Quasinormal mode solvers for resonators with dispersive materials.

Optical resonators are widely used in modern photonics. Their spectral response and temporal dynamics are fundamentally driven by their natural resonances, the so-called quasinormal modes (QNMs), with complex frequencies. For optical resonators made of dispersive materials, the QNM computation requires solving a nonlinear eigenvalue problem. This raises a difficulty that is only scarcely documented in the literature. We review our recent efforts for implementing efficient and accurate QNM solvers for computing and normalizing the QNMs of micro- and nanoresonators made of highly dispersive materials. We benchmark several methods for three geometries, a two-dimensional plasmonic crystal, a two-dimensional metal grating, and a three-dimensional nanopatch antenna on a metal substrate, with the perspective to elaborate standards for the computation of resonance modes.

Electromagnetic analysis for optical coherence tomography based through silicon vias metrology.

This paper reports on progress in the analysis of time-domain optical coherence tomography (OCT) applied to the dimensional metrology of through-silicon vias (TSVs), which are vertical interconnect accesses in silicon, enabling three-dimensional (3D) integration in microelectronics, and estimates the deviations from earlier, simpler models. The considered TSV structures are 1D trenches and circular holes etched into silicon with a large aspect ratio. As a prerequisite for a realistic modeling, we work with spectra obtained from reference interferograms measured at a planar substrate, which fully includes the dispersion of the OCT apparatus. Applying a rigorous modal approach, we estimate the differences to a pure ray tracing technique. Accelerating our computations, we focus on the relevant fundamental modes and apply a Fabry-Perot model as an efficient approximation. Exploiting our results, we construct and present an iterative procedure based on the minimization of a merit function, which concludes TSV heights reliably, accurately, and rapidly from measured interferograms.

The prevalence of healthcare-associated infection in medical intensive care units in Tunisia. Results of the multi-centre nosorea1 study.

OBJECTIVES: To determine the prevalence of Healthcare-Associated Infection (HAI) in medical Intensive Care Unit (ICU), risk factors for these infections and identify the predominant infecting organisms. METHODS: A 1-day point-prevalence study within all medical ICUs in Tunisia, all patients occupying an ICU bed over a 48-hour period were included. Rates of HAI, resistance patterns of microbiological isolates and potential risk factors for HAI were recorded. RESULTS: One hundred and three patients were collected from 15 Tunisian medical ICUs. HAI prevalence was 25.2% CI 95% [15-35].The most frequent HAIs were hospital acquired pneumonia in 19 cases (59%) and catheter related infection in 5 cases (15%). Independent factors associated with HAI occurrence were SAPSII score ≥ 33 with OR 1.047; CI 95% [1.015-1.077], p=0.003 and recent hospitalization with OR 4.14 CI 95% [1.235-13.889], p=0.021. Non-fermenting pathogens were the most frequent microorganisms reported in ICUs ecology, prior colonization and HAIs of the screened patients. CONCLUSION: HAIs are frequent in medical ICUs in Tunisia, which emphasize the importance of specific measures for surveillance and infection control in critically ill patients. Implementing a national monitoring system of HAI should be a major priority of public health in Tunisia.

Coherent Scattering of Near-Resonant Light by a Dense Microscopic Cold Atomic Cloud.

We measure the coherent scattering of light by a cloud of laser-cooled atoms with a size comparable to the wavelength of light. By interfering a laser beam tuned near an atomic resonance with the field scattered by the atoms, we observe a resonance with a redshift, a broadening, and a saturation of the extinction for increasing atom numbers. We attribute these features to enhanced light-induced dipole-dipole interactions in a cold, dense atomic ensemble that result in a failure of standard predictions such as the "cooperative Lamb shift". The description of the atomic cloud by a mean-field model based on the Lorentz-Lorenz formula that ignores scattering events where light is scattered recurrently by the same atom and by a microscopic discrete dipole model that incorporates these effects lead to progressively closer agreement with the observations, despite remaining differences.

