Filter for microliter volumes

The construction of a filter for 1-30 microliters volumes of liquid is described in detail. It is a modification of the readily available Millipore Swinex filter made by adding parts constructed from PE20 Intramedic tubing which are formed in a heated die. The die can be constructed easily in the laboratory.     

Removal of polycyclic aromatic hydrocarbons and linear alkylbenzene sulfonates from domestic wastewater in pilot constructed wetlands and a gravel filter

Removal efficiencies of polycyclic aromatic compounds (PAHs) and linear alkyl benzene sulfonates (LAS) were evaluated in a pilot-scale constructed wetland (CW) system combining a free water surface wetland, a subsurface wetland and a gravel filter in parallel. The effect of parameters such as temperature and mass loading rate was also examined. The subsurface constructed wetland system was found to have the overall best performance on pollutants removal. In particular, the average removal of PAHs and LAS was 79.2% and 55.5% for the SSF (Subsurface Flow) constructed wetland, 68.2% and 30.0% for the FWS (Free Water Surface) constructed wetland and 73.3% and 40.9% for the gravel filter, respectively. Removal efficiency and the estimated first-order volumetric removal rate constant (k_v) for both PAHs and LAS decreased with increasing water temperature. The experimental results suggest that the absorption in solid media is the main mechanism for xenobiotics removal in constructed wetlands and that the overall performance of the SSF wetland is significantly better than the FWS wetland or the gravel filter.     

Über den Feinbau der Filterkammer der Kleinzikade Euscelidius variegatus Kbm. (Jassidae)

Zusammnfssung Nach lichtmikroskopischen Studien am Darmtrakt der Kleinzikade Euscelidius variegatus wird die Filterkammer dieser Tierart elektronenmikroskopisch untersucht. Alle Epithelien der Magentasche, des Filterkammerdarmes und der in diesen Organkomplex einbezogenen Kryptonephridien besitzen den gleichen Aufbau und stellen Transport-gewebe dar. Aussagen über eine bestimmte Transportrichtung und über die Art der transportierten Stoffe können nicht gemacht werden. Der Bau der Filterepithelien wird beschrieben. Im Anschluß wird die Funktionsmöglichkeit der Filterkammer in Form einer Arbeitshypothese erörtert.

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Summary After histological investigations of the alimentary tract of the leafhopper Euscelidius variegatus the submicroscopical structure of the filter chamber is investigated electronmicroscopically. The construction of the filter epithelia is described. All epithelia in the filter chamber have the same fine structure and serve as transport tissues. A definite direction of the supposed transport of substances cannot be asserted yet. A hypothesis of the function of the filter chamber is discussed.

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Herrn Privatdozent Dr. Zebe (Physiologischer Lehrstuhl) danke ich für das Entgegenkommen, die elektronenmikroskopischen Untersuchungen in seiner Abteilung durchführen zu können, den Herren Doktoren Beinbrecht und Heumann sowie Fräulein Behrsing für technische Beratung.     

A high–performance compact filter system treating domestic wastewater

A new compact wastewater treatment system for use in single houses has been constructed in eastern Norway. The system is based on the principles of sub-surface flow constructed wetlands using various types of Filtralite as filter media. It consists of a septic tank followed by an aerobic biofilter succeeded by an upflow saturated filter. The aerobic biofilter is essential to remove organic matter and achieve nitrification, while the upflow filter polishes the wastewater and removes microorganisms and phosphorus. During the first 3 years of operation, the system has show stable and high removal with the following average values measured from the outlet of septic tank to the outlet of the upflow filter: 97.0%-BOD₇, 30%-N, 99.4%-P, and 70.8%-SS. No Escherichia coli or somatic coliphages have been detected in the effluent. Due to considerable removal of organic mater, nutrients, and pathogens, the effluent will not negatively affect water and soil ecosystems. The system requires low maintenance and is designed to remove phosphorus for 5 years before renewal of the upflow filter media. When saturated with phosphorus, the media is a suitable fertilizer for plant production.     

