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排序方式: 共有58条查询结果,搜索用时 15 毫秒
1.
Riikka Susitaival Ilmari Juva Markus Peuhkuri Samuli Aalto 《Telecommunication Systems》2006,33(1-3):67-88
In this paper we analyze measurements gathered from a 2.5~Gbps link in the Finnish university network (Funet) in 2004. The
traffic is broken down into origin-destination (OD) pair components based on source and destination IP address. We study the
traffic characteristics of these components, and identify four typical representative OD pairs. For these pairs we investigate
the validity of a moving IID Gaussian model. We find that the statistical properties of these OD pairs differ significantly
from each other, with only some of them close to Gaussian. The OD pairs are also found to have some cross-correlation between
each other, contradicting an often made assumption about OD pair independence. Furthermore, the existence of a mean-variance
relation between the OD pairs is studied. We find that there is a relation between mean and variance, but for some periods
of time it is rather weak. 相似文献
2.
I Gonzalez-Gomez I Mononen N Heisterkamp J Groffen V Kaartinen 《Canadian Metallurgical Quarterly》1998,153(4):1293-1300
Aspartylglycosaminuria (AGU) is one of the most common lysosomal storage disorders in humans. A mouse model for AGU has been recently generated through targeted disruption of the glycosylasparaginase gene, and at a young age the glycosyl asparaginase-deficient mice demonstrated many pathological changes found in human AGU patients (Kaartinen V, Mononen I, Voncken J-W, Gonzalez-Gomez I, Heisterkamp N, Groffen J: A mouse model for aspartylglycosaminuria. Nat Med 1996, 2:1375-1378). Our current findings demonstrate that after the age of 10 months, the general condition of null mutant mice gradually deteriorated. They suffered from a progressive motoric impairment and impaired bladder function and died prematurely. A widespread lysosomal hypertrophy in the central nervous system was detected. This neuronal vacuolation was particularly severe in the lateral thalamic nuclei, medullary reticular nuclei, vestibular nuclei, inferior olivary complex, and deep cerebellar nuclei. The oldest animals (20 months old) displayed a clear neuronal loss and gliosis, particularly in those regions, where the most severe vacuolation was found. The severe ataxic gait of the older mice was likely due to the dramatic loss of Purkinje cells, intensive astrogliosis and vacuolation of neurons in the deep cerebellar nuclei, and the severe vacuolation of the cells in vestibular and cochlear nuclei. The impaired bladder function and subsequent hydronephrosis were secondary to involvement of the central nervous system. These findings demonstrate that the glycosylasparaginase-deficient mice share many neuropathological features with human AGU patients, providing a suitable animal model to test therapeutic strategies in the treatment of the central nervous system effects in AGU. 相似文献
3.
Niemi R Martikainen PJ Silvola J Holopainen T 《The Science of the total environment》2002,289(1-3):1-12
Microcosms of a boreal peatland originating from an oligotrophic fen in Eastern Finland were fumigated under four ozone concentrations (0, 50, 100 and 150 ppb O3) in laboratory growth chambers during two separate experiments (autumn and summer) for 4 and 6 weeks, respectively. Ozone effects on Sphagnum mosses and the fluxes of carbon dioxide and methane were evaluated. In both experiments, the three Sphagnum species studied showed only a few significant responses to ozone. In the autumn experiment, membrane permeability of S. angustifolium, measured as conductivity and magnesium leakage, was significantly higher under ozone fumigation (P = 0.005 and < 0.001, respectively), and there was a distinct dose-dependence. S. magellanicum showed no clear responses, either for membrane leakage or pigment content. There were no substantial ozone responses in the gross photosynthesis or net CO2 exchange during the 6-week-long summer experiment, but dark ecosystem respiration was transiently increased by ozone concentration of 100 ppb after 14 days of exposure (P < 0.05). Fumigation with 100 ppb of ozone, however, more than doubled (P < 0.05) methane emission from the peatland monoliths. Our results suggest that increasing tropospheric ozone concentration may cause substantial changes in the carbon gas cycling of boreal peatlands, even though these changes are not closely associated with the changes in Sphagnum vegetation. 相似文献
4.
Rheological properties of aqueous solutions and hydrogels formed by an amphiphilic star block copolymer, poly(acrylic acid)-block-polystyrene (PAA54-b-PS6)4, were investigated as a function of the polymer concentration (Cp), temperature, and added salt concentration. The water-soluble polymer synthesised by atom transfer radical polymerization (ATRP) was found to form hydrogels at room temperature at polymer concentrations, Cp, over 22 g/L due to the interpolymer hydrophobic association of the PS blocks. Increasing Cp leads to stronger elastic networks at room temperature that show a gel-to-solution transition with increasing temperature. Increase of ionic strength decreases the moduli compared with the pure hydrogel but did not affect the gel-sol transition temperature significantly. Small-angle X-ray experiments showed two distinct scattering correlation peaks for samples above the gelling Cp, which indicates the aggregates formed due to hydrophobic association. Upon heating the intensity of the scattering correlation peaks was found to decrease indicating the loss of the network structure due to thermal motion. 相似文献
5.
