65 research outputs found
Effect of self-consistent electric field on characteristics of graphene p-i-n tunneling transit-time diodes
We develop a device model for p-i-n tunneling transit-time diodes based on
single- and multiple graphene layer structures operating at the reverse bias
voltages. The model of the graphene tunneling transit-time diode (GTUNNETT)
accounts for the features of the interband tunneling generation of electrons
and holes and their ballistic transport in the device i-section, as well as the
effect of the self-consistent electric field associated with the charges of
propagating electrons and holes. Using the developed model, we calculate the dc
current-voltage characteristics and the small-signal ac frequency-dependent
admittance as functions of the GTUNNETT structural parameters, in particular,
the number of graphene layers and the dielectric constant of the surrounding
media. It is shown that the admittance real part can be negative in a certain
frequency range. As revealed, if the i-section somewhat shorter than one
micrometer, this range corresponds to the terahertz frequencies. Due to the
effect of the self-consistent electric field, the behavior of the GTUNNETT
admittance in the range of its negativity of its real part is rather sensitive
to the relation between the number of graphene layers and dielectric constant.
The obtained results demonstrate that GTUNNETTs with optimized structure can be
used in efficient terahertz oscillators.Comment: 8 pages, 9 figure
Spherical magnetic nanoparticles fabricated by laser target evaporation
Magnetic nanoparticles of iron oxide (MNPs) were prepared by the laser target evaporation technique (LTE). The main focus was on the fabrication of de-aggregated spherical maghemite MNPs with a narrow size distribution and enhanced effective magnetization. X-ray diffraction, transmission electron microscopy, magnetization and microwave absorption measurements were comparatively analyzed. The shape of the MNPs (mean diameter of 9 nm) was very close to being spherical. The lattice constant of the crystalline phase was substantially smaller than that of stoichiometric magnetite but larger than the lattice constant of maghemite. High value of Ms up to 300 K was established. The 300 K ferromagnetic resonance signal is a single line located at a field expected from spherical magnetic particles with negligible magnetic anisotropy. The maximum obtained concentration of water based ferrofluid was as high as 10g/l of magnetic material. In order to understand the temperature and field dependence of MNPs magnetization, we invoke the core-shell model. The nanoparticles is said to have a ferrimagnetic core (roughly 70 percent of the caliper size) while the shell consists of surface layers in which the spins are frozen having no long range magnetic order. The core-shell interactions were estimated in frame of random anisotropy model. The obtained assembly of de-aggregated nanoparticles is an example of magnetic nanofluid stable under ambient conditions even without an electrostatic stabilizer
