Modeling analyte transport and capture in porous bead sensors

Porous agarose microbeads, with high surface to volume ratios and high binding densities, are attracting attention as highly sensitive, affordable sensor elements for a variety of high performance bioassays. While such polymer microspheres have been extensively studied and reported on previously and are now moving into real-world clinical practice, very little work has been completed to date to model the convection, diffusion, and binding kinetics of soluble reagents captured within such fibrous networks. Here, we report the development of a three-dimensional computational model and provide the initial evidence for its agreement with experimental outcomes derived from the capture and detection of representative protein and genetic biomolecules in 290 μm porous beads. We compare this model to antibody-mediated capture of C-reactive protein and bovine serum albumin, along with hybridization of oligonucleotide sequences to DNA probes. These results suggest that, due to the porous interior of the agarose bead, internal analyte transport is both diffusion and convection based, and regardless of the nature of analyte, the bead interiors reveal an interesting trickle of convection-driven internal flow. On the basis of this model, the internal to external flow rate ratio is found to be in the range of 1:170 to 1:3100 for beads with agarose concentration ranging from 0.5% to 8% for the sensor ensembles here studied. Further, both model and experimental evidence suggest that binding kinetics strongly affect analyte distribution of captured reagents within the beads. These findings reveal that high association constants create a steep moving boundary in which unbound analytes are held back at the periphery of the bead sensor. Low association constants create a more shallow moving boundary in which unbound analytes diffuse further into the bead before binding. These models agree with experimental evidence and thus serve as a new tool set for the study of bioagent transport processes within a new class of medical microdevices.     

A Life or Death InfoSec Subversion

Details about failures of complex and well-implemented information-based attacks on systems are extremely difficult to obtain. However, here the authors examine a real-life analogue - an information attack on a highly complex security system, that of the Colombian guerrilla group FARC. This operation included a man-in-the-middle attack, targeted denial of service (DoS), and authentication subversion. The attack on FARC's communications structure is interesting not only because of its electronic and analog components, but also because it was a life or death matter. The authors examine the hostages' liberation from an information security perspective, compiling data from several Colombian newspapers and magazines and using the most accepted version of the events.     

Privacy concerns in assisted living technologies

The challenges of an aging population require the adoption of in-home and medical technologies to complement the traditional caregiver model. Adoption of such technologies is, however, impinged by privacy concerns. This study investigates a four-dimensional framework that explains the trade-offs between functionality and privacy as constructed by older adults. The four dimensions constitute perceived utility, data granularity, data recipient, and activity sensitivity. We conducted a survey-based study to empirically examine the applicability and robustness of this framework. Our results have implications for the adoption of a wide range of privacy-enhancing technologies. By focusing on the intersection of an under-studied group (nontechnical older adults) and sensitive data (medical and at home), this work has the potential to enable privacy enhancing technologies (PETs) that might be widely adopted.     

Cardiac and autonomic evaluation in a pediatric population with human immunodeficiency virus

OBJECTIVE: To determine the incidence and complications related to manual removal of the placenta. METHODS: Review of hospital medical records from 1990 throughout 1994. One thousand five hundred and two vaginal deliveries from 1984 1992 were used for comparisons. RESULTS: A total of 24,750 deliveries were registered during the five year study period. Placenta was removed manually in 165 women (0.6%). The use of general anesthesia for manual removal of placenta decreased from 74% in 1990 to 19% in 1994. Spinal analgesia was applied from 1993, and it was used in 42% of the women in 1994. Of 74 parous women, 12 (16%) had experienced retained placenta before. The average difference in the hemoglobin concentration between the prenatal and the postoperative values was 3.4 g/dl among the patients, and 10% required blood transfusion (1-4 units). Among the controls, there was no decrease in the average hemoglobin concentration, and only 0.5 needed blood transfusion. Endometritis following manual removal was detected in 1.8% of the patients and 1.5% among the controls. Despite manual removal, five women (3%) were considered to have retained placental fragments two days or later after delivery, which required curettage. CONCLUSIONS: Placenta needed to be removed manually in 0.60% of all deliveries in our department. It was associated with increased incidence of hemorrhage and consequently low hemoglobin values. Women with a history of retained placenta have an increased risk of recurrence of retained placenta in subsequent deliveries.     

Nitric oxide breath testing by tunable-diode laser absorption spectroscopy: application in monitoring respiratory inflammation

We used a high-resolution mid-IR tunable-laser absorption spectroscopy (TLAS) system with a single IV-VI laser operating near 5.2 microm to measure the level of exhaled nitric oxide (eNO) in human breath. A method of internal calibration using simultaneous eNO and exhaled CO2 measurements eliminated the need for system calibration with gas standards. The results observed from internally calibrating the instrument for eNO measurements were compared with measurements of eNO calibrated to gas standards and were found to be similar. Various parameters of the TLAS system for eNO breath testing were examined and include gas cell pressure, exhalation time, and ambient NO concentrations. A reduction in eNO from elevated concentrations (approximately 44 parts in 10(9)) to near-normal levels (<20 parts in 10(9)) from an asthmatic patient was observed after the patient had received treatment with an inhaled glucocorticoid anti-inflammatory medication. Such measurements can help in evaluating airway inflammation and in monitoring the effectiveness of anti-inflammatory therapies.     

