1,024 research outputs found
Interaction of bovine serum albumin with anionic surfactants
The effect of binding and conformational changes induced by anionic surfactants sodium dodecyl sulfate (SDS) and sodium octyl sulfate (SOS) on bovine serum albumin (BSA) have been studied using differential scanning calorimetry (DSC), circular dichroism (CD), fluorescence and UV spectroscopic methods. The denaturation temperature, van't Hoff enthalpy and calorimetric enthalpy of BSA in the presence of SDS and SOS and urea at pH 7 have been determined. The results indicate that SDS plays two opposite roles in the folding and stability of BSA. It acts as a structure stabiliser at a low molar concentration ratio of SDS/BSA and as a destabilizer at a higher concentration ratio as a result of binding of SDS to denatured BSA. The Brandts and Lin model has been used to simulate the results
High Photovoltaic Quantum Efficiency in Ultrathin van der Waals Heterostructures
We report experimental measurements for ultrathin (< 15 nm) van der Waals
heterostructures exhibiting external quantum efficiencies exceeding 50%, and
show that these structures can achieve experimental absorbance > 90%. By
coupling electromagnetic simulations and experimental measurements, we show
that pn WSe2/MoS2 heterojunctions with vertical carrier collection can have
internal photocarrier collection efficiencies exceeding 70%.Comment: ACS Nano, 2017. Manuscript (25 pages, 7 figures) plus supporting
information (7 pages, 4 figures
Electrical Control of Linear Dichroism in Black Phosphorus from the Visible to Mid-Infrared
The incorporation of electrically tunable materials into photonic structures
such as waveguides and metasurfaces enables dynamic control of light
propagation by an applied potential. While many materials have been shown to
exhibit electrically tunable permittivity and dispersion, including transparent
conducting oxides (TCOs) and III-V semiconductors and quantum wells, these
materials are all optically isotropic in the propagation plane. In this work,
we report the first known example of electrically tunable linear dichroism,
observed here in few-layer black phosphorus (BP), which is a promising
candidate for multi-functional, broadband, tunable photonic elements. We
measure active modulation of the linear dichroism from the mid-infrared to
visible frequency range, which is driven by anisotropic quantum-confined Stark
and Burstein-Moss effects, and field-induced forbidden-to-allowed optical
transitions. Moreover, we observe high BP absorption modulation strengths,
approaching unity for certain thicknesses and photon energies
ROLE OF PATHYAPATHYAS IN THE ADMINISTRATION OF RASOUSHADHAS
Ayurveda is a medical system which has well developed systems of diagnosis and treatment. It is the only medical system in world, which has apparatus to deal with complete human being, which comprises of mind, body and soul. The treatment is highly personalized according to the patients physical nature, age, immunity, mind power, habit etc. A customized diet, life style, exercise, mental support, breathing and meditation techniques also form the part of the treatment. There is a section in Ayurveda called Rasasastra which describes the use of metals, minerals, and poisons with their actions to combat chronic and complicated diseases. As we all know most of the Rasa drugs are toxic. These pass through extensive processing before they are declared fit for internal use. These preparations are sustaining themselves since centuries in clinical use. A thing that does not adversely affect the body and mind is known as Pathya (wholesome) the diet and regimens opposite to these qualities are said to be Apathya (unwholesome). Many Pathyapathya ahara viharas are mentioned in the Rasa classics. The rationale behind the selection of Aharas and Viharas as Pathya (wholesome) or Apathya (unwholesome) mainly depends on the properties of drugs which are used as Pathya as well as that of drug which is used as medicine. The implied meaning is rules and regulations about diet and movements etc. to be advised by the Physician along with treatment. The medicines are ineffective unless these are followed. In the case of Pathya most probable drug interaction will be synergism and of Apathya dravyas will be antagonism. However, their improper processing, misuse, improper mode of administration may cause adverse effects in the human body. Even though the drugs are in assimilable forms, there should be suitable vehicles for their absorption. Here comes the importance of Pathyapathya while using these metallic forms. Suitable Pathya is necessary while using these Rasa drugs for proper absorption of drug, to reduce its adverse effects, to increase its bio-availability etc
Methane and carbon dioxide adsorption on edge-functionalized graphene: A comparative DFT study
With a view towards optimizing gas storage and separation in crystalline and
disordered nanoporous carbon-based materials, we use ab initio density
functional theory calculations to explore the effect of chemical
functionalization on gas binding to exposed edges within model carbon
nanostructures. We test the geometry, energetics, and charge distribution of
in-plane and out-of-plane binding of CO2 and CH4 to model zigzag graphene
nanoribbons edge-functionalized with COOH, OH, NH2, H2PO3, NO2, and CH3.
Although different choices for the exchange-correlation functional lead to a
spread of values for the binding energy, trends across the functional groups
are largely preserved for each choice, as are the final orientations of the
adsorbed gas molecules. We find binding of CO2 to exceed that of CH4 by roughly
a factor of two. However, the two gases follow very similar trends with changes
in the attached functional group, despite different molecular symmetries. Our
results indicate that the presence of NH2, H2PO3, NO2, and COOH functional
groups can significantly enhance gas binding with respect to a
hydrogen-passivated edge, making the edges potentially viable binding sites in
materials with high concentrations of edge carbons. To first order, in-plane
binding strength correlates with the larger permanent and induced dipole
moments on these groups. Implications for tailoring carbon structures for
increased gas uptake and improved CO2/CH4 selectivity are discussed.Comment: 12 pages, 7 figure
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