170,544 research outputs found
[Stammbuch C. F. Clasen]
No full text[STAMMBUCH C. F. CLASEN]
[Stammbuch C. F. Clasen] (1)
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Identification of freshwater Phycodnaviridae and their potential phytoplankton hosts, using DNA pol sequence fragments and a genetic-distance analysis
No full textViruses that infect phytoplankton are an important component of aquatic ecosystems, yet in lakes they remain largely unstudied. In order to investigate viruses (Phycodnaviridae) infecting eukaryotic phytoplankton in lakes and to estimate the number of potential host species, samples were collected from four lakes at the Experimental Lakes Area in Ontario, Canada, during the ice-free period (mid-May to mid-October) of 2004. From each lake, Phycodnaviridae DNA polymerase (pol) gene fragments were amplified using algal-virus-specific primers and separated by denaturing gradient gel electrophoresis; 20 bands were extracted from the gels and sequenced. Phylogenetic analysis indicated that freshwater environmental phycodnavirus sequences belong to distinct phylogenetic groups. An analysis of the genetic distances "within" and "between" monophyletic groups of phycodnavirus isolates indicated that DNA pol sequences that differed by more than 7% at the inferred amino acid level were from viruses that infect different host species. Application of this threshold to phylogenies of environmental sequences indicated that the DNA pol sequences from these lakes came from viruses that infect at least nine different phytoplankton species. A multivariate statistical analysis suggested that potential freshwater hosts included Mallomonas sp., Monoraphidium sp., and Cyclotella sp. This approach should help to unravel the relationships between viruses in the environment and the phytoplankton hosts they infect.final article publishedphytoplanktonChlorophytadiatomsFresh WaterPhycodnavirida
Dissertatio Inauguralis De Iure Detractionis / Quam Favente Divino Numine Ex Decreto Et Autoritate Magnifici In Illustri Iulia ICtorum Ordinis Sub Praesidio Danielis Clasen ... Pro Licentia Summos In Utroque Iure Honores Et Privilegia Doctoralia Consequendi Solenni Eruditorum Examini Subiicit Dietericus Thesingh Oldenb. Ad Diem XXII. Februarii Horis Ante Et Pomeridianis
No full textThe Non-Linear Flow Properties of Snail Mucus
No full textBiopolymers in aqueous solution have a wide range of applications as their highly tailored designs lead to sophisticated material properties [1] for the daily fight of survival. Snails employ a unique combination of polysaccharides and proteins to produce a mucus with material properties that allow for the stunning capability to crawl on vertical walls or even overhead without loosing contact to the surface. In this paper we present rheological investigations [2] of the material properties of minute amounts of mucus under nonlinear deformation conditions as they are created under the snail foot. For this purpose we present a new technique [3] that enables the investigation in natural film thicknesses of 10 – 20 m. The time and strain-dependent structural changes of the complex mucus gels, presented in the form of Pipkin diagrams [4], show how the deformation of the snail foot exploits the physically-crosslinked structure of the aqueous mucin gels to obtain a maximum adhesion with minimum energy consumption during locomotion.
1. Clasen, C. and W.M. Kulicke, Rheo-optical studies of barley (1 -> 3)(1 -> 4)-beta-glucan solution: Detection of the flow behavior of aggregates in the sol state. Journal of Rheology, 2003. 47(2): p. 321-335.
2. Clasen, C. and W.M. Kulicke, Determination of viscoelastic and rheo-optical material functions of water-soluble cellulose derivatives. Progress in Polymer Science, 2001. 26(9): p. 1839-1919.
3. Clasen, C. and G.H. McKinley, Gap-Dependent Microrheometry of Complex Liquids. Journal of Non-Newtonian Fluid Mechanics, 2004. 124: p. 1-10.
