Microstructuring of 3D movie theater metallic screens to improve radiant intensity homogeneity and reduce crosstalk

We present analytical and experimental results of the microstructuring of movie theater metallic screens. Our objective is to maintain the polarization state of reflected light and to control the distribution of light intensity avoiding hotspots. We derive analytical solutions of surface functions with an axial symmetry (kernel) that produces isotropic and Lambertian scattering. Then we model the diffraction that can occur with such kernels, ranging from a few microns to several hundred microns, and we give illustrations when illuminated by laser beams corresponding to future use of laser projectors. Finally, we discuss some of the challenges associated with the tiling of such kernels and their manufacturing.

Involvement of cyan and ester groups in surface interactions of aerosil-cyanophenyl alkyl benzoate systems with high silica density: Infrared investigations

Composites prepared from aerosil A380 and liquid crystals (LCs) of 4-n-alkyl-4'-cyanophenyl benzoate type, with four to six carbon atoms in the alkyl chain were investigated by infrared spectroscopy. Their high silica content (of 2-7 g aerosil/1 g of LC) was given by thermogravimetric investigations and allows the observation of a rather thin LC layer on the silica particles. Several surface species onto the external surface of the grains were demonstrated. Arguments are given that monomer and dimer species are present in the bulk cyanophenyl benzoate materials while bulk-like species along with hydrogen-bonded ones coexist in the so-called surface layer of the composites. The main interaction of LC molecules with the aerosil surface is by hydrogen bonding taking place with the involvement of the cyan group. There is a contribution of ester carbonyl group to these surface interactions but this cannot be well quantified.

Composites containing confined n-octyl-cyanobiphenyl: monomer and dimer species in the surface layer by in situ FTIR spectroscopy

Confinement of 4-n-octyl-4'-cyanobiphenyl (8CB) to nanoporous molecular sieves with hexagonal structure of cylindrical pores (4.6nm diameter) is studied. Thermogravimetric investigations have indicated that the pores are completely filled. Several surface species inside the pores and onto the external surface of the grains were demonstrated by differential thermal analysis and by in situ infrared spectroscopy. Arguments are given that bulk-like monomer and dimer species along with hydrogen bonded ones might coexist in the so-called surface layer, but their population varies drastically as function of the temperature. In addition, chemical changes of the confined liquid crystal are quite possible inside these nanopores, at temperatures lower than for the bulk.

The complex phase behaviour of suspensions of goethite (α-FeOOH) nanorods in a magnetic field

In 1902, Majorana reported the magneto-optical properties of aqueous colloidal suspensions of mixed iron oxides. Oddly enough, the magnetic-field induced birefringence displayed a non-monotonic dependence upon field intensity. This behaviour was later interpreted as due to the existence in these sols of at least two different chemical species. During the course of our studies of mineral liquid crystals, we have revisited this problem by examining aqueous suspensions of pure goethite (alpha-FeOOH) nanorods. Although they are comprised of a single chemical species, these suspensions show the same odd behaviour reported by Majorana. Moreover, we show that, as the volume fraction increases, the suspensions have an isotropic liquid/nematic/rectangular columnar phase sequence, with first-order transitions between these phases. The non-monotonic dependence of the field-induced birefringence can be explained by the existence of a remanent magnetic moment of the nanorods and the negative anisotropy of their magnetic susceptibility. Therefore, the nanorods align parallel to a weak field but realign perpendicular to the field beyond Bc approximately 375 mT. In addition, other interesting phenomena appear upon application of a magnetic field: the disordered (i.e. isotropic in zero-field) phase becomes highly anisotropic and difficult to distinguish from the nematic phase. Both phases then acquire not only quadrupolar order but also dipolar order. The rectangular columnar phase is strongly stabilised versus the nematic one. Our experimental observations raise new theoretical questions about the phase diagram of these suspensions with respect to volume fraction and magnetic field intensity.

Physical properties of aqueous suspensions of goethite (alpha-FeOOH) nanorods. Part II: In the nematic phase

At volume fractions larger than 8.5%, aqueous suspensions of lath-like goethite (alpha-FeOOH) nanorods form a lyotropic nematic phase. In this article, we first discuss the nematic ordering within statistical-physics models of the isotropic/nematic phase transition. We then describe the influence of a magnetic field on the nematic phase. Because the nanorods bear permanent magnetic moments, the nematic suspensions have dipolar order and very low Frederiks thresholds. Moreover, the nematic phase aligns parallel to a small magnetic field but realigns perpendicular to a high field because of a competition between the permanent moments of the nanorods and their negative anisotropy of magnetic susceptibility. This magneto-optical study of the nematic phase is completely consistent with that of the isotropic phase of the same suspensions published in Part I (this issue, p. 291). Besides, we demonstrate the field-induced biaxiality of a nematic single domain aligned perpendicular to the field. We also describe here preliminary experiments where an a.c. electric field is applied to the nematic phase. Both field amplitude and frequency were found to control the alignment direction and homeotropic-to-planar alignment transitions were observed. From this data, simple models were used to estimate some physical constants of the nematic phase.

[The use of viscoelastic compounds in cataract surgery]

The viscoelastic substances are very useful generally in cataract surgery, but absolutely useful in phacoemulsification. In present is used for viscoelastic compounds two terms that assemble the rheologic and physics-chemical properties: is said about the viscoelastic substance that is cohesive and dispersive (respective cohesivity or dispersivity property). Thus both types of viscoelastic substances--cohesive and dispersive--is used, sequentially, in one system. This double technique provides a fluid, heterogeneous work environment, which differ from the other techniques that use only one viscoelastic substance and provide a fluid, homogeneous work environment.

