Dynamic Response Function and the Theory of Spin Waves in Metallic Overlayers

A general recursion method (method of adlayers) for calculating the exact Green function in an arbitrary overlayer is developed. The method as presented applies to an s-band tight-binding Hamiltonian with hopping between nearest-neighbours only. The general.isation of the method to a multi-orbital band structure is described. The overlayer we consider is deposited above the (100) surface of a simple cubic semi-infinite nonmagnetic metallic substrate occupying the half-space z<O. The aim of the present thesis is twofold: firstly, the ground state of a ferromagnetic overlayer is investigated. In particular, the local densities of states (LOOS) of an overlayer are calculated using the method of adlayers. The method of adlayers is very simple, computationally stable and extremely accurate. The numerical results for the LOOS and the Hartree-Fock (HF) occupation numbers of a single-adlayer and a seven-adlayer overlayer are presented. The surface and bulk DOSs for an overlayer of seven atomic planes are compared. The presence of an adlayer may induce surface states if a strong enough perturbation occurs at the surface. Such surface states are automatically included in our method of adlayers. Secondly, spin waves in a transition metal overlayer are investigated within the framework of the itinerant theory of magnetism. The overlayer is modelled by a single-orbital tight-binding band with a strong intra-atomic repulsion U (one band Hubbard model). All the matrix elements of the HF dynamic unenhanced susceptibility in the overlayer are computed from the HF one-electron Green functions. Spin waves are then poles of the full dynamic enhanced susceptibility which is determined in the random phase approximation (RPA). It is demonstrated that a very high accuracy in solving the HF ground state is needed to determine correctly spin wave modes. When this requirement is fulfilled, the Goldstone theorem at zero wavevector and zero frequency is very well satisfied. Numerical results for the spin wave spectra of a single-adlayer are presented for a range of values of U. Spin wave energies for a single-adlayer, for an unsupported layer and the exchange stiffness constant 0 of an unsupported layer are compared. Finally, all the computed spin wave branches of an overlayer of seven atomic planes are presented and discussed. The disappearance of spin waves in the Stoner continuum is illustrated and the possibility that a surface spin wave mode might occur is briefly discussed

Study on the Chemistry and Antimicrobial Activity of Psychotria reevesii Wall. (Rubiaceae)

The first chemical investigation on Vietnamese medicinal plant Psychotria reevesii Wall. (Rubiaceae) led to the isolation and structural determination of β-sitosterol and stigmasterol as a mixture, 1-octacosene, and asperglaucide from n-hexane- and CHCl3-soluble fractions of MeOH extract from the aerial parts of P. reevesii. Phytochemical screening based on color reactions, HPLC analysis, and NMR spectroscopy revealed the concentration of condensed tannins in EtOAc- and n-BuOH soluble fractions. The high accumulation of tannins may be responsible for the antibacterial activities of the polar fractions against Staphylococcus aureus, Pseudomonas aeruginosa, Shigella sonnei, and Shigella flexneri. However, they did not exhibit any inhibitory effect against Escherichia coli, Candida albicans, and Candida stellatoides.Keywords: Psychotria reevesii; Rubiaceae; asperglaucide; antibacterial activity; antifungal activity

A fatty acid, flavonoids, and steroids from Zingiber penisulare. I. Theilade (zingiberaceae)

The first chemical study of Zingiber penisulare I. Theilade (Zingiberaceae) resulted in the isolation of a fatty acid, eicosanoic acid (1), three kaempferol derivatives, 5-hydroxy-3,4',7-trimethoxyflavone  (2), 4',5-dihydroxy-7-methoxyflavonol (5), and 4',5-dihydroxy-3,7-dimethoxyflavone (6), b-sitosterol (3), and 6b-hydroxystigmast-4-ene-3-one (4). Their chemical structures were determined by spectroscopic analyses. Keywords: Zingiber penisulare; Zingiberaceae; kaempferol; flavonol; stigmastane

LPS-Induced Systemic Inflammation Affects the Dynamic Interactions of Astrocytes and Microglia with the Vasculature of the Mouse Brain Cortex

The Neurovascular Unit (NVU), composed of glia (astrocytes, oligodendrocytes, microglia), neurons, pericytes and endothelial cells, is a dynamic interface ensuring the physiological functioning of the central nervous system (CNS), which gets affected and contributes to the pathology of several neurodegenerative diseases. Neuroinflammation is a common feature of neurodegenerative diseases and is primarily related to the activation state of perivascular microglia and astrocytes, which constitute two of its major cellular components. Our studies focus on monitoring in real time the morphological changes of perivascular astrocytes and microglia, as well as their dynamic interactions with the brain vasculature, under physiological conditions and following systemic neuroinflammation triggering both microgliosis and astrogliosis. To this end, we performed 2-photon laser scanning microscopy (2P-LSM) for intravital imaging of the cortex of transgenic mice visualizing the dynamics of microglia and astroglia following neuroinflammation induced by systemic administration of the endotoxin lipopolysaccharide (LPS). Our results indicate that following neuroinflammation the endfeet of activated perivascular astrocytes lose their close proximity and physiological cross-talk with vasculature, an event that most possibly contributes to a loss of blood–brain barrier (BBB) integrity. At the same time, microglial cells become activated and exhibit a higher extent of physical contact with the blood vessels. These dynamic responses of perivascular astrocytes and microglia are peaking at 4 days following LPS administration; however, they still persist at a lower level at 8 days after LPS injection, revealing incomplete reversal of inflammation affecting the glial properties and interactions within the NVU

