Structure and physical properties of nickel manganite NiMn2O4 obtained from nickel permanganate precursor

In this paper we present the structural, magnetic and dielectric properties of ceramic nickel manganite NiMn₂O_4+δ produced by using nickel permanganate Ni(MnO₄)₂xH₂O as a precursor. We have characterized the NiMn₂O_4+δ stoichiometry using quantitative energy-dispersive analysis of X-rays and thermal gravimetry under reducing conditions. Increased oxygen and Mn⁴⁺ contents were detected. X-ray diffraction and Rietveld refinement of X-ray data were carried out. Temperature dependent magnetization measurements were performed and the ferri-magnetic transition was identified at ≈100 K. The ferri-magnetic moment was found to be ≈1μ_B and hysteretic magnetization vs applied field curves were obtained. Dielectric properties were measured using impedance spectroscopy. Two dielectric relaxation processes were detected, which were associated with grain boundary and bulk contributions. The Arrhenius plots of resistivity and the temperature dependent dielectric permittivity were obtained for the two relaxations by means of an equivalent circuit model based on a series of two parallel RC elements.     

Bio-hydrogen production from waste fermentation: Mixing and static conditions

One of the main disadvantages of the dark fermentation process is the cost associated with the stages needed for obtaining H₂ producing microorganisms. Using anaerobic microflora in fermentation systems directly is an alternative which is gaining special interest when considering the implementation of large-scale plants and the use of wastes as substrate material. The performance of two H₂ producing microflora obtained from different anaerobic cultures was studied in this paper. Inoculum obtained from a waste sludge digester and from a laboratory digester treating slaughterhouse wastes were used to start up H₂ fermentation systems. Inoculum acclimatized to slaughterhouse wastes gave better performance in terms of stability. However, due to the limited availability of this seed material, further work was performed to study the behaviour of the inoculum obtained from the municipal wastewater treatment plant. The process was evaluated under static and mixing conditions. It was found that application of a low organic loading rate favoured the performance of the fermentation systems, and that agitation of the reacting mass could alleviate unsteady performance. Specific H₂ production obtained was in the range of 19–26 L/kg SV_fed with maximum peak production of 38–67 L/kg SV_fed. Although the performance of the systems was unsteady, recovery could be achieved by suspending the feeding process and controlling the pH in the range of 5.0–5.5. Testing the recovery capacity of the systems under temperature shocks resulted in total stoppage of H₂ production.     

Scheduling on a proportionate flowshop to minimise total late work

We study a scheduling problem to minimise total late work, i.e. each job is penalised according to the duration of its parts scheduled after its due-date. The machine setting is an m-machine proportionate flow shop. Two versions of the problem are studied: (i) the case that total late work refers to the last operation of the job (i.e. the operation performed on the last machine of the flow shop); (ii) the case that total late work refers to all the operations (on all machines). Both versions are known to be NP-hard. We prove a crucial property of an optimal schedule, and consequently introduce efficient pseudo-polynomial dynamic programming algorithms for the two versions. The dynamic programming algorithms are tested numerically and proved to perform well on large size instances.     

Distinct magnetic response of nanograined Zn1−xMnxO (x = 0, 0.02, 0.1) powders and thin films: Focus on the effect of the working atmosphere

Nanocrystalline Zn_1?xMn_xO (where x = 0, 0.02, 0.1) powders and thin films were prepared by a polymeric precursor method and pulsed laser deposition, respectively. The wet chemistry method was chosen to synthesize the powders in order to improve key parameters as purity and grain-size distribution. Optimization procedures, encompassing substrate temperature, laser fluence and background gas conditions were performed and are intended to improve the crystalline quality of the films. X-ray diffraction studies reveal no clear evidence (within the detection limit of the technique) of affectation by impurities generated during the synthesis. Films prepared under optimized conditions feature a mosaic spread <0.3° and nearly bulk-like c-axis lattice parameter (5.198 Å). The substitution of Mn²⁺ cations in the tetrahedral sites of the wurtzite structure of pristine ZnO is confirmed both X-ray diffraction and Raman spectroscopy. Magnetic measurements, in turn, show that the powders are paramagnetic for temperatures above 3 K, while the thin films, grown in vacuum, are ferromagnetic at room temperature. These results indicate that variations in the preparation parameters have a marked influence on the magnetic responses of the Zn_1?xMn_xO system.     

Heuristics for scheduling problems with an unavailability constraint and position-dependent processing times

We study a single machine scheduling problem, where the machine is unavailable for processing for a pre-specified time period. We assume that job processing times are position-dependent. The objective functions considered are minimum makespan, minimum total completion time and minimum number of tardy jobs. All these problems are known to be NP-hard even without position-dependent processing times. For all three cases we introduce simple heuristics which are based on solving the classical assignment problem. Lower bounds, worst case analysis and asymptotic optimality are discussed. All heuristics are shown numerically to perform extremely well.     

Analysis of electricity bills using visual continuous maps

The information from the electricity bills of an institution such as the University of León, with several billing points, constitutes a high-dimensional data set which is quite complicated to visualize at a glance. The use of techniques for dimensionality reduction enables to obtain a two-dimensional representation of the original data set which highlights main features in data and is easier to visualize. If these techniques are combined with interpolation methods, the resulting continuous maps allow comparison and interpretation of a whole range of possible electric data sets, not only the original one. These tools allow us to generate interactive maps that can be used by untrained people to exploit and analyze the information in electricity bills, detect penalties due to a power demand excess or power factor decrease, and make decisions with regard to electricity contracts.     

The mTORC2 Regulator Homer1 Modulates Protein Levels and Sub-Cellular Localization of the CaSR in Osteoblast-Lineage Cells

We recently found that, in human osteoblasts, Homer1 complexes to Calcium-sensing receptor (CaSR) and mediates AKT initiation via mechanistic target of rapamycin complex (mTOR) complex 2 (mTORC2) leading to beneficial effects in osteoblasts including β-catenin stabilization and mTOR complex 1 (mTORC1) activation. Herein we further investigated the relationship between Homer1 and CaSR and demonstrate a link between the protein levels of CaSR and Homer1 in human osteoblasts in primary culture. Thus, when siRNA was used to suppress the CaSR, we observed upregulated Homer1 levels, and when siRNA was used to suppress Homer1 we observed downregulated CaSR protein levels using immunofluorescence staining of cultured osteoblasts as well as Western blot analyses of cell protein extracts. This finding was confirmed in vivo as the bone cells from osteoblast specific CaSR−/− mice showed increased Homer1 expression compared to wild-type (wt). CaSR and Homer1 protein were both expressed in osteocytes embedded in the long bones of wt mice, and immunofluorescent studies of these cells revealed that Homer1 protein sub-cellular localization was markedly altered in the osteocytes of CaSR−/− mice compared to wt. The study identifies additional roles for Homer1 in the control of the protein level and subcellular localization of CaSR in cells of the osteoblast lineage, in addition to its established role of mTORC2 activation downstream of the receptor.