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Solubility measurements are essential in various research and industrial fields. With the automation of processes, the importance of automatic and real-time solubility measurements has increased. Although end-to-end learning methods are commonly used for classification tasks, the use of handcrafted features is still important for specific tasks with the limited labeled images of solutions used in industrial settings. In this study, we propose a method that uses computer vision algorithms to extract nine handcrafted features from images and train a DNN-based classifier to automatically classify solutions based on their dissolution states. To validate the proposed method, a dataset was constructed using various solution images ranging from undissolved solutes in the form of fine particles to those completely covering the solution. Using the proposed method, the solubility status can be automatically screened in real time by using a display and camera on a tablet or mobile phone. Therefore, by combining an automatic solubility changing system with the proposed method, a fully automated process could be achieved without human intervention.

Jeong-Eun Park,1,2,&ast; Woo Cheol Kim,3,&ast; Sung Kyun Kim,4,5,&ast; Yeji Ahn,1,2 Sun Mok Ha,1,2 Gahee Kim,3 Seonmin Choi,3 Wan Su Yun,3 Tae Hoon Kong,1,2 Su Hoon Lee,1,2 Dong Jun Park,1,2 Jin Sil Choi,1,2 Jaehong Key,3 Young Joon Seo1,2 1Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, Wonju, 26426, South Korea; 2Research Institute of Hearing Enhancement, Yonsei University Wonju College of Medicine, Wonju, 26426, South Korea; 3Department of Biomedical Engineering, Yonsei University, Wonju, South Korea; 4Department of Otorhinolaryngology Head and Neck Surgery, Hallym University College of Medicine, Dongtan Sacred Heart Hospital, Hwaseong, South Korea; 5Laboratory of Brain & Cognitive Science for Convergence Medicine, Hallym University College of Medicine, Anyang, South Korea&ast;These authors contributed equally to this workCorrespondence: Young Joon Seo, Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 26426, South Korea, Tel +82 33 741 0644, Email okas2000@hanmail.net Jaehong Key, Department of Biomedical Engineering, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwon-do, 26493, South Korea, Tel +82 33 760 2857, Email jkey@yonsei.ac.krBackground: Ototoxicity currently has no available treatment other than medication withdrawal as soon as toxicity is suspected. The human inner ear organs have little potential for regeneration; thus, ototoxicity-induced hair cell injury is deemed permanent. Dexamethasone (Dexa) is a synthetic steroid analog that has significant potential for otoprotection in the treatment of various inner ear diseases; however, its low absorption into the inner ear prevents significant recovery of function. Nanoparticles facilitate targeted drug delivery, stabilize drug release, and increase half-life of the drug.Methods: This study aimed to develop poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded superparamagnetic iron oxide nanoparticles (SPIONs) and Dexa (PSD-NPs) to control localized drug delivery by magnetic attraction in the treatment of ototoxicity-induced hearing loss. PSD-NPs and without SPIONs (PD-NPs) were prepared using a nanoprecipitation method.Results: Using an inner ear simulating system, we confirmed that PSD-NPs has an otoprotective effect in organotypic culture that is enhanced by magnetic attraction. PSD-NPs delivered via intrabullar injection in a magnetic field penetrated the inner ear and prevented hearing loss progression to a greater degree than equivalent doses of Dexa or PSD-NPs alone (day 28: ototoxic: 80.0 ± 0.0 dB; Dexa 100: 60.0 ± 15.5 dB; PSD 100: 50.0 ± 8.2 dB; PSD 100 with magnet: 22.5 ± 5.0 dB; P < 0.05). The protective effects were confirmed in various in vivo and in vitro models of ototoxicity.Conclusion: Our findings suggest that SPIONs with Dexa and magnetic field application prevent the progression of ototoxicity-induced hearing loss through anti-apoptotic mechanisms in the inner ear.Graphical Abstract: Keywords: superparamagnetic iron oxide nanoparticles, ototoxicity, hearing loss, magnetic attraction, dexamethasone

