Reproductive resilience but not root architecture underpins yield improvement under drought in maize.

Because plants capture water and nutrients through roots, it was proposed that changes in root systems architecture (RSA) might underpin the 3-fold increase in maize (Zea mays L.) grain yield over the last century. Here we show that both RSA and yield have changed with decades of maize breeding, but not the crop water uptake. Results from X-ray phenotyping in controlled environments showed that single cross (SX) hybrids have smaller root systems than double cross (DX) hybrids for root diameters between 2465 µm and 181µm (P<0.05). Soil water extraction measured under field conditions ranged between 2.6 mm d-1 and 2.9 mm d-1 but were not significantly different between SX and DX hybrids. Yield and yield components were higher for SX than DX hybrids across densities and irrigation (P<0.001). Taken together, the results suggest that changes in RSA were not the cause of increased water uptake but an adaptation to high-density stands used in modern agriculture. This adaptation may have contributed to shift in resource allocation to the ear and indirectly improved reproductive resilience. Advances in root physiology and phenotyping can create opportunities to maintain long-term genetic gain in maize, but a shift from ideotype to crop and production system thinking will be required.

Glenohumeral joint penetration with a 21-gauge standard needle.

BACKGROUND: This study assessed whether a standard 21-gauge needle (length, 38.1 mm [1.5 inches]) is more likely to penetrate the glenohumeral joint through an anterior or a posterior approach. METHODS: Seventy-nine patients underwent an arthroscopic procedure on the glenohumeral joint. The depth from the skin to the joint capsule was compared between the posterior approach (10 mm medial and inferior to the posterolateral tip of the acromion) and the anterior approach (direct visualization through the rotator interval). Each approach was measured twice and the mean used. The data were analyzed using a 2-sided paired t test. RESULTS: The anterior approach was shorter than the posterior approach in all patients (P < .001). This was less than the length of a standard needle in 98.7% of patients. The mean skin-to-joint capsule depth was 43.5 mm (range, 24-58 mm) with the posterior approach and 27.1 mm (range, 12.5-40 mm) with the anterior approach. On average, the posterior approach was 16.3 mm deeper (range, 0.5-31.5 mm) than the anterior approach. CONCLUSIONS: Injections through the anterior approach are more likely to penetrate the glenohumeral joint than through the posterior approach if a standard needle is used.

A generic model of real-world non-ideal behaviour of FES-induced muscle contractions: simulation tool.

Functional electrical stimulation (FES) applications are frequently evaluated in simulation prior to testing in human subjects. Such simulations are usually based on the typical muscle responses to electrical stimulation, which may result in an overly optimistic assessment of likely real-world performance. We propose a novel method for simulating FES applications that includes non-ideal muscle behaviour during electrical stimulation resulting from muscle fatigue, spasms and tremors. A 'non-idealities' block that can be incorporated into existing FES simulations and provides a realistic estimate of real-world performance is described. An implementation example is included, showing how the non-idealities block can be incorporated into a simulation of electrically stimulated knee extension against gravity for both a proportional-integral-derivative controller and a sliding mode controller. The results presented in this paper illustrate that the real-world performance of a FES system may be vastly different from the performance obtained in simulation using nominal muscle models. We believe that our non-idealities block should be included in future simulations that involve muscle response to FES, as this tool will provide neural engineers with a realistic simulation of the real-world performance of FES systems. This simulation strategy will help engineers and organizations save time and money by preventing premature human testing. The non-idealities block will become available free of charge at www.toronto-fes.ca in late 2011.

Including nonideal behavior in simulations of functional electrical stimulation applications.

Simulations of functional electrical stimulation (FES) systems are usually based on the typical or ideal stimulated muscle response, which may result in an overly optimistic prediction of the FES system's performance in real-world applications. We have developed a Simulink block that allows actual nonideal behavior of electrically stimulated muscles to be incorporated into existing FES simulations. This block is based on data collected from complete spinal cord injuries (SCI) subjects, and it modifies the nominal stimulated muscle response to reflect undesirable behavior seen in real-world FES applications, including spasms, tremors, and fatigue. The severity of each type of undesirable behavior can be specified by the user. In this paper, we discuss the design of the block and also present an example of how the block can be used to more accurately assess the probable real-world performance of FES systems prior to testing with SCI subjects.