Human action recognition based on pyramid histogram of oriented gradients

Human action recognition has been attracted lots of interest from computer vision researchers due to its various promising applications. In this paper, we employ Pyramid Histogram of Orientation Gradient (PHOG) to characterize human figures for action recognition. Comparing to silhouette-based features, the PHOG descriptor does not require extraction of human silhouettes or contours. Two state-space models, i.e.; Hidden Markov Model (HMM) and Conditional Random Field (CRF), are adopted to model the dynamic human movement. The proposed PHOG descriptor and the state-space models with respect to different parameters are tested using a standard dataset. We also testify the robustness of the method with respect to various unconstrained conditions and viewpoints. Promising experimental result demonstrates the effectiveness and robustness of our proposed method.

Image retrieval based on the combination of color and keyword

In this paper, color information and keyword information are combined for image retrieval. In detail, each image is divided into several blocks and then the color histograms of each block are derived. Users could feed back some annotations represented by keywords. Then, the keywords may spread in the image database so that both color-based and keyword-based retrieval could be utilized together. A prototype system shows that the proposed method is effective and efficient in performing image retrieval tasks.

Comparative evaluation of pedestrian detection methods for mobile bus surveillance

We present a comparative evaluation of the state-of-art algorithms for detecting pedestrians in low frame rate and low resolution footage acquired by mobile sensors. Four approaches are compared: a) The Histogram of Oriented Gradient (HoG) approach [1]; b) A new histogram feature that is formed by the weighted sum of both the gradient magnitude and the filter responses from a set of elongated Gaussian filters [2] corresponding to the quantised orientation, called Histogram of Oriented Gradient Banks (HoGB) approach; c) The codebook based HoG feature with branch-and-bound (efficient subwindow search) algorithm [3] and; d) The codebook based HoGB approach. Results show that the HoG based detector achieves the highest performance in terms of the true positive detection, the HoGB approach has the lowest false positives whilst maintaining a comparable true positive rate to the HoG, and the codebook approaches allow computationally efficient detection.

Coiled polymeric growth factor gradients for multi-luminal neural chemotaxis

In the injured adult nervous system, re-establishment of growth-promoting molecular gradients is known to entice and guide nerve repair. However, incorporation of three-dimensional chemotactic gradients in nerve repair scaffolds, particularly in those with multi-luminal architectures, remains extremely challenging. We developed a method that establishes highly tunable three-dimensional molecular gradients in collagen-filled multi-luminal nerve guides by anchoring growth-factor releasing coiled polymeric fibers onto the walls of collagen-filled hydrogel microchannels. Differential pitch in the coiling of neurotrophin-eluting fibers generated sustained three-dimensional chemotactic gradients that appropriately induced the differentiation of Pheochromocytoma (PC12) cells into neural-like cells along an increasing concentration of nerve growth factor (NGF). Computer modeling estimated the stability of the molecular gradient within the luminal collagen, which we confirmed by observing the significant effects of neurotrophin gradients on axonal growth from dorsal root ganglia (DRG). Neurons growing in microchannels exposed to a NGF gradient showed a 60% increase in axonal length compared to those treated with a linear growth factor concentration. In addition, a two-fold increment in the linearity of axonal growth within the microchannels was observed and confirmed by a significant reduction in the turning angle ratios of individual axons. These data demonstrate the ability of growth factor-loaded polymeric coiled fibers to establish three-dimensional chemotactic gradients to promote and direct nerve regeneration in the nervous system and provides a unique platform for molecularly guided tissue repair.

Climatic, vegetation and edaphic influences on the probability of fire across mediterranean woodlands of south-eastern Australia

