JAAL-Net: a joint attention and adversarial learning network for skin lesion segmentation.

Objective.Skin lesion segmentation plays an important role in the diagnosis and treatment of melanoma. Existing skin lesion segmentation methods have trouble distinguishing hairs, air bubbles, and blood vessels around lesions, which affects the segmentation performance.Approach.To clarify the lesion boundary and raise the accuracy of skin lesion segmentation, a joint attention and adversarial learning network (JAAL-Net) is proposed that consists of a generator and a discriminator. In the JAAL-Net, the generator is a local fusion network (LF-Net) utilizing the encoder-decoder structure. The encoder contains a convolutional block attention module to increase the weight of lesion information. The decoder involves a contour attention to obtain edge information and locate the lesion. To aid the LF-Net generate higher confidence predictions, a discriminant dual attention network is constructed with channel attention and position attention.Main results.The JAAL-Net is evaluated on three datasets ISBI2016, ISBI2017 and ISIC2018. The intersection over union of the JAAL-Net on the three datasets are 90.27%, 89.56% and 80.76%, respectively. Experimental results show that the JAAL-Net obtains rich lesion and boundary information, enhances the confidence of the predictions, and improves the accuracy of skin lesion segmentation.Significance.The proposed approach effectively improves the performance of the model for skin lesion segmentation, which can assist physicians in accurate diagnosis well.

Perceptions of cruise travel during the COVID-19 pandemic: Market recovery strategies for cruise businesses in North America.

The study aims to identify consumer perceptions of the cruise industry amid the COVID-19 pandemic and seeks to provide market recovery strategies for cruise businesses. The relationship between perceptions among cruise experience and COVID-19 financial status groups were explored. The results of analyses of data from 759 respondents indicated that travel constraints negatively influence behavioral intention through negativity bias. Further, perceived crisis management positively affects behavioral intention through attitude-trust. New consumers' behavioral intention is significantly affected by the negativity bias, and the perceived crisis management manipulates the trust of financial-affected consumers.

Developing a Functional Poly(dimethylsiloxane)-Based Microbial Nanoculture System Using Dimethylallylamine.

Here, a novel poly(dimethylsiloxane) (PDMS)-based microbial culture system was investigated. Bacteria were encapsulated in functional and semipermeable membranes, mimicking the cell microenvironment and facilitating mass transport for interrogating microbial dynamics, thereby overcoming one of the major challenges associated with commercially available PDMS such as Sylgard 184. The hydrophobic nature and lack of control in the polymer network in Sylgard 184 significantly impede the the tunability of the transport and mechanical properties of the material as well as its usage as an isolation chamber for culturing and delivering microbes. Therefore, a novel PDMS composition was developed and functionalized with dimethylallylamine (DMAA) to alter its hydrophobicity and modify the polymer network. Characterization techniques including NMR spectroscopy, contact angle measurements, and sol-gel process were utilized to evaluate the physical and chemical properties of the newly fabricated membranes. Furthermore, the DMAA-containing polymer mixture was used as a proof of concept to generate hydrodynamically stable microcapsules and cultivate Escherichia coli cells in the functionalized capsules. The membrane exhibited a selective permeability to tetracycline, which diffused into the capsules to inhibit the growth of the encapsulated microbes. The functionality achieved here with the addition of DMAA, coupled with the high-throughput encapsulation technique, could prove to be an effective testing and diagnostic tool to evaluate microbial resistance, growth dynamics, and interspecies interaction and lays the foundation for in vivo models.

Electric Double-Layer Gating of Two-Dimensional Field-Effect Transistors Using a Single-Ion Conductor.

