Intercalated theophylline-smectite hybrid for pH-mediated delivery

On the basis of their large specific surface areas, high adsorption and cation exchange capacities, swelling potential and low toxicity, natural smectite clays are attractive substrates for the gastric protection of neutral and cationic drugs. Theophylline is an amphoteric xanthine derivative that is widely used as a bronchodilator in the treatment of asthma and chronic obstructive pulmonary disease. This study considers the in vitro uptake and release characteristics of the binary theophylline-smectite system. The cationic form of theophylline was readily ion exchanged into smectite clay at pH 1.2 with a maximum uptake of 67±2 mg g−1. Characterisation of the drug-clay hybrid system by powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy confirmed that the theophylline had been exclusively intercalated into the clay system in an amorphous form. The drug remained bound within the clay under simulated gastric conditions at pH 1.2; and the prolonged release of approximately 40% of the drug was observed in simulated intestinal fluid at pH 6.8 and 7.4 within a 2-h timeframe. The incomplete reversibility of the intercalation process was attributed to chemisorption of the drug within the clay lattice. These findings indicate that smectite clay is a potentially suitable vehicle for the safe passage of theophylline into the duodenum. Protection from absorption in the stomach and subsequent prolonged release in the small intestine are advantageous in reducing fluctuations in serum concentration which may impact therapeutic effect and toxicit

Testing 10GHMBA steel for vessel ballistic shields

This paper presents the methods of testing the materials subjected to static and dynamic tensile tests, presented for 10GHMBA - E620 bainitic steel. The tests were conducted on the MTS 810.12 universal strength testing machine, a rotary hammer, a station especially designed for the conditions required for the Taylor test, an equipped ballistic pendulum and high-speed digital camera Phantom v12. The data collected in the tests are necessary for strength calculations of these constructions. The calculations are performed with the use of numerical methods and computing techniques, including constitutive equations for the performance description of a given material. Specific parameters and material constant values for the missile and the shield are accounted for in the equations. The parameters and constant values are either determined in experiments or 'selected', which is a significant issue in the case of high deformation speed. The final section presents examples of numerical simulations which enable the analysis of quick change processes which occur when a construction is subjected to strains due to strike with an object moving at a high speed, such as a 12.7 mm calibre missile moving at approx. 1000 ms-1. The knowledge of mechanical properties of materials is crucial in designing constructions exposed to direct fire and other dynamic effects. The results are presented in the form of charts and graphs

Metamorphoses of resonance curves in systems of coupled oscillators

We study dynamics of two coupled periodically driven oscillators in a general case and compare it with two simplified models. Periodic steady-state solutions to these system equations are determined within the Krylov-Bogoliubov-Mitropolsky approach. Amplitude profiles are computed. These two equations, each describing a surface, define a 3D curve – intersection of these surfaces. In the present paper, we analyse metamorphoses of amplitude profiles induced by changes of control parameters in three dynamical systems studied. It is shown that changes of the dynamics occur in the vicinity of singular points of these 3D curves

Test for penetrability of 10GHMBA steel used for the ballistic safety shields

There are elaborated some dependences which make it possible to compute some materials resistant to hits with the energy greater than in so far tests of the bullets of 7,62 mm caliber. The tests of being resistant to hit have been carried out with the 10GHMBA steel which has been overshot by the bullets of 12.7 mm. In order to do that the single cover plates with changeable thickness have been placed in the ballistic pendulum. On the basis of the obtained measurements like speed before and behind the specimen, the pendulum deflection angle, the force passed to the dynamometer sleeve, it is possible to define the maximum thickness of the penetrated material. The comparison with the bullets proof of various materials like steel with composites, ceramics or the mathematical models verification by an experiment can be done with direct comparison of some chosen measured parameters. For example the bullet speed behind the specimen has to be related to its thickness similarly to some other parameters which are possible to be measured. All the quantities like the bullet speed behind the specimen are the functions of the specimen thickness for the defined type of bullet. The penetration process of the material is a kind of transformation of the energy carried by the bullet into the energy of the specimen deformation, the emitted warm or into the pendulum work. In order to compare the bullet proof with various materials or the mathematical models with experiment there is proposed getting in some non-dimensional factors which define the change of the kinetic energy or the system impulse

The analysis of properties of platers used for the structural - ballistic safety shields in marine vessels

Some selected parameters of steel for structural-ballistic shields (OKB) used in the Navy vessels have been presented. The standards for steel to be used for ballistic shields are established by safety standards institutions and committees. There has been made an analysis of steel used for OKB of the vessels. The bullet-proof of the platters has been carried out on the appropriate position. The results of bullet-proof test of selected platters have been presented. The analysis made allowed to select the platters used for the structural-ballistic safety shields in marine vessels and give the direction for further research determined by contemporary threats of both military and terroristic nature. To produce the platters there have been used two types of armoured metal sheet which had been milled to flats made of the basic steel and which can be applied in shipbuilding. The structural-ballistic platters have had the form of flats with the total thickness of 8.5-9.2 mm. The prepared structural-ballistic platters have been technological processed in order to increase the degree of their strength. There have been also presented mechanical and technological properties of platters after heat treatment. The results of the bullet-proof have been presented in graphs form defining the dependence between the hit force and time. The effects of fire of specimen made of platters, by 7.62 mm cal. bullets with the proper speed have been seen on photographs