Proton therapy analysis using the Monte Carlo method

The range and straggling data obtained from the transport of ions in matter (TRIM) computer program were used to determine the trajectories of monoenergetic 60 MeV protons in muscle tissue by using the Monte Carlo technique. The appropriate profile for the shape of a proton pencil beam in proton therapy as well as the dose deposited in the tissue were computed. The good agreements between our results as compared with the corresponding experimental values are presented here to show the reliability of our Monte Carlo method.     

Development of agribiotechnology and biosafety regulations used to assess safety of genetically modified crops in Bangladesh

Bangladesh is on the verge of adopting genetically modified (GM) crops for commercial cultivation and consumption as feed and food. Most of the laboratories are engaged in tissue culture and molecular characterization on plants, whereas some have started living modified organism research with shortages of trained manpower, infrastructure, and funding. Nutritionally improved Golden Rice, biotech brinjal, and late blight-resistant potato are in contained trials in a greenhouse, and potato ring spot virus-resistant papaya is in the process of approval for a field trial. The government has taken some initiative in support of GM organism research, which include the formation of a Biotechnology Department in all institutes and the formation of the apex body, the National Task Force Committee on Biotechnology of Bangladesh under the chairpersonship of the Prime Minister. Biosafety policy guidelines and related aspects of biotechnology issues have been approved, and the laws are in the process of being promulgated. Being a party to the Cartagena Protocol, proper biosafety measures are regulated by the appropriate authority as stated. Although there are no laws made yet directly for biosafety of GM crops/foods, the relevant laws on agriculture, medicine, food, import, trade, environment, etc. may suffice and explain the situation.     

Tractor cabin’s passive suspension parameters optimization via experimental and numerical methods

Reduction of transmitted vibrations of tractor cabin which is caused by road roughness is the major objective of this study; consequently operator health can be achieved. This objective is carried out via experimental measurements and finite element modeling. For this purpose the vertical acceleration of the cabin as well as the rear axle of the tractor is measured in different road conditions and forward speeds. However, it should be mentioned that tests were carried out according to the ISO 2631-1985 but no measurements were done on the driver’s seat. Then the finite element model of the cabin’s tractor is developed and the dynamic response of the cabin interior (with the measured axle acceleration as input dynamic force) is obtained. At the third step the suspension parameters are calculated by comparing the accelerations obtained from the model and measurements. Finally the suspension parameters are optimized according to ISO 2631-1985 via iterative method.     

Numerically gas radiation heat transfer modeling in chemically nonequilibrium reactive flow

A numerical method for calculation of strong radiation for 2D reactive air is developed. Governing equations are taken to be 2D, compressible Reynolds-average Navier–Stokes and species transport equations. Also, radiation heat flux is evaluated using a model of discrete ordinate method. A multiband model is used to construct absorption coefficients. Tangent slab approximation is assumed to determine the characteristic parameters needed in the Discrete Ordinates Method.     

Vacancy growth and migration dynamics in atomically thin hexagonal boron nitride under electron beam irradiation

Atomically thin hexagonal boron nitride (h‐BN) is investigated using aberration‐corrected ultra‐high resolution electron microscopy under 80 kV electron beam. This study focuses on the in situ formation, growth and migration of vacancies in h‐BN. This study also reveals interaction dynamics of edges and vacancies with adatoms and molecules under the electron beam. According to this investigation, boron monovacancies migrate through their second neighbor to reduce the surface energy of the membrane. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermodynamic and physical interactions between novel polymeric surfactants and lipids: toward designing stable polymer-lipid complexes

