Determination of particle size by using the angular distribution of backscattered light as measured with low-coherence interferometry

We employ a novel interferometer to measure the angular distribution of light backscattered by a turbid medium. Through comparison of the measured data with the predictions of Mie theory, we are able to determine the size of the scatterers comprising the medium with subwavelength precision. As the technique is based on low-coherence interferometry, we are able to examine the evolution of the angular distribution of scattered light as it propagates into the medium. The effects of multiple scattering as a function of penetration depth in the medium are analyzed. We also present various considerations for extending this technique to determining structural information in biological tissues, such as the effects of a distribution of particle sizes and the need to average out speckle contributions

Silk-fibronectin protein alloy fibres support cell adhesion and viability as a high strength, matrix fibre analogue

Silk is a natural polymer with broad utility in biomedical applications because it exhibits general biocompatibility and high tensile material properties. While mechanical integrity is important for most biomaterial applications, proper function and integration also requires biomaterial incorporation into complex surrounding tissues for many physiologically relevant processes such as wound healing. In this study, we spin silk fibroin into a protein alloy fibre with whole fibronectin using wet spinning approaches in order to synergize their respective strength and cell interaction capabilities. Results demonstrate that silk fibroin alone is a poor adhesive surface for fibroblasts, endothelial cells, and vascular smooth muscle cells in the absence of serum. However, significantly improved cell attachment is observed to silk-fibronectin alloy fibres without serum present while not compromising the fibres' mechanical integrity. Additionally, cell viability is improved up to six fold on alloy fibres when serum is present while migration and spreading generally increase as well. These findings demonstrate the utility of composite protein alloys as inexpensive and effective means to create durable, biologically active biomaterials.T32 EB006359 - NIBIB NIH HH

Evaluation of Neimann-pick type C1 disease using mixed effects models

Niemann-Pick Type C1 (NPC1) is an autosomal neurologic pediatric orphan disease, with death occurring by age 20-25. It is estimated that 1 in 150,000 people in the United States (US) and 1 in 100,000 people in the European Union (EU) suffers from NPC1. The disease results from NPC1 gene mutations which cause defective protein activity, leading to harmful levels of cholesterol and sphingolipids in cells. Using data from a natural history study and a phase 1 study we investigated the efficacy of a potential treatment for NPC1 in patients aged 6 to 26 with multiple follow-up visits. To evaluate the change in severity of neurologic manifestations, we focused on nine different measures: dietary restrictions, diminished lip strength, diminished tongue strength, dysarthria, ability to consume liquids, risk of laryngeal penetration when consuming liquids or solids, ability to consume solids, speech difficulties, and swallowing difficulties. The primary objective of our analysis evaluated the efficacy of the proposed treatment in reducing the aforementioned symptoms of NPC1. For each symptom, a random intercept mixed-effects model was fit incorporating the factors of time, treatment, and their interaction as potential predictors. Our strategy has certain advantages over a traditional randomized clinical trial (RCT) as it uses patients enrolled from an ongoing natural history study for which we already have some data on the progression of the disease. Furthermore, it provides a pool of patients from which to recruit phase 1 participants. From an analytic point of view, it provides an efficient use of the available data and an alternative design to an RCT that requires greater sample sizes which would be difficult to obtain in the setting of a rare disease. The utilization of our study design can expedite orphan disease research by decreasing the amount of patients necessary to reach meaningful conclusions from efficacy studies. For these reasons, our approach provides a practical alternative in evaluating efficacy of treatment in rare/orphan disease research, a very current public health issue

Estimation of liquidus temperatures in silicate glasses

Two models for estimating liquidus temperature from composition are presented and compared with thermodynamically calculated temperature as well as primary phase. Α simple polynomial model is given for high silica glasses, while a model covering a wide composition range and several primary phase fields is more complex. Thermodynamic calculations generally give too high liquidus temperatures in the devitrite field and too low in the primary field for Na2O · 2 CaO · 3 SiO2. In the wollastonite field the values are scattered, but in general too high

Measuring the Interplanetary Medium with a Solar Sail

NASA has been considering a solar sail that would accelerate a craft to a high velocity (~ 14 AU/yr) by the time it reached 5 AU. Then the sail would be dropped and the craft would coast alone to deep space. We propose that the sail be retained longer. Then the density of the interplanetary medium could be determined by measuring the drag force on the huge sail using radiometric navigational data. Such an experiment would yield an independent, new type of measurement of the interplanetary medium and should be pursued.Comment: 12 page

