Consecutive Operations Research Articles

Characteristics of pediatric ocular trauma in a tertiary hospital in Israel 2011-2020 - How can public prevention policy be improved?

To describe and analyze characteristics and trends of pediatric ocular trauma during 2011-2020. Retrospective descriptive study. Data were collected on all pediatric ocular trauma cases that presented to a Rambam Health Care Campus during 2011-2020. Data included age, gender, visual acuity, diagnosis, injury mechanism and surgical repair. Median BCVA at presentation was 0.96 (logMAR). Males and non-adolescent males specifically were the most prominent groups (70.6% and 44.7%, respectively). The ratio of ocular trauma cases to total pediatric emergency department (ED) visits was stable during 2011-2020 (p = 0.714) regardless of gender (p = 0.832 and p = 0.545 for boys and girls, respectively). The leading causes were partial thickness eyelid laceration, periorbital hematoma, and extraocular muscle contusion, all of which were stable over the study period (p = 0.678, p = 0.203 and p = 0.398, respectively). Falls and children play were the most common mechanisms (25.8% and 18.4%, respectively), but differed between age groups. Most patients did not require consecutive operation and were treated conservatively (p < 0.01). Pediatric ocular injuries to pediatric ED visits ratio remained stable during 2011-2020, regardless of gender. Non-adolescent males accounted for nearly half of all cases, with different mechanisms for each age group. Consecutive surgery was rarely necessary.

Predictors of Intraoperative Difficulty and Postoperative Examination Abnormalities in 164 Orbital Operations

Although orbital fractures are common, prediction of outcomes in orbital surgery can be quite challenging. We aim to identify predictors of intraoperative difficulty, operating time, and postoperative examination abnormalities in subjects undergoing post-traumatic orbital reconstructions. This is a retrospective cohort study of all consecutive orbital operations performed at a private, Level 1 trauma center in Portland, Oregon, USA over an 82-month period. All subjects that underwent exploration of the internal orbit for traumatic indications during the study period were included in the cohort. Four plating styles, surgical approach (transorbital vs transantral), days from injury to first surgery, fracture size (approximated as a rectangle using linear measurements from computed tomography scans), anteroposterior fracture position, and medial wall involvement were examined. The primary outcome variable was intraoperative difficulty (defined as requiring revision after intraoperative imaging or return to the operating room). Secondary outcome variables included operating time and postoperative examination abnormalities. Age and sex were included. χ2 and Regression analyses were performed using a significance level of P<.05. One hundred and sixty four orbital operations were performed (90 isolated injuries and 74 combined orbital/midface injuries) on 155 subjects (73% male, mean age 39.8years, standard deviation 16.7). In subjects with isolated orbital fractures, medial wall involvement was associated with intraoperative difficulty (P=.01). When using a transantral approach, intraoperative difficulty was more likely in more anterior fractures (P=.02). Plating style was associated with operating time (P=.03), with median times from 81 to 105minutes (range 21 to 248minutes). Postoperative examination abnormalities were more likely in the transorbital approach group (P=.01). Neither days to first surgery nor intraoperative difficulty were associated with postoperative examination abnormalities. Postoperative eyelid changes were seen in 13.6% of transorbital approaches and 0% of transantral approaches. Correction of gaze restriction and enophthalmos were more likely than correction of diplopia (P<.01). Medial wall involvement is associated with intraoperative difficulty in orbital surgery. Anteriorly positioned fractures are better treated transorbitally, while posterior fractures may be amenable to transantral repair, thus avoiding risk of lower eyelid changes.

SP8.10 Auditing periprocedural antibiotic prophylaxis (PAP) in emergency surgery using NAPS surgical ™

