Design, construction and evaluation of a 12.2 GHz, 4.0 kW-CW high efficiency klystron amplifier

An analytical and experimental program is described, for studying design techniques for optimizing the conversion efficiency of klystron amplifiers, and to utilize these techniques in the development and fabrication of an X-band 4 kW cw klystron, for use in satellite-borne television broadcast transmitters. The design is based on a technique for increasing the RF beam current by using the second harmonic space charge forces in the bunched beam. Experimental analysis was also made of a method to enhance circuit efficiency in the klystron cavities. The design incorporates a collector which is demountable from the tube to facilitate multistage depressed collector experiments employing an axisymmetric, electrostatic collector for linear beam microwave tubes

Internetnutzung in der deutschen Agrarwirtschaft: Online-Handelsportale als neue Organisationsform

This paper describes the concept of E-commerce portals, so called E-hubs, in its basic characteristics and analyses their potential impacts on agribusiness enterprises and agricultural markets. Since these impacts depend on the level of market penetration of this new type of organisation, it is further attempted to identify the most relevant factors that determine future acceptance and utilisation of internet portals at sector and enterprise level.E-commerce, agriculture, farm trade, Farm Management, Research and Development/Tech Change/Emerging Technologies,

Nanoparticle- and microparticle-based luminescence imaging of chemical species and temperature in aquatic systems: a review

© 2019, Springer-Verlag GmbH Austria, part of Springer Nature. Most aquatic systems rely on a multitude of biogeochemical processes that are coupled with each other in a complex and dynamic manner. To understand such processes, minimally invasive analytical tools are required that allow continuous, real-time measurements of individual reactions in these complex systems. Optical chemical sensors can be used in the form of fiber-optic sensors, planar sensors, or as micro- and nanoparticles (MPs and NPs). All have their specific merits, but only the latter allow for visualization and quantification of chemical gradients over 3D structures. This review (with 147 references) summarizes recent developments mainly in the field of optical NP sensors relevant for chemical imaging in aquatic science. The review encompasses methods for signal read-out and imaging, preparation of NPs and MPs, and an overview of relevant MP/NP-based sensors. Additionally, examples of MP/NP-based sensors in aquatic systems such as corals, plant tissue, biofilms, sediments and water-sediment interfaces, marine snow and in 3D bioprinting are given. We also address current challenges and future perspectives of NP-based sensing in aquatic systems in a concluding section. [Figure not available: see fulltext.]

Führungsverhalten beziehungsweise Führungsstile in Agrarunternehmen

The development of the relationship between employer and employee is an important aspect of management, i. e. management behaviour and management style play an important role with regard to the employee as a critical factor for success. Increasing average sizes of agricultural enterprises and numbers of employees and the missing hierarchical structures create the need for additional motivation opportunities. In the agricultural sector the quality performance of labour activities is difficult to control, therefore, it becomes even more important to discuss management behaviour and management styles. Management styles are mainly described theoretically in the literature but rarely for agricultural enterprises. An empirical study demonstrates that in practice agricultural entrepreneurs are aware of numerous management styles. Although various standard management styles are known to the managers, the successful manager quickly adapts his individual management style to the current situation.management behaviour, management styles, Farm Management, Labor and Human Capital,

Responding to the Challenges of Gifted Education in Rural Communities

There are both achievement and opportunity gaps for low-income students when compared to their economically advantaged peers; and, for rural students, these gaps may be even more pronounced. In this manuscript we draw from our ongoing work in a five-year federally-funded, Jacob K. Javits grant focusing on promoting gifted education in rural schools. To address issues of under-identification of gifted students in these settings, and to investigate ways to maximize achievement, we established an alternative process for identifying gifted students in rural schools; and we created units integrating place-based pedagogy within an evidence-based curriculum model as an intervention. Finally, we discuss preliminary findings from the pilot year and first half of the second year of the study documenting success in augmenting the pool of identified students and engaging teachers in implementing the curriculum. Perhaps more importantly, we document lessons learned and more global takeaways for the field. Specifically, we discuss the influence of deficit thinking with regard to rural schooling (and subsequent recognition of gifts and talents), the risk of generalizing rural to all rural places, and the nuances of rural poverty not captured in commonly used metrics, such as Free and Reduced Lunch

Seagrass rhizosphere microenvironment alters plant-associated microbial community composition

© 2018 Society for Applied Microbiology and John Wiley & Sons Ltd The seagrass rhizosphere harbors dynamic microenvironments, where plant-driven gradients of O2 and dissolved organic carbon form microhabitats that select for distinct microbial communities. To examine how seagrass-mediated alterations of rhizosphere geochemistry affect microbial communities at the microscale level, we applied 16S rRNA amplicon sequencing of artificial sediments surrounding the meristematic tissues of the seagrass Zostera muelleri together with microsensor measurements of the chemical conditions at the basal leaf meristem (BLM). Radial O2 loss (ROL) from the BLM led to ∼ 300 µm thick oxic microzones, wherein pronounced decreases in H2S and pH occurred. Significantly higher relative abundances of sulphate-reducing bacteria were observed around the meristematic tissues compared to the bulk sediment, especially around the root apical meristems (RAM; ∼ 57% of sequences). Within oxic microniches, elevated abundances of sulphide-oxidizing bacteria were observed compared to the bulk sediment and around the RAM. However, sulphide oxidisers within the oxic microzone did not enhance sediment detoxification, as rates of H2S re-oxidation here were similar to those observed in a pre-sterilized root/rhizome environment. Our results provide novel insights into how chemical and microbiological processes in the seagrass rhizosphere modulate plant-microbe interactions potentially affecting seagrass health

Geographic variation in the PRNP gene and its promoter, and their relationship to chronic wasting disease in North American deer

PRNP genotypes, number of octarepeats (PHGGGWGQ) and indels in the PRNP promoter can influence the progression of prion disease in mammals. We found no relationship between presence of promoter indels in white-tailed deer and mule deer from Nebraska and CWD presence. White-tailed deer with the 95 H allele and G20D mule deer were more likely to be CWD- free, but unlike other studies white-tailed deer with the 96S allele(s) were equally likely to be CWD-free. We provide the first information on PRNP genotypes and indels in the promoter for Key deer (all homozygous 96SS) and Coues deer (lacked 95 H and 96S alleles, but possessed a uniquely high frequency of 103 T). All deer surveyed were homozygous for three tandem octarepeats

Effectiveness of Composting as a Biosecure Disposal Method for Porcine Epidemic Diarrhea Virus (PEDV)-Infected Pig Carcasses

Porcine epidemic diarrhea virus (PEDV) is an enteric disease of swine that has emerged as a worldwide threat to swine herd health and production. Substantial research has been conducted to assess viability of the virus on surfaces of vehicles and equipment, in feed and water, and on production building surfaces, but little is known about the persistence in PEDV-infected carcasses and effective disposal methods thereof. This study was conducted to quantify the persistence of PEDV RNA via quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) at various time-temperature combinations and in infected piglet carcasses subjected to composting. Although this method does not distinguish between infectious and noninfectious virus, it is a rapid and sensitive test to evaluate materials for evidence of virus genome