214 research outputs found
IT and telecom companies in Kista Science City, Northern Stockholm
No full textThe Kista area north of Stockholm is a symbol of Sweden’s IT and telecom sector, which has great importance for the economy and working life. The report gives a current, empirically founded description of the IT sector in Kista (including the districts Akalla and Husby), which to a high extent previously has not been available. What do the establishments in Kista look like and what are the relations between them? The management of one hundred IT and telecom establishments in Kista with up to 200 employees have answered a substantial number of survey questions about their activities, their staff and about Kista. The report is descriptive and includes a short description of Kista’s history from the ideas of a city with an integration of work, housing and services until today’s Kista Science City, the year of establishment, number and size of the IT establishments in Kista and their activities. Some results in brief are: • Most of the companies have developed during the last five to ten years. • They are to a very high degree focused on IT and telecom. The most common activity is consulting followed by production of software, R&D and commerce. • More than half of the establishments have an exchange of experiences with other companies in Kista, and almost half of them are involved in strategic cooperation within e.g. development, production and marketing. • Quite a few outsource IT activities to other companies and work as subcontractors to them, but only a limited part of the contracts are with companies in Kista. The networks are regional and international rather than local. • About a quarter cooperate with interactive media companies in Stockholm. • The managements are throughout satisfied with Kista. On all the five factors they see as most important for their operations, Kista comes out well: communications, telecom, premises, competent staff and customers. Kista also comes out well on the criterion proximity to university; although few regard this as important, which is discussed in the report. • One fifth of the employees are women and the top manager is a woman in less then ten per cent of the establishments. • The average age of employees is 38 years. • The staff is well educated, almost 70 percent have three years university education or more. Still, managements view learning on the establishment as the most important source of skills. Perhaps university education is taken for granted.
Iso-acoustic focusing of cells for size-insensitive acousto-mechanical phenotyping
No full textMechanical phenotyping of single cells is an emerging tool for cell classification, enabling assessment of effective parameters relating to cells’ interior molecular content and structure. Here, we present iso-acoustic focusing, an equilibrium method to analyze the effective acoustic impedance of single cells in continuous flow. While flowing through a microchannel, cells migrate sideways, influenced by an acoustic field, into streams of increasing acoustic impedance, until reaching their cell-type specific point of zero acoustic contrast. We establish an experimental procedure and provide theoretical justifications and models for iso-acoustic focusing. We describe a method for providing a suitable acoustic contrast gradient in a cell-friendly medium, and use acoustic forces to maintain that gradient in the presence of destabilizing forces. Applying this method we demonstrate iso-acoustic focusing of cell lines and leukocytes, showing that acoustic properties provide phenotypic information independent of size.Swedish Research Council (Grant 2012-6708)Royal Physiographic SocietyHertz Foundatio
Harmonic microchip acoustophoresis: a route to online raw milk sample precondition in protein and lipid content quality control
No full textA microfluidic approach for raw milk sample preconditioning prior to protein and lipid content analysis has been developed. The system utilizes microchip acoustophoresis and is a further extension of our previously reported multiple node ultrasonic standing wave focusing platform ( Grenvall , C. , Augustsson , P. , Matsuoka , H. and Laurell , T. Proc. Micro Total Anal. Syst. 2008 , 1, 161-163 ). The microfluidic approach offers a method for rapid raw milk quality control using Fourier transform infrared spectroscopy (FT-IR). Two acoustophoresis modes are explored, 2 lambda/2 and 3 lambda/2, offering lipid content enrichment or depletion, respectively. Lipid content depletion above 90% was accomplished. FT-IR data on microchip-processed raw milk samples, enabling direct lipid and protein content analysis, are reported. Most importantly, the harmonic operational modes bypass the problem of lipid aggregation and subsequent clogging, inherent in lambda/2 acoustophoresis systems
