Results 1 - 10 of 10813
Results 1 - 10 of 10813. Search took: 0.029 seconds
|Sort by: date | relevance|
[en] MAXINE is an EXCEL© spreadsheet, which is used to estimate dose to individuals for routine and accidental atmospheric releases of radioactive materials. MAXINE does not contain an atmospheric dispersion model, but rather doses are estimated using air and ground concentrations as input. Minimal input is required to run the program and site specific parameters are used when possible. Complete code description, verification of models, and user’s manual have been included.
[en] Ensemble modeling (EM), the creation of multiple atmospheric simulations for a given time period, has become an essential tool for characterizing uncertainties in model predictions. We explore two novel ensemble modeling techniques: (1) perturbation of model parameters (Adaptive Programming, AP), and (2) data assimilation (Ensemble Kalman Filter, EnKF). The current research is an extension to work from last year and examines transport on a small spatial scale (<100 km) in complex terrain, for more rigorous testing of the ensemble technique. Two different release cases were studied, a coastal release (SF6) and an inland release (Freon) which consisted of two release times. Observations of tracer concentration and meteorology are used to judge the ensemble results. In addition, adaptive grid techniques have been developed to reduce required computing resources for transport calculations. Using a 20- member ensemble, the standard approach generated downwind transport that was quantitatively good for both releases; however, the EnKF method produced additional improvement for the coastal release where the spatial and temporal differences due to interior valley heating lead to the inland movement of the plume. The AP technique showed improvements for both release cases, with more improvement shown in the inland release. This research demonstrated that transport accuracy can be improved when models are adapted to a particular location/time or when important local data is assimilated into the simulation and enhances SRNL's capability in atmospheric transport modeling in support of its current customer base and local site missions, as well as our ability to attract new customers within the intelligence community.
[en] We have analyzed the transport regimes and the asymptotic forms of the impurity concentration in a randomly inhomogeneous fractal medium in the case when an impurity source is surrounded by a weakly permeable degrading barrier. The systematization of transport regimes depends on the relation between the time t0 of emergence of impurity from the barrier and time t* corresponding to the beginning of degradation. For t0 < t*, degradation processes are immaterial. In the opposite situation, when t0 > t*, the results on time intervals t < t* can be formally reduced to the problem with a stationary barrier. The characteristics of regimes with t* < t < t0 depend on the scenario of barrier degradation. For an exponentially fast scenario, the interval t* < t < t0 is very narrow, and the transport regime occurring over time intervals t < t* passes almost jumpwise to the regime of the problem without a barrier. In the slow power-law scenario, the transport over long time interval t* < t < t0 occurs in a new regime, which is faster as compared to the problem with a stationary barrier, but slower than in the problem without a barrier. The asymptotic form of the concentration at large distances from the source over time intervals t < t0 has two steps, while for t > t0, it has only one step. The more remote step for t < t0 and the single step for t > t0 coincide with the asymptotic form in the problem without a barrier.
[en] Post-exposure bioassays are used in environmental assessment as a cost-effective tool, but the effects of organism's recovery after exposure to pollutant has not yet been addressed in detail. The recoveries of post-exposure feeding rates after being exposed to two sublethal concentrations of cadmium during two different exposure periods (48 h and 96 h) were evaluated under laboratory conditions using the estuarine isopod Cyathura carinata. Results showed that feeding depression was a stable endpoint up to 24 h after cadmium exposure, which is useful for ecotoxicological bioassays. - Highlights: • We studied recovery of post-exposure feeding rates 48–96 h after cadmium exposure. • The assay is based on the isopod Cyathura carinata. • Post-exposure feeding inhibition is a stable sublethal endpoint
[en] We have proposed a peculiar model of the plasma of dense metal vapors, containing atoms embedded into the electron jelly, as well as free (thermally ionized) electrons and ions. The main feature of the model is the presence of the electron jelly existing at any density of the atomic component. The number of electrons in the jelly increases under compression. The process of its formation can be called the “cold” ionization, or pressure ionization. The composition of the gas–plasma mixture, including the concentration of atoms and electrons in the jelly, as well as the concentration of free thermally ionized electrons and ions, has been calculated. The conductivity of dense vapors is determined by the sum of the conductivities of thermal electrons (which is calculated using the Frost formula) and jelly electrons (which is calculated by the Regel–Ioffe formula for the minimal metal-type conductivity). The concentration of thermal electrons decreases and the concentration of jelly electrons increases upon compression of the vapor. Accordingly, the conductivity varies from the conductivity of thermal electrons to the conductivity of jelly electrons, continuously passing through the minimum. The calculated values of the conductivity of supercritical metal vapors are in satisfactory agreement with experimental results.
