UV resonance raman spectroscopic detection of nitrate and nitrite in wastewater treatment processes

The 204- and 229-nm excited UV resonance Raman spectra of wastewater solutions containing sodium nitrite and nitrate were measured in the concentration range 7 microM to 3.5 mM (0.1-50 ppm nitrogen). The other chemical species present in wastewater do not interfere with Raman measurements of NO2-/NO3- bands. We observe detection limits of < 14 microM (< 200 ppb) for both NO2- and NO3-. UV resonance Raman spectroscopy appears to be an excellent tool for on-line monitoring of NO2-/NO3- in wastewater for the real-time control of water treatment plants.     

Measurement of the Loss and Depolarization Probability of UCN on Beryllium and Diamond Like Carbon Films

Currently several institutes worldwide are working on the development of a new generation of ultracold neutron (UCN) sources. In parallel with source development, new materials for guiding and storage of UCN are developed. Currently the best results have been achieved using ⁵⁸Ni, Be, solid O₂ and low temperature Fomblin oil (LTF). All of these materials have their shortcomings like cost, toxicity or difficulty of use. A novel very promising material is diamond like carbon (DLC). Several techniques exist to coat surfaces, and industrial applications (e.g., for extremely hard surfaces) are already wide spread. Preliminary investigations using neutron reflectometry at PSI and Los Alamos yielded a critical velocity for DLC of about 7 m/s thus comparable to Beryllium. A low upper limit of depolarization probability for stored polarized UCN has been measured at the PF2 facility of the Institut Laue-Langevin (ILL) by North Carolina State University (NCSU), Los Alamos National Laboratory (LANL), and Petersburg Nuclear Physics Institute (PNPI), thus making it also a good material for storage and guidance of polarized UCN. Still missing is the loss probability per bounce. We will be able to extract this number and a more stringent value for the depolarization from our experiment thus proving the suitability of DLC as a wall material for a wide range of UCN applications.     

Steady-state and transient ultraviolet resonance Raman spectrometer for the 193-270 nm spectral region

We describe a state-of-the-art tunable ultraviolet (UV) Raman spectrometer for the 193-270 nm spectral region. This instrument allows for steady-state and transient UV Raman measurements. We utilize a 5 kHz Ti-sapphire continuously tunable laser (approximately 20 ns pulse width) between 193 nm and 240 nm for steady-state measurements. For transient Raman measurements we utilize one Coherent Infinity YAG laser to generate nanosecond infrared (IR) pump laser pulses to generate a temperature jump (T-jump) and a second Coherent Infinity YAG laser that is frequency tripled and Raman shifted into the deep UV (204 nm) for transient UV Raman excitation. Numerous other UV excitation frequencies can be utilized for selective excitation of chromophoric groups for transient Raman measurements. We constructed a subtractive dispersion double monochromator to minimize stray light. We utilize a new charge-coupled device (CCD) camera that responds efficiently to UV light, as opposed to the previous CCD and photodiode detectors, which required intensifiers for detecting UV light. For the T-jump measurements we use a second camera to simultaneously acquire the Raman spectra of the water stretching bands (2500-4000 cm(-1)) whose band-shape and frequency report the sample temperature.     

Sparse non Gaussian component analysis by semidefinite programming

Sparse non-Gaussian component analysis is an unsupervised linear method of extracting any structure from high-dimensional distributed data based on estimating a low-dimensional non-Gaussian data component. In this paper we discuss a new approach with known apriori reduced dimension to direct estimation of the projector on the target space using semidefinite programming. The new approach avoids the estimation of the data covariance matrix and overcomes the traditional separation of element estimation of the target space and target space reconstruction. This allows to reduced the sampling size while improving the sensitivity to a broad variety of deviations from normality. Moreover the complexity of the new approach is limited to O(dlogd). We also discuss the procedures which allows to recover the structure when its effective dimension is unknown.     

Systematische vergleichende Kostenanalyse von destillativen und extraktiven Stofftrennverfahren

Systematic Comparative Cost Analysis of Separation Processes Based on Distillation and Extraction . Rectification is the most commonly used but not always the most economical method of thermal separation. Above all in the case of closely boiling mixtures it becomes very demanding with regard to both equipment and energy. It is often possible to replace rectification by another energetically more favourable separation process such as liquid-liquid distillation, decantation, or absorption. Owing to the resulting wealth of possibilities for the separation of a mixture it is desirable to gain further knowledge about the economics of individual processes and about the selection of suitable entrainers under given conditions.