Invited Article: Refractive index matched scanning of dense granular materials

We review an experimental method that allows to probe the time-dependent structure of fully three-dimensional densely packed granular materials and suspensions by means of particle recognition. The method relies on submersing a granular medium in a refractive index matched fluid. This makes the resulting suspension transparent. The granular medium is then visualized by exciting, layer by layer, the fluorescent dye in the fluid phase. We collect references and unreported experimental know-how to provide a solid background for future development of the technique, both for new and experienced users.     

Large deformations and stability in topology optimization

The present contribution focuses on the influence of geometrical nonlinearities on the structural behavior in the design process. The notion of the stiffest structure loses its clear definition in the case of nonlinear kinematics; here we will discuss this concept on the basis of different objectives. Apparently topology optimization is often a generator of slender struts, which tend to buckle before the structure is completely loaded. To include the instability phenomena into the design process, the critical load level will be determined directly; this condition will be included as an inequality constraint. Further on, to reduce the imperfection sensitivity, a geometrically modified structure including the imperfection shape is also introduced. The present optimization procedures are demonstrated by examples showing rather the principal effects of the enhancements than real practical design problems.     

Germicidal Properties of Ozonated Sunflower Oil

The aim of this work was to establish the minimal inhibition concentration (MIC) of ozonated sunflower oil for various microorganisms. To determine the influence of the ozonated medium on the growth of bacteria Bacillus subtilis, Escherichia coli and yeast Candida albicans the Petri dish method was used. Chemical and physical properties of ozonated sunflower oil were additionally studied. Microbiological studies proved that these microbes have various sensibility against ozonated oil. The most resistant are gram-negative bacteria E. coli and the yeast C. albicans. Gram-positive bacteria, B. subtilis turned out to be less resistant, because no growth was observed for preparation with an ozone dose of 200 mgO₃/g oil.     

High-temperature performance of GaAs-based HFET structurecontaining LT-AlGaAs and LT-GaAs

Using low-temperature grown layers a GaAs-based HFET structure was developed, which demonstrates for the first time high performance at high temperatures up to 540°C, where the gate diode shunts through. The device was designed for operation in the hot electron regime using an LT-AlGaAs passivation layer. Thus, the open channel current density and gain bandwidth product are exceptionally stable (I_D500°C /I_DR.T.=0.9; f^T200°Cf_TR.T.=0.9). The f_max cutoff frequency is the most temperature sensitive parameter {(f_max/f_T)_R.T.=3.9 and (f_max/f_T)_200°C=2.8} due to the thermal activation of the buffer layer leakage, which is kept extremely small using LT-GaAs     

The level of available methionine and the biological value of fish protein]

Food value of fish protein in fish canning was evaluated biologically and chemically (by available methionine). High-temperature sterilization (126 degrees) proved the least adequate for it causes the greatest loss in the protein food value. The chemical method by available methionine showing close correlation with biological techniques (NPU and PER rates) is thought demonstrative and convenient for technological control in fish processing industry.     

Comparative studies on the electroless deposition of Ni-P, Co-P and their composites with SiC particles

Electroless deposition of nickel and cobalt from alkaline baths as well as their codeposition with SiC particles were compared. It was found that despite similarity in properties of the metals their behavior in the electroless process was different. Maleic acid was used to stabilize plating baths, however the optimal concentration of the additive depended on the type of deposited metal. The electroless deposition characterized with low plating efficiency and it was higher for nickel than for cobalt. The composition as well as the morphology of Ni-P and Co-P deposits were also dissimilar. SiC particles inhibited the metal deposition, affected the plating potential, but did not alter the matrix composition. SiC entrapment was more preferential within the cobalt matrix than the nickel one. Some adsorption phenomena on SiC powder were also studied.     

Endothelial Cells as Tools to Model Tissue Microenvironment in Hypoxia-Dependent Pathologies

Endothelial cells (ECs) lining the blood vessels are important players in many biological phenomena but are crucial in hypoxia-dependent diseases where their deregulation contributes to pathology. On the other hand, processes mediated by ECs, such as angiogenesis, vessel permeability, interactions with cells and factors circulating in the blood, maintain homeostasis of the organism. Understanding the diversity and heterogeneity of ECs in different tissues and during various biological processes is crucial in biomedical research to properly develop our knowledge on many diseases, including cancer. Here, we review the most important aspects related to ECs’ heterogeneity and list the available in vitro tools to study different angiogenesis-related pathologies. We focus on the relationship between functions of ECs and their organo-specificity but also point to how the microenvironment, mainly hypoxia, shapes their activity. We believe that taking into account the specific features of ECs that are relevant to the object of the study (organ or disease state), especially in a simplified in vitro setting, is important to truly depict the biology of endothelium and its consequences. This is possible in many instances with the use of proper in vitro tools as alternative methods to animal testing.     

Development of an electrochemical metal-ion biosensor using self-assembled peptide nanofibrils

This article describes the combination of self-assembled peptide nanofibrils with metal electrodes for the development of an electrochemical metal-ion biosensor. The biological nanofibrils were immobilized on gold electrodes and used as biorecognition elements for the complexation with copper ions. These nanofibrils were obtained under aqueous conditions, at room temperature and outside the clean room. The functionalized gold electrode was evaluated by cyclic voltammetry, impedance spectroscopy, energy dispersive X-ray and atomic force microscopy. The obtained results displayed a layer of nanofibrils able to complex with copper ions in solution. The response of the obtained biosensor was linear up to 50 μM copper and presented a sensitivity of 0.68 μA cm?2 μM?1. Moreover, the fabricated sensor could be regenerated to a copper-free state allowing its reutilization.     

Sensor properties of ZnO:Al nanofibres obtained by electrospinning

An electrospinning technology have been developed to obtain zinc oxide nanofibres doped with aluminum. Properties of the obtained nanostructures can be controlled by both the composition of a precursor and subsequent annealing treatment. The gas sensors manufactured with the use of ZnO:Al nanofibres exhibit good response to NO₂ at relatively low operating temperatures. For some samples it was observed that interaction with ambient NO₂ gas causes the change of conductivity from n-type to p-type at higher operating temperatures. This phenomenon was not observed for the samples annealed at higher temperature.     

Spontaneous bacterial peritonitis in liver failure

Cirrhosis of the liver results from a variety of mechanisms that cause progressive hepatic injury. It is the sixth leading cause of death in all patients between the ages of 35 and 55. This study attempts to correlate the morbidity and mortality of spontaneous bacterial peritonitis in liver failure patients to numerous etiologic and clinical variables. A retrospective review of 26 patients with spontaneous bacterial peritonitis associated with chronic liver disease was performed in a university hospital. Demographics (age and gender), clinical variables (etiology of liver failure, Child's classification, prior history of ascites, fever, abdominal pain, encephalopathy, and upper gastrointestinal hemorrhage), and laboratory variables (ascitic polymorphonuclearcyte count and cultures, serum albumin, bilirubin, creatinine, and prothrombin time) were studied. All of the patients had Child's C liver disease. Mortality rate was 46 per cent. Alcohol (46%) and hepatitis (30%) were the most common etiologies. Escherichia coli and Klebsiella pneumoniae were the most common culture isolates. All of the infections were monomicrobial. The only significant predictor of mortality (P < 0.05) in this study was the peritoneal fluid polymorphonuclear (PMN) cell count. PMN count >1000 PMN/mm3 was associated with a mortality of 88 per cent. Few patients with spontaneous bacterial peritonitis are ultimately transplanted.