11 research outputs found
Improvements in Gakushin Wear Testing through Laboratory Automation
No full textCoatings designed for leather finishes are subjected to ever increasing performance specifications, requiring accurate assessments to properly judge performance. Unfortunately, the results of many tests utilized to determine leather finish performance are plagued by high levels of variability. One such test is the Gakushin wear resistance test, which is required by a number of Japanese auto manufacturers, but can be used more generally to measure wear performance important to most automotive OEMs. Gakushin wear testing also requires intensive operator monitoring over lengthy test cycles and does not present an easily determined endpoint. It is therefore often run unmonitored as a pass/fail test, forfeiting the potential to detect performance gradients among samples.In order to address these challenges, a new system has been developed that preserves the critical components of the wearing system, but adds automation and imaging systems that allow it to run completely unattended. A digital control circuit that periodically interrupts the wearing cycle initiates the capture and storage of high resolution images of the leather samples under test. After the test is completed, the operator is able to view the sequential images, selecting the exact point of coating failure. One benefit of this system is higher productivity, since the test can be run unattended. Also, since the operator is able to evaluate images of the coating both before and after the selected endpoint, the error associated with endpoint detection is minimized and the test yields more precise data than when performed in pass/fail mode. This combination of higher productivity and more precise endpoint detection facilitates the use of statistical data analysis on the results. In addition, the images showing coating wear following the endpoint allow an analysis of failure mode. These factors combine to make the improved Gakushin instrument a potent product development tool for wear resistant topcoats. RESUMENLos acabados diseñados para las terminaciones del cuero son sometidos cada vez a mayores especificaciones de performance, lo que requiere de una evaluación exacta a fin de juzgar adecuadamente el desempeño. Desafortunadamente, los resultados de varios ensayos utilizados para determinar la performance del acabado del cuero se ven afectadas por altos niveles de variabilidad. Uno de estos ensayos es la prueba de resistencia al desgaste Gakushin, el cuál es requerido por una serie de fabricantes japoneses de automóviles, pero puede ser utilizado generalmente para medir la performance de desgaste, importante para los fabricantes de autopartes. La prueba de resistencia al desgaste Gakushin también requiere un seguimiento intensivo del operador en largos ciclos de prueba y no presenta un punto final fácilmente determinable. Por lo tanto, a menudo se ejecuta sin monitoreo como un test pasa/no pasa, perdiendo el potencial de detectar gradientes de performance entre las muestras.Para hacer frente a estos desafíos, un nuevo sistema ha sido desarrollado protegiendo los componentes críticos del sistema de desgaste, y añadiendo los sistemas de automatización y de imagen que permiten que se ejecute completamente sin monitoreo. Un circuito de control digital periódicamente interrumpe el ciclo iniciando la captura y el almacenamiento de imágenes de alta resolución de las muestras de cuero a ensayar. Después que la prueba se ha completado, el operador es capaz de ver las imágenes secuenciales, seleccionando el punto exacto de la falla del acabado. Una ventaja de este sistema es una mayor productividad, ya que la prueba se puede ejecutar sin vigilancia. También, puesto que el operador es capaz de evaluar las imágenes del acabado, tanto antes como después de que el punto final seleccionado, el error asociado con la detección del punto final se minimiza y el ensayo proporciona datos más precisos que cuando se realiza en modo pasa/no pasa. Esta combinación de una mayor productividad y mayor precisión en la detección de punto final facilita el uso de análisis de datos estadísticos sobre los resultados. Además, las imágenes que muestran el desgaste del acabado tras el punto final permiten un análisis de modo de falla. Estos factores se combinan para hacer del instrumento Gakushin mejorado una herramienta potente para el desarrollo de productos acabados resistentes al desgaste
Influence of immediate predation risk by lions on the vigilance of prey of different body size
No full textThe effects on vigilance behavior of environmental cues that affect perceived risk of predation have been widely measured in gregarious herbivores. How extrinsic (e.g., predator activity within certain habitats) and intrinsic (e.g., within-group competition) cues interact depends on the biology of the prey species. However, very little is known about the impact of the actual presence of the predator in the vicinity on fine scale prey vigilance behavior. For this study, we monitored the vigilance of plains zebra (Equus quagga) and impala (Aepyceros melampus) in and around Hwange National Park, Zimbabwe. We assessed how the presence of radio-collared lions (Panthera leo) affected the vigilance of their prey. To evaluate the factors affecting vigilance behavior, we measured routine and intense vigilance. Routine vigilance can be conducted while chewing, although during intense vigilance chewing is halted and thus imposes foraging costs as food processing is delayed. As the most acute form of vigilance, we predicted that the presence of lions would lead to an increase in intense vigilance in both species. We found this to be the case for zebra, a key prey species for lions, while impala adjusted their intense vigilance to risk cues less specific to the presence of lions. Potential predation risk posed by lions in the immediate vicinity differs not only between species but also for a given species in different contexts. Our results also reveal how other environmental risk indicators influence the structure of vigilance behavior of large prey species in a manner that reflects their respective ecologies. © 2012 The Author