[en] The Old Rifle Site is a former vanadium and uranium ore-processing facility located adjacent to the Colorado River and approximately 0.3 miles east of the city of Rifle, CO. The former processing facilities have been removed and the site uranium mill tailings are interned at a disposal cell north of the city of Rifle. However, some low level remnant uranium contamination still exists at the Old Rifle site. In 2002, the United States Nuclear Regulatory Commission (US NRC) concurred with United States Department of Energy (US DOE) on a groundwater compliance strategy of natural flushing with institutional controls to decrease contaminant concentrations in the aquifer. In addition to active monitoring of contaminant concentrations, the site is also used for DOE Legacy Management (LM) and other DOE-funded small-scale field tests of remediation technologies. The purpose of this laboratory scale study was to evaluate the effectiveness of a hydroxyapatite (Ca10(PO4)6(OH)2) permeable reactive barrier and source area treatment in Old Rifle sediments. Phosphate treatment impact was evaluated by comparing uranium leaching and surface phase changes in untreated to PO4-treated sediments. The impact of the amount of phosphate precipitation in the sediment on uranium mobility was evaluated with three different phosphate loadings. A range of flow velocity and uranium concentration conditions (i.e., uranium flux through the phosphate-treated sediment) was also evaluated to quantify the uranium uptake mass and rate by the phosphate precipitate.
[en] Chloride ion (Cl−) is one of the most abundant anions in our body. Increasing evidence suggests that Cl− plays fundamental roles in various cellular functions. We have previously reported that electroneutral cation-chloride cotransporters, such as Na+-K+-2Cl− cotransporter 1 (NKCC1) and K+-Cl− cotransporter 1 (KCC1), are involved in neurite outgrowth during neuronal differentiation. In the present study, we studied if there is correlation between intracellular Cl− concentrations ([Cl−]i) and the length of growing neurites. We measured [Cl−]i in the cell body and growing neurite tips using halide-sensitive fluorescent dye N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE), revealing that [Cl−]i in the tip of growing neurite was higher than that in cell body in a single cell. Importantly, there was a significant positive correlation between the length of growing neurite and [Cl−]i in neurite tip. Bumtanide (BMT), an inhibitor of NKCC1, significantly inhibited neurite outgrowth and decreased [Cl−]i in neurite tip. The results obtained in the present study and our previous studies together strongly suggest that high [Cl−]i in neurite tip region is crucial for efficient neurite outgrowth. - Highlights: • Intracellular Cl− concentrations ([Cl−]i) in the tip of growing neurite is higher than that in cell body in a single cell. • There is a significant positive correlation between the length of growing neurite and [Cl−]i in neurite tip. • Bumetanide significantly inhibits neurite outgrowth and decreased [Cl−]i in neurite tip. • High [Cl−]i in neurite tip region is crucial for efficient neurite outgrowth.
