract
- AIMS/HYPOTHESIS: The aim of this study of type 2 diabetic patients in the Swedish National Diabetes Register was to study the associations of BMI, overweight (BMI 25-29.9 kg/m(2)) and obesity (BMI >or= 30 kg/m(2)) with cardiovascular disease in type 2 diabetes, as these associations have not previously been clarified. METHODS: Patients aged 30-74 years with no previous CHD or stroke (N = 13,087) were followed for a mean of 5.6 years until 2003 for fatal or non-fatal CHD, stroke, cardiovascular disease (CHD or stroke) and total mortality. In total, 1,922 cardiovascular-disease events occurred, based on 64,864 person-years. RESULTS: The relative risks of CHD, stroke, cardiovascular disease and total mortality for a 5 unit increase in BMI at baseline were 15%, 11%, 13% and 27%, respectively, using Cox regression analysis, after adjusting for age, sex, diabetes duration, hypoglycaemic treatment and smoking (model 1), and were 9%, 4% (not significant), 7% and 20%, respectively, when adjusting also for HbA(1c), blood pressure, antihypertensive drugs, lipid-reducing drugs and microalbuminuria (model 2). Adjusted hazard ratios (model 1) for CHD, cardiovascular disease and total mortality with overweight were 1.27 (95% CI 1.09-1.48), 1.24 (1.09-1.41) and 1.16 (0.94-1.45), respectively, and 1.49 (1.27-1.76), 1.44 (1.26-1.64) and 1.71 (1.36-2.14) with obesity, as compared with normal weight. Significant hazard ratios were attenuated when adjusted according to model 2. For a 1 unit increase in BMI during follow-up, the relative risk of CHD (model 2) was 1.13 (1.04-1.23; p = 0.005). CONCLUSIONS/INTERPRETATION: Both overweight and obesity independently increased the risk of CHD and cardiovascular disease in patients with type 2 diabetes. The CHD risk was higher with increasing BMI than with stable or decreasing BMI during the study.
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| 9. |
- Liedberg, Fredrik, et al.
(author)
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Long-term follow-up after radical cystectomy with emphasis on complications and reoperations: A Swedish population-based survey
- 2012
-
In: Scandinavian Journal of Urology and Nephrology. - : Informa Healthcare. - 0036-5599 .- 1651-2065. ; 46:1, s. 14-18
-
Journal article (peer-reviewed)abstract
- Objective. To evaluate outcome after radical cystectomy for primary bladder cancer in a large population-based material. Material and methods. Between 1997 and 2002 all patients treated with radical cystectomy within 3 months after diagnosis of primary bladder cancer without distant metastasis were retrieved through the Swedish Bladder Cancer Registry. A follow-up questionnaire was distributed to all units where the primary registration of patients was performed. Follow-up data on recurrence date were retrieved from the patient charts and causes of death were obtained from the Swedish Cause of Death Registry until 2003. Results. During the study period radical cystectomy was performed in 39 units in Sweden, of which only five units were considered high-volume hospitals performing 10 or more procedures annually. Mean blood loss was 2300 ml (median 2000 ml) and the 90-day mortality rate was 5.7%. Blood loss was higher in high-volume units than in hospitals with lower hospital volumes, but the 90-day mortality rates were similar. During a median follow-up of 3.5 years, 24% of the patients were submitted to a reoperation. Reoperation rates were significantly higher in patients who received a continent urinary diversion (29%) compared with an ileal conduit (22%, p andlt; 0.015). Conclusions. Radical cystectomy was associated with a reoperation rate of 24% in Sweden during the study period. The reoperation rates were higher in patients receiving a continent cutaneous diversion or bladder substitution. Blood loss was higher in high-volume units; otherwise, surgical volume did not affect mortality rates, cancer-specific survival or reoperation rates.
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| 10. |
- Najafi, Leyla, et al.