Streamline integration using MPI-hybrid parallelism on a large multicore architecture

Streamline computation in a very large vector field data set represents a significant challenge due to the nonlocal and data-dependent nature of streamline integration. In this paper, we conduct a study of the performance characteristics of hybrid parallel programming and execution as applied to streamline integration on a large, multicore platform. With multicore processors now prevalent in clusters and supercomputers, there is a need to understand the impact of these hybrid systems in order to make the best implementation choice. We use two MPI-based distribution approaches based on established parallelization paradigms, parallelize over seeds and parallelize over blocks, and present a novel MPI-hybrid algorithm for each approach to compute streamlines. Our findings indicate that the work sharing between cores in the proposed MPI-hybrid parallel implementation results in much improved performance and consumes less communication and I/O bandwidth than a traditional, nonhybrid distributed implementation.     

The socialist network

We develop and test machine learning-based tools for the classification of personal relationships in biographical texts, and the induction of social networks from these classifications. A case study is presented based on several hundreds of biographies of notable persons in the Dutch social movement. Our classifiers mark relations between two persons (one being the topic of a biography, the other being mentioned in this biography) as positive, neutral, or unknown, and do so at an above-baseline level. A training set centering on a historically important person is contrasted against a multi-person training set; the latter is found to produce the most robust generalization performance. Frequency-ranked predictions of positive and negative relationships predicted by the best-performing classifier, presented in the form of person-centered social networks, are scored by a domain expert; the mean average precision results indicate that our system is better in classifying and ranking positive relations (around 70% MAP) than negative relations (around 40% MAP).     

Index Properties-Based Criteria for Liquefaction Susceptibility of Clayey Soils: A Critical Assessment

The Cooper marl in Charleston, S.C., a deep layer of clayey soils approximately 5–21?m below the ground surface, is generally recognized as nonliquefiable material. Data from field cone penetration tests and laboratory tests of samples taken from the Cooper marl are used to investigate the adequacy of index properties-based criteria for assessing liquefaction susceptibility of clayey soils. In particular, the criterion based on soil behavior type index (Ic) and that based on Atterberg limits are examined. The results show that the Atterberg limits-based criterion adequately reflected the characteristics of the marl, whereas the Ic-based criterion erroneously identified the marl as being liquefiable. A possible reason for the deficiency of Ic and a modification to overcome this deficiency are presented.     

Effect of pan-frying in different culinary fats on the fatty acid profile of pork

This study was set up to determine how pan-frying either without culinary fat or with different culinary fats (polyunsaturated fatty acids (PUFA)-enriched culinary fat, olive oil and margarine) affects the fatty acid (FA) composition of pork. The meat samples (longissimus thoracis (LT)) originated from pigs fed different dietary fat sources (animal fat, soybean oil or linseed oil) and thus had different FA compositions before frying. Pan-frying resulted in considerable increases in the meat total-FA content, although this was not always significant and highly variable, despite standardisation of the frying process. The FA composition of the pan-fried meat tended to become similar to that of the culinary fat used, and the extent of changes in the content of a particular FA was relative to the FA gradient from the culinary fat to the meat. However, this was also dependent on the culinary fat used, since frying in olive oil appeared to affect the FA composition of the meat more than did frying in the other culinary fats. Differences in FA composition of meat resulting from different animal feeding treatments remained unchanged after pan-frying without fat, they became smaller after frying in margarine and PUFA-enriched culinary fat, whereas frying in olive oil largely masked the initial FA profile differences. Long chain PUFA (LCPUFA) in the meat were not significantly lost by the frying process, but their proportion was influenced by the uptake of the culinary fat.     

Dynamic analyses of multiple-degree-of-freedom structures using a modified heun method

A simple explicit solution technique for problems in structural dynamics, based on Heun's numerical method for ordinary differential equations, is developed. The resulting conditionally stable modified Heun method (MHM) is easily implemented and provides a more accurate dynamic response than the modified Euler's method. To examine the effectiveness, strengths, and limitations of MHM, error analyses for the natural period, the displacement, the velocity and associated phase angle for a free and undamped simple mass-spring system are derived. Numerical examples for a single-degree-of-freedom system and a multi-degree-of-freedom (MDOF) system are presented. In direct integration of MDOF systems, the amplitude decay characteristic exhibited by MHM provides a total system solution in which the low mode response is accurately calculated.