Chemically cross-linked poly(acrylic-co-vinylsulfonic) acid hydrogel for the delivery of isosorbide mononitrate.

We report synthesis, characterization, and drug release attributes of a series of novel pH-sensitive poly(acrylic-co-vinylsulfonic) acid hydrogels. These hydrogels were prepared by employing free radical polymerization using ethylene glycol dimethacrylate (EGDMA) and benzyl peroxide (BPO) as cross-linker and initiator, respectively. Effect of acrylic acid (AA), polyvinylsulfonic acid (PVSA), and EGDMA on prepared hydrogels was investigated. All formulations showed higher swelling at high pHs and vice versa. Formulations containing higher content of AA and EGDMA show reduced swelling, but one with higher content of PVSA showed increased swelling. Hydrogel network was characterized by determining structural parameters and loaded with isosorbide mononitrate. FTIR confirmed absence of drug polymer interaction while DSC and TGA demonstrated molecular dispersion of drug in a thermally stable polymeric network. All the hydrogel formulations exhibited a pH dependent release of isosorbide mononitrate which was found to be directly proportional to pH of the medium and PVSA content and inversely proportional to the AA contents. Drug release data were fitted to various kinetics models. Results indicated that release of isosorbide mononitrate from poly(AA-co-VSA) hydrogels was non-Fickian and that the mechanism was diffusion-controlled

Exchange rate regimes and trade: Is Africa different?

This paper revisits the link between exchange rate regimes and trade in the context of Africa's exchange rate arrangements. Applying an augmented gravity model that includes measures of currency unions and pegged regimes, the paper compares Africa's experience with that of the world. Our results suggest that both currency unions and direct pegs promote bilateral trade in Africa vis-à-vis more flexible exchange rate regimes,and that their effect is almost double for the region than that for an average country in the world sample. Further, we find evidence that the effect of conventional pegs is at least as large as that of currency unions in Africa, and that the benefits of fixed exchange rate regimes stem through channels in addition to reduced exchange rate volatility

Improving time–frequency domain sleep EEG classification via singular spectrum analysis

Background: Manual sleep scoring is deemed to be tedious and time consuming. Even among automatic methods such as Time-Frequency (T-F) representations, there is still room for more improvement. New method: To optimise the efficiency of T-F domain analysis of sleep electroencephalography (EEG) a novel approach for automatically identifying the brain waves, sleep spindles, and K-complexes from the sleep EEG signals is proposed. The proposed method is based on singular spectrum analysis (SSA). The single-channel EEG signal (C3-A2) is initially decomposed and then the desired components are automatically separated. In addition, the noise is removed to enhance the discrimination ability of features. The obtained T-F features after preprocessing stage are classified using a multi-class support vector machines (SVM) and used for the identification of four sleep stages over three sleep types. Furthermore, to emphasize on the usefulness of the proposed method the automatically-determined spindles are parameterised to discriminate three sleep types. Result: The four sleep stages are classified through SVM twice: with and without preprocessing stage. The mean accuracy, sensitivity, and specificity for before the preprocessing stage are: 71.5 ± 0.11%, 56.1 ± 0.09% and 86.8 ± 0.04% respectively. However, these values increase significantly to 83.6 ± 0.07%, 70.6 ± 0.14% and 90.8 ± 0.03% after applying SSA. Comparison with existing method: The new T-F representation has been compared with the existing benchmarks. Our results prove that, the proposed method well outperforms the previous methods in terms of identification and representation of sleep stages. Conclusion: Experimental results confirm the performance improvement in terms of classification rate and also representative T-F domain

Effect of Class F Fly Ash on Fine Sand Compaction through Soil Stabilization

This paper presents the results of an experimental investigation carried out to evaluate the effect of fly ash (FA) on fine sand compaction and its suitability as a material for embankments. The literature review demonstrates the lack of research on stabilization of sandy material using FA. The study is concerned with the role of FA content in stabilized soil physical characteristics. The main aim of this paper is to determine the optimum quantity of FA content for stabilization of this type of soil. This is achieved through particle size distribution and compaction (standard proctor) tests. The sand was stabilized with three proportions of FA (5%, 10% and 15%) and constant cement content of 3% was used as an activator. For better comparison, the sand was also stabilized by 3% cement only so that the effect of FA could be observed more clearly. The results were in line with the literature for other types of soil, i.e. as the % of FA increases, reduction in maximum dry density and higher optimum moisture content were observed

Capital inflow surges and consequences

While capital flows to emerging markets bring numerous benefits, they are also known to create macroeconomic imbalances (economic overheating, currency overvaluation) and increase financial vulnerabilities (domestic credit growth, bank leverage, foreign currency-denominated lending). But are all inflows the same? In this paper, we examine whether the source of the inflow - residents repatriating foreign assets or nonresidents investing in the country - or the type of inflow (foreign direct investment, portfolio, other investment, etc.) makes any difference to the consequences of the capital flow. Our results, based on a sample of 53 emerging markets over 1980 - 2013, show that when it comes to the source of the inflow, the macroeconomic and financial stability consequences of flows driven by residents (asset flows) and nonresidents (liability flows) are broadly similar in economic terms. Formal statistical tests, however, suggest that liability flows are more prone to causing economic overheating and domestic credit expansion than asset flows. On the types of inflows, we find that compared to direct investment, portfolio debt and other investment flows are associated with larger macroeconomic imbalances and financial vulnerabilities. We conclude that policy should try to mitigate the untoward consequences of inflows, and shift their composition from risky to safer forms of liabilities

