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Cloud computing Provides resource security service over the internet using the data center, under the risk of multiple attacks. Interoperability in cloud computing will share the information from one to another cloud environment over the internet. Sharing information between user and server, there will be a risk attacking the information. Interoperability deals with security and privacy. It is a major development; it is convenient for the individual user as well as for the enterprise-level. Frequently the private and public sectors are using. Organizations and enterprises are transferring the data into the cloud. There is a possibility of one user can operate another user’s information present on the cloud. Due to the security issues they provide a virtual machine for the user, the machine has a separate user id and password to access the cloud. CC is popular in the business, and public sectors. It has hedge method, and also provide the suspension for the existing attack. In this report, we led an analysis of the attacks in cloud computing. We discussed a whole range of different approaches to these attacks.

The criminal activity of hackers to retrieve the highly secured information on multimedia application generates major security concerned problems towards the human life. Basically, the visual cryptographic scheme generates numerous unreasonable image shares with specific information. The secret information hidden in the image can be retrieved by accumulating all the shares. The basic idea that relays on this cryptographic scheme is the encryption of image which hides the secret into m numerous image shares. By this process, it turns to be complex for the hackers to retrieve an original data of the image. Moreover, to increase the confidentiality and privacy of the original image there is in demand to make use of the efficient encryption algorithm. In this paper, the proposed visual cryptographic scheme is divided into three phases namely, (a) Separation of color bands, (b) Generation of numerous shares and (c) Optimal Encryption and Decryption. For optimal encryption and decryption of the image, we propose an OGWO based ECC (Elliptic Curve Cryptographic) approach. Initially, the input color image is separated into three color bands such as R, G and B. Subsequently, multiple image shares are generated based on the pixel measures. After this process, the shares of the image are partitioned into blocks and decrypt the original image using the optimal key generated by the OGWO (Oppositional Gray Wolf Optimization) algorithm. From the experimental analysis, we inferred that for the decrypted image PSNR achieved is 59.012, 0.11 for MSE and the CC is 1, without experiencing any deviations in the original image.

The study was aimed at producing bio-diesel from lipids accumulated by micro-organisms grown in distillery wastewater. The raw waste was inoculated with Metschnikowia pulcherrima and was grown under varying conditions of pH, temperature, culture times etc. The raw wastewater had a COD of 86 g/l and total dissolved solids of 46.9 g/l. The conditions for maximum growth were analysed for the available C/N ratio of 11.4. The culture conditions for maximum growth were found to be pH 6.2, 300 C and 120 hours. The lipid extraction was done and lipids were used for Bio-diesel conversion. In-situ trans-esterification reaction was effected by base-catalysis using NaOH and methanol to form fatty acid methyl esters. The yield reached up to 1.4 g/l.

INEPT- and HMQC-based pulse sequences are widely used to transfer polarization between heteronuclei, particularly in biomolecular spectroscopy: they are easy to setup and involve low power deposition. Still, these short-pulse polarization transfers schemes are challenged by fast solvent chemical exchange. An alternative to improve these heteronuclear transfers is J-driven cross polarization (J-CP), which transfers polarization by spin-locking the coupled spins under Hartmann-Hahn conditions. J-CP provides certain immunity against chemical exchange and other T2-like relaxation effects, a behavior that is here examined in depth by both Liouville-space numerical and analytical derivations describing the transfer efficiency. While superior to INEPT-based transfers, fast exchange may also slow down these J-CP transfers, hurting their efficiency. This study therefore explores the potential of repeated projective operations to improve 1H->15N and 1H->15N->13C J-CP transfers in the presence of fast solvent chemical exchanges. It is found that while repeating J-CP provides little 1H->15N transfer advantages over a prolonged CP, multiple contacts that keep both the water and the labile protons effectively spin-locked can improve 1H->15N->13C transfers in the presence of chemical exchange. The ensuing Looped, Concatenated Cross Polarization (L-CCP) compensates for single J-CP losses by relying on the 13C longer lifetimes, leading to a kind of algorithmic cooling that can provide high polarization for the 15N as well as carbonyl and alpha 13Cs. This can facilitate certain experiments, as demonstrated with triple resonance experiments on intrinsically disordered proteins involving labile, chemically exchanging protons.

