Publications

Classical trajectory computations for thermal reactants on a six-atom potential show a forward scattering component which is correlated with the HF product being formed with high vibrational excitation. These trajectories are peripheral collisions where the F atom approaches CH4 with a high impact parameter and reaction is through a nearly collinear F-H-C configuration with a stretched F-H bond. Other trajectories are well described by a hard-sphere model whose cutoff is below the range of peripheral collisions. Comparison is made with the F + H(2 )and other reactions where nearly thermoneutral channels correlate with forward scattering. (C) 1998 Elsevier Science B.V. All rights reserved.

Appeared also in his 'An Alternative Path to Modernity' (2000). In Hebrew: 'Pe'amim' 69 (1996).

Classical trajectory computations and a kinematic analysis of the collision of two CH3I molecules are presented. The yield of molecular and atomic iodine is examined as a function of reactant translational and vibrational energy. The potential energy function is of the LEP form, which has a high late barrier where all bonds are extended. Vibrational excitation of CH3I enhances the barrier crossing and molecular products are formed highly vibrationally excited. Kinematic considerations indicate the same trends. The results are discussed as a possible mechanism for the formation of molecular iodine via ultrafast heating achieved in wall collisions of CH3I clusters. (C) 1998 Elsevier Science B.V. All rights reserved.

We report here on the fabrication and optimization of composites of conjugated polymer in Sol-Gel and PVA matrices. FTIR spectroscopy as well as other observations show that efficient phase and absorption holograms can be created in the material upon illumination, via the photochromic effect. The main contribution to the absorption change is chain scission and photo-oxidation mechanism. Optimized holographic composites with diffraction efficiencies as high as 26% are shown. Beam interaction between the writing beams is observed for these composites, while the diffraction efficiencies was improved by an order of magnitude.

The nuclear envelope plays many roles, including organizing nuclear structure and regulating nuclear events. Molecular associations of nuclear envelope proteins may contribute to the implementation of these functions. Lamin, otefin, and YA are the three Drosophila nuclear envelope proteins known in early embryos. We used the yeast two-hybrid system to explore the interactions between pairs of these proteins. The ubiquitous major lamina protein, lamin Dm, interacts with both otefin, a peripheral protein of the inner nuclear membrane, and YA, an essential, developmentally regulated protein of the nuclear lamina. In agreement with this interaction, lamin and otefin can be coimmunoprecipitated from the vesicle fraction of Drosophila embryos and colocalize in nuclear envelopes of Drosophila larval salivary gland nuclei. The two-hybrid system was further used to map the domains of interaction among lamin, otefin, and YA. Lamin's rod domain interacts with the complete otefin protein, with otefin's hydrophilic NH2-terminal domain, and with two different fragments derived from this domain. Analogous probing of the interaction between lamin and YA showed that the lamin rod and tail plus part of its head domain are needed for interaction with full-length YA in the two-hybrid system. YA's COOH-terminal region is necessary and sufficient for interaction with lamin. Our results suggest that interactions with lamin might mediate or stabilize the localization of otefin and YA in the nuclear lamina. They also suggest that the need for both otefin and lamin in mediating association of vesicles with chromatin might reflect the function of a protein complex that includes these two proteins.

The separation of radial electronic and nuclear motions is discussed with special reference to high Rydberg states of molecules. An inverse separation is obtained when the rapid nuclear motion instantaneously adjusts itself to the position of the Rydberg electron. The electron moves in the potential averaged over the position of the nuclei (and their valence electrons). This inverse separation is useful when omega n(3) > 1, where omega is the spacing of nuclear energy states (in au) and n is the principal quantum number of the Rydberg electron whose orbital period increases as n(3). The inverse Born-Oppenheimer separation can break down owing to the finite kinetic energy of the Rydberg electron. Like the Born-Oppenheimer separation, its inverse can also be formulated in an adiabatic or a diabatic basis. The diabatic inverse Born-Oppenheimer is practical both for interpretation of zero electron kinetic energy (ZEKE) spectra and for computations. Explicit results are given for a model system of an electron orbiting a vibrating dipole, identifying the relevant coupling constants. The discussion emphasizes the radial motion and the limits discussed here are not quite equivalent to the four (or, actually, five) Hund's coupling cases relevant to angular momentum coupling schemes. (C) 1998 John Wiley & Sons, Inc.

