The Burdens of Occupational Heat Exposure-related Symptoms and Contributing Factors Among Workers in Sugarcane Factories in Ethiopia: Heat Stress Wet Bulb Globe Temperature Meter

Debela Mitiku B.,Begosaw Achenef M.,Deyessa Negussie,Azage Muluken 한국산업안전보건공단 산업안전보건연구원 2023 Safety and health at work Vol.14 No.3

Background: Heat stress is a harmful physical hazard in many occupational settings. However, consequences of occupational heat exposure among workers in a sugarcane factory in Ethiopia are not well characterized. This study aimed to assess the level of occupational heat exposure-related symptoms and contributing factors. Methods: In this cross-sectional study, five workstations were selected for temperature measurement. Heat stress levels were measured using a wet-bulb globe temperature index meter. A stratified random sampling technique was used to select 1,524 participants. Heat-related symptoms were assessed using validated questionnaires. Results: The level of occupational heat exposure was 72.4% (95% CI: 70.2%–74.8%), while 71.6% (95% CI: 69.3%–74.9%) of participants experienced at least one symptom related to heat stress. The most common heat-related symptoms were swelling of hands and feet (78%), severe thirst (77.8%) and dry mouth (77.4%). The identified risk factors were a lack of reflective shields (AOR: 2.20, 95% CI: 1.53, 3.17), not-enclosed extreme heat sources (AOR: 1.76, 95% CI: 1.23, 2.51), a lack of access to shade (AOR: 9.62, 95% CI: 6.20, 14.92), and inappropriate protective clothing provision (AOR: 1.58, 95% CI: 1.27, 2.71). Conclusions: The burden of occupational heat exposure and heat-induced symptoms was high. Lack of reflective shields, the absence of enclosed extreme heat sources, a lack of access to shade, and inappropriate protective clothing provision were considerable attributes of heat stress. Therefore, the use of mechanical solutions to stop heat emissions at their sources and the key factors identified were areas for future intervention.

Phase polymorphism and electronic structures of TeSe₂

Debela, Tekalign Terfa,Kang, Hong Seok The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.38

<P>Structure prediction complemented by density functional theory (DFT) calculation indicates that TeSe2 is the most stable among the various Te(1−x)Sex compounds. Different from the case of bulk Te, the material can equally adopt three different crystal structures: HγT, MH, and Mβα phases, which are similar to 1T-TiSe2, trigonal Te, and orthorhombic Te, respectively. These phases can be transformed from one to another by uniaxial tensile and shear stress of less than 1 MPa; they can be even transformed to their chiral mirror images. Band structure calculations including spin-orbit coupling (SOC) show that all three phases are semiconductors. The band gap (= 0.43 eV) increases with density, being the largest (= 1.86 eV) in the Mβα phase with the highest density. The HγT phase exhibits a hidden spin texture because of centrosymmetry. The other two phases display chiral spin texture due to the lack of symmetry, in that two spin components of frontier bands can split by more than 100 meV in opposite directions.</P>

Two-Dimensional WS₂@Nitrogen-Doped Graphite for High-Performance Lithium Ion Batteries: Experiments and Molecular Dynamics Simulations

Debela, Tekalign Terfa,Lim, Young Rok,Seo, Hee Won,Kwon, Ik Seon,Kwak, In Hye,Park, Jeunghee,Cho, Won Il,Kang, Hong Seok American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.44

