Watching the growth of bulk grains during recrystallization of deformed metals.

We observed the in situ growth of a grain during recrystallization in the bulk of a deformed sample. We used the three-dimensional x-ray diffraction microscope located at the European Synchrotron Radiation Facility in Grenoble, France. The results showed a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical characterization of microstructures. For recrystallization, the in situ method includes direct measurements of nucleation and boundary migration through a deformed matrix.

Grain nucleation and growth during phase transformations.

The mechanical properties of polycrystalline materials are largely determined by the kinetics of the phase transformations during the production process. Progress in x-ray diffraction instrumentation at synchrotron sources has created an opportunity to study the transformation kinetics at the level of individual grains. Our measurements show that the activation energy for grain nucleation is at least two orders of magnitude smaller than that predicted by thermodynamic models. The observed growth curves of the newly formed grains confirm the parabolic growth model but also show three fundamentally different types of growth. Insight into the grain nucleation and growth mechanisms during phase transformations contributes to the development of materials with optimal mechanical properties.

In situ measurement of grain rotation during deformation of polycrystals.

Texture evolution governs many of the physical, chemical, and mechanical properties of polycrystalline materials, but texture models have only been tested on the macroscopic level, which makes it hard to distinguish between approaches that are conceptually very different. Here, we present a universal method for providing data on the underlying structural dynamics at the grain and subgrain level. The method is based on diffraction with focused hard x-rays. First results relate to the tensile deformation of pure aluminum. Experimental grain rotations are inconsistent with the classical Taylor and Sachs models.

Adsorption and Interactions of Methyl Green with Montmorillonite and Sepiolite.

The divalent organic cation, methyl green (MG), undergoes a slow transformation (6 h) to a monovalent cation, carbinol (MGOH(+)) upon dilution of its solution (10 mM), or in a buffer at neutral pH. Adsorption isotherms of MG on montmorillonite were determined by two procedures, both of which yield a final pH of suspensions between 7 to 7.4. When the amounts of MG in suspension were lower than the cation-exchange capacity (CEC) of the clay (0.8 mol(c)/kg clay), no measurable amount of MG remained in solution. The maximal amounts of MGOH(+) adsorbed were larger than those of MG(2+), being 1.15 and 0.75 mol MG/kg clay, respectively, corresponding to 140% of the CEC in the first case. On a charge basis the adsorption of added MG(2+) amounts to 185% of the CEC, which raises the possibility that a certain fraction of MG(2+) transformed into the monovalent form during the incubation period, since other divalent organic cations previously studied only adsorbed up to the CEC (paraquat), or slightly above it (diquat). Adsorption of MG on sepiolite (CEC=0.15 mol(c)/kg) further emphasizes the two patterns of its adsorption. The maximal adsorbed amounts of MG(2+) and MGOH(+) were 0.09 and 0.30 mol/kg clay, respectively. X-ray diffraction measurements gave lower values for the basal spacings for montmorillonite-MG(+) than for MGOH(+), suggesting that MG(2+) binds two clay platelets together, as in the case of other divalent cations. A competition for adsorption between MG and the monovalent organic cation, acriflavin (AF), gave lower adsorbed amounts of AF when competing with MG(+), which is interpreted to be due to the smaller basal spacing in this case, which partially inhibits the entry of AF molecules into the interlammelar space. Spectra of montmorillonite-MG particles in the visible range exhibited significant differences between clay-MG and clay-carbinol. Copyright 2000 Academic Press.

Measurements of electromagnetic fields radiated from communication equipment and of environmental electromagnetic noise: impact on the use of communication equipment within the hospital.

The increasing use of all types of cellular telephones requires the formulation of new standards to ensure the immunity of electronic medical equipment to electromagnetic radiation. It will be many years before all hospital medical equipment conforms to new and higher standards. Until that time, the medical, security, maintenance, and other staff will need to be ever vigilant regarding restrictions on the use of wireless equipment within the hospital, to prevent potential danger to the lives of the patients. A comprehensive hospital policy must be formulated to reduce risks to patients from equipment susceptible to electromagnetic interference (EMI). Such an aim should address the following needs: To devise a uniform policy for the instruction of hospital staff, visitors, and patients, thereby reducing confusion regarding the use of cellular telephones, beepers, and portable transceivers. To implement a policy that avoids unwarranted restrictions but does not ignore statistical evidence regarding potential EMI problems. To allow comparison, with other clinical facilities, of the benefits derived from such a policy.

