17,522 research outputs found
Accurate quantification of microorganisms in PCR-inhibiting environmental DNA extracts by a novel Internal Amplification Control approach using Biotrove OpenArrays
No full textPCR-based detection assays are prone to inhibition by substances present in environmental samples, thereby potentially leading to inaccurate target quantification or false-negative results. Internal amplification controls (IACs) have been developed to help alleviate this problem but are generally applied in a single concentration, thereby yielding less-than-optimal results across the wide range of microbial gene target concentrations possible in environmental samples (J. Hoorfar, B. Malorny, A. Abdulmawjood, N. Cook, M. Wagner, and P. Fach, J. Clin. Microbiol. 42:1863-1868, 2004). Increasing the number of IACs for each quantitative PCR (qPCR) sample individually, however, typically reduces sensitivity and, more importantly, the reliability of quantification. Fortunately, current advances in high-throughput qPCR platforms offer the possibility of multiple reactions for a single sample simultaneously, thereby allowing the implementation of more than one IAC concentration per sample. Here, we describe the development of a novel IAC approach that is specifically designed for the state-of-the-art Biotrove OpenArray platform. Different IAC targets were applied at a range of concentrations, yielding a calibration IAC curve for each individual DNA sample. The developed IACs were optimized, tested, and validated by using more than 5,000 unique qPCR amplifications, allowing accurate quantification of microorganisms when applied to soil DNA extracts containing various levels of PCR-inhibiting compounds. To our knowledge, this is the first study using a suite of IACs at different target concentrations to monitor PCR inhibition across a wide target range, thereby allowing reliable and accurate quantification of microorganisms in PCR-inhibiting DNA extracts. The developed IAC is ideally suited for high-throughput screenings of, for example, ecological and agricultural samples on next-generation qPCR platforms.
Duurzame transformatie - Een tweede kans voor industrieel erfgoed
No full textOnderzoek naar de mogelijke duurzaamheidsingrepen bij het duurzaam transformeren van industrieel erfgoed. Hierbij wordt gekeken naar de motieven van de opdrachtgever om in te spelen op duurzaamheid en de haalbaarheid van duurzame transformatie. Uiteindelijk worden scenario's met bijbehorende aandachtspunten geformuleerd. - Research on possible sustainability aspects that can be used in a sustainable building transformation of industrial heritage. Motives from the initiator to make use of sustainability aspects and the feasability of the sustianable building transformation are taken into account. Different scenarios and their issues are formulated.Design and Construction ManagementReal Estate & HousingArchitectur
Van de grond af opgebouwd
No full textBundeling van de lezingen ter gelegenheid van de 80e verjaardag van prof. Agema, naast de lezingen staan er twee interviews met prof. Agema in deze publicatie. De bijdragen van de overige sprekers zijn: Rijkswaterstaat: de (te) grote opdrachtgever in de GWW (Struik), De fundamenten onder het ontwerp (vd Meer), Buitenland en waterbouw (Zanetti), Uitvoeren met verstand (Beerda), Techniek en grote projecten (Korf)Hydraulic EngineeringCivil Engineering and Geoscience
Vascular occlusion in stems of cut rose flowers
No full textThe quality of cut rose flowers, a major horticultural crop in the Netherlands, is often unsatisfactory. During vase-life premature signs of water stress occur, such as slow growth of the bud which often results in poor flower opening, wilting of both the flowers and the leaves, and bending of the stem just underneath the flower. These symptoms are due to an inability to take up adequate amounts of water from the vase solution, which in turn is due to an occlusion in the lower part of the stem. Experiments in which a razor blade was introduced into the stem showed that more than 66% of all xylem conduits must become non-functional before a reduction in the rate of water uptake becomes apparent. This study distinguishes between the occlusion which occurs when the stems are placed in water immediately after harvest, and the occlusion which occurs as a result of dry storage.When the stems are placed in water directly after harvest the blockage could be due to processes inherent in the stem, e.g. as a result of a wound-reaction, in which ethylene is generally involved. Alternatively, it could be due to microbial growth. Inhibition of the production or action of ethylene had no effect on the blockage. Light- and electron microscopy revealed no tyloses in the lumen of the xylem conduits (vessels and tracheids) and in only a few conduits a deposit of gummy material occurred in the absence of bacteria. This material stained with ruthenium red, a dye on polysaccharides. Slime on the colonies of bacteria isolated