Adiabatic corrections for velocity-gauge simulations of electron dynamics in periodic potentials

We show how to significantly reduce the number of energy bands required to model the interaction of light with crystalline solids in the velocity gauge. We achieve this by deriving analytical corrections to the electric current density. These corrections depend only on band energies, the matrix elements of the momentum operator, and the macroscopic vector potential. Thus, the corrections can be evaluated independently from modeling the interaction with light. In addition to improving the convergence of velocity-gauge calculations, our analytical approach overcomes the long-standing problem of divergences in expressions for linear and nonlinear susceptibilities.Comment: Submitted to Computer Physics Communication

TAPCHA: An Invisible CAPTCHA Scheme

TAPCHA is a universal CAPTCHA scheme designed for touch-enabled smart devices such as smartphones, tablets and smartwatches. The main difference between TAPCHA and other CAPTCHA schemes is that TAPCHA retains its security by making the CAPTCHA test ‘invisible’ for the bot. It then utilises context effects to maintain the readability of the instruction for human users which eventually guarantees the usability of the scheme. Two reference designs, namely TAPCHA SHAPE & SHADE and TAPCHA MULTI are developed to demonstrate the use of this scheme

Macroalgae removal on coral reefs: realised ecosystem functions transcend biogeographic locations

Coral reef ecosystems are at the forefront of biodiversity loss and climate change-mediated transformations. This is expected to have profound consequences for the functioning of these ecosystems. However, assessments of ecosystem function on reefs are often spatially limited, within biogeographic realms, or rely on presumed proxies such as traits. To address these shortcomings and assess the effects of biogeography and fish presence on the critical ecosystem function of macroalgal removal, we used assays of six algal genera across three reef habitats in two biogeographically distinct locations: Little Cayman in the Caribbean and Lizard Island on the Great Barrier Reef (GBR). Patterns of fish feeding and realised ecosystem function were strikingly similar between the two geographic locations, despite a threefold difference in the local diversity of nominally herbivorous fishes, a 2.4-fold difference in the diversity of fishes feeding and differences in the biogeographic history of the two locations. In both regions, a single species dominated the function: a surgeonfish, Naso unicornis, at the GBR location and, surprisingly, a triggerfish, Melichthys niger, at the Caribbean location. Both species, especially M. niger, were relatively rare, compared to other nominally herbivorous fishes, in censuses covering more than 14,000 m(2) at each location. Our study provides novel insights into the critical function of macroalgal removal in hyperdiverse coral reef ecosystems, highlighting: (a) that function can transcend biogeographic, taxonomic and historical constraints; and (b) shortcomings in our assumptions regarding fish presence and realised ecosystem function on coral reefs

Cue-based decision rules of cleaner fish in a biological market task

To develop an evolutionary theory of social decision making, we require an understanding of how individuals utilize environmental cues to form decision rules. We exposed ‘cleaner’ fish (bluestreak cleaner wrasse, Labroides dimidiatus) to a biological market task, where giving priority to an ephemeral (i.e. ‘visitor’ client) food plate, over a permanent (i.e. ‘resident’ client) plate, doubled the food reward. Previously published experiments revealed that adult cleaners from a complex social environment regularly solved this task and outperformed adult cleaners from a simple social environment as well as juveniles from both habitat types. In these studies, plates were differentiated by colour and/or colour pattern. However, client size is another potentially useful cue that may be used by cleaners to solve the biological market task in nature, as visitor clients are typically larger than resident clients. Here, we tested cleaners in a setting where plates differed only in size and not colour/pattern: the majority of cleaners exhibited a spontaneous preference for inspecting larger plates or were more likely to reach the task-solving criterion if the visitor plate was larger. All cleaners were able to solve the task when we incorporated both size and colour/pattern cues; however, only cleaners from the complex social environment settled on the more precise colour/pattern cue. In contrast, cleaners from the simple social environment relied on size as the primary, yet less precise, cue to solve the task. In conclusion, our results strongly suggest that intraspecific variation in the performance of cleaners in the biological market task is based on variation in the relative salience of available cues and correlates with variation in a cleaner's natural social environment. Variation in the relative salience of available cues may therefore explain a portion of the intra- and interspecific variance in cognitive performance and social behaviour documented in other animal species

Current strategies for treatment of intervertebral disc degeneration: substitution and regeneration possibilities

