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1.
Ann Ig ; 35(2): 136-148, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-35603971

RESUMO

Aim: To explore the reasons for Italian midwives' decision to migrate, and their lived professional and emotional experiences. Methods: A descriptive phenomenological study was conducted recruiting Italian midwives who were working abroad in European countries. We offered a telephone or web interview. Two researchers conducted, audio-recorded, and fully transcribed the interviews and other two researchers, independently, performed a content analysis. Results: Thirty-two midwives having professional experiences in the UK, Ireland, Germany, Switzerland, and Spain were interviewed. Five themes emerged: 1) Education, 2) Migration decision-making, 3) Professional experience abroad, 4) Midwives' perceptions of their role, 5) Satisfaction versus desire to return. Our findings show a general dissatisfaction with Italian job opportunities in terms both of access to employment and work conditions. This scenario is complicated by the status of the professional midwifery in Italy. Conclusion: Stakeholders should ensure that the migration of Italian midwives is not synonymous with dispersion but is a channel of professional growth and mutual exchange.


Assuntos
Tocologia , Enfermeiros Obstétricos , Gravidez , Humanos , Feminino , Enfermeiros Obstétricos/psicologia , Pesquisa Qualitativa , Europa (Continente) , Itália
2.
Adv Comput Math ; 47(4): 51, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34220169

RESUMO

We investigate the use of the so-called variably scaled kernels (VSKs) for learning tasks, with a particular focus on support vector machine (SVM) classifiers and kernel regression networks (KRNs). Concerning the kernels used to train the models, under appropriate assumptions, the VSKs turn out to be more expressive and more stable than the standard ones. Numerical experiments and applications to breast cancer and coronavirus disease 2019 (COVID-19) data support our claims. For the practical implementation of the VSK setting, we need to select a suitable scaling function. To this aim, we propose different choices, including for SVMs a probabilistic approach based on the naive Bayes (NB) classifier. For the classification task, we also numerically show that the VSKs inspire an alternative scheme to the sometimes computationally demanding feature extraction procedures.

3.
Food Chem Toxicol ; 153: 112247, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33951485

RESUMO

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium molds. Grain-based foods account for most human dietary exposures to OTA. OTA is a teratogen, but its reproductive and developmental effects are poorly understood. A one-generation reproductive toxicity study was conducted with groups of 16 male and 16 female Fischer rats exposed to 0, 0.026, 0.064, 0.16, 0.4 or 1.0 mg OTA/kg in diet. Dams exposed to 1.0 mg OTA/kg diet had statistically significant F1 pup losses between implantation and postnatal day (PND 4). Delays in preputial separation (PPS) and vaginal opening (VO) were indicative of delayed puberty in F1 rats. Mild renal lesions in nursing pups indicated that exposure prior to weaning impacted the kidneys. The developing kidney was more susceptible to OTA than the adult kidney. Significant increases in multi-oocyte follicles (MOFs) and proportional changes in resting and growing follicles were observed in F1 female ovaries. Plasma testosterone was reduced in F0 males, and there were negative effects on sperm quality in F0 and F1 male rats. The results confirm that continuous dietary exposure to OTA causes post-implantation fetotoxicity in dams, and renal and reproductive toxicity in their male and female offspring.


Assuntos
Blastocisto/efeitos dos fármacos , Infertilidade Feminina/induzido quimicamente , Infertilidade Masculina/induzido quimicamente , Nefropatias/induzido quimicamente , Ocratoxinas/toxicidade , Motilidade dos Espermatozoides/efeitos dos fármacos , Animais , Animais Lactentes , Bloqueadores dos Canais de Cálcio/toxicidade , Relação Dose-Resposta a Droga , Feminino , Masculino , Ocratoxinas/administração & dosagem , Folículo Ovariano/efeitos dos fármacos , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Ratos , Ratos Endogâmicos F344
4.
J Biol Regul Homeost Agents ; 34(4 Suppl. 1): 37-45. SPECIAL ISSUE: OZONE THERAPY, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33176416

