Getting the Word Out in the Last Green Valley: Integrating Digital Video, Direct Mail, and Web-Based Information for Specific Target Audiences

A direct mail mini CD-Rom was developed to bring attention to the Green Valley Institute\u27s (an Extension Partnership Program) new Web site. A quasi-experimental survey design with random assignment to either a treatment or control group was employed to assess the effectiveness of the CD-Rom. The study revealed successes as well as limitations to this approach. Nearly a quarter of the recipients did not recall receiving it, but those who received and viewed the CD were significantly more familiar with the organization\u27s programs and goals, considered the Web site more useful, and had greater intentions to contact the organization for additional information and/or assistance in the future

Theory and design of Inx_{x}Ga1−x_{1-x}As1−y_{1-y}Biy_{y} mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 μ\mum on InP substrates

We present a theoretical analysis and optimisation of the properties and performance of mid-infrared semiconductor lasers based on the dilute bismide alloy In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$, grown on conventional (001) InP substrates. The ability to independently vary the epitaxial strain and emission wavelength in this quaternary alloy provides significant scope for band structure engineering. Our calculations demonstrate that structures based on compressively strained In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ quantum wells (QWs) can readily achieve emission wavelengths in the 3 -- 5 $\mu$m range, and that these QWs have large type-I band offsets. As such, these structures have the potential to overcome a number of limitations commonly associated with this application-rich but technologically challenging wavelength range. By considering structures having (i) fixed QW thickness and variable strain, and (ii) fixed strain and variable QW thickness, we quantify key trends in the properties and performance as functions of the alloy composition, structural properties, and emission wavelength, and on this basis identify routes towards the realisation of optimised devices for practical applications. Our analysis suggests that simple laser structures -- incorporating In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ QWs and unstrained ternary In$_{0.53}$Ga$_{0.47}$As barriers -- which are compatible with established epitaxial growth, provide a route to realising InP-based mid-infrared diode lasers.Comment: Submitted versio

Impact of alloy disorder on the band structure of compressively strained GaBiAs

The incorporation of bismuth (Bi) in GaAs results in a large reduction of the band gap energy (E$_g$) accompanied with a large increase in the spin-orbit splitting energy ($\bigtriangleup_{SO}$), leading to the condition that $\bigtriangleup_{SO} > E_g$ which is anticipated to reduce so-called CHSH Auger recombination losses whereby the energy and momentum of a recombining electron-hole pair is given to a second hole which is excited into the spin-orbit band. We theoretically investigate the electronic structure of experimentally grown GaBi$_x$As$_{1-x}$ samples on (100) GaAs substrates by directly comparing our data with room temperature photo-modulated reflectance (PR) measurements. Our atomistic theoretical calculations, in agreement with the PR measurements, confirm that E$_g$ is equal to $\bigtriangleup_{SO}$ for $\textit{x} \approx$ 9$$. We then theoretically probe the inhomogeneous broadening of the interband transition energies as a function of the alloy disorder. The broadening associated with spin-split-off transitions arises from conventional alloy effects, while the behaviour of the heavy-hole transitions can be well described using a valence band-anticrossing model. We show that for the samples containing 8.5% and 10.4% Bi the difficulty in identifying a clear light-hole-related transition energy from the measured PR data is due to the significant broadening of the host matrix light-hole states as a result of the presence of a large number of Bi resonant states in the same energy range and disorder in the alloy. We further provide quantitative estimates of the impact of supercell size and the assumed random distribution of Bi atoms on the interband transition energies in GaBi$_{x}$As$_{1-x}$. Our calculations support a type-I band alignment at the GaBi$_x$As$_{1-x}$/GaAs interface, consistent with recent experimental findings

GaAs-based dilute bismide semiconductor lasers:Theory vs. experiment

We present a theoretical analysis of the electronic and optical properties of near-infrared dilute bismide quantum well (QW) lasers grown on GaAs substrates. Our theoretical model is based upon a 12-band k·p Hamiltonian which explicitly incorporates the strong Bi-induced modifications of the band structure in pseudomorphically strained GaBi x As 1-x alloys. We outline the impact of Bi on the gain characteristics of ideal GaBi x As 1-x /(Al)GaAs devices, compare the results of our theoretical calculations to experimental measurements of the spontaneous emission (SE) and optical gain - a first for this emerging material system - and demonstrate quantitative agreement between theory and experiment. Through our theoretical analysis we further demonstrate that this novel class of III-V semiconductor alloys has strong potential for the development of highly efficient GaAs-based semiconductor lasers which promise to deliver uncooled operation at 1.55 μm

Dilute bismide alloys grown on GaAs and InP substrates for improved near- and mid-infrared semiconductor lasers

We present an analysis of dilute bismide quantum well (QW) lasers grown on GaAs and InP substrates. Our theoretical analysis is based upon a 12-band k·p Hamiltonian which directly incorporates the strong impact of Bi incorporation on the band structure using a band-anticrossing approach. For GaBiAs QWs grown on GaAs we analyse the device performance as a function of Bi composition, and quantify the potential to use GaBiAs alloys to realise highly efficient, temperature stable 1.55 μm lasers. We compare our calculations to measured spontaneous emission (SE) and gain spectra for first-generation GaBiAs lasers and demonstrate quantitative agreement between theory and experiment. We also present a theoretical analysis of InGaBiAs alloys grown on InP substrates. We show that this material system is well suited to the development of mid-infrared lasers, and offers the potential to realise highly efficient InP-based diode lasers incorporating type-I QWs and emitting at > 3 μm. We quantify the theoretical performance of this new class of mid-infrared lasers, and identify optimised structures for emission across the application-rich 3 - 5 μm wavelength range. Our results highlight and quantify the potential of dilute bismide alloys to overcome several limitations associated with existing GaAs- and InP-based near- and mid-infrared laser technologies