Evaluation of anti-biofilm activity of acidic amino acids and synergy with ciprofloxacin on Staphylococcus aureus biofilms
Acidic amino acids, aspartic acid (Asp) and glutamic acid (Glu) can enhance the solubility of many poorly soluble drugs including ciprofloxacin (Cip). One of the mechanisms of resistance within a biofilm is retardation of drug diffusion due to poor penetration across the matrix. To overcome this challenge, this work set to investigate novel counter ion approach with acidic amino acids, which we hypothesised will disrupt the biofilm matrix as well as simultaneously improve drug effectiveness. The anti-biofilm activity of D-Asp and D-Glu was studied on Staphylococcus aureus biofilms. Synergistic effect of combining D-amino acids with Cip was also investigated as a strategy to overcome anti-microbial resistance in these biofilms. Interestingly at equimolar combinations, D-Asp and D-Glu were able to significantly disperse (at 20âmM and 40âmM) established biofilms and inhibit (at 10âmM, 20âmM and 40âmM) new biofilm formation in the absence of an antibiotic. Moreover, our study confirmed L-amino acids also exhibit anti-biofilm activity. The synergistic effect of acidic amino acids with Cip was observed at lower concentration ranges (<40âmM amino acids and <90.54â”M, respectively), which resulted in 96.89% (inhibition) and 97.60% (dispersal) reduction in CFU with exposure to 40âmM amino acids. Confocal imaging indicated that the amino acids disrupt the honeycomb-like extracellular DNA (eDNA) meshwork whilst also preventing its formation
A Promiscuous DNA Packaging Machine from Bacteriophage T4
Packaged viral genome can be removed from bacteriophage T4 capsid and the capsid refilled with any double-stranded DNA, single or multiple molecules, using a powerful ATP-fueled DNA packaging machine
ĐĐ”ĐčŃĐŸĐČОзŃалОзаŃĐžĐŸĐœĐœŃĐ” ĐŒĐ”ŃĐŸĐŽĐžĐșĐž ĐŸŃĐ”ĐœĐșĐž ĐłĐŸĐ»ĐŸĐČĐœĐŸĐłĐŸ ĐŒĐŸĐ·ĐłĐ° ĐżŃĐž ŃĐ°Ń Đ°ŃĐœĐŸĐŒ ЎОабДŃĐ” (лОŃĐ”ŃĐ°ŃŃŃĐœŃĐč ĐŸĐ±Đ·ĐŸŃ)
