The abundance and distribution of microplastics within 5 sediment size classes (>5000 μm, 1000-5000 μm, 250-1000 μm, 250-0.63 μm and < 0.63 μm) were determined for 16 sites within Lambert Channel and ...Baynes Sound, British Columbia, Canada. This region is Canada's premier growing area for the Pacific oyster (Crassostrea gigas). Microplastics were found at all sampling locations indicating widespread contamination of this region with these particles. Three types of microplastics were recovered: microbeads, which occurred in the greatest number (up to 25000/kg dry sediment) and microfibers and microfragments, which were much less in number compared with microbeads and occurred in similar amounts (100-300/kg dry sediment). Microbeads were recovered primarily in the < 0.63 μm and 250-0.63 μm sediment size class, whereas microfragments and microfibers were generally identified in all 5 sediment size classes. Abundance and distribution of the three types of microplastics were spatially dependent with principal component analysis (PCA) indicating that 84 percent of the variation in abundance and distribution was due to the presence of high numbers of microbeads at three locations within the study region. At these sites, microbeads expressed as a percent component of the sediment by weight was similar to key geochemical components that govern trace metal behavior and availability to benthic organisms. Microbeads have been shown to accumulate metals from the aquatic environment, hence in addition to the traditional geochemical components such as silt and organic matter, microplastics also need to be considered as a sediment component that can influence trace metal geochemistry. Our findings have shown that BC's premier oyster growing region is highly contaminated with microplastics, notably microbeads. It would be prudent to assess the degree to which oysters from this region are ingesting microplastics. If so, it would have direct implications for Canada's oyster farming industry with respect to the health of the oyster and the quality of product that is being farmed and sets an example for other shellfish growing regions of the world.
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The purpose of the article is to show the advantages of a new design of a high-voltage rectangular pulse generator. Known analogues combine modules: signal generator; high-voltage key of
N
identical ...transistors (
Q
k
,
k
= 1….
N
) connected in series; gate driver of leading
Q
k
; high-voltage power source, its electromotive force, emf (
E
), feeds all
Q
k
and load (
R
) of the key. In analogs, divider resistors (
r
k
) and snubbers balance equality of voltages
U
k
on all
Q
k
. Under nonideal balance conditions
E
≈ 0.7
NU
max
, where
U
max
is the maximum operating voltage of
Q
k
. The new solution differs in that the high-voltage power source sets not one but
N
emf
E
k
(
E
i
/
E
j
= const (
i
,
j
);
i
≠
j
;
i
,
j =
1, 2, …,
N
) and each
E
k
feeds its
Q
k
through the load
R
k
. Experiments and simulations have revealed advantages of the new design: (1) the simplicity of the circuit and key tuning, (2) the fast transition ON→OFF for all
Q
k
(as
R
k
is small,
R
k
r
k
), (3) the high pulse repetition rate, and (4) the greatly improved balancing of
U
k
voltages allows the
E
k
emf to be set so that Σ
U
k
≈ Σ
U
k
, max
at
U
i
, max
≠
U
k
, max
. The generator with the key based on two different MOSFETs (IXTL2N450 and IXTT1N450HV,
U
max
= 4500 V) and with a source where the
E
2
= 2
E
1
were used to excite vacuum ion emission from liquid Ga-based alloys.
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New directions and trends in nature protection hydraulic engineering are analyzed. The combined use of hydraulic structures, various treatment approaches, and the aesthetic properties of macrophytes, ...allows the creation of effective systems for preventing the pollution of water bodies with such new types of pollutants as microplastics. This is especially true for urban areas where high concentrations of microplastics are observed in stormwater, along with a social need to create green areas.
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The purpose of the paper is to determine the differences in the technique of body inrun position at the beginning of take-off in junior ski jumpers of different qualifications (athletic ...preparedness).
Materials and methods. The study participants were 22 junior ski jumpers aged 14-15 (a group of junior ski jumpers) during the Ukrainian Ski Jumping Championship (October 9, 2010, Vorokhta, Ukraine) and 33 ski jumpers aged 16-17 (a group of senior ski jumpers) who took part in the international competitions “Lotos Cup” in January 2010. The study analyzed the videos of take-offs of 22 athletes aged 14-15 and 33 athletes aged 16-17. The parameters of ski jumping technique and sports results were processed on the basis of video materials of the first competition series.
