Diffractionless image propagation and frequency conversion via four-wave mixing exploiting the thermal motion of atoms

A setup to frequency-convert an arbitrary image encoded in the spatial profile of a probe field onto a signal field using four-wave mixing in a thermal atom vapor is proposed. The atomic motion is exploited to cancel diffraction of both signal and probe fields simultaneously. We show that an incoherent probe field can be used to enhance the transverse momentum bandwidth which can be propagated without diffraction, such that smaller structures with higher spatial resolution can be transmitted. It furthermore compensate linear absorption with non-linear gain, to improve the four-wave mixing performance since the propagation dynamics of the various field intensities is favorably modified.Comment: 12 pages, 7 figure

Flexible Sensor Network Reprogramming for Logistics

Besides the currently realized applications, Wireless Sensor Networks can be put to use in logistics processes. However, doing so requires a level of flexibility and safety not provided by the current WSN software platforms. This paper discusses a logistics scenario, and presents SensorScheme, a runtime environment used to realize this scenario, based on semantics of the Scheme programming language. SensorScheme is a general purpose WSN platform, providing dynamic reprogramming, memory safety (sandboxing), blocking I/O, marshalled communication, compact code transport. It improves on the state of the art by making better use of the little available memory, thereby providing greater capability in terms of program size and complexity. We illustrate the use of our platform with some application examples, and provide experimental results to show its compactness, speed of operation and energy efficiency

Control of beam propagation in optically written waveguides beyond the paraxial approximation

Beam propagation beyond the paraxial approximation is studied in an optically written waveguide structure. The waveguide structure that leads to diffractionless light propagation, is imprinted on a medium consisting of a five-level atomic vapor driven by an incoherent pump and two coherent spatially dependent control and plane-wave fields. We first study propagation in a single optically written waveguide, and find that the paraxial approximation does not provide an accurate description of the probe propagation. We then employ coherent control fields such that two parallel and one tilted Gaussian beams produce a branched waveguide structure. The tilted beam allows selective steering of the probe beam into different branches of the waveguide structure. The transmission of the probe beam for a particular branch can be improved by changing the width of the titled Gaussian control beam as well as the intensity of the spatially dependent incoherent pump field.Comment: 10 pages, 9 figure

Efficient and automatic methods for flexible regression on spatiotemporal data, with applications to groundwater monitoring

Fitting statistical models to spatiotemporal data requires finding the right balance between imposing smoothness and following the data. In the context of P-splines, we propose a Bayesian framework for choosing the smoothing parameter which allows the construction of fully-automatic data-driven methods for fitting flexible models to spatiotemporal data. An implementation, which is highly computationally efficient and which exploits the sparsity of the design and penalty matrices, is proposed. The findings are illustrated using a simulation study and two examples, all concerned with the modelling of contaminants in groundwater. This suggests that the proposed strategy is more stable that competing methods based on the use of criteria such as GCV and AIC

The Deelen infrasound array for recording sonic booms and events of CTBT interest

The Seismology Division of the Royal Netherlands Meteorological Institute (KNMI) has build up expertise in infrasound measurements by investigating low frequency events in order to distinguish between seismic and sonic events. KNMI operates, amongst others, a sixteen element microbarometer array with an aperture of 1.5 km, the Deelen Infrasound Array (DIA). Sonic booms and events of Comprehensive Test Ban Treaty (CTBT) interest are recorded within the frequency range of 100 seconds and 40 Hertz. Recently, KNMI and Microflown Technologies B.V. started a collaboration concerning infrasound measurements. This paper reports the use of a novel sensor. The so-called Microflown [1] is an acoustic sensor, sensitive for frequencies from 0Hz up to 1kHz. The Microflown is developed at the University of Twente and commercialised by Microflown Technologies B.V [3]

The role of forest stream corridor characteristics in influencing stream and riparian ecology

This PhD thesis seeks to consider conifer forestry stream corridor design in relation to both in-stream and riparian zone biodiversity and functioning. The contribution, availability and source of basal resources within varying corridor conditions are the focus of this project. This approach is combined with surveys of community diversity on a number of key trophic scales in order to determine how the corridor characteristics and their associated resource availability, affects community structure. The effects of varying design and management of the riparian buffer zones within afforested stream systems on in-stream and overall habitat diversity and functioning remains largely unknown. Although guidelines have been implemented for several years (Forest and Water Guidelines, Forestry Commission), recommendations, although based on sound assumptions, are subjective assessments and tend not based on scientific research or data. As such, the premise of this project is to consider a variety of corridor physical parameters adjacent to low-order streams within two afforested catchments in South-West Scotland, between 2003 and 2005, in order to contribute to the understanding of system functioning within the limitations of forestry land-use and management. A number of different approaches were employed in order to define the proportional contributions of allochthonous and autochthonous material within the benthos of the stream systems. This was done in order to define resource availability, biofilm characteristics, stream functioning and the role of corridor design in influencing resource availability. Yet, despite significant autochthonous productivity, allochthonous organic matter was the primary resource utilised by many taxa. However, conversely, light regime was found to be fundamental in shaping production and community structure within these ecosystems. Consequently, here I explore a number of different trophic scale responses to riparian conditions in order to define the biotic responses to variation of resource availability, with the aim of contributing information which may aid in design and management of afforested riparian zones

The Effects of Trauma on Early Childhood Development/Building Resilience and Repair in Children after Trauma

The Effects of Trauma on Early Childhood Development The purpose of this paper is to review research literature on how trauma and traumatic events impact early childhood development. If children experience trauma early in life, will their development be impacted? Fortunately, infant mental health and early childhood mental health are at the forefront of early childhood research to discover if and how trauma impacts development. Qualitative and quantitative research was reviewed and used to create this paper. All six studies were reviewed regarding the effects of trauma on early childhood development and young children’s brains. Changes in brain formation, the brain’s response to stimuli, and impacts on child development were main focal points all articles shared. Educators and those working with young children must be aware of the symptoms of trauma and the effects on child development. Building Resilience and Repair in Children after Trauma The purpose of this paper is to review research literature on how educators can build resilience and repair in children after trauma and stress. Training educators, child care professionals, and other individuals who work with or around children on a daily basis, to build resilience, is a major goal in the world of Early Childhood Education. Many of these trainings include promoting repair in children after trauma and ongoing stress and supplying caregivers and educators with a variety of resources. I review five qualitative and quantitative studies reported over the last five years that examine building resilience and repair in children after experiencing trauma

Economic Analysis of High Fertilizer Input, Over-seeded Clover and Native Pasture Production Systems in the Texas Coastal Bend

This paper examined the cost and risk of three grazing systems to provide information on economically sustainable systems for cattle producers in the Texas Coastal Bend. Results indicate the medium input (over-seeded clover) grazing system displays first degree stochastic dominance relative to the high input and no input grazing systems.grazing system economics, forage production economics, Crop Production/Industries, Livestock Production/Industries, Production Economics,