344 research outputs found
Modelling the deceleration of COVID-19 spreading
No full textBy characterizing the time evolution of COVID-19 in term of its 'velocity' (log of the new cases per day) and its rate of variation, or 'acceleration', we show that in many countries there has been a deceleration even before lockdowns were issued. This feature, possibly due to the increase of social awareness, can be rationalized by a susceptible-hidden-infected-recovered model introduced by Barnes, in which a hidden (isolated from the virus) compartment H is gradually populated by susceptible people, thus reducing the effectiveness of the virus spreading. By introducing a partial hiding mechanism, for instance due to the impossibility for a fraction of the population to enter the hidden state, we obtain a model that, although still sufficiently simple, faithfully reproduces the different deceleration trends observed in several major countries
Co-existence of distinct supramolecular assemblies in solution and in the solid state
Get PDFThe formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet based assemblies are formed in chloroform depending on the nature of the cation, anion and salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy. Distinct N-H∙∙∙N and N-H∙∙∙O intermolecular hydrogen bonding interactions drive quartet and ribbon-like self-assembly resulting in markedly different 2D 1H solid-state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible - further demonstrating the changes that occur in the self-assembly process of a lipophilic nucleoside upon a solid-state to solution-state transition and vice versa. A systematic study for complexation with different cations (K+, Sr2+) and anions (picrate, ethanoate and iodide) emphasises that the existence of a stable solution or solid-state structure may not reflect the stability of the same supramolecular entity in another phase
Use of stable isotopes, organic and inorganic chemistry to identify pollution sources and weathering processes in two small tropical rivers in southwestern India
Get PDFThe two main objectives of this study were to assess pollution dynamic from organic and inorganic major ion chemistry and stable isotopes (δ15N and δ18O) and to determine the weathering processes using carbon isotopes in two tropical river basins, i.e. Nethravati and Swarna, along southwest coast of India. These short length river basins (around 100 km) are characterized by high annual rainfall, warm temperature, high runo" (~3300mm) draining Precambrian basement rocks composed of green-stones, granitic-gneiss, charnockite and meta sediments. Intense silicate weathering is induced by high runo" and warm temperature (Gurumurthy et al., 2012). In this study, stable isotopes (δ15N & δ18O)of organic molecules from sewage and agricultural effluents,and carbon isotopes (δ13C) of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) were measured to trace agricultural and domestic pollution and to identify the sources of inorganic carbon and the nature of chemical weathering in these river basins. Carbon isotopes measured on DIC reveals sources of carbon into the river, such as carbonate/silicate weathering of rocks, mineralization of organic matter from C3/C4 plants, soil and atmospheric CO2. The nitrate and phosphate levels remain low, with values ranging from 5 to 9 μM, and 0 to 2 μM respectively. The δ13C DIC values range from =-9.03 +/- 0.99 for the Swarna basin to -8.08 +/-0.78 for the Nethravati basin. These values point to a mixing of carbonate and silicate weathering products with a dominance of C3 vegetation, prevalent in the Western Ghats. The DOC values for both river basins are very low and very close: 0.72 +/- 0.09 mg/L (Swarna river) and 0.62 +/-0.11 mg/L (Nethravati river). This indicates that the contributions of organic matter from the adjacent forests and the $ood plains are very low during the sampling period. The analysis of organic acids reveals low amount of Oxalate and Acetate, and trace of Malate and Tartaric acids. The dissolved and particulate organic carbon (DOC and POC) concentrations are very low in these two rivers. During the dry season, river discharge is mainly supplied by groundwater with generally low contents in dissolved and particulate fractions. Even if we observe low concentration, we measured higher DOC and POC in the Swarna river. These higher DOC concentrations are accompanied with lower SUVA value. This indicates that more labile DOC (less aromaticity) is exported within this basin during dry season. C/N values in POC also show that the organic carbon is “fresher” and is probably more autochtonous than in the Nethravati river. Indeed, C/N value are closer of an autochthonous production (C/N : 2-6) than allochthonous one (C/N: 8-20). These observations can be explained as the Svarna watershed land use is more agricultural than in Nethravati. Agricultural lands generally export signi%cant amount of nutrients to rivers and participate to enhance autochthonous productivity. Autochthonous organic carbon production is more labile and less aromatic
A G<sub>4</sub>·K<sup>+</sup> Hydrogel Stabilized by an Anion
No full textSupramolecular
hydrogels derived from natural products have promising
applications in diagnostics, drug delivery, and tissue engineering.