Surfactant amphiphilic macromolecules (AMs) were complexed with a 1:1 ratio of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), either by a coevaporation (CE) or postaddition (PA) method, to form AM-lipid complexes with enhanced drug delivery applications. By characterizing the surfactant-lipid interactions, these heterogeneous drug delivery systems can be better controlled and engineered for optimal therapeutic outcomes. In this study, the physical interactions between DOPE:DOTAP liposomes and AM surfactants were investigated. Langmuir film balance and isothermal calorimetry studies showed cooperative intermolecular interactions between pure lipids and AM in monolayers and high thermostability of structure formed by the addition of AM micelles to DOTAP:DOPE vesicles in buffer solution respectively. Increasing the AM weight ratio in the complexes via the CE method led to complete vesicle solubilization--from lamellar aggregates, to a mixture of coexisting vesicles and micelles, to mixed micelles. Isothermal calorimetry evaluation of AM-lipid complexes shows that, at higher AM weight ratios, PA-produced complexes exhibit greater stability than complexes at lower AM weight ratios. Similar studies show that AM-lipid complexes produced by the CE methods display stronger interactions between AM-lipid components than complexes produced by the PA method. The results suggest that the PA method produces vesicles with AM molecules associated with its outer leaflet only (i.e., an AM-coated vesicle), while the CE method produces complexes ranging from mixed vesicles to mixed micelle in which the AM-lipid components are more intimately associated. These results will be helpful in the design of AM-lipid complexes as structurally defined, stable, and effective drug delivery systems.     

Novel synthesis and antitumor evaluation of polyfunctionally substituted heterocyclic compounds derived from 2-cyano-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-acetamide

The reaction of 2-amino-3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophene with ethyl cyanoacetate gave 2-cyano-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-acetamide. The latter was used to synthesize different heterocyclic derivatives comprising thiophene, thiazole, pyrazole, pyridine, pyrimidine, and coumarin rings. The mechanistic and synthetic pathways depended on regioselective attack and/or cyclization by the cyanoacetamido moiety in the key precursor on various chemical reagents. The competition of the reaction pathways including dipolar cyclization, dinucleophilic-bielectrophilic attack, β-attack, Gewald-type attack, and condensation reactions led to the diversity of the synthesized products. The antitumor activities of the synthesized products were studied and evaluated. Most of the compounds revealed high inhibitory effects when screened in vitro for their antiproliferative activity. Three human cancer cell lines, namely, breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460) and CNS cancer (SF-268) were used in the screening tests. The simplicity of the synthetic procedures which mainly involved one-pot reactions under mild reaction conditions, the convenience of yield production and the diversity of the reactive sites in the produced systems play a valuable role for further heterocyclic transformations and further biological investigations.     

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble?s dynamics

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack.     

Organoselenium/Tellurium-Bearing Macroacyclic and Cyclic Ligand Systems and Their Complexation Reactions

Abstract

A series of phenol-substituted acyclic Schiff bases, 2,6-{RE(CH₂) _n N═C(CH₃)}₂-C₆H₂(4-CH₃)(OH), (E = Te: R = C₆H₅, n = 2(L _a), 3(L _b); R = C₆H₄-4-OCH₃, n = 2(L _c), 3(L _d); E = Se: R = C₆H₅, n = 2(L _e), 3(L _f)), of the type E₂N₂O have been synthesized by condensation of 2,6-diacetyl-4-methylphenol with arylchalcogenoalkylamines. This ligand framework is useful for designing molecular complexes with a variety of coordination modes depending upon the nature of the central metal atom. The reactivity of the tellurium-bearing macroacyclics ligands towards Zn(II), Cd(II), and Hg(II) has been examined. The ligands L _a?L _d with Zn(II) and Cd(II), and only L _a and L _b with Hg(II) form complexes of composition M₂X₄L, (X = Cl or Br), whereas L _c and L _d with Hg(II) give products of composition HgBr₂L. The modes of ligand interaction with Zn(II) and Cd(II) are different than that with Hg(II).

Following a multistep reaction involving abstraction of bridged Br atoms and subsequent addition of more ligand, the mercury complex, Hg₂Br₄L has been used for developing metallocyclic system of the type [Hg₂Br₂L₂]²⁺. The latter has been found to encapsulate Zn(II) and Cd(II) to give multimetallic systems.