Molecular and functional phenotypes of melanoma cells with abnormalities in HLA class I antigen expression.

Analysis of melanoma cell lines with abnormalities in HLA Class I antigen expression has identified two serological phenotypes caused by distinct molecular defects. One is characterized by lack of HLA Class I antigen expression which is not induced by IFN-gamma or by incubation at 25 degrees C for 24 hrs. This phenotype reflects structural changes in the beta(2)m gene which interfere with its transcription and/or translation or result in the synthesis of a defective beta(2)-mu polypeptide unable to associate with HLA Class I heavy chains. The other phenotype manifests very low HLA Class I antigen expression which is enhanced by IFN-gamma or by incubation at 25 degrees C for 24 hrs. This phenotype reflects abnormalities in TAP heterodimer expression, which cause defects in stable assembly and intracellular transport of the HLA Class I antigen trimolecular complex. Loss of HLA Class I antigens renders melanoma cells resistant to lysis by HLA Class I antigen-restricted cytotoxic T cells which specifically recognize melanoma associated antigens. Therefore, abnormalities in HLA Class I antigen expression may have a negative impact on the outcome of T cell based immunotherapy. Characterization of the molecular defects underlying loss of HLA Class I antigens may suggest approaches to restore their expression. Inclusion of these approaches in the protocols of T cell based immunotherapy may improve its efficacy.

Ocular manifestations of cardiovascular and hematologic disorders.

During the past year, there has been increased understanding of the ocular manifestations of various cardiovascular and hematologic disorders. Carotid and vertebral artery lesions may lead to significant and varied ophthalmic pathology. Disorders of blood pressure may influence the intraocular pressure and play a role in the progression of glaucoma. Cardiovascular risk factors such as smoking, hyperlipidemia, hypertension, and diabetes mellitus, may also play a role in the development of anterior ischemic optic neuropathy. Several cardiac anomalies as well as the cardiac use of streptokinase have been reported to have secondary ocular involvement. Both benign and malignant hematologic disorders may result in serious ocular morbidity. Recent publications have focused on the secondary ophthalmic complications from the hemoglobinopathies, problems with blood viscosity, the lymphomas, the leukemias, and bone marrow transplantation.

Manejo perinatal del teratoma sacrococcígeo gigante hipervascularizado / Perinatal management of hypervascularized sacrococcygeal teratoma

El teratoma Sacrococcigeo (TSC) es el teratoma mas frecuente del período neonatal. Los Teratomas Sacrococcígeos Gigantes Hipervascularizado(TSCGH) conforman un subgrupo dentro de los tumores congénitos. Provocan una alta mortalidad fetal y perinatal debido a su gran tamaño (siendo su peso muchas veces mayor al del feto) que provoca distocia y ruptura del tumor, polihidramnios que favorece el parto prematuro e hipervascularización del tumor que genera un estado hiperdinámico en el feto,provocando insuficiencia cardíaca fetal y eclam psia materna. La posibilidad de efectuar un correcto diagnóstico prenatal y la reciente comprensión de su fisiopatología han permitido la sobrevida de algunos de estos pacientes, que en algunos casos requieren cirugía fetal por su gravedad.En el último año hemos diagnosticado y tratado 2 casos de TSCGH. Mediante la ultrasonografía convencional y el Doppler Color confirmamos el estado hiperdinámico y el polihidramnios. Esta última condición ocasionó el parto prematuro de ambos fetos que no presentaban signos de hidrops.La fisiopatología de las entidades malformativas fetales y su manejo por un equipo especializado, permiten la sobrevida de pacientes que hasta hace poco tiempo fallecían en el 100 por ciento de los casos