Abstract Aim The study aimed to investigate the compliance with guidelines and the appropriateness of periprocedural antibiotic prophylaxis (PAP) in emergency surgery at the John Radcliffe Hospital. The study also aimed to determine the usefulness of NAPS surgical™ in monitoring and evaluating PAP usage. Methods The study conducted a retrospective analysis of medical charts for 97 consecutive emergency general surgical operations in August 2022. Data collected included the type of surgery, antibiotics administered, and compliance with local guidelines. The data was analyzed using NAPS surgical™. Results In 97 cases, 40 patients did not receive PAP, 26 of which were deemed appropriate. 57 patients received 76 doses of antibiotics, 51 of which were deemed inappropriate, mainly due to the administration of PAP to low-risk cases or outside of the recommended timing. Cefazolin was the most commonly used drug and no adverse effects were reported. Conclusions The study highlights the value of NAPS surgical™ in monitoring prophylactic antibiotic usage and the need for ongoing monitoring and education. NAPS surgical™ provides a comprehensive evaluation of antibiotic use, is cost-effective, and allows for direct comparison with other hospitals, providing insight into best practices. The hospital found NAPS surgical™ useful in assessing antibiotic stewardship and monitoring stewardship interventions.

Nutritional support in the complex therapy of clostridial infection after surgery

This article presents the tactics of nutritional support in a patient with pseudomembranous colitis after repeated consecutive operations on the abdominal organs, which led to significant violations of the nutritional status. Competent, individually selected correction of protein-energy deficiency in patients with pseudomembranous colitis allows achieving an effective treatment result, avoiding severe complications such as perforation, toxic dilatation, and bleeding. The peculiarity of this clinical case is that a patient with perforation of Meckels diverticulum and abdominal abscess developed a complication secondary widespread peritonitis, phlegmon, which required repeated surgical interventions. Surgical treatment and massive antibiotic therapy led to the development of Clostridium difficile infection: during the treatment the patient developed multiple loose stools and C. difficile toxins A and B were detected. Severe pseudomembranous colitis was accompanied by protein-energy deficiency (hypoproteinemia, hypoalbuminemia), severe dehydration, hypokalemia, hyponatremia, and moderately severe anemia of complex genesis. When selecting nutritional support for patients with clostridial infection, it is important to take into account severe systemic inflammation, which affects the absorption and absorption of the intestinal wall, which in turn determines the route of introduction of nutrient substrates. In this case we needed to choose the right method for correcting the patients nutritional status.

Anterior cruciate ligament reconstruction learning curve study – Comparison of the first 50 consecutive patients of five orthopaedic surgeons during a 5-year follow-up

BackgroundThe goal of all surgical and orthopaedic training is to ensure necessary education and surgical skills without compromising the quality of operations or patient safety. Anterior cruciate ligament reconstruction (ACLR) is a common multi-staged orthopaedic surgical procedure with a learning curve. Previous studies focus mainly on learning or the learning curve of one surgeon and tunnel placements. The aims of this study were to define the learning curve in arthroscopic ACLRs, define the number of procedures needed before the surgical “knifetime” plateaus, examine the effect of experience on complications, and identify possible individual differences in the surgical learning curve. MethodsThe study included the first 50 consecutive ACLR operations of five orthopaedic surgeons, thus, a total of 250 patients. For comparison and statistical analysis, patients were arranged into five groups, each comprising 50 patients (=order group). Order group 1 comprised the first 10 patients operated on by each of the five surgeons, group 2 patients 11–20, group 3 patients 21–30, group 4 patients 31–40, and group 5 the last 10 patients. The learning curve was defined with a LOESS curve. Surgical time and complications, including graft failure and postoperative knee instability, were analysed between order groups and between surgeons. ResultsMedian surgical time was 105 (interquartile range 82–124) min. The learning curve showed the first steep decline in surgical time and started to settle slowly after 20 reconstructions. Surgical time was significantly longer when order group 1 was compared with order group 2 (p = 0.031), and when order group 1 was compared separately with order groups 3, 4, and 5 (p < 0.001). Operation order alone explained only 17.1% of the alteration in surgical time. No significant difference emerged in graft failure rate between the order groups or the surgeons. Objective instability of the knee showed a significant difference when order group 1 was compared separately with order group 3 and with order group 4 (p = 0.004). Surgical time differed between surgeons (p < 0.001), and the shape of the learning curve showed great individual variability. ConclusionIn the first 10 to 20 ACLR operations, the surgical time was longer and the complication rate higher, but thereafter both started to settle down. We recommend that first 10–20 ACLR operations should be supervised.

