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91.
Context and objectives: The buccal mucosa presents a unique surface for non-invasive drug delivery and also avoids first-pass metabolism. The objective of this study was the formulation development of polymeric mucoadhesive lyophilized wafers as a matrix for potential buccal drug delivery.Materials and methods: Differential scanning calorimetry (DSC) was used to develop an optimum freeze-cycle, incorporating an annealing step. The wafers were prepared by lyophilization of gels containing three polymers, κ-carrageenan (CAR 911), poloxamer (P407) and polyethylene glycol 600 (PEG 600). The formulations were characterized using texture analysis (for mechanical and mucoadhesion properties), hydration studies, thermogravimetric analysis (TGA), DSC, X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM).Results and discussion: DSC showed the eutectic temperature (12.8?°C) of the system where the liquid solution and pure solids both existed at a fixed pressure which helped determine the freeze-annealing cycle at 55?°C for 7?h. Mechanical resistance to compression, hydration and mucoadhesion studies showed that optimized wafers were obtained from aqueous gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600. TGA showed residual water of approximately 1% and SEM showed a porous polymeric network that made ease of hydration possible.Conclusions: Lyophilized wafers by freeze-drying gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600 with optimum physico-mechanical properties has been achieved. 相似文献
92.
Daily observations of dissolved aluminum, iron, and manganese in an estuary downstream of a coastal acid sulfate soil (CASS) catchment provided insights into how floods and submarine groundwater discharge drive wetland metal exports. Extremely high Al, Fe, and Mn concentrations (up to 40, 374, and 8 mg L(-1), respectively) were found in shallow acidic groundwaters from the Tuckean Swamp, Australia. Significant correlations between radon (a natural groundwater tracer) and metals in surface waters revealed that metal loads were driven primarily by groundwater discharge. Dissolved Fe, Mn, and Al loads during a 16-day flood triggered by a 213 mm rain event were respectively 80, 35, and 14% of the total surface water exports during the four months of observations. Counter clockwise hysteresis was observed for Fe and Mn in surface waters during the flood due to delayed groundwater inputs. Groundwater-derived Fe fluxes into artificial drains were 1 order of magnitude higher than total surface water exports, which is consistent with the known accumulation of monosulfidic black ooze within the wetland drains. Upscaling the Tuckean catchment export estimates yielded dissolved Fe fluxes from global acid sulfate soil catchments on the same order of magnitude of global river inputs into estuaries. 相似文献
93.
Isaac Seoane Gerson Rodríguez de los Santos José Alberto Hernández Manuel Urueña Ricardo Romeral Ángel Cuevas David Larrabeiti 《Photonic Network Communications》2011,21(3):278-287
In Tunable-Transmitter Fixed-Receiver (TT-FR)-based Wavelength Division Multiplexed (WDM) ring topologies, each node is provided
with a dedicated wavelength (home channel) for reception, which must be shared by the upstream nodes willing to communicate
with it. Thus, to avoid channel collisions, it is necessary to define a Medium Access Control (MAC) mechanism that arbitrates
access to a given destination wavelength. This work proposes and analyses a simple MAC mechanism that avoids channel collisions
by recirculating traffic on the upstream ring segment where congestion was detected. Essentially, whenever a given node has
got any traffic to transmit, it must first block access to in-transit traffic, which is reflected back to the upstream node
over a second optical fibre. Such blocked traffic is given a second chance to pass through the congested node after a round
segment delay, thus making use of the ring topology as buffering units. This work analyses the performance operation of such
a MAC protocol under two policies applied to recirculated traffic: (1) recirculation bypass and (2) recirculation store-and-forward. 相似文献
94.
Sudip Misra P. Venkata Krishna Kiran Isaac Abraham 《Wireless Personal Communications》2011,56(1):55-72
Providing effective medium access for wireless networks is a challenging task. Most of the existing protocols of IEEE 802.11
Medium Access Control (MAC) work towards the goal of achieving effective channel access by developing various backoff procedures.
In this paper, we make an attempt to develop a new medium access protocol named Learning Automata (LA) based Wireless Channel
Reservation (LAWCR). We use an LA approach to implement reservation for channel access for single hop wireless networks. Also,
sequence procedure is used to improve the reservation mechanism. The performance of the proposed LAWCR scheme show significant
improvements over the legacy DCF protocol with respect to important criteria such as the average time spent in the buffer
and the throughput. 相似文献
95.
Probability and convexity concepts are not antagonistic 总被引:1,自引:0,他引:1
96.
