Kalman filter applied to setpoint control in continuous titrations

A state-space model is described for continuous titrations based on first-order dynamics. The Kalman filter allows on-line monitoring of an empirically established setpoint in the titration curve. The algorithm advocated is examined for potentiometric titrations of ca. 10^?3 M solutins of acids, silver(I) and copper(II). Only gross indications of the essential parameters such as the time constant and noise covariances are required. The computer-controlled titration system is compared with a conventional setpoint titrator. Especially in cases of slow response times and steep inflections, there are advantages in both accuracy and speed when the Kalman filter is applied.     

Hindered coarsening of a phase-separating microemulsion due to dispersed colloidal particles

The addition of sterically stabilized colloidal particles to a phase-separating microemulsion leads to dramatic changes in its demixing behavior, especially during the later stages. Our microemulsion is composed of reverse micelles of sodium dodecyl sulfate, pentanol, and water in a dodecane continuous phase which separates into micelle-rich and micelle-poor phases above a lower critical solution temperature. The poly(methyl methacrylate) particles preferentially partition into the less structured, micelle-poor phase. Nucleation of the minority phase or spinodal decomposition close to criticality continue to occur in the presence of particles, albeit with pronounced pretransitional clustering of particles when the micelle-poor phase is in the minority. The coalescence of micelle-poor droplets and the coarsening of micelle-rich domains are both strongly modified due to the presence of colloidal particles. We use our observations of the early stages of phase separation to understand these late stage changes.     

A software package for computer-controlled flow-injection analysis

An automated flow-injection system is described, with a computer-controlled sample changer, injection device and photometer. The modular software package is understandable, flexible and easily adaptable to different computers.     

Transducers in medical ultrasound: Part Three. Transducer applications in echocardiology

A comparison is made between phased arrays and mechanical sector scanners in transcutaneous echocardiographic applications. Aspects such as contact area, beam control, side lobes, grating lobes and image quality are discussed in the context of transducer frequency. The incorporation of simultaneous acquisition of Doppler velocity information and display of M-mode signals is considered. Transoesophageal and intraoperative scanning systems for cardiology are also compared, in particular linear arrays, phased arrays and mechanical scanners, and their advantages and disadvantages in relation to the above mentioned aspects are discussed. The general conclusion is that electronic sector scanners may have a considerably improved cost/benefit ratio in the near future and thereby will become the leading systems for echocardiography.     

Optical homogeneous linewidths in organic glasses below 1 K: a hole-burning study of free-base porphin in 2-methyltetrahydrofuran

Photochemical hole-burning has been used to determine the temperature dependence of the homogeneous linewidth Γ_hom of the 0-0 S₁ - S₀ transition of free-base porphin (H₂P) in 2-methyltetrahydrofuran (MTHF) from T ≈ 5 K down to 0.4 K. A _T^1.30±0.05 dependence for Γ_hom is observed which extrapolates to the lifetime-limited value (≈ 10 MHz) at T ≈ 0.05K.     

Proton MR spectroscopy in a child with pyruvate dehydrogenase complex deficiency.

The purpose of this study was the non-invasive quantitative determination by proton MR Spectroscopy (1H MRS) of alterations in cerebral metabolism in a 19-month-old male infant with severe global developmental delay caused by a Pyruvate Dehydrogenase Complex (PDHC) deficiency due to a mutation at the thiamine binding site. Two investigations were performed at different CSF thiamine concentrations to assess the effect of thiamine supplementation. 1H MR spectra were collected at different echo times (20-270 ms) from a voxel located in the striatum; spectroscopic imaging was done on a larger region including occipital white matter. The tissue levels of N-acetylaspartate and choline were in the normal range, while creatine appeared elevated. Abnormally high lactate and alanine signals were observed both in and outside the striatum; the levels of these metabolites were higher during the second measurement at a lower thiamine concentration. Abnormal cerebral levels of alanine have only been described once before in PDHC deficiency. The 1H MRS profile of this patient reflects the diversity of brain metabolite alterations in patients with this genetically heterogeneous disease.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

State estimation in discrete titrations with kalman filtering and fixed-interval smoothing

The suitability of a state space model for processing titration curves and their derivatives is described. The Kalman filter gives a systematic deviation in the evaluated inflection points, which is removed completely by subsequent fixed-interval smoothing. The estimation procedures can be used for on-line control in order to obtain equidistant measurements with variable volume increments. The precision is shown to depend on the minimal delivery of the buret and on the noise variance of the detector. The algorithms are illustrated with a simulated example and applied successfully in practice.