Surface water availability and cattle herding practices shape the human-wildlife interface at the edge of a protected area
No full textPresented at the 9th international wildlife ranching symposium: wildlife - the key to prosperity for rural communities, held on 12-16 September 2016 at Hotel Safari & the Safari Court, Windhoek, Namibia in conjuction with the IUCN 2nd African Buffalo Symposium.Spatial and temporal partitioning of key resources promotes species coexistence. On the edge of unfenced protected areas, livestock and wild herbivores share foraging and watering resources. We investigated whether effective resource partitioning was maintained in African savannas as surface water availability declined during the dry season. We quantified avoidance between African elephant (Loxodonta Africana), African buffalo (Syncerus caffer) and cattle (Bos taurus & indicus) at multiple scales using habitat selection models with GPS relocation data according to seasonal changes in surface water distribution on the eastern fringe of Hwange National Park, Zimbabwe. The range and duration of cattle incursions into the protected area varied seasonally by shifting from consistent selection of open habitats close to water pans during the rainy season to the less predictable selection of areas far away from the now dried up water pans at the end of the dry season. During the rainy and cold dry season, buffalo successfully avoid cattle at large (overlap<3%) and fine spatial scales. By the end of the dry season, buffalo herds, which are restricted to the vicinity of water, still avoid the boundary of the protected area but tolerate higher overlap with cattle (10%) and do not avoid them as strongly at fine scales. Elephant home-ranges overlap extensively with cattle (15-68%) throughout the year but elephant avoid cattle by staying away from the boundary during the day and getting closer to it at night. As the dry season advances, elephant bulls range closer to the boundary especially at night and may even make excursions into the communal land in their search of forage. Synthesis: Wild herbivores strongly avoid livestock and people at the boundary of a protected area as long as their foraging and drinking resources allow. In the advent of a drought, artificial water provisioning and cattle husbandry determine the level of avoidance and may be used to mitigate disease transmission and crop-raiding
Seasonal herding practices influence predation on domestic stock by African lions along a protected area boundary
No full textLivestock depredation frequently results in retaliatory killing of carnivores by people. An understanding of the ecological and sociological factors that precipitate this conflict is essential to mitigation. We investigated the seasonality of lion (Panthera leo) depredation incidents in relation to cattle (Bos primigenius) herding patterns in Tsholotsho Communal Land and Ngamo Forest adjacent to Hwange National Park, Zimbabwe. Cattle from 14 villages along the protected area (PA) boundaries were fitted with GPS data loggers (2010–2012), and depredation incidents systematically recorded (2008–2012). More cattle were killed by lions during the wet season (October to May) than during the dry months (June to September). In the wetter months, corresponding to the growing season and the need to protect crops, cattle were herded further from their home enclosures, closer to PA boundaries and into more wooded habitats. By contrast, cattle remained closer to home, further from PAs and were left to graze in fallow fields close to villages in the dry months. Seasonal use of wooded areas distant to villages and close to PA boundaries during the growing season increases vulnerability of cattle to lion depredation. In the dry months, cattle grazing close to villages benefit from the close proximity of people, resulting in a lower incidence of depredation. Approaches to mitigate livestock depredation should focus on improving herd protection during the wet season when cattle graze far from villages. Strategies such as communal herding, more intensive livestock guarding and, where possible, avoidance of heavily wooded habitats close to PAs should be encouraged
Bells, bomas and beefsteak: complex patterns of human-predator conflict at the wildlife-agropastoral interface in Zimbabwe
