Filter integrity specifications

Filter tests must be performed by the manufacturer before release to the market and by the individual user also, to ensure that the membrane filter complies with the specifications, is undamaged, and is eventually placed correctly in the filter case by the user. As described before in this chapter, such a test should in fact be performed with Brevundimonas diminuta. However, in daily practice this is not possible for the user in the pharmacy, and thus test methods have been derived, which are based on the physical properties of the membrane filter. Such test methods are called filter integrity tests. 

It is both convenient and reasonable in continuous filtration, except for precoat filters, to assume that the resistance of the filter cloth plus filtrate drainage is neghgible compared to the resistance of the filter cake and to assume that both pressure drop and specific cake resistance remain constant throughout the filter cycle. Equation (18-51), integrated under these conditions, may then be manipulated to give the following relationships ... 

By computing the appropriate integrals with filtered data and generating the corresponding plots, you must determine first which section of the data is best suited for the estimation of the specific uptake and production rates. 

The way in which the active microzone is retained also depends on its relationship to the detector (Fig. 2.6) and the type of interaction with the analyte or its reaction product. If the microzone is an integral part of the probe, an additional support (usually a membrane) is often required, so contact with the sample is hindered to some extent. On the other hand, a microzone located in a flow-cell can be retained in various ways. Thus, if the microzone consists of a porous solid or particle, the flow-cell is simply packed with two filters in order to avoid washing out (e.g. see [21]). Too finely divided solids (viz. particle sizes below 30-40 pm) should be avoided as they require pressures above atmospheric level, which complicates system design and precludes use of microzones with a high specific surface. Placing a separation membrane in a flow-cell is... 

Unlike sterilizing and virus removal filters, tangential flow filtration (TFF) filters are often reused. Flow and integrity tests are necessary to ensure the filter remains the same after usage and cleaning. Consistency of filtrate and retentate streams is validated using relevant validated assays that are specific for each process and product. 

Filters used for the prefiltration and final filtration should be maintained to operate to their design specifications. Deterioration of filters is caused by leakage and/or accumulation of particles. The former is tested by periodical integrity test (usually dioctylphthalate DOP test), and the latter is tested by the increase of air pressure differentials between the upstream and downstream sides of the fdter. 

The experimental setup employed 785 nm excitation with a 90° collection geometry. Each spectrum was obtained with excitation power 300 mW and integration time equivalent to 2.5 min. Because filtered serum is nearly transparent at 785 nm, excitation of Raman scattering is effectively along the entire laser path, creating a line source in the cuvette. Thus, the authors surmise that better collection efficiency could be obtained with optics designed specifically for this type of source, as opposed to the standard spherical lens they employed. 

As explained in Section 2, we collect from the different honeypot platforms tcpdump files which contain observed suspicious packets. We also collect other information, such as application log files to verify the integrity of the platforms but these lie outside the scope of the paper as they are not used to analyze the attacks we face. It is worth noting that broadcast and multicast traffic is filtered out from the tcpdump files we collect (e.g., arp traffic, Cisco Discovery Protocol CDP, Spanning-Tree Protocol STP, etc.). In other words, we only are interested in packets from/to the honeypot virtual machines specifically. At the network level, these are mainly IP and ICMP packets. At the transport protocol, they are mainly UDP and TCP ones. 

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