Judul: Frequency and Risk of Consuming Processed Smoked Stingray Fish on the North Coast of Java Island
Abstrak: Ikan pari asap merupakan salah satu olahan populer di Indonesia. Penelitian ini bertujuan menentukan frekuensi konsumsi olahan ikan pari asap di sembilan daerah utara Pulau Jawa, yaitu Lamongan, Tegal, Jakarta, Surabaya, Kendal, Batang, Indramayu, Demak, dan Pemalang, menghitung cemaran merkuri (Hg) dan metil merkuri (MeHg), menghitung tingkatan cemaran Polycylic Aromatic Hydrocarbon (PAH), dan menentukan risiko konsumsi olahan ikan pari asap. Penentuan cemaran dengan Inductively Coupled Plasma Mass Spectrometry (ICP-MS) untuk merkuri, Gas Chromatography Mass Spectrometry (GC-MS) untuk PAH dan Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (LC-ICP-MS) untuk metil merkuri. Uji logam berat menunjukkan sampel produk tercemar merkuri berada di atas batas aman konsumsi menurut Standar Nasional Indonesia (SNI). Hasil uji PAH menunjukkan sampel berada di bawah batas aman konsumsi menurut SNI. Hasil perhitungan Hazard Question (HQ) dan Hazard Index (HI) > 1, menunjukkan bahwa responden yang terkena dampak mungkin menghadapi risiko kesehatan non-karsinogenik.
Keyword: Logam berat, Frekuensi konsumsi, Risiko konsumsi

Judul: Correlation of Consumption Frequency with Species Identity and Heavy Metal Contamination in Processed Smoked Stingray
Abstrak: Ikan pari asap termasuk olahan populer yang meningkat produksinya. Pemanfaatan komoditas yang tinggi berakibat pada status konservasi komoditas pari di Indonesia menurut Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) ataupun International Union for Conservation of Nature (IUCN), dan kesehatan akibat akumulasi logam berat. Penelitian bertujuan mengidentifikasi spesies pada sampel olahan berbasis DNA barcoding dan status konservasi berdasarkan CITES/IUCN, menentukan cemaran logam berat, serta korelasi antara frekuensi konsumsi dengan beberapa variabel terhadap sustainability komoditas dan dampak akumulasi logam berat yang dikonsumsi. Penentuan cemaran dengan ICP OES untuk tembaga dan ICP MS untuk selain tembaga. Spesies yang teridentifikasi adalah Neotrygon kuhlii status Data Deficient dan Maculabatis macrura status Endangered menurut IUCN. Uji logam berat menunjukkan sampel produk tercemar merkuri berada di bawah batas aman konsumsi menurut SNI, namun logam berat lain seperti timbal, kadmium, dan tembaga tidak terdeteksi. Frekuensi konsumsi olahan pari masih tinggi di kalangan masyarakat., Smoked stingray is a popular dish that has led to an increase in production. The high utilization can impact the conservation status of stingrays’ commodity in Indonesia based on Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) or International Union for Conservation of Nature (IUCN). Excessive consumption can also be harmful because ray can accumulate heavy metals. The research aims to identify stingray species based on DNA barcoding, their conservation status based on CITES/IUCN, determine heavy metal contamination and the correlation between the frequency of consumption with several variables related to sustainability and the impact of heavy metal consumed. Heavy metal analysis was determined using the ICP OES for copper and the ICP MS for other than copper. The results are Neotrygon kuhlii with Data Deficient and Maculabatis macrura with Endangered according to IUCN. Heavy metal testing shows that the contaminated product sample is below the safe consumption limit according to SNI, but other heavy metals such as lead, cadmium, and copper are not detected. However, frequency consumption products are still high in the public.
Keyword: DNA barcoding, heavy metals, Maculabatis macrura, Neotrygon kuhlii

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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