<P>As promising candidates for anode materials in lithium ion batteries (LIB), two-dimensional tungsten disulfide (WS<SUB>2</SUB>) and WS<SUB>2</SUB>@(N-doped) graphite composites were synthesized, and their electrochemical properties were comprehensibly studied in conjunction with calculations. The WS<SUB>2</SUB> nanosheets, WS<SUB>2</SUB>@graphite, and WS<SUB>2</SUB>@N-doped graphite (N-graphite) exhibit outstanding cycling performance with capacities of 633, 780, and 963 mA h g<SUP>-1</SUP>, respectively. To understand their lithium storage mechanism, first-principles calculations involving a series of ab initio <I>NVT</I>-<I>NPT</I> molecular dynamics simulations were conducted. The calculated discharge curves for amorphous phase are well matched with the experimental ones, and the capacities reach 620, 743, and 915 mA h g<SUP>-1</SUP> for WS<SUB>2</SUB>, WS<SUB>2</SUB>@graphite, and WS<SUB>2</SUB>@N-graphite, respectively. The large capacities of the two composites can be attributed to the tendency of W and Li atoms to interact with graphite, suppressing the formation of W metal clusters. In the case of WS<SUB>2</SUB>@N-graphite, vigorous amorphization of the N-graphite enhances the interaction of W and Li atoms with the fragmented N-graphite in such a way that unfavorable Li-W repulsion is avoided at very early stage of lithiation. As a result, the volume expansion in WS<SUB>2</SUB>@graphite and WS<SUB>2</SUB>@N-graphite is calculated to be remarkably small (only 6 and 44%, respectively, versus 150% for WS<SUB>2</SUB>). Therefore WS<SUB>2</SUB>@(N-)graphite composites are expected to be almost free of mechanical pulverization after repeated cycles, which makes them promising and excellent candidates for high-performance LIBs.</P> [FIG OMISSION]</BR>

Automatic Creation of a Semantic Network Encoding part of Relations

( Michael Zock ),( Debela Tesfaye ) 서울대학교 인지과학연구소 2015 Journal of Cognitive Science Vol.16 No.4

We describe here the principles underlying the automatic creation of a semantic map to support navigation in a lexicon. Whenever we read a book, write a letter, or launch a query on Google, we always use words, the short- hand labels for more or less well-specified thoughts. The problem is that words may refuse to come to our mind when we need them most, at the very moment of speaking or writing. This is when we tend to reach for a dictionary. Yet, even dictionaries may fail to reveal the target word, although they contain them. This is not only a problem of input (poor query word), but also a problem of design : the way how words are organized and the kind of information associated to each one of them. We will consider in this paper one of the most original hand-crafted resources, WordNet, discussing its relative strengths and weaknesses with respect to word access. We will then describe an attempt to build automatically a subset of this resource, to conclude with the presentation of an approach meant to help authors (speakers/writers) to overcome the tip-of-the-tongue-problem (TOT) even in cases where other resources, including Wordnet or Roget’s Thesaurus, would fail.

[Retraction] A Review on the Role of Irisin in Insulin Resistance and Type 2 Diabetes Mellitus

Gizaw, Mamo,Anandakumar, Pandi,Debela, Tolessa KOREAN PHARMACOPUNCTURE INSTITUTE 2017 Journal of pharmacopuncture Vol.20 No.4

Irisin is a novel hormone like polypeptide that is cleaved and secreted by an unknown protease from fibronectin type III domain-containing protein 5 (FNDC5), a membrane-spanning protein and which is highly expressed in skeletal muscle, heart, adipose tissue, and liver. Since its discovery in 2012, it has been the subject of many researches due to its potent physiological role. It is believed that understanding irisin's function may be the key to comprehend many diseases and their development. Irisin is a myokine that leads to increased energy expenditure by stimulating the 'browning' of white adipose tissue. In the first description of this hormone, increased levels of circulating irisin, which is cleaved from its precursor fibronectin type III domain-containing protein 5, were associated with improved glucose homeostasis by reducing insulin resistance. Irisin is a powerful messenger, sending the signal to determine the function of specific cells, like skeletal muscle, liver, pancreas, heart, fat and the brain. The action of irisin on different targeted tissues or organs in human being has revealed its physiological functions for promoting health or executing the regulation of variety of metabolic diseases. Numerous studies focus on the association of irisin with metabolic diseases which has gained great interest as a potential new target to combat type 2 diabetes mellitus and insulin resistance. Irisin is found to improve insulin resistance and type 2 diabetes by increasing sensitization of the insulin receptor in skeletal muscle and heart by improving hepatic glucose and lipid metabolism, promoting pancreatic ${\beta}$ cell functions, and transforming white adipose tissue to brown adipose tissue. This review is a thoughtful attempt to summarize the current knowledge of irisin and its effective role in mediating metabolic dysfunctions in insulin resistance and type 2 diabetes mellitus.

