5,888 research outputs found
Quantum cascade laser light propagation through hollow silica waveguides
In this paper, the transmission characteristics of hollow silica waveguides with bore diameters of 300 and 1000 μm are investigated using a 7.8-μm quantum cascade laser system. We show that the bore diameter, coiling and launch conditions have an impact on the number of supported modes in the waveguide. Experimental verification of theoretical predictions is achieved using a thermal imaging camera to monitor output intensity distributions from waveguides under a range of conditions. The thermal imaging camera allowed for more detailed images than could be obtained with a conventionally used beam profiler. The results show that quasi-single-mode transmission is achievable under certain conditions although guided single-mode transmission in coiled waveguides requires a smaller bore diameter-to-wavelength ratio than is currently available. Assessment of mode population is made by investigating the spatial frequency content of images recorded at the waveguide output using Fourier transform techniques
Maximum Normalized Rate as a Flying Qualities Parameter
Discrete attitude commands have become a standard task for flying qualities evaluation and control system testing. Much pilot opinion data is now available for ground-based and in-flight simulations, but adequate performance measures and prediction methods have not been established. The Step Target Tracking Prediction method, introduced in 1978, correlated time-on-target and rms tracking data with NT-33 in-flight longitudinal simulations, but did not employ parameters easily measured in manned flight and simulation. Recent application of the Step Target Tracking Prediction method to lateral flying qualities analysis has led to a new measure of performance. This quantity, called Maximum Normalized Rate (MNR), reflects the greatest attitude rate a pilot can employ during a discrete maneuver without excessive overshoot and oscillation. MNR correlates NT-33 lateral pilot opinion ratings well, and is easily measured during flight test or simulation. Futhermore, the Step Target MNR method can be used to analyze large amplitude problems concerning rate limiting and nonlinear aerodynamics
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British research in accounting and finance (2001–2007): the 2008 research assessment exercise
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Polymorphisms of the glucose transporter (GLUT1) gene are associated with diabetic nephropathy
Polymorphisms of the glucose transporter (GLUT1) gene are associated with diabetic nephropathy.BackgroundDiabetic nephropathy (DN) is a major cause of morbidity and mortality in patients with type 1 diabetes mellitus. Recent studies suggest that genetic factors, including polymorphisms in the flanking region of the aldose reductase gene (5′ALR2), play an important role in the pathogenesis of nephropathy. Glucose transporter (GLUT1) activity has been implicated in renal hypertrophy and extracellular matrix formation in mesangial cells. The aim was to investigate the frequency of a polymorphism within the GLUT1 gene in 186 Caucasoid patients with type 1 diabetes and 104 normal controls.MethodsAmplimers flanking the Xba-I polymorphic site in the second intron were employed to amplify DNA from subjects. The amplified DNA was restricted with endonuclease Xba-I, separated by gel electrophoresis, and visualized. In the absence of an Xba-I site, a fragment of 1.1 kilobase was seen, whereas fragments of 0.9 and 0.2 were generated if the Xba-I site was present.ResultsThere was a highly significant increase in the frequency of the 1.1 allele in those patients with nephropathy (N = 70) compared with those with no proteinuria or retinopathy after 20 years of diabetes (uncomplicated N = 44, 61.4 vs. 40.9%, respectively, P < 0.001). The 1.1/1.1 genotype was also significantly increased in the nephropathy group compared with the uncomplicated group of patients (37.1 vs. 13.6%, respectively, P < 0.01). The frequency of the 1.1/1.1 genotype was similar in 30 patients with retinopathy but not nephropathy when compared with the uncomplicated group of patients (13.6 vs. 16.7%). Furthermore, only 8 out of 49 patients with DN had the Z+2 5′ALR2 DN “protective” allele and the 0.9 GLUT1 allele in contrast to 21 out of 39 uncomplicated patients (P < 0.0002).ConclusionThese results suggest that the GLUT1 gene together with the aldose reductase gene are associated with susceptibility to DN in patients with type 1 diabetes
Blending of nanoscale and microscale in uniform large-area sculptured thin-film architectures
The combination of large thickness ( m), large--area uniformity (75
mm diameter), high growth rate (up to 0.4 m/min) in assemblies of
complex--shaped nanowires on lithographically defined patterns has been
achieved for the first time. The nanoscale and the microscale have thus been
blended together in sculptured thin films with transverse architectures.
