Review on Cell Structure Regulation and Performances Improvement of Porous Poly(Lactic Acid).

Recent advances in the cell structure regulation and performances improvement of porous poly(lactic acid) materials (PPMs) are systematically reviewed in this feature article. First, the typical processing methods, including template method, non-solvent induced phase separation, freeze-drying, and supercritical CO2  foaming, of PPMs are introduced emphatically. Their various cell morphologies by different processing methods are summarized: finger-like, honeycomb-like, fiber-like, through cell, open cell, closed cell, ball-like, and flower-like. Meanwhile, the transformation among different cell morphologies as well as the changes in cell size and cell density, having impact on the performances, is described. Second, the influence of stereo-complex crystals on the cell structure of PPMs is emphatically reviewed. Furthermore, the relationships between cell structure and properties that includes mechanical properties, thermal stability, heat insulation, and hydrophobicity, are elaborated. Eventually, the issues of PPMs worthy of further study are discussed.

Superhydrophobic Thermoplastic Polyurethane Foam Fabricated by Phase Separation and Silica Coating for Oil-Water Separation.

Oil spills and the presence of oily wastewater have resulted in substantial ecological damage. Superhydrophobic polymer foam with selectivity and adsorption capacity is a promising candidate for efficient oil-water separation. In this study, a method that combines phase separation and silica coating to produce superhydrophobic thermoplastic polyurethane (TPU) foam is proposed. The TPU foam demonstrates superhydrophobicity with a water contact angle of 155.62°, and exhibits a maximum saturated adsorption capacity of 54.11 g g-1 . Furthermore, the foam can be utilized as a filter for oil-water separation, maintaining its filtration efficiency (41.2 m3  m2  h-1 ) even after ten filtration cycles.

Simple Design of a Porous Solar Evaporator for Salt-Free Desalination and Rapid Evaporation.

Solar-driven interfacial evaporation is considered to be one of the promising and efficient ways of producing clean water in recent years. However, it remains a challenge to develop solar evaporation devices with high solar evaporation rates and salt-free blocking properties. Here, a porous solar evaporator with directed water transport and salt-free desalination through excellent photothermal conversion and purposefully guided migration of the salt solution was developed. The designed porous photothermal sponge with the synergistic effect of MXene and polypyrrole can achieve evaporation rates of 1.47 and 2.27 kg m-2 h-1, respectively, in the capillary model and siphon model water-transporting solar evaporation devices. More interestingly, the designed zigzag-shaped device with an evaporation rate of 2.45 kg m-2 h-1 was achieved. In addition, the evaporator can operate stably under 9 h in the siphon model solar evaporation device and achieves the effect of salt-free desalination. The above design provides a good strategy for solar-powered desalination applications.

High expression of SH2B adaptor protein 1 (SH2B1) indicates poor prognosis in colorectal cancer.

SH2B1, an adaptor protein associated with obesity, is closely related to the occurrence and development of a variety of tumors. To investigate the clinical significance of SH2B1 in colorectal cancer (CRC), expression of SH2B1 in colorectal normal tissues, adenomas, paracarcinoma tissues, carcinoma tissues, and metastatic tissues from 1003 CRC patients was detected by immunohistochemistry (IHC). The prediction power of SH2B1 for CRC prognosis was evaluated by Kaplan-Meier survival analysis and Cox regression model. Results revealed the expression of SH2B1 in carcinoma tissues was significantly higher than that in other tissues. High expression of SH2B1 was an independent risk factor for both disease-free survival (DFS) and disease-specific survival (DSS) and predicted unfavorable prognosis of CRC as well as poor chemotherapeutic response. Conclusively, SH2B1 can serve as an effective predictor for CRC survival and chemotherapeutic outcomes.

Low tumour PPM1H indicates poor prognosis in colorectal cancer via activation of cancer-associated fibroblasts.

