Siphons are devices that transport liquids uphill between two containers. It has been proposed that a siphon principle operates in closed circulatory systems, as best exemplified by the circulation ...of blood in mammals. This principle is supposed to ensure that no additional work is necessary to pump blood above the level of the heart, and that there is no gravitational static pressure gradient in the column of blood. The first statement is correct, while we demonstrate that, ignoring hydraulic resistance to blood flow, the static pressure gradient is equal to the hydrostatic gradient in a siphon model of blood circulation, although the details of the proof do not depend on the geometry of the circulatory system and the proof can be trivially extended to other models such as a vascular waterfall. This implies that the controversy over the siphon principle has no implications for the description of blood circulation, and that mechanisms such as the “baffle,” which some authors have appealed to in order to obtain the expected gradient, are not necessary. In our discussion, we also discuss empirical data that appear to provide additional verification of our results, as well as several everyday occurrences that provide additional support.
Cilj je ovoga rada povezivanje temeljnih karakteristika tkiva s rezultatima dobivenim na rendgenskoj slici, analizirajući fizikalne principe interakcije koje vode do atenuacije rendgenskih fotona u ...tkivu. Na slikovitom primjeru dokazujemo da nećemo moći imati superdijagnostički uređaj koji bi mogao zamijeniti sve moderne i buduće dijagnostičke uređaje. Svaka
se tehnika oslikavanja tkiva temelji na jedinstvenim fizikalnim principima te stoga ona vidi točno određene kakateristike tkiva koja drugi dijagnostički uređaji (tehnike) ne mogu vidjeti. Oslikavanje se rendgenskim uređajem temelji na atenuaciji (slabljenju) snopa rendgenskih zraka nakon prolaska kroz tkivo. Glavni su mehanizmi interakcije rendgenskih fotona i tkiva fotoelektrični efekt (potpuna apsorpcija energije fotona) te Comptonovo raspršenje (djelomična apsorpcija energije fotona). Fotoelektrični efekt dominira na niskim i djelomično srednjim energijama i s povećanjem energije jako slabi, dok na srednjim i višim energijama dominira Comptonovo raspršenje. Analizom oba raspršenja, nakon dekompozicije linearnoga koeficijenta atenuacije na uobičajene fizikalne veličine, nalazimo da u režimu Comptonovoga raspršenja kontrast na slici je određen razlikama u gustoći tkiva, a u režimu fotoelektričnoga efekta ovisi o gustoći tkiva te snažno o rednom broju elemenata od kojih je tkivo sastavljeno. U radu su grafički prikazane vrijednosti kontrasta na rendgenskoj slici za osnovne tvorbe i tkiva i opisane njihove karakteristike, gustoća i redni broj elemenata od kojih su sastavljeni. Kompjuterizirana tomografija (CT) vidi potpuno iste karakteristike tkiva kao i klasična rendgenska tehnika. U radu je na eksplicitnom dvodimenzionalnom primjeru objašnjen princip komjuterizirane tomografije. On se temelji na zamišljenoj podjeli tkiva na male volumene (voksele) i snimanju tkiva iz više pozicija, pri čemu se za svaku poziciju postavljaju jednadžbe za apsorpciju zračenja. U dobivenom sustavu jednadžbi nepoznate vrijednosti su vrijednosti linearnog koeficijenta atenuacije za svaki voksel, koje se odrede numeričkim rješavanjem sustava jednadžbi, i prikažu na prikladnoj skali boja u trodimenzionalnom prikazu.
In this study, oxidative stress and lipid peroxidation in honey bee larvae, pupae and the midguts of adult bees were investigated during a one-year exposure to radiofrequency electromagnetic fields ...(RF-EMFs) at a frequency of 900 MHz under field conditions. The experiment was carried out on honey bee colonies at three locations with electric field levels of 30 mV m
, 70 mV m
and 1000 mV m
. Antioxidant enzymes, glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS) as indicators of lipid peroxidation were measured spectrophotometrically. The GST activity within the same developmental stage showed no significant differences regardless of electric field level or sampling time. The highest GST activity was found in the pupae, followed by activity in the larvae and midguts. Both CAT activity and TBARS concentration were the highest in the midguts, regardless of field level and sampling time. The larvae showed a significantly higher TBARS concentration at the location with an electric field level of 1000 mV m
compared to the locations with lower levels. Our results show that RF-EMFs at a frequency of 900 MHz can cause oxidative stress in honey bees, with the larval stage being more sensitive than the pupal stage, but there was no linear relationship between electric field level and effect in any of the developmental stages.