Psychological principles of successful aging technologies: A mini-review

Based on resource-oriented conceptions of successful life-span development, we propose three principles for evaluating assistive technology: (a) net resource release; (b) person specificity, and (c) proximal versus distal frames of evaluation. We discuss how these general principles can aid the design and evaluation of assistive technology in adulthood and old age, and propose two technological strategies, one targeting sensorimotor and the other cognitive functioning. The sensorimotor strategy aims at releasing cognitive resources such as attention and working memory by reducing the cognitive demands of sensory or sensorimotor aspects of performance. The cognitive strategy attempts to provide adaptive and individualized cuing structures orienting the individual in time and space by providing prompts that connect properties of the environment to the individual's action goals. We argue that intelligent assistive technology continuously adjusts the balance between `environmental support' and `self-initiated processing' in person-specific and aging-sensitive ways, leading to enhanced allocation of cognitive resources. Furthermore, intelligent assistive technology may foster the generation of formerly latent cognitive resources by activating developmental reserves (plasticity). We conclude that `lifespan technology', if co-constructed by behavioral scientists, engineers, and aging individuals, offers great promise for improving both the transition from middle adulthood to old age and the degree of autonomy in old age in present and future generations. Copyright (C) 2008 S. Karger AG, Basel

Unselected brain imaging in suspected meningitis delays lumbar puncture, can prolong hospitalisation and may increase antibiotic costs - a pilot study

Background: Antibiotics reduce mortality in bacterial meningitis; a lumbar puncture (LP) will demonstrate that many patients with suspected meningitis do not need them; but delays reduce chances of culture, particularly if N8 h. Guidelines advise a LP without brain imaging unless specific features are present. Objective: We assessed the duration of hospitalisation and inpatient costs incurred with delays in LP in a Northwest of England teaching hospital. Methods: We screened the cerebrospinal fluid (CSF) database to identify patients with suspected meningitis over 3 months (07–09/ 2010). Data were recorded from clinical case notes; costs were calculated with established datasets and the British national formulary. Results: 142 patients were screened; 35 had a suspected CNS infection; 10 had a CNS infection proven: 3 bacterial meningitis; 4 aseptic meningitis and 3 viral encephalitis. Brain imaging delayed the LP for 19 (54%), (11.08 vs 5.29 hrs, p= 0.10); ten (53%) did not need imaging. 11 (42%) of those given antibiotics before the LP were delayed N8 h. For patients with aseptic meningitis and those who had a CNS infection excluded, without prior antibiotics, the delay in LP increased duration of hospitalisation (r=0.94, p=0.02 and r=0.96, p=0.01 respectively). Overall there was no trend with LP delays and antibiotic cost. However, 4 patients had antibiotics continued despite negative cultures; 2 of whom had the LP delayed N8 h, with an antibiotic cost of £215.96. Conclusion: Inappropriate brain imaging often delayed the LP; in patients who did not need antibiotics this led to longer hospitalisation

Formation and Evolution of Planetary Systems (FEPS): Properties of Debris Dust around Solar-type Stars

We present Spitzer photometric (IRAC and MIPS) and spectroscopic (IRS low resolution) observations for 314 stars in the Formation and Evolution of Planetary Systems (FEPS) Legacy program. These data are used to investigate the properties and evolution of circumstellar dust around solar-type stars spanning ages from approximately 3 Myr to 3 Gyr. We identify 46 sources that exhibit excess infrared emission above the stellar photosphere at 24um, and 21 sources with excesses at 70um. Five sources with an infrared excess have characteristics of optically thick primordial disks, while the remaining sources have properties akin to debris systems. The fraction of systems exhibiting a 24um excess greater than 10.2% above the photosphere is 15% for ages < 300 Myr and declines to 2.7% for older ages. The upper envelope to the 70um fractional luminosity appears to decline over a similar age range. The characteristic temperature of the debris inferred from the IRS spectra range between 60 and 180 K, with evidence for the presence of cooler dust to account for the strength of the 70um excess emission. No strong correlation is found between dust temperature and stellar age. Comparison of the observational data with disk models containing a power-law distribution of silicate grains suggest that the typical inner disk radius is > 10 AU. Although the interpretation is not unique, the lack of excess emission shortwards of 16um and the relatively flat distribution of the 24um excess for ages <300~Myr is consistent with steady-state collisional models.Comment: 85 pages, 18 figures, 4 tables; accepted for publication in ApJ

Spitzer/IRAC Limits to Planetary Companions of Fomalhaut and epsilon Eridani

Fomalhaut and epsilon Eridani are two young, nearby stars that possess extended debris disks whose structures suggest the presence of perturbing planetary objects. With its high sensitivity and stable point spread function, Spitzer/IRAC is uniquely capable of detecting cool, Jupiter-like planetary companions whose peak emission is predicted to occur near 4.5 um. We report on deep IRAC imaging of these two stars, taken at 3.6 and 4.5 um using subarray mode and in all four channels in wider-field full array mode. Observations acquired at two different telescope roll angles allowed faint surrounding objects to be separated from the stellar diffraction pattern. No companion candidates were detected at the reported position of Fomalhaut b with 3 sigma model-dependent mass upper limits of 3 MJ (for an age of 200 Myr). Around epsilon Eridani we instead set a limit of 4 and <1 MJ (1 Gyr model age) at the inner and outer edge of the sub-millimeter debris ring, respectively. These results are consistent with non-detections in recent near-infrared imaging searches, and set the strongest limits to date on the presence of planets outside epsilon Eridani sub-millimeter ring.Comment: Accepted by The Astrophysical Journal. Request electronic-only plates to M. Marengo ([email protected]