from the stems also stained with ruthenium red, indicating that the material found in some conduits might be bacterial polysaccharide that was able to pass the pit membranes between the conduits. These membranes contain small pores, through which the water flows from one conduit to the next. During vase-life a population of bacteria developed on the cut surface and inside the opened xylem conduits. The bacteria were always accompanied by extracellular polysaccharides. Fungi were also observed at the cut surface, but only after the occlusion had already occurred, and yeasts were not observed. When bacterial growth was excluded the blockage was absent. It was concluded, therefore, that the blockage occurring in the stems that are placed in water directly after harvest is caused by bacteria.Isolated living or dead bacteria both resulted in vascular blockage, when given either at room temperature or at 1°C This indicates that physiological activity, either from the part of the bacteria or from the part of the stem, is not a prerequisite in the bacterial blockage. Isolated bacterial polysaccharides and proteins such as cellulase and the inert ovalbumin, both with a molecular mass of about 50 kilodaltons, also resulted in rapid blockage. It is concluded, therefore, that the occlusion is due to a purely physical effect of living bacteria with their extracellular polysaccharides, as well as dead bacteria and their degradation products. The blockage is probably mainly due to the obstruction of the passage of water at the pit membranes between the xylem conduits.The effects of dry storage can also be partially microbial in origin, as the number of bacteria associated with the cut surface and the xylem interior increase during dry storage. When the stems are not temporarily placed in water after harvest, however, they do not become contaminated with bacteria. When such stems are held dry an occlusion also develops. Among rose cultivars great differences were found in the time-course of this blockage. In Cara mia roses, for example, it occurred within 3-4 h (at 20°C), in Madelon within 9-14 h, in Sonia after 24-36 h, and in Frisco after about 48 h of dry storage. The last cultivar apparently conserves water as its stomates often closed more rapidly, and its rate of cuticular transpiration was lower. However, in Cara mia, Madelon, and Sonia roses stomatal response, water loss, and water potential during dry storage, showed the same time course.The blockage that is not microbial in origin could be due to processes in the stem, for instance as a response to the low water potential. A microscopical investigation, however, did not show evidence for any material, be it tyloses, amorphous plugs or hydrophobic substances, in the xylem lumen.After cutting air absorption occurs at the cut surface, due to the receding water columns in the xylem conduits opened by cutting. This absorption ceased already within half an hour. In the absence of a leaf nearby the cut surface the amount of absorbed air corresponded with the volume of the lumen of the opened conduits. The occlusion related to dry storage, however, occurs only after three hours in the most sensitive cultivar tested. It was concluded, therefore, that the mere presence of air in the lumen of the conduits opened by cutting is no obstacle to the subsequent flow of water.Three hypotheses were tested as to the origin of the blockage due to dry storage:Firstly, when the lumen of the conduits that are opened by cutting is blocked by the presence of air, the water might follow the xylem walls until reaching non-opened conduits filled with water. When the walls would dehydrate this second pathway could become inoperative. This hypothesis was tested using rose stems of which the cut surface was covered with laboratory grease, and a pan of the bark higher on the stem was cut away (girdling), thus exposing cell walls adjacent to the xylem. Girdled Sonia rose stems which were placed in water without dry storage remained turgid, provided that the wall area in contact with water was more than 0.6 cm 2. When the girdled stems were held dry and then placed in water the uptake of water was strongly inhibited, with a time course reminiscent of the blockage in normal stems. These results support the above hypothesis. When the dry-stored girdled stems were placed in a surfactant solution, however, the rate of water uptake was not improved, whereas the rate of uptake was greatly improved in dry-stored non-girdled stems. It was concluded, therefore, that a reduced access via the cell wall pathway is not the cause of the occlusion.Secondly, water might initially be able to partially compress the embolus in the conduits opened by cutting, thereby providing contact with adjacent conduits filled with water. An occlusion would occur only when the walls dehydrate to the extent that water, because of its surface tension, is no longer able to contact these walls. This hypothesis was tested by placing stems in a suspension of india