Ultra-narrow (sub-MHz) linewidth emission from discrete mode laser diodes

A class of laser which exhibits ultra-narrow sub MHz linewidth emission necessary for numerous applications in optical communications and sensors is described. The spectral performance of commercial discrete mode (DM) and distributed feedback (DFB) lasers is compared. The devices used in this work are asymmetrically coated ridge waveguide Fabry Perot lasers which incorporated etched slot features and emitting around lambda = 1.55 mum. The active region of the devices consisted of a strained compensated InAlGaAs MQW structure

Quinnat salmon (oncorhynchus tshawytscha) spawning in the Rangitikei river

The occurrence of adult quinnat salmon {Oncorhynchus tshawytscha (Walbaum)) in the Rangitikei River, North Island, New Zealand, has been confirmed on several occasions since 1922, but juvenile salmon have not previously been recorded. In late February 1981 a 79-mm-fork-length smolt was caught in a stranded side channel 180 km upstream from the mouth. This suggests that quinnat salmon can spawn successfully in this river

Self-pulsation at 480 GHz from a two-color discrete mode laser diode

A discrete mode Fabry-Pérot laser is designed and fabricated to achieve two-color lasing. We demonstrate beating between the two laser modes and self-pulsation at 480 GHz

Low sensitivity to optical feedback and optical injection of discrete mode lasers

In this paper, we demonstrate the low sensitivity to both external optical feedback and external optical injection of a new type of extremely low cost single-mode lasers, called "discrete mode" (DM) lasers. The DM lasers are obtained from ridge waveguide Fabry Perot (FP) lasers, in which the effective refractive index of the lasing mode has been perturbed. These lasers exhibit a low sensitivity to external optical feedback since the coherence collapse threshold is around 5 dB higher in comparison to a commercial DFB laser

An assessment of key risk factors for surgical site infection in patients undergoing surgery for spinal metastases

Objectives This study aimed to determine the rate of surgical site infection (SSI) in patients undergoing surgery for spinal metastases, and identify key risk factors for SSI among this patient group. Methods A retrospective case note review was undertaken in 152 adult patients being treated at a single specialist centre for spinal surgery. Results Overall SSI rate was 11.2% per patients (9.7% per procedure). An increase in the risk of SSI was observed when surgery involved a greater number of vertebral levels (odds ratio 1.26, P=0.019) when controlling for primary spinal region. Controlling for the number of spinal levels, the odds of SSI increased by a factor of 5.6 (P=0.103) when the primary surgical region was thoracic, as opposed to cervical or lumbar. Conclusions In conclusion, surgery associated with multiple vertebral levels for treatment of spinal metastases, particularly of the thoracic spine, is associated with increased risk of SSI

Inverse scattering approach to multiwavelength Fabry-Pérot laser design

A class of multiwavelength Fabry-Pérot lasers is introduced where the spectrum is tailored through a patterning of the cavity effective index. The cavity geometry is obtained using an inverse scattering approach and can be designed such that the spacing of discrete Fabry-Pérot lasing modes is limited only by the bandwidth of the inverted gain medium. A specific two-color semiconductor laser with a mode spacing in the THz region is designed, and measurements are presented demonstrating the simultaneous oscillation of the two wavelengths. The nonperiodic effective index profile of the particular two-color device considered is shown to be related to a Moiré or superstructure grating

Seasonal patterns of protoplankton and calanoid copepods in the Firth of Forth : an investigation or Copepod grazing and the effect of diatoms upon reproductive processes

Seasonal variability in the zooplankton of the Firth of Forth, including mesozooplankton and microplankton, were investigated across a full annual cycle. Grazing rates and prey selectivity by the dominant calanoid copepods (Acartia discaudata, Acartia clausi, Centropages hamatus and Temora longicornis) were also examined. Investigations were conducted upon Acartia discaudata and field collected prey under simulated diatom bloom conditions, using the species Thalassiosira rotula, in order to test the hypothesis of diatom inhibition of calanoid copepod reproductive processes. There were fundamental differences between the spring and autumn blooms, typical of temperate estuaries. The spring bloom was composed of highly abundant, small cells amounting to less than half the biomass of larger, less numerous microplankton present in autumn. Copepods dominated the mesozooplankton undergoing seasonal shifts in species’ dominance primarily in response to physical factors. Results of grazing experiments indicate a disproportionate preference for motile prey compared to ubiquitous concentrations of diatoms. Copepods switch to blooming diatom species when present in concentrations > 80 cells ml-1. Ciliates generally contributed < 25% to copepod carbon ingestion. Acartia discaudata, Acartia clausi, and Centropages hamatus selectively consumed dinoflagellate and ciliate taxa whereas Temora longicornis remained an indiscriminate grazer during the entire study. Despite increasing rates of egg production in Acartia discaudata, at high concentrations (> 1 x 103 cells ml-1), Thalassiosira rotula inhibited hatching success such that recruitment to naupliar stage 2 was severely impaired compared with eggs hatched from females fed ~0.3 x 103 cells ml-1 concentrations of T. rotula. This is the first recorded evidence of embryogenic inhibition in A. discaudata

The Maximum Number of Appearances of a Word in a Grid

How can you fill a $3\times 3$ grid with the letters A and M so that the word ``AMM'' appears as many times as possible in the grid? More generally, given a word $w$ of length $n$, how can you fill an $n\times n$ grid so that $w$ appears as many times as possible? We solve this problem exactly for several families of words, and we asymptotically solve this problem in higher-dimensional grids.Comment: 21 pages, American Mathematically Monthl