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Nonlinear increase,invisibility,and sign inversion of a localized fs-laser-induced refractive index change in crystals and glasses

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Light(Science & Applications) 2020年第1期9卷 1398-1409页

作者： Jerome Lapointe Jean-Philippe Berube yannick.ledemi Albert Dupont Vincent Fortin Younes Messaddeq Real Vallee Centre d’Optique Photonique et Laser2375 Rue de la TerrasseUniversite LavalG1V 0A6 QuebecQCCanada

Multiphoton absorption via ultrafast laser focusing is the only technology that allows a three-dimensional structural modification of transparent ***,the magnitude of the refractive index change is rather limited,preventing the technology from being a tool of choice for the manufacture of compact photonic integrated *** propose to address this issue by employing a femtosecond-laser-induced electronic band-gap shift(FLIBGS),which has an exponential impact on the refractive index change for propagating wavelengths approaching the material electronic resonance,as predicted by the Kramers–Kronig *** by theoretical calculations,based on a modified Sellmeier equation,the Tauc law,and waveguide bend loss calculations,we experimentally show that several applications could take advantage of this ***,we demonstrate waveguide bends down to a submillimeter radius,which is of great interest for higher-density integration of fs-laser-written quantum and photonic *** also demonstrate that the refractive index contrast can be switched from negative to positive,allowing direct waveguide inscription in ***,the effect of the FLIBGS can compensate for the fs-laser-induced negative refractive index change,resulting in a zero refractive index change at specific wavelengths,paving the way for new invisibility applications.

关键词： waveguide millimeter refractive

Prevalence and Factors Associated with Dry Eyes Syndrome in Glaucomatous Patients on Anti-Glaucoma Eye Drops Followed up at the Garoua Regional Hospital-Northern Cameroon

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Open Journal of Ophthalmology 2024年第3期14卷 350-360页

作者： Josiane Mare Njoya Dodo Balkissou Bimingo Noelle Bra’ Eyatcha Viola Dohvoma yannick Bilong Godefroy Koki Faculty of Medicine and Biomedical Sciences University of Garoua Garoua Cameroon Faculty of Medicine and Biomedical Sciences University of Yaounde I Yaounde Cameroon

Background: Dry eye and glaucoma are two common pathologies in the elderly, and are very often associated. This association suggests a link between them and between their treatments. Our purpose for this study is to determine the prevalence of dry eye in our glaucoma patients treated with eye drops and deduce the factors associated with it. Patients and Methods: We conducted a cross-sectional, analytical study from October 2022 to September 2023 in the ophthalmology department of Garoua Regional Hospital in glaucoma patients aged over 15 years able to answer the Ocular Surface Disease Index (OSDI) questionnaires and treated with antiglaucoma eye drops for more than 3 months. These patients underwent a complete ophthalmological examination and a tear film break-up time test. Results: A total of 73 patients (146 eyes) were examined. The average age of the patients was 47.2 ± 16.5 years, with a male predominance of 54.8%. The prevalence of dry eye syndrome in our patients according to the OSDI score was 56.2% (95% CI) (44.8;67.6). The prevalence of dry eye syndrome on clinical examination of the BUT in the right eye was 83.7% (95% CI) (75.1;92.1) and 79.4% (70.2;88.7) in the left eye. The duration of antiglaucoma treatment was the factor associated with dry eye syndrome (p < 0.05) in glaucoma patients in our setting. Conclusion: Dry Eye Syndrome is common in glaucoma patients on drops in our setting. Treatment duration of more than 1 year seems to be associated with dry eyes.

关键词： Dry Eyes Glaucoma Conservative Eye Drops Médications Garoua-Cameroon

Photonic properties of novel Yb3＋ doped germanium-lead oxyfluoride glass-ceramics for laser cooling applications

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Frontiers of Optoelectronics 2018年第2期11卷 189-198页

作者： Lauro J. Q. MAIA Jyothis THOMAS yannick.ledemi Kummara V. KRISHNAIAH Denis SELETSKIY Younes MESSADDEQ Raman KASHYAP Instituto de Fisica Universidade Federal de Goias Av. Esperanga 1533 Campus Samambaia Goiania GO 74690-900 Brazil Department of Electrical Engineering Ecole Polytechnique de Montrral P.O. Box 6079 Station Centre-ville Montreal QC H3C 3A7 Canada Department of Engineering Physics Ecole Polytechnique de Montrral P.O. Box 6079 Station Centre-ville Montreal QC H3C 3A7 Canada Centre d'Optique Photonique et Laser 2375 Rue de la Terrasse Universite Laval Qurbec QC G1V 0A6 Canada