4. Pipkin, A.C., Lectures on Viscoelasticity Theory. 1972, Heidelberg: Springer-Verlag.status: Publishe
Genetic and chemical variation of *Tanacetum vulgare* in plants of native and invasive origin
No full textWolf VC, Gassmann A, Clasen BM, Smith AG, Müller C. Genetic and chemical variation of *Tanacetum vulgare* in plants of native and invasive origin. Biological Control. 2012;61(3):240-245
The effect of host Chlorella NC64A carbon: Phosphorus ratio on the production of Paramecium bursaria Chlorella Virus-1
No full text1. We used the freshwater alga Chlorella NC64A (Division Chlorophyta) and its virus Paramecium bursaria Chlorella virus-1 (PBCV-1) as a model system to test for potential stoichiometric constraints on a virus–host interaction. 2. Media phosphorus concentrations were manipulated to create Chlorella NC64A host cells with low (91 ± 23) or high (453 ± 246) C : P ratio. In contrast, the C : P ratio of PBCV-1, calculated from its biochemical composition, was 17 : 1. 3. Stoichiometric theory predicts that infection success and postinfection viral production should be depressed in high C : P cultures due to insufficient intracellular P for production of P-rich viral particles. 4. Consistent with this hypothesis, viral production was strongly affected by host C : P ratio. While host C : P ratio did not affect viral attachment or the percentage of new viral particles that were infectious, in the low C : P Chlorella NC64A treatment, nine times more viruses were produced per infected cell than in the high C : P treatment (158 ± 138 versus 18 ± 18), indicating that the low C : P cells were higher quality for PBCV-1 proliferation. 5. This result implies that the stoichiometric quality of algal cells can have a major effect on host–virus population dynamics. [ABSTRACT FROM AUTHOR]Peer reviewedfinal article publishedChlorella NC64Aviral ecologyphosphorusParamecium bursaria Chlorella virus‐1ecological stoichiometr
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The impact of a school-based water, sanitation and hygiene program on health and absenteeism of primary school children
No full textThis thesis describes research designed to quantify and describe the impact
of improved access to school water, sanitation, and hygiene (WASH) access
on pupils' helminth infection and diarrhoeal disease and absence from school.
The research was undertaken as part of a five-year cluster-randomized trial in
185 public primary schools in Nyanza Province, Kenya that addressed school
WASH impacts, knowledge diffusion, sustainability, and advocacy. One
hundred eighty-five schools were randomly selected and assigned to five
study arms to receive various water treatment, hygiene promotion, sanitation,
and water supply improvements. All pupils at enrolled schools were
dewormed at baseline and at two follow-up time pOints. A total of 11,458
pupils were interviewed over two years to compare rates of school absence,
rates and intensity of reinfection with soil transmitted helminths, and risk of
diarrhoeal disease.
We found no overall impact of our school-based WASH intervention on pupil
absence. However, a domain analysis revealed a substantial and significant
reduction in absence for girls attending schools that received WASH
improvements. Schools that received a hygiene promotion and water
treatment (HP&WT) intervention showed statistically similar reductions to
those that received HP&WT in addition to sanitation improvements.
Gender-specific effects were also found for reduced reinfection of soiltransmitted
helminth infection. Girls showed a significant decline in prevalence and intensity of infection with Ascaris lumbricoides, while boys
showed reduced reinfection for Hookworm. Household WASH characteristics
significantly modified the effect of the school-based intervention, revealing
potential questions about exposure to fecal pathogens at home and at school.
Schools that received HP&WT and those that received HP&WT plus
sanitation improvements showed no reduction in diarrhoeal disease
prevalence. However, schools allocated to the water "scarce" research group,
which received water supply improvements in addition to HP&WT and
sanitation, did show significant and substantial reductions in both prevalence
and duration of diarrhoeal illness.
While household-level WASH has been investigated extensively, this is the
first comprehensive study to investigate the impact of improved WASH at
schools. Overall, our results reveal the important role that school WASH can
play in mitigating disease burden and lowering pupil absence. Additional
research is necessary to fully explore these issues
Cover page Macromol. Mater. Eng. 9/2013 - Extensional flow and relaxation of semi-dilute solutions of schizophyllan
No full textCover: Extensional rheological properties determine the flow behavior of polymer solutions through porous media. The biopolymer schizophyllan, which experiences such flows in enhanced oil recovery operations, shows drastic changes in its conformational structure depending on the nature of the solvent. As a result, the extensional relaxation time is found to exhibit a strong change in scaling with concentration for solutions in water (in which a triple-helical structure is reported), compared to solutions in DMSO with a random coil structure. Further details can be found in the article by R. De Dier, W. Mathues, and C. Clasen* on page 944.status: Publishe
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
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