Keberadaan logam berat krom dari limbah industri elektroplating dapat membahayakan kesehatan manusia, di antaranya menyebabkan kanker dan gagal ginjal. Untuk mengatasi masalah ini, dilakukan upaya ...pengolahan limbah dengan cara adsorpsi menggunakan arang aktif dari kayu. Tulisan ini mempelajari kondisi optimal uji adsorpsi arang aktif kayu Muntingia calabura dan kemampuan bakteri Escherichia coli melakukan biodegradasi krom (VI) menjadi krom (III) pada pengolahan limbah krom industri elektroplating. Arang kayu dibuat pada suhu 500˚C selama 1 jam dan diaktivasi dengan uap air panas pada suhu 800˚C pada variasi waktu kontak 70-110 menit dengan tekanan 120 dan 150 mBar. Uji adsorpsi dilakukan dengan variasi konsentrasi awal adsorbat 20-100 mg/L, waktu kontak 45-105 menit, dan kecepatan pengadukan 100-300 rpm. Uji biodegradasi menggunakan bakteri Escherichia coli yang diinkubasi di dalam nutrient broth yang mengandung limbah hasil adsorpsi. Hasil penelitian memperlihatkan bahwa kondisi optimal uji adsorpsi adalah konsentrasi awal 70 mg/L, kecepatan pengadukan 150 rpm dan waktu kontak pada 75 menit, dengan efektivitas sebesar 86,7%. Efektifitas biodegradasi krom (VI) menjadi krom (III) adalah 98,6%.
Mediterranean climate river systems are among the most threatened ecosystems worldwide, due to a long history of anthropogenic impacts and alien invasive species introductions. Many of such rivers ...naturally exhibit a non-perennial flow regime, with distinct seasonal, inter-annual and spatial heterogeneity. The present study seeks to detect diatom community patterns and to understand the processes that cause these structures in an Austral Mediterranean river system among different months and river sections. In general, most environmental variables showed an increasing trend downstream for both months, with the exception of pH, dissolved oxygen, PO₄3− and substrate embeddedness, which decreased downstream. A total of 110 diatom species between the two study months (October – 106 taxa; January – 78 taxa) were identified, dominated by 30 species with at least >2% abundance. Diatom community structure differed significantly across river zones, while no significant differences were observed between the study months. A boosted regression trees model showed that B (43.3%), Cu (20.8%), Fe (3.4%) and water depth (3.2%) were the most significant variables structuring diatoms. Diatom species communities reflected environmental variables (i.e., sediment and water chemistry) in this Mediterranean climate river system, as sediment metals such as B, Cu and Fe were found to be important in structuring diatom communities. Biotic influences from fish communities had little effect on diversity, but shifted diatom community structure. Therefore, the current study highlights how river systems have complex interactions that play an important role in determining diatom species composition.
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•Sediment and water chemistry variables increased downstream in both events.•110 diatom species across the two study events identified.•Significant differences observed in diatom community across river zones and events.•Boron and copper most important variables in structuring diatoms.
In this work, gelatin (G)-polyacrylamide (PAAm)-based interpenetrating polymer network (IPN) hydrogels involving maleic acid (MA) was prepared using by radical polymerization. Full-IPN and semi-IPN ...hydrogels were synthesized by using glutaraldehyde and ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The water absorbency of hydrogels was investigated, and the values increased with MA and G. The chemical structures of full-IPN and semi-IPN hydrogels were tested by Fourier Transform Infrared Spectroscopy (FTIR). Morphological test was done by using Scanning Electron Microscope/ Energy Dispersive X-ray Spectroscopy (SEM/EDX). Thermal properties were examined with Differential scanning calorimeter (DSC) analyzer and Thermogravimetric analysis (TGA). The mechanical analysis was performed with Zwick Universal Testing Machine. Thermal and mechanical stabilities of full-IPN hydrogel was higher than semi-IPN. The efficiency of adsorption parameters (contact time, initial feed concentration, and pH) on Chromium (VI) ion adsorbing property of Full-IPN hydrogel was also determined. Isotherms were explained with the Langmuir or Freundlich equations. According to the results of both isotherms, it can be said that the hydrogel surface was homogeneous, and the adsorption of Chromium (VI) occurred in a monolayer.