RESUMO

The pathologies of the musculoskeletal apparatus are the most common cause of chronic diseases, with a huge impact on people and society. Scientific literature has discovered how experiencing chronic pain directly affects peoples' well-being, lifestyle, social relationships and can also cause psychological distress. The present study aims to investigate pain experience in patients with hernias or protrusions of the cervical and lumbosacral tract on a sample of 120 patients, recruited from patients of Poliambulatorio Oberdan, medical centre in Brescia (Italy) specialized in physical rehabilitation and CT-guided oxygen ozone therapy. In a bio-psychosocial perspective, the research aimed to investigate how the perception of pain, the mood state associated with it, the coping strategies adopted and the quality of life differ according to each patient's gender and to the more or less prolonged use of pain medication. The data were collected by means of medical and psychological anamnestic interviews and self-report tests (WHOQOL-BREF, COPE-NVI, POMS). The quantitative analysis, carried out through SPSS 25 (2017) software, showed how functional impairment of one's autonomy (walking, driving) affects mood states. In particular, the female sample expressed a more deflected mood, despite the greater use of relational and/or transcendent support (coping strategies) compared to men. The study suggests that the greater impairment of the moods of women can be attributed both to the caregiving role they play, which often results in a greater fatigue and difficulties in redefining this role following the algic condition, and more general differences in the expression of suffering, which, on a cultural level, sees men emotionally coerced. The analysis also shows how taking pain medication for a long period of time has a negative impact on the quality of life. The results suggest that the patients treated with analgesic therapy tend to adopt avoidant coping styles, which usually escalate into postponement of the time when dealing with a stressful situation and, if used in the long run, may lead to worsening health condition.


Assuntos
Adaptação Psicológica , Qualidade de Vida , Feminino , Humanos , Itália , Masculino , Fatores Sociológicos , Estresse Psicológico
6.
Artigo em Inglês | MEDLINE | ID: mdl-29875074

RESUMO

Mutations in germ cells pose potential genetic risks to offspring. However, de novo mutations are rare events that are spread across the genome and are difficult to detect. Thus, studies in this area have generally been under-powered, and no human germ cell mutagen has been identified. Whole Genome Sequencing (WGS) of human pedigrees has been proposed as an approach to overcome these technical and statistical challenges. WGS enables analysis of a much wider breadth of the genome than traditional approaches. Here, we performed power analyses to determine the feasibility of using WGS in human families to identify germ cell mutagens. Different statistical models were compared in the power analyses (ANOVA and multiple regression for one-child families, and mixed effect model sampling between two to four siblings per family). Assumptions were made based on parameters from the existing literature, such as the mutation-by-paternal age effect. We explored two scenarios: a constant effect due to an exposure that occurred in the past, and an accumulating effect where the exposure is continuing. Our analysis revealed the importance of modeling inter-family variability of the mutation-by-paternal age effect. Statistical power was improved by models accounting for the family-to-family variability. Our power analyses suggest that sufficient statistical power can be attained with 4-28 four-sibling families per treatment group, when the increase in mutations ranges from 40 to 10% respectively. Modeling family variability using mixed effect models provided a reduction in sample size compared to a multiple regression approach. Much larger sample sizes were required to detect an interaction effect between environmental exposures and paternal age. These findings inform study design and statistical modeling approaches to improve power and reduce sequencing costs for future studies in this area.


Assuntos
Variação Genética , Células Germinativas/patologia , Modelos Estatísticos , Mutagênicos , Mutação , Sequenciamento Completo do Genoma/métodos , Estudos de Casos e Controles , Biologia Computacional , Células Germinativas/metabolismo , Humanos , Taxa de Mutação , Linhagem , Fatores de Risco , Tamanho da Amostra
8.
Parkinsons Dis ; 2016: 7536862, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26977334

RESUMO

Aim. Recent evidence suggested that the use of treadmill training may improve gait parameters. Visual deprivation could engage alternative sensory strategies to control dynamic equilibrium and stabilize gait based on vestibulospinal reflexes (VSR). We aimed to investigate the efficacy of a blindfolded balance training (BBT) in the improvement of stride phase percentage reliable gait parameters in patients with Parkinson's Disease (PD) compared to patients treated with standard physical therapy (PT). Methods. Thirty PD patients were randomized in two groups of 15 patients, one group treated with BBT during two weeks and another group treated with standard PT during eight weeks. We evaluated gait parameters before and after BBT and PT interventions, in terms of double stance, swing, and stance phase percentage. Results. BBT induced an improvement of double stance phase as revealed (decreased percentage of double stance phase during the gait cycle) in comparison to PT. The other gait parameters swing and stance phase did not differ between the two groups. Discussion. These results support the introduction of complementary rehabilitative strategies based on sensory-motor stimulation in the traditional PD patient's rehabilitation. Further studies are needed to investigate the neurophysiological circuits and mechanism underlying clinical and motor modifications.

