The vector algebra war: a historical perspective

There are a wide variety of different vector formalisms currently utilized in engineering and physics. For example, Gibbs' three-vectors, Minkowski four-vectors, complex spinors in quantum mechanics, quaternions used to describe rigid body rotations and vectors defined in Clifford geometric algebra. With such a range of vector formalisms in use, it thus appears that there is as yet no general agreement on a vector formalism suitable for science as a whole. This is surprising, in that, one of the primary goals of nineteenth century science was to suitably describe vectors in three-dimensional space. This situation has also had the unfortunate consequence of fragmenting knowledge across many disciplines, and requiring a significant amount of time and effort in learning the various formalisms. We thus historically review the development of our various vector systems and conclude that Clifford's multivectors best fulfills the goal of describing vectorial quantities in three dimensions and providing a unified vector system for science.Comment: 8 pages, 1 figure, 1 tabl

Shallow-water Habitat Change Detection of Kaledupa Island, Wakatobi National Park (Wnp) for 14 Years

Metode penginderaan jauh sangat membantu dalam pemetaan kondisi habitat perairan dangkal secara spasial pada cakupan area yang luas. Penelitian ini bertujuan untuk menganalisis Perubahan habitat perairan dangkal Pulau Kaledupa, Taman Nasional Wakatobi (TNW), selama 14 tahun, dari tahun 2002 hingga 2016. Data citra yang digunakan dalam penelitian ini adalah Landsat 8 OLI (2016), Landsat 5TM (2009), dan Landsat 7ETM+ (2002), yang dikombinasikan dengan data in-situ dan TNW. Klasifikasi Mahalanobis dimanfaatkan untuk memproduksi peta habitat perairan dangkal (karang hidup, karang mati, lamun, dan pasir) dan mendeteksi Perubahannya. Hasil yang diperoleh bahwa Perubahan yang terjadi dari tahun 2002 sampai 2016 adalah tutupan karang hidup menurun dari 2217 ha menjadi 2039 ha, tutupan karang mati juga menurun dari 3327 ha menjadi 2108 ha, luas pasir meningkat dari 1201 ha menjadi 1346 ha, area lamun naik dari 4130 ha menjadi 5294 ha. Metode ini merupakan alat analisis yang baik untuk menilai efektivitas upaya perlindungan ekosistem terumbu karang dan lamun di perairan Pulau Kaledupa, serta dapat diterapkan pada 3 pulau utama lainnya di TNW dan pulau-pulau kecil di Indonesia

Generalised Minkowski spacetime

The four dimensional spacetime continuum, as first conceived by Minkowski, has become the default framework within which to describe physical laws. In this paper, we show how a four-dimensional Minkowski spacetime structure naturally arises from three-dimensional physical space when modeled with Clifford geometric algebra $C\ell(\Re^3)$. This expanded eight-dimensional framework allows a generalisation of the invariant interval and the Lorentz transformations. Also, with this geometric oriented approach the fixed speed of light, the laws of special relativity and the form of Maxwell's equations, arise naturally from the intrinsic properties of the algebra without recourse to physical arguments. We also find new insights into the nature of time, a unified treatment of energy-momentum and spin, a Lagrangian unifying gravity and electromagnetism as well as predictions of a new class of physical effects and interactions.Comment: 20 pages, no figure

Nilai-Nilai Perdamaian Dalam Buku Teks Pendidikan Agama Islam (Akhlak) Di Sekolah Muhammadiyah

The article examines whether the textbooks on Islamic Ethics (akhlak) taught in-the Muhammadiyah schools promote peace. Studying the content of schools' text-books is nececessary due to the increase of social conflicts and violent actions among-students. In particular, this article explores the Islamic teaching of peace within-Islamic Ethics textbooks published by the Board of Basic and Secondary Education-of Muhammadiyah (DIKDASMEN) in Yogyakarta Special Territory. By the use of-content analysis, this article finds that teaching materials in the Islamic Ethics text--books promote the values of peace. However, the texbooks editing quality needs to-be improved so that the narrratives (story tellings) and pictures (ilustration) can fit-the students' need

Low back pain and association with whole body vibration among military armoured vehicle drivers in Malaysia.

A cross sectional study was conducted among military armoured vehicle drivers in the two largest mechanized battalions with the objective to determine the prevalence of low back pain (LBP), and its association with whole body vibration (WBV) and other associated factors. A self-administered questionnaire and Human Vibration Meter were used in this study. A total of 159 respondents participated in this study and 102 (64.2%) of them were subjected to WBV measurement. One-hundred-and-seventeen respondents complained of LBP for the past 12 months giving a prevalence of 73.6%. The prevalence of LBP among tracked armoured vehicle drivers was higher (81.7%) as compared to wheeled armoured vehicle drivers (67.0%). The mean acceleration at Z-axis in tracked armoured vehicles (1.09 ± 0.26 ms-2) and wheeled armoured vehicles (0.33 ± 0.07 ms-2) were the dominant vibration directions. The mean estimated vibration dose value (eVDV) for eight-hour daily exposure at Z-axis (19.86 ± 4.72 ms-1.75) in tracked armoured vehicles showed the highest estimation. Based on the European Vibration Directive (2002), the mean eVDV at Z-axis in tracked armoured vehicles exceeded exposure action value (EAV) (> 9.1 ms-1.75), but did not exceed exposure limit value (ELV) (<21.0 ms-1.75). Logistic regression analysis revealed that only driving in forward bending sitting posture (OR=3.63, 95% CI 1.06-12.42) and WBV exposure at X-axis (OR=1.94, 95% CI 1.02-3.69) were significant risk factors to LBP. Preventive measures should be implemented to minimize risk of WBV and to improve ergonomic postures among drivers

Magnetic table for levitating food for entertainment

In this paper, we discuss our work towards a new dining platform that uses magnetic levitating food and magnetic utensils in an initial prototype device. The ultimate goal of the project is a complete table with dynamic levitating food, but the current implementation is a set of levitating magnets that can be encased in food hovering over static locations. We investigated different weights and shapes of 3-D printed objects to mimic food and found that the levitating magnets are strong enough to support lightweight food. This magnetic levitating table can produce a playful and entertaining dining experience by moving and rotating to stay in place. The key novelties of this paper are the integration of food with a magnetic levitating table for playful interactions and novel dining experiences

Growth factor stimulation of cardiomyocytes induces changes in the transcriptional contents of secreted exosomes

Exosomes are nano-sized extracellular vesicles, released from various cells, which can stimulate or repress responses in targets cells. We recently reported that cultured cardiomyocytes are able to release exosomes and that they, in turn, are involved in facilitating events in target cells by alteration of gene expression. We investigated whether external stimuli of the cardiomyocyte might influence the transcriptional content of the released exosomes.Exosomes were isolated from media collected from cultured cardiomyocytes (HL-1) with or without growth factor treatment (TGF-&#x03B2;2 and PDGF-BB), with a series of differential centrifugations, including preparative ultracentrifugation and separation with a sucrose gradient. The exosomes were characterized with dynamic light scattering (DLS), electron microscopy (EM) and Western blot and analyzed with Illumina whole genome microarray gene expression.The exosomes were rounded in shape and had an average size of 50&#x2013;90 nm in diameter with no difference between treatment groups. Analysis of the mRNA content in repeated experiments conclusively revealed 505 transcripts in the control group, 562 in the TGF-&#x03B2;2-treated group and 300 in the PDGF-BB-treated group. Common transcripts (217) were found in all 3 groups.We show that the mode of stimulation of parental cells affects the characteristics of exosomes released. Hence, there is a difference in mRNA content between exosomes derived from cultured cardiomyocytes stimulated, or not stimulated, with growth factors. We also conclude that all exosomes contain a basic package consisting of ribosomal transcripts and mRNAs coding for proteins with functions within the energy supply system. To access the supplementary material to this article, please see Supplementary files under Article Tools online