| 1. |
- Lind, Lars, et al.
(författare)
-
Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)
- 2021
-
Ingår i: eLife. - : eLife Sciences Publications Ltd. - 2050-084X. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions.
|
|
| 2. |
- Mishra, A, et al.
(författare)
-
Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
-
Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
|
|
| 3. |
|
|
| 4. |
- Wu, Jingnan, 1994, et al.
(författare)
-
On the Conformation of Dimeric Acceptors and Their Polymer Solar Cells with Efficiency over 18 %
- 2023
-
Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 62:45
-
Tidskriftsartikel (refereegranskat)abstract
- The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive "conformational lock" mechanism, arising from the intensified intramolecular & pi;-& pi; interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs.
|
|
| 5. |
- Du, Wenhui, et al.
(författare)
-
New fast curing isotropic conductive adhesive for electronic packaging application
- 2010
-
Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5582446, s. 199-201
-
Konferensbidrag (refereegranskat)abstract
- With the rapid development of technologies on high density assembly and packaging in electronic industry, isotropic conductive adhesive (ICA) has been paid more and more attention as a potential substitute of solder, due to its advantages of low processing temperature, simple processing conditions and good manufacturability. However, the curing time of most traditional ICA is more than half an hour. The process duration of ICA is 2 or 3 times longer than that of solder. Thus, low efficiencies of energy using and product manufacturing has been one of factors which limits widely application of ICA. Generally, the curing speed of ICA depends on types and amount of curing agent as well as curing temperature. In our previous experiments, the effects of curing temperature and amount of curing agent have been investigated. So, the present work attempts to choose a new kind of curing agent to shorten process duration of ICA. By using new curing agent, the curing duration of ICA could be shortened in 5 minutes with a high curing rate compared with the previous version. In addition, the basic performance including bulk resistivity and viscosity are also investigated in this work. Finally, we present some discussions about the further optimization of performance, for example regarding the ways of achieving better electrical conductivity with lower filler content and improvement of viscosity etc. © 2010 IEEE.
|
|
| 6. |
- Kattge, Jens, et al.
(författare)
-
TRY plant trait database - enhanced coverage and open access
- 2020
-
Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
-
Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
|
|
| 7. |
- Lai, Huaxiang, et al.
(författare)
-
Effects of BN and SiC nanoparticles on properties of conductive adhesive
- 2010
-
Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5582434, s. 235-239
-
Konferensbidrag (refereegranskat)abstract
- Isotropic conductive adhesives (ICAs) are a type of interconnect material used more and more widely in computer, robot, mobile phone, LED and so on. Compared with traditional solders, isotropic conductive adhesives have better working plasticity, creep resistance and heat resistance. In particular, isotropic conductive adhesives are more responsive in high density packaging than solder, which determines the dominance of ICAs in high density packaging in the future. In order to improve the thermal conductivity of ICA with acceptable electrical conductivity, Ag flakers, BN and SiC nanoparticles were added into the matrix. The content of silver flakes was 75wt%, and the content of nanoparticles (BN or SiC) in the isotropic conductive adhesives were 0wt%, 0.5wt%, 1.5wt%, 2.5wt%, 3wt%, 5wt% in weight. The conductive adhesives were coated on the PCBs with stencil printing and fifty SR1206 chip components were mounted on a PCB using conductive adhesive. All samples were cured at 150°for 1h. Further research into the reliability of the above isotropic conductive adhesives after temperature & humidity and thermal-cycling was carried out to analyze the effects of BN and SiC nanoparticals on the properties of ICA. The condition of the temperature & humidity test was 85 ° /85%RH, 500h. The thermal-cycling test was -40 °∼125°, 500 cycles and the soaking time and ramping rate were 19min and ±15°/min. Changes to electrical resistance were used to estimate the reliability of the isotropic conductive adhesives in this study. The microstructure of the failure samples was observed using a Scanning Electron Microscope (SEM). The water absorption of all ICAs is the same after 94h temperature and humidity aging and the rate of water absorption is also the same during the aging. The ICA with 3% boron nitride nanoparticles and 75% micron silver flakes shows the best temperature and humidity reliability, with the fewest cracks on the interface between ICA and component. After 500h thermal cycling aging, the resistance reduces in the first 100h and maintains in a certain value after 332h cycled thermal. The samples have no wide cracks but a few small ones on the interface. © 2010 IEEE.
|
|
| 8. |
- Chen, Si, 1981, et al.
