Multi-product Firms and Product Variety

A preliminary version of this paper was circulated under the title "Too many or too few varieties: the role of multi-product firms" (CEPR Discussion Papers; 5938, Nov. 2006).-- Trabajo publicado como artículo en Economica 79(314): 303-328 (2012).-- http://dx.doi.org/10.1111/j.1468-0335.2011.00897.xThe goal of this paper is to study the role of multi-product firms in the market provision of product variety. The analysis is conducted using the spokes model of non-localized competition proposed by Chen and Riordan (2007). Firstly, we show that multi-product firms are at a competitive disadvantage vis-a-vis single-product firms and can only emerge if economies of scope are sufficiently strong. Secondly, under duopoly product variety may be higher or lower with respect to both the first best and the monopolistically competitive equilibrium. However, within a relevant range of parameter values duopolists drastically restrict their product range in order to relax price competition, and as a result product variety is far below the efficient level.We thank the CREA Barcelona Economics Program and the Spanish Ministry of Education and Science (grants SEJ2005-01427 and SEJ2006-13768) for their support.Peer reviewe

ЛЕВ ПАДАЛКА ЯК ДОСЛІДНИК ЗАПОРОЖЖЯ

Нові публікації останнього часу про формування ідейних та теоретичних засад української історичної науки дають підстави для переконливих висновків про тяглість і цілеспрямованість історіографічного процесу в Україні, а також про роль у ньому як окремих, справді видатних особистостей, так і істориків „другого плану”. Важливе значення для їх становлення мало навчання і залучення до наукової діяльності під егідою і за уважним сприянням фундаторів вітчизняної історичної науки. Переважну більшість серед них склали регіональні школи наукових досліджень, які ввели до наукового обігу величезний комплекс архівних джерел, даних топографії, археології, статистики, етнографії

Anterior column acetabulum fracture fixation with a screw-augmented acetabular cup-a biomechanical feasibility study

BACKROUND: The beneficial effects of unrestricted postoperative full weight bearing for elderly patients suffering hip fractures have been demonstrated. However, there is still existing disagreement regarding acetabular fractures.The aim of this biomechanical study was to evaluate the initial load bearing capabilities of different fixation constructs of anterior column fractures (ACFs) in osteoporotic bone. METHODS: Artificial pelvises with ACFs were assigned to three groups (n = 8) and fixed with either a 7.3 mm partially threaded antegrade cannulated screw (group AASS), an anteriorly placed 3.5 mm plate (group AAPF), or a press-fit acetabular cup with screw augmentation (group AACF). All specimens underwent ramped loading from 20 N preload to 200 N at a rate of 18 N/s, followed by progressively increasing cyclic testing at 2 Hz until failure performed at a rate of 0.05 N/cycle. Relative displacements of the bone fragments were monitored by motion tracking. FINDINGS: Initial stiffness (N/mm) was 118.5 ± 34.3 in group AASS, 100.4 ± 57.5 in group AAPF, and 92.9 ± 44.0 in group AACF, with no significant differences between the groups, p = 0.544. Cycles to failure were significantly higher in groups AACF (8364 ± 2243) and AAPF (7827 ± 2881) compared to group AASS (4440 ± 2063), p ≤ 0.041. INTERPRETATION: From a biomechanical perspective, the minimally invasive cup fixation with screw augmentation demonstrated comparable stability to plate osteosynthesis of ACFs in osteoporotic bone. The results of the present study do not allow to conclusively answer whether immediate full weight bearing following cup fixation shall be allowed. Given its similar performance to plate osteosynthesis, this remains rather an utopic wish and a more conservative approach deems more reasonable

Anterior column acetabulum fracture fixation with a screw-augmented acetabular cup-a biomechanical feasibility study.