Manejo perinatal del teratoma sacrococcígeo gigante hipervascularizado / Perinatal management of hypervascularized sacrococcygeal teratoma

El teratoma Sacrococcigeo (TSC) es el teratoma mas frecuente del período neonatal. Los Teratomas Sacrococcígeos Gigantes Hipervascularizado(TSCGH) conforman un subgrupo dentro de los tumores congénitos. Provocan una alta mortalidad fetal y perinatal debido a su gran tamaño (siendo su peso muchas veces mayor al del feto) que provoca distocia y ruptura del tumor, polihidramnios que favorece el parto prematuro e hipervascularización del tumor que genera un estado hiperdinámico en el feto,provocando insuficiencia cardíaca fetal y eclam psia materna. La posibilidad de efectuar un correcto diagnóstico prenatal y la reciente comprensión de su fisiopatología han permitido la sobrevida de algunos de estos pacientes, que en algunos casos requieren cirugía fetal por su gravedad.En el último año hemos diagnosticado y tratado 2 casos de TSCGH. Mediante la ultrasonografía convencional y el Doppler Color confirmamos el estado hiperdinámico y el polihidramnios. Esta última condición ocasionó el parto prematuro de ambos fetos que no presentaban signos de hidrops.La fisiopatología de las entidades malformativas fetales y su manejo por un equipo especializado, permiten la sobrevida de pacientes que hasta hace poco tiempo fallecían en el 100 por ciento de los casos

Ocular manifestations of cardiovascular and hematologic disorders.

The past year's important advancements in the ocular manifestations of cardiovascular and hematologic diseases are reviewed. Systemic changes related to blood pressure and carotid artery disease are commonly manifested on the ophthalmic examination. Ocular ischemic changes have been observed in patients with unusual aortic or congenital cardiac disorders. The ophthalmologist plays an important role in the detection of patients who are at risk for cardiovascular and cerebrovascular events. The hematologic disorders affecting the eye are subdivided into benign and malignant categories. A spectrum of diseases that include sickle cell hemoglobinopathy, aplastic anemia, leukemia, lymphoma, and multiple myeloma are discussed. With increased patient survival time after bone marrow transplantation, secondary ophthalmic complications are being identified. Although the ocular findings in the hematologic maladies are diverse, they may be an indication of serious systemic complications and have significant visual consequences.

Cell-type- and promoter-dependent ts phenotype of p53 Val135.

The p53 mutant Val135 is widely considered to have a wild-type (wt) phenotype at 32.5 degrees C, but not at 37 degrees C. The ability of wt murine p53 and its Val135 mutant to modulate transcription from the muscle-specific creatine kinase promoter (-3.3 kb pMCK), from a reporter construct containing two copies of the p53-binding DNA element from within MCK (p50-2), and from the interleukin-6 (IL-6) promoter (pIC225) was evaluated in transient transfection experiments in CV1 and HeLa cells. In CV1 cells, wt p53 was confirmed to activate the pMCK and p50-2 reporters, but to repress the IL-6 promoter. However, although in these cells p53 Val135 had the expected wt-like phenotype with respect to activation of the p50-2 reporter at 32.5 degrees C (32.5 degrees C > 37 degrees C), this mutant had little effect on expression from pMCK at either temperature, and activated rather than repressed the IL-6 promoter at 32.5 degrees C. In HeLa cells, although wt p53 activated p50-2 but repressed the MCK and IL-6 promoters, p53 Val135 activated all three reporters. Unexpectedly, in these cells the upregulation of p50-2 and pIC225 was basically temperature-independent, and that of pMCK was inversely ts (37 degrees C > 32.5 degrees C). The novel ts properties of p53 Val135 show that this mutant is not always wt-like at 32.5 degrees C but exhibits strong cell-type and promoter-dependent differences in its ts phenotype for transcriptional modulation.

The nanophase iron mineral(s) in Mars soil.

