Oxidation-induced changes in mechanical properties of silicon nitride ceramics

The effect of oxidation on the room-temperature mechanical properties of four different silicon nitride ceramics is investigated. The strength and the elastic modulus of the whole material and the hardness, the fracture toughness and the elastic modulus of the internal region (without surface oxide layer) are determined for the materials oxidized at temperatures up to 1400°C. It is found that the fracture toughness decreases during oxidation at 1000°C. Reduction of the elastic modulus of the materials oxidized at 1400°C is also observed. A part of the changes in the mechanical properties is interpreted by the changes in the phase composition

Laser induced distortion of band structure in solids: an analytic model

We consider a spatially periodic (cosine) potential as a model for a crystalline solid that interacts with a harmonically oscillating external electric field. This problem is periodic both in space and time and can be solved analytically using the Kramers-Henneberger co-moving frame. By analyzing the stability of the closely related Mathieu-type differential equation, the electronic band structure can be obtained. We demonstrate that by changing the field intensity, the width of the zero-field band gaps can be drastically modified, including the special case when the external field causes the band gaps to disappearComment: 8 pages, 3 figure

Gene polymorphisms in primary biliary cirrhosis: association with the disease and hepatic osteopathy

Genetic factors have been implicated in the pathogenesis of osteoporosis, a common disorder in primary biliary cirrhosis (PBC). Estrogen receptor-alpha gene (ER-�), vitamin-D-receptor gene (VDR) and IL-1-receptor-antagonist gene (IL-1RN) are all attractive candidates for osteoporosis susceptibility. Furthermore insulin-like growth factor-I (IGF-I) gene microsatellite repeat polymorphism was found to be associated with osteoporosis in some studies and collagen-I�1 (COLIA1) Sp1 s allele was associated with lower bone mineral density (BMD) in one study in PBC. IGF-I treatment restored osteopenia and reduced fibrogenesis in experimental cirrhosis. In this study we summarize our results on polymorphisms of the above genes and bone disease in Hungarian PBC patients. Patients and methods: 70 female patients with PBC were enrolled (age:57.6yrs, range:37-76yrs, each AMA-M2 positive, stage II-IV). 139 age-matched female subjects served as controls (age: 55.9 yrs, range:43-72 yrs). COLIA1 Sp1 and IGF-I microsatellite polymorphisms were determined by PCR in all patients and controls. VDR BsmI, IL-1RN variable-number tandem repeat (VNTR) and ER-� PvuII and XbaI polymorphisms were detected in 33 patients and controls. BMD was measured by dual energy x-ray absorptiometry (Lunar,Prodigy,USA) in lumbar spine (LS) and femoral neck (FN). Results: There was no difference in IGF-I microsatellite repeat polymorphism (192/192=34.2%, 194/192=28.6%, other=37.2%) and COLIA1 Sp1 polymorphism (SS=72.9%, Ss=22.8% and ss=4.3%) and IL-1 VNTR polymorphism between PBC patients and controls, however, the COLIA1 Sp1 s allele was significantly less frequent in patients with PBC (p=0.038). The genotype frequency of VDR BsmI (BB=57.5%, Bb=33.3%, bb=9.1%, p=0.01) and ER-a PvuII (PP=18.2%, Pp=75.6%, pp=6.2%, p=0.03) and XbaI (XX=9.1%, Xx=90.9%, xx=0%, p=0.0003) of the patients was different from that of the control group, with higher frequency of the BB, Pp and Xx genotypes in PBC. Osteoporosis (t score<-2.5) was detected in 22 patients (31.4%). Osteoporotic patients were elder and had longer disease history (p=0.01 for both). An association was found between the IGF-I genotypes and ODM data, the 192/192 genotype was associated with higher FN Z-score compared to other genotypes (p=0.036). Conclusions: In contrast to previous studies the COLIA1 Sp1 s allele was less frequent in patients with PBC, and its presence was not associated with BMD. We confirmed previous findings on higher frequency of VDR BsmI BB genotype in patients with PBC. The ER-α PvuII and XbaI Pp and Xx genotypes were more frequent in PBC patients, while IL-1RN VNTR and IGF-I microsatellite repeat polymorphism was not different. Since IGF-I polymorphism was associated to BMD, it may be hypothesized that not COLIA1 but IGF-I together with other genetic and environmental factors may be involved in the complex regulation of BMD in PBC

