Fakultät II - Maschinenbau und Bioverfahrenstechnik
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Background: Despite penicillin having a longstanding reputation as being scientifically approved for the treatment of bovine mastitis, its market share and practical application rate seem rather low. While in some countries, cases of mild and moderate mastitis are treated almost completely with simple penicillin, in other countries, penicillin is rarely used as a mono-substance in udder tubes.
Methods: Based on minimal inhibitory concentration (MIC) studies of 1489 isolates of Gram-positive microorganisms isolated from bovine mastitis cases, the extent to which penicillin preparations can fulfil their role as first-line treatment and in how many cases insufficient efficacy must be assumed was assessed in comparison with more recent studies on the achievable levels of active substances in milk.
Results: Of the isolates, 76% had an MIC of ≤0.125 µg/mL and 95% of the isolates had an MIC of ≤1 µg/mL.
Conclusions: The data show that in Northern Germany, it can be assumed that penicillin is a good choice in most cases of mastitis caused by Gram-positive mastitis pathogens, at least from the perspective of antibiotic resistance.
Late blowing is a prevalent and costly cheese defect caused by clostridia. In organic cheese production, the use of additives that inhibit the growth of clostridia is prohibited. Furthermore, mechanical methods for the removal of clostridia are impractical in organic dairies due to the small batch sizes involved and separation process temperatures (~55 °C) that are incompatible with the standards required for raw milk cheese production. The aim of this study was to investigate whether sufficient spore reduction can be achieved at lower temperatures (10, 35 °C) with a downsized separator (CSC18-01-077, GEA Westfalia) by varying the process parameters to describe the influence on the suitability of the treated milk for cheese production. In addition to spore reduction, total mesophilic bacteria count, the effects of separation on fat and casein losses, and damage to milk fat globules were assessed, as they can affect the yield and cheese quality. A significant reduction (p < 0.01) in spore concentration and total bacteria count in milk was achieved, regardless of the process parameters employed. Casein losses are reduced at 35 °C compared to 55 °C. The extent of fat loss in the sludge at 35 °C was minimal. The reduction in milk fat globule size was significant. Nonetheless, the results of this study demonstrate that a downsized centrifuge can be employed to augment the quality of small-batch raw milk cheese, particularly at a temperature of 35 °C.
In this work polymer nanofibers were functionalized by incorporation of the spin transition (ST) compound [Fe(H2btm)2(H2O)2]Cl2 (FeH2btm) (H2btm=di(1H‐tetrazol‐5‐yl)methane). FeH2btm is an interesting compound due to its ability to reversibly and sensitively switch between high spin (HS) and low spin (LS) state when exposed to common volatile compounds (VOC) like ammonia and methanol. By using polyvinylidene fluoride (PVDF) as the main compound, inhibiting interactions between the complex and polymer were minimized. By using UV‐Vis spectroscopy, the visible and reversible switching between HS and LS state when exposed to an ammonia or hydrochloric acid atmosphere was confirmed. Powder X‐Ray diffraction (PXRD), scanning electron microscopy (SEM) and energy dispersive X‐Ray spectroscopy (EDX) show a homogenous distribution of FeH2btm with no major crystalline accumulations and a mean fiber diameter of 106±20 nm. The composite fiber has a similarly high thermal stability as the pure FeH2btm, as shown by thermogravimetric analysis (TGA). Mössbauer spectroscopy indicates an incomplete spin transition after exposition to ammonia. This could be due to low permeability of the VOC into the composite fiber.
