Intra- and Inter-Channel Competition in Local-Service Sectors

Although economically very important, local-service sectors have received little attention in the extensive literature on competitive interactions. Detailed data gathering in these sectors is hard, not only because of the multitude of local players, but also because key service dimensions are hard to quantify. Using empirical entry models, we show how to infer information on these sectors’ degree of intra- and inter-channel competition from the observed entry decisions in different local markets. The approach also controls for relevant socio-demographic characteristics of the trading area that may affect performance. We apply the proposed empirical entry model to the video-rental market. Additional entries of video stores are found to significantly increase the level of intra-channel competition. Unlike the predictions of many normative economic models, we find this increase to be larger when the entry occurs in a duopoly than in a monopoly, a pattern consistent with recent experimental research on collusive behavior in oligopolies. We also find evidence of inter-channel cannibalization from the upstream channel (movie theatres), but not from the downstream channel (premium cable). Finally, various socio-demographic characteristics of the trading zone, such as income and household size, are found to also have a significant impact on store performance

Development and evaluation of interleukin-2 derived radiotracers for PET imaging of T-cells in mice

Recently, N-(4-18F-fluorobenzoyl)-interleukin-2 (18F-FB-IL2) was introduced as a PET tracer for T cell imaging. However, production is complex and time-consuming. Therefore, we developed 2 radiolabeled IL2 variants, namely aluminum 18F-fluoride-(restrained complexing agent)-IL2 (18F-AlF-RESCA-IL2) and 68Ga-gallium-(1,4,7-triazacyclononane-4,7-diacetic acid-1-glutaric acid)-IL2 (68Ga-Ga-NODAGA-IL2), and compared their in vitro and in vivo characteristics with 18F-FB-IL2. Methods: Radiolabeling of 18F-AlF-RESCA-IL2 and 68Ga-Ga-NODAGA-IL2 was optimized, and stability was evaluated in human serum. Receptor binding was studied with activated human peripheral blood mononuclear cells (hPBMCs). Ex vivo tracer biodistribution in immunocompetent BALB/cOlaHsd (BALB/c) mice was performed at 15, 60, and 90 min after tracer injection. In vivo binding characteristics were studied in severe combined immunodeficient (SCID) mice inoculated with activated hPBMCs in Matrigel. Tracer was injected 15 min after hPBMC inoculation, and a 60-min dynamic PET scan was acquired, followed by ex vivo biodistribution studies. Specific uptake was determined by coinjection of tracer with unlabeled IL2 and by evaluating uptake in a control group inoculated with Matrigel only. Results:68Ga-Ga-NODAGA-IL2 and 18F-AlF-RESCA-IL2 were produced with radiochemical purity of more than 95% and radiochemical yield of 13.1% ± 4.7% and 2.4% ± 1.6% within 60 and 90 min, respectively. Both tracers were stable in serum, with more than 90% being intact tracer after 1 h. In vitro, both tracers displayed preferential binding to activated hPBMCs. Ex vivo biodistribution studies on BALB/c mice showed higher uptake of 18F-AlF-RESCA-IL2 than of 18F-FB-IL2 in liver, kidney, spleen, bone, and bone marrow. 68Ga-Ga-NODAGA-IL2 uptake in liver and kidney was higher than 18F-FB-IL2 uptake. In vivo, all tracers revealed uptake in activated hPBMCs in SCID mice. Low uptake was seen after a blocking dose of IL2 and in the Matrigel control group. In addition, 18F-AlF-RESCA-IL2 yielded the highest-contrast PET images of target lymph nodes. Conclusion: Production of 18F-AlF-RESCA-IL2 and 68Ga-Ga-NODAGA-IL2 is simpler and faster than that of 18F-FB-IL2. Both tracers showed good in vitro and in vivo characteristics, with high uptake in lymphoid tissue and hPBMC xenografts

Chain-store pricing and the structure of retail markets

This paper examines competition between chain-stores and independent retailers in the UK retail opticians' market. We demonstrate that the pricing policy adopted by chain-stores can determine the impact their entry has on independent retailers. Crucially, in this market the chain-store retailers set an identical national price across all local markets. Our results suggest that this pricing strategy lessens the detrimental effect competition from chain-stores has on independent retailers

Intra- and Inter-Channel Competition in Local-Service Sectors

Although economically very important, local-service sectors have received little attention in the extensive literature on competitive interactions. Detailed data gathering in these sectors is hard, not only because of the multitude of local players, but also because key service dimensions are hard to quantify. Using empirical entry models, we show how to infer information on these sectors’ degree of intra- and inter-channel competition from the observed entry decisions in different local markets. The approach also controls for relevant socio-demographic characteristics of the trading area that may affect performance.We apply the proposed empirical entry model to the video-rental market. Additional entries of video stores are found to significantly increase the level of intra-channel competition. Unlike the predictions of many normative economic models, we find this increase to be larger when the entry occurs in a duopoly than in a monopoly, a pattern consistent with recent experimental research on collusive behavior in oligopolies. We also find evidence of inter-channel cannibalization from the upstream channel (movie theatres), but not from the downstream channel (premium cable). Finally, various socio-demographic characteristics of the trading zone, such as income and household size, are found to also have a significant impact on store performance.channel competition;empirical entry models;movie industry

