1,588 research outputs found
Building geometric models with hand-drawn sketches
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 49-51).Architects work on drawings and models, not buildings. Today, in many architectural practices, drawings and models are produced in digital format using Computer-aided Design (CAD) tools. Unquestionably, digital media have changed the way in which many architects perform their day to day activities. But these changes have been limited to the more prosaic aspects of practice. To be sure, CAD systems have made the daily operations of many design offices more efficient; nevertheless, they have been of little use - and indeed are often a hindrance - in situations where the task at hand is more conjectural and speculative in nature, as it is during the early stages of a project. Well-intentioned efforts to insinuate CAD into these aspects of practice have only served to reveal the incongruities between the demands of designer and the configuration of the available tools. One of the chief attributes of design practice is that it is action performed at a distance through the agency of representations. This fundamental trait implies that we have to understand how computers help architects describe buildings if we are to understand how they might help architects design buildings. As obvious as this claim might seem, CAD programs can be almost universally characterized by a tacit denigration of visual representation. In this thesis, I examine properties of design drawings that make them useful to architects. I go on to describe a computer program that I have written that allows a designer to build geometric models using freehand sketches. This program illustrates that it is possible to design a software tool in a way that profits from, rather than negates, the power of visual representations.by Ewan E. Branda.M.S
Optical properties of an atomic ensemble coupled to a band edge of a photonic crystal waveguide
We study the optical properties of an ensemble of two-level atoms coupled to
a 1D photonic crystal waveguide (PCW), which mediates long-range coherent
dipole-dipole interactions between the atoms. We show that the long-range
interactions can dramatically alter the linear and nonlinear optical behavior,
as compared to a typical atomic ensemble. In particular, in the linear regime,
we find that the transmission spectrum reveals multiple transmission dips,
whose properties we show how to characterize. In the many-photon regime the
system response can be highly non-linear, and under certain circumstances the
ensemble can behave like a single two-level system, which is only capable of
absorbing and emitting a single excitation at a time. Our results are of direct
relevance to atom-PCW experiments that should soon be realizable
Gene-knockdown in the honey bee mite Varroa destructor by a non-invasive approach : studies on a glutathione S-transferase
Peer reviewedPublisher PD
CMB Spectral Distortion Constraints on Thermal Inflation
Thermal inflation is a second epoch of exponential expansion at typical
energy scales . If the usual
primordial inflation is followed by thermal inflation, the primordial power
spectrum is only modestly redshifted on large scales, but strongly suppressed
on scales smaller than the horizon size at the beginning of thermal inflation,
. We calculate the spectral distortion of
the cosmic microwave background generated by the dissipation of acoustic waves
in this context. For , thermal inflation
results in a large suppression of the -distortion amplitude, predicting
that it falls well below the standard value of .
Thus, future spectral distortion experiments, similar to PIXIE, can place new
limits on the thermal inflation scenario, constraining if were found.Comment: 18 pages, 7 figure
Interactive Teaching Tools for Spatial Sampling
The statistical analysis of data which is measured over a spatial region is well established as a scientific tool which makes considerable contributions to a wide variety of application areas. Further development of these tools also remains a central part of the research scene in statistics. However, understanding of the concepts involved often benefits from an intuitive and experimental approach, as well as a formal description of models and methods. This paper describes software which is intended to assist in this understanding. The role of simulation is advocated, in order to explain the meaning of spatial correlation and to interpret the parameters involved in standard models. Realistic scenarios where decisions on the locations of sampling points in a spatial setting are required are also described. Students are provided with a variety of sampling strategies and invited to select the most appropriate one in two different settings. One involves water sampling in the lagoon of the Mururoa Atoll while the other involves sea bed sampling in a Scottish firth. Once a student has decided on a sampling strategy, simulated data are provided for further analysis. This extends the range of teaching activity from the analysis of data collected by others to involvement in data collection and the need to grapple with issues of design. It is argued that this approach has significant benefits in learning.
Transcriptome analysis of the synganglion from the honey bee mite, Varroa destructor and RNAi knockdown of neural peptide targets
Acknowledgements This work was funded by BBSRC-LINK grant # BB/J01009X/1 and Vita Europe Ltd. We are grateful to the Scottish Beekeepers Association, especially Mr Phil McAnespie in supporting this work at its inception. We acknowledge partial funding from a Genesis Faraday SPARK Award, part of a Scottish Government SEEKIT project for the early part of this work. We are grateful to Prof David Evans for his advice on Varroa destructor viruses.Peer reviewedPostprin
Hard ticks (Acari: Ixodidae) and tick-borne diseases of sheep and goats in Africa: A Review
Ticks are leading vectors of economically important pathogens that affect small ruminants due to favourable climatic conditions across different regions of the African continent. They are responsible for both direct and indirect economic losses in the livestock industry. This review focuses on the species diversity of hard ticks, their biology, tick-borne diseases of sheep and goats including non-infectious disease, and risk factors to tick infestation in Africa. Furthermore, our review provides recent updates on distribution of ticks and tick-borne pathogens of small ruminants in Africa. It was observed that several species and subspecies of hard ticks belonging to the genera Hyalomma (Hy), Rhipicephalus (Rh), Ixodes (I) and Amblyomma (Am) were found infesting small ruminants across the different regions of the continent. Of these genera, Rhipicephalus ticks accounts for the majority of the registered species, with exactly 27 different species infesting small ruminant stocks comprising of different developmental instars and adults of the tick. Rhipicephalus decolaratus, Rh. e. evertsi and Rh. appendiculatus were the three most common Rhipicephalus species reported. Both protozoal (Babesia and Theileria) and bacterial (Anaplasma, Rickettsia, Ehrlichia, Coxiella and Mycoplasma) pathogens have being reported to be amplified in several hard tick species and/or small ruminant hosts. Furthermore, tick paralysis and lameness were non-infectious conditions attributed to tick infestations. Amblyomma hebraeum and Rh. glabroscutatum may cause lameness in goats, while Hy. rufipes is responsible for the same condition in Merino sheep. Host paralysis due to a neurotoxin released by female Rh. e. evertsi and I. rubicundus has been documented within the continent. We therefore advocate for the need of integrated control measures against tick-borne pathogens (TBPs) including their arthropod vectors, to be performed simultaneously to ease the burden of vector-borne diseases in small ruminant production.<br/
Population mixing due to dipole-dipole interactions in a 1D array of multilevel atoms
We examine theoretically how dipole-dipole interactions arising from multiple
photon scattering lead to a modified distribution of ground state populations
in a driven, ordered 1D array of multilevel atoms. Specifically, we devise a
level configuration in which a ground-state population accumulated due solely
to dipole-dipole interactions can be up to 20\% in regimes accessible to
current experiments with neutral atom arrays. For much larger systems, the
steady state can consist of an equal distribution of population across the
ground state manifold. Our results illustrate how dipole-dipole interactions
can be accentuated through interference, and regulated by the geometry of
ordered atom arrays. More generally, control techniques for multilevel atoms
that can be degraded by multiple scattering, such as optical pumping, will
benefit from an improved understanding and control of dipole-dipole
interactions available in ordered arrays.Comment: paper is now identical to published versio
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