9.
Ann Ig ; 27(5): 705-10, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26661911

RESUMO

BACKGROUND: Antigens contained in vaccines are inherently unstable biologically; such a characteristic is conferred by their three-dimensional structure. Preserving the ability of the vaccines to protect against disease is necessary to ensure the supervision and monitoring of all steps of the cold chain. DTPa-HBV-IPV/Hib vaccine (Infanrix hexaTM, GSK Vaccines, Belgium) is designed to prevent disease due to diphtheria, tetanus, pertussis (DTP), hepatitis B virus (HBV), poliomyelitis and Haemophilus influenzae type b (Hib); it was first licensed for use in Europe in 2000 and is currently licensed in at least 95 countries. Since October 2013, more than 102 million doses of GSK's DTPa-HBV-IPV/Hib vaccine have been distributed globally, with nearly 15 million doses distributed in Italy. DTPa-HBV-IPV/Hib components are stable up to a temperature of 25°C for 72 hours. Lacking of officially approved stability data may generate some concern in case of cold chain accidents. METHODS: An analysis based on collected data was carried out to estimate potential costs attributable to events of "out-of-temperature" in the stockpiling of hexavalent vaccines occurring in Italy in 2014. RESULTS: The analysis, based on real data, documented that the loss for the National Health Service (NHS) was in the range of 100,000 - 400,000 euros in one year. However, the amount of money that in principle could have been lost would have ranged between nearly half and one million euros/year. CONCLUSIONS: A substantial loss of money was avoided thanks to the availability of officially approved stability data for GSK's DTPa-HBV-IPV/Hib vaccine.


Assuntos
Vacina contra Difteria, Tétano e Coqueluche/provisão & distribuição , Vacinas Anti-Haemophilus/provisão & distribuição , Vacinas contra Hepatite B/provisão & distribuição , Vacina Antipólio de Vírus Inativado/provisão & distribuição , Antígenos/imunologia , Custos e Análise de Custo , Vacina contra Difteria, Tétano e Coqueluche/economia , Vacina contra Difteria, Tétano e Coqueluche/imunologia , Estabilidade de Medicamentos , Armazenamento de Medicamentos/economia , Armazenamento de Medicamentos/normas , Vacinas Anti-Haemophilus/economia , Vacinas Anti-Haemophilus/imunologia , Vacinas contra Hepatite B/economia , Vacinas contra Hepatite B/imunologia , Humanos , Itália , Vacina Antipólio de Vírus Inativado/economia , Vacina Antipólio de Vírus Inativado/imunologia , Refrigeração , Vacinas Combinadas/economia , Vacinas Combinadas/imunologia , Vacinas Combinadas/provisão & distribuição
10.
Dalton Trans ; 44(33): 14887-95, 2015 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-26225470

RESUMO

Five new complexes Ln(Q(C17))3(H2O)(Solv) (Ln = Y, Solv = H2O, Ln = Tb, Dy, Sm or Eu, Solv = EtOH) were synthesized with the acylpyrazolonato ligand Q(C17) bearing a long aliphatic C17H35 chain in the acyl moiety, and the crystal structure of Y(Q(C17))3(H2O)2 shows the three aliphatic chains from the coordinated ligands positioned in the same direction, affording plane layers built by Y(Q(C17))3(H2O)2 molecules connected through H-bonding interactions. The layers are stitched to each other like in "hook & loop" tapes. Luminescence of complexes was determined and the complex Tb(Q(C17))3(H2O)(EtOH) was immobilized on the surface of silica preprocessed using a C17H35CONH(CH2)3Si(OEt)3 reagent via hydrophobic interactions of long aliphatic chains. Luminescent properties and micromorphology of the obtained hybrid particles and hybrid films were investigated. Intensive green emission of the complex retains after grafting onto the silica surface. Inclusion of the complex on the surface of silica materials occurs as separate molecules, after the disruption of the H-bonding network present in the crystalline phase of the pure terbium sample.