A series of surface-modified clays containing nanophase (np) iron oxide/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these "Mars-soil analogs" were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging, specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The clay acted as an effective matrix, both chemically and sterically, preventing the major part of the synthesized iron oxides from ripening, i.e., growing and developing larger crystals. The precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1-10 nm, having large specific surface area. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (gamma-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxy mineral such as "green rust," or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable maghemite (gamma-Fe2O3) by mild heat treatment and then to nanophase hematite (alpha-Fe2O3) by extensive heat treatment. After mild heating, the iron-enriched clay became slightly magnetic, to the extent that it adheres to a hand-held magnet, as was observed with Mars soil. The chemical reactivity of the iron-enriched clays strongly resembles, and offers a plausible mechanism for, the somewhat puzzling observations of the Viking biology experiments. Their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide/oxyhydroxides and silicate phase surfaces. The reflectance spectrum of the clay-iron preparations in the visible range is generally similar to the reflectance curves of bright regions on Mars. This strengthens the evidence for the predominance of nanophase iron oxides/oxyhydroxides in Mars soil. The mode of formation of these nanophase iron oxides on Mars is still unknown. It is puzzling that despite the long period of time since aqueous weathering took place on Mars, they have not developed from their transitory stage to well-crystallized end-members. The possibility is suggested that these phases represent a continuously on-going, extremely slow weathering process.

Mutability, sterility and suppression in P-M hybrid dysgenesis: the influence of P subline, cross, chromosome, sex and P-element structure.

Three Harwich P sublines with different P-element activity potential were used to investigate the influence of P-derived chromosomes on snw mutability and vg suppression and to relate the induction of these dysgenic traits to the number and structure of P elements. Destabilization of the snw allele, a measure of P transposase activity, was differentially influenced by the major autosomes. Chromosome 2 of the standard Harwich subline, Hw, induced only 60% of the level of mutability relative to chromosome 3, whereas chromosome 3 of the weakest Harwich subline, Hf, induced only 50% of the mutability relative to chromosome 2. In somatic suppression of the vg21-3 allele, chromosome 3 of the Hf subline produced a lower level of complete suppression as compared to chromosome 3 of the Hw or the Hs subline (the high hybrid-dysgenesis-inducing subline). The level of these dysgenic traits and GD sterility, was not correlated with the number of P elements per individual (67-68) or per chromosome arm which was very similar among the sublines. The number of complete P elements per genome, based on Southern blot analysis of the X and major autosomes, ranged from 15 to 19. Destabilization of the snw allele and vg suppression by chromosome 3 was correlated with a greater number of complete P elements. Two novel unexpected observations emerged from these studies: both snw mutability and vg suppression data demonstrated high P-element activity in hybrids derived from non-dysgenic crosses irrespective of Harwich subline, indicating a lack of P-cytotype regulation. Mutability in non-dysgenic males ranged from 40 to 60% of the level found in dysgenic males. The high snw mutability and low GD sterility in non-dysgenic hybrids suggests that these traits may arise by a different mechanism.

Modulation of the human interleukin-6 promoter (IL-6) and transcription factor C/EBP beta (NF-IL6) activity by p53 species.

Constitutive up-regulation of interleukin-6 (IL-6) gene expression is observed in many neoplastic cell lines. The contribution of mutations in p53 to the up-regulation of the IL-6 promoter was evaluated in transient transfection experiments. In HeLa cells, wild-type (wt) human or murine p53 preferentially repressed the IL-6 promoter. The p53 mutants Val-135 and Phe-132 up-regulated IL-6 promoter activity in these cells at both 32.5 and 37 degrees C. The temperature-sensitive Val-135 mutant was not only not inhibitory or "wt-like" at the lower temperature, but had gained a transcriptional activator phenotype which was temperature-independent in HeLa cells. The functional DNA target for transcriptional modulation of the IL-6 promoter by p53 species included the multiple cytokine- and second messenger-response element (-173 to -145); point mutations in the transcription factor C/EBP beta-binding site within the second messenger-response element largely blocked the ability of p53 mutants Val-135 and Phe-132 to up-regulate this promoter. The up-regulation of IL-6 promoter constructs by co-transfection into HeLa cells of a C/EBP beta constitutive expression vector was blocked in a dominant negative manner by wt p53. In contrast, the p53 mutants Val-135 and Phe-132 further enhanced C/EBP beta-mediated up-regulation of IL-6 promoter constructs. The modulation of C/EBP beta function by p53 species provides a basis for the involvement of p53 not only in the regulation of cytokine synthesis but also in the altered responsiveness of tumor cells to cytokines.