Multiple-Channel Plasmonic Filter Based on Metal-Insulator-Metal Waveguide and Fractal Theory

Plasmonics - A multiple-channel plasmonic filter based on metal-insulator-metal waveguide and fractal theory is proposed. The sandwiched insulator layer is constructed by a series of dielectrics...     

Hydraulic performance of horizontal subsurface flow constructed wetlands for different strategies of filling the filter medium into the filter basin

A quasi-two-dimensional flow cell model of a horizontal subsurface flow constructed wetland was used to investigate how partitioning the wetland into smaller vertical sections prior to filling a heterogeneous filter medium into the filter basin altered the filter material packing and thereby the flow distribution. The flow through the filter medium was visualized using Nigrosine dye. Breakthrough curves for the flow cell were obtained using chloride tracer. Three inlet–outlet configurations were examined to assess the effects of the inlet and outlet positions on the flow since the inlet–outlet locations in addition to the filter medium heterogeneity may promote the development of preferential paths and dead zones. The filter medium packing patterns were dependent on the number of sections. If the wetland model was not partitioned prior to filling (one section), the filter material formed roughly horizontal layers with alternate layers of coarse and fine material. However, increasing the number of sections reduced the layer continuity and increased the flow distribution. This yielded longer retention times and higher hydraulic efficiency factors. The effect of the inlet–outlet configuration on the hydraulic parameters was greater when the number of sections was small. These results suggest that dividing the constructed wetland into several sections prior to filling the filter medium into the basin will improve the treatment efficiency.     

Improving the treatment efficiency of constructed wetlands with zeolite-containing filter sands

In this study the physical and chemical properties of three different lava sands used in constructed wetlands for municipal wastewater treatment were investigated. The aim was to identify those properties and mechanisms that render lava sands as highly efficient filter media which could substitute conventional, fluviatile sands. It was shown that although lava sands per se may be suitable filter materials, the presence of zeolite minerals within the lava sands enhances the purification efficiency tremendously. Zeolites not only increase the sorption capacity, but even more important, they are able to absorb water in large amounts, which in turn leads to stronger swelling. The latter reduces hydrological conductivity considerably, resulting in a longer contact time to eliminate pollutants. A simple mineralogical survey of filter materials for the presence of zeolites may render many installations of constructed wetlands successful.     

Filter bed systems treating domestic wastewater in the Nordic countries – Performance and reuse of filter media

Nine filter beds have been constructed in the Nordic countries, Denmark, Finland, Norway and Sweden. Filter beds consist of a septic tank followed by an aerobic pre-treatment biofilter and a subsequent saturated flow grass-covered filter. Thus, filter beds are similar to subsurface flow constructed wetlands with pre-treatment biofilters, but do not have wetland plants with roots submerged into the saturated filter. All saturated filters contain Filtralite^®P, a light-weight expanded clay aggregate possessing high phosphorus sorption capacity. The filter bed systems showed stable and consistent performance during the testing period of 3 years. Removal of organic matter measured as biochemical oxygen demand (BOD) was >80%, total phosphorus (TP) >94% and total nitrogen (TN) ranged from 32 to 66%. Effluent concentrations of fecal indicator bacteria met the European bathing water quality criteria in all systems. One system was investigated for virus removal and somatic viruses were not detected in the effluent. The investigations revealed that the majority of the BOD and nitrogen removal occurred in the pre-treatment filters and the phosphorus and bacteria removal was more prominent in the saturated filters. The saturated filters could be built substantially smaller than the current design guidelines without sacrificing treatment performance. The used filter material met the Norwegian regulations for reuse in agriculture with respect to heavy metals, bacteria and parasites. When saturated with phosphorus, the light-weight aggregate, Filtralite^®P used in the saturated bed is a suitable phosphorus fertilizer and additionally has a liming effect.     