Results. There are significant differences (p < 0.001) in the mean values of corresponding parameters of the body position at the beginning of take-off. The data point to a tighter tuck of the body of the athletes aged 16-17. The structure coefficients of the first canonical discriminant function indicate that the function is most significantly related to the values of angles 10 (ν); 8 (ζ); 6 (θ): the inclination angle of the segment of the straight line passing through the axes of the hip and ankle joints (ν) towards the direction of the skier’s movement; the inclination angle of the segment of the straight line passing through the general center of body weight and the axis of the ankle joint (ζ) towards the direction of the skier’s movement; the inclination angle of the head towards the trunk (θ). The athletes aged 16-17 differ from the athletes aged 14-15 by the parameters characterizing the body’s tuck in the starting position – the position at the beginning of take-off.
Conclusions. The unstandardized canonical discriminant function coefficients can be used to classify the levels of proficiency in the body’s tuck in the starting position – the position at the beginning of take-off in athletes aged 14-17.
Hudson Bay, at the southern margin of the Arctic Ocean, receives nearly one-third of Canada’s river discharge and approximately 5.5 Tg of riverine dissolved organic carbon (DOC) annually. Riverine ...DOC fluxes to Hudson Bay are expected to increase with climate change, but how this increase will influence the biogeochemistry of the coastal waters is largely unknown. In particular, the fate of riverine DOC that enters Hudson Bay during the dark, frozen winter period (roughly January to April) is poorly known despite high discharge from the large, regulated rivers of Hudson and James Bays at that time. Few studies have assessed the degradability of riverine DOC transported in winter anywhere across the Arctic, leaving unanswered questions regarding the impact of riverine DOC on the Arctic carbon budget, CO2 fluxes, and local food webs. Here, we assessed the biodegradability of DOC in riverine and coastal waters of southern Hudson Bay in late winter using 45-day incubation experiments. We found 24%–60% of the DOC in the rivers and on average 21% of the DOC in the immediate coastal waters to be biodegradable. Differences in biodegradability appeared to depend on properties of the rivers/watersheds and physical and biochemical processes in the aquatic environments. DOC biodegradability correlated strongly with DOC concentration, which was higher during winter than summer in all studied rivers and higher in the Nelson and Hayes Rivers, draining the Hudson Bay Lowlands than in most previously studied large rivers of the Arctic watershed. The Nelson River, regulated for hydropower production, had the highest winter DOC concentrations and most degradable DOC. The high biodegradability of Hudson Bay riverine DOC in late winter and high concentrations and fluxes of riverine DOC at that time imply strong leverage for future increases in DOC fluxes to impact the carbon cycle of these coastal waters.
The model presented in this work allows simulation of isotopic exchange reactions at chemical equilibrium catalyzed by a glutamine synthetase. To simulate the functioning of the enzyme the algorithm ...based on the stochastic approach was applied. The dependence of exchange rates for 14C and 32P on metabolite concentration was estimated. The simulation results confirmed the hypothesis of the ascertained validity for preferred order random binding mechanism. Corresponding values of K0.5 were also obtained.
Metabolism of glutamate and glutamine in brain is highly dependent on regional distribution and proper regulation of the phosphate activated glutaminase. Being predominantly a mitochondrial enzyme, ...glutaminase has a catalytically active form on the inner mitochondrial membrane, but to date, the exact localization of its active center remains a controversial and unresolved issue. In this paper, we used a multi-compartment kinetic modeling to simulate metabolism of glutamate and glutamine in astrocytes. The simulation results confirmed the experimental hypothesis, in which the active site of glutaminase faces the outer surface of the inner mitochondrial membrane.
The work considers a method for processing signals in a scanning electron microscope equipped with an additional focusing electrode. The method is based on the dependence of signal contrast on the ...potential of a focusing electrode. In turn, the dependence of the signal contrast on the height of the focusing point relative to the base surface of the sample allows us to establish unambiguous agreement: the value of the electrode potential is the height of the beam focusing point above the surface of the sample. The proposed method solves the problem of determining the plane of exact focusing of the electron beam relative to the microrelief of the sample and setting this plane to a given height relative to the base surface of the sample with increased accuracy by changing the potential of the focusing electrode, thereby reducing the time required to correct the position of the beam focusing point.
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