The new method of fabrication of submicron structures by optical lithography with mask shifting and mask rotation

This paper presents the methods of fabricating narrow parallel submicrometric stripes in silicon dioxide and a resist layer. The experiments were conducted by two techniques: double patterning lithography and double exposure lithography. In addition to the above mentioned processes, mask translation was applied. For all conducted experiments, chrome masks and a 405 nm line of the high pressure mercury lamp of an MA-56 Mask Aligner System were used. The main aim of the performed tests was to establish the utility and the possible applications of the methods used.     

Interactions of polar hydrogen bond donor solvents with ions: a theoretical study

Structural Chemistry - Intermolecular interactions between molecules of protic solvents (water, methanol, formic acid, formamide, methylamine and ammonia) and monatomic ions (Li+, Na+, K+,...     

The Computer-Aided Design,Synthesis, and Activity Prediction of New Leucine Aminopeptidase Inhibitors

The design, stereo-, and enantioselective synthesis and activity prediction of aminophosphonic acids as new leucine aminopeptidase inhibitors will be discussed.     

The shape of the halogen atom—anisotropy of electron distribution and its dependence on basis set and method used

A search through Crystal Structure Database was performed and the distances in contacts of X···N,O, X···H(N,O), and X···C type were collected together with the information on spatial arrangement of the interacting fragments. A detailed statistical analysis showed that the shape of the halogen atom cannot be simply concluded on the basis of interatomic distances in crystal state although originally the concept of anisotropic charge distribution around halogen nuclei was postulated on the basis of such an analysis. It was proven that the conclusions in that case strongly depend on the type of center interacting with the halogen atom. Therefore, it was postulated that the shape of the halogen atom can be estimated for the unperturbed (due to intermolecular interactions) halogen atom. For this purpose, a method was provided to make possible a numerical quantification of the anisotropy of the halogen atom on the basis of electron density measurements performed within the framework of Atoms in Molecules Quantum Theory. The anisotropy of Cl and Br atoms in H₃C–X and F₃C–X (X=Cl, Br) was estimated for MP2 and DFT-B3LYP methods and several different basis sets. The influence of the method and the basis set on the degree of anisotropic distribution of electron density around halogen nuclei was discussed.     

Molecular Separation Barriers and Their Application to Catalytic Reactor Design

The use of semipermeable membranes for multicomponent separations based on molecular size has long been recognized. In certain applications, however, it is often desirable not to effect a separation of chemical constituents, but to sustain a separation which already exists. As an example, the efficient and economical design of a. chemical reactor using an enzyme as a catalyst depends on the accessibility of the reactant to the catalyst as well as on the degree to which a physical separation between the enzyme and the reactor product stream is maintained. A particularly simple and attractive means of achieving this is through the use of semipermeable asymmetric hollow fiber membranes. For example, by sequestering an enzyme solution within the annular macroporous support regions of an asymmetric hollow fiber, a physical separation between enzyme and a reactant solution flowing through the fiber lumen is achieved. In this way, small reactant molecules are free to diffuse across the ultrathin membrane skin into the opencell support structure where reaction will occur. Product molecules will diffuse back into the lumen, and a compact chemical reactor results. The operating behavior of this type of catalytic reactor will be described and its application to the hydrolysis of o-nitro-phenyl-B-d-galactopyranoside and of lactose is discussed.     

Enantioselective Extraction System Containing Binary Chiral Selectors and Chromatographic Enantioseparation Method for Determination of the Absolute Configuration of Enantiomers of Cyclopentolate

The distribution coefficients and enantioseparation of cyclopentolate were studied in an extraction system containing d-tartaric acid ditertbutyl ester in organic phase and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous phase. Various parameters involved in the enantioseparation such as the type and the concentration of chiral selectors, pH value and a wide range of organic solvents were investigated. The maximum enantioselectivity (α = 2.13) and optimum distribution coefficients (K _R = 0.85, K _S = 0.40) were obtained under the following conditions: 0.10 mol/L HP-β-CD in aqueous phase and 0.20 mol/L d-tartaric acid ditertbutyl ester in decanol as organic phase. Cyclopentolate is present as a racemic mixture to the aqueous phase. The potentially different biological activities of cyclopentolate enantiomers have not been examined yet. Two chiral liquid chromatography methods have been developed for the direct separation of the enantiomers of cyclopentolate. First method was used for the quantification analysis of cyclopentolate enantiomers in aqueous phase. Second method used two chiroptical detectors: electronic circular dichroism (ECD) and optical rotation (OR) for the identification of individual cyclopentolate enantiomers from the organic phase enriched with (R)-enantiomer. The absolute stereochemistry was determined by means of the comparison of the experimental and computed ECD spectra and signs of OR. The ECD spectra of chiral analytes were measured on-line using HPLC-ECD technique.

     

HPLC Method for the Simultaneous Determination of the UV-Filters Butyl Methoxy Dibenzoylmethane and Octocrylene in the Presence of Their Photodegradants

Butyl methoxy dibenzoylmethane (BMDM) and octocrylene (OC), common UV-filters in sunscreen products are often used in combination. Together they provide broad spectrum photoprotection from exposure to both UVA- and UVB-light. These UV-filters may, however, undergo photodegradation and generate photodegradants, resulting in a potential loss of photoprotection. It is thus a concern that the photostability testing as described by the ICH Guideline Q1B is not a requirement for sunscreen products in Australia, Europe or the USA. UV-filter photodegradants have in addition been shown to be toxic, highlighting the importance of their separation from the parent UV-filters. An HPLC method was developed and validated to quantitatively determine a combination of these UV-filters in the presence of their photodegradants. Reverse-phase chromatography was employed, using a C18 column and an isocratic mobile phase consisting of methanol/water/acetic acid (89/10/1 v/v). Validation according to the ICH guidelines for linearity, accuracy, precision, sensitivity, specificity and robustness was confirmed. The developed and validated method was then successfully applied to the determination of BMDM and OC in an aqueous cream base, typically used in sunscreens, after photostability testing, according to the ICH Guideline Q1B. In addition, the diketo-enol ratio of BMDM in methanol-d ₄ was determined by NMR and the two major photodegradants were identified by FTMS and LC–MS.