Her village: experiences of drug-involved women in a female-only aftercare program in the Philippines.

PURPOSE: Women are exposed to vulnerabilities that can lead to drug use or hinder recovery. However, there is a dearth of studies on recovery programs for women. This study aims to add to the literature by examining the feasibility of a women-only aftercare program for recovering users in the Philippines. DESIGN/METHODOLOGY/APPROACH: The study used a mixed-method design with pre and post-program surveys used to measure changes in participants' recovery capital. Focused group discussions elicited participants' context, their reactions, perceived outcomes and suggestions on the program. FINDINGS: Women in the program shared narratives of pain, trauma and abuse before treatment. Participants reported significant improvements in personal, community and family recovery capital dimensions. The program enabled personal growth in the form of new knowledge, skills and self-confidence. The women-only program also provided a safe space for women, to receive support from other women, community members and family. However, the women continue to face continuing challenges related to stigma and discrimination and a lack of livelihood opportunities. RESEARCH LIMITATIONS/IMPLICATIONS: A limitation of the study was its small sample size and the lack of a control group. Another limitation was the variability in treatment received by the women, which could have affected overall outcomes. Future studies using a randomized control trial and longitudinal designs may provide more robust conclusions on the effectiveness of the program. PRACTICAL IMPLICATIONS: Given punitive contexts, gender-sensitive and trauma-informed programs and services for women involved in drug use could potentially mitigate the abuse, stigma and vulnerabilities they experience. ORIGINALITY/VALUE: This study contributes to the sparse literature on women-only aftercare, particularly in countries that criminalize drug use.

Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials.

Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.

A concomitant and complete set of nonvolatile all-optical logic gates based on hybrid spatial solitons.

We theoretically demonstrate the realization of a complete canonical set of all-optical logic gates (AND, OR, NOT), with a persistent (stored) output, by combining propagative spatial solitons in a photorefractive crystal and dissipative cavity solitons in a downstream broad-area vertical cavity surface emitting laser (VCSEL). The system uses same-color, optical-axis aligned input and output channels with fixed readout locations, while switching from one gate to another is achieved by simply varying the potential applied to the photorefractive crystal. The inputs are Gaussian beams launched in the photorefractive crystal and the output is a bistable, persistent soliton in the VCSEL with a 'robust' eye diagram and large signal-to-noise ratio (SNR). Fast switching and intrinsic parallelism suggest that high bit flow rates can be obtained.

Observation of electro-activated localized structures in broad area VCSELs.

We demonstrate experimentally the electro-activation of a localized optical structure in a coherently driven broad-area vertical-cavity surface-emitting laser (VCSEL) operated below threshold. Control is achieved by electro-optically steering a writing beam through a pre-programmable switch based on a photorefractive funnel waveguide.

Adherence and genotypic drug resistance mutations in HIV-1-infected patients failing current antiretroviral therapy.

The aim of this study was to assess the correlation between the estimated adherence of HIV-1 infected patients with antiretroviral (ARV) therapy failure and drug-resistant mutations. We studied 40 patients with virological and immunological ARV-therapy failure. In order to assess the adherence of patients we used the SERAD questionnaire. Genomic sequencing of the HIV-1 pol gene was performed. 100% adherence was reported by 27 patients (67.5%) (adherent patients). Multivariate analysis showed that only baseline and nadir CD4+ counts maintained a significant correlation with the adherence. For PR and NNRTI mutations, we did not find any difference between the two groups of patients. Baseline NRTI mutations were higher in adherent patients than in non-adherent patients (p<0.05). No differences were found between plasma mutations and PBMC mutations. The authors conclude that genotypic resistance mutations were found in the majority of patients with ARV-therapy failure despite a good self-reported adherence to therapy. Adequate adherence to therapy is not the only key factor in viral suppression.

Multistability at arbitrary low optical intensities in a metal-dielectric layered structure.

We show that a nonlinear metal-dielectric layered slab of subwavelength thickness and very small average dielectric permittivity displays optical multistable behavior at arbitrary low optical intensities. This is due to the fact that, in the presence of the small linear permittivity, one of the multiple electromagnetic slab states exists no matter how small is the transmitted optical intensity. We prove that multiple states at ultra-low optical intensities can be reached only by simultaneously operating on the incident optical intensity and incidence angle. By performing full wave simulations, we prove that the predicted phenomenology is feasible and very robust.

