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45212. Why do we have purkinje fibers deep in our heart?

Creator:
Sedmera, D. and Gourdie, R. G.
Format:
print
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, srdce, fyziologie, heart, physiology, 14, and 612
Language:
English
Description:
Purkinje fibers were the first discovered component of the cardiac conduction system. Origin ally described in sheep in 1839 as pale subendocardial cells, they were found to be present, although with different morphology, in all mammalian and avian hearts. Here we review differences in their appearance and extent in different species, summarize the current state of knowledge of their function, and provide an update on markers for these cells. Special emphasis is given to popular model species and human anatomy., D. Sedmera, R. G. Gourdie., and Obsahuje bibliografii a bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

45214. Why does the Namib Desert tenebrionid Onymacris unguicularis (Coleoptera: Tenebrionidae) fog-bask?

Creator:
Naidu, Strinivasan G.
Type:
article, model:article, and TEXT
Subject:
Water balance, osmoregulation, lipid, Tenebrionidae, Onymacris unguicularis, Namib Desert, and glycerol
Language:
English
Description:
Dehydration of Onymacris unguicularis (Haag) for 10 days at 27°C resulted in a weight loss of 14.9%, and a 37% decrease in haemolymph volume. Although there was an overall decrease in the lipid content during this period, metabolic water production was insufficient to maintain total body water (TBW). Rehydration resulted in increases in body weight (6.2% of initial weight), TBW (to normality), and haemolymph volume (sub-normal at the end of rehydration). Despite an increase of 44.0 mg in the wet weight of O. unguicularis after drinking for 1h, there was little change in the water content at this time, although the total lipid content increased significantly. Increases in haemolymph osmolality, sodium, potassium, chloride, amino acid and total sugar concentrations during dehydration were subject to osmoregulatory control. No evidence of an active amino acid-soluble protein interchange was noted during dehydration or rehydration. Haemolymph trehalose levels were significantly increased at the end of rehydration (relative to immediate pre-rehydration values), indicating de novo sugar synthesis at this time. Osmotic and ionic regulation was evident during rehydration, but control of OP during haemolymph-dilution is poor and accomplished largely by the addition to the haemolymph of free amino acids and solute(s) not measured in this study. There was little mobilization of sodium and chloride ions from storage sites at this time. The lesser osmoregulatory ability of Onymacris unguicularis and perhaps earlier susceptibility to osmotic stress, a significantly high normal blood glycerol level (relative to other diurnal adesmiine tenebrionids), and a water storage mechanism associated with synthesis of fat, probably all contribute to the development of fog-basking behaviour in this species. Water gain in O. unguicularis during periods of relative drought is probably largely accomplished by a greater food consumption.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

45215. Why don't migrants with secondary education return?

Creator:
Ivanova, Renata, Jeong, Byeongju, Kejak, Michal, Univerzita Karlova. Centrum pro ekonomický výzkum a doktorské studium, and Národohospodářský ústav (Akademie věd ČR)
Publisher:
CERGE-EI
Format:
electronic and 45 s.
Type:
model:monograph and TEXT
Subject:
Demografie. Populace, emigrace a imigrace, reemigrace, středoškolské studium, vzdělávání, matematické modelování, 314.15-026.44, 314.151.7, 373.5/.6+377.1/.3, 519.673, (048.8), 18, and 314
Language:
English and Czech
Description:
Tento článek se pokouší vysvětlit schema ve tvaru U v míře návratu migrantů ve vztahu k dosaženému vzdělání. Vytváříme OLG model na dvě období, kde jsou rozhodnutí emigrovat a navrátit se udělána činiteli, kteří jsou heterogenní z pohledu dosaženého vzdělání. Imigrační politika je brána v potaz jako další determinanta migračního rozhodnutí. Model předpovídá, že kombinace dvou sil - relativní návratnost vzdělávání a nejisté příležitosti pro přizpůsobení statusu - vede ke kladným podmínkám k tomu, aby migranti se středoškolským vzděláním zůstali v zahraničí natrvalo., Renata Ivanova, Byeongju Jeong ; editor: Michal Kejak., and born digital
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

45217. Why has the COVID-19 pandemic had a limited impact on the primary housing market in Poland?

Creator:
Augustyniak, Hanna, Łaszek, Jacek, Olszewski, Krzysztof, and Waszczuk, Joanna
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
housing market, COVID-19, accelerator, and structural change
Language:
English
Description:
In this paper we present the first insight about the impact of the COVID epidemic on the pri-mary housing market in Poland, with a focus on Warsaw which is the largest market. We ex-plain the structural features that allowed the market to return to pre-shock levels after the pandemic shock. Contrary, after the 2007-2008 global financial crisis the negative consequences lasted for several years. This time a sharp monetary policy and fiscal intervention was carried out. Moreover, the developer sector is much more mature, has expanded its production capaci-ties. We show empirically that the monopolistic competition of developers allowed them to restrict excessive demand that was observed before the COVID broke out. In this way they were able to increase prices despite the economic problems. Another important structural change was the increased housing demand, mainly for investment housing, which was fi-nanced predominantly with cash and contributed to the development of the rental market. We approximate the investment demand, which was generated by private households that pur-chased flats for rental, with the help of a simple demand and supply model.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

45218. Why is Coccinella septempunctata so successful? (A point-of-view)

Creator:
Hodek, Ivo and Michaud, J.P.
Type:
article, model:article, and TEXT
Subject:
Coccinellidae, ladybirds, Coccinella septempunctata, Harmonia axyridis, Adalia bipunctata, Coleomegilla maculata, biological control, diapause, diet, foraging, intraguild predation, migration, oviposition, polyphenism, reproduction, and voltinism
Language:
English
Description:
Factors were examined that could be responsible for the predominance of Coccinella septempunctata (C7) in most habitats of the Palaearctic and for its successful invasion of the Nearctic Region. C7 is euryphagous, but less polyphagous than Harmonia axyridis or Coleomegilla maculata in that it cannot develop or reproduce on non-aphid food. The intraguild status of C7 is intermediate. Although adult size is large, preimaginal stages are palatable to those of H. axyridis and Adalia bipunctata, whereas it is not an intraguild predator of these species. Although these traits appear to be neutral or negative, many aspects of population plasticity are advantageous for C7, often acting in concert with a bet-hedging strategy. Given its high mobility and eurytopy, the inhibition of oviposition in the presence of conspecific larval trails represents an adaptive advantage that favors increased egg dispersal and lowers the risk of offspring mortality due to cannibalism. The ability to temporarily suspend oviposition, combined with heterogenous voltinism and diapause tendencies, enable a portion of C7 populations to feed and reproduce on unpredictably occurring aphid populations. An absence of reproductive diapause in males and pre-hibernation mating are other significant adaptations, along with the tendency to produce offspring in excess of the carrying capacity of local food resources. We suggest that one explanation for the broad geographic success of C7 resides in an ecological plasticity that is based on both genetic and phenotypic polymorphisms.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

45219. Why is the class number of ℚ(3√11) even?

Creator:
Lemmermeyer, F.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
class number, pure cubic field, and elliptic curve
Language:
English
Description:
In this article we will describe a surprising observation that occurred in the construction of quadratic unramified extensions of a family of pure cubic number fields. Attempting to find an explanation will lead us on a magical mystery tour through the land of pure cubic number fields, Hilbert class fields, and elliptic curves.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

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