964 research outputs found

    The principle of symmetric bracket invariance as the origin of first and second quantization

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    The principle of invariance of the c-number symmetric bracket is used to derive both the quantum operator commutator relation [q^,p^]=i[\hat q, \hat p]=i\hbar and the time-dependent Schr\"odinger equation. A c-number dynamical equation is found which leads to the second quantized field theory of bosons and fermions.Comment: 14 pages. Contributed Paper: XIX International Symposium on Lepton and Photon Interactions at High Energies, Stanford University, August 9-14, 199

    Spacetime metric from linear electrodynamics

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    The Maxwell equations are formulated on an arbitrary (1+3)-dimensional manifold. Then, imposing a (constrained) linear constitutive relation between electromagnetic field (E,B)(E,B) and excitation (D,H)({\cal D},{\cal H}), we derive the metric of spacetime therefrom.Comment: 4 pages' latex-scrip

    Non-grassmann "classicization" of fermion dynamics

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    A carefully motivated symmetric variant of the Poisson bracket in ordinary (not Grassmann) phase space variables is shown to satisfy identities which are in algebraic correspondence with the anticommutation postulates for quantized Fermion systems. "Symplecticity" in terms of this symmetric Poisson bracket implies generalized Hamilton's equations that can only be of Schroedinger type (e.g., the Dirac equation but not the Klein-Gordon or Maxwell equations). This restriction also excludes the old "four-Fermion" theory of beta decay

    Service Learning: Making the Camp Connection

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    Service learning, today\u27s buzzword for education through service, is as diverse as are camp programs in our nation. From providing environmental education to tutoring to feeding the homeless, it is both a method and a philosophy. Programming for service opportunities in today\u27s camps offers a variety of options, from short-term experiences to a fully integrated curriculum that links action and reflection. Service learning, therefore, may be best understood as a method to encourage campers to act, reflect, develop, and learn through community-organized service that connects the needs of a community with the knowledge and experience of campers

    How to increase the mobilization of Climate Financing Instruments

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    The session on Climate Financing Instruments in Mediterranean landscapes at the IV Mediterranean Forest Week attracted several participants, project partners and international donors. The discussion was inspired by several presentations focusing on the initiatives undertaken at the pilot site, national and regional level in the framework of two regional projects. They clearly showed the potential for accessing mitigation and adaptation financing mechanisms for the Mediterranean forest sector but also the complexity of the subject in the region. The discussion flagged the synergies between adaptation and mitigation in Mediterranean forests and the opportunities presented by financing mechanisms to support the sustainable management of Mediterranean forests

    Unraveling Plant Responses to Bacterial Pathogens through Proteomics

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    Plant pathogenic bacteria cause diseases in important crops and seriously and negatively impact agricultural production. Therefore, an understanding of the mechanisms by which plants resist bacterial infection at the stage of the basal immune response or mount a successful specific R-dependent defense response is crucial since a better understanding of the biochemical and cellular mechanisms underlying these interactions will enable molecular and transgenic approaches to crops with increased biotic resistance. In recent years, proteomics has been used to gain in-depth understanding of many aspects of the host defense against pathogens and has allowed monitoring differences in abundance of proteins as well as posttranscriptional and posttranslational processes, protein activation/inactivation, and turnover. Proteomics also offers a window to study protein trafficking and routes of communication between organelles. Here, we summarize and discuss current progress in proteomics of the basal and specific host defense responses elicited by bacterial pathogens

    An Experimental and Numerical Study on Glass Frit Wafer-to-Wafer Bonding

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    A thermo-mechanical wafer-to-wafer bonding process is studied through experiments on the glass frit material and thermo-mechanical numerical simulations to evaluate the effect of the residual stresses on the wafer warpage. To experimentally characterize the material, confocal laser profilometry and scanning electron microscopy for surface observation, energy dispersive X-ray spectroscopy for microstructural investigation, and nanoindentation and die shear tests for the evaluation of mechanical properties are used. An average effective Young’s modulus of 86.5 ± 9.5 GPa, a Poisson’s ratio of 0.19 ± 0.02, and a hardness of 5.26 ± 0.8 GPa were measured through nanoindentation for the glass frit material. The lowest nominal shear strength ranged 1.13 ÷ 1.58 MPa in the strain rate interval to 0.33 ÷ 4.99 × 10 (Formula presented.) s (Formula presented.). To validate the thermo-mechanical model, numerical results are compared with experimental measurements of the out-of-plane displacements at the wafer surface (i.e., warpage), showing acceptable agreement

    Evaluation of the weight loss of raw beef cuts vacuum-packaged with two different techniques

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    In the present study, 25 cuts of shank form adult cattle coming from the same slaughtering batch, were withdrawn just after manual sectioning/deboning, and each divided into two pieces (Prox and Dist) of approximately the same weight, that were vacuum packaged by using two different packaging systems: vacuum chamber machine with a bag material and a thermo-forming packaging machine with top and bottom webs named BAG and THF respectively. The packed cuts were stored at 2-3\ub0C for 20 days. The drip loss was calculated at the end of the storage as the difference between drained weight and net. Internal muscle pH and pH of the exudate present in the package and microbiological analyses (by pooling the samples) were performed at T0 and at the end of the storage. The drip loss, was significantly lower with BAG packaging: this difference was evident after 20 days of storage (average \ub1 STD BAG vs THF = 1.04\ub10.36% vs 1.71\ub10.42%; P<0.01). The values were, in general, low for both the packaging systems, never above 2%. Moreover, shrink bag packages are characterized by better overall pack appearance and less plastic weight per pack. Forming step reduce the thickness of ther-moforming material lowering the mechanical resistance and the barrier to oxygen, on the contrary after shrinking bag materials are thickened. The pH of muscles was stable, although a slight increase was evidenced after 20 (average \ub1 STD BAG vs THF= 5.73\ub10.05 vs 5.78\ub10.09; P<0.01), due to the ageing of meat. The pH of the exudate was equal at T20 (average \ub1 STD BAG vs THF = 5.34\ub10.20 vs 5.33\ub10.17). The drip loss didn\u2019t influence the development of all the microflora; in particular LAB, that represented the main microbial population, showed a gradual increase from T0 (2.20\ub10.41 Log CFU/g) to T20 (average \ub1 STD BAG vs THF= 4.76\ub10.29 Log CFU/g vs 4.75\ub10.0.15 Log CFU/g). No Enterobacteriaceae showed an increase, if compared to the initial counts, due to the prolonged storage and the gradual growth of ephemeral microorganisms, without differences among the two series (Enterobacteriaceae: T0=<1.7 Log CFU/g to T20 average \ub1 STD BAG vs THF = 2.83\ub10.77 Log CFU/g vs 3.09\ub10.0.70 Log CFU/g). In conclusion, the use of the BAG system demonstrated to have an effect in reducing the drip loss of beef cuts during the refrigerated storage, with only slight influence on the other characteristics of raw meat

    Extruded Expanded Polystyrene Sheets Coated by TiO2 as New Photocatalitic Materials for Foodstuffs Packaging

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    Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas–solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX mapping allowing to monitor the surface morphology and the distribution of TiO2 particles. Finally thermoforming of these sheets in industrial standard equipment leads to useful containers for foodstuffs
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