579 research outputs found

    Starch-Polycaprolactone Nanocomposites From Reactive Extrusion: Synthesis, Characterization, Properties And Scale-up Considerations

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    Biodegradable starch-polyester polymer composites are useful in many applications ranging from numerous packaging end-uses to tissue engineering. However the amount of starch that can form composites with polyesters without significant property deterioration is typically less than 25% because of thermodynamic incompatibility between the two polymers. A reactive extrusion process was developed in which approximately 60% by weight of plasticized starch was blended with a biodegradable polyester (polycaprolactone, PCL) resulting in tough nanocomposite blends with elongational properties approaching that of 100% PCL. During the extrusion process, starch was cross-linked with polycaprolactone in the presence of hydrogen peroxide and montmorillonite (MMT) organoclay, thus compatibilizing the two polymers. The objectives of this study were to evaluate the mechanical properties of reactively extruded starch-PCL nanocomposite blends, study changes in the morphology of polymer-polymer interface, monitor dispersion of organoclay in the polymer matrix, quantify the effects of reactive extrusion on polymer glass transition, develop a rheological model and scale up the reactive extrusion process from a batch type micro-extruder to continuous twin-screw extruder. Starch and PCL (36-39 wt% each), glycerol (18-19 wt%), MMT organoclay (3-9 wt%), hydrogen peroxide (0.067 ml/g starch) and ferrous sulfate catalyst (0.0025 g/g starch) were extruded in a co-rotating twin-screw extruder at 120 C and injection molded at 150 C. Elongational properties of reactively extruded starch-PCL nanocomposite blends approached that of 100% PCL at 3 and 6 wt% organoclay. Strength and modulus remained the same as starch-PCL composites prepared from simple physical mixing (non-reactive extrusion). X-ray diffraction results showed mainly intercalated flocculated behavior of clay at 3, 6, and 9 wt% organoclay. Scanning electron microscopy (SEM) showed that there was improved starch-PCL interfacial adhesion in reactively extruded blends than in non-reactive starch-PCL composites. Dynamic mechanical analysis showed changes in primary alpha- transition temperatures for both the starch and PCL fractions, reflecting cross-linking changes in the nanocomposite blends at different organoclay content. Starch-PCL reactive blends were more pseudoplastic than 100% PCL and showed typical shear-thinning behavior and lower shear viscosities than non-reactive starch-PCL composites. Results from scale-up studies indicated that screw configuration, screw speed and feed rates were important process variables that affected material properties. These were optimized to obtain mechanical properties equivalent to those from the micro-extruder.USDA-National Research Initiativ

    Changing Trends in Telecommunications Industry

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    The mobile telecommunication industry is one of the fastest growing and continually changing markets in the world today. The greatest achievement of wireless technology is that it has made communications possible in the most remote of places at a much lower cost and at a much lesser time to deploy. The US market is largely considered an early adopter market in the wireless technology domain. A wide variety of products are designed in US and the service providers have the opportunity of bringing these devices first to customers locally. On the voice side the US market is seen as a fairly stable and saturated market. With the sudden proliferation of data services and aligned equipment, new markets in the same geography have opened up and have created a huge opportunity to restructure the way wireless services are sold to customers. The US model has traditionally been a model where the service provider sells the equipments needed for the service on a contract basis. There are some obvious advantages and some disadvantages with this model. Businesses may assume they are using the right method to deliver services to attract and retain their customers, but in reality they may miss the part of understanding the user needs. The industries involved in this study include the wireless service provider industry, the equipment manufacture industry and the wireless chipset industry. Through this study it was found that customers are happy to stay with the current model of buying services on a monthly plan from their service provider but are not happy with the contract they need to sign during activation. It was also found that there is a need to look more closely at the current wireless service provider and handset manufacturer relationship and in some cases decouple the closed structure it is in place today. The consumers want more freedom in terms of the devices and services they want to buy. The wireless chipset manufacturers have not much of a change in role they play today. They would work almost the same way they function today to deliver the state-of-the-art chipsets that go into handsets irrespective of the changes in the relationship between the service provider and equipment manufacturer. That said they need to closely understand the changing dynamics in the product portfolio and create systems with multiple technologies that would work more seamless together. This project has helped understand various aspects of the mobile telecommunications market better from a consumer perspective

    Going Deeper with Semantics: Video Activity Interpretation using Semantic Contextualization