BACKGROUND: Vimentin (VIM) is considered a prognostic marker in colorectal cancer (CRC). Our aim is to identify genes that fulfil a "X-low implies VIM-high" Boolean relationship and to evaluate their prognostic value and potential mechanism. METHODS: Potential biomarkers related to VIM expression were searched using a bioinformatics approach across gene-expression arrays. Based on subgroup analysis of 2 CRC cohorts, the selected gene was tested for its association with patient's survival outcomes. The regulatory link between the selected gene and VIM was further examined with in vitro models. RESULTS: PPM1H was identified as the top candidate in our search. Patients with PPM1H-low tumours have a lower 5-year disease-free survival rate than patients with PPM1H-high tumours in 2 independent cohorts. In multivariate Cox analysis, patients with PPM1H-low tumours were independently associated with relapse in both the discovery cohort (hazard ratio [HR], 1.362; 95% confidence interval [CI], 1.015-1.826; P = 0.039) and the validation cohort (HR for DFS, 4.052; 95% CI, 2.634-6.234; P < 0.001). PPM1H knockdown in CRC cells and growth in the corresponding conditional medium increased VIM expression and colon fibroblast proliferation, indicating a transformation of cancer-association fibroblasts (CAFs). Conversely, educated CAFs also facilitated the growth of CRC cells with low PPM1H expression. CONCLUSIONS: Lack of tumour PPM1H expression identifies a patient subgroup with a high relapse risk, and CRC cells with low expression of PPM1H activate CAFs and inversely get promoted by CAFs.

Facile Thermally Impacted Water-Induced Phase Separation Approach for the Fabrication of Skin-Free Thermoplastic Polyurethane Foam and Its Recyclable Counterpart for Oil-Water Separation.

Developing a facile large-scale strategy to fabricate polymer foams with excellent wettability and recycling its counterpart for oil-water separation is in urgent demand. Here, a facile template-free thermally impacted water-induced phase separation approach for the fabrication of skin-free thermoplastic polyurethane foam with a water contact angle of 147°, porosity more than 90%, density less than 14 mg cm-3 , and excellent compressibility (>1000 cycles) is proposed. The foams show high efficiency of oil recovery (>98%) during the squeezing and pumping oil-water separation test. Moreover, the used foams could be recycled and reused to form refresh foams without sacrificing their high performance, which makes this method a promising prospect for environmental applications.

Conductivity and phase morphology of carbon black-filled immiscible polymer blends under creep: an experimental and theoretical study.

Blends of carbon black (CB)-filled co-continuous immiscible polystyrene/poly(methyl-methacrylate) (PS/PMMA) with a PS/PMMA ratio of 50/50 and CB selectively located in the PS phase have been prepared by melt blending. The simultaneous evolution of conductivity and phase morphology of blend composites was investigated under shear and in the quiescent state at 200 °C. It was found that shear deformation had a significant influence on the conductivity of the unfilled PS/PMMA blend and its composites, which was attributed to the change of phase morphology during shear. After the shear stress of 10 kPa, the conductivity of PS/PMMA blends filled with 2 vol% of CB decreased by about two orders of magnitude and the phase morphology transformed from a fine co-continuous structure into a highly elongated lamellar structure. The deformation of phase morphology and the decrease of conductivity were weakened upon decreasing the shear stress or increasing the CB concentration. During subsequent recovery, pronounced phase structure coarsening was observed in the mixture and the conductivity increased as well. A simple model describing the behavior of conductivity under shear deformation was derived and utilized for the description of the experimental data. For the first time, the Burgers model was used to describe the conductivity, and the viscoelastic and viscoplastic parameters were deduced by fitting the conductivity under shear. The results obtained in this study provide a deeper insight into the evolution of phase structure in the conductive polymer blend composite induced by shear deformation.

Endotherapy versus surgery for early neoplasia in Barrett's esophagus: a meta-analysis.