Background Varicella-zoster virus (VZV) infection is known to occur in 13-55% of patients within the first year after hematopoietic stem cell transplant (HSCT). The dynamics of recovery of VZV-specific T cell- mediated immunity (CMI) and its role for prevention and control of VZV reactivation are rarely reported in pediatric allogenic HSCT recipients. Methods From April 2019 to February 2020, subjects aged younger than 19 years who underwent allogenic HSCT with at least 1 year of follow up at Asan Medical Center Children`s Hospital were prospectively enrolled. All of them underwent VZV-specific enzyme-linked immune absorbent spot (ELISPOT) assays just before HSCT and then at 1, 3 months following HSCT. Extension study, which measures VZV-specific CMI before and after VZV vaccination at 24 months post-HSCT, is currently underway. Results A total of 32 HSCT recipients with a median age of 11years were enrolled. 37.5% underwent haploidentical HSCT and VZV R+ were in 78.1%. Antiviral prophylaxis was applied to all HSCT recipients, of which 65.6% were applied up to 365 days after HSCT. During this study period, only 1 patient (3.1%) experienced herpes zoster at 23 months following HSCT, whose VZV-specific ELISPOT assay showed 0, 1, and 0 spot-forming cells (SFC)/2.0x105 cells before HSCT, 1 and 3 months following HSCT, respectively. The presence of VZV-specific CMI ≥ 1 SFC/ 2.0 × 105 cells was observed in 62.5 % before HSCT, 65.6 % at 1 month, 59.4 % at 3 months, and 70% at 24 months after HSCT, respectively. However, only 18.8 % ,12.5 % and 21.9 % recovered VZV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cells at 1, 3 and 24 months following HSCT. Meanwhile, all the 4 recipients who got the 1st VZV vaccination at 24 months following HSCT showed recovery of VZV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cell. Recovery of VZV-specific CMI after HSCT was not associated with VZV serostatus, chickenpox history, type of HSCT, conditioning regimens, and GVHD. Conclusion Only a few pediatric allogenic HSCT recipients recovered VZV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cell up to 2 years following HSCT. In addition, the association between VZV-specific CMI and VZV reactivation could not be analyzed because no one experienced VZV reactivation within 1 year after HSCT. More long-term large-scale multicenter study is mandatory to supplement these parts. Disclosures All Authors: No reported disclosures.

Background Methicillin-resistant Staphylococcus aureus (MRSA) colonization pressure (CP) is a useful indicator for measuring the extent of MRSA reservoir in healthcare settings. The purpose of this study is to determine the MRSA colonization rate and invasive MRSA infection rate in severely ill pediatric patients requiring pediatric intensive care unit (PICU) stay, and to evaluate the association between MRSA CP and MRSA acquisition/invasive infection. Methods From January 2016 to December 2020, pediatric patients admitted to 2 PICUs with a total of 25 beds were retrospectively analyzed. Routine nasal and/or endotracheal cultures were performed on MRSA at the time of PCIU admission and thereafter, every week. MRSA CP was defined as the ratio of the monthly MRSA positive number of patients to 100 patient days. Among MRSA colonizers, MRSA obtained after 2 days of PICU admission was defined as an acquired colonizer, and imported colonizer was defined when it was confirmed as an MRSA colonizer at the time or within 2 days of entry. When MRSA was cultured in a normally sterile body fluids, it was defined as an invasive MRSA infection. Results Of the total 6,907 patients admitted to the PICUs during this study period, 8.4% (487/6,907) were MRSA colonizers; 30% (139/487) were acquired colonizers, and invasive MRSA infections occurred in 3.3% (16/487). During the stay in the PICUs, the MRSA acquisition rate was 4.1%. A total of 22 invasive MRSA infections occurred during this study period, with an incidence rate of 3.1/1,000 patient days, of which 72.7% (n=16) occurred to the patients with MRSA colonization. Invasive MRSA infection occurred in 2.4% (8/348) of imported colonizers, and 5.2% (8/139) of acquired colonizers (p=0.108). The median duration from the time of colonization to invasive infection was 24 days(IQR; 2.25-49.75). Although MRSA CP was not correlated with the incidence of invasive MRSA infection (p=0.101), MRSA CP itself affected MRSA acquisition in PICU (p< 0.001). Conclusion MRSA CP influenced the new acquisition of MRSA during PICU stay, and newly acquired colonizers are more likely to experience invasive MRSA infection. Continuous multi-faceted efforts to minimize MRSA CP can provide opportunities for reducing MRSA colonization and infections rates in PICU settings. Disclosures All Authors: No reported disclosures.