In this work we investigate in detail the underlying spin-dynamics associated with 1H-14N double CP experiments under fast MAS, recently demonstrated by Carnevale et al. We employ matrix logarithm and Floquet theory to compute numerically the effective Hamiltonian associated to the time-dependent problem. Certain common features related to construction of effective Hamiltonians by both approaches are discussed. The main observations related to 1H-14N CPMAS/double CP transfer are: (a) various spin terms of the effective Hamiltonian strongly depend on the crystallite orientation; (b) significant CP transfer occurs only when the magnitudes of the effective 1H and 14N RF strengths are comparable, and simultaneously all pure 14N terms in the effective Hamiltonian are small, except for the longitudinal and the RF terms; (c) the sign of 14N CPMAS signal follows the sign of 14N effective RF strength; (d) sign of the double CP signal is largely independent of crystallite orientation. We predict and verify matching conditions employing multiples of the spinning frequency or involving different 14N RF strengths. We provide an analytical proof for (d). The proof also provides an estimate for the ratio of 1H-14N and 14N-1H transfer amplitudes which is further substantiated through simulations. In addition, we find that double CP signals include contributions from several single-quantum coherences present after the first CP process. The uneven contribution from different coherences leads to a reversal of signal at very short contact times, a feature noted experimentally by Carnevale et al. The connection between CPMAS transfer and efficient spin-lock is discussed and illustrated. The factors affecting second-order quadrupolar lineshapes in double CP experiment are examined. With a linear ramp of 1H RF amplitude we have observed that significant CP transfer occurs for more crystallite orientations resulting in improved sensitivity.

We demonstrate sensitivity enhancement via recycling of proton magnetization in 2D Double Cross Polarization (Double CP) experiments performed on fully protonated and uniformly labeled (13C, 15N) samples at a magic angle spinning rate of 60 kHz. Unused proton magnetization is preserved during t1 evolution either by locking it with CW irradiation or by employing rotor-synchronized pi pulses. A flip-back pulse together with a modified second CP block preserves unused proton magnetization resulting in enhanced sensitivity. We have achieved sensitivity enhancements of 15–20% and 25–28% in 1H–13C and 1H–15N 2D Double CP experiments respectively. At shorter recycle delays (∼0.25T1), relative sensitivity enhancements of 40–45% and 55% were obtained in 1H–13C and 1H–15N 2D Double CP experiments respectively. An analysis of the sensitivity enhancements and theoretical estimation of lineshapes in indirect dimension in the presence of proton recycling is provided.

Background Candida is a part of the normal oropharyngeal flora and the upper respiratory tract. Candida albicans(C. albicans), is the predominant species causing respiratory tract infections associated with pneumonia. Resistance to azole antifungal agents among the C. albicans may be due to alteration of the target enzymes, which are encoded in ERG11 gene. The biofilm formation may also be a cause to antifungal resistance. Materials and methods This study was conducted at Chettinad Hospital and Research Institute. Samples were collected from June 2018–June 2019, for a period of 1 year. After species confirmation, virulence factor among the Candida species were identified by hemolysis test, coagulase test and biofilm formation. Genotypic confirmation of C. albicans and their azole resistance due to ERG 11 gene were done using multiplex PCR. Results In our study, 31 (55%) C. albicans, 8 (14%) Candida glabrata(C. glabrata) and 10 (17%) Candida tropicalis(C. tropicalis), three Aspergillus flavus(A. flavus), two Aspergillus fumigatous (A. fumigatous), one Aspergillus niger (A. niger) and one Mucor species were isolated. In C. albicans, 31 were positive for Germ tube and Chalmydospore formation. Six of candida species were isolated along with bacterial co infection. Among the Candida isolates, 17 (55%) C. albicans strains were strongly biofilm positive and 14(45%) were negative. The susceptibility pattern of (n = 31) C. albicans were as follows: fluconazole (21(68%) S, 10(32%) R), voriconazole (22(71%)S),9(21%) R) and Amphotericin B 31(100%) S). Among the 19 C. albicans, four were positive for ERG11 gene. Conclusion The isolation of C. albicans and non - albicans from respiratory specimens should be reconsidered as these organisms are re-emerging pathogens. Speciation is needed due to variation in species pathogenicity and their susceptibility.

