Theory of ultrasonic diffraction by damage developed in thin laminated composites

The apparent attenuation which would result if certain damage states (transverse cracks and delaminations) are introduced into a graphite/epoxy laminate through which an ultrasonic wave passes is investigated. Experimental data for two different laminates are presented which shows changes in the apparent attenuation of about one db. These changes generally occur at loads which correspond to the range predicted for the formation of the damage. The predicted changes in the attenuation for several simple and common damage states are well within the range of experimental values

Pseudo-Sylvester domains and skew laurent polynomials over firs

Building on recent work of Jaikin-Zapirain, we provide a homological criterion for a ring to be a pseudo-Sylvester domain, that is, to admit a division ring of fractions over which all stably full matrices become invertible. We use the criterion to study skew Laurent polynomial rings over free ideal rings (firs). As an application of our methods, we prove that crossed products of division rings with free-by-{infinite cyclic} and surface groups are pseudo-Sylvester domains unconditionally and Sylvester domains if and only if they admit stably free cancellation. This relies on the recent proof of the Farrell--Jones conjecture for normally poly-free groups and extends previous results of Linnell--L\"uck and Jaikin-Zapirain on universal localizations and universal fields of fractions of such crossed products

Growth study of coi fish larvae fed chydoridae

First culture media for chydoridae used horse manure dried in the sun with a composition of 10 grams and 50 grams of soil dissolved in 1 L of water for 5 days, then filtered and diluted three times. Laboratory-scale cultures were carried out in a 500 ml volume jar containing horse manure culture media; then in the process fed with bread yeast and rice bran (0.05 gr yeast and rice bran/500 ml) every 3 days. Mass culture uses 12 jar containers with a volume of 3 L.The administration of chydoridae to two-day old koi fish larvae was carried out with the following treatments: treatment A, which was ornamental fish fed with boiled egg yolk in ad libitum; treatment B is ornamental fish fed with 5 individual chydoridae/ml and treatment C, which is not given any food with three replications. The design of the response in this study was to see the survival rate of ornamental fish larvae (%).The results of measurements of water quality during the study showed that the temperature during the study was 27°C, while the pH was 7. From the statistical analysis it was found that administration of chydoridae had a significant effect on the survival of two-day-old koi fish larvae which were kept for 14 days.Keywords: chydoridae, life feed, ornamental fish larvae, growthABSTRAKMedia kultur awal chydoridae menggunakan kotoran kuda yang dikeringkan di bawah sinar matahari dengan komposisi 10 gram kotoran kuda serta 50 gram tanah yang dilarutkan dalam 1 L air selama 5 hari, kemudian dilakukan penyaringan dan diencerkan sebanyak tiga kali.  Kultur skala laboratorium dilakukan dalam wadah toples dengan volume 500 ml berisi media kultur kotoran kuda; selanjutnya dalam proses kultur chydoridae diberi makan ragi roti dan dedak (0,05 gr ragi dan dedak /500 ml) setiap 3 hari sekali. Kultur massal menggunakan wadah toples sebanyak 12 buah dengan volume 3 L dengan mengikuti metode pada kultur skala laboratorium.Pemberian chydoridae kepada larva ikan koi yang berumur dua hari dilakukan dengan beberapa perlakuan sebagai berikut : perlakuan A yaitu  ikan hias diberi makan kuning telur rebus secara ad libitum; perlakuan B yaitu  ikan hias diberi makan chydoridae 5 individu/ml dan perlakuan C yaitu  ikan hias tidak diberi makan apapun dengan tiga ulangan.  Rancangan respons dalam penelitian ini adalah melihat laju kelangsungan hidup larva ikan hias (%).Hasil pengukuran kualitas air selama penelitian menunjukkan, suhu selama penelitian adalah 27 °C, sedangkan pH adalah 7.  Dari hasil analisis statistik diperoleh bahwa pemberian chydoridae sangat memberi pengaruh nyata kepada kelangsungan hidup larva ikan koi berumur dua hari yang dipelihara selama 14 hari.Kata kunci: chydoridae, pakan alami, larva ikan hias, pertumbuha

The use of Sponge Crude Extract to Increase Growth and Immune Response of Nile Tilapia Oreochromis niloticus

