Keeping a Clean Surface under Water: Nanoscale Nipple Array Decreases Surface Adsorption and Adhesion Forces

While nanoscale nipple arrays are expected to reduce light reflection and/or dust contamination in some insects, similar structures have been reported in various marine invertebrates. To evaluate the anti-contamination property of the structure in aquatic regimes, we measured the adsorption and adhesion forces on the flat surface and MOSMITE™ (Mitsubishi Chemical Corporation, Tokyo, Japan), a synthetic material mimicking the nipple array, under water. A small force toward the surface occurred when the probe approached the substrate surface. This adsorption force was significantly smaller on MOSMITE™ than on the flat surface. The adhesion force toward the surface occurred when the probe was detached from the surface, and it was also significantly smaller on MOSMITE™ than on the flat surface. The adhesion force in the air was much greater than the force under water, and the force was also significantly smaller on MOSMITE™ than on the flat surface. In the aquatic regime, the nipple array provides less adsorption/adhesion properties for the surface and thus, the organisms would have less contamination of microparticles on their body surface. As the adsorption and adhesion forces are also involved in the attachment of cells, tissue, and larvae, less adhesive body surfaces should be beneficial for survival in aquatic environments, as well as land environments.

Fabrication of High-Density Out-of-Plane Microneedle Arrays with Various Heights and Diverse Cross-Sectional Shapes

Out-of-plane microneedle structures are widely used in various applications such as transcutaneous drug delivery and neural signal recording for brain machine interface. This work presents a novel but simple method to fabricate high-density silicon (Si) microneedle arrays with various heights and diverse cross-sectional shapes depending on photomask pattern designs. The proposed fabrication method is composed of a single photolithography and two subsequent deep reactive ion etching (DRIE) steps. First, a photoresist layer was patterned on a Si substrate to define areas to be etched, which will eventually determine the final location and shape of each individual microneedle. Then, the 1st DRIE step created deep trenches with a highly anisotropic etching of the Si substrate. Subsequently, the photoresist was removed for more isotropic etching; the 2nd DRIE isolated and sharpened microneedles from the predefined trench structures. Depending on diverse photomask designs, the 2nd DRIE formed arrays of microneedles that have various height distributions, as well as diverse cross-sectional shapes across the substrate. With these simple steps, high-aspect ratio microneedles were created in the high density of up to 625 microneedles mm−2 on a Si wafer. Insertion tests showed a small force as low as ~ 172 µN/microneedle is required for microneedle arrays to penetrate the dura mater of a mouse brain. To demonstrate a feasibility of drug delivery application, we also implemented silk microneedle arrays using molding processes. The fabrication method of the present study is expected to be broadly applicable to create microneedle structures for drug delivery, neuroprosthetic devices, and so on.

Solomon Islands tension reflects regional importance

Significance After rioting in the capital, Honiara, late last month Sogavare sought Australian assistance under a bilateral security accord and Canberra dispatched a small force of police and troops to help stabilise the situation. The riots are linked to Sogavare’s decision to switch diplomatic recognition from Taiwan to China in 2019; Beijing has condemned the Australian response. Impacts The Solomon Islands and Papua New Guinea will remain the chief focus of regional rivalries between China and the West. Australia will step up efforts to shut Beijing out of sensitive telecoms services in the region. China’s shift from aid to concessionary loans for infrastructure projects will deepen political concerns over indebtedness.

Texas, Mobile, and Wilson’s Raid

Civil wars in both the United States and Mexico during the 1850s–1860s fostered the most serious challenge to the Monroe Doctrine in American history. Taking advantage of Mexico’s internal troubles, Emperor Napoleon III of France installed a Hapsburg prince as the new emperor of Mexico. Although invited to intervene by Mexican conservatives, no one liked the prince who remained on the throne only at the point of thirty thousand French Army bayonets. The U.S. government tried to intimidate Napoleon to withdraw his troops by placing a small force in the lower Rio Grande Valley, but it failed to have an effect. Two campaigns closed the war in the West by capturing Mobile, Alabama, and destroying Confederate war industries in Alabama and Georgia before the Federals could shift large numbers of troops to Texas and finally bring an end to the French intervention in Mexico.

Design and Modeling of Series-Parallel Compliant Device for Reliable Assembly Under Position/Angle Deviation

Automatic assembly using manipulator has attracted increasing attention due to low cost and high quality of assembly. As the manipulator is entirely rigid, it often causes assembly failure and even damages the manipulator when there is a position or angle deviation. A series-parallel compliant device is developed here to realize the reliable assembly under the position or the angle deviation and does not produce a significant contact force. Its core idea is that when the contact force exceeds a specific value, this device becomes compliant and can move in a particular direction. It guarantees that this assembly allows a relatively significant misalignment and produces a small force, protecting parts and manipulators. This device has two compliant components, and these two components are connected using a rigid block. Each compliant component consists of the rigid frame, the four elastic limbs with a similar ‘n’ shape, and the square block. Due to using the elastic material, each elastic limb is equivalent to a compliant hinge (or spring), making this designed device equal to a series-parallel compliant structure. In this way, this device becomes compliant and can move in a particular direction when the contact force exceeds a specific value. On this basis, the desired compliance of the device is realized in various directions depending on the compliant device, and an optimization method is designed to achieve the parameters of this device based on the kinematic model and the stiffness analysis. Experiments under different working conditions are carried out and demonstrate the reliable assembling performance of this designed device even if there exists the position deviation or the angle deviation.

