1,352 research outputs found
Extraction of Silymarin Compounds from Milk Thistle (Silybum Marianum) Seed Using Hot, Liquid Water as the Solvent
High value specialty chemicals are usually obtained from natural products by extracting with generally regarded as safe (GRAS) solvents. Because organic solvents are quite often used, high operating and disposal costs often occur. When compared to traditional solvents, water can be viewed as an interesting alternative because of its low operating and disposal costs. Milk thistle contains compounds (taxifolin, silychristin, silydianin, silybinin A and silybinin B) that display hepatoxic protection properties. This paper examines the batch extraction of silymarin compounds from milk thistle seed meal in 50\u27C, 70\u27C, 85\u27C and 100\u27C water as a function of time. For taxifolin, silychristin, silybinin A and silybinin B, extraction with 100\u27 C water resulted in the highest yields. After 210 min of extraction at 100\u27C, the yield of taxifolin was 1.2 mg per g of seed, while the yields of silychristin, silybinin A and silybinin B were 5.0, 3. 7 and 6.5 mg per g of seed, respectively. The overall diffusion coefficients for the four compounds increased with temperature and ranged from 0.14 x 10^ 10 to 4 x10 ^ 10 m2 /sec, indicating that the diffusion coefficients could potentially be used for quantitative comparisons of extraction conditions. The ratios of the extracted compounds, and particularly the ratios at long extraction times, showed that the more polar compounds (taxifolin and silychristin) were preferentially extracted at 85\u27C, while the less polar silybinin was preferentially extracted at 100\u27C
Renormalized Kaluza-Klein theories
Using six-dimensional quantum electrodynamics () as an example we
study the one-loop renormalization of the theory both from the six and
four-dimensional points of view. Our main conclusion is that the properly
renormalized four dimensional theory never forgets its higher dimensional
origin. In particular, the coefficients of the neccessary extra counterterms in
the four dimensional theory are determined in a precise way. We check our
results by studying the reduction of on a two-torus.Comment: LaTeX, 36 pages. A new section added; references improved, typos
fixe
CCD measurements of visual double stars at Calar Alto.
342 CCD measurements of relative positions and magnitude differences for 145 visual double stars are presented. Observations were carried out at the 1.23m telescope of the German-Spanish Astronomical Center at Calar Alto (Spain), all of them in V and R photometric bands
New Phenomenon of Nonlinear Regge Trajectory and Quantum Dual String Theory
The relation between the spin and the mass of an infinite number of particles
in a -deformed dual string theory is studied. For the deformation parameter
a root of unity, in addition to the relation of such values of with the
rational conformal field theory, the Fock space of each oscillator mode in the
Fubini-Veneziano operator formulation becomes truncated. Thus, based on general
physical grounds, the resulting spin-(mass) relation is expected to be
below the usual linear trajectory. For such specific values of , we find
that the linear Regge trajectory turns into a square-root trajectory as the
mass increases.Comment: 12 pages, Latex, HU-SEFT R 1994-0
T-duality of axial and vector dyonic integrable models
A general construction of affine Non Abelian (NA) - Toda models in terms of
axial and vector gauged two loop WZNW model is discussed. They represent {\it
integrable perturbations} of the conformal -models (with tachyons
included) describing (charged) black hole type string backgrounds. We study the
{\it off-critical} T-duality between certain families of axial and vector type
of integrable models for the case of affine NA- Toda theories with one global
U(1) symmetry. In particular we find the Lie algebraic condition defining a
subclass of {\it T-selfdual} torsionless NA Toda models and their zero
curvature representation.Comment: 20 pages, latex, no figures,improvments in the text of Sects.1,2 and
6;typos corrected,references added, to appear in Ann. of Physics (NY
Combination of polymeric superplasticizers, water repellents and pozzolanic agents to improve air lime-based grouts for historic masonry repair