In this paper a modified fourth order compact scheme for solving unsteady 2-D Navier-stokes equation in stream function-vorticity formulation is proposed. The proposed scheme involves domain transformation and the governing cartesian equations are transformed to body fitted coordinate system. Explicit Euler’s forward discretization in time and central difference in space are applied except for few nodes adjacent to the computational boundaries. The scheme is tested on two benchmark problems Taylor vortex flow, Burgraff flow. The results in numerical form are compared with exact solutions and are in excellent agreement. Keywords: Compact scheme, Body fitted coordinates, Navier-Stokes equation

Cloud providers offer several storage services for their users in efficient manner. Cloud users are allowed to store their data in cloud server using cloud storage and reduce the burden of storing and retrieving in local machine. The data can be shared by a user in a group and the facility shakes the integrity of the shared data due to access by many users as well as hardware and software for users. It is necessary to ensure the integrity of shared data before using that data for some process as well as the correctness of the cloud storage. Public auditing mechanism is employed to audit the correctness of the shared data. Both data owner and the Third Party Auditor (TPA) can audit shared data integrity without downloading the data from cloud server. This research paper attempts to point out various techniques to solve the privacy and security issues of the data in public auditing scheme in cloud environment.

A Floquet description of a phase alternated homonuclear recoupling scheme for perdeuterated systems is presented. As a result, we demonstrate improvements in the recoupling efficiency of the DOuble Nucleus Enhanced Recoupling [DONER; J. Am. Chem. Soc. 131 (2009) 17054] technique by utilizing Phase Alternated Recoupling Irradiation Schemes [PARIS; Chem. Phys. Lett. 469 (2009) 342]. The effect of proton and deuterium radio frequency irradiation during recoupling has been systematically studied and theoretical observations have been verified experimentally using a deuterated model compound, L-Alanine, at 10 and 20 kHz magic angle spinning frequency. Experimental results are well in agreement with theoretical observations, thereby significantly increasing the recoupling efficiency of conventional DONER in perdeuterated systems.

For studying systems containing nitrogen, limited use of N-14 NMR spectroscopy has been made because of the large quadrupolar interaction experienced by the N-14 nucleus and the absence of a central transition. To overcome the above problem, use of overtone spectroscopy has been suggested. Though this approach has limited applicability for powder samples due to second order quadrupole broadening, it is useful for studying oriented samples and single crystals. Here, we demonstrate the use of the recently proposed dipolar assisted polarization transfer (DAPT) pulse scheme for exciting the overtone transitions. The pulse sequence may also be utilized as a two-dimensional experiment to obtain H-1-N-14 dipolar couplings and H-1 chemical shifts. (C) 2010 Elsevier B.V. All rights reserved.

Separated Local Field (SLF) spectroscopy is a powerful tool for the determination of structure and dynamics of oriented systems such as membrane proteins oriented in lipid bilayers and liquid crystals. Of many SLF techniques available, Polarization Inversion Spin Exchange at Magic Angle (PISEMA) has found wide application due to its many favorable characteristics. However the pulse sequence suffers from its sensitivity to proton resonance frequency offset. Recently we have proposed a new sequence named 2(4)-SEMA (J. Chem. Phys. 132 (2010) 134301) that overcomes this problem of PISEMA. The present work demonstrates the advantage of 2(4)-SEMA as a highly sensitive SLF technique even for very large proton offset. 2(4)-SEMA has been designed for obtaining reliable dipolar couplings by switching the magic-angle spin-lock for protons over four quadrants as against the use of only two quadrants in PISEMA. It is observed that for on-resonance condition, 2(4)-SEMA gives rise to signal intensity comparable to or slightly higher than that from PISEMA. But under off-resonance conditions, intensities from 2(4)-SEMA are several fold higher than those from PISEMA. Comparison with another offset compensated pulse sequence, SAMPI4, also indicates a better intensity profile for 2(4)-SEMA. Experiments carried out on a single crystal of N-15 labeled N-acetyl-DL-valine and simulations have been used to study the relative performance of the pulse sequences considered. (C) 2010 Elsevier Inc. All rights reserved.

