One-Photon Absorption-Based Direct Laser Writing of Three- Dimensional Photonic Crystals

A simple and low-cost technique called low one-photon absorption (LOPA) direct laser writing (DLW) is demonstrated as an efficient method for structuration of multidimensional submicrostructures. Starting from the diffraction theory of the electromagnetic field distribution of a tightly focused beam, the crucial conditions for LOPA-based DLW are theoretically investigated, and then experimentally demonstrated using a simple optical confocal microscope. Various 1D, 2D, and 3D submicrostructures were successfully fabricated in different materials, such as commercial SU8 photoresist and magnetic nanocomposite. The advantages and drawbacks of this LOPA-based DLW technique were also studied and compared with the conventional two-photon absorption based DLW. Several methods were proposed to overcome the existing problem of the DLW, such as the dose accumulation and shrinkage effect, resulting in uniform structures with a small lattice constant. The LOPA-based DLW technique should be useful for the fabrication of functionalized structures, such as magneto-photonic and plasmon photonic crystals and devices, which could be interesting for numerous applications

PREPARATION AND FTIR STUDIES OF PMMA/PVC POLYMER BLENDS, PVC-g-PMMA GRAFT COPOLYMERS AND EVALUATING GRAFT CONTENT

This study presents the qualitative and quantitative analyses of Fourier Transform Infrared (FTIR) spectra of poly(methyl methacrylate)/poly(vinyl chloride) blends (PMMA/PVC), as well as PVC-g-PMMA graft copolymers. Graft copolymerizations of methyl mathacrylate (MMA) onto PVC macromolecules were carried out mixture of cyclohexanone/N,N-dimethylformamide as solvents, dibenzoyl peroxide as initiator and nitrogen medium. FTIR spectra of PMMA/PVC blends showed that there were molecular interactions between C=O groups of PMMA and C-Cl groups of PVC. Assignments of infrared absorption bands for specific groups of PMMA/PVC blends have been contributed. Using regression method, linear calibration curve between PMMA mole content and peak areas of C=O groups in FTIR spectra of the blends has been found when C=O peak areas were multiplied by an appropriate factor. PMMA grafted content and total PMMA formed content in PVC-g-PMMA graft copolymers have been evaluated. The results showed that grafted PMMA content was increased since PVC was initiatly dechlorinated by NaOH solution. The grafted PMMA content and total formed PMMA content were 5.05 wt.% and 11.25 wt.% respectively when MMA monomers were grafted onto neat PVC and modified PVC molecules

