Range Of Effects Research Articles

Biologic risk and source diagnose of 16 PAHs from Haihe River Basin, China

Surface sediments of rivers can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations. As to pollution control and remediation of watershed, large-scale and further background data on PAHs in China were required urgently. Spatial distribution and compositional characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Haihe River Basin were investigated. A method based on effects range (ER) was used to assess ecosystem risk of ΣPAHs (the total of 16 PAH) sensitively and accurately. The results indicated that ΣPAHs content levels ranged from 257 to 16901 μg·kg−1 dry weight. The lower rings predominated in the samples, and 2-, 3-, 4-, 5- and 6-ring PAHs accounted for 12%, 21%, 30%, 30%, and 7% respectively in total PAHs. The ratio of Fl / (Fl + Py) uniformly distributed in the interval 0.20–0.80, indicating that it may be affected by petroleum origin, oil combustion, biomass and coal combustion jointly. ΣPAHs in Cetian (S6), Dongwushi (S19), Handan (S20), Aixinzhuang (S21) and Tianjin (S37) exceeded effects range low (ERL), in which biologic effects were in a medium level with an adverse effect on biologic organisms. Thus, it is necessary to strengthen the PAHs monitoring and research of the Haihe River Basin.

Analytic Continuation of Scattering Function and Asymptotic Normalization Constants for 6Li

A new method of determining asymptotic normalization coefficients (ANC) corresponding to the two-channel virtual process A → B + C is suggested. The method makes use of the Coulomb-modified effective range (ER) expansion for the two-channel elastic BC scattering. The coefficients of the ER expansion are found using the results of the phase-shift analysis of the BC scattering. Then the ER expansion is analytically continued in energy to the pole corresponding to the bound state A. The ANC is directly related to the residue of the BC scattering amplitude at that pole. The method suggested is applied to the 6Li nucleus in the α + d channel. The ANCs for the S and D states of the relative αd motion are evaluated.

Reliability Analysis of One-Hop Safety-Critical Broadcast Services in VANETs

Reliability is an important issue for safety-critical broadcast services in vehicular ad hoc networks (VANETs). So far, most investigations of such broadcast networks focus on multihop connectivity, taking all one-hop links for granted. In this paper, four reliability metrics for one-hop broadcast communication in VANETs, including the packet reception rate (PRR), the packet delivery ratio (PDR), the node successful packet delivery probability (PDP), and the effective range (ER), are introduced and evaluated analytically and by simulations. Expressions of these reliability metrics for one-hop broadcast in IEEE-802.11-based 1-D VANETs are derived with consideration of the IEEE 802.11 distributed coordination function (DCF), the hidden terminal problem, and collisions caused by concurrent transmissions. The impacts of network parameters such as distinct transmission, carrier sensing, and interference ranges; the density of nodes in the networks; the distances of receivers to the senders; the message generation rates; the backoff window sizes; and the channel data rates on the reliability of the broadcast communication in VANETs are investigated and discussed. As an example, the proposed model is applied to the evaluation of the dedicated short-range communication (DSRC) safety-critical message propagation in a highway setting. As a result, some important observations to the design and analysis of such communication systems are provided.

Mendel's Accountant: a biologically realistic forward-time population genetics program

Mendel's Accountant (hereafter referred to as Mendel ) is a user-friendly biologically realistic simulation program for investigating the processes of mutation and selection in sexually reproducing diploid populations. Mendel represents an advance over previous forward-time programs in that it incorporates several new features that enhance biological realism including: (a) variable mutation effect and (b) environmental variance that affects phenotype. In Mendel, as in nature, mutations have a continuous range of effect from lethal to beneficial, and may vary in expression from fully dominant to fully recessive. Mendel allows mutational effects to be combined in either a multiplicative or additive manner to determine overall genotypic fitness and provides the option of either truncation or probability selection. Environmental variance is specified via a heritability parameter and a non-scaling noise standard deviation. Mendel is computationally efficient, so many problems of interest can be run on ordinary personal computers. Parallelized using MPI, Mendel readily handles large population size and population substructure on cluster computers. We report a series of validation experiments which show consistently that Mendel results conform to theoretical predictions. Its graphical user interface is designed to make problem specification intuitive and simple, and it provides a variety of visual representations in the program output. The program is a versatile research tool and is useful also as an interactive teaching resource.