A native feather-degrading keratinophilic fungus, Trichophyton sp. HA-2, was isolated from feather dumping soil in India and screened for extracellular keratinase using keratin-agar medium (chicken feathers as substrate). The fungus was grown in mineral salt medium and keratinase production was tested. The highest keratinase production was observed at pH 8.0 and a temperature of 35 °C for a period of 5 weeks. Keratinase secretion was enhanced when cultures were supplemented with a carbon source and keratin source (chicken feathers). This novel keratinase was purified by DEAE-cellulose and sephadex G-100 column chromatography and characterized. The molecular weight of the keratinase was estimated to be 34 kDa by SDS-PAGE. The optimum pH and temperature were determined to be 7.8 and 40 °C, respectively. This enzyme was completely inhibited by phenylmethylsulfonyl fluoride (PMSF), indicating the presence of serine protease.

Twenty five clinical isolates of high level gentamicin resistant Enterococcus faecalis were tested for their biofilm formation and pheromone responsiveness. The biofilm assay was carried out using microtiter plate method. Two isolates out of the 25 (8%) were high biofilm formers and 19 (76%) and four (16%) isolates were moderate and weak biofilm formers respectively. All the isolates responded to pheromones of E. faecalis FA2-2 strain. On addition of pheromone producing E. faecalis FA2-2 strain to these isolates, seven of 19 (37%) moderate biofilm formers developed into high biofilm formers. Similarly one of the 4 (25%) weak biofilm formers developed into high level biofilm former. Twelve (48%) of the 25 isolates were transconjugated by cross streak method using gentamicin as selective marker. This proves that the genetic factor for gentamicin resistance is present in the pheromone responsive plasmid. Among these twelve transaconjugants, seven isolates and one isolate were high biofilm formers on addition of E. faecalis FA2-2 and prior to its addition respectively. Out of the total 25 isolates, eight transconjugants for gentamicin resistance could turn to high biofilm formers on addition of the pheromone producing strain. All the isolates were resistant to more than two antibiotics tested. All the isolates were sensitive to vancomycin. The results indicate the significance of this nosocomial pathogen in biofilm formation and the role of pheromone responding clinical isolates of E. faecalis in spread of multidrug resistance genes.

Phase-singular Mg 4 Al 2 Ti 9 O 25 ceramics with the pseudobrookite structure suitable for microwave devices such as antenna substrate have been prepared by gel-carbonate method with the dielectric permittivity of 24.7 (at 2–8 GHz), Q -values > 30,000 and temperature coefficients in permittivity (TCK) of less than + 17 ppm K − 1 . The dielectric characteristics are accountable in terms of ordering in the cation sub-lattice.

A new method for polarization transfer between heteronuclei for static oriented samples is presented. The method employs an INEPT like sequence for the transfer of polarization through heteronuclear dipolar couplings. A $90^o$ pulse on the S spin sandwiched between two I spin evolution periods under BLEW-12 blocks of pulses with appropriate phases enables polarization transfer. The method has been demonstrated on a nematic liquid crystal oriented in a magneticfield. Further experiments on samples of chloroform and dichloromethane oriented in the liquid crystalline matrix demonstrate that the technique can also be used for estimating heteronuclear dipolar couplings. Calculation of scaling factors based on average Hamiltonian theory and simulations are shown to match with experiment.

The effect of variable viscosity on non-Darcy free or mixed convective heat transfer along a vertical surface embedded in a porous medium saturated with a non-Newtonian fluid has been analysed. The viscosity of the fluid is assumed to be an inverse linear function of temperature. Furthermore, the coordinates and dependent variables are transformed to yield computationally efficient numerical solutions which are compared with the existing results, for a few particular cases. The results show that the variable viscosity parameter, viscosity index, mixed convection parameter, Ergun number, Peclet number, Rayleigh number and temperature variation parameter have significant influence on the velocity and heat transfer rate at the surface.

This paper analyzes the variable viscosity effects on non-Darcy free or mixed convection flow on a vertical surface in a fluid saturated porous medium. The viscosity of the fluid is assumed to be a inverse linear function of temperature. Velocity and heat transfer are found to be significantly affected by the variable viscosity parameter, Ergun number, Peclet number or Rayleigh number.