This paper presents the experimental procedure to develop air lime-based injection grouts including polymeric superplasticizers, a water repellent agent and pozzolanic agents as additives. Research focuses on the development of grouts to improve various characteristics simultaneously combining different additions and admixtures. Aiming to improve the injectability of the grouts, in this study different polymeric superplasticizers were added, namely polycarboxylated-ether derivative (PCE), polynaphthalene sulfonate (PNS) and condensate of melamine-formaldehyde sulfonate (SMFC). Sodium oleate was also used as a water repellent agent to reduce the water absorption. The enhancement of the strength and setting time was intended by using microsilica and metakaolin as pozzolanic mineral additions. Compatibility between the different admixtures and action mechanism of the different polymers were studied by means of zeta potential and adsorption isotherms measurements. Diverse grout mixtures were produced and investigated assessing their injectability, fluidity, stability, compressive strength, hydrophobicity and durability. This research leads to several suitable mixtures produced by using more than one component to enhance efficiency and to provide better performance of grouts. According to the results, the grout composed of air lime, metakaolin, sodium oleate and PCE was found the most effective composition improving the mechanical strength, injectability and hydrophobicity
Acceleration-Enlarged Symmetries in Nonrelativistic Space-Time with a Cosmological Constant
By considering the nonrelativistic limit of de-Sitter geometry one obtains
the nonrelativistic space-time with a cosmological constant and Newton-Hooke
(NH) symmetries. We show that the NH symmetry algebra can be enlarged by the
addition of the constant acceleration generators and endowed with central
extensions (one in any dimension (D) and three in D=(2+1)). We present a
classical Lagrangian and Hamiltonian framework for constructing models
quasi-invariant under enlarged NH symmetries which depend on three parameters
described by three nonvanishing central charges. The Hamiltonian dynamics then
splits into external and internal sectors with new non-commutative structures
of external and internal phase spaces. We show that in the limit of vanishing
cosmological constant the system reduces to the one presented in [1] which
possesses accelaration-enlarged Galilean symmetries.Comment: 13 pages; small changes like a couple of footnotes et
Making the hyper--K\"ahler structure of N=2 quantum string manifest
We show that the Lorentz covariant formulation of N=2 string in a curved
space reveals an explicit hyper--K\"ahler structure. Apart from the metric, the
superconformal currents couple to a background two--form. By superconformal
symmetry the latter is constrained to be holomorphic and covariantly constant
and allows one to construct three complex structures obeying a
(pseudo)quaternion algebra.Comment: 8 pages, no figures, PACS: 04.60.Ds; 11.30.Pb, Keywords: N=2 string,
hyper-K\"ahler geometry. Presentation improved, references added. The version
to appear in PR
Differential geometry construction of anomalies and topological invariants in various dimensions
In the model of extended non-Abelian tensor gauge fields we have found new
metric-independent densities: the exact (2n+3)-forms and their secondary
characteristics, the (2n+2)-forms as well as the exact 6n-forms and the
corresponding secondary (6n-1)-forms. These forms are the analogs of the
Pontryagin densities: the exact 2n-forms and Chern-Simons secondary
characteristics, the (2n-1)-forms. The (2n+3)- and 6n-forms are gauge invariant
densities, while the (2n+2)- and (6n-1)-forms transform non-trivially under
gauge transformations, that we compare with the corresponding transformations
of the Chern-Simons secondary characteristics. This construction allows to
identify new potential gauge anomalies in various dimensions.Comment: 27 pages, references added, matches published versio
Systematic approach to cyber resilience operationalization in SMEs
The constantly evolving cyber threat landscape is a latent problem for todayâs companies. This
is especially true for the Small and Medium-sized Enterprises (SMEs) because they have limited resources
to face the threats but, as a group, represent an extensive payload for cybercriminals to exploit. Moreover, the
traditional cybersecurity approach of protecting against known threats cannot withstand the rapidly evolving
technologies and threats used by cybercriminals. This study claims that cyber resilience, a more holistic
approach to cybersecurity, could help SMEs anticipate, detect, withstand, recover from and evolve after
cyber incidents. However, to operationalize cyber resilience is not an easy task, and thus, the study presents
a framework with a corresponding implementation order for SMEs that could help them implement cyber
resilience practices. The framework is the result of using a variation of Design Science Research in which
Grounded Theory was used to induce the most important actions required to implement cyber resilience and
an iterative evaluation from experts to validate the actions and put them in a logical order. Therefore, this
study proposes that the framework could benefit SME managers to understand cyber resilience, as well as
help them start implementing it with concrete actions and an order dictated by the experience of experts.
This could potentially ease cyber resilience implementation for SMEs by making them aware of what cyber
resilience implies, which dimensions it includes and what actions can be implemented to increase their cyber
resilience
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