The impact of loads on standard diameter, small diameter and mini implants: A comparative laboratory study

Objectives: While caution in the use of small-diameter (≤3.5 mm) implants has been advocated in view of an increased risk of fatigue fracture under clinical loading conditions, a variety of implant designs with diameters <3 mm are currently offered in the market for reconstructions including fixed restorations. There is an absence of reported laboratory studies and randomized-controlled clinical trials to demonstrate clinical efficacy for implant designs with small diameters. This laboratory study aimed to provide comparative data on the mechanical performance of a number of narrow commercially marketed implants. Materials and methods: Implants of varying designs were investigated under a standardized test set-up similar to that recommended for standardized ISO laboratory testing. Implant assemblies were mounted in acrylic blocks supporting laboratory cast crowns and subjected to 30° off-axis loading on an LRX Tensometer. Continuous output data were collected using Nexygen software. Results: Load/displacement curves demonstrated good grouping of samples for each design with elastic deformation up to a point of failure approximating the maximum load value for each sample. The maximum loads for Straumann (control) implants were 989 N (±107 N) for the 4.1 mm RN design, and 619 N (±50 N) for the 3.3 mm RN implant (an implant known to have a risk of fracture in clinical use). Values for mini implants were recorded as 261 N (±31 N) for the HiTec 2.4 mm implant, 237 N (±37 N) for the Osteocare 2.8 mm mini and 147 N (±25 N) for the Osteocare mini design. Other implant designs were also tested. Conclusions: The diameters of the commercially available implants tested demonstrated a major impact on their ability to withstand load, with those below 3 mm diameter yielding results significantly below a value representing a risk of fracture in clinical practice. The results therefore advocate caution when considering the applicability of implants ≤3 mm diameter. Standardized fatigue testing is recommended for all commercially available implants

The thyroid gland and its variations: a cadaveric study

The size and shape of the thyroid gland is subject to much variation, as stated by Wood Jones. Literature is replete with a large number of variations of the gland. By utilizing various techniques like gross dissection, histology, developmental anatomy, and recently thyroid scans and scintigraphy, some common and certain rare anomalies of the thyroid with their possible developmental bases are described in the literature. An attempt has been made to study the thyroid glands in 90 male cadavers available in our department, with ages ranging from 60 to 75 years with mean height of 5&#8217;4&#8221;. The parameters that were observed included the length and width of lobes, presence or absence of pyramidal lobe, levator glandulae thyroideae, and isthmus with its relation to the tracheal rings. The average length of the right lobe was 4.32 cm, and the left lobe was 4.22 cm. The thickness of the right lobe was 1.13 cm, and the left lobe was 1.18 cm. Pyramidal lobe was present in 34 (37.77%) cases, frequently arising from the left lobe, while the levator glandulae thyroideae was present in 27 (30%) instances, mostly attached superiorly to the body of the hyoid bone. The isthmus was absent in 15 (16.66%) cases; its relation with the tracheal rings greatly varied from the cricoid cartilage to the fourth tracheal ring. Knowledge of variations of the thyroid assumes significance as this has relevance in the resection of thyroid, tumours, and tracheostomy. Folia Morphol 2010; 69, 1: 47&#8211;5

Distribution pattern analysis of epiphytic bacteria on ethnomedicinal plant surfaces: A micrographical and molecular approach

AbstractThe epiphytic bacterial community prevalent on ethnomedicinal plant surfaces were studied for their diversity, niche localization and colonization using the micrographical and molecular approaches. Scanning electron microscopy (SEM) revealed the presence of large aggregates of bacterial communities. The bacterial localization was observed in the grooves along the veins, stomata and near the trichomes of leaves and along the root hairs. A total of 20 cultivable epiphytes were characterized which were analyzed for richness, evenness and diversity indices. Species belonging to the genera Bacillus and Pseudomonas were the most abundant. Bacillus thuringiensis was the most prevalent epiphyte with the ability to form biofilm, as a mode of adaptation to environmental stresses. Biofilm formation explains the potential importance of cooperative interactions of epiphytes among both homogeneous and heterogeneous populations observed under SEM and influencing the development of microbial communities. The study has revealed a definite pattern in the diversity of culturable epiphytic bacteria, host-dependent colonization, microhabitat localization and biofilm formation which play a significant role in plant–microbe interaction

