Luteale en follikulere telling in tewe : beoordeling deur middel van magnetiese resonansie beelding

No abstract availableResearchers require an accurate measurement of fertility in the bitch for the comparison ofinsemination methods, assessing the effects of procedures on fertility and assessing the effectsof drugs on fertility. In clinical practice, a prospective measurement would enable thepractitioner to select bitches with the largest numbers of follicles for breeding by artificialmeans or natural mating with valuable semen or studs. The ratio between the numbers ofcorpora lutea or follicles and litter size is a more sensitive measurement of fertility than islitter size, as the latter does not reflect the total number of oocytes that were available forfertilization. Magnetic resonance imaging (MRI) has proven to be of value in diagnosticimagery of particularly soft tissues. This is the first study that evaluated the use of MRI incanine reproduction and was done to determine whether the numbers of corpora lutea orfollicles can be counted accurately by means of MRI.The study was divided into two experiments. In Experiment 1, 16 bitches were used. Apartfrom one bitch that was in anoestrus, they were either in the follicular, early, or late lutealphase. Their ovaries were collected via ovariohysterectomy and placed into a phantom forMRI. The phantom was then scanned in three planes with a slice interval and slice thickness of 1 mm, using a 1.5 Tesla SIEMENS Magnetom Symphony scanner. A circular polarizedhead array coil was also used around the phantom. The T2-weigthed images were consideredbetter than T1-weighted images. This study showed that although the corpora lutea or folliclescould be identified in most but not all images, it was not possible to accurately count thenumber of corpora lutea or follicles in the ovaries of bitches using MRI techniques andapparatus commonly used in human MRI units. Follicles were commonly confused withcorpora lutea on the images. Although the study was not designed to detect ovarian pathology,MRI of the ovary in the phantom study, showed promise in detecting cystic ovarian disease.In Experiment 2, it was attempted to find the ovaries, and count the structures in them, bydoing MRI on two live, sedated bitches that were in the late follicular phase, whereafter thebitches were spayed and the ovarian structures counted. The effect of motion was so great thatno image could be generated on which any ovary or its structures could be identified.There still exists no reliable, non-invasive means by which the number corpora lutea orfollicles can be counted in the bitch. Further studies are required to evaluate more advancedMRI techniques and apparatus.Navorsers benodig 'n akurate meting van vrugbaarheid in die teef vir die vergelyking vaninseminasiemetodes en vir die beoordeling van die effekte van prosedures en middels opvrugbaarheid. In praktyk sou veral 'n prospektiewe meting van vrugbaarheid nuttig wees,omdat dit die klinikus in staat sal stel om daardie tewe met die grootste aantal follikels teselekteer vir teling in gevalle waar die koste van òf die semen òf dekking baie hoog is. Dieverhouding tussen die aantal korpora lutea of follikels en werpselgrootte is 'n sensitiewermaatstaf van vrugbaarheid as werpselgrootte op sigself; omdat laasgenoemde nie dievolledige aantal oösiete wat beskikbaar was vir bevrugting in bereken bring nie. Magnetieseresonansie beelding (MRB) is reeds bewys as 'n waardevolle tegniek vir die verkryging vandiagnostiese beelde van veral sagte weefsels. Hierdie is die eerste studie wat die gebruik vanMRB op die geslagstelsel van honde beoordeel en was spesifiek uitgevoer om vas te stel ofdie korpora lutea of follikels in die eierstokke van tewe d.m.v. MRB akkuraat getel kan word.Die studie was verdeel in 2 eksperimente. In Eksperiment 1 was 16 tewe gebruik. Behalwe vireen teef wat in anestrus was, was hulle òf in die follikulêre fase, òf in die vroeë òf in die laatluteale fases. Hul eierstokke was versamel deur middel van ovariohistorektomie en in 'nfantoom geplaas vir MRB. Die fantoom was geskandeer in drie oriëntasies reghoekig totmekaar, en 'n snitdikte en 'n snitinterval van 1mm is gebruik. Die MRB aparaat was 'n 1.5 Tesla SIEMENS Magnetom Symphony skandeerder. 'n Kopspoel was gebruik rondom diefantoom. Die T2-gerigte beelde was beter as die T1-gerigte beelde. Hierdie studie het getoondat alhoewel die korpora lutea of follikels in die meeste beelde van die eierstokkegeïdentifiseer kan word, dit nie moontlik is om hierdie strukture in die eierstokke van tewe tetel m.b.v. die apparaat wat oor die algemeen in die gemidelde privaathospitaal beskikbaar isnie. Dit was ook nie moontlik om altyd korpora lutea van follikels te onderskei nie. Alhoeweldie studie nie ontwerp was om vir patologiese letsels op die eierstokke te soek nie, was diemeeste ovariële siste duidelik sigbaar op die beelde in die fantoomstudie, wat daarop dui datMRB in hierdie verband belowend mag wees.In Eksperiment 2 is gepoog om die eierstokke in twee lewendige tewe wat laat in diefollikulêre fase en onder berusting was, d.m.v. MRB op te spoor en die strukture daarin te tel,waarna 'n ovariohisterektomie op elke teef uitgevoer was en die strukture getel was. Die effekvan beweging wat deur asemhaling teweeg gebring is was egter só groot dat daar geen beeldgegenereer kon word waarop 'n eierstok of sy strukture herken kon word nie.Daar bestaan steeds geen betroubare manier, anders as disseksie van die eierstokke, om diefollikels of korpora lutea indie eierstokke van tewe akkuraat te tel nie. Verdere navorsing isnodig om meer gevorderde MRB tegnieke en apparaat vir hierdie doel te evalueer.Dissertation (MMedVet (Reproduction))--University of Pretoria, 2005.Production Animal Studiesunrestricte