On enchytraeids and naidids: Life history traits and responses to environmental stress
No full textPopular Abstract in Swedish Enchytraeider och naidider, och deras reaktioner på miljöbetingad stress. Syftet med denna avhandling var att studera naidider och enchytraeider. Tonvikten är lagd på deras fortplantningsbeteende och hur de påverkas av miljöbetingad stress. Maskarna utsattes för stress i form av varierande kvalitet på födan, torka, och giftiga ämnen. Enchytraeider och naidider är båda ringmaskar tillhörande släktet Oligochaeta. Den mest kända medlemmen i detta släkte är vår vanliga daggmask. Enchytraeider är vanliga i de flesta jordar och återfinns i tätheter av 30 000 till 60 000 individer per m2. De är små, ungefär en cm långa och vita. De är särskilt vanliga i sura jordar som t.ex. i skandinavisk granskogsjord. Precis som daggmaskar är enchytraeider viktiga organismer för att bibehålla en frisk jord. De är aktiva i näringskedjan i marken genom att de bryter ner organiskt material och på så sätt återbördar näringsämnen till jorden som växterna sedan kan tillgodogöra sig. Naidider hittar man vanligen i sjöar och vattendrag. Under senare år har man funnit marklevande naidider i Amazonas regnskog. Där har man tidigare funnit dem i skogar som översvämmas upp till sex månader varje år. Deras roll i näringskedjan i marken har man ännu inte studerat, men i de översvämmade skogarna anses de ha en viktig betydelse för nedbrytningen av organiskt material. De flesta markorganismer befinner sig i jordens översta 20 cm vilket medför att de är mycket utsatta för föroreningar. När markdjuren påverkas negativt störs jordens funktion. I en illa fungerande jord hämmas nedbrytningsprocesserna och näringskretsloppet, vilket leder till en utarmning av jorden. Föroreningarna kan också påverka djur högre upp i näringskedjan som har markdjur föda, såsom fåglar, mullvadar och grävlingar. För att övervaka förändringar i markkvalitet behövs tester där man kan slå fast hur markdjuren påverkas av föroreningar. För sådana tester kan enchytraeider och naidider lämpa sig utmärkt. Enchytraeider och naidider är hermafroditer dvs tvåkönade. De kan fortplanta sig både sexuellt och asexuellt. Asexuell fortplantning kan ske medelst jungfrufödsel (partenogenes), eller genom att maskarna delar på sig i två till flera fragment. Hos naididerna sker en avknoppning av ”zooider” (små ofullständigt utvecklade maskar) från maskens bakre del. Markmiljön är vanligen mycket heterogen beroende på faktorer såsom jordens vattenhalt, pH och hur mycket organiskt material jorden innehåller. Följaktligen är områden med goda livsbetingelser för en markorganism oftast fläckvis utspridda. I en så varierande miljö kan det vara en fördel att fortplanta sig asexuellt, eftersom det då bara behövs en individ för att starta en population. Fördelarna med asexuell fortplantning visade jag i ett experiment där enchytraeider och naidider koloniserade påsar fyllda med löv. De asexuella naididerna nådde snabbt höga tätheter, upp till 2000 maskar per påse, jämfört med enchytraeiderna som aldrig blev fler än 78 individer per påse. När maskarna utsattes för stress var en vanlig reaktion hos dem att de slutade fortplanta sig. Naididerna reagerade på låg fuktighet i substratet (en lövblandning) med att sluta fortplanta sig. Den låga fuktigheten orsakade också att få maskar överlevde. För att observera hur naididerna reagerar på varierande födotillgång tillsatte jag en sockerlösning till lövblandningen de levde i. Sockret stimulerar tillväxten av mikroorganismer, dvs svampar och bakterier. Svamparna och bakterierna antas i sin tur utgöra föda åt naididerna. Jag jämförde hur antalet naidider ökade med tiden i lövblandningen med socker, med hur de tillväxte i en lövblandning utan sockertillsats. I början ökade antalet lika mycket i båda behandlingarna men efter 12 dagar minskade de i antal i lövblandningen utan socker, medan de fortsatte att öka i antal i lövblandningen med socker. Jag gjorde mätningar som visade att mängden mikroorganismer vid denna tidpunkten var lika stor i båda lövblandningarna. Minskningen kunde alltså inte direkt relateras till minskad mängd