This study aims to examine the effect of sponge crude extract addition to the fish feed on growth and non-specific immune response of nile tilapia (O. niloticus) and determine the most effective dose of the extract in raising the growth and the non-specific immune response of nile tilapia (O. niloticus). The sponge sample was macerated and then evaporated using a rotary vacuum evaporator until the sample became a paste and mixed with feed. The fish were fed for 14 days respectively as much as 5% of body weight per day with feeding frequency of two times a day. The results showed that addition of sponge crude extract to the fish feed gave good effect on the growth and the non-specific immune response of nile tilapia (O. niloticus) with best dose of  40 g / kg feed.Keywords: Sponge extract, fish immune response, fish growth, immune response, immunostimulant. ABSTRAKPenelitian ini bertujuan untuk menguji pengaruh penambahan ekstrak kasar spons pada pakan ikan terhadap pertumbuhan dan respon imun  non spesifik ikan nila (Oreochromis niloticus) serta menentukan dosis ekstrak kasar spons yang paling efektif dalam meningkatkan pertumbuhan dan respon imun non spesifik ikan nila (Oreochromis niloticus). Sampel spons dimaserasi kemudian dievaporasi menggunakan rotary vacuum evaporator sehingga diperoleh ekstrak kasar berbentuk pasta yang kemudian dicampurkan pada pakan. Ikan uji diberi pakan perlakuan 5% dari bobot biomassa selama 14 hari dengan frekuensi pemberian pakan dua kali sehari. Hasil penelitian menunjukan bahwa penambahan ekstrak kasar spons pada pakan ikan memberikan pengaruh yang baik terhadap pertumbuhan dan respon imun non spesifik ikan nila (Oreochromis niloticus), yang mana dosis yang terbaik adalah 40 gr / Kg pakan.Kata Kunci : Ekstrak spons, respon imun ikan, pertumbuhan ikan, respon imun, imunostimulan

Using Of Fish Silase Different Composition Toward The Growth Of Nile Tilapia Oreochromis niloticus

Silage is prepared by adding the probiotic into the material of bones and flesh of waste from the market.  Silage is used as element substituted with fish meal as feed for tilapia with initial weight of 19.14 to 24.86 grams and a length of 3-5 cm.  There are three types of feed using silage replacing fish meal as much as 10% (treatment A), 20% (treatment B) and 30% (treatment C) and a control used commercial feed (treatment D).  The results obtained are feed in treatment D gives very significant results to the three other feed (A, B and C) in the case of weight, rate of growth and feed efficiency; but in a further test of Duncan, statistical results showed that feed C and D more efficient than feed A.Keywords: low cost artificial feed, silage, growth, tilapia ABSTRAKSilase dipersiapkan melalui penambahan probiotik ke dalam bahan tulang dan daging dari bahan-bahan yang tidak terpakai yang diambil dari pasar.  Silase ini digunakan sebagai elemen yang disubsitusikan dengan tepung ikan untuk diberikan sebagai pakan pada ikan nila dengan berat awal 19,14-24,86 gr dan panjang 3-5 cm.  Ada tiga jenis pakan dengan menggunakan silase menggantikan tepung ikan sebanyak 10 (perlakuan A), 20 (perlakuan B) dan 30% (perlakuan C) dan sebagai kontrol digunakan pakan komersial (perlakuan D). Hasil yang diperoleh adalah pakan uji pada perlakuan D sangat memberikan hasil berbeda yang sangat nyata dengan ketiga pakan lainnya (A, B dan C) dalam hal pertumbuhan berat, laju pertumbuhan dan efisiensi pakan; namun pada uji lanjut Duncan, hasil statistik menunjukkan bahwa pakan C dan pakan D lebih efisien dibandingkan pakan A.Kata kunci: akuakultur, pakan buatan murah, silase, pertumbuhan, ikan nil

Phytoplankton Community Structure in Seagrass Beds in Tiwoho Village, North Minahasa Regency