Management of large wood in streams of Colorado's Front Range: a risk analysis based on physical, biological, and social factors

March 2017.Includes bibliographical references.Instream and floodplain wood can provide many benefits to river ecosystems, but can also create risks to inhabitants, infrastructure, property, and recreational users in the river corridor. In this report we outline a decision process for managing large wood, and particularly for assessing the relative benefits and risks associated with individual wood pieces and with accumulations of wood. This process can be applied at varying levels of effort, from a relatively cursory visual assessment to more detailed numerical modeling. Decisions of whether to retain, remove, or modify wood in a channel or on a floodplain are highly dependent on the specific context: the same piece of wood might require removal in a highly urbanized setting, for example, but provide sufficient benefits to justify retention in a natural area. Our intent is that the decision process outlined here can be used by individuals with diverse technical backgrounds and in a range of urban to natural river reaches

Assessing Impact of Dual Sensor Enhanced Flight Vision Systems on Departure Performance

Synthetic Vision (SV) and Enhanced Flight Vision Systems (EFVS) may serve as game-changing technologies to meet the challenges of the Next Generation Air Transportation System and the envisioned Equivalent Visual Operations (EVO) concept - that is, the ability to achieve the safety and operational tempos of current-day Visual Flight Rules operations irrespective of the weather and visibility conditions. One significant obstacle lies in the definition of required equipage on the aircraft and on the airport to enable the EVO concept objective. A motion-base simulator experiment was conducted to evaluate the operational feasibility and pilot workload of conducting departures and approaches on runways without centerline lighting in visibility as low as 300 feet runway visual range (RVR) by use of onboard vision system technologies on a Head-Up Display (HUD) without need or reliance on natural vision. Twelve crews evaluated two methods of combining dual sensor (millimeter wave radar and forward looking infrared) EFVS imagery on pilot-flying and pilot-monitoring HUDs. In addition, the impact of adding SV to the dual sensor EFVS imagery on crew flight performance and workload was assessed. Using EFVS concepts during 300 RVR terminal operations on runways without centerline lighting appears feasible as all EFVS concepts had equivalent (or better) departure performance and landing rollout performance, without any workload penalty, than those flown with a conventional HUD to runways having centerline lighting. Adding SV imagery to EFVS concepts provided situation awareness improvements but no discernible improvements in flight path maintenance

Summer habitat use and movements of invasive wild pigs (Sus scrofa) in Canadian agro-ecosystems

Resource selection informs understanding of a species’ ecology and is especially pertinent for invasive species. Since introduced to Canada, wild pigs (Sus scrofa Linnaeus, 1978) remain understudied despite recognized negative impacts on native and agricultural systems globally. Elsewhere in North America, pigs typically use forests and forage in agricultural crops. We hypothesized Canadian wild pigs would behave similarly, and using GPS locations from 15 individuals, we examined diel and seasonal resource selection and movement in the Canadian prairie region. Forests were predominately selected during the day, while corn (Zea mays L.), oilseeds, and wheat (Triticum aestivum L.) were predominately selected at night. Forests and corn were consistently selected throughout the growing season.Wetlands and forests showed greater use rates than other habitats, with evident trade-offs as crop use increased with the timing of maturation. Activity was consistent with foraging in growing crops. Results indicate diel patterns were likely a function of short-term needs to avoid daytime anthropogenic risk, while seasonal patterns demonstrate how habitats that fill multiple functional roles——food, cover, and thermoregulation——can be optimized. Understanding selection by invasive species is an important step in understanding their potential environmental impacts in novel environments and informs their management

Effects of Wild Pig Disturbance on Forest Vegetation and Soils

In North America, wild pigs (Sus scrofa; feral pigs, feral swine, wild boars) are a widespread exotic species capable of creating large‐scale biotic and abiotic landscape perturbations. Quantification of wild pig environmental effects has been particularly problematic in northern climates, where they occur only recently as localized populations at low densities. Between 2016 and 2017, we assessed short‐term (within ~2 yrs of disturbance) effects of a low‐density wild pig population on forest features in the central Lower Peninsula of Michigan, USA. We identified 16 8‐ha sites using global positioning system locations from 7 radio‐collared wild pigs for sampling.Within each site, we conducted fine‐scale assessments at 81 plots and quantified potential disturbance by wild pigs. We defined disturbance as exposure of overturned soil, often resulting from rooting behavior by wild pigs.We quantified ground cover of plants within paired 1‐m2 frames at each plot, determined effects to tree regeneration using point‐centered quarter sampling, and collected soil cores from each plot. We observed less percent ground cover of native herbaceous plants and lower species diversity, particularly for plants with a coefficient of conservatism ≥5, in plots disturbed by wild pigs.We did not observe an increase in colonization of exotic plants following disturbance, though the observed prevalence of exotic plants was low. Wild pigs did not select for tree species when rooting, and we did not detect any differences in regeneration of light‐ and heavy‐seeded tree species between disturbed or undisturbed plots. Magnesium and ammonium content in soils were lower in disturbed plots, suggesting soil disturbance accelerated leaching of macronutrients, potentially altering nitrogen transformation. Our study suggested that disturbances by wild pigs, even at low densities, alters short‐term native herbaceous plant diversity and soil chemistry. Thus, small‐scale exclusion of wild pigs from vulnerable and rare plant communities may be warranted

Enhanced Flight Vision Systems Operational Feasibility Study Using Radar and Infrared Sensors

Approach and landing operations during periods of reduced visibility have plagued aircraft pilots since the beginning of aviation. Although techniques are currently available to mitigate some of the visibility conditions, these operations are still ultimately limited by the pilot's ability to "see" required visual landing references (e.g., markings and/or lights of threshold and touchdown zone) and require significant and costly ground infrastructure. Certified Enhanced Flight Vision Systems (EFVS) have shown promise to lift the obscuration veil. They allow the pilot to operate with enhanced vision, in lieu of natural vision, in the visual segment to enable equivalent visual operations (EVO). An aviation standards document was developed with industry and government consensus for using an EFVS for approach, landing, and rollout to a safe taxi speed in visibilities as low as 300 feet runway visual range (RVR). These new standards establish performance, integrity, availability, and safety requirements to operate in this regime without reliance on a pilot's or flight crew's natural vision by use of a fail-operational EFVS. A pilot-in-the-loop high-fidelity motion simulation study was conducted at NASA Langley Research Center to evaluate the operational feasibility, pilot workload, and pilot acceptability of conducting straight-in instrument approaches with published vertical guidance to landing, touchdown, and rollout to a safe taxi speed in visibility as low as 300 feet RVR by use of vision system technologies on a head-up display (HUD) without need or reliance on natural vision. Twelve crews flew various landing and departure scenarios in 1800, 1000, 700, and 300 RVR. This paper details the non-normal results of the study including objective and subjective measures of performance and acceptability. The study validated the operational feasibility of approach and departure operations and success was independent of visibility conditions. Failures were handled within the lateral confines of the runway for all conditions tested. The fail-operational concept with pilot in the loop needs further study