Assuntos
Compostos Organometálicos/química , Dióxido de Silício/química , Térbio/química , Acilação , Interações Hidrofóbicas e Hidrofílicas , Elementos da Série dos Lantanídeos/síntese química , Elementos da Série dos Lantanídeos/química , Ligantes , Luminescência , Modelos Moleculares , Compostos Organometálicos/síntese química , Pirazóis/síntese química , Pirazóis/química , Dióxido de Silício/síntese química
11.
Eur J Pain ; 19(7): 984-93, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25381898

RESUMO

BACKGROUND: This work summarizes the efficiency, failures and adverse effects of oral administration of ketamine at home for intractable pain. METHODS: This 5-year retrospective study involved testing ketamine by intravenous in-hospital administration, then a conversion to an oral route, or oral treatment directly administered at home. The daily intravenous dose was increased by steps of 0.5 mg/kg to attain an effective daily dose of 1.5-3.0 mg/kg. Pain was evaluated on a numeric scale from 0 to 10, and evidence of adverse effects was collected every day. The effective daily dose was delivered orally (three to four intakes). If effective, ketamine was continued for 3 months. Short infusions or direct oral treatment began with a 0.5-mg/kg dose, then the daily ketamine dose was increased in 15- to 20-mg increments. RESULTS: Among 55 cases (51 patients, neuropathic pain 60%), the mean effective oral dose was 2 mg/kg. Ketamine was effective in 24 patients (44%, mean pain reduction 67 ± 17%), partially effective in 20% (mean pain reduction 30 ± 11%), with a mean opioid sparing of 63 ± 32%, and failure in 22%. Half of the patients experienced adverse effects, but only eight had to stop treatment. For patients with opioid therapy, failure of ketamine was less frequent (7% vs. 36%; p < 0.02), with fewer adverse effects (33% vs. 68%; p < 0.01). CONCLUSIONS: Pain was reduced or abolished in two-thirds of patients under ketamine therapy; ketamine was effective for patients taking opioids and resulted in few adverse effects.


Assuntos
Anestésicos Dissociativos/uso terapêutico , Dor Crônica/tratamento farmacológico , Ketamina/uso terapêutico , Dor Intratável/tratamento farmacológico , Administração Intravenosa , Administração Oral , Adulto , Idoso , Analgésicos Opioides/administração & dosagem , Analgésicos Opioides/uso terapêutico , Anestésicos Dissociativos/administração & dosagem , Anestésicos Dissociativos/efeitos adversos , Feminino , Humanos , Ketamina/administração & dosagem , Ketamina/efeitos adversos , Masculino , Pessoa de Meia-Idade , Neuralgia/tratamento farmacológico , Medição da Dor/efeitos dos fármacos , Segurança do Paciente , Estudos Retrospectivos
12.
Phys Rev Lett ; 113(21): 216405, 2014 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-25479511

RESUMO

We consider the possible phases of microcavity polaritons tuned near a bipolariton Feshbach resonance. We show that, as well as the regular polariton superfluid phase, a "molecular" superfluid exists, with (quasi-)long-range order only for pairs of polaritons. We describe the experimental signatures of this state. Using variational approaches we find the phase diagram (critical temperature, density, and exciton-photon detuning). Unlike for ultracold atoms, the molecular superfluid is not inherently unstable, and our phase diagram suggests it is attainable in current experiments.

