Impurity analysis of gentamicin bulk samples by improved liquid chromatography-ion trap mass spectrometry

Several gentamicin bulk samples from different origins were investigated using an LC/MS method.LC equipped with ion trap MS with positive ionization was performed on a Capcell Pak C18(AQ) column with the mobile phase containing 50 mM trifluoroacetic(TFA) and methanol.Impurities present in batches of gentamicin bulk samples were elucidated and compared according to their fragmentation behavior.In total seventeen impurities present in samples,five impurities were not elucidated and two compounds were identifi...     

Aminomethylations via cross-coupling of potassium organotrifluoroborates with aryl bromides

[reaction: see text] The Suzuki-Miyaura cross-coupling reaction of N,N-dialkylaminomethyltrifluoroborates with aryl halides allows the construction of an aminomethyl aryl linkage through a disconnection based on dissonant reactivity patterns. A variety of these aminomethyltrifluoroborate substrates were prepared in good to excellent yields and then shown to cross-couple with equal facility to both electron-rich and electron-poor aryl halides as well as to a variety of heteroaromatic bromides.     

Reinvestigation of aminomethyltrifluoroborates and their application in Suzuki-Miyaura cross-coupling reactions

A reinvestigation into the chemical composition of potassium aminomethyltrifluoroborates is reported. These trifluoroborato salts have been reassigned as zwitterionic ammoniomethyltrifluoroborates. Minor adjustments to the previously disclosed reaction conditions are reported that permit a similar level of activity as nucleophiles in Suzuki-Miyaura cross-coupling reactions.     

Pulsed laser action of Pr:GdLiF4 at room temperature

We realized, to our knowledge for the first time, laser emission in Pr:GdLiF₄ at seven wavelengths: 522 nm, 545 nm, 604.5 nm, 607 nm, 639 nm, 697 nm, and 720 nm. The crystal was pumped with an excimer laser pumped dye laser at 468 nm. All laser experiments were carried out at room temperature. We also achieved pulsed room temperature laser oscillation of Pr:KYF₄ at 642.5 nm pumped at 465 nm wavelength.     

Accelerated thermal decomposition of AlH3 for hydrogen-fueled vehicles

The potential for using aluminum hydride, AlH₃, for vehicular hydrogen storage is explored. It is shown that particle-size control and doping of AlH₃ with small levels of alkali-metal hydrides (e.g. LiH) results in accelerated desorption rates. For AlH₃–20 mol% LiH, 100 °C desorption kinetics are nearly high enough to supply vehicles. It is highly likely that 2010 gravimetric and volumetric vehicular system targets (6 wt% H₂ and 0.045 kg/L) can be met with onboard AlH₃. However, a new, low-cost method of off-board regeneration of spent Al back to AlH₃ is needed. PACS 68.43.Vx; 68.43.Mn; 83.80.Fg; 84.60.Ve; 51.30.+i; 61.10.Nz     

Ternäre Chloride in den Systemen ACl/GdCl3 (A = Na?Cs)

Ternary Chlorides in the Systems ACl/GdCl₃ (A = Na? Cs) The phase diagrams of the pseudobinary systems ACl/GdCl₃ (A = Na? Cs) were investigated by DTA. Their powder diffractograms were indexed in analogy to known structure families. By solution calorimetry and measurements of e.m.f. = f(T) in galvanic cells for solid electrolytes the enthalpies ΔH⁰ and free enthalpies ΔG⁰ for the formation of the ternary chlorides from the compounds adjacent in the systems were determined. The systems with A = K, Rb, Cs are analogous to those with Sm³⁺ and Eu³⁺. There exist compounds A₃GdCl₆, A₂GdCl₅ and AGd₂Cl₇. Cs₂GdCl₅ is crystallysing in the Cs₂DyCl₅ type; the Rb- and K-compounds and also Na₂GdCl₅ have the K₂PrCl₅?structure. In the system NaCl/GdCl₃ additionally the compounds NaGdCl₄ and Na₃GdCl₆ were found. L? Na₃GdCl₆ is metastable compared with (NaCl + Na₂GdCl₅); above 265°C stable H? Na₃GdCl₆ is existing (cryolite-structure).     

Dark Energy： Relating the Evolutions of the Universe from the Past to the Future

Using the evolution history of the universe, one can make constraint on the parameter space of dynamic dark energy models. We discuss two different parameterized dark energy models. Our results further restrict the combined constraints obtained from supernova and the first-year Wilkinson-microwave-anisotropy-probe observations. From the allowed parameter space, it is found that our universe will experience an eternal acceleration. We also estimate the bound on the physically relevant regions both in the re-inflationary and inflationary phases.     

High-power continuous-wave upconversion fiber laser at room temperature

We report cw laser emission of a Pr, Yb-doped ZrF(4)-BaF(2)-LaF(3)-AlF(3)-NaF fiber in the red spectral region. Laser emission was achieved on the transition P(0)(3)?F(2)(3)(lambda(L)=635 nm) with a Ti:sapphire pump laser tuned to lambda(p)=850 nm . A maximum output power of P(out)=675 mW was obtained at an incident pump power of P(in)=3.37 W . The output power was increased to P(out)=1020 mW when pumping with P(in)=5.51 W was provided by two Ti:sapphire lasers. A photon avalanche process was found to contribute strongly to the population of the upper laser level.     

Zur Stabilität von Doppelchloriden in den Systemen ACI/PrCl3(A  Na?Cs)

Stability of Double Chlorides in the Systems ACl/PrCl₃(A = Na? Cs) The pseudobinary systems ACl/PrCl₃(A = Na? Cs) were reinvestigated by means of DTA. The following chlorides were found. (Primary detected compounds are underlined.): K₃PrCl₆; K₂PrCl₅; Rb₂PrCl₅, Cs₃PrCl₆, , CsPr₂Cl₇. Measurements of the solution enthalpies and of the free (Gibbs) enthalpies of formation from ACl and PrCl₃ together with the free enthalpies of synproportionation from the adjacent compounds in the phase diagrams with a galvanic cell for solid electrolytes revealed, that only the chlorides A₂PrCl₅ are stable at ambient temperature. All other compounds are high temperature forms. The crystal structures of the compounds were determined by X-ray analysis on powders; the compounds are isotypic with the analogous double chlorides of La and Ce. Magnetic susceptibilities in the range from 80—300 K were measured with a Gouy-balance.