Abstract In recent years, our research group has developed and studied new rare-earth doped materials for the promising technology of solid-state laser cooling, which is based on anti-stokes fluorescence. To the best of our knowledge, our group is the only one in Canada leading the research into the properties of nanoparticles, glasses and glass-ceramics for optical refrigeration appli- cations. In the present work, optical properties of 50GeO2- 30PbF2-18PbO-2YbF3 glass-ceramics for laser cooling are presented and discussed as a function of crystallization temperature. Spectroscopic results show that samples have near infrared photoluminescence emission due to the 2F5/2 - 2F7/2 Yb3＋ transition, centered at -1016 nm with an excitation wavelength of 920 nm or 1011 nm, and the highest photoluminescence emission efficiency occurs for heat-treatment for 5 h at 350℃. The internal photolumi- nescence quantum yield varies between 99% and 80%, depending on the temperature of heat-treatment, being the most efficient under 1011 nm excitation. The 2F5/2 lifetime increases from 1.472 to 1.970 ms for heat treatments at 330℃ to 350℃, respectively, due to energy trapping and the low phonon energy of the nanocrystals. The sample temperature dependence was measured with a fiber Bragg grating sensor, as a function of input pump laser wavelength and processing temperature. These measure- ments show that the heating process approaches near zero for an excitation wavelength between 1020 and 1030 nm, which is an indication that phonons are removed effectivelly from the glass-ceramic materials, and they can be used for optical laser cooling applications. On theother hand, the temperature increase as a function of input laser power into samples remains constant between 920 and 980 nm wavelength excitation, a temperature variation of 36 K/W （temperature of 58℃/W） was attained under excitation at 950 nm, showing a possible use for biomedical applications to be explored.

关键词： optical refrigeration oxyfluoride glass-cera-mics Yb3+ doping quantum yield infrared emission lifetime

Single-emitter super-resolved imaging of radiative decay rate enhancement in dielectric gap nanoantennas

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Light(Science & Applications) 2024年第1期13卷 47-54页

作者： R.Margoth Córdova-Castro Bart van Dam Alberto Lauri Stefan A.Maier Riccardo Sapienza yannick De Wilde Ignacio Izeddin Valentina Krachmalnicoff Institut Langevin ESPCI ParisPSL UniversityCNRSParisFrance The Blackett Laboratory Department of PhysicsImperial College LondonLondonUK School of Physics and Astronomy Monash UniversityClaytonVictoriaAustralia Chair in Hybrid Nanosystems Ludwig-Maximilians Universität MünchenMuenchenGermany Department of Physics University of OttawaOttawaONCanada

High refractive index dielectric nanoantennas strongly modify the decay rate via the Purcell effect through the design of radiative *** to their dielectric nature,the field is mainly confined inside the nanostructure and in the gap,which is hard to probe with scanning probe *** we use single-molecule fluorescence lifetime imaging microscopy(smFLIM)to map the decay rate enhancement in dielectric GaP nanoantenna dimers with a median localization precision of 14 *** measure,in the gap of the nanoantenna,decay rates that are almost 30 times larger than on a glass *** comparing experimental results with numerical simulations we show that this large enhancement is essentially radiative,contrary to the case of plasmonic nanoantennas,and therefore has great potential for applications such as quantum optics and biosensing.

关键词： dielectric decay radiative

Management of Penetrating Cranioencephalic Trauma Caused by Sharp Metal Objects—Therapeutic and Evolutionary Aspects: 12 Cases at the Renaissance University Hospital in N’Djamena

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Open Journal of Modern Neurosurgery 2024年第2期14卷 170-178页

作者： Goumantar Félicien Toudjingar Li-Iyane Olivier Ouambi yannick Canton Kessely Donal Djasdé Mahouli Fata Vounki Momar Codé Ba Neurosurgery Unit of Center Hospitalier Universitaire la Renaissance N&#8217Djamena Chad Neurosurgery Unit of CHU la Ré f&#233rence Nationale N&#8217Djamena Chad Neurosurgery Department of Centre Hospitalier National Universitaire de Fann Dakar Senegal

Introduction: Cranioencephalic trauma caused by bladed weapons is rare, and that caused by sharp objects is exceptional. The aim of our study was to describe the clinical, therapeutic and evolutionary aspects. Materials and method: This was a descriptive and analytical study over a 48-month period at CHU la Renaissance from January 1, 2018 to December 31, 2021, concerning patients admitted for penetrating cranioencephalic trauma by pointed object. Results: Twelve cases, all male, of penetrating cranioencephalic sharp-force trauma were identified. The mean age was 34 ± 7 years, with extremes of 11 and 60 years. Farmers and herders accounted for 31% and 25% of cases respectively. The average admission time was 47 hours. Brawls were the circumstances of occurrence in 81.2% of cases. Knives (33%), arrows (25%) and iron bars (16.6%) were the objects used. Altered consciousness was present in 43.8% of cases, and focal deficit in 50%. Scannographic lesions were fracture and/or embarrhment (12 cases), intra-parenchymal haematomas (6 cases) and presence of object in place (4 cases). Surgery was performed in 11 patients. Postoperative outcome was favorable in 9 patients. After 12 months, 2 patients were declared unfit. Conclusion: Penetrating head injuries caused by sharp objects are common in Chad. Urgent surgery can prevent disabling after-effects.