(author)
-
Hybrid Organic/Inorganic Photocathodes Based on WS2 Flakes as Hole Transporting Layer Material
- 2021
-
In: Small Structures. - : John Wiley & Sons. - 2688-4062. ; 2:3
-
Journal article (peer-reviewed)abstract
- The efficient production of molecular hydrogen (H2) is a fundamental step toward an environmentally friendly economy. Photocathodes using organic bulk heterojunction (BHJ) films as light harvesters represent an attracting technology for low-cost photoelectrochemical water splitting. These photocathodes need charge transporting layers (CTLs) to efficiently separate and transport either holes or electrons toward the back-current collector and electrolyte, respectively. Therefore, it is pivotal to control the energy band edge levels and the work function (WF) of the CTLs to match the ones of the BHJ film, current collector, and electrolyte. Herein, the use of 2D p-doped WS2 flakes as hole transporting material for H2-evolving photocathodes based on the regioregular poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (rr-P3HT:PCBM) BHJ film is proposed. The WS2 flakes are produced through scalable liquid-phase exfoliation of the bulk crystal, whereas p-type chemical doping allows the tuning of the WS2 WF. This approach boosts the performances of the photocathodes, reaching photocurrent densities up to 4.14 mA cm−2 at 0 V versus reversible hydrogen electrode (RHE), an onset potential of 0.66 V versus RHE, and a ratiometric power-saved metric of 1.28% (under 1 sun illumination). To the best of the authors' knowledge, these performances represent the current record for 2D materials-based CTLs.
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| 11. |
- Najafi, Leyla, et al.
(author)
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Microwave-Induced Structural Engineering and Pt Trapping in 6R-TaS2 for the Hydrogen Evolution Reaction
- 2020
-
In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 16:50
-
Journal article (peer-reviewed)abstract
- The nanoengineering of the structure of transition metal dichalcogenides (TMDs) is widely pursued to develop viable catalysts for the hydrogen evolution reaction (HER) alternative to the precious metallic ones. Metallic group-5 TMDs have been demonstrated to be effective catalysts for the HER in acidic media, making affordable real proton exchange membrane water electrolysers. Their key-plus relies on the fact that both their basal planes and edges are catalytically active for the HER. In this work, the 6R phase of TaS2 is "rediscovered" and engineered. A liquid-phase microwave treatment is used to modify the structural properties of the 6R-TaS2 nanoflakes produced by liquid-phase exfoliation. The fragmentation of the nanoflakes and their evolution from monocrystalline to partly polycrystalline structures improve the HER-activity, lowering the overpotential at cathodic current of 10 mA cm(-2) from 0.377 to 0.119 V. Furthermore, 6R-TaS2 nanoflakes act as ideal support to firmly trap Pt species, which achieve a mass activity (MA) up 10 000 A g(Pt)(-1) at overpotential of 50 mV (20 000 A g(Pt)(-1) at overpotentials of 72 mV), representing a 20-fold increase of the MA of Pt measured for the Pt/C reference, and approaching the state-of-the-art of the Pt mass activity.
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| 12. |
- Najafi, Leyla, et al.
(author)
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Topochemical Transformation of Two-Dimensional VSe2 into Metallic Nonlayered VO2 for Water Splitting Reactions in Acidic and Alkaline Media
- 2022
-
In: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 16:1, s. 351-367
-
Journal article (peer-reviewed)abstract
- The engineering of the structural and morphological properties of nanomaterials is a fundamental aspect to attain desired performance in energy storage/conversion systems and multifunctional composites. We report the synthesis of room temperature-stable metallic rutile VO2 (VO2 (R)) nanosheets by topochemically transforming liquid-phase exfoliated VSe2 in a reductive Ar-H2 atmosphere. The asproduced VO2 (R) represents an example of two-dimensional (2D) nonlayered materials, whose bulk counterparts do not have a layered structure composed by layers held together by van der Waals force or electrostatic forces between charged layers and counterbalancing ions amid them. By pretreating the VSe2 nanosheets by O-2 plasma, the resulting 2D VO2 (R) nanosheets exhibit a porous morphology that increases the material specific surface area while introducing defective sites. The assynthesized porous (holey)-VO2 (R) nanosheets are investigated as metallic catalysts for the water splitting reactions in both acidic and alkaline media, reaching a maximum mass activity of 972.3 A g(-1) at -0.300 V vs RHE for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 (faradaic efficiency = 100%, overpotential for the HER at 10 mA cm(-2) = 0.184 V) and a mass activity (calculated for a non 100% faradaic efficiency) of 745.9 A g(-1) at +1.580 V vs RHE for the oxygen evolution reaction (OER) in 1 M KOH (overpotential for the OER at 10 mA cm(-2) = 0.209 V). By demonstrating proof-of-concept electrolyzers, our results show the possibility to synthesize special material phases through topochemical conversion of 2D materials for advanced energy-related applications.
