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Statistical modelling of molecular descriptors in QSAR/QSPR
This handbook and ready reference presents a combination of statistical, information-theoretic, and data analysis methods to meet the challenge of designing empirical models involving molecular descriptors within bioinformatics.
eBook
The stuff of bits : an essay on the materialities of information
\"The central topic of 'The Stuff of Bits' is the materialities of information. This term often brings to mind the materiality of information infrastructures - server farms, air conditioning, fiber optic cable routes, and distributed storage. By contrast, 'The Stuff of Bits' focuses on digital information itself as something with which we - as designers, as users, as citizens, as customers, and as human beings - have a material engagement. The book is anchored by four case studies - one on computer emulation, one on spreadsheets, one on databases, and one on network architectures - organized in terms of the scopes of engagement. Through these cases, a common analytic strategy is to identify not just their materiality but their materialities, that is, not just the brute fact of their material forms but the specific material properties that they display and the consequences of those properties - properties like granularity, transparency, directness, weight, and malleability. The idea is that, in the realm of the digital, everything may be reduced to 'bits' but those bits are not all of equal significance; particular encodings reflect particular needs and expectations of change, adaptation, and evolution. To a certain extent this is similar to 'constraints' and 'affordances' in Don Norman's Six Principles of Design and the driving force behind the Platform Studies series, in that different mediums, or materialities, promote distinct use and reception. As Paul Dourish writes in the Introduction to this book, 'material arrangements of information - how it is represented and how that shapes how it can be put to work - matters significantly for our experience of information and information systems'\"-- Provided by publisher.
Book
Simultaneous phase and size control of upconversion nanocrystals through lanthanide doping
A shining example of doping
Many technological materials are intentionally 'doped' by the introduction of trace amounts of foreign elements to impart new and useful properties — a classic example is the doping of semiconductors. Feng Wang
et al
. describe a system in which lanthanide doping can be used to control the growth of NaYF
4
nanocrystals, making it possible to simultaneously tune the size, crystallographic phase and optical properties of the resulting materials. These findings increase our understanding of doping-induced structural transformations, and provide a straightforward route for the controlled synthesis of luminescent nanocrystals for many applications.
Many technological materials are intentionally 'doped' with foreign elements to impart new and desirable properties, a classic example being the doping of semiconductors to tune their electronic behaviour. Here lanthanide doping is used to control the growth of nanocrystals, allowing for simultaneous tuning of the size, crystallographic phase and optical properties of the hybrid material.
Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase
1
, modifying electronic properties
2
,
3
,
4
, modulating magnetism
5
as well as tuning emission properties
6
,
7
,
8
,
9
. Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF
4
nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion
10
,
11
,
12
emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF
4
upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels
12
to volumetric three-dimensional displays
13
.
Journal Article
Preferential Growth of Single-Walled Carbon Nanotubes with Metallic Conductivity
Single-walled carbon nanotubes can be classified as either metallic or semiconducting, depending on their conductivity, which is determined by their chirality. Existing synthesis methods cannot controllably grow nanotubes with a specific type of conductivity. By varying the noble gas ambient during thermal annealing of the catalyst, and in combination with oxidative and reductive species, we altered the fraction of tubes with metallic conductivity from one-third of the population to a maximum of 91%. In situ transmission electron microscopy studies reveal that this variation leads to differences in both morphology and coarsening behavior of the nanoparticles that we used to nucleate nanotubes. These catalyst rearrangements demonstrate that there are correlations between catalyst morphology and resulting nanotube electronic structure and indicate that chiral-selective growth may be possible.
Journal Article