Enhanced Surface Icephobicity on an Elastic Substrate.

Ice accumulation on exposed surfaces is unavoidable as time elapses and the temperature decreases sufficiently. To mitigate icing problems, various types of icephobic substrates have been rationally designed, including superhydrophobic substrates (SHSs), aqueous lubricating layers, organic lubricating layers, organogels, polyelectrolyte brush layers, electrolyte-based hydrogels, elastic substrates, and multicrack initiator-promoted surfaces. Among these surfaces, elastic substrates show excellent enhanced surface icephobicity during dynamic processes (i.e., water-impacting and de-icing tests). Herein, we summarize recent progress in elastic icephobic substrates and discuss the reasons that surface icephobicity can be enhanced on elastic substrates in terms of enhanced water repellency and further lowering the ice adhesion strength. For enhanced water repellency, we focus on reducing the contact time of water impacting such that water droplets can be easily shed from an elastic substrate before ice occurs. Reducing the contact time of water impacting various substrates (i.e., micro/nanostructured rigid SHSs, macrotextured rigid SHSs, and elastic SHSs) is discussed, followed by exploring their mechanisms. We argue that the ice adhesion strength can be further lowered on an elastic substrate by rationally tuning the elastic modulus and surface textures (i.e., surface textured and hollow subsurface textured) and combining elastic substrate with other passive anti-icing strategies (or functioning passive icephobic substrates with an electrothermal or photothermal stimulus). In short, the introduction of an elastic substrate into a passive or active icephobicity surface opens an avenue toward designing a versatile icephobic surface, providing great potential for outdoor anti-icing applications.

Durable Hydrate-phobic Coating with In Situ Self-Replenishing Hydrocarbon Barrier Films for Low Clathrate Hydrate Adhesion.

Clathrate hydrate growth, deposition, and plug formation during oil and gas transportation causes blockage of pipelines. An effective strategy to solve this problem is to mitigate the hydrate formation and reduce its adhesion on pipe walls through a coating process. However, durability failure, corrosion, inability to self-heal, high cost, and strong hydrate adhesion remain unsolved issues. To address these challenges, in this work, we present an in situ self-replenishing nonfluorinated durable hydrate-phobic coating of candle soot particles. The candle soot coating reduces hydrate adhesion by promoting a thick barrier film of hydrocarbons between the hydrate and the soot coated substrate. The hydrocarbons permeating the soot coating display a high contact angle for water and inhibit the formation of water bridges between the hydrate and soot coated substrate. The spherical cyclopentane hydrate slides off easily on the candle soot coating inside the cyclopentane environment. The hydrate former, cyclopentane-water emulsion, and THF-water mixture have high contact angles as well as low hydrate adhesion on soot coating simultaneously. In addition, the coating is flow-induced long-term slippery, durable, low cost, anticorrosion, self-cleaning, and suitable for practical applications.

Comparative Analysis of Ethylene/Diene Copolymerization and Ethylene/Propylene/Diene Terpolymerization Using Ansa-Zirconocene Catalyst with Alkylaluminum/Borate Activator: The Effect of Conjugated and Nonconjugated Dienes on Catalytic Behavior and Polymer Microstructure.

