A numerical method is given for effecting nonlinear local density functional evolution. Within a given time interval, Chebyshev quadrature points are used to sample the evolving orbitals. An implicit equation coupling wave functions at the different time points is then set up. The equation is solved iteratively using the ‘‘direct inversion in iterative space’’ acceleration technique. Spatially, the orbitals are represented on a Fourier grid combined with soft pseudopotentials. The method is first applied to the computation of the 3Pg adiabatic potential energy curves of Al2 . Next, the electronic dynamics of a toy molecular wire is studied. The wire consists of a C2H4 molecule connected via sulfur atoms to two gold atoms, the ‘‘electrodes.’’ The molecule is placed in a homogeneous electric field and a dynamical process of charge transfer is observed. By comparing the transient with that of a resistance-capacitance circuit, an effective Ohmic resistance and capacitance is estimated for the system.
A review is given on scanning electrochem. microscopy (SECM) as a tool for surface modification. It is distinguished between the direct mode and the feedback mode of the SECM. In the direct mode, the substrate serves as the auxiliary electrode, while, in the feedback mