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.
Display omitted
•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.
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.
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.
This qualitative investigation explores the role of dance in maintaining spiritual identity in the context of popular culture. The focus of the investigation is the Fon Buang Suang dance of Udon ...Thani. Drawing on the documentary review and field data gathered from observations and interviews, this article examines how the use of traditional and contemporary dance elements in Fon Buang Suang reflects a cultural shift toward modernity, while still maintaining spiritual and ritualistic elements. This article argues that this dance, along with other examples of ritualistic dance in the region, serves as important markers of cultural identity and helps to maintain a sense of spiritual continuity in a rapidly changing world. Overall, this investigation contributes to the growing body of research on the role of dance in popular culture and its impact on the preservation of traditional cultural and religious practices.