The copolymerization of ethylene‒diene conjugates (butadiene (BD), isoprene (IP) and nonconjugates (5-ethylidene-2-norbornene (ENB), vinyl norbornene VNB, 4-vinylcyclohexene (VCH) and 1, 4-hexadiene (HD)), and terpolymerization of ethylene-propylene-diene conjugates (BD, IP) and nonconjugates (ENB, VNB, VCH and HD) using two traditional catalysts of C2-symmetric metallocene-silylene-bridged rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (complex A) and ethylene-bridged rac-Et(Ind)2ZrCl2 (complex B)-with a [Ph3C][B(C6F5)4] borate/TIBA co-catalyst, were intensively studied. Compared to that in the copolymerization of ethylene diene, the catalytic activity was more significant in E/P/diene terpolymerization. We obtained a maximum yield of both metallocene catalysts with conjugated diene between 3.00 × 106 g/molMt·h and 5.00 × 106 g/molMt·h. ENB had the highest deactivation impact on complex A, and HD had the most substantial deactivation effect on complex B. A 1H NMR study suggests that dienes were incorporated into the co/ter polymers' backbone through regioselectivity. ENB and VNB, inserted by the edo double bond, left the ethylidene double bond intact, so VCH had an exo double bond. Complex A's methyl and phenyl groups rendered it structurally stable and exhibited a dihedral angle greater than that of complex B, resulting in 1, 2 isoprene insertion higher than 1, 4 isoprene that is usually incapable of polymerization coordination. High efficiency in terms of co- and ter- monomer incorporation with higher molecular weight was found for complex 1. The rate of incorporation of ethylene and propylene in the terpolymer backbone structure may also be altered by the conjugated and nonconjugated dienes. 13C-NMR, 1H-NMR, and GPC techniques were used to characterize the polymers obtained.

Biomass-Derived, Water-Induced Self-Recoverable Composite Aerogels with Robust Superwettability for Water Treatment.

Polluted water is a worldwide problem; therefore, effective separation of oil/water and removal of dyes, organic micropollutants, and heavy metals in wastewater are the need of the hour. Herein, hydrophilic ß-cyclodextrin-grafted carboxymethyl cellulose, biodegradable polyvinyl alcohol, and chitosan were used as main raw materials to construct a multifunctional aerogel framework by simple sol-gel and directional freeze-drying methods. Featuring intrinsic superamphiphilic wettability in air, robust superoleophobic wettability underwater, and excellent shape-recovery characteristics, the biomass-derived aerogel presents durable oil/water separation even after 10 cycles. The aerogels possess prominent adsorption capacity for methyl blue, 1-naphthylamine, and Cu2+, which was as high as 121.55 mg/g, 33.96 mg/g, and 122.6 mg/g, respectively. In addition, various pollutant mixtures could be effectively adsorbed by the aerogel at the same time with the adsorption capacity of 121.75 mg/g for methyl blue, 0.97 mg/g for bisphenol A, and 20.11 mg/g for Cu2+.

Icephobic Strategies and Materials with Superwettability: Design Principles and Mechanism.

Ice formation and accretion on surfaces is a serious economic issue in energy supply and transportation. Recent strategies for developing icephobic surfaces are intimately associated with superwettability. Commonly, the superwettability of icephobic materials depends on their surface roughness and chemical composition. This article critically categorizes the possible strategies to mitigate icing problems from daily life. The wettability and classical nucleation theories are used to characterize the icephobic surfaces. Thermodynamically, the advantages/disadvantages of superhydrophobic surfaces are discussed to explain icephobic behavior. The importance of elasticity, slippery liquid-infused porous surfaces (SLIPSs), amphiphilicity, antifreezing protein, organogels, and stimuli-responsive materials has been highlighted to induce icephobic performance. In addition, the design principles and mechanism to fabricate icephobic surfaces with superwettability are explored and summarized.

Justification For Re-Look Cystoscopy After Posterior Urethral Valve Fulguration.

BACKGROUND: Posterior urethral valve (PUV) is life-threatening congenital anomaly of the urinary tract that results in vesicoureteric reflux, recurrent UTI, voiding dysfunction and renal insufficiency if not treat timely. Endoscopic ablation of posterior urethral valves using cold knife or laser is the current gold standard therapy. Many urologists go for repeat cystoscopy to see residual valve or stricture while others repeat VCUG to measure the posterior to anterior urethral ratio for residual obstruction. In this study, we have standardized by regularly doing re-look cystoscopy at 3 months whether the child is symptomatic or not to see justification for re-look cystoscopy after PUV ablation. METHODS: In this prospective study, first 50 cases that underwent posterior urethral valve fulguration were included. Diagnosis of posterior urethral valve was made by voiding symptoms, ultrasonography and confirmed by voiding cysto-urethrogram (VCUG). All children were treated by endoscopic fulguration of posterior urethral valves (PUV) using cold knife as urethral valvotome and were followed clinically for voiding symptoms and with ultrasonography and laboratory test at 3 and 6 months. All patients underwent re-look cystoscopy at three months to see residual valves irrespective of their clinical improvement. RESULTS: Mean age at presentation was 4.9±3.2 years. The most common symptoms were poor stream (76%), straining at voiding (72%), dribbling of urine (54%), fever (42%) and urinary retention (14%). Residual valves on re-look cystoscopy were seen in 78%. Four (8%) patients had urethral stricture on re-look cystoscopy. CONCLUSIONS: We suggest routine re-look cystoscopy after primary fulguration of PUV to pick more residual obstructive valves.

