Is there a common water-activity limit for the three domains of life?

Archaea and Bacteria constitute a majority of life systems on Earth but have long been considered inferior to Eukarya in terms of solute tolerance. Whereas the most halophilic prokaryotes are known for an ability to multiply at saturated NaCl (water activity (a w) 0.755) some xerophilic fungi can germinate, usually at high-sugar concentrations, at values as low as 0.650-0.605 a w. Here, we present evidence that halophilic prokayotes can grow down to water activities of <0.755 for Halanaerobium lacusrosei (0.748), Halobacterium strain 004.1 (0.728), Halobacterium sp. NRC-1 and Halococcus morrhuae (0.717), Haloquadratum walsbyi (0.709), Halococcus salifodinae (0.693), Halobacterium noricense (0.687), Natrinema pallidum (0.681) and haloarchaeal strains GN-2 and GN-5 (0.635 a w). Furthermore, extrapolation of growth curves (prone to giving conservative estimates) indicated theoretical minima down to 0.611 a w for extreme, obligately halophilic Archaea and Bacteria. These were compared with minima for the most solute-tolerant Bacteria in high-sugar (or other non-saline) media (Mycobacterium spp., Tetragenococcus halophilus, Saccharibacter floricola, Staphylococcus aureus and so on) and eukaryotic microbes in saline (Wallemia spp., Basipetospora halophila, Dunaliella spp. and so on) and high-sugar substrates (for example, Xeromyces bisporus, Zygosaccharomyces rouxii, Aspergillus and Eurotium spp.). We also manipulated the balance of chaotropic and kosmotropic stressors for the extreme, xerophilic fungi Aspergillus penicilloides and X. bisporus and, via this approach, their established water-activity limits for mycelial growth (∼0.65) were reduced to 0.640. Furthermore, extrapolations indicated theoretical limits of 0.632 and 0.636 a w for A. penicilloides and X. bisporus, respectively. Collectively, these findings suggest that there is a common water-activity limit that is determined by physicochemical constraints for the three domains of life

Dielectric and Raman Studies of 0.935(Bi0.5Na0.5TiO3)−0.065BaTiO30.935(Bi_{0.5}Na_{0.5}TiO_3)-0.065BaTiO_3 Lead Free Ceramics

The $0.935(Na_{0.5}Bi_{0.5})TiO_3-0.065BaTiO_3$ lead free ceramic was synthesized by conventional solid state reaction technique. Sintering was done at 1200°C for 4 h in air atmosphere. Dielectric and Raman spectroscopic studies have been performed as a function of temperature from 25 to 450°C. The phase transitions from ferroelectric to antiferroelectric and from antiferroelectric to paraelectric order were observed through the dielectric measurements. Further support for the obtained results was drawn from the Raman spectroscopy measurements

New relaxor ceramic with composition BaTi1-x(Zn1/3Nb2/3)xO3

New ferroelectric ceramics of ABO3 perovskite type were synthesized in the BaTi1-x(Zn1/3Nb2/3)xO3 system by solid state reaction technique. The effect of the replacement of titanium by zinc (Zn) and niobium (Nb) in the B cationic site on structural and dielectric properties were investigated. As a function of composition, these compounds crystallize with tetragonal or cubic symmetry. The material is classical ferroelectric for 0 ≤ x ≤ 0.05 and presents a relaxor behavior for 0.075 ≤ x ≤ 0.2 and for 0.75 ≤ x ≤ 0.975. Dielectric permittivity in the temperature range from 85 to 500 K with frequencies range from 0.1 to 200 kHz, was studied. In the region when 0.75 ≤ x ≤ 0.975, ΔTm presents the important values which go more then 100 K for BaTi0.05(Zn1/3Nb2/3)0.95O3 composition with values of Tm near room temperature. These values make these ceramic compositions in the families of relaxors with interest properties for applications. © 2007 Elsevier B.V. All rights reserved

Testicular tumours in prepubertal children: About eight cases

Background: To analyze the spectrum of testicular tumors in prepubertal children and the therapeutic resultants in an unselected population. Materials and Methods: Our hospital database was analyzed for testicular tumors from January 1995 to December 2010 concerning clinical presentation, treatment and therapeutic results. Results: Eight patients were operated on because of testicular tumors.In six cases (75%) the tumor was benign: benign teratoma (four cases), epidermoid cyst (one case) and immature teratoma (one case). Two  patients (25%) had a malignant tumour: yolk-sac tumour (two cases). All this children underwent surgery. Radical inguinal orchidectomy was  performed in six cases and conservative surgery was performed in two cases. One patient has received adjuvant chemotherapy. Followup was uneventfully three years after primary surgery.Conclusion: In prepubertal children, most testicular tumours are benign. If tumour markers were negative testis-preserving surgery can be proposed,  complete excision of the tumour should be ascertained. In the case of testicular teratoma, the possibility of contralateral tumour should be    considered in the follow-up.Key words: Children, Testis, Tumour, Teratoma,yolk-sac tumou

Congenital diaphragmatic hernia in neonate: A retrospective study about 28 observations

Objective:Our purpose was to review our experience with congenital diaphragmatic hernia emphasizing diagnosis, management, and outcome. StudyDesign: We conducted a retrospective review of all cases of babies with congenital diaphragmatic hernia diagnosed and treated in our centre from1998 to 2010. Results: There were 28 congenital diaphragmatic hernia cases, 13 girls and 15 boys with a mean weight birth of 3 kg. Three  patients (10,6% of cases) died within a few hours after admission. In the remaining cases, surgery was performed after a stabilization period of 2 days. The diaphragmatic defect was sitting in the posterolateral left in 23 cases and right in 2 cases. Its dimensions were on average 4,5 cm, tow cases of agenesis of the cupola were seen and required the placement of  gortex prosthesis. The remaining cases are treated by direct closure ofdefect. Postoperative course was marked by an early death in context of respiratory distress in six cases and later with sepsis in tow cases. The  outcome was favourable in 17 cases (60, 7%), despite the occurrence of sepsis in four cases and evisceration in two cases.Conclusions: Congenital diaphragmatic hernia remains a serious disease with high mortality and morbidity despite advances in prenatal diagnosis and neonatal  resuscitation.Key words: Congenital diaphragmatic hernia, pulmonary hypoplasia,  tracheal occlusion, paediatric surger

Structural investigation, dielectric, ferroelectric, and elecrocaloric properties of lead-free Ba(1−x)CaxTi(1−x)(Li1/3Nb2/3)xO3−δ (x = 0.02 and x = 0.07) ceramics

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