Association between preoperative glucose- lowering medication agents and the status of type 2 diabetes mellitus after bariatric surgery

Introduction: Bariatric surgery is an effective treatment for type 2 diabetes mellitus (T2DM) in patients with morbid obesity. This study investigates whether duration of diabetes and anti-diabetes therapy are associated with glycaemic control after surgery in a routine clinical setting. Method: A cohort analysis of a prospectively maintained database was carried out for consecutive bariatric operations performed between April 2017 and March 2018 for patients with T2DM. Results: A total 105 patients with T2DM underwent bariatric surgery (89 Roux-en-Y gastric bypass and 16 sleeve gastrectomy). Median follow-up was 19 months ([interquartile range] IQR 13-24 months). Median weight and body mass index (BMI) on the day of surgery were 125 kg (IQR 103.9- 138.7) and 42.4 kg/m2 (IQR 39-46.8), respectively. At follow- up, 68 patients (64.8%) had achieved remission of diabetes. Patients who were pre-operatively on more than one glucose-lowering medication were less likely to go into remission (odds ratio [OR] 0.13, 95% CI 0.04-0.44, p=0.001) compared to those that were on a single glucose-lowering medication agent. Pre-operative use of insulin therapy (OR 0.09, 95% CI 0.03-0.31, p=&lt;0.001) and SGLT2 inhibitors (OR 0.23, 95% CI 0.05-0.92, p=0.038) were significant negative predictors of remission. Type of operation (p=0.34), pre-operative BMI (p=0.99), and % total weight loss (TWL) (p=0.83) did not predict remission from T2DM after surgery. Conclusions: Most patients who are medicated for T2DM can stop their glucose-lowering medication after bariatric surgery. Patients who are on multiple glucose-lowering medication agents or those dependent on insulin or SGLT2 inhibitors before bariatric surgery are less likely to undergo complete remission &gt;12 months after bariatric surgery.

Multi-level lot-sizing and job shop scheduling with lot-streaming: Reformulation and solution approaches

This paper addresses a multi-level lot-sizing and job shop scheduling problem with lot-streaming. In the multi-level production system, workstations receive materials from the lower level, and after some operation, materials are shipped to the next level. Hence, establishing a material balance between the different levels is the most challenging part of multi-level production planning and scheduling. The material balance can be performed with or without lot-streaming. Lot-streaming effectively enables consecutive operations to overlap by splitting a processing lot into several sub-lots. In small-bucket time models, this capability is taken into account by establishing the material balance in each small unit of time (micro-period), which makes the models computationally expensive. In the present work, a novel and much less complicated big-bucket time formulation has been developed, which incorporates lot-streaming considering sequence-dependent setup times and capacitated machines. Computational experiments affirm the promising results of the proposed model compared to the well-known models in the literature. Moreover, two efficient heuristics have been developed for solving larger-size problems. First, the fix-and-relax algorithm as a constructive heuristic is combined with the fix-and-optimize algorithm as an improvement heuristic. Next, a decomposition heuristic is proposed using mixed-integer programming (MIP) and constraint programming (CP) in the master and sub-problem, respectively. The computational results show that the proposed heuristics are very efficient, even in solving large-sized problems.

High buffering capacity cobalt-doped nickel hydroxide electrode as redox mediator for flexible hydrogen evolution by two-step water electrolysis

Two-step water electrolysis has been proposed to tackle the ticklish H2/O2 mixture problems in conventional alkaline water electrolysis recently. However, low buffering capacity of pure nickel hydroxide electrode as redox mediator limited practical application of two-step water electrolysis system. A high-capacity redox mediator (RM) is urgently needed to permit consecutive operation of two-step cycles and high-efficiency hydrogen evolution. Consequently, a high mass-loading cobalt-doped nickel hydroxide/active carbon cloth (NiCo-LDH/ACC) RM is synthesized via a facile electrochemical method. The proper Co doping can apparently enhance the conductivity and simultaneously remain the high-capacity of the electrode. Density functional theory results further confirms more negative values in redox potential of NiCo-LDH/ACC than Ni(OH)2/ACC on account of the charge redistribution induced by Co doping, which can prevent the parasitic O2 evolution on RM electrode during decoupled H2 evolution step. As a result, the NiCo-LDH/ACC combined the superiorities of high-capacity Ni(OH)2/ACC and high-conductivity Co(OH)2/ACC, and the NiCo-LDH/ACC with 4:1 ratio of Ni to Co presented a large specific capacitance of 33.52F/cm2 for reversible charge–discharge and high buffering capacity with two-step H2/O2 evolution duration of 1740 s at 10 mA/cm2. The necessary input voltage (2.00 V) of the whole water electrolysis was broken into two smaller ones, 1.41 and 0.38 V, for H2 and O2 production, respectively. NiCo-LDH/ACC provided a favorable electrode material for the practical application of two-step water electrolysis system.