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    A deeper understanding of video activities extends beyond recognition of underlying concepts such as actions and objects: constructing deep semantic representations requires reasoning about the semantic relationships among these concepts, often beyond what is directly observed in the data. To this end, we propose an energy minimization framework that leverages large-scale commonsense knowledge bases, such as ConceptNet, to provide contextual cues to establish semantic relationships among entities directly hypothesized from video signal. We mathematically express this using the language of Grenander's canonical pattern generator theory. We show that the use of prior encoded commonsense knowledge alleviate the need for large annotated training datasets and help tackle imbalance in training through prior knowledge. Using three different publicly available datasets - Charades, Microsoft Visual Description Corpus and Breakfast Actions datasets, we show that the proposed model can generate video interpretations whose quality is better than those reported by state-of-the-art approaches, which have substantial training needs. Through extensive experiments, we show that the use of commonsense knowledge from ConceptNet allows the proposed approach to handle various challenges such as training data imbalance, weak features, and complex semantic relationships and visual scenes.Comment: Accepted to WACV 201

    Digital microfluidics for drug metabolism research in droplet-scale

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    Drug metabolism is a detoxification process by which the body converts pharmaceuticals into more hydrophilic metabolites. Understanding of the drug metabolism process and metabolic profiling plays a vital role in drug development processes by ensuring the safety and efficacy of treatments. Cytochromes P450 (CYP) are a superfamily of enzymes that are primarily responsible for metabolizing the majority of clinically relevant drugs. In preclinical drug development research, there is a constant need for the identification of metabolites and their CYP isoenzyme-specific elimination route, as well as possible drug-drug interactions thereof using high speed in vitro techniques. Miniaturization of the drug metabolism assays and related processes could further improve the throughput via parallelism and integration of several analytical steps on a single platform, as well as reducing the consumption of expensive reagents substantially. Micro total analysis systems (µTAS) usually refer to microfabricated devices that integrate several analytical unit operations, such as sample preparation, extraction, separation, and analysis on a single platform. These µTAS platforms can be either continuous-flow microchannel based systems or discrete droplet systems. Digital microfluidics (DMF) is one such technology, where sample droplets are manipulated individually on an array of electrodes. In DMF, the droplets of hundreds of nanolitres to a few microliters of volume can be dispensed, split, mixed, and merged independently via programmed and automated voltage application. In this thesis, several DMF-based bioanalytical concepts were developed and their feasibility for implementing droplet-scale drug metabolism assays was evaluated. In the first sub-project, droplet-scale immobilized enzyme reactors were developed by immobilizing CYP enzymes on porous polymer monoliths affixed onto a DMF platform. Assay incubation at physiological temperature was facilitated by localized heating of the DMF platform using integrated inkjet-printed microheaters. For the on-chip detection of drug metabolites, a protocol facilitating interfacing of the DMF device with a commercial wellplate reader was developed. In the second sub-project, the developed DMF platform, featuring the CYP reactors, were interfaced with ambient mass spectrometry (MS) via desorption atmospheric pressure photoionization (DAPPI). For in situ identification of the drug metabolites by DAPPI-MS, the chip design was optimized to be able to control the critical surface sensitive processes, such as sample precipitation and subsequent desorption/ionization directly from DMF surfaces. In addition, the feasibility of the same platform for a droplet-based liquid-liquid extraction of pharmaceuticals was demonstrated. All pharmaceuticals and metabolites analyzed could be detected with lower limits of detection in the range of a few picomoles. In the third sub-project, DMF droplet manipulation was interfaced with channel microfluidics to facilitate more versatile sample preparation such as separation of target analytes after the droplet-based enzyme reactions and prior to detection. To support the scaling up of the developed technology toward mass manufacturing, the entire device was assembled using low-cost inkjet printing and non-cleanroom polymer processing techniques. To achieve this interfacing, off-stoichiometric thiol-ene (OSTE) polymers were introduced as a new alternative dielectric material for the coating of inkjet-printed DMF electrode arrays, as well as for the integration of the microchannels with a DMF platform. In the fourth sub-project, magnetic bead based enzyme immobilization protocol was developed to facilitate screening the individual variation of CYP activities in donor-derived human liver microsomes (HLM) in droplet-scale. A CYP1A isoenzyme-specific model reaction was chosen to assess the inter-individual variation in the activities of this metabolic route in the liver microsomes collected from five individuals. The demonstrated protocol was shown to be technically feasible for biopsy-scale samples. In all, the new droplet-scale concepts developed in