Bud and Root Rot of Windmill Palm (Trachycarpus fortunei) Caused by Simultaneous Infections of Phytophthora palmivora and P. nicotianae in Sicily.

In June 2009 in a commercial nursery in eastern Sicily (Italy), 3-year-old potted windmill palms (Trachycarpus fortunei (Hooker) H. Wendl.) showed a decline in growth, wilt, droop, and basal rot of the youngest leaves. The rot progressed inward and killed the bud. Initially, older leaves remained green but eventually the entire plant collapsed. Root rot was consistently associated with aboveground symptoms. Two Phytophthora species were consistently isolated from the petiole base, heart, roots, and rhizosphere soil of symptomatic plants on a selective medium (2) and occasionally recovered from roots and rhizosphere soil of asymptomatic plants. Pure cultures were obtained by single-hypha transfers and the two species were identified on the basis of morphological and molecular characters as Phytophthora palmivora and P. nicotianae. Both species were recovered from all symptomatic plants. From multiple tissue samples per plant, we recovered either or both species. On potato dextrose agar (PDA), P. palmivora isolates grew between 10 and 35°C, with the optimum at 27°C. On V8 juice agar, they produced elliptical to ovoid, papillate, caducous sporangia (32 to 78 × 23 to 39 µm) with a mean length/breadth (l/b) ratio of 1.8:1 and a short pedicel (mean pedicel length = 5 µm). Isolates of P. nicotianae produced arachnoid colonies on PDA, grew at 37°C but did not grow at 40°C. Sporangia (29 to 55 × 23 to 45 µm) were spherical to ovoid (l/b ratio 1.3:1), papillate and often bipapillate, and noncaducous. Isolates of both species produced amphigynous antheridia and oogonia only when paired with reference isolates of P. nicotianae of the A2 mating type. The internal transcribed spacer (ITS) region of rDNA of two isolates of P. palmivora (IMI 398987 and IMI 398988) and an isolate of P. nicotianae (IMI 398989) from T. fortunei was amplified with primers ITS6/ITS4 and sequenced (1). Blast analysis of the sequences of isolates IMI 398987 and IMI 398988 (GenBank Accession Nos. HQ596556 and HQ596558) showed 99% homology with the sequence of two reference isolates of P. palmivora (GQ398157.1 and GU258862), while the sequence of isolate IMI 398989 (HQ596557) showed 99% homology with a reference isolate of P. nicotianae (EU331089.1). Pathogenicity of isolates IMI 398987 and IMI 398989 was proved by inoculating separately each isolate on 1-year-old potted plants of T. fortunei (10 plants per isolate). A zoospores suspension (2 × 104 zoospores/ml) was pipetted onto the petiole base of the three central leaves (200 µl per leaf) of each plant. Sterile water was used for control plants. All plants were incubated at 25 ± 2°C with 100% humidity for 48 h and then maintained in a greenhouse at 24 to 28°C. Within 3 weeks, all inoculated plants showed symptoms of bud rot. Control plants remained healthy. P. palmivora and P. nicotianae were reisolated only from inoculated plants. Bud rot of palms caused by P. palmivora was reported previously in Italy (3). However, to our knowledge, this is the first report of simultaneous infections of P. palmivora and P. nicotianae as causal agents of this disease. Outbreak of bud rot may have been favored by overhead sprinkler irrigation. The recovery of P. palmivora and P. nicotianae from rhizosphere soil and roots of asymptomatic plants suggests infested soil was the primary inoculum source. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) H. Masago et al. Phytopathology 67:425, 1977. (3) A. Pane et al. Plant Dis. 91:1059, 2007.

First Report of Root and Basal Stem Rot Caused by Phytophthora nicotianae on Tree Aeonium (Aeonium arboreum) in Italy.