Diabetes mellitus (DM) is associated with changes in the structure of the brain and deterioration of cognitive functions from mild to moderate according to neuropsychological testing. With the growing DM epidemic and the increasing number of people living to old age, cognitive dysfunctions associated with DM can have serious consequences for the future of public and practical health. Chronic hyperglycemia, severe episodes of hypoglycemia, and microvascular complications are important risk factors common for type 1 and type 2 diabetes. DM is also associated with structural and functional changes in the brain, which can be diagnosed by various types of magnetic resonance imaging (MRI) of the brain. In this review, we investigate studies conducted over the past two decades to improve the understanding of how DM effects the brain function and structure. We also describe the changes characteristic of type 1 and type 2 diabetes during standard MRI, functional MRI and proton magnetic-resonance spectroscopy (proton MRS) as well as their features.ĐĄĐ°Ń
Đ°ŃĐœŃĐč ĐŽĐžĐ°Đ±Đ”Ń (ĐĄĐ) ŃĐČŃĐ·Đ°Đœ Ń ĐžĐ·ĐŒĐ”ĐœĐ”ĐœĐžŃĐŒĐž ĐČ ŃŃŃŃĐșŃŃŃĐ” ĐłĐŸĐ»ĐŸĐČĐœĐŸĐłĐŸ ĐŒĐŸĐ·ĐłĐ° Đž ŃŃ
ŃĐŽŃĐ”ĐœĐžĐ”ĐŒ ĐșĐŸĐłĐœĐžŃĐžĐČĐœŃŃ
 ŃŃĐœĐșŃĐžĐč ĐŸŃ Đ»Đ”ĐłĐșĐŸĐč ĐŽĐŸ ŃĐŒĐ”ŃĐ”ĐœĐœĐŸĐč ŃŃĐ”ĐżĐ”ĐœĐž ĐżĐŸ ĐŽĐ°ĐœĐœŃĐŒ ĐœĐ”ĐčŃĐŸĐżŃĐžŃ
ĐŸĐ»ĐŸĐłĐžŃĐ”ŃĐșĐŸĐłĐŸ ŃĐ”ŃŃĐžŃĐŸĐČĐ°ĐœĐžŃ. Đ ŃŃĐ»ĐŸĐČĐžŃŃ
 ŃĐ°ŃŃŃŃĐ”Đč ŃĐżĐžĐŽĐ”ĐŒĐžĐž ĐĄĐ Đž ŃĐČДлОŃĐ”ĐœĐžŃ ŃĐžŃла Đ»ŃĐŽĐ”Đč, ĐŽĐŸĐ¶ĐžĐČĐ°ŃŃĐžŃ
ĐŽĐŸ ŃŃĐ°ŃĐŸŃŃĐž, ĐșĐŸĐłĐœĐžŃĐžĐČĐœĐ°Ń ĐŽĐžŃŃŃĐœĐșŃĐžŃ, аŃŃĐŸŃООŃĐŸĐČĐ°ĐœĐœĐ°Ń Ń ĐĄĐ, ĐŒĐŸĐ¶Đ”Ń ĐžĐŒĐ”ŃŃ ŃĐ”ŃŃĐ”Đ·ĐœŃĐ” ĐżĐŸŃлДЎŃŃĐČĐžŃ ĐŽĐ»Ń Đ±ŃĐŽŃŃĐ”ĐłĐŸ ĐŸĐ±ŃĐ”ŃŃĐČĐ”ĐœĐœĐŸĐłĐŸ Đž ĐżŃĐ°ĐșŃĐžŃĐ”ŃĐșĐŸĐłĐŸ Đ·ĐŽŃĐ°ĐČĐŸĐŸŃ
ŃĐ°ĐœĐ”ĐœĐžŃ. Đ„ŃĐŸĐœĐžŃĐ”ŃĐșĐ°Ń ĐłĐžĐżĐ”ŃглОĐșĐ”ĐŒĐžŃ, ŃŃжДлŃĐ” ŃĐżĐžĐ·ĐŸĐŽŃ ĐłĐžĐżĐŸĐłĐ»ĐžĐșĐ”ĐŒĐžĐž Đž ĐŒĐžĐșŃĐŸŃĐŸŃŃĐŽĐžŃŃŃĐ”Â ĐŸŃĐ»ĐŸĐ¶ĐœĐ”ĐœĐžŃ ŃĐČĐ»ŃŃŃŃŃ ĐČĐ°Đ¶ĐœŃĐŒĐž ŃĐ°ĐșŃĐŸŃĐ°ĐŒĐž ŃĐžŃĐșĐ°, ĐŸĐ±ŃĐžĐŒĐž ĐŽĐ»Ń ĐĄĐ 1-ĐłĐŸ Đž 2-ĐłĐŸ ŃОпа. йаĐșжД ĐĄĐ ŃĐČŃĐ·Đ°Đœ ŃĐŸÂ ŃŃŃŃĐșŃŃŃĐœŃĐŒĐž Đž ŃŃĐœĐșŃĐžĐŸĐœĐ°Đ»ŃĐœŃĐŒĐž ĐžĐ·ĐŒĐ”ĐœĐ”ĐœĐžŃĐŒĐž ĐČ ĐłĐŸĐ»ĐŸĐČĐœĐŸĐŒ ĐŒĐŸĐ·ĐłĐ”, ĐșĐŸŃĐŸŃŃĐ” ĐČĐŸĐ·ĐŒĐŸĐ¶ĐœĐŸ ĐŽĐžĐ°ĐłĐœĐŸŃŃĐžŃĐŸĐČĐ°ŃŃÂ ĐżĐŸŃŃДЎŃŃĐČĐŸĐŒ ŃазлОŃĐœŃŃ
ĐČĐ°ŃĐžĐ°ĐœŃĐŸĐČ ĐŒĐ°ĐłĐœĐžŃĐœĐŸ-ŃĐ”Đ·ĐŸĐœĐ°ĐœŃĐœĐŸĐč ŃĐŸĐŒĐŸĐłŃĐ°ŃОО (ĐĐ Đą) ĐłĐŸĐ»ĐŸĐČĐœĐŸĐłĐŸ ĐŒĐŸĐ·ĐłĐ°. Đ ĐżŃДЎŃŃĐ°ĐČĐ»Đ”ĐœĐœĐŸĐŒ ĐŸĐ±Đ·ĐŸŃĐ” ŃĐ°ŃŃĐŒĐŸŃŃĐ”ĐœŃ ĐžŃŃĐ»Đ”ĐŽĐŸĐČĐ°ĐœĐžŃ, ĐżŃĐŸĐČĐ”ĐŽĐ”ĐœĐœŃĐ” Đ·Đ° ĐżĐŸŃĐ»Đ”ĐŽĐœĐžĐ” ĐŽĐČĐ° ĐŽĐ”ŃŃŃОлДŃĐžŃ, ŃŃĐŸĐ±Ń ŃĐ»ŃŃŃĐžŃŃÂ ĐżĐŸĐœĐžĐŒĐ°ĐœĐžĐ” ŃĐŸĐłĐŸ, ĐșĐ°Đș ĐĄĐ ĐČлОŃĐ”Ń ĐœĐ° ŃŃĐœĐșŃĐžŃ Đž ŃŃŃŃĐșŃŃŃŃ ĐłĐŸĐ»ĐŸĐČĐœĐŸĐłĐŸ ĐŒĐŸĐ·ĐłĐ°. йаĐșжД ĐŸĐżĐžŃĐ°ĐœŃ ĐžĐ·ĐŒĐ”ĐœĐ”ĐœĐžŃ, Ń
Đ°ŃĐ°ĐșŃĐ”ŃĐœŃĐ” ĐŽĐ»Ń ĐĄĐ 1-ĐłĐŸ Đž 2-ĐłĐŸ ŃОпа ĐżŃĐž ĐżŃĐŸĐČĐ”ĐŽĐ”ĐœĐžĐž ŃŃĐ°ĐœĐŽĐ°ŃŃĐœĐŸĐč, ŃŃĐœĐșŃĐžĐŸĐœĐ°Đ»ŃĐœĐŸĐč ĐĐ Đą Đž ĐżŃĐŸŃĐŸĐœĐœĐŸĐč ĐŒĐ°ĐłĐœĐžŃĐœĐŸ-ŃĐ”Đ·ĐŸĐœĐ°ĐœŃĐœĐŸĐč ŃпДĐșŃŃĐŸŃĐșĐŸĐżĐžĐž, Đž ĐžŃ
ĐŸŃĐŸĐ±Đ”ĐœĐœĐŸŃŃĐž
Inverting family GH156 sialidases define an unusual catalytic motif for glycosidase action