13.
Hum Reprod ; 29(10): 2148-55, 2014 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-25069502

RESUMO

STUDY QUESTION: Is there an association between human sperm sex chromosome disomy and sperm DNA damage? SUMMARY ANSWER: An increase in human sperm XY disomy was associated with higher comet extent; however, there was no other consistent association of sex chromosome disomies with DNA damage. WHAT IS KNOWN ALREADY: There is limited published research on the association between sex chromosome disomy and sperm DNA damage and the findings are not consistent across studies. STUDY DESIGN, SIZE, AND DURATION: We conducted a cross-sectional study of 190 men (25% ever smoker, 75% never smoker) from subfertile couples presenting at the Massachusetts General Hospital Fertility Clinic from January 2000 to May 2003. PARTICIPANTS/MATERIALS, SETTING, METHODS: Multiprobe fluorescence in situ hybridization for chromosomes X, Y and 18 was used to determine XX, YY, XY and total sex chromosome disomy in sperm nuclei using an automated scoring method. The neutral comet assay was used to measure sperm DNA damage, as reflected by comet extent, percentage DNA in the comet tail, and tail distributed moment. Univariate and multiple linear regression models were constructed with sex chromosome disomy (separate models for each of the four disomic conditions) as the independent variable, and DNA damage parameters (separate models for each measure of DNA damage) as the dependent variable. MAIN RESULTS AND THE ROLE OF CHANCE: Men with current or past smoking history had significantly greater comet extent (µm: regression coefficients with 95% CI) [XX18: 15.17 (1.98, 28.36); YY18: 14.68 (1.50, 27.86); XY18: 15.41 (2.37, 28.45); Total Sex Chromosome Disomy: 15.23 (2.09, 28.38)], and tail distributed moment [XX18: 3.01 (0.30, 5.72); YY18: 2.95 (0.24, 5.67); XY18: 3.04 (0.36, 5.72); Total Sex Chromosome Disomy: 3.10 (0.31, 5.71)] than men who had never smoked. In regression models adjusted for age and smoking, there was a positive association between XY disomy and comet extent. For an increase in XY disomy from 0.56 to 1.47% (representing the 25th to 75th percentile), there was a mean increase of 5.08 µm in comet extent. No other statistically significant findings were observed. LIMITATIONS, REASONS FOR CAUTION: A potential limitation of this study is that it is cross-sectional. Cross-sectional analyses by nature do not lend themselves to inference about directionality for any observed associations; therefore we cannot determine which variable is the cause and which one is the effect. A small sample size may be a further limitation. Comparison of these findings to other studies is limited due to methodological differences. WIDER IMPLICATIONS OF THE FINDINGS: Although consistent associations across sex chromosome disomies or DNA damage measures were not observed, this study highlights the need to explore etiologies of sperm DNA damage and sex chromosome disomy to better understand the potential mechanistic overlaps between the two. STUDY FUNDING/COMPETING INTERESTS: This work was supported by NIOSH Grant T42 OH008416, and NIH/NIEHS Grants ES 009718, ES 000002, and R01 ES017457. During the study M.E.M. was affiliated with the Department of Environmental Health at the Harvard School of Public Health. TRIAL REGISTRATION NUMBER: N/A.


Assuntos
Dano ao DNA , Aberrações dos Cromossomos Sexuais , Fumar , Adulto , Aneuploidia , Cromossomos Humanos X , Cromossomos Humanos Y , Ensaio Cometa , Estudos Transversais , Fragmentação do DNA , Humanos , Hibridização in Situ Fluorescente , Masculino , Análise de Regressão , Análise do Sêmen , Espermatozoides
14.
Biochimie ; 99: 146-52, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24316375

RESUMO

Curcumin, the main component of Curcuma longa, shows an anti-hyperglycemic effect and improved insulin sensitivity. This action may be attributed at least in part to its anti-inflammatory properties and also to its possible interaction with dipeptidyl peptidase-4 (DPPIV), the enzyme that the conversion of glucagon-like peptide-1 (GLP-1), responsible for glucose tolerance into inactive GLP-1. In this work we evaluated the inhibitory activities of a series of different arene-Ru(II)-curcumin complexes on bovine kidney dipeptidyl peptidase-4 (DPPIV). We studied also the interaction of these inhibitors on the enzyme with fluorescence studies displaying the binding poses with molecular docking studies. Specifically organometallic ruthenium(II) complexes of general formula [(η(6)-arene)Ru(curcuminato)Cl], with arene being p-(i)PrC6H4Me (1), C6H6 (2), and C6Me6 (3), were evaluated for their inhibition activity toward the mammalian enzyme. Among them, 2 suppressed DPPIV activities more potently (Ki = 20.2(±0.8) µM) than 1, 3, or free curcumin, and all complexes showed an antioxidant activity as free curcumin. As shown from our docking simulations a putative binding site of the compound 2 was found on subdomains S1 and S2 of DPP-IV, where S1 hydrophobic pocket includes catalytic residues and is the primary determinant of substrate specificity for the enzyme. Collectively, our results demonstrate that the complexation of curcumin with ruthenium(II) could be a promising starting point for the development of curcumin-based DPPIV inhibitors.


