Superradiant scattering is a radiation enhancement process that takes place in many contexts, and which has recently found exciting applications in astrophysics and particle physics. In the framework ...of curved spacetime physics, it has been associated with the classical Penrose process for particles. Superradiance is usually also associated with bosonic fields around geometries with ergoregions and horizons. These notions are in clear tension however: the Penrose process occurs for horizonless geometries, and particles are composed of fermions. Here, we resolve the tension in its different aspects, by showing that (i) superradiance occurs for self-interacting fermions on flat spacetime. (ii) Superradiance occurs also for horizonless geometries, where it leads to an ergoregion instability. Ultracompact, horizonless geometries will usually respond with echoes of growing amplitude, until rotational (or electrostatic) energy is extracted from the object. (iii) The Fourier-domain analysis leads to absence of superradiance when horizons are not present. We elucidate why this analysis fails to give meaningful results. (iv) Finally, we show that superradiant, ergoregion instabilities have a particle analog of similar growth timescales and which can power the formation of a structure outside a compact, rotating star.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
AbstractGiven that PVC membranes are a current solution for waterproofing flat roofs, and their use has been increasing in Portugal, it is important to analyze the main reasons for the occurrence of ...unusual anomalies in membranes mechanically fastened to the roof (not protected, directly exposed to the normal atmospheric agents) such as the premature occurrence (after less than 8 years old) of very localized dark spots on its surface that are longitudinally along all the rolls of the membrane. An experimental study was carried out and essentially it showed a clear decrease in the thickness of the top layer of the membrane and its total mass in these areas—already with the presence of the knots of the reinforcement mesh on the surface of the membrane, seen through an electron microscope—which is associated with very low levels of plasticizer for the service life of this membrane. From the analysis done, it can be concluded that the defect in question is associated with a less careful formulation of the PVC compound (or mix) during the manufacturing process for unprotected membranes on the roof.
Buildings and other constructed facilities form the essential framework of a country’s physical and economic infrastructure. Construction serves as a key capital input to production, driving economic ...growth and wealth generation. This impact can be particularly transformative in low-to-middle-income countries. Physical infrastructure, including construction, is a powerful engine of economic growth and is closely related to national economic performance. However, not all studies agree with the commonly held belief that construction investment has a positive impact on economic growth, particularly concerning the amount of investment and the relationship between construction investment and economic growth. So far, cross-country studies dealing with the construction sector-economic growth relationship have used indicators of national output and construction that are not strictly comparable between countries. This article reviews the main strands of the literature on the role that the construction sector plays in the national economy and economic development. It also uses novel data drawn from the “capital file” of the PENN World Table (version 10.1) to assess the development pattern of the construction sector in two groups of sub-Saharan African (SSA) countries on the middle-income status of economic development, for the period between 1990 and 2019. The study reveals that construction shares, measured as the proportion of gross fixed capital formation attributable to construction in the gross domestic product, revolve around a norm determined by the level of built assets preceding the reference period. The results of the study could have policy implications for the economic sustainability of the construction industry in SSA.
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CEKLJ, IZUM, KILJ, NUK, PILJ, SAZU, UL, UM, UPUK
Building and other construction assets constitute a significant part of a country’s physical and economic infrastructure. According to several writers, the knowledge of reliable data of building and ...other construction assets of a specific country or region is a crucial element for the long-term management of these assets. Built capital stock statistics at the national or international levels have been available for most countries of the world, both developed and less developed ones, for some time, but construction infrastructure stock statistics at the disaggregated level are very scarce, even for most developed countries. Furthermore, the methodologies to produce the estimates of built capital stock, at the international level, do not consider countries’ specificities. This paper discusses the methodologic issues for producing construction infrastructure stock statistics for Cape Verde, and makes estimates for the period 1980–2019. The paper outlines the Perpetual Inventory Method (PIM) used to produce capital estimation, data employed, and the assumptions made to estimate missing data. The paper analyses the level of the construction infrastructure stock estimates for Cape Verde, as well as their impact on the development pattern of the country’s construction industry, and suggests how further studies can enhance our comprehension of the relationship between construction investment and economic growth and development.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The aims of this study were (1) to synthesize evidence of the general health-related quality of life in children with DCD compared to their typically developing peers, and (2) to verify which domains ...of HRQOL are more compromised in children with DCD. A systematic search was carried out to identify cross-sectional studies that evaluated self-perception and/or the parent's perception of the HRQOL in children with and without DCD as an outcome. The methodological quality of the studies was assessed, and the effect size calculated. Initial searches in the databases identified 1092 articles. Of these, six were included. Most of the articles (5/6) included noted that children with DCD show a significantly lower HRQOL than their typically developing peers. Regarding the most compromised HRQOL domains, the results are heterogeneous. Most studies (3/6) had moderate methodological quality, and two studies were classified as high methodological quality. Effect sizes ranged from low to high.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Numerous movement skills and physical fitness tests have been developed for children in high-income countries. However, adaptation of these tests to low-resource settings has been slow and norms are ...still unavailable for children living in low-income communities. The aim of this paper was to describe the development and validation of the Performance and Fitness (PERF-FIT) test battery, a new test to assess motor skill-related physical fitness in children in low-resource settings.