ink for 1-5 h, after dry storage. After 5-180 min of dry storage water was still able to partially penetrate the conduits of Sonia roses, and even after 24 h this was true, although the penetration depth was smaller after 24 h as compared to 3 h. When the stems were placed in a surfactant solution after 24 h of dry storage the penetration depth of the water was much higher than after 5-180 min of dry storage, but not as high as in controls that were not stored dry. These results are in agreement with the hypothesis. In Cara mia roses, however, the results were the same as in Sonia. As the occlusion occurs already within 180 min in the former cultivar, it is not correlated in time with a reduction of the penetration depth of water in the conduits opened by cutting.Thirdly, the occlusion may be related to cavitation of the conduits that am not opened by cutting. Cavitation is the sudden filling with gas of a liquid-filled conduit; it may occur spontaneously when the water potential becomes low, or as a result of pulling gas from an adjacent conduit that is already gas- filled. Cavitation results in ultrasonic acoustic emissions (UAEs) which can be detected by placing a microphone at the surface of the stem. The frequency of UAEs always increased prior to the development of the occlusion, in Cara mia, Madelon, and Sonia roses. As these cultivars show a different time until the occlusion occurs, the results suggest that cavitation is an important cause of the occlusion. In Cara mia roses cavitation appears to be the only cause of the occlusion, in the other cultivars tested the incapacity of water to penetrate the conduits opened by cutting may also be part of the blockage
Vascular occlusion in stems of cut rose flowers
No full textThe quality of cut rose flowers, a major horticultural crop in the Netherlands, is often unsatisfactory. During vase-life premature signs of water stress occur, such as slow growth of the bud which often results in poor flower opening, wilting of both the flowers and the leaves, and bending of the stem just underneath the flower. These symptoms are due to an inability to take up adequate amounts of water from the vase solution, which in turn is due to an occlusion in the lower part of the stem. Experiments in which a razor blade was introduced into the stem showed that more than 66% of all xylem conduits must become non-functional before a reduction in the rate of water uptake becomes apparent. This study distinguishes between the occlusion which occurs when the stems are placed in water immediately after harvest, and the occlusion which occurs as a result of dry storage.When the stems are placed in water directly after harvest the blockage could be due to processes inherent in the stem, e.g. as a result of a wound-reaction, in which ethylene is generally involved. Alternatively, it could be due to microbial growth. Inhibition of the production or action of ethylene had no effect on the blockage. Light- and electron microscopy revealed no tyloses in the lumen of the xylem conduits (vessels and tracheids) and in only a few conduits a deposit of gummy material occurred in the absence of bacteria. This material stained with ruthenium red, a dye on polysaccharides. Slime on the colonies of bacteria isolated from the stems also stained with ruthenium red, indicating that the material found in some conduits might be bacterial polysaccharide that was able to pass the pit membranes between the conduits. These membranes contain small pores, through which the water flows from one conduit to the next. During vase-life a population of bacteria developed on the cut surface and inside the opened xylem conduits. The bacteria were always accompanied by extracellular polysaccharides. Fungi were also observed at the cut surface, but only after the occlusion had already occurred, and yeasts were not observed. When bacterial growth was excluded the blockage was absent. It was concluded, therefore, that the blockage occurring in the stems that are placed in water directly after harvest is caused by bacteria.Isolated living or dead bacteria both resulted in vascular blockage, when given either at room temperature or at 1°C This indicates that physiological activity, either from the part of the bacteria or from the part of the stem, is not a prerequisite in the bacterial blockage. Isolated bacterial polysaccharides and proteins such as cellulase and the inert ovalbumin, both with a molecular mass of about 50 kilodaltons, also resulted in rapid blockage. It is concluded, therefore, that the occlusion is due to a purely physical effect of living bacteria with their extracellular polysaccharides, as well as dead bacteria and their degradation products. The blockage is probably mainly due to the obstruction of the passage of water at the pit membranes between the xylem conduits.The effects of dry storage can also be partially microbial in origin, as the number of bacteria associated with the cut surface and the xylem interior increase during