 Aim: We investigated how the probability of burning is influenced by the time since fire (TSF) and gradients of climate, soil and vegetation in the fire-prone mediterranean-climate mallee woodlands of south-eastern Australia. This provided insight into the processes controlling contemporary fuel dynamics and fire regimes across biogeographical boundaries, and the consequent effects of climate change on potential shifts in boundaries between fuel systems and fire regimes, at a subcontinental scale. Location: South-eastern Australia. Methods: A desktop-based GIS was used to generate random sampling points across the study region to collect data on intersecting fire interval, rainfall, vegetation and soil type. We used a Bayesian framework to examine the effects of combinations of rainfall, vegetation and soil type on the hazard-of-burning and survival parameters of the Weibull distribution. These analyses identify the nature of environmental controls on the length of fire intervals and the age-dependence of the hazard of burning. Results: Higher rainfall was consistently associated with shorter fire intervals. Within a single level of rainfall, however, the interaction between soil and vegetation type influenced the length of fire intervals. Higher-fertility sands were associated with shorter fire intervals in grass-dominated communities, whereas lower-fertility sands were associated with shorter fire intervals in shrub-dominated communities. The hazard of burning remained largely independent of TSF across the region, only markedly increasing with TSF in shrub-dominated communities at high rainfall. Main conclusions: Rainfall had a dominant influence on fire frequency in the mediterranean-climate mallee woodlands of south-eastern Australia. Predicted changes in the spatial distribution and amount of rainfall therefore have the potential to drive changes in fire regimes, although the effects of soil fertility and rainfall on fire regimes do not align on a simple productivity gradient. Reduced soil fertility may favour plant traits that increase the rate of woody litter fuel accumulation and flammability, which may alter the overriding influence of rainfall gradients on fire regimes.

A hybrid FIA/HPLC system incorporating monolithic column chromatography

We have combined the generation of solvent gradients using milliGAT pumps, chromatographic separations with monolithic columns and chemiluminescence detection in an instrument manifold that approaches the automation and separation efficiency of HPLC, whilst maintaining the positive attributes of flow injection analysis (FIA), such as manifold versatility, speed of analysis and portability. As preliminary demonstrations of this hybrid FIA/HPLC system, we have determined six opiate alkaloids (morphine, pseudomorphine, codeine, oripavine, ethylmorphine and thebaine) and four biogenic amines (vanilmandelic acid, serotonin, 5-hydroxyindole-3-acetic acid and homovanillic acid) in human urine, using tris(2,2′-bipyridyl)ruthenium(III) and acidic potassium permanganate chemiluminescence detection.

Illusions promote mating success in great bowerbirds

Sexual selection studies normally compare signal strengths, but signal components and sensory processing may interact to create misleading or attention-capturing illusions. Visual illusions can be produced by altering object and scene geometry in ways that trick the viewer when seen from a particular direction. Male great bowerbirds actively maintain size-distance gradients of objects on their bower courts that create forced-perspective illusions for females viewing their displays from within the bower avenue. We show a significant relationship between mating success and the female's view of the gradient; this view explains substantially more variance in mating success than the strength of the gradients. Illusions may be widespread in other animals because males of most species display to females with characteristic orientation and distance, providing excellent conditions for illusions.

Size-frequency distributions along a latitudinal gradient in middle permian fusulinoideans

Geographic gradients in body size within and among living species are commonly used to identify controls on the long-term evolution of organism size. However, the persistence of these gradients over evolutionary time remains largely unknown because ancient biogeographic variation in organism size is poorly documented. Middle Permian fusulinoidean foraminifera are ideal for investigating the temporal persistence of geographic gradients in organism size because they were diverse and abundant along a broad range of paleo-latitudes during this interval (~275–260 million years ago). In this study, we determined the sizes of Middle Permian fusulinoidean fossils from three different paleo-latitudinal zones in order to examine the relationship between the size of foraminifers and regional environment. We recovered the following results: keriothecal fusulinoideans are substantially larger than nonkeriothecal fusulinoideans; fusulinoideans from the equatorial zone are typically larger than those from the north and south transitional zones; neoschwagerinid specimens within a single species are generally larger in the equatorial zone than those in both transitional zones; and the nonkeriothecal fusulinoideans Staffellidae and Schubertellidae have smaller size in the north transitional zone. Fusulinoidean foraminifers differ from most other marine taxa in exhibiting larger sizes closer to the equator, contrary to Bergmann's rule. Meridional variation in seasonality, water temperature, nutrient availability, and carbonate saturation level are all likely to have favored or enabled larger sizes in equatorial regions. Temporal variation in atmospheric oxygen concentrations have been shown to account for temporal variation in fusulinoidean size during Carboniferous and Permian time, but oxygen availability appears unlikely to explain biogeographic variation in fusulinoidean sizes, because dissolved oxygen concentrations in seawater typically increase away from the equator due to declining seawater temperatures. Consequently, our findings highlight the fact that spatial gradients in organism size are not always controlled by the same factors that govern temporal trends within the same clade.

