Active Mean Fields for Probabilistic Image Segmentation: Connections with Chan-Vese and Rudin-Osher-Fatemi Models

Segmentation is a fundamental task for extracting semantically meaningful regions from an image. The goal of segmentation algorithms is to accurately assign object labels to each image location. However, image-noise, shortcomings of algorithms, and image ambiguities cause uncertainty in label assignment. Estimating the uncertainty in label assignment is important in multiple application domains, such as segmenting tumors from medical images for radiation treatment planning. One way to estimate these uncertainties is through the computation of posteriors of Bayesian models, which is computationally prohibitive for many practical applications. On the other hand, most computationally efficient methods fail to estimate label uncertainty. We therefore propose in this paper the Active Mean Fields (AMF) approach, a technique based on Bayesian modeling that uses a mean-field approximation to efficiently compute a segmentation and its corresponding uncertainty. Based on a variational formulation, the resulting convex model combines any label-likelihood measure with a prior on the length of the segmentation boundary. A specific implementation of that model is the Chan-Vese segmentation model (CV), in which the binary segmentation task is defined by a Gaussian likelihood and a prior regularizing the length of the segmentation boundary. Furthermore, the Euler-Lagrange equations derived from the AMF model are equivalent to those of the popular Rudin-Osher-Fatemi (ROF) model for image denoising. Solutions to the AMF model can thus be implemented by directly utilizing highly-efficient ROF solvers on log-likelihood ratio fields. We qualitatively assess the approach on synthetic data as well as on real natural and medical images. For a quantitative evaluation, we apply our approach to the icgbench dataset

An Observational Study of Scent-Marking in Coyotes, Canis latrans

Urination and defaecation patterns of free-ranging coyotes (Canis latrans) were studied in the Grand Teton National Park, Jackson, Wyoming, for two years. The vast majority of urinations by adult males and females were involved in \u27marking,\u27 and differentiating between \u27marking\u27 and \u27elimination\u27 may not be necessary. Our results may be summarized as follows: 1) Raised-leg urinations (RLU) performed by males were most frequently used in marking. (2) Females marked throughout the year using the squat (SQU) posture. (3) Snow tracking and reading snow sign resulted in a gross underestimate of the relative frequency of SQU\u27s and a large overestimate in the relative frequency of defaecations (DEF) when compared to results obtained by direct observation. (4) There was sexual dimorphism for the contexts in which marking occurred. Overall, marking by males was associated with courtship and mating, with travelling, and with aggression. Marking by females was associated with the acquisition and possession of food and with the denning season. (5) Marking rates per coyote increased in groups larger than two animals. (6) RLU marking rates were greatest in areas of high intrusion when compared to denning areas and areas in which non-group me hers infrequently trespassed. SQU marking rates were highest in denning areas and high-intrusion areas. We suggest that scent odours are important in orienting individuals in space but do not represent in and of themselves barriers to movement

Predation by Wild Coyotes: Behavioral and Ecological Analyses

Predatory behavior of coyotes (Canis latrans) was studied between 1977 and 1980 in the Grand Teton National Park, Jackson, Wyoming. Major prey were voles (Microtus spp.), Uinta ground squirrels (Spermophilus armatus), pocket gophers (Thomomys talpoides), and grasshoppers (Locustidae). Coyotes typically rushed and ran down squirrels; when hunting mice, coyotes pounced and stabbed at them with their forepaws. Sequence structure was similar, though sequences directed to squirrels were significantly more variable. When juvenile coyotes hunted mice, sequences were similar to those performed by adults that hunted mice. Adults and juveniles were about equally successful. The size of prey last eaten influenced the interval until the next search was initiated; the larger the prey, the longer the interval. However, the time interval since the last capture and the outcome (capture or failure) of the next predatory attempt were not correlated. Durations of search, orient, and stalk were longer in short (\u3c 10 em) grass than in tall grass; stalk, orient, and total durations also were more variable in short grass. Coyotes that hunted in short grass were more successful. Durations of all acts were shorter and coyotes were more successful in snow less than 10 cm deep than in deeper snow. Mean orient and total durations were more variable in deep snow. Height of ground-cover apparently affected coyote movements and the way in which cues from prey were perceived. Local wind conditions did not affect capture success. Coyotes were least successful when they hunted mice and more successful when they hunted squirrels. More time was spent searching and stalking squirrels