Broad working bandwidth and "endlessly" single-mode guidance within hybrid silicon photonics.

The successes of nonlinear photonics and hybrid silicon photonics with a growing variety of functional materials entail ever-enlarging bandwidths. It is best exemplified by parametric comb frequency generation. Such operation challenges the dielectric channel waveguide as the basis for guidance, because of the adverse advent of higher order modes at short wavelengths. Surprisingly, the popular mechanism of endlessly single-mode guidance [Opt. Lett.22, 961 (1997).] operating in photonic crystal fibers has not been transposed within silicon photonics yet. We outline here the strategy and potential of this approach within planar and hybrid silicon photonics, whereby in-plane and vertical confinement are shown to be amenable to near-single-mode behavior in the typical silicon band, i.e., λ=1.1 µm to ∼5 µm.

Coinfection with Mycobacterium tuberculosis and Pneumocystis Jirovecii in immunocompetent young woman.

Pneumocystis pneumonia is a severe opportunistic infection in immunocompromised patients, caused by Pneumocystis jirovecii (P. jirovecii). The co-infection with community-acquired P. jirovecii and Mycobacterium tuberculosis (M. tuberculosis) is exceptionally described in non immunocompromised patients. We herein report the case of a young woman, with no medical history, who developed an acute respiratory failure due to P. jirovecii pneumonia associated with miliary tuberculosis. An extensive immunological investigation ruled out any acquired or primary immunodeficiency, suggesting that she was most likely immunocompetent. This report shows that such infections are not restricted to immunocompromised hosts. Moreover, it is tempting to speculate that the development of M. tuberculosis infection in this patient could be a risk factor for transition from colonization status of respiratory tract by P. jirovecii to pneumocystosis.

Metal-coated nanocylinder cavity for broadband nonclassical light emission.

A novel metal-coated nanocylinder-cavity architecture fully compatible with III-V GaInAs technology and benefiting from a broad spectral range enhancement of the local density of states is proposed as an integrated source of nonclassical light. Because of a judicious selection of the mode volume, the cavity combines good collection efficiency (≈45%), large Purcell factors (≈15) over a 80 nm spectral range, and a low sensitivity to inevitable spatial mismatches between the single emitter and the cavity mode. This represents a decisive step towards the implementation of reliable solid-state devices for the generation of entangled photon pairs at infrared wavelengths.

Prediction improvement of potential PV production pattern, imagery satellite-based.

The results obtained by using an existing model to estimate global solar radiation (GHI) in three different locations in Tunisia. These data are compared with GHI meteorological measurements and PV_Gis satellite imagery estimation. Some statistical indicators (R, R2, MPE, AMPE, MBE, AMBE and RMSE) have been used to measure the performance of the used model. Correlation coefficient for the different stations was close to 1.0. The meteorology and satellite determination coefficient (R2) were also near 1.0 except in the case of Nabeul station in which the meteorology measurements (R) were equals to 0.5848 because of the loss of data in this location due to meteorological conditions. This numerical model provides the best performance according to statistical results in different locations; therefore, this model can be used to estimate global solar radiation in Tunisia. The R square values are used as a statistical indicator to demonstrate that the model's results are compatible with those of meteorology with a percentage of error less than 10%.

[Radiotherapy in the treatment of retinoblastoma: about 40 cases]. / Place de la radiothérapie dans le traitement du rétinoblastome : à propos de 40 cas.

