| 497891. |
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| 497892. |
- Mahlin, Denny, et al.
(författare)
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The influence of PVP incorporation on moisture-induced surface crystallization of amorphous spray-dried lactose particles
- 2006
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 321:1-2, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- We have recently shown that atomic force microscopy (AFM) may be an appropriate method for characterisation of the re-crystallization of amorphous particles. In this study, spray-dried composite particles consisting of lactose and polyvinyl pyrrolidon (PVP) were characterised by AFM and electron spectroscopy for chemical analysis (ESCA), and their response on increasing the relative humidity (RH) was investigated. The PVP content in the particles used was 0, 5 or 25 wt.% of either PVP K 17 or PVP K90. All composite particles were found to be enriched with PVP at the surface. The incorporation of PVP in the particles influenced the way the particles responded to an increase in RH. The specific RH interval in which the surface of the particles smoothened and the RH where crystallization could be detected, increased with an increase in the amount and molecular weight of the PVP in the particles. The crystallization kinetics of single particles was analysed with AFM and by utilising the JMAK equation. The rate constant for this transformation increased in an exponential manner with increasing RH. Furthermore, above the RH needed for the crystallization to occur, the exponential increase in the crystallization rate was larger for particles with higher polymer content which indicates that the stabilising effect decreases as the water content in the particles becomes higher. In this study we report a method for determination of crystallization kinetics on single composite particles, which is valuable when evaluating the effect of stabilisers in amorphous powders.
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| 497893. |
- Mahlin, Denny, et al.
(författare)
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Toward In Silico Prediction of Glass-Forming Ability from Molecular Structure Alone : A Screening Tool in Early Drug Development
- 2011
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Ingår i: Molecular Pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 8:2, s. 498-506
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel computational tool which predicts the glass-forming ability of drug compounds solely from their molecular structure. Compounds which show solid-state limited aqueous solubility were selected, and their glass-forming ability was determined upon spray-drying, melt-quenching and mechanical activation. The solids produced were analyzed by differential scanning calorimetry (DSC) and powder X-ray diffraction. Compounds becoming at least partially amorphous on processing were classified as glass-formers, whereas those remaining crystalline regardless of the process method were classified as non-glass-forming compounds. A predictive model of the glass-forming ability, designed to separate between these two classes, was developed through the use of partial least-squares projection to latent structure discriminant analysis (PLS-DA) and calculated molecular descriptors. In total, ten of the 16 compounds were determined experimentally to be good glass-formers and the PLS-DA model correctly sorted 15 of the compounds using four molecular descriptors only. An external test set was predicted with an accuracy of 75%, and, hence, the PLS-DA model developed was shown to be applicable for the identification of compounds that have the potential to be designed as amorphous formulations. The model suggests that larger molecules with a low number of benzene rings, low level of molecular symmetry, branched carbon skeletons and electronegative atoms have the ability to form a glass. To conclude, we have developed a predictive, transparent and interpretable computational model for the identification of drug molecules capable of being glass-formers. The model allows an assessment of amorphization as a formulation strategy in the early drug development process, and can be applied before compound synthesis.
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| 497894. |
- Mahlknecht, Philipp, et al.