föda. En möjlig förklaring är att maskarna också gynnades av sockerlösningen och lagrade energi som de använde när näringen började ta slut. Därför kunde de fortsätta att tillväxa i antal i lövblandningen med sockertillsats. Enchytraeider som utsattes för stress i jorden i form av metallerna koppar och zink producerade färre nya maskar när metallhalterna i jorden ökade. De växte också mindre. Vid höga metallhalter varken växte de eller fortplantade de sig. Vid ännu högre metallhalter var dödligheten hög. När de gavs möjlighet så undvek de den metallförorende jorden. I jordbruket är användningen av olika gifter för att bekämpa ohyra och sjukdomar snarare regel än undantag. Jag studerade hur enchytraeiderna påverkades av ett medel mot svampinfektion på säd (stråknäckarsjuka), både i ett laboratorieförsök och i ett fältförsök. I laboratorieförsöket påverkades maskarna av höga doser av gifter (7x den mängd man normalt sprider på åkrarna) med minskad fortplantning. I fältförsöket hämtade jag hem jordprover som jag sprutade med gift och sedan satte ut i fält igen. Efter tre veckor fann jag färre enchytraeider i jordprover med de giftmängder som normalt sprids på åkrarna. Eftersom tiden i fält var för kort för att påverka fortplantningen är den troligaste orsaken till minskningen att maskarna har flytt från den jord de fann mindre tilltalande. Det finns få testsystem utvecklade för att testa föroreningar i jord. Det mest använda är ett test som baseras på överlevnad och fortplantning av kompostmasken Eisenia foetida. Denna daggmask förekommer tyvärr sällan naturligt i fält, vilket gör att effekter som mäts på laboratoriet kanske inte säger så mycket om vad som verkligen händer ute i naturen. I Sverige och i övriga länder på norra halvklotet finns mycket skog och sumpmark. Här hittar man överhuvudtaget sällan daggmask utan maskfaunan domineras av enchytraeider, särskilt arten Cognettia sphagnetorum. För att kunna testa effekter av föroreningar på markdjuren i dessa jordar har jag utvecklat ett test baserat på C. sphagnetorum. Detta test visar vad jag inlednigsvis nämnde, nämligen att man bland gruppen enchytraeider bör man kunna finna arter som är väl ägnade att användas i testsystem.My thesis shows that enchytraeids and naidids are sensitive to various forms of environmental stress, which in combination with the wide distribution of both families make them highly suitable for use in risk assessment and soil monitoring. Enchytraeids were subject to chemical stress under both laboratory and field conditions. In laboratory experiments enchytraeids reacted to chemical stress with decreased reproduction and growth. When given the possibility the enchytraeids avoided metal polluted soil. A standardized test based on the enchytraeid Cognettia sphagnetorum was developed to provide a method for monitoring the quality of forest, bog and pasture soils. Exposure of enchytraeids to a fungicide in the field resulted in reduced abundance of the indigenous enchytraeid fauna. The combined stress due to the fungicide and competition from added enchytraeid individuals increased the reduction further. To study possible impacts of forest management on litter fauna in a primary terra firme rain forest in the Amazonas, colonization of leaf litter by oligochaetes (Enchytraeidae, Naididae, Tubificidae) was studied in a litter bag experiment. Naidid worms were the most rapid colonizers and showed the highest reproductive output owing to asexual reproduction. To investigate what factor limits terrestrial naidid population dynamics in tropical soils, population growth of the naidid Pristinella jenkinae was studied in a laboratory experiment. Soil moisture and food abundance were the most important limiting factors
Thermal acoustic flow inside ultrasound resonants
No full textLAUREA MAGISTRALEIl lavoro di tesi qui presentato riguarda l’acustofluidica ed intende investigare l’interazione tra campi acustici e termici in chip microfluidici. Questa applicazione nasce dall’osservazione che inomogeneità nei fluidi sono in grado di influenzare il moto indotto dal suono in un canale micrometrico. È consolidato in letteratura l’uso di gradienti chimici per variare le proprietà termofisiche dei fluidi, così da alterarne densità e comprimibilità. Questo, a seconda delle diverse situazioni, può causare rilocazione o stabilizzazione di fluidi tramite la cosiddetta acoustic body force. Si vuole quindi osservare come questa forza agisca su un fluido sottoposto ad un gradiente di temperatura.