Bu çalışmada, jelatin (G) -poliakrilamid (PAAm) bazlı, maleik asit (MA) içeren iç içe geçen polimer ağı (IPN) hidrojelleri, radikal polimerizasyon kullanılarak hazırlanmıştır. Tam-IPN ve yarı-IPN hidrojeller, çapraz bağlayıcı olarak glutaraldehit ve etilen glikol dimetakrilat (EGDMA) kullanılarak sentezlendi. Hidrojellerin su emiciliği incelendi ve değerler MA ve G ile arttı. Tam IPN ve yarı IPN hidrojellerin kimyasal yapıları Fourier Dönüşümü Kızılötesi Spektroskopisi (FTIR) ile test edildi. Taramalı Elektron Mikroskobu/ Enerji Dağılımlı X-ışını Spektroskopisi (SEM/EDX) kullanılarak morfolojik test yapıldı. Termal özellikler Diferansiyel taramalı kalorimetre (DSC) analizörü ve Termogravimetrik analiz (TGA) ile incelenmiştir. Mekanik analiz, Zwick Universal Test Makinesi ile yapıldı. Tam IPN hidrojelin termal ve mekanik stabiliteleri yarı IPN'den daha yüksekti. Tam-IPN hidrojelinin Krom (VI) iyonu adsorbe etme özelliği üzerindeki adsorpsiyon parametrelerinin (temas süresi, başlangıç besleme konsantrasyonu ve pH) etkinliği de belirlendi. İzotermler Langmuir veya Freundlich denklemleriyle açıklandı. Her iki izotermin sonucuna göre, hidrojel yüzeyinin homojen olduğu ve Krom (VI) adsorpsiyonunun bir tek tabakada meydana geldiği söylenebilir.
This work describes the uncertainty calculation for the determination of chromium oxide in leather. Following the various steps for the calculation of uncertainty which includes assembling a list of ...sources of uncertainty, with the help of basic formula used to calculate the measure and as all parameters cause an influence on the result because of the uncertainty value associated with it then the basic cause and effect diagram is made which shows the correlation between these and indicates their effect on the uncertainty of the result.All individual sources of uncertainty are evaluated by quantification. Mass, purity, and molecular mass of potassium dichromate are calculated against the volume of sodium thiosulphate following the first step in the test method is the standardization of sodium thiosulphate with the primary standard, potassium dichromate. So the overall uncertainty value depends on the uncertainties associated with the mass, purity, and molecular mass of potassium dichromate.
Bu çalışma, deride krom oksit tayini için belirsizlik hesaplamasını açıklamaktadır. Ölçümü hesaplamak için kullanılan temel formül yardımıyla ve tüm parametreler kendisiyle ilişkili belirsizlik değeri nedeniyle sonuç üzerinde bir etkiye neden olduğundan, belirsizlik kaynaklarının bir listesinin bir araya getirilmesini içeren belirsizliğin hesaplanması için çeşitli adımların ardından bunlar arasındaki korelasyonu gösteren ve sonucun belirsizliği üzerindeki etkisini gösteren temel neden-sonuç diyagramı yapılmaktadır.Tüm bireysel belirsizlik kaynakları niceleme ile değerlendirilir. Potasyum dikromatın kütlesi, saflığı ve moleküler kütlesi, sodyum tiyosülfatın hacmine göre hesaplanır ve test yöntemindeki ilk adım, sodyum tiyosülfatın birincil standart olan potasyum dikromat ile standardizasyonudur. Dolayısıyla genel belirsizlik değeri, potasyum dikromatın kütlesi, saflığı ve moleküler kütlesi ile ilişkili belirsizliklere bağlıdır.
On Sub-Propositional Fragments of Modal Logic Davide Bresolin; Emilio Muñoz-Velasco; Guido Sciavicco
Logical methods in computer science,
06/2018, Letnik:
14, Issue 2
Journal Article
Recenzirano
Odprti dostop
In this paper, we consider the well-known modal logics $\mathbf{K}$, $\mathbf{T}$, $\mathbf{K4}$, and $\mathbf{S4}$, and we study some of their sub-propositional fragments, namely the classical Horn ...fragment, the Krom fragment, the so-called core fragment, defined as the intersection of the Horn and the Krom fragments, plus their sub-fragments obtained by limiting the use of boxes and diamonds in clauses. We focus, first, on the relative expressive power of such languages: we introduce a suitable measure of expressive power, and we obtain a complex hierarchy that encompasses all fragments of the considered logics. Then, after observing the low expressive power, in particular, of the Horn fragments without diamonds, we study the computational complexity of their satisfiability problem, proving that, in general, it becomes polynomial.