Flexible waveguide integrated thermo-optic switch based on TiO2 platform.

Mechanically flexible photonic devices are critical components of novel bio-integrated optoelectronic and high-end wearable systems, in which thermo-optic switches (TOSs) as optical signal control devices are crucial. In this paper, flexible titanium oxide (TiO2) TOSs based on a Mach-Zehnder interferometer (MZI) structure were demonstrated around 1310 nm for, it is believed, the first time. The insertion loss of flexible passive TiO2 2 × 2 multi-mode interferometers (MMIs) is -3.1 dB per MMI. The demonstrated flexible TOS achieves power consumption (Pπ) of 0.83 mW, compared with its rigid counterpart, for which Pπ is decreased by a factor of 18. The proposed device could withstand 100 consecutive bending operations without noticeable degradation in TOS performance, indicating excellent mechanical stability. These results provide a new perspective for designing and fabricating flexible TOSs for flexible optoelectronic systems in future emerging applications.

Time and Motion Studies to assess surgical productivity in cataract theatre lists within the National Health Service: Immediate Sequential Bilateral Cataract Surgery versus Delayed Sequential Bilateral Cataract Surgery.

To compare productivity of National Health Service cataract lists performing unilateral cataract (UC) surgery vs Immediate Sequential Bilateral Cataract Surgery (ISBCS). Five 4-hour lists with ISBCS cases and five with UC were observed using time and motion studies (TMS). Individual tasks and timings of each staff member in theatre was recorded by two observers. All operations were performed by consultant surgeons under local anaesthesia (LA). Median number of eyes operated per 4-hour list was 8 (range 6-8) in the ISBCS group and 5 (5-7) in the UC group (p = 0.028). Mean total theatre time (defined as time between the entry of the first patient and the exit of the last patient from theatre) was 177.12 (SD 73.62) minutes in the ISBCS group and 139.16 (SD 47.73) minutes in the UC group (p = 0.36). Mean time to complete two consecutive unilateral cataract surgery operations was 48.71 minutes compared to 42.23 minutes for a single ISBCS case (13.30% time saved). Based on our collected TMS data, a possible 5 consecutive ISBCS cases and 1 UC (total 11 cataract surgeries) could be performed during a four-hour theatre session, with a theatre utilisation quotient of 97.20%, contrasting to nine consecutive UC, with a theatre utilisation quotient of 90.40%. Performing consecutive ISBCS cases under LA on routine cataract surgery lists can increase surgical efficiency. TMS are a useful way to investigate surgical productivity and test theoretical models for efficiency improvements.

Моделирование технологии очистки леса с помощью многооперационной машины

A conceptual model of a forest multi-operator machine for clearing debris caused by tree mortality is presented. A technological process of sanitary forest clearing that minimizes manual labour with the help of a machine and a winch is considered, including the technology of litter removal with its processing into firewood in the forest. Two variants of multi-operating machine's work with a winch are given: sequential, when the machine processes the wood from the fell as it is received from the winch, and parallel, when the winch and machine work independently of each other. It is established that the productivity at debris removal at parallel operation of the machine and winch is higher by 7...14 % than at their consecutive operation. It is revealed that the productivity of a multi-operator machine when the machine and a winch work in parallel increases by 53...55 %. It is determined that the load of the machine, when working together with a winch, is less than 50 % of working time. It is recommended that the winch and the machine work together at close capacities, if the winch capacity is very different from the machine capacity, then they should work separately.