No full textReports of livestock depredation by large predators were systematically collected at three study sites in northwestern Zimbabwe from 2008–2013. We recorded 1,527 incidents (2,039 animals killed and 306 injured). Lions (Panthera leo) and spotted hyaenas (Crocuta crocuta) were mostly responsible, and cattle and donkeys most frequently attacked. Patterns of predation were variable among study sites. Nevertheless, some overall patterns were apparent. Predators selected livestock close to the size of their preferred wild prey, suggesting behaviours evolved to optimise foraging success may determine the domestic species primarily preyed upon. Most attacks occurred when livestock were roaming outside and away from their ‘home’ protective enclosures at night. Hyaena attacks were largely nocturnal; lions and leopards (Panthera pardus) were more flexible, with attacks occurring by day and at night. Livestock fitted with bells suffered a disproportionate number of attacks; the sound of bells appears to have conditioned predators to associate the sound with foraging opportunities. Lion and hyaena attacks on cattle were more frequent in the wet season suggesting that seasonal herding practices may result in cattle vulnerability. Only a small proportion of conflict incidents were reported to wildlife management officials with a bias towards lion predation events, potentially prejudicing conflict management policies. Predation on domestic stock involves an intricate interplay between predator behaviour and ecology on the one hand and human behaviour and husbandry practices on the other. Our data suggest that improved livestock husbandry (supervision of grazing animals, protection at night in strong enclosures) would greatly reduce livestock depredation
Water and cattle shape habitat selection by wild herbivores at the edge of a protected area
No full textUnderstanding the spatiotemporal dynamics of human‐wildlife interfaces is important for the sustainable management of protected areas and wildlife conservation. We investigated the drivers of domestic and wild herbivore habitat selection at the edge of an unfenced protected area adjacent to Hwange National Park, Zimbabwe. We used GPS data to quantify the movement patterns of elephant bulls, buffalo and cattle at multiple scales and according to seasonal changes of surface water availability. Cattle, elephant and buffalo prefer open grassland habitats found close to water but elephant and buffalo avoid cattle differently. During the rainy season, cattle enter the protected area daily; buffalo avoid cattle completely at the home range scale, whereas elephant bulls avoid cattle at finer scales by favoring temporal niche shift. Elephant bulls avoid direct encounters with cattle (or people) during the day but come closer to the boundary and to water at night when cattle are kept in enclosures close to the homesteads. During the dry season, when cattle range further into the protected area in search of forage, buffalo and cattle spatial overlap increases as water dependence takes precedence over avoidance. Elephant bulls range closer to the boundary at night and increase the number of excursions into the Communal Area. Cattle herding creates a buffer zone between wildlife areas and human settlements because wild herbivores strongly avoid livestock and people. However, avoidance only lasts as long as resources are abundant. Our study suggests that long‐term planning of both artificial water provisioning and traditional cattle herding practices could help maintaining spatial segregation and thus mitigate conservation conflicts such as pathogen transmission, crop raiding or livestock depredation
Drivers of foot-and-mouth disease in cattle at wild/domestic interface: Insights from farmers, buffalo and lions
No full textHumans live increasingly in the proximity of natural areas, leading to increased interactions between people, their livestock and wildlife. Aim We explored the role of these interactions in the risk of disease transmission (foot-and-mouth disease [FMD]) between cattle and the African buffalo (the maintenance host) and how a top predator, the lion, may modulate these interactions. Location The interface of Hwange National Park (HNP) and surrounding communal lands, Zimbabwe. Method We combined a longitudinal serological cattle survey for FMD, GPS-collar data and cattle owners' interviews during four seasons in 2010–2011. Results Overall FMD incidence in cattle was low, but showed a peak during the rainy season. The incidence dynamic was significantly explained by cattle incursion into the protected area (i.e., buffer zone of 3 km inside HNP) and not by contacts with buffalo or contacts among cattle. These results suggest that FMD virus either survives in the environment or is transmitted by other ungulate groups or species. The analysis of incursion frequency in the buffer suggests that (1) buffalo and cattle are avoiding each other up to 2 months after one species track and that (2) lions make frequent incursions in the buffer few days to few weeks after buffalo had used it, whereas buffalo did not use areas occupied by lions. Lions could thus reduce the spatio-temporal overlap between cattle and buffalo in the interface, which could contribute to the low level of FMD incidence. Main conclusions During the rainy season, traditional herding practices push cattle away from growing crops near villages into the HNP but not during the dry season, suggesting that cattle owners may decide to rely on lower quality resources in the communal land in the dry season to avoid the risks of infection and/or predation in the HNP. This study highlights the complex dynamics that operates at human/livestock/wildlife interfaces
Complementing surgical with biomedical and engineering methods to evolve lip and nose reconstruction
No full textFacial integrity and self-perception are intimately related to each other. A facial defect therefore affects a patient in his physical and psychosocial health as well. Every reconstructive method exhibit certain imperfections or burden for the patient, which motivates the surgeon’s to strive for improvements. While many imperfections can be improved by refinements of the surgical techniques, some aspects might be not solvable by surgical principles alone. At that stage, biomedical and engineering methods should be considered to complement the surgical treatment for further improvements.
