Enantiospecific synthesis of isomers of AES, a new environmentally friendly chelating agent

Three four-step enantiospecific syntheses of different diastereomers of AES, a new biodegradable chelating agent, are described. The stereocenters in each of the isomers are accessible from l- and d-malic and aspartic acids.     

Thermoanalytical study of acetylacetonate-modified titanium(IV) isopropoxide as a precursor for TiO<Subscript>2</Subscript> films

Thermal decomposition of dried TiO₂ gel, obtained by hydrolysing acetylacetonate-modified titanium(IV) isopropoxide, was monitored by simultaneous TG/DTA/EGA-FTIR measurements in dynamic air up to 900&deg;C. XRD and FTIR were employed to identify the solid reaction products. Thermal degradation of the TiO₂ gel consists of five distinct mass loss steps, the total mass loss being 43.8&percnt;. EGA by FTIR revealed the release of H₂O below 120&deg;C; followed by acetone, isopropyl acetate and 1-propanol around 200-300&deg;C, and finally CO and CO₂ up to 550&deg;C. Highly exothermic reaction at 410-550&deg;C is caused by the combustion of carbon residues. Crystalline TiO₂-anatase is formed around 500&deg;C and TiO₂-rutile close to 800&deg;C.     

Alnumycins A2 and A3: new inverse-epimeric pairs stereoisomeric to alnumycin A1

Two new pairs of stereoisomeric alnumycin As, A2 {(2)-(1R,1′RS,4′SR,5′SR)} and A3 {(2)-(1R,1′RS,4′SR,5′RS)}, are described. Similar to alnumycin A1 {(2)-(1R,1′RS,4′RS,5′SR)}, each of these naturally occurring compounds is also a pair of C-1 inverse epimers. The relative configurations of the dioxane ring sidechains were assigned on the basis of ¹H NMR NOE contacts and molecular modeling using density functional theory (DFT) at the M06-2X/6-31G(d) level of theory. The absolute configurations of C-1 and the determination of inverse epimeric relationships were achieved by experimental electronic circular dichroism (ECD) measurements, with both aspects confirmed by using the chiral derivatizing agent (CDA) Mosher′s acid chloride {α-methoxy-α-trifluorophenylacetyl chloride (MTPACl)} to effect enantiodifferentiation. The absolute configurations of the dioxane ring using the CDA could only be effected in the case of alnumycin A1, the results of which were in agreement with previous assignments. The dioxane ring conformational mobility and the likely interaction between the MTPA groups coupled with the structural novelty of the diols in the dioxane ring with respect to CDA analysis precluded an absolute configuration assignment for alnumycins A2 and A3 based on empirical comparisons or by computational analysis of through-space NMR shieldings (TSNMRS) emanating from the phenyl groups of the MTPA moieties.     

Reacting to spontaneous feedback from external customers in a university hospital laboratory

Modern quality standards for laboratories recommend the use of customer feedback in quality improvement. Spontaneous customer feedback is one method to obtain information from customers. In the present study, we analysed the feedback data from external customers (health centres and other hospitals) to our university hospital laboratory during 2001–2006. The most common subject matters of the feedback, covering 87% of a total of 95 reports, were lacking test results, suspicion of the validity of test results, return of samples in transportation boxes to customers and delays in service. On investigation, errors or defects were revealed in 78 cases. The most common errors were lacking (45 cases; 58%), erroneous (20 cases; 26%) or delayed test results (7 cases; 9%). As much as 68% of these errors took place in the pre-analytical phase of the laboratory process, occurring most commonly during specimen transfer, when entering orders into the laboratory information system at the university hospital or during sample processing. The most common underlying causes for errors were unintended errors and non-compliance with operating instructions. Latent errors were identified in 14% of the cases. Corrective actions were performed in 79% of the reported cases. It is important that the feedback reports are investigated to find out possible errors and their underlying causes so that appropriate corrective actions can be taken. When processed properly, spontaneous customer feedback is a method that can be used supplementarily to other methods to detect errors and defects in clinical laboratories and to aid in quality improvement.     

Heat Transport in Unsaturated Zone Thermal Energy Storage – Analysis with Two-Phase and Single-Phase Models

We analyze a field experiment where ambient air is injected into the soil during the summer and extracted again during the winter. A multiphase model accounting for the conductive transport as well as the convective transport with the moving liquid and gas phases is used along with a more simplified single-phase model where the convective transport is due to the gas alone. The latter model also accounts for subzero wintertime temperatures. The multiphase model captures well both the seasonal variations and the actual test sequence, the main calibration being in the adjustment of medium permeabilities based on the observed pressure responses. The effect of the injection pump on the temperature and humidity of the injection air needs to be known accurately. Taking into account the humidity of the injection air explicitly instead of using humidity-corrected enthalpy values also has an effect. The effect of various humidity and specific enthalpy assumptions is of the order of 1–1.5°C, while ignoring the wintertime subzero temperatures has an effect of 1–2°C. These differences are of the same order of magnitude as the heterogeneity-introduced differences in field data. Using the simplified single-phase model typically appears to cause a difference of 1–2°C, but can yield an even higher deviation of the order of 3–4°C.