PURPOSE: The aim of this study is to analyze the results and the complications of radiotherapy in the treatment of retinoblastoma. PATIENTS AND METHODS: Between 1994 and 2004, 40 children received radiotherapy for a retinoblastoma in Salah Azaiz Institute. The average age of the patients was 36 months (four to 132 months). There were 16 girls and 24 boys. Sixteen children presented a bilateral disease and 24 children a unilateral disease. Twenty eyes and thirty-six orbital cavities in 40 children with retinoblastoma were treated by radiotherapy. One child with a unilateral anterior retinoblastoma was treated with 106 ruthenium brachytherapy. External radiotherapy has been used to treat the 39 patients. In 20 cases the irradiation was conservative and in 36 cases postoperatively. The latter (n=36) presented at least one risk factor of relapses noted in the histological examination. The average dose was 44 Gy (1.8 to 2 Gy per fraction, five fractions weekly). This radiotherapy was associated with chemotherapy in 24 cases. RESULTS: Thirty-five children were followed with an average follow-up of 53 months (3-108 months). The average delay of relapses was of 10 months (two to 26 months). We found four orbital relapses and seven metastasis in nine children. The conservation of the eye with a useful visual field was noted in 18 cases among the 20 conservative irradiated eyes. The major therapeutic complication was the growth defect of the bones face. A femoral bone sarcoma was noted five years after the end of the irradiation and chemotherapy in one case. CONCLUSION: If the radiotherapy offers the advantage of the functional conservation and the improvement of the local control, its indications are more and more restricted in favor of the other therapeutic methods (chemotherapy, thermochemotherapy) and this considering the iatrogene risk. The development of new techniques of brachytherapy and the progresses of the conformational radiotherapy appear to reduce considerably this risk.

[Frontal relapse of medulloblastoma. Causes and consequences (a case report)]. / Rechute frontale du médulloblastome. Causes et conséquences (à propos d'un cas).

Medulloblastoma is a common paediatric brain tumor. Its prognosis is improved since the use of radiotherapy after surgery. This radiotherapy, so widely and complex, has one purpose: tumor control with less toxicity. Frontal relapse of medulloblastoma is not rare. Two hypothesis were proposed to explain this failure pattern: a geographic miss in cribriform plate due to targeting deviation and the migration of tumor cells to the cribriform plate caused by the "face down position" of the patient during surgery. We report the case of a 10-year-old boy who was treated in 1998 for a medulloblastoma with surgery and radiotherapy of the craniospinal axis (24 Gy) and the posterior fossa (54 Gy). Four years later, tumor relapsed only in the frontal area. A new surgery and chemotherapy were used with a complete response. A second frontal relapse associated with posterior fossa recurrence was detected after one year of the second treatment and treated by chemotherapy. Frontal relapse in medulloblastoma is an avoidable failure pattern when surgical and radiotherapeutic procedures are well controlled.

[Should chest wall irradiation be included after mastectomy and negative node breast cancer?]. / L'irradiation pariétale est-elle justifiée après mastectomie et curage négatif ?

PURPOSE: This study aims to evaluate local failure patterns in node negative breast cancer patients treated with post-mastectomy radiotherapy including internal mammary chain only. PATIENTS AND METHODS: Retrospective analysis of 92 internal or central-breast node-negative tumours with mastectomy and external irradiation of the internal mammary chain at the dose of 50 Gy, from 1994 to 1998. RESULTS: Local recurrence rate was 5 % (five cases). Recurrence sites were the operative scare and chest wall. Factors associated with increased risk of local failure were age < or = 40 years and tumour size greater than 20mm, without statistical significance. CONCLUSION: Post-mastectomy radiotherapy should be discussed for a sub-group of node-negative patients with predictors factors of local failure such as age < or = 40 years and larger tumour size.

[Experimental determination of correction factors of four detectors used in small field radiotherapy]. / Détermination expérimentale des facteurs de correction de quatre détecteurs actifs utilisés pour la dosimétrie des minifaisceaux utilisés en radiothérapie.

