Controlled release of 2‐heptanone using starch gel and polycaprolactone matrices and polymeric films

Varroa jacobsoni is a parasitic mite that is threatening the honeybee industry in many parts of the world. 2‐Heptanone, a natural product made by honeybees at low concentrations, is effective at elevated concentrations in controlling mite populations in honeybee colonies, especially when released over a 42 day period. An extrusion process was used to encapsulate 14, 18, and 25% 2‐heptanone in a polycaprolactone (PCL) matrix. Less than 18% of the 2‐heptanone was encapsulated in the PCL matrix. The high vapor permeability of PCL to 2‐heptanone resulted in a high flux rate and limited the usefulness of PCL as an encapsulation matrix for controlled‐release devices. A starch gel containing three times its weight in 2‐heptanone was prepared from starch‐based microcellular foam (MCF). The gel had compressive, tensile, and flexural strength values in the range of 0.56 to 1.9 MPa. 2‐Heptanone quickly evaporated from non‐laminated gels. However, when the gel was laminated with different polymeric films, a wide range of flux rates was obtained. The T₅₀ for gels laminated or coated with poly(vinyl alcohol) (PVAL, 99% hydrolyzed) and ethylene‐vinyl alcohol copolymer (EVAL) was 72 and 1030 days, respectively. The most promising film was a starch/glycerol film that released 50% of the 2‐heptanone (T₅₀) in approximately 13 days. Copyright © 2007 John Wiley & Sons, Ltd.     

Neue Synthesen von 1α,25-Dihydroxycholesterin

New Syntheses of 1α,25-Dihydroxycholesterol Five convergent syntheses of 1α,25-dihydroxycholesterol (2) essentially achieved by combining 1α-hydroxylated C_21? and C_22?steroids with C_4? or C_5?side-chain building blocks, are described. The l,3-bis(tetrahydropyranyloxy)pregnen-21-ol-Ptoluenesulfonate (4) was used as a C_22?unit in three approaches involving sulfone 24 as a C_4?, sulfone 43 and 2-propynyl ether 49 as C_5?side-chain building blocks. In a further preparation, the 1,3-diacetoxypregnen-21 -al 5 and the phosphorane 59 , a C_22? and a C_5?unit, respectively, were connected. For the last one, the 1,3-bis(tetrahydropyranyloxy)pregnen-20-one (6) , a C_2l?unit and the C_5?phosphorane building block 66 were chosen. Furthermore, new routes for the preparation of the 3-hydroxy-27-norcholestenone (29) and of 25-hydroxycholesterol (3) are described for which the p-toluenesulfonates 21 and 23 served as the steroidal units and the sulfones 24 and 43 , respectively, as the side chain fragments. Finally, the 1,3-diacetoxypregnen-21-al (5) and the C5-phosphorane unit 60 gave a novel approach to 1α-hydroxycholesterol (53).     

Optimisation of short term commercial bank loans to corporates in terms of financing operating activities in Slovenia

This paper presents the mathematical model for determination of the optimal amount of short term commercial bank loans to corporate sector in Slovenia which is based on probabilistic inventory models. The goal of this paper is complete optimisation of cash inventories of corporate sector in the national economy. The results of optimisation are important for the corporate sector and for commercial banks. The optimal order quantity is an amount of short term commercial bank loan to corporates and defines a lending potential of commercial banks in a national economy. As such is important for the central bank when conducting monetary policy. Special emphasis has been given to determinants of optimal order quantity, which reflect market conditions in national economy.     

Investigation of refractive index modifications in CW CO2 laser written planar optical waveguides

This paper presents the measurement of the refractive index profile of buried channel waveguides fabricated by a CW CO₂ direct writing technique. A reflectance method is used to assess the refractive index distribution n(x,y) in these structures as it is a key parameter determining the propagation properties of guided wave devices. Beam propagation method (BMP) is used with experimentally determined cross-sectional data and refractive index profile to model the waveguides. The spatial resolution is 1.3 μm and, 5.10⁻⁴ for the refractive index.