Effect of dopants on the magnetic properties of MnZn ferrites forhigh frequency power supplies

The effect of additions on the magnetic properties of MnZn ferrites for high frequency power supplies was studied. The investigation revealed that various combinations of dopants added to the ferrite modify the grain boundary resistivity and the magnetic permeability spectra at constant microstructure. Particularly, the combined effect of Sn⁴⁺, Ti⁴⁺ and Ta⁵⁺ was found to increase the grain boundary resistivity in the ferrites studied and remarkably decrease the power loss at higher frequencies     

Glass-ceramic bonding in alumina/CBN abrasive systems

A glass-ceramic bond which can be applied in alumina/CBN abrasive systems was developed by the method of liquid-phase sintering of a homogenized mixture of alumina abrasives and bonding medium containing various amounts of B₂O₃. Microstructural and mechanical examinations have shown that the amount of B₂O₃ present in the starting glass frit determines the ultimate properties of the glass-ceramic bond which can be successfully used in the Al₂O₂/CBN abrasive systems.     

Dual representation of spatial rational Pythagorean-hodograph curves

In this paper, the dual representation of spatial parametric curves and its properties are studied. In particular, rational curves have a polynomial dual representation, which turns out to be both theoretically and computationally appropriate to tackle the main goal of the paper: spatial rational Pythagorean-hodograph curves (PH curves). The dual representation of a rational PH curve is generated here by a quaternion polynomial which defines the Euler–Rodrigues frame of a curve. Conditions which imply low degree dual form representation are considered in detail. In particular, a linear quaternion polynomial leads to cubic or reparameterized cubic polynomial PH curves. A quadratic quaternion polynomial generates a wider class of rational PH curves, and perhaps the most useful is the ten-parameter family of cubic rational PH curves, determined here in the closed form.     

Relative efficiency of police directorates in Slovenia: A non-parametric analysis

The main purpose of the paper is to apply a non-parametric methodology for measuring public police performance in Slovenia. The paper considers how previous studies have modeled the role of policing in their specifications of inputs and output. In particular, the multiple-stage Data Envelopment Analysis (DEA) technique is presented and then applied to measure the relative efficiency of police-work-related data for eleven Police Directorates (PDs) in 2010 and also compared with the efficiency scores in 2005. The data obtained from the police databases is analyzed through the Frontier Analyst 4.0 and SPSS 19.0 statistical package software. The results show that the technical efficiency varies significantly across the police directorates and across the selected years, even when we allow for environmental factors and control for these non-discretionary inputs. Most police directorates in Slovenia could attain a higher output if they were fully efficient. Indeed, all of the inefficient police directorates can learn how to ensure a “good” performance from the efficient ones (i.e. the Maribor PD and the Novo mesto PD) by observing how they are processing their inputs and outputs. Finally, the empirical results of the paper are important indicators of the relative efficiency (or inefficiency) of police directorates that can serve as a guide to the General Police Directorate when further investigating how to enhance the performance efficiency of the various units.     

Influence of Ag on the Composition and Electromagnetic Properties of Low-Temperature Cofired Hexaferrites

We have studied the compatibility of Ag and (Co,Cu)Z-hexaferrite with the composition Ba₃Co_1.4Cu_0.6Fe₂₄O₄₁ (Z). In order to do this, the (Co,Cu)Z-hexaferrite was cofired with various amounts of Ag at 900°C. The degradation of the (Co,Cu)Z-hexaferrite to Y- and U-hexaferrite occurred during the cofiring and was confirmed by X-ray diffraction as well as by thermomagnetic measurements. The permeability and permittivity of the cofired ceramics were measured in the range 1 MHz to 10 GHz. For the (Co,Cu)Z-hexaferrite, both these properties were significantly influenced by the Ag when the amount of Ag exceeded a minimum of 4.5 wt%. The influence of the Ag and the degradation of the (Co,Cu)Z-hexaferrite on the permeability were evaluated using the Bruggeman effective media theory.     

The mechanism of the low-temperature formation of barium hexaferrite

We have investigated the formation of barium hexaferrite via the coprecipitation method. Fine precursor powders were obtained with coprecipitation from water and ethanol solutions of various reagent salts. The coprecipitates were calcined at 300–800 °C for 0–50 h. The samples were characterized with X-ray powder diffraction, thermal analysis, electron microscopy and magnetometry. The formation of barium hexaferrite was a combination of two competing mechanisms and was not influenced by the reagent salts or the solvent. The formation temperature of the barium hexaferrite was reduced to 500 °C by optimizing the coprecipitation conditions.     