PURPOSE: The aim of this work is to determine experimentally the correction factors [Formula: see text] for four active commercial dosimeters: two microchambers and two diode detectors based on the output factor measured with radiochromic film for a radiotherapy linear accelerator equipped with circular cones. MATERIALS AND METHODS: Initially, a radiochromic film dosimetry measurement protocol with an accuracy of 2% was developed to approach the "reference output factor". Afterwards, the corrective factors of four detectors were determined for two ionization chambers (PinPoint PTW 31016 3D, Micropoint Extradin A16) and two diodes (PTW T60017 Diode, PTW-60019 Micro-Diamond). These measurements were carried out under conical BrainLAB® collimators defining circular fields with diameters equal to 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm, 25mm, 30mm, 35mm and 45mm of a 6MV X-ray beam generated by the ClinaciX linear accelerator (Varian®). These factors are weakly dependent on the type of accelerator, whether the model and the collimation type. This allowed their comparisons with those published for the same type of detector and for an accelerator with the same index of beam quality. RESULTS: The correction factors obtained experimentally were comparable in maximum deviation of 1.9% with published ones of the works using the same type of detector (mark and model) and an accelerator delivering the same beam quality for the same field size at the measurement point. CONCLUSION: The measurement protocol using the EBT3 film, which was used as a passive dosimeter to determine the "reference output factor", was validated by comparing measured and published data of active detector correction factors.

Brachytherapy for primary and recurrent nasopharyngeal carcinoma: treatment techniques and results.

PURPOSE: Nasopharyngeal cancer is the commonest head and neck cancer in Tunisia treated with radiotherapy. A dose effect relationship is established in this tumor. The aim of this study is to describe our Low-dose-rate endocavitary brachytherapy using a personalized mold called Tunis applicator. PATIENTS AND METHODS: Seven patients (4 males and 3 females) with histologically confirmed undifferentiated nasopharyngeal carcinoma (UCNT) were treated between 2002 and 2005. Five patients with primary cancer and 2 with recurrent disease received external beam radiation followed by endocavitary brachytherapy. The mean applied dose of endocavitary brachytherapy was 5.5 Gy for primary site after external beam radiation (70-74 Gy) and 30 Gy for recurrent disease after external beam radiation (38 Gy). We have developed a personalized applicator with a balloon to optimize the placement of sources and a better conformity using the computer tomography scanning. Critical normal structures were identified on orthogonal radiographs and the dose was optimized to avoid excessive doses to these structures. RESULTS: With a follow up of 18 months (8-41), only one local failure was observed, 3 years after external beam radiation therapy for a recurrent disease. Moderate grade mucositis was seen in most patients. One patient was diagnosed with bulb necrosis. CONCLUSION: Endobrachytherapy can provide effective treatment for nasopharyngeal carcinoma with an easy application of the brachytherapy procedure.

[Brain radionecrosis in patients irradiated for nasopharyngeal carcinoma: about nine cases]. / Radionécrose cérébrale chez les patients irradiés pour cancer du nasopharynx: à propos de neuf cas.

PURPOSE: To study the clinical, radiological, therapeutic and progressive aspects of brain radionecrosis after treatment for nasopharyngeal carcinoma. PATIENTS AND METHODS: Nine patients (seven men and two women) of mean age 47.7 years old (extremes: 18-57 years old) were treated for UCNT (undifferentiated carcinoma of the nasopharynx) between 1989 and 2003 and developed cerebral radionecrosis. All patients were treated with radical radiotherapy. The mean total dose was 73.5 Gy (70-75 Gy). Dose per fraction was 2 to 2.5 Gy, one fraction daily. One patient received adjuvant brachytherapy to the dose of 8 Gy and four patients also received chemotherapy. RESULTS: Brain radionecrosis was authenticated by brain imaging (CT scan+/-MRI): the imaging was ordered in seven cases to elucidate non-specific neurological signs and two cases were discovered fortuitously. The time to the appearance of neurological signs was 40.3 months (10 to 108 months). The localization was temporal in six cases, parieto-occipital (one case) and bulbomedullar (two cases). After a mean follow-up period of 30.6 months (12-84 months), clinical outcomes were favorable in all cases receiving medical treatment (corticoids), with a stabilization of the radiological lesions in eight cases and complete radiological regression in one patient. CONCLUSION: Brain radionecrosis is a late complication rarely occurring in patients irradiated for UCNT. Imaging techniques (CT scan but more so MRI) play a major role in the diagnosis. Corticotherapy resulted in a durable objective response in all patients and, in most cases, resulted in radiological stabilization.

