Effect of injected sample amount on the shape of chromatographic peaks under condition of linear partition isotherm

In a previous paper a model function was tested in order to approximate the peak shape obtained on non-polar column by injecting different compounds. The simulation of the symmetrical or non-symmetrical shape of gas chromatographic peaks was satisfactory. In this paper, the influence of the amount of injected substance was investigated at different values of inlet pressure and carrier gas velocity, in order to evaluate the relative contribution to the total peak area and shape of the symmetrical distribution due to partition phenomena and of the non-symmetrical and tailing distribution due to adsorption-desorption kinetics. The effect of the molecular mass and of the chain length of compounds belonging to the homologous series of 1-alcohols and n-alkanes on the adsorption phenomena was evaluated.     

Asymmetric nitrogen

The possibility of tranferring chirality from nitrogen to carbon by a three-step transformation of racemic dimethyl 1-methoxyaziridine-2,2-dicarboxylate into 3-amino-2-chloromethyl-2-methoxyaminopropan-1-ol was demonstrated. The first representative of 1-silyloxyaziridines,viz., dimethyl 1-(tert-butyldimethylsilyloxy)aziridine-2,2-dicarboxylate, was synthesized by acidolysis or thermolysis of triazoline, obtained by the reaction oftert-butyldimethylsilyloxime of dimethy mesoxalate with CH₂N₂     

Rapid and sensitive high-performance liquid chromatographic method for the analysis of tryptophan, tyrosine and phenylalanine in biological samples.

In order to overcome problems related to the determination of free tryptophan in biological fluids using conventional methods, we have developed an accurate and reliable procedure based on a specific pretreatment of samples followed by a very rapid and sensitive reversed-phase high-performance liquid chromatographic analysis. The pretreatment consists of adding to the samples of a very low amount of 3 M phosphate buffer to maintain pH in the physiological range followed by ultrafiltration. The precision, reproducibility and sensitivity of our method were also evaluated. The recovery of each amino acid was greater than 92%. The use of a microbore column allows the detection of up to 0.2 pmol/microliter of amino acid. The method has been applied to the analysis of samples obtained from 25 normal and 10 phenylketonuric subjects.     

Enantioselective Syntheses of α-Amino Acids from 10-(Aminosulfonyl)-2-bornyl Esters and Di(tert-butyl) Azodicarboxylate. Preliminary Communication

Succesive treatment of chiral esters 1 with LiN(i-Pr)₂/Me₃SiCl and di(tert-butyl) azodicarboxylate/TiCl₄/Ti(i-PrO)₄ gave N,N′ -di[(tert-butoxy)carbonyl]hydrazino esters 9 which on deacylation, hydrogenolysis, transesterification, and acidic hydrolysis furnished (2S)-α-amino acids 6 in high enantiomeric purity with efficient recovery of the auxiliary alcohol 7 .     

Identification of N,N-dimethyltryptamine and beta-carbolines in psychotropic ayahuasca beverage

Recently many people have shown great interest in traditional indigenous practices and popular medicine, involving the ingestion of natural psychotropic drugs. We received a request to analyze and determine the nature of a dark green liquid with a dark brown plant sediment, which the police had seized at an airport and inside the home of a person belonging to the 'Santo Daime' religious movement. Gas chromatography/mass spectrometry analysis of the extract identified N,N-dimethyltryptamine, a potent hallucinogen, and the beta-carboline alkaloids harmine and harmaline, revealing monoamine oxidase A-inhibiting properties. These substances are typical components of Ayahuasca, a South American psychotropic beverage obtained by boiling the bark of the liana Banisteriopsis caapi together with the leaves of various admixture plants, principally Psychotria viridis.     

Probing the light neutral Higgs boson scenario of the <Emphasis Type="Italic">CP</Emphasis>-violating MSSM Higgs sector at the LHC

In the CP-violating minimal supersymmetric standard model (MSSM), for certain values of the CP-violating phases associated to the universal trilinear couplings (A_t, A_b) and the gluino mass , e.g., or , for GeV and -5, the lightest Higgs boson mass ( ) is GeV. This mass interval is still allowed by results of standard LEP Higgs searches because of a strongly suppressed H₁ZZ coupling. However, in the same region of parameter space in which these two conditions occur, the coupling is enhanced because the two mentioned sets of couplings satisfy a sum rule. In this paper we probe such a light Higgs scenario at the Large Hadron Collider (LHC) by studying associate production, leading to a signal. We show that the latter is readily accessible at the CERN hadron collider, upon the application of suitable selection cuts against the standard model (SM) backgrounds. Our parton level Monte Carlo (MC) analysis yields -45 signal events, completely free of SM background, for - 30 fb^-1 of accumulated luminosity, after taking into account the overall efficiency for tagging four b-jets.Received: 21 February 2005, Published online: 6 July 2005     