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| 13. |
- Najafi, Leyla, et al.
(author)
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Transition metal dichalcogenides as catalysts for the hydrogen evolution reaction : The emblematic case of "inert" ZrSe2 as catalyst for electrolyzers
- 2022
-
In: Nano Select. - : Wiley-VCH Verlagsgesellschaft. - 2688-4011. ; 3:6, s. 1069-1081
-
Journal article (peer-reviewed)abstract
- The development of earth-abundant electrocatalysts (ECs) operating at high current densities in water splitting electrolyzers is pivotal for the widespread use of the current green hydrogen production plants. Transition metal dichalcogenides (TMDs) have emerged as promising alternatives to the most efficient noble metal ECs, leading to a wealth of research. Some strategies based on material nanostructuring and hybridization, introduction of defects and chemical/physical modifications appeared as universal approaches to provide catalytic properties to TMDs, regardless of the specific material. In this work, we show that even a theoretically poorly catalytic (and poorly studied) TMD, namely zirconium diselenide (ZrSe2), can act as an efficient EC for the hydrogen evolution reaction (HER) when exfoliated in the form of two-dimensional (2D) few-layer flakes. We critically show the difficulties of explaining the catalytic mechanisms of the resulting ECs in the presence of complex structural and chemical modifications, which are nevertheless evaluated extensively. By doing so, we also highlight the easiness of transforming 2D TMDs into effective HER-ECs. To strengthen our message in practical environments, we report ZrSe2-based acidic (proton exchange membrane [PEM]) and alkaline water electrolyzers operating at 400 mA cm–2 at a voltage of 1.88 and 1.92 V, respectively, thus competing with commercial technologies.
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| 14. |
- Strandhagen, Elisabeth, 1960, et al.
(author)
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Selection bias in a population study with registry linkage – potential effect on social gradient in cardiovascular risk
- 2010
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In: European Journal of Epidemiology. - 1573-7284. ; 25:3, s. 163-172
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Journal article (peer-reviewed)abstract
- Non-participation in population studies is likely to be a source of bias in many types of epidemiologic studies, including those describing social disparities in health. The objective of this paper is to present a non-attendance analysis evaluating the possible impact of selection bias, when investigating the association between education level and cardiovascular risk factors. Data from the INTERGENE research programme including 3,610 randomly selected individuals aged 25-74 (1,908 women and 1,702 men), in West Sweden were used. Only 42% of the invited population participated. Non-attendance analyses were done by comparing data from official registries (Statistics Sweden) covering the entire invited study population. This analysis revealed that participants were more likely to be women, have university education, high income, be married and of Nordic origin compared to non-participants. Among participants, all health behaviours studied were significantly related to education. Physical activity, alcohol use and breakfast consumption were higher in the more educated group, while there were more smokers in the less educated group. Central obesity, obesity and hypertension were also significantly associated with lower education level. Weaker associations were observed for blood lipids, diabetes, high plasma glucose level and perceived stress. The socio-demographic differences between participants and non-participants indicated by the register analysis imply potential biases in epidemiological research. For instance, the positive association between education level and frequent alcohol consumption, may, in part be explained by participation bias. For other risk factors studied, an underestimation of the importance of low socioeconomic status may be more likely.