A novel transformer-based network with attention mechanism for automatic pavement crack detection

Currently, there is an urgent need to utilize automatic approaches to detecting pavement cracks for roadway maintenance. Taking advantage of the development of convolutional neural networks (CNNs), previous studies put more effort into the detection of the pavement crack with local feature extraction using consecutive convolutional operations. However, it results in the loss of detailed information, making CNNs fail to accurately inspect the long and complicated cracks under noisy conditions, which are common on the pavement surface, negatively impacting detection accuracy. In order to cope with this issue, this study proposes a Transformer-based semantic segmentation network that unifies the Swin Transformer as the Encoder and the UperNet with the attention module as the Decoder for robust and accurate pixel-level pavement crack detection. Leveraging the hierarchical architecture of Swin Transformer, the global and long-range semantic features of the pavement crack are learned for improved segmentation accuracy. With the assistance of the attention module, the Decoder can retrieve more details of the crack information, presenting accurate detection results on the fine and tiny pavement cracks. To validate the superiority of the proposed network, we have trained and tested six semantic segmentation models on three public pavement crack datasets. Compared to other models, the proposed model achieves the best performance on visualization and evaluation metrics of mean F1(mF1) and mean Recall (mRecall) with 0-pixel tolerance. It paves the way for future applications of automatic pavement crack detection using Transformed-based networks.

Prognostic utility of a novel risk prediction model of 1-year mortality in patients surviving to discharge after surgery for congenital or acquired heart disease

ObjectiveWe sought to develop a novel risk prediction model of 1-year mortality after congenital heart surgery that accounts for clinical, anatomic, echocardiographic, and socioeconomic factors. MethodsThis was a single-center, retrospective review of consecutive index operations for congenital or acquired heart disease, from January 2011 to January 2021, among patients with known survival status at 1 year after discharge from the index hospitalization. The primary outcome was postdischarge mortality at 1 year. Variables of interest included age, prematurity, noncardiac anomalies or syndromes, the Childhood Opportunity Index, primary procedure, major adverse postoperative complications, and the Residual Lesion Score. Logistic regression was used to develop a weighted risk score for the primary outcome. Internal validation using a bootstrap-resampling approach was performed. ResultsOf 10,412 consecutive operations for congenital or acquired heart disease, 8808 (84.6%) cases met entry criteria, including survival to discharge. There were 190 (2.2%) deaths at 1 year postdischarge. A weighted risk score was formulated on the basis of the variables in the final risk prediction model, which included all aforementioned risk factors of interest. This model had a C-statistic of 0.82 (95% confidence interval, 0.80-0.85). The median risk score was 6 (interquartile range, 4-8) points. Patients were categorized as low (score 0-5), medium (score 6-10), high (score 11-15), or very high (score 16-20) risk. The expected probability of mortality was 0.4% ± 0.2%, 2.0% ± 1.1%, 10.1% ± 5.0%, and 36.6% ± 9.6% for low-risk, medium-risk, high-risk, and very high-risk patients, respectively. ConclusionsA risk prediction model of 1-year mortality may guide prognostication and follow-up of patients after discharge after surgery for congenital or acquired heart disease.

Long-Term Results of Femorodistal Sequential Composite-Bypass Combining Heparin-Bonded PTFE-Prosthesis and Autologous Vein Using the Deutsch Bridge Technique in Critical Limb-Threatening Ischemia.

Autologous vein bypass provides excellent long-term results in critical limb-threatening ischemia (CLTI), but a substantial portion of patients have insufficient vein length. In limbs with two distal outflow vessels and limited vein length, a vascular prosthesis may be combined with autologous vein for a sequential composite bridge bypass (SCBB). Results regarding graft function, limb salvage and reinterventions are presented. Between January 2010 and December 2019, 47 consecutive SCBB operations with a heparin-bonded PTFE-prosthesis and autologous vein were performed. Grafts were followed with a duplex scan with prospective documentation in a computerized vascular database. Retrospective analysis of graft patency, limb salvage and patient survival was performed. Mean follow-up was 34 months (range 1-127 months). 30-day mortality was 10.6% and 5-year patient survival 32%. Postoperative bypass occlusion occurred in 6.4% and late occlusions or graft stenoses in 30%. Two prostheses developed late infection and seven legs were amputated. Primary, primary assisted, secondary patency and limb salvage rate were 54%, 63%, 66% and 85% after 5 years, respectively. SCBB patency and limb salvage were good despite a high early postoperative mortality. Combination of a heparin-bonded PTFE-prosthesis and autologous vein appears to be a valuable tool in CLTI in case of insufficient vein.

