Backscattered electron SEM imaging of cells and determination of the information depth.

Backscattered electron imaging of HT29 colon carcinoma cells in a scanning electron microscope was studied. Thin cell sections were placed on indium-tin-oxide-coated glass slides, which is a promising substrate material for correlative light and electron microscopy. The ultrastructure of HT29 colon carcinoma cells was imaged without poststaining by exploiting the high chemical sensitivity of backscattered electrons. Optimum primary electron energies for backscattered electron imaging were determined which depend on the section thickness. Charging effects in the vicinity of the SiO2 nanoparticles contained in cell sections could be clarified by placing cell sections on different substrates. Moreover, a method is presented for information depth determination of backscattered electrons which is based on the imaging of subsurface nanoparticles embedded by the cells.

Daily life activity routine discovery in hemiparetic rehabilitation patients using topic models.

BACKGROUND: Monitoring natural behavior and activity routines of hemiparetic rehabilitation patients across the day can provide valuable progress information for therapists and patients and contribute to an optimized rehabilitation process. In particular, continuous patient monitoring could add type, frequency and duration of daily life activity routines and hence complement standard clinical scores that are assessed for particular tasks only. Machine learning methods have been applied to infer activity routines from sensor data. However, supervised methods require activity annotations to build recognition models and thus require extensive patient supervision. Discovery methods, including topic models could provide patient routine information and deal with variability in activity and movement performance across patients. Topic models have been used to discover characteristic activity routine patterns of healthy individuals using activity primitives recognized from supervised sensor data. Yet, the applicability of topic models for hemiparetic rehabilitation patients and techniques to derive activity primitives without supervision needs to be addressed. OBJECTIVES: We investigate, 1) whether a topic model-based activity routine discovery framework can infer activity routines of rehabilitation patients from wearable motion sensor data. 2) We compare the performance of our topic model-based activity routine discovery using rule-based and clustering-based activity vocabulary. METHODS: We analyze the activity routine discovery in a dataset recorded with 11 hemiparetic rehabilitation patients during up to ten full recording days per individual in an ambulatory daycare rehabilitation center using wearable motion sensors attached to both wrists and the non-affected thigh. We introduce and compare rule-based and clustering-based activity vocabulary to process statistical and frequency acceleration features to activity words. Activity words were used for activity routine pattern discovery using topic models based on Latent Dirichlet Allocation. Discovered activity routine patterns were then mapped to six categorized activity routines. RESULTS: Using the rule-based approach, activity routines could be discovered with an average accuracy of 76% across all patients. The rule-based approach outperformed clustering by 10% and showed less confusions for predicted activity routines. CONCLUSION: Topic models are suitable to discover daily life activity routines in hemiparetic rehabilitation patients without trained classifiers and activity annotations. Activity routines show characteristic patterns regarding activity primitives including body and extremity postures and movement. A patient-independent rule set can be derived. Including expert knowledge supports successful activity routine discovery over completely data-driven clustering.

Analysis of munitions constituents in IMX formulations by HPLC and HPLC-MS.

The use of Insensitive Munitions eXplosives (IMX) is increasing as the Army seeks to replace certain conventional munitions constituents, such as 2,4,6-trinitrotolene (TNT), for improved safety. The IMX formulations are more stable and therefore less prone to accidental detonation while designed to match the performance of legacy materials. Two formulations, IMX 101 and 104 are being investigated as a replacement for TNT in artillery rounds and composition B Army mortars, respectively. The chemical formulations of IMX-101 and 104 are comprised of four constituents;2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), 1-nitroguanidine (NQ), and Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) which are mixed in various ratios to achieve the desired performance. The current work details the analysis of the IMX constituents by single column HPLC-UV-ESI-MS. Detection limits determined are in agreement with similar HPLC analysis of compounds, ranging from 7 to 9µg/L. Gradient mobile phases are used to allow separation of the 4 target compounds in more complex mixture of other concomitant compounds. Mass spectra are used to confirm analyte identity with chromatographic retention time.

Characterization of metals released from coal fly ash during dredging at the Kingston ash recovery project.

A storage-pond dike failure occurred on December 22, 2008 at the Tennessee Valley Authority Kingston Fossil Plant resulting in the release of over 4million cubic meters (5million cubic yards) of fly ash. Approximately half of the released ash was deposited in the main channel of the Emory River, Tennessee, USA. Remediation efforts of the Emory River focused on hydraulic dredging, as well as mechanical excavation in targeted areas. However, agitation of the submerged fly ash during hydraulic dredging introduces river water into the fly ash material, which could promote dissolution and desorption of metals from the solid fly ash material. Furthermore, aeration of the dredge slurry could alter the redox state of metals in the fly ash material and thereby change their sorption, mobility, and toxicity properties. The research presented here focuses on the concentrations and speciation of metals during the fly ash recovery from the Emory River. Our results indicate that arsenite [As(III)] released from the fly ash material during dredging was slowly oxidized to arsenate [As(V)] in the slurry recovery system with subsequent removal through precipitation or sorption reactions with suspended fly ash material. Concentrations of other dissolved metals, including iron and manganese, also generally decreased in the ash recovery system prior to water discharge back to the river.

Mechanical properties and structure of the biological multilayered material system, Atractosteus spatula scales.

During recent decades, research on biological systems such as abalone shell and fish armor has revealed that these biological systems employ carefully arranged hierarchical multilayered structures to achieve properties of high strength, high ductility and light weight. Knowledge of such structures may enable pathways to design bio-inspired materials for various applications. This study was conducted to investigate the spatial distribution of structure, chemical composition and mechanical properties in mineralized fish scales of the species Atractosteus spatula. Microindentation tests were conducted, and cracking patterns and damage sites in the scales were examined to investigate the underlying protective mechanisms of fish scales under impact and penetration loads. A difference in nanomechanical properties was observed, with a thinner, stiffer and harder outer layer (indentation modulus ∼69 GPa and hardness ∼3.3 GPa) on a more compliant and thicker inner layer (indentation modulus ∼14.3 GPa and hardness ∼0.5 GPa). High-resolution scanning electron microscopy imaging of a fracture surface revealed that the outer layer contained oriented nanorods embedded in a matrix, and that the nanostructure of the inner layer contained fiber-like structures organized in a complex layered pattern. Damage patterns formed during microindentation show complex deformation mechanisms. Images of cracks identify growth through the outer layer, then deflection along the interface before growing and arresting in the inner layer. High-magnification images of the crack tip in the inner layer show void-linking and fiber-bridging exhibiting inelastic behavior. The observed difference in mechanical properties and unique nanostructures of different layers may have contributed to the resistance of fish scales to failure by impact and penetration loading.

Geochemical investigations of metals release from submerged coal fly ash using extended elutriate tests.

A storage pond dike failure occurred at the Tennessee Valley Authority Kingston Fossil Plant that resulted in the release of over 3.8 million cubic meters (5 million cubic yards) of fly ash. Approximately half of this material deposited in the main channel of the Emory River, 3.5 km upstream of the confluence of the Emory and Clinch Rivers, Tennessee, USA. Remediation efforts to date have focused on targeted removal of material from the channel through hydraulic dredging, as well as mechanical excavation in some areas. The agitation of the submerged fly ash during hydraulic dredging introduces river water into the fly ash material, which could alter the redox state of metals present in the fly ash and thereby change their sorption and mobility properties. A series of extended elutriate tests were used to determine the concentration and speciation of metals released from fly ash. Results indicated that arsenic and selenium species released from the fly ash materials during elutriate preparation were redox stable over the course of 10d, with dissolved arsenic being present as arsenate, and dissolved selenium being present as selenite. Concentrations of certain metals, such as arsenic, selenium, vanadium, and barium, increased in the elutriate waters over the 10d study, whereas manganese concentrations decreased, likely due to oxidation and precipitation reactions.