BACKROUND The beneficial effects of unrestricted postoperative full weight bearing for elderly patients suffering hip fractures have been demonstrated. However, there is still existing disagreement regarding acetabular fractures.The aim of this biomechanical study was to evaluate the initial load bearing capabilities of different fixation constructs of anterior column fractures (ACFs) in osteoporotic bone. METHODS Artificial pelvises with ACFs were assigned to three groups (n = 8) and fixed with either a 7.3 mm partially threaded antegrade cannulated screw (group AASS), an anteriorly placed 3.5 mm plate (group AAPF), or a press-fit acetabular cup with screw augmentation (group AACF). All specimens underwent ramped loading from 20 N preload to 200 N at a rate of 18 N/s, followed by progressively increasing cyclic testing at 2 Hz until failure performed at a rate of 0.05 N/cycle. Relative displacements of the bone fragments were monitored by motion tracking. FINDINGS Initial stiffness (N/mm) was 118.5 ± 34.3 in group AASS, 100.4 ± 57.5 in group AAPF, and 92.9 ± 44.0 in group AACF, with no significant differences between the groups, p = 0.544. Cycles to failure were significantly higher in groups AACF (8364 ± 2243) and AAPF (7827 ± 2881) compared to group AASS (4440 ± 2063), p ≤ 0.041. INTERPRETATION From a biomechanical perspective, the minimally invasive cup fixation with screw augmentation demonstrated comparable stability to plate osteosynthesis of ACFs in osteoporotic bone. The results of the present study do not allow to conclusively answer whether immediate full weight bearing following cup fixation shall be allowed. Given its similar performance to plate osteosynthesis, this remains rather an utopic wish and a more conservative approach deems more reasonable

High sensitive optical microelectronics sensors for the control or pollutants

10 páginas, 8 figuras.The determination of organic contaminants is done, nowadays, mostly by laboratory-based analytical techniques. This analytical methodology involves multistep time-consuming preparation procedures together with expensive and sophisticated techniques, that even leave unsolved problems (i.e. polar and non- volatile degradation compounds). Although the development of immunochemical kits, a few years ago, improved the performance of the result in the environment control, there is still a clear requirement for the development of sensors of small size, reliable, sensitive and selective, which can be operated in-situ and on-line and can be produced by a low cost technology.This research has been supported by the CICYT project TIC97-0594-C04.Peer reviewe

Маркетинговая политика клуба виртуальной реальности «Virtual Reality Playground»

Объектом исследования является клуб виртуальной реальности "Virtual Reality Playground". Предметом исследования является маркетинговая политика клуба виртуальной реальности "Virtual Reality Playground". Цель работы – разработать рекомендации по совершенствованию маркетинговой политики клуба виртуальной реальности "Virtual Reality Playground". Актуальность работы. Рост и развитие сферы услуг обуславливает высокую актуальность темы данной дипломной работы. Высокая конкурентная насыщенность рынка требует незаурядных усилий при планировании и проведении маркетинговой политики, для выделения предприятия в глазах потребителя. В результате исследования были разработаны рекомендации по совершенствованию маркетинговой политика клуба виртуальной реальности "Virtual Reality Playground".The object of the study is the virtual reality club "Virtual Reality Playground". The subject of the study is the marketing policy of the virtual reality club "Virtual Reality Playground". The purpose of the work is to develop recommendations for improving the marketing policy of the virtual reality club "Virtual Reality Playground". Actuality of work. The growth and development of the service sector determines the high relevance of the topic of this thesis. High competitive saturation of the market requires extraordinary efforts in planning and implementing marketing policies, to distinguish the enterprise in the eyes of the consumer. As a result of the research, recommendations were developed to improve the marketing policy of the virtual reality club "Virtual Reality Playground"

A Bio-Catalytic Approach to Aliphatic Ketones

Depleting oil reserves and growing environmental concerns have necessitated the development of sustainable processes to fuels and chemicals. Here we have developed a general metabolic platform in E. coli to biosynthesize carboxylic acids. By engineering selectivity of 2-ketoacid decarboxylases and screening for promiscuous aldehyde dehydrogenases, synthetic pathways were constructed to produce both C5 and C6 acids. In particular, the production of isovaleric acid reached 32 g/L (0.22 g/g glucose yield), which is 58% of the theoretical yield. Furthermore, we have developed solid base catalysts to efficiently ketonize the bio-derived carboxylic acids such as isovaleric acid and isocaproic acid into high volume industrial ketones: methyl isobutyl ketone (MIBK, yield 84%), diisobutyl ketone (DIBK, yield 66%) and methyl isoamyl ketone (MIAK, yield 81%). This hybrid “Bio-Catalytic conversion” approach provides a general strategy to manufacture aliphatic ketones, and represents an alternate route to expanding the repertoire of renewable chemicals