Geochemistry and Organic Contaminants in the Sediments of Great Slave Lake, Northwest Territories, Canada

A study was carried out in the summer of 1987 to determine the geochemistry and distribution of trace elements, PCBs and 16 other chlorinated hydrocarbons in sediments from selected areas in Great Slave Lake, Northwest Territories, Canada. Sediment cores were collected at three sampling stations in the west basin of the lake on a transect from the Slave River delta to the outlet of the Mackenzie River. The geotechnical composition of the sediments showed the deposition of similar material at all sampling stations. Sediment dating indicated a very high sedimentation rate (46.6 g/cm&sup2;/year) at a 110 m water depth in the vicinity of the Slave River delta and mixing of bottom sediments at the southwestern part of the lake. The concentrations of trace elements (Cu, Ni, Co, Cr, V, Pb and Zn) were uniform in all sediment profiles. However, surficial sediments were enriched by arsenic, Canadian standard CLB-1 containing 51 PCB congeners was used in the determination of PCBs in the sediment. Thirty-three PCB congeners were detected and their concentrations determined in selected sections of sediment cores. The most abundant congeners were 15 and 18, 44, 49, 52 and 101 (IUPAC numbering) with maximum concentrations 3.52, 2.68, 2.44, 6.20 and 2.44, 6.20 and 2.13 ng/g respectively. The concentration pattern of PCBs in Great Slave Lake sediments indicated considerably greater quantities of lower than higher chlorinated biphenyls. Several congeners, particularly those having 7-10 chlorine atoms, were determined in concentrations smaller than 0.20 ng/g only at one sediment depth. Hexachlorobutadiene, 1, 2, 3, 4-tetrachlorobenzene, pentachlorobenzene, alpha-HCH, hexachlorobenzene, pentachloroanisol and alpha-chlordane were present at all stations at different sediment depths. Maximum concentrations of the 16 chlorinated hydrocarbons analyzed in Great Slave Lake sediments were between 0.08 and 1.04 ng/g. The concentrations of PCBs and other chlorinated hydrocarbons were about two orders of magnitude lower than those in Lake Ontario sediments.Key words: Great Slave Lake, sediments, geochemistry, PCBs, chlorinated hydrocarbonsR&Eacute;SUM&Eacute;. Au cours de l&rsquo;&eacute;t&eacute; de 1987, on a proc&eacute;d&eacute; &agrave; une &eacute;tude pour d&eacute;terminer la geochimie et la r&eacute;partition des oligo-&eacute;l&eacute;ments, des BPC et de 16 autres hydrocarbures chlorts dans des sediments provenant de zones s&eacute;lectionn&eacute;es du Grand Lac de l&rsquo;Esclave dans les Territoires du Nord-Ouest auCanada. On a pr&eacute;lev&eacute; des carottes de s&eacute;diments &agrave; trois postes d&rsquo;&eacute;chantillonnage dans le bassin ouest du lac le long d&rsquo;un axe allant du delta de la rivi&egrave;re Slave &agrave; l&rsquo;embouchure du fleuve Mackenzie. La composition g&eacute;ochimique des sediments a r&eacute;v&eacute;l&eacute; un d&eacute;p&ocirc;t de mat&eacute;riau similaire &agrave; tous les postes d&rsquo;&eacute;chantillonnage. La datation des s&eacute;diments a montr&eacute; un fort taux de sedimentation (46,6 g.cm-* par an) h 110 m sous l&rsquo;eau, dans la zone du delta de la Slave, et un m&eacute;lange des s&eacute;diments de fond dans la partie sud-ouest du lac. Les concentrations d&rsquo;oligo-&eacute;l&eacute;ments (Cu, Ni, Co, Cr, V, Pb, et Zn) &eacute;taient uniformes dans tous les profils de s&eacute;diments. Les s&eacute;diments de surface cependant contenaient en plus de l&rsquo;arsenic. On a utilis&eacute; des CLB-1 canadiens normalists contenant 51 cong&eacute;n&egrave;res de BPC pour d&eacute;terminer+les BPC dans les s&eacute;diments. On a d&eacute;tect&eacute; 33 congtntres de BPC et d&eacute;termin&eacute; leurs concentrations dans des sections choisies des carottes de suiments. Les cong&eacute;n&egrave;res les plus abondants &eacute;taient les num&eacute;ros 15 et 18,44,49,52et 101 (num&eacute;rotation de I&rsquo;IUPAC) avec des concentrations maximales respectives de 3.52, 2.68, 2,44,6,20 et 2,13 ng.g-l. Le sch&eacute;ma de concentration des BPC dans les sediments du Grand Lac de l&rsquo;Esclave r&eacute;v&eacute;l&eacute; des quantit&eacute;s considerablement plus importantes de biphenyles peu chlor&eacute;s parrapport aux biph&egrave;nyles tr&eacute;s chlor&eacute;s. On a trouv&eacute; plusieurs cong&eacute;n&egrave;res, en particulier ceux ayant de 7 &agrave; 10 atomes de chlore, en concentrations inf&eacute;rieures &agrave; 0,20 ng.g&rdquo; &agrave; seulement une certaine profondeur de s&eacute;diments. On a trouv&eacute; de l&rsquo;hexachlorobutadi&egrave;ne, du t&eacute;trachlorobenz&egrave;ne-1,2,3,4, du pentachlorobenz&egrave;ne, du H.C.H.-A, de l&rsquo;hexachlorobenz&egrave;ne, du pentachloroanisole et du chlordane-A &agrave; tous les postes &agrave; diff&eacute;rentes profondeurs de s&eacute;diments. Les concentrations maximales des 16 hydrocarbures chlor&eacute;s analysts dans les sediments du Grand Lac de l&rsquo;Esclave se situaient entre 0,08 et 1,04 ng.g&rdquo;. Les concentrations de BPC et d&rsquo;autres hydrocarbures chlor&eacute;s &eacute;taient d&rsquo;environ deux ordres de grandeur inf&eacute;rieures &agrave; celles contenues dans les s&eacute;diments du lac Ontario.Mots cl&eacute;s: Grand Lac de l&rsquo;Esclave, s&eacute;diments, g&eacute;ochimie, BPC, hydrocarbures chlor&eacute;

