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Multi-locus variable-number tandem repeat analysis for outbreak studies of Salmonella enterica serotype Enteritidis
Burkhard Malorny, Ernst Junker, Reiner Helmuth
BMC Microbiology , 2008, DOI: 10.1186/1471-2180-8-84
Abstract: Seventy-nine different MLVA types were identified in 240 S. Enteritidis strains. The Simpson's diversity index for the MLVA method was 0.919 and Nei diversity values for the nine VNTR loci ranged from 0.07 to 0.65. Twenty-four MLVA types could be assigned to 62 PT4 strains and 21 types to 81 PT8 strains. All outbreak isolates had an indistinguishable outbreak specific MLVA type. The in vitro stability experiments showed no changes of the MLVA type compared to the original isolate.This MLVA method is useful to discriminate S. Enteritidis strains even within a single phage type. It is easy in use, fast, and cheap compared to other high-resolution molecular methods and therefore an important tool for surveillance and outbreak studies for S. Enteritidis.Salmonella enterica subspecies enterica serovar Enteritidis (S. Enteritidis) is the world-leading cause of salmonellosis and is often implicated in over 60% of cases of human salmonellosis in Europe [1]. In the United States it remains the second most common serotype of salmonellae [2]. The current worldwide epidemic of S. Enteritidis started in the middle of the 1980s [3]. The reservoir for S. Enteritidis is mainly poultry often carrying asymptomatic infections, which pass the human pathogen along the food production chain. Especially undercooked or raw eggs and frozen poultry meat represent a high risk for humans.S. Enteritidis is one of the most clonal Salmonella serotype [4,5]. Consequently, highly discriminative typing methods are needed for surveillance and outbreak studies. Phage typing is the traditional phenotypic method for subtyping salmonellae but has limited discriminative power and requires standardized phage collections [6]. Molecular-based typing methods like plasmid profiling, RAPD and pulsed-field gel electrophoresis (PFGE) have been applied with limited discriminatory power as well [7]. Ribotyping using the restriction enzymes PstI and SphI is currently the most useful method for discrimination [8]. Ho
Salmonella Prevalence in Turkey Flocks before and after Implementation of the Control Program in Germany
Annemarie K?sbohrer,Andreas Schroeter,Reiner Helmuth,Bernd-Alois Tenhagen
Agriculture , 2013, DOI: 10.3390/agriculture3030342
Abstract: The objective of the study was to describe the Salmonella prevalence in turkey flocks before and after the implementation of the Salmonella control program in Germany and to identify factors that are potentially associated with the presence of Salmonella in the flocks. To achieve this, all breeding flocks and a representative sample of the fattening flocks were tested for Salmonella. None of the 98 turkey breeding flocks but 31 (10.3%) of 300 turkey fattening flocks were positive for Salmonella spp. in the baseline study during 2006/2007. In 11 (3.7%) fattening flocks S. Enteritidis (1 flock; 0.3%) or S. Typhimurium (8 flocks; 2.7%) or monophasic S. Typhimurium (2 flocks; 0.3%), which are of special public health relevance in Germany, were detected. Logistic regression analysis confirmed that production type and season were significant risk factors for the presence of Salmonella spp. in fattening turkey flocks in Germany. Data from mandatory official testing within the Salmonella control program in 2010 and 2011 revealed that Salmonella prevalence in turkey fattening flocks has decreased significantly to 3.3% and 2.6%. In line with this result, prevalence of S. Enteritidis or S. Typhimurium had decreased to 2.6% and 1.5%. Results indicate that the prevalence of Salmonella in turkey fattening flocks has decreased significantly.
HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
Resch,Helmuth;
Maderas. Ciencia y tecnología , 2006, DOI: 10.4067/S0718-221X2006000200001
Abstract: among the many interesting topics in the field of wood science and technology is a fascinating story about research and development on drying wood products with high-frequency electric current. historically, it can be traced back over decades. heat transfer to and evaporation of moisture from wood may be accomplished with high frequency current depending on its dielectric properties. because wood is generally heterogeneous, these properties vary not only with the frequency of the current and the field orientation, but also with the moisture content, temperature, and density of wood. considering these parameters and the specific heat of the material, estimates of power absorption can be made. in an attempt to develop this technology, research covered many products from paper and veneer to lumber and heavy timbers. much emphasis, however, has been placed on wood species and/or products with larger dimensions that are difficult or impossible to dry when using conventional drying methods. the advantages of employing dielectric heating were found to be rapid and fairly uniform heat transfer often to solidly stacked timbers, very high drying rates, and avoidance of various drying defects including any significant case-hardening and oxidative discoloration of the wood. during the last two decades, the development focused mainly on drying lumber in vacuum kilns using dielectric heating, often termed high-frequency/vacuum drying. it has been justified economically on the basis of increased throughput and higher quality. existing industrial installations provide a positive picture for higher value products. the economics should improve with advances in available equipment, better basic understanding and more practical experience with industrial units now operating. also, the combination of high-frequency/vacuum drying with other systems, such as moisture leveling after primary drying or pre-heating prior to the high-frequency/vacuum step, hold promise for further technical im
CONSIDERING CHANGES IN WOOD UTILIZATION -A EUROPEAN PERSPECTIVE
Resch,Helmuth;
Maderas. Ciencia y tecnología , 2008, DOI: 10.4067/S0718-221X2008000100006
Abstract: worldwide, continuous change is evident. what impact does it have on the utilization of wood? what should be considered when educating professionals in wood science and technology (ws&t)? where did we come from and where do we need to go? .throughout history, forests provided important social, ecological, and economic values. wood utilization advanced along with an unprecedented and exciting industrial evolution and ws&t became an interdisciplinary field. recently, stronger environmental concerns and "globalization" impacted societies in major ways influencing timber availability, processing, and trade. demand is growing for bio-energy, "green" chemicals and composites. co2 savings are to be made by using timber in construction. globalization created entirely new business that communicate and network worldwide. quality assurance for products and manufacturing increases in importance. globalization demands interdisciplinary education in ws&t. while recognized as a material science, it must retain its identity and association with related industries. undergraduate education requires a broad knowledge base, then specialized topics, and finally, integration of information with options available. graduate programs are ideally tailored to background and professional needs of students, but thesis topics are best selected from faculty research. bodies for accreditation of curricula may be wise to require a standardized core of subjects, but show flexibility
HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
Helmuth Resch
MADERAS : Ciencia y Tecnología , 2006,
Abstract: Among the many interesting topics in the field of Wood Science and Technology is a fascinating story about research and development on drying wood products with high-frequency electric current. Historically, it can be traced back over decades. Heat transfer to and evaporation of moisture from wood may be accomplished with high frequency current depending on its dielectric properties. Because wood is generally heterogeneous, these properties vary not only with the frequency of the current and the field orientation, but also with the moisture content, temperature, and density of wood. Considering these parameters and the specific heat of the material, estimates of power absorption can be made. In an attempt to develop this technology, research covered many products from paper and veneer to lumber and heavy timbers. Much emphasis, however, has been placed on wood species and/or products with larger dimensions that are difficult or impossible to dry when using conventional drying methods. The advantages of employing dielectric heating were found to be rapid and fairly uniform heat transfer often to solidly stacked timbers, very high drying rates, and avoidance of various drying defects including any significant case-hardening and oxidative discoloration of the wood. During the last two decades, the development focused mainly on drying lumber in vacuum kilns using dielectric heating, often termed high-frequency/vacuum drying. It has been justified economically on the basis of increased throughput and higher quality. Existing industrial installations provide a positive picture for higher value products. The economics should improve with advances in available equipment, better basic understanding and more practical experience with industrial units now operating. Also, the combination of high-frequency/vacuum drying with other systems, such as moisture leveling after primary drying or pre-heating prior to the high-frequency/vacuum step, hold promise for further technical improvement
CONSIDERING CHANGES IN WOOD UTILIZATION -A EUROPEAN PERSPECTIVE
Helmuth Resch
MADERAS : Ciencia y Tecnología , 2008,
Abstract: Worldwide, continuous change is evident. What impact does it have on the utilization of wood? What should be considered when educating professionals in Wood Science and Technology (WS&T)? Where did we come from and where do we need to go? .Throughout history, forests provided important social, ecological, and economic values. Wood utilization advanced along with an unprecedented and exciting industrial evolution and WS&T became an interdisciplinary field. Recently, stronger environmental concerns and "globalization" impacted societies in major ways influencing timber availability, processing, and trade. Demand is growing for bio-energy, "green" chemicals and composites. CO2 savings are to be made by using timber in construction. Globalization created entirely new business that communicate and network worldwide. Quality assurance for products and manufacturing increases in importance. Globalization demands interdisciplinary education in WS&T. While recognized as a material science, it must retain its identity and association with related industries. Undergraduate education requires a broad knowledge base, then specialized topics, and finally, integration of information with options available. Graduate programs are ideally tailored to background and professional needs of students, but thesis topics are best selected from faculty research. Bodies for accreditation of curricula may be wise to require a standardized core of subjects, but show flexibility
Ising Model Observables and Non-Backtracking Walks
Tyler Helmuth
Mathematics , 2012, DOI: 10.1063/1.4881723
Abstract: This paper presents an alternative proof of the connection between the partition function of the Ising model on a finite graph $G$ and the set of non-backtracking walks on $G$. The techniques used also give formulas for spin-spin correlation functions in terms of non-backtracking walks. The main tools used are Viennot's theory of heaps of pieces and turning numbers on surfaces.