Redundant chemical sensors for calibration-impossible applications.

Multiple chemical sensors are used to measure the same analyte simultaneously to determine whether the redundant signals can improve the long-term accuracy and circumvent the need for periodic calibrations. A specific marine chemistry application was investigated where six glass pH electrodes were placed in a synthetic seawater solution for nearly 2 months without recalibration. The pH accuracy was evaluated by comparison with spectrophotometric pH measurements. The standard deviation, t-test and principal-component analysis were used to evaluate the redundant signals. The average signal standard deviation was useful for determining the onset of drift, whereas, the principal-component analysis readily identified specific sensors that were drifting. The sensor signals, shown through t-tests to be outliers, were eliminated from the data set, resulting in a significant improvement in measurement accuracy. After 56 days, the signals from non-drifting and drifting sensors resulted in a pH accuracy of +/-0.012 and +/-0.040, respectively, over a threefold improvement. The residual +/-0.012 inaccuracy was limited by the performance of the remaining sensors, which appeared to drift with similar magnitude and could therefore not be statistically separated. These results indicate that redundant sensors coupled with a principal-component analysis are a potential alternative for situations where calibrations are not feasible.

Comparison of direct serial dilution and most-probable-number methods for determining endotoxins in meats by the Limulus amoebocyte lysate test.

When the endotoxin content of ground beef was determined by direct serial dilution and by three-tube most-probable-number methods, the results were not significantly different, although the latter method provided more specific values for individual samples.

Evidence of low gene flow in a neotropical clustered tree species in two rainforest stands of French Guiana.

The spatial genetic structure of the neotropical, clustered tree species Vouacapoua americana (Aublet) was studied in two natural forest stands (Paracou and Nouragues) in French Guiana. Using eight microsatellite loci, V. americana is characterized by a marked genetic structure at small spatial distances (under 30-60 m), in agreement with the limited seed dispersal by rodent species. Gene flow through pollen is also shown to be mainly restricted to less than 100 m. This result suggests that most pollination events (mediated through small insects) are probably limited to within-patches of individuals, which might explain the high genetic differentiation among patches (F(ST) = 0.11) separated by less than 2 km. We also assume that stronger genetic structure in Paracou is likely to be due to lower seed dispersal by rodents, large spatial distances separating patches, or a recent recolonization event.

Culture medium for selective isolation and enumeration of Gram-negative bacteria from ground meats.

We developed a new medium, designated peptone bile amphotericin cycloheximide (PBAC) agar, which contains (per liter) 10 g of peptone, 300 mg of bile salts, 1 mg of amphotericin B, 1 g of cycloheximide, and 15 g of agar. When 21 samples of fresh ground beef were studied and plate count agar counts were used as references, we obtained a mean recovery of 28% of total counts with violet red bile agar overlay, whereas we obtained 48% recovery with PBAC agar. With 12 samples of frozen ground beef, recovery on violet red bile agar overlay was 29% of the recovery on plate count agar, whereas the corresponding value on PBAC agar was 45%. PBAC agar allowed the enumeration of 1.4 times as many gram-negative bacteria as violet red bile agar overlay. None of eight strains of gram-positive bacteria and none of eight strains of yeasts grew on PBAC agar. Of 158 colonies randomly selected from pour plates of eight fresh ground meat samples, 95% stained gram negative. In comparison, only 70% of 151 colonies selected from corresponding plate count agar plates were gram negative. The lack of background color, turbidity, and ease of use make PBAC agar easier to handle than other media used for gram-negative bacteria, such as violet red bile agar, violet red bile agar overlay, and crystal violet tetrazolium agar. In the preparation PBAC agar, all ingredients are autoclaved together except amphotericin B, which is filter sterilized and added before the plates are poured.