Bio-inspired functional surfaces for advanced applications

Over millions of years, biological subjects have been in continuous combat with extreme environmental conditions. The fittest have survived through continuous evolution, an ongoing process. In particular, biological surfaces, which are the active interfaces between subjects and the environment, are being evolved to a higher state of intelligent functionality. These surfaces became more efficient by using combinations of available materials, along with unique physical and chemical strategies. Noteworthy physical strategies include features such as texturing and structure, and chemical strategies such as sensing and actuation. These strategies collectively enable functional surfaces to deliver extraordinary adhesion, hydrophobicity, multispectral response, energy scavenging, thermal regulation, antibiofouling, and other advanced functions. Production industries have been intrigued with such biological surface strategies in order to learn clever surface architectures and implement those architectures to impart advanced functionalities into manufactured consumer products. This keynote paper delivers a critical review of such inspiring biological surfaces and their nonbiological product analogs, where manufacturing science and engineering have adopted such advanced functional surface architectures.     

Substituted Mo–V(Ti)–Te(Ce)-oxide M2 Catalysts for Propene Ammoxidation

One of the most effective propane to acrylonitrile ammoxidation catalyst is comprised of the two phases M1 (orthorhombic) Mo_7.5V_1.5NbTeO₂₉ and M2 (pseudo-hexagonal) Mo₄V₂Te₂O₂₀. Under reaction conditions, the two phases work in symbiosis with each other where M1 is the paraffin activating component and M2 is the olefin activating component. Since the catalytic improvement of either phase should result in an enhancement of the overall acrylonitrile yield, controlled substitution of certain elements in either or both phases might result in the desired improvement. Our current study concentrates on the partial substitutions of V with Ti and Te with Ce in the M2 phase. Ti substitution results in a considerable propene activity improvement, whereas the selectivity to acrylonitrile is unaffected. Substitution with Ce, on the contrary, substantially improves the selectivity to acrylonitrile. Also, a minor improvement of the activity is notable. The acrylonitrile selectivity improvement is a result of better NH₃ utilization and comes at the expense of reduced acrolein make. XRD reveals that all of the substituted compositions retain the M2 structure and essentially are monophasic. XANES recordings show for the bulk that the Mo is 6+, the V is 4+, or 4+ and 5+ when Ce is present, the Ti is 4+, the Ce is 3+, and the Te 4+ with some 6+ also present. According to the ESR data, in the M2 with Ce (7Te/3Ce) only 21% of the V is 4+, the remainder being 5+, which tentatively can be explained by the existence of some cation vacancies in the hexagonal channels. HRTEM imaging reveals little if any differences between the materials, all have the typical pseudo-hexagonal habit of the M2 phase and expose a 1–2 nm thick surface layer without any apparent long-range ordering. XPS data show that all catalysts, including the base, are highly enriched at the surface with Te at the expense of other metals. The 7Te/3Ce composition exhibits also substantial Ce surface enrichment. Moreover, the valences of the cations at the surface differ from the bulk in that for all fresh catalysts V is 5+ and Te is 6+ on the surface. Characterization by XPS of catalysts used in propene ammoxidation, reveals reduction of Te and, except when Ce is present, also Mo. Therefore, it might be inferred that the surfaces of the catalysts studied here are comprised essentially of one or a few monolayers of TeMoO or TeCeMoO on an interacting M2 crystalline base.     

Arteriovenous malformations of the head and neck: natural history and management

This is a retrospective review of 81 patients with extracranial arteriovenous malformation of the head and neck who presented to the Vascular Anomalies Program in Boston over the last 20 years. This study focused on the natural history and effectiveness of treatment. The male to female ratio was 1:1.5. Arteriovenous malformations occur in anatomic patterns. Sixty-nine percent occurred in the midface, 14 percent in the upper third of the face, and 17 percent in the lower third. The most common sites were cheek (31 percent), ear (16 percent), nose (11 percent), and forehead (10 percent). A vascular anomaly was apparent at birth in 59 percent of patients (82 percent in men, 44 percent in women). Ten percent of patients noted onset in childhood, 10 percent in adolescence, and 21 percent in adulthood. Eight patients first noted the malformation at puberty, and six others experienced exacerbation during puberty. Fifteen women noted appearance or expansion of the malformation during pregnancy. Bony involvement occurred in 22 patients, most commonly in the maxilla and mandible. In seven patients, the bone was the primary site; in 15 other patients, the bone was involved secondarily. Arteriovenous malformations were categorized according to Schobinger clinical staging: 27 percent in stage I (quiescence), 38 percent in stage II (expansion), and 38 percent in stage III (destruction). There was a single patient with stage IV malformation (decompensation). Stage I lesions remained stable for long periods. Expansion (stage II) was usually followed by pain, bleeding, and ulceration (stage III). Once present, these symptoms and signs inevitably progressed until the malformation was resected. Resection margins were best determined intraoperatively by the bleeding pattern of the incised tissue and by Doppler. Subtotal excision or proximal ligation frequently resulted in rapid progression of the arteriovenous malformation. The overall cure rate was 60 percent, defined as radiographic absence of arteriovenous malformation. Cure rate for small malformations was 69 percent with excision only and 62 percent for extensive malformations with combined embolization-resection. The cure rate was 75 percent for stage I, 67 percent for stage II, and 48 percent for stage III malformations. Outcome was not affected significantly by age at treatment, sex, Schobinger stage, or treatment method. Mean follow-up was 4.6 years.     

