Diffusive growth of a single droplet with three different boundary conditions

We study a single, motionless three-dimensional droplet growing by adsorption of diffusing monomers on a 2D substrate. The diffusing monomers are adsorbed at the aggregate perimeter of the droplet with different boundary conditions. Models with both an adsorption boundary condition and a radiation boundary condition, as well as a phenomenological model, are considered and solved in a quasistatic approximation. The latter two models allow particle detachment. In the short time limit, the droplet radius grows as a power of the time with exponents of 1/4, 1/2 and 3/4 for the models with adsorption, radiation and phenomenological boundary conditions, respectively. In the long time limit a universal growth rate as $[t/\ln(t)]^{1/3}$ is observed for the radius of the droplet for all models independent of the boundary conditions. This asymptotic behaviour was obtained by Krapivsky \cite{krapquasi} where a similarity variable approach was used to treat the growth of a droplet with an adsorption boundary condition based on a quasistatic approximation. Another boundary condition with a constant flux of monomers at the aggregate perimeter is also examined. The results exhibit a power law growth rate with an exponent of 1/3 for all times

Cloning and characterisation of the Schizosaccharomyces pombe rad32 gene: A gene required for repair of double strand break and recombination

A new Schizosaccharomyces pombe mutant (rad32) which is sensitive to gamma and UV irradiation is described. Pulsed field gel electrophoresis of DNA from irradiated cells indicates that the rad32 mutant, in comparison to wild type cells, has decreased ability to repair DNA double strand breaks. The mutant also undergoes decreased meiotic recombination and displays reduced stability of minichromosomes. The rad32 gene has been cloned by complementation of the UV sensitive phenotype. The gene, which is not essential for cell viability and is expressed at a moderate level in mitotically dividing cells, has significant homology to the meiotic recombination gene MRE11 of Saccharomyces cerevisiae. Epistasis analysis indicates that rad32 functions in a pathway which includes the rhp51 gene (the S. pombe homologue to S. cerevisiae RAD51) and that cells deleted for the rad32 gene in conjunction with either the rad3 deletion (a G2 checkpoint mutation) or the rad2 deletion (a chromosome stability and potential nucleotide excision repair mutation) are not viable

Chemical composition and evaluation of antimicrobial properties of Rosmarinus officinalis L. essential oil

Preservatives used in the food industry are undergoing increasing scrutiny and reappraisal. There is therefore a renewed interest in the antimicrobial properties of herbs and spices. Rosemary (Rosmarinus officinalis L.) belonging to the Lamiaceae family, is a pleasant-smelling perennial herb. The antimicrobial activities of the R. officinalis oil against Leuconostoc mesenteroides (PTCC1591), Lactobacillus delbruekii (PTCC1333), Saccharomyces cerevisia (PTCC5269) and Candida krusei (PTCC 5295) were determined. The results indicate that among the tested microbes, the essential oil had a stronger inhibitory effect on the bacteria as compared to yeasts. Minimum inhibitory concentration (MIC) values for bacteria L. mesenteroides, L. delbruekii, S. cerevisia and C. krusei ranged between 0.5 and 1.5 mg/ml. The oil was analyzed by GC and GC/MS. The major components of R. officinalis oil were 1,8-cineole (23.14%), camphor (12.35%), α-pinene (9.87%), β-pinene (6.10%), borneol (5.61%), camphene (5.58%) and α-terpineol (4.30%), respectively. These results indicate the latent potency of essential oil of R. officinalis as a natural preservative in food products against L. mesenteroides, L. delbruekii, S. cerevisia and C.krusei.Key words: Rosmarinus officinalis L., essential oil, chemical composition, antimicrobial properties

Structural and functional conservation of the human homolog of the Schizosaccharomyces pombe rad2 gene, which is required for chromosome segregation and recovery from DNA damage

The rad2 mutant of Schizosaccharomyces pombe is sensitive to UV irradiation and deficient in the repair of UV damage. In addition, it has a very high degree of chromosome loss and/or nondisjunction. We have cloned the rad2 gene and have shown it to be a member of the Saccharomyces cerevisiae RAD2/S. pombe rad13/human XPG family. Using degenerate PCR, we have cloned the human homolog of the rad2 gene. Human cDNA has 55% amino acid sequence identity to the rad2 gene and is able to complement the UV sensitivity of the rad2 null mutant. We have thus isolated a novel human gene which is likely to be involved both in controlling the fidelity of chromosome segregation and in the repair of UV-induced DNA damage. Its involvement in two fundamental processes for maintaining chromosomal integrity suggests that it is likely to be an important component of cancer avoidance mechanisms

Heterogeneous nucleation near a metastable vapour-liquid transition: the effect of wetting transitions

