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.

[Cataract and the exfoliative syndrome]. / Cataracta si sindromul exfoliativ.

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 use of viscoelastic compounds in cataract surgery]. / Utilizarea compusilor vâscoelastici în chirurgia cataractei.

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.

[The ocular manifestations in rheumatic diseases in young adults]. / Manifestari oculare în bolile reumatismale ale adultului tanar.

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.