Background Haemophilus influenzae is known to develop resistance to β-lactam antibiotics by either producing β-lactamase or modifying structure of penicillin-binding protein 3 (PBP3) by ftsI gene mutation. Since 2017, H. influenzae with ceftriaxone resistance has been continuously appearing in our hospital, and the genotypic characteristics of these strains was analyzed. Methods Among a total of 69 H. influenzae isolated from the patients who admitted to Asan Medical Center Children’s Hospital from March 2014 to April 2019, 23 isolates resistant to ceftriaxone by EUCAST disk diffusion method were included. The ceftriaxone MIC was checked again with the E-test and ceftriaxone MIC ≤ 0.125 mg/L were categorized as susceptible. As test for β-lactamase production, the cefinase test and PCR amplification for blaTEM-1 and blaROB-1 were performed. The sequencing of the ftsI encoding PBP3 amplified by PCR was performed, and amino acid sequences were compared with H. influenzae Rd KW20. Results Among total 23 ceftriaxone-resistant isolates by disk diffusion method, 21 isolates restored for further molecular characterization were included, and 19% (4/21) were reported as susceptible by E-test. Among the 21 ceftriaxone-resistant isolates, 76.2% (16/21) were non-susceptible to amoxicillin/clavulanate, and one of them were resistant to meropenem. The prevalence of b-lactamase-producers was 57.1% (12/21), all of which were positive for blaTEM-1. For ftsI gene sequencing, either R517H or N526K amino acid substitution was observed, and none had both. The number of isolates having S385T was 17, of which 15 isolates accompanied with both M377I and L389F. The median ceftriaxone MIC of 3 isolates with only N526K was 0.012 ug/ml (range 0.008-0.125 ug/ml), and 12 isolates with N526K, M377I, S385T, and L389F was 0.19 ug/ml (0.19-0.25 ug/ml). Lastly, the three isolates with R517H, M377I, S385T, and L389F showed the highest median ceftriaxone MIC with 0.25 ug/ml (0.19-0.75 ug/ml). Conclusion Ceftriaxone-resistant H. influenzae isolates in Korea seems to be related to the combination of R517H, M377I, S385T, and L389F by ftsI gene mutation. Although clinical concerns about treatment failure may be low, continuous monitoring of the emergence of highly resistant strains is necessary. Disclosures All Authors: No reported disclosures.

Separation anxiety is a common behavior disorder, but our understanding of its etiology and underlying neurochemical mechanisms remains limited. The purpose of this study was to compare serum brain-derived neurotrophic factor (BDNF) levels in dogs with and without separation anxiety. BDNF, one of several neurotrophins, is prevalent in the limbic region and prefrontal cortex, which are key areas related to the regulation of mood, emotion, and cognition. Although an enriched environment increases BDNF levels, stress and glucocorticoid exposure decrease the expression of BDNF in the hippocampus and prefrontal cortex. As separation anxiety is associated with chronic stress, we hypothesized that BDNF levels in dogs affected by separation anxiety would be lower than BDNF levels in nonaffected dogs. A total of forty-eight dogs were classified by a board-certified behaviorist as affected (n = 15) or nonaffected (n = 33) by separation anxiety based on review of video clips of the dogs when left alone and owner reports of the dogs’ behavior. Groups did not differ in regard to age, body weight, body condition score, or sex, and most dogs were mixed breed. Fasted serum samples were analyzed with a canine BDNF ELISA. Nine (60%) dogs in the affected group and 12 (36%) dogs in the nonaffected group had a BDNF level

Introduction: Pre-(PRE) and post-ejection (POE) velocities by mitral annular tissue Doppler (TD) are biphasic and may be related to myocardial deformations. We investigated the predominance and concordance of TD-PRE and POE velocities and their effect on myocardial functions in controls and in HF patients. Methods: Retrospectively, 84 HF patients [57.6±8 years, 28(33%) females, NYHA: 2.3±0.6, EF: 55±15%, 52(62%) preserved EF, and 32(38%) reduced EF], 42 normal young controls [27±4 years, 5(12%) females], and 26 asymptomatic age matched controls without cardiac abnormalities [53±12 years, 28(65%) females] were included. Results: While controls had almost always predominantly positive PRE and negative POE, HF had more negative PRE (Controls: 2%, HFpEF: 10%, HFrEF: 35%, p Conclusions: In physiological state, TD signals are predominantly positive during PRE and negative during POE. Opposite PRE and POE velocities corelate, representing the PRE-generation and POE-reversal of shortening-stretch relationships, the attenuation of which in HF may be related to elevated LV filling pressures. In HF, partially or completely reversed concordance of PRE and POE is associated with progressive worsening of clinical and hemodynamic profiles.

