Dipping Solution Research Articles

Control of Listeria monocytogenes with Combined Antimicrobials on Beef Franks Stored at 4°C

Contamination of ready-to-eat meat products such as beef franks with Listeria monocytogenes has become a major concern for the meat processing industry and an important food safety issue. The objective of this study was to determine the effectiveness of combinations of antimicrobials as aqueous dipping solutions to control L. monocytogenes on vacuum-packaged beef franks stored at 4°C for 3 weeks. Commercial beef franks were dipped for 5 min in three antimicrobial solutions: pediocin (6,000 AU), 3% sodium diacetate and 6% sodium lactate combined, and a combination of the three antimicrobials. Samples were then inoculated with 107 CFU/g of either four L. monocytogenes strains individually or a cocktail of the four strains, vacuum packaged, and stored at 4°C for 3 weeks. Sampling was carried out at day 0 and after 2 and 3 weeks of storage. Individual strains, as well as the cocktail, exhibited different responses to the antimicrobial treatments. After 2 and 3 weeks of storage at 4°C, pediocin-treated beef franks showed a less than 1-log reduction for all bacterial strains. Samples treated with the sodium diacetate–sodium lactate combination showed about a 1-log reduction after 2 weeks of storage for all strains and between a 1- and 2-log reduction after 3 weeks of storage, depending on the bacterial strain. When the three antimicrobials were combined, reductions ranged between 1 and 1.5 log units and 1.5 to 2.5 log units after 2 and 3 weeks of storage, respectively, at 4°C. These results indicate that the use of combined antimicrobial solutions for dipping treatments is more effective at inhibiting L. monocytogenes than treatments using antimicrobials such as pediocin separately.

Analysis of the December 1998 Santa Cruz Mountains, California, Earthquake Sequence

We studied a sequence of ∼150 earthquakes (magnitude [ M L, M D] < 0.8-4.0) that began in December 1998 in an area of complex faulting in the Santa Cruz Mountains, California. Epicenters plot west of the San Andreas Fault, east of the San Gregorio Fault, and just south of the Zayante Fault. Data for systematic hypocenter relocations and focal mechanisms were acquired from temporary deployment of eight IRIS/PASSCAL digital three-component 1-2 Hz seismographs and Northern California Seismic Network data. Our event relocations indicate this sequence is linked to the Zayante fault zone, along a segment previously considered inactive. In addition to detecting the 51 events listed by the Northern California Earthquake Data Center, 99 uncataloged events, presumably of lesser magnitude, were also recorded by our instruments. All data were processed using a waveform correlation program and shear-wave rotation for high-resolution P - and S -wave arrival times. Relocations were done using the master event method. Relocated hypocenters group tightly within approximately ±1 km about latitude 37° 04.62′, longitude 122° 03.26′, and range in depth from 2.1 to 8.0 km with a mean depth of 5.1 km. Epicenters plot in a roughly N60-70° W alignment ∼3.5 km south of the main branch of the mapped Zayante Fault. A plot of hypocenters in 3D also shows a N60-70° W alignment. Aftershocks occurred in rapid succession, with most of the early events within seconds of each other. Spatiotemporal analysis shows a rapid expansion of the aftershock field. Focal mechanisms are primarily thrust with small components of lateral slip. Average nodal plane strike is N37° W ± 15°, dipping 54° ± 8° southwest (range of 46-65°), and N82° W ± 17°, dipping 47° ± 14° northeast. We interpret the former as representing the fault plane, which is more consistent with the geology, and the resultant right-lateral strike-slip is consistent with the regional stress regime. The projection of the fault-plane solution dip from the hypocenters to the surface, within the range of error, conforms to the mapped trace of the Zayante Fault, and the sense of motion is also in agreement with the down-to-the-northeast mapped offset. Stress orientation indicates that the fault is favorably oriented to accommodate some convergent strain between the San Andreas and San Gregorio fault zones. Manuscript received 24 October 2003.