Developing a National Perspective of Interrelated Preparation: Educational Administration Leading Teacher Leadership Programs

This NCPEA Position Paper articulates a national perspective for the development of teacher leadership programs with leadership from educational administration professors. The National Council of Professors of Educational Administration (NCPEA), as the professional organization that provides direction and leadership for its members, presents a vision for dialogue and action to collaboratively develop teacher leadership programs among professors of educational administration and teacher education faculty. We believe that leadership matters and thus we submit there is a sense of urgency for professors to collaboratively develop teacher leadership programs embedded within educational administration programs. It is crucial that these programs articulate knowledge and skills aligned to the national standards for preparing school leaders–leaders who know excellent instruction, but who also are excellent leaders. We envision programs of teacher leadership that include both content and leadership instruction, integrating concepts from curriculum from teacher education, and leadership from educational administration that cultivate skills. These leadership skills are applied in authentic educational environments where experiences are cultivated and guided by both university professors and school practitioners. Appropriate instructional methods for adults provide learning through problem-based concepts where teacher leader candidates can plan, experience, and evaluate on-the-job activities to develop voice, confidence, and actions as leaders and change agents, without ever assuming an official role or title of school administrators. In this document we present three principles for consideration, which correlate with three audiences that could advance these principles

Socioeconomic Disparities in the Use of College Admission-Enhancing Strategies among High School Seniors from the 1990s to 2000s

This study examines whether strategies commonly used by high school students for enhancing their chances of gaining college admission may contribute to social inequality in postsecondary education. Comparisons are made between nationally representative samples of high school seniors across two decades, from the early 1990s to the early 2000s. The analyses identify the extent to which students’ SES was associated with the use of admission-enhancing strategies, determine the extent to which the relationships changed across a two-decade period, and examine the role of academic achievement in this process. Results confirm that higher SES students are more likely to employ admission-enhancing strategies than lower SES students, but more importantly that this gap widened over time. These findings suggest that admission-enhancing strategies may be partially responsible for maintaining socioeconomic disparities through education

Effects of power variation on cycle performance during simulated hilly time-trials

It has previously been shown that cyclists are unable to maintain a constant power output during cycle time-trials on hilly courses. The purpose of the present study is therefore to quantify these effects of power variation using a mathematical model of cycling performance. A hypothetical cyclist (body mass: 70 kg, bicycle mass: 10 kg) was studied using a mathematical model of cycling, which included the effects of acceleration. Performance was modelled over three hypothetical 40-km courses, comprising repeated 2.5-km sections of uphill and downhill with gradients of 1%, 3%, and 6%, respectively. Amplitude (5–15%) and distance (0.31–20.00 km) of variation were modelled over a range of mean power outputs (200–600 W) and compared to sustaining a constant power. Power variation was typically detrimental to performance; these effects were augmented as the amplitude of variation and severity of gradient increased. Varying power every 1.25 km was most detrimental to performance; at a mean power of 200 W, performance was impaired by 43.90 s (±15% variation, 6% gradient). However at the steepest gradients, the effect of power variation was relatively independent of the distance of variation. In contrast, varying power in parallel with changes in gradient improved performance by 188.89 s (±15% variation, 6% gradient) at 200 W. The present data demonstrate that during hilly time-trials, power variation that does not occur in parallel with changes in gradient is detrimental to performance, especially at steeper gradients. These adverse effects are substantially larger than those previously observed during flat, windless time-trials

Structure and Function in Homodimeric Enzymes:Simulations of Cooperative and Independent Functional Motions

