Highly selective PVC-membrane electrodes based on Co(II)-Salen for determination of nitrite ion.

A cobalt(II) derivative was used as a suitable ionophore for the preparation of a polymeric membrane nitrite-selective electrode. The electrode reveals a Nemstian behavior over a very wide NO2- ion concentration range (1.0 x 10(-6)-1.0 x 10(-1) M) and a very low detection limit (5.0 x 10(-7) M). The potentiometric response is independent of the pH of solution in the pH range 4.0-9.5. The electrode shows advantages such as low resistance, fast response and, most importantly, good selectivity relative to a wide variety of inorganic and organic anions. In fact, the selectivity behavior of the proposed NO2- ion-selective electrode shows great improvements compared to the previously reported electrodes for nitrite ion. The proposed electrodes could be used for at least 2 months without any significant changes in potentials. The electrode was successfully applied to the determination of nitrate ion concentrations in sausage and milk samples.     

Excitation of plant growth in dormant temperature by steady magnetic field

Experimental results of applying a steady magnetic field (20 and 30 mT) on agricultural plants reveal that their growth is more than that of control plants. Considering that these plants have ferritin cells, and each ferritin cell has 4500 Fe atoms, it is obvious that they have an outstanding role in the plants’ growth. As the last spin magnetic moment (SMM) of the Fe atom posed to an external magnetic field (EMF), the composition of SMM and EMF create an oscillator in the system. Then we have a moment of force on ferritin cells. This oscillator exerts its energy, then damps and finally locates in the field direction. The relaxed energy increased the internal temperature (i.e., the effective temperature of the magnetic spin system of plant) so that it is situated in a proper temperature for growing. This phenomenon (temperature increasing) occurs in the initial minutes of applying the magnetic field. So it depends on the number of times of locating the plant in magnetic field in a day (n). If this number (n) passes the critical value, the plant reaches a burning temperature and growth is perturbed. In this paper, the plant growth rate and critical temperature in a steady magnetic field were investigated and formulated theoretically. An innovative result in this research is as follows: if a plant's environment was in the dormant temperature, we could increase the internal temperature of the plant by applying a magnetic field n times in a day (for growth).     

A neutron polarization analysis study of Ce2Fe17 in its paramagnetic phase

Spin-flip (paramagnetic) scattering and neutron depolarization studies were performed on Ce₂Fe₁₇ in its paramagnetic phase on the Dhruva neutron polarization analysis spectrometer. The absence of normalQ dependence of the scattered spin flip intensity shows that Ce₂Fe₁₇ is not a normal paramagnetic and there exist superparamagnetic clusters of sufficiently large dimensions (～100Å). The observed neutron depolarization gives an indication of the dynamics of these Ce₂Fe₁₇ superparamagnetic clusters.     

Novel monohydrogenphosphate sensor based on vanadyl salophen

A novel PVC-based membrane sensor based on vanadyl salophen (VNSP) for determination of trace amounts of monohydrogenphosphate (MHP) ions is introduced. The electrode revealed Nernstian response towards monohydrogenphosphate over the wide concentration range from 1.0×10⁻¹ to 1.0×10⁻⁶ M at the pH of 8.2. The effect of solvent mediator, cationic additives and amount of ion-carrier on the behavior of the sensor was investigated. The sensor shows a short response time (<20 s) in the whole concentration ranges. The selectivity of the electrode is very high, and it can be used for detection of trace amounts of monohydrogenphosphate in the presence of large amounts of other anions. The detection limit of the electrode was 5.0×10⁻⁷ M (48 ng/ml) and it could be used for 14 weeks without any measurable changes in the slope. The potentiometric selectivity coefficients data revealed negligible interference from 16 common anions. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer samples and, as an indicator electrode, in potentiometric titration of HPO₄²⁻ ion with barium nitrate.     

Trichloroisocyanuric acid as a novel oxidizing agent for the oxidation of 1,3,5-trisubstituted pyrazolines under both heterogeneous and solvent free conditions

Trichloroisocyanuric acid is used as an effective oxidizing agent for the oxidation of 1,3,5-trisubstituted pyrazolines to their corresponding pyrazoles under both heterogeneous and also solvent free conditions with good yields at room temperature.     

Group theory for tetraammineplatinum(II) withC 2v andC 4v point group in the non-rigid system

The non-rigid molecule group theory (NRG) in which the dynamical symmetry operations are defined as physical operations is a new field of chemistry. Smeyers in a series of papers applied this notion to determine the character table of restricted NRG of some molecules. In this work, a simple method is described, by means of which it is possible to calculate character tables for the symmetry group of molecules consisting of a number of NH3 groups attached to a rigid framework. We study the full non-rigid group (f-NRG) of tetraammineplatinum (II) with two separate symmetry groups C2v and C4v. We prove that they are groups of order 216 and 5184 with 27 and 45 conjugacy classes, respectively. Also, we will compute the character tables of these groups.     

Headspace SPME–GC Method for Acetone Analysis and its Biomedical Application

A new method for extraction and analysis of acetone in human urine based on headspace solid phase microextraction using a mixture of activated carbon and zeolite as sorbents in a PVC matrix coated on a silver wire and its application to the determination of ketone bodies is described. Unlike commercial fibers, which are coated on fused silica, the coating adheres strongly to the silver wire and is thermally stable up to 250 °C. After optimization of coating composition and microextraction conditions the fiber was used for the analysis of acetone in human urine.     

Solid-liquid extraction and preconcentration of trace nickel using 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and TDBA onto benzophenone and determination by atomic absorption spectrometry.

Nickel was quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA Cl) onto benzophenone in the pH range 5.0-6.0 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of a nickel complex and benzophenone was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by atomic absorption spectrometry (AAS). About 0.6 microg of nickel could be concentrated from 200 ml of an aqueous sample, where its concentration was as low as 3.0 ng/ml. Eight replicate determinations of 2.5 microg/ml of nickel in the final DMF solution gave a mean absorbance of 0.112 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 98 ng/ml. The interference of a number of anions and cations was studied and the developed optimized conditions were utilized for the trace determination of nickel in various alloys and biological samples.     

Isolating the most recent entry in a random recursive tree by random cuts

A recursive tree is constructed by starting with a root node and repeatedly adjoining new nodes to one node of the tree already constructed. Such a tree can represent, for example, the heirarchy of a workforce of a company that grows via recruiting. At times of economic depression, the company may decide to lay off participants, and in some cases it is a fair policy to relieve the last senior worker (most recent entry in the tree). If we remove an edge from such a tree then it falls into two subtrees one of which contains the most recent entry. If we continue to remove edges from the successively smaller subtrees that contain the most recent entry, we eventually isolate the most recent entry. We consider how many randomly selected edges must be removed in average before isolating the most recent entry by this procedure.