The Emergence of a Dominant Design – a study on hydrogen prototypes

The notion of dominant designs deals with dominance in the market and the dominant design is thought to be dominant because of market selection forces. The notion thus ignores the possible selection that takes place in pre-market R&D stages of technological trajectories. In this paper we ask the question whether pre-market selection takes place and if this can lead to an early dominant design. Furthermore we study what selection criteria apply during this phase, in the absence of actual market criteria. We do so through an analysis of prototyping trajectories for hydrogen vehicles. Prototypes are used by firms in their internal search process towards new designs and at the same time they are means of communicating technological expectations to outsiders. In both senses, prototypes can be taken as indicators of technological trajectories in the ongoing search process of an industry for the dominant prototype design of the future. Using prototypes as representation of intermediate outcomes of the search process, a dominant design can possibly be recognized also in a pre-market phase of development. We analyzed the designs of prototypes of hydrogen passenger cars from the 1970s till 2008. In our analysis we try to show to what extent the designs configurations of the technological components, converge or diverge over time. For this we compiled a database of 224 prototypes of hydrogen passenger cars. The database describes: the car’s manufacturer, year of construction, type of drivetrain, fuel cell type, and capacity of its hydrogen storage system. We draw conclusions with regard to the convergence/divergence of the prototypes’ designs and the role of diverse performance criteria therein. We conclude that there is convergence towards a dominant design in the prototyping phase; the PEM fuel cell combined with high pressure storage. Performance played a role as selection criterion, but so did regulation and strategic behaviour of the firms. Especially imitation dynamics, with industry leaders and followers, seems to be the major explanatory factor.Dominant design, expectations, prototypes, hydrogen, fuel cell

Arenas of Expectations for Hydrogen Technologies

Technological options can be regarded as variations in an evolutionary development process. The variations are put forward by their respective technological communities and are selected by technology selectors. Building on the notion of quasi-evolutionary technology development we show how technological communities secure their position on R&D agendas through feeding and maintaining expectations in arenas of expectations. We examine this process by studying the expectations work of the community that tries to develop metal hydrides for the on-board storage of hydrogen for mobile applications. Metal hydrides are proposed as a promising alternative to gaseous and liquid hydrogen storage but are yet underdeveloped. Its proponents however, succeed in convincing their sponsors of the future potential of metal hydrides. In this paper we show how expectations of this technological option are raised and maintained by its developers and how this has kept them on hydrogen technology agendas for over 40 years.alternative fuel, energy storage, hydrogen, mobility, on-board

Immunogenicity of standard and low dose vaccination using yeast-derived recombinant hepatitis B surface antigen in elderly volunteers

There is no conclusive evidence that age influences the response to vaccination against hepatitis B virus. We therefore studied the immunogenicity of yeast-derived rHBsAg vaccine in elderly volunteers. The study was conducted in the outpatient clinics of an academic and a regional hospital, in a rural family practice and in an urban community centre. We recruited 112 healthy volunteers aged 59 years and over, to whom 10 or 20 μg yeast-derived HBsAg was given at 0, 1 and 6 months. Anti-HBs titres were measured by radioimmunoassay at 2, 6 and 7 months. Responders and non-responders were compared using univariate non-parametric tests and multivariate logistic regression analysis. Of the 116 subjects who volunteered to take part in the study, 106 vaccinees completed it. The percentage of subjects with an anti-HBs titre ⩾10 1U1−1 at 7 months was 60% (95% confidence interval: 51–70%; geometric mean titre: 253 1U1−1). Of the factors studied, i.e. setting, age, sex, alcohol consumption, current medication and vaccine dose, the use of medication at the time of the first vaccination was the only independent factor related to the response to vaccination, with a response rate of 78% (95% confidence interval: 66–89%) in those without medication. In elderly subjects, the proportion with protective concentrations of anti-HBs after vaccination with 10 or 20 μg yeast-derived recombinant HBsAg in a standard scheme is lower than in healthy adolescents. Within the older age group studied here, the use of medication, probably reflecting general health, is the only significant factor influencing the response to vaccination

Postural change in volunteers: sympathetic tone determines microvascular response to cardiac preload and output increases

Purpose: Microvascular perfusion may be a non-invasive indicator of fluid responsiveness. We aimed to investigate which of the microvascular perfusion parameters truly reflects fluid responsiveness independent of sympathetic reflexes. Methods: Fifteen healthy volunteers underwent a postural change from head up tilt (HUT) to the supine position, diminishing sympathetic tone, followed by a 30° passive leg raising (PLR) with unaltered tone. Prior to and after the postural changes, stroke volume (SV) and cardiac output (CO) were measured, as well as sublingual microcirculatory perfusion (sidestream dark field imaging), skin perfusion, and oxygenation (laser Doppler flowmetry and reflectance spectroscopy). Results: In responders (subjects with >10 % increase in CO), the HUT to supine change increased CO, SV, and pulse pressure, while heart rate, systemic vascular resistance, and mean arterial pressure decreased. Additionally, microvascular flow index, laser Doppler flow, and microvascular hemoglobin oxygen saturation and concentration also increased. Conclusion: When preload and forward flow increase in association with a decrease in sympathetic activity, microvascular blood flow increases in the skin and in the sublingual area. When preload and forward flow increase with little to no change in sympathetic activity, only sublingual functional capillary density increases. Therefore, our results indicate that sublingual functional capillary density is the best pa

Ways to Improve the Diagnosis of Growth Hormone Deficiency

Developmen

Biopsy prostate cancer perineural invasion and tumour load are associated with positive posterolateral margins at radical prostatectomy:implications for planning of nerve-sparing surgery

Aims: Radical prostatectomy (RP) for prostate cancer is frequently complicated by erectile dysfunction and urinary incontinence. However, sparing of the nerve bundles adjacent to the posterolateral sides of the prostate reduces the number of complications at the risk of positive surgical margins. Preoperative selection of men eligible for safe, nerve-sparing surgery is therefore needed. Our aim was to identify pathological factors associated with positive posterolateral surgical margins in men undergoing bilateral nerve-sparing RP. Methods and results: Prostate cancer patients undergoing RP with standardised intra-operative surgical margin assessment according to the NeuroSAFE technique were included. Preoperative biopsies were reviewed for grade group (GG), cribriform and/or intraductal carcinoma (CR/IDC), perineural invasion (PNI), cumulative tumour length and extraprostatic extension (EPE). Of 624 included patients, 573 (91.8%) received NeuroSAFE bilaterally and 51 (8.2%) unilaterally, resulting in a total of 1197 intraoperative posterolateral surgical margin assessments. Side-specific biopsy findings were correlated to ipsilateral NeuroSAFE outcome. Higher biopsy GG, CR/IDC, PNI, EPE, number of positive biopsies and cumulative tumour length were all associated with positive posterolateral margins. In multivariable bivariate logistic regression, ipsilateral PNI [odds ratio (OR) = 2.98, 95% confidence interval (CI) = 1.62–5.48; P &lt; 0.001] and percentage of positive cores (OR = 1.18, 95% CI = 1.08–1.29; P &lt; 0.001) were significant predictors for a positive posterolateral margin, while GG and CR/IDC were not. Conclusions: Ipsilateral PNI and percentage of positive cores were significant predictors for a positive posterolateral surgical margin at RP. Biopsy PNI and tumour volume can therefore support clinical decision-making on the level of nerve-sparing surgery in prostate cancer patients.</p