关键词： Penetrating Trauma Skull Encephalon Sharp Object Surgery Patient Outcome

Ceramic Properties of Three Specimens of Alluvial Clays Used in Local Constructions from Mbouda Clay Deposit, West Cameroon

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Journal of Minerals and Materials Characterization and Engineering 2024年第5期12卷 265-279页

作者： Philémon Zo’o Zame Sylvain Kouayep Lawou Philippe Samba Assomo Audrey Erman Moutsou yannick Lontchi Dzoti Véronique Kamgang Kabeyene Beyala Faculty of Science University of Yaound I Yaound Cameroon Higher Teacher Training College Bertoua University of Bertoua Bertoua Cameroon Faculty of Science University of Dschang Dschang Cameroon

The Mbouda alluvial deposit is located at the foot of the Bamboutos mountains (West Cameroon) where three types of clayey materials are widespread. The populations collect these clays in their natural state in view of constructions using fired bricks or compressed blocks. Unfortunately, these buildings are not strong. This study investigates the causes of the strengthlessness of buildings and suggests solutions to overcome the difficulty. The research content includes field and laboratory studies. The methodology consists of sampling black (AN), white (AB) and red (AR) clays specimens identified in the study area and analysing them simultaneously at MIPROMALO (Cameroon) and at ACME LAB in Vancouver (Canada). The results obtained show a high sand content in the samples AN (64%), AB (55.2%), AR (30.9%). The compressive strength of the built specimens is low at 900˚C considered as the traditional firing temperature AN (0.94 MPa), AB (5.25 MPa), AR (2.18 MPa). The mineralogical series are identically made by kaolinite, chlorite, gibbsite, quartz, muscovite, biotite, goethite, magnetite and hematite. Silica (SiO2) presents higher contents AN (52.87%), AB (48.02%), AR (47.68%) followed by alumina (Al2O3) AN (29.96%), AB (28.13%), AR (24.72%). The other elements are poorly represented.

关键词： Sand Bricks Clays Mechanical Properties Local Constructions

Massive Epistaxis Revealing a Post-Traumatic Aneurysm of the Internal Carotid Artery: A Clinical Case and Review of the Literature

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International Journal of Otolaryngology and Head & Neck Surgery 2024年第2期13卷 120-125页

作者： yannick Mossus Maguy Mbede Roger Meva’a Biouélé Leonel Atanga Adèle-Rose Ngo Nyeki Pierre Ongolo Zogo François Djomou Alexis Ndjolo Department of Ophthalmology ENT and Stomatology Faculty of Medicine and Biomedical Sciences University of Yaoundé 1 Yaoundé Cameroon Department of Medical Imaging Faculty of Medicine and Biomedical Sciences University of Yaoundé 1 Yaoundé Cameroon

Internal carotid artery (ICA) aneurysms are an unusual but serious cause of epistaxis. This epistaxis is massive and sometimes uncontrollable threatening the vital prognosis of patients. We report the case of a 16-year-old adolescent received in emergency with severe bilateral epistaxis, asthenia and grade-3 left exophthalmos. In his history, the subject had been the victim of an assault six months before consultation. He had received blows on the cephalic extremity with light but repeated epistaxis. The treatment consisted to blood products transfusion and local compression by sterile gazes. An ICA aneurysm in sphenoid sinus has been confirmed in a craniofacial CT scan coupled to vascular opacification. Although the ICA has a variable course in contact with the sphenoid sinus, massive epistaxis would be the consequence of a pronounced dehiscence of the ICA in the sphenoid sinus, particularly in a traumatic context. In front of this type of epistaxis in our context, general practitioners must be able to suspect a ruptured ICA aneurysm in the presence of exophthalmos and a notion of old or recent cranio-encephalic injury. Additionally, due to the high morbidity and mortality of this condition, a monitoring algorithm is necessary for patients with head trauma to facilitate early detection.

