Impulse-response functions of several detectors used in flow-injection analysis

A procedure for the determination of the impulse-response function of a detector is given. Its application to photometers, ion-sensitive field effect transistors, a potentiometric detector at constant current and a voltammetric detector shows that the impulse-response function can be used to obtain specific information about the performance of the detector in the manifold. This function clearly shows the contribution of the detector to the peak broadening and how the detector generates the final signal from the presented concentration profile. From this information one could derive improvements to the detector, such as changing the construction of the detector cell, minimizing the influence of other parts of the manifold or adapting the attached electronics

Sponge Aquaculture Trials in the East-Mediterranean Sea: New Approaches to Earlier Ideas

Aquaculture trials were conducted in the East Aegean Sea with Dysidea avara and Chondrosia reniformis to test the possibility of growing these sponges in the vicinity of sea-based fish farms. Culturing sponges in the vicinity of fish farms may have two benefits: the sponges may grow faster due to an increased availability of organic food and the pollution caused by the fish farms is remediated by the filtering activities of the sponges. An initial trial was conducted to compare growth of the two sponge species under floating fish cages to growth in a natural, pristine environment. Explants of D. avara were grown suspended on nylon threads, explants of C. reniformis were grown in cages constructed of stainless steel. After being one year in culture, nearly 100% of all explants of D. avara survived. Growth was highest underneath the fish cages, but growth rates were low compared to earlier studies. For C. reniformis survival at the pristine site was 100%, and growth was estimated at 800% per year. All explants cultured underneath the fish cages died due to smothering with sediment. After the initial trial, a new, cost-saving and growth promoting method for D. avara was tested at the fish farm location. Explants were grown on PVC pins that were mounted into a metal frame. Growth of the sponges on the pins was eight times faster than that of sponges growing on threads. We conclude that culturing D. avara under floating fish cages is feasible when using the new methodolog

Untangling cosmic collisions: a study of particle acceleration and magnetic fields in merging galaxy clusters

On the largest scale, the Universe resembles a cosmic spiderweb. Most galaxies coexist in small groups within the threads of this web. At the nodes of the threads are enormous groups of galaxies forming the largest structures in the universe still held together by gravity: clusters of galaxies.Clusters of galaxies consist of thousands of galaxies, although the galaxies constitute only a few per cent of the total cluster mass. The majority of the (non-dark) mass of a cluster is in a hot and dilute gas that resides in the space between galaxies and is permeated by magnetic fields. Clusters grow by collisions with other clusters, shocking and heating the gas causing amplification of magnetic fields and acceleration of particles to near the speed of light. This makes clusters a source of radio synchrotron radiation.This thesis investigates the particle acceleration process and the magnetic fields of merging clusters using the LOFAR and VLA radio telescopes. The thesis presents, among other things, one of the few radio maps of clusters at ultra-low frequencies and examines clusters of lower mass than usual. Additionally, the thesis includes observations of a sample of over a hundred clusters to statistically determine the properties of the magnetic field in clusters in a novel way.Large scale structure and cosmolog

Why do firms invest in consumer advertising with limited sales response? A shareholder perspective

Marketing managers increasingly recognize the need to measure and communicate the impact of their actions on shareholder returns. This study focuses on the shareholder value effects of pharmaceutical direct-to-consumer advertising (DTCA) and direct-to-physician (DTP) marketing efforts. Although DTCA has moderate effects on brand sales and market share, companies invest vast amounts of money in it. Relying on Kalman filtering, the authors develop a methodology to assess the effects from DTCA and DTP on three components of shareholder value: stock return, systematic risk, and idiosyncratic risk. Investors value DTCA positively because it leads to higher stock returns and lower systematic risk. Furthermore, DTCA increases idiosyncratic risk, which does not affect investors who maintain well-diversified portfolios. In contrast, DTP marketing has modest positive effects on stock returns and idiosyncratic risk. The outcomes indicate that evaluations of marketing expenditures should include a consideration of the effects of marketing on multiple stakeholders, not just the sales effects on consumers