We studied the formation of a long-lived hydrogel made by mixing guanosine
(G, <b>1</b>) with 0.5 equiv of KB(OH)<sub>4</sub>. This ratio
of borate anion to ligand is crucial for gelation as it links two
molecules of <b>1</b>, which facilitates cation-templated assembly
of G<sub>4</sub>·K<sup>+</sup> quartets. The guanosine–borate
(GB) hydrogel, which was characterized by cryogenic transmission electron
microscopy and circular dichroism and <sup>11</sup>B magic-angle-spinning
NMR spectroscopy, is stable in water that contains physiologically
relevant concentrations of K<sup>+</sup>. Furthermore, non-covalent
interactions, such as electrostatics, π-stacking, and hydrogen
bonding, enable the incorporation of a cationic dye and nucleosides
into the GB hydrogel
Pyrrolo[3,4-c]pyridine-1,3(2H)-diones: A new anti-mycobacterial class that targets mycobacterial energy metabolism
No full textPhenotypic whole-cell high throughput screening of a library of small polar molecules led to the identification of a phthalimide-containing ester hit compound (1), which was optimized for metabolic stability by replacing the ester moiety with a methyl oxadiazole bioisostere. A route utilizing polymer-supported reagents was designed and executed to explore structure activity relationships with respect to the N-benzyl substituent, leading to compounds with nanomolar activity against Mycobacterium tuberculosis. The frontrunner compound (5h) from these studies was well tolerated in mice. A M. tuberculosis cytochrome bd oxidase deletion mutant (∆cydKO) was hyper-susceptible to compounds from this series, and a strain carrying a single point mutation in qcrB, the gene encoding a subunit of the menaquinol cytochrome c oxidoreductase (bc1 complex), was resistant to compounds in this series. In combination, these observations indicate that this novel class of anti-mycobacterial compounds inhibits the cytochrome bc1 complex, a validated drug target in M. tuberculosis.
Author list: Renier van der Westhuyzen, Susan Winks, Colin R. Wilson, Grant A. Boyle, Richard K. Gessner, Candice Soares de Melo, Dale Taylor, Carmen de Kock, Mathew Njoroge, Christel Brunschwig, Nina Lawrence, Frik Sirgel, Paul van Helden, Ronnett Seldon, Atica Moosa, Digby Warner, Luca Arista, Srinivasa Rao, Ujjini H. Manjunatha, Paul W. Smith, Leslie J. Street, Kelly Chibal
Polyvinylidene Fluoride Nasal Sensor : Design, Development and Its Biomedical Applications
Get PDFThe growth of sensors and sensing technologies have made significant impact in our day-to-day life. The five principle sensory organs of our body should perform effectively, so that we can lead a good healthy life. Apart from these natural sensors, there are man-made sensors that helps us to cope with diseases, organ failure etc. and enable us to lead a normal life. In recent years, with the prevalence of new kind of diseases, the need for new type of biomedical sensors is becoming very important. As a result, sensors used for biomedical applications have become an emerging technology and rapidly growing field of research.
The aim of the present thesis work is to use the piezoelectric property of Polyvinylidene Fluoride (PVDF) film for the development of biomedical sensor and studying its application for human respiration/breathing related abnormalities. PVDF nasal sensor was designed in cantilever configuration and detailed theoretical analysis of the same was performed. Based on theoretical and experimental results, the PVDF nasal sensor dimensions were optimized. Suitable signal conditioning circuitry was designed and a measurement system for biomedical application was developed. The developed PVDF nasal sensor was calibrated using MEMS low-pressure sensor.
The PVDF nasal sensor system has been applied in different biomedical applications namely, (i) to monitor human respiration pattern, (ii) to identify different Respiration Rates (RR), (iii) to evaluate Deviated Nasal Septum (DNS) in comparison with other objective method and, (vi) to clinically investigate nasal obstruction in comparison with subjective method. The thesis is divided into seven chapters.
Chapter 1
This chapter gives a general introduction about biomedical sensors, piezoelectric sensing principle and PVDF polymer films along with the relevant literature survey. The brief introduction as well as literature survey of techniques used to monitor human respiration and to measure nasal obstruction is also included in this chapter.
Chapter 2
This chapter gives details about the design of the PVDF nasal sensor in the cantilever configuration for sensing nasal airflow along with the relevant theoretical equations. Also, the details on the optimization of the PVDF nasal sensor dimensions based on the theoretical and experimental analysis are presented.