(författare)
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Parkinsonian signs in patients with cervical dystonia treated with pallidal deep brain stimulation
- 2018
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Ingår i: Brain. - : Oxford University Press. - 0006-8950 .- 1460-2156. ; 141, s. 3023-3034
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Tidskriftsartikel (refereegranskat)abstract
- Pallidal deep brain stimulation is an established treatment in patients with dystonia. However, evidence from case series or uncontrolled studies suggests that it may lead in some patients to specific parkinsonian symptoms such as freezing of gait, micrographia, and bradykinesia. We investigated parkinsonian signs using the Movement Disorder Society Unified Parkinson's Disease Rating Scale motor score by means of observer-blinded video ratings in a group of 29 patients treated with pallidal stimulation and a non-surgical control group of 22 patients, both with predominant cervical dystonia. Additional assessments included MRI-hased models of volume of neural tissue activated to investigate areas of stimulation related to dystonic symptom control and those likely to induce parkinsonian signs as well as an EMG analysis to investigate functional vicinity of stimulation fields to the pyramidal tract. Compared with controls, stimulated patients had significantly higher motor scores (median, 25th-75th percentile: 14.0, 8.0-19.5 versus 3.0, 2.0-8.0; P < 0.0001), as well as bradykinesia (8.0, 6.0-14.0 versus 2.0, 0.0-3.0; P < 0.0001) and axial motor subscores (2.0, 1.0-4.0 versus 0.0, 0.0-1.0; P= 0.0002), while rigidity and tremor subscores were not different between groups. Parkinsonian signs were partially reversible upon switching stimulation off for a median of 90 min in a subset of 19 patients tolerating this condition. Furthermore, the stimulation group reported more features of freezing of gait on a questionnaire basis. Quality of life was better in stimulated patients compared with control patients, but parkinsonian signs were negatively associated with quality of life. In the descriptive imaging analysis maximum efficacy for dystonia improvement projected to the posteroventrolateral internal pallidum with overlapping dusters driving severity of bradykinesia and axial motor symptoms. The severities of parkinsonian signs were not correlated with functional vicinity to the pyramidal tract as assessed by EMG. In conclusion, parkinsonian signs, particularly bradykinesia and axial motor signs, due to pallidal stimulation in dystonic patients are frequent and negatively impact on motor functioning and quality of life. Therefore, patients with pallidal stimulation should be monitored closely for such signs both in clinical routine and future clinical trials. Spread of current outside the internal pallidum is an unlikely explanation for this phenomenon, which seems to be caused by stimulation of neural elements within the stimulation target volume.
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| 497895. |
- Mahloo, Mozhgan, et al.
(författare)
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PON versus AON : Which is the best solution to offload core network by peer-to-peer traffic localization
- 2015
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 15:0, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Video streaming and video-on-demand are gaining popularity nowadays which dictates a need of bandwidth upgrade for Internet users. Many next generation optical access network architectures have been proposed to meet high capacity requirement on a per-user basis. However, the capacity upgrade in access networks, may lead to a huge traffic growth in the aggregation/core network. One way to avoid this problem is to keep the traffic locally (i.e., inside the access network area) as much as possible. It can be obtained by using locality-aware peer-to-peer (P2P) applications for content distribution and has the potential to offload the core segment. However, various optical access network architectures accommodate the P2P traffic in different ways. Thus, it is important to study these differences in order to identify the best architecture option for capacity offloading in the core network, energy efficiency and network resource utilization. By deploying a proper architecture in the access segment along with an efficient traffic locality aware strategy, the extra investment and capacity upgrade of the expensive core network resources needed to support the future traffic expansion can be minimized. However, to the best of our knowledge this kind of assessment is so far not available. Therefore, in this paper, we analyze the efficiency of supporting locality-aware P2P video distribution algorithm in three main types of optical access network architectures, i.e., active optical network (AON), wavelength division multiplexing passive optical network (WDM PON) and time/wavelength division multiplexing PON (TWDM PON). Our goal is to provide important design guidelines for the next generation broadband access architectures, while minimizing the need for the core network upgrade. We obtain this objective by utilizing the unique characteristics of each access network architecture in accommodating P2P video delivery applications. We have done an extensive literature study and for the first time we have compared performance of these architectures with respect to the amount of the traffic on the links in different aggregation levels, power consumption taking into account sleep mode functionality at the user premises, and required switching capacity in the nodes. Our results reveal that both active and passive architectures have good ability to localize P2P traffic, whereas they show distinct performance with respect to the other aforementioned aspects. This is caused by the different number of aggregation levels, link capacity, and resource allocation protocols. Considering the overall performance evaluation, it is shown that TWDM PON is the most promising option for the future broadband access, where locality-aware P2P video distribution is applied, thanks to its low energy consumption and required switching capacity of the network equipment needed to deliver this service. This conclusion is against the general intuition because of the PON׳s centralized control plane and passive infrastructure without switching capability in the field. Our unexpected conclusion can be of particular interest to operators as it is perfectly aligned with next generation optical access architecture identified by Full Service Access Networks (FSAN).
