101 research outputs found
The Fourth-Century AD Expansion of the Graeco-Roman Settlement of Karanis (Kom Aushim) in the Northern Fayum*
The Graeco-Roman town of Karanis, founded during the Ptolemaic Period in the north-eastern Fayum in the third century bc and long thought to have been abandoned in the third century ad actually saw a substantial expansion during the fourth century AD. With the creation of an 3 extension towards the west and the expansion of the eastern part, the town grew in both directions. We argue that this expansion may be related to a sudden rise of the water level in Lake Moeris (Lake Qarun), perhaps linked to a catastrophic dam breach in the eastern part of the Fayum, and the subsequent relocation of the inhabitants of the low-lying settlements north and east of the lake
A compact dual atom interferometer gyroscope based on laser-cooled rubidium
We present a compact and transportable inertial sensor for precision sensing
of rotations and accelerations. The sensor consists of a dual Mach-Zehnder-type
atom interferometer operated with laser-cooled Rb. Raman processes are
employed to coherently manipulate the matter waves. We describe and
characterize the experimental apparatus. A method for passing from a compact
geometry to an extended interferometer with three independent atom-light
interaction zones is proposed and investigated. The extended geometry will
enhance the sensitivity by more than two orders of magnitude which is necessary
to achieve sensitivities better than rad/s/.Comment: 9 pages, 8 figure
Versatile compact atomic source for high resolution dual atom interferometry
We present a compact Rb atomic source for high precision dual atom
interferometers. The source is based on a double-stage magneto-optical trap
(MOT) design, consisting of a 2-dimensional (2D)-MOT for efficient loading of a
3D-MOT. The accumulated atoms are precisely launched in a horizontal moving
molasses. Our setup generates a high atomic flux ( atoms/s) with
precise and flexibly tunable atomic trajectories as required for high
resolution Sagnac atom interferometry. We characterize the performance of the
source with respect to the relevant parameters of the launched atoms, i.e.
temperature, absolute velocity and pointing, by utilizing time-of-flight
techniques and velocity selective Raman transitions.Comment: uses revtex4, 9 pages, 12 figures, submitted to Phys. Rev.
Gauss sum factorization with cold atoms
We report the first implementation of a Gauss sum factorization algorithm by
an internal state Ramsey interferometer using cold atoms. A sequence of
appropriately designed light pulses interacts with an ensemble of cold rubidium
atoms. The final population in the involved atomic levels determines a Gauss
sum. With this technique we factor the number N=263193.Comment: 4 pages, 5 figure
Phase-locking of two self-seeded tapered amplifier lasers
We report on the phase-locking of two diode lasers based on self-seeded
tapered amplifiers. In these lasers, a reduction of linewidth is achieved using
narrow-band high-transmission interference filters for frequency selection. The
lasers combine a compact design with a Lorentzian linewidth below 200 kHz at an
output power of 300 mW. We characterize the phase noise of the phase-locked
laser system and study its potential for coherent beam-splitting in atom
interferometers.Comment: 7 pages, 4 figure
A manifesto for the study of the ancient Egyptian environment
The study of ancient Egypt lags behind other historical and archaeological disciplines
by failing to prioritize the study of the environment. In order to generate meaningful
knowledge about past societies situated along the Nile, it is necessary to pursue holistic
research agendas with interdisciplinary frameworks that incorporate a broader range of
specialists, including those drawn from the sciences. More robust data must be sought and
assessed, including geomorphological and paleo-climatic data, and methodology must
be expanded to incorporate ecological models of occupation and land-use and of human
responses to environmental change. The participants of the 2017 Colloquium on Ancient
Egypt and the Environment propose the following three goals for the study of ancient
Egypt and, more generally, for historical inquiry.
Proceedings of the conference Gift of the Nile? A Symposium and Workshop on Ancient Egypt and the Environment held at Quest University Canada, April 2, 2017, and at the University of British Columbia, April 3, 201
Interferometry with Bose-Einstein Condensates in Microgravity
Atom interferometers covering macroscopic domains of space-time are a
spectacular manifestation of the wave nature of matter. Due to their unique
coherence properties, Bose-Einstein condensates are ideal sources for an atom
interferometer in extended free fall. In this paper we report on the
realization of an asymmetric Mach-Zehnder interferometer operated with a
Bose-Einstein condensate in microgravity. The resulting interference pattern is
similar to the one in the far-field of a double-slit and shows a linear scaling
with the time the wave packets expand. We employ delta-kick cooling in order to
enhance the signal and extend our atom interferometer. Our experiments
demonstrate the high potential of interferometers operated with quantum gases
for probing the fundamental concepts of quantum mechanics and general
relativity.Comment: 8 pages, 3 figures; 8 pages of supporting materia
Diffusible repression of cytokinin signalling produces endodermal symmetry and passage cells.
In vascular plants, the root endodermis surrounds the central vasculature as a protective sheath that is analogous to the polarized epithelium in animals, and contains ring-shaped Casparian strips that restrict diffusion. After an initial lag phase, individual endodermal cells suberize in an apparently random fashion to produce 'patchy' suberization that eventually generates a zone of continuous suberin deposition. Casparian strips and suberin lamellae affect paracellular and transcellular transport, respectively. Most angiosperms maintain some isolated cells in an unsuberized state as so-called 'passage cells', which have previously been suggested to enable uptake across an otherwise-impermeable endodermal barrier. Here we demonstrate that these passage cells are late emanations of a meristematic patterning process that reads out the underlying non-radial symmetry of the vasculature. This process is mediated by the non-cell-autonomous repression of cytokinin signalling in the root meristem, and leads to distinct phloem- and xylem-pole-associated endodermal cells. The latter cells can resist abscisic acid-dependent suberization to produce passage cells. Our data further demonstrate that, during meristematic patterning, xylem-pole-associated endodermal cells can dynamically alter passage-cell numbers in response to nutrient status, and that passage cells express transporters and locally affect the expression of transporters in adjacent cortical cells
Different expressions of the same mode: a recent dialogue between archaeological and contemporary drawing practices
In this article we explore what we perceive as pertinent features of shared experience at the excavations of an Iron Age Hillfort at Bodfari, North Wales, referencing artist, archaeologist and examples of seminal art works and archaeological records resulting through inter-disciplinary collaboration. We explore ways along which archaeological and artistic practices of improvisation become entangled and productive through their different modes of mark-making. We contend that marks and memories of artist and archaeologist alike emerge interactively, through the mutually constituting effects of the object of study, the tools of exploration, and the practitioners themselves, when they are enmeshed in the cross-modally bound activities. These include, but are not limited to, remote sensing, surveying, mattocking, trowelling, drawing, photographing, videoing and sound recording. These marks represent the co-signatories: the gesture of the often anonymous practitioners, the voice of the deposits, as well as the imprint of the tools, and their interplay creates a multi-threaded narrative documenting their modes of intra-action, in short our practices. They occupy the conceptual space of paradata, and in the process of saturating the interstices of digital cognitive prosthetics they lend probity to their translations in both art form and archive
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