[en] In this study, we examined whether the peroxisome proliferator-activated receptor γ (PPARγ) agonists, ciglitazone (CGZ) and troglitazone (TGZ), induce cell death in human cervical cancer HeLa cells. The cells were treated with a range of CGZ or TGZ doses for 24 or 48 h. Low concentrations of CGZ (≤10 μM) or TGZ (≤20 μM) had no effect on cell viability whereas higher doses induced cell death in a time- and dose-dependent manner as evidenced by the detection of activated caspase-3 and PARP cleavage. Treatment with the PPARγ antagonist GW9662 followed by PPARγ agonists did not increase CGZ- or TGZ-induced cell death, indicating that PPARγ agonists induced HeLa cell death independently of PPARγ. Moreover, ERK1/2 activation was observed at a CGZ concentration of 25 μM and a TGZ concentration of 35 μM, both of which induced cell death. To elucidate the role of ERK1/2 activated by the two PPARγ agonists, the effect of U0126, an inhibitor of ERK1/2, on PPARγ-agonist-induced cell death was examined. Treatment with 10 or 20 μM U0126 followed by CGZ or TGZ induced the down-regulation of ERK1/2 activity and a decrease in Bcl-2 expression accompanied by the collapse of mitochondrial membrane potential, which in turn significantly enhanced CGZ- or TGZ-induced apoptotic cell death. Our results suggest that PPARγ agonists are capable of inducing apoptotic cell death in HeLa cells independently of PPARγ and that inhibition of ERK1/2 activity offers a strategy to enhance the cytotoxicity of PPARγ agonists in the treatment of cervical cancer. - Highlights: • The PPARγ agonists CGZ and TGZ induce apoptotic cell death in HeLa cells. • CGZ or TGZ induces apoptotic cell death independently of PPARγ in HeLa cells. • Inhibition of ERK1/2 enhances CGZ- or TGZ-induced cell death via the collapse of MMP.
[en] The dimensions of accumulation of 90Sr and 137Cs by mushrooms depends on the stores of forest litter: The greater they are, the higher the concentration. As the nuclides migrate from the forest litter, the dimensions of their accumulation decrease: In the tenth year of the investigation the concentration of 90Sr in mushrooms had diminished by 1.5-3 times; and 137Cs, by as much as 30 times. The fruit bodies of mushrooms accumulate 2.5-5 times more 137Cs, and in individual cases up to 40 times more, than 90Sr. The maximum amount of 90Sr and 137Cs is accumulated by annulated boletus; the minimum amount, by rough boletus
[en] The extended DLVO (XDLVO) theory was applied to elucidate the potential effects of CeO2 nanoparticles (CeO2 NPs) on sludge aggregation and the role of extracellular polymeric substances (EPS). In this study, seven different concentrations of CeO2 NPs were added to activated sludge cultured in sequencing batch reactors (SBRs) and compared with a control test that received no CeO2 NPs. After exposure to 50 mg/L CeO2 NPs, a negligible change (p>0.1) occurred in the sludge volume index (SVI), whereas the flocculability and aggregation of the sludge decreased by 18.8% and 11.2%, respectively, resulting in a high effluent turbidity. The XDLVO theory demonstrated that the adverse effects of the CeO2 NPs on sludge aggregation were due to an enhanced barrier energy. Compared to the van der Waals energies (WA) and the electric double layer (WR), the acid-base interaction (WAB) markedly changed for the various concentrations of CeO2 NPs. The EPS played a decisive role in the sludge surface characteristics, as the removal of EPS equals to the negative effects induced by 5–10 mg/L CeO2 NPs on the sludge flocculability and aggregation. The presence of CeO2 NPs induced negative contributions to the tight boundary EPS (TB-EPS) and core bacteria while positive contributions to the total interaction energy of the loose boundary EPS (LB-EPS). - Highlights: • CeO2 NPs adversely affected the flocculability and aggregation of the sludge. • The presence of CeO2 NPs increased the energy barrier and led to a stable suspension. • The removal of EPS equals to the negative effects induced by 5–10 mg/L CeO2 NPs. • The acid-base interaction was dominate and markedly changed for the CeO2 NPs. • CeO2 NPs induced negative contributions to the TB-EPS while positive to the LB-EPS.