Diversity of vaccination-induced immune responses can prevent the spread of vaccine escape mutants

Pathogens that are resistant against drug treatment are widely observed. In contrast, pathogens that escape the immune response elicited upon vaccination are rare. Previous studies showed that the prophylactic character of vaccines, the multiplicity of epitopes to which the immune system responds within a host, and their diversity between hosts delay the evolution and emergence of escape mutants in a vaccinated population. By extending previous mathematical models, we find that, depending on the cost of the escape mutations, there even exist critical levels of immune response diversity that completely prevent vaccine escape. Furthermore, to quantify the potential for vaccine escape below these critical levels, we propose a concept of escape depth which measures the fraction of escape mutants that can spread in a vaccinated population. Determining this escape depth for a vaccine could help to predict its sustainability in the face of pathogen evolution.

Prediction of signs/symptoms of decompression sickness following submarine tower escape

Crew survival in a distressed submarine (DISSUB) scenario may be enhanced by the knowledge of the risks of different types of decompression sickness (DCS) should the crew attempt tower escape. Four models were generated through calibration against DCS outcome data from 3,919 pressure exposures, each for the prediction of one of four categories of DCS: neurological, limb pain, respiratory and cutaneous. The calibration data contained details of human, goat, sheep and pig exposures to raised pressure while breathing air or oxygen/nitrogen mixtures. No exposures had substantial staged decompression or cases of suspected pulmonary barotrauma. DCS risk was scaled between species and with body mass. A parameter was introduced to account for the possibility of the occurrence of some symptom types masking others. The calibrated models were used to estimate likelihood of DCS occurrence for each symptom category following submarine tower escape. Escape depth was found to have a marked effect only on predicted rates of neurological DCS. Saturation at raised internal DISSUB pressure prior to escape was found to affect predicted rates of all symptom types. The iso-risk curves presented are offered as guidance to submarine crews and rescue forces in preparation for, or in the event of, a DISSUB scenario.

FORMULAE FOR MAXIMUM ESCAPE DEPTH OF REDIFFUSED ELECTRONS AND BACKSCATTERING COEFFICIENT OF METAL FILMS

Based on the experimental maximum escape depth [Formula: see text], [Formula: see text] of rediffused electrons from atomic number [Formula: see text] metal at incident energy of primary electron [Formula: see text], the relationship among [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in the energy range of 9.3[Formula: see text]keV[Formula: see text]40[Formula: see text]keV was obtained and proved to be true by experimental data. According to the experimental results of rediffused electrons, the characteristics of secondary electron emission, relationships among parameters of rediffused electrons and the main processes of rediffused electrons emission, the formula for [Formula: see text] backscattering coefficient [Formula: see text], [Formula: see text], [Formula: see text] of [Formula: see text] metal films with film thickness [Formula: see text] as a function of [Formula: see text], Z and was deduced, and the results were analyzed. It is concluded that the deduced formula for [Formula: see text], [Formula: see text], [Formula: see text] can be used to calculate [Formula: see text], [Formula: see text], [Formula: see text] in the energy range of 9.3[Formula: see text]keV[Formula: see text]40[Formula: see text]keV. The secondary electron yield [Formula: see text] from thin films are applied in more and more fields such as electronic information technology, accelerator and space flight, and [Formula: see text], Z, [Formula: see text] is an important parameter of [Formula: see text] from [Formula: see text] metal films. So deducing the formula for [Formula: see text], [Formula: see text], [Formula: see text] in this study is necessary.

Formulae for maximum yield and mean escape depth of secondary electrons emitted from metals

Based on the characteristics of secondary electron emission, the former formulae for the maximum yield of metals [Formula: see text] and primary range in the energy range of [Formula: see text] eV, relation [Formula: see text] among secondary electron escape probability [Formula: see text], average energy required to produce an internal secondary electron [Formula: see text], [Formula: see text], primary energy of [Formula: see text] ([Formula: see text] and parameter [Formula: see text] was deduced. On the basis of [Formula: see text] and the former formula for [Formula: see text], relation [Formula: see text] among mean escape depth of secondary electrons emitted from metals [Formula: see text], atomic number [Formula: see text], back-scattering coefficient [Formula: see text], material density [Formula: see text], [Formula: see text], atomic weight [Formula: see text] and [Formula: see text] was deduced. According to the deduced [Formula: see text], the formula for the ratio of [Formula: see text] to [Formula: see text] and experimental ratio of [Formula: see text] to [Formula: see text], relation [Formula: see text] among [Formula: see text], original work function [Formula: see text] and [Formula: see text] were empirically obtained. According to the characteristics of metal surface, [Formula: see text], [Formula: see text] and [Formula: see text], the formula for [Formula: see text] as a function of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] and that for [Formula: see text] as a function of [Formula: see text], [Formula: see text] and [Formula: see text] were deduced, respectively. The influences of surface change on [Formula: see text] and [Formula: see text] were analyzed. Calculated [Formula: see text] and [Formula: see text] were compared with the corresponding experimental ones. It was concluded that the deduced formulae for [Formula: see text] and [Formula: see text] can be used to estimate [Formula: see text] and [Formula: see text], respectively.