Grain size,strain rate,and temperature dependence of flow stress in ultra-fine grained and nanocrystalline Cu and Al: Synthesis,experiment, and constitutive modeling

For the first time, high quality bulk nanocrystalline (nc) fcc metals, with least amounts of imperfections, exhibiting high strength and ductility at room and different temperatures, under quasi-static and dynamic types of loading, were prepared and a comprehensive study on their post-yield mechanical properties was performed. This investigation included study of the effect of temperature on stress–strain responses of mechanically milled bulk nc Cu and Al. The samples after preparation through mechanical milling and consolidation processes were subjected to uniaxial compressive loading at quasi-static and dynamic strain rates of 10⁻² s⁻¹ and 1840–3105 s⁻¹, respectively, at temperatures ranging from 223 to 523 K. In both materials strong dependency of flow stress to temperature was observed; this dependency was rather more pronounced when the materials were tested at the quasi-static strain rate. Further, a new grain size and temperature dependent viscoplastic phenomenological constitutive equation, Khan–Liang–Farrokh (KLF) model was developed based on the Khan–Huang–Liang (KHL) constitutive equation. The model was featured to correlate different characteristic behaviors of polycrystalline materials in the plastic regime, as the result of grain refinement. In addition, the viscoplastic responses of bulk Cu and Al of different grain sizes (from sub-micron to nanometer range), and those from bulk nc Cu and Al at different strain rates (quasi-static to dynamic), recently published (21 and 22), were simulated using the newly developed equation. The results confirmed reasonable capability of the developed model to correlate a wide spectrum of the viscoplastic responses of these fcc metals.     

Understanding the Interaction of Glutamate Salts with Serum Albumin Protected Prism‐Shaped Silver Nanoparticles toward Glutamate Sensing

Surface plasmon spectroscopy of serum albumin protected prism‐shaped silver nanoparticles is used as simple and effective sensing tool to detect glutamate salts. The approach does not require any electrochemical setup to detect glutamates, in contrast to common techniques to detect glutamates in general. Experiments reveal that upon presence of high concentrations of glutamate salts, the prism‐shaped nanoparticles are transformed to smaller‐sized nanoclusters, while the remaining nanoparticles are assembled to form aggregates. Control experiments confirm that the interaction is specific to the serum albumin coating, the prism shape of the nanoparticles, and to silver.     

Theoretical Encapsulation of Fluorouracil (5-FU) Anti-Cancer Chemotherapy Drug into Carbon Nanotubes (CNT) and Boron Nitride Nanotubes (BNNT)

Introduction: Chemotherapy with anti-cancer drugs is considered the most common approach for killing cancer cells in the human body. However, some barriers such as toxicity and side effects would limit its usage. In this regard, nano-based drug delivery systems have emerged as cost-effective and efficient for sustained and targeted drug delivery. Nanotubes such as carbon nanotubes (CNT) and boron nitride nanotubes (BNNT) are promising nanocarriers that provide the cargo with a large inner volume for encapsulation. However, understanding the insertion process of the anti-cancer drugs into the nanotubes and demonstrating drug-nanotube interactions starts with theoretical analysis. Methods: First, interactions parameters of the atoms of 5-FU were quantified from the DREIDING force field. Second, the storage capacity of BNNT (8,8) was simulated to count the number of drugs 5-FU encapsulated inside the cavity of the nanotubes. In terms of the encapsulation process of the one drug 5-FU into nanotubes, it was clarified that the drug 5-FU was more rapidly adsorbed into the cavity of the BNNT compared with the CNT due to the higher van der Waals (vdW) interaction energy between the drug and the BNNT. Results: The obtained values of free energy confirmed that the encapsulation process of the drug inside the CNT and BNNT occurred spontaneously with the free energies of −14 and −25 kcal·mol⁻¹, respectively. Discussion: However, the lower value of the free energy in the system containing the BNNT unraveled more stability of the encapsulated drug inside the cavity of the BNNT comparing the system having CNT. The encapsulation of Fluorouracil (5-FU) anti-cancer chemotherapy drug (commercial name: Adrucil^®) into CNT (8,8) and BNNT (8,8) with the length of 20 Å in an aqueous solution was discussed herein applying molecular dynamics (MD) simulation.     

Solvent Effects on Protonation Constants of Imatinib in Different Aqueous Solutions of Methanol at T = 298.15 K

Russian Journal of Physical Chemistry A - Imatinib (Gleevec) is a drug that is applied to treat cancer. It inhibits the Bcr-Abl tyrosine-kinase and therefore, it can slow growth or result in...     

A Parham Cyclization route to the 2,3-dihydro-1H-indazole-1,2-dicarboxylate ring systems via condensation of thermolabile aryllithium reagents and azodicarboxylate esters

The Parham Cyclization reaction of o-lithiobenzyl chlorides (generated by low temperature halogen-metal exchange of the corresponding o-bromobenzyl chlorides with n-butyllithium) with azodicarboxylate esters provides a new entry to the 2,3-dihydro-1H-indazole-1,2-dicarboxylate ring system in moderate to good yield.     

Effect of a series of essential oil molecules on DPPC membrane fluidity: a biophysical study

Monoterpenes (MTs) were known to cause biological membranes perturbation. Here, the interaction of four (eucalyptol, pulegone, terpineol, and thymol) with dipalmitoylphosphatidylcholine (DPPC) liposomes was studied by Raman spectroscopy, differential scanning calorimetry and fluorescence anisotropy. Liposomes were prepared by the thin-film hydration method, and MTs were added to DPPC at various molar percentages (from 0 to 25%). All the studied MT abolished the pre-transition of DPPC membrane and modified the intensity of the Raman peak at 715 cm^?1, proving their interaction with the choline head group of phospholipids. MTs decreased also the main transition temperature suggesting their interaction with the alkyl chains of DPPC membrane. Besides, a splitting of the main transition peak was obtained with thymol. The results of fluorescence anisotropy showed that the studied molecules fluidized the liposomal membrane at 25, 41, and 50 °C. A mixture of isomers of terpineol fluidized the membrane more than α-terpineol. The presence of a hydroxyl group in the MT structure seems to improve the membrane fluidizing effect of MTs.     

Fluid surface imaging using microlens arrays

 The paper describes a new technique for measuring surface slopes at the air–water interface. A microlens array is employed to optically sample the fluid surface at a large number of measurement points in parallel. The focal plane image of the lenslet array is recorded by a standard video camera, generating a data set of typically 4000 candidate samples for each video frame. The displacement of the focal spots is analyzed using a cross-correlation technique augmented by a topological identification algorithm which makes use of the hexagonal structure of the lenslet array. Surface height profiles are computed by integrating the surface slope field. Received: 19 March 1997 / Accepted: 5 January 1998