New perspectives for direct PDMS microfabrication using a CD-DVD laser.

A simple and inexpensive alternative to high-power lasers for the direct fabrication of microchannels and rapid prototyping of poly-dimethylsiloxane (PDMS) is presented. By focusing the infrared laser beam of a commercial, low-power CD-DVD unit on absorbing carbon micro-cluster additives, highly localized PDMS combustion can be used to etch the polymer, which is otherwise transparent at such wavelengths. Thanks to a precise and automated control of laser conditions, laser-induced incandescence is originated at the material surface and produces high-resolution micropatterns that present properties normally induced with lasers of much greater energies in PDMS: formation of in situ nanodomains, local fluorescence and waveguide patterns. An extensive study of the phenomenon and its performance for PDMS microfabrication are presented.

Bose-Einstein condensation in the relativistic ideal Bose gas.

The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.

Rapid high-performance liquid chromatography method for the analysis of sodium benzoate and potassium sorbate in foods.

A rapid and reliable method is presented for the determination of the preservatives sodium benzoate and potassium sorbate in fruit juices, sodas, soy sauce, ketchup, peanut butter, cream cheese, and other foods. The procedure utilizes high-performance liquid chromatography (HPLC) followed by UV diode array detection for identification and quantitation of the two preservatives. Liquid samples were prepared by diluting 1 ml of the sample with 10 ml of an acetonitrile/ammonium acetate buffer solution. Samples of viscous or solid foods were prepared by blending the sample with the same buffer solution in a 1:5 ratio followed by a dilution identical to liquid samples. All samples were filtered to remove particulate matter prior to analysis. The HPLC determination of the preservatives was performed using a reversed-phase C18 column and UV detection at 225 nm for sodium benzoate and 255 nm potassium sorbate. The percentage of preservative in the sample was calculated by external standard using authentic sodium benzoate and potassium sorbate. Apple juice, apple sauce, soy sauce, and peanut butter, spiked at 0.10 and 0.050% for both sodium benzoate and potassium sorbate, yielded recoveries ranging from 82 to 96%. The method can detect 0.0010% (10 mg/l) of either preservative in a juice matrix.

Genetic and biochemical characterization of the yeast spo12 protein.

We have performed a genetic and biochemical analysis of the SPO12 gene, which regulates meiotic nuclear divisions in budding yeast. When sporulated, spo12 mutants undergo a single meiotic nuclear division most closely resembling meiosis II. We observed that Spo12 protein is localized to the nucleus during both meiotic divisions and that Clb1-Cdc28, Clb3-Cdc28, Clb4-Cdc28, and Clb5-Cdc28 kinase activities during meiosis were not affected by a spo12 mutation. Using two-hybrid analysis, we identified several genes, three of which are meiotically induced, that may code for proteins that interact with Spo12p. We also observed that two genes, BNS1 (Bypasses Need for Spo12p), which has homology to SPO12, and SPO13, whose mutant phenotype is like that of spo12, can partially suppress the meiotic defect of spo12 mutants when overexpressed. We found that Spo12p is also localized to the nucleus in vegetative cells and that its level peaks during G2/M. We observed that a spo12 mutation is synthetically lethal in vegetative cells with a mutation in HCT1, a gene necessary for cells to exit mitosis, suggesting that Spo12p may have a role in exit from mitosis.

The head involution defective gene of Drosophila melanogaster functions in programmed cell death.

Deletions of chromosomal region, 75C1,2 block virtually all programmed cell death (PCD) in the Drosophila embryo. We have identified a gene previously in this interval, reaper (rpr), which encodes an important regulator of PCD. Here we report the isolation of a second gene in this region, head involution defective (hid), which plays a similar role in PCD. hid mutant embryos have decreased levels of cell death and contain extra cells in the head. We have cloned the hid gene and find that its expression is sufficient to induce PCD in cell death defective mutants. The hid gene appears to encode a novel 410-amino-acid protein, and its mRNA is expressed in regions of the embryo where cell death occurs. Ectopic expression of hid in the Drosophila retina results in eye ablation. This phenotype can be suppressed completely by expression of the anti-apoptotic p35 protein from baculovirus, indicating that p35 may act genetically downstream from hid.

Programmed cell death in Drosophila.

