Letter to the Editor

Sir, Comments on ‘Are all photon radiations similar in largeabsorbers?—A comparison of electron spectra’ byA. M. Kellerer and H. Roos In a recent publication⁽¹⁾, Kellerer and Roos demonstrate thatthe secondary electron spectrum inside a large absorber exposedto 1 MeV photons, compared to the secondary electron spectruminside a small absorber, is substantially shifted to lower energies.This phenomenon is     

Adaptive response by single cell radiation hits--implications to nuclear workers

Radiation Protection Dosimetry, 116: 387–391 (2005) The above cited RPD     

Properties of the feynman-{alpha} method applied to accelerator-driven subcritical systems

Radiation Protection Dosimetry, 115(1–4): 58–62(2005) Equation (1) on page     

Delft Conference Proceedings Editorial 2008: safety and efficacy for new techniques and imaging using new equipment to support European Legislation

Radiation Protection Dosimetry, 129 (1-3): 1–2     

Letters to the Editor

Sir, The following are comments on ‘The ThermoluminescenceDose—Response and other characteristics of the high-temperatureTL in LiF:Mg,Ti (TLD-100)’, Radiat. Prot. Dosim., doi:10.1093/rpd/ncm241,and Letter to the Editor, doi:10.1093/rpd/ncm381, both of themavailable online, by Prof. Y. S. Horowitz. The first article, an Invited Review, includes a discussionon our published work about the TLD-100 response to gamma rays⁽¹⁾,whereas the second one analyses our measurements of the TLD-100response to intermediate-energy ions⁽²⁾. Given the criticaltone of both contributions, we felt it necessary to write thefollowing clarifying comments, which we kindly ask you to sharewith the readers of RPD. In the Invited Review, Horowitz et al. discuss two main aspectsof     

The stock market and innovative capability in the New Economy: the optical networking industry

The purpose of this paper is to analyze the impact of the stockmarket on the innovative capabilities of high-technology companiesthat have been central to what in the last half of the 1990scame to be called the ‘New Economy’. The empiricalfocus is on equipment suppliers in optical networking—anindustry that integrates the bandwidth potential of fiber opticswith the data communications potential of the internet. Thestudy covers the period from 1996 to 2003, during which theoptical networking industry was, first, central to the New Economyboom, and, then from 2001, ensnared by the bursting of the NewEconomy bubble. This paper shows how, responding to the NewEconomy business model brought into the industry by Cisco Systems,three Old Economy companies—Nortel Networks, Lucent Technologies,and Alcatel—sought to use their corporate stock as a currencyto acquire technology companies and compensate talented people,and thus accumulate innovative capability. To understand therelation between the stock market and innovative capabilityin the Cisco ‘growth-through-acquisition-and-integration’model and in the ‘creative responses’ of the OldEconomy companies to the Cisco challenge, we apply an analyticalframework that links four functions of the stock market—control,combination, compensation and cash—with three social conditionsof innovative enterprise: strategic control—the abilitiesand incentives of strategic decision makers to allocate resourcesto uncertain investments in innovative capabilities; organizationalintegration—the structure of incentives that motivatesemployees to apply their skills and efforts to collective learningprocesses; and financial commitment—the availability tothe enterprise of resources to sustain cumulative learning processesuntil, by accessing markets, they can generate financial returns.Using this framework, we show that the ways in which the OldEconomy companies used their stock to accumulate innovativecapability in the New Economy boom of 1998–2000 made themmore vulnerable to the stock market collapse and the slowdownin the optical networking industry in 2001–2003.     

Radon transport through concrete and determination of its diffusion coefficient

Radiation Protection Dosimetry, 104 (1), 65–70 (2003) Dear Editor, We have published a paper treating radon diffusion through concreteslabs. Since some misunderstanding related to this paper hasarisen recently, we are writing to clarify     

Comments on 'Increasing film-focus distance (FFD) reduces radiation dose for X-ray examinations' by P.C. Brennan, S. McDonnell and D. O'Leary

Sir, Comments on ‘Increasing film-focus distance (FFD) reducesradiation dose for X-ray examinations’ by P.C. Brennan,S. McDonnell and D. O'Leary. In a recent publication, Brennan et al.⁽¹⁾ claim that increasingthe film-focus distance (FFD) from 100 to 130 cm will reduceeffective doses (E) by 33% for a pelvic X-ray examination. Thisconclusion is based on a reported 33% reduction in the entrancesurface dose (ESD), by the use of the same effective dose perunit ESD conversion coefficient (E/ESD) at both FFD values.However, E/ESD values are only valid for the specific     

Chandlerism in post-war Europe: strategic and structural change in France, Germany and the United Kingdom, 1950-1993: a comment

Whittington et al. (Industrial and Corporate Change, 1999, 8,519–550) argue that the conglomerate is a relatively transientphenomenon. However, this comment on their article argues thatexamination of their data suggests that the conglomerate maybe more persistent than is generally believed. It is arguedthat the reason for this may be found in the contribution thisstrategy may make to dealing with technologically turbulentenvironments. The results of Whittington et al. are comparedwith other studies of large firm strategies, and some testableimplications are suggested.     