Assuntos
Complexos de Coordenação/química , Curcumina/análogos & derivados , Curcumina/química , Dipeptidil Peptidase 4/química , Inibidores da Dipeptidil Peptidase IV/química , Rutênio/química , Animais , Domínio Catalítico , Bovinos , Avaliação Pré-Clínica de Medicamentos , Sequestradores de Radicais Livres/química , Humanos , Cinética , Simulação de Acoplamento Molecular , Ligação Proteica , Estrutura Secundária de Proteína
16.
J Phys Condens Matter ; 24(23): 235802, 2012 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-22588118

RESUMO

We study the linear response of a coherently driven polariton fluid in the pump-only configuration scattering against a point-like defect and evaluate analytically the drag force exerted by the fluid on the defect. When the system is excited near the bottom of the lower polariton dispersion, the sign of the interaction-renormalised pump detuning classifies the collective excitation spectra into three different categories (Ciuti and Carusotto 2005 Phys. Status Solidi b 242 2224): linear for zero, diffusive-like for positive and gapped for negative detuning. We show that both cases of zero and positive detuning share a qualitatively similar crossover of the drag force from the subsonic to the supersonic regime as a function of the fluid velocity, with a critical velocity given by the speed of sound found for the linear regime. In contrast, for gapped spectra, we find that the critical velocity exceeds the speed of sound. In all cases, the residual drag force in the subcritical regime depends on the polariton lifetime only. Also, well below the critical velocity, the drag force varies linearly with the polariton lifetime, in agreement with previous work (Cancellieri et al 2010 Phys. Rev. B 82 224512), where the drag was determined numerically for a finite-size defect.

17.
Phys Rev Lett ; 108(14): 145304, 2012 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-22540805

RESUMO

We study the density instabilities of a two-dimensional gas of dipolar fermions with aligned dipole moments. The random phase approximation (RPA) for the density-density response function is never accurate for the dipolar gas, and so we incorporate correlations beyond RPA via an improved version of the Singwi-Tosi-Land-Sjölander scheme. In addition to density-wave instabilities, our formalism captures the collapse instability that is expected from Hartree-Fock calculations but is absent from RPA. Crucially, we find that when the dipoles are perpendicular to the layer, the system spontaneously breaks rotational symmetry and forms a stripe phase, in defiance of conventional wisdom.

18.
Phys Rev Lett ; 108(6): 065301, 2012 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-22401081

RESUMO

We study the properties of a binary microcavity polariton superfluid coherently injected by two lasers at different momenta and energies. The crossover from the supersonic to the subsonic regime, where motion is frictionless, is described by evaluating the linear response of the system to a weak defect potential. We show that the coupling between the two components requires that either both components flow without friction or both scatter against the defect, though scattering can be small when the two fluids are weakly coupled. By analyzing the drag force exerted on a defect, we give a recipe to experimentally address the crossover from the supersonic to the subsonic regime.

19.
Phys Rev Lett ; 109(26): 266407, 2012 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-23368594

RESUMO

We investigate the cross interactions in a two-component polariton quantum fluid coherently driven by two independent pumping lasers tuned at different energies and momenta. We show that both the hysteresis cycles and the on-off threshold of one polariton signal can be entirely controlled by a second polariton fluid. Furthermore, we study the ultrafast switching dynamics of a driven polariton state, demonstrating the ability to control the polariton population with an external laser pulse, in less than a few picoseconds.

20.
Phys Rev Lett ; 107(3): 036401, 2011 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-21838381

RESUMO

We study, both theoretically and experimentally, the occurrence of topological defects in polariton superfluids in the optical parametric oscillator (OPO) regime. We explain in terms of local supercurrents the deterministic behavior of both the onset and dynamics of vortex-antivortex pairs generated by perturbing the system with a pulsed probe. Using a generalized Gross-Pitaevskii equation, including photonic disorder, pumping and decay, we elucidate the reason why topological defects form in couples and can be detected by direct visualizations in multishot OPO experiments.

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