BACKGROUND: Esophagectomy is the conventional treatment for Barrett's esophagus with high-grade dysplasia and intramucosal cancer. Endotherapy is an alternative treatment. OBJECTIVE: To compare the efficacy and safety of these 2 treatments. DESIGN: PubMed, Web of Science, EMBASE, Cochrane Library and momentous meeting abstracts were searched. Studies comparing endotherapy with esophagectomy were included in the meta-analysis. Pooling was conducted in a random-effects model. SETTING: Tertiary-care facility. PATIENTS: Seven studies involving 870 patients were included. INTERVENTION: Endotherapy and esophagectomy. MAIN OUTCOME MEASUREMENTS: Neoplasia remission rate, neoplasia recurrence rate, overall survival rate, neoplasia-related death, and major adverse events. RESULTS: Meta-analysis showed that there was no significant difference between endotherapy and esophagectomy in the neoplasia remission rate (relative risk [RR] 0.96; 95% CI, 0.91-1.01); overall survival rate at 1 year (RR 0.99; 95% CI, 0.94-1.03), 3 years (RR 1.03; 95% CI, 0.96-1.10), and 5 years (RR 1.00; 95% CI, 0.93-1.06); and neoplasia-related mortality (risk difference [RD] 0; 95% CI, -0.02 to 0.01). Endotherapy was associated with a higher neoplasia recurrence rate (RR 9.50; 95% CI, 3.26-27.75) and fewer major adverse events (RR 0.38; 95% CI, 0.20-0.73). LIMITATIONS: Relatively small number of retrospective studies available, different types of endoscopic treatments were used. CONCLUSION: Endotherapy and esophagectomy show similar efficacy except in the neoplasia recurrence rate, which is higher after endotherapy. Prospective, randomized, controlled trials are needed to confirm these results.

Antireflux stents to reduce the risk of cholangitis in patients with malignant biliary strictures: a randomized trial.

BACKGROUND AND STUDY AIMS: There are limited data on the role of antireflux biliary stents. This single-center randomized trial compared the endoscopic use of partly covered antireflux metal stents (pcARMS) with that of standard uncovered self-expandable metal stents (ucSEMS) for the palliation of nonhilar malignant biliary obstruction. PATIENTS AND METHODS: Between August 2007 and February 2012, patients with nonhilar malignant biliary obstruction were randomly assigned to treatment with either pcARMS or ucSEMS. Subsequent follow-up was conducted in clinic or by phone. The primary outcome was onset of cholangitis within 12 months of stenting. Secondary outcomes included other morbidities, stent dysfunctions, and survival. RESULTS: Altogether 112 patients were included, 56 in each group. The stents were successfully deployed in all patients. Satisfactory jaundice control was achieved in 49 cases in the pcARMS group, compared with 47 in the ucSEMS group (P = 0.135). Fewer patients experienced cholangitis in the pcARMS group than in the ucSEMS group (10 vs. 21 patients; P = 0.035), and the frequency of episodes was less (P = 0.022). Respectively, 17 and 29 stent dysfunctions before death were observed in the pcARMS and ucSEMS groups (P = 0.051) and the median stent patency was 13.0 (standard deviation [SD] 3.4) and 10.0 (1.2) months, respectively (P = 0.044). At final follow-up, in January 2013, 50 /52 and 52 /55 patients had died and no difference in median survival was seen between the two groups (8.0 vs. 9.0 months, P = 0.56). CONCLUSIONS: Stenting with pcARMS compared with standard ucSEMS reduces risk of ascending cholangitis and has longer stent patency, but does not increase patient survival. Chictr.org. number, ChiCTR-TRC-11001800.

Covered versus uncovered self-expandable metallic stents for palliation of malignant gastric outlet obstruction: a systematic review and meta-analysis.

BACKGROUND: Self-expandable metallic stents (SEMSs) are widely used for palliation of malignant gastric outlet obstruction (GOO). There are two types of SEMS, covered and uncovered, each with its own advantages and disadvantages. We aimed to compare the efficacy and safety between uncovered and covered SEMSs in the palliation of malignant gastric outlet obstruction. METHODS: Databases including PubMed, EMBASE, the Cochrane Library, the Science Citation Index and momentous meeting abstracts were searched and evaluated by two reviewers independently. RESULTS: Nine trials involving 849 patients were analyzed. Meta-analysis showed there was no significant difference in technical success rate (RR 1.0, 95% CI [0.98, 1.01]), clinical success rate (RR 1.04, 95% CI [0.98, 1.11]), post-stenting dysphagia score (WMD -0.01, 95% CI [-0.52, 0.50]), stent patency (WMD -0.31, 95% CI [-1.73, 1.11]), overall complications (RR 1.07, 95% CI [0.87, 1.32]) and reintervention rate (RR 1.30, 95% CI [0.92, 1.83]) between covered and uncovered SEMSs group. However, covered SEMSs were associated with higher migration rate (RR 3.48, 95% CI [2.16, 5.62], P < 0.00001) and lower obstruction rate (RR 0.42, 95% CI [0.24, 0.73], P = 0.002). CONCLUSIONS: In the palliative treatment of malignant gastric outlet obstruction, both covered and uncovered SEMSs are safely and effective. Covered stents can reduce the risk of restenosis, whereas uncovered stents are effective in decreasing stent migration.

