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41.
Roman Jandarov Murali Haran Matthew Ferrari 《Journal of Agricultural, Biological & Environmental Statistics》2012,17(3):395-416
The timing and size of many infectious disease outbreaks depend on climatic influences. Meningitis is an example of such a disease. Every year countries in the so-called African meningitis belt are afflicted with meningococcal meningitis disease outbreaks. The timing of these outbreaks coincide with the dry season that starts in February and ends in late May. There are two main hypotheses about this strong seasonal effect. The first hypothesis assumes that during the dry season there is an increase in the risk that an individual will transition from being an asymptomatic carrier to having invasive disease. The second hypothesis states that the incidence of meningitis increases due to higher transmission of the infection during the dry season. These two biological hypotheses suggest dynamics that would necessitate different public health responses: the first would result in broadly correlated outbreak dynamics, and thus a regional vaccination response; the second would result in locally correlated outbreaks, spreading from location to location, for which a localized response may be effective in containing regional spread. In this paper, we develop a statistical model to investigate these hypotheses. Easily interpretable parameters of the model allow us to study and compare differences in the attack rates, rates of transmission and the possible underlying environmental effect during the dry and non-dry seasons. Standard maximum likelihood or Bayesian inference for this model is infeasible as there are potentially tens of thousands of latent variables in the model and each evaluation of the likelihood is expensive. We therefore propose an approximate Bayesian computation (ABC) approach to infer the unknown parameters. Using simulated data examples, we demonstrate that it is possible to learn about some of the important parameters of our model using our methodology. We apply our modeling and inferential approach to data on cases of meningitis for 34 communities in Nigeria from Medecins Sans Frontières (MSF) and World Health Organization (WHO) for 2009. For this particular data set we are able to find weak evidence in favor of the first hypothesis, suggesting a regional vaccination response. 相似文献
42.
Takuji Sawamoto Ryusuke Hatano Masato Shibuya Kunihide Takahashi Alexander P. Isaev Roman V. Desyatkin 《Soil Science and Plant Nutrition》2013,59(4):493-501
Abstract The effect of sucrose on the growth of rice plants under gnotobiotic conditions was studied at test tube scale in vinyl isolators under weak or strong light. Under weak light (500 lux) the growth of rice plants on agar medium containing only inorganic nutrients during the 20 days after transplanting stopped at 3rd leaf stage, whereas plants on agar medium containing inorganic nutrient plus 2% sucrose grew to 5th or 6th leaf stage. Under strong light (1.5 × 104 lux) the stage of tillering was promoted by supplying sucrose. The growth of rice plants in pot-hydroculture under weak light had the same tendency as that obtained in test tube culture under weak light. Considering the concentration of inorganic elements in rice shoots, it seems most likely that the uptake of inorganic elements. especially phosphorus and potassium, was enhanced by the supplements of 2% sucrose under weak light. An increase of calcium and manganese uptake was observed in plants grown in medium containing 2% sucrose compared with that of plants grown in inorganic medium alone under strong light. The uptake of inorganic elements from medium containing inorganic nutrients plus 2% sucrose depended chiefly on light energy under strong light in the phytotron used. 相似文献
43.
Jason?M.?ConderEmail author Roman?P.?LannoEmail author 《Journal of Soils and Sediments》2003,3(1):13-20
Background. Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy
metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as
earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms,
total earthworm metal concentrations may not relate well with toxicity.
Objective The objectives of this research were to: i) develop LD50s (total earthworm metal concentration associated with 50% mortality) for Cd, Pb, and Zn; ii) evaluate the LD50 for Zn in a lethal Zn-smelter soil; iii) evaluate the lethal mixture toxicity of Cd, Pb, and Zn using earthworm metal concentrations
and the toxic unit (TU) approach; and iv) evaluate total and fractionated earthworm concentrations as indicators of sublethal
exposure.
Methods Earthworms (Eisenia fetida (Savigny)) were exposed to artificial soils spiked with Cd, Pb, Zn, and a Cd-Pb-Zn equitoxic mixture to estimate lethal CBRs
and mixture toxicity. To evaluate the CBR developed for Zn, earthworms were also exposed to Zn-contaminated field soils receiving
three different remediation treatments. Earthworm metal concentrations were measured using a procedure devised to isolate
toxicologically active metal burdens via separation into cytosolic and pellet fractions.