In 2017, the Korean government launched an unprecedentedly large-scaled latent tuberculosis infection (LTBI) screening project which covered more than a million individuals in congregate settings. A total of 1,047,689 participants of source population (n = 2,336,157) underwent LTBI testing from 2017 to 2018. The overall LTBI test uptake rate during this project was 44.8%. Workers in daycare centers (83.5%) and kindergartens (78.9%) showed high participation rate. A total of 1,012,206 individuals with valid results of interferon-gamma release assay (IGRA) were selected to constitute the IGRA cohort. Most of the enrolled participants in the IGRA cohort were in their working age. Approximately, three-quarters of total enrolled population were female. Investigating the LTBI prevalence, stages of LTBI care cascade, natural history of LTBI, efficacy of LTBI treatment and cost-effectiveness of LTBI screening are feasible within this IGRA cohort., Graphical Abstract

The textile industry in South Korea is characterized by excessive water consumption, high concentrations of wastewater, hazardous chemicals, and high energy consumption. This study aimed to analyze Best Available Techniques Reference Documents (BREFs) based on best available techniques (BATs) and BAT-associated emission levels (BAT-AELs) and identify potential solutions for tackling environmental pressure from the South Korean textile industry. Therefore, the existing practices of the textile dyeing and finishing industry in South Korea were compared with those from the BREFs of the European Union. Many existing BATs in South Korea are related to reducing water consumption. There is also a strong focus on BATs for reducing wastewater discharge and achieving energy-saving during treatment rather than after treatment, which differs from other industries. Moreover, BAT-AELs were derived for chemical oxygen demand, suspended solids, and total nitrogen for treating non-biodegradable, highly polluted wastewater. Furthermore, BREFs related to atmospheric pollution included dust generated from the heated fabrics in the finishing process that contained cadmium and phenolic hydrogen chloride from dyes and raw materials in the fabrics. Notably, the European Union has not specified BAT-AELs for the textile industry, whereas South Korea has tailored BAT-AELs for toxic and hazardous chemicals. Thus, numerous green techniques to reduce emissions and energy consumption are being implemented in South Korea.

Since the first synthesis curves were reported, a number of social surveys have been conducted to assess community response to noise, and determine a suitable exposure-response relationship for each socio-cultural area within different environments. Generalized exposure-response relationships have been reported using meta-analysis, which are used for predicting noise annoyance and as the basis for noise policy. However, these studies were primarily conducted in European and English-speaking communities, and studying community response in different cultural contexts is important to the development of more comprehensive exposure-response relationships. Furthermore, in some cases, case-specific exposure-relationships may better predict community response than generalized exposure-response relationships. This study presents the exposure-response relationships for the subjective annoyance of people exposed to commercial aircraft, railway, and road traffic noise for an extended period of time. Using our new analysis standard, we re-analyzed data from large-scale investigations conducted as part of a 4-year comprehensive survey comprising 52 datasets, and established modified exposure-response relationships for three types of transport noise in Korea. We found significant differences in annoyance response compared to previous studies, including the study which was used in the development process of WHO/Europe’s environmental noise guidelines. We propose that the exposure-response relationships established in our study are the most optimal curves currently available for predicting community annoyance to transportation noise in Korea. Furthermore, we suggest that future research focus on differences in annoyance responses due to the effects of non-acoustic factors.