dry storage. When the stems are not temporarily placed in water after harvest, however, they do not become contaminated with bacteria. When such stems are held dry an occlusion also develops. Among rose cultivars great differences were found in the time-course of this blockage. In Cara mia roses, for example, it occurred within 3-4 h (at 20°C), in Madelon within 9-14 h, in Sonia after 24-36 h, and in Frisco after about 48 h of dry storage. The last cultivar apparently conserves water as its stomates often closed more rapidly, and its rate of cuticular transpiration was lower. However, in Cara mia, Madelon, and Sonia roses stomatal response, water loss, and water potential during dry storage, showed the same time course.The blockage that is not microbial in origin could be due to processes in the stem, for instance as a response to the low water potential. A microscopical investigation, however, did not show evidence for any material, be it tyloses, amorphous plugs or hydrophobic substances, in the xylem lumen.After cutting air absorption occurs at the cut surface, due to the receding water columns in the xylem conduits opened by cutting. This absorption ceased already within half an hour. In the absence of a leaf nearby the cut surface the amount of absorbed air corresponded with the volume of the lumen of the opened conduits. The occlusion related to dry storage, however, occurs only after three hours in the most sensitive cultivar tested. It was concluded, therefore, that the mere presence of air in the lumen of the conduits opened by cutting is no obstacle to the subsequent flow of water.Three hypotheses were tested as to the origin of the blockage due to dry storage:Firstly, when the lumen of the conduits that are opened by cutting is blocked by the presence of air, the water might follow the xylem walls until reaching non-opened conduits filled with water. When the walls would dehydrate this second pathway could become inoperative. This hypothesis was tested using rose stems of which the cut surface was covered with laboratory grease, and a pan of the bark higher on the stem was cut away (girdling), thus exposing cell walls adjacent to the xylem. Girdled Sonia rose stems which were placed in water without dry storage remained turgid, provided that the wall area in contact with water was more than 0.6 cm 2. When the girdled stems were held dry and then placed in water the uptake of water was strongly inhibited, with a time course reminiscent of the blockage in normal stems. These results support the above hypothesis. When the dry-stored girdled stems were placed in a surfactant solution, however, the rate of water uptake was not improved, whereas the rate of uptake was greatly improved in dry-stored non-girdled stems. It was concluded, therefore, that a reduced access via the cell wall pathway is not the cause of the occlusion.Secondly, water might initially be able to partially compress the embolus in the conduits opened by cutting, thereby providing contact with adjacent conduits filled with water. An occlusion would occur only when the walls dehydrate to the extent that water, because of its surface tension, is no longer able to contact these walls. This hypothesis was tested by placing stems in a suspension of india ink for 1-5 h, after dry storage. After 5-180 min of dry storage water was still able to partially penetrate the conduits of Sonia roses, and even after 24 h this was true, although the penetration depth was smaller after 24 h as compared to 3 h. When the stems were placed in a surfactant solution after 24 h of dry storage the penetration depth of the water was much higher than after 5-180 min of dry storage, but not as high as in controls that were not stored dry. These results are in agreement with the hypothesis. In Cara mia roses, however, the results were the same as in Sonia. As the occlusion occurs already within 180 min in the former cultivar, it is not correlated in time with a reduction of the penetration depth of water in the conduits opened by cutting.Thirdly, the occlusion may be related to cavitation of the conduits that am not opened by cutting. Cavitation is the sudden filling with gas of a liquid-filled conduit; it may occur spontaneously when the water potential becomes low, or as a result of pulling gas from an adjacent conduit that is already gas- filled. Cavitation results in ultrasonic acoustic emissions (UAEs) which can be detected by placing a microphone at the surface of the stem. The frequency of UAEs always increased prior to the development of the occlusion, in Cara mia, Madelon, and Sonia roses. As these cultivars show a different time until the occlusion occurs, the results suggest that cavitation is an important cause of the occlusion. In Cara mia roses cavitation appears to be the only cause of the occlusion, in the other cultivars tested the incapacity of water to penetrate the conduits opened by cutting may also be part of the blockage
Verruiming van de toegangsgeul naar Tees Port