Sialic acids are a family of related sugars that play essential roles in many biological events intimately linked to cellular recognition in both health and disease. Sialidases are therefore orchestrators of cellular biology and important therapeutic targets for viral infection. Here, we sought to define if uncharacterized sialidases would provide distinct paradigms in sialic acid biochemistry. We show that a recently discovered sialidase family, whose first member EnvSia156 was isolated from hot spring metagenomes, defines an unusual structural fold and active centre constellation, not previously described in sialidases. Consistent with an inverting mechanism, EnvSia156 reveals a His/Asp active center in which the His acts as a Bronsted acid and Asp as a Bronsted base in a single-displacement mechanism. A pre-dominantly hydrophobic aglycone site facilitates accommodation of a variety of 2-linked sialosides; a versatility that offers the potential for glycan hydrolysis across a range of biological and technological platforms
Viral capsids: Mechanical characteristics, genome packaging and delivery mechanisms
The main functions of viral capsids are to protect, transport and deliver their genome. The mechanical properties of capsids are supposed to be adapted to these tasks. Bacteriophage capsids also need to withstand the high pressures the DNA is exerting onto it as a result of the DNA packaging and its consequent confinement within the capsid. It is proposed that this pressure helps driving the genome into the host, but other mechanisms also seem to play an important role in ejection. DNA packaging and ejection strategies are obviously dependent on the mechanical properties of the capsid. This review focuses on the mechanical properties of viral capsids in general and the elucidation of the biophysical aspects of genome packaging mechanisms and genome delivery processes of double-stranded DNA bacteriophages in particular
International Consensus Statement on Rhinology and Allergy: Rhinosinusitis
Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICARâRS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICARâRSâ2021 as well as updates to the original 140 topics. This executive summary consolidates the evidenceâbased findings of the document. Methods: ICARâRS presents over 180 topics in the forms of evidenceâbased reviews with recommendations (EBRRs), evidenceâbased reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICARâRSâ2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidenceâbased management algorithm is provided. Conclusion: This ICARâRSâ2021 executive summary provides a compilation of the evidenceâbased recommendations for medical and surgical treatment of the most common forms of RS
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