Sublimation of ice particles from rocket exhausts in the upper atmosphere

The process of sublimation of ice particles from a rocket exhaust in the upper atmosphere is examined. Heating by solar radiation and losses of energy by means thermal radiation and sublimation are taken into account in the thermal balance of the ice particles. The time dependences of size and temperature of the ice particles are obtained. An estimation of water vapor concentration around the rocket trajectory is made. The process of sublimation of the rocket exhaust ice particles may be important for the interpretation of optical phenomena in the upper atmosphere connected with rocket launches and for propagation of disturbances at a large distance from the rocket

Calculation of disease dynamics in a population of households

Early mathematical representations of infectious disease dynamics assumed a single, large, homogeneously mixing population. Over the past decade there has been growing interest in models consisting of multiple smaller subpopulations (households, workplaces, schools, communities), with the natural assumption of strong homogeneous mixing within each subpopulation, and weaker transmission between subpopulations. Here we consider a model of SIRS (susceptible-infectious-recovered-suscep​tible) infection dynamics in a very large (assumed infinite) population of households, with the simplifying assumption that each household is of the same size (although all methods may be extended to a population with a heterogeneous distribution of household sizes). For this households model we present efficient methods for studying several quantities of epidemiological interest: (i) the threshold for invasion; (ii) the early growth rate; (iii) the household offspring distribution; (iv) the endemic prevalence of infection; and (v) the transient dynamics of the process. We utilize these methods to explore a wide region of parameter space appropriate for human infectious diseases. We then extend these results to consider the effects of more realistic gamma-distributed infectious periods. We discuss how all these results differ from standard homogeneous-mixing models and assess the implications for the invasion, transmission and persistence of infection. The computational efficiency of the methodology presented here will hopefully aid in the parameterisation of structured models and in the evaluation of appropriate responses for future disease outbreaks

The limits of spatial resolution achievable using a 30kHz multibeam sonar: model predictions and field results

A Simrad EM300 multibeam sonar was used to attempt to resolve small (-5m high) targets in 450m of water. The targets had previously been surveyed using a deeply towed 59 kHz sidescan sonar. Using multisector active yaw, pitch and roll compensation, together with dynamically altering angular sectors, the sonar is capable of maintaining sounding densities of as tight as 10m spacing in these water depths. This is significantly smaller than the largest dimension of the projected beam footprints (1 6-64m). The observed data suggest that the targets are intermittently resolved. The field results compare well to the output of a numerical model which reproduces the imaging geometry. Possible variations in the imaging geometry are implemented in the model, comparing equiangular and equidistant beam spacings, differing angular sectors and all the different combinations of transmit and receive beam widths that are available for this model of sonar. While amplitude detection is significantly aliased by targets smaller than the across track beam footprint, under conditions where the signal to noise ratio is favorable, phase detection can be used to reduce the minimum size of target observed to about the scale of the across track beam width. Thus having the beam spacing at the scale is justifiable. The phase distortion due to smaller targets, however, is generally averaged out

Nodular lymphocyte predominant Hodgkin lymphoma behaves as a distinct clinical entity with good outcome: evidence from 14-year followup in the West of Scotland Cancer Network

Clinically and biologically, nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) has much more in common with germinal-center derived B-cell non-Hodgkin lymphoma (NHL) than with classical Hodgkin lymphoma (cHL). Management of NLPHL remains controversial. In a 14-year multicenter series, 69 cases were analyzed, and the median follow-up was 53 months (range 11–165.) B-symptoms were present in only 4.3% of patients, and 81.1% of patients had stage I/II disease. Treatment was with radiotherapy (53.6%), chemotherapy (21.7%), combined modality (17.4%), and observation (7.2%). In all, 10.1% of patients relapsed and 2.9% of patients developed high-grade transformation to DLBCL. All relapses and transformations were salvageable. No patient died of their disease. The 5-year relapse-free survival was 92%, transformation-free survival 98.4%, and overall survival 100%. We conclude that NLPHL behaves as a distinct clinical entity, often presenting at an early stage without risk factors. It has an excellent outcome. It may be possible, in early-stage disease, to reduce the intensity of therapy in NLPHL, to single-modality radiotherapy, without affecting OS