this thesis are first-in-their-kind examples of droplet-scale drug metabolism assays on DMF platform. The methods developed are generally qualitative or semi-quantitative and thus, in their present form, best feasible for the preliminary determination of metabolic clearance via CYP or identification of the produced metabolites of new drug candidates in vitro. Further development of the technology, particularly the enzyme immobilization process and the quantification of the produced metabolites, is needed to improve the wider applicability of the assays. It is noteworthy however that all of the fabrication processes and interfacing approaches taken in this thesis were carried out in regular, non-cleanroom laboratory conditions, which is foreseen to significantly improve the adaptability of the technology in any bioanalytical laboratories.Lääkeainemetabolia on elimistön suojamekanismi, joka muuntaa yleensä hyvin rasvaliukoiset lääkeaineet entsymaattisesti vesiliukoisemmiksi metaboliiteiksi. Lääkeainemetabolialla on siksi keskeinen rooli lääkkeenkehityksessä lääkehoidon tehon ja turvallisuuden varmistamiseksi. Valtaosa kliinisessä käytössä olevista lääkeaineista metaboloituu sytokromi P450 (CYP) –entsyymien kautta. Yksi prekliinisen lääkekehityksen tärkeimpiä tehtäviä on tunnistaa lääkeaineiden metaboliitit ja niiden CYP-isoentsyymikohtaiset eliminaatioreitit sekä ennakoida mahdollisia lääkkeiden haitallisia yhteisvaikutuksia nopeiden in vitro –tekniikoiden avulla. Lääkeainemetaboliatutkimuksessa käytettävien menetelmien miniatyrisointi mahdollistaa paralleelien ja toisiinsa integroitujen analyysiyksiköiden valmistamisen, mikä tehostaa lääkkeiden seulontaa sekä vähentäisi kalliiden reagenssien kulutusta. TAS-konsepti (engl. Micro total analysis systems) viittaa mikrovalmistusmenetelmillä tuotettuihin analyysilaitteisiin, joissa samalle alustalle on integroitu useita analyyttisiä yksikköoperaatioita kuten näytteenkäsittely, uutto, erotus ja havainnointi. µTAS-laitteet voivat olla esimerkiksi mikrokanavia sisältäviä jatkuvan virtauksen laitteita tai yksittäisten pisaroiden liikuttelun mahdollistavia laitteita. Digitaalimikrofluidistiikka (engl. digital microfluidics, DMF) on eräs tekniikka, joka mahdollistaa pisaroiden kontrolloidun käsittelyn sähköelektrodien päällä. DMF:ssa pisarat ovat tilavuudeltaan satoja nanolitroja – muutama mikrolitra ja niitä voidaan syöttää, jakaa, sekoittaa ja yhdistää yksitellen käyttäen ohjelmoitavaa ja automaattista jännitteen syöttöä. Tässä väitöskirjassa kehitettiin useita DMF:aan perustuvia bioanalyyttisia sovelluksia tavoitteena selvittää DMF-teknologian soveltuvuutta lääkeainemetaboliatutkimukseen pisaramittakaavassa. Ensimmäisessä osajulkaisussa kehitettiin pisarakokoluokan entsyymireaktori kiinnittämällä CYP-entsyymejä huokoiseen polymeerimonoliittiin, joka oli kiinnitetty DMF-alustaan. Entsyymireaktorin lämmittämiseksi fysiologiseen lämpötilaan kehitettiin mustesuihkutulostettu lämmitinelementti, joka kiinnitettiin DMF-alustaan. Metaboliittien havainnoimiseksi kehitettiin menetelmä, joka mahdollisti DMF-mikrosirun yhdistämisen kaupalliseen kuoppalevylukijaan. Toisessa osajulkaisussa DMF-pohjaisia CYP-entsyymireaktorit liitettiin massaspektrometriaan hyödyntämällä desorptio/fotoionisaatiota ilmanpaineessa (engl. desoprtion atmospheric pressure photoionization, DAPPI). Jotta lääkeainemetaboliitit voitiin tunnistaa massaspektrometrisesti suoraan DMF-alustalta, mikrosiru optimoitiin siten, että näytteen haihtumista ja desoprtio/ionisaatio-prosessia pystyttiin kontrolloimaan pinnan ominaisuuksien avulla. Kehitetyn DMF-alustan soveltuvuus osoitettiin myös lääkeaineiden pisarapohjaisessa neste-neste-uutossa. Kaikkien lääkeaineiden ja metaboliittien havaintoalarajat olivat pikomolaarisella tasolla. Kolmannessa osajulkaisussa pisaroiden käsittelyyn kehitetty DMF-alusta yhdistettiin mikrokanavarakenteisiin, mikä mahdollistaa monipuolisemman näytteenkäsittelyn kuten reaktiotuotteiden erotuksen ennen havainnointia. Tässä osajulkaisussa käytettiin edullisia, massatuotantoon skaalautuvia valmistusmenetelmiä, kuten mustesuihkutulostusta ja polymeeriprosessointia. DMF-alustan ja mikrokanavien yhdistämiseksi osajulkaisussa tutkittiin uuden, epästoikiometrisen tioleenipolymeerin soveltuvuutta DMF-teknologiaan sekä dielektrisenä kerroksena että mikrokanavien valmistusmateriaalina. Neljännessä osajulkaisussa kehitettiin magneettipartikkelipohjainen entsyymi-immobilisointimenetelmä, joka mahdollisti luovuttajakohtaisten maksamikrosomien käytön pisarakokoluokan CYP-aktiivisuusmäärityksissä. DMF-alustan soveltuvuutta yksilöllisten erojen selvittämiseen tutkittiin CYP1A-entsyymille spesifisen mallireaktion avulla viiden eri luovuttajan maksamikrosomeilla. Menetelmän todettiin teknisten ominaisuuksiensa puolesta soveltuvan CYP-aktiivisuuden määrittämiseen jopa biopsianäytteistä. Kokonaisuudessaan tässä väitöskirjassa kehitetyt pisarapohjaiset, bioanalyyttiset menetelmät ovat ensimmäisiä DMF-teknologian sovelluksia lääkeainemetaboliatutkimuksessa. Kaikki kehitetyt menetelmät ovat joko kvalitatiivisia tai semikvantatiivisia ja soveltuvat siten nykyisessä muodossaan lähinnä alustaviin lääkeaineen metaboliareittiä selvittäviin tutkimuksiin tai uusien lääkeainekandidaattien metaboliittien nopeaan tunnistamiseen in vitro. Tekniikan jatkokehitys, erityisesti entsyymien immobilisoinnin sekä metaboliittien kvantitoinnin osalta, on kuitenkin tarpeellista menetelmien laajemman käytettävyyden parantamiseksi. Huomionarvoista kuitenkin on, että kaikki tässä työssä käytetyt valmistusmenetelmät soveltuvat normaaleihin laboratorio-olosuhteisiin, myös puhdastilojen ulkopuolelle, mikä mahdollistaa kehitettyjen tekniikoiden soveltamisen missä tahansa bioanalytiikan laboratoriossa

