Anisotropy in the helicity modulus of a 3D XY-model: application to YBCO

We present a Monte Carlo study of the helicity moduli of an anisotropic classical three-dimensional (3D) XY-model of YBCO in superconducting state. It is found that both the ab-plane and the c-axis helicity moduli, which are proportional to the inverse square of the corresponding magnetic field penetration depth, vary linearly with temperature at low temperatures. The result for the c-axis helicity modulus is in disagreement with the experiments on high quality samples of YBCO. Thus we conclude that purely classical phase fluctuations of the superconducting order parameter cannot account for the observed c-axis electrodynamics of YBCO.Comment: 7 pages, 1 figur

On the theory of diamagnetism in granular superconductors

We study a highly disordered network of superconducting granules linked by weak Josephson junctions in magnetic field and develop a mean field theory for this problem. The diamagnetic response to a slow {\it variations} of magnetic field is found to be analogous to the response of a type-II superconductor with extremely strong pinning. We calculate an effective penetration depth $\lambda_g$ and critical current $j_c$ and find that both $\lambda_g^{-1}$ and $j_c$ are non-zero but are strongly suppressed by frustration.Comment: REVTEX, 12 pages, two Postscript figure

Towards a Learning-Aware Application Guided by Hierarchical Classification of Learner Profiles

Learner profiling is a methodology that draws a parallel from user profiling. Implicit feedback is often used in recommender systems to create and adapt user profiles. In this work the implicit feedback is based on the learner's answering behaviour in the Android application UnlockYourBrain, which poses different basic mathematical questions to the learners. We introduce an analytical approach to model the learners' profile according to the learner's answering behaviour. Furthermore, similar learner's profiles are grouped together to construct a learning behaviour cluster. The choice of hierarchical clustering as a means of classification of learners' profiles derives from the observations of learners behaviour. This in turn reflects the similarities and subtle differences of learner behaviour, which are further analysed in more detail. Building awareness about the learner's behaviour is the first and necessary step for future learning-aware applications

Nonlinear Seebeck Effect in a Model Granular Superconductor

The change of the Josephson supercurrent density of a weakly-connected granular superconductor in response to externally applied arbitrary thermal gradient dT/dx (nonlinear Seebeck effect) is considered within a model of 3D Josephson junction arrays. For dT/dx>(dT/dx)_c, where (dT/dx)_c is estimated to be of the order of 10^4 K/m for YBCO ceramics with an average grain's size of 10 microns, the weak-links-dominated thermopower S (Seebeck coefficient) is predicted to become strongly dT/dx-dependent.Comment: REVTEX, no figure

Evaluation of small mammal pet supplies offered in German retail under animal welfare aspects

German retailers offer a large variety of accessories for pets. However, not all products are suitable for pet husbandry. Several articles can negatively influence the wellbeing of pets or cause injuries, but empirical studies that evaluate accessories for small pets under animal welfare aspects are rare. In the present study, we assessed articles manufactured or sold in Germany in the product categories pet cages, hay racks, running wheels, exercise balls, harnesses and leashes, tube systems, and hamster bedding. To do so, we searched 28 German websites, visited 50 pet shops and 13 home improvement and garden centers on site and afterwards examined the animal welfare compliance of the products according to various evaluation criteria. Most of the examined products were rated not suitable for pet husbandry and were animal-welfare-adverse. This result applies to 86.1% (n = 87) of the 101 assessed running wheel models, 82.7% (n = 172) of the 208 assessed pet cage models and 55.6% (n = 40) of the 72 assessed hay rack models. The articles in the product categories exercise balls, harnesses and leashes, tube systems, and hamster bedding were also found unsuitable due to animal welfare concerns. Furthermore, we found clear shortcomings regarding article declarations. In some cases, relevant product information (e.g., dimensions) were missing, or the presented information was too general (e.g., rodent cage). Improperly declared pet accessories make it difficult for pet owners to decide whether a product is suitable or unsuitable for the species they keep. A declaration duty for manufacturers of pet products could ensure that German retailers only offer properly declared pet accessories and facilitate the decision for pet owners to purchase products appropriate for the pets they keep. Furthermore, a voluntary product certification for manufacturers would allow retailers to check the animal welfare compliance of articles before including them in their assortment. If a product is unsuitable for pet husbandry because it does not meet the set requirements, it must be considered animal-welfare-adverse and removed from the assortment. As done for the Austrian “animal welfare label,” an independent, qualified third party could do the certification

