Orientation dependent fracture toughness of lamellar bone

The critical energy release rate of human bone was determined for different crack propagation directions with three-point-bending tests using controlled crack extension. The local structure was characterised by small-angle X-ray scattering, SEM and polarised light microscopy and related to the energy required for crack extension. It turns out the collagen angle is decisive for switching the fracture behaviour of bone from brittle to quasi-ductile. A significant increase in the critical energy release rate as well as a change of the appearance of the crack path from straight and smooth to deflected and zig-zag is observed.     

Mössbauer Spectroscopy and X-ray Diffraction Study of Fe-Labeled Tetrachloroferrate(III)-Based Magnetic Ionic Liquids

Four ⁵⁷Fe-labeled tetrachloroferrates(III) of organic cations (1-butyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, 1-methyl-1-propylpyrrolidinium, tetraphenylphosphonium) were examined by temperature-dependent Mössbauer spectroscopy. The hyperfine and dynamic parameters of the iron(III) site were determined. Single crystal X-ray diffraction data of [Ph₄P][FeCl₄] were collected at four temperatures (295, 223, 173, and 123 K), and the dynamics of the iron atom inferred from the Mössbauer data and the single crystal U_i,j parameters have been compared.     

Second law analysis of momentum and heat transfer in unit operations

Momentum and heat transfer in complex systems always is the sum of single and simple transfer elements here called unit operations. They are usually characterised by head loss coefficients and Nusselt numbers as far as the flow and the heat transfer aspect is concerned. In our study we show that this is insufficient for a complete assessment and that additional parameters should be introduced. They take into account that energy, its use and conversion always is subject to the constraints set by the second law of thermodynamics.     

An analytic study of a scalable video buffer

In this contribution, we investigate the performance of the output buffer of an ‘on-demand’ video streaming server. The server maintains a local database of stored video clips and movies which can be streamed to the users upon request. We assume that the stored video is encoded in a scalable way, which means that the data streams contain a base layer ensuring a minimum of guaranteed quality and a stack of additional enhancement layers progressively improving the quality of the video. For the purpose of performance analysis, we assume that a video stream is split up in logical units called frames. Every frame consists of a number of packets, each containing information of one layer only. When the output buffer gets congested, one may choose to drop the transmission of some of the layers in a frame, thus reducing the frame transmission time and expediting the restoration of the buffer size to normal levels. A discrete-time finite capacity queueing model with buffer size dependent transmission times is proposed. Using a probability generating function approach, we focus on the characteristics of idle and busy periods. We obtain performance measures such as the frame loss ratio and the average frame transmission time. The latter measure relates to the quality of the video stream. We conclude with some numerical examples, including a realistic case study.     

Performance analysis of a discrete-time queueing system with priority jumps

Supporting multiple types of traffic with different Quality of Service (QoS) requirements is not an easy task in modern communication networks. An efficient priority scheduling scheme is thus of great importance. The static, Head-Of-Line (HOL) priority scheme achieves differentiation between different types of traffic, but may have a too severe impact on the performance level of lower-priority traffic. We therefore propose a priority scheme with priority jumps in this paper: the Head-Of-Line Jump-If-Arrival (HOL-JIA) scheme. We show that the use of probability generating functions (pgfs) is suitable for analytically studying the system, and for illustrating the impact of priority jumps on the performance of the system.     

On the evolution of traffic characteristics inside multistage switching systems

In this paper, a method is developed to analyze the evolution of the traffic characteristics of information streams crossing the consecutive stages of an ATM multistage switching structure. Specifically, we develop a generic model for characterizing the traffic streams at the input of the consecutive stages, based on the assumption that the queueing processes in subsequent stages are independent. In our model, the parameters that determine the arrival process on the inlets of a switching element in a given stage solely depend on the output process on the outlets of the switching elements belonging to the previous stage. As a result, we are able to calculate the mean value and variance, as well as the whole distribution of the buffer contents and the packet delay in a tagged switching element, anywhere in the structure, based on earlier work. Furthermore, we can prove that, under the assumptions of the model, the traffic characteristics converge to a spatial steady state after a few stages in the system, i.e., the traffic parameters reach limiting values which are independent of the characteristics of the traffic sources at the entrance of the first stage. Although the present study focuses on the specific case of ATM switching systems, the authors believe similar results to hold also for more general multistage structures in which routing and multiplexing occurs in each stage.     

Altered DNA Methylation Profiles in SF3B1 Mutated CLL Patients

Mutations in splicing factor genes have a severe impact on the survival of cancer patients. Splicing factor 3b subunit 1 (SF3B1) is one of the most frequently mutated genes in chronic lymphocytic leukemia (CLL); patients carrying these mutations have a poor prognosis. Since the splicing machinery and the epigenome are closely interconnected, we investigated whether these alterations may affect the epigenomes of CLL patients. While an overall hypomethylation during CLL carcinogenesis has been observed, the interplay between the epigenetic stage of the originating B cells and SF3B1 mutations, and the subsequent effect of the mutations on methylation alterations in CLL, have not been investigated. We profiled the genome-wide DNA methylation patterns of 27 CLL patients with and without SF3B1 mutations and identified local decreases in methylation levels in SF3B1^mut CLL patients at 67 genomic regions, mostly in proximity to telomeric regions. These differentially methylated regions (DMRs) were enriched in gene bodies of cancer-related signaling genes, e.g., NOTCH1, HTRA3, and BCL9L. In our study, SF3B1 mutations exclusively emerged in two out of three epigenetic stages of the originating B cells. However, not all the DMRs could be associated with the methylation programming of B cells during development, suggesting that mutations in SF3B1 cause additional epigenetic aberrations during carcinogenesis.     

A review on microfabrication of thermoplastic polymer‐based microneedle arrays

This article will provide an overview of recent developments for microneedles made using injection molding and hot embossing techniques for active transdermal drug delivery. Microneedle arrays are developed for pain‐free and efficient drug delivery without using a cold chain. The focus of this article will be on the use of engineering thermoplastics and microneedle manufacturing techniques including patterning. Recent developments demonstrate that commercialization of polymer‐based microneedle systems is feasible. POLYM. ENG. SCI., 59:877–890, 2019. © 2019 Society of Plastics Engineers