Carbon-centered radicals as oxygen sensors for in vivo electron paramagnetic resonance: screening for an optimal probe among commercially available charcoals

It is known that some charcoals possess paramagnetic centers with an electron paramagnetic resonance (EPR) linewidth which can be broadened by oxygen. In order to identify potential candidates as sensors for in vivo EPR oximetry, we carried out a systematic study among commercially available charcoals. A total of 34 charcoals were tested. The steps used for the screening were: (1) to check the presence of paramagnetic centers in the material; (2) to measure the EPR linewidth in nitrogen and in air on the dry material and on a aqueous suspension of particles; (3) to calibrate the oxygen sensitive materials (EPR linewidth vs. pO₂); (4) to test the sensitivity and stability of the response to changes of pO₂ in a simple model of hypoxia induced in mice. Seventeen charcoals contained paramagnetic centers detectable by low-frequency EPR (1.1 GHz). The EPR spectrum consist of one single line which is typical of carbon-centered radicals (g-factor ∼2). Eight charcoals presented sufficient interesting EPR properties (linewidth in nitrogen <0.1 mT, linewidth in air for an aqueous suspension of particles >0.15 mT) to be further characterized in vivo. Only three charcoals presented a stable, reproducible, and sensitive response to pO₂ for more than 2 months. These three coals should be considered as good candidates to be used as oxygen sensor using in vivo EPR spectroscopy.     

Should extended disability be an exclusion criterion for tertiary rehabilitation? Socioeconomic outcomes of early versus late functional restoration in compensation spinal disorders

STUDY DESIGN: A prospective cohort design with two groups of patients representing short-term or long-term disability (n = 497) who were selected from a larger cohort (n = 938) of consecutively treated spinal disorder patients with chronic compensation injuries. OBJECTIVES: To prospectively evaluate the impact of length of spinal disability on socioeconomic outcomes of medically directed rehabilitation. SUMMARY OF BACKGROUND DATA: Despite an increasing tendency of managed care organizations to limit rehabilitation services for disabled workers with chronic spinal disorders, there has been a surprising lack of prospective research evaluating the impact of length of disability on objective socioeconomic treatment outcomes. Although only approximately 10% of all patients with spinal disorders are disabled beyond 4 months, they account for nearly 80% of all workers' compensation expenditures. Little is known about whether relatively early intervention improves outcomes after chronicity has been established or whether any predictors distinguish between these groups. METHODS: Two comparison groups of functional restoration tertiary treatment graduates were identified from the same community referral pool. The "long-term disabled" group involved a minimum of 18 months of disability (n = 252). This group was compared with a "short-term disabled" group (n = 245), no more than 8 months since injury, but chronic based on a minimum of 4 months after injury. The long-term disabled group showed significantly higher rates of pretreatment surgery than the short-term disabled group (P < 0.001). All patients were evaluated prospectively with specific physical, psychological, and occupational measurements. They also underwent a structured interview 1 year after treatment evaluating work status, health care use, and recurrent injury. RESULTS: The short-term disabled group showed statistically higher return to work (P < 0.001) and work retention (P < 0.05) relative to the long-term disabled group. However, health care use and recurrent lost time injury claims were low in both groups and did not differ significantly. No predictors of outcome were found among the prospectively collected physical performance or psychosocial variables. CONCLUSIONS: This study suggests that early tertiary nonoperative care, once patients with chronic spinal disorders are identified as having potentially high-cost chronic pain and disability, is efficacious in achieving goals of better work return and work retention. Such early rehabilitation may also prevent significant indemnity expense, as well as some late surgical interventions sought by progressively more desperate patients. However, individuals with long-term disability achieve respectable work return and retention rates, while faring no worse on other socioeconomic outcomes that represent major "cost drivers" to the workers' compensation system. Early intervention is not a panacea or a necessary condition for the successful rehabilitation of workers with disabling chronic spinal disorders.     

The static and dynamic properties of the avalanche injection diode

Since the proposal of the avalanche injection diode, AID, by Gunn, it has become necessary to incorporate fundamental knowledge regarding collision multiplications and other high field, high current density effects into models that approximate actual devices. Previous approaches to the problem have been inadequate for all but a qualitative appreciation of the behavior of the device. This investigation has produced a more comprehensive model for the AID; one that encompasses to some extent both high and low electric field effects, and explains the observed, low-level dynamic response of the device in terms of conductivity modulation effects. The steps leading to a numerical evaluation of the high frequency behavior of the device in terms of geometric and material parameters have been developed and have been used to explain the characteristics of typical units.     