The incidence and aetiology of hospitalised community-acquired pneumonia among Vietnamese adults: a prospective surveillance in Central Vietnam

Abstract Background Lower respiratory tract infection (LRTI) including Community-acquired pneumonia (CAP) is a common infectious disease that is associated with significant morbidity and mortality. The patterns of aetiological pathogens differ by region and country. Special attention must be paid to CAP in Southeast Asia (SEA), a region facing rapid demographic transition. Estimates burden and aetiological patterns of CAP are essential for the clinical and public health management. The purposes of the study are to determine the incidence, aetiological pathogens, clinical pictures and risk factors of community-acquired pneumonia (CAP) in the Vietnamese adult population. Methods A prospective surveillance for hospitalised adult CAP was conducted in Khanh Hoa Province, Central Vietnam. All adults aged ≥15 years with lower respiratory tract infections (LRTI) admitted to a provincial hospital from September 2009 to August 2010 were enrolled in the study. Patients were classified into CAP and non-pneumonic LRTI (NPLRTI) according to the radiological findings. Bacterial pathogens were identified from sputum samples by the conventional culture and polymerase chain reaction (PCR) for Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis; 13 respiratory viruses were identified from nasopharyngeal specimens by PCR. Results Of all 367 LRTI episodes examined, 174 (47%) were CAP. Older age, the presence of underlying respiratory conditions, and higher index score of smoking were associated with CAP. The one-year estimated incidence of hospitalised adult CAP in our study population was 0.81 per 1,000 person years. The incidence increased considerably with age and was highest among the elderly. The case fatality proportion of hospitalised CAP patients was 9.8%. Among 286 sputum samples tested for bacterial PCR, 79 (28%) were positive for H. influenzae, and 65 (23%) were positive for S. pneumoniae. Among 357 samples tested for viral PCR, 73 (21%) were positive for respiratory viruses; influenza A (n = 32, 9%) was the most common. Conclusions The current adult CAP incidence in Vietnam was relatively low; this result was mainly attributed to the young age of our study population

Synthesis of Silica-Coated Magnetic Nanoparticles and Application in the Detection of Pathogenic Viruses

Magnetic Fe3O4 nanoparticles were prepared by coprecipitation and then coated with silica. These Fe3O4/SiO2 nanoparticles consisted of a 10–15 nm magnetic core and a silica shell of 2–5 nm thickness. The superparamagnetic property of the Fe3O4/SiO2 particles with the magnetization of 42.5 emu/g was confirmed by vibrating sample magnetometer (VSM). We further optimized buffers with these Fe3O4/SiO2 nanoparticles to isolate genomic DNA of hepatitis virus type B (HBV) and of Epstein-Barr virus (EBV) for detection of the viruses based on polymerase chain reaction (PCR) amplification of a 434 bp fragment of S gene specific for HBV and 250 bp fragment of nuclear antigen encoding gene specific for EBV. The purification efficiency of DNA of both HBV and EBV using obtained Fe3O4/SiO2 nanoparticles was superior to that obtained with commercialized Fe3O4/SiO2 microparticles, as indicated by (i) brighter PCR-amplified bands for both HBV and EBV and (ii) higher sensitivity in PCR-based detection of EBV load (copies/mL). The time required for DNA isolation using Fe3O4/SiO2 nanoparticles was significantly reduced as the particles were attracted to magnets more quickly (15–20 s) than the commercialized microparticles (2-3 min)

Improvement in neoantigen prediction via integration of RNA sequencing data for variant calling

IntroductionNeoantigen-based immunotherapy has emerged as a promising strategy for improving the life expectancy of cancer patients. This therapeutic approach heavily relies on accurate identification of cancer mutations using DNA sequencing (DNAseq) data. However, current workflows tend to provide a large number of neoantigen candidates, of which only a limited number elicit efficient and immunogenic T-cell responses suitable for downstream clinical evaluation. To overcome this limitation and increase the number of high-quality immunogenic neoantigens, we propose integrating RNA sequencing (RNAseq) data into the mutation identification step in the neoantigen prediction workflow.MethodsIn this study, we characterize the mutation profiles identified from DNAseq and/or RNAseq data in tumor tissues of 25 patients with colorectal cancer (CRC). Immunogenicity was then validated by ELISpot assay using long synthesis peptides (sLP).ResultsWe detected only 22.4% of variants shared between the two methods. In contrast, RNAseq-derived variants displayed unique features of affinity and immunogenicity. We further established that neoantigen candidates identified by RNAseq data significantly increased the number of highly immunogenic neoantigens (confirmed by ELISpot) that would otherwise be overlooked if relying solely on DNAseq data.DiscussionThis integrative approach holds great potential for improving the selection of neoantigens for personalized cancer immunotherapy, ultimately leading to enhanced treatment outcomes and improved survival rates for cancer patients