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91.
Concentrations of trace elements (Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Pb, Sb, Se, Sn, Tl, U, V, Zn) and total mercury (THg) were determined in skin samples collected from free-ranging bottlenose dolphin (Tursiops truncatus) populations. Dolphins were captured in the estuarine waters of Charleston (CHS), South Carolina (n=74) and the Indian River Lagoon (IRL), Florida (n=75) during 2003, 2004 and 2005. A subset of the skin tissue samples were used to determine methylmercury (MeHg) levels in CHS (n=17) and IRL (n=8) bottlenose dolphins. Distributions of trace element concentrations by age (adult vs. juvenile), gender (male vs. female) and study area (CHS vs. IRL) were examined. In general, higher elemental skin concentrations were found in CHS adult males than those of IRL adult males, except for THg and MeHg. For CHS dolphins, adult females showed significantly higher THg levels than juvenile females while higher Mn levels were found in juvenile females. For IRL dolphins, adult males showed significantly higher As concentrations than that in juvenile males and females while higher Co and V levels were found in juvenile males than adult males. Of all elements measured in this study, significantly higher levels of Fe, Se and Zn concentrations in skin tissue of both dolphin populations were similar to other studies reported previously. Percentage of MeHg/THg in skin tissue of CHS and IRL dolphin was about 72% and 73%, respectively. Dietary levels of trace elements may play an important role in contributing to concentration differences for As, Co, Mn, Sb, Se, THg and Tl between CHS and IRL dolphins. Total Hg concentrations were significantly correlated with the age of CHS dolphins, while an inverse relationship was detected for Cu, Mn, Pb, U and Zn. The only significant correlation found between trace element concentration and IRL dolphins' age was Mn. Geographic differences in several trace element concentrations (As, Co, Mn, Sb, Se, THg and Tl) in skin tissue may be potentially useful to discriminate between dolphin populations and is a possibility that warrants further investigation. 相似文献
92.
This letter focuses on a possible pitfall that can occur in the DFT calculation of graphite–hydrogen interactions under tokamaks conditions. Calculations based on the BLYP functional, in fact, result in a stable –C2H3 group that other functionals (OLYP, XLYP, PBE and BP) do not confirm. 相似文献
93.
Alessandro Leonardi Franco Furgiuele Stavros Syngellakis Robert J. K. Wood 《Journal of the American Ceramic Society》2009,92(5):1093-1097
In the present paper, an analytical solution for the stress intensity factor in the case of cracks produced by Vickers indenters has been extended to the cases of triangular indenters, i.e., Berkovich and cube-corner. According to the adopted approach, median/radial cracks produced by indentations are modeled as loaded by either a point-force or a symmetric disk-shaped wedge. The wedge diameter is assumed to be equal to the plastic zone size whereas the wedge thickness is evaluated by comparing the wedge volume with the hardness-impression volume. The point-force and the disk-shaped wedge analyses produce an upper and a lower bound, respectively, of the geometry-dependent parameter appearing in the expression for the fracture toughness. The predictions of the present analysis are in good agreement with similar experimental and numerical results. 相似文献
94.
Stavros N. Politis 《Drug development and industrial pharmacy》2017,43(4):545-557
A novel hot melt direct pelletization method was developed, characterized and optimized, using statistical thinking and experimental design tools. Mixtures of carnauba wax (CW) and HPMC K100M were spheronized using melted gelucire 50–13 as a binding material (BM). Experimentation was performed sequentially; a fractional factorial design was set up initially to screen the factors affecting the process, namely spray rate, quantity of BM, rotor speed, type of rotor disk, lubricant–glidant presence, additional spheronization time, powder feeding rate and quantity. From the eight factors assessed, three were further studied during process optimization (spray rate, quantity of BM and powder feeding rate), at different ratios of the solid mixture of CW and HPMC K100M. The study demonstrated that the novel hot melt process is fast, efficient, reproducible and predictable. Therefore, it can be adopted in a lean and agile manufacturing setting for the production of flexible pellet dosage forms with various release rates easily customized between immediate and modified delivery. 相似文献
95.