[Acute respiratory failure as the sol inaugural sign of Arnold-Chiari malformation. Two cases]. / Insuffisance respiratoire aiguë isolée révélant une malformation d'Arnold-Chiari.

Arnold-Chiari malformation is an occipitocervical malformation where the cerebellar amygdales descend below the occipital foramen. Acute respiratory failure is an exceptional inaugural sign. We report two cases disclosed by alveolar hypoventilation associated with type I Arnold-Chiari malformation. The two patients age 51 and 52 years had an uneventful past history and presented with hypercapnic encephalopathy with acute respiratory failure requiring ventilatory assistance. Respiratory function tests, helicoidal thoracic computed tomographic angiography, electromyogram, cardiac echography, and thyroid and immunological tests were normal. Blood gases and polysomnography were in favor of central hypoventilation without sleep apnea. Magnetic resonance imaging demonstrated type I Arnold-Chiari malformation. The course was complicated by recurrent respiratory failure in both patients. Surgical decompression performed for the first patient provided no improvement. This patient died two months after surgery subsequent to aspiration pneumonia. The second patient was treated with continuous positive pressure noninvasive ventilatory assistance and had a good outcome at 25 months. These two cases illustrate the absence of any neurological sign, acute respiratory failure being the only sign of Arnold-Chiari malformation.

[Primary non-Hodgkin lymphoma of the liver: case report and review of the literature]. / Lymphome non hodgkinien primitif du foie: à propos d'un cas et revue de la littérature.

Purpose was to describe the clinical, radiological and therapeutic features in primary liver lymphoma. We report the case of a 54-year-old patient, who is followed since the age of 20 years for neutropenia associated with mediastinal adenopathy. Systematical ultrasound find a mass of the left liver confirmed by Computed tomography (CT). Histological examination of laparoscopic liver biopsy specimens confirmed diffuse large-cell non-Hodgkin's lymphoma. The disease was confined to the liver without any evidence of extrahepatic involvement. The serology of Epstein Barr virus was highly positive. PET-scan show increased FDG uptake at the site of hepatic lesion and the mediastin. The patient received chemotherapy followed by radiation therapy of the left liver at the dose of 31 Gy. The patient was alive and free of disease 20 months after the diagnosis of primary liver lymphoma. The primary hepatic lymphoma is a rare malignancy, which classically affects 50-year-old patients with a male preponderance. The incidence is increased in immunosuppressed patients and some authors have suggested an association with hepatitis B or C infection, and with the Epstein Barr virus. The imaging studies including ultrasound, CT, magnetic resonance imaging (MRI) and now PET-scan help to establish the diagnosis and to the following. Treatment options are surgery, radiation, chemotherapy, or a combination.

[Hypothyroidism following cervical irradiation in the management of carcinoma of the nasopharynx and of the breast: a prospective study on eighty-four cases]. / Hypothyroïdie après irradiation cervicale dans le traitement des cancers du nasopharynx et du sein: étude prospective à propos de 84 patients.