Selective electrochemical reduction of carbon dioxide to formic acid using indium-zinc bimetallic nanocrystals

Kwon, Ik Seon,Debela, Tekalign Terfa,Kwak, In Hye,Seo, Hee Won,Park, Kidong,Kim, Doyeon,Yoo, Seung Jo,Kim, Jin-Gyu,Park, Jeunghee,Kang, Hong Seok The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.40

<P>For the electrochemical reduction of CO2 (CRR) with high selectivity for HCOOH, In-Zn bimetallic nanocrystals (NCs) were synthesized as catalysts by <I>in situ</I> reduction of In2O3-ZnO NCs with various compositions. All In-containing bimetallic catalysts exhibited excellent selectivity to produce HCOOH, while Zn NCs favor CO production. A composition with In : Zn = 0.05 has higher catalytic activity than In NCs, with a faradaic efficiency of 95% and a HCOOH production rate of 0.40 mmol h<SUP>−1</SUP> cm<SUP>−2</SUP> at −1.2 V <I>vs.</I> RHE. The enhanced catalytic performance is in part ascribed to the fewer surface oxide layers, which increase the conductivity and facilitate the charge transfer. Density functional theory calculations revealed that the In-Zn interfacial sites make the HCOOH pathway significantly energy-favorable, which supports the higher production rate of Zn0.95In0.05 than that of In.</P>

Two-dimensional MoS2-melamine hybrid nanostructures for enhanced catalytic hydrogen evolution reaction

Kwak, In Hye,Kwon, Ik Seon,Debela, Tekalign Terfa,Seo, Jaemin,Ahn, Jae-Pyoung,Yoo, Seung Jo,Kim, Jin-Gyu,Park, Jeunghee,Kang, Hong Seok The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.39

<P>Two-dimensional (2D) MoS2 nanostructures have attracted much attention in recent years because of their excellent electrocatalytic activity toward the hydrogen evolution reaction (HER). Herein, we report unique 2D hybrid nanostructures of MoS2 and melamine synthesized <I>via</I> a one-step solvothermal process. Remarkably, few-layer metallic 1T′ phase MoS2 nanoflakes and orthorhombic phase melamine aggregate to form nanoplates. At a controlled concentration, the melamine molecules intercalated into the 1T′ phase MoS2 by forming charge-transfer complexes. The hybrid complexes with 7% intercalated melamine exhibited excellent performance for the catalytic HER, with a current of 10 mA cm<SUP>−2</SUP> at 0.136 V (<I>vs.</I> RHE) and a Tafel slope of 37 mV dec<SUP>−1</SUP>. First-principles calculations showed that the intercalation of hydrogen-bonded melamine clusters could stabilize the 1T′ phase MoS2<I>via</I> substantial charge transfer. The activation barrier was calculated for the Volmer-Heyrovsky reactions, by identifying the active sites of the Volmer reaction as the basal S atoms above the hydrogen-bonded amine group of melamine. This rationalizes the dependence of the catalytic activity on the concentration of intercalated melamine. The present study highlights the opportunities for producing unique 2D hybrid complexes to enhance the HER catalytic activity by controlling the intercalating organic molecules.</P>

A Review on the Role of Irisin in Insulin Resistance and Type 2 Diabetes Mellitus

Mamo Gizaw,Pandi Anandakumar,Tolessa Debela 대한약침학회 2017 Journal of pharmacopuncture Vol.20 No.4

Irisin is a novel hormone like polypeptide that is cleaved and secreted by an unknown protease from fibronectin type III domain-containing protein 5 (FNDC5), a membrane- spanning protein and which is highly expressed in skeletal muscle, heart, adipose tissue, and liver. Since its discovery in 2012, it has been the subject of many researches due to its potent physiological role. It is believed that understanding irisin's function may be the key to comprehend many diseases and their development. Irisin is a myokine that leads to increased energy expenditure by stimulating the 'browning' of white adipose tissue. In the first description of this hormone, increased levels of circulating irisin, which is cleaved from its precursor fibronectin type III domain-containing protein 5, were associated with improved glucose homeostasis by reducing insulin resistance. Irisin is a powerful messenger, sending the signal to determine the function of specific cells, like skeletal muscle, liver, pancreas, heart, fat and the brain. The action of irisin on different targeted tissues or organs in human being has revealed its physiological functions for promoting health or executing the regulation of variety of metabolic diseases. Numerous studies focus on the association of irisin with metabolic diseases which has gained great interest as a potential new target to combat type 2 diabetes mellitus and insulin resistance. Irisin is found to improve insulin resistance and type 2 diabetes by increasing sensitization of the insulin receptor in skeletal muscle and heart by improving hepatic glucose and lipid metabolism, promoting pancreatic β cell functions, and transforming white adipose tissue to brown adipose tissue. This review is a thoughtful attempt to summarize the current knowledge of irisin and its effective role in mediating metabolic dysfunctions in insulin resistance and type 2 diabetes mellitus.