Phase-pure samples of barium magnesiotitanate, BaMg 6 Ti 6 O 19 (BMT) are prepared by the wet chemical ‘gel–carbonate’ method wherein the formation of BMT is complete below 950 °C as a result of the reaction between nanoparticles of BaCO 3 , MgO and TiO 2 . BMT powders are sintered at 1350–1450 °C to dense ceramics. Extensive melting is noticed when the bulk composition falls between (0.4MgTiO 3 + 0.6BaTiO 3 ) and (0.6MgTiO 3 + 0.4BaTiO 3 ) along the MgTiO 3 –BaTiO 3 tie-line in BaO–MgO–TiO 2 phase diagram. Dielectric properties of sintered (BMT) ceramics have been investigated which showed ɛ ≃ 39 at 2 GHz, quality factor Q ≥ 10,000 and positive temperature coefficient of dielectric constant around 370 ppm °C − 1 .

Steady state solutions are obtained for non-Darcy free convection flow along a horizontal cylinder in a non-Newtonian fluid saturated porous medium. The boundary-layer equations governing the flow are solved numerically by using an implicit finite-difference method developed by Keller. Numerical results are obtained for the velocity and heat transfer at the wall for various values of the parameters namely, the Ergun number, Rayleigh number, power-law index and transpiration parameter.

Ca-substituted BaTiO 3 with extended homogeneity range upto ∼50 mol% CaTiO 3 have been prepared by three different chemical routes namely carbonate-oxalate (COBCT), gel-carbonate (GCBCT), and gel-to-crystallite conversion (GHBCT) followed by heat treatment above 1150 °C. X-ray powder diffraction (XRD) data show continuous decrease in the tetragonal unit cell parameters as well as c 0 / a 0 ratio with CaTiO 3 content, which are in accordance with the substitution of smaller sized Ca 2+ ions at the barium sites. The microstructure as well as the dielectric properties are greatly influenced by the cationic ratio, α =(Ba+Ca)/Ti. The grain size decreases with CaTiO 3 content for the stoichiometric samples ( α =1), whereas ultrafine microstructure is observed in the case of off-stoichiometric samples ( α >1) for the whole compositional range of CaTiO 3 concentrations. Sharper e r – T characteristics at lower calcium content and broader e r – T with decreased e max , in the higher calcium range are observed in the case of α =1. Whereas nanometer grained ceramics exhibiting diffuse e r – T characteristics are obtained in the case of α >1. The positive temperature coefficient of resistivity (PTCR) is realized for barium calcium titanate ceramics having 0.3 at.% Sb as the donor dopant for higher CaTiO 3 (typically 30 mol%) containing samples ( α =1), indicating that Ca 2+ ions do not behave as acceptors if they were to substitute at the Ti 4+ sites. Whereas the off-stoichiometric ( α >1) ceramics retained high resistivity, indicative of the Ti-site occupancy for Ca 2+ in fine grain ceramics.

Zinc oxide nano particles can be synthesized using a simple solvent free, economic and eco friendly combustion method. The structural characterization of synthesized nano particles are carried out using XRD and SEM. The optical characterization was carried out using UV and Photoluminescence spectrofluorimeter. The XRD result shows that the nano particles are of hexagonal shape and the average crystal size of the Zinc oxide nano particle is in the range of 70 nm. The SEM analysis shows that the shape of the nano particles is of nano rods. The quality and purity of the Zinc oxide nano particles are confirmed using XRD and EDAX spectral analysis.

A simple, sensitive and rapid, high-performance liquid chromatography (HPLC) method has been developed for the simultaneous determination of cardiolipin, cholesterol and egg phosphatidylcholine from lyophilized lipid formulations. The proposed HPLC method utilizes a μPorosil column (300×3.9 mm I.D., 10 μm) and UV detection at 205 nm. A good resolution was observed with a mobile phase of water-methanol-acetonitrile (5:70:25) at a flow-rate of 2 ml/min. This method is capable of measuring levels of about 0.2–0.8 mg/ml of cardiolipin, 0.25–1.0 mg/ml of cholesterol and 0.8–3.2 mg/ml of egg phosphatidylcholine (EPC). The proposed analytical method has been validated according to USP compliance standards for accuracy, precision and reproducibility and thus may be employed for routine analysis of the lipid components from a typical placebo liposomal formulation.