EFFICACY OF ENDOSCOPIC TREATMENT FOR PRIMARY VESICOURETERIC REFLUX IN CHILDREN.

BACKGROUND: Vesicoureteral reflux (VUR) is a common anomaly affecting 1-3% of all children and 30-50% of those with urinary tract infection (UTI). In the past febrile vesicoureteric reflux on chronic antibiotic prophylaxis were treated by open surgery. Now a day's endoscopic injection of a bulking material has replaced open surgical procedure in cases of primary VUR. Our objective was to assess the efficacy of endoscopic treatment for primary vesico-ureteric reflux in children. METHODS: This was a descriptive case series. One hundred and five patients with either unilateral or bilateral VUR (181 ureters) underwent endoscopic treatment for primary VUR between January 2011 and January 2014. Children from 1 to 12 years of age with grade-II to IV reflux on preoperative voiding cystourethrogram (VCUG) were enrolled through consecutive non-probability sampling. Efficacy of treatment was evaluated at three months post injection by a standard VCUG. Ureters with no or grade-I reflux were considered successful treatment. RESULTS: Out of 105 patients 76 had bilateral while 29 had unilateral reflux. Mean age was 5.7 years (SD ± .7). Among 181 refluxing ureters, 116 (64%) were free of reflux, while 49 (27%) showed down gradation and 16 (8.8%) showed no response to treatment on postoperative VCUG. CONCLUSION: Endoscopic treatment for VUR is a viable option for patients with primary VUR and may be considered in management of such cases.

Neuroblastoma in horseshoe kidney.

Neuroblastoma is one of the commonest malignancy of childhood. Neuroblatoma in horseshoe kidney is an extremely rare condition. There is only one case of this tumour occurring in horseshoe kidney described in the literature. Recently we successfully treated a boy with neuroblastoma in horseshoe kidney.

Female epispadias: spot diagnosis and simple reconstruction.

Isolated female epispadias without bladder exstrophy is a rare congenital anomaly. Patients present with total or partial urinary incontinence. The diagnosis can only be made on careful genitalia examination by separating the labia majora. That is why it is often missed by most physicians even after being extensively investigated. The physical findings include patulous urethra, flattened mons pubis, and bifid clitoris with lack of anterior labial commissure. In most of the cases, single stage reconstruction of urethra, labia minora and clitoris is enough to achieve urinary continence with cosmetically acceptable genitalia.

Designing small organic non-fullerene acceptor molecules with diflorobenzene or quinoline core and dithiophene donor moiety through density functional theory.

