Chitosan nanoparticle coatings reduce microbial growth on fresh‐cut apples while not affecting quality attributes

This study addressed the effects of chitosan‐based nanoparticles on microbiological quality, colour, polyphenol oxidase (PPO) and peroxidase (POD) and firmness of fresh‐cut ‘Gala’ apple slices during storage at 5 °C for 10 days. The treatments carried out were as follows: (i) slices pulverised with 110‐nm chitosan nanoparticles, (ii) slices pulverised with 300‐nm chitosan nanoparticles, (iii) 2 g L^?1 chitosan dissolved in 2% citric acid and (iv) noncoated samples. There was an increase in chroma and a proportional decrease in hue angle and lightness. Browning of the slices coated with conventional chitosan and control was slightly intense than those coated with chitosan nanoparticles of 110 and 300 nm. The PPO and PDO activities increased with time for all samples, with irrelevant difference among the treatments. Flesh firmness did not change for any treatment and period. Coatings with chitosan nanoparticles of 110 nm showed higher antimicrobial activity against moulds and yeasts, and mesophilic and psychrotrophic bacteria than the other treatments. No Salmonella, and total and faecal coliforms were detected. This investigation supports the potential use of chitosan nanoparticles as edible coatings in controlling microbial activity in fresh‐cut apples.     

Software tools to improve note-taking in the classroom

This paper describes the functionalities and some implementation details of software tools to assist and to improve the process of note taking by students during a traditional lecture. The software tools allow professors to interact effectively with the students during lectures and help students to take relevant notes. They are based on a previously described software, and use a network of pen-based computers as well as a large screen projection system     

Radiative heat transfer in enhanced hydrogen outgassing of glass

This paper explores the physical mechanisms responsible for experimental observations that led to the definition of “photo-induced hydrogen outgassing of glass”. Doped borosilicate glass samples were placed inside an evacuated silica tube and heated in a furnace or by an incandescent lamp. It was observed that hydrogen release from the glass sample was faster and stronger when heated by an incandescent lamp than within a furnace. Here, sample and silica tube were modeled as plane-parallel slabs exposed to furnace or to lamp thermal radiation. Combined conduction, radiation, and mass transfer were accounted for by solving the one-dimensional transient mass and energy conservation equations along with the steady-state radiative transfer equation. All properties were found in the literature. The experimental observations can be qualitatively explained based on conventional thermally activated gas diffusion and by carefully accounting for the participation of the silica tube to radiation transfer along with the spectral properties of the silica tube and the glass samples. In brief, the radiation emitted by the incandescent lamp is concentrated between 0.5 and 3.0 μm and reaches directly the sample since the silica tube is nearly transparent for wavelengths up to 3.5 μm. On the contrary, for furnace heating at 400 °C, the silica tube absorbs a large fraction of the incident radiation which reduces the heating rate and the H₂ release rate. However, between 0.8 and 3.2 μm undoped borosilicate does not absorb significantly. Coincidentally, Fe₃O₄ doping increases the absorption coefficient and also reacts with H₂ to form ferrous ions which increase the absorption coefficient of the sample by two orders of magnitude. Thus, doped and reacted samples heat up much faster when exposed to the heating lamp resulting in the observed faster response time and larger H₂ release rate.     

The effectiveness of remedial computer use for mathematics in a university setting (Botswana)

This paper describes the evaluation of the effects of the Mathematics and Science Computer Assisted Remedial Teaching (MASCART) software on students from the Pre-Entry Science Course at the University of Botswana. A general significant improvement of basic algebra knowledge and skills could be measured, demonstrating that the combination of increased time on task and computer-assisted remedial instruction is effective. This result is relevant for this setting of a university in a less developed country, because other ways of remedial teaching, for example increased staff time, are not possible. By applying Markov chain analysis it could be proved that the improvement in the experimental group was caused by the increased time on task, and that in a situation where students are expected to attain high mastery levels, especially high ability students profit from the MASCART approach. Students like to work with MASCART because they could work individually and at their own pace.     

Pyroelectric energy converter using co-polymer P(VDF-TrFE) and Olsen cycle for waste heat energy harvesting

This study was concerned with designing, building, and testing a pyroelectric energy converter to directly convert waste heat into electricity. The pyroelectric effect refers to the flow of charges to or from the surface of a material upon heating or cooling. The device consisted of a teflon cylindrical chamber with a piston oscillating vertically and driving a working fluid back and forth between a heat source and a cold heat exchanger. The Olsen cycle was performed on co-polymer 60/40 poly(vinylidene fluoride–trifluoroethylene) [P(VDF-TrFE)] thin films sandwiched between metallic electrodes. Their temperature oscillation, charge, voltage and the overall heat input and output were measured experimentally. Then, the electrical power generated and the energy efficiency were computed. The effects of channel width, frequency, and stroke length on temperature swing, heat input, as well as energy and power densities were investigated. Reducing the channel width and increasing the stroke length had the largest effect on device performance. A maximum energy density of 130 J/l was achieved at 0.061 Hz frequency with temperature oscillating between 69.3 and 87.6 °C. Furthermore, a maximum power density of 10.7 W/l was obtained at 0.12 Hz between 70.5 and 85.3 °C. In both cases, the low and high electric fields in the Olsen cycle were 202 and 739 kV/cm. To the best of our knowledge, this is the largest energy density achieved by any pyroelectric energy converter using P(VDF-TrFE). It also matches performances reported in the literature for more expensive lead zirconate stannate titanate (PZST) ceramic films operated at higher temperatures.     