Chapter 3
This chapter reports the designing of the necessary signal conditioning hardware along with the data acquisition unit for the PVDF nasal sensor. The signal conditioning hardware unit made consists of charge amplifier, low-pass filter and an amplifier. Besides, a complete measurement system for biomedical application was developed using PVDF nasal sensor and its merits and demerits were discussed.
Chapter 4
In this chapter, an experimental set-up for measuring human respiration/breathing pressure using water U-tube manometer has been described. Also, the calibration procedure followed for the developed PVDF nasal sensor using a Micro Electro Mechanical Systems(MEMS) low pressure sensor is reported. Apart from these, the details on the measurement of deflection of the PVDF cantilever sensing element using laser displacement setup are provided. In addition, the PVDF nasal sensor was also calibrated for various air flow rates. At the end, a study has been reported on optimizing the position the PVDF nasal sensor with respect to human nose.
Chapter 5
This chapter is divided into two sections, Section 5.1: This section describes the applicability of the PVDF nasal sensor using its piezoelectric property to monitor the human respiration pattern of each nostril simultaneously. The results of the PVDF nasal sensor have also been evaluated by comparing with Respiratory Inductive Plethysmograph(RIP) technique in normal subjects. Section 5.2: In this section, PVDF nasal sensor, RIP and Nasal Prongs (NP) techniques were used to measure the RR of
healthy adults. The aim here was to evaluate the presently developed PVDF nasal sensor for identifying different RR compared to „Gold standard‟ RIP and NP methods.
Chapter 6
This chapter is divided into two sections. Section 6.1: This section reports about the utilization of the developed PVDF nasal sensor for clinical application on the patient population. For this purpose, the performance of the PVDF nasal sensor measurements has been compared with the Peak Nasal Inspiratory Flow(PNIF) objective technique and visual analog scale (VAS). Section 6.2: This section describes about the use of PVDF nasal sensor system to measure nasal obstruction caused due to DNS objectively. Further, the results of the PVDF nasal sensor were compared with subjective techniques namely, VAS and clinician scale in patients and control group.
Chapter 7
This chapter is composed of two sections. Section 7.1: This section summarizes the salient features of the work presented in this thesis. Section 7.2: This section reports a scope for carrying out further work
Delayed Onset, Protracted Delirium and Aspiration Pneumonitis Associated with a Combination of Clozapine and Electroconvulsive Therapy
No full textFew studies reported the efficacy and safety in combination of clozapine and electroconvulsive therapy (ECT) in schizophrenia; systematic studies are lacking. Side effects like seizure, and confusional state are reported. Authors report two cases of delayed onset/protracted delirium with ECT and clozapine in schizophrenia, one of whom developed aspiration pneumonitis possibly due to clozapine hyper-salivation. Delirium improved with stopping of ECT and clozapine. Clozapine monotherapy restarted to previous dosages in both cases without recurrence of delirium. Authors recommend for careful monitoring for delirium in ECT augmentation on high dose clozapine. Unilateral ECT may be preferred for augmenting clozapine
Effect of retrogression duration on the grain boundary microstructure and microchemistry of AA7010
No full textA G4·K+Hydrogel stabilized by an anion
Get PDFSupramolecular hydrogels derived from natural products have promising applications in diagnostics, drug delivery, and tissue engineering. We studied the formation of a long-lived hydrogel made by mixing guanosine (G, 1) with 0.5 equiv of KB(OH)4. This ratio of borate anion to ligand is crucial for gelation as it links two molecules of 1, which facilitates cation-templated assembly of G4·K+ quartets. The guanosine–borate (GB) hydrogel, which was characterized by cryogenic transmission electron microscopy and circular dichroism and 11B magic-angle-spinning NMR spectroscopy, is stable in water that contains physiologically relevant concentrations of K+. Furthermore, non-covalent interactions, such as electrostatics, π-stacking, and hydrogen bonding, enable the incorporation of a cationic dye and nucleosides into the GB hydrogel
Generalized inverses of matrices over commutative rings
No full textAbstractA Rao-regular matrix and the Rao idempotent of a matrix over a commutative ring are defined. We prove that a matrix A over a commutative ring is regular if and only if A is a sum of Rao-regular matrices with mutually orthogonal Rao idempotents. We find necessary and sufficient conditions for a matrix to have group inverse over a commutative ring. Also, we give a method for computing minors of reflexive g-inverse whenever it exists
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