Direct and Inverse Variational Problems on Time Scales: A Survey

We deal with direct and inverse problems of the calculus of variations on arbitrary time scales. Firstly, using the Euler-Lagrange equation and the strengthened Legendre condition, we give a general form for a variational functional to attain a local minimum at a given point of the vector space. Furthermore, we provide a necessary condition for a dynamic integro-differential equation to be an Euler-Lagrange equation (Helmholtz's problem of the calculus of variations on time scales). New and interesting results for the discrete and quantum settings are obtained as particular cases. Finally, we consider very general problems of the calculus of variations given by the composition of a certain scalar function with delta and nabla integrals of a vector valued field.Comment: This is a preprint of a paper whose final and definite form will be published in the Springer Volume 'Modeling, Dynamics, Optimization and Bioeconomics II', Edited by A. A. Pinto and D. Zilberman (Eds.), Springer Proceedings in Mathematics & Statistics. Submitted 03/Sept/2014; Accepted, after a revision, 19/Jan/201

Transcatheter closure of a fenestration in intracardiac Fontan circulation

We present a case of tricuspid atresia and the treatment that was used in a child now aged 12. The malformation was corrected at the age of five through intracardiac Fontan circulation. Later, the child developed a right-to-left shunt due to dehiscence in the intra-atrial conduit, causing significant desaturation. This was treated by transcatheter closure with a 10 mm Amplatzer device at 8 years of age. Currently the child is asymptomatic with no residual shunts, and the position of the device is normal. The percutaneous closure of Fontan fenestrations using the Amplatzer device is a therapeutic approach that provides good results. It results in normal oxygen saturation and has low morbidity. The technique is simple, available to most cardiac catheterization laboratories, safe, and offers a reasonable cost-benefit ratio. In addition, the design of the device is suitable for this type of defect

Histological changes and impairment of liver mitochondrial bioenergetics after long-term treatment with alpha-naphthyl-isothiocyanate (ANIT)

This study was designed to evaluate the effects of long-term treatment with alpha-naphthyl-isothiocyanate (ANIT) on liver histology and at the mitochondrial bioenergetic level. Since, ANIT has been used as a cholestatic agent and it has been pointed out that an impairment of mitochondrial function is a cause of hepatocyte dysfunction leading to cholestatic liver injury, serum markers of liver injury were measured and liver sections were analyzed in ANIT-treated rats (i.p. 80 mg/kg/week x 16 weeks). Mitochondrial parameters such as transmembrane potential, respiration, calcium capacity, alterations in permeability transition susceptibility and ATPase activity were monitored. Histologically, the most important features were the marked ductular proliferation, proliferation of mast cells and the presence of iron deposits in ANIT-treated liver. Mitochondria isolated from ANIT-treated rats showed no alterations in state 4 respiration, respiratory control ratio and ADP/O ratio, while state 3 respiration was significantly decreased. No changes were observed on transmembrane potential, but the repolarization rate was decreased in treated rats. Consistently with these data, there was a significant decrease in the ATPase activity of treated mitochondria. Associated with these parameters, mitochondria from treated animals exhibited increased susceptibility to mitochondrial permeability transition pore opening (lower calcium capacity). Since, human cholestatic liver disease progress slowly overtime, these data provide further insight into the role of mitochondrial dysfunction in the process

Can an aversive, extinction-resistant memory trigger impairments in walking adaptability? An experimental study using adult rats

Cognitive demands can influence the adaptation of walking, a crucial skill to maintain body stability and prevent falls. Whilst previous research has shown emotional load tunes goal-directed movements, little attention has been given to this finding. This study sought to assess the effects of suffering an extinction-resistant memory on skilled walking performance in adult rats, as an indicator of walking adaptability. Thus, 36 Wistar rats were divided in a two-part experiment. In the first part (n = 16), the aversive, extinction-resistance memory paradigm was established using a fear-conditioning chamber. In the second, rats (n = 20) were assessed in a neutral room using the ladder rung walking test before and tree days after inducing an extinction-resistance memory. In addition, the elevated plus-maze test was used to control the influence of the anxiety-like status on gait adaptability. Our results revealed the shock group exhibited worse walking adaptability (lower skilled walking score), when compared to the sham group. Moreover, the immobility time in the ladder rung walking test was similar to the controls, suggesting that gait adaptability performance was not a consequence of the fear generalization. No anxiety-like behavior was observed in the plus maze test. Finally, correlation coefficients also showed the skilled walking performance score was positively correlated with the number of gait cycles and trial time in the ladder rung walking test and the total crossings in the plus maze. Overall, these preliminary findings provide evidence to hypothesize an aversive, extinction-resistant experience might change the emotional load, affecting the ability to adapt walking