A tandem liquid chromatography–mass spectrometry (LC–MS) method for profiling small molecules in complex samples

Liquid chromatography–mass spectrometry (LC–MS) methods using either aqueous normal phase (ANP) or reversed phase (RP) columns are routinely used in small molecule or metabolomic analyses. These stationary phases enable chromatographic fractionation of polar and non-polar compounds, respectively. The application of a single chromatographic stationary phase to a complex biological extract results in a significant proportion of compounds which elute in the non-retained fraction, where they are poorly detected because of a combination of ion suppression and the co-elution of isomeric compounds. Thus coverage of both polar and non-polar components of the metabolome generally involves multiple analyses of the same sample, increasing the analysis time and complexity. In this study we describe a novel tandem in-line LC–MS method, in which compounds from one injection are sequentially separated in a single run on both ANP and RP LC-columns. This method is simple, robust, and enables the use of independent gradients customized for both RP and ANP columns. The MS signal is acquired in a single chromatogram which reduces instrument time and operator and data analysis errors. This method has been used to analyze a range of biological extracts, from plant and animal tissues, human serum and urine, microbial cell and culture supernatants. Optimized sample preparation protocols are described for this method as well as a library containing the retention times and accurate masses of 127 compounds.

Interpreting behaviors from accelerometry: a method combining simplicity and objectivity.

Quantifying the behavior of motile, free-ranging animals is difficult. The accelerometry technique offers a method for recording behaviors but interpretation of the data is not straightforward. To date, analysis of such data has either involved subjective, study-specific assignments of behavior to acceleration data or the use of complex analyses based on machine learning. Here, we present a method for automatically classifying acceleration data to represent discrete, coarse-scale behaviors. The method centers on examining the shape of histograms of basic metrics readily derived from acceleration data to objectively determine threshold values by which to separate behaviors. Through application of this method to data collected on two distinct species with greatly differing behavioral repertoires, kittiwakes, and humans, the accuracy of this approach is demonstrated to be very high, comparable to that reported for other automated approaches already published. The method presented offers an alternative to existing methods as it uses biologically grounded arguments to distinguish behaviors, it is objective in determining values by which to separate these behaviors, and it is simple to implement, thus making it potentially widely applicable. The R script coding the method is provided.

On the production of randomly-oriented recrystallization nuclei for selective growth experiments

The ideal starting condition for selective growth experiments is one having a layer of randomly-oriented nuclei adjacent to a matrix with negligible orientational variation but sufficient stored energy to promote growth. In practice, cutting or deformation processes are used in an attempt to approximate these ideal conditions, but the degree to which this is achieved has not been rigorously quantified. In this work, Fe-3wt%Si single crystals were cut or deformed using six different processes. The variation in texture with distance from the cut or deformed surface was measured using electron backscatter diffraction (EBSD) in a field emission gun scanning electron microscope (FEG-SEM) in order to assess the ability of each process to create conditions suitable for selective growth experiments. While grooving with a machine tool produced the best spread of orientations at the cut surface, the suitability of this process is diminished by the presence of a differently-textured deformed layer between the cut surface and the single crystal matrix. Grinding produced a less ideal distribution of orientations at the cut surface, but the presence of these orientations in a very thin layer adjacent to the matrix makes this process preferable for preparing crystals for selective growth experiments, provided the results are corrected for the deviation in the distribution of nuclei orientations from a random distribution.

Deformation and annealing of (011)[011] oriented A1 single crystals

High purity Al single crystals of the (011)[011] orientation have been deformed in plane strain compression in a channel die. Deformation was carried out at a strain rate of 0.01 s−1 to true strains of 0.5 and 1.0, and at temperatures of 25, 200 and 300 °C. The as-deformed microstructure has been characterized using electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). No recrystallization was detected after deformation, and the deformation texture analysis showed that the stability of the orientation decreased with increasing temperature, contrary to reports for other orientations.

Annealing was carried out for various times at 300 °C. Nucleation of recrystallization exhibited periodicity, with distinct bands of recrystallized grains forming parallel to the transverse direction. This recrystallized microstructure has been examined using EBSD. A model is proposed to account for the origin of the periodicity of nucleation and the retention of rods or cylinders of unrecrystallized material after significant annealing times.