Molecular dynamics study of the thermal conductivity of amorphous nanoporous silica

This study reports, for the first time, non-equilibrium molecular dynamics (MD) simulations predicting the thermal conductivity of amorphous nanoporous silica. The heat flux was imposed using the Müller-Plathe method and interatomic interactions were modeled using the widely used van Beest, Kramer and van Santen potential. Monodisperse spherical pores organized in a simple cubic lattice were introduced in an amorphous silica matrix by removing atoms within selected regions. The simulation cell length ranged from 17 to 189 Å, the pore diameter from 12 to 25 Å, and the porosity varied between 10% and 35%. Results establish that the thermal conductivity of nanoporous silica at room temperature was independent of pore size and depended only on porosity. This qualitatively confirms recent experimental measurements for cubic and hexagonal mesoporous silica films with pore diameter and porosity ranging from 3 to 18 nm and 20% to 48%, respectively. Moreover, predictions of MD simulations agreed well with predictions from the coherent potential model. By contrast, finite element analysis simulating the same nanoporous structures, but based on continuum theory of heat conduction, agreed with the well-known Maxwell Garnett model.     

Modeling radiation characteristics of semitransparent media containing bubbles or particles

Modeling of radiation characteristics of semitransparent media containing particles or bubbles in the independent scattering limit is examined. The existing radiative properties models of a single particle in an absorbing medium using the approaches based on (1) the classical Mie theory neglecting absorption by the matrix, (2) the far field approximation, and (3) the near field approximation are reviewed. Comparison between models and experimental measurements are carried out not only for the radiation characteristics but also for hemispherical transmittance and reflectance of porous fused quartz. Large differences are found among the three models predicting the bubble radiative properties when the matrix is strongly absorbing and/or the bubbles are optically large. However, these disagreements are masked by the matrix absorption during calculation of radiation characteristics of the participating medium. It is shown that all three approaches can be used for radiative transfer calculations in an absorbing matrix containing bubbles.     

Golem95C: A library for one-loop integrals with complex masses

We present a program for the numerical evaluation of scalar integrals and tensor form factors entering the calculation of one-loop amplitudes which supports the use of complex masses in the loop integrals. The program is built on an earlier version of the golem95 library, which performs the reduction to a certain set of basis integrals using a formalism where inverse Gram determinants can be avoided. It can be used to calculate one-loop amplitudes with arbitrary masses in an algebraic approach as well as in the context of unitarity-inspired numerical reconstruction of the integrand.

Program summary

Program title: golem95-1.2.0Catalogue identifier: AEEO_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEO_v2_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 182 492No. of bytes in distributed program, including test data, etc.: 950 549Distribution format: tar.gzProgramming language: Fortran95Computer: Any computer with a Fortran95 compilerOperating system: Linux, UnixRAM: RAM used per integral/form factor is insignificantClassification: 4.4, 11.1External routines: Some finite scalar integrals are called from OneLOop [1,2], the option to call them from LoopTools [3,4] is also implemented.Catalogue identifier of previous version: AEEO_v1_0Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 2317Does the new version supersede the previous version?: YesNature of problem: Evaluation of one-loop multi-leg integrals occurring in the calculation of next-to-leading order corrections to scattering amplitudes in elementary particle physics. In the presence of massive particles in the loop, propagators going on-shell can cause singularities which should be regulated to allow for a successful evaluation.Solution method: Complex masses can be used in the loop integrals to stand for a width of an unstable particle, regulating the singularities by moving the poles away from the real axis.Reasons for new version: The previous version was restricted to massless particles in the loop.Summary of revisions: Real and complex masses are supported, a general μ parameter for the renormalization scale is introduced, improvements in the caching system and the user interface.Running time: Depends on the nature of the problem. A single call to a rank 6 six-point form factor at a randomly chosen kinematic point, using complex masses, takes 0.06 seconds on an Intel Core 2 Q9450 2.66 GHz processor.References:

• [1] 

  A. van Hameren, C.G. Papadopoulos, R. Pittau, Automated one-loop calculations: a proof of concept, JHEP 0909 (2009) 106, arXiv:0903.4665.

• [2] 

  A. van Hameren, OneLOop: for the evaluation of one-loop scalar functions, arXiv:1007.4716.

• [3] 

  T. Hahn, M. Perez-Victoria, Automatized one-loop calculations in four and D dimensions, Comput. Phys. Commun. 118 (1999) 153–165, hep-ph/9807565.

• [4] 

  T. Hahn, Feynman diagram calculations with FeynArts, FormCalc, and LoopTools, arXiv:1006.2231.