Natural fiber‐reinforced composites (NFRCs) suffer from water absorption and low temperature stability, resulting in fiber degradation and subsequent material failure. Built‐in piezoresistive sensors are investigated to monitor the deformation/strain of the component. As a low‐cost material from renewable resources biochar particles derived from olive stones were applied on flax plies and yarn bundles that served as model systems. Carbon black samples as petrochemical variants were used as a reference material. Biochar and carbon black‐covered fiber systems were laminated in epoxy resin followed by tensile tests. The electrical resistance was recorded simultaneously during testing. Biochar with a broad size distribution from nano to high micrometer range (D < 200 μm) was superior in sensor performance compared to carbon black and biochar with a smaller particle size range D < 20 μm. Gauge factors (GF) of NFRC samples with integrated biochar particles reached 30–80 while carbon black could not exceed a GF of 8. To obtain maximum GFs, yarn count of flax yarn/ply substrate should be as thin as possible, but still enable percolation of the adhering particle network. Comparatively large particle size was identified as a contributing factor enabling the high GF for coarse biochar compared to carbon black.
Highlights
- A nonfossil biochar built‐in piezoresistive sensor in natural fiber‐reinforced composites was fabricated
- Deposing biochar directly on flax fibers facilitates processing
- The biochar piezoresistive sensor exhibits superior sensitivity compared to carbon black
Tensegrity structures are structures in which elements stabilize each other by bearing compressive or tensile loads. They have a high potential for lightweight design. As structures with tensile loads, wires can be used that are connected to other structures using a laser bonding process. Investigations of bonding a mild steel wire with a diameter of 1 mm onto a flat substrate have been conducted using a coaxial deposition welding head. The influence of the parameters focus position, laser power, wire feed rate and bonding processing time has been investigated regarding the bonding quality. A process window for a stable process and a sufficient bond of wire and substrate was determined. The laser intensity and stickout length have a significant influence on the bonding. High intensities and stickout lengths lead to wire burn back and no bond with the substrate while wire backup occurred at low intensities and stickout lengths.
Postpartum excretion of internal teat sealant after selective dry cow treatment of dairy cows
(2024)
To comply with antibiotic restriction policies in the European Union, internal teat sealants (TS) are increasingly used at dry off (DO) in selective dry cow treatment protocols to maintain udder health. Postcalving TS residue attachment to milking equipment and associated cleaning difficulties is a reason some farmers stay away from blanket TS use. Our objective was therefore to improve insight into TS excretion visibility and to compare quantity, pattern, and presence versus absence of TS excretion postcalving between the typical 2 cow categories at DO: high (H)- and low (L)-SCC cows, treated with antibiotic (AB) plus TS (H-ABTS) or TS only (L-TS), respectively. In herds in the Netherlands (n = 3), and Germany (n = 4), cows were enrolled at DO, and categorized as H-ABTS (n = 93), or L-TS (n = 99). Postcalving, quarter-level TS visibility, quantities, patterns, and percentage of TS infused and excreted postcalving were recorded from 50 mL of premilk of every quarter at each of the first 15 or 16 milkings. Udder quarter health status was determined by bacteriological culture and SCC of quarter milk samples taken at DO and at d 3 postcalving and by clinical mastitis incidence from DO until 30 DIM. Univariable and multivariable models were created to explore associations of TS excretion presence versus absence at the first 3 milkings. Irrespective of SCC category, both laboratory personnel and farmers saw TS residues at the first milking in an equal 72% of quarters. Compared with laboratory as the gold standard, farmer sensitivity to spotting TS in premilk was 74.5% at the first milking and decreased to a maximum of 8.3% at the last 3 milkings. At the first milking, TS excretion quantities showed a bimodal distribution pattern and the mean percentage of TS infused (3.83 g) that was excreted in premilk at the first milking, was higher in the L-TS cows (45.5%) compared with the H-ABTS cows (32%). At the second and third milking, mean-adjusted TS percentage excreted was higher in the H-ABTS cows (8.5% and 1.8%, respectively) compared with the L-TS cows (4.6% and 0.4%, respectively). The multivariable model of the first 3 milkings showed parity at both the first and second milking, and the study group at both the second and third milking was significantly associated with TS presence. The univariable model showed no association between TS presence at the first milking and udder health. In conclusion, in premilk of the first milking, TS residue excretion was bimodal, higher in L-TS cows, more likely to be present in multiparous cows, and not associated with udder health. At the second and third milking, excretion was higher in H-ABTS cows and TS presence was only more likely in multiparous cows at the second milking.
