Size,chromatic number,and connectivity

We consider the minimum number of edges in ak-edge-connected graph of ordern with chromatic number at leastc, obtaining the optimal bounds in most cases.     

Two New and a Known Compound from Lawsonia inermis

A new obtusafuran derivative, lawsonicin ( 1 ), and a new naphthaquinone, lawsonadeem ( 2 ), along with a known constituent, vomifoliol ( 3 ), were isolated from the aerial parts of Lawsonia alba and characterized by chemical transformation and spectroscopic experiments, including 2D‐NMR techniques.     

Molten lithium carbonate—sodium carbonate—potassium carbonate eutectic: The reaction of ten main group acidic oxides and oxyanions

The reactions of ten main group acidic oxides and oxyanions with molten alkali metal carbonate eutectics have been studied by thermogravimetry. Products have been identified by IR and Raman spectroscopy and stoichiometries suggested for the several reactions as oxide is progressively incorporated. Ultimately the tetrahedral ortho-oxyanion was formed except with the less acidic oxides (As₂O₃, Sb₂O₃, SiO₂). Sulphite was partially oxidised by the carbon dioxide atmosphere to sulphate.     

Synthesis, Characterization, and Biological Activity of n-Tributyltin Derivatives of Pharmaceutically Active Carboxylates

Summary.  Tributyltin(IV) derivatives of six different pharmaceutically active carboxylates were synthesized. The complexes were characterized by different analytical techniques (elemental analysis; infrared, NMR, and mass spectroscopy). ¹¹⁹Sn NMR data were also recorded in six different coordinating and non-coordinating solvents. The antibacterial activities of the compounds were tested using ten different bacteria relative to the reference drugs ampicillin and cephalexin. Received September 20, 2001. Accepted (revised) December 6, 2001     

Molten nitrate eutectics: The reaction of four lanthanide chlorides

The reactions of lanthanum(III), cerium(III), praseodymium(III) and europium(III) chlorides have been studied in the molten lithium nitrate-potassium nitrate and sodium nitrate-potassium nitrate eutectics. The ultimate reaction products have been shown to be oxides (La₂O₃, CeO₂, Pr₆O₁₁ and Eu₂O₃, respectively) which increased the rate of decomposition of the melts, while in three cases an intermediate oxide nitrate was formed (LaONO₃, PrONO₃ and EuONO₃). The temperatures and stoichiometries of the reactions have been established.     

A spectrophotometric method for the determination of nitrite

Nitrite reacts with dichromate quantitatively under suitable conditions of temperature and acid concentration. A linear relationship was found to exist between nitrite concentration and the absorbance at 580 nm of the chromium (III) species produced. This was used to determine the nitrite. The influence of a number of ions on the determination of nitrite was investigated; up to 100-fold excess nitrate has no influence on the determination of nitrite.     

Détermination du facteur de multiplication M pour un fonctionnement optimal des photodétecteurs à avalanche

The purpose of this paper is relative to the determination of the multiplication factor Mfor an optimum behaviour of the avalanche photodetector. Two types of avalanche photodetector s are compared: a silicon structure n ⁺ πpπp ⁺ Read diode and a GaAlAs heterostructure. Calculating the Noise Equivalent Power (nep)of the whole system, the law S_i(f) =2q I_phoM_x is used, where the parameter x is determined experimentally in both avalanche photodetectors. The exponent x (between 2 and 4) dominates in the nep expression and the ideal nep for the avalanche photodetector system is obtained when x equals 2.     

New dirhenium(III) compounds bridged by carboxylate ligands: N(C(4)H(9))(4)[Re(2)(OOCCF(3))Cl(6)] and Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2)

The solvothermal reaction of (N(C(4)H(9))(4))(2)[Re(2)Cl(8)] with trifluoroacetic acid and acetic anhydride leads to the new rhenium trifluoroacetate dimer N(C(4)H(9))(4)[Re(2)(OOCCF(3))Cl(6)] (1) and to the rhenium carbonyl dimer Re(2)(mu(2)-Cl)(2)(CO)(8) as the rhenium-reduced byproduct. The reaction of the precursor complex, N(C(4)H(9))(4)[Re(2)(OOCCF(3))Cl(6)] (1), with the organometallic carboxylic acid (CO)(6)Co(2)HCCCOOH leads to the cluster of clusters compound Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2) (2), which has the dimer structure of Re(2)(OOCR)(4)Cl(2). Cyclic voltammetric measurements show that Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2) (2) has one reduction centered on the dirhenium core and a reduction centered on the cobalt atoms. DFT calculations have been used to rationalize the observed displacements of the voltammetric signals in Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2) (2) compared to the parent ligand (CO)(6)Co(2)HCCCOOH and rhenium pivalate.