The genus Aeonium, family Crassulaceae, comprises approximately 35 species that are native to northern Africa and the Canary Islands. Tree aeonium (Aeonium arboreum (L.) Webb & Berthel.) is a bushy, perennial succulent with rosettes of tender, waxy leaves at the apex of few-branched or occasionally single, naked stems. Mature rosettes bear yellowish inflorescences. Aeoniums are cultivated as ornamentals in gardens and containers. During the summer of 2009, in a garden in eastern Sicily (southern Italy), 3-year-old potted plants of tree aeonium showed stunting, shrivelling, and chlorosis of leaves and drop of external leaves associated with root and basal stem rot. Drops of an amber exudate oozed from the basal stem. Tissues of the basal stem were soft, but no external necrosis was visible. A species of Phytophthora was consistently isolated from symptomatic roots and basal stem tissues on a medium selective for Oomycetes (2). Axenic cultures were obtained by single-hypha transfers. The pathogen was identified by morphological criteria as Phytophthora nicotianae B. de Haan; it formed stoloniferous colonies on potato dextrose agar and grew between 8 and 38°C, with the optimum at 30°C. On V8 juice agar it produced spherical, intercalary chlamydospores (mean diameter of 26 µm) and persistent, mono- and bipapillate, spherical to ovoid, ellipsoid, obpyriform sporangia that measured 29 to 56 × 22 to 45 µm with a mean length/breadth ratio of 1.3:1. All isolates were A2 mating type and formed spherical oogonia (mean diameter 28 ± 2 µm) with smooth walls and amphigynous antheridia in dual cultures with a reference isolate of the A1 mating type of P. nicotianae. BLAST analysis of the internal transcribed spacer (ITS) region of rDNA of a representative isolate from aeonium (IMI 398812, GenBank Accession No. HQ433333) amplified by PCR using the ITS6/ITS4 universal primers (1), revealed 99% similarity with the sequences of a reference isolate of P. nicotianae available in GenBank (Accession No. EU331089.1). Pathogenicity of isolate IMI 398812 was demonstrated by transplanting cuttings of A. arboreum into pots filled with a mixture of steam-sterilized sandy loam soil and inoculum (4% vol/vol) produced by growing the isolate for 20 days on wheat kernels. Ten plants were transplanted into 3-liter pots (two plants per pot) while 10 plants, transplanted into pots filled with a mixture of steam-sterilized soil and noninoculated kernels, were used as controls. Plants were kept in a greenhouse at 25 to 28°C and watered daily to field capacity. Thirty to forty days after the transplanting into infested soil, cuttings developed the same symptoms observed on plants with natural infections. Control plants remained symptomless. P. nicotianae was reisolated from symptomatic plants, thereby completing Koch's postulates. To our knowledge, this is the first report of P. nicotianae on an Aeonium species worldwide. The economic relevance of this disease is minor because aeoniums are not cultivated on a large scale. Moreover, the disease may be easily prevented by avoiding excess irrigation water since aeoniums need a well-drained soil or potting mix and do not tolerate soil waterlogging. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) H. Masago et al. Phytopathology 67:425, 1977.

Transmissivity directional hysteresis of a nonlinear metamaterial slab with very small linear permittivity.

We investigate propagation of a transverse magnetic field through a nonlinear metamaterial slab of subwavelength thickness and with a very small and negative linear dielectric permittivity. We prove that, for a given input intensity, the output intensity is a multivalued function of the field incidence angle so that the transmissivity exhibits angular multistability and a pronounced directional hysteresis behavior. The predicted directional hysteresis is a consequence of the fact that the linear and nonlinear contributions to the overall dielectric response can be comparable so that the electromagnetic matching conditions at the output slab boundary allow more than one field configuration within the slab to be compatible with the transmitted field.

Highly nonparaxial (1+1)-D subwavelength optical fields.

A general approach for describing (1+1)-D subwavelength optical field whose waist is much smaller than the wavelength is presented. Exploiting the vectorial Rayleigh-Sommerfeld diffraction theory, a suitable expansion in the ratio between the beam waist and the wavelength allows us to prove the a (1+1)D highly nonparaxial field is generally the product of a cylindrical wave carrier and an envelope which is angularly slowly varying. We apply our general approach to the case of highly nonparaxial Hermite-Gaussian beams whose description is fully analytical.

Transverse power flow reversing of guided waves in extreme nonlinear metamaterials.

We theoretically prove that electromagnetic beams propagating through a nonlinear cubic metamaterial can exhibit a power flow whose direction reverses its sign along the transverse profile. This effect is peculiar of the hitherto unexplored extreme nonlinear regime where the nonlinear response is comparable or even greater than the linear contribution, a condition achievable even at relatively small intensities. We propose a possible metamaterial structure able to support the extreme conditions where the polarization cubic nonlinear contribution does not act as a mere perturbation of the linear part.

Root and Basal Stem Rot of Mandevillas Caused by Phytophthora spp. in Eastern Sicily.