PH-Sensitive Bipolar Ion-Permselective Ultrathin Films

pH-Sensitive bipolar ion-permselective films of polyelectrolyte multilayers were prepared by layer-by-layer (LbL) assembly and photo-cross-linking of benzophenone-modified poly(acrylic acid) (PAA-BP) and poly(allylamine hydrochloride) (PAH-BP). The multilayer structure and ionizable group composition was finely tuned by changing the pH of the dipping solution. This structure and composition was in turn "preserved" by photo-cross-linking, forming highly stable membrane films. Since PAA-BP and PAH-BP are weak polyelectrolytes, it is possible to control the number of unbound, un-ionized -COOH or -NH2 groups in the multilayer by changing the pH. Moreover, the pH of the deposited film also plays an important role in determining selective latter permselectivity. For example, PAA-BP/PAH-BP multilayers deposited from two pH conditions, pH = 3 (PAA-BP) and pH = 6 (PAH-BP), showed pH-switchable permselectivity for both cationic (pH = 10) and anionic (pH = 3) probe molecules in a single film. The system offers advantages in film stability and introducing reversible selective ion permeability over previous multilayer film and cross-linking methods.

Inactivation of Salmonella during Drying and Storage of Roma Tomatoes Exposed to Predrying Treatments Including Peeling, Blanching, and Dipping in Organic Acid Solutions

The objective of this study was to evaluate the influence of predrying treatments, i.e., peeling, blanching prior to inoculation, and dipping in organic acid solutions, on inactivation of Salmonella during drying (60°C for 14 h) and aerobic storage (25°C for 28 days) of inoculated (five-strain composite, 7.1 to 7.4 log CFU/g) Roma tomato halves. Four predrying treatments groups were established. One group received no treatment (C). In the other three groups, unpeeled-unblanched, unpeeled-blanched (steam blanched at 88°C for 3 min), peeled-unblanched, and peeled-blanched tomato halves were immersed for 10 min in water (W), ascorbic acid solution (AA; 3.40%, pH 2.48), or citric acid solution (CA; 0.21%, pH 2.51). Appropriate dilutions of homogenized tomato samples were spread plated on tryptic soy agar with 0.1% pyruvate and XLT4 agar for bacterial enumeration during drying and storage. Ten minutes of immersion in W, AA, or CA reduced bacterial populations by 0.7 to 1.6 log CFU/g. After 14 h of dehydration, total log reductions in the populations of bacteria were 3.2 to 4.5 (C), 3.7 to 4.9 (W), >5.6 to >6.1 (AA), and 4.5 to 5.5 (CA) log CFU/g, depending on type of agar used and condition of tomato samples. During drying and storage, the order of pathogen inactivation for predrying dipping treatments was AA > CA > W > C, with AA and CA rendering bacterial populations below detectable levels (<1.3 log CFU/g) prior to storage and between 7 and 14 days of storage, respectively. The results also indicated that peeling and blanching of tomatoes prior to inoculation may not necessarily affect destruction of Salmonella during the drying process. Use of predrying acid dipping treatments of tomatoes, especially in AA, may improve destruction of Salmonella during the dehydration process.

Surface chemical modification of thermoplastic starch: reactions with isocyanates, epoxy functions and stearoyl chloride

Thermoplastic starch (TPS) films plasticized with 20 and 30 wt.% of glycerol were treated with various reagents in order to make their surface less sensitive to moisture. Phenyl isocyanate (PhNCO), a phenol blocked polyisocianate of trimethylol propane and toluene diisocyanate (TMP-TDI-Phenol), a styrene-co-glycidyl methacrylate (PS-GMA) co-polymer and stearoyl chloride (StCl) were used for these superficial chemical modifications. Two reaction procedures were adopted, viz., suspension at room temperature or under reflux and dipping in the reactant solution followed by heating. The treated films were characterized by contact angle measurements, from which the corresponding surface energies were calculated in terms of, polar and dispersive components. In all instances, the polar contribution was drastically reduced by the treatment, indicating that the surfaces had become more hydrophobic. The most effective treatment was achieved with phenyl isocyanate in xylene. The dipping + heating treatment seems to be the most appropriate procedure for practical applications.

