1,721,672 research outputs found
Principles of odor coding in vertebrates and artificial chemosensory systems
No full textThe biological olfactory system is the sensory system responsible for the detection of the chemical composition of the environment. Several attempts to mimic biological olfactory systems have led to various artificial olfactory systems using different technical approaches. Here we provide a parallel description of biological olfactory systems and their technical counterparts. We start with a presentation of the input to the systems, the stimuli, and treat the interface between the external world and the environment where receptor neurons or artificial chemosensors reside. We then delineate the functions of receptor neurons and chemosensors as well as their overall input-output (I/O) relationships. Up to this point, our accounts of the systems go along similar lines. The next processing steps differ considerably: whereas in biology the processing step following the receptor neurons is the "integration" and "processing" of receptor neuron outputs in the olfactory bulb, this step has various realizations in electronic noses. For a long period of time, the signal processing stages beyond the olfactory bulb, i.e., the higher olfactory centers, were little studied. Only recently has there been a marked growth of studies tackling the information processing in these centers. In electronic noses, a third stage of processing has virtually never been considered. In this review, we provide an up-to-date overview of the current knowledge of both fields and, for the first time, attempt to tie them together. We hope it will be a breeding ground for better information, communication, and data exchange between very related but so far little-connected fields
Self-Repairing classification algorithms for chemical sensor array
No full textChemical sensors are usually affected by drift, have low fabrication reproducibility and can experience failure or breaking events over the long term. Albeit improvements in fabrication processes are often slow and inadequate for completely surmounting these issues, data analysis can be used as of now to improve the available device performances. The present paper illustrates an algorithm, called Self-Repairing (SR), developed for repairing classification models after the occurrences of failures in sensor arrays. The procedure considers replacing broken sensors with replicas and eventually Self-Repairing algorithm trains these blank elements. Unlike the habitual alternatives reported in literature, SR performs this operation without the need of a whole new recalibration, references gas measurements or transfer dataset and, at the same time, without interrupting the on-going procedure of gas identification. Furthermore, Self-Repairing algorithm can utilize most of the standard classifiers as core algorithm; in this paper SR has been applied to k-NN, PLS-DA and LDA as examples. Models have been tested in a synthetic and real scenario considering sensor arrays affected by drift and eventually by failures. Real experiment has been performed with a set of metal oxide sensors over an 18-months period. Finally, the algorithm has been compared with standard version of chosen classifiers (k-NN, LDA and PLS-DA) showing superior performances of Self-Repairing and increasing the tolerance versus consecutive failures
Corroles at work: a small macrocycle for great applications
No full textCorrole chemistry has witnessed an impressive boost in studies in the last 20 years, thanks to the possibility of preparing corrole derivatives by simple synthetic procedures. The investigation of a large number of corroles has highlighted some peculiar characteristics of these macrocycles, having features different from those of the parent porphyrins. With this progress in the elucidation of corrole properties, attention has been focused on the potential for the exploitation of corrole derivatives in different important application fields. In some areas, the potential of corroles has been studied in certain detail, for example, the use of corrole metal complexes as electrocatalysts for energy conversion. In some other areas, the field is still in its infancy, such as in the exploitation of corroles in solar cells. Herein, we report an overview of the different applications of corroles, focusing on the studies reported in the last five years
The long-lasting story of one sensor development: from novel ionophore design toward the sensor selectivity modeling and lifetime improvement
