22 research outputs found
Online teaching and learning effectiveness for kindergartens, primary and secondary schools
No full textOnline teaching was adopted in Hong Kong and many other places around the world due to lockdown policies during the COVID-19 pandemic. This research explores the online teaching and learning effectiveness of Kindergarten, Primary and Secondary students in Hong Kong as perceived by teachers. Factors including students’ family support, school support, teachers’ technology competence, and perceived teaching and learning effectiveness were measured by a questionnaire. 427 teachers from kindergartens, primary schools and secondary schools completed the questionnaire in 2023. Analysis by Confirmatory Factor Analysis supports the reliability and discriminant validity of the questionnaire. Structural Equation Modeling was used to test the hypotheses. The findings show that family support, school support and teaching effectiveness positively affect students’ online learning effectiveness. Teaching effectiveness is associated with school support and teachers’ technology competence in online teaching preparation. The relationships among various variables are the same for kindergartens, primary schools to secondary schools. It can cast light on strategies to improve online teaching and learning effectiveness for kindergartens, primary and secondary schools
Online-Learning Effectiveness of Secondary Students
No full textThis research study examines various factors that influence the effectiveness of online learning and students’ interest in applying technology in learning for secondary schools in Hong Kong. Confirmatory Factor Analysis confirmed the questionnaire developed for this study, demonstrating reliability and validity in measuring five factors: family support, students’ engagement, perceived online learning effectiveness, satisfaction with the online learning experience, and students’ interest in using technology in the future. Structural Equation Modeling was utilized to test the hypotheses. The findings confirmed that family support and students’ engagement have a positive effect on students’ perceived online-learning effectiveness, satisfaction with online learning, and interest in using technology in future studies. This research sheds light on the crucial effects of family support and students’ engagement on learning effectiveness and students’ satisfaction with online learning. Educators and policymakers can make informed decisions to optimize and enhance students’ online learning effectiveness, and apply these insights to future educational applications
A question of belonging : imagining the Chinese in the British West Indies
No full textThis study examines what effect the presence of the Chinese in the West
Indies had on understandings of belonging in terms of nation. It examines the
construction of the category "Chinese" across different modes, particularly literary
texts, from the nineteenth century to the present, and from the positions of colonial,
creole and Chinese spaces. The results of this research challenge the common view
that the Chinese have had a marginal impact on the perception of nationhood in the
West Indies. Instead, images of the Chinese were, and continue to be, a key means of
exploring the ambiguities, potentialities and limitations of nation as it developed in
the West Indies. In particular, they reveal that neither "nation" nor "belonging" are
static positions; rather, they signify continuing renegotiations of power relationships
and cultural identities.
Several factors impact on representations of the Chinese. In the nineteenth
century, such images were molded by the specific aims of colonial enterprises,
entangled at the intersection of the discursive constructs of "East" and "West" during
a period of mass migrations and the peculiar tensions of post-emancipation West
Indian societies. In the twentieth century, "the Chinese" have been created in response
to a need to assert ownership of what was once colonised space and to perform nation
before a global audience. Of late, Chinese West Indians have taken a more visibly
active role in the construction and dissemination of images of themselves and their
communities. In the process they have sometimes radically redefined the imaginative
nation space of the West Indies and, in the process, challenge established boundaries
of belonging, and contest "belonging" itself
Author Correction: Comprehensive analysis of chromothripsis in 2,658 human cancers using whole-genome sequencing
No full textauthor correctio
Growth of single-wall carbon nanotubes by chemical vapor deposition for electrical devices
No full textCarbon emerges in di®erent forms. Diamond and graphite have been well known mate-
rials for centuries. Moreover fullerenes and nanotubes were discovered only a few years ago.
H. W. Kroto et al. depicted the fullerenes in 1985 [1]. A few years later, in 1991, S. Iijima
described carbon nanotubes (CNTs) for the ¯rst time [2] (Figure 1.1).
CNTs have a close relation to graphite, since a single-wall carbon nanotube is like a rolled-up
graphite mono layer. However a nanotube has with its curved shape a higher chemical reacti-
vity than a °at graphite layer. Both the side wall and the caps can be modi¯ed chemically [3].