재난약자 및 재난 특성에 따라 여성가족부, 보건복지부, 행정안전부 등 소관 부처에 따라 개별적 정책 수립 및 지원이 이루어지고 있다. 또한 재난발생시 대응 및 복구 과정에서의 재난약자에 대한 지원 대책도 갖추고 있지 않다. 이에 이 연구는 재난약자에 대한 지원체계 개선 방안 제시를 목적으로 하고 있다. 또한 연구 목적 달성을 위해, 미국, 일본 등 재난관리 선진국의 재난약자 보호 및 지원을 위한 제도 및 체계를 비교분석하여 그 시사점을 찾고자 한다. 연구의 목적을 달성하기 위해, 이 연구는 우리나라의 재난약자 지원 현황을 분석하였으며, 외국의 재난약자 지원체계 사례를 분석하여 시사점 을 도출하였다. 이 연구는 해외사례에서 도출된 시사점을 바탕으로 우리나라의 재난약자 지원체계 개선을 위한 3가지 방안을 제시하였다. 첫째 법령체계 개선과 관련하여 재난약자 관련 대상 및 업무의 명확화와 지방자치단체의 재난약자 지원 관련 조례의 개선을 제시하였다. 둘째, 재난약자 피해경감을 위하여, 재난약자 신속 대피지원 강화, 재난약자 지원을 위한 공공 및 민간 조직간 협력 강화 등이 요구된다. 셋째, 노인, 장애인, 영유아 등에 따라 주관하는 부처 및 부서가 다르기 때문에 통합적 지원체계 구축에는 어려움이 있다. 이에 재난약자 지원체계는 재난약자 지원관련 계획 수립 및 교육은 각 개별기관에서 진행하며, 지원에 필요한 인력⋅예산⋅장비 등은 총괄기관에서 담당하는 방향으로 구축하는 것이 효율적일 것으로 판단된다.

New approaches and techniques are required for environmental management in workplaces that emit pollutants. The best available techniques (BATs) that are suggested by the integrated environmental permit system (IEPS) play a pivotal role in providing state-of-the-art approaches and techniques to workplaces. For the workplaces that install facilities with the BATs, it is necessary to perform real-time monitoring to determine whether pollutant emission facilities and treatment facilities are operating normally and whether such facilities can maintain the optimal condition during the emission of pollutants. The environmental management measures used before the IEPS had limitations for workplaces that are subjected to integrated environmental management because they consider the entire workplace as a single pollution source by combining all media. In addition, only the emission concentrations and amounts of pollutants were monitored because only the points at which most pollutants are discharged, i.e., stacks for air pollutant emission facilities and final effluent outlets for water pollutant emission facilities, are monitored. These monitoring approaches in a variety of facilities involve considerable costs, and most of them (95% for stacks in workplaces under IEPS, Korea) cannot perform real-time observation even though some of them are capable of it (5% for stacks managed by Tele Monitoring System, TMS). In this study, the applicability of a wireless sensor monitoring network was examined as a new approach for environmental management in workplaces. Based on the sensor monitoring network, surrogate parameters that can indirectly monitor the critical operating factors of pollutant emission and prevention facilities were developed and then measured in real time to examine the status of these facilities. Surrogate parameters can be used instead of directly measuring pollutants as the former has high efficiency, such as cost reduction, and can provide reliable data on the emission characteristics of pollutants. The wireless network is based on an Internet of Things (IoT) platform under real-time conditions in the emission and production facilities in a workplace. This study suggested that a wireless network using the IoT platform improves the BAT assessment methodology to understand the efficiency of environmental pollution reduction and the economic contribution to the workplace.

Phosphatidylinositol 3-kinases (PI3Ks) mediate intracellular signal transduction. Aberrant PI3K signaling is associated with oncogenesis and disease progression in solid tumors and hematologic malignancies. Idelalisib (1), a first-in-class PI3Kδ inhibitor for the treatment of hematologic malignancies, was developed, but its sales were limited by black box warnings due to unexpected adverse effects. Therefore, to overcome these adverse events, various quinazolinone derivatives were synthesized and evaluated in vitro based on their inhibitory activity against the PI3K enzyme and the viability of cell lines such as MOLT and SUDHL. Among them, 6f (IC50 = 0.39 nM) and 6m (IC50 = 0.09 nM) showed excellent enzyme activity, and 6m displayed an approximately four-fold higher selectivity for PI3Kγ/δ compared with Idelalisib (1). Furthermore, in vivo PK experiments with 6f and 6m revealed that 6f (AUClast = 81.04 h*ng/mL, Cmax = 18.34 ng/mL, Tmax = 0.5 h, t1/2 = 10.2 h in 1 mpk dose) had improved PK compared with 1. Finally, further experiments will be conducted with 6f selected as a candidate, and the potential for it to be developed as a treatment with good efficacy for hematologic malignancies will be determined.