Full text linkThe metalloporphyrin ligand bearing incorporated anion-exchanger fragment, 5-[4-(3-trimethylammonium)propyloxyphenyl]-10,15,20-triphenylporphyrinate of Co(II) chloride, CoTPP-N, has been tested as anion-selective ionophore in PVC-based solvent polymeric membrane sensors. A plausible sensor working mechanism includes the axial coordination of the target anion on ionophore metal center followed by the formed complex aggregation with the second ionophore molecule through positively charged anion-exchanger fragment. The UV-visible spectroscopic studies in solution have revealed that the analyte concentration increase induces the J-type porphyrin aggregation. Polymeric membranes doped with CoTPP-N showed close to the theoretical Nernstian response toward nitrite ion, preferably coordinated by the ionophore, and were dependent on the presence of additional membrane-active components (lipophilic ionic sites and ionophore) in the membrane phase. The resulting selectivity was a subject of specific interaction and/or steric factors. Moreover, it was demonstrated theoretically and confirmed experimentally that the selection of a proper ratio of ionophore and anionic additive can optimize the sensor selectivity and lifetime
Domande frequenti, credenze e luoghi comuni sul bilinguismo
No full textIl capitolo risponde alle domande più comunemente rivolte agli specialisti sugli effetti del bilinguismo e la relazione con gli apprendimenti e lo sviluppo cognitivo e affettivo
The polymorphism of enzyme MTHFR in children suffering from migraine ad epilepsy
No full textThe C677T variant in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with increased levels of circulating homocysteine and is a mild risk factor for vascular disease. Mild Hcy elevation (>15 mmol L−1) in the adult population is associated with increased risk of myocardial infarction, stroke, peripheral arterial disease and venous thrombosis.[1,2,3] The MTHFR 677CT mutation is frequent in Caucasians; MTHFR mutant allele occurs commonly in 5% to 15% of the population, and the heterozygosis is over 40%. The C677T polymorphism of the MTHFR gene has been associated with different diseases such as stroke, coronary artery disease, bipolar disorder, schizophrenia and depression. Homozygosis for MTHFR 677 CT mutations is more frequent in epileptic patients compared with healthy controls (23% vs. 12%) and heterozygosis is about 52%. Lipton[1] showed that Hcy may have excitotoxicity to neurons as an agonist of the glutamate binding site of the N-methyl-Daspartate (NMDA) receptors. Migraine, with and without aura (MA and MO), is a prevalent and complex neurovascular disorder that may also be affected by genetically influenced hyperhomocysteinaemia
Aim of this study is the evaluation of incidence of mutation of enzyme MTHFR in the children suffering from two disease, epilepsy and migraine as in comorbility, as without comorbility.
MATERIALS AND METHODS
32 patients suffering from headache observed during 3 months and 34 children affected by epilepsy observed during the same time represent the sample of this study. At the first observation in day hospital are determined the homocisteinaemia levels and mutation C677 of enzyme MTHFR. In the sample is studied MR brain and EEG. In the familial history is considered the headache, the epilepsy, the stroke and cardiovascular disease. The homocisteinaemia is evaluated by immunological fluorescent method (FPIA) The mutation of enzyme C677 is studied by technique of qualititative Real-Time PCR.
RESULTS
27 patients suffering from generalized epilepsy, 7 from partial epilepsy. In the 18%of these patients there is C677 enzyme mutation and 7% show homozygous condition. Among 32 children suffering from headache, 17 have TTH, 9 MO, and 6 MA. 50% show MTHFR mutation. The allele is present in the 83% of MO and in 87% of MA and homozygosis condition is present in 22% of children. The values of homocisteinaemia are higher in the homozygous than heterozygous patients (9.48 μmol/L vs. 8.3 μmol/L) and this condition is more evident in the migraines than epileptic patients. In the 50% of the sample with C677 mutation there are MR lesions as cerebrovascular disease. 1 child shows the results of ischemic event in the foetal life. We underline the history of 2 patient’s hemiplegic suffering, one from migraine, one from epilepsy.
DISCUSSION
Kowa et al. [1] originally reported a positive association between the MTHFR C677T variant and migraine in a Japanese case control cohort. These researchers indicated an increased risk of migraine in Japanese individuals possessing the homozygous T/T genotype. Stratified analyses specifically showed that the T/T genotype was significantly over-represented in these Japanese patients with MA compared to non-migraine controls (40% vs. 9.6%), producing an OR of ~6. These positive findings were reinforced by another recent migraine case-control study conducted in a Turkish population. These researchers reported that the MTHFR C677T is associated with migraine and also indicated that the T/T genotype specifically increased risk of MA (OR ~10). It is important to note that the frequency of the MTHFR 677T allele, and indeed migraine prevalence, is known to vary substantially among different ethnic populations. Thus, this study supports the findings of other authors and shows the hypothetical role of this genetically aspects in the comorbility migraine - epilepsy.
1. BMC Medicine 2 (2004):3
2. Cephalalgia 28 (2008): 376-382
3 Eur J Radiol 2009 feb 1
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