We developed and explored a variety of biomedical and engineering methods to overcome shortcomings of current lip-nose reconstruction techniques.
The unknown shape of a missing nose was computed from a morphable face model that comprise the facial shape information of 200 healthy individuals. It led to a more natural shape planning than by hand carving. A biocompatible facial prosthesis was then made out of polyamide using computer assisted design and manufacturing. Alternatively to facial prosthesis large facial defects can be covered by means of tissue transfer from a distant body site performing a microsurgical vascular anastomosis. In this area, the importance to develop and use monitoring devices and pharmaceutical drugs for anastomosis patency remained unclear. We assessed therefore the current practice for microsurgical head and neck tissue transfer in clinics of Germany, Switzerland and Austria. There was a high variability with equal success rate, technical monitoring devices and pharmaceutical drugs seemed to have a negligible effect on the success rate, while the surgical anastomosis having the main effect. To repair small naso-labial defects of inborn cleft lips, the use of the adjoining tissue is sufficient. However, since both lip parts contain a labial artery of normal thickness they could be as well unified by a microsurgical anastomosis, however its biological rational needed exploration. We measured the lip artery blood flow and nose-lip microcirculation in cleft lip patients before and after surgical repair and in normal using laser Doppler flowmetry and white light tissue spectrometry. We found no circulation deficit in cleft patients and therefore no need to strive for a surgical anastomosis. Nonetheless, since blood flow is a precondition for growth and development, visible vessels in the surgical field should be preserved best possible. We therefore studied the intraoperative vascular anatomy for constant vascular findings. A perforating artery of the Musculus transversus nasalis was identified at the nasal ala on the cleft side, which could be constrantly preserved after it became aware.
The aim to refine a surgical treatment should not exclusively focus on the surgical technique but need also consider the burden of the entire treatment plan. More than 95% of the European cleft surgery centers use 2 to 4 surgeries to close the cleft of the lip, alveolus, hard, and soft palate –considering that this optimizes growth of the cleft maxilla. But facing the burden of repetitive surgeries for patient and family, Dr. Honigmann introduced in Basel 1991 the cleft repair in one single operation at “one-stage”. We were now able to assess the long-term growth effect of this procedure, which showed the same growth results as compared to multi-stage procedure. But when compared to normal, 20% to 45% of the cleft patients still showed a growth deficit that would require surgery to normalize the dental relation and facial profile. The orthognathic surgery rate in cleft patients from the literature ranges also widely from about 20% to 45%, whatever surgical technique and treatment plan is applied. It is therefore doubtful that by surgical means alone the growth deficit can be avoided. This prompted us to assess the in-vitro and in-vivo osteogenic capacity of stem cells from the umbilical cord Wharton’s jelly (WJMSC) under fully defined conditions allowing for clinical translation. Due to prenatal ultrasound the cleft lip malformation is frequently known before birth, and the umbilical cord could thus serve as an autologous stem cell donor site without any harvesting morbidity. Both, Osteogenically differentiated WJMSCs and WJ tissue biopsies produced a mineralized extracellular matrix. The expression of genes of osteoblastic lineage increased significantly after 3 weeks of osteodifferentiation. Although the WJMSCs formed in-vitro a dense collageneous matrix with signs of osteoblastic differentiation, no mature bone tissue was found after 8 weeks after subcutaneous implantation in immunoincompetent mice. Further in-vivo tests are therefore necessary applying more favorable bone forming conditions by using ostegenic predifferentiated cells and implantation into a bone defect.