Film-ovojnica smjese pektina, kitozana i Eudragita® RS za bimodalno oslobađanje lijeka iz peleta s teofilinom: Priprava i evaluacija

Pellets containing theophylline as a model drug and microcrystalline cellulose, in a ratio of 6:4, were prepared by extrusion-spheronization method. The pellets were coated with Eudragit® RS aqueous dispersions, containing various amounts of pectin-chitosan complex and different coating mass gains, using a fluidized-bed apparatus. Twelve formulations were developed, which differed in two factors: coating mass gain (10, 15 and 20%, m/m) and amount of pectin-chitosan complex (5, 10, 15 and 20%, m/m). Drug release studies were conducted using the USP apparatus Ι (basket) in dissolution media, mimicking the conditions pertaining in the stomach, small intestine and colon, respectively. Studies have shown that drug release rate and pattern were dependent on both two mentioned factors. Some formulations showed bimodal and burst drug release, being triggered in the colonic medium by the action of pectinolytic enzymes. In formulations with 15 or 20% (m/m) of coating mass gain and 5 or 10% (m/m) of pectin-chitosan amount, the burst drug release was eliminated and replaced by lag phase of drug release. In viewpoint of burst drug release in the colonic medium, formulations with 20% (m/m) of coating mass gain and 15 or 20% (m/m) of pectin-chitosan amount were found to be better than the other formulations. Studies on the surface SEMs of uncoated and coated pellets show that after coating, coated pellets became smoother and exposure to pectinolytic enzymes in the colonic medium may result in surface erosion.Pelete s teofilinom kao modelnim lijekom i mikrokristaliničnom celulozom u omjeru 6:4 pripravljeni su metodom ekstruzije i sferonizacije. Pelete su presvučene vodenom disperzijom Eudragita® RS koja sadrži različite količine kompleksa pektina i kitozana i različite mase ovojnice, koristeći uređaj za fluidizaciju. Pripravljeno je 12 peleta koji se razlikuju po masi ovojnice (10, 15 i 20%, m/m) i udjelu kompleksa pektina i kitozana (5, 10, 15 i 20%, m/m). Oslobađanje ljekovite tvari proučavano je u USP aparaturi Ι (s košaricama) u medijima koji odgovaraju pH probavnog sustava. Dobiveni rezultati ukazuju da brzina i način oslobađanja lijeka ovisi o oba spomenuta parametra. Iz nekih pripravaka oslobađanje je bimodalno, a posljedica je djelovanja pektinolitičkih enzima iz kolona. U pripravcima u kojima je udio ovojnice 15 ili 20% (m/m), a udio pektin-kitozana 5 ili 10% (m/m) oslobađanje je bilo polagano. Najbolji pripravci za naglo oslobađanje u pH mediju područja kolona sadržavali su 20% (m/m) ovojnice i 15 ili 20% (m/m) pektin-kitozana. Proučavanje obloženih i neobloženih peleta SEM metodom pokazuje da obložene pelete imaju glatkiju površinu, koja erodira djelovanjem pektinolitičkih enzima

Polyhydroxylated fullerene nanoparticles attenuate brain infarction and oxidative stress in rat model of ischemic stroke

Oxidative stress is the common underlying mechanism of damage in ischemic stroke. Therefore, we aimed to evaluate the possible protective effects of polyhydroxylated fullerene derivatives on brain infarction and oxidative/nitrosative stress in a rat model of ischemic stroke. The experiment was performed by four groups of rats (each; n=12); Sham, Control ischemia, and ischemic treatment groups (Pretreatment and Posttreatment). Brain ischemia was induced by 90 min middle cerebral artery occlusion (MCAO) followed by 24 hours reperfusion. Rats received fullerene nanoparticles at dose of 1 mg/kg 30 min before MCAO and immediately after beginning of reperfusion. Infarct volume, contents of malondialdehyde (MDA), glutathione (GSH) and nitrate as well as superoxide dismutase (SOD) activity were assessed 24 hours after termination of MCAO. Brain infarct volume was 310 ± 21 mm3 in control group. Administration of fullerene nanoparticles before and after MCAO significantly decreased the infarct volume by 53 % (145 ± 45 mm3) and 81 % (59 ± 13 mm3), respectively. Ischemia also enhanced MDA and nitrate contents of ischemic hemispheres by 45 % and 25 % , respectively. Fullerene nanoparticles considerably reduced the MDA and nitrate contents of ischemic hemispheres before MCAO by 58 % and 17 % , respectively, and after MCAO by 38 % and 21 % , respectively. Induction of MCAO significantly decreased GSH content (19 % ) and SOD activity (52 % ) of ischemic hemispheres, whereas fullerene nanoparticles increased the GSH content and SOD activity of ischemic hemispheres by 19 % and 52 % before MCAO, respectively, and 21 % and 55 % after MCAO, respectively. Our findings indicate that fullerene nanoparticles, as a potent scavenger of free radicals, protect the brain cells against ischemia/reperfusion injury and inhibit brain oxidative/nitrosative damage