A rapid method for detection of genetically modified organisms based on magnetic separation and surface-enhanced Raman scattering

In this study, a new method combining magnetic separation (MS) and surface-enhanced Raman scattering (SERS) was developed to detect genetically modified organisms (GMOs). An oligonucleotide probe which is specific for 35 S DNA target was immobilized onto gold coated magnetic nanospheres to form oligonucleotide-coated nanoparticles. A self assembled monolayer was formed on gold nanorods using 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) and the second probe of the 35 S DNA target was immobilized on the activated nanorod surfaces. Probes on the nanoparticles were hybridized with the target oligonucleotide. Optimization parameters for hybridization were investigated by high performance liquid chromatography. Optimum hybridization parameters were determined as: 4 μM probe concentration, 20 min immobilization time, 30 min hybridization time, 55 °C hybridization temperature, 750 mM buffer salt concentration and pH: 7.4. Quantification of the target concentration was performed via SERS spectra of DTNB on the nanorods. The correlation between the target concentration and the SERS signal was found to be linear within the range of 25-100 nM. The analyses were performed with only one hybridization step in 40 min. Real sample analysis was conducted using Bt-176 maize sample. The results showed that the developed MS-SERS assay is capable of detecting GMOs in a rapid and selective manner.     

Barrier height enhancement of metal/semiconductor contact by an enzyme biofilm interlayer

A metal/interlayer/semiconductor (Al/enzyme/p-Si) MIS device was fabricated using α-amylase enzyme as a thin biofilm interlayer. It was observed that the device showed an excellent rectifying behavior and the barrier height value of 0.78?eV for Al/α-amylase/p-Si was meaningfully larger than the one of 0.58?eV for conventional Al/p-Si metal/semiconductor (MS) contact. Enhancement of the interfacial potential barrier of Al/p-Si MS diode was realized using enzyme interlayer by influencing the space charge region of Si semiconductor. The electrical properties of the structure were executed by the help of current–voltage and capacitance–voltage measurements. The photovoltaic properties of the structure were executed under a solar simulator with AM1.5 global filter between 40 and 100?mW/cm² illumination conditions. It was also reported that the α-amylase enzyme produced from Bacillus licheniformis had a 3.65?eV band gap value obtained from optical method.     

A new current model flux observer for wide speed range sensorless control of an induction machine

A new closed loop current model flux observer is designed to estimate the rotor flux, position and velocity of an induction machine. The current observer includes carefully designed sliding mode functions which are derivative of the fluxes along the /spl alpha/ and /spl beta/ axes. Therefore, when the estimated current converges to the measured one, the flux estimation is a mere integration of the sliding mode function. The rotor speed can then be derived from the sliding mode functions and the estimated flux. In the current and flux observers all of the terms that contain the rotor time constant and the rotor speed have been replaced by the sliding mode functions, thus making the proposed current and flux estimations completely insensitive to the rotor time constant variation and any error in the estimated speed. Simulations and experiments are performed under a variety of conditions to validate the effectiveness of the proposed algorithm.     

Yang–Mills theory à la string

A surface of codimension higher than one embedded in an ambient space possesses a connection associated with the rotational freedom of its normal vector fields. We examine the Yang–Mills functional associated with this connection. The theory it defines differs from Yang–Mills theory in that it is a theory of surfaces. We focus, in particular, on the Euler-Lagrange equations describing this surface, introducing a framework which throws light on their relationship to the Yang–Mills equations. Dedicated to Octavio Obregón, on the occasion of his 60th birthday.     

A Three—Dimensional Lead(II) Polymer with Bridging Saccharinate and Unusually Coordinated Acetate Ligands — Synthesis,IR Spectra,and Crystal Structure of [Pb(H2O)(μ‐OAc)(μ‐sac)]n

The complex [Pb(H₂O)(μ‐OAc)(μ‐sac)]n with acetate (OAc) and saccharinate (sac) ligands was characterized by IR, elemental analysis and X‐ray crystallography. The mixed‐anion lead(II) complex crystallizes in the triclinic crystal system with the space group of P1¯. The single crystal X‐ray analysis shows that the complex is a coordination polymer in which the lead(II) ions have a highly distorted pentagonal bipyramidal coordination geometry. Lead(II) ions are bridged by carboxylate groups in a zigzag arrangement forming one‐dimensional infinite chains, which are also linked by sac bridges and aromatic π‐π contacts between the adjacent phenyl rings of sac ligands, resulting in a three‐dimensional network. One water molecule coordinates the lead(II) ion and also forms weak hydrogen bonds with the sulfonyl oxygen atoms of the neighboring sac ligands. The sac ligand acts as a bridging ligand through the nitrogen and carbonyl oxygen atoms, while the carboxylate moiety of the acetate ligand shows an unusual (bidentate, and bridging) coordination behaviour, which was observed for the first time in the structure.     

The composition and antifungal bioassay of the essential oils of differentBetula species growing in Turkey

FiveBetula species,B. pendula, B. browicziana, B. medwediewii, B. litwinowii, andB. recurvata, were collected from different parts of Turkey. The leaves of these species were hydrodistilled to yield the consequent essential oils. The essential oil compositions were investigated by GC/MS. 14-Hydroxy--caryophyllene was the main constituent in the oil ofB. pendula. 14-Hydroxy-4,5-dihydro--caryophyllene, a new compound, was identified as the main constituent in the oils ofB. browicziana, B. litwinowii, and B. recurvata. In the oil ofB. medwediewii methyl salicylate was the main compound. Various phytopathogenic fungi were studied by the agar tube dilution technique to test the antifungal activities of the essential oils at 400 g/ml concentration. The essential oils showed strong antifungal activity againstCephalosporium aphidicola, Drechslera sorokinianse, Fusarium solani, andRhizoctonia cerealis.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 126–130, March–April, 2000.     

trans‐Bis(diethanolamine‐N,O)bis(saccharinato‐N)cadmium(II)

The structure of the title complex consists of isolated [Cd(C₇H₄NO₃S)₂(C₄H₁₁NO₂)₂] units. The Cd²⁺ cation lies on an inversion centre and is octahedrally coordinated by two N,O‐bidentate diethanol­amine (dea) and two N‐bonded saccharinate (sac) ligands [saccharin is 1,2‐benziso­thia­zol‐3(2H)‐one 1,1‐dioxide]. The dea ligands constitute the equatorial plane of the octahedron, forming two five‐membered chelate rings around the Cd^II ion, while the sac ligands are localized at the axial positions. The Cd—N_sac, Cd—N_dea and Cd—O_dea bond distances are 2.3879 (12), 2.3544 (14) and 2.3702 (13) Å, respectively. The H atoms of the free and coordinated hydroxyl groups of the dea ligands are involved in hydrogen bonding with the carbonyl and sulfonyl O atoms of the neighbouring sac ions, while the amine H atom forms a hydrogen bond with the free hydroxyl O atom. The individual mol­ecules are held together by strong hydrogen bonds, forming an infinite three‐dimensional network.