Background: Intervertebral disc degeneration has an annual worldwide socioeconomic impact masked as low back pain of over 70 billion euros. This disease has a high prevalence over the working age class, which raises the socioeconomic impact over the years. Acute physical trauma or prolonged intervertebral disc mistreatment triggers a biochemical negative tendency of catabolic-anabolic balance that progress to a chronic degeneration disease. Current biomedical treatments are not only ineffective in the long-run, but can also cause degeneration to spread to adjacent intervertebral discs. Regenerative strategies are desperately needed in the clinics, such as: minimal invasive nucleus pulposus or annulus fibrosus treatments, total disc replacement, and cartilaginous endplates decalcification. Main Body: Herein, it is reviewed the state-of-the-art of intervertebral disc regeneration strategies from the perspective of cells, scaffolds, or constructs, including both popular and unique tissue engineering approaches. The premises for cell type and origin selection or even absence of cells is being explored. Choice of several raw materials and scaffold fabrication methods are evaluated. Extensive studies have been developed for fully regeneration of the annulus fibrosus and nucleus pulposus, together or separately, with a long set of different rationales already reported. Recent works show promising biomaterials and processing methods applied to intervertebral disc substitutive or regenerative strategies. Facing the abundance of studies presented in the literature aiming intervertebral disc regeneration it is interesting to observe how cartilaginous endplates have been extensively neglected, being this a major source of nutrients and water supply for the whole disc. Conclusion: Severalinnovative avenues for tackling intervertebral disc degeneration are being reported â from acellular to cellular approaches, but the cartilaginous endplates regeneration strategies remain unaddressed. Interestingly, patient-specific approaches show great promise in respecting patient anatomy and thus allow quicker translation to the clinics in the near future.The authors would like to acknowledge the support provided by the Portuguese Foundation for Science and Technology (FCT) through the project EPIDisc (UTAP-EXPL/BBBECT/0050/2014), funded in the Framework of the “International Collaboratory for Emerging Technologies, CoLab”, UT Austin|Portugal Program. The FCT distinctions attributed to J. Miguel Oliveira (IF/00423/2012 and IF/01285/ 2015) and J. Silva-Correia (IF/00115/2015) under the Investigator FCT program are also greatly acknowledged.info:eu-repo/semantics/publishedVersio

Attosecond optoelectronic field measurement in solids

The sub-cycle interaction of light and matter is one of the key frontiers of inquiry made accessible by attosecond science. Here, we show that when light excites a pair of charge carriers inside of a solid, the transition probability is strongly localized to instants slightly after the extrema of the electric field. The extreme temporal localization is utilized in a simple electronic circuit to record the waveforms of infrared to ultraviolet light fields. This form of petahertz-bandwidth field metrology gives access to both the modulated transition probability and its temporal offset from the laser field, providing sub-fs temporal precision in reconstructing the sub-cycle electronic response of a solid state structure. Characterization of light pulses is important in order to understand their interaction with matter. Here the authors demonstrate a nonlinear photoconductive sampling method to measure electric field wave-forms in the infrared, visible and ultraviolet spectral ranges

Factors related to the practice of breast self examination (BSE) and Pap smear screening among Malaysian women workers in selected electronics factories

BACKGROUND: The Malaysian Ministry of Health promotes breast self-examination (BSE) for all women, and Pap smear screening every three years for all sexually active women ages 20 years and above. The objectives of this paper were to examine the practice of these two screening tests among women production workers in electronics factories, and to identify factors related to practice. METHODS: This was a cross-sectional survey of women production workers from ten electronics factories. Data was collected by a self-administered questionnaire from a total of 1,720 women. The chi-square test, odds ratio and binomial logistic regression were used in bivariate and multivariate analysis. RESULTS: Prevalence rates were 24.4% for BSE once a month, and 18.4% for Pap smear examination within the last three years. Women who were significantly more likely to perform BSE every month were 30 years and older, Malays, with upper secondary education and above, answered the BSE question correctly, and had a Pap smear within the last three years. The proportion of women who had a Pap smear within the last three years were significantly higher among those who were older, married, with young children, on the contraceptive pill or intra-uterine device, had a medical examination within the last five years, answered the Pap smear question correctly, and performed BSE monthly. CONCLUSION: Screening practice rates in this study were low when compared to national rates. Socio-demographic and health care factors significantly associated with screening practice are indicative of barriers which should be further understood so that more effective educational and promotional strategies could be developed