High-energy electron induced gain degradation in bipolar junction transistors

This paper describes the effect of 8 MeV electron beam on the forward current gain of space borne commercial indigenous bipolar junction transistors 2N2219A (npn), 2N3019 (npn) and 2N2905A (pnp). The devices are exposed to 8 MeV electron in the biased condition. The collector characteristics and Gummel plots are obtained as a function of accumulated dose. An excess base current model as well as Messenger-Spratt equation have been used to account for the observed gain degradation. The results indicate that 8 MeV electrons of high dose rate induce gain degradation by increasing the base current as well as decrease in collector current. The current gain degradation appears to be predominantly due to displacement damage in the bulk of the transistor. Off-line measurements of the hFE of the irradiated transistors indicate that the displacement induced defect and recombination centers do not anneal even at 150 °C. © 2006 Elsevier B.V. All rights reserved

Neutrino lensing and modification of Newtonian gravity at large distances

The nature of the modification to neutrino lensing from galaxies, as caused by possible modifications to Newtonian gravity at large distances, is studied.Comment: 6 pages, 1 figur

Signature of Randall-Sundrum Quantum Gravity model in γγ\gamma\gamma scattering in the TeV range

We examine the implications of the Randall-Sundrum gravity models on $\gamma\gamma$ scattering in the TeV range.Comment: 7 pages, 4 figure

CP violation in the decay mode B→πγγB\to \pi \gamma \gamma

Within the framework of Standard Model, the exclusive decay mode $B\to \pi \gamma \gamma$ is studied. Although the usual short distance contribution is small compared to the similar $B\to K\gamma\gamma$ mode, the process offers the possibility of studying the CP violation, a feature absent in the $B \to K$ counterpart.Comment: 11 page latex file including 2 ps figures. Typos corrected, minor changes. To appear in PR