Bench-scale selective bioflotation tests were carried out in a 1 L Denver cell using Rhodococcus opacus ( R. opacus ) cells as a collector in malachite–silica binary mixture and copper (Cu) oxide ore systems. Through the first set of tests carried out on the binary mixture, cell concentration and malachite fraction in the feed were optimized, and further the role of shear force by varying impeller speed (800, 1000, and 1200 rpm) and adhesive force by varying pH (7 and 11) and ionic strength (1, 100, and 300 mM) were examined. Overall, high malachite selectivity was observed under optimized conditions (both recovery and grade > 90%). In addition, the recovery and grade of malachite were very sensitive to pH changes, with greater values being obtained at pH 7, whereas the impeller speed and the ionic strength did not seem to play a big role over the range tested. The trend was in qualitative agreement with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profiles, which show the relative magnitudes of the adhesive forces between the mineral and the attached cell under equal hydrodynamic conditions. The second set of tests was conducted using Cu oxide ores with two different particle sizes (74–150 μm and − 74 μm) under the optimized conditions determined from the first set of tests. The recovery and grade of malachite were found to be much greater for finer ores (recovery = 29.15% and grade = 5.17%) than those for coarser ones (recovery = 1.34% and grade = 3.06%), which is likely due to differences in malachite liberation. Further comparison of the finer ore result with that obtained from the conventional process (i.e., sulfidization followed by xanthate adsorption) indicated that the malachite selectivity of bioflotation is much higher than that of the conventional process (grade = 1.43%).

Humans spend approximately 90% of the daytime in buildings, and greenhouse gases (GHGs) emitted by buildings account for approximately 20% of total GHG emissions. As the energy consumed during building operation from a building life-cycle perspective amounts to approximately 70–90% of the total energy, it is essential to accurately predict the energy consumption of buildings for their efficient operation. This study aims to optimize a model for predicting the thermal energy consumption of buildings by (i) first extracting major variables through feature selection and deriving significant variables in addition to the collected data and (ii) predicting the thermal energy consumption using a machine learning model. Feature selection using random forest was performed, and 11 out of 17 available data were selected. The accuracy of the prediction model was significantly improved when the hour of day variable was added. The prediction model was constructed using an artificial neural network (ANN), and the improvement in the prediction accuracy was analyzed by comparing different cases of variable combinations. The ANN prediction accuracy was improved by 15% using the feature selection process compared to when all data were used as input data, and 25% coefficient of variation of the root mean square error (CVRMSE) accuracy was achieved.

Significance This report describes an opportunity for the bacterial cellulose nanofiber (BCNF) membrane, which has recently been attracting much attention due to its sustainability and high thermal stability, as a “single-layer,” good alternative membrane to the existing chemical-derived one in batteries, and thus allows us to find possible solutions to the environmental and safety issues. We achieved highest BCNF yield ever reported so far and fabricated a cylindrical lithium ion battery (LIB) by roll-to-roll process to realize remarkable cycle stability with 80% capacity retention even after 1,000 cycles, which is comparable to those of commercialized batteries. Finally, we introduced a Lewis base to improve thermal safety of the battery to a level comparable to that of a commercial ceramic-coated separator.

In this study, the effects of the type (ammonium sulfide (NH4)2S and sodium sulfide (Na2S)) and amount (8 × 10−5 mol/L and 2 × 10−3 mol/L) of sulfidizing reagents used in malachite flotation with xanthate as a collector on flotation recovery were investigated in a well-controlled Hallimond tube. The results showed that the average flotation recovery of malachite was similar regardless of the type of sulfidizing agent; however, a significant difference was observed when the amount of sulfidizing agents varied. Specifically, malachite had a higher flotation recovery when sulfidized at a low concentration than at a high concentration. This result was not explained by either the differences in the extent of sulfidization or by the electrostatic interaction between xanthate and malachite, which was supported by XPS and XRD analyses, adsorption tests of sulfidizing agents, and zeta potential measurements. Notably, malachite without excess sulfide ions exhibited significantly greater flotation recovery than that with excess sulfide ions regardless of the type of sulfidizing agent. These results were well supported by the results from the potentiometric titration tests, which showed greater xanthate adsorption onto the surface of malachite without excess sulfide ions than that with excess sulfide ions. Therefore, the excessive use of sulfidizing agents was confirmed to inhibit xanthate adsorption onto the malachite surface, and consequently, to decrease the flotation recovery of malachite.