[Cataract and the exfoliative syndrome]

Exfoliation syndrome is more frequently in the older age and represents a risk factor for cataract surgery. This paper presents the results of a clinical trial made on 436 patients with troubles of transparency of the lens who were investigate in our clinic during January 1995-January 1997, and in whom, clinic and paraclinic exams have not revealed any associated ocular disease. In 14% of these patients who presented troubles of transparency of the lens were found uni- or bilateral exfoliation. The authors present the treatment applied both in patients in clinical follow-up (50% of patients with exfoliation syndrome develop secondary glaucoma) and patients who underwent surgical treatment. The patients with exfoliation syndrome and cataract have had a high risk to develop intra- and postoperative complications. The surgical treatment suggested by authors is extracapsular cataract extraction, either or without lens implantation and peripheral iridectomy which represents a compulsory step.

[The ocular manifestations in rheumatic diseases in young adults]

The paper presents the ocular clinical manifestations and its immunopathology in the main rheumatic diseases. The study shows that the most frequent ocular involvement in ankylosing spondylitis is anterior uveitis and HLA-B27 + uveitis are more severe, with a longer evolution and more frequent complications.

Dermatoglyphics in thyroid cancer

Digito-palmar dermatoglyphics in 93 subjects with thyroid cancer (34 males, 59 females) of which 87.1% had folliculo-papillar adenocarcinoma were studied qualitatively and quantitatively. The findings were compared to the dermatoglyphics of 100 males and 100 females from the clinically healthy autochthonous population. The thyroid cancer subjects had a lower total digital ridge count (TDRC) and a reduced number of papillar ridges between the a-d triradii, than the control subjects. The A line showed a more marked transversality in cancer males and a more marked obliquity in cancer females. Qualitative examination showed more patterns in the second interdigital area and a higher incidence of typical and atypical form of sulcus transversus in the cancer group as against the controls. Qualitative and quantitative variations in dermatoglyphics were found with respect to the relation between the anatomo-pathologic form and the A, B, or O blood group. However, this variation is not conclusive enough to support the hypothesis of an association between dermatoglyphics and the blood groups in the A, B, O system on the one hand, and dermatoglyphics and the anatomo-pathologic form of thyroid cancer, on the other.

Considerations on some anatomo-clinical phenomena of thyroid cancer. Treatment and prognosis. Personal experience with 1515 operated cases

The authors present a retrospective study on 1515 histologically confirmed cases of thyroid cancer encountered along a period of 30 years of activity. These cases were found among 15,200 patients operated on for thyroid disorders. Of these 1515 cases, 1310 were differentiated carcinomas of the follicular, papillary or trabecular type, 156 nondifferentiated carcinomas and 49 medullary carcinomas. The treatment for all these forms of cancer was a complex one, depending on the clinical stage and the anatomo-pathologic form. The authors advocate total or quasi-total thyroidectomy in all the forms of differentiated cancer, followed by administration of radioactive iodine and hormones. Under these conditions, the prognosis is extremely favourable. For nondifferentiated and medullary cancer the authors propose a wide resection followed by application of X-ray or cobalt and hormonal substitution therapy. The prognosis of these cases is poor.

Surgical indications in endemic goiter. Pre- and postoperative care

The authors express their opinion with respect to anatomo-clinical forms of endemic goiter. First they suggest preoperative thyroid re-equilibration to avoid postoperative complications such as hypothyroidism or recurrence. Then operative indications for endocrine goiter, especially in an endemic area are discussed. Opinions are also expressed with respect to diffuse parenchymatous (endemic) goiter, nodular and polynodular goiter together with the various forms that may have a nodular or polynodular aspect both anatomically and as localization. Extemporaneous examination is viewed by the authors as compulsory in all such goiters, whereas preoperative thyroid puncture is counterindicated. Surgical care of mixed endemic goiter (diffuse hyperplasia with nodules imbedded in the hyperplasia) is also reviewed. It is recommended that each operation be preceded by an adequate preoperative treatment, for which therapeutic schemes are indicated as well as postoperative care directions taking into account the anatomo-clinical form. The surgical approach recommended is subtotal thyroidectomy. The paper also provides some statistical figures concerning surgery in the Institute of Endocrinology in Bucharest.

The thyroglobulin variations during the thyroid surgery for polynodular goiter, hyperthyroidism and cancer

A radioimmunoassay (RIA) double antibody system for human thyroglobulin (Tgl) was developed with a sensitivity of 2.5 ng/ml T3 and T4 did not interfere in the antibody Tgl binding. The blood was collected pre-, intra- and 24 hrs post-thyroidectomy from 50 females and 4 males diagnosed as polynodular goiter, hyperthyroidism, chronic thyroiditis and thyroid cancer. The ratios of the intra- and post-operatory values versus pre-operatory values were calculated. The basal values in the patients having thyroid troubles varied within very large limits (two orders of magnitude) and these values could not be clearly correlated to the thyroid pathology, However, in untreated hyperthyroid patients the basal values exceeded 100 ng/ml, while in medullary carcinoma they were near the sensitivity limit of the technique. The intra-operatory values varied within the percentual area (thyroid carcinoma), multiplicative area (polynodular goiter and some cases of hyperthyroidism) and the order of magnitude area (hyperthyroid patients and some of the polynodular goiters). The value of the RIA measurement of the Tgl in the serum as an adjuvant in the post-treatment follow up of thyroid patients is discussed.