Feature selection environment for genomic applications

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Migraine aura: retracting particle-like waves in weakly susceptible cortex

Cortical spreading depression (SD) has been suggested to underlie migraine aura. Despite a precise match in speed, the spatio-temporal patterns of SD and aura symptoms on the cortical surface ordinarily differ in aspects of size and shape. We show that this mismatch is reconciled by utilizing that both pattern types bifurcate from an instability point of generic reaction-diffusion models. To classify these spatio-temporal pattern we suggest a susceptibility scale having the value [sigma]=1 at the instability point. We predict that human cortex is only weakly susceptible to SD ([sigma]&#x3c;1), and support this prediction by directly matching visual aura symptoms with anatomical landmarks using fMRI retinotopic mapping. We discuss the increased dynamical repertoire of cortical tissue close to [sigma]=1, in particular, the resulting implications on migraine pharmacology that is hitherto tested in the regime ([sigma]&#x3e;&#x3e;1), and potentially silent aura occurring below a second bifurcation point at [sigma]=0 on the susceptible scale

Dhvar5 antimicrobial peptide (AMP) chemoselective covalent immobilization results on higher antiadherence effect than simple physical adsorption

Bacterial colonization and subsequent biofilm formation is still one of the major problems associated with medical devices. Antimicrobial peptides (AMP) immobilization onto biomaterials surface is a promising strategy to avoid bacterial colonization. However, a correct peptide orientation and exposure from the surface is essential to maintain AMP antimicrobial activity. This work aims to evaluate the effect of the immobilization on antibacterial activity of Dhvar5 (LLLFLLKKRKKRKY), an AMP with a head-to-tail amphipathicity. Dhvar5 was linked to thin chitosan coatings in i) a controlled orientation and exposure, testing covalent immobilization of its N- or C-terminus and using spacers with different lengths and flexibilities or in ii) a random orientation by physical adsorption. Chitosan coating was chosen due to its antimicrobial properties and readiness to be functionalized. Surface characterization demonstrated the chemoselective immobilization of the peptide with different spacers in a similar concentration (∼2 ng/cm2). Efficacy assays demonstrated that covalent immobilization of Dhvar5 exposing its cationic end, improves the chitosan coating antimicrobial effect by decreasing Methicillin-resistant Staphylococcus aureus (MRSA) colonization. This effect was enhanced when longer spacers were used independently of their flexibility. In opposite, immobilized Dhvar5 exposing its hydrophobic end has no effect on bacterial adhesion to chitosan, and when adsorbed in a random orientation even induces bacterial adhesion to chitosan coating.This work was financed by FEDER funds through the Programa Operacional Factores de Competitividade (COMPETE) and by Portuguese funds through FCT (Fundacao para a Ciencia e a Tecnologia) in the framework of the projects: PTDC/CTM/101484/2008; PEst-C/SAU/LA0002/2013; Pest-C/QUI/UI0081/2013. Fabiola Costa acknowledges FCT for the PhD grant SFRH/BD/72471/2010

Symptom appraisal and help-seeking in men with symptoms of possible prostate cancer: a qualitative study with an ethnically diverse sample in London

This is the final version. Available on open access from the Royal College of General Practitioners via the DOI in this recordBACKGROUND: Prostate cancer mortality in Black males is disproportionately high. This problem may be overcome by reducing delays in the pathway to diagnosis, particularly those occurring before initial medical help seeking. A greater understanding of symptom appraisal and help seeking could support the development of targeted interventions for improving early presentation among Black males. AIM: To provide an in-depth understanding of males' pre-consultation experiences following the onset of symptoms of possible prostate cancer, identifying both general trends as well as potential differences that may exist between Black and White males. DESIGN AND SETTING: Qualitative study of 18 males (nine Black, nine White) in London, UK, who had recently seen their GP with urinary symptoms, erectile dysfunction, or haematuria. METHOD: Semi-structured interviews from a previous multi-methods study of primary care use by males with symptoms of possible prostate cancer were analysed using thematic framework analysis. RESULTS: Symptoms were often interpreted by patients as unimportant. Most delays occurred due to the absence of reasons to seek help, which, in Black males, often stemmed from poor awareness of prostate cancer. This lack of awareness could have been a consequence of their reluctance to seek health information and discuss health issues with others in their social network. Friends and relatives played an important role in symptom appraisal and help seeking. CONCLUSION: Cognitive biases, cultural stigmas, and everyday interpersonal interactions should be important areas at which to target strategies seeking to reduce delays and improve early presentation in males with possible prostate cancer, particularly Black males.Cancer Research UKNational Institute for Health and Care Research (NIHR