Buckling of a growing tissue and the emergence of two-dimensional patterns

The process of biological growth and the associated generation of residual stress has previously been considered as a driving mechanism for tissue buckling and pattern selection in numerous areas of biology. Here, we develop a two-dimensional thin plate theory to simulate the growth of cultured intestinal epithelial cells on a deformable substrate, with the goal of elucidating how a tissue engineer might best recreate the regular array of invaginations (crypts of Lieberkühn) found in the wall of the mammalian intestine. We extend the standard von Kármán equations to incorporate inhomogeneity in the plate’s mechanical properties and surface stresses applied to the substrate by cell proliferation. We determine numerically the configurations of a homogeneous plate under uniform cell growth, and show how tethering to an underlying elastic foundation can be used to promote higher-order buckled configurations. We then examine the independent effects of localised softening of the substrate and spatial patterning of cellular growth, demonstrating that (within a two-dimensional framework, and contrary to the predictions of one-dimensional models) growth patterning constitutes a more viable mechanism for control of crypt distribution than does material inhomogeneity

Are joint torque models limited by an assumption of monoarticularity?

This study determines whether maximal voluntary ankle plantar flexor torque could be more accurately represented using a torque generator that is a function of both knee and ankle kinematics. Iso velocity and isometric ankle plantar flexor torques were measured on a single participant for knee joint angles of 111° to 169° (approximately full extension) using a Contrex M J dynamometer. Maximal voluntary torque was represented by a 19-parameter two-joint function of ankle and knee joint angles and angular velocities with the parameters determined by minimizing a weighted root mean square difference between measured torques and the two-joint function. The weighted root mean square difference between the two-joint function and the measured torques was 10 N-m or 3% of maximum torque. The two-joint function was a more accurate representation of maximal voluntary ankle plantar flexor torques than an existing single-joint function where differences of 19% of maximum torque were found. It is concluded that when the knee is flexed by more than 40°, a two-joint representation is necessary

An isovelocity dynamometer method to determine monoarticular and biarticular muscle parameters

This study aimed to determine whether subject-specific individual muscle models for the ankle plantar flexors could be obtained from single joint isometric and isovelocity maximum torque measurements in combination with a model of plantar flexion. Maximum plantar flexion torque measurements were taken on one subject at six knee angles spanning full flexion to full extension. A planar three-segment (foot, shank and thigh), two muscle (soleus and gastrocnemius) model of plantar flexion was developed. Seven parameters per muscle were determined by minimizing a weighted root mean square difference (wRMSD) between the model output and the experimental torque data. Valid individual muscle models were obtained using experimental data from only two knee angles giving a wRMSD score of 16 N m, with values ranging from 11 to 17 N m for each of the six knee angles. The robustness of the methodology was confirmed through repeating the optimization with perturbed experimental torques (±20%) and segment lengths (±10%) resulting in wRMSD scores of between 13 and 20 N m. Hence, good representations of maximum torque can be achieved from subject-specific individual muscle models determined from single joint maximum torque measurements. The proposed methodology could be applied to muscle-driven models of human movement with the potential to improve their validity

Input and Output Optimization in Linux for Appropriate Resource Allocation and Management

There is one evident area of operating systems that has enormous potential for growth and optimization. Only recently has focus been put on upgrading resources in the input/output (I/O) mechanisms of Linux operating systems. This focus has proven that there is no real optimal methodology for I/O scheduling devices in Linux. In order to allocate resources efficiently for time-intensive experiments on metadata and mobile devices, which both rely heavily on energy resources, Linux operating system developers must create new techniques for appropriately allocating these integral parts of computation. Advances must also be made to reduce the traffic in the file system alongside the optimization of energy resources in order to ensure that the system runs as efficiently as possible while aggregating different requests. Coupling the improvement of energy resources with that of request aggregation, as seen in the research presented in the collaboration of several national laboratories and universities, helps to maintain a higher throughput during run-time. With the advent of an ideal scheduler choice based on the I/O request, maximum energy efficiency methodologies, and the unification of I/O requests into a singular block, there are increases in the potential for throughput, execution time, state transition power consumption, and other expensive resources used by the Linux operating for their full capabilities. Even though these advancements are revolutionary and unique in many ways, they will only ultimately prove one thing: the process of diversification concerning research of I/O mechanisms in Linux plagues the majority of professionals in the field

Sino-Cyber Espionage: An Introduction to the Exploits of Units 61398 and 61486 in the People’s Liberation Army of China