Microdosimetric response of physical and biological systems to low- and high-let radiations. theory and applications to dosimetry: Y. Horowitz, Ed., 2006, Elsevier, The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK ISBN: 0-444-51643-3, 500 pp, 170.00 Euros (hardbound)

Microdosimetry deals with the deposition of energy by ionisingradiation in matter and its consequences on a small scale. Itshistorical role in radiation biology has been the measurementand characterisation of events and changes produced by radiationin cellular and subcellular environments. In early pioneeringefforts, Rossi and Rosenzweig succeeded in measuring energy-depositionspectra in proportional counters with micrometer dimensionson a scale of unit density [Radiology 64, 404–411 (1955)].The     

Moving base into high-value integrated solutions: a value stream approach

Some of the world’s leading suppliers are developing strategiesto move into the provision of innovative combinations of productsand services as ‘high-value integrated solutions’tailored to each customer’s needs. Rather than simply‘moving downstream’ into services (as much of thebusiness strategy literature assumes), this paper argues thatthe provision of integrated solutions is attracting firms—traditionallybased in manufacturing and services—to occupy a new basein the value stream centred on ‘systems integration’.In addition to an ability to design and integrate systems usinginternal or external sources of product supply, these firmsare developing novel combinations of service capabilities (operations,business consultancy and finance) required to provide completesolutions to each customer’s needs.     

Where do small worlds come from?

Interfirm networks often take on characteristics consistentwith the notion of a small world—they are locally clusteredinto dense sub-networks or cliques that are sparsely connectedby a small number of ties that cut across the cliques, linkingnetwork members through a relatively small number of intermediaries.Are these characteristics an emergent property of interfirmnetworks that result from chance connections among firms, ormore strategic partnering by firms to improve or protect theirnetwork positions? After outlining a behavioral account forthis frequently observed network topology, we show that theevolving investment bank syndicate network in Canada exhibitedsmall world properties from 1952 to 1990. We then identify theinvestment bank cliques comprising the network and the ‘spanning’ties that cut across them, and test three distinct scenariosthat may explain the formation of these ties, which are responsiblefor the small worldliness of the network: (i) chance partneringof firms in different cliques; (ii) insurgent partnering byperipheral firms to destabilize the network and improve theirnetwork positions; and (iii) control partnering by core firmsto maintain the network status quo and their positions withinit. All three scenarios played a role in explaining the formationof clique-spanning ties; however, chance and insurgent partneringplayed a greater role in our empirical setting. Our analysisof how small world structures emerge and evolve over time offersnew insight into the origins of a prevalent interfirm networktopology, and a baseline for constructing future models of interfirmnetwork evolution and dynamics.     

Radiation quality of photons in small and large receptors--a microdosimetric analysis

The quality of different photon radiations in small and largereceptors is assessed in terms of microdosimetry. Monte Carlosimulations are performed for the electrons released by photons.To represent the case of a small receptor, only electrons releasedby the non-degraded incident photons are tracked. For a largereceptor, all electrons released in the complete degradationprocess are followed. Dose averaged values, y_D, of the linealenergy are derived from the simulated tracks for monoenergeticphotons from 10 keV to 2 MeV. In microdosimetry, the dose meanlineal energy is the major parameter of radiation quality. Theresults demonstrate distinct differences in radiation qualitybetween high-energy gamma rays and conventional X rays thatare present not just in small cell samples but also in largereceptors, such as the human body. The values of y_D suggestthat, for both small and large receptors, conventional X raysshould be about twice as effective as gamma rays from ⁶⁰Co.     

Letters to the Editor

Sir, Comments on ‘The thermoluminescence dose-response andother characteristics of the high-temperature TL in LiF:Mg,Ti(TLD-100)’ by Y. S. Horowitz, L. Oster and H. Datz This recent article⁽¹⁾ was intended to be a review on the subjectand it reflects the view of its authors, as already publishedin the past. When discussing the dose–response issue (bygas and contact heating) the works of two groups (us being oneof them) are discussed at length and in much detail, somewhatoutside the scope of a balanced review. The article containsclaims that     

Specialized supply firms, property rights and firm boundaries

The proper specification of intellectual property rights (IPRs)is a delicate and controversial matter. In this paper, we considerone specialized context in which IPRs can add to efficiency.We build on contributions of both ‘firm capabilities’scholars (e.g. Teece, Pisano et al.) and ‘property rights’economists (e.g. Hart) to show that IPRs can affect efficiencyby influencing the location of technological innovation. Usinga simple set up, where the key choice is whether a technology-intensiveinput will be supplied by an independent firm or produced in-house,we analyze how the choice is affected by the strength of IPRsand by the existence (and nature) of information spillovers.Specifically, we show that when the supply relationship is likelyto produce new information of value to the supplier, strongerproperty rights favor independent suppliers over vertical integration.An important implication of our model (backed by empirical casestudies) is that strong IPRs therefore encourage investmentsin specialized firms with strong ‘firm capabilities’in the area of innovative input supply. IPRs therefore may playa role—along with multiple other factors—in thelocation of firm boundaries in some cases. This contributionto the viability of small, specialized firms, with their superiorability to innovate in some cases, must be taken into accountin evaluating recent criticisms of over-fragmented IPR ownership(i.e. the ‘anticommons’ problem). It also contributesto an understanding of IPRs in the ‘post-Chandlerian’economy, where smaller, specialized firms play a prominent role.     

