Numerical simulation of turbulent heat transfer from perforated plate-fin heat sinks

Excessive heat from microelectronic components is essential to remove to increase the reliability of the system. In this paper, various types of perforations in the form of small channels such as square, circular, triangular and hexagonal cross sections are introduced and thermal performances are compared to improve the cooling performance of heat sink. The governing equations are solved by adopting a control volume based finite element method with an unstructured non-uniform grid system. Flow and heat transfer characteristics are presented for Reynolds numbers from 2 × 10⁴ to 4 × 10⁴ based on the fin length and Prandtl number is taken as Pr = 0.71. RANS based k-ε turbulence model is used to predict the turbulent flow parameters. The predicted results are validated by the previously published experimental data and in reasonable agreement with the experiment. Results show that fins having circular perforations have better thermal and fluid dynamic performances than the other types of fins considered here.     

Subacute Assessment of the Toxicity and Antidepressant-Like Effects of Origanum Majorana L. Polyphenols in Swiss Albino Mice

Origanum majorana L. is a plant commonly used in folk medicine to treat depression and several neurological disorders. This study aims to evaluate the antidepressant-like effect of the Origanum majorana L. polyphenols (OMP) obtained from the aerial parts using two different depression model tests: The forced swimming test (FST) and the tail suspension test (TST) in Swiss albino mice. The experiments were performed on days 1, 7, 14, and 21 with daily administration of different treatments. Two different doses were chosen for this study (50 and 100 mg/kg), and paroxetine was used as a positive control. Immobility as a consequence of the depression state was significantly reduced following the treatment with OMP, indicating an antidepressant effect. A subacute toxicity study was also performed following the Organization for Economic Co-operation and Development (OECD) Guidelines (407), showing no sign of toxicity for the studied doses. The phytochemical screening revealed the presence of 12 components, all belonging to polyphenols: Arbutin, rosmarinic acid, ursolic acid, quercetin-3-O-glucoside, quercetin-7-O-glucuronic acid, luteolin-7-O-glucoside, kaempferol-3-0-glucuronic acid, Kaempferol-3-0-pentose, caffeic acid, catechin, quercetin, and rutin. These findings suggest that O. majorana has interesting antidepressant-like properties, which deserve further investigation.     

Phototriggered Release of a Transmembrane Chloride Carrier from an o‐Nitrobenzyl‐Linked Procarrier

While there have been many studies on synthetic chloride carriers and a recent application for apoptotic cell death, so far, the proposed huge potential of these systems in targeting cancer has not been realized due to their cytotoxicity to healthy cells. Herein, we describe the development of an indole‐2‐carboxamide receptor as an efficient membrane chloride carrier while the corresponding o‐nitrobenzyl‐linked derivative is a procarrier of the ion. Photoirradiation of the procarrier in liposomes results in release of the active carrier with up to 90 % transport efficiency. Such photorelease of the carrier also works within cancer cells, resulting in efficient cell killing. Such photocleavable procarriers have great potential as a photodynamic therapy to combat various types of cancers.     

Green synthesized selenium nanoparticles for ovarian cancer cell apoptosis

Research on Chemical Intermediates - Over recent years, selenium nanoparticles (Se-NP) have been widely applied in nanomedicine science due to their exceptional physicochemical and biological...     

Tunable Supramolecular Gel Properties by Varying Thermal History

The possibility of using differential pre-heating prior to supramolecular gelation to control the balance between hydrogen-bonding and aromatic stacking interactions in supramolecular gels and obtain consequent systematic regulation of structure and properties is demonstrated. Using a model aromatic peptide amphiphile, Fmoc-tyrosyl-leucine (Fmoc-YL) and a combination of fluorescence, infrared, circular dichroism and NMR spectroscopy, it is shown that the balance of these interactions can be adjusted by temporary exposure to elevated temperatures in the range 313–365 K, followed by supramolecular locking in the gel state by cooling to room temperature. Distinct regimes can be identified regarding the balance between H-bonding and aromatic stacking interactions, with a transition point at 333 K. Consequently, gels can be obtained with customizable properties, including supramolecular chirality and gel stiffness. The differential supramolecular structures also result in changes in proteolytic stability, highlighting the possibility of obtaining a range of supramolecular architectures from a single molecular structure by simply controlling the pre-assembly temperature.     

Esterase-Activatable Synthetic M+/Cl− Channel Induces Apoptosis and Disrupts Autophagy in Cancer Cells

The formation of a supramolecular synthetic M⁺/Cl⁻ channel in the membrane phospholipid bilayer has been reported upon activation of a methyl pivalate-linked N¹,N³-dialkyl-2-hydroxyisophthalamide by esterases. The channel formation induces apoptosis in cancer cells via the intrinsic pathway. Interestingly, the supramolecular channel was also shown to disrupt autophagy in cancer cells by causing alkalization of lysosomes – a feature that has been confirmed at the cellular and protein level.     

Generalized multiplicities of edge ideals

We explore connections between the generalized multiplicities of square-free monomial ideals and the combinatorial structure of the underlying hypergraphs using methods of commutative algebra and polyhedral geometry. For instance, we show that the j-multiplicity is multiplicative over the connected components of a hypergraph, and we explicitly relate the j-multiplicity of the edge ideal of a properly connected uniform hypergraph to the Hilbert–Samuel multiplicity of its special fiber ring. In addition, we provide general bounds for the generalized multiplicities of the edge ideals and compute these invariants for classes of uniform hypergraphs.     

Compactness by the Hausdorff measure of noncompactness

In the present paper, we establish some identities or estimates for the operator norms and the Hausdorff measures of noncompactness of certain operators given by infinite matrices that map an arbitrary BK-space into the sequence spaces c₀, c, ?_∞ and ?₁, and into the matrix domains of triangles in these spaces. Furthermore, by using the Hausdorff measure of noncompactness, we apply our results to characterize some classes of compact operators on the BK-spaces.     

Formulation and application of models for anisotropic hardening in sheet metals subject to complex loading-path changes

In this work material models for the simulation of forming processes involving non-uniform loading path changes are investigated. Materials exhibiting an evolution of the yield surface due to the formation and interaction of dislocation structures on the micro structural level are modeled by employing evolving structural tensors. These account for the evolution of anisotropy and hardening behavior known from technical alloys on a phenomenological basis. In a first step material parameters are identified from experiments for non-uniform loading conditions. In a second step, the evolution of structural tensors for varying loading conditions is investigated and related to the evolution of kinematic quantities. Finally applications relevant to the simulation of sheet metal forming processes are presented. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)