PURPOSE: 1/ To evaluate the incidence of hypothyroidism following radiotherapy in the management of breast and nasopharyngeal carcinomas, 2/ to define the role of a systematic post therapeutic screening. PATIENTS AND METHODS: From January 1996 through March 2001 a systematic evaluation of the clinical and the biological thyroid function was performed on a cohort of 84 patients that received supraclavicular irradiation. Selected patients had either a mammary (37 cases) or a nasopharyngeal (47 cases) carcinoma. Initial work up included thyroid inspection and palpation, and biological tests: serum FT4 and TSH levels, radioimmunochemistry, completed by dynamic thyroid stimulation, using TRH, in case of border line low T4 or isolated high TSH levels. Tests were repeated every three months the first year, and then every six months. Replacement therapy with L Thyroxin was administered in case of hypothyroidism. RESULTS: All selected patients had a normal function initially. With a mean two years follow up (1-5 years), 24 patients (29%) experienced hypothyroidism, half of whom (13 cases) being purely biological. Five patients (11%), with a nasopharyngeal carcinoma, presented also with associated pituitary failure. Clinical symptoms were minor or mild in all cases. Hypothyroidism was detected at a mean 21 months follow up. In 2 patients, hypothyroidism disappeared spontaneously within 6 months. Possible predictive factors were evaluated: age of the time of radiation, gender, percentage of irradiated thyroid, total dose, dose per fraction, tumour type and chemotherapy. Only age appeared significantly correlated with thyroid dysfunction (range: 10-30 years, P=0.002). CONCLUSION: Hypothyroidism is a frequent and certainly underestimated complication following radiotherapy of the neck. In such patients, a systematic clinical and biological evaluation every three months the first year, and then every six months until five years is recommended.

[Ovarian irradiation in recurrent endometriosis]. / Irradiation ovarienne pour endométriose réfractaire inopérable.

We describe a case of a young woman with a history of an aplastic anaemia in which pelvic radiotherapy was used successfully in the management of a recurrent and inoperable endometriosis. The use of therapeutic pelvic or ovarian irradiation in endometriosis may be considered, when surgical and medical treatments have been exhausted and have failed.

[Analysis of severe Legionellosis hospitalized in intensive care units in Tunisia]. / Analyse des cas de légionellose grave hospitalisés dans les services de réanimation en Tunisie.

This study is the first one that describes the situation of Legionnaires' disease (LD) in Tunisia, with its clinical and epidemiological characteristics and investigates the risk factors associated with Legionella infections in our country. We conducted a retrospective multicentric study during 5 years (2008-2012) concerning all confirmed LD cases in Tunisia and we investigated risk factors for infection. The total of confirmed LD cases was 14. Incidence was 0.03. Mean age: 53.1, sex ratio (M/F): 2.6. Summer-autumnal peak was noted. Risk factors for infection were: the great humidity at home (n=4), living in community (n=3) and practice ablutions (before prayer) in public places (n=4). Community acquired legionellosis (n=9) and nosocomial (n=2). Pulmonary symptoms (n=11)+/-gastrointestinal (n=6) and/or neurological signs (n=4). Beta lactams therapy failed (n=11). CXR showed bilateral lesions (n=6). Abnormalities in laboratory values were noted: hyponatremia (n=9), high CPK levels (n=9). Diagnosis was confirmed by positive urinary Legionella antigens test (n=10) and by direct immunofluorescence (n=1). Treatment was based on bitherapy (n=10). Five patients died. The incidence of LD appears lower than other countries. Some risk factors, as ablutions, are different from that reported in Western countries and seem to be specific to our society. Given the seriousness of its consequences, it is strongly recommended to improve the national surveillance system up and register LD as notifiable disease.

Modification of oxygen extraction ratio by change in oxygen transport in septic shock.

To help clarify the oxygen uptake/transport (VO2/TO2) relationship and because the oxygen extraction ratio (OER) and TO2 share no common variable such as cardiac index, we examined the changes in OER when TO2 was decreased in 12 patients with sepsis in whom a PEEP trial was performed. From zero end-expiratory pressure (ZEEP) to PEEP (12 +/- 3 cm H2O), a significant increase in OER from 30 +/- 10 percent to 38 +/- 12 percent (p less than 0.005) was observed, and individual percentage changes in OER were well correlated with individual percentage changes in TO2. The VO2 measured (VO2m) by respiratory gas analysis was unchanged, while VO2 calculated by the Fick equation (VO2f) decreased, suggesting a mathematical coupling between VO2f and TO2. Patients with hyperlactacidemia (n = 5) exhibited the same relationships between OER, VO2m, and TO2 as those without hyperlactacidemia. Our results suggest an adaptive response in the OER when TO2 is decreased in patients with established septic shock.