The non-fullerene acceptors A1-A5 with diflourobenzene or quinoline core (bridge) unit, donor cyclopenta[1,2-b:3,4-b']dithiophene unit and 2-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile as acceptor unit with additional phenyl, fulvene or thieno[3,2-d]pyrimidinyl 5-oxide groups have been designed through DFT calculations. The optimization of molecular geometries were performed with density functional theory (DFT) at B3LYP 6-31G (d,p) level of theory. The frontier molecular orbital (FMO) energies, band gap energies and dipole moments (ground and excited state) have been calculated to probe the photovoltaic properties. The band gap (1.42-2.01 eV) and dipole moment values (5.5-18. Debye) showed that these designed acceptors are good candidates for organic solar cells. Time-Dependent Density Functional Theory (TD-DFT) results showed λmax (wave length at maximum absorption) value (611-837 nm), oscillator strength (f) and excitation energies (1.50-2.02 eV) in gas phase and in CHCl3 solvent (1.48-1.89 eV) using integral equation formalism variant (IEFPCM) model. The λmax in CHCl3 showed marginal red shift for all designed acceptors compared with gas phase absorption. The partial density of states (PDOS) has been plotted by using multiwfn which showed that all the designed molecules have more electronic distribution at the donor moiety and lowest at the central bridge. The reorganization energies of electron (λe) (0.0007 eV to 0.017 eV), and the hole reorganization energy values (0.0003 eV to - 0.0403 eV) were smaller which suggested that higher charged motilities. The blends of acceptors A1-A5 with donor polymer D1 provided open circuit voltage (Voc) and ∆HOMO off-set of the HOMO of donor and acceptors. These blends showed 1.04 to 1.5 eV values of Voc and 0 to 0.38 eV ∆HOMO off set values of the donor-acceptor bends which indicate improved performance of the cell. Finally, the blend of D1-A4 was used for the study of distribution of HOMO and LUMO. The HOMO were found distributed on the donor polymer (D1) while the A4 acceptor was found with LUMO distribution. Based on λmax values, and band gap energies (Eg), excitation energies (Ex), reorganization energies; the A3 and A4 will prove good acceptor molecules for the development of organic solar cells.

Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure.

The kinetics of ethylene and propylene polymerization catalyzed by homogeneous metallocene were investigated using 2-thiophenecarbonyl chloride followed by quenched-flow methods. The studied metallocene catalysts are: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I), rac-Et(Ind)2ZrCl2 (Mt-II) activated with ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II), and were co-catalyzed with different molar ratios of alkylaluminum such as triethylaluminium (TEA) and triisobutylaluminium (TIBA). The change in molecular weight, molecular weight distribution, microstructure and thermal properties of the synthesized polymer are discussed in detail. Interestingly, both Mt-I and Mt-II showed high activity in polyethylene with productivities between 3.17 × 106 g/molMt·h to 5.06 × 106 g/molMt·h, activities were very close to each other with 100% TIBA, but Mt-II/borate-II became more active when TEA was more than 50% in cocatalyst. Similarly, Polypropylene showed the highest activity of 11.07 106 g /molMt·h with Mt-I/Borate-I/TIBA. The effects of alkylaluminum on PE molecular weight were much more complicated; MWD curve changed from mono-modal in Mt-I/borate-I/TIBA to bimodal type when TIBA was replaced by different amounts of TEA. In PE, the active center fractions [C*]/[Zr] of Mt-I/borate were higher than that of Mt-II/borate and average chain propagation rate constant (k p) value slightly decreased with the increase of TEA/TIBA ratio, but the Mt-II/borate systems showed higher k p 1007 k p (L/mol·s). In PP, the Mt-I/borate presented much higher [C*]/[Zr] and k p value than the Mt-II. This work also extend to investigate the mechanistic features of zirconocenes catalyzed olefin polymerizations that addressed the largely unknown issues in zirconocenes in the distribution of the catalyst, between species involved in polymer chain growth and dormant state. In both metallocene systems, chain transfer with alkylaluminum is the dominant way of chain termination. To understand the mechanism of cocatalyst effects on PE Mw and (MWD), the unsaturated chain ends formed via ß-H transfer have been investigated by 1H NMR analysis.

Facile approach to design a stable, damage resistant, slippery, and omniphobic surface.

Creating a robust omniphobic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture. The present omniphobic surfaces still have the problems of complex fabrication methods, high cost, and being environmentally harmful. To address these challenges, here we report a novel process to design a non-fluorinated, long-term slippery omniphobic surface of candle soot nanoparticles with a silicone binder that cures at room temperature. The porosity, nanoscale roughness, strong affinity of the substrate with the silicone lubricant, and retention of lubricant after curing of the binder play an important role in its stability and low ice adhesion strength at sub-zero temperature. The developed surface exhibits damage resistant slippery properties, repellency to several liquids with different surface tensions including blood, delay in freezing point along with ultra-low ice adhesion strength (2 kPa) and maintains it even below 7 kPa under harsh environmental conditions; 90 frosting/defrosting cycles at -90 °C; 2 months under an ice layer; 2 months at 60 °C; 9 days flow in acidic/basic water and exposure to super-cold water. In addition, this novel technique is cheap, easy to fabricate, environmentally benign and suitable for large-scale applications.