Intra- and interformat competition among discounters and supermarkets

The price-aggressive discount format, popularized by chains such as Aldi and Lidl, is very successful in most Western economies. Its success is a major source of concern for traditional supermarkets. Discounters not only have a direct effect on supermarkets' market shares, but they also exert considerable pressure to improve operational efficiency and/or to decrease prices. We use an empirical entry model to study the degree of intra- and interformat competition between discounters and supermarkets. Information on the competitive impact of new entrants is derived from the observed entry decisions of supermarkets and discounters in a large cross section of local markets, after controlling for a number of local market characteristics. In our modeling framework, we endogenize the number of retailers and allow for asymmetric intra- and interformat competitive effects in a flexible way. We apply our modeling approach to the German grocery industry, where the discount format has stabilized after two decades of continued growth. We find evidence of intense competition within both the supermarket and discounter format, although competition between supermarkets is found to be more severe. Most importantly, discounters only start to affect the profitability of conventional supermarkets from the third entrant onwards. This may explain why many retailers rush to add a discount chain to their portfolio: early entrants may benefit from the growth of the discount-prone segment without cannibalizing the profits of their more conventional supermarket stores

Recovery of parathyroid hormone secretion during correction of tumor- associated hypercalcemia

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Cross-layer energy-throughput evaluation of multi-hop/path communication and link adaptation for IEEE 802.11a

Future wireless communication devices are expected to support a wide range of applications, while coping with stringent energy budget requirements. Delivering at each moment in time the required performance with minimal energy consumption is a promising energy management technique to enable pervasive wireless networking. Considering transmission energy only, the use of multiple small hops results in a decrease of the energy consumption. On the other hand, decreasing the transmission rate of a single hop similarly results in a decrease of the energy needed to deliver a bit. In this paper we compare the use of multiple small hops along different paths with a single large hop in the Energy-Throughput design space. In contrast with earlier work, realistic transceiver models are used, that cover the complete MAC, transmit and receive chain and support different transmission rates. Results show that, compared to single hop link adaptation, the use of multiple hops in indoor environments is only optimal in the Energy-Throughput space for distances larger than 30m or when there are obstacles present that can be avoided in alternative paths. For those larger distances, significant gains are possible though. Hence, to achieve energy optimal operation in 802.11a networks, it is important to adapt jointly the physical layer constellation and network layer path selection

New Chelators for Low Temperature Al18F-Labeling of Biomolecules

The AlF labeling method is a relatively new approach that allows radiofluorination of biomolecules such as peptides and proteins in a one-step procedure and in aqueous solution. However, the chelation of the {AlF} core with the macrocyclic chelators NOTA or NODA requires heating to 100-120 °C. Therefore, we have developed new polydentate ligands for the complexation of {AlF} with good radiochemical yields at a temperature of 40°C. The stability of the new AlF-complexes was tested in phosphate buffered saline (PBS) at pH 7.4 and in rat serum. The stability of the AlF-L3 complex was found to be comparable to that of the previously reported AlF-NODA complex up to 60 min in rat serum. Moreover, the biodistribution of AlF-L3 in healthy mice showed the absence of in vivo defluorination since no significant bone uptake was observed, whereas the major fraction of activity at 60 min p.i. was observed in liver and intestines, indicating hepatobiliary clearance of the radiolabeled ligand. The acyclic chelator HL3 proved to be a good lead candidate for labeling of heat-sensitive biomolecules with fluorine-18. In order to obtain a better understanding of the different factors influencing the formation and stability of the complex, we carried out more in-depth experiments with ligand HL3. As a proof of concept, we successfully conjugated the new AlF-chelator with the urea-based PSMA inhibitor Glu-NH-CO-NH-Lys to form Glu-NH-CO-NH-Lys(Ahx)L3, and a biodistribution study in healthy mice was performed with the AlF-labeled construct. This new class of AlF-chelators may have a great impact on PET radiochemical space as it will stimulate the rapid development of new fluorine-18 labeled peptides and other heat-sensitive biomolecules

Micro-flow photosynthesis of new dienophiles for inverse-electron-demand Diels-Alder reactions : potential applications for pretargeted in vivo PET imaging

Pretargeted PET imaging has emerged as an effective two-step in vivo approach that combines the superior affinity and selectivity of antibodies with the rapid pharmacokinetics and favorable dosimetry of smaller molecules radiolabeled with short-lived radionuclides. This approach can be based on the bioorthogonal inverse-electron-demand Diels–Alder (IEDDA) reaction between tetrazines and trans-cyclooctene (TCO) derivatives. We aimed to develop new [18F]TCO–dienophiles with high reactivity for IEDDA reactions, and favorable in vivo stability and pharmacokinetics. New dienophiles were synthesized using an innovative micro-flow photochemistry process, and their reaction kinetics with a tetrazine were determined. In vivo stability and biodistribution of the most promising 18F-radiolabeled-TCO-derivative ([18F]3) was investigated, and its potential for in vivo pretargeted PET imaging was assessed in tumor-bearing mice. We demonstrated that [18F]3 is a suitable dienophile for IEDDA reactions and for pretargeting applications