In sum, biomedical and engineering methods have been applied to solve surgical problems or to establish new therapeutic strategies where conventional lip and nose reconstruction methods reach their limits. This has been demonstrated at different lip and nose reconstructive levels reaching from prosthetics, over microsurgery, to stem cell tissue engineering
Das Brezis-Nirenberg-Problem auf der Sphäre Sn
No full textIn dieser Arbeit betrachten wir einf¨uhrend im Kapitel 1 nichtlineare partielle
Differenzialgleichungen von der Form:
−"pu − b(x)up−1 = f(x, u) + c(x) up!−1 in"
u > 0 in"
u = 0 auf !",
wobei "pu = div(a(x)|#u|p−2#u) mit a(x) > 0 in " und 1 < p < n. Das
Gebiet " sei beschr¨ankt in Rn mit n 3 und p" = n p
n−p der kritische Sobolev-
Exponent. Da die Sobolev-Einbettung von W1,p
0 (") nach Lp!(") nur stetig
und nicht mehr kompakt ist, lassen sich die Standard-Methoden der Variationsrechnung
nicht anwenden. Wir werden jedoch im Kapitel 1 zeigen,
dass das zum obigen Problem geh¨orige Funktional # einer lokalen Kompaktheitsbedingung
gen¨ugt. Mit Hilfe dieser Kompaktheitseigenschaft und dem
Mountainpass-Lemma bzw. dem Variationsprinzip von Ekeland werden wir
die Existenz von schwachen L¨osungen beweisen. Die Beweismethode h¨angt
vom Wachstum der St¨orung f(x, ·) in null ab.
Im Hauptteil der Arbeit, dem Kapitel 2, wenden wir uns dem Brezis-
Nirenberg-Problem auf der Sph¨are zu. Unter dem (verallgemeinerten) Brezis-
Nirenberg-Problem auf der Sph¨are Sn verstehen wir das Problem
−"p,Snu − " uq−1 = up!−1 in"# % Sn
u > 0 in"#
u = 0 auf !"#,
(&)
wobei "# '= Sn ein Gebiet auf der Sph¨are Sn ist. Die Parameter abh¨angige
St¨orung sei von niedrigerer Ordnung, daher gilt 1 < q < p".
Das Problem hat seine urspr¨ungliche Motivation im Yamabe Problem
(siehe Aubin [3]). Brezis und Nirenberg untersuchten in der Arbeit [13] das
nichtlineare elliptische Randwertproblem f¨ur den Laplace-Operator in beschr
¨ankten Gebieten im euklidischen Raum Rn. Ebenfalls f¨ur den Laplace-
Operator untersuchten Ambrosetti, Brezis und Cerami in [2] das in null superlineare Randwertproblem
−"u − " uq−1 = u
n+2
n−2 in" % Rn
u > 0 in"
u = 0 auf !",
mit 1 < q < 2. Sie beweisen die Existenz von zwei positiven L¨osungen. Das
in null superlineare p-Laplace Problem behandelten Azorero und Alonso in
[24] und [26]. Unter geeigneten Voraussetzungen konnten sie ebenfalls die
Existenz von zwei positiven L¨osungen beweisen.
Im Artikel [10] stellt Brezis fest, dass die Existenz von L¨osungen f¨ur das
Brezis-Nirenberg-Problem einerseits von ", andererseits aber auch von der
Topologie des Gebiets " abh¨angt. Ausgehend davon betrachteten Bandle,
Brillard und Flucher [5] dieses Problem auf Gebieten in R¨aumen konstanter
skalarer Kr¨ummung. In ihrer Doktorarbeit [40] untersuchte S. Stapelkamp
das Brezis-Nirenberg Problem im hyperbolischen Raum Hn und in
[4] untersuchten Bandle und Benguria die Existenz und Nichtexistenz von
rotationssymmetrischen L¨osungen f¨ur p = q = 2 in geod¨atischen Kugeln auf
der S3. In dem Zusammenhang konnten Bandle und Benguria ein sehr interessantes
Ph¨anomen beobachten. So beschrieben sie in [4] als erste numerisch
berechnete L¨osungen in grossen Kugeln f¨ur " ( 0.
