Water Resistant Cellulose Acetate Based Photopolymer for Recording of Volume Phase Holograms

The development of environmentally robust photosensitive materials for holographic recording is crucial for applications such as outdoor LED light redirection, holographic displays and holographic sensors. Despite the progress in holographic recording materials development, their sensitivity to humidity remains a challenge and protection from the environment is required. One approach to solving this challenge is to select substrate such as cellulose acetate, which is water resistant. This work reports the development of a cellulose-based photopolymer with sensitivity of 3.5 cm2/mJ and refractive index modulation of 2.5 × 10−3 achieved in the transmission mode of recording. The suitability for holographic recording was demonstrated by recording gratings with the spatial frequency of 800 linepairs/mm. The intensity dependence of the diffraction efficiency of gratings recorded in 70 μm thick layers was studied and it was observed that the optimum recording intensity was 10 mW/cm2. The robustness of the structures was studied after immersing the layer in water for one hour. It was observed that the diffraction efficiency and the surface characteristics measured before and after exposure to water remain unchanged. Finally, the surface hardness was characterized and was shown to be comparable to that of glass and significantly higher than the one of PVA-based acrylamide photopolymer.

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EXPERIMENTAL INVESTIGATION OF THE PHOTOCHROMIC EFFECT AND TWO-COLOR HOLOGRAPHIC RECORDING IN NEAR-STOICHIOMETRIC LiNbO3:Fe:Mn CRYSTALS

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s021886351250052x ◽

2012 ◽

Vol 21 (04) ◽

pp. 1250052 ◽

Cited By ~ 4

Author(s):

YOUWEN LIU ◽

YUANYUAN ZHOU ◽

MINJUN ZHU ◽

CONGJUN HE

Keyword(s):

Diffraction Efficiency ◽

Red Light ◽

Oxidation Time ◽

Oxygen Atmosphere ◽

Holographic Recording ◽

Pump Probe ◽

Holographic Gratings ◽

Speed Increase ◽

Before And After ◽

Photochromic Effect

Near-stoichiometric LiNbO3:Fe:Mn crystals are grown, then annealed in the oxygen atmosphere at 900°C for 6, 10 and 18 h. The photochromic effect of samples are investigated by measuring UV/VIS/NIR spectra before and after illumination of sensitizing light of 405 nm, and the dynamic characteristics were evaluated by use of the pump–probe method. Both the saturated absorption change and the photochromic speed increase with increases in the sensitizing intensity and the Fe concentration. In the two-color recording experiment, the holographic gratings were recorded by a red light of 633 nm, simultaneously sensitized by a violet light of 405 nm. The results show that the saturated diffraction efficiency increases with an increase in the ratio of recording light to sensitizing beam intensities, however, the sensitivity decreases. Higher concentration of Fe enables higher diffraction efficiency and higher sensitivity. In our investigation, the photochromic effect, and the two-color recording properties have little dependence on the oxidation time in the oxygen atmosphere when the oxidation time is longer than 6 h. An optimization may be obtained by further modifying these conditions appropriately.

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Full-Color See-Through Three-Dimensional Display Method Based on Volume Holography

Sensors ◽

10.3390/s21082698 ◽

2021 ◽

Vol 21 (8) ◽

pp. 2698

Author(s):

Taihui Wu ◽

Jianshe Ma ◽

Chengchen Wang ◽

Haibei Wang ◽

Ping Su

Keyword(s):

Diffraction Efficiency ◽

Three Dimensional ◽

Holographic Recording ◽

Refractive Index Modulation ◽

3D Display ◽

Light Modulator ◽

Compact Structure ◽

Simultaneous Exposure ◽

Full Color ◽

Volume Holography

We propose a full-color see-through three-dimensional (3D) display method based on volume holography. This method is based on real object interference, avoiding the device limitation of spatial light modulator (SLM). The volume holography has a slim and compact structure, which realizes 3D display through one single layer of photopolymer. We analyzed the recording mechanism of volume holographic gratings, diffraction characteristics, and influencing factors of refractive index modulation through Kogelnik’s coupled-wave theory and the monomer diffusion model of photopolymer. We built a multiplexing full-color reflective volume holographic recording optical system and conducted simultaneous exposure experiment. Under the illumination of white light, full-color 3D image can be reconstructed. Experimental results show that the average diffraction efficiency is about 53%, and the grating fringe pitch is less than 0.3 μm. The reconstructed image of volume holography has high diffraction efficiency, high resolution, strong stereo perception, and large observing angle, which provides a technical reference for augmented reality.

