Non-templated hydrothermal growth of anisotropic magnetite nanostructures using hexamine as the directing agent.

Anisotropic growth of magnetite (Fe3O4) nanoparticles is achieved in a hydrothermal growth process using hexamine to play a dual role of oxide forming and directing agent. The samples are characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, squid magnetometry, ferromagnetic resonance technique, diffuse reflectance spectroscopy and Mössbauer spectroscopy, which collectively establish the formation of Fe3O4 phase. Anisotropic structures such as nanorods and nanotubules are revealed and these are shown to exhibit good humidity sensing properties.

Hydrazine based facile synthesis and ordered assembly of metal nanoparticles (Au, Ag) on a bacterial surface layer protein template.

An efficient and facile procedure is developed for concurrent in situ synthesis and ordered assembly of metal nanoparticles on a periodic two dimensional protein array. The S-layer protein of Bacillus subtilis exhibiting uniform pore size is used as template. Synthesis of gold and silver nanoparticles anchoring on the pores of S-layer is achieved by chemical reduction of respective metal salt laden protein template. Transmission electron microscopy reveals formation of well ordered and separated gold and silver nanoparticles with an average diameter of 6 +/- 1 nm and 4 +/- 1 nm, respectively. The periodic arrangement of nanoparticles is dictated by the native structure of S-layer protein array as the nanoparticle locations are found to be correlated to the nanosized pores of the crystalline S-layer array.

Peculiarities of the adsorption kinetics of mixed convex plus concave contour objects.

Random sequential adsorption of mixed convex plus concave contour (MC) objects exhibits some distinctly different peculiar characteristics than the cases of purely convex objects. Though the substrate coverage approaches the jamming limit with time t as t;{-p} , same as that for convex objects, the law p approximately 1d_{f} , valid for convex objects with d_{f} degrees of freedom, does not hold for MC objects. Interestingly, for a fixed number of degrees of freedom, the exponent p changes with the degree of nonconvexity and bears a near perfect correlation with the same.

Universality of the power-law approach to the jamming limit in random sequential adsorption dynamics.

Random sequential adsorption (RSA), on a two-dimensional continuum substrate, of different types of zero area objects that disallow domain formation and hence lead to jamming, is examined by simulation. In all the cases, in the asymptotic time regime, the approach of the number density rho(t) at instant t to jamming density rho(infinity) is found to exhibit power law rho(infinity)-rho(t) approximately t{-p} as that for RSA of finite area objects. These results suggest the possibility of the power law being universal for all jamming systems in RSA on a continuum substrate. A generalized analytical treatment is also proposed.

Demonstration of cytokeratin-5 non-expression in tobacco related oral carcinogenesis--use of reverse transcriptase polymerase chain reaction as a sensitive assay.

Cytokeratins (CK) are the epithelia specific intermediate filament proteins. We have shown consistent non-expression of CK-5 protein in human oral pre-cancer and cancer, in earlier studies. To investigate whether non-expression of CK-5 protein is the result of transcriptional or translational block and to evaluate the possibility if CK-5 non-expression can be used as a marker for early diagnosis of tobacco related oral cancer, RT-PCR using CK-5 specific primers was conducted. Out of 36 precancerous lesions and 29 squamous cell carcinomas (SCC) of buccal mucosa (BM) samples studied, 11 and 13 samples respectively of precancer and SCC did not show CK-5 product in RT-PCR. Down regulation of CK-5 mRNA expression was also observed in some samples. Thus, in conclusion, our results have shown that CK-5 non-expression is the result of transcriptional block. We proposed CK-5 non-expression as a potential marker for the early diagnosis of tobacco related oral cancer.

Cytokeratin expression in precancerous lesions of the human oral cavity.