Kunststoffe sind wertvolle Werkstoffe für unterschiedlichste Anwendungen. Doch die durch sie verursachten Umweltverschmutzungen sind weltweit ein großes Problem. Ein Trend für mehr Nachhaltigkeit ist Mehrweg- statt Einwegnutzung. Eine Kooperation aus Hannover arbeitet am Einsatz von Biokunststoffen in Pfandsystemen für To-go-Lebensmittel.
Schmalspurfahrzeuge als kompaktes Mittel zur Beförderung von Personen oder Gütern auf der Straße neigen insbesondere bei schneller Kurvenfahrt zum Umkippen. Sowohl Tüftler und Kleinserienhersteller als auch einige Großkonzerne der Automobilindustrie haben in den letzten Jahrzehnten immer wieder versucht, ein Fahrzeug mit geringer Verkehrsfläche zu konstruieren, welches dennoch die erforderliche Kurvenstabilität aufweist. Durch den Einsatz der Neigetechnik bei Straßenfahrzeugen entstand die Fahrzeugklasse der Kurvenleger.
Im Rahmen dieses Berichtes werden die Grundlagen der Neigetechnik in Kurvenlegern erläutert und die verschiedenen Ansätze und Technologien zur Umsetzung bei unterschiedlichen Beispielfahrzeugen beleuchtet.
Continuous fiber-reinforced material extrusion is an emerging additive manufacturing process that builds components layer by layer by extruding a continuous fiber-reinforced thermoplastic strand. This novel manufacturing process combines the benefits of additive manufacturing with the mechanical properties and lightweight potential of composite materials, making it a promising approach for creating high-strength end products. The field of design for additive manufacturing has developed to provide suitable methods and tools for such emerging processes. However, continuous fiber-reinforced material extrusion, as a relatively new technology, has not been extensively explored in this context. Designing components for this process requires considering both restrictive and opportunistic aspects, such as extreme anisotropy and opportunities for functional integration. Existing process models and methods do not adequately address these specific needs. To bridge this gap, a tailored methodology for designing continuous fiber-reinforced material extrusion is proposed, building on established process models. This includes developing process-specific methods and integrating them into the process model, such as a process selection analysis to assess the suitability of the method and a decision model for selecting the process for highly stressed components. Additionally, a detailed design process tailored to continuous fiber-reinforced material extrusion is presented. The application of the developed process model is demonstrated through a case study.
Verantwortlicher Umgang mit Ressourcen – ein Praxisbeispiel zu interdisziplinärem Lehren und Lernen
(2024)
Der Beitrag basiert auf den Erfahrungen aus einem Drittmittelprojekt, das den Aufbau innovativer Lehr- und Lernstrukturen für interdisziplinäre Zusammenarbeit zum Ziel hatte. An dem Projekt beteiligt waren Lehrende und Studierende aus fünf Fachrichtungen der Hochschule Hannover. Die Lehrenden haben gemeinsam mit einer Hochschuldidaktikerin ein neues Lehr-Lernangebot entwickelt, in dessen Mittelpunkt die Bearbeitung von Fragestellungen nachhaltiger Entwicklung in interdisziplinären Teams stand. Dabei hat sich gezeigt, wie vielfältig die Perspektiven auf das Thema und die Zusammenarbeit sind, wie unterschiedlich die fachspezifische Sprache ist und wie sehr sich die generellen Denk- und Arbeitsweisen der Disziplinen unterscheiden. Für das Gelingen der Zusammenarbeit trotz Heterogenität, sind Mut, Geduld und Offenheit nötig, um sich auf das Fremde einzulassen. Gleichzeitig ist es elementar, eine gemeinsame ‚Sprache‘ zu finden, damit Verständigung über Disziplingrenzen hinweg möglich ist.