Effectiveness of Acidic Calcium Sulfate with Propionic and Lactic Acid and Lactates as Postprocessing Dipping Solutions To Control Listeria monocytogenes on Frankfurters with or without Potassium Lactate and Stored Vacuum Packaged at 4.5°C

The safety of ready-to-eat meat products such as frankfurters can be enhanced by treating with approved antimicrobial substances to control the growth of Listeria monocytogenes. We evaluated the effectiveness of acidic calcium sulfate with propionic and lactic acid, potassium lactate, or lactic acid postprocessing dipping solutions to control L. monocytogenes inoculated (ca. 108 CFU/ml) onto the surface of frankfurters with or without potassium lactate and stored in vacuum packages at 4.5° C for up to 12 weeks. Two frankfurter formulations were manufactured without (control) or with potassium lactate (KL, 3.3% of a 60% [wt/wt] commercially available syrup). After cooking, chilling, and peeling, each batch was divided into inoculated (four strains of L. monocytogenes mixture) and noninoculated groups. Each group was treated with four different dips: (i) control (saline solution), (ii) acidic calcium sulfate with propionic and lactic acid (ACS, 1:2 water), (iii) KL, or (iv) lactic acid (LA, 3.4% of a 88% [wt/wt] commercially available syrup) for 30 s. Noninoculated frankfurters were periodically analyzed for pH, water activity, residual nitrite, and aerobic plate counts (APCs), and L. monocytogenes counts (modified Oxford medium) were determined on inoculated samples. Surface APC counts remained at or near the lower limit of detection (<2 log CFU per frank) on franks with or without KL and treated with ACS or LA throughout 12 weeks at 4.5° C. L. monocytogenes counts remained at the minimum level of detection on all franks treated with the ACS dip, which indicated a residual bactericidal effect when L. monocytogenes populations were monitored over 12 weeks. L. monocytogenes numbers were also reduced, but not to the same degree in franks made without or with KL and treated with LA. These results revealed the effectiveness of ACS (bactericidal effect) or LA (bacteriostatic effect) as postprocessing dipping solutions to inhibit or control the growth of L. monocytogenes on vacuum-packaged frankfurters stored at 4.5° C for up to 12 weeks.

Synthesis, self-assembly and photoinduced surface-relief gratings of a polyacrylate-based Azo polyelectrolyte

A polyacrylate-based azo polyelectrolyte was synthesized and characterized by the spectroscopic methods and thermal analysis. Layer-by-layer self-assembly of the azo polyelectrolyte through electrostatic adsorption was explored. By using a dipping solution of the anionic azo polyelectrolyte in anhydrous DMF, together with an aqueous solution of cationic poly(diallyldimethylammonium chloride) (PDAC), high quality multilayer films were obtained through the sequential deposition of the oppositely charged polyelectrolytes. With interfering illumination of Ar + laser beams (488 nm), significant surface-relief gratings formed on the self-assembled multiplayer films were observed.

Behavior of hepatocytes inoculated in gelatin-immobilized polyurethane foam

We have fabricated gelatin-immobilized polyurethane foams (PUFG) by dipping polyurethane foam (PUF) in an aqueous solution containing gelatin and by subsequent reaction with glutaraldehyde after freeze-drying. Gelatin aqueous solutions of different concentrations were used as the dipping solutions to control the amount of immobilized gelatin. The average pore size of PUF decreased with an increase in gelatin concentration. It was found from the hepatocyte adhesion experiment that the amount of hepatocytes seeded on PUFG1, prepared by using a 1% aqueous gelatin solution, was higher than that on other PUFGs. The hepatocytes inoculated in PUFG1 were slightly aggregated as the incubation time increased. The cells inoculated in PUFG1 showed higher ammonia removal ability than those monolayer-cultured on a gelatin-immobilized polystyrene dish (PSG) after 1 and 4 days of incubation time. The inoculated cells exhibited higher albumin secretion relative to monolayer-cultured hepatocytes on PSG. Albumin secretion by hepatocytes seeded on PUFG1 was increased by the presence of serum and was further increased by both the presence of serum and cytokines. The results obtained from a 3-(3,4-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated that PUFG can provide a better microenvironment for hepatocyte culture along with nutrition and metabolite transfer through the high porosity of PUF.