This paper begins with an overview of the two most notorious hacking divisions of the People’s Liberation Army. It draws from several different articles concerning the state of the internet from Congress, CrowdStrike, Verizon, and Akamai as well as reports from the United States Department of Justice. The scope of this paper is limited because of the level of security clearance needed to access the real information on the exploits of the Chinese in the corporate sector, but the ramifications of said exploits are clear. The discussion provides examples from the Department of Justice on what the Chinese have done to American companies and some of the strategies that they have used. It also expounds on some of the repercussions of the strategies on the markets that were affected. Statistics are given from The Economist and Wired magazines that sourced the state of the internet reports from Verizon and Akamai. The recommendations are mainly ideas of International Relations to try to keep peace between the People’s Republic of China and the United States of America. Extreme measures must, however, be considered if there are any more exploited vulnerabilities in the federal sector. This paper mainly serves to inform the reader of the attacks that the Chinese use, who they target and why, and possible solutions to the problem of cyber corporate espionage

N=1 extension of minimal model holography

The CFT dual of the higher spin theory with minimal N = 1 spectrum is determined. Unlike previous examples of minimal model holography, there is no free parameter beyond the central charge, and the CFT can be described in terms of a non-diagonal modular invariant of the bosonic theory at the special value of the 't Hooft parameter lambda=1/2. As evidence in favour of the duality we show that the symmetry algebras as well as the partition functions agree between the two descriptions.Comment: 28 page

COMPARISON OF THE PERFORMANCE AND LOWER LIMB BIOMECHANICS OF DROP JUMP AND 10-5 REPETITVE REBOUND TESTS IN ACLR ATHLETES.

Double and single leg drop jump (DLDJ & SLDJ) assessments tend to be performed during the later stages of rehabilitation from an anterior cruciate ligament (ACL) injury due to the mechanical demands these assessments place on the lower limbs. Double and single leg 10-5 repetitive rebound tests (DLRJT and SLRJT) may be effective alternatives to examine lower limb mechanics at an earlier stage of rehabilitation. The purpose of this study was 1) to compare inter-limb performance and biomechanical differences within each jump test and 2) to compare biomechanical differences between the double and single leg versions of each test. Significant (

On the coset duals of extended higher spin theories

We study the holographic duality between the M x M matrix extension of Vasiliev higher spin theories on AdS3 and the large N limit of SU(N+M)/SU(N) x U(1) type cosets. We present a simplified proof for the agreement of the spectra and clarify the relation between this duality and the version in which the cosets are replaced by Kazama-Suzuki models of Grassmannian type.Comment: 27 pages, 1 tabl

Do users care about ad's performance costs? Exploring the effects of the performance costs of in-app ads on user experience

Context: In-app advertising is the primary source of revenue for many mobile apps. The cost of advertising (ad cost) is non-negligible for app developers to ensure a good user experience and continuous profits. Previous studies mainly focus on addressing the hidden performance costs generated by ads, including consumption of memory, CPU, data traffic, and battery. However, there is no research on analyzing users’ perceptions of ads’ performance costs to our knowledge. / Objective: To fill this gap and better understand the effects of performance costs of in-app ads on user experience, we conduct a study on analyzing user concerns about ads’ performance costs. / Method: First, we propose RankMiner, an approach to quantify user concerns about specific app issues, including performance costs. Then, based on the usage traces of 20 subject apps, we measure the performance costs of ads. Finally, we conduct correlation analysis on the performance costs and quantified user concerns to explore whether users complain more for higher performance costs. / Results: Our findings include the following: (1) RankMiner can quantify users’ concerns better than baselines by an improvement of 214% and 2.5% in terms of Pearson correlation coefficient (a metric for computing correlations between two variables) and NDCG score (a metric for computing accuracy in prioritizing issues), respectively. (2) The performance costs of the with-ads versions are statistically significantly larger than those of no-ads versions with negligible effect size; (3) Users are more concerned about the battery costs of ads, and tend to be insensitive to ads’ data traffic costs. / Conclusion: Our study is complementary to previous work on in-app ads, and can encourage developers to pay more attention to alleviating the most user-concerned performance costs, such as battery cost

Supersymmetric holography on AdS3

The proposed duality between Vasiliev's supersymmetric higher spin theory on AdS3 and the 't Hooft limit of the 2d superconformal Kazama-Suzuki models is analysed in detail. In particular, we show that the partition functions of the two theories agree in the large N limit.Comment: 25 pages, 3 figures, improved fig.