Electroacupuncture treatment ameliorates depressive-like behavior and cognitive dysfunction via CB1R dependent mitochondria biogenesis after experimental global cerebral ischemic stroke.

This study aimed to identify the effect of electroacupuncture (EA) treatment on post-stroke depression (PSD) and explore whether cannabinoid receptor 1 (CB1R)-mediated mitochondrial biogenesis accounts for the treatment effect of EA. The PSD mouse model was induced by a consecutive 14-day chronic unpredictable stress operation after 7 days of recovery from the bilateral common carotid artery occlusion surgery. Either EA treatment or sham stimulation was performed for 14 consecutive days from Day 7 after the BCCAO operation. Subjects' PSD-like behaviors were tested via open field test, sucrose preference test, novelty suppressed feeding test, tail suspension test, and forced swim test, and subjects' cognitive function was examined using Y-maze and novelty object recognition test. In addition, the levels of CB1R, mitochondrial biogenesis-related proteins (nuclear transcription factor 1, NRF1; mitochondrial transcription factor A, TFAM), proteins related to mitochondrial function (Cytochrome C, Cyto C; AIF, COX IV), and mitochondrial DNA were measured. To elucidate the role of CB1R in EA treatment, CB1R antagonists AM251 and CB1R-shRNA were given to mice before EA treatment. Likewise, subjects' depressive-like behaviors, cognitive function, mitochondrial function, and mitochondrial biogenesis were examined after the PSD procedure. It has been showed that EA successfully ameliorated depressive-like behaviors, improved cognitive dysfunctions, and upregulated CB1R, NRF1 and TFAM expressions. However, the supplementation of AM251 and CB1R-shRNA blocked the antidepressant-like effects generated by EA, and EA failed to improve cognitive dysfunction, upregulate CB1R protein expression, and increase mitochondrial function and biogenesis. Altogether, these results indicated that EA ameliorated PSD-like behaviors in mice, improved cognitive dysfunctions after PSD, and promoted mitochondrial biogenesis by activating CB1R, a novel mechanism underlying EA's antidepressant-like effects in treating PSD.

Experimental Assessment of Multilevel RRAM-Based Vector-Matrix Multiplication Operations for In-Memory Computing

Resistive random access memory (RRAM)-based hardware accelerators are playing an important role in the implementation of in-memory computing (IMC) systems for artificial intelligence applications. The latter heavily rely on vector-matrix multiplication (VMM) operations that can be efficiently boosted by RRAM devices. However, the stochastic nature of the RRAM technology is still challenging real hardware implementations. To study the accuracy degradation of consecutive VMM operations, in this work we programed two RRAM subarrays composed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times $ </tex-math></inline-formula> 8 one-transistor-one-resistor (1T1R) cells following two different distributions of conductive levels. We analyze their robustness against 1000 identical consecutive VMM operations and monitor the inherent devices’ nonidealities along the test. We finally quantize the accuracy loss of the operations in the digital domain and consider the trade-offs between linearly distributing the resistive states of the RRAM cells and their robustness against nonidealities for future implementation of IMC hardware systems.

Minimizing Makespan in a Permutation Flow Shop Environment: Comparison of Scatter Search, Genetic Algorithm and Greedy Randomized Adaptive Search Procedures

Solving scheduling problems enables more efficient use of production capacity. It involves defining the sequence of operations, determining the capacity of resources, and balancing workloads. Different methods, especially metaheuristics, have been used to solve these problems. This study presents the application of Scatter Search (SS), Genetic Algorithm (GA), and Greedy Randomized Adaptive Search Procedures (GRASP) for minimizing makespan in a permutation flow shop environment. In this study, the performances of these methods are compared through various test problems in the literature and a real-life problem of a company operating in the automotive sector. Study comprises 48 jobs that must be planned within a day for eight consecutive operations. In cellular manufacturing, the sequence in which each job is processed in eight operations is the same. In solving permutation flow shop scheduling problems (PFSP), one of the NP-hard problems, meta-heuristic methods are widely applied due to their successful results. From this point of view, SS, GA, and GRASP are employed in this study, and their performances are compared.