Proses pengolahan limbah dengan proses lumpur aktif pada sisi lain menimbulkan permasalahan baru, yaitu persoalan pengolahan lumpur (wastage sludge). Meningkatnya penggunaan sistem ini menyebabkan ...meningkat pula jumlah lumpur yang harus diolah. Hal tersebut meningkatkan eban ekonomi bagi industri yang mengguanakan sistem pengolahan limbah secara lumpur aktif. Pemanfaatan lumpur aktif sebagai adsorben tentunya mengurangi beban ekonomi pengolahan lumpur. Disamping itu pemanfaatan tersebut memberukan nilai tambah bagi industri karena dapat dijual dan digunakan pada proses penghilangan logam berat dalam suatu air limah sebagai penggantti karbon aktif maupun adsorben lain. Tujuan penelitian ini adalah menentukan kapasitas optimumadsorpsi sebagai suatu parameter untuk mengkuantifikasi keefektifan aktifitas suatu adsorben lumpur aktif dalam mengadsorpsi logam berat cadmium dan kromium dari suatu air limbah industri. Dalam penelitian ini, variabel yang divariasikan adalah konsentrasi adsorbat yaitu, cadmium dan kromium dalam rentang 0,97-13,68 mg/L. Variabel lain yang divariasikan adalah ph (dalam rentang 1-14) dan 3 jenis lumpur aktif yaitu lumpur slurry, lumpur cake dan lumpur powder. Hasil dari prnrlitian yang dilakukan menunjukkan lumpur aktif tipe cake memberikan tingkat jumlah logam teradsorpsi paling tinngi dibandingkan lumpur slurry maupun powder waktu kesetimbangan adsorpsi Cd (II) dan Cr (III) menggunakan adsorben lumpur aktif adalah 24 jam. Persentasi efisiensi penghilangan (removal)logam berat Cd(II) dengan menggunakan lumpur aktif tipe cake untuk rentang konsentrasi 0,97-11,85 mg/l ada pada rentang yang cukup tinggi yaitu 88,44-95,38%. Demikian juga dengan persentase sfisiensi penghulangan logam berat Cr(III) untuk rentang konsentrasi 1,66-13,68 mg/l memberikan angka yang sangat tinggi yaitu 98,26-99,73%. Nilai ph optimum untuk adsorpsi logam Cd(II) dan Cr(III) oleh lompur aktif terjadi pada ph antara 6,0 dan 8,0. Persamaan isotherm yang sesuai untuk adsorpsi Cd(II) dan Cr(III) menggunakan lumpur aktif adalah model isotherm Langmuir, dengan demikian merupakan adsorpsi satu lapis. Khusus untuk adsorpsi Cd(II), prosesnya juga mengikuti model Freundlich. Kapasitas adsorbs maksimum (qm) untuk Cd (II) menggunakan lumpur aktif adalah 6,25 mg/g adsorben, sedangkan untuk Cr(III) adalah 6,13 mg/g adsorben. Tetapan lamgmuir, b, untuk konsetrasi logam Cd(II) adalah 1,06 l/mg dan untukk Cr(III) adalah 23,99 l/mg.Kata kunci : adsorpsi, cadmium, krom, lumpur aktif, model isotherm
We study the expressive power and complexity of second-order revised Krom logic (SO-KROM$^{r}$). On ordered finite structures, we show that its existential fragment $\Sigma^1_1$-KROM$^r$ equals ...$\Sigma^1_1$-KROM, and captures NL. On all finite structures, for $k\geq 1$, we show that $\Sigma^1_{k}$ equals $\Sigma^1_{k+1}$-KROM$^r$ if $k$ is even, and $\Pi^1_{k}$ equals $\Pi^1_{k+1}$-KROM$^r$ if $k$ is odd. The result gives an alternative logic to capture the polynomial hierarchy. We also introduce an extended version of second-order Krom logic (SO-EKROM). On ordered finite structures, we prove that SO-EKROM collapses to $\Pi^{1}_{2}$-EKROM and equals $\Pi^1_1$. Both SO-EKROM and $\Pi^{1}_{2}$-EKROM capture co-NP on ordered finite structures.
