Gas chromatograph injection port protective device

To prevent samples containing foreign matter from poisoning the gas chromatographic columns, a pre-filter insertion is placed in the injection port. The packing becomes a variable reactant, for example, acids are removed by using an alkaline liquid

Filament identification and dominance of Eikelboom Type 0092 in activated sludge from wastewater treatment facilities in Cape Town, South Africa

Routine characterisation of activated sludge and identification of the filamentous population by microscopic and/or other non-culture dependent techniques can assist in diagnosing the aetiology of poor performance of wastewater treatment works (WWTWs). In South Africa, most facilities rely solely on physicochemical indicators, treating reactors as ‘black-boxes’, with the result that process adjustments are often delayed, to the detriment of the environment. This study was performed in order to gain insight into the filamentous population found in activated sludge in Cape Town WWTWs, to compare these with other global and local literature findings, and to build capacity in this science. Physicochemical and plant performance parameters, in terms of nutrient removal and settling, were obtained from routine operational data and assessed in conjunction with the microscopic analyses of activated sludge samples taken over a 6-month period. Hypotheses on the links between filament types and/or plant  configurations and/or operational parameters were formulated using  existing literature. In order of prevalence, the five most common dominant filament species in 96 activated sludge samples were: Eikelboom Type  0092, Eikelboom Type 1851, nocardioforms, Microthrix parvicella and  Eikelboom Type 021N. In order to compile a statistically significant  database, it is recommended that an extensive nationwide study is  conducted to link filament types with plant configurations, operational parameters and geographical locations.Keywords: activated sludge, bulking, identification, filament, Type 009

Two-photon interference with true thermal light

Two-photon interference and "ghost" imaging with entangled light have attracted much attention since the last century because of the novel features such as non-locality and sub-wavelength effect. Recently, it has been found that pseudo-thermal light can mimic certain effects of entangled light. We report here the first observation of two-photon interference with true thermal light.Comment: 4 pages, 5 figures, PRA72, 043805 (2005

Three-dimensional structure of the radiation beam in atomic absorption spectrometry

The results of an investigation of the three-dimensional distribution of radiant intensity in the probing radiation beam produced in a conventional atomic absorption spectrometer by hollow cathode lamps and electrodeless discharge lamps are presented. The investigation is based on the use of a photodiode array-based digital imaging system. The results obtained revealed that the probing radiation beam is highly non-uniform, both longitudinally and radially. The character of the non-uniformities is greatly dependent on the type of the primary source. An interpretation of the results is given and the possible consequences of the radiation beam non-uniformities for the application of Beer-Lambert's law are discussed

Quasi-1D spin-1/2 Heisenberg magnets in their ordered phase: correlation functions

We study weakly coupled antiferromagnetic spin chains in their ordered phase by combinining an exact solution of the single-chain problem with an RPA analysis of the interchain interaction. A single chain is described by a quantum Sine-Gordon model and dynamical staggered susceptibilities are determined by employing the formfactor approach to quantum correlation functions. We consider both antiferromagnetic order encountered in quasi-1D materials like $KCuF_3$ and spin-Peierls order as found in $CuGeO_3$.Comment: 16 pages of revtex, 12 figure

Spatial distribution of radiant intensity from primary sources for atomic absorption spectrometry. Part II: Electrodeless discharge lamps

The spatial distribution of radiant intensity from electrodeless discharge lamps (EDLs) used as radiation sources in atomic absorption spectrometry is investigated with a digital photodiode array imaging system. Intensity distribution over the radial and longitudinal sections of Pb and Hg lamps is measured for both atomic and ionic lines of the analyte and the filler gas. The plasma in the EDLs is highly structured, with metal and filler gas excited species being distributed nonuniformly but in different ways. The clouds of emitting metal and Ar atoms are spatially separated in the volume of the Pb EDL. The excited Pb atoms detected from both the resonance and nonresonance lines have the form of a thin layer concentric to the bulb walls located near the surface of the bulb ("optical skin effect"). In contrast, the emission distribution for Ar atomic lines is bell-shaped with a maximum at the center of the plasma. The spatial distribution of emitting Ar ions is more complex - there is a bulk maximum coinciding with Ar atomic emission maximum and another maximum concentric to the walls coinciding with the maximum of metal atom emission. In the Hg EDL the difference between the spatial intensity profiles of metal and filler gas (Ar) lines is less pronounced because of the use of an increased filler gas pressure in the lamp. Emitting species of both Ar and metal are primarily located in the bulk of the plasma with, however, a small depletion in the vicinity of the lamp axis. Evolution of the spatial intensity profiles during warm-up of the lamps is investigated as well. In both lamps the radial and longitudinal intensity distributions of metal lines are established during the first minutes after lamp ignition, after which there is a slow and monotonic increase of the established intensity profiles. This result implies thermal vaporization as a mechanism of analyte supply to the plasma. The spatial intensity profiles for Ar lines are established in the first seconds after lamp ignition, after which only the absolute values of the established distributions change. The approach to the steady-state intensity of Ar atomic and ionic lines is nonmonotonic; there is a clearly pronounced initial overshoot in intensity of Ar atomic lines that coincides with a decline in the intensity of Ar ion lines. An interpretation for the observed spatial intensity profiles is given on the basis of radial cataphoresis theory

Selection of diazotrophic bacterial communities in biological sand filter mesocosms used for the treatment of phenolic-laden wastewater

Agri effluents such as winery or olive mill waste-waters are characterized by high phenolic concentrations. These compounds are highly toxic and generally refractory to biodegradation. Biological sand filters (BSFs) represent inexpensive, environmentally friendly, and sustainable wastewater treatment systems which rely vastly on microbial catabolic processes. Using denaturing gradient gel electrophoresis and terminal-restriction fragment length polymorphism, this study aimed to assess the impact of increasing concentrations of synthetic phenolic-rich wastewater, ranging from 96 mg L−1 gallic acid and138 mg L−1 vanillin (i.e., a total chemical oxygen demand (COD) of 234 mg L−1) to 2,400mg L−1 gallic acid and 3,442 mg L−1 vanillin (5,842 mg COD L−1), on bacterialcommunities and the specific functional diazotrophic community from BSF mesocosms. This amendment procedure instigated efficient BSF phenolic removal, significant modifications of the bacterial communities, and notably led to the selection of a phenolic-resistant and less diverse diazotrophic community. This suggests that bioavailable N is crucial in the functioning of biological treatment processes involving microbial communities, and thus that functional alterations in the bacterial communities in BSFs ensure provision of sufficient bioavailable nitrogen for the degradation of wastewater with a high C/N ratio.Web of Scienc

Cohort Profile: Mamanengane or the Africa Centre Vertical Transmission Study

How did the study come about? From the mid-1990s, the success of antiretroviral prophylaxis to reduce HIV RNA viral load in plasma and avoidance of breastfeeding provided the real possibility that mother-to-child transmission (MTCT) of HIV-1 could be markedly reduced, 1 with an implicit understanding that these measures could be effectively applied to all HIV-infected women in developing countries. 2,3 The latter constitute the overwhelming majority of HIV-positive pregnancies resulting in approximately half a million new infant infections annually. 4 However, the inappropriate use of formula milks amongst impoverished populations resulted in major adverse effects; without the nutritiona