Covalent organic polymers with azido group for efficient recovery of gold from gold-bearing waste

BackgroundGold is a rare precious metal. Efficient and selective adsorption of Au(III) is of great significance for gold recovery. MethodsA covalent organic polymer with azido group (N3-COP) was synthesized utilizing enaminone covalent organic polymer and Ts-N3 as raw materials. Significant FindingsThe adsorption capacity of N3-COP for gold ions was up to 1220 mg·g−1 under the condition that the adsorption process took place at room temperature and at a pH value of 4. The results of adsorption thermodynamic and adsorption kinetic experiments illustrated that the adsorption process of N3-COP for the trivalent gold ion is consistent with the Langmuir adsorption model and Quasi second-order adsorption model. Additionally, this adsorbent has high adsorption selectivity when it is used to adsorb trivalent gold ion from effluent containing gold (III), cadmium (II), nickel (II), cobalt (II), and copper (II) ions. This adsorbent also has good reusability for it maintains excellent adsorption performance after five consecutive adsorption operations.

Enhanced peroxymonosulfate activation by Co-bHAP catalyst for efficient degradation of sulfamethoxazole

The abuse of antibiotics has drawn wide attention owing to their potential risk in human health and ecosystem. As one of the most commonly used sulfonamide antibiotics, sulfamethoxazole (SMX) can hardly be removed by conventional wastewater treatment methods, and thus it has become one of the most frequently detected antibiotics in water environment. In this study, a new cobalt-based heterogeneous catalyst (Co-bHAP) was successfully prepared using the simple impregnation method with animal bone-derived hydroxyapatite (bHAP) as the support, and applied to activate peroxymonosulfate (PMS) for the degradation of SMX in water. The physicochemical properties of Co-bHAP catalyst were investigated by series of characterization methods, and the results showed that this catalyst has a rough and porous morphological structure, as well as homogeneously distributed active component, which is mainly in the form of Co3O4. The developed Co-bHAP can provide abundant reaction active sites and exhibit excellent catalytic activity and stability in PMS activation. The kinetic constant of Co-bHAP activating PMS to degrade SMX is up to 0.1524 min−1, which is 4.5 times larger than that of bare Co3O4. The SMX (20 mg/L) degradation efficiency within 30 min in Co-bHAP/PMS system reached as high as 98.7% and still maintained at 86% after 5 times consecutive operation, with slight cobalt ions leaching less than 0.1 mg/L. Based on radical quenching experiment, electron paramagnetic resonance (EPR) test and XPS analysis, the reaction mechanism was proposed. The balance among Co3+/Co2+, O2−/O2 and PMS decomposition in Co-bHAP/PMS system ensured the continuous generation of sulfate radical (SO4•–) and hydroxyl radical (HO•), both of which are responsible for SMX degradation, while SO4•– plays a leading role. In addition, four possible pathways of SMX degradation were proposed according to the eight detected intermediate products. All the results suggested that this catalyst could have a promising potential in activating PMS to degrade sulfonamide antibiotic pollutants in water.

Interfacial variation in HfO2-based resistive switching devices with titanium electrodes under asymmetric bias operation

Resistance fluctuations are persistent and critical issues in memory device applications. In recent years, several investigations have been conducted to unravel such fluctuations to further improve the retention and endurance of random resistance access memory (RRAM). Elucidating the switching mechanisms and causes of delamination at the insulator/electrode interface during practical bias operations is thus essential for improving RRAM performance. In this work, we first investigated the changes at the Ti/HfO2 interface in the Ti/HfO2/TiN RRAM device for consecutive bias operations. After the negative forming process and the following asymmetric bias operation conditions, the electrical output of the device decreased as a result of abnormal current degradation during iterative set/reset operations, during which the current high-resistance state (HRS) and low-resistance state (LRS) appeared to decrease. Transmission electron microscopy images and energy dispersive spectroscopy point data indicated that titanium oxides are formed at the Ti/HfO2 interface after asymmetric bias operation compared to the Ti/HfO2 interface of the pristine device, which provides direct evidence for validating the current degradation. In addition, to verify the influence of the electric fields on the devices during bias operation, we modulated the rising time of the set pulse triangle wavefront to further verify that the formation of TiO x depends on the amplitude of the electric field. Finally, the fitted current results indicate that the conduction mechanism after asymmetric bias operation in HRS and LRS is hopping conduction. Accordingly, a plausible physical model for bias operation in RRAM devices is proposed.