During Drosophila development, large numbers of cells undergo natural cell death. Even though the onset of these deaths is controlled by many different signals, most of the dying cells undergo common morphological and biochemical changes that are characteristic of apoptosis in vertebrates. We have surveyed a large fraction of the Drosophila genome for genes that are required for programmed cell death by examining the pattern of apoptosis in embryos homozygous for previously identified chromosomal deletions. A single region on the third chromosome (in position 75C1,2) was found to be essential for all cell deaths that normally occur during Drosophila embryogenesis. We have cloned the corresponding genomic DNA and isolated a gene, reaper, which is capable of restoring apoptosis when reintroduced into cell death defective deletions. The reaper gene is specifically expressed in cells that are doomed to die, and its expression precedes the first morphological signs of apoptosis by 1-2 h. This gene is also rapidly induced upon X-ray irradiation, and reaper deletions offer significant protection against radiation-induced apoptosis. Our results suggest that reaper represents a key regulatory switch for the activation of apoptosis in response to a variety of distinct signals.

Genetic control of programmed cell death in Drosophila.

A gene, reaper (rpr), that appears to play a central control function for the initiation of programmed cell death (apoptosis) in Drosophila was identified. Virtually all programmed cell death that normally occurs during Drosophila embryogenesis was blocked in embryos homozygous for a small deletion that includes the reaper gene. Mutant embryos contained many extra cells and failed to hatch, but many other aspects of development appeared quite normal. Deletions that include reaper also protected embryos from apoptosis caused by x-irradiation and developmental defects. However, high doses of x-rays induced some apoptosis in mutant embryos, and the resulting corpses were phagocytosed by macrophages. These data suggest that the basic cell death program is intact although it was not activated in mutant embryos. The DNA encompassed by the deletion was cloned and the reaper gene was identified on the basis of the ability of cloned DNA to restore apoptosis to cell death defective embryos in germ line transformation experiments. The reaper gene appears to encode a small peptide that shows no homology to known proteins, and reaper messenger RNA is expressed in cells destined to undergo apoptosis.

Piezoelectric ceramic implants: in vivo results.

The suitability of barium titanate (BaTiO3) ceramic for direct substitution of hard tissues was evaluated using both electrically stimulated (piezoelectric) and inactive (nonpolarized) test implants. Textured cylindrical specimens, half of them made piezoelectric by polarization in a high electric field, were implanted into the cortex of the midshaft region of the femora of dogs for various periods of time. Interfacial healing and bio-compatibility of the implant material were studied using mechanical, microradiographical, and histological techniques. Our results indicate that barium titanate ceramic shows a very high degree of biocompatibility as evidenced by the absence of inflammatory or foreign body reactions at the implant-tissue interface. Furthermore, the material and its surface porosity allowed a high degree of bone ingrowth as evidenced by microradiography and a high degree of interfacial tensile strength. No difference was found between the piezoelectric and the electrically neutral implant-tissue interfaces. Possible reasons for this are discussed. The excellent mechanical properties of barium titanate, its superior biocompatibility, and the ability of bone to form a strong mechanical interfacial bond with it, makes this material a new candidate for further tests for hard tissue replacement.

Piezoelectric ceramic implants: a feasibility study.

A piezoelectric ceramic has been investigated as a direct substitute for hard tissues. Barium titanate (BaTiOz) power was slipcast and fired at 1430 degrees C for 2 hr, then made piezoelectric by polarizing. After 16 and 86 days of implantation in the cortex of the femoral midshafts, the femora with test specimens were sectioned into about 4-cm lengths. Their voltage outputs were measured under cyclic load at 1 Hz. The present results show that the voltage gradient at the implant surface is 0.15 mV/mm for the 16-day implantation with a 445-N (100-lbs.) load. This in turn can give rise to about 0.01 microA current flow in the adjacent area of the 16-day implant. The 86-day implant showed an order of magnitude higher voltage output compared to the 16-day implant with the same magnitude of loads. This is probably due to the "load-transfer" efficiency through the implants, since the voltage output is directly proportional to the actual load transferred to the implant. The more bone implant interface matures, the better the load transfer occurs through the implant, resulting in higher voltage output.

The mechanical stability of barium titanate (ceramic) implants in vitro.

Dense, polycrystalline barium titanate (BaTiO3) specimens showed a modulus of rupture of 85.5 +/- 9.0 MPa and a compressive strength of 486 +/- 75 MPa. These values are considerable higher than those which had been previously reported. In addition, there was no significant drop in compressive strength after in vitro aging for 4 weeks in saline solution.