Small Force Sensor to Measure the Three Components of the Ground Reaction Forces in Mice

The measurement of ground reaction forces (GRFs) helps in determining the role of each limb for support and propulsion in predicting muscle activities, and in determining the strain conditions experienced by bones. Measuring the GRFs in mice models is therefore a cornerstone for understanding rodent musculoskeletal and neuromotor systems, as well as for improved translation of knowledge to humans. Current force plates are too big in size to allow the measurement of forces for each paw. This limitation is mainly due to the large size of the used sensors. The goal of our study was therefore to develop a small 3D force sensor for application in rodent gait analysis. We designed a flexible and small mechanical structure (8 mm × 8 mm) to isolate force components. Using FEM simulation, we chose the area with the highest strain to fix two strain gauges for each direction. The small size of the sensor allows us to fix four of them under a plate on the mouse paw size (approximately 17 mm). According to our primary results, the force plate has a resolution of 2 mN in the vertical direction and 1 mN in the fore-aft and mediolateral directions. The construction of a runway with such a force plate will allow the measurement of GRFs and the centre of pressure of each rodent paw for different steps. Such techniques thus provide a basis for assessing functionality in mice models, towards improved translation of rodent research.

Sir Henry Clinton to the Rescue

The chapter discusses the attempt by Lieutenant General Sir Henry Clinton to support Burgoyne’s army. Clinton was Howe’s second-in-command and remained in New York with a small force while Howe went to Philadelphia with the main army. Clinton had received only positive reports from Burgoyne, but on September 22, he received a message that Burgoyne was in dire trouble. Clinton organized a small force to go up the Hudson River, hoping to pull Gates south and away from Burgoyne. Burgoyne dug in to wait for Clinton. Clinton quickly captured the American forts Clinton and Montgomery in the Hudson Highlands, but after burning Esopus, New York (present-day Kingston), Clinton’s force—now under Major General John Vaughan—was forced to return to New York City. In the meantime, Howe had captured Philadelphia, but was unable to defeat Washington in a decisive battle, despite winning the battles of Brandywine and Germantown.

Nanomechanical Effects

This chapter discusses the effect of force and deformation of the tip apex and the sample surface in the operation and imaging mechanism of STM and AFM. Because the contact area is of atomic dimension, a very small force and deformation would generate a large measurable effect. Three effects are discussed. First is the stability of the STM junction, which depends on the rigidity of the material. For soft materials, hysterisis is more likely. For rigid materials, the approaching and retraction cycles are continuous and reproducible. Second is the effect of force and deformation to the STM imaging mechanism. For soft material such as graphite, force and deformation can amplify the observed corrugation. For hard materials as most metals, force and deformation can decrease the observed corrugation. Finally, the effect of force and deformation on tunneling barrier height measurements is discussed.

On quasisymmetric plasma equilibria sustained by small force

We construct smooth, non-symmetric plasma equilibria which possess closed, nested flux surfaces and solve the magnetohydrostatic (steady three-dimensional incompressible Euler) equations with a small force. The solutions are also ‘nearly’ quasisymmetric. The primary idea is, given a desired quasisymmetry direction $\xi$ , to change the smooth structure on space so that the vector field $\xi$ is Killing for the new metric and construct $\xi$ –symmetric solutions of the magnetohydrostatic equations on that background by solving a generalized Grad–Shafranov equation. If $\xi$ is close to a symmetry of Euclidean space, then these are solutions on flat space up to a small forcing.

Quantifying resolution in cosmological N-body simulations using self-similarity

We demonstrate that testing for self-similarity in scale-free simulations provides an excellent tool to quantify the resolution at small scales of cosmological N-body simulations. Analysing two-point correlation functions measured in simulations using Abacus, we show how observed deviations from self-similarity reveal the range of time and distance scales in which convergence is obtained. While the well-converged scales show accuracy below 1%, our results show that, with a small force softening length, the spatial resolution is essentially determined by the mass resolution. At later times the lower cut-off scale on convergence evolves in comoving units as a−1/2 (a being the scale factor), consistent with a hypothesis that it is set by two-body collisionality. A corollary of our results is that N-body simulations, particularly at high red-shift, contain a significant spatial range in which clustering appears converged with respect to the time-stepping and force softening but has not actually converged to the physical continuum result. The method developed can be applied to determine the resolution of any clustering statistic and extended to infer resolution limits for non-scale-free simulations.