The electromagnetic field near a dielectric half-space

We compute the expectations of the squares of the electric and magnetic fields in the vacuum region outside a half-space filled with a uniform non-dispersive dielectric. This gives predictions for the Casimir-Polder force on an atom in the `retarded' regime near a dielectric. We also find a positive energy density due to the electromagnetic field. This would lead, in the case of two parallel dielectric half-spaces, to a positive, separation-independent contribution to the energy density, besides the negative, separation-dependent Casimir energy. Rough estimates suggest that for a very wide range of cases, perhaps including all realizable ones, the total energy density between the half-spaces is positive.Comment: Latex2e, IOP macros, 15 pages, 2 eps figure

Dynamical Coulomb Blockade and the Derivative Discontinuity of Time-Dependent Density Functional Theory

The role of the discontinuity of the exchange-correlation potential of density functional theory is studied in the context of electron transport and shown to be intimately related to Coulomb blockade. By following the time evolution of an interacting nanojunction attached to biased leads, we find that, instead of evolving to a steady state, the system reaches a dynamical state characterized by correlation-induced current oscillations. Our results establish a dynamical picture of Coulomb blockade manifesting itself as a periodic sequence of charging and discharging of the nanostructure.Comment: to appear in Physical Review Letter

Synthesis and crystallographic characterization of new heterotrinuclear oxo-centered complex

New oxo-centered trinuclear mixed-metal complex, of [Fe2ZnO(CHCl2CO2)6(CHCl2CO2)3].NO3 was synthesized by the direct reaction between metal nitrates and dichloroacetic acid. These compounds have a typical μ3-oxo trinuclear structure: (a) three metal atoms are situated in the apexes of the equilateral triangle; (b) μ3-oxygen atom and six dichloroacetate ligands fulfil the bridge functions and (c) the monodentate CHCl2CO2 ligands complete the octahedral geometry of the metal ions. This complex were characterized by elemental analyses (CHN), atomic absorption spectroscopy and spectral (IR, electronic) studies. This is new types of oxo-bridged mixed-metal complex in which the carboxylate ligand is dichloroacetic acid. The UV spectra of the complex exhibited strong bands in the region 213 and 257 nm which are related to the (π → π*) and (n → π*) transitions of the CHCl2CO2 ligands, respectively. The IR spectra of this compound showed two strong stretching vibrations bands, indicating a bridging coordination mode of the carboxylic group by presence of νasym (M2M'O) vibrations of the ligand in the infrared spectra.               KEY WORDS: Oxo-centered, Trinuclear complexes, Carboxylic ligand, Crystallographic data, IR spectra Bull. Chem. Soc. Ethiop. 2018, 32(3), 491-500.DOI: https://dx.doi.org/10.4314/bcse.v32i3.

Impact of the COVID-19 pandemic on patients suffering from musculoskeletal tumours

Background The aim of the current study was to evaluate the impact of the coronavirus disease (COVID-19) pandemic on musculoskeletal tumor service by conducting an online survey of physicians. Methods The survey was conducted among the members of the ISOLS (International Society of Limb Salvage) and the EMSOS (EuropeanMusculo-Skeletal Oncology Society). The survey consisted of 20 questions (single,multiple-response, ranked): origin and surgical experience of the participant (four questions), potential disruption of healthcare (12 questions), and influence of the COVID-19 pandemic on the particular physician (four questions). A matrix with four different response options was created for the particular surgical procedures). Results One hundred forty-nine physicians from five continents completed the survey. Of the respondents, 20.1% and 20.7% stated that surgery for life-threatening sarcomas were stopped or delayed, respectively. Even when the malignancy was expected to involve infiltration of a neurovascular bundle or fracture of a bone, still 13.8% and 14.7% of the respondents, respectively, stated that surgery was not performed. In cases of pending fractures of bone tumors, 37.5 to 46.2% of operations were canceled. Conclusion The SARS-CoV-2 pandemic caused a significant reduction in healthcare (surgery, radiotherapy, chemotherapy) for malignancies of the musculoskeletal system. Delaying or stopping these treatments is life-threatening or can cause severe morbidity, pain, and loss of function. Although the coronavirus disease causes severe medical complications, serious collateral damage including death due to delayed or untreated sarcomas should be avoided

Evaluation of physiological aspects and molecular identification of Saprolegnia isolates from rainbow trout (Oncorhynchus mykiss) and Caspian trout (Salmo trutta caspius) eggs based on RAPD–PCR