Results and Discussion Lethal CBRs inducing 50% mortality (LD50, 95% CI) were calculated to be 5.72 (3.54-7.31), 3.33 (2.97-3.69), and 8.19 (4.78-11.6) mmol/kg for Cd, Pb, and Zn, respectively.
Zn concentrations of dead earthworms exposed to a lethal remediated Zn-smelter soil were 3-fold above the LD50 for Zn and comparable to earthworm concentrations in lethal Zn-spiked artificial soils, despite a 14-fold difference in total
soil Zn concentration between lethal field and artificial soils. An evaluation of the acute mixture toxicity of Cd, Pb, and
Zn in artificial soils using the Toxic Unit (TU) approach revealed an LD50 (95% CI) of 0.99 (0.57-1.41) TU, indicating additive toxicity.
Conclusions Total Cd, Pb, and Zn concentrations in earthworms were good indicators of lethal metal exposure, and enabled the calculation
at LD50s for lethality. The Zn-LD50 developed in artificial soil was applicable to earthworms exposed to remediated Zn-smelter soil, despite a 14-fold difference
in total soil Zn concentrations. Mixture toxicity evaluated using LD50s from each single metal test indicated additive mixture toxicity among Cd, Pb, and Zn. Fractionation of earth worm tissues
into cytosolic and pellet digests yielded mixed results for detecting differences in exposure at the sublethal level
Recommendation and Outlook CBRs are useful in describing acute Cd, Pb, and Zn toxicity in earthworms, but linking sublethal exposure to total and/or
fractionated residues may be more difficult. More research on detoxification, regulation, and tissue and subcellular partitioning
of heavy metals in earthworms and other invertebrates is needed to establish the link between body residue and sublethal exposure
and toxicity. Keywords: Bioavailability; Cd; critical body residues; earthworms; metals; Pb; soil; Zn
An erratum to this article is available at . 相似文献
44.
Effect of temperature on growth and survival of maraena whitefish Coregonus maraena (Bloch 1779) larvae in controlled conditions 下载免费PDF全文
Roman Sebesta Dariusz Kucharczyk Joanna Nowosad Mateusz Sikora Vlastimil Stejskal 《Aquaculture Research》2018,49(9):3151-3157
This 28‐day study investigated the effect of three rearing temperatures, 11, 15 and 19°C, on survival and growth of maraena whitefish fry in a recirculating aquaculture system. Three groups of larvae in three repetitions were reared in recirculating system. Each group comprised 200 larvae. Feeding level was fixed at 500–700 Artemia sp. metanauplii per fish per day. Larvae were fed fresh live brine shrimp at 10 ml/tank every 3 hr. Significantly higher body weight (p = 0.00), total length (p = 0.00), larval yield (p = 0.00) and condition factor (p = 0.00) were obtained at 19°C compared to 15 and 11°C, as well as at 15°C compared to 11°C. Significantly higher survival (p = 0.00) was observed in larvae reared at 11 and 15°C compare to 19°C and no significant differences were observed between 11°C compared to 15°C. No significant differences in size heterogeneity among treatments were found (p = 0.46). In larviculture, the optimal assessed temperature for growth of maraena whitefish was 19°C, with highest survival observed at 11°C, at the end of this 28 days trial. The findings in this study apply to the particular study location and may not be applicable more broadly. 相似文献
45.
Körner C Asshoff R Bignucolo O Hättenschwiler S Keel SG Peláez-Riedl S Pepin S Siegwolf RT Zotz G 《Science (New York, N.Y.)》2005,309(5739):1360-1362
Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees. 相似文献
46.
Alexandra S. Silchenko Anatoly I. Kalinovsky Sergey A. Avilov Pelageya V. Andrijaschenko Roman S. Popov Pavel S. Dmitrenok Ekaterina A. Chingizova Vladimir I. Kalinin 《Marine drugs》2020,18(11)
Six new monosulfated triterpene tetra-, penta- and hexaosides, namely, the kurilosides A1 (1), A2 (2), C1 (3), D (4), E (5) and F (6), as well as the known earlier kuriloside A (7), having unusual non-holostane aglycones without lactone, have been isolated from the sea cucumber Thyonidium (= Duasmodactyla) kurilensis (Levin) (Cucumariidae, Dendrochirotida), collected in the Sea of Okhotsk near Onekotan Island from a depth of 100 m. Structures of the glycosides were established by 2D NMR spectroscopy and HR-ESI mass spectrometry. Kurilosides of the groups A and E contain carbohydrate moieties with a rare architecture (a pentasaccharide branched by C(4) Xyl1), differing from each other in the second monosaccharide residue (quinovose or glucose, correspondingly); kurilosides of the group C are characterized by a unique tetrasaccharide branched by a C(4) Xyl1 sugar chain; and kurilosides of the groups D and F are hexaosides differing from each other in the presence of an O-methyl group in the fourth (terminal) sugar unit. All these glycosides contain a sulfate group at C-6 of the glucose residue attached to C-4 Xyl1 and the non-holostane aglycones have a 9(11) double bond and lack γ-lactone. The cytotoxic activities of compounds 1–7 against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells and erythrocytes were studied. Kuriloside A1 (1) was the most active compound in the series, demonstrating strong cytotoxicity against the erythrocytes and JB-6 cells and a moderate effect against Neuro 2a cells. 相似文献
47.