关键词： Aneurysm Internal Carotid Artery Head Trauma Epistaxis

Contribution of CT in the Exploration of Non-Traumatic Pathologies of the Lumbar Spine in Adults in Bangui

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Open Journal of Radiology 2024年第3期14卷 125-134页

作者： Bangue Songrou Francky Kouandongui Timothée Mobima yannick Héritier Sombot Borel Tambala Stéphane Kouzou Judith Guiaba Kette Euloge Tapiade Bidan Richard Bazogo National Center of Medical Imaging of Bangui Bangui Central Africa Republic Maman Elisabeth DOMITIEN Hospital Bangui Central Africa Republic Community Hospital of Bangui Bangui Central Africa Republic

Background: In Central African Republic, a study carried out in 2019 highlighted the limits of conventional radiography in the diagnosis of non-traumatic lower back pain in adults. Objective: The objective of this study is to show the value of CT scanning in the exploration of non-traumatic pathologies of the lumbar spine in adults. Patients and Method: Retrospective and descriptive cross-sectional study covering the files of patients aged at least 18 years old, sent for lumbar scanning from March 1 to December 31, 2021 at the medical imaging center. Results: In total, 593 scan examinations were performed including 159 (26.8%) examinations of the lumbar spine. The average age of the patients was 49.84 years. The majority were male (66%). 127 (79.8%) were referred mainly to the neurology and rheumatology departments. Common low back pain (n = 97, 61%) was the main reason for requesting a CT scan. The lumbar scan was performed without contrast product in 88.7% of cases. In total, 148 (93.1%) examinations were pathological and dominated by overall disc overhang (62.2%) and somatic and interapophyseal osteoarthritis (16.9%). The other lesions were spondylodiscitis (7.4%), tumor-like lesions (3.4%) and narrow lumbar canal (1.4%).

关键词： CT Scanning Lumbar Bangui Adults

Treatment of Synovial Cysts in Relation to the Tibial Tunnel of Anterior Cruciate Ligament Grafts by Filling the Tunnel with Acrylic Cement

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Surgical Science 2024年第4期15卷 289-298页

作者： Saint Luc Mungina Sedou Charlène Tshitala Mbombo yannick Toko Kiama Kevin Ndangi Ezechiel Nkodia Dieudonné Mwangala Rossyl Kivudi Dominique Saragaglia Luc Mokassa Bakumobatane Department of Surgery University Clinics of Kinshasa Faculty of Medicine University of Kinshasa Kinshasa Democratic Republic of Congo Matete General Reference Hospital Kinshasa Democratic Republic of Congo Department of Orthopedic Surgery Osteoarthritis Surgery and Sports Tromatology at the Grenoble Hospital and University Center Grenoble France National Border Hygiene Program Kinshasa Democratic Republic of Congo

Introduction: Synovial cyst of the tibial tunnel in connection with anterior cruciate ligament (ACL) reconstruction is a rare but particularly troublesome complication. Medical treatment is often doomed to failure, and surgical treatment usually consists of excising the cyst and filling the tunnel with bone. The aim of this study was to evaluate the results of filling the tunnel with acrylic cement. Hypothesis: Filling the tibial bone tunnel with acrylic cement should eliminate communication between the joint cavity and the pre-tibial surface and prevent cyst recurrence. Patients and Methods: This retrospective series is composed of 13 patients, 9 men and 4 women, mean age 48.5 years (31 to 64) operated on between 2011 and 2019 for an intra- and extraosseous synovial cyst consecutive to the tibial tunnel of an ACL graft. Between 1983 and 2016, 12 of the patients had had a bone graft without bone block fixation (DI-DT or Mac Intosh) and one patient, a bone-bone transplant (KJ). The cyst was of variable size, located on the anteromedial aspect of the proximal end of the tibia, and often painful, warranting consultation. At the time of the initial operation, 9 patients had undergone meniscectomies (6 medial, 2 lateral, 1 double). In 7 knees, there were 7 cartilage lesions in the femorotibial and/or patellofemoral compartments (one stage 1 lesion, 2 stage 2 lesions, 4 stage 3 lesions, and no stage 4 lesions). Only 2 knees had neither cartilage nor meniscus lesions. After curettage of the bone tunnel /− removal of the non-resorbed or PEEK interference screw, the tunnel was filled with acrylic cement /− reinforced with a ligament staple to prevent expulsion. All patients underwent regular follow-up consultations until recovery. Results: At a maximum follow-up of 8 years, only 1 cyst recurred, representing a 7.69% failure rate. It was reoperated with another technique, which involved filling the tibial bone tunnel with bone graft taken from a half-bank head. After recovery

关键词： Arthro-Synovial Cyst Tibial Tunnel ACL Graft Filling Acrylic Cement