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Effect of Glycerol on an N-Vinylpyrrolidone-Based Photopolymer for Transmission Holography

Polymers ◽

10.3390/polym13111754 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1754

Author(s):

Huishi Pi ◽

Weiping Li ◽

Zhiwei Shi ◽

Haining Chen ◽

Xiaoyu Jiang

Keyword(s):

Molecular Structure ◽

Refractive Index ◽

Diffraction Efficiency ◽

Optimal Concentration ◽

Diffractive Optics ◽

Holographic Recording ◽

Control Group ◽

Refractive Index Modulation ◽

Spatial Frequencies ◽

Index Modulation

N-vinylpyrrolidone (NVP) has a large molecular structure, so it is difficult to diffuse during holographic recording, especially at low spatial frequencies. We used glycerol to promote the diffusion of NVP, and successfully improved the holographic performance of the photopolymer at low spatial frequencies. As the concentration of glycerol increases, the holographic performance first increases and then remains stable. The optimal concentration of glycerol is 0.21 mol/L. At this concentration, the maximum diffraction efficiency of the photopolymer is 84%, the refractive index modulation is 1.95 × 10−3, and the photosensitive sensitivity is 7.91 × 10−4 cm2/mJ. Compared with the control group, the maximum diffraction efficiency, maximum refractive index modulation and photosensitivity at low spatial frequencies (800 lp/mm) have increased by 11.19 times, 4.69 times and 1.71 times, respectively. Using the optimized photopolymer for transmission holographic recording and reproduction, we have obtained a clear and bright transmission hologram. The photopolymer modified with glycerol is expected to be applied to the fields of holography, diffractive optics, and so on.

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Study of the Effect of Methyldiethanolamine Initiator on the Recording Properties of Acrylamide Based Photopolymer

Polymers ◽

10.3390/polym12040734 ◽

2020 ◽

Vol 12 (4) ◽

pp. 734

Author(s):

Brian Rogers ◽

Suzanne Martin ◽

Izabela Naydenova

Keyword(s):

Refractive Index ◽

Diffraction Efficiency ◽

Prolonged Exposure ◽

Uv Light ◽

Holographic Recording ◽

Refractive Index Modulation ◽

Optical Elements ◽

The Stability ◽

Angular Selectivity ◽

Index Modulation

The use of Holographic Optical Elements (HOEs) in applications, such as in light shaping and redirection, requires certain characteristics such as a high Diffraction Efficiency, low angular selectivity and stability against UV damage. In order to maximize the performance of the HOEs, photosensitive materials are needed that have been optimised for the characteristics that are of particular importance in that application. At the core of the performance of these devices is the refractive index modulation created during holographic recording. Typically, a higher refractive index modulation will enable greater light Diffraction Efficiency and also operation with thinner devices, which in turn decreases the angular selectivity and the stability of the refractive index modulation introduced during recording, which is key to the longevity of the device. Solar concentrators based on volume HOEs can particularly benefit from thinner devices, because, for a solar concentrator to have a high angular working range, thinner photopolymer layers with a smaller angular selectivity are required. This paper presents an optimisation of an acrylamide-based photopolymer formulation for an improved refractive index modulation and recording speed. This was achieved by studying the effect of the concentration of acrylamide and the influence of different initiators in the photopolymer composition on the diffraction efficiency of holographic gratings. Two initiators of different molecular weights were compared: triethanolamine (TEA) and methyldiethanolamine (MDEA). A fivefold increase in the rate of grating formation was achieved through the modification of the acrylamide concentration alone, and it was also found that holograms recorded with MDEA as the initiator performed the best and recorded up to 25% faster than a TEA-based photopolymer. Finally, tests were carried out on the stability of the protected and unprotected photopolymer layers when subjected to UV light. The properties exhibited by this photopolymer composition make it a promising material for the production of optical elements and suitable for use in applications requiring prolonged exposure to UV light when protected by a thin melinex cover.

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Lost in Migration – Mirandese at a Crossroads

Open Linguistics ◽

10.1515/opli-2019-0026 ◽

2019 ◽

Vol 5 (1) ◽

pp. 488-495

Author(s):

Cláudia Martins ◽

Sérgio Ferreira

Keyword(s):