This research was carried out from May to July 2022. A sampling at the study site included seawater for the needs of plankton identification as well as the measurement of water nitrate & phosphate levels and measurement of physical and chemical parameters such as temperature, pH, salinity and dissolved oxygen which were carried out on an ongoing basis In situ (in the field). The technique for determining plankton sampling was carried out purposively, namely with certain considerations to obtain samples that represent the research location area. Plankton sampling was carried out horizontally using a plankton net. Sample bottles containing seawater were identified at the Marine Biology Laboratory, Faculty of Fisheries and Marine Sciences. The composition of the phytoplankton found in the Tiwoho seagrass bed ecosystem consists of three classes, namely the Bacillariophyceae, Dynophyceae, and Cyanophyceae classes, with 28 genera. The results of chopped phytoplankton are expressed in Cells/l. The qualitative determination of plankton is made up to the genus level. The composition of the phytoplankton found in the Tiwoho seagrass bed ecosystem consists of three classes, namely the Bacillariophyceae, Dynophyceae, and Cyanophyceae classes, with 28 genera. The results of calculating the abundance of phytoplankton in the Tiwoho seagrass ecosystem are in the range of 29 - 66 cells/l. The highest abundance was found at station two, namely 66 cells/l with 21 genera, then station three (65 cells/l) with 24 genera, and station one (29 cells/l) with a total of 23 genera. The diversity index of seagrass beds in Tiwoho waters is in the range of 1.9330 - 2.4083, which means that community stability is categorized as moderate. The uniformity index is in the range of 0.4614 - 0.7154, this means that the uniformity between species is relatively the same, or the difference is not striking. While the domination index is in the range of 0.1494 - 0.2404, it means that the condition of the community structure is stable, and there is no ecological pressure (stress) on biota. Keywords: Phytoplankton, Biological Index, Abundance, Environmental parameters Abstrak Penelitian ini dilaksanakan pada bulan Mei sampai bulan Juli 2022. Pengambilan sampel di lokasi penelitian meliputi air laut untuk kebutuhan identifikasi fitoplankton dan pengukuran kadar nitrat, fosfat perairan serta pengukuran parameter fisika kimia seperti suhu, pH, salinitas dan oksigen terlarut yang dilakukan secara In situ (di lapangan). Teknik penentuan pengambilan sampel plankton dilakukan secara purposif yaitu dengan pertimbangan tertentu untuk mendapatkan sampel yang mewakili area lokasi penelitian. Pengambilan sampel plankton dilakukan secara horisontal dengan menggunakan plankton net. Sampel plankton diberi pengawet formalin 4% dan  diidentifikasi di laboratorium Biologi Kelautan Fakultas Perikanan dan Ilmu Kelautan. Komposisi fitoplankton yang dijumpai di ekosistem padang lamun Perairan Tiwoho terdiri dari tiga kelas yaitu kelas Bacillariophyceae, Dynophyceae, dan Cyanophyceae, dengan 28 genera. Hasil perhitungan kelimpahan fitoplankton di ekosistem padang lamun Perairan Tiwoho berada di kisaran 29 - 66 sel/l. Kelimpahan tertinggi ditemukan di stasiun dua (depan kampung) yaitu 66 sel/l dengan 21 genera, kemudian stasiun tiga (depan dermaga) yaitu 65 sel/l dengan 24 genera, dan stasiun satu (ujung kampung) sebanyak 29 sel/l dengan jumlah 23 genera. Indeks keanekaragaman ekosistem padang lamun Perairan Tiwoho berada pada kisaran 1,9330 - 2,4083, yang berarti stabilitas komunitas dikategorikan sedang. Indeks keseragaman yaitu pada kisaran 0,4614 - 0,7154, ini berarti keseragaman antar spesies relatif sama, atau perbedaannya tidak menyolok. Sedangkan indeks dominasi yaitu pada kisaran  0,1494 - 0,2404, berarti kondisi struktur komunitas dalam keadaan stabil, dan tidak terjadi tekanan ekologi (stress) terhadap biota. Kata kunci: Fitoplankton, Indeks Biologi, Kelimpahan, Parameter lingkunga

Nondestructive Inspection and Evaluation of Metal Matrix Composites

A review is presented of work performed in our laboratory on the nondestructive inspection of metal matrix composites. In order to obtain damage representative of that which occurs in service, the specimens were mechanically loaded to intermediate load levels below that which causes final, catastrophic failure. Various nondestructive techniques were used both during and after the applied loadings to follow damage initiation and progress.</p