No full textIn deel A wordt beschreven hoe de benodigde geulbreedte kan worden bepaald. De benodigde geulbreedte is bepaald met behulp van een fast-time simulatie model: SHIPMA . SHIPMA is een fast-time simulatieprogramma, waarmee gesimuleerd wordt hoe goed een schip de gewenste route kan afleggen onder verschillende omstandigheden. De geulbreeedte die het schip nodig heeft kan uit de door het schip gevolgde route bepaald worden. Het grootste schip dat de haven (met een geulbreedte van 244 m) kan bezoeken volgens de SHIPMA berekening is een schip van 310 m lang en 55 m breed. Ter vergelijking is er ook een geulbreedte bepaald met behulp van richtlijnen van het PIANC. Volgens de PIANC-richtlijnen kan een iets breder schip, namelijk 55,5m breed, toegelaten worden. Men wil met schepen varen met een breedte van maximaal 55m. De huidige geul is dus breed genoeg om aan die wensen te voldoen. In deel B van dit afstudeerwerk wordt nagegaan wat de benodigde underkeel clearance is voor de voorgedragen schepen. Om de geuldiepte te kunnen bepalen moet eerst de benodigde underkeel clearance van de schepen worden bepaald. In dit onderzoek is er voor gekozen om met een semi-probabilistische methode te werken, de methode van Kimon. Met de methode van Kimon is underkeel clearance berekend, die hoort bij een kans dat het schip tijdens de passage de bodem raakt, van 1%. benodigde underkeel clearance varieert van 1,82m tot 2,08m voor een schepen met een diepgang van respectievelijk 17m en 23m, bij golven tot 2,25m hoog. Voor de toelating van schepen met een diepgang van meer dan 17,5m moet de vaargeul verdiept worden. In deel C is onderzocht wat de effecten zijn van de geulverdieping op de hoeveelheid sedimentatie in de vaargeul. De geulvarianten die onderzocht worden zijn de een geul met de huidige geulafmetingen en twee verdiepte varianten, die respectievelijk 2m en 6m dieper zijn dan de huidige geul. Om het sedimenttransport over een gebaggerde geul te berekenen heeft Bijker een eenvoudige transportformule bedacht. Met een eenvoudige berekening kan de hoeveelheid sedimenttransport, onder stroming en golven, buiten de geul en boven de geul worden berekend. Het verschil tussen beide hoeveelheden is de hoeveelheid gesedimenteerd materiaal in de geul. Deze hoeveelheid sediment moet gebaggerd worden om de benodigd geuldiepte voor de scheepvaart te kunnen garanderen. Uit de berekening blijkt duidelijk dat de hoeveelheid sediment in de approach channel (het stuk geul buiten de golfbrekers) bij geulverdieping zal toenemen. Zeker bij een geulverdieping van zes meter is de toename groot, namelijk meer dan 100%. Deze toename voor het onderhoudsbaggerwerk zal extra kosten met zich meebrengen en ook hinder voor de scheepvaart. Dit zijn ongewenste effecten. Op de river channel (het beschutte gedeelte van de geul) zal de hoeveelheid sediment nauwelijks veranderen. Het sediment dat daar wordt afgezet komt voor 70% met de vloedstroom mee. Bij een geulverdieping blijft de grootte van de vloedstroom ongeveer gelijk en zo ook de getransporteerde hoeveelheid sediment. De andere 30% sediment wordt aangevoerd door de rivier. Ook aan deze hoeveelheid zal door geulverdieping niet veel veranderen.Hydraulic EngineeringCivil Engineering and Geoscience
De dijkdoorbraak bij Ouderkerk (Z-H) in 1953
No full textDagboekverslag van Johan van Veen over zijn activiteiten bij het stroomgat bij Ouderkerk en zijn pogingen om dat te dichten. Met een transcriptie door Willem van der Ha
Taluds van losgestorte materialen: Golfneerloop op statisch stabiele stortsteen taluds onder golfaanval
No full textIn dit verslag worden neerloopmetingen gepresenteerd en geanalyseerd welke zijn verkregen uit onderzoeken naar de statische stabiliteit van stortsteen taluds onder golfaanval. De analyse van deze proeven heeft geleid tot de relatie voor de relatieve neerloop die door 2% van de neerlopen wordt overschreden. Deze empirische relatie wordt beschreven aan de hand van dimensieloze parameters, welke zijn afgeleid van de in de onderzoeken gevarieerde grootheden. De relatieve neerloop wordt belnvloed door de volgende dimensieloze parameters : \u95 golfsteilheid (sm) \u95 taludhelling (cot alpha) \u95 doorlatendheid van de constructie (P) \u95 spectrumvorm (K) \u95 relatieve waterdiepte (h/Hs)Applied Geophysics and PetrophysicsHydraulic EngineeringCivil Engineering and Geoscience
Rapport betreffende de wateronttrekking aan, en de afzanding van de duinen langs de Nederlandsche kust: uitgebracht in 1912 door de hoofdingenieurs-directeuren van den Rijkswaterstaat in de 11de, 10de en 9de directiën, J.C. Ramaer, N.A.M. van den Thoorn en H. Wortman
No full textOnderzoek naar het effect van zandwinning op de duinwaterwinning.Overzicht van welke duinen in beheer zijn bij het Rijk en bij waterschappe
Delayed interval delivery in multiple pregnances. Is optimism justified?
No full textHelena C. Van Doorn, Gerda van Wezel-Meijler, Herman P. Van Geijn and Gustaaf A. Dekke
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