Electric double-layer (EDL) gating using a custom-synthesized polyester single-ion conductor (PE400-Li) is demonstrated on two-dimensional (2D) crystals for the first time. The electronic properties of graphene and MoTe2 field-effect transistors (FETs) gated with the single-ion conductor are directly compared to a poly(ethylene oxide) dual-ion conductor (PEO:CsClO4). The anions in the single-ion conductor are covalently bound to the backbone of the polymer, leaving only the cations free to form an EDL at the negative electrode and a corresponding cationic depletion layer at the positive electrode. Because the cations are mobile in both the single- and dual-ion conductors, a similar enhancement of the n-branch is observed in both graphene and MoTe2. Specifically, the single-ion conductor decreases the subthreshold swing in the n-branch of the bare MoTe2 FET from 5000 to 250 mV/dec and increases the current density and on/off ratio by two orders of magnitude. However, the single-ion conductor suppressed the p-branch in both the graphene and the MoTe2 FETs, and finite element modeling of ion transport shows that this result is unique to single-ion conductor gating in combination with an asymmetric gate/channel geometry. Both the experiments and modeling suggest that single-ion conductor-gated FETs can achieve sheet densities up to 1014 cm-2, which corresponds to a charge density that would theoretically be sufficient to induce several percent strain in monolayer 2D crystals and potentially induce a semiconductor-to-metal phase transition in MoTe2.

Carbon dioxide-in-oil emulsions stabilized with silicone-alkyl surfactants for waterless hydraulic fracturing.

The design of surfactants for CO2/oil emulsions has been elusive given the low CO2-oil interfacial tension, and consequently, low driving force for surfactant adsorption. Our hypothesis is that waterless, high pressure CO2/oil emulsions can be stabilized by hydrophobic comb polymer surfactants that adsorb at the interface and sterically stabilize the CO2 droplets. The emulsions were formed by mixing with an impeller or by co-injecting CO2 and oil through a beadpack (CO2 volume fractions (ϕ) of 0.50-0.90). Emulsions were generated with comb polymer surfactants with a polydimethylsiloxane (PDMS) backbone and pendant linear alkyl chains. The C30 alkyl chains are CO2-insoluble but oil soluble (oleophilic), whereas PDMS with more than 50 repeat units is CO2-philic but only partially oleophilic. The adsorbed surfactants sterically stabilized CO2 droplets against Ostwald ripening and coalescence. The optimum surfactant adsorption was obtained with a PDMS degree of polymerization of ∼88 and seven C30 side chains. The emulsion apparent viscosity reached 18 cP at a ϕ of 0.70, several orders of magnitude higher than the viscosity of pure CO2, with CO2 droplets in the 10-150 µm range. These environmentally benign waterless emulsions are of interest for hydraulic fracturing, especially in water-sensitive formations.

Prevention of seroma formation with TissuGlu® surgical adhesive in a canine abdominoplasty model: long term clinical and histologic studies.

BACKGROUND: Seroma formation is a common postoperative complication following many surgical procedures including abdominoplasty. Recently, a lysine-derived urethane (LDU) surgical adhesive was shown to prevent seroma formation in short term studies in a canine model of abdominoplasty. This current study evaluates efficacy of the adhesive (TissuGlu®, Cohera Medical, Inc.) in the same model at longer time points, and examines the histological tissue response to extended exposure to the adhesive. MATERIALS AND METHODS: Bilateral subcutaneous pockets were created in the ventrolateral abdominal wall and additional tissue damage was inflicted using electrocautery. On one side, the tissue layers were treated with the adhesive prior to closure, whereas the control side received no treatment prior to standard closure of the incision. Seroma fluid accumulation was measured and histologic analysis was performed at 3 and 12 weeks. RESULTS: Seroma formation (mean±SD, 690±870 ml; median volume of 348.5 ml) was observed on the control side, whereas the treated side had adherence between the tissue layers, and minimal if any fluid accumulation (mean±SD, 44±53 ml; median volume of 15 ml) (p<0.01) (n=8) at 3 week necropsy. In animals survived to 12 weeks, two of the four control sides required aspiration of serous fluid, and dead space persisted for the entirety of the study in one animal. For the adhesive treated sites, none of the four animals showed signs of seroma at euthanasia, although serial aspiration was performed in one treatment site within the first month and resulted in resolution of the process. The adhesive was detected in the surgical site at 3 and 12 weeks, and independent histological analysis found it to be a non-irritant compared to control (no treatment). CONCLUSIONS: Long term evaluation of TissuGlu® Surgical Adhesive showed that it is capable of preventing the formation of seroma in this canine abdominoplasty model, indicating that it may be of clinical benefit in the prevention of seroma formation in patients undergoing abdominoplasty.