PAH and other emissions from burning of JP-8 and diesel fuels in diffusion flames

Jet fuel JP-8 is of technical interest to the military aviation industry. JP-8 is now the single battlefield fuel for all US Army and Air Force equipment, replacing gasoline altogether and gradually replacing diesel fuel. Hence, emissions from the combustion of this fuel are the subject for this investigation. The emissions from the combustion of JP-8 fuel are examined and are compared to those from diesel fuel No. 2, burned under identical conditions. Combustion occurred inside a laboratory furnace in sooty diffusion flames, under adverse conditions that typically emit large amounts of products of incomplete combustion (PIC). Under such conditions, even compounds that otherwise might appear only in trace amounts were present in sufficient quantities for detection. The study reports on emissions of CO, light volatile organic compounds, semi-volatile organic compounds with an emphasis on polycyclic aromatic hydrocarbons (PAH), particulate emissions, oxides of nitrogen (NO_x) and oxides of sulfur (SO₂). Some PAH compounds are suspected of posing a threat to human health, benzo[a]pyrene being listed as a bio-accumulative toxin by the EPA. An afterburner was also used to examine the effects of longer furnace residence time. Results have demonstrated that PAH emissions from the combustion of diesel fuel were higher than those of JP-8, under most conditions examined. Moreover, as the temperature of the primary furnace was increased, in the range of 600–1000 °C, most of the emissions from both fuels increased. Particulate emissions were reduced by the afterburner, which was operated at 1000 °C, only when the primary furnace was operated at the lowest temperature (600 °C), but that condition increased the CO emissions. Overall, transient combustion of these two fuels, burning in laminar and sooty diffusion flames, did not reveal major differences in the emissions of the following PIC: C1–C4 light aliphatic hydrocarbons, PAH, CO and particulate matter.     

Thermal Stability of Air Plasma Spray and Solution Precursor Plasma Spray Thermal Barrier Coatings

Yttria-stabilized zirconia (7YSZ) thermal barrier coatings (TBCs) were produced by conventional air plasma spray (APS) and solution precursor plasma spray (SPPS) processes. Both TBCs were isothermally heat treated from 1200° to 1500°C for 100 h. Changes in the phase content, microstructure, and hardness were investigated. The nontransformable tetragonal ( t ') phase is the predominant phase in both the as-sprayed APS and SPPS TBCs. APS and SPPS coatings exhibit similar thermal stability behavior such as densification rate, hardness increase, and grain coarsening rate. Both the as-received and heat-treated APS and SPPS TBCs show a bimodal pore size distribution with nano- and micro-size pores. After 1400°C/100 h heat treatment, equiaxed grains replace the columnar structure in APS TBCs and the splat structure disappears. Vertical cracks remain after the 1500°C/100 h exposure in SPPS TBCs. The monoclinic phase appears in APS TBCs after a 1400°C/100 h exposure and in SPPS coatings after a 1500°C/100 h exposure.     

Interactions of HIV‐1 Antibodies 2F5 and 4E10 with a gp41 Epitope Prebound to Host and Viral Membrane Model Systems

Point of recognition : Surface plasmon resonance was used to study the role of the viral membrane in HIV immunogen recognition by the monoclonal antibodies 2F5 and 4E10. The different behaviour of the antibodies towards membranes and immunogens embedded within membranes, provide insight into the emerging membrane‐based or membrane‐conformation strategies of immunogen design.

     

Detection of Human Neutrophil Elastase by Fluorescent Peptide Sensors Conjugated to TEMPO-Oxidized Nanofibrillated Cellulose

Peptide–cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1−10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1−10) orientations of crystals extracted from cotton demonstrates a preference for the (1−10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.     

Laser photothermal non-destructive inspection method for hairline crack detection in unsintered automotive parts: A statistical approach

A statistical non-contacting and non-intrusive method for revealing the presence of cracks in unsintered (green) parts manufactured by powder metallurgy (PM) technology was developed based on photothermal radiometry (PTR). The technique relies on the interaction of a modulated laser-generated thermal wave with the crack resulting in change of amplitude and phase of the detected signal. The crack existence at points in high stress regions of a group of green sprockets was evaluated through the proposed method. The results were validated by an independent destructive technique—microscope observation of the tested green sprockets following sintering, sectioning, and polishing at the locations where signal changes were observed in the green state. Statistical analysis confirmed the excellent sensitivity (91%) of the method in detecting the presence of hairline (～5–10 μm) cracks. This PTR diagnostic technique may lead to a simple and reliable on-line inspection methodology in high-stress locations of PM manufactured industrial steel products. Ultimately, the method can be developed for non-destructive quality and feedback control of the metal forming process of green automotive parts.