Svrha: Iz postojeće literature poznato je da metalni ioni iz ortodontskih naprava mogu korodirati zbog djelovanja sline i bakterija u usnoj šupljini. Rezultati većine studija upućuju na to da se ...razina nikla i kroma u slini ne povisuje nakon postavljanja ortodontskih naprava. No nema istraživanja o razini titanija, kobalta, bakra i cinka u slini ortodontskih pacijenata. Ispitanici i postupci: Razina nikla (Ni), titanija (Ti), kroma (Cr), kobalta (Co), bakra (Cu) i cinka (Zn) mjerena je u slini četrdeset i dvoje pacijenta s keramičkim metalnim bravicama i isto toliko njih s konvencionalnima i to prije postavljanja ortodontskih naprava s pomoću induktivne spregnute plazme/masene spektrometrije i šest mjeseci poslije toga. U statističkoj analizi korištena su dva testa – Wilcoxonov signed rank i Mann-Whitneyev s razinom značajnosti od 0,05. Rezultati: Rezultati su pokazali da se razina titana u slini povisila šest mjeseci nakon postavljanja ortodontskih naprava. Razina kroma i cinka, pak, značajno se snizila nakon postavljanja ortodonskih naprava. Nije bilo statistički značajne razlike u razini nikla, titanija, kroma, bakra, kobalta i cinka u slini između pacijenata s metalnim i keramičkim ortotontskim
bravicama. Zaključak: Možemo zaključiti da se razina titanija u slini značajno povisila šest mjeseci nakon postavljanja ortodontskih naprava za razliku od razine kroma i cinka koja se značajno snizila šest mjeseci poslije njihova postavljanja, bez obzira na vrstu korištenih bravica.
Wetlands occupy broad, gently sloping valleys characterised by net deposition. Consequently, gully incision is viewed as an agent of wetland destruction. However, little attention has been given to ...the role of gullies in natural wetland formation. This paper determines if gully cutting and filling cycles have led to wetland formation in both an extant eroding wetland and a semi‐arid environment that once supported wetlands. At both sites, the valley fill was investigated to identify infilled gullies, and a 14C date was obtained from the gully fill. The longitudinal slopes of the valley floor prior to incision, the valley bedrock floor, and the gully fill were also measured. In the Krom wetland, four infilled gullies (5–8.2 m deep) were found adjacent to alluvial fans and dated to 470–7060 bp. Ten infilled gullies were found at Zuurplaats (Karoo), which were more recent, although one gully started filling 1260 bp. At both sites, large gullies were grounded on bedrock. Alluvial fans deposited by tributaries cause a reduction in mainstem valley width and locally increase longitudinal slope, leading to gully initiation. The slope of the gully beds was less than the surface prior to erosion, and the slope of the gully fill was comparable with the valleys' regional slope. The bedrock on both valley floors had a near‐horizontal cross‐sectional profile, suggesting that repeated gully incisions had led to valley floor planing. A new model of wetland formation is proposed where gully cut‐and‐fill cycles laterally plane valley bottoms and contribute to valley widening and longitudinal slope reduction.
Distributions of arsenic and metals in surface sediments collected from the coastal and estuarine areas of the northern Bohai and Yellow Seas, China, were investigated. An ecological risk assessment ...of arsenic and metals in the sediments was evaluated by three approaches: the Sediment Quality Guidelines (SQGs) of the United States Environmental Protection Agency (USEPA), the degree of contamination, and two sets of SQGs indices. Sediments from the estuaries of the Wuli and Yalu Rivers contained some of the greatest concentrations of arsenic, cadmium, copper, mercury, lead, and zinc. Median concentrations of cadmium and mean concentrations of lead and zinc were greater than background concentrations determined for the areas. All sediments were considered to be heavily polluted by arsenic, but moderately polluted by chromium, lead, and cadmium. Current concentrations of arsenic and metals are unlikely to be acutely toxic, but chronic exposures would be expected to cause adverse effects on benthic invertebrates at 31.4% of the sites.
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