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| 497896. |
- Mahloo, Mozhgan, et al.
(författare)
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Protection cost evaluation of WDM-based next generation optical access networks
- 2013
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 10:1, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- New technologies and advanced network devices make it possible to move towards high capacity access networks able to satisfy the growing traffic demand. Wavelength division multiplexing (WDM) is considered as one of the promising technologies for the next generation access networks since it offers higher bandwidth and longer reach compared to the current technologies (such as time division multiplexing (TDM) based networks). However, the migration to a new technology is typically based on an overall techno-economic study which should assure the network operator that the new implementation is cost effective and profitable while able to provide the required services to the users. Another important aspect in the access network design is the network reliability performance, which can be improved by providing a certain level of protection for equipment and/or infrastructure with high failure impact ratio in order to prevent a big number of the users being affected by a single failure. The cost of protection should be carefully evaluated since providing the backup resources may be too expensive for a network operator. In this paper, we investigate the capital and operational expenditures for two next generation optical access (NGOA) networks based on the WDM technology in dense urban areas. Three scenarios with different splitting ratios are studied for each technology, with and without protection. The aim of this work is to investigate the impact of providing protection on the total cost of NGOA networks. The results show that in the dense urban areas the fibers and digging costs are highly shared among the end users but still vary according to the splitting ratios for different scenarios and the fiber layout. It also can be seen that with a proper fiber layout design, minor extra investment for protection of NGOA networks can make a significant saving on failure related operational cost and that operational expenditures depend significantly on the fiber layout.
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| 497897. |
- Mahloo, Mozhgan, et al.
(författare)
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Toward Reliable Hybrid WDM/TDM Passive Optical Networks
- 2014
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Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 52:2, s. S14-S23
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Tidskriftsartikel (refereegranskat)abstract
- Individual users and enterprises are increasingly relying on the access to internet services and cannot accept long interruption time as easily as before. Moreover, the main characteristics of next generation optical access (NGOA) networks, such as long reach and a large number of users per feeder line, turn the network reliability to an important design parameter to offer uninterrupted service delivery. In this regard, protection mechanisms become one of the crucial aspects that need to be considered in the design process of access networks. On the other hand, it should be noted that not all users can afford to pay a high extra cost for protection; hence, it is important to provide resilience in a cost-efficient way. A PON combining WDM and TDM technologies, referred to as hybrid WDM/TDM PON or HPON, is one of the most promising candidates for NGOA networks due to its ability to serve a large number of subscribers and offer high capacity per user. For these reasons, in this article, we propose HPON architecture offering different degrees of resilience depending on the user profiles (i.e., partial and full protection for residential and business access, respectively). Also, the investment cost of providing resilience for the proposed schemes is investigated considering various protection upgrade road maps. Our results confirm that protecting the shared part of network with a large number of users is required in order to keep the failure impact at an acceptable level, with less than 5 percent increase of investment cost compared to the unprotected case. Meanwhile, the proposed end-to-end protection for business users considerably reduces the risk of service interruption for this type of demanding user without a need to duplicate the deployment cost of an unprotected connection. Furthermore, a sensitivity analysis is performed to investigate the impact of changes in business user percentage and protection upgrade time on the deployment cost. The results may be used as advice on cost-efficient deployment of reliable fiber access networks.
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| 497898. |
- Mahltig, Boris, et al.