Minority Language ◽

Three Dimensions ◽

Highly Qualified ◽

Linguistic Rights ◽

The Bible ◽

Literary Forms ◽

Before And After ◽

The 1960S ◽

The One ◽

The 19Th Century

AbstractThe linguistic rights of Mirandese were enshrined in Portugal in 1999, though its “discovery” dates back to the very end of the 19th century at the hands of Leite de Vasconcellos. For centuries, it was the first or only language spoken by people living in the northeast of Portugal, particularly the district of Miranda do Douro. As a minority language, it has always moved among three dimensions. On the one hand, the need to assert and defend this language and have it acknowledged by the country, which proudly believe(d) in their monolingual history. Unavoidably, this has ensued the action of translation, especially active from the mid of the 20th century onwards, with an emphasis on the translation of the Bible and Portuguese canonical literature, as well as other renowned literary forms (e.g. The Adventures of Asterix). Finally, the third axis lies in migration, either within Portugal or abroad. Between the 1950s and the 1960s, Mirandese people were forced to leave Miranda do Douro and villages in the outskirts in the thousands. They fled not only due to the deeply entrenched poverty, but also the almost complete absence of future prospects, enhanced by the fact that they were regarded as not speaking “good” Portuguese, but rather a “charra” language, and as ignorant backward people. This period coincided with the building of dams on the river Douro and the cultural and linguistic shock that stemmed from this forceful contact, which exacerbated their sense of not belonging and of social shame. Bearing all this in mind, we seek to approach the role that migration played not only in the assertion of Mirandese as a language in its own right, but also in the empowerment of new generations of Mirandese people, highly qualified and politically engaged in the defence of this minority language, some of whom were former migrants. Thus, we aim to depict Mirandese’s political situation before and after the endorsement of the Portuguese Law no. 7/99.

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Real-World Experience of the One-Year Efficacy of Rifaximin Add-On to Lactulose Is Superior to Lactulose Alone in Patients with Cirrhosis Complicated with Recurrent Hepatic Encephalopathy in Taiwan

Journal of Personalized Medicine ◽

10.3390/jpm11060478 ◽

2021 ◽

Vol 11 (6) ◽

pp. 478

Author(s):

Ching Chang ◽

Chien-Hao Huang ◽

Hsiao-Jung Tseng ◽

Fang-Chen Yang ◽

Rong-Nan Chien

Keyword(s):

Hepatic Encephalopathy ◽

Real World ◽

Ammonia Level ◽

Decompensated Cirrhosis ◽

Control Group ◽

Multivariable Logistic Regression Model ◽

Before And After ◽

One Year ◽

The One ◽

Serum Ammonia

Background: Hepatic encephalopathy (HE), a neuropsychiatric complication of decompensated cirrhosis, is associated with high mortality and high risk of recurrence. Rifaximin add-on to lactulose for 3 to 6 months is recommended for the prevention of recurrent episodes of HE after the second episode. However, whether the combination for more than 6 months is superior to lactulose alone in the maintenance of HE remission is less evident. Therefore, the aim of this study is to evaluate the one-year efficacy of rifaximin add-on to lactulose for the maintenance of HE remission in Taiwan. Methods: We conducted a real-world single-center retrospective cohort study to compare the long-term efficacy of rifaximin add-on to lactulose (group R + L) versus lactulose alone (group L, control group). Furthermore, the treatment efficacy before and after rifaximin add-on to lactulose was also analyzed. The primary endpoint of our study was time to first HE recurrence (Conn score ≥ 2). All patients were followed up every three months until death, and censored at one year if still alive. Results and Conclusions: 12 patients were enrolled in group R + L. Another 31 patients were stratified into group L. Sex, comorbidity, ammonia level, and ascites grade were matched while age, HE grade, and model for end-stage liver disease (MELD) score were adjusted in the multivariable logistic regression model. Compared with group L, significant improvement in the maintenance of HE remission and decreased episodes and days of HE-related hospitalizations were demonstrated in group R + L. The serum ammonia levels were significantly lower at the 3rd and 6th month in group 1. Concerning changes before and after rifaximin add-on in group R + L, mini-mental status examination (MMSE), episodes of hospitalization, and variceal bleeding also improved at 6 and 12 months. Days of hospitalization, serum ammonia levels also improved at 6th month. Except for concern over price, no patients discontinued rifaximin due to adverse events or complications. The above results provide evidence for the one-year use of rifaximin add-on to lactulose in reducing HE recurrence and HE-related hospitalization for patients with decompensated cirrhosis.

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Holographic Recording Performance of Acrylate-Based Photopolymer under Different Preparation Conditions for Waveguide Display

Polymers ◽

10.3390/polym13060936 ◽

2021 ◽

Vol 13 (6) ◽

pp. 936

Author(s):

Zhongwen Shen ◽

Yishi Weng ◽

Yuning Zhang ◽

Chuang Wang ◽

Ao Liu ◽

...

Keyword(s):

Augmented Reality ◽

Diffraction Efficiency ◽

Green Light ◽

Holographic Recording ◽

Holographic Gratings ◽

Preparation Conditions

This work proposes a green light-sensitive acrylate-based photopolymer. The effects of the preparation conditions for the waveguide applied volume holographic gratings (VHGs) were experimentally investigated. The optimum preparation conditions for holographic recording were revealed. After optimization, the peak of VHG diffraction efficiency reached 99%, the diffractive wavelength bandwidth increased from 13 nm to 22 nm, and the corresponding RIM was 0.06. To prove the wide application prospect of the acrylate-based photopolymer in head-mounted augmented reality (AR) displays, green monochromatic volume holographic waveguides were fabricated. The display results showed that the prototype was able to achieve a 28° diagonal FOV and possessed a system luminance of 300 cd/m2.