DẪN LIỆU MỚI VỀ MÔI TRƯỜNG NƯỚC VÀ SINH VẬT TRONG CÁC HANG NGẦM VÀ HỒ NƯỚC MẶN KHU VỰC VỊNH HẠ LONG, CÁT BÀ

Submerged caves and saltwater lakes are 2 common habitat types in Ha Long and Cat Ba. However, depending on many different reasons so far they have been poorly studied both on environmental and biological characteristics. The initial results on environment and biological communities in 3 submerged caves (Hang Sang, Hang Toi, Qua Bang) and 3 saltwater lakes (Ang Dau Be, Ang Du, Ang Qua Bang) showed that: status of water environment was different among lakes, especially in the closed lake as Ang Du where salinity was low (9‰), while salinity in the lakes connected to the sea was equal to marine environment (23 - 27‰). Concentration of dissolved oxygen (DO) in saltwater lakes was high from 7.63 - 9.03 mg/L and higher than that in submerged caves and surrounding marine environment. Physical and chemical factors of water in the submerged caves were equivalent to the marine environment because these caves are connected to the sea and water regularly goes in and out according to tidal fluctuation. Organism communities in the submerged caves were abundant with over 142 species being found. The popular groups, sponge and soft coral, were distributed along the length of the caves. Several species with high economic value were commonly observed in the caves, including stone crab Myomenippe hardwickii, flower crab Portunus pelagicus, cone snails Trochus pyramis, shoemaker spinefoot Siganus sutor, snapper Lutjanus russelii ... Species that permanently live in cave were not detected. In the lakes where water is well exchanged to the sea, coral reefs were found and they formed a narrow reef around the lake. Sandy bars often appeared around the lake at the depth of 0.5 - 2 m, containing specialty species as phi (Sanguinolaria diphos), snout otter clam (Lutraria rhynchaena), sea cucumbers with high density (Ang Dau Be, Ang Qua Bang). There was no coral reef in the closed lake (Ang Du) because of low salinity. In this lake, stratification of temperature and salinity led to temperature on surface lower than that on bottom from 30C to 60C, this phenomenon is unusual.Hang ngầm và hồ nước mặn là 2 dạng sinh cảnh khá phổ biến ở Hạ Long và Cát Bà, do nhiều nguyên nhân khác nhau đến nay chúng rất ít được quan tâm nghiên cứu. Các kết quả nghiên cứu bước đầu về môi trường và quần xã sinh vật trong 3 hang ngầm (Hang Sáng, Hang Tối, Hang Quả Bàng) và 3 hồ nước mặn (Áng Đầu Bê, Áng Dù, Áng Quả Bàng) cho thấy: Môi trường nước có sự khác biệt giữa các hồ, đặc biệt là trong hồ kín như Áng Dù có độ muối thấp (9‰), trong khi các hồ có cửa thông với biển có độ muối gần tương đương với môi trường ngoài (23 - 27‰). Hàm lượng chất khí hòa tan như DO trong các hồ nước mặn khá cao từ 7,63 - 9,03 mg/l, cao hơn trong hang ngầm và cao hơn ở môi trường biển xung quanh. Các yếu tố vật lý và hóa học trong môi trường nước tại các hang ngầm gần tương đương với môi trường bên ngoài do có các hang ngầm đều thông với biển và có nước chảy thường xuyên theo sự lên xuống của thủy triều. Quần xã sinh vật trong các hang khá phong phú với trên 142 loài được tìm thấy, phổ biến nhất là hải miên và san hô mềm, chúng phân bố dọc chiều dài hang. Có một số loài có giá trị kinh tế cao thường gặp trong hang là Cù kì Myomenippe hardwickii, ghẹ Portunus pelagicus, ốc nón Trochus pyramis, cá dìa Siganus sutor, cá hồng Lutjanus russellii ... Chưa phát hiện thấy các loài chuyên biệt sống cố định trong hang. Ở các hồ nước lưu thông với môi trường bên ngoài có sự xuất hiện của rạn san hô, chúng tạo thành một dải hẹp bao quanh hồ. Các bãi cát thường xuất hiện quanh hồ ở độ sâu 0,5 - 2 m có các loài đặc sản như phi phi, tu hài, hải sâm với mật độ khá cao (Áng Đầu Bê, Áng Quả Bàng). Trong áng kín không có rạn san hô do nước có độ muối thấp, có sự phân tầng của nhiệt độ và độ muối làm cho nhiệt độ ở tầng mặt thấp hơn tầng đáy 3 - 60C đây là hiện tượng bất thường ở các hồ này

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke

Etudes théorique et expérimentale du couplage des nanoparticules uniques dans des structures photoniques à base de polymère

In this study, we investigate theoretically and experimentally the nanoparticles/photonic structures coupling. In detail, the work focuses on the elaboration and applications of structured polymer materials, as well as the manipulation of optical properties of various kinds of nano-objects such as gold nanoparticles, magnetic and nonlinear nanoparticles, etc. The coupling of each kind of nanoparticles addresses a specific goal. In order to conduct research, we first build and test an optical confocal setup, which allows us to both image and fabricate nanostructures at a sub-lambda resolution. Besides, we propose a method exploiting the thermal effect caused by a continuous-wave laser source to optimize 2D and 3D structures realized by low one-photon absorption (LOPA)-based direct laser writing (DLW). Then by using this technique, we are capable of precisely determining the position and embedding various kinds of nanoparticles (gold nanoparticles, nonlinear nanoparticles, and magnetic nanoparticles) into arbitrary polymeric photonic structures. The characterization of the fabricated structures is carried out using the same confocal setup. We demonstrate a good enhancement of the optical properties of the nanoparticles embedded inside photonic structures. We also perform numerical calculations by using a FDTD method to confirm the experimental results.Dans ce travail, nous étudions théoriquement et expérimentalement le couplage entre une nanoparticule unique de différentes natures, comme fluorescente, non-linéaire, plasmonique, etc., et une structure photonique en matériau polymère. Dans un premier temps, nous avons optimisé la méthode dite écriture directe par laser par absorption à un photon pour réaliser des structures photoniques de bonne qualité à la demande. Ensuite, nous avons également exploité l'effet thermique induit par le laser d’excitation continue, pour simplifier la méthode de fabrication LOPA et améliorer les structures fabriquées. Puis nous avons introduit de façon précise une seule nanoparticule unique à un endroit désiré dans la structure photonique. Le couplage nanoparticule/structure photonique a été réalisé par le même système optique. Ce couplage a été démontré par une augmentation du nombre de photon émis par la nanoparticule fluorescente et par une forte amélioration du signal de génération de seconde harmonique. Parallèlement, nous avons effectué des calculs numériques par la méthode FDTD pour prédire les propriétés optiques intéressantes des structures photoniques et pour confirmer les résultats expérimentaux

Deterministic Insertion of KTP Nanoparticles into Polymeric Structures for Efficient Second-Harmonic Generation

International audienc

One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect

International audienc

Optical lithography of three-dimensional magnetophotonic microdevices

International audienc

Rapid direct laser writing of desired plasmonic nanostructures

International audienc