A Filter Method for Processing Small Samples of Marine Ova Through Fixation, Dehydration, and Embedding Without Changing Containers

Free-floating cells can be fixed, dehydrated, and embedded in a single container. The container was constructed from stainless steel, and the paraffin block formed by the shape and size of a container was perfect for microtoming. Eight containers were embedded in a fiberglass holder. This holder was designed so that it could be used with a 47 mm Millipore filter. Cells were pipetted into the top of a container while the Millipore filter sealed the bottom; thus the cells were retained on the filter while fluids were allowed to pass through it. The exposure of the cells to histological reagents was regulated by applying a vacuum to control the rate of flow through the filter.     

Multilayer immobilized-enzyme filter reactors: urease bound to nylon fabric filters.

Urease was bound to commercially available nonwoven nylon fabric filters. Multilayer immobilized-enzyme filter reactors were constructed by packing varying numbers of urease-nylon filters in a column. Owing to the relatively open structure and high mechanical strength of the filter fabric, compaction and pressure drop effects were minimal. The reactors could be operated in a wide range of substrate concentrations and flow rates under conditions where mass-transfer limitations could be neglected. The kinetic behavior of the immobilized-enzyme filter reactors could be described by a linear form of the integrated Michaelis-Menten equation using a model based on the sequential action of the enzyme filters.     

Construction of recombinant plasmids containing rat thyroglobulin mRNA sequences

Two plasmids containing rat thyroglobulin cDNA sequences have been constructed and characterized. A plasmid with a 500-bp insert (pRT6) was isolated and identified as thyroglobulin-specific on the basis of the tissue specificity of the inserted sequence and of its ability to retain thyroglobulin mRNA on a nitrocellulose filter. The cDNA insert in pRT6 was subsequently used to screen a rat thyroid cDNA library constructed with large cDNA. A plasmid was found containing a 1700-bp insert. The polarity and the fidelity of the insert is demonstrated by S1 mapping.     

Autoradiographische Untersuchungen des Transportes einiger Nahrungsbestandteile im Darmtrakt zweier Kleinzikaden: Euscelidius variegatus Kbm. (Jassidae) und Triecphora vulnerata Germ. (Cercopidae)

Zusammenfassung Durch Verfütterung von radioaktiv markierten Nahrungsbestandteilen, geboten in synthetischer Nährlösung, wird die Richtigkeit der Hypothese von Berlese (1909) und Licent (1913) über die Funktion der Filterkammer für Euscelidius variegatus (Jassidae) und Triecphora vulnerata (Cercopidae) bewiesen. Während Wasser und Saccharose bzw. deren Spaltprodukte zum großen Teil die Filterepithelien passieren, in den Enddarm gelangen und als Honigtau vorzeitig ausgeschieden werden, verbleiben Aminosäuren und Protein im Verdauungstrakt. Eine Art Druckfiltration in der Filterkammer wird vermutet, da sich keine Hinweise für einen aktiven Transport durch die Filterepithelien erkennen lassen.

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Autoradiographic experiments on the transport of some nutritional elements in the digestive tract of two leafhoppers: Euscelidius variegatus Kbm. (Jassidae) and Triecphora vulnerata Germ. (Cercopidae)

Summary By feeding of radioactive nutritional elements in a synthetic diet the hypothesis of Berlese (1909) and Licent (1913) is proved for Euscelidius variegatus (Jassidae) and Triecphora vulnerata (Cercopidae). Most of the water and the sucrose or its monosaccharides pass the filter epithelia, reach the hind gut immediately and are defecated precociously as honey dew. Amino acids and protein on the other hand remain in the digestive tract. Some sort of filtration by pressure in the filter chamber is to be supposed as there are no hints on an active transport through the filter epithelia.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Bioaugmentation in a newly established LECA-based horizontal flow soil filter reduces the adaptation period and enhances denitrification

The possibility of enhancing the denitrification of a newly established LECA-based horizontal subsurface flow (HSSF) soil filter receiving pretreated wastewater from a vertical flow filter was studied. The pilot-scale experiment offers evidence regarding the survival and reproduction of introduced microbes taken from an LECA-based HSSF constructed wetland (CW) that has similar internal conditions, after bioaugmentation into newly established LECA-based HSSF CW mesocosms. Bioaugmentation resulted in a trend towards higher and more stable denitrification in the supplemented mesocosms during the nearly half-year study period.     