Il progetto è iniziato con il design e la successiva prototipazione di un supporto avente le qualità necessarie a generare e mantenere un gradiente di temperatura nella sezione trasversale di un canale. Poi la piattaforma è stata automatizzata, controllandola tramite interfaccia da PC. In seguito questa è stata testata su un dispositivo microfluidico. Il gradiente di temperatura è stato quindi caratterizzato ed il movimento del fluido è stato studiato tramite l’utilizzo di particelle micrometriche usate come traccianti. Le traiettorie 3D di quest’ultime sono state ottenute grazie al General Defocusing Particle Tracking (GDPT), in grado di fornire informazioni sulla profondità grazie ad un algoritmo di analisi d’immagini. Il tracciamento è stato effettuato in tre condizioni: con solo il gradiente di temperatura, con solo il campo acustico e con la combinazione dei due.
I risultati ottenuti dimostrano la capacità della piattaforma progettata nel generare e mantenere un gradiente di temperatura nella sezione del microcanale. Inoltre, i dati sul moto generato dal campo acustico sono in accordo con la letteratura sull’argomento. Riguardo all’interazione tra i due campi, si è osservata una velocità del fluido molto elevata, con però degli strani fenomeni sviluppatosi nella lunghezza del canale. Il progetto necessita ancora di esperimenti in condizioni più standard per poter dare risposte certe agli interrogativi riguardanti l’interazione tra campo termico e acustico.This thesis aims at investigating the interaction between thermal gradients and acoustic fields in microfluidic devices. In the research branch of acoustofluidics, which bridges together acoustics and fluid dynamics, inhomogeneity in the medium has gained great interest due to the novel physics behind and the potential in manipulating submicrometer particles. Concentration gradients of solute molecules have already been proven in previous studies to be effective means to obtain differences in fluid properties, such as density and compressibility, which induce acoustic body force and heavily affect the acoustic streaming. In this project another approach was taken, i.e. generating the inhomogeneity by thermal fields, to achieve a more stable and smooth variation in the thermophysical properties of the medium across the microchannel.
The thesis work developed mainly in two subsequent phases. Firstly, a set-up which is able to generate and maintain a temperature gradient across a channel cross-section was designed, built, and then automated via software control. Secondly, this platform was tested with a glass-silicon-glass microfluidic chip, recording the fluid motion by tracking micrometric particles via extit{General Defocusing Particle Tracking} (GDPT) technique. This experiment was done for three conditions: only with thermal field, only with acoustic field and with the two combined.
The results validate the effectiveness of the platform in generating and maintaining the thermal field and have a good agreement with literatures, although the acoustic field is undesirable due to the channel geometry flaws. The novelty of the project, i.e. the thermal-acoustic interaction, revealed itself to be quite complex. As predicted, high velocity fields were observed, associated with some unexpected flow behaviours, particularly along the length of the channel. Further measurements using a device with ideal channel geometry, together with a closer collaboration with the theoreticians who are able to explain the underlying physics, are needed to reveal the full picture of this novel phenomenon
Shaping acoustofluidic landscapes to profile and separate cells and sub-micron particles
No full textAcoustophoresis, where flow and acoustic fields are used to separate suspended objects, is getting increasingly more attention for cell and bacteria-handling applications relating to medicine and biology. Major benefits are flexibility in design, gentleness to cells and that relatively large forces can be exerted on suspended objects compared to competing technologies. Two important features limit acoustophoresis. First, the strong size dependency hampers separation of cells based on the underlying properties density and compressibility. Second, the presence of acoustic streaming introduces a lower size limit of objects that can be manipulated by primary radiation forces. To address these problems, we explore the action of acoustic fields on liquids of inhomogeneous acoustic properties which introduce stabilizing forces in the bulk
Two-step acoustofluidic cancer cell enrichment
