A space division multiplexed free-space-optical communication system that can auto-locate and fully self align with a remote transceiver

Free-Space Optical (FSO) systems offer the ability to distribute high speed digital links into remote and rural communities where terrain, installation cost or infrastructure security pose critical hurdles to deployment. A challenge in any point-to-point FSO system is initiating and maintaining optical alignment from the sender to the receiver. In this paper we propose and demonstrate a low-complexity self-aligning FSO prototype that can completely self-align with no requirement for initial manual positioning and could therefore form the opto-mechanical basis for a mesh network of optical transceivers. The prototype utilises off-the-shelf consumer electrical components and a bespoke alignment algorithm. We demonstrate an eight fibre spatially multiplexed link with a loss of 15 dB over 210 m

Does Habitat Management for Northern Bobwhites Benefit the Red Imported Fire Ant?

Red imported fire ants (Solenopsis invicta) have caused damage to agricultural, economic, and wildlife resources since their accidental introduction. Previous studies have suggested that red imported fire ant (RIFA) mound densities are positively correlated to habitats maintained through disturbance. Prescribed burning and disking are two techniques commonly used to disturb portions of the landscape to maintain early successional habitats for northern bobwhite (Colinus virginianus). We tested the hypothesis that prescribed burning and disking would increase RIFA mound densities. This study was conducted in Refugio County, Texas in the Texas Coastal Prairie on Loamy Prairie range sites. Red imported fire ant mound densities were different between years (F = 5.05, df = 2, P = 0.0148). However, burning and disking had no impact (F = 0.22, df = 2, P = 0.8044) on RIFA mound densities. Initially high RIFA mound densities in our study area coupled with the territoriality of predominantly monogyne (single-queen) colonies may have limited increases in RIFA mound density in response to treatments on these study sites

Degraded Rangeland: Can the Balance Be Restored in the Absence of Satisfactory Range Management Practices?

The rangelands of KwaZulu-Natal play a fundamental role in the wealth and security of communal populations who are dependent on these forage-producing lands for their livelihoods. In most communal areas of the Province, there is an absence of satisfactory range management practices and the utilization of resources is generally non-sustainable. A major threat to the productivity of rangeland is inappropriate land use, such as overgrazing and incorrect burning practices, leading to extensive degradation of both the vegetative and soil components. Range vegetation and soil reserves show vastly reduced productivity. Degradation also results in increased susceptibility to erosion, loss of vegetative cover and palatable species, loss of biodiversity and reduced productivity, directly threatening food security of vast numbers of people in the rural areas. Social issues such as weakened and marginalized traditional authorities and reduced control of resource utilization is partly responsible. In addition, the value placed on livestock for draught power, meat, milk and other products, and for financial security against calamity, entrenches a reluctance to diminish stock numbers. Alternative strategies to reduce pressure on stressed range systems need to be formulated in participation with affected communities to, among other benefits, increase the contribution from animals to household security

Risk factors for delay in symptomatic presentation: a survey of cancer patients

Background: Delay in symptomatic presentation leading to advanced stage at diagnosis may contribute to poor cancer survival. To inform public health approaches to promoting early symptomatic presentation, we aimed to identify risk factors for delay in presentation across several cancers. Methods: We surveyed 2371 patients with 15 cancers about nature and duration of symptoms using a postal questionnaire. We calculated relative risks for delay in presentation (time from symptom onset to first presentation >3 months) by cancer, symptoms leading to diagnosis and reasons for putting off going to the doctor, controlling for age, sex and deprivation group. Results: Among 1999 cancer patients reporting symptoms, 21% delayed presentation for >3 months. Delay was associated with greater socioeconomic deprivation but not age or sex. Patients with prostate (44%) and rectal cancer (37%) were most likely to delay and patients with breast cancer least likely to delay (8%). Urinary difficulties, change of bowel habit, systemic symptoms (fatigue, weight loss and loss of appetite) and skin symptoms were all common and associated with delay. Overall, patients with bleeding symptoms were no more likely to delay presentation than patients who did not have bleeding symptoms. However, within the group of patients with bleeding symptoms, there were significant differences in risk of delay by source of bleeding: 35% of patients with rectal bleeding delayed presentation, but only 9% of patients with urinary bleeding. A lump was a common symptom but not associated with delay in presentation. Twenty-eight percent had not recognised their symptoms as serious and this was associated with a doubling in risk of delay. Embarrassment, worry about what the doctor might find, being too busy to go to the doctor and worry about wasting the doctor’s time were also strong risk factors for delay, but were much less commonly reported (<6%). Interpretation: Approaches to promote early presentation should aim to increase awareness of the significance of cancer symptoms and should be designed to work for people of the lowest socioeconomic status. In particular, awareness that rectal bleeding is a possible symptom of cancer should be raised

Recognition of cancer warning signs and anticipated time to help-seeking in a population sample of adults in the UK