Performance analysis of a class of GSC receivers over nonidentical Weibull fading channels 总被引:1,自引:0,他引:1
Bithas P.S. Karagiannidis G.K. Sagias N.C. Mathiopoulos P.T. Kotsopoulos S.A. Corazza G.E. 《Vehicular Technology, IEEE Transactions on》2005,54(6):1963-1970
The performance of a class of generalized-selection combining (GSC) receivers operating over independent but nonidentically distributed Weibull fading channels is studied. We consider the case where the two branches with the largest instantaneous signal-to-noise ratio (SNR), from a total of L available, GSC(2, L) are selected. By introducing a novel property for the product of moments of ordered Weibull random variables, convenient closed form expressions for the moments of the GSC(2,L) output SNR are derived. Using these expressions, important performance criteria, such as average output SNR and amount of fading, are obtained in closed form. Furthermore, employing the Pade/spl acute/ approximants theory and the moment-generating function approach, outage and bit-error rate performance are studied. An attempt is also made to identify the equivalency between the Weibull and the Rice fading channel, which is typically used to model the mobile satellite channel. We present various numerical performance evaluation results for different modulation formats and channel conditions. These results are complemented by equivalent computer simulated results which validate the accuracy of the proposed analysis. 相似文献
96.
97.
Diversity reception over generalized-K (KG) fading channels 总被引:2,自引:0,他引:2
Bithas P.S. Mathiopoulos P.T. Kotsopoulos S.A. 《Wireless Communications, IEEE Transactions on》2007,6(12):4238-4243
A detailed performance analysis for the most important diversity receivers operating over a composite fading channel modeled by the generalized-K (Kg) distribution is presented. The Kg distribution has been recently considered as a generic and versatile distribution for the accurate modeling of a great variety of short term fading in conjunction with long term fading (shadowing) channel conditions. For this relatively new composite fading model, expressions for important statistical metrics of maximal ratio combining (MRC), equal gain combining (EGC), selection combining (SC) and switch and stay combining (SSC) diversity receivers are derived. Using these expressions and by considering independent but not necessarily identical distributed fading channel conditions, performance criteria, such as average output signal-to-noise ratio, amount of fading and outage probability are obtained in closed form. Moreover, following the moments generating function (MGF) based approach for MRC and SSC receivers, and the Pade approximants method for SC and EGC receivers, the average bit error probability is studied. The proposed mathematical analysis is complemented by various performance evaluation results which demonstrate the accuracy of the theoretical approach. 相似文献
98.
The mountain pine beetle epidemic is destroying an extensive volume of the lodgepole pine forests being one of the most commercially harvested trees in British Columbia. The purpose of this study was to test the permeability of wood of four different classes regarding the time of the beetle attack. The experiments used the ‘‘falling water’’ unsteady-steady method of measuring superficial air permeability. The results showed that the specific permeability is not significantly different between the infested classes tested. The same conclusion could be reached for comparisons of uninfected and infested wood. 相似文献
99.
100.
Ka Wong Chong Stavros D. Nikolopoulos Leonidas Palios 《Theory of Computing Systems》2004,37(4):527-546
In this paper we consider the problem of computing
the connected components of the complement of a given graph.
We describe a simple sequential algorithm for this problem,
which works on the input graph and not on its complement,
and which for a graph on n vertices and m edges
runs in optimal O(n+m) time.
Moreover, unlike previous linear co-connectivity algorithms,
this algorithm admits efficient parallelization, leading to
an optimal O(log n)-time and O((n+m)log n)-processor
algorithm on the EREW PRAM model of computation.
It is worth noting that, for the related problem
of computing the connected components of a graph, no optimal
deterministic parallel algorithm is currently available.
The co-connectivity algorithms find applications in
a number of problems.
In fact, we also include a parallel recognition algorithm
for weakly triangulated graphs, which takes advantage of
the parallel co-connectivity algorithm and achieves
an O(log2 n) time complexity using
O((n+m2) log n) processors on the EREW PRAM model of computation. 相似文献