Mechanical properties of glass fabric/polyester composites: Effect of silicone coatings on the fabrics

AbstractAn experimental investigation was carried out to study the effect of a silicone coating on the mechanical properties of polyester/woven glass fabric composites, fabricated by resin transfer molding. E‐glass woven fabrics were coated with a silicone elastomer by solution dip coating. The effect of variation of silicone amounts on the impact resistance, toughness, and mechanical properties of the composite was determined. Short beam shear tests were performed to assess the effect of coating on the adhesion of the fiber to the matrix. The coated specimens exhibited worse interlaminar shear strength over that of uncoated fabrics. Three‐point bending tests were also performed to investigate the effect of the coating on flexural properties. Whereas flexural strength and Young's modulus decreased with increasing amount of coating, the toughness, represented by the area under the stress–strain curve, presented a maximum. Finally, notched Izod impact tests were carried out and the curve for the energy absorbed during impact versus the amount of coating also appeared to have a maximum, indicating an interesting slot for optimum impact performance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1300–1308, 2004

Growth of Gold Nanorods on Surfaces

The surfactant-assisted seeded growth method was adapted for growth of gold nanorods directly on mica surfaces. Spherical gold seed particles were first linked to the surface and then dipped in a cationic surfactant growth solution. Part of the grown particles were nanorods with a typical length of several hundred nanometers and diameter of 10−20 nm. The probability to grow elongated particles out of a seed on the surface was found to be larger than the comparable solution growth process. Successive dipping in the growth solution was found to increase the length and thickness of the gold nanorods without a significant increase in aspect ratio.

Polyelectrolyte Multilayers as Nanocontainers for Functional Hydrophilic Molecules

We report on the introduction of small organic hydrophilic molecules (fluorescein, rhodamine B, and two coumarin-based dyes) in multilayers of strong polyelectrolytes, studied by X-ray reflectometry, UV/visible spectroscopy, and fluorescence measurements. Very low diffusion coefficients (about 10(-17) cm(2.)s(-1)) were found for the inward diffusion of fluorescein in preformed multilayers. In addition, diffusion was accompanied by substantial variations of the thickness of the multilayer (up to 300%), ruling out the practical significance of inward diffusion as a tool to dope multilayers. We then attempted to coadsorb the fluorophores simultaneously with the polyions during the construction of the multilayer. However, displacement of small molecules by polyions of identical charge and outward diffusion of the fluorophores during the rinsing step resulted in very limited inclusion of the dye by this procedure. This issue was solved by introducing the fluorophore in all baths, including the rinsing ones. Then, the concentration of the multilayers in dye is directly related to the concentration of the dipping solutions and is dependent on the nature of the dye and of the multilayer. The outward diffusion of the fluorophores from these multilayers was studied, and very low diffusion coefficients were again determined, depending on the net charge of the dye. The ability to load rapidly polyelectrolyte multilayers with a variety of hydrophilic organic molecules of small molar mass, in tunable concentration, is a major outcome of the present study. It offers new opportunities to use these multilayers as templates for the confinement of active molecules in functional devices.

Layer-by-layer self-assembly of Prussian blue colloids

The adsorption of Prussian blue (PB) colloids within layers of polyelectrolytes has been achieved by a reiterative immersion–rinse approach. Multilayer assemblies consisting of alternate layers of these components have been prepared by the layer-by-layer (LbL) self-assembly technique. Both processes have been carefully monitored by cyclic voltammetry and infrared and UV–visible spectroscopy. Linear increase in the IR and UV–visible light absorbance with the number of deposited layers indicates that well-organized lamellar systems have been elaborated. Size and distribution of Prussian blue nanoparticles in these systems have been investigated by AFM. The effect of the molar concentration of the PB dipping solution on the adsorption process and the distribution of the PB colloids has also been described. Finally, magnetic properties of these assemblies have been studied by low-temperature ESR measurements. Indeed, this new approach of hybrid LbL films opens the way to a new class of nanostructured lamellar compounds.

Silver-modified titanium dioxide thin films for efficient photodegradation of methyl orange

Silver-modified, rough, high surface area titanium dioxide thin films resulting via a two-step dipping and UV-irradiation process were examined for their catalytic activity towards photodegradation of methyl orange (MO). Optimization of the photocatalyst’s performance as a function of the dipping time, irradiation time and the dipping solution concentration was performed. The optimum silver nitrate concentration of the dipping solution was found to be 10−3M. The modified materials present enhanced photocatalytic efficiency and can decompose the organic pollutant three-times faster than the undoped original films (Degussa P25). A further Ag+-ion concentration increase in dipping solution results a decrease of the films photocatalyst efficiency due to a shading of the available semiconductor surface by the silver layer. This performance is consistent with the unique structural, morphological, and surface characteristics of the composite silver/titania materials. The lower the average particle size, roughness and fractal dimension, the higher the photodegradation percentage and rate constants. The surface doping effect is synergetic to the charge separation process and the photocatalytic results are explained on the basis of a mechanism involving efficient separation of electron–hole pairs induced by silver-ions (Ag+). Reproducibility tests proved that the photocatalytic activity of the silver-modified films remains intact even after six consecutive experiments of new added pollutant quantities.