A simple method for determining the boundary layer resistance in leaf cuvettes

Abstract. A new method is described for determining the boundary layer resistance over wet filter paper exposed within a leaf cuvette, based on the energy balance of the filler paper. The boundary layer resistance is calculated by an iterative procedure from measurements of the relative humidity and temperature of the air in the cuvette. Comparisons between the new and the conventional method, involving measurement of the filter paper temperature, show close agreement.
To simplify the method further, a graph has been constructed for the relationship between boundary layer resistance and cuvette relative humidity at temperatures from 15 to 35°C, determined at one value of the ratio of the flow rate through the cuvette to the filter paper area.
An analysis of errors suggests that the new method is less sensitive than the conventional to errors in temperature and humidity.     

视觉皮层复杂细胞时空编码特性

针对输入在视皮层的编码表达,在地空滤波窗口基础上构建了一个复杂细胞时空编码模型,对几种特殊的输入函数进行了编码仿真实验,结果说明了视皮层复杂细胞时空整合编码序列的精细时间结构进行视觉输入的神经表象。     

Search filters for finding prognostic and diagnostic prediction studies in Medline to enhance systematic reviews

Background

The interest in prognostic reviews is increasing, but to properly review existing evidence an accurate search filer for finding prediction research is needed. The aim of this paper was to validate and update two previously introduced search filters for finding prediction research in Medline: the Ingui filter and the Haynes Broad filter.

Methodology/Principal Findings

Based on a hand search of 6 general journals in 2008 we constructed two sets of papers. Set 1 consisted of prediction research papers (n = 71), and set 2 consisted of the remaining papers (n = 1133). Both search filters were validated in two ways, using diagnostic accuracy measures as performance measures. First, we compared studies in set 1 (reference) with studies retrieved by the search strategies as applied in Medline. Second, we compared studies from 4 published systematic reviews (reference) with studies retrieved by the search filter as applied in Medline. Next – using word frequency methods – we constructed an additional search string for finding prediction research. Both search filters were good in identifying clinical prediction models: sensitivity ranged from 0.94 to 1.0 using our hand search as reference, and 0.78 to 0.89 using the systematic reviews as reference. This latter performance measure even increased to around 0.95 (range 0.90 to 0.97) when either search filter was combined with the additional string that we developed. Retrieval rate of explorative prediction research was poor, both using our hand search or our systematic review as reference, and even combined with our additional search string: sensitivity ranged from 0.44 to 0.85.

Conclusions/Significance

Explorative prediction research is difficult to find in Medline, using any of the currently available search filters. Yet, application of either the Ingui filter or the Haynes broad filter results in a very low number missed clinical prediction model studies.     

Wound healing in the cornea of the chick embryo. IV. Promotion of the migratory activity of isolated corneal epithelium in culture by the application of tension.

The influence of tensile stresses on the migratory activity of isolated corneal epithelia of 8-day embryos in culture was examined with the use of newly devised compound Millipore filter. These are constructed of a half-disk of a filter conducive to epithelial movement (0.3 MF) combined with a second half (1.2 MF) which is not, or of two parts of the latter (1.2 MF) which can be moved on a support disk and thus allow stretching of the epithelia. It is shown here that tensile stresses promote the migratory activity of the epithelial sheets, and a theory is proposed which may account for the action of tension on the migration of epithelial cells and for the role of intercellular junctions.     