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On the measurement of the ratio of the specific heats using small volumes of gas.—The ratios of the specific heat of air and of hydrogen at atmospheric pressure and a temperatures between 20°C. and —183°C

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1925.0039 ◽

1925 ◽

Vol 107 (743) ◽

pp. 510-543 ◽

Cited By ~ 14

Keyword(s):

Systematic Error ◽

Low Temperatures ◽

Room Temperature ◽

Expansion Chamber ◽

Small Vessels ◽

Specific Heats ◽

Large Expansion ◽

Before And After ◽

The One ◽

Chamber Capacity

Introduction .—In nearly all the previous determinations of the ratio of the specific heats of gases, from measurements of the pressures and temperature before and after an adiabatic expansion, large expansion chambers of fror 50 to 130 litres capacity have been used. Professor Callendar first suggests the use of smaller vessels, and in 1914, Mercer (‘Proc. Phys. Soc.,’ vol. 26 p. 155) made some measurements with several gases, but at room temperature only, using volumes of about 300 and 2000 c. c. respectively. He obtained values which indicated that small vessels could be used, and that, with proper corrections, a considerable degree of accuracy might be obtained. The one other experimenter who has used a small expansion chamber, capacity about 1 litre, is M. C. Shields (‘Phys. Rev.,’ 1917), who measured this ratio for air and for hydrogen at room temperature, about 18° C., and its value for hydroger at — 190° C. The chief advantage gained by the use of large expansion chambers is that no correction, or at the most, a very small one, has to be made for any systematic error due to the size of the containing vessels, but it is clear that, in the determinations of the ratio of the specific heats of gases at low temperatures, the use of small vessels becomes a practical necessity in order that uniform and steady temperature conditions may be obtained. Owing, however, to the presence of a systematic error depending upon the dimensions of the expansion chamber, the magnitude of which had not been definitely settled by experiment, the following work was undertaken with the object of investigating the method more fully, especially with regard to it? applicability to the determination of this ratio at low temperatures.

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Doing politics by other means: Abdelmalek Sayad and the political sociology of a collective intellectual

The Sociological Review ◽

10.1177/0038026119900104 ◽

2020 ◽

Vol 68 (5) ◽

pp. 999-1014

Author(s):

Amín Pérez

Keyword(s):

International Organizations ◽

Political Action ◽

The Political ◽

Host Society ◽

Intellectual Work ◽

Academic Fields ◽

The Social ◽

Social Fields ◽

Before And After ◽

The One

This article proposes a new understanding of the constraints and opportunities that lead intellectuals engaged in different political and social fields to create alternative modes of resistance to domination. The study of the Algerian sociologist Abdelmalek Sayad offers insights into the social conditions of this mode of committed scholarship. On the one hand, this article applies Sayad’s theory of immigration to his transnational intellectual engagements. It establishes how immigrants’ intellectual work are conditioned by their trajectories, both before and after leaving their country, and by the stages of emigration (from playing a role in the society of origin to becoming caught up in the reality of the host society). On the other hand, the article illuminates the constraints and the spaces of possible action intellectuals face while moving across national universes and disparate political and academic fields. Sayad’s marginal position within the academy constrained him to work for the French and Algerian governments and international organizations while he was simultaneously engaged with political dissidents, unionists, writers, and social movements. In tracking Sayad’s roles as an academic, expert and public sociologist, the article uncovers the conditions that grounded improbable alliances between those fields and produced new forms of critique and political action. The article concludes by drawing out some reflections that ‘collective intellectual’ engagements elicit to the sociology of intellectuals.

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Numerical investigation of the propagation of shock waves in rigid porous materials: development of the computer code and comparison with experimental results

Journal of Fluid Mechanics ◽

10.1017/s0022112096007872 ◽

1996 ◽

Vol 324 ◽

pp. 163-179 ◽

Cited By ~ 21

Author(s):

A. Levy ◽

G. Ben-Dor ◽

S. Sorek

Keyword(s):

Porous Materials ◽

Initial Conditions ◽

Computer Code ◽

Experimental Results ◽

Numerical Code ◽

Materials Development ◽

Numerical Predictions ◽

Wide Range ◽

Dimensional Version ◽

The One

The governing equations of the flow field which is obtained when a thermoelastic rigid porous medium is struck head-one by a shock wave are developed using the multiphase approach. The one-dimensional version of these equations is solved numerically using a TVD-based numerical code. The numerical predictions are compared to experimental results and good to excellent agreements are obtained for different porous materials and a wide range of initial conditions.

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