Phase transformations such as freezing typically start with heterogeneous nucleation. Heterogeneous nucleation near a wetting transition, of a crystalline phase is studied. The wetting transition occurs at or near a vapour-liquid transition which occurs in a metastable fluid. The fluid is metastable with respect to crystallisation, and it is the crystallisation of this fluid phase that we are interested in. At a wetting transition a thick layer of a liquid phase forms at a surface in contact with the vapour phase. The crystalline nucleus is then immersed in this liquid layer, which reduces the free energy barrier to nucleation and so dramatically increases the nucleation rate. The variation in the rate of heterogeneous nucleation close to wetting transitions is calculated for systems in which the longest-range forces are dispersion forces.Comment: 11 pages including 3 figure

Homogeneous nucleation near a second phase transition and Ostwald's step rule

Homogeneous nucleation of the new phase of one transition near a second phase transition is considered. The system has two phase transitions, we study the nucleation of the new phase of one of these transitions under conditions such that we are near or at the second phase transition. The second transition is an Ising-like transition and lies within the coexistence region of the first transition. It effects the formation of the new phase in two ways. The first is by reducing the nucleation barrier to direct nucleation. The second is by the system undergoing the second transition and transforming to a state in which the barrier to nucleation is greatly reduced. The second way occurs when the barrier to undergoing the second phase transition is less than that of the first phase transition, and is in accordance with Ostwald's rule.Comment: 11 pages, 5 figure

Secretory breast carcinoma with metastatic sentinel lymph node

BACKGROUND: Secretory mammary carcinoma is a rare breast neoplasia originally described in children but sometimes also found in adults. It presents a more favourable outcome than more common histological types of breast carcinoma; published literature in fact reports only a few cases with axillary lymph node metastases and only four cases with distant metastases. CLINICAL PRESENTATION: In this paper we report a rare case of secretory breast carcinoma with axillary lymph node metastases in a 33-year-old woman. To our knowledge, this is the first case of secretory carcinoma involving biopsy of the sentinel lymph node and investigation of the e-cadherin expression. We found positivity for e-cadherin, which would support the hypothesis that this type of tumour is a variant of the infiltrating ductal carcinoma. CONCLUSION: After a careful analysis of reported data, we have come to the conclusion that the treatment of choice for patients with secretory breast carcinoma should be conservative surgery with sentinel lymph node biopsy, followed by accurate follow-up. We are of the opinion that while post-operative radiotherapy is indicated in adult patients who have undergone quadrantectomy, it should not be used in children. Although several cases of secretory carcinoma have been treated with adjuvant chemotherapy, there are still no reliable data regarding the real value of such a choice

Expression of miR-21 and its targets (PTEN, PDCD4, TM1) in flat epithelial atypia of the breast in relation to ductal carcinoma in situ and invasive carcinoma

<p>Abstract</p> <p>Background</p> <p>Flat epithelial atypia (FEA) of the breast is characterised by a few layers of mildly atypical luminal epithelial cells. Genetic changes found in ductal carcinoma in situ (DCIS) and invasive ductal breast cancer (IDC) are also found in FEA, albeit at a lower concentration. So far, miRNA expression changes associated with invasive breast cancer, like miR-21, have not been studied in FEA.</p> <p>Methods</p> <p>We performed miRNA in-situ hybridization (ISH) on 15 cases with simultaneous presence of normal breast tissue, FEA and/or DCIS and 17 additional cases with IDC. Expression of the miR-21 targets PDCD4, TM1 and PTEN was investigated by immunohistochemistry.</p> <p>Results</p> <p>Two out of fifteen cases showed positive staining for miR-21 in normal breast ductal epithelium, seven out of fifteen cases were positive in the FEA component and nine out of twelve cases were positive in the DCIS component. A positive staining of miR-21 was observed in 15 of 17 IDC cases. In 12 cases all three components were present in one tissue block and an increase of miR-21 from normal breast to FEA and to DCIS was observed in five cases. In three cases the FEA component was negative, whereas the DCIS component was positive for miR-21. In three other cases, normal, FEA and DCIS components were negative for miR-21 and in the last case all three components were positive. Overall we observed a gradual increase in percentage of miR-21 positive cases from normal, to FEA, DCIS and IDC. Immunohistochemical staining for PTEN revealed no obvious changes in staining intensities in normal, FEA, DCIS and IDC. Cytoplasmic staining of PDCD4 increased from normal to IDC, whereas, the nuclear staining decreased. TM1 staining decreased from positive in normal breast to negative in most DCIS and IDC cases. In FEA, the staining pattern for TM1 was similar to normal breast tissue.</p> <p>Conclusion</p> <p>Upregulation of miR-21 from normal ductal epithelial cells of the breast to FEA, DCIS and IDC parallels morphologically defined carcinogenesis. No clear relation was observed between the staining pattern of miR-21 and its previously reported target genes.</p