Cytokeratin (CK) expression was studied in buccal mucosa (BM) from 20 leucoplakia and 7 submucous fibrosis patients using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting and two-dimensional gel electrophoresis with iso-electric focussing (IEF) as the first dimension. Normal BM expresses CK 4, 5, 13, 14 and perhaps 19. Of 20 leucoplakia samples analysed, CK 5 was not detected in 17 samples, while CK 14 was not found in 13 samples. CK 1 and CK 8 were aberrantly expressed in six and seven samples, respectively. CK expression in contralaterally collected uninvolved tissues from 3 patients showed a normal pattern in two samples. Non-expression of CK 5 was observed in five of seven submucous fibrosis samples, while CK 14 was not detected in only two samples. CK 8 was aberrantly expressed in three samples. All the leucoplakia patients were chronic tobacco chewers. Thus, non-expression of CK 5 may be an early event occurring in tobacco-associated pathological changes in the BM.

Transtympanic facial nerve needling: a curvative surgical option for hemifacial spasms.

Ten patients with idiopathic hemifacial spasm were subjected to transtympanic needling of the horizontal segment of the affected facial nerve. Seven patients showed relief of symptoms. This treatment modality is advocated.

Fate of middle ear implants.

During the period 1981 through 1993, 613 cases out of a total of 4340 ear operations performed, needed ossicular chain reconstruction. This excludes stapedectomy operations. Out of 613 cases, 371 were cholesteatomatous and the rest were of safe chronic otitis media. Various graft materials used in ossicular reconstruction consisted of autologous ossicles or tragal cartilage, homologous preserved ossicles, cortical bone, human dentine, cadaveric styloid process and gold prosthesis. Results of the study show the extrusion rate of 1.54% with autologous ossicles, 1.43% with homologous ossicles, 1.19% with tragal cartilage, 3.61% with human cadaveric costal cartilage, 5.45% with cadaveric styloid process, 7.14% with dentine and 8.70% with gold prosthesis. These results are largely comparable with other studies. Natural graft materials like autologous and homologous ossicles have been found to have better take-up and long-term acceptance.

The styloid process in ossicular chain reconstruction (a pilot study).

Our pilot study reports twenty-six cases of resolved chronic otitis media in which the human, cadaveric styloid process was used as an ossicular graft material. A maximum follow-up of one year is presented in this paper. There was no extrusion or rejection of the styloid processes. Hearing improvement with a closure of the air-bone gap to within 10-15 dB. of the pre-operative bone conduction was found in most cases. So far the styloid process has proved to be an ideal ossicular graft though the long-term results are yet to be seen.

Is vidian neurectomy worthwhile?

Vasomotor rhinitis is a frustrating experience both for the consultant and for the patient. The purpose of vidian neurectomy is to destroy the secretomotor nerve supply to the nasal mucosa, the main indication being severe intractable non-atopic vasomotor rhinitis. A review of 208 cases which have undergone transnasal vidian neurectomy by diathermy coagulation in the last five years is presented. The operation has proved worthwhile, the patients remaining symptom-free in 92 per cent of cases (longest follow-up 5 years). There have been no complications.

Expression of GSTM1 in angiofibromas.

The aetiology of juvenile nasopharyngeal angiofibroma (JNA) is largely unknown. In this study, we have investigated the expression of glutathione S transferase M1 (GSTM1) gene in angiofibroma. The GSTM1 allele gene locus is normally found in all human beings. When this is not expressed there is an increased risk of developing a malignancy of the upper aerodigestive tract. In this study, we have assessed eight samples of JNA for the expression of GSTM1, by the polymerase chain reaction (PCR) followed by polyacrylamide gel electrophoresis (PAGE), three of the eight patients studied failed to express this gene. Further investigation in this area is warranted.

The styloid process in ossicular chain reconstruction. II: Long-term analysis.

The human cadaveric styloid process was used as a homograft material for ossicular chain reconstruction in 41 cases of chronic suppurative otitis media over a five-year period. Although technical success was achieved in about 88.23 per cent of the cases, actual patient benefit was around 70.58 per cent; this is comparable to results obtained with most other homologous graft materials. The problem of breakage while remodelling the bone has also increased the risk of transmitting the AIDS virus and consequently undermines the use of this material.