(författare)
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Hydroxyl functional polyester dendrimers as stabilizing agent for preparation of colloidal silver particles-a study in respect to antimicrobial properties and toxicity against human cells
- 2012
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Ingår i: Colloid and Polymer Science. - : Springer Science and Business Media LLC. - 0303-402X .- 1435-1536. ; 290:14, s. 1413-1421
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Tidskriftsartikel (refereegranskat)abstract
- The presented study concerns the preparation and investigation of silver particles in presence of hydroxylated polyester dendrimers used as stabilizing agent. Altogether a full series of water soluble and aliphatic bis-MPA dendrimers from first to fifth generation was used as to stabilize silver nanoparticles in situ. A special focus is set on the biological properties. The antibacterial properties of the dendrimer stabilized silver particles are tested against Escherichia coli and the toxicity against human cells is tested with the human epithelial cell line A549. Under the chosen testing arrangement, it was observed that the silver particles contain a significant antibacterial effect against E. coli. Silver particles stabilized in situ with dendrimers of higher generation seem to contain a stronger antibacterial property. No toxicity against human cells was observed for the silver particles even in case of the highest investigated silver concentration. Altogether the here prepared and investigated silver particles could offer a great potential for application as antibacterial agent with low human toxicity.
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| 497899. |
- Mahmmoud Sayed, Abd El-sadek, et al.
(författare)
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CdTe@Cu(OH)(2) nanocomposite: Aqueous synthesis and characterization
- 2011
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 184:5, s. 1135-1140
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Tidskriftsartikel (refereegranskat)abstract
- CdTe@Cu(OH)(2) nanocomposites were synthesized in aqueous solution by a seed-mediated growth approach. The effect of refluxing time and the concentration of Cu2+ on the preparation of these samples were measured using UV-visible absorption and photoluminescence analysis. The emission peak of the synthesized nanocomposites (CdTe@Cu(OH)(2)) was shifted from 605 (CdTe seed) to 621 nm. The size of CdTe nanoparticles were averaged about 3.22 nm, and the CdTe@Cu(OH)(2) nanocomposites were averaged as 5.19 nm. The synthesized CdTe@Cu(OH)(2) nanocomposite were characterized with XRD, EDAX, TEM, FT-IR, EPR, and thermal analysis (TG/DTG curves). The results indicate that as-prepared nanoparticles with core/shell structure exhibit interesting optical properties. (C) 2011 Elsevier Inc. All rights reserved.
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| 497900. |
- Mahmmoud Sayed, Abd El-sadek, et al.
(författare)
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Electronic transport mechanism of CdTe nanocrystalline
- 2011
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584. ; 130:1-2, s. 591-597
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Tidskriftsartikel (refereegranskat)abstract
- CdTe nanocrystalline powder was synthesized by chemical process. The structure of CdTe nanocrystalline was investigated by means of X-ray diffraction (XRD) technique, energy-dispersive X-ray analysis (EDAX) spectrum and transmission electron microscopy (TEM). The selected area electron diffraction (SAED) study confirms the crystallinity of the CdTe nanocrystalline. Some structural parameters such as the mean crystallite size, the dislocation density and the strain were calculated. The temperature dependence of the dc and ac conductivity was measured in the temperature range 293-423 K. It was found that the dc conductivity is thermally activated type. Values of dc activation energy and the pre-exponential were determined. The ac conductivity was found to increase with increasing both the temperature and frequency and follows the power low. The frequency exponent s was found to decrease with increasing temperature. The correlated barrier hopping (CBH) model was found to be applying to the ac conductivity data. The maximum barrier height W(m) and the density of localized states N(E(F)) were calculated and equal to 0.47 eV and 8.82 x 10(22) to 1.43 x10(23) eV(-1) cm(-3), respectively. CdTe nanomaterial is a good candidate for semiconductor devices due to its high conductivity. (C) 2011 Elsevier B.V. All rights reserved.
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