| 18311. |
- Nurhussen, Filli
(författare)
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Experimental studies on mouse slow and fast twitch muscles
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with physiological and mechanical properties of fast and slow twitch mouse muscles. It discusses isometric, concentric and eccentric contractions of mouse extensor digitorum longus ('EDL') and soleus ('SOL') muscles. This project primarily investigated the behaviors of muscles, to give better understanding and improved descriptions for the human system, when subjected to impact or sustained high loading conditions. Muscle force has been shown to be length and activation dependent. The effect of passive or active length changes on muscle force production was studied. Isometric activation showed a maximal force at optimum length for each individual muscle, to which all experiments were related. This optimum length was stimulation frequency dependent and maximum produced force shifted towards shorter length with increasing frequency. Active shortening of maximally stimulated muscle was shown to produce reduced force, but also a reduced isometric force (force depression) following shortening, regardless of the shortening conditions and the method of muscle stimulation. Steady state force depression (ΔFstdep) was correlated with the instant force depression ΔFidep, pre-activation time, t0-t1 and the work (WS), performed by the muscle during shortening. It was positively correlated with the ΔFidep when the shortening magnitude was varied ('VSM'). But in varying the shortening velocity ('VST'), it was negatively correlated with the instant force depression. In active stretch, force was analogously enhanced during stretch, and this effect remained after stretch. Steady state force enhancement (ΔFstenh)following muscle stretch was correlated with the instant force enhancement,ΔFienh, pre-activation time, t0-t1 and the work (WL), done on the muscle during stretch. It was positively correlated with ΔFienh when the stretch magnitude was varied ('VLM'). But in varying the stretch velocity ('VLT'), ΔFstenh was negatively correlated with ΔFienh. Furthermore, the rise time constant, (Tr) of redeveloped isometric forces following the shortening and the fall time constant, (Tf) of the relaxed isometric force following muscle stretch were calculated. In VSM, Tr and Fstdep were positively correlated with each other, while in VST, they were negatively correlated. Tf and Fstenh were negatively correlated in both VLM and VLT.
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| 18312. |
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| 18313. |
- Nussbaum, Ralph
(författare)
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Surface interactions of wood with adhesives and coatings
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The theme of this thesis is the properties of wood surfaces,and particularly some important aspects of their interactionswith adhesives and coatings.The surface inactivation of wood due to the development ofchemical weak boundary layers was monitored by wettabilitystudies based on contact angle measurements. The timedependence of the formation of such weak boundary layers wasdetermined for Scots pine and Norway spruce. To evaluate thewettability data, aconstant wetting rate angle(cwra), representing thesituation when a liquid droplet spreads on the surface at aconstant rate, was determin-ed. For planed surfaces there wastypically a linear reduction in wettability during a week aftermachining, whereas sawn surfaces exhibited a time-lag of a fewdays before the wettability started to decrease. A comparisonof surface wettability data with quantitative and qualitativeanalytical determinations of lipophilic wood extractivesrevealed a rather complex picture, the wetting behaviour beingdependent on the storage time after the machining of thesurface. The time-dependent surface inactivation data presentedin the thesis can be used to assess performance requirementsfor optimum adhesion in industrial coating and gluingpro-cesses.In order to improve the adhesion properties of inactivatedwood surfaces, an oxidative activation technique based on flametreatment was employed. A substantial increase in surfacewettability was obtained by optimizing parameters such asspeed, flame burner output, distance between wood surface andflame burner, and the number of passes under the burner. Ahigher treatment level was needed for teak, having a highcontent of lipophilic extractives, than for species with alower content (pine and birch). The oxidative effect wasconfirmed by ESCA measurements. In addition to improvedwettability, flame treatment also resulted in a considerablesurface sterilization effect.The relation between glue adhesion properties and woodextractives content was evaluated by a standard shear strengthtest and a non-standard fracture test on pine heartwoodmaterial classified according to its content of lipophilicextractives. For specimens assembled with a water-resistantpolyvinyl acetate adhesive, glue adhesion properties were tosome extent negatively affected by the existence of resinousweak boundary layers. Failure was more like-ly to occur at highwood extractive contents, roughly above 7%.The ability of coating materials to penetrate a wood surfaceand facilitate mechanical interlocking has been evaluated forvarious wood primers. Penetration was mainly demonstrated bymicroautoradiography, a technique superior to most othermethods for studying how monomeric and polymeric substancesinteract with the wood cell structure. Coating viscosity had amajor effect on the penetration, which in the radial directionnormally varied between 0.1 and 0.5 mm into longitudinaltracheids of pine sapwood. Penetration into spruce was at asignificantly lower level. It was further established thatsolvent-borne alkyd primers and water-borne alkyd emulsionprimers of comparable viscosities had a similar ability topenetrate the wood.Keywords:adhesion, adhesives, alkyd, autoradiography,coatings, contact angles, extractives, flame treatment,fracture test, glue bond strength, inactivation, interaction,penetration, pine, spruce, surface activation, weak boundarylayer, wettability, wood
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| 18314. |
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| 18315. |
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| 18316. |
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| 18317. |
- Nutakki, Tirumala Uday Kumar
(författare)
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Integration of Membrane Distillation and Solar Thermal Systems for Coproduction of Purified Water and Heat
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the Middle East and North Africa region fresh water resources are very scarce and theexisting sources are depleting rapidly. Desalination is the method to fulfill increasing waterdemand, and people depend mostly upon bottled water for drinking purposes. Bottledwater is resource and energy demanding, hence there is a need for supplying drinkablewater in a sustainable way. The main objective of this research is to develop solutions forproviding potable water to urban communities through integrating membrane distillationwater purification units with solar driven hot water installations. A single-cassette Air GapMembrane Distillation (AGMD) unit was tested on laboratory scale to investigate theinfluence of various operating parameters on the distillate production. Particular attentionwas given for identifying process conditions relevant to the design of solar energyintegrated systems. In parallel, a simplified empirical model using response surfacemethods was developed and validated against bench scale experimental results. Thedeveloped model for performance indicators was later employed in dynamic simulations ofa solar thermal integrated membrane distillation system. A pilot plant was designed andinstalled at RAK Research and Innovation Center in UAE. Experimental investigations wereconducted on this integrated system for co-production of pure water (around 15-25 l/day)along with hot water production equivalent to the needs of a family of five. A dynamicsimulation model was developed in TRNSYS to analyze optimum operating conditions ofthe system. Economic analysis showed an impressive payback period and savings for theintegrated system as compared with standalone counterparts. A second pilot facility using alarger multi-cassette AGMD module and absorption cooler was designed and installed.Performance of this solar co-production system for heat, cooling, and pure water is analyzedfor various integration modes.
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| 18318. |
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| 18319. |
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| 18320. |
- Nuur, Cali
(författare)
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Att forska om periferin i periferin- en personlig odyssey
- 2007
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Ingår i: Samtal och samhandling- erfarenheter från FOU-Centrum i Söderhamn interaktiv forskning i praktiken. - Söderhamn : Söderhams förlag. - 9789185085033
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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