First report of the in vitro antileishmanial properties of extremophile plants from the Algarve Coast

This work reports for the first time the in vitro anti Leishmania infantum activity of acetone and dichloromethane (DCM) extracts from 25 extremophile plants from Southern Portugal. DCM extracts from Inula chritmoides and Spergularia rubra were active against axenic promastigotes and intracellular amastigotes, had anti-inflammatory properties on lipopolysaccharide (LPS)-stimulated macrophages, inhibited acetylcholinesterase and had no haemolytic activity on human erythrocytes. Eleven phenolics were identified by high-performance liquid chromatography with diode-array detection (HPLC-DAD) in I. crithmoides and one phenolic in S. rubra. Isolation and identification of the active molecules is in progress.     

High efficiency cw far infrared lasers at 119 μm and 127 μm

The optically pumped FIR laser lines at 119 m from CH₃OH and at 127 m from¹³CD₃OH are known to be the most powerful in the far infrared spectral region. We report on efficiency measurements for our waveguide laser system. The effect of various parameters was investigated, resulting in the highest efficiency ever reported for the 119 m line. The Stark effect and others parameters of the 127 m were measured, and a new¹³CD₃OH laser line at 175 m discovered, with the same pump transition. These measurements are helpful for completing the assignment already proposed for the 127 m line.     

Heavy charged Higgs boson production at next generation e^\pm\gamma colliders

We assess the potential of future electron-positron linear colliders operating in the mode in detecting charged Higgs bosons with mass around and larger than the top quark mass, using Compton back-scattered photons from laser light. We compare the pair production mode, , to a variety of channels involving only one charged Higgs scalar in the final state, such as the tree-level processes ( and ) and ( and ) as well as the loop-induced channel . We show that, when the charged Higgs boson mass is smaller than or comparable to half the collider energy, , single production cross sections are of the same size as the pair production rate, whereas, for charged Higgs boson masses larger than , all processes are heavily suppressed. In general, production cross sections of charged Higgs bosons via scatterings are smaller than those induced at an collider and the latter represents a better option to produce and analyse such particles. Received: 29 August 2001 / Published online: 23 November 2001     

A dive counting density estimation method for Blainville’s beaked whale (Mesoplodon densirostris) using a bottom-mounted hydrophone field as applied to a Mid-Frequency Active (MFA) sonar operation

We present a passive acoustic method for estimating the density of echolocating cetaceans that dive synchronously, based on isolation of dive starts using a field of distributed bottom-mounted hydrophones. The method assumes that all dive starts of the target species within a defined area are detected, and that independent estimates of dive rate and group size are available. We apply the method to estimate the density of Blainville’s beaked whales (Mesoplodon densirostris) at the Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahamas during the time of a multi-ship active sonar exercise. Estimated densities for the 65 h before the exercise, 68 h during, 65 h after, and the final 43 h monitored were 16.99 (95% CI 13.47-21.43), 4.76 (3.78-6.00), 8.67 (6.87-10.94), and 24.75 (19.62-31.23) respectively, illustrating a possible avoidance reaction. Results for the 65 h before were compared with those from the click count density estimation algorithm developed by Marques et al. [Marques T, Thomas L, Ward J, DiMarzio N, Tyack P. Estimating cetacean population density using fixed passive acoustic sensors. An example with Blainville’s beaked whales. J Acoust Soc Am 2009;125(4):1982-1994]. The click count-based estimate was 19.23 animals/1000 km² (95% CI 12.69-29.13)—similar (13% higher), but with higher variance (CV 21% for click count method versus 12% for the dive count method). We discuss potential reasons for the differences, and compare the utility of the two methods. For both, obtaining reliable estimates of the factors that scale the measured quantity (dive starts or detected clicks) to density is the key hurdle. Defining the area monitored in the dive count method can also be problematic, particularly if the array is small.