Approximately 150,000 potted mandevillas (Apocynaceae) are produced each year in the Etna District of eastern Sicily. Since 2004, leaf chlorosis, wilt, and sudden collapse of the entire plant associated with root and basal stem rot of 6- to 12-month-old potted mandevillas, including Mandevilla × amabilis 'Alice du Pont', M. splendens, and M. sanderi 'Alba', 'My Fair Lady', and 'Scarlet Pimpernel', have been observed in six nurseries. Incidence of affected plants varied from 5 to 40%. Four Phytophthora species were consistently isolated from rotted roots and stems on a selective medium (2). Pure cultures of the first species produced colonies with a camellia pattern on potato dextrose agar and grew between 10 and 37°C with an optimum of 27°C. On V8 juice agar they produced ellipsoid to obpyriform (length/breadth [l/b] 1.45:1), nonpapillate sporangia with internal proliferation, coralloid, spherical hyphal swellings and both terminal and intercalary chlamydospores. In dual cultures with A1 and A2 isolates of P. nicotianae, all isolates produced oogonia with amphyginous antheridia only with A2 isolates. Isolates of the second species formed petaloid colonies, had an optimum growth temperature of 25°C, and produced mono- and bipapillate, ovoid to limoniform sporangia (l/b 1.40:1); they did not produce gametangia. Isolates of the third species formed colonies with a slight petaloid pattern and grew between 2 and 30°C with an optimum of 25°C. Sporangia were obpyriform (l/b 1.48:1), nonpapillate, and proliferous. All isolates were A2 mating type. The isolates of the fourth species formed arachnoid colonies, grew between 8 and 38°C with an optimum of 30°C, and produced mono- and bipapillate, ellipsoid, and obpyriform (l/b 1.3:1) sporangia and apical chlamydospores. All isolates were A2 mating type. DNA was extracted from mycelium and amplified by PCR using the ITS 4/ITS 6 primers (1). Blast search of the rDNA-ITS sequence of isolate IMI 397618 (GenBank Accession No. GQ388261) of the first species showed 100% identity with the ITS sequence of an isolate of P. cinnamomi var. parvispora (EU748548). The sequences (GQ463703 and GQ463704) of isolates IMI 397471 and IMI 397472 of the second species showed 99% similarity with the sequences of a P. citrophthora isolate (EU0000631). The sequence of isolate IMI 397473 (GQ463702) of the third species showed 99% similarity with the sequence of a P. cryptogea isolate (AY659443.1), while the sequence of isolate IMI 397474 (GU723474) of the fourth species showed 99% similarity with the sequence of a P. nicotianae isolate (EU331089). The pathogenicity of individual isolates IMI 397618, IMI 397471, IMI 397472, IMI 397473, and IMI 397474 was tested on 3-month-old potted plants (10 plants per isolate) of mandevilla 'Alice du Pont' by applying 10 ml of a suspension (2 × 104 zoospores/ml) to the root crown. Plants were maintained at 25°C and 95 to 100% relative humidity. All inoculated plants wilted after 4 weeks, while noninoculated control plants remained healthy. The four Phytophthora spp. were subsequently reisolated only from symptomatic plants. To our knowledge, this is the first report of P. cinnamomi var. parvispora in Italy and on mandevilla worldwide. In recent years, Phytophthora root and stem rot has become the most serious disease of potted mandevillas in Sicily. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) H. Masago et al. Phytopathology 67:425, 1977.

Light-induced dielectric structures and enhanced self-focusing in critical photorefractive ferroelectrics.

We consider the nonlinear dynamics occurring when an optical beam couples to dielectric material polarization in an unbiased photorefractive crystal undergoing a ferroelectric phase transition. The polarization profile produced by the light-induced electric field is evaluated by means of the Landau-Ginzburg approach and is found to manifest new thermodynamical states with their own specific nonlinear optical effects. We show that a temperature T(C), lower than the critical one, exists such that (a) if T>T(C) the optical beam experiences an increasing self-focusing for decreasing temperatures and (b) if T

Collision and fusion of counterpropagating micrometer-sized optical beams in periodically biased photorefractive crystals.

We theoretically investigate collision of optical beams traveling in opposite directions through a centrosymmetric photorefractive crystal biased by a spatially periodic voltage. We analytically predict the fusion of counterpropagating solitons in conditions in which the applied voltage is rapidly modulated along the propagation axis, so that self-bending is suppressed by the "restoring symmetry" mechanism. Moreover, when the applied voltage is slowly modulated, we predict that the modified self-bending allows conditions in which the two beams fuse together, forming a curved light-channel splice.