Das Kapitel 2 ist folgendermassen aufgebaut: In einem ersten Schritt
wird im Kapitel 2.3 ein Existenzresultat von Bandle, Fleckinger und de
Th´elin [6] f¨ur " > 0 verallgemeinert. Im Kapitel 2.4 wird die Nichtexistenz
von L¨osungen f¨ur (&) betrachtet. Es zeigt sich, dass aus der Pohozaev-
Identit¨at f¨ur den p-Laplace-Beltrami-Operator in sternf¨ormigen Gebieten
keine Aussage gewonnen werden kann. Wir werden uns daher auf rotationssymmetrische
L¨osungen in geod¨atischen Kugeln konzentrieren. Das Resultat
schliesst eine L¨ucke zwischen Existenz und Nichtexistenz f¨ur p )
!n+2
3 , n+1
2
"
der Arbeit von Bandle, Fleckinger und de Th´elin [6]. Im Folgenden werden
die F¨alle abh¨angig von p ! q f¨ur das Problem (&) separat betrachtet,
wobei jeweilen der Laplace-Beltrami-Operator (p = 2) und der p-Laplace-
Beltrami-Operator (p '= 2) getrennt diskutiert wird. Der lineare Fall (p = q)
erg¨anzt f¨ur n 4 die Arbeit von Bandle und Benguria [4]. Im superlinearen
Fall (1 < q < p) wird durch Minimieren eines abgeschnittenen Funktionals
eine L¨osung f¨ur (&) gefunden. Mit Hilfe von diesem Minimierer folgt aus
dem Mountainpass-Lemma unter geeigneten Voraussetzungen eine zweite
L¨osung f¨ur (&). F¨ur den sublinearen Fall (p < q < p") folgt aus dem Kapitel
1 die Existenz eines "" ) R so, dass f¨ur alle " > "" eine L¨osung f¨ur (&)
existiert. Es wird daher in dem Kapitel darum gehen, "" genauer zu beschreiben.
Mit Hilfe der in Kapitel 3 beschriebenen numerischen Methoden
werden im Kapitel 2.9 die von Bandle und Benguria numerisch gefundenen
L¨osungen systematisch untersucht. Es stellt sich dabei heraus, dass die
L¨osungen eine grosse Struktur aufweisen und unabh¨angig vom kritischen Sobolev-Exponent berechnet werden k¨onnen. Der Existenzbeweis f¨ur diese
L¨osungen ist nach wie vor offen.
Das Kapitel 3 behandelt die verwendeten numerischen Methoden zum
Berechnen von L¨osungen, sowie von L¨osungspfaden des Brezis-Nirenberg-
Problems. Da die Dimension n W1,p
0
|u|Lp! =1
#
! |#u|pdx
bezeichnen wir (bis auf die Potenz −1/p) die beste Konstante f¨ur die Sobolev-
Einbettung W1,p
0 (") % Lp!("). Es gilt daher
#
! |u|p!dx
%1/p!
+ S−1/p
p
#
! |#u|pdx
%1/p
.
Die Konstante ist gegeben durch
(Sp)1/p =
(n − p)
p − 1
n (p − 1)
n − p
%1
p
&
(1 + n − np
) (np
) #(n − 1)
(1 + n)
'1
n
,
wobei
#(n) = (n/2 + 1)
=
1
n|Sn−1|
das Volumen der n dimensionalen Einheitskugel ist. Mit |Sn−1| bezeichnen
wir die Oberfl¨ache der n − 1 dimensionalen Sph¨are
Sn−1 =
(
x ) Rn : |x| =
)
x21
+ . . . + x2
n = 1
*
.
Es gilt
|Sn−1| =
2(n/2). Mit
Sp,q(", a, c) = inf
u$K
#
!
a|#u|pdx, K =
(
u ) W1,p
0 (") :
#
!
c |u|qdx = 1
*
bezeichnen wir (bis auf die Potenz −1/p) die beste Konstante f¨ur die Sobolev-
Einbettung W1,p
0 (") % Lq(") mit den Gewichten a ) C1(") mit a(x) > 0
in " und c ) L%(") mit c(x) > 0 in "