Loop-weighted Walk
Tyler Helmuth
Mathematics , 2014,
Abstract: Loop-weighted walk with parameter $\lambda\geq 0$ is a non-Markovian model of random walks that is related to the loop $O(N)$ model of statistical mechanics. A walk receives weight $\lambda^{k}$ if it contains $k$ loops; whether this is a reward or punishment for containing loops depends on the value of $\lambda$. A challenging feature of loop-weighted walk is that it is not purely repulsive, meaning the weight of the future of a walk may either increase or decrease if the past is forgotten. Repulsion is typically an essential property for lace expansion arguments. This article circumvents the lack of repulsion and proves, via the lace expansion, that for any $\lambda\geq 0$ loop-weighted walk is diffusive in high dimensions.
Diversity of Plasmids Encoding Virulence and Resistance Functions in Salmonella enterica subsp. enterica Serovar Typhimurium Monophasic Variant 4,[5],12:i:- Strains Circulating in Europe
Patricia García, Katie L. Hopkins, Vanesa García, Janine Beutlich, M. Carmen Mendoza, John Threlfall, Dik Mevius, Reiner Helmuth, M. Rosario Rodicio, Beatriz Guerra, on behalf of the Med-Vet-Net WP21 Project Group
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0089635
Abstract: Plasmids encoding resistance and virulence properties in multidrug resistant (MDR) Salmonella enterica (S.) serovar Typhimurium monophasic variant 4,[5],12:i:- isolates recovered from pigs and humans (2006-2008) in Europe were characterised. The isolates were selected based on the detection by PCR-amplification of S. Typhimurium virulence plasmid pSLT genes and were analysed by multi-locus sequence typing (MLST). The resistance genes present in the isolates and the association of these genes with integrons, transposons and insertion sequences were characterised by PCR-sequencing, and their plasmid location was determined by alkaline lysis and by S1-nuclease pulsed-field gel electrophoresis (PFGE) Southern-blot hybridisation. Plasmids were further analysed by replicon typing, plasmid MLST and conjugation experiments. The 10 S. 4,[5],12,i:- selected isolates belonged to ST19. Each isolate carried a large plasmid in which MDR with pSLT-associated virulence genes were located. After analysis, eight different plasmids of three incompatibility groups (IncA/C, IncR and IncF) were detected. Two IncA/C plasmids represented novel variants within the plasmid family of the S. 4,[5],12:i:- Spanish clone, and carried an empty class 1 integron with a conventional qacEΔ1-sul1 3′ conserved segment or an In-sul3 type III with estX-psp-aadA2-cmlA1-aadA1-qacH variable region linked to tnpA440-sul3, part of Tn2, Tn21 and Tn1721 transposons, and ISCR2. Four newly described IncR plasmids contained the resistance genes within In-sul3 type I (dfrA12-orfF-aadA2-cmlA1-aadA1-qacH/tnpA440-sul3) and part of Tn10 [tet(B)]. Two pSLT-derivatives with FIIs-ST1+FIB-ST17 replicons carried cmlA1-[aadA1-aadA2]-sul3-dfrA12 and blaTEM-1 genes linked to an In-sul3 type I integron and to Tn2, respectively. In conclusion, three emerging European clones of S. 4,[5],12:i:- harboured MDR plasmids encoding additional virulence functions that could contribute significantly to their evolutionary success.
The Use of Organic Waste as an Eco-Efficient Energy Source in Ghana  [PDF]
Robert Ohene Adu, Reiner Lohmueller
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.37066
Abstract: The problem of municipal solid waste (MSW) management has been an issue of global concern in recent times and has engaged governments and local authorities in their quest to manage solid waste in a sustained manner. One proposition which has the potential of solving three problems at the same time is the use of the biodegradable component of MSW as a source of energy to augment energy supply. This research therefore assessed the use of the organic fraction of MSW as an eco-efficient energy source in Ghana. A study of Ghana’s solid waste profile was undertaken and the fraction of biodegradable component was found to be approximately 60%, with a heating value of 17 MJ/kg and a moisture content of 50%. Moreover, it was established that 0.5 kg of solid waste is generated daily by each Ghanaian, meaning that about 5610 tons of the organic fraction could be made available every day to generate energy to the national grid. It was also established that waste disposal in Ghana is largely by way of open dumping as primary collection of waste from households in Ghana is limited to high-income communities which represent only 11% of the population, whereas secondary collection from transfer points to the disposal facilities is inefficient. With representative power output of 1.66 MWh/tonne a total of 3320 GWh of energy can be produced annually from the 4 proposed plants, generating net revenue of about $111,600,000. As an optimizing step, a waste incineration scheme was suggested in which the off-gases produced from organic waste combustion could be used to produce electrical power with steam in a multi-stage heat exchanger-steam turbine configuration, and the off gases again used for pre-drying of the organic waste in a cycle. A state-of-the art waste incineration technology was used as a model and adapted to suit Ghana’s tropical conditions. MSW combustion releases less CO2 for the same power output (837 Ib/MWh) than any of the other conventional fuels do, and is therefore a good fuel for the fight against climate change.
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