Roman Gancarz Witold Wielkopolski Elbieta Jaskuska Pawel Kafarski Barbara Lejczak Przemyslaw Mastalerz Jan Sylwester Wieczorek 《Pest management science》1985,16(3):234-238
9-Aminofluoren-9-ylphosphine oxides and the corresponding 9-hydroxy analogues were synthesised and evaluated for herbicidal activity using Spirodela oligorrhiza (Kurz.) Hegelm. All the test compounds were highly active at concentrations of about 10 μM and were comparable with the corresponding phosphonic esters. 相似文献
48.
Barbara Lejczak Pawel Kafarski Roman Gancarz Elzbieta Jaskulska Przemyslaw Mastalerz Jan Sylwester Wieczorek Marta Krl 《Pest management science》1985,16(3):227-233
Peptides of 9-aminofluoren-9-ylphosphonic or 1-aminocyclohexylphosphonic acids were synthesised and found to have typical morphactin activity when tested on Lepidium sativum and Triticum vulgare. The observed effects included root elongation with simultaneous stem shortening. The results obtained indicate that these phosphonic acid derivatives of cyclohexylamine and fluoren-9-ylamine may have a similar mechanism of action. 相似文献
49.
Hubert Wojtasek Piotr Wieczorek Barbara Lejczak Bogdan Boduszek Roman Gancarz Pawel Kafarski 《Pest management science》1991,32(2):245-252
A series of derivatives of 9-aminofluoren-9-ylphosphonic acid (phosphonic analogues of morphactins) were synthesized and screened for herbicidal activity against Lepidium sativum, Cucumis sativus and Lycopersicon esculentum. Ethyl 9-(N-alkylamino)fluoren-9-yl(phenyl)phosphinates appeared to be equipotent with glyphosate and thus may be recognized as new lead compounds for further structural modifications. 相似文献
50.
Timothy A Georoff Priscilla H Joyner John P Hoover Mark E Payton Roman M Pogranichniy 《Journal of zoo and wildlife medicine》2008,39(3):335-341
Laboratory records of serology results from captive macropodidae sampled between 1997 and 2005 were reviewed to assess the seroprevalence of retrovirus exposure. Serum samples from 269 individuals (136 males, 133 females) representing 10 species of macropods housed in 31 North American captive collections were analyzed for retrovirus antibody using an indirect immunofluorescent assay. The prevalence of positive antibody titers comparing male versus female, between species, between age groups, and among animals with identified parentage was examined by nonparametric statistical analyses. Median age of animals at time of sample collection was 36 mo (range 2-201 mo). Total percentage seropositive was 20.4%. Serum antibody was detected in 31 of 47 (66.0%) tammar wallaby (Macropus eugenii), nine of 24 (37.5%) yellow-footed rock wallaby (Petrogale xanthopus), four of 11 (36.4%) swamp wallaby (Wallabia bicolor), 10 of 80 (12.5%) red-necked wallaby (Macropus rufogriseus), and one of 54 (1.9%) parma wallaby (Macropus parma). No individuals of western gray kangaroo (n=3) (Macropus fuliginosus), eastern gray kangaroo (n=19) (Macropus giganteus), common wallaroo (n=6) (Macropus robustus), red kangaroo (n=11) (Macropus rufus), or Matschie's tree kangaroo (n=14) (Dendrolagus matschiei) were positive for retrovirus antibody. These results demonstrate that five species of captive macropods have a history of exposure to retrovirus, with the highest percentage seropositive and highest statistical correlation in M. eugenii (pair-wise Fisher's exact test, alpha = 0.05). Additionally, one wild-caught M. eugenii was confirmed seropositive during quarantine period, indicating that retrovirus exposure may exist in wild populations. 相似文献