Transparent ultrahigh-molecular-weight polyethylene/MXene films with efficient UV-absorption for thermal management.

The rational use and conversion of energy are the primary means for achieving the goal of carbon neutrality. MXenes can be used for photothermal conversion, but their opaque appearance limits wider applications. Herein, we successfully develop visible-light transparent and UV-absorbing polymer composite film by solution blending the MXene with polyethylene and then vacuum pressing. The resulting film could be quickly heated to 65 °C under 400 mW cm-2 light irradiation and maintained over 85% visible-light transmittance as well as low haze (<12%). The findings of the indoor heat insulation test demonstrate that the temperature of the glass house model covered by this film was 6-7 °C lower than that of the uncovered model, revealing the potential of transparent film in energy-saving applications. In order to mimic the energy-saving condition of the building in various climates, a typical building model with this film as the outer layer of the window was created using the EnergyPlus building energy consumption software. According to predictions, they could reduce yearly refrigeration energy used by 31-61 MJ m-2, and 3%-12% of the total energy used for refrigeration in such structures. This work imply that the film has wide potential for use as transparent devices in energy-related applications.

Feasibility of using wire-guided needle-knife electrocautery for refractory biliary and pancreatic strictures.

BACKGROUND: Endoscopic management of biliary or pancreatic strictures by stent insertion is well established. However, some high-grade strictures are refractory to dilation and stent placement with conventional methods. OBJECTIVE: To evaluate the safety and efficacy of the wire-guided electrotomy technique in dilating stiff biliary and/or pancreatic stenoses when ordinary methods failed. DESIGN: Retrospective analysis of a prospective database. SETTING: Tertiary referral university hospital. PATIENTS: This study involved 279 patients with biliary or pancreatic strictures who underwent ERCP for stenting. INTERVENTION: After conventional dilation failed, wire-guided needle-knife electrocautery was attempted to facilitate insertion of the dilating devices and eventually endoprosthesis. MAIN OUTCOME MEASUREMENTS: The successful treatment and drainage of biliary or pancreatic strictures. RESULTS: With wire-guided needle-knife cauterization, the success rate of stricture dilatation increased from 95.7% (267 of 279 patients) to 98.9% (276 of 279 patients). Dilation of stenoses was successful in 9 of 10 patients (90%) by using electrocautery with the wire-guided needle-knife technique. Postprocedure adverse events included self-limited bleeding, mild acute pancreatitis, hyperamylasemia, cholangitis, and biliary perforation. No procedure-related death occurred. LIMITATIONS: Retrospective, single-center study and small sample size. CONCLUSIONS: Wire-guided needle-knife electroincision appears to be effective for traversing refractory biliary or pancreatic strictures and can be considered as an alternative approach to conventional methods. However, the safety of such a technique needs to be further evaluated.

A Shish-Kebab Superstructure Film for Personal Radiative Cooling.

Due to global warming and the energy crisis, incorporating passive radiative cooling into personal thermal management has attracted extensive attention. However, developing a wearable textile that reflects incoming sunlight and allows mid-infrared radiation transmission is still a tough challenge. Herein, a shish-kebab superstructure film was produced via a flow-induced crystallization strategy for personal radiative cooling. The resulting film endowed a high infrared transmittance (87%) and improved sunlight reflectivity (83%). A device was developed to simulate the human body skin, and the temperatures of the shish-kebab film were 2.5 and 2.6 °C lower than that of traditional textile in outdoor and indoor tests, respectively. In order to make the shish-kebab film more wearable, a series of modifications were then carried out. This study demonstrates the substantial potential to personal thermal management textiles.

Ag Nanoparticles-Coated Shish-Kebab Superstructure Film for Wearable Heater.