Radiation and transposon-induced genetic damage in Drosophila melanogaster: X-ray dose-response and synergism with DNA-repair deficiency.

The interaction of X-ray-induced and transposon-induced damage was investigated in P-M hybrid dysgenesis in Drosophila melanogaster. The X-ray dose-response of 330-1320 rad was monitored for sterility, fecundity and partial X/Y chromosome loss among F2 progeny derived from the dysgenic cross of M strain females xP strain males (cross A) and its reciprocal (cross B), using a weaker and the standard Harwich P strain subline. The synergistic effect of P element activity and X-rays on sterility was observed only in cross A hybrids and the dose-response was nonlinear in hybrids derived from the strong standard reference Harwich subline, Hw. This finding suggests that the lesions induced by both mutator systems which produce the synergistic effect are two-break events. The effect of increasing dose on the decline of fecundity was synergistic, but linear, in hybrids of either subline. There was no interaction evident and thus no synergism in X/Y nondisjunction and in partial Y chromosome loss measured by the loss of the Bs marker alone or together with the y+ marker. Interaction was detected in the loss of the y+ marker alone from the X and Y chromosomes. The possible three-way interaction of X-rays (660 rad), post-replication repair deficiency and P element mobility was assessed by measuring transmission distortion in dysgenic males derived from the II2 P strain. X-Irradiation of spermatids significantly increased the preferential elimination of the P-element-bearing second chromosome in mei-41, DNA-repair-deficient dysgenic males, but had no effect in their DNA-repair-proficient brothers. These findings indicate that the post-replication repair pathway is required for processing lesions induced by the combined effect of P element mobility and X-rays, and that the unrepaired lesions ultimately lead to chromosome loss.

The synergistic effect of X-rays and deficiencies in DNA repair in P-M hybrid dysgenesis in Drosophila melanogaster.

X-rays and deficiencies in DNA repair had a synergistic effect on genetic damage associated with P-element mobility in Drosophila melanogaster. These interactions, using sterility and fecundity as endpoints, were tested in dysgenic males deficient in either excision or post-replication DNA repair. Three sublines of the Harwich P strain were used for the construction of hybrid males. These sublines differ in P-induction ability based on gonadal dysgenesis sterility (GD) and snw mutability tests, in P-element insertion site pattern, and in the types of defective P-elements, such as KP elements, they possess. A lower degree of gonadal dysgenesis was correlated with the presence of KP elements. GD sterility and snw mutability were not always correlated. Dysgenic hybrids originating from the standard reference subline, Harwich(white), were much more sensitive to the post-replication repair than the excision repair defect. In contrast, sterility of hybrids derived from the weak subline was least affected by, and that of hybrids of the strongest subline was most affected by either DNA repair deficiency. The exacerbation by X-rays of the effects of DNA repair deficiencies on genetic damage indicates that both repair mechanisms are required for processing DNA lesions induced by the combined effect of P activity and ionizing radiation.

Photoprotection of Bacillus thuringiensis kurstaki from ultraviolet irradiation.

Irradiation of Bacillus thuringiensis var. kurstaki HD1 at 300-350 nm for up to 12 hr using a photochemical reactor results in a rapid loss of its toxicity to larvae of Heliothis armigera. Photoprotection of the toxic component was obtained by adsorption of cationic chromophores such as acriflavin (AF), methyl green, and rhodamine B to B. thuringiensis. AF gave the best photoprotection and a level of 0.42 mmol/g dye absorbed per gram of B. thuringiensis was highly toxic even after 12 hr of ultraviolet (uv) irradiation as compared to the control (77.5 and 5% of insect mortality, respectively). Ultraviolet and Fourier-transform infrared spectroscopic studies indicate molecular interactions between B. thuringiensis and AF. The nature of these interactions and energy or charge transfer as possible mechanisms of photoprotection are discussed. It is speculated that tryptophan residues are essential for the toxic effect of B. thuringiensis. It is suggested that photoprotection is attained as energy is transferred from the excited tryptophan moieties to the chromophore molecules.

