Adsorption hysteresis exhibits a wide range of phenomena dependent on the nature of both the adsorbent and the adsorptive, and on the tenperature. some of these features are described and an outline is given of their interpretation in terms of the physical processes involved. Particular attention is paid to the changes in the size and shape of hysteresis loops brought about by changes in tenperature, which are discussed in terms of hysteresis phase diagram .Hysteresis critical temperatures' are identified and linked t o recent theories of capillary condensation.

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N-Nitroso-N-methylurea (NMU) is a highly potent direct-acting carcinogen that has been shown to induce cancer in a number of animal species. Although previous research has indicated that nitrosation of creatinine (CRN), a common constituent of meats, dried fish, and seafoods, can form traces of NMU, there is uncertainty as to (1) the yield of NMU and (2) whether detectable amounts of NMU can be formed from cured meats following nitrosation under acidic conditions given the low residual levels of nitrite found in cured meats at the present time. Lack of sensitive and specific analytical methods most likely has hindered progress in research in these areas. An HPLC postcolumn denitrosation-thermal energy analyzer technique and a GC-MS confirmation technique were developed for the determination of NMU in cured meats. Both techniques are highly sensitive (0.5 and 0.03 ppb, respectively) and specific. The optimum pH for NMU formation from CRN ranged between pH 1 and pH 3, and the yields of NMU under variable reactant concentrations ranged between 0.00004 and 0.0046%. When 27 samples of various cured meats (10 g aliquots each) were acidified with HCl (final pH values of 0.8-2.5) and incubated at room temperature for 2 h, without any additional nitrite, 24 gave results below detectable levels but 3 formed 2-26 ng of NMU/10 g of meat. Incubation of the negative meats with additional nitrite (50-500 microg/g of meat) formed 0.6-176 ng of NMU/10 g of sample. Although the amounts of NMU formed were extremely small, this seems to be the first reported formation of NMU from cured meats with and without additional nitrite.

In continuation of our previous studies on N-nitroso-N-methylurea (NMU) formation in cured meats following incubation with nitrite at gastric pH, we extended the investigation to other foods mentioned in the title of this paper. The main objective was to determine whether these foods have the potential to form NMU at pH's that can be found in the human stomach. This was done by nitrosating an aliquot (5 g for fish sauce, 10 g for the others) of each with 7.25 microM to 1.59 mM levels of sodium nitrite for 2 h at room temperature at pH 0.8--1.5 and measuring the amounts of NMU formed. Of the samples tested, fish sauce formed 2--712 ng of NMU, followed in decreasing order by herring (<0.3--688 ng); dried anchovy, shrimp, and other fishes (<0.3--134 ng); crab and lobster paté (<0.3--342 ng); sardines (6--59 ng); oysters and mussels (11--31 ng); dried squid (3--47 ng); kimchi (7--107 ng); and Japanese pickled radish (<0.3--72 ng). Incorporation of 200-2000 ppm of ascorbic acid in the fish sauce and other foods, prior to nitrosation, appreciably inhibited such NMU formation. Although previous researchers in China reported NMU formation in nitrosated samples of fish sauce, this is the first reported formation of NMU upon nitrosation of the other foods mentioned above, and the first reported inhibition of such formation by added ascorbic acid.

The functionalization of nanoporous zeolite L crystals with β-cyclodextrin (CD) has been demonstrated. The zeolite surface was first modified with amino groups by using two different aminoalkoxysilanes. Then, 1,4-phenylene diisothiocyanate was reacted with the amino monolayer and used to bind CD heptamine by using its remaining isothiocyanate groups. The use of the different aminoalkoxysilanes, 3-aminopropyl dimethylethoxysilane (APDMES) and 3-aminopropyl triethoxysilane (APTES), led to drastic differences in uptake and release properties. Thionine was found to be absorbed and released from amino- and CD-functionalized zeolites when APDMES was used, whereas functionalization by APTES led to complete blockage of the zeolite channels. Fluorescence microscopy showed that the CD groups covalently attached to the zeolite crystals could bind adamantyl-modified dyes in a specific and reversible manner. This strategy allowed the specific immobilization of His-tagged proteins by using combined host-guest and His-tag-Ni-nitrilotriacetic acid (NTA) coordination chemistry. Such multifunctional systems have the potential for encapsulation of drug molecules inside the zeolite pores and non-covalent attachment of other (for example, targeting) ligand molecules on its surface.