Fracture Toughness Test with a Sharp Notch Introduced by Focussed Ion Beam

The validity of fracture toughness data obtained from tests with V-notched bending bars is affected by the notch root radius and the presence of R-curve behavior. A macroscopic test specimen has been developed that contains a notch introduced by focused ion beam machining. This produces a notch root radius of less than 0.1 μm, so that notch effects can be ignored for most ceramics. Also, due to the very small notch depths the influence of a rising R-curve should be very close to that of natural cracks. First tests, carried out on a Ce-doped zirconia ceramic resulted in a toughness of K _Ic ≈ 5.9 MPa√m.     

Multifunctional substrates of thin porous alumina for cell biosensors

We have fabricated anodic porous alumina from thin films (100/500 nm) of aluminium deposited on technological substrates of silicon/glass, and investigated the feasibility of this material as a surface for the development of analytical biosensors aiming to assess the status of living cells. To this goal, porous alumina surfaces with fixed pitch and variable pore size were analyzed for various functionalities. Gold coated (about 25 nm) alumina revealed surface enhanced Raman scattering increasing with the decrease in wall thickness, with factor up to values of approximately 10⁴ with respect to the flat gold surface. Bare porous alumina was employed for micro-patterning and observation via fluorescence images of dye molecules, which demonstrated the surface capability for a drug-loading device. NIH-3T3 fibroblast cells were cultured in vitro and examined after 2 days since seeding, and no significant (P > 0.05) differences in their proliferation were observed on porous and non-porous materials. The effect on cell cultures of pore size in the range of 50–130 nm—with pore pitch of about 250 nm—showed no significant differences in cell viability and similar levels in all cases as on a control substrate. Future work will address combination of all above capabilities into a single device.     

Energy loss of energetic Ar, Kr, Au and U ions in mylar, aluminum and isobutane

The BigSol Superconducting Solenoid Beam Line at the Texas A&M Superconducting Cyclotron has been used to measure energy losses of ⁴⁰Ar, ⁸⁴Kr, ¹⁹⁷Au and ²³⁸U ions in mylar, aluminum and isobutane at energies ranging from the Bragg peak up to several MeV/nucleon. The experimental data are compared with predictions from the SRIM code. In general experimental data for ⁴⁰Ar and ⁸⁴Kr are in agreement with model predictions whereas differences on the order of 10% are evidenced in some cases for ¹⁹⁷Au and ²³⁸U ions especially at and around the Bragg peak energies.     

Modeling the Drying of Grass Seeds (Brachiaria brizantha) in Fluidized Beds

A modified three-phase model is developed to simulate the drying of Brachiaria brizantha in fluidized beds. In this new model, the constitutive equation of drying kinetics is formulated including both the constant rate and the falling rate mechanisms; the seed shrinkage is taken into account during all drying operation and the transition between bubbling to slugging regime is delineated for estimating the bubble velocity and size. Such modifications improve the mathematical model to better simulate the drying of coarse particles in fluidized beds. The best estimation of the five adjustable model parameters, which are required to define heat and mass transfer mechanisms between interstitial gas and seed particles and to specify the heat loss from dryer walls to ambient air, is attained by incorporating an optimization routine into the computer model program. Having been specially designed to supply data for this model, experiments are performed in a bath laboratory-scale fluidized bed. Additional data are generated to validate the model and program routines. Results show a good agreement between simulated and experimental data, validating the approach used to describe drying kinetics and particle shrinkage.     

Some simple distributed algorithms for sparse networks

Summary. We give simple, deterministic, distributed algorithms for computing maximal matchings, maximal independent sets and colourings. We show that edge colourings with at most colours, and maximal matchings can be computed within deterministic rounds, where is the maximum degree of the network. We also show how to find maximal independent sets and -vertex colourings within deterministic rounds. All hidden constants are very small and the algorithms are very simple. Received: August 2000 / Accepted: November 2000     

Green’s functions for the T-stress of small kink and fork cracks

Green’s functions for T-stresses used so far are restricted to symmetric crack problems, for instance, edge cracks normal to the free surface of a rectangular plate. In the case of more complicated cracks, component geometries, and loading cases, a more general formulation of the Green’s function has to be used. Such a relation was recently proposed by the authors. As an example, Green’s functions for T-stresses acting at the tip of a kinked crack were determined by extending the Cotterell-Rice procedure. Application to the edge-cracked plate revealed an excellent agreement of local T-stress with results obtained directly from FE computations. A simple approximate relation with a high accuracy for kink angles of up to 30° is proposed that allows an estimate of the T-stress from the stress field of the unkinked crack. It is shown that the T-stress of a kinked crack under pure mode-I loading can be computed roughly as the difference of the radial and tangential stresses of the unkinked crack at the tip of the kink.     

Big BU/CY is associated with a favorable long-term outcome in patients allotransplanted for chronic myelogenous leukemia in chronic phase

Twenty-six adult patients, median age 36 years (range 21-53) with chronic myeloid leukemia in first chronic phase were allotransplanted between October 1989 and May 1995. The preparative regimen consisted of busulphan 16 mg/kg and cyclophosphamide 200 mg/kg (big BU/CY). Cyclosporin A and methotrexate were used for GVHD prophylaxis. Twenty-two donors were HLA-identical siblings and four donors were mismatched for one antigen of class I. The global incidence of acute GVHD was 50%, that of severe aGVHD (grades 3-4) was 11%; the global incidence of chronic GVHD was 30%. No patients developed veno-occlusive disease of the liver or interstitial pneumonia. Five patients died, one of relapse, four of transplant-related causes, mostly related to aGVHD; thus, the transplant-related mortality was 16%. Twenty-one patients are alive, in remission, with a median follow-up of 55 months (range 24-90); actuarial probability of survival is 78% (CI 64-96). Our study shows that this conditioning regimen is relatively easy to administer and seems to be as effective as, if not superior to, regimens containing TBI, in patients with chronic myeloid leukemia in chronic phase and the transplant-related mortality is not excessive even in older patients.     

Characterisation of different typical Italian breads by means of traditional,spectroscopic and image analyses

In this paper a complete characterisation of four typical durum wheat breads produced in Italy was performed, from the starting semolinas to the final product, also considering the intermediate dough. An evaluation of the quality of durum wheat re-milled semolinas was carried out by means of routine investigations, together with nuclear magnetic resonance (NMR) and isotope ratio mass spectrometry (IRMS) analyses, that were also applied to dough ready for baking and bread to monitor the variations that occur during processing. The experimental data obtained from routine and spectroscopic determinations were investigated using multivariate statistical analysis to evaluate the possibility of differentiating flours, doughs and breads according to their geographical origin. Computerised image analysis was applied to quantify the crumb grain features of different bread types, and to try to characterise each bread type through a set of crumb morphological and colour parameters.