Degradative-release as a function of drug structure from LDI-glycerol polyurethanes.

Naphthalene analogs with differing hydroxyl and amine functionality were incorporated into degradable polyurethane foams synthesized from lysine diisocyanate and glycerol to determine if chemical structure can be used in controlled release systems. Excitation and emission spectra of the various naphthalene analogs in aqueous solution were collected to ensure they were capable of being quantitatively detected in aqueous solution at low concentrations. The fluorescence stability of the compounds was assessed over a 2-week period at 70°C; the analogs were all found to exhibit signal decay to varying degrees. Polyurethane foam materials containing the naphthalene analogs were synthesized and examined via scanning electron microscopy; incorporating naphthalene ligands did not grossly alter the polyurethane morphology. The analog distribution was then assessed via fluorescence microscopy, and the naphthalene analogs were found evenly dispersed throughout the polyurethane materials. Foam samples containing various analogs were then incubated in PBS buffer solution (pH 7.4) at 4, 22, 37 and 70°C for 11-weeks. Temperature dependent release of naphthalene analogs from the polyurethane foams was found to depend upon the functional groups present on the naphthalene analog. These results suggest that the chemical structure of a drug plays a unique role in controlling release from hydrolytically degradable drug delivery systems.

Sustainability metrics: life cycle assessment and green design in polymers.

This study evaluates the efficacy of green design principles such as the "12 Principles of Green Chemistry," and the "12 Principles of Green Engineering" with respect to environmental impacts found using life cycle assessment (LCA) methodology. A case study of 12 polymers is presented, seven derived from petroleum, four derived from biological sources, and one derived from both. The environmental impacts of each polymer's production are assessed using LCA methodology standardized by the International Organization for Standardization (ISO). Each polymer is also assessed for its adherence to green design principles using metrics generated specifically for this paper. Metrics include atom economy, mass from renewable sources, biodegradability, percent recycled, distance of furthest feedstock, price, life cycle health hazards and life cycle energy use. A decision matrix is used to generate single value metrics for each polymer evaluating either adherence to green design principles or life-cycle environmental impacts. Results from this study show a qualified positive correlation between adherence to green design principles and a reduction of the environmental impacts of production. The qualification results from a disparity between biopolymers and petroleum polymers. While biopolymers rank highly in terms of green design, they exhibit relatively large environmental impacts from production. Biopolymers rank 1, 2, 3, and 4 based on green design metrics; however they rank in the middle of the LCA rankings. Polyolefins rank 1, 2, and 3 in the LCA rankings, whereas complex polymers, such as PET, PVC, and PC place at the bottom of both ranking systems.

Adhesive use in oral and maxillofacial surgery.

Presently, tissue adhesives and sealants have limited use in oral and maxillofacial surgical procedures. Skin closure occurs regularly with cyanoacrylate adhesives. Sealing of dural tears in conjunction with dural closure has been shown to be very successful. With the development of more head and neck reconstructive procedures and cosmetic procedures, demand will increase for better surgical adhesives. Clinical trials are beginning for newly developed adhesives with the chemical characterizations, the safe reabsorptive profile, and the adhesive strength necessary to benefit oral and maxillofacial surgery patients in the near future. Adhesives for bone fixation, while in early development, also show a promising chemical profile and will be of significant benefit to oral and maxillofacial surgical patients.

Incorporation of ionic ligands accelerates drug release from LDI-glycerol polyurethanes.