    Efficient broadcasting by selective forwarDing

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    A major challenge faced in MANETs is locating the devices for communication, especially with high node mobility and sparse node density. Present solutions provided by the ad hoc routing protocols range from flooding [1] the entire network with route requests, to deploying a separate location management scheme to maintain a device location database. Many applications as well as various unicast routing protocols such as Dynamic Source Routing (DSR), Ad Hoc On Demand Distance Vector (AODV), Zone Routing Protocol (ZRP), and Location Aided Routing (LAR) use broadcasting or a derivation of it. Flooding, which is often deployed to achieve the above objective, is expensive in terms of overhead and wastes valuable resources such as bandwidth and power. We propose to develop a strategy to reduce the redundant transmission of packets in normal flooding used in broadcasting, and we describe strategies for choosing only an optimal set of nodes for rebroadcast in a grid network. The main contribution is to reduce the redundant transmission of packets and to forward packets with minimum transmissions. To determine the minimal set of nodes for efficient transmission, we propose a new algorithm, Efficient Broadcasting by Selective Forwarding, using a distance-based approach; The distance-based approach [2] is implemented for broadcast and rebroadcast to a set of nodes with the help of a threshold value [3] that is taken to be threshold = n* transmission-radius, where n is a real number. This reduces the number of redundant transmission. This threshold value can be tuned to show performance enhancement

    Security Enhanced Location-aided Level-based Disjoint Multipath Routing Algorithm for Mobile Ad Hoc Networks

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    In mobile ad hoc networks (MANET), the location-based multipath routing protocols involves less routing overhead compared to non-location-based protocols. This paper proposes two location-based algorithms, Enhanced Location-aided Level-based node Disjoint Multipath routing (ELLDMR) and Secure Location-aided Level-based node Disjoint Multipath routing (SLLDMR), to enhance the link lifetime and the security of the MANET. The objective of ELLDMR is to build multiple paths with non-critical nodes so that the lifetime of the routing path is significantly increased. It also hides the source, destination and path identity in intermediate nodes to avoid intrusion of routing attacks in the routing path. The SLLDMR is an enhancement over ELLDMR where it aims to overcome rushing attack and exhibit secure data transmission using two-level cryptographic processes. The performances of ELLDMR and SLLDMR are simulated using NS2 where it shows a minimum routing overhead, less end to end delay and high packet delivery compared to existing Location-aided Level-based node Disjoint Multipath routing (LLDMR) algorithm and Topology Hiding multipath protocol (TOHIP)
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