A high level of hybrid dysgenesis in Drosophila: high thermosensitivity, dependence on DNA repair, and incomplete cytotype regulation.

An unusually high level of P-M hybrid dysgenesis in Drosophila melanogaster is characteristic of hybrid offspring originating from both, A (M female x P male) and B (P female x M male) crosses of a subline of the Harwich P strain, termed Hs. The novel properties induced by mobility of P elements carried by Hs paternal chromosomes include: very high (over 95%) gonadal dysgenesis (GD) in both sexes at the low restrictive temperature of 21 degrees C, and highly premature sterility when males are reared at 18 degrees C and aged at 21 degrees C. Although all three major chromosomes of the Hs subline contributed to this atypical pattern of gonadal dysgenesis, chromosome 3 had the largest effect. Gonadal dysgenesis showed a temperature- and sex-dependent repression pattern by the defective P elements of Muller-5 Birmingham chromosomes; at 21 degrees C there was virtually no repression of male sterility, but most effective repression of GD in females. At 29 degrees C repression was effective in males, but declined in females. The high thermosensitive sterility, low fecundity, and premature aging of the male germ line were greatly exacerbated when males derived from either A or B crosses were deficient either in excision repair (mei-9 mutation) or in post-replication repair (mei-41 mutation). These findings demonstrate that both DNA repair pathways are essential for the repair of lesions induced by P element transposition and support the hypothesis that P element-induced chromosome breaks are responsible for the virtual abolition of the germ line. The relatively high premature sterility of cross B DNA repair-deficient males, reared at 18 degrees C and aged at 21 degrees C, indicates that there is incomplete cytotype regulation in Hs subline hybrids.

The interaction between X-rays and transposon mobility in Drosophila: hybrid sterility and chromosome loss.

Genetic traits associated with P-M hybrid dysgenesis in Drosophila melanogaster were synergistically affected by X-rays. The interaction between damages induced by these two mutator systems was evident when sterility and X/Y chromosome loss were used as endpoints. No interaction was detected in partial chromosome loss, monitored by the loss of BS and y+ markers. The synergism in sterility, measured either as all-or-none or premature sterility (fecundity) was observed when male hybrids derived from different P strains fathers, namely Harwich or II2, were X-irradiated and the effects compared relative to similarly treated non-dysgenic hybrids. Brooding of sperm showed that the effects of ionizing radiation were ionizing radiation were dependent upon the stage of spermatogenesis during which cells were irradiated. The highly synergistic effect on sterility was found when either spermatids or spermatocytes, but not mature sperm, were irradiated with 550 rad of X-rays. These findings were consistent with the higher radiosensitivity of spermatocytes and spermatids to genetic damage and with the correlation between the incidence of sterility and aging of dysgenic hybrids. The latter observation was particularly evident in the case of Harwich P strain-derived male hybrids whose fertility was greatly reduced due to P element mobility. The synergistic effect of X-rays in these dysgenic hybrids resulted in the virtual abolition of the germ line, increasing the sterility from 50% of the untreated 9-10-day old males, to 85% of the treated males when spermatocytes were irradiated. The synergism observed between transposon mobility and ionizing radiation can best the attributed to an interaction between X-ray-induced and P element-induced chromosome breaks. This interpretation is consistent with the more than additive increase in X or Y chromosome loss in irradiated, Harwich P strain-derived hybrid sons. The induction of these events was 1.164% in dysgenic irradiated males as compared to 0.234% in X-irradiated nondysgenic hybrids and 0.40% in dysgenic untreated males. No synergism was observed in X/Y loss in hybrids derived from II2 P strain fathers where the frequency of the events due to P element mobility alone was only one tenth (0.037%) of that found in Harwich-derived hybrids.