Fracture and contact problems for an elastic wedge

The plane elastostatic contact problem for an infinite elastic wedge of arbitrary angle is discussed. The medium is loaded through a frictionless rigid wedge of a given symmetric profile. Using the Mellin transform formulation the mixed boundary value problem is reduced to a singular integral equation with the contact stress as the unknown function. With the application of the results to the fracture of the medium in mind, the main emphasis in the study has been on the investigation of the singular nature of the stress state around the apex of the wedge and on the determination of the contact pressure

On The Dynamics Of The Difference Equation

In this paper, we studied the global behavior of the difference equation nbspwith non-negative parameters and the initial conditions nbspare non-negative real numbers

Modeling growth of Si1−xGex epitaxial films from disilane and germane

A Langmuir–Hinshelwood‐type kinetic model is developed for modeling growth of silicon–germanium alloys from disilane and germane on Si substrates. Gas source molecular beam epitaxy was employed to grow Si1−xGex films at various germanium fractions, x, in the alloy and at different temperatures. The model correctly predicts experimentally observed and previously reported behavior; a monotonic decrease with germanium fraction at higher substrate temperatures (700 °C) and a maximum in the growth rate for lower temperatures (550 °C and 610 °C).  Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70836/2/JAPIAU-73-10-5193-1.pd

Effect of heparin in the intraocular irrigating solution on postoperative inflammation in the pediatric cataract surgery

Yelda B Özkurt, Arzu Taskiran, Nadire Erdogan, Baran Kandemir, Ömer K Dog?anDepartment of Ophthalmology, Kartal Training and Research Hospital, Istanbul, TurkeyPurpose: To evaluate the influence of irrigation of the anterior chamber with heparin sodium on postoperative inflammation after pediatric cataract surgery. Setting: Kartal Training and Research Hospital, First Eye Clinic, Istanbul, Turkey.Design: Randomized prospective double-blind study.Methods: Fourteen consecutive eyes from 14 patients aged 8.9 ± 5.9 years, (range 3–18 years) (group 1) and 19 eyes from 19 patients aged 9.1 ± 5.2 (range 1.5–18 years) (group 2) underwent pediatric cataract surgery. Five patients in group 1 were between three and five years old. One patient was 1.5 years old and six patients in group 2 were between three and five years old. During the procedure, group 1 received anterior chamber irrigation with heparin sodium (5 IU/cc) and 1 ml of heparin sodium (concentration 10 IU/ml) added to the irrigating balanced salt solution (BSS Plus; Alcon Laboratories, Inc., Fort Worth, TX, USA) while group 2 received BSS without heparin sodium only. Cases aged under three years received anterior vitrectomy in addition to posterior capsulorrhexis. One eye received anterior vitrectomy in group 1 and two eyes received anterior vitrectomy in group 2. Cases with preoperative complications were not included in the study. Early and late postoperative inflammatory complications, including fibrin formation, anterior and posterior synechia, cyclitic and pupillary membrane formation were recorded and compared.Results: Mild anterior chamber reaction was observed in three patients in Group 1, while nine cases in group 2 experienced marked anterior chamber reaction. In four of nine patients from group 2, anterior chamber reaction was severe and resulted in pupillary membrane and synechia despite treatment in the postoperative 7th day, while in all three cases in group 1, reaction disappeared by the 7th day.Conclusion: Anterior chamber irrigation with heparin during pediatric cataract surgery may minimize early inflammatory reaction and decrease the number of postoperative inflammatory related complications.Keywords: pediatric, cataract, surgery, inflammatio

Regularized reconstruction in quantitative SPECT using CT side information from hybrid imaging

A penalized-likelihood (PL) SPECT reconstruction method using a modified regularizer that accounts for anatomical boundary side information was implemented to achieve accurate estimates of both the total target activity and the activity distribution within targets. In both simulations and experimental I-131 phantom studies, reconstructions from (1) penalized likelihood employing CT-side information-based regularization (PL-CT), (2) penalized likelihood with edge preserving regularization (no CT) and (3) penalized likelihood with conventional spatially invariant quadratic regularization (no CT) were compared with (4) ordered subset expectation maximization (OSEM), which is the iterative algorithm conventionally used in clinics for quantitative SPECT. Evaluations included phantom studies with perfect and imperfect side information and studies with uniform and non-uniform activity distributions in the target. For targets with uniform activity, the PL-CT images and profiles were closest to the 'truth', avoided the edge offshoots evident with OSEM and minimized the blurring across boundaries evident with regularization without CT information. Apart from visual comparison, reconstruction accuracy was evaluated using the bias and standard deviation (STD) of the total target activity estimate and the root mean square error (RMSE) of the activity distribution within the target. PL-CT reconstruction reduced both bias and RMSE compared with regularization without side information. When compared with unregularized OSEM, PL-CT reduced RMSE and STD while bias was comparable. For targets with non-uniform activity, these improvements with PL-CT were observed only when the change in activity was matched by a change in the anatomical image and the corresponding inner boundary was also used to control the regularization. In summary, the present work demonstrates the potential of using CT side information to obtain improved estimates of the activity distribution in targets without sacrificing the accuracy of total target activity estimation. The method is best suited for data acquired on hybrid systems where SPECT-CT misregistration is minimized. To demonstrate clinical application, the PL reconstruction with CT-based regularization was applied to data from a patient who underwent SPECT/CT imaging for tumor dosimetry following I-131 radioimmunotherapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85409/1/pmb10_9_007.pd

A case of pulmonary aspergillosis in white storks

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗAspergillosis is a fungal infection affecting respiratory system both in mammals and avian species. It is more commonly encountered in birds, in comparison with its mammalian counterpart. Mostly isolated strains are Aspergillus fumigatus (95%) and Aspergillus flavus (5%). Affected lungs and air sacs reveal miliary to gross lesions like gray-yellowish or white-grayish granulomatous foci surrounded by white halos indicative of inflammatory infiltration. Five storks found dead in the rural areas near Istanbul were submitted to our faculty between years 2008 and 2014. Two of them were thought to be younger than 1-year-old and the other three were older than one year of age. Necropsies were performed right after their submissions. Aspergillosis lesions were observed in the lungs and thoracic air sacs of the first four storks. In addition to these changes the lesions were detected at the aortic bifurcation and on the testicular and renal capsule of the fifth stork. Histopathology revealed encapsulated granulomas with foci of caseous necrosis at the center surrounded by numerous macrophages, heterophil leukocytes, lymphocytes and foreign body giant cells in all the storks. Following the gross, histopathological and mycological examinations the agents were detected as Aspergillus fumigatus. Although, the number of reported deaths due to Aspergillosis is not high in storks, we believe that these birds are quite susceptible to the disease and stress factors such as migration increases the risk of pathogenicity. This report was designed as a contribution to literature since there is only one reported case available with respect to aspergillosis associated death in storks and stress factors such as migration may also predispose storks to the disease

Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers

Cataloged from PDF version of article.We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns. (C) 2011 Optical Society of Americ