Maghemite (hematite) core (shell) nanorods via thermolysis of a molecular solid of Fe-complex.

An Fe-metal complex with 2'-hydroxy chalcone (2'-HC) ligands [Fe(III) (2'-hydroxy chalcone)(3)] is synthesized by a chemical route and is subjected to different thermal treatments. Upon thermolysis in air at 450 °C for 3 h the complex yields maghemite (γ-Fe(2)O(3)) nanorods with a thin hematite (α-Fe(2)O(3)) shell. X-Ray diffraction (XRD), Mössbauer spectroscopy, diffuse reflectance spectroscopy (UV-DRS), high resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry (VSM) are used to characterize the samples. The stability of the ligand and the Fe-complex is further examined by using thermogravimmetric/differential thermal analysis (TGA/DTA). We suggest a residual ligand controlled mechanism for the formation of an anisotropic nanostructure in a crumbling molecular solid undergoing ligand decomposition. Since the band gap of iron oxide is in the visible range, we explored the use of our core shell nano-rod sample for photocatalytic activity for H(2) generation by H(2)S splitting under solar light. We observed high photocatalytic activity for hydrogen generation (75 ml h(-1)).

On the change in bacterial size and magnetosome features for Magnetospirillum magnetotacticum (MS-1) under high concentrations of zinc and nickel.

The characteristic size, shape and specific alignment of magnetite crystals synthesized by magnetotactic bacteria is a highly coordinated process with precise control over magnetosome vesicle formation, uptake and transport of Fe, and magnetite biomineralization. Magnetosome membranes along with some specific membrane proteins regulate crystal nucleation and morphology of magnetite. Several previous works have indicated that the morphology of mature magnetite crystals is largely unaffected by environmental conditions, though some recent studies have shown the possibility of manipulation of the biomineralization process. In this study we have examined the effects of high concentrations of Zinc and Nickel on the growth of Magnetospirillum magnetotacticum (MS-1) and the corresponding magnetosome formation. Using various characterizations it is shown that the growth of the bacterial cells, as well as the size, shape and magnetosome chain alignment is significantly influenced in the presence of high concentrations of Zn or Ni.

Electric field effect in diluted magnetic insulator anatase Co: TiO2.

An external electric field induced reversible modulation of a room temperature magnetic moment and coercive field is achieved in an epitaxial and insulating thin film of dilutely cobalt-doped anatase TiO2. This first demonstration of an electric field effect in any oxide-based diluted ferromagnet is realized in a high quality epitaxial heterostructure of PbZr(0.2)Ti(0.8)O(3)/Co: TiO(2)/SrRuO(3) grown on (001) LaAlO3. The observed effect, which is about 15% in strength in a given heterostructure, can be modulated over several cycles. Possible mechanisms for electric field induced modulation of insulating ferromagnetism are discussed.

Malignant melanoma of the nasal cavity (a case report).

A case of malignant melanoma of the nasal cavity is reported. The rarity of its occurrence warrants its mention.

Tympanosclerosis-how we look at it.

Tympanosclerosis (TS) is a common sequelae of chronic otitis media found in all age groups. Over a period of 3 years, out of 520 surgical cases, 68 (13%) were found to have varying amounts of Tympanosclerotic plaques (TSP) warranting surgical removal. 60% had extension of TSP over the ossicular chain thus affecting its mobility. Deliberate surgical removal of TSP was undertaken for hearing improvement.Systematic and meticulous removal of TSP rather than en-bloc removal has been found to improve the hearing as close to as in, non-tympanosclerotic ear surgery.

Profile of congenital cholesteatomas of the petrous apex.

Congenital cholesteatomas of the petrous apex are now frequently being approached by otologists. Involvement of the cerebello pontine angle by this lesion produces a myriad of signs and symptoms. Otological as well as neurosurgical literature is reviewed to achieve an overall understanding of the nature and behaviour of this uncommon but interesting lesion.