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| 15. |
- Tsikritzis, Dimitris, et al.
(author)
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A two-fold engineering approach based on Bi2Te3 flakes towards efficient and stable inverted perovskite solar cells
- 2020
-
In: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 1:3, s. 450-462
-
Journal article (peer-reviewed)abstract
- Perovskite solar cells (PSCs) are currently the leading thin-film photovoltaic technology owing to their high power conversion efficiency (PCE), as well as their low-cost and facile manufacturing process. Two-dimensional (2D) materials have been reported to improve both the PCE and the stability of PSCs when incorporated across the device's layered configuration. Hereby, a two-fold engineering approach is implemented in inverted PSCs by using ultra-thin Bi2Te3 flakes, i.e.: (1) to dope the electron transport layer (ETL) and (2) to form a protective interlayer above the ETL. Thorough steady-state and time-resolved transport analyses reveal that our first engineering approach improves the electron extraction rate and thus the overall PCE (+6.6% vs. reference cells), as a result of the favourable energy level alignment between the perovskite, the ETL and the cathode. Moreover, the Bi2Te3 interlayer, through the second engineering approach, facilitates further the electron transport and in addition protects the underlying structure against chemical instability effects, leading to enhanced device performance and stability. By combining the two engineering approaches, our optimised PSCs reach a PCE up to 19.46% (+15.2% vs. reference cells) and retain more than 80% of their initial PCE, after the burn-in phase, over 1100 h under continous 1 sun illumination. These performances are among the highest reported in the literature for inverted PSCs.
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| 16. |
- Zappia, Marilena, I, et al.
(author)
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Two-Dimensional Gallium Sulfide Nanoflakes for UV-Selective Photoelectrochemical-type Photodetectors
- 2021
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:22, s. 11857-11866
-
Journal article (peer-reviewed)abstract
- Two-dimensional (2D) transition-metal monochalcogenides have been recently predicted to be potential photo(electro)catalysts for water splitting and photoelectrochemical (PEC) reactions. Differently from the most established InSe, GaSe, GeSe, and many other monochalcogenides, bulk GaS has a large band gap of similar to 2.5 eV, which increases up to more than 3.0 eV with decreasing its thickness due to quantum confinement effects. Therefore, 2D GaS fills the void between 2D small-band-gap semiconductors and insulators, resulting of interest for the realization of van der Waals type-I heterojunctions in photocatalysis, as well as the development of UV light-emitting diodes, quantum wells, and other optoelectronic devices. Based on theoretical calculations of the electronic structure of GaS as a function of layer number reported in the literature, we experimentally demonstrate, for the first time, the PEC properties of liquid-phase exfoliated GaS nanoflakes. Our results indicate that solution-processed 2D GaS-based PEC-type photodetectors outperform the corresponding solid-state photodetectors. In fact, the 2D morphology of the GaS flakes intrinsically minimizes the distance between the photogenerated charges and the surface area at which the redox reactions occur, limiting electron-hole recombination losses. The latter are instead deleterious for standard solidstate configurations. Consequently, PEC-type 2D GaS photodetectors display a relevant UV-selective photoresponse. In particular, they attain responsivities of 1.8 mA W-1 in 1 M H2SO4 [at 0.8 V vs reversible hydrogen electrode (RHE)], 4.6 mA W-1 in 1 M Na2SO4 (at 0.9 V vs RHE), and 6.8 mA W--(1) in 1 M KOH (at 1.1. V vs RHE) under 275 nm illumination wavelength with an intensity of 1.3 mW cm(-2). Beyond the photodetector application, 2D GaS-based PEC-type devices may find application in tandem solar PEC cells in combination with other visible-sensitive low-band-gap materials, including transition-metal monochalcogenides recently established for PEC solar energy conversion applications.
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