Callistemon citrinus and Cistus salvifolius, Two New Hosts of Phytophthora taxon niederhauserii in Italy.

Bottlebrush (Callistemon citrinus (Curtis.) Skeels., Myrtaceae) and rock rose (Cistus salvifolius L., Cistaceae) are evergreen shrubs native to Australia and the Mediterranean Region, respectively. In the spring of 2003, approximately 2% of a nursery stock of 12-month-old potted plants of C. citrinus and 8% of a nursery stock of 12-month-old potted plants of Cistus salvifolius grown in the same nursery in Sicily, showed symptoms of leaf chlorosis, defoliation, and wilt associated with root and collar rot. A Phytophthora species was consistently isolated from roots and basal stems on BNPRAH selective medium (2). One isolate from rock rose (IMI 391708) and one from bottlebrush (IMI 391712) were characterized. On potato dextrose agar (PDA), the colonies showed stoloniform mycelium and irregular margins; on V8 juice agar (V8A), colonies were stellate to radiate. Minimum and maximum temperatures on PDA were 10 and 35°C, respectively, with the optimum at 30°C. Mean radial growth rate of isolates on this substrate was 9.9 and 11.3 mm/day, respectively. In saline solution (1), both isolates produced catenulate hyphal swellings and ellipsoid, nonpapillate, persistent sporangia with internal proliferations and dimensions of 52 to 70 × 30 to 42 µm and 51 to 85 × 39 to 45 µm. Mean l/b ratio of sporangia for both isolates was 1.8 ± 1. On V8A plus ß-sytosterol, both isolates produced amphyginous antheridia and spherical oogonia in dual cultures with an A2 tester of P. drechsleri Tucker. Conversely, they did not produce gametangia with an A1 tester of P. cryptogea Pethybr., indicating they were A1 mating type. The internal transcribed spacer (ITS)-rDNA sequences of rock rose and bottlebrush isolates showed 100% similarity with those of two reference isolates of P. taxon niederhauserii from GenBank (Accession Nos. FJ648808 and FJ648809). On the basis of the analysis of the DNA, the species isolated from bottlebrush and rock rose were identified as Phytophthora taxon niederhauserii. Pathogenicity tests were carried out on 6-month-old potted plants of C. salvifolius and C. citrinus (10 plants of each plant species for each isolate) transplanted into pots (12 cm in diameter) containing a mixture of 1:1 steam-sterilized, sandy loam soil (vol/vol) with 4% inoculum produced on autoclaved kernel seeds. Plants were maintained at 25 to 28°C and watered to soil saturation once a week. After 2 to 3 weeks, all inoculated plants developed symptoms identical to those observed on plants with natural infections. Ten control plants transplanted into pots containing noninfested soil remained healthy. P. taxon niederhauserii was reisolated solely from inoculated plants. To our knowledge, this is the first report of P. taxon niederhauserii on C. citrinus and C. salvifolius in Italy. This Phytophthora taxon has been reported recently on rock rose in Spain (3). References: (1) D. W. Chen and G. A. Zentmyer. Mycologia 62:397, 1970. (2) H. Masago et al. Phytopathology 67:425, 1977. (3) E. Moralejo et al. Plant Pathol. 58:100, 2009.

Phytophthora taxon niederhauserii, a New Root and Crown Rot Pathogen of Banksia spp. in Italy.