Background: Not recognising a symptom as suspicious is a common reason given by cancer patients for delayed help-seeking; but inevitably this is retrospective. We therefore investigated associations between recognition of warning signs for breast, colorectal and lung cancer and anticipated time to help-seeking for symptoms of each cancer. Methods: Computer-assisted telephone interviews were conducted with a population-representative sample (N=6965) of UK adults age greater than or equal to50 years, using the Awareness and Beliefs about Cancer scale. Anticipated time to help-seeking for persistent cough, rectal bleeding and breast changes was categorised as >2 vs less than or equal to2 weeks. Recognition of persistent cough, unexplained bleeding and unexplained lump as cancer warning signs was assessed (yes/no). Associations between recognition and help-seeking were examined for each symptom controlling for demographics and perceived ease of health-care access. Results: For each symptom, the odds of waiting for >2 weeks were significantly increased in those who did not recognise the related warning sign: breast changes: OR=2.45, 95% CI 1.47–4.08; rectal bleeding: OR=1.77, 1.36–2.30; persistent cough: OR=1.30, 1.17–1.46, independent of demographics and health-care access. Conclusion: Recognition of warning signs was associated with anticipating faster help-seeking for potential symptoms of cancer. Strategies to improve recognition are likely to facilitate earlier diagnosis

Moyal star product approach to the Bohr-Sommerfeld approximation

The Bohr-Sommerfeld approximation to the eigenvalues of a one-dimensional quantum Hamiltonian is derived through order $\hbar^2$ (i.e., including the first correction term beyond the usual result) by means of the Moyal star product. The Hamiltonian need only have a Weyl transform (or symbol) that is a power series in $\hbar$, starting with $\hbar^0$, with a generic fixed point in phase space. The Hamiltonian is not restricted to the kinetic-plus-potential form. The method involves transforming the Hamiltonian to a normal form, in which it becomes a function of the harmonic oscillator Hamiltonian. Diagrammatic and other techniques with potential applications to other normal form problems are presented for manipulating higher order terms in the Moyal series.Comment: 27 pages, no figure

High- and mid-latitude quasi-2-day waves observed simultaneouslyby four meteor radars during summer 2000

International audienceResults from the analysis of MLT wind measurements at Dixon (73.5°N, 80°E), Esrange (68°N, 21°E), Castle Eaton (UK) (53°N, 2°W), and Obninsk (55°N, 37°E) during summer 2000 are presented in this paper. Using S-transform or wavelet analysis, quasi-two-day waves (QTDWs) are shown to appear simultaneously at high- and mid-latitudes and reveal themselves as several bursts of wave activity. At first this activity is preceded by a 51?53h wave with S=3 observed mainly at mid-latitudes. After a short recess (or quiet time interval for about 10 days near day 205), we observe a regular sequence of three bursts, the strongest of them corresponding to a QTDW with a period of 47?48h and S=4 at mid-altitudes. We hypothesize that these three bursts may be the result of constructive and destructive interference between several spectral components: a 47?48h component with S=4; a 60-h component with S=3; and a 80-h component with S=2. The magnitudes of the lower (higher) zonal wave-number components increase (decrease) with increasing latitude. The S-transform or wavelet analysis indicates when these spectral components create the wave activity bursts and gives a range of zonal wave numbers for observed bursts from about 4 to about 2 for mid- and high-latitudes. The main spectral component at Dixon and Esrange latitudes is the 60-h oscillation with S=3. The zonal wave numbers and frequencies of the observed spectral components hint at the possible occurrence of the nonlinear interaction between the primary QTDWs and other planetary waves. Using a simple 3-D nonlinear numerical model, we attempt to simulate some of the observed features and to explain them as a consequence of the nonlinear interaction between the primary 47?48h and the 9?10day waves, and the resulting linear superposition of primary and secondary waves. In addition to the QTDW bursts, we also infer forcing of the 4-day wave with S=2 and the 6?7day wave with S=1, possibly arising from nonlinear decoupling of the 60-h wave with S=3. The starting mechanism for this decoupling is the Rossby wave instability (e.g. Baines, 1976). This result is consistent with the day-to-day wind variability during the observed QTDW events. An interesting feature of the final stage of the observed QTDW activity in summer 2000 is the occurrence of strong 4?5 day waves with S=3. Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides; general or miscellaneous

A high-speed, wavelength invariant, single-pixel wavefront sensor with a digital micromirror device

The wavefront measurement of a light beam is a complex task, which often requires a series of spatially resolved intensity measurements. For instance, a detector array may be used to measure the local phase gradient in the transverse plane of the unknown laser beam. In most cases, the resolution of the reconstructed wavefront is determined by the resolution of the detector, which in the infrared case is severely limited. In this paper, we employ a digital micro-mirror device (DMD) and a single-pixel detector (i.e., with no spatial resolution) to demonstrate the reconstruction of unknown wavefronts with excellent resolution. Our approach exploits modal decomposition of the incoming field by the DMD, enabling wavefront measurements at 4 kHz of both visible and infrared laser beams

The Growing Block’s past problems

The Growing-Block view of time has some problems with the past. It is committed to the existence of the past, but needs to say something about the difference between the past and present. I argue that we should resist Correia and Rosenkranz’ (Oxford studies in metaphysics, vol 8, pp 333–350, 2013) response to Braddon-Mitchell’s (Analysis 64:199–203, 2004) argument that the Growing-Block leads to scepticism about whether we are present. I consider an approach, similar to Peter Forrest (Analysis 64:358–362, 2004), and show it is not so counter-intuitive as Braddon-Mitchell suggests and further show that it requires no ‘semantic and metaphysical gymnastics’, as Chris Heathwood (Analysis 65:249–251, 2005) has suggested. In doing these things I make the problem of the past on the Growing-Block view a problem in its history, not its present