Durable and Scalable Candle Soot Icephobic Coating with Nucleation and Fracture Mechanism.

Ice formation and accretion affect residential and commercial activities. Icephobic coatings decrease the ice adhesion strength (τice) to less than 100 kPa. However, rare icephobic coatings remove the ice under the action of gravity or natural winds. The icephobicity of such coatings depends on materials with low interfacial toughness. We develop durable candle soot icephobic coating with RTV-1 as a low-modulus binding material. Heterogeneous nucleation on 20-40 nm candle soot particles and their fracture mechanism are discussed. The developed coating always shows durable Cassie-Baxter superhydrophobic state with low ice adhesion (18 kPa) and maintains the τice value of about 25 kPa after severe mechanical abrasion, 30 liquid nitrogen/water cycles, 100 frosting/defrosting cycles, 100 icing/deicing cycles, acid/base exposure, under UV light, and exposure to natural freezing rain in Hangzhou. In addition, the proposed technique is time-efficient, inexpensive, and suitable for large-scale applications.

Highly Stable Amphiphilic Organogel with Exceptional Anti-icing Performance.

Various organogel materials with either a liquid or solid surface layer have recently been designed and prepared. In this work, amphiphilic organogels (AmOG) are innovatively developed from copolymer P(PDMS-r-PEG-r-GMA) and 2,2'-diaminodiphenyldisulfide via epoxy group addition reaction and then infiltrated with amphiphilic lubricants instead of traditional hydrophilic or hydrophobic lubricants. Because of synergistic effects of hydrophilic and hydrophobic segments of amphiphilic lubricants, the AmOG surfaces showed high stability and excellent anti-icing performance. The delay in the freezing point of water was 1000 s on AmOG surfaces, which is 40 times longer as compared to the untreated hydrophilic glass surface. More importantly, low ice adhesion strength (15.1 kPa) was observed on AmOG which remained about 40 kPa even after 20 icing-deicing cycles. The novel amphiphilic organogels provide a new idea to prepare long-term anti-icing materials for practical applications.

The Effect of Two Weeks Preoperative Finasteride Therapy in Reducing Prostate Vascularity.

OBJECTIVE: To determine the effect of two weeks preoperative finasteride therapy in reducing prostate vascularity in terms of mean microvessel density (MVD) and expression of VEGF in prostate urothelium among patients of BPH by comparing with controls. STUDY DESIGN: Randomized controlled trial. PLACE AND DURATION OF STUDY: Shifa International Hospital, Islamabad, from January 2013 to January 2014. METHODOLOGY: A total of 80 patients of Benign Prostatic Hyperplasia (BPH) planned for Trans-Urethral Resection of Prostate (TURP) having prostate size of more than 40 grams on trans-abdominal ultrasonography was randomized into two groups, each group having 40 patients. The finasteride group (Group A) was prescribed oral 5 mg of finasteride daily for 2 weeks before surgery. The control group (Group B) did not receive any agent. After 2 weeks, TURP was performed and prostate samples were sent for histopathological determination of MVD and expression of VEGF. RESULTS: The mean age of patients was 66.21 ±10.08 years, ranging from 48 to 86 years. The mean prostate gland size was comparable in both groups (55 ±10.7 vs. 58.1 ±10.8 grams, p=0.21). Mean MVD in finasteride group (20.25 ±10.3) was significantly lower as compared to control group (48.9 ±22.6, p < 0.001). Similarly expression of VEGF was also significantly lower in finasteride group (30%) as compared to control group (65%) [p= 0.0017]. Mean MVD had a significant weak correlation with the size of prostate gland on Pearson correlation test (2-tailed) with r = 0.222. CONCLUSION: Finasteride reduces microvessel density and hence prostate vascularity with only 2-week therapy and the mean MVD is clearly correlated with size of prostate.