We conducted a survey on the beekeeping production, practices and attitudes of 117 beekeepers in Croatia, via a questionnaire. The beekeepers were divided into three groups: full-time ...(professionals), part-time (side-liners) and hobby (hobbyists) beekeepers. The questions covered the purpose and size of their beekeeping production, the production interests of the beekeepers, treatment of the economically most important honeybee diseases, and the possibilities of the growth of their operation. Professional beekeepers were the youngest (39 years of age on average), with the largest average number of beehives per beekeeper (135 beehives), the largest proportion of LR hives and migratory apiaries, and the largest yearly per hive production of 17.04 kg of honey. The results show that the most marketable beekeeping product was honey, and that professional beekeepers also value propolis as equally interesting for production. They all inherited their beekeeping operations from their predecessors. Varroosis is perceived as the largest cause of honeybee colony death, followed by bad beekeeping practices. About 56% of the beekeepers are prepared to switch to organic/ecological beekeeping. Almost all the beekeepers (96.46%) support the introduction of the early diagnostics of American foulbrood. We found that professional beekeepers prefer the conservative economic model of growth based on their own equity, while hobbyists prefer a more expansive but riskier model of growth based on financial leverage (debt). Professional beekeepers are not inclined to create a mutual beekeepers' fund to cover losses. On the other hand, they strongly support the idea of creating an alliance for the purpose of joint market penetration. Key words: beekeeping economics; honey production; treatment of honeybee diseases; organic beekeeping, Croatia
In the survey, some variables were analyzed of cross-compliance control on livestock production farms in Croatia from 2011 to 2018. Collected data covered three animal production groups: cattle, ...sheep and goats, and pigs, for which the following parameters were monitored: wrongly marked breed, wrong gender, incorrect labeling, no animal on the holding, and no evidence of the animal in the farm register or in the national one. A total of 621,146 animals were surveyed, and in 92,523 (14.89%) of them noncompliance was found. It ranged from 9.66% in 2012 to 26.30% in 2018. Out of 221,311 investigated cattle, 373,515 sheep and goats and 26,320 pigs, noncompliance was found in 18.74%, 13.28% and 5.58% respectively. More noncompliance was detected in 2011 when the on-the-spot control started, followed by a decrease in the amount of noncompliance observed in 2012. However, in 2013, 2014 and 2018 an increase in the proportion of noncompliance was detected (17.54%, 16.86% and 26.30% respectively), due to the introduction of new parameters, i.e. new risk factors used in monitoring, and a lack of adequate education of farmers to adapt to new conditions. The value of the correlation coefficient (r) between the proportion of a particular production group of animals in the total number of animals, and the proportion of non-compliant animals in that production group for cattle was -0.232, for sheep and goats 0.637, and for pigs -0.317. For cattle and pigs this implies a negative but very weak correlation, and for sheep and goats a positive but moderate correlation. This means that there is not sufficient evidence of a strong negative correlation between those two variables, which was the hypothesis. The most important noncompliance item in cattle was no identification in the central register (26.25%), and the wrong gender (25.00%) in sheep and goats. The findings imply that more frequent training, as well as improvement of cooperation between all stakeholders should be obligatory measures for better farm management, resulting in reduced frequency of noncompliance. Key words: Common Agricultural Policy; livestock production farms; income support; cross-compliance; control strategy
Exposure to radiofrequency electromagnetic fields (RF-EMF) at the operating frequencies of different communication devices can cause various biological effects. However, there is a lack of studies on ...the oxidative stress response and genotoxicity in the honey bee (Apis mellifera) after exposure to RF-EMF. In this study, we investigated the oxidative stress and DNA damage in honey bee larvae situated in waxcomb cells, exposed to modulated RF-EMF 23 Vm-1. The glutathione S-transferase activity decreased, whereas the catalase activity increased significantly in the honey bee larvae upon RF-EMF exposure. Superoxide dismutase activity, the level of lipid peroxidation, and DNA damage were not statistically altered in exposed honey bee larvae when compared to the control group. These results suggest that the biological effects of modulated RF-EMF in honey bee larvae depend on the exposure design.
We have investigated Fourier transform infrared (FTIR) spectra, Raman spectra and ultraviolet and visible absorption spectra of the (Ge
2S
3)
x
(As
2S
3)
1−
x
chalcogenide glass thin films with 0.1≤
...x≤0.9 and the average coordination number
Z between 2.52 and 2.76. The relation of the structural and optical properties to the average coordination number is demonstrated by varying the composition parameter
x of the glass. All measured quantities energy gap, sound velocity, IR and Raman peak intensities, position and the intensity of the boson peak showed the extreme values at
Z=2.67, indicating that structural phase transition occur at this coordination number.