In the last 10 years, various species of Banksia (family Proteaceae) endemic to Australia have been introduced into Italy where cultivation as flower plants is expanding. In the spring of 2003, a decline associated with root and basal stem rot of 2- to 3-year-old plants of Banksia speciosa R. Br., B. baxteri R. Br., and B. prionotes Lindl. grown in the ground was observed in a commercial nursery in Liguria (northern Italy). Aboveground symptoms included leaf chlorosis and wilt. Plants collapsed within 1 to 2 weeks after the appearance of leaf symptoms. A Phytophthora species was consistently isolated from roots and basal stem on BNPRAH selective medium (3). On V8 juice agar (V8A), axenic cultures obtained by single hyphal transfers formed stellate to radiate colonies with aerial mycelium; on potato dextrose agar (PDA). the colonies showed stoloniform mycelium. Minimum and maximum growth temperatures on PDA and V8A were between 5 and 10°C and 38 and 40°C, respectively, with the optimum at 30°C on PDA (mean radial growth rate of 10 isolates ranged between 9.3 and 10.2 mm per day) and 25 to 30°C on V8A (14 mm per day). In saline solution and soil extract, all isolates produced catenulate hyphal swellings and ellipsoid, nonpapillate, persistent sporangia. Sporangia in saline solution varied from 47 to 70 × 30 to 44 µm (mean l/b ratio of 1.5). All isolates were A1 mating type and produced oogonia with amphyginous antheridia when paired with A2 mating type of P. drechsleri Tucker on V8A plus ß-sytosterol (3). The electrophoretic patterns of total mycelial proteins and two isozymes (esterase and malate dehydrogenase) (2) of all isolates from Banksia plants were identical, but distinct from the patterns of isolates of other Phytophthora species, including P. drechsleri, P. megasperma sensu stricto, and P. sojae. Internal transcribed spacer (ITS) regions of rDNA were amplified with primers ITS4/ITS6 and sequences of two isolates, IMI 393960 from B. speciosa and 466/03 from B. baxteri (GenBank Nos. FJ648808 and FJ648809), were 100% identical to sequences of isolates identified as Phytophthora taxon niederhauserii Z. G. Abad and J. A. Abad (GenBank Nos. AY550916, AM942765, and EU244850). Pathogenicity tests were performed on 1-year-old potted plants of B. speciosa with isolates IMI 393960 and 466/03. Twenty plants per each isolate were transplanted into 12-cm-diameter pots containing infested soil prepared by mixing steam-sterilized sandy loam soil with 1% of inoculum produced on autoclaved wheat kernels. Twenty control plants were grown in autoclaved soil mix. Plants were kept in the greenhouse with natural light at 25 ± 2°C and watered to field capacity weekly. All Banksia plants transplanted in infested soil showed symptoms of wilt, leaf chlorosis, and basal stem rot within 2 to 3 weeks. Noninoculated plants remained healthy. P. taxon niederhauserii was reisolated solely from inoculated plants. P. taxon niederhauserii has been reported recently from Banksia spp. in Australia (1), but to our knowledge this is the first report from Italy. P. taxon niederhauserii may represent a threat to the cultivation of many ornamentals including Cystus spp., English ivy, and laurel (4). References: (1) T. I. Burgess et al. Plant Dis. 93:215, 2009. (2) S. O. Cacciola et al. EPPO Bull. 20:47, 1990. (3) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (4) E. Moralejo et al. Plant Pathol, 58:100, 2009.

Wiggling and bending-free micron-sized solitons in periodically biased photorefractives.

Considering nonlinear optical propagation through photore-fractive crystals in which the bias voltage is periodically modulated along the propagation direction, we are able to identify the conditions in which a beam forms a soliton in a straight line down to micron-sized widths. The effect, which is numerically investigated considering the full (3+1)D spatio-temporal light-matter dynamics, emerges when the period of modulation of the bias is smaller than the beam diffraction length. In conditions in which the two scales are comparable, the soliton follows a characteristic wiggling trajectory, oscillating in response to the oscillating bias. The finding indicates a method to achieve highly miniaturized soliton-based photonic applications that do not require specific off-axis alignment.

Counterpropagating spatial solitons in reflection gratings with a longitudinally modulated Kerr nonlinearity.

We investigate quasi-Bragg-matched counterpropagating spatial solitons in a reflection grating in the presence of a longitudinally modulated Kerr nonlinearity. The physical interplay of linear reflection and Kerr self-focusing with the modulation in the nonlinearity yields a variety of elaborate self-action mechanisms. We first analytically predict the existence of symmetric soliton pairs supported by a pure Kerr-like effective nonlinearity. We then analytically derive two families of solitons, associated with the linear grating eigenmodes, supported by an effective "incoherent" Kerr-like coupling arising from the exact balance between the modulation in the nonlinearity and the Kerr interaction due to beam interference.

Counterpropagating nondiffracting beams through reflection gratings.

We investigate the counterpropagation of paraxial non-diffracting optical beams through a medium hosting a bulk reflection grating in the quasi-Bragg matching condition. The impact of the relative magnitude of the Bragg detuning parameter and the grating depth on the plane wave dispersion relation allows us to identify three distinct regimes where counterpropagation and interaction of nondiffracting beams show qualitatively different features, encompassing longitudinally invariant, periodic or exponential intensity profiles. In one of the identified regimes the dispersion relation is not monotonic and the consequent "longitudinal degeneracy" allows the investigation of new class of nondiffracting beams characterized by a double spectral ring profile.