SiO () nanowires were grown by electron--beam evaporation onto
silicon substrates both with and without photoresist lines (1--D arrays) and
checkerboard (2--D arrays) patterns. Atomic self--shadowing due to
oblique--angle deposition enables the nanowires to grow continuously, to change
direction abruptly, and to maintain constant cross--sectional diameter. The
selective growth of nanowire assemblies on the top surfaces of both 1--D and
2--D arrays can be understood and predicted using simple geometrical shadowing
equations.Comment: 17 pages, 9 figure
Perspective: Current advances in solid-state NMR spectroscopy
In contrast to the rapid and revolutionary impact of solution-state Nuclear Magnetic Resonance (NMR) on modern chemistry, the field of solid-state NMR has matured more slowly. This reflects the major technical challenges of much reduced spectral resolution and sensitivity in solid-state as compared to solution-state spectra, as well as the relative complexity of the solid state. In this perspective, we outline the technique developments that have pushed resolution to intrinsic limits and the approaches, including ongoing major developments in the field of Dynamic Nuclear Polarisation, that have enhanced spectral sensitivity. The information on local structure and dynamics that can be obtained using these gains in sensitivity and resolution is illustrated with a diverse range of examples from large biomolecules to energy materials and pharmaceuticals and from both ordered and highly disordered materials. We discuss how parallel developments in quantum chemical calculation, particularly density functional theory, have enabled experimental data to be translated directly into information on local structure and dynamics, giving rise to the developing field of “NMR crystallography
Spatiotemporal dispersion and wave envelopes with relativistic and pseudorelativistic characteristics
A generic nonparaxial model for pulse envelopes is presented. Classic Schro¨dinger-type descriptions of
wave propagation have their origins in slowly-varying envelopes combined with a Galilean boost to the
local time frame. By abandoning these two simplifications, a picture of pulse evolution emerges in which
frame-of-reference considerations and space-time transformations take center stage. A wide range of
effects, analogous to those in special relativity, then follows for both linear and nonlinear systems. Explicit
demonstration is presented through exact bright and dark soliton pulse solutions
Reinstating the 'no-lose' theorem for NMSSM Higgs discovery at the LHC
The simplest supersymmetric model that solves the mu problem and in which the
GUT-scale parameters need not be finely tuned in order to predict the correct
value of the Z boson mass at low scales is the Next-to-Minimal Supersymmetric
Standard Model (NMSSM). However, in order that fine tuning be absent, the
lightest CP-even Higgs boson h should have mass ~100 GeV and SM couplings to
gauge bosons and fermions. The only way that this can be consistent with LEP
limits is if h decays primarily via h->aa->4 tau or 4j but not 4b, where a is
the lighter of the two pseudo-scalar Higgses that are present in the NMSSM.
Interestingly, m_a 2 m_tau somewhat
preferred. Thus, h -> 4 tau becomes a key mode of interest. Meanwhile, all
other Higgs bosons of the NMSSM are typically quite heavy. Detection of any of
the NMSSM Higgs bosons at the LHC in this preferred scenario will be very
challenging using conventional channels. In this paper, we demonstrate that the
h -> aa -> 4 tau decay chain should be visible if the Higgs is produced in the
process pp -> p+h+p with the final state protons being measured using suitably
installed forward detectors. Moreover, we show that the mass of both the h and
the a can be determined on an event-by-event basis.Comment: 23 page
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