Oxalate, the major renal stone forming constituent, from dietary sources like - spinach, rhubarb, strawberries, tea etc., has been reported to induce lipid peroxidation and alter the lipid profiles. Physiological availability or biosynthesis of DL α-lipoic acid, a shadow nutrient, from arachidonic acid is diminished when health is impaired. DL α-lipoic acid has been reported to counteract calcium oxalate crsytallisation in renal tubules of dogs. DL α-lipoic acid, apart from its antilipemic action, has been reported to exert its therapeutic effect in pathologies where free radicals are involved. This motivated us to study the role of this nutrient in relation to lipids, lipoproteins and lipid peroxidative changes in blood of calcium oxalate stone forming rats. Serum cholesterol, triglycerides and phospholipids were significantly increased in the calculogenic rats. Lipoate treatment decreased the cholesterol and triglyceride levels in both controls and stone forming rats. In contrast, phospholipid level remained unchanged in both controls and stone formers with lipoate administration. In the calculogenic rats, the LDLHDL cholesterol ratio showed no change whereas with lipoate administration there was a decrease in the treated groups. An increase in lipid peroxidation and superoxide dismutase activity associated with a decrease in catalase activity and reduced glutathione levels, were observed in the erythrocytes of stone forming rats. There was a pronounced decrease in peroxidation levels and an increase in antioxidant status in the lipoate treated rats. The antilithic, antilipemic and antioxidant effect of DL α-lipoic acid paves way for its therapeutic effectiveness in urolithiasis.

Certain biochemical constituents were analysed in small intestinal tract tissues of rats fed a normal and a calculi-producing diet. Changes were seen in calculogenic rats with respect to the carbohydrate and sialic acid residues of glycoproteins along with some lipid fractions. Treatment with Crataeva nurvala bark decoction lowered levels of small intestinal (Na+,K+)-ATPases. The action of the decoction on the small intestinal tract seems to be mediated through (Na+,K+)-ATPases, which in turn may affect the transport of metabolites.

Background : Necrotizing enterocolitis (NEC) has been documented in up to 20% of infants after repair of gastroschisis and is responsible for significant morbidity. NEC is reported to occur up to 10 times more in preterm infants receiving standard formula compared with those who have been fed exclusively with breast milk. Does breast milk confer a similar protection against NEC in infants who have undergone surgery for gastroschisis? Methods : All newborns with gastroschisis delivered between 1990 and 1996 and treated in a single neonatal unit were analyzed retrospectively. Clinical data, details of feeding regimens, and episodes of definite NEC were recorded. Results : Of 60 infants with gastroschisis, 6 (10%) died but none had evidence of NEC. Of the remaining 54 infants, clinical and radiological signs of NEC developed in 8 (15%). All recovered with medical treatment including the three patients with recurrent episodes. NEC developed in none of the 12 babies exclusively fed with expressed breast milk (EBM) in contrast to 1 (5%) of the 19 who received both EBM and formula, and 7 (30%) of the 23 who were fed solely on formula. There was no significant difference in gestation, incidence of primary versus silo closure, or incidence of intestinal atresia/stenosis in those with NEC (n = 8) compared with those without (n = 46), but birth weight in the NEC group was lower. NEC was less likely to develop in infants who received EBM than those who were exclusively formula fed ( P Conclusion : After gastroschisis repair, feeding with maternal expressed breast milk may help to protect the infant from developing NEC.

Twenty five clinical isolates of high level gentamicin resistant Enterococcus faecalis were tested for their biofilm formation and pheromone responsiveness. The biofilm assay was carried out using microtiter plate method. Two isolates out of the 25 (8%) were high biofilm formers and 19 (76%) and four (16%) isolates were moderate and weak biofilm formers respectively. All the isolates responded to pheromones of E. faecalis FA2-2 strain. On addition of pheromone producing E. faecalis FA2-2 strain to these isolates, seven of 19 (37%) moderate biofilm formers developed into high biofilm formers. Similarly one of the 4 (25%) weak biofilm formers developed into high level biofilm former. Twelve (48%) of the 25 isolates were transconjugated by cross streak method using gentamicin as selective marker. This proves that the genetic factor for gentamicin resistance is present in the pheromone responsive plasmid. Among these twelve transaconjugants, seven isolates and one isolate were high biofilm formers on addition of E. faecalis FA2-2 and prior to its addition respectively. Out of the total 25 isolates, eight transconjugants for gentamicin resistance could turn to high biofilm formers on addition of the pheromone producing strain. All the isolates were resistant to more than two antibiotics tested. All the isolates were sensitive to vancomycin. The results indicate the significance of this nosocomial pathogen in biofilm formation and the role of pheromone responding clinical isolates of E. faecalis in spread of multidrug resistance genes.