Spatial relationships between snow contaminant content, grain size, and surface temperature from multispectral images of Mt. Rainier, Washington (USA)

We use multispectral MODIS/ASTER Airborne Simulator (MASTER) data collected at Mt. Rainier, Washington (USA) to map spatial covariance between snowpack properties and to evaluate techniques for quantitative estimation of reflectance, grain size, and temperature. The late-August MASTER images reveal a distinct pattern of snow contaminant content, grain size, and temperature related to a recent snowfall and late-summer melting. Spatial correlation between grain size and temperature patterns suggests that rapid destructive metamorphism of the fresh snow occurred when temperatures were near 0 °C. We use 10 specific locations to evaluate hemispherical-directional reflectance factor (HDRF), grain size, and temperature retrievals. We map relative snow contaminant content using visible (0.4-0.8 μm) HDRF spectra. Atmospheric correction and topographic modeling limit the accuracy of HDRF estimates. We use MASTER-derived spectra near 1.8 and 2.2 μm to estimate optical grain size (by comparison to modeled layers of ice spheres) and physical grain size (by comparison to measured spectra with known physical grain size and by correlation to ground measurements). Estimated physical grain sizes were less than estimated optical grain sizes. Differing definitions of optical and physical grain sizes could contribute to this discrepancy. Limitations at 1.8 and 2.2 μm, including reduced discrimination between larger grain radii (>∼500 μm physical, >∼200 μm optical) and low signal-to-noise ration with atmospheric effects and decreasing solar irradiance, suggest that grain size retrieval may be improved at other wavelengths (e.g., 1.1 μm). Accounting for uncertainty in emissivity, atmospheric correction, and detector noise, we estimate systematic errors in our radiant temperatures at <1.8 °C. This study shows both strengths and limitations for coregistered visible, short-wave infrared, and thermal infrared images to estimate snowpack properties and reveal their spatial coherence.     

Interplay of energies in circuit breaker and fuse combinations

Some of the operating principles of contemporary molded-case circuit breakers and fuses are reviewed. Emphasis is placed on energy levels. It is shown how, in combination, these products and energies interact. This analysis of cause and effect shows why analytical selection of fuses for circuit breaker protection may yield unsafe combinations     

Polyubiquitin up-regulation in corpora lutea of prostaglandin-treated ewes

Genes that encode mRNAs for ubiquitin are activated by cells in metabolic distress. Cytosolic proteins that consequently become conjugated to ubiquitin are targeted for degradation. We hypothesized that ubiquitin mediates the endocrine demise of the corpus luteum induced by prostaglandin (PG) F2alpha. Indeed, polyubiquitin gene expression increased abruptly (within 2 h) in luteal tissues of ewes treated with PGF2alpha--before the precipitous decline in glandular progesterone accumulation indicative of functional luteolysis. A corresponding elevation in ubiquitin immunostaining was localized to large (PG-sensitive) luteal cells. It is suggested that luteal progesterone biosynthesis is disrupted by ubiquitination of steroidogenic regulatory proteins--perhaps those involved in the mechanics of mitochondrial delivery and side-chain cleavage of cholesterol.     

The influence of advance information about target location and visual feedback on movement planning and execution.

This study was designed to determine if movement planning strategies incorporating the use of visual feedback during manual aiming are specific to individual movements. Advance information about target location and visual context was manipulated using precues. Participants exhibited a shorter reaction time and a longer movement time when they were certain of the target location and that vision would be available. The longer movement time was associated with greater time after peak velocity. Under conditions of uncertainty, participants prepared for the worst-case scenario. That is, they spent more time organizing their movements and produced trajectories that would be expected from greater open-loop control. Our results are consistent with hierarchical movement planning in which knowledge of the movement goal is an essential ingredient of visual feedback utilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mice lacking ataxin-1 display learning deficits and decreased hippocampal paired-pulse facilitation

Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disorder characterized by ataxia, progressive motor deterioration, and loss of cerebellar Purkinje cells. To investigate SCA1 pathogenesis and to gain insight into the function of the SCA1 gene product ataxin-1, a novel protein without homology to previously described proteins, we generated mice with a targeted deletion in the murine Sca1 gene. Mice lacking ataxin-1 are viable, fertile, and do not show any evidence of ataxia or neurodegeneration. However, Sca1 null mice demonstrate decreased exploratory behavior, pronounced deficits in the spatial version of the Morris water maze test, and impaired performance on the rotating rod apparatus. Furthermore, neurophysiological studies performed in area CA1 of the hippocampus reveal decreased paired-pulse facilitation in Sca1 null mice, whereas long-term and post-tetanic potentiations are normal. These findings demonstrate that SCA1 is not caused by loss of function of ataxin-1 and point to the possible role of ataxin-1 in learning and memory.