Riikka Suhonen Ralf Krause Fryderyk Kozlowski Wiebke Sarfert Ralph Pätzold Albrecht Winnacker 《Organic Electronics》2009,10(2):280-288
We have studied the phenomena resulting from the combination of a hole-conducting poly(phenylene vinylene) (PPV) based light emitting polymer with a highly efficient electron injection layer of caesium carbonate (Cs2CO3) in light emitting diodes. A strong dependence between the thickness of the applied Cs2CO3 and the electro-optical performance of the diodes is detected and already with ultrathin Cs2CO3 layers high efficiency diodes are achieved. The Cs2CO3 is shown to diffuse into the polymer layer leading to an increased electron density but also quenching of both electro and photoluminescence when the amount of applied Cs2CO3 is increased. During electrical stressing the electron density decreases assumably through degradation of the n-doping and quenching Cs2CO3 species inducing an unusual increasing luminescence behavior. 相似文献
6.
Riikka Laukkanen‐Ninios Maria Fredriksson‐Ahomaa Hannu Korkeala 《Comprehensive Reviews in Food Science and Food Safety》2014,13(6):1165-1191
Enteropathogenic Yersinia comprising pathogenic Yersinia enterocolitica and Yersinia pseudotuberculosis, are zoonotic pathogens causing foodborne intestinal illness in humans. Y. enterocolitica is common in pork production and pork is associated with infections in humans. Therefore, there is a need to reduce the occurrence and spread of these pathogens within the pork production chain. It would be most effective to control enteropathogenic Yersinia at the farm level. However, at present, feasible intervention methods are lacking and more research is needed. The most effective way to prevent the spread of Y. enterocolitica is to buy piglets from Y. enterocolitica‐negative farms. At slaughterhouses, the occurrence of enteropathogenic Yersinia can be reduced but not completely removed by slaughter hygiene and changing slaughter methods. After slaughter, it is difficult to control enteropathogenic Yersinia, since they can survive and even multiply during cold storage and under modified atmosphere. In addition, current knowledge and actions in both domestic and professional kitchens are insufficient for the prevention of yersiniosis. The significance of Y. pseudotuberculosis carried by pigs is uncertain. Although data are still lacking for pathogenic Y. enterocolitica in many aspects, there is even a greater lack of information regarding Y. pseudotuberculosis in pork production. There is a definite need for further research on these pathogens. 相似文献
7.
Puurunen RL Sajavaara T Santala E Miikkulainen V Saukkonen T Laitinen M Leskelä M 《Journal of nanoscience and nanotechnology》2011,11(9):8101-8107
The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS). In this work, TiO2 films made by atomic layer deposition (ALD) with the TiCl4-H2O process were characterized for their growth, roughness and crystallinity as function of deposition temperature (110-300 degrees C), film thickness (up to approximately 100 nm) and substrate (thermal SiO2, RCA-cleaned Si, Al2O3). TiO2 films got rougher with increasing film thickness and to some extent with increasing deposition temperature. The substrate drastically influenced the crystallization behaviour of the film: for films of about 20 nm thickness, on thermal SiO2 and RCA-cleaned Si, anatase TiO2 crystal diameter was about 40 nm, while on Al2O3 surface the diameter was about a micrometer. The roughness could be controlled from 0.2 nm up to several nanometers, which makes the TiO2 films candidates for adhesion engineering in MEMS. 相似文献
8.
Mika Horttanainen Juha Kaikko Riikka Bergman Minna Pasila-Lehtinen Janne Nerg 《Applied Thermal Engineering》2010,30(2-3):110-118
Expectations on wastewater sludge treatment and recovery of its energy and material contents are increasing because of the tightening legislation and the obligation to reduce environmental impacts of sludge disposal. The objective of this study was to analyze the performance of a heat and power generating sludge combustion plant from technical and economical viewpoints and to compare the studied concept to optional sludge treatment technologies. The plant performance was modeled for sewage sludge produced by approximately 200,000 inhabitants. Two plant sizes below 1000 kWe range were investigated, the smaller plant using sludge as the only fuel and the larger plant with wood chips as the additional fuel. The plants were compared with heat-only plants of similar size. The payback periods for heat-only plants are typically shorter than with the cogenerating plants because the changes in plant investment affect stronger the economy than do the revenues from selling electricity. The gate fee of sludge treatment has the strongest effect on the payback period. The selection of the plant concept (cogeneration, heat only or pure electricity generation) is, however, affected more by the local demand of heat and electricity than pure economy. The selection of the optimal technology for sludge treatment is a complicated task. The studied concept can be the optimal choice, for example, if there is no cement kiln or co-combustion possibility near the source of sludge, if there is no land enhancement demand for the digested sludge, or if the energy surplus from combustion compared to anaerobic digestion is considered more valuable than nutrient recovery possibility from digestion. If the new technology concept is found competitive, it still has to meet the challenge of acceptability from the business, social and cultural points of view. 相似文献
9.