Staying on your feet: the effectiveness of posture and handles in counteracting balance perturbation

Stairways, public transport and inclined walkways are often considered as sites with higher likelihood of falls due to a sudden loss of balance. Such sites are usually marked with warning signs, equipped with non-slip surfaces and handles or handrails to avert or decrease this likelihood. Especially, handles are supposed to provide additional support in cases of a sudden loss of balance. However, the mechanisms of using handles for balance at different heights are not yet fully disclosed. We simulated full body perturbations by applying an anterior force to the waist and investigated effectiveness and mechanisms of balance recovery in five different postures: step stance and normal stance with or without holding handles at different heights. Results indicate that both step stance and holding handles at different vertical positions sufficiently assist balance recovery, compared to normal stance. While there was no significant effect of handle in CoM displacement, the shoulder height handle required the lowest handle force, indicating a difference in using the handle.

Practitioner summary: To investigate handle use for balance recovery, we perturbed healthy young adults in different standing positions. Even though the use of different handles had a similar effect, the lowest forces were exerted on the shoulder height handle indicating a preferred handle position for balance recovery.

Abbreviation: AP: antero-posterior; CNS: Central nervous system; CoM: Center of Mass; CoMmax: Maximal displacement of the center of mass; CoP: Center of pressure; FHmax: Maximal resultant force exerted on the handle; hFHmax: Maximal horizontal force exerted on the handle; vFHmax; Maximal vertical force exerted on the handle; M1-M8: Perturbation force magnitude     

Development of New Microsatellite Markers for Salvia officinalis L. and Its Potential Use in Conservation-Genetic Studies of Narrow Endemic Salvia brachyodon Vandas

Nine new microsatellite markers (SSR) were isolated from Salvia officinalis L. A total of 125 alleles, with 8 to 21 alleles per locus, were detected in a natural population from the east Adriatic coast. The observed heterozygosity, expected heterozygosity, and polymorphic information content ranged from 0.46 to 0.83, 0.73 to 0.93 and 0.70 to 0.92, respectively. New microsatellite markers, as well as previously published markers, were tested for cross-amplification in Salvia brachyodon Vandas, a narrow endemic species known to be present in only two localities on the Balkan Peninsula. Out of 30 microsatellite markers tested on the natural S. brachyodon population, 15 were successfully amplified. To obtain evidence of recent bottleneck events in the populations of both species, observed genetic diversity (H_E) was compared to the expected genetic diversity at mutation-drift equilibrium (H_EQ) and calculated from the observed number of alleles using a two-phased mutation model (TPM). Recent bottleneck events were detected only in the S. brachyodon population. This result suggests the need to reconsider the current threat category of this endemic species.     

Experimental evidence for the interaction of C-60 fullerene with lipid vesicle membranes

There are some molecular dynamic simulations but a paucity of experimental evidence of the effects of C-60 fullerene on lipid bilayers. The aim of this study is to assess the potential for disruption of the lipid bilayer by C-60 suspended in water. We selected a C-60 suspension that has previously been shown to provoke cell membrane destabilisation in vivo. Electromobility measurements show significant negative surface charge on the C-60 nanoparticles suspended in a glucose solution and a zeta potential of ?26 mV. The prevalent C-60 clusters have hydrodynamic radii of approximately 2 nm. Phase contrast microscopy and computer aided image analysis results show that C-60 causes shape transformations and rupture of unilamellar phospholipid vesicles, indicative of changes in their average mean curvature. Small-angle X-ray scattering reveals that C-60 provokes disruptions of external membranes of multilamellar vesicles only after freeze and thaw cycles. Here, the liposomes undergo breakage and annealing steps which increase the probability for fullerenes to insert into the MLVs. Our experimental findings confirm the potential of C-60 to reconstruct lipids in biological membranes. This research enhances our understanding of the impact of engineered nanoparticles on cell membranes.     

Small Reduction of the Piezoelectric d33 Response in Potassium Sodium Niobate Thick Films

We have investigated the electromechanical response of potassium sodium niobate (K_0.5Na_0.5NbO₃ or KNN) thick films. The high‐field strain hysteresis loops and weak‐field converse piezoelectric d₃₃ coefficient of the films were measured and compared with those of KNN bulk ceramics under the same electric field conditions. The converse d₃₃ values of the thick films and bulk ceramics were equal to 82.5 and 138 pm/V, respectively, at 0.4 kV/mm. The fundamental difference between the piezoelectric response of the KNN films and the ceramics was studied in terms of the effective (“clamped”) piezoelectric d₃₃ coefficient. The reduction in the piezoelectric d₃₃ coefficient of the KNN films, resulting from the clamping by the substrate, was compared to lead‐based ferroelectric thick films, including Pb(Zr,Ti)O₃ (PZT) and (1 ? x)Pb(Mg_1/3Nb_2/3)O₃?xPbTiO₃ (PMN‐PT). We propose a possible explanation, based on the particular elastic properties of KNN, for the small relative difference observed between the “clamped” and “unclamped” (“bulk”) d₃₃ of KNN, in comparison with lead‐based systems.