Passive and active wearable heaters have received widespread attention due to their efficient utilization of solar energy and all-weather heating capabilities, but the current challenges are their preparation processes being time-consuming and equipment expensive. Herein, a simple and facilitated preparation method for the multifunctional wearable heater was developed, which springs Ag nanoparticles on the shish-kebab superstructure film via deposited melanin-like polydopamine as the adhesive. The light absorption ability of the resultant wearable heater in the visible region can be significantly enhanced by the addition of polydopamine, realizing a highly efficient photothermal conversion ability. Accordingly, it can achieve rapid warming ability whether passive heating (up to 45 °C about 60 s at 100 mW/cm2) or active heating (up to 72 °C about 40 s at 0.6 V), compared to ordinary cotton fabric. In addition, it can realize a 6.3 °C temperature difference with Cotton, showing excellent heat preservation ability. This study demonstrates a simple and low-cost approach for the prepared shish-kebab superstructure-based wearable heaters.

Controllable-morphology polymer blend photonic metafoam for radiative cooling.

Incorporating radiative cooling photonic structures into the cooling systems of buildings presents a novel strategy to mitigate global warming and boost global carbon neutrality. Photonic structures with excellent solar reflection and thermal emission can be obtained by a rational combination of different materials. The current preparation strategies of radiative cooling materials are dominated by doping inorganic micro-nano particles into polymers, which usually possess insufficient solar reflectance. Here, a porous polymer metafoam was prepared with polycarbonate (PC) and polydimethylsiloxane (PDMS) using a simple thermally induced phase separation method. The metafoam exhibits strong solar reflectivity (97%), superior thermal emissivity (91%), and low thermal conductivity (46 mW m-1 K-1) due to the controllable morphology of the randomly dispersed light-scattering air voids. Cooling tests demonstrate that the metafoam could reduce the average temperature by 5.2 °C and 10.2 °C during the daytime and nighttime, respectively. In addition, the simulation of a cooling energy system of buildings indicates that the metafoam can save 3.2-26.7 MJ m-2 per year in different cities, which is an energy-saving percentage of 14.7-41%. The excellent comprehensive performances, including the passive cooling property, thermal insulation and self-cleaning of the metafoam makes it appropriate for practical outdoor applications, exhibiting its great potential as an energy-saving building cooling material.

SHP2 inhibition improves celastrol-induced growth suppression of colorectal cancer.

This study aimed to explore novel targets for celastrol sensitization in colorectal cancer (CRC) based on differentially regulated signals in response to high- or low-dose celastrol. Targeting signals were investigated using Western blotting or phosphorylated receptor tyrosine kinase (RTK) arrays. Corresponding inhibitors for the signals were individually combined with low-dose celastrol for the assessment of combined anti-CRC effects, based on proliferation, apoptosis, colony assays, and xenograft models. The potential mechanism for the combination of celastrol and SHP2 inhibition was further examined. Low-dose celastrol (<1 µM) did not effectively suppress AKT and ERK signals in CRC cells compared to high-dose celastrol (>1 µM). However, when combined with an AKT or ERK inhibitor, low-dose celastrol could cooperatively suppress CRC proliferation. Furthermore, failed AKT or ERK inhibition by low-dose celastrol may be due to reactivated RTK-SHP2 signaling with negative feedback. The combination of celastrol and the SHP2 inhibitor resulted in greatly reduced AKT and ERK signals, as well as greater inhibition of CRC growth than celastrol alone. Moreover, the mechanism underlying combination suppression was also involved in the activation of immune cell infiltration (mainly for CD8+ cells) in CRC tissues. Failure to inhibit RTK-SHP2-AKT/ERK signaling contributed to the lack of CRC growth suppression by low-dose celastrol. However, the combination of celastrol and the SHP2 inhibitor resulted in synergistic inhibition of CRC growth and provided a promising therapeutic target.

Ni Flower/MXene-Melamine Foam Derived 3D Magnetic/Conductive Networks for Ultra-Efficient Microwave Absorption and Infrared Stealth.

The development of multifunctional and efficient electromagnetic wave absorbing materials is a challenging research hotspot. Here, the magnetized Ni flower/MXene hybrids are successfully assembled on the surface of melamine foam (MF) through electrostatic self-assembly and dip-coating adsorption process, realizing the integration of microwave absorption, infrared stealth, and flame retardant. Remarkably, the Ni/MXene-MF achieves a minimum reflection loss (RLmin) of - 62.7 dB with a corresponding effective absorption bandwidth (EAB) of 6.24 GHz at 2 mm and an EAB of 6.88 GHz at 1.8 mm. Strong electromagnetic wave absorption is attributed to the three-dimensional magnetic/conductive networks, which provided excellent impedance matching, dielectric loss, magnetic loss, interface polarization, and multiple attenuations. In addition, the Ni/MXene-MF endows low density, excellent heat insulation, infrared stealth, and flame-retardant functions. This work provided a new development strategy for the design of multifunctional and efficient electromagnetic wave absorbing materials.