Modular production networks: a new American model of industrial organization

This paper uses the case of contract manufacturing in the electronicsindustry to illustrate an emergent American model of industrialorganization, the modular production network. Lead firms inthe modular production network concentrate on the creation,penetration and defense of markets for end products—andincreasingly the provision of services to go with them—whilemanufacturing capacity is shifted out-of-house to globally operatingturn-key suppliers. The modular production network relies oncodified inter-firm links and the generic manufacturing capacityresiding in turn-key suppliers to reduce transaction costs,build large external economies of scale and reduce risk fornetwork actors. I test the modular production network modelagainst some of the key theoretical tools that have been developedto predict and explain industry structure: Joseph Schumpeter'snotion of innovation in the giant firm; Alfred Chandler's ideasabout economies of speed and the rise of the modern corporation;Oliver Williamson's transaction cost framework; and a rangeof other production network models that appear in the literature.I argue that the modular production network yields better economicperformance in the context of globalization than more spatiallyand socially embedded network models. I view the emergence ofthe modular production network as part of a historical processof industrial transformation in which nationally specific modelsof industrial organization co-evolve in intensifying roundsof competition, diffusion and adaptation.     

A Bayesian approach to the multivariate Behrens-Fisher problem under the assumption of proportional covariance matrices

Summary Two independent random samples of sizesN ₁ andN ₂ from multivariate normal populationsN _p (θ₁,∑₁) andN _p (θ₂,∑₂) are considered. Under the null hypothesisH ₀: θ₁=θ₂, a single θ is generated from aN _p(μ, Σ) prior distribution, while underH ₁: θ₁≠θ₂ two means are generated from the exchangeable priorN _p(μ,σ). In both cases Σ will be assumed to have a vague prior distribution. For a simple covariance structure, the Bayes factorB and minimum Bayes factor in favour of the null hypotheses is derived. The Bayes risk for each hypothesis is derived and a strategy is discussed for using the Bayes factor and Bayes risks to test the hypothesis.     

Optical and photoelectric properties of α-Dy<Subscript>2</Subscript>S<Subscript>3</Subscript> and α-Dy<Subscript>2</Subscript>S<Subscript>3</Subscript>〈Pb〉 films

A process is described for the growth of thin crystalline α-Dy₂S₃ films by thermal evaporation from separate dysprosium and sulfur sources. The films were doped with Pb, and their reflection and transmission spectra were measured at room temperature and photon energies in the range (0.3−5.2) × 10⁻¹⁹ J. The α-Dy₂S₃ films were shown to have an exponential absorption edge. The photoconductivity of the doped films was measured at photon energies in the range (0.3−5.2) × 10⁻¹⁹ J and temperatures from 115 to 400 K.     

Crack significance evaluation with special reference to welded structures

Fracture mechanics parameters (stress intensity factorK _I and its critical valueK _Ic , crack opening displacement, and the contourJ integral) are originally defined for static and quasistatic loading conditions. On the basis of theoretical background, standard test methods for the experimental determination of their specific values were developed. Structural integrity analysis requires the extension of application of these parameters to other types of loading. We propose new parameters for stress corrosion (stress corrosion cracking thresholdK _1sco ), for cyclic loading (stress intensity factor range ΔK and fatigue threshold ΔK _th), and for creeping at elevated temperatures (C ^* andC _t integrals). The structural integrity of welded structures is mainly affected by cracks in welded joints. We demonstrate the practical application of fracture mechanics parameters to the evaluation of structural integrity under the above-mentioned loading conditions. Faculty of Technology and Metallurgy, University of Belgrade, Yugoslavia. Faculty of Mechanical Engineering, University of Belgrade, Yugoslavia. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 2, pp. 107–118, March–April, 1996.     

Studies on compensating valency substituted BaTi(1−x)Mn x/2Nb x/2O3 ceramics

The paper reports investigations of relative permittivity, ε_r, electrical conductivity, σ, saturation polarization, P_s, infrared absorption and structural properties of compensating valency substituted BaTiO₃. The compositions investigated are BaTi_(1−x)Mn_x/2Nb_x/2O₃ forx = 0.00; 0.025; 0.05; 0.1; 0.2; 0.4. The compositions forx < 0.1 are observed to be ferroelectric and the transition temperature and value of ε_r are observed to decrease as concentration of substitution is increased. The dielectric investigations are carried out on two sets of samples (i) as sintered and (ii) annealed. Annealing is observed to improve quality factor‘Q’ of the materials with a consequent reduction in the ε_r. The observations on ε_r and saturation polarization suggest that additional material engineering efforts are required to improve the material properties.