The genus of saprolegnia is one of the most important pathogenic aquatic fungi in farmed and wild fish. In the present study, fungal infected egss were collected from rainbow trout (Oncorhyncus mykiss) and Caspian trout (Salmo trutta caspius). After purification, 16 isolates were obtained (8 isolates from rainbow trout and 8 isolates from Caspian salmon, respectively). The isolates were then coded as R2 – R9 (rainbow trout) and S2 – S9 (Caspian trout).The registered DNA for S. parasitica (ACTT # 200048) and S. diclina (ACTT # 4206) were used and coded as R1 and S1, respectively. Based on the RAPD profile obtained all samples were divided to 3 groups and members of each group had more than 90% similarity among themselves. According to matrix of similarity and reference strains, the isolates were classified as three groups. Therefore, all of isolates in group 1 and 3 were S. parasitica and S. diclina, respectively, and the members of group 2 were known as Saprolegnia sp. The results of thermal resistance assessment showed that the isolates of rainbow trout and Caspian salmon eggs had slow growth in the temperature between 18 – 20 °C. Thus, R2 and S8 isolates had the lowest radial growth compared to other isolates. The isolates categorized in S. parasitica (group 1) created secoundry zoospores but not observed in two other groups. Thus, catenulated gamme was found in 78% and 55.55% isolates of rainbow trout and Caspian trout eggs, respectively. This study indicated that molecular methods were the best methods for identification of Saprolegnia spp. and it could be applied as a supplementary confirming method

Gastrointestinal microflora of captured stellate sturgeon (Acipenser stellatus, Pallas, 1771) from Southeast Caspian Sea, Iran

Acipenser stellatus is one of the most invaluable species of Sturgeon fishes in the world. The purpose of this study was to identify the resident microbial community from the gastrointestinal tract (GIT) of Acipenser stellatus. One hundred and twenty three fungi were isolated from the GIT of 7 Acipenser stellatus samples including Aspergillus spp (45.5%), Trichoderma spp (8.9%) and Cladophialophora spp (8.1%). Among different Aspergillus isolates, A. niger was the predominant species. Although, fungi were predominantly isolated from stomach (36.6%), but with respect to frequency of fungal isolates there were no significant differences between stomach and other parts of GI. In general, the bacterial isolates recovered were mostly gram negative and related to Enterobacteriaceae family such as Aeromonas, Pseudomonas and Salmonella species. The most bacterial species were isolated from intestine and pre stomach region (88.2%). It is concluded that A. niger and Aeromonas species were predominant fugal and bacterial microbes isolated from understudy fish GIT, respectively

On the error term in Weyl's law for the Heisenberg manifolds (II)

In this paper we study the mean square of the error term in the Weyl's law of an irrational $(2l+1)$-dimensional Heisenberg manifold . An asymptotic formula is established

Non-commutative multi-dimensional cosmology

A non-commutative multi-dimensional cosmological model is introduced and used to address the issues of compactification and stabilization of extra dimensions and the cosmological constant problem. We show that in such a scenario these problems find natural solutions in a universe described by an increasing time parameter.Comment: 9 pages, 1 figure, to appear in JHE

The effect of dandelion hydro-alcoholic extract and its active constituent on radiosensitivity of glioblastoma cancer cells: an in vitro study

OBJECTIVE: Radiation therapy is one of the many methods that are used to cure cancers. Considering the high resistance of cancer cells to radiation therapy and its many side effects, and considering that in recent years the high medicinal potential of plants has been noticed, the aim of this study is to investigate the effects of the dandelion hydro-alcoholic extract and its active constituent on the radiation therapy cytotoxic effect in glioblastoma cancer cells. MATERIALS AND METHODS: After treatment with extract and taraxasterol, the cell viability was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay. Then the effect of the combination of extract and taroxasterol with ionizing radiation was tested. The apoptosis cell death was investigated by diphenylamine assay and real-time technic. RESULTS: After treatment with extract and taraxasterol, cell viability was decreased in a dose-dependent manner. The extract and taraxasterol increased the sensitivity of cells to ionizing radiation. In addition, after treatment with the extract and taraxasterol, the amount of apoptosis induced by ionizing radiation in the cells increased. After treatment with extract, taraxasterol and ionizing radiation, the expression of Bax and p53 increased and the expression of Bcl-2 decreased. CONCLUSIONS: Using the dandelion along with radiation therapy may show a better response to treatment in glioblastoma patients

Evolution of Thick Walls in Curved Spacetimes

We generalize our previous thick shell formalism to incorporate any codimension-1 thick wall with a peculiar velocity and proper thickness bounded by arbitrary spacetimes. Within this new formulation we obtain the equation of motion of a spherically symmetric dust thick shell immersed in vacuum as well as in Friedmann-Robertson-Walker spacetimes.Comment: 8 pages, 1 figur