I read with much interest the review article ‘‘Mechanisms of neutrophil-induced parenchymal cell injury’’(H. Jaeschke and C.W. Smith, J. Leukoc. Biol. 61, 647–653). As I read through the text it became apparent that very basic and relevant concepts as well as publications regarding the possible mecha- nisms by which phagocytes kill targets had not been included in the review. The authors rightfully write, ‘‘The question regarding the molecular mechanism of neutrophil-induced target cell injury is controversial.’’ Yet despite the common knowledge and understanding that the mechanisms of cell damage most probably involve an interaction among a multiplicity of agonists (a multicomponent system), the section, ‘‘Mechanisms of neutro- phil-induced parenchymal cell injury’’ had adopted an ex- tremely reductionist and oversimplified approach to the prob- lem. It considered (see Fig. 1) what seems to be the exclusive role of oxidants and proteinases as potential cell injuring agents, as if these are the sole noxious agents generated by activated phagocytes. Although I fully respect the prerogatives and choices by the authors to refer exclusively to hepatocytes and parenchymal cells and to select citations from the literature pertaining to these tissues in order to support their thesis, it is still intriguing why not a single word was mentioned about the obvious possibility that oxidants, proteinases, and additional agonists might perhaps act mainly in concert (synergize) to injure any cell type? To the best of our knowledge and experience in this field of research (see list of recommended literature), even a normal cell line, as well as some of the tumor cells tested in vitro by us and by others, which could not readily be killed by physiologi- cal amounts of oxidants (H2O2 ROO, HCIO, NO) alone, were nevertheless rapidly killed in a synergistic manner if the oxidants were combined with any of a long list of membrane- perforating agents. These included phospholipase A2, phospho- lipase C, lysophosphatides, fatty acids, microbial hemolysins, cationic peptides and proteins, bile salts, complement compo- nents, and xenobiotics such as ethanol, methanol, and lindane. The inclusion of proteinases (trypsin, plasmin, elastase chymotrypsin), together with oxidants and the membrane perforators, further significantly enhanced cellular damage. It is also of great interest and is perhaps paradoxical that microbial agents might also synergize with phagocyte-derived agonists, but in an adverse fashion, to injure host tissues. It is also important to consider that all these proinflammatory agonists might be simultaneously present in infectious and inflammatory sites. Our studies also suggested that the induction of a sublethal membrane injury abolished, to a large extent, the potent antioxidant defenses of the cells— a finding of great significance. The readers of the Journal of Leukocyte Biology might be interested in a series of publications dealing with the ‘‘syner- gism’’ concept of cellular injury as related to infectious and inflammatory conditions, which have been published since 1986 (see list of recommended literature). An invited overview by Ginsburg and Kohen [8] undertook to discuss, in great detail, those papers that described the role of synergism in cellular injury. Unfortunately and enigmatically, publications that have described the ‘‘synergism concept’’ of cellular injury published since 1986 are hardly ever cited. If the synergism concept of cellular injury is logical and conforms with the current knowledge in the field, publications describing this phenom- enon should be quoted. If on the other hand these ideas are extreme, bizarre, and scientifically unacceptable, such papers should be discussed and challenged properly and even ridi- culed. However, it is totally unacceptable that such publica- tions be simply ignored. Approaching the third millennium, the readers of scientific journals deserve not an oversimplified approach to complicated scientific issues, but more realistic, integrated, and updated appraisals of the literature even if these might not always fully conform with the investigator’s own concepts or with the prevailing paradoxes, dogmas, cliches, and myths. It is also very surprising, and of great concern, why the referees of the papers did not bring any of these publications and concepts to the attention of the authors. After all, the main task of the referees and the editorial board is to criticize the validity and novelty of investigations brought to their attention and to strongly instruct negligent authors to give proper credit to relevant papers and concepts in their field of research. It is regrettable that this has not happened. Unfortunately, this is how, for the sake of brevity and a reductionist approach to the solution of complex biological phenomena, very basic and pioneering investigations and ‘‘novel’’ concepts may be simply ignored and buried for good. It is obvious that the ones who might suffer most from such an approach to the compilation of reviews and papers are the investigators, the readers, and perhaps most importantly, the credibility of journals at large. I shall greatly appreciate receiving comments and sugges- tions about these matters.