This study seeks to determine the effect of ionic ligands on the drug delivery characteristics of biodegradable polyurethane materials synthesized from lysine diisocyanate (LDI) and glycerol. Two naturally occurring, structurally related ionic species, choline chloride (CC) and isethionic acid (ISE), along with 3,3-dimethyl-butanol (DMB), their neutral carbon analog, were covalently incorporated into LDI-glycerol polyurethane materials. Selected organometallic and tertiary amine catalysts were used to fashion films and foams, respectively. The potent anticancer compound DB-67, a fluorescent camptothecin derivative, was also covalently linked to the polyurethane constructs. It was first determined that the sulfonate functional group on ISE does not react to a significant degree with isocyanate. The morphological characteristics of the polyurethane films and foams were assessed via scanning electron microscopy, showing significant differences related to the ionic ligands. The ionic materials displayed increased swelling in aqueous media over the neutral control materials. Differences in the distribution of DB-67 throughout the films and foams were then detected by fluorescence microscopy. The drug delivery characteristics of the materials were then evaluated in vitro, revealing accelerated release from ionic materials. The results of this study demonstrate the unique effects that incorporation of ionic ligands into LDI-glycerol polyurethanes have on the morphology and drug distribution of the materials. These differences have a significant impact on the drug delivery characteristics of the materials, and this information should prove useful in the design and synthesis of biodegradable controlled release systems.

Design and evaluation of nonfluorous CO2-soluble oligomers and polymers.

Ab initio molecular modeling is used to design nonfluorous polymers that are potentially soluble in liquid CO2. We have used calculations to design three nonfluorous compounds meant to model the monomeric repeat units of polymers that exhibit multiple favorable binding sites for CO2. These compounds are methoxy isopropyl acetate, 2-methoxy ethoxy-propane, and 2-methoxy methoxy-propane. We have synthesized oligomers or polymers based on these small compounds and have tested their solubility in CO2. All three of these exhibit appreciable solubility in CO2. At 25 degrees C, oligo(3-acetoxy oxetane)6 is 5 wt % soluble at 25 MPa, the random copolymer (vinyl methoxymethyl ether30-co-vinyl acetate9) is 5 wt % soluble at 70 MPa and random copolymer (vinyl 1-methoxyethyl ether30-co-vinyl acetate9) is 3 wt % soluble at 120 MPa. These oligomers and polymers represent new additions to the very short list of nonfluorous CO2-soluble polymers. However, none of these are more soluble than poly(vinyl acetate), which exhibits the highest CO2 solubility of any known polymer containing only the elements C, H, and O.

Simultaneous drug release at different rates from biodegradable polyurethane foams.

In this study, we present an approach for the simultaneous release of multiple drug compounds at different rates from single-phase polyurethane foams constructed from lysine diisocyanate (LDI) and glycerol. The anti-cancer compounds DB-67 and doxorubicin were covalently incorporated into polyurethane foams, whereby drug release can then occur in concert with material degradation. To begin, the reactions of DB-67 and doxorubicin with LDI in the presence of a tertiary amine catalyst were monitored with infrared spectroscopy; each compound formed urethane linkages with LDI. Fluorescent spectra of DB-67 and doxorubicin were then recorded in phosphate-buffered saline, pH 7.4 (PBS), to ensure that each anti-cancer compound could be quantitatively detected alone and in combination. Doxorubicin and DB-67 were then incorporated into a series of degradable LDI-glycerol polyurethane foams alone and in combination with one another. The sol content, average porosity and drug distribution throughout each foam sample was measured and found to be similar amongst all foam samples. The stability of DB-67 and doxorubicin's fluorescent signal was then assessed over a 2-week period at 70 degrees C. Release rates of the compounds from the foams were assessed over a 10-week period at 4, 22, 37 and 70 degrees C by way of fluorescence spectroscopy. Release was found to be temperature-dependent, with rates related to the chemical structure of the incorporated drug. This study demonstrates that differential release of covalently bound drugs is possible from simple single-phase, degradable polyurethane foams.

An extracellular matrix scaffold for esophageal stricture prevention after circumferential EMR.

