Ultra-Broadband Excitations of Plasmonic Waveguides by Bowtie Apertures

Plasmonics - The plasmonic bowtie antenna constantly attracts researchers’ interests recently. In this paper, we design and demonstrate polarization sensitive and ultra-broadband excitations...     

Rule for Scaling Shoulder Rotation Angles while Walking through Apertures

Background

When an individual is trying to fit into a narrow aperture, the amplitude of shoulder rotations in the yaw dimension is well proportioned to the relative aperture width to body width (referred to as the critical ratio value). Based on this fact, it is generally considered that the central nervous system (CNS) determines the amplitudes of shoulder rotations in response to the ratio value. The present study was designed to determine whether the CNS follows another rule in which a minimal spatial margin is created at the aperture passage; this rule is beneficial particularly when spatial requirements for passage (i.e., the minimum passable width) become wider than the body with an external object.

Methodology/Principal Findings

Eight young participants walked through narrow apertures of three widths (ratio value = 0.9, 1.0, and 1.1) while holding one of three horizontal bars (short, 1.5 and 2.5 times the body width). The results showed that the amplitude of rotation angles became smaller for the respective ratio value as the bar increased in length. This was clearly inconsistent with the general hypothesis that predicted the same rotation angles for the same ratio value. Instead, the results were better explained with a new hypothesis which predicted that a smaller rotation angle was sufficient to produce a constant spatial margin as the bar-length increased in length.

Conclusion

The results show that, at least under safe circumstances, the CNS is likely to determine the amplitudes of shoulder rotations to ensure the minimal spatial margin being created at one side of the body at the time of crossing. This was new in that the aperture width subtracted from the width of the body (plus object) was taken into account for the visuomotor control of locomotion through apertures.     

Calculation of Leaf Photosynthetic Parameters Considering the Statistical Distribution of Stomatal Apertures

It was shown earlier (Laisk, Oja, and Kull, 1980) that differentstomata on a barley leaf are open to different degrees. Therefore,stomatal conductance is a quantity which is statistically distributedover a large range in the geometry of one leaf. Gas exchangemeasurements based on transpiration rates represent the averagevalue of stomatal conductance in the leaf chamber. The conventionalmethod of calculating mesophyll resistance involves subtractingstomatal resistance from total leaf resistance. It is incorrect,however, to average the stomatal resistance before this subtraction.Therefore, the conventional method for calculating the mesophyllresistance contains an error as it neglects the statisticaldistribution of stomatal apertures. The error is significantwhen the diffusion resistance between neighbouring substomatalcavities is large and when stomatal apertures vary over a widerange. Key words: Mesophyll resistance, Stomatal conductance, Statistics     

The Evolution of Complex Organs

The origin of complex biological structures has long been a subject of interest and debate. Two centuries ago, natural explanations for their occurrence were considered inconceivable. However, 150 years of scientific investigation have yielded a conceptual framework, abundant data, and a range of analytical tools capable of addressing this question. This article reviews the various direct and indirect evolutionary processes that contribute to the origins of complex organs. The evolution of eyes is used as a case study to illustrate these concepts, and several of the most common misconceptions about complex organ evolution are discussed.

Inactivation of Calcitonin by Specific Organs

THE greater biological potency of salmon calcitonin (SCT) as compared with mammalian calcitonins may be due to the relative resistance of SCT to inactivation in vivo^1,2. SCT infused into dogs disappears from the circulation more slowly than does porcine calcitonin (PCT) or human calcitonin (HCT)^1–3. For example, the metabolic clearance rate (MCR) of PCT in the dog is approximately 10 times greater than that of SCT^1,2. Neither renal excretion^3,4 nor inactivation by plasma^1,2 is sufficient to account for the rapid clearance of the calcitonins that we have observed in vivo and thus it seemed likely that inactivation of the hormones must occur during passage through one or more organs. Here we present data that suggest the kidney, the liver and muscle and/or bone as the sites of inactivation of the calcitonins in the dog. SCT is relatively resistant to inactivation in the latter two sites.     

Time-of-Flight Model for the Extraordinary Transmission Through Periodic Arrays of Subwavelength Apertures at THz Frequencies

A qualitative model explaining the extraordinary optical transmission of terahertz (THz) radiation through two-dimensional periodic arrays of subwavelength apertures is presented. Systematic terahertz time-domain spectroscopy studies have been undertaken to investigate the combined effects of the lattice arrangement, aperture shape, area and aspect ratio on the transmission properties of electroformed copper arrays. The extensive results presented provide a unified example of how aperture geometry dictates SPP activity. The novel fabrication method creates exemplary peak resonances, allowing the onset of surface plasmon polariton (SPP) decoupling to be distinguished from direct transmission. Furthermore, we provide the first evidence as to how the temporal properties of SPPs are governed by the single-cycle THz pulse. The time-of-flight model presented can not only be used to explain the results observed in both the presented and previously published experiments but serves as a method to engineer specific resonances for sensor applications.     

Storage Organs and Plant Growth

The purpose of this activity is to model the expansion of the universe by investigating the behavior of water waves. It is designed for students in the upper grades of physics and physical science who are learning about the wave nature of light and are ready to discover such important questions about science. The article explains first the Doppler effect through water waves and then extends to how to interpret light waves coming from other galaxies. Therefore, in addition to raising the scientific curiosity of the students, this activity also gives them an understanding of the hypothesis–evidence relation and the interpretation of data.     

Dealing Death and Retrieving Organs

It has recently been argued by Miller and Truog (2008) that, while procuring vital organs from transplant donors is typically the cause of their deaths, this violation of the requirement that donors be dead prior to the removal of their organs is not a cause for moral concern. In general terms, I endorse this heterodox conclusion, but for different and, as I think, more powerful reasons. I end by arguing that, even if it is agreed that retrieval of vital organs causes the deaths of those who provide them, that does not pose any new substantive difficulties for efforts to justify “opt-out” organ procurement systems.     

Statistical Distribution of Stomatal Apertures of Vicia faba and Hordeum vulgare and the Spannungsphase of Stomatal Opening

Plants of Vicia faba and Hordeum vulgare were grown in growthboxes with 7 mW cm^–2 PAR, 14 h day/10 h night, at 22/20°C. Stomata of attached leaves were measured under controlledconditions by means of an optical microscope and the distributionfunctions of the widths of pores were established. For Viciafaba they appeared to be symmetrical bell-shaped functions.In the process of stomatal opening or closure the shape of thedistribution remained constant, its maximum sliding left andright along the aperture axis. This result has been interpretedto mean that increments or decrements of apertures were equalfor all stomata independent of their individual apertures. Theconclusion has been drawn that the ‘driving force’is evenly distributed, equal for all stomata, and varies withinwider limits than is possible for stomatal apertures. Stomatalopening is limited by the closed state from below and by ananatomically possible maximum aperture from above.