New double column system for heteroazeotropic batch distillation

A new double column system (DCS) operated in closed mode is suggested for heterogeneous batch distillation. This configuration is investigated by feasibility studies based on the assumption of maximal separation and is compared with the traditional batch rectifier (BR). We study the configurations also by dynamic simulation based on a detailed model using a professional simulator. For the new configuration the minimal duration of the process is determined. The influence of the most important operational parameters is studied. The calculations and the simulations are performed for a binary (n-butanol–water) and for a ternary heteroazeotropic mixture (isopropanol–water + benzene as entrainer). One of the advantages of the DCS is that distillation of binary and ternary systems is performed in only one step. Furthermore the recovery of components is usually higher and the amount of byproducts is lower

Római térdfibulák az alföldi szarmata Barbaricum területéről

In the course of my research, I collected and typologized 87 knee brooches from 47 sites. The knee brooches were unearthed all over the Great Hungarian Plain. A large number of these sites are situated in Csongrád-Csanád and Jász-Nagykun-Szolnok county. Out of the 12 types identified, three were the most common: I.1.1. being the most common (24%), followed closely by type I.1.4. (15%) and type I.1.2. (11%). The three most common types was followed by the Germanic type knee brooches with their 10%. This was the most varied type too within the examined material. The Germanic type was followed by type I.1.3. (9%) and type II.1. (8%). The most uncommon types were I.2. (5%), I.5. (2%), I.3. (1%) and I.4. (1%), with often just one specimen representing it in the material. The uncertain specimens (which cannot be classified as either type I.1.1. or I.1.2. due to the low grade photos in publications or because these pieces were no longer available in the museums) took up 6% of the material. Based on the current results of my research, it seems that the most common types of the knee brooches originate from the area of Pannonia and Noricum. Two types, however, seem to come from somewhere else: type I.2., probably, from the province of Moesia (based on the research of Andrea Vaday) and type II.1. was most commonly used in Dacia, with a few examples from Pannonia and Bohemia. About 1/3 of the brooches were decorated, most oftenly with engraving, but there are cases of embossing, carving and with pearls. The brooches were mostly made out of copper-alloy, except three which were made out of silver. Based on my current results, the most common types of knee brooches (I.1.1., I.1.2., I.1.4.) appeared in the area of the Great Hungarian Plain at the end of the 2nd century AD, and their use can be attested until the 4th century

The hard life of air bubbles crossing a fluid/fluid interface

We investigate the dynamics of isolated air bubbles crossing the horizontal interface separating two Newtonian immiscible liquids initially at rest by means of experiments and DNS. High-speed video imaging is used to obtain a detailed evolution of the various interfaces involved in the system. The size of the bubbles and the viscosity contrast between the two liquids are varied by more than one and four orders of magnitude, respectively, making it possible to obtain bubble shapes ranging from spherical to toroidal. A variety of flow regimes is observed, including that of small bubbles remaining trapped at the fluid–fluid interface in a film-drainage configuration. In most cases, the bubble succeeds in crossing the interface without being stopped near its undisturbed position and, during a certain period of time, tows a significant column of lower fluid which sometimes exhibits a complex dynamics as it lengthens in the upper fluid. Direct numerical simulations of several selected experimental situations are performed with a code employing a volume-of-fluid type formulation of the incompressible Navier–Stokes equations. Comparisons between experimental and numerical results confirm the reliability of the computational approach in most situations but also points out the need for improvements to capture some subtle but important physical processes, most notably those related to film drainage. Influence of the physical parameters highlighted by experiments and computations, especially that of the density and viscosity contrasts between the two fluids and of the various interfacial tensions, is discussed and analysed in the light of simple models