BACKGROUND: EMR is an accepted treatment for early esophageal cancer and high-grade dysplasia. One of the limitations of this technique is that extensive mucosal resection and endoscopic submucosal dissection may be required to obtain complete removal of the neoplasm, which may result in significant stricture formation. OBJECTIVE: The objective of the current study was to evaluate the efficacy of an endoscopically deployed extracellular matrix (ECM) scaffold material for prevention of esophageal stenosis after circumferential EMR. DESIGN: Ten mongrel dogs were subjected to surgical plane anesthesia and circumferential esophageal EMR by the cap technique. In 5 animals, an ECM scaffold material was endoscopically placed at the resection site; the remaining 5 animals were subjected to circumferential esophageal EMR without ECM placement. Follow-up endoscopy was performed at 4 and 8 weeks; necropsy with histologic assessment was performed at 8 weeks. SETTING: Animal laboratory. INTERVENTIONS: Circumferential esophageal EMR by the cap technique, followed by endoscopic placement of an ECM scaffold material. MAIN OUTCOME MEASUREMENTS: Degree of esophageal stricture and histologic assessment of remodeled esophageal tissue. RESULTS: All 5 control dogs had endoscopic evidence of esophageal stenosis. Three required early euthanasia because of inability to tolerate oral intake. Incomplete epithelialization and inflammation persisted at the EMR site in control animals. Endoscopic placement of an ECM scaffold material prevented clinically significant esophageal stenosis in all animals. Histologic assessment showed near-normal esophageal tissue with a lack of inflammation or scar tissue at 8 weeks. CONCLUSIONS: Endoscopic placement of an ECM scaffold material prevented esophageal stricture formation after circumferential EMR in this canine model during short-term observation.

Lysine-derived urethane surgical adhesive prevents seroma formation in a canine abdominoplasty model.

BACKGROUND: Seroma formation is a common postoperative complication following many surgical procedures, including abdominoplasty. Several approaches have been investigated to prevent seroma formation by draining fluid or attempting to eliminate dead space, but these approaches have limited effectiveness. METHODS: A canine model of abdominoplasty was developed that reliably produced seroma formation. Bilateral subcutaneous pockets were created in the ventrolateral abdominal wall and additional tissue damage was inflicted using electrocautery. On one side, the tissue layers were treated with a lysine-derived urethane adhesive before closure, whereas the control side received no treatment before standard closure of the incision. RESULTS: Seroma formation (60 +/- 45 ml) was observed on the control side, whereas the treated side had adherence between the tissue layers and minimal if any fluid accumulation (1.7 +/- 1.4 ml) (p < 0.01) (n = 7). The adhesive invoked little or no cellular response, based on histologic examination of the tissue. CONCLUSION: The urethane surgical adhesive was effective in preventing the formation of seroma in this canine abdominoplasty model.

LDI-glycerol polyurethane implants exhibit controlled release of DB-67 and anti-tumor activity in vitro against malignant gliomas.

The purpose of the present study was to develop a biodegradable and biocompatible polyurethane drug delivery system based on lysine diisocyanate (LDI) and glycerol for the controlled release of 7-tert-butyldimethylsilyl-10-hydroxy-camptothecin (DB-67). DB-67 has yet to be implemented in any clinical therapies due to the inability to delivered it in sufficient quantities to impact tumor growth and disease progression. To remedy this, DB-67 was covalently incorporated into our delivery system by way of an organometallic urethane catalyst and was found to be dispersed evenly throughout the LDI-glycerol polyurethane discs. Scanning electron micrographs indicate that the LDI-glycerol discs are uniform and possess a pore distribution typical of the non-solvent casting technique used to prepare them. The release rates of DB-67 from the LDI-glycerol discs were found to vary with both time and temperature and were shown capable of delivering therapeutic concentrations of DB-67 in vitro. Cellular proliferation assays demonstrate that empty LDI-glycerol discs alone do not significantly alter the growth of malignant human glioma cell lines (U87, T98G, LN229 and SG388). DB-67-loaded LDI-glycerol polyurethane discs were found to inhibit cellular proliferation by 50% on average in all the malignant glioma cell lines tested. These results clearly demonstrate the long-term, slow release of DB-67 from LDI-glycerol polyurethane discs and their potential for postoperative intracranial chemotherapy of cancers.

Catalyst-dependent drug loading of LDI-glycerol polyurethane foams leads to differing controlled release profiles.

