Effect of cold work on the dissolution kinetics in the precipitating Al-2 wt% Mg alloy

The fracture stress _f was taken to assess the mechanism of dissolution of the -phase in the Al-2 wt% Mg alloy. The role of pre-cold working the polycrystalline samples was investigated. The dissolution of the -phase was carried out at different temperatures. The relation between the fracture stress and the time of dissolution showed peaky curves. The rise of _f towards a maximum was attributed to the progressive dissolution of the precipitates. The position of the peak was found to shift towards lower times of dissolution with the increase of the dissolution temperature or the increase of the pre-cold work. Considering the peak position indicative of a certain degree of dissolution, equivalent times and temperatures of the dissolution mechanism were thus found and the activation energy was calculated. Pre-cold working the samples before the dissolution act decreased the activation energy responsible for the process from 1·95×10^–19 J to about 0·48× 10^–19 J. The initial drop in _f observed for heavily cold worked samples pointed towards the possible effect of excess vacancies created by cold work.The authors are really grateful for the enlightening discussions with Prof. R. Kamel.     

Alpha particle absorption and inclined incidence track parameters evaluation in plastic detectors

In this work the use of our recently constructed irradiation chamber was involved in the current experiments. The absorption of alpha particle in air has been studied through a set of experiments in which the stopping power has been measured. A comparison between the calculated values and the present experimental results is given and a good agreement has been found. Critical angle (θ_c) determination has been carried out using two different techniques, via indirect and direct measurements, under different etching conditions and at various alpha energies. An empirical fit of θ_c−h (h is the removal thickness layer) dependence has been calculated and found to work well in the studied h ranges. Also, the inclined alpha tracks parameters of energies between 1.0 and 5.0 MeV have been studied. Results can be successfully applicable in alpha autoradiography studies and detector efficiency determination for track registration in plastic recorders.     

Enantioselective Synthesis of (−)‐Halenaquinone

The efficient, 12–14 step (LLS) total synthesis of (?)‐halenaquinone has been achieved. Key steps in the synthetic sequence include: (a) proline sulfonamide‐catalyzed, Yamada–Otani reaction to establish the C6 all‐carbon quaternary stereocenter, (b) multiple, novel palladium‐mediated oxidative cyclizations to introduce the furan moiety, and (c) oxidative Bergman cyclization to form the final quinone ring.     

Natural radioactivity and radon exhalation rates in building materials used in Egypt

Natural and fabricated building materials commonly used in Egypt were surveyed for both natural radionuclides content and radon exhalation rate. These include raw as well as construction products. Concentration of natural radionuclides in all samples were determined by γ-ray spectroscopy with HPGe detector. For Radon exhalation rate measurements of fabricated samples, the seal can-technique has been applied using CR-39 plastic track detectors. The radiation hazard indices of the total natural radioactivity in the studied samples were estimated. The results were compared with the corresponding results of different countries and were found to be lying within the average world values. Radon exhalation rate in the studied samples varied between 197 (cement brick) and 907 mBq m⁻² h⁻¹ (blast furnace slag cement). The results of this survey suggest that, using blast furnace slag cement for pre-coating the internal walls of buildings in the Urban region of Egypt is discouraged and the replacement of clay brick by cement brick will be more healthy for the public.     

Investigation of modified orange peel in the removal of Cd2+, Co2+ and Zn2+ from wastewater

Journal of Radioanalytical and Nuclear Chemistry - Eco-friendly and cost-effective adsorbent material was successfully synthesized from orange peel (OP). Using H2O2, the modification of the...     

Modeling sound transmission through the pulmonary system and chest with application to diagnosis of a collapsed lung

A theoretical and experimental study was undertaken to examine the feasibility of using audible-frequency vibro-acoustic waves for diagnosis of pneumothorax, a collapsed lung. The hypothesis was that the acoustic response of the chest to external excitation would change with this condition. In experimental canine studies, external acoustic energy was introduced into the trachea via an endotracheal tube. For the control (nonpneumothorax) state, it is hypothesized that sound waves primarily travel through the airways, couple to the lung parenchyma, and then are transmitted directly to the chest wall. In contradistinction, when a pneumothorax is present the intervening air presents an added barrier to efficient acoustic energy transfer. Theoretical models of sound transmission through the pulmonary system and chest region to the chest wall surface are developed to more clearly understand the mechanisms of intensity loss when a pneumothorax is present, relative to a baseline case. These models predict significant decreases in acoustic transmission strength when a pneumothorax is present, in qualitative agreement with experimental measurements. Development of the models, their extension via finite element analysis, and comparisons with experimental canine studies are reviewed.     

Generation of Molecular Complexity from Cyclooctatetraene: Preparation of Optically Active Protected Aminocycloheptitols and Bicyclo[4.4.1]undecatriene

The racemic (6‐cyclo‐heptadienyl)Fe(CO)₃⁺ cation ((±)‐ 7 ), prepared from cyclooctatetraene, was treated with a variety of carbon and heteroatom nucleophiles. Attack took place at the less hindered C¹ dienyl carbon and decomplexation of the (cycloheptadiene)Fe(CO)₃ complexes gave products rich in functionality for further synthetic manipulation. In particular, a seven‐step route was developed from racemic (6‐styryl‐2,4‐cycloheptadien‐1‐yl)phthalimide ((±)‐ 9 d ) to afford the optically active aminocycloheptitols (?)‐ 20 and (+)‐ 20 .     

Generation of Molecular Complexity from Cyclooctatetraene: Preparation of Aminobicyclo[5.1.0]octitols

A series of eight stereoisomeric N‐(tetrahydroxy bicyclo‐[5.1.0]oct‐2S*‐yl)phthalimides were prepared in one to four steps from N‐(bicyclo[5.1.0]octa‐3,5‐dien‐2‐yl)phthalimide (±)‐ 7 , which is readily available from cyclooctatetraene (62 % yield). The structural assignments of the stereoisomers were established by ¹H NMR spectral data as well as X‐ray crystal structures for certain members. The outcomes of several epoxydiol hydrolyses, particularly ring contraction and enlargement, are of note. The isomeric phthalimides as well as the free amines did not exhibit β‐glucosidase inhibitory activity at a concentration of less than 100 μM .