Carbon nanotubes are regular carbon clusters with attractive mechanical and electronic pro-
perties [4]. Nanotubes have a high mechanical strength due to a very large Young's modu-
lus [5]. They can be used for the storage of hydrogen [5, 6], to store energy in electrochemical
double layer capacitors [7] or to reinforce composite materials [3]. A single nanotube can be
used as a sensor [8{12], a nanorelay [13], a vessel [14] or as a template [3, 15]. It is possible
to produce light bulbs [16] and ¯bers [17] with carbon nanotubes. An array of CNTs can act
as a °at panel display [3, 5] using their feature to act as ¯eld emitting devices [18{21].
CNTs are either metallic (1/3) or semiconducting (2/3). Nowadays it is not possible to select
the desired characteristic of a nanotube in advance. It is only possible to separate metallic
from semiconducting tubes by using an electrical ¯eld [22]. Metallic nanotubes with their
diameter of a few nm represent the ultimate conducting wire whereas the semiconducting
ones can be used as transistors [23{25] even on a transparent and °exible substrate [26]. The
transistors can be optimized by the chemical control of the nanotube-electrode interface [27].
Quantum dots [28, 29] and spin valves [30{32] can be built alike simple logic gates [33] and a
Y-junction recti¯er [34].
Carbon nanotubes have a very interesting property: they are "1-dimensional" molecules [35].
This has to be explained in a few words. In general, quantum con¯nement leads to a spacing
of the allowed eigenenergies. Electrons cannot hop into a higher energy level if the thermal
energy is much smaller than this energy di®erence. In a nanotube an electron is con¯ned in the
directions perpendicular to the tube axis. The nanotube becomes a 1-dimensional conductor.
For several years members of our research group are exploring the electrical properties of
this very special conductor. The behavior of carbon nanotubes is investigated with electrical
transport measurements at low temperatures (down to 50 mK) and in high magnetic ¯elds
(up to 10 T).
The raw material for the ¯rst experiments [36{38] were multi-wall carbon nanotubes ob-
tained from L. Forr¶o (Ecole Polytechnique F¶ed¶erale de Lausanne) which were produced using
laser ablation. The multi-wall carbon nanotubes were used to investigate the suppression of
tunnelling [36, 39], multiple Andreev re°ection [28, 37], electrical spin injection [30{32] and
quantum dots [37, 40{43].
The next step was to grow single-wall carbon nanotubes using chemical vapor deposition
(CVD) [8,44{46]. This procedure has the advantage to be faster than an external collaboration
and in addition the growth of the tubes directly on the device makes the samples ready for
use without an additional treatment.
It was veri¯ed that the CVD grown tubes are suitable of for electrical devices [47]. Vibrating
nanotubes [48] and an ambipolar ¯eld-e®ect transistor [23] were studied. Kondo e®ect [49]
and Fano-Resonances [50] were investigated as well.
The latter experiments reveal one common de¯ciency. The grown tubes are often not sepa-
rated but bundled [47] (Figure 6.10). Moreover it is not clear if they are multi- or single-wall
tubes. This means for electronic transport measurements that several tubes are measured si-
multaneously. Thus the tube with the best conductivity dominates the measurement, whereas
the other tubes perturb the measured signal by there presence.
The main focus of this thesis is the development of a growth process of single-wall carbon
nanotubes by using CVD. The aim is to overcome the problem of bundling. The grown
nanotubes have to be free of lattice defects and they need to have good electrode-nanotube
contacts in order to make them suitable for electronic transport measurements. They have
to lay °at, well separated and optimally distributed on SiO2 our standard substrate. On the
one hand the tube density should not be too high since this would increase the probability
of shortcuts between the electrodes due to nanotube-nanotube contacts. On the other hand
it should not be too low since this would make the localization of an appropriate nanotube
much more time consuming (Figure 1.2).
Two ways to achieve this goal were tried. The single-wall nanotubes can be bought, dissolved
in a solvent and spread after cleaning and separation [51{57], as in the thesis [46]. The second
possibility is to grow the tubes directly on the device as presented in this thesis.
Growing carbon nanotubes with CVD is very simple, at least in principle. There are only
a few essential things needed: an oven, a substrate, a catalyst and a carbon feedstock. The
main challenge is to acquire the right knowhow.
