A linear-time algorithm for the longest path problem in rectangular grid graphs

The longest path problem is a well-known NP-hard problem and so far it has been solved polynomially only for a few classes of graphs. In this paper, we give a linear-time algorithm for finding a longest path between any two given vertices in a rectangular grid graph.     

A simple, solvent and catalyst-free green synthesis of novel N-[(1H-indol-3-yl)arylmethyl]heteroarylamines

One-pot, three-component coupling reactions of indole, aromatic aldehydes, and heteroaryl amines under solvent-free conditions lead to the formation of the corresponding novel 3-[(N-heteroaryl)(aryl)methyl]indoles in moderate to high yields. The key features of this multi-component reaction are the simple reaction procedure, no organic solvent or acid catalyst, and easy product separation without further purification.     

Development of radiogallium–ethylenecysteamine cysteine complex as a possible renal imaging agent

[⁶⁷Ga]-ethylenecysteamine cysteine ([⁶⁷Ga]ECC) was prepared using freshly prepared [⁶⁷Ga]GaCl₃ and ethylenecysteamine cysteine (ECC) for 30 min at 90 °C (radiochemical purity ≈97 ± 0.88% ITLC, specific activity: 210 ± 5 GBq/mM). Stability of the complex was checked in human serum for 24 h at 37 °C. Partition co-efficient of the tracer in octanol:saline mixture was determined (log P; 0.8). The biodistribution of the radiolabeled compound in vital organs of wild-type rats were compared with that of free Ga³⁺ cation up to 48 h. Initial biodistribution results showed significant kidney excretion of the tracer comparable to that of homologous ^99mTc compound.     

Cloning and Expression of Functional Full-Length Human Tissue Plasminogen Activator in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Human tissue plasminogen activator (t-PA) plays a pivotal role in the treatment of acute myocardial infarction, ischemic stroke, and deep vein thrombosis. It has the benefit of generating no adverse effects such as fibrinogen depletion, systemic hemorrhage, and immunologic reactions. Human t-PA is a serine-protease enzyme containing 527 amino acid residues in five structural domains. The correct folding of t-PA requires the correct pairing of 17 disulfide bridges in the molecule. A gene encoding full-length human t-PA was cloned into pPICZαA expression vector downstream of alcohol oxidase promoter and α-mating signal sequence from Saccharomyces cerevisiae and flush with the kex2 cleavage site to express the protein with a native N terminus. The methylotrophic yeast, Pichia pastoris GS115 strain, was transformed with this cassette, and methanol utilizing (mut+) transformants were selected for production and secretion of human t-PA into culture media. SDS–PAGE and Western blot analysis showed the expressed bands of t-PA protein. Zymography test indicated suitable folding and proper function of the expressed recombinant human t-PA in conversion of plasminogen to plasmin and gelatin lysis. Amidolytic activity test showed the amidolytic activity of 1,650 IU/ml. The results of this study concluded that P. pastoris methylotrophic yeast can be a suitable alternative for mammalian and prokaryotic expression systems to produce t-PA.     

A novel chelating acid-assisted thermolysis procedure for preparation of tin oxide nanoparticles

Pure tin dioxide (SnO₂) nanoparticles were synthesized via thermolysis of tin phthalate and tin oxalate in the presence of oleic acid (OA) as solvent. Oleic acid (OA) was employed as an organic solvent, which can be applied to control particle growth and to stabilize the particles. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The orthorhombic phase SnO₂ nanoparticles with average size about 12 nm were synthesized through thermolysis of tin phthalate in the presence of oleic acid.     

Spin polarization and magnetoresistance through a ferromagnetic barrier in bilayer graphene

We study spin dependent transport through a magnetic bilayer graphene nanojunction configured as a two-dimensional normal/ferromagnetic/normal structure where the gate voltage is applied on the layers of ferromagnetic graphene. Based on the four-band Hamiltonian, conductance is calculated by using the Landauer-Buttiker formula at zero temperature. For a parallel configuration of the ferromagnetic layers of bilayer graphene, the energy band structure is metallic and spin polarization reaches its maximum value close to the resonant states, while for an antiparallel configuration the nanojunction behaves as a semiconductor and there is no spin filtering. As a result, a huge magnetoresistance is achievable by altering the configurations of ferromagnetic graphene around the band gap.     

Compressed sensing in random access networks with applications to underwater monitoring

For networks that are deployed for long-term monitoring of environmental phenomena, it is of crucial importance to design an efficient data gathering scheme that prolongs the life-time of the network. To this end, we consider a Random Access Compressed Sensing (RACS) scheme that considerably reduces the power and bandwidth usage of a large network. Motivated by underwater applications, we propose a continuous-time RACS that eliminates the need for synchronization and scheduling which are difficult to achieve in a distributed acoustic network. We provide an analytical framework for system design that ensures fast recovery and power-efficiency. Through analysis and examples, we demonstrate that recovery of the field can be attained using only a fraction of the resources used by a conventional TDMA network, while employing a scheme which is simple to implement.     

Acetalization of Carbonyl Compounds as Pentaerythritol Diacetals and Diketals in the Presence of Cellulose Sulfuric Acid as an Efficient,Biodegradable and Reusable Catalyst

This paper reports a practical and green method for the acetalization of carbonyl compounds as pentaerythritol diacetals and diketals derivatives using cellulose sulfuric acid as a biodegradable and reusable solid acid catalyst under thermal solvent‐free conditions.     

A new approach to solving Poisson system for free surface nonhydrostatic flow simulations

A nonhydrostatic finite volume model is presented to simulate free surface flow in a two‐dimensional vertical plane. The algorithm is based on a projection method including the solution of the pressure Poisson equation (PPE). The model is developed in a Cartesian grid in which the size of all the cells in the computational domain, excluding those of the top layer, is constant in time. To simulate the variable water surface, the heights of the top layer cells are variable and proportional to the local water elevation. Taking the layout of the grid system into consideration, a new method is proposed to solve the PPE derived in Cartesian coordinates. In this method, the system of pressure equations is divided into two subsystems, namely a subsystem for the upper layer cells and another for the remaining cells. The coefficient matrix of the former is variable with respect to time, whereas that of the latter remains constant. Therefore, the coefficient matrix of the latter subsystem can be inversed once and saved throughout the simulation. The application of this procedure reduces the computational cost compared with other PPE solvers in certain conditions. The model is applied to simulate a series of numerical tests including strong vertical accelerations and is verified against analytical and experimental results, demonstrating satisfactory performance. Copyright © 2011 John Wiley & Sons, Ltd.     

An efficient Stille cross‐coupling reaction catalyzed by ortho‐palladated complex of tribenzylamine under microwave irradiation

The catalytic activity of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(μ‐Br)]₂ complex as an efficient, stable and catalyst that is non‐sensitive to air and moisture was investigated in the Stille cross‐coupling reaction of various aryl halides with phenyltributyltins under microwave irradiation. The substituted biaryls were produced in excellent yield in short reaction times using a catalytic amount of this complex in DMF at 100 C. The combination of dimeric complex as homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields in shorter reaction times. Copyright © 2011 John Wiley & Sons, Ltd.