C/EBP Transcription Factors in Human Squamous Cell Carcinoma: Selective Changes in Expression of Isoforms Correlate with the Neoplastic State

The CCAAT/Enhancer Binding Proteins (C/EBPs) are a family of leucine-zipper transcription factors that regulate physiological processes such as energy metabolism, inflammation, cell cycle, and the development and differentiation of several tissues including skin. Recently, a role for C/EBPs in tumor cell proliferation and differentiation has been proposed, but the incomplete characterization in the literature of multiple translational isoforms of these proteins has made interpretation of these roles difficult. Therefore, we have carefully reexamined C/EBP isoform expression in human non-melanoma skin cancers. C/EBPα, C/EBPβ, and C/EBPδ were analyzed histologically in squamous cell carcinomas (SCC). The individual isoforms of C/EBPα and C/EBPβ were examined by immunofluorescent digital imaging, western blotting and DNA binding activity (electrophoretic mobility shift analysis). Expression of all C/EBP family proteins was decreased in SCC tumors. Suppression was greatest for C/EBPα, less for C/EBPβ, and least for C/EBPδ. Western analyses confirmed that C/EBPα p42 and p30 isoforms were decreased. For C/EBPβ, only the abundant full-length isoform (C/EBPβ−1, LAP*, 55 kD) was reduced, whereas the smaller isoforms, C/EBPβ−2 (LAP, 48 kD) and C/EBPβ−3 (LIP, 20 kD), which are predominantly nuclear, were significantly increased in well- and moderately-differentiated SCC (up to 14-fold for C/EBPβ−3). These elevations correlated with increases in PCNA, a marker of proliferation. Although C/EBPβ displayed increased post-translational modifications in SCC, phosphorylation of C/EBPβ−1 (Thr 235) was not altered. C/EBP-specific DNA binding activity in nuclear and whole-cell extracts of cultured cells and tumors was predominantly attributable to C/EBPβ. In summary, two short C/EBPβ isoforms, C/EBPβ−2 and C/EBPβ−3, represent strong candidate markers for epithelial skin malignancy, due to their preferential expression in carcinoma versus normal skin, and their strong correlation with tumor proliferation

Novel “nano-phage” interfaces for wireless biosensors

The prevention of food-borne illness has become a very important factor in public health. Meantime, the conventional microbiological detection techniques are time consuming, require proficiency and appropriate laboratory conditions. Recently, there has been an extensive work undertaken towards the development of diagnostic biosensor devices for on-site detection of biological threats that explore a diversity of transduction mechanisms and bio-recognition elements. In particular, the environmentally robust filamentous phages have been successfully used as an alternative to fragile antibodies in wireless biosensor system for real-time pathogen detection. However, when phages are used as interface, they can aggregate forming bundles of fibers that cannot cover completely the sensor’s interface leading to the decrease in sensor’s performance. In this work we developed novel wireless magnetoelastic biosensors with interface formed by biorecognition nanoparticles called “nano-phage”. “Nano-phage” comprises nanoparticles with diameter ~11 nm composed of self-assembled fusion major coat protein of landscape phages selected against the target analyte. For proof-of-concept, we investigated interfaces formed by three model phages selected from landscape libraries: streptavidin binders 7b1 and SAE10 and clone E2 highly specific and selective for S. typhimurium. Beside food borne pathogens, this new approach can be used to develop biosensors with increased performance for early detection of cancer diseases and other pathologies

Stability of vortex lines in liquid 3He-4He mixtures at zero temperature

At low temperatures and 3He concentrations below 6.6 %, there is experimental evidence about the existence in liquid helium mixtures, of stable vortices with 3He-rich cores. When the system is either supersaturated or submitted to a tensile strength, vortices lose stability becoming metastable and eventually completely unstable, so that their cores freely expand. Within a density functional approach, we have determined the pressure-3He concentration curve along which this instability appears at zero temperature.Comment: Typeset using Revtex, 9 pages and 5 Postscript figure

Indication of Superconductivity at 35 K in Graphite-Sulfur Composites

We report magnetization measurements performed on graphite--sulfur composites which demonstrate a clear superconducting behavior below the critical temperature T$_{c0}$ = 35 K. The Meissner-Ochsenfeld effect, screening supercurrents, and magnetization hysteresis loops characteristic of type-II superconductors were measured. The results indicate that the superconductivity occurs in a small sample fraction, possibly related to the sample surface.Comment: published versio