Assessing Dual Sensor Enhanced Flight Vision Systems to Enable Equivalent Visual Operations

Flight deck-based vision system technologies, such as Synthetic Vision (SV) and Enhanced Flight Vision Systems (EFVS), may serve as a revolutionary crew/vehicle interface enabling technologies to meet the challenges of the Next Generation Air Transportation System Equivalent Visual Operations (EVO) concept - that is, the ability to achieve the safety of current-day Visual Flight Rules (VFR) operations and maintain the operational tempos of VFR irrespective of the weather and visibility conditions. One significant challenge lies in the definition of required equipage on the aircraft and on the airport to enable the EVO concept objective. A motion-base simulator experiment was conducted to evaluate the operational feasibility, pilot workload and pilot acceptability of conducting straight-in instrument approaches with published vertical guidance to landing, touchdown, and rollout to a safe taxi speed in visibility as low as 300 ft runway visual range by use of onboard vision system technologies on a Head-Up Display (HUD) without need or reliance on natural vision. Twelve crews evaluated two methods of combining dual sensor (millimeter wave radar and forward looking infrared) EFVS imagery on pilot-flying and pilot-monitoring HUDs as they made approaches to runways with and without touchdown zone and centerline lights. In addition, the impact of adding SV to the dual sensor EFVS imagery on crew flight performance, workload, and situation awareness during extremely low visibility approach and landing operations was assessed. Results indicate that all EFVS concepts flown resulted in excellent approach path tracking and touchdown performance without any workload penalty. Adding SV imagery to EFVS concepts provided situation awareness improvements but no discernible improvements in flight path maintenance

Behavioral states in space and time: Understanding landscape use by an invasive mammal

Animal movement models can be used to understand species behavior and assist with implementation of management activities. We explored behavioral states of an invasive wild pig (Sus scrofa) population that recently colonized central Michigan, USA, 2014–2018. To quantify environmental factors related to wild pig movement ecology and spatio‐temporal landscape use, we predicted wild pig behavioral states relative to land cover type, landscape structure (i.e., edge and patch cohesion), and weather conditions. We used global positioning system (GPS)‐collars and monitored 8 wild pigs from 2014–2018. We fit local convex hulls and calculated movement metrics revealing 3 wild pig behavioral states (resting, exploratory, and relocating) and constructed a 3‐level model to predict behavioral state probabilities relative to biotic and abiotic conditions. Probabilities of exploratory and resting behaviors were higher nearer to riparian and open herbaceous cover types (oftentimes emergent marsh), indicating that these cover types provided security cover during activity and bedding. Hard mast cover types had a strong positive association with relocating behaviors. More cohesive patches of agriculture and shrub cover types were associated with higher probabilities of exploratory behaviors, while resting was more likely in continuous patches of agriculture (mostly mid‐summer corn). The probability of exploratory behaviors increased exponentially with warming ambient temperature. Our results may be used by managers to develop control strategies conducive to landscape and environmental conditions where the likelihood of encountering wild pigs is highest or targeting wild pigs when in a behavioral state most vulnerable to a particular removal technique

Initial Flight Testing of an eXternal Vision System (XVS) for the Low Boom Flight Demonstrator (LBFD)

NASA will design an eXternal Vision System (XVS) that, with other aircraft systems and subsystems, will ensure safe and efficient operations in all phases of flight for its Low Boom Flight Demonstrator vehicle. XVS is a combination of display, sensor, and computing technologies, creating an electronic means of forward visibility for the pilot. A flight test was performed evaluating a preliminary design of an XVS to quantify, by direct comparison, the ability of a pilot using an XVS to see and recognize airborne traffic compared to that of a pilot using forward-facing windows during challenging see-and-avoid scenarios. The data showed that the XVS and forward-facing windows were essentially equivalent in detecting and recognizing incurring traffic aircraft. The data also showed that the pilot using the XVS could see and recognize the incurring traffic at no less than 0.7 nm prior to the pilot using the forward-facing windows. The performance of the XVS was dependent upon the application of image contrast enhancement. Recommendations for future improvements were captured from evaluation pilot commentary