Intravitreal antisense oligonucleotide sepofarsen in Leber congenital amaurosis type 10: a phase 1b/2 trial

CEP290-associated Leber congenital amaurosis type 10 (LCA10) is a retinal disease resulting in childhood blindness. Sepofarsen is an RNA antisense oligonucleotide targeting the c.2991+1655A>G variant in the CEP290 gene to treat LCA10. In this open-label, phase 1b/2 (NCT03140969), 12-month, multicenter, multiple-dose, dose-escalation trial, six adult patients and five pediatric patients received ≤4 doses of intravitreal sepofarsen into the worse-seeing eye. The primary objective was to evaluate sepofarsen safety and tolerability via the frequency and severity of ocular adverse events (AEs); secondary objectives were to evaluate pharmacokinetics and efficacy via changes in functional outcomes. Six patients received sepofarsen 160 µg/80 µg, and five patients received sepofarsen 320 µg/160 µg. Ten of 11 (90.9%) patients developed ocular AEs in the treated eye (5/6 with 160 µg/80 µg; 5/5 with 320 µg/160 µg) versus one of 11 (9.1%) in the untreated eye; most were mild in severity and dose dependent. Eight patients developed cataracts, of which six (75.0%) were categorized as serious (2/3 with 160 µg/80 µg; 4/5 with 320 µg/160 µg), as lens replacement was required. As the 160-µg/80-µg group showed a better benefit–risk profile, higher doses were discontinued or not initiated. Statistically significant improvements in visual acuity and retinal sensitivity were reported (post hoc analysis). The manageable safety profile and improvements reported in this trial support the continuation of sepofarsen development

A unified approach for a posteriori high-order curved mesh generation using solid mechanics

The paper presents a unified approach for the a posteriori generation of arbitrary high-order curvilinear meshes via a solid mechanics analogy. The approach encompasses a variety of methodologies, ranging from the popular incremental linear elastic approach to very sophisticated non-linear elasticity. In addition, an intermediate consistent incrementally linearised approach is also presented and applied for the first time in this context. Utilising a consistent derivation from energy principles, a theoretical comparison of the various approaches is presented which enables a detailed discussion regarding the material characterisation (calibration) employed for the different solid mechanics formulations. Five independent quality measures are proposed and their relations with existing quality indicators, used in the context of a posteriori mesh generation, are discussed. Finally, a comprehensive range of numerical examples, both in two and three dimensions, including challenging geometries of interest to the solids, fluids and electromagnetics communities, are shown in order to illustrate and thoroughly compare the performance of the different methodologies. This comparison considers the influence of material parameters and number of load increments on the quality of the generated high-order mesh, overall computational cost and, crucially, the approximation properties of the resulting mesh when considering an isoparametric finite element formulation

Missed injuries in trauma patients: A literature review

<p>Abstract</p> <p>Background</p> <p>Overlooked injuries and delayed diagnoses are still common problems in the treatment of polytrauma patients. Therefore, ongoing documentation describing the incidence rates of missed injuries, clinically significant missed injuries, contributing factors and outcome is necessary to improve the quality of trauma care. This review summarizes the available literature on missed injuries, focusing on overlooked muscoloskeletal injuries.</p> <p>Methods</p> <p>Manuscripts dealing with missed injuries after trauma were reviewed. The following search modules were selected in PubMed: Missed injuries, Delayed diagnoses, Trauma, Musculoskeletal injuires. Three time periods were differentiated: (n = 2, 1980–1990), (n = 6, 1990–2000), and (n = 9, 2000-Present).</p> <p>Results</p> <p>We found a wide spread distribution of missed injuries and delayed diagnoses incidence rates (1.3% to 39%). Approximately 15 to 22.3% of patients with missed injuries had clinically significant missed injuries. Furthermore, we observed a decrease of missed pelvic and hip injuries within the last decade.</p> <p>Conclusion</p> <p>The lack of standardized studies using comparable definitions for missed injuries and clinically significant missed injuries call for further investigations, which are necessary to produce more reliable data. Furthermore, improvements in diagnostic techniques (e.g. the use of multi-slice CT) may lead to a decreased incidence of missed pelvic injuries. Finally, the standardized tertiary trauma survey is vitally important in the detection of clinically significant missed injuries and should be included in trauma care.</p