The ¯rst step was to build up the CVD system. Afterwards the proper growth conditions
and a simple method to check the demanded properties of the grown tubes had to be found.
Scanning electron microscopy (SEM) is the standard characterization tool used in this thesis.
Transmission electron microscopy (TEM) is a helpful mean in order to show that the tubes
are separated and single-wall, since it allows the investigation of the tubes' internal structure.
Atomic force microscopy (AFM) and Raman spectroscopy are used in addition.
Outline of this thesis
² Chapter 2 gives a short overview with respect to the properties, the growth and the
characterization of carbon nanotubes.
² The oven and the gas system are delineated in Chapter 3. Di®erent carbon feedstocks
were used: ethylene/hydrogen, methane, methane/ethylene and methane/hydrogen.
² The steps towards a suitable catalyst are presented in Chapter 4. Evaporated and
liquid based catalysts were tested. An iron molybdenum alumina catalyst dissolved in
2-propanol provides the best results.
² Chapter 5 gives a comparison of the results obtained utilizing di®erent growth processes,
and describes the formation of amorphous carbon and the oxidation of nanotubes.
² Chapter 6 summarizes experiments on di®erent TEM grids (Au, Cu, Mo, Ni, stainless
steel, Ti, quantifoils) and silicon nitride windows.
² The results from collaborations with other group members are presented in Chapter 7.
These experiments show the good quality of the grown tubes
Civil society and political change in Morocco
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Author Correction: Pan-cancer analysis of whole genomes
No full textCell adhesion molecules are ubiquitous in multicellular organisms, specifying precise cell-cell interactions in processes as diverse as tissue development, immune cell trafficking and the wiring of the nervous system(1-4). Here we show that a wide array of synthetic cell adhesion molecules can be generated by combining orthogonal extracellular interactions with intracellular domains from native adhesion molecules, such as cadherins and integrins. The resulting molecules yield customized cell-cell interactions with adhesion properties that are similar to native interactions. The identity of the intracellular domain of the synthetic cell adhesion molecules specifies interface morphology and mechanics, whereas diverse homotypic or heterotypic extracellular interaction domains independently specify the connectivity between cells. This toolkit of orthogonal adhesion molecules enables the rationally programmed assembly of multicellular architectures, as well as systematic remodelling of native tissues. The modularity of synthetic cell adhesion molecules provides fundamental insights into how distinct classes of cell-cell interfaces may have evolved. Overall, these tools offer powerful abilities for cell and tissue engineering and for systematically studying multicellular organization. Synthetic cell adhesion molecules yield customized cell-cell interactions with adhesion properties that are similar to native interactions, and offer abilities for cell and tissue engineering and for systematically studying multicellular organization
Three SNPs in chromosome 11q23.3 are independently associated with systemic lupus erythematosus in Asians
No full textSystemic lupus erythematosus (SLE) has a complex etiology and is affected by both genetic and environmental factors. Althoughmorethan 40 loci haveshownrobust association withSLE, the details of these loci,suchas the independent contributors and the genes involved, are still unclear. In this study, we performed meta-analysis of two existing genome-wide association studies (GWASs) on Chinese Han populations from Hong Kong and Anhui, China, and followed the findings by further replication on three additional Chinese and Thailand cohorts with a total of 4254 cases and 6262 controls matched geographically and ethnically. We discovered multiple susceptibility variants for SLE in the 11q23.3 region, including variants in/near PHLDB1 (rs11603023, P_combined 5 1.25E208, OR 5 1.20), DDX6 (rs638893, P_combined 5 5.19E207, OR 5 1.22) and CXCR5 (rs10892301, P_combined 5 2.51E208, OR 5 0.85). Genetic contributions from the newly identified variants were all independent of SNP rs4639966, whose association was reported from the previous GWAS. In addition, the three newly identified variants all showed independent association with the disease through modeling by both stepwise and conditional logistic regression. The presence of multiple independent variants in this region emphasizes its role in SLE susceptibility, and also hints the possibility that distinct biological mechanisms might be involved in the disease involving this genomic region. © The Author 2013. Published by Oxford University Press. All rights reserved.link_to_subscribed_fulltex
Author Correction: Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples
No full text: Correction to this paper has been published: https://doi.org/10.1038/s41467-020-20128-w