Clinical implications of the oncometabolite succinate in SDHx-mutation carriers

Succinate dehydrogenase (SDH) mutations lead to the accumulation of succinate, which acts as an oncometabolite. Germline SDHx mutations predispose to paraganglioma (PGL) and pheochromocytoma (PCC), as well as to renal cell carcinoma and gastro-intestinal stromal tumors. The SDHx genes were the first tumor suppressor genes discovered which encode for a mitochondrial enzyme, thereby supporting Otto Warburg's hypothesis in 1926 that a direct link existed between mitochondrial dysfunction and cancer. Accumulation of succinate is the hallmark of tumorigenesis in PGL and PCC. Succinate accumulation inhibits several α-ketoglutarate dioxygenases, thereby inducing the pseudohypoxia pathway and causing epigenetic changes. Moreover, SDH loss as a consequence of SDHx mutations can lead to reprogramming of cell metabolism. Metabolomics can be used as a diagnostic tool, as succinate and other metabolites can be measured in tumor tissue, plasma and urine with different techniques. Furthermore, these pathophysiological characteristics provide insight into therapeutic targets for metastatic disease. This review provides an overview of the pathophysiology and clinical implications of oncometabolite succinate in SDHx mutations

Cytochrome oxidase subunit VI of Trypanosoma brucei is imported without a cleaved presequence and is developmentally regulated at both RNA and protein levels

Mitochondrial respiration in the African trypanosome undergoes dramatic developmental stage regulation. This requires co-ordinated control of components encoded by both the nuclear genome and the kinetoplast, the unusual mitochondrial genome of these parasites. As a model for understanding the co-ordination of these genomes, we have examined the regulation and mitochondrial import of a nuclear-encoded component of the cytochrome oxidase complex, cytochrome oxidase subunit VI (COXVI). By generating transgenic trypanosomes expressing intact or mutant forms of this protein, we demonstrate that COXVI is not imported using a conventional cleaved presequence and show that sequences at the N-terminus of the protein are necessary for correct mitochondrial sorting. Analyses of endogenous and transgenic COXVI mRNA and protein expression in parasites undergoing developmental stage differentiation demonstrates a temporal order of control involving regulation in the abundance of, first, mRNA and then protein. This represents the first dissection of the regulation and import of a nuclear-encoded protein into the cytochrome oxidase complex in these organisms, which were among the earliest eukaryotes to possess a mitochondrion

Improved density functional theory results for frequency-dependent polarizabilities, by the use of an exchange-correlation potential with correct asymptotic behavior.

The exchange‐correlation potentials vxc which are currently fashionable in density functional theory (DFT), such as those obtained from the local density approximation (LDA) or generalized gradient approximations (GGAs), all suffer from incorrect asymptotic behavior. In atomic calculations, this leads to substantial overestimations of both the static polarizability and the frequency dependence of this property. In the present paper, it is shown that the errors in atomic static dipole and quadrupole polarizabilities are reduced by almost an order of magnitude, if a recently proposed model potential with correct Coulombic long‐range behavior is used. The frequency dependence is improved similarly. The model potential also removes the overestimation in molecular polarizabilities, leading to slight improvements for average molecular polarizabilities and their frequency dependence. For the polarizability anisotropy we find that the model potential results do not improve over the LDA and GGA results. Our method for calculating frequency‐dependent molecular response properties within time‐dependent DFT, which we described in more detail elsewhere, is summarized