(författare)
-
A High Performance Ag Alloyed Nano-scale n-type Bi2Te3 Based Thermoelectric Material
- 2015
-
Ingår i: Materials Today: Proceedings. - : Elsevier BV. - 2214-7853. ; 2:2, s. 610-619
-
Konferensbidrag (refereegranskat)abstract
- A silver alloyed n-type bismuth telluride (Bi2Te3) thermoelectric (TE) bulk material with nano crystalline structure was studied and characterized in this paper. The Bi2Te3 nanopowders used in this study were first fabricated via a patented explosion based process. Then, the various concentrations of Ag nanoparticles (0-20 wt. %) were added into the Bi2Te3 nanopowders in order to increase the electrical conductivity. Combining the benefits of high electrical conductivity (1.51x10(5) S.m(-1)) and low thermal conductivity (0.441 W.m(-1).K-1), the dimensionless figure of merit (ZT value) of 1.48 for this n-type Bi2Te3 TE material is achieved at 300 K temperature.
|
|
| 9. |
- Chen, Si, 1981
(författare)
-
Application of Metallic Nanoparticles and Vertically Aligned Carbon Nanotubes as Interconnect Materials for Electronics Packaging
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the electronics industry, packaging is responsible to protect chip from atmosphere and provide the path for signal communication as well as thermal dissipation. The realization of these functions in a packaging system depends on the performance of interconnect materials. Any failure on the interconnect materials could make entire system down. Currently, one of the most popular interconnect materials is lead-free solder, which has been used for two decades instead of toxic Sn-Pb solder. The updates on processes, equipments and standards for lead-free solder have been completed. However, as continuous increase on the chip power and the miniaturization of consumer electronics, lead-free solder is facing big challenges. The disadvantages of traditional lead-free solder, such as high process temperature, grain coarsening and thermal fatigue failure, are gradually exposed. Therefore, one of the urgent needs for packaging is to develop new interconnect materials. In recent years, as the development of nanotechnology, nanostructured materials are gradually applied on the packaging. Following this tendency, two promising nanostructured interconnect materials are presented in this thesis. The first part of this thesis shows a nanocomposite material. It consists of Sn-3.0Ag-0.5Cu nanoparticles and Sn-58Bi solder matrix. Sn-58Bi solder has the advantage on low process temperature. However the inherent brittleness of Sn-58Bi limits its application. For this reason, the Sn-3.0Ag-0.5Cu nanoparticles are added into the Sn-58Bi in order to improve the mechanical properties. The result of shear test shows that the shear strength of Sn-58Bi increases by two times by the addition of Sn-3.0Ag-0.5Cu nanoparticles. The result also indicates that the nanocomposite solder has excellent thermal fatigue resistance. The demonstrated properties make nanocomposite solder can be a potential candidate for replacing Sn-Ag-Cu in future. In this thesis, we also present another kind of interconnect material based on vertically aligned carbon nanofibers. High stability and compatibility of carbon nanofibers are always attractive to the packaging industry. By using a series of processes, such as plasma-enhanced chemical vapor deposition, sputtering, transfer and bonding, the vertically aligned carbon nanofibers are successfully assembled in the packaging system. As interconnect material, vertically aligned carbon nanofibers exhibit acceptable electrical resistance and shear strength. The positive preliminary results motivate further research on the aspects of thermal fatigue resistance and stability.
|
|
| 10. |
- Chen, Si, 1981
(författare)
-
Characterization of Nanomaterials for Interconnect and Thermal Management in Electronic Packaging
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electronic packaging, protecting the fragile chip from atmosphere and providing the paths for signal transmission as well as heat dissipation, is one of the most important parts in electronic devices. The cost, dimensions, performance, and reliability of an electronic device therefore strongly depend on its packaging structures and materials. In recent years, the miniaturization and diversification of electrical devices, having increased packaging and power density, pose a serious challenge to the reliability of traditional packaging materials. To address this challenge, several nanomaterials were thus fabricated and used for either interconnection or heat dissipation in the electronic packaging.For interconnection, vertically aligned carbon nanotubes (VACNT) grown with thermal chemical vapor deposition (TCVD) method were used as filling materials of through silicon vias (TSV). Meanwhile, vertically aligned carbon nanofibers (VACNF) fabricated with plasma enhanced chemical vapor deposition (PECVD) method were used as not only the bump material for chips, but also for the reinforcement material for solder joints. By using these carbon nanomaterials, some failure modes, such as burnout, electromigration, and coarseness, can be avoided. Besides carbon, alloy and semiconductor nanomaterials were also fabricated in this thesis for interconnection. Sn3.0Ag0.5Cu (SAC305) alloy and Bi2Te3 semiconductor nanopowders were mixed with traditional Sn58Bi and SAC305 lead free solders respectively in order to improve the shear strength and thermal fatigue resistance of solder joints. The dislocation movement and crack propagation can be effectively delayed by uniformly distributed nanoparticles in the solder matrix. However, it always shows a performance degradation when the content of nanoparticles passes a threshold. This phenomenon could be caused by increased voids and the agglomeration of nanoparticles in the solder matrix with increased content of nanoparticles.For heat dissipation, a polyimide (PI) network enhanced indium thermal interface material (TIM) was developed as a passive heat dissipation solution, and meanwhile a nanostructured bulk thermoelectric (TE) material constructed of Ag and Bi2Te3 nanopowders is presented as an active heat dissipation solution. The mechanical properties of pure indium TIM can be improved by the PI network without any degradation of heat dissipation ability. This is attributed to the Ag-coated PI fibers which formed solid bonding with the indium matrix and constrained the crack propagation. For the TE material, the thermal conductivity of nanostructured Bi2Te3 samples was much lower than that of raw materials due to the increased phonon scattering at the grain boundaries, which consequently led to a higher figure of merit (ZT value).
|
|