The PERF-FIT test was developed in a stepwise manner. This involved defining the relevant domains of the construct of interest and selecting and evaluating test items. The Content Validity Index (CVI) was used to estimate content validity. Following development of the PERF-FIT test, a preliminary study was performed to validate items and to examine the feasibility of implementing the test in a low-resource community. Structural validity was also determined based on data from eighty (n = 80) children (aged 7-12 years) using principal component analysis.
The CVI for the throw and catch item was 0.86 and 1.00 for the other nine items, leading to a total CVI score of 0.99. The hierarchical sequence of the item series was demonstrated by highly significant (p < 0.001) linear trends, confirming the increase in difficulty of subsequent items. Principal component analysis revealed three factors; the first component is represented by locomotor skills that require static and dynamic balance, the second component by throwing and catching items and the third component by agility and power items. These findings suggest that it is feasible to implement the PERF-FIT in low-resource settings.
The PERF-FIT test battery is easy to administer and may be suitable for measuring skill-related physical fitness in in low-resource settings. It has excellent content validity and good structural validity. After minor adaptions, further studies should be conducted to establish normative values, evaluate reliability, and document criterion and cross-cultural validity of this test.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Additive manufacturing (AM) is one of the pillars of Industry 4.0, where automation to create smart factories is the main target. The hybridization of processes is one of the leading strategies to ...implement a more flexible, efficient, and interconnected manufacturing environment. Nowadays, different researches are focused on the hybridization of metal AM and subtractive manufacturing (SM). Based on the working principles of AM and SM, it can be established that they are complementary processes. Hence, a synergy between them allows conceiving a unique process. As a result, the advantages are magnified, and the limitations of each one are minimized or eliminated. This review presents the latest developments, challenges, limitations, and future perspectives for the integration between directed energy deposition (DED) and SM. DED is a versatile AM process for metal parts fabrication, where the geometrical complexity is its main advantage. Nevertheless, the low surface quality and the difficult dimensional control of the parts create the need for post-processing. Traditional post-processing involves a higher production time, and the barriers cannot be completely overcome. Then, a hybrid process constitutes a powerful concept to combine both technologies efficiently, to produce complex parts with less waste of material and energy.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Despite the benefits highlighted by motor interventions based on virtual reality for children with Developmental Coordination Disorder (DCD), there are still doubts as to whether these are greater ...than those obtained with conventional interventions due to the absence of systematized protocols, and lack of evidence. Here, we present a protocol to systematically compare the effects of two motor-training programs (one Nintendo® Wii-based and the other no-Wii motor activities) on the motor learning in children with DCD.
Two intervention protocols (one based on Nintendo® Wii and the other no-Wii motor activities) will be carried out, with interventions occurring twice a week in 60-min sessions, with a minimum of 12 and a maximum of 16 sessions per child. The protocols were developed based on the domains of the Movement Assessment Battery for Children - Second Edition (MABC-2) (Manual Dexterity, Aiming and Catching, Balance), with two activities for each of the MABC - two domains. The study will include children aged 7 to 10 years with a total MABC-2 score ≤ 16, and a Developmental Coordination Disorder Questionnaire (DCDQ) score < 46 (age of 7 years), score < 55 (age group of 8 to 9 years and 11 months), or score < 57 (age of 10 years) as scored by the parents. Children will be randomly allocated by draw in one of the two intervention protocols. MABC-2 and DCDQ will be applied before and after intervention to evaluate the effects of the interventions on motor performance and parents' perception, respectively. Motor learning will be assessed by means of the scores obtained in the games. Evaluators and therapists will be trained and evaluators will be blind regarding the data of the children in the study.
Owing to its motivating aspects, training with Nintendo® Wii may be particularly beneficial for children with DCD. The results of this study protocol should help researchers and therapists to better understand the benefits of Nintendo® Wii-based motor intervention over those obtained with no-Wii interventions in children with DCD. It should also create references about more systematized protocols for replication in clinical practice, seeking the improvement of the motor components of these children.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The present study aims to investigate how commercialisation and knowledge transfer between the SMEs of the tourism sector and the higher education institutions (HEIs) are made, as well as to find out ...whether the SMEs of the tourism sector are part of tourism networks, and what their motivations are. We used a qualitative methodology, applying the triangulation method to eight SMEs and one HEI. The results indicate that the commercialisation and knowledge transfer between the SMEs and the HEIs are not effective. SMEs are part of regional networks of business innovation; however, they do not participate in R&D activities with HEIs. Some suggestions were made to SMEs, HEIs, and regional governments to speed up commercialisation and knowledge transfer in the tourism sector. We adapted the Triple Helix Model to the tourism sector, thus creating the “Triple Helix in the Tourism Context”. Only a few studies have researched knowledge commercialisation in the tourism sector, a gap that this article aims to compensate.
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