Time is vision in recurrent optic neuritis

In optic neuritis (ON) inflammation precedes onset of demyelination and axonal loss. The anti-inflammatory properties of corticosteroids may be most effective in the early inflammatory phase, but rapid patient recruitment remains a logistic challenge. The aim of the study was to review the effect of time to initiation of treatment on visual outcome in recurrent ON. A retrospective case note review of patients known to our centre with recurrent ON. The primary clinical outcome was change of best corrected high contrast visual acuity (BCVA). The secondary outcome was the change of optical coherence tomography (OCT) thickness of the peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell layer (mGCL) from baseline and after a minimum of 3months following the episode of recurrent ON. Of 269 patients with a previous episode of ON, 54 experienced recurrent ON. In total 40 OCT documented episodes of relapsing ON were captured in 19 patients. Treatment within <2days led to better recovery of the BCVA (+0.02) and mGCL (-2.4µm) if compared to delayed treatment (BCVA -0.2, p=0.036, mGCL -25.6µm, p=0.019) or no corticosteroids treatment (BCVA -0.2, p=0.045, GCL -5.0µm, p=0.836). These data suggest a beneficial effect of hyperacute corticosteroid treatment. A pragmatic approach for a prospective treatment trial should consider patients with recurrent ON for logistic reasons

The detection of cluster magnetic fields via radio source depolarisation

It has been well established that galaxy clusters have magnetic fields. The exact properties and origin of these magnetic fields are still uncertain even though these fields play a key role in many astrophysical processes. Various attempts have been made to derive the magnetic field strength and structure of nearby galaxy clusters using Faraday rotation of extended cluster radio sources. This approach needs to make various assumptions that could be circumvented when using background radio sources. However, because the number of polarised radio sources behind clusters is low, at the moment such a study can only be done statistically. In this paper, we investigate the depolarisation of radio sources inside and behind clusters in a sample of 124 massive clusters at $z<0.35$ observed with the Karl G. Jansky Very Large Array. We detect a clear depolarisation trend with the cluster impact parameter, with sources at smaller projected distances to the cluster centre showing more depolarisation. By combining the radio observations with ancillary X-ray data from Chandra, we compare the observed depolarisation with expectations from cluster magnetic field models using individual cluster density profiles. The best-fitting models have a central magnetic field strength of $5-10\,\mu$G with power-law indices between $n=1$ and $n=4$. We find no strong difference in the depolarisation trend between sources embedded in clusters and background sources located at similar projected radii, although the central region of clusters is still poorly probed by background sources. We also examine the depolarisation trend as a function of cluster properties such as the dynamical state, mass, and redshift. Our findings show that the statistical depolarisation of radio sources is a good probe of cluster magnetic field parameters. [abridged]Comment: Replaced with Published version (A&A). 32 pages, 34 figure

A MeerKAT-meets-LOFAR study of Abell 1413: a moderately disturbed non-cool-core cluster hosting a ∼500\sim 500 kpc 'mini'-halo

Many relaxed cool-core clusters host diffuse radio emission on scales of hundreds of kiloparsecs: mini-haloes. However, the mechanism responsible for generating them, as well as their connection with central active galactic nuclei, is elusive and many questions related to their physical properties and origins remain unanswered. This paper presents new radio observations of the galaxy cluster Abell 1413 performed with MeerKAT (L-band; 872 to 1712 MHz) and LOFAR HBA (120 to 168 MHz) as part of a statistical and homogeneous census of mini-haloes. Abell 1413 is unique among mini-halo clusters as it is a moderately-disturbed non-cool-core cluster. Our study reveals an asymmetric mini-halo up to 584 kpc in size at 1283 MHz, twice as large as first reported at similar frequencies. The spectral index is flatter than previously reported, with an integrated value of $\alpha = -1.01 \pm 0.06$, shows significant spatial variation, and a tentative radial steepening. We studied the point-to-point X-ray/radio surface brightness correlation to investigate the thermal/non-thermal connection: our results show a strong connection between these components, with a super-linear slope of $b = 1.63 \pm 0.10$ at 1283 MHz and $b = 1.20 \pm 0.12$ at 145 MHz. We also explore the X-ray surface brightness/radio spectral index correlation, finding a slope of $b = 0.59 \pm 0.11$. Both investigations support the evidence of spectral steepening. Finally, in the context of understanding the particle acceleration mechanism, we present a simple theoretical model which demonstrates that hybrid scenarios - secondary electrons (re-)accelerated by turbulence - reproduce a super-linear correlation slope.Comment: 19 pages, 11 figures, 4 tables. Accepted for publication in MNRA