The effects were measured of low-doses of gamma radiation within 24 hours after irradiation on the activity of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT) and levels ...of glutathione (GSH) and lipid peroxide concentrations (malondialdehyde, MDA) in embryonic chick liver. The chick embryos were irradiated with doses of gamma radiation of 0.05, 0.15, 0.3, 0.5 and 0.8 Gy at the dose rate of 0.0117 Gy/s on day 19 of incubation. All parameters were measured 1, 3, 6, 12 and 24 hours after irradiation by spectrophotometry, apart from the level of lipid peroxidation, which was assessed using high performance liquid chromatography (HPLC). A versatile analysis of the data was made and it consisted of: 1) a comparison of the means of antioxidant enzyme activities and GSH and MDA concentrations for each radiation dose and the time after irradiation with the corresponding control samples; 2) research into the temporal dynamics of enzyme activities and concentrations a) for each value of radiation dose and b) when the data for radiation doses were merged, i.e. regardless of the radiation doses. A significant increase in GSH-Px activities in time after irradiation was found in dose intervals from 0.05 to 0.5 Gy, which was well described by linear function. This is a highly reliable result, because it was obtained as a result of all the analyses applied. For other parameters, we did not find any dependence of activities and concentrations on time. The analysis of comparison of means of the irradiated and control samples gave statistically significant results for some dose-time pairs. Key words: antioxidants; chick; embryo; liver; low-dose radiation; gamma irradiation
Od početka svjetske gospodarske recesije 2008. godine pa i uoči nje, praćene su promjene gospodarskih pokazatelja u veterinarskim stanicama i ambulantama. Neki autori su u nekoliko navrata pisali o ...potencijalnim uzrocima i posljedicama krize na poslovanje veterinarskih organizacija. U žarištu interesa bilo je više pokazatelja od kojih su tri praćena u ovom istraživanju. To su: prosječna neto plaća, broj zaposlenih i ukupni prihod. Oni su prikazani za razdoblje od 2003. do 2017. godine. Radi stjecanja jasnijeg uvida u okolnosti u kojima su poslovale, našu smo pažnju proširili i na općenitije pokazatelje gospodarske aktivnosti na razini ukupnog gospodarstva (bruto domaći proizvod, jav- ni dug, zaposlenost, broj i dobna struktura stanovništva, uvoz i izvoz) i poljoprivrede kao bitne odrednice aktivnosti veterinarskih organizacija. Naime, rezultati istraživanja pojedinih autora pokazuju da je recesija više naštetila veterinarstvu negoli ukupnom gospodarstvu pa smo željeli u široj ekonomskoj slici uočiti naznake buduće gospodarske stvarnosti i upozoriti na njih. S obzirom na to da su gospodarski trendovi potaknuti i vođeni potrebama ljudi, demografski podatci mogu pomoći pri otkrivanju makro i mikro trendova. Zato smo u promatranje uključili i demografske pokazatelje. Ukupni prihod i broj zaposlenih u veterinarskim stanicama smanjivali su se, dok su plaće lagano rasle do 2008. a zatim stagnirale. U veteri- narskim ambulantama, za razliku od stanica, svi pokazatelji su rasli, no u godinama nakon početka recesije plaće su uglavnom stagnirale ili lagano padale. U 2017. godini zabilježen je lagani porast neto plaća i u veterinarskim stanicama i u veterinarskim ambulantama. Zabilježene promjene u kretanju poljoprivrednih i općih demografskih i gospodarskih trendova poput: bitnog smanjenja broja reproduktivnih životinja i proizvodnje mlijeka i jaja, starenja ljudske populacije i smanjenja nataliteta, stalno rastućeg uvoza hrane i pića i uvoza općenito te uočena jaka korelacija između duga i broja stanovnika, i rastući pritisak na novo zaduživanje upućuju na izvjesnu daljnju stagnaciju ili smanjivanje gospodarskih aktivnosti veterinarskih organizacija. Porast proizvodnje bio je najizraženiji u broju košnica i proizvonji meda, u uzgoju ovaca i konja te tovu pilića. Evidentno je da su se najviše smanjivale one stočarske proivodnje koje zahtijevaju više vještine, potrošenog vremena i intenzivnijeg rada, dok su porasle one koje traže manje rada i jednostavnije postupke. Struktura proizvodnje prilagođavala se potrebama i mogućnostima koje proizlaze iz strurkture radne snage.
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