Microcontact printing of novel co-polymers in combination with proteins for cell-biological applications

Microcontact printing (μcP) is a cost effective and simple method to create chemically micropatterned surfaces for cell biological applications. We have combined the technique with the spontaneous molecular assembly of a polycationic PEG-grafted copolymer, poly- l-lysine- g-poly(ethylene glycol) (PLL- g-PEG). PLL- g-PEG with ω-functionalized PEG chains was print-transferred onto tissue culture polystyrene (TCPS) or glass substrates, resulting in patterns with a lateral resolution down to 1 μm. Subsequently, dipping in an aqueous solution of non-functionalized PLL- g-PEG was used to backfill the non-printed regions of the surface, rendering them highly protein and thus cell resistant. In a second approach, proteins were stamped and a PLL- g-PEG backfill was applied for passivation of the bare surface regions. Printing of peptide(RGD)-functionalized PLL- g-PEG or proteins combined with a subsequent PLL- g-PEG backfill can be applied to a wide variety of substrate materials with negatively charged surfaces such as TCPS, glass and many metal oxides. We have tested the printed surfaces with human foreskin fibroblasts for cell adhesion and long-term performance and with fish epidermal keratocytes for cell motility and short-time behaviour. Both cell types reacted selectively to the surface micropatterns. Fibroblasts adhered to the printed (adhesive) regions only, where they remained attached up to at least 1 week and were even able to proliferate. Keratocyte spreading and motility were also directed by the geometry of the underlying patterns. The results prove that μcP in conjunction with the use of PLL- g-PEG and its derivatives provides a simple and robust alternative to previously reported micropatterning methods for future cell biological and biotechnological applications.

Self-Assembly of a Dendron through Multiple Ionic Interaction to Give Mesospacing between Reactive Amine Groups on the Surface

A dendron having nine carboxylic acid groups at the end of the branches and a protected amine at the apex was allowed to form a molecular layer on the aminosilylated surface through multipoint ionic attraction. It was found that a compact and smooth monolayer was obtained at appropriate condition. The film quality was maintained successfully after deprotecting CBZ group with trimethylsilyl iodide. Tapping mode AFM showed individual dendron molecules self-assembled on the aminosilylated surface. The molecular layer formed through the multipoint ionic interaction was strong enough to survive heating at 100 °C for 1−2 h in water and dipping in aqueous solutions of pH 4−10 for 3 h. The surface density of the primary amine after the deprotection was measured with fluorometry, and 0.1−0.2 amine group per 100 A2 was observed. This implies that the spacing between the amine functional groups is 24−34 A in hexagonal close-packing (hcp) model.

Enhanced activity of silver modified thin‐film TiO2 photocatalysts

Novel, composite silver/titania immobilized on glass substrates were prepared, characterized and their photocatalytic activity was evaluated. The undoped original material consists of rough, high surface area nanocrystalline titanium dioxide (TiO2) thin films. To increase their efficiency, the TiO2 films were modified by silver cations deposition and subsequent UV‐C irradiation. SEM pictures confirmed the existence of an open porous network of interconnected titania particles on the semiconductor surface. AFM analysis proved the presence of spherical silver particles on the catalyst surface and provided quantitative surface parameters as fractal dimension, surface roughness and mean particle diameter. Spectroreflectometry showed the presence of an increase in optical absorbance attributed to plasmon resonance absorption of the silver clusters. The photocatalytic properties of the surface modified materials were investigated through photodegradation of Methyl Orange. The silver deposition conditions were optimized for maximum photocatalytic efficiency and crucial parameters such as dipping period, UV irradiation time, and concentration of the dipping solution were determined. The optimum silver nitrate concentration of the dipping solution was found to be 10-3 M. This silver doped photocatalyst decomposes the azo‐dye pollutant 3‐times faster than the un‐doped Degussa P25 TiO2 film. A concentration increase results in a decrease of the films photocatalytic performance. Strength and reproducibility tests proved that the photocatalytic activity of the silver doped titania was perfectly reproducible.