No full textWe have previously proposed and evaluated acoustophoresis for the enrichment of circulating tumor cells (CTC) and clusters thereof from the blood of patients with prostate cancer [1]. In that protocol, the cells were fixed and preserved in paraformaldehyde before processing and were thus non-viable. To enable future enrichment of also viable CTCs from patients, we have in this study investigated the ability to discriminate cancer cell line cells from sub-groups of viable white blood cells (WBC). We found that acoustophoresis alone has poorer performance for viable cells than for fixed cells. Therefore, we added a second step of acoustic gradient separation wherein cells migrate into a medium of increasing acoustic impedance. The resulting separation results in >80% of cancer cells reaching the target outlet while 99.8% of all WBCs are removed
On microchannel acoustophoresis - Experimental considerations and life science applications
No full textThis thesis presents experimental studies of microchannel acoustophoresis, a technique for manipulation of microscopic objects in suspension by means of acoustic radiation forces induced by ultrasonic standing wave fields. By arranging an acoustic resonance across the width of a microchannel, the path of individual cells or microparticles can be deflected orthogonally to the fluid flow. The propagation of acoustic waves in a microchip is discussed and a theory for the acoustic eigenmodes within the fluid filled channel is presented. With the intention to derive the trajectories of particles, expressions are recapitulated for the acoustic radiation force exerted on a particle in an acoustic field, the induced acoustic streaming in the fluid, and for the microchannel flow velocity profile. The introduced transport phenomena are thereafter used for evaluation of merits and limitations in microchannel acoustophoresis separating systems. In five studies, microchannel acoustophoresis has been adapted for applications in life science. Three of these relate to sample preparation through transfer of cells and microparticles from one suspending fluid to another, for bead based bio-affinity assays, or cell suspension conditioning. A fourth study addresses on-chip elution of surface bound molecules from cells and microparticles. In study five, a system is described for pre-alignment and subsequent separation of cancer cells from blood cells based on their intrinsic acoustic and morphological properties. In study six, a method is presented for measurement of the acoustophoretic velocity field of microparticles. This was done to test the extent to which the resonances in an acoustophoresis microchannel are well described by the current model
Sound to guide cells
No full textBy combining acoustic fields and liquid flows in microchannels we develop tools to chart and separatebiological particles based on their bio-mechanical properties. I will present an overview of three ongoingprojects where acoustic forces are utilized to separate blood cells.We studied the packing behavior of whole blood in a sound field. We discovered that cells self-organizesuch that red blood cells occupy a region nearest the acoustic pressure node while cancer cells migrateto the plasma interface. This can be done in a flow-through device and more than 90% of red blood cellscan be removed in continuous flow while recovering >50% of the target cells. [1]In a second project, we developed a method to separate and measure the acoustic properties ofthousands of single cells by tracking their location in a media that forms a gradient in acoustic properties.The cells migrate due to the sound field until reaching their point of zero acoustic contrast. From single-cell properties, we can predict the behavior of cells in any medium and acoustic field and design andoptimize separation schemes. [2]In another project, we showed that we can enrich clusters of circulating tumor cells from white bloodcells by acoustic separation, Fig 1. We analyzed blood from 12 patients with advanced-stage prostatecancer and compared that to blood from 20 healthy donors. We found that circulating tumor cell clustersin most patients but in very few of the control subjects. [3]Our vision is that we will be able to integrate the different unit operations for cell separation that we havedemonstrated into one process flow, thus building a system that can take whole blood as input andhighly refined sub-populations of cells as output. References[1] Soller, in https://acoustofluidics.net/archive/materials/Acoustofluidics_2023_Materials.pdf (2023).[2] https://doi.org/10.1038/ncomms11556 (2016).[3] https://doi.org/10.1021/acs.analchem.3c05371 (2024)
Transient buildup and decay of thermoacoustic streaming
No full textWe recently introduced the concept of thermoacoustic streaming in microchannels wherein a thermal field is generated inside an acoustic cavity. The result is a fast and controllable streaming for which the thermal energy is provided either by an LED light source [1], or a laser [2]. While in previous works we have measured this effect at steady state, we now present measurements of the build-up and decay. We believe that the presented approach can offer the basis for particle sorting or manipulation applications
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