A novel antireflux metal stent for the palliation of biliary malignancies: a pilot feasibility study (with video).

BACKGROUND: Antireflux stents that prevent duodenal biliary reflux may improve biliary drainage and prolong stent patency. However, the use of antireflux metal stents (ARMSs) in the human biliary system has not been reported. OBJECTIVE: To evaluate the safety and efficacy of ARMSs for the palliation of unresectable distal biliary malignancies. DESIGN AND SETTING: A retrospective case series in a tertiary referral center. PATIENTS: From August 2007 to April 2009, a total of 23 patients with unresectable nonhilar malignant biliary obstruction. INTERVENTION: Endoscopic placement of an ARMS. MAIN OUTCOME MEASUREMENTS: Technical success and early complications with follow-up of stent patency and patient survival. RESULTS: Placement of an ARMS was successful on the first attempt in all patients. There were no procedure-related complications. Follow-up was obtained in 22 cases. Serum bilirubin level returned to normal within 1 month of stenting in 20 patients. Six stent malfunctions occurred as a result of tumor ingrowth (1 patient), tumor overgrowth (2 patients), and stent migration (3 patients). The remaining patients were free of biliary symptoms until death or final follow-up. The median duration of stent patency of ARMSs was 14 months, with cumulative patency rates at 3, 6, and 12 months of 95%, 74%, and 56%, respectively. The median survival of the patients was 7.9 months (range, 1-14 months). LIMITATIONS: Small number of patients in single endoscopy center. CONCLUSIONS: Endoscopic insertion of an ARMS is technically feasible, safe, and effective in patients with distal malignant biliary obstruction. The impact of ARMSs in prolonging stent patency and life expectancy deserves further randomized evaluation.

Asymmetric Superhydrophobic Textiles for Electromagnetic Interference Shielding, Photothermal Conversion, and Solar Water Evaporation.

Flexible and multifunctional textiles have potential applications in self-cleaning and portable electronic product applications, but the current problem that needs to be solved is to maintain their inherent breathability and flexibility while expanding other functional applications. Herein, we adopt the layer-by-layer assembly method to develop a multifunctional textile with superior asymmetric superhydrophobicity, excellent electromagnetic interference (EMI) shielding, outstanding photothermal conversion, and solar water evaporation. The synergistic effect of SiO2 nanoparticles/poly(dimethylsiloxane) (PDMS) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) endows the textile with a water contact angle of 160°. MXene provides high conductivity (1200 S/m) and EMI shielding effects (36 dB) for multifunctional textiles. In addition, the multifunctional textile exhibits excellent photothermal conversion, and satisfactory solar water evaporation efficiency (80%) and rate (1.22 kg/(m2 h)) under 1 sun. Therefore, the prepared multifunctional textile has great potential in multiscene applications.

Flexible Ag Microparticle/MXene-Based Film for Energy Harvesting.

Ultra-thin flexible films have attracted wide attention because of their excellent ductility and potential versatility. In particular, the energy-harvesting films (EHFs) have become a research hotspot because of the indispensability of power source in various devices. However, the design and fabrication of such films that can capture or transform different types of energy from environments for multiple usages remains a challenge. Herein, the multifunctional flexible EHFs with effective electro-/photo-thermal abilities are proposed by successive spraying Ag microparticles and MXene suspension between on waterborne polyurethane films, supplemented by a hot-pressing. The optimal coherent film exhibits a high electrical conductivity (1.17×104 S m-1), excellent Joule heating performance (121.3 °C) at 2 V, and outstanding photo-thermal performance (66.2 °C within 70 s under 100 mW cm-1). In addition, the EHFs-based single-electrode triboelectric nanogenerators (TENG) give short-circuit transferred charge of 38.9 nC, open circuit voltage of 114.7 V, and short circuit current of 0.82 µA. More interestingly, the output voltage of TENG can be further increased via constructing the double triboelectrification layers. The comprehensive ability for harvesting various energies of the EHFs promises their potential to satisfy the corresponding requirements.