Morphological and hemodynamical alterations in brachial artery and cephalic vein. An image‐based study for preoperative assessment for vascular access creation

The current study aims to computationally evaluate the effect of right upper arm position on the geometric and hemodynamic characteristics of the brachial artery (BA) and cephalic vein (CV) and, furthermore, to present in detail the methodology to characterise morphological and hemodynamical healthy vessels. Ten healthy volunteers were analysed in two configurations, the supine (S) and the prone (P) position. Lumen 3D surface models were constructed from images acquired from a non-contrast MRI sequence. Then, the models were used to numerically compute the physiological range of geometric (n = 10) and hemodynamic (n = 3) parameters in the BA and CV. Geometric parameters such as curvature and tortuosity, and hemodynamic parameters based on wall shear stress (WSS) metrics were calculated with the use of computational fluid dynamics. Our results highlight that changes in arm position had a greater impact on WSS metrics of the BA by altering the mean and maximum blood flow rate of the vessel. Whereas, curvature and tortuosity were found not to be significantly different between positions. Inter-variability was associated with antegrade and retrograde flow in BA, and antegrade flow in CV. Shear stress was low and oscillatory shear forces were negligible. This data suggests that deviations from this state may contribute to the risk of accelerated intimal hyperplasia of the vein in arteriovenous fistulas. Therefore, preoperative conditions coupled with post-operative longitudinal data will aid the identification of such relationships

Optical gain in GaAsBi/GaAs quantum well diode lasers

Electrically pumped GaAsBi/GaAs quantum well lasers are a promising new class of near-infrared devices where, by use of the unusual band structure properties of GaAsBi alloys, it is possible to suppress the dominant energy-consuming Auger recombination and inter-valence band absorption loss mechanisms, which greatly impact upon the device performance. Suppression of these loss mechanisms promises to lead to highly efficient, uncooled operation of telecommunications lasers, making GaAsBi system a strong candidate for the development of next-generation semiconductor lasers. In this report we present the first experimentally measured optical gain, absorption and spontaneous emission spectra for GaAsBi-based quantum well laser structures. We determine internal optical losses of 10–15 cm−1 and a peak modal gain of 24 cm−1, corresponding to a material gain of approximately 1500 cm−1 at a current density of 2 kA cm−2. To complement the experimental studies, a theoretical analysis of the spontaneous emission and optical gain spectra is presented, using a model based upon a 12-band k.p Hamiltonian for GaAsBi alloys. The results of our theoretical calculations are in excellent quantitative agreement with the experimental data, and together provide a powerful predictive capability for use in the design and optimisation of high efficiency lasers in the infrared

Dysfunctional play and dopamine physiology in the Fischer 344 rat

Juvenile Fischer 344 rats are known to be less playful than other inbred strains, although the neurobiological substrate(s) responsible for this phenotype is uncertain. In the present study, Fischer 344 rats were compared to the commonly used outbred Sprague-Dawley strain on several behavioral and physiological parameters in order to ascertain whether the lack of play may be related to compromised activity of brain dopamine (DA) systems. As expected, Fischer 344 rats were far less playful than Sprague-Dawley rats, with Fischer 344 rats less likely to initiate playful contacts with a playful partner and less likely to respond playfully to these contacts. We also found that Fischer 344 rats showed less of a startle response and greater pre-pulse inhibition (PPI), especially at higher prepulse intensities. The increase in PPI seen in the Fischer 344 rat could be due to reduced DA modulation of sensorimotor gating and neurochemical measures were consistent with Fischer 344 rats releasing less DA than Sprague-Dawley rats. Fast scan cyclic voltammetry (FSCV) revealed Fischer 344 rats had less evoked DA release in dorsal and ventral striatal brain slices and high-performance liquid chromatography revealed Fischer 344 rats to have less DA turnover in the striatum and prefrontal cortex. We also found DA-dependent forms of cortical plasticity were deficient in the striatum and prefrontal cortex of the Fischer 344 rat. Taken together, these data indicate that deficits in play and enhanced PPI of Fischer 344 rats may be due to reduced DA modulation of corticostriatal and mesolimbic/mesocortical circuits critical to the execution of these behaviors

A genome-wide association study of Hodgkin Lymphoma identifies new susceptibility loci at 2p16.1 (REL), 8q24.21, and 10p14 (GATA3)

To identify predisposition loci for classical Hodgkin Lymphoma (cHL) we conducted a genome-wide association study of 589 cHL cases and 5,199 controls with validation in 4 independent samples totaling 2,057 cases and 3,416 controls. We identified three new susceptibility loci at 2p16.1 (rs1432295, REL; odds ratio [OR]=1.22, Pcombined=1.91×10−8), 8q24.21 (rs2019960, PVT1; OR=1.33, Pcombined=1.26×10−13) and 10p14 (rs501764, GATA3; OR=1.25, Pcombined=7.05×10−8). Furthermore, we confirmed the role of the MHC in disease etiology by revealing a strong HLA association (rs6903608; OR=1.70, Pcombined=2.84×10−50). These data provide new insight into the pathogenesis of cHL