Atypical Antipsychotics: Mechanism of Action

Although the principal brain target that all antipsychotic drugs attach to is the dopamine D2 receptor, traditional or typical antipsychotics, by attaching to it, induce extrapyramidal signs and symptoms (EPS). They also, by binding to the D2 receptor, elevate serum prolactin. Atypical antipsychotics given in dosages within the clinically effective range do not bring about these adverse clinical effects. To understand how these drugs work, it is important to examine the atypical antipsychotics' mechanism of action and how it differs from that of the more typical drugs. This review analyzes the affinities, the occupancies, and the dissociation time-course of various antipsychotics at dopamine D2 receptors and at serotonin (5-HT) receptors, both in the test tube and in live patients. Of the 31 antipsychotics examined, the older traditional antipsychotics such as trifluperazine, pimozide, chlorpromazine, fluphenazine, haloperidol, and flupenthixol bind more tightly than dopamine itself to the dopamine D2 receptor, with dissociation constants that are lower than that for dopamine. The newer, atypical antipsychotics such as quetiapine, remoxipride, clozapine, olanzapine, sertindole, ziprasidone, and amisulpride all bind more loosely than dopamine to the dopamine D2 receptor and have dissociation constants higher than that for dopamine. These tight and loose binding data agree with the rates of antipsychotic dissociation from the human-cloned D2 receptor. For instance, radioactive haloperidol, chlorpromazine, and raclopride all dissociate very slowly over a 30-minute time span, while radioactive quetiapine, clozapine, remoxipride, and amisulpride dissociate rapidly, in less than 60 seconds. These data also match clinical brain-imaging findings that show haloperidol remaining constantly bound to D2 in humans undergoing 2 positron emission tomography (PET) scans 24 hours apart. Conversely, the occupation of D2 by clozapine or quetiapine has mostly disappeared after 24 hours. Atypicals clinically help patients by transiently occupying D2 receptors and then rapidly dissociating to allow normal dopamine neurotransmission. This keeps prolactin levels normal, spares cognition, and obviates EPS. One theory of atypicality is that the newer drugs block 5-HT2A receptors at the same time as they block dopamine receptors and that, somehow, this serotonin-dopamine balance confers atypicality. This, however, is not borne out by the results. While 5-HT2A receptors are readily blocked at low dosages of most atypical antipsychotic drugs (with the important exceptions of remoxipride and amisulpride, neither of which is available for use in Canada) the dosages at which this happens are below those needed to alleviate psychosis. In fact, the antipsychotic threshold occupancy of D2 for antipsychotic action remains at about 65% for both typical and atypical antipsychotic drugs, regardless of whether 5-HT2A receptors are blocked or not. At the same time, the antipsychotic threshold occupancy of D2 for eliciting EPS remains at about 80% for both typical and atypical antipsychotics, regardless of the occupancy of 5-HT2A receptors. The "fast-off-D2" theory, on the other hand, predicts which antipsychotic compounds will or will not produce EPS and hyperprolactinemia and which compounds present a relatively low risk for tardive dyskinesia. This theory also explains why L-dopa psychosis responds to low atypical antipsychotic dosages, and it suggests various individualized treatment strategies.

Removing symbiotic Wolbachia bacteria specifically inhibits oogenesis in a parasitic wasp.

Wolbachia are bacteria that live in the cells of various invertebrate species to which they cause a wide range of effects on physiology and reproduction. We investigated the effect of Wolbachia infection in the parasitic wasp, Asobara tabida Nees (Hymenoptera, Braconidae). In the 13 populations tested, all individuals proved to be infected by Wolbachia. The removal of Wolbachia by antibiotic treatment had a totally unexpected effect-aposymbiotic female wasps were completely incapable of producing mature oocytes and therefore could not reproduce. In contrast, oogenesis was not affected in treated Asobara citri, a closely related species that does not harbor Wolbachia. No difference between natural symbiotic and cured individuals was found for other adult traits including male fertility, locomotor activity, and size, indicating that the effect on oogenesis is highly specific. We argue that indirect effects of the treatments used in our study (antibiotic toxicity or production of toxic agents) are very unlikely to explain the sterility of females, and we present results showing a direct relationship between oocyte production and Wolbachia density in females. We conclude that Wolbachia is necessary for oogenesis in these A. tabida strains, and this association would seem to be the first example of a transition from facultative to obligatory symbiosis in arthropod-Wolbachia associations.

Soil solution chemistry of contrasting soils amended with heavy metals

The soil solution chemistry of heavy metal amended soils is of great importance in assessing the bioavailability of heavy metals and their toxicity to the soil biota. Three contrasting soils were amended with Cd(II), Cu(II), Ni(II), Pb(II), Zn(II), and Cr(III) nitrate salts at rates of 10–100 mmol/kg. This concentration range was chosen to encompass a wide range of effects on sensitive soil biochemical properties as part of a larger project. Soil solutions were extracted and analysed for pH, and for concentrations of heavy metals, and major cations and anions. Heavy metal speciation was calculated with the GEOCHEM-PC model. Heavy metal concentrations in the soil solutions increased both in absolute terms and as a percentage of added heavy metal as amendment rates increased. This observation is due to decreasing specific adsorption (caused by decreasing pH induced by the amendments), and to increasing saturation of cation exchange sites. For all 3 soils, the percentage increase commonly follows the order Cr(III) < Pb < Cu < Ni < Cd < Zn. The percentage of each metal held in the soil solution increased from soil to soil as cation exchange capacity, and therefore sorptivity, decreased. Both the concentration and activity of free heavy metal ions were substantially lower than the corresponding total metal concentration. This was ascribed to ion-pairing of metal ions with anions, particularly nitrate introduced in the amending solutions, as well as to increases in ionic strength as a result of amendment. Metal-anion species were mainly inorganic but where Cu and Pb were relatively low in concentration because of strong adsorption by the soils, organic complexation was likely to be significant. Speciation trends were similar for the 3 soils but different in magnitude.

Modification of Effective-Range Theory in the Presence of a Long-Range (r−4) Potential

Modification of Effective-Range Theory in the Presence of a Long-Range (<i>r</i>−4) Potential