High sensitivity in gas analysis with photoacoustic detection

Introduction of a new type of pressure sensor has been shown to improve orders of magnitude the sensitivity of a photoacoustic measurement system using a black body radiation source. A new pressure sensor was developed to overcome the limitations in the capacitive microphone technology and to obtain ultimate sensitivity in photoacoustic gas detection when using low modulation frequency below 500 Hz. The pressure sensor is a cantilever-type microphone with interferometric measurement of the sensor displacement. By using conventional filter-type photoacoustic setup with the cantilever microphone and a black body radiation source, we obtained a detection limit in the sub-ppb range for methane gas with 100 s measurement time.     

Identification of the hydrolysis products of AlCl3.6H2O by electrospray ionization mass spectrometry

The hydrolysis reactions of AlCl3 in 0.1 M aqueous solutions at pH 3.27-4.20 were monitored by electrospray ionization time-of-flight mass spectrometry (ESI-ToF MS) as a function of time. The cationic and anionic ESI mass spectra of aluminum(III) solutions gave strong evidence of the presence of a variety of monomeric and polymeric complexes. Competition between the OH- and Cl- ligands within the same aluminum core was observed. The influence of the sample cone voltage on the product distribution was also explored. The optimum sample cone voltage for the cationic spectra was 70 V. For the anionic spectra no optimum sample cone voltage was found and the appearance of the anionic spectra was strongly dependent on the sample cone voltage within the whole range explored.     

Trypsin-like enzyme fromStreptomyces 771

Electrophoretically homogenous proteolytic enzyme with molecular weight 31,500 and pI 3.75 was obtained from a culture medium ofStreptomyces 771 by chromatography onN-benzyl chitin adsorbent, subsequent chromatography on CM-cellulose, and preparative isofocusing and chromatography on Sephadex G-75. The enzyme hydrolyzesN- benzoyl-DL-arginine-p-nitroanilideN-benzoyl-DL-lysine-p-nitro-anilideN-benzoyl-DL-arginine ethyl ester, and Na-caseinate. It also exhibits pronounced thrombolytic activity. The activity of the enzyme was suppressed by soya bean inhibitor, but remained unaffected by chelating agents and phenylmethylsulfonyl fluoride. The enzyme was immobilized on aldehyde dextran, and some kinetic parameters of the immobilized enzyme were determined. The thrombolytic activity of native and immobilized enzyme was studied as well.     

Comparison theorems for hyperbolic type metrics

The connection between several hyperbolic type metrics is studied in subdomains of the Euclidean space. In particular, a new metric is introduced and compared to the distance ratio metric.     

Some properties of the gamma and psi functions, with applications

In this paper, some monotoneity and concavity properties of the gamma, beta and psi functions are obtained, from which several asymptotically sharp inequalities follow. Applying these properties, the authors improve some well-known results for the volume of the unit ball , the surface area of the unit sphere , and some related constants.

     

Separation of physiological very low frequency fluctuation from aliasing by switched sampling interval fMRI scans

Anesthetized children have dominant blood-oxygen-level-dependent (BOLD) signal sources presenting high-power fluctuations at very low frequencies (VLF <0.05 Hz). Aliasing of frequencies higher than critically sampled has been regarded as one probable origin of the VLF fluctuations. Aliased signal frequencies change when the sampling rate of the data is altered. In this study, the aliasing of VLF BOLD signal fluctuation was analysed by switching the repetition time (TR) of magnetic resonance (MR) images. Eleven anesthetized children were imaged at 1.5 T using TRs of 500 and 1200 ms. The BOLD signal sources were separated with independent component analysis (ICA). Occipital cortex signal sources had nonaliased VLF fluctuation ( approximately 0.03 Hz) in 9 of 11 subjects. Arterial signal sources failed to present stable power peaks at frequencies lower than 0.42 Hz presumably due to aliasing. Cerebrospinal fluid (CSF)-related signal sources showed nonaliased VLF in four subjects. In conclusion, the VLF BOLD signal fluctuation in the occipital cortex is a true physiological fluctuation, not a result of signal aliasing.     

Digital Predistortion for 5G Small Cell: GPU Implementation and RF Measurements

In this paper, we present a high data rate implementation of a digital predistortion (DPD) algorithm on a modern mobile multicore CPU containing an on-chip GPU. The proposed implementation is capable of running in real-time, thanks to the execution of the predistortion stage inside the GPU, and the execution of the learning stage on a separate CPU core. This configuration, combined with the low complexity DPD design, allows for more than 400 Msamples/s sample rates. This is sufficient for satisfying 5G new radio (NR) base station radio transmission specifications in the sub-6 GHz bands, where signal bandwidths up to 100 MHz are specified. The linearization performance is validated with RF measurements on two base station power amplifiers at 3.7 GHz, showing that the 5G NR downlink emission requirements are satisfied.

     

Defect theorems with compatibility relations

We consider words together with a compatibility relation induced by a relation on letters. Unique factorization with respect to two arbitrary word relations R and S defines the (R,S)-freeness of the semigroup considered. We generalize the stability theorem of Schützenberger and Tilson’s closure result for (R,S)-free semigroups. The inner and the outer (R,S)-unique factorization hull and the (R,S)-free hull of a set of words are introduced and we show how they can be computed. We prove that the (R,S)-unique factorization hulls possess a defect effect, which implies a variant of a cumulative defect theorem of word semigroups. In addition, a defect theorem of partial words is proved as a corollary.