Thickness-dependent bandgap and electrical properties of GeP nanosheets

Kim, Doyeon,Park, Kidong,Shojaei, Fazel,Debela, Tekalign Terfa,Kwon, Ik Seon,Kwak, In Hye,Seo, Jaemin,Ahn, Jae Pyoung,Park, Jeunghee,Kang, Hong Seok The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.27

<P>Recently there have been extensive efforts to develop novel two-dimensional (2D) layered structures, owing to their fascinating thickness-dependent optical/electrical properties. Herein, we synthesized thin GeP nanosheets that had a band gap (<I>E</I>g) of 2.3 eV, which is a dramatic increase from the value in the bulk (0.9 eV) upon exfoliation. This <I>E</I>g value is close to that of the GeP monolayer predicted by first-principles calculations (HSE06 functional). The calculations also indicate a strong dependence of <I>E</I>g on the number of layers (2.306, 1.660, 1.470, and 1.397 eV for mono-, bi-, tri-, and tetralayers, respectively), and that the band edge positions are suitable for water splitting reactions. Field-effect transistor devices were fabricated using the p-type GeP nanosheets of various thicknesses, and the devices demonstrated a significant decrease in the hole mobility but an increased on-off ratio as the layer number decreased. The larger on-off ratio (10<SUP>4</SUP>) for the thinner ones is promising for use in novel 2D (photo)electronic nanodevices. Further, liquid-exfoliated GeP nanosheets (thickness = 1-2 nm) deposited on Si nanowire arrays can function as a promising photoanode for solar-driven water-splitting photoelectrochemical (PEC) cells. Based on the calculated band offset with respect to the Fermi levels for the two half-reactions in the water splitting reaction, the performance of the PEC cell can be explained by the formation of an effective p-GeP/n-Si heterojunction.</P>

Two-dimensional MoS2/Fe-phthalocyanine hybrid nanostructures as excellent electrocatalysts for hydrogen evolution and oxygen reduction reactions

Kwon, Ik Seon,Kwak, In Hye,Kim, Ju Yeon,Abbas, Hafiz Ghulam,Debela, Tekalign Terfa,Seo, Jaemin,Cho, Min Kyung,Ahn, Jae-Pyoung,Park, Jeunghee,Kang, Hong Seok The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.30

<P>Two-dimensional (2D) MoS2 nanostructures have been extensively investigated in recent years because of their fascinating electrocatalytic properties. Herein, we report 2D hybrid nanostructures consisting of 1T′ phase MoS2 and Fe-phthalocyanine (FePc) molecules that exhibit excellent catalytic activity toward both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). X-ray absorption spectra revealed an increased Fe-N distance (2.04 Å) in the hybrid complex relative to the isolated FePc. Spin-polarized density functional theory calculations predicted that the Fe center moves toward the MoS2 layer and induces a non-planar structure with an increased Fe-N distance of 2.05 Å, which supports the experimental results. The experiments and calculations consistently show a significant charge transfer from FePc to stabilize the hybrid complex. The excellent HER catalytic performance of FePc-MoS2 is characterized by a low Tafel slope of 32 mV dec<SUP>−1</SUP> at a current density of 10 mA cm<SUP>−2</SUP> and an overpotential of 0.123 V. The ORR catalytic activity is superior to that of the commercial Pt/C catalyst in pH 13 electrolyte, with a more positive half-wave potential (0.89 <I>vs</I>. 0.84 V), a smaller Tafel slope (35 <I>vs</I>. 87 mV·dec<SUP>−1</SUP>), and a much better durability (9.3% <I>vs</I>. 40% degradation after 20 h). Such remarkable catalytic activity is ascribed to the HER-active 1T′ phase MoS2 and the ORR-active nonplanar Fe-N4 site of FePc.</P>