The purpose of the present study was to develop biodegradable and biocompatible polyurethane foams based on lysine diisocyanate (LDI) and glycerol to be used as drug-delivery systems for the controlled release of 7-tert-butyldimethylsilyl-10-hydroxy-camptothecin (DB-67). The impact of urethane catalysts on cellular proliferation was assessed in an attempt to enhance the biocompatibility of our polyurethane materials. DB-67, a potent camptothecin analog, was then incorporated into LDI-glycerol polyurethane foams with two different amine urethane catalysts: 1,4-diazobicyclo[2.2.2]-octane (DABCO) and 4,4'-(oxydi-2,1-ethane-diyl)bismorpholine (DMDEE). The material morphologies of the polyurethane foams were analyzed via scanning electron microscopy, and DB-67 distribution was assessed by way of fluorescence microscopy. Both foam morphology and drug distribution were found to correlate to the amine catalyst used. Hydrolytic release rates of DB-67 from the polyurethane foams were catalyst dependent and also demonstrated greater drug loads being released at higher temperatures. The foams were capable of delivering therapeutic concentrations of DB-67 in vitro over an 11week test period. Cellular proliferation assays demonstrate that empty LDI-glycerol foams did not significantly alter the growth of malignant human glioma cell lines (P<0.05). DB-67 loaded LDI-glycerol polyurethane foams were found to inhibit cellular proliferation by at least 75% in all the malignant glioma cell lines tested (P<1.0x10(-8)). These results clearly demonstrate the long-term, catalyst-dependent release of DB-67 from LDI-glycerol polyurethane foams, indicating their potential for use in implantable drug-delivery devices.

The effect of multifunctional polymer-based gels on wound healing in full thickness bacteria-contaminated mouse skin wound models.

We determined whether a two-part space-conforming polyethylene glycol/dopa polymer-based gel promoted healing of contaminated wounds in mice. This silver-catalysed gel was previously developed to be broadly microbiocidal in vitro while being biocompatible with human wound cell functioning. Full-thickness wounds were created on the backs of mice. The wounds were inoculated with 10(4) CFU of each of four common skin wound contaminants, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumanii and Clostridium perfringens. The wounds were then treated with our multifunctional polymer-based gel, the commercially available NewSkin product, or left to heal untreated. The untreated wounds were overtly infected, and presented detectable bacterial loads over the entire 21-day healing period, while the gel and NewSkin groups presented significantly smaller rises in bacterial levels and were cleared of detectable colonies by the third week, with the gel group clearing the bacteria earlier. While all three groups healed their wounds, the polymer-based gel-treated group demonstrated significantly earlier re-epithelialization and dermal maturation (P<0.05). This was reflected in a quick regain of tensile strength. This accelerated dermal maturation and regain in strength was noted in mice treated with the polymer-based gel when compared to wound treated with the commercially available Aquacel-Ag dressing (P<0.05). What distinguishes the polymer-based gel from these other products is that it is incorporated within the healing wound. These preclinical studies show that the anti-microbial polymer gel not only supports but also accelerates healing of bacterially contaminated wounds.

Antimicrobial activities of silver used as a polymerization catalyst for a wound-healing matrix.

Wound healing is a complex and orchestrated process that re-establishes the barrier and other functions of the skin. While wound healing proceeds apace in healthy individual, bacterial overgrowth and infection disrupts this process with significant morbidity and mortality. As such, any artificial matrix to promote wound healing must also control infecting microbes. We had earlier developed a two-part space-conforming gel backbone based on polyethyleneglycol (PEG) or lactose, which used ionic silver as the catalyst for gelation. As silver is widely used as an in vitro antimicrobial, use of silver as a catalyst for gelation provided the opportunity to assess its function as an anti-microbial agent in the gels. We found that these gels show bacteriostatic and bactericidal activity for a range of Gram-negative and Gram-positive organisms, including aerobic as well as anaerobic bacteria. This activity lasted for days, as silver leached out of the formed gels over a day in the manner of second-order decay. Importantly the gels did not limit either cell growth or viability, though cell migration was affected. Adding collagen I fragments to the gels corrected this effect on cell migration. We also found that the PEG gel did not interfere with hemostasis. These observations provide the basis for use of the gel backbones for incorporation of anesthetic agents and factors that promote wound repair. In conclusion, silver ions can serve dual functions of catalyzing gelation and providing anti-microbial properties to a biocompatible polymer.