CHEMICAL MODIFICATION OF GATE DIELECTRIC SURFACES IN ORGANIC THIN FILM TRANSISTOR (OTFT) THROUGH MOLECULAR SELF-ASSEMBLY

To modify SiO2 dielectric surface of bottom-contact OTFT device, octadecyltriethoxysilane (OTES) was used to find optimum condition of surface modification for triethoxysilane derivatives. Either spin-coating method or solution dipping method was applied to modify the dielectric surface with OTES. Optimization process was performed with varying solution concentration, reaction time and so on. Through surface modification of OTFT, 0.01–0.04 cm2/V/s of hole mobilities were observed depending on modification conditions.

Formation of Tungsten Oxide Defects during Tungsten CMP

Most tungsten chemical mechanical polishing (CMP) processes utilize a subsequent cleaning process referred to as post-CMP cleaning for removal of contaminated layers. Even after a proper post-CMP cleaning has treated polished wafers, several defects such as slurry particles, microscratches, and metallic impurities are still easily observable. In this study, a new kind of defect has been observed at the stage between overpolishing and post-CMP clean in the course of the tungsten CMP. The circular-shape defect was composed of very thin tungsten oxide, which could be removed by several treatments such as HF solution dipping, additional oxide CMP, and the treatment of concentrated ammonium hydroxide solution during poly(vinyl alcohol) brushing. Among them, the most available method without any further process issues was the use of concentrated ammonium hydroxide solution. © 2003 The Electrochemical Society. All rights reserved.

Surface wettability and platelet adhesion studies on Langmuir–Blodgett films

Because Langmuir–Blodgett (LB) deposition technique is known to be capable of preparing highly ordered monomolecular films with densely packed structure, LB technique is used to prepare films of DPPC, DMPC, cholesterol, octadecylamine (ODA), and stearic acid, with thickness of one molecular layer. The film surfaces were characterized by dynamic contact angle measurement and the interaction between blood and these materials were investigated. The properties of LB films were also compared with the results obtained on continuous films prepared by solution dipping. The results show that the contact angles of water on LB films of the five compounds decreases as the following order: ODA> DMPC≈ DPPC> stearic acid > cholesterol . The hydrophobic property reflects the highest organization of ODA molecules on the substrate, which is related to its interaction between the molecule and substrate. The advancing contact angle of ODA is equivalent to that of a methyl-terminated SAM, but its receding contact angle is smaller which implies the exposing of hydrophilic pole or glass substrate on LB film. The irregular orientation of molecules on LB film increases with decreasing of contact angle and is especially significant on LB film of cholesterol which has highest hydrophilic property. The plate adhesion experiments on the continuous films show that the hemocompatibility of the five materials decreases as the order: DPPC≈ DMPC> ODA> cholesterol> stearic acid ≈ glass . This result implies that the lipid has highest blood compatibility, and then –NH 2, and then –OH functionality. On the contrary, the glass surface, –COOH and –CH 3 functionalities have high reactivity to platelet. Due to the possibility of glass exposure on LB films, as estimated from the surface wettability, the LB films have higher platelet reactivity, especially for the cholesterol, compared with the continuous films. Because the interaction of the LB film to the substrate is physical force, the deposited molecules may be peeled off from the substrate by dipping in Hepes–Tyrodes buffer solution. As a consequence, the LB films after equilibrating with Hepes–Tyrodes buffer solution have high platelet reactivity as that on glass surface.

Gray optical dips in the subpicosecond regime.

Narrow optical dip solutions are investigated when, besides self-phase modulation and group velocity dispersion, also third-order dispersion, nonlinear dispersion, and stimulated Raman scattering are taken into account. By using the inverse scattering transform for the higher-order optical nonlinear Schrödinger (HNLS) equation under Hirota parameter conditions, the dark N-soliton solution is constructed. The explicit forms of the one- and two-soliton solutions are investigated in detail. The results show an interesting property of the gray two-soliton solution. Two gray dips do not interact provided their modulation depths are appropriately chosen. In addition, when generalizing the HNLS equation (to regions beyond the Hirota parameter conditions), it can be shown that also quite stable generalized two-dip solitary wave solutions exist. The latter, although not belonging to integrable systems, approximately preserve most of the interesting properties detected for the integrable Hirota equation.