Large-scale conformational change is a common feature in the catalytic cycles of enzymes. Many enzymes function as homodimers with active sites that contain elements from both chains. Symmetric and anti-symmetric cooperative motions in homodimers can potentially lead to correlated active site opening and/or closure, likely to be important for ligand binding and release. Here, we examine such motions in two different domain-swapped homodimeric enzymes: the DcpS scavenger decapping enzyme and citrate synthase. We use and compare two types of all-atom simulations: conventional molecular dynamics simulations to identify physically meaningful conformational ensembles, and rapid geometric simulations of flexible motion, biased along normal mode directions, to identify relevant motions encoded in the protein structure. The results indicate that the opening/closure motions are intrinsic features of both unliganded enzymes. In DcpS, conformational change is dominated by an anti-symmetric cooperative motion, causing one active site to close as the other opens; however a symmetric motion is also significant. In CS, we identify that both symmetric (suggested by crystallography) and asymmetric motions are features of the protein structure, and as a result the behaviour in solution is largely non-cooperative. The agreement between two modelling approaches using very different levels of theory indicates that the behaviours are indeed intrinsic to the protein structures. Geometric simulations correctly identify and explore large amplitudes of motion, while molecular dynamics simulations indicate the ranges of motion that are energetically feasible. Together, the simulation approaches are able to reveal unexpected functionally relevant motions, and highlight differences between enzymes

Gastrocnemius Mass Is Lower 28 Days After Recovery From A Cycle Of Cisplatin In Mice

Platinum-based chemotherapeutic agents, such as cisplatin, are widely employed as a primary treatment modality for various cancer types. Despite their efficacy, cisplatin\u27s mechanism of action involves inducing DNA damage in cells, leading to pronounced acute and long-term side effects. One well established side effect is rapid loss in muscle mass. However, very little is known about the long-term effects of chemotherapy treatment on muscle size. PURPOSE: of this study was to analyze the long-term effects of cisplatin on muscle mass recovery. We hypothesized that cisplatin would have a negative long-term effect on muscle recovery. METHODS: 5-6 month-old CD2F1 mice were divided into two groups receiving injections of either Cisplatin (Cis) or Vehicle (Veh); n = 10 per group. A clinically relevant chemotherapy cycle was completed by a once weekly injection of 5mg/kg body weight of cisplatin for four weeks. Veh mice received an equal volume of saline. Following the cycle, mice recovered in their cage for 28 days and then hindlimb muscles were taken. Data were analyzed using independent t-test and presented as mean ± standard error. RESULTS: The gastrocnemius mass was significantly lower (p=0.008) in cisplatin-treated mice (139.20 ± 4.98) compared to the vehicle-treated group (147.50 ± 2.26). Conversely, the soleus did not show a significant difference (p=0.756) between Cis (9.90 ± 0.46) and Veh (10.10 ± 0.44) groups. Similarly, the Plantaris did not demonstrate a significant difference (p=0.950) in Cis treatment (18.65 ± 0.57) compared to Veh (18.65 ± 0.54). CONCLUSION: These data indicate a diminished ability of the gastrocnemius, the primary hindlimb flexor, to recover after a bout of cisplatin drug treatment. Further research is needed to better understand the mechanisms behind muscle specific differences and failed muscle mass recovery in the gastrocnemius

A transcriptomic time-series reveals differing trajectories during pre-floral development in the apex and leaf in winter and spring varieties of Brassica napus

Oilseed rape (Brassica napus) is an important global oil crop, with spring and winter varieties grown commercially. To understand the transcriptomic differences between these varieties, we collected transcriptomes from apex and leaf tissue from a spring variety, Westar, and a winter variety, Tapidor, before, during, and after vernalisation treatment, until the plants flowered. Large transcriptomic differences were noted in both varieties during the vernalisation treatment because of temperature and day length changes. Transcriptomic alignment revealed that the apex transcriptome reflects developmental state, whereas the leaf transcriptome is more closely aligned to the age of the plant. Similar numbers of copies of genes were expressed in both varieties during the time series, although key flowering time genes exhibited expression pattern differences. BnaFLC copies on A2 and A10 are the best candidates for the increased vernalisation requirement of Tapidor. Other BnaFLC copies show tissue-dependent reactivation of expression post-cold, with these dynamics suggesting some copies have retained or acquired a perennial nature. BnaSOC1 genes, also related to the vernalisation pathway, have expression profiles which suggest tissue subfunctionalisation. This understanding may help to breed varieties with more consistent or robust vernalisation responses, of special importance due to the milder winters resulting from climate change