A forced-air individually ventilated caging system for rodents

The practice of using a protective filter apparatus when housing five mice per cage resulted in ammonia levels exceeding 25 ppm. A forced-air individually ventilated caging system was constructed using polyvinyl-chloride tubing fitted to a rodent rack. The ammonia level was decreased using this ventilation system.     

The fate of light air ions in the respiratory pathways

From an analysis of the fate of the light air ions it was concluded that the most effective mechanism of deposition is the diffusion depriving the inhaled air of light ions at the level of intrasegmental bronchi and bronchioles. A natural electrostatic filter exists in the isthmus faucium.This filter influences the retention of light air ions during mouth-breathing. The electrostatic filter acts on electrically charged particles such as microbes as shown by an investigation of the density of microflora. An increase of the ion retention rate,although quite high in comparison with the same condition in the absence of an electric field,does not radically change the whole deposition pattern. However, a permanent supply of the opposite charge to the electrodes of the natural electrostatic filter may be of some importance to mouth-breathers.

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Zusammenfassung Es wurde das Schicksal der leichten Luftionen mit dem Ergebnis analysiert, dass der wirksamste Mechanismus der Ablagerung die Diffusion ist, durch die sich die inhalierte Luft mit leichten Ionen in der Höhe der Bronchien und Bronchiolen absetzt. Ein natürliches elektrostatisches Filter existiert in Form des isthmus faucium. Dieses Filter beeinflusst das Zurückhalten leichter Luftionen während der Mundatmung. Das elektrostatische Filter wirkt auf die elektrisch geladenen Teilchen wie Mikroben, wie man sie bei einer Untersuchung über die Dichte der Mikroflora beobachtet hat. Eine verstärkte Zurückhaltung der Ionen,obwohl sie im Vergleich zu denselben Bedingungen ohne elektrisches Feld recht hoch ist, ändert den ganzen Ablagerungsmechanismus nicht. Jedoch mag eine dauernde Zufuhr der den Elektoden des natürlichen elektrostatischen Filters entgegengesetzten Ladung von einiger Bedeutung für die Mundatmung sein.

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Resume On a analysé la destinée des ions légers de l'air.Il en découle que le mécanisme le plus efficace de déposition réside dans la diffusion qui prive l'air de ses ions légers au niveau des bronches et des bronchioles.Un filtre électrostatique naturel se trouve dans l'isthmus faucium. Ce filtre influence la rétention des ions légers de l'air durant la respiration par la bouche. Ce filtre électrostatique agit sur les particules chargées électriquement telles que les microbes,comme il découle de recherches effectuées sur la densité de la micro-flore. Un accroissement du taux de retenue des ions, même s il reste élevé en comparaison de ce qui se passe dans des conditions analogues mais en l'absence d'un champ électrique,ne modifie pas radicalement le mécanisme de sédimentation. Pourtant, un apport permanent de charges opposées aux électrodes du filtre électrostatique naturel peut avoir une certaine importance pour les individus respirant par la bouche.

     

Eine besonders wirksame Aquarienfilterung und die Messung ihrer Leistung

Zusammenfassung 1. Ein Spezialinnenfilter wird beschrieben, welches sich besonders für die Hälterung und Zucht kleinerer Wassertiere eignet.2. Das Filter ist mit einfachen Mitteln herzustellen und ermöglicht — nach Herstellung einer Sprungschicht im Aquarium — eine genaue Bestimmung der pro Zeiteinheit geförderten Wassermenge.

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An especially effective aquarium filter and the measurements of its efficiency

A new inside filter is described, which is especially suited for keeping and rearing small aquatic animals. The filter is simple in construction and allows — after establishment of a discontinuity layer in the aquarium — the determination of the amount of water processed per unit time.

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Herrn Professor Dr.Adolf Bückmann zum 65. Geburtstag in Verehrung gewidmet.