An assessment of the sewage occurrence and biodegradability of seven parabens and three halogenated derivatives of methyl paraben (MeP) is presented. Several wastewater samples were collected at three different wastewater treatment plants (WWTPs) during April and May 2010, concentrated by solid-phase extraction (SPE) and analysed by liquid chromatography-electrospray-quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS). The performance of the QTOF system proved to be comparable to triple-quadrupole instruments in terms of quantitative capabilities, with good linearity (R2 > 0.99 in the 5-500 ng mL−1 range), repeatability (RSD < 5.6%) and LODs (0.3-4.0 ng L−1 after SPE). MeP and n-propyl paraben (n-PrP) were the most frequently detected and the most abundant analytes in raw wastewater (0.3-10 μg L−1), in accordance with the data displayed in the bibliography and reflecting their wider use in cosmetic formulations. Samples were also evaluated in search for potential halogenated by-products of parabens, formed as a result of their reaction with residual chlorine contained in tap water. Monochloro- and dichloro-methyl paraben (ClMeP and Cl2MeP) were found and quantified in raw wastewater at levels between 0.01 and 0.1 μg L−1. Halogenated derivatives of n-PrP could not be quantified due to the lack of standards; nevertheless, the monochlorinated species (ClPrP) was identified in several samples from its accurate precursor and product ions mass/charge ratios (m/z). Removal efficiencies of parabens and MeP chlorinated by-products in WWTPs exceeded 90%, with the lowest percentages corresponding to the latter species. This trend was confirmed by an activated sludge biodegradation batch test, where non-halogenated parabens had half-lives lower than 4 days, whereas halogenated derivatives of MeP turned out to be more persistent, with up to 10 days of half-life in the case of dihalogenated derivatives. A further stability test performed with raw wastewater also showed that parabens degrade rapidly in real sewage, with half-lives lower than 10 h for n-butyl-paraben, while dihalogenated species again turned out to be more stable, with half-lives longer than a week. 相似文献
97.
Isaac Vaghefi Liette Lapointe Camille Boudreau‐Pinsonneault 《Information Systems Journal》2017,27(2):125-169
To date, information systems (IS) research mainly has provided a monolithic view of information technology (IT) use, considering it to be a desired behaviour with positive outcomes. However, given the dramatic increase in the use of technology during the last few years, susceptibility to IT addiction is increasingly becoming an important issue for technology users and IS researchers. In this paper, we report the results of a study that focuses on identifying variations in user liability to IT addiction, which reflects the susceptibility of individual users to develop IT addiction. First, a review of the literature in different disciplines (e.g. health, psychology and IS) allows us to better understand the concepts of IT addiction and liability to addiction. The literature review also provides an overview of the antecedents and consequences associated with IT addiction. Then, building on the analysis of 15 in‐depth interviews and 182 exploratory open‐ended surveys collected from smartphone users, we apply the concept of liability to addiction in the IT use context and propose a typological theory of user liability to IT addiction. Our typology reveals five ideal types; each can be associated to a user profile (addict, fanatic, highly engaged, regular and thoughtful ). Building upon both the extant literature and our results, we put forth propositions to extend the theoretical contributions of the study. We finally discuss the contributions and implications of our paper for research and practice. 相似文献
98.
A numerical simulation of nonisothermal gas flows in the hot-gas filter vessel at the Power Systems Development Facility in Wilsonville, Alabama is presented. The gas velocity and thermal simulations are based on the Reynolds stress transport turbulence model of the FLUENT TM commercial CFD computer code. While earlier modeling studies were limited to isothermal conditions, in this study, the energy transport equation was solved in addition to the mass and momentum equations. The gas flow and temperature field inside the filter vessel were also studied. Results reveal that the gas flow shows strong rotating flow regions outside the shroud and in the upper and lower parts of the body of the vessel. It is also shown that the temperature distribution is nonuniform with somewhat higher temperatures in the upper part of the filter. The simulated results qualitatively agree with the experimental field observations of the filter vessel.
filter vessel numerical simulation nonisothermal FLUENT 相似文献
filter vessel numerical simulation nonisothermal FLUENT 相似文献
99.
100.
Esteban López-Salinas M. Elena Llanos Serrano M. Antonia Cortés Jácome Isaac Schifter Secora 《Journal of Porous Materials》1995,2(4):291-297
A lamellar hydrocalumite-type [Ca2Al(OH)6]NO3·mH2O, (HC), was synthesized and characterized by X-ray diffraction analysis (XRD), surface area, pore size measurements, CO2-Thermal Programmed Desorption, and later tested as catalysts in the double bond isomerization of 1-butene. The layered structure of HC collapses above 523 K yielding an amorphous material at 573 K which upon calcination at 873–973 K transforms into a mixture of CaO and mayenite Ca12Al14O33. The calcination temperature has a marked effect in the formation of basic sites. Thus for example, HC calcined at 1073 K shows 90% of strong basic sites (CO2 desorption at 1023 K) while they are absent in HC calcined at 573–673 K. HC calcined at 973 K shows high catalytic activity (74% conversion) in the isomerization of 1-butene without any appreciable deactivation after 4 h on stream. 相似文献