Tensions in the adoption of e-Learning in the mining industry of South Africa

The mining industry in South Africa contributes signi cantly to the national economy. Training is an important component in these environments and e-Learning is often used to train the large workforce. In the face of current labour unrest and job cuts in this sector, it is foreseen that e-Learning might play an increasing important role to upskill the remaining work force. However, it appears that low motivation and resistance to e-Learning exist amongst learners. The aim of this research was to examine the factors that may contribute to this resistance and/or adoption as perceived by e-Learning managers and practitioners. An interpretive approach was used to conduct two case studies. Activity theory was used as the theoretical lens and its main elements (tools, subjects, rules, objects, community) were used to analyse interviews with participants from two mining companies. Potential contradictions or tensions were identi ed in order to explore resistance to e-Learning. The main ndings indicate that: 1. proper communication of expectations by di erent stakeholders of e-Learning is imperative, 2. top management support for e-Learning should stem from integration into the organisational goals, 3. quality content is a necessary condition for successful adoption, 4. more attention should be given to interaction between learners and facilitators and also between learners, 5. a focus on people development rather than only compliance may lead to lower resistance, and 6. top management support and involvement should be made visible.http://www.journals.co.za/ej/ejour_comp.htmlam201

Antibacterial Activity and Zoochemical Analysis of Sea Urchin Diadema setosum (Leske, 1778) Extract From Aertembaga Waters, Bitung City

Sea urchin is one of the marine biotas that produce bioactive compounds and has biological activity, one of which is antibacterial. This study aims to determine the antibacterial activity of the crude extract of D. setosum gonad and its fractionation against test bacteria Staphylococcus aureus and Escherichia coli and to conduct a zoochemical analysis to determine the content of bioactive compounds. The antibacterial test used the disc diffusion method while the chemical analysis was carried out qualitatively. The results showed that the methanol, ethyl acetate, and n-hexane fraction had antibacterial activity against the two test bacteria. The ethyl acetate fraction was the fraction that showed the highest antibacterial activity, its inhibition zone was 8 mm against S. aureus and 7,5 mm against E. coli. The zoochemical analyses of the ethyl acetate fraction from gonads extract showed positive results for alkaloid compound, phenolic, and saponinKeywords: Sea urchin Gonad, Antibacterial, Disc diffusion, Zoochemistry, ExtractionAbstrakBulu babi merupakan salah satu biota laut yang memproduksi senyawa bioaktif dan memiliki aktivitas biologis salah satunya adalah antibakteri. Tujuan penelitian ini mengetahui aktivitas antibakteri dari ekstrak kasar gonad bulu babi D. setosum dan hasil fraksinasi terhadap bakteri Staphylococcus aureus dan Escherichia coli serta melakukan analisis zookimia untuk mengetahui kandungan senyawa bioaktif. Pengujian antibakteri menggunakan metode difusi cakram sedangkan analisis kimia dilakukan secara kualitatif. Hasil penelitian menunjukkan baik fraksi metanol, fraksi etil asetat, dan fraksi n-heksana memiliki aktivitas antibakteri terhadap kedua bakteri uji. Fraksi etil asetat merupakan fraksi yang memperoleh aktivitas antibakteri tebaik dengan diameter zona hambat 8 mm terhadap bakteri S.aureus dan 7,5 mm terhadap bakteri E. coli. Hasil uji zookimia fraksi etil asetat menunjukkan bahwa ekstrak gonad D. setosum mengandung senyawa dari golongan alkaloid, fenolik, dan saponin.Kata kunci : Gonad Bulu Babi (D. setosum ), Antibakteri, difusi cakram, Zookimia, Ekstraks

Utilization of Life Feed Alona SP., Boiled Egg Yolk and Commercial Feed Toward Survival Rate of Betta Fish Larvae

Tujuan penelitian ini adalah untuk mendapatkan laju kelangsungan hidup larva ikan betta (cupang) yang dibeerikan pakan alami Alona sp., rebusan kuning telur dan pakan komersil selama 21 hari. Analisis data dilakukan dengan ANOVA one way, dan dilanjutkan dengan uji BNJ (Tukey). Hasil laju kelangsungan hidup adalah sebagai berikut, perlakuan dengan pakan alami Alona sp. 56%, perlakuan dengan rebusan kuning telur 26%, dan perlakuan dengan pakan komersil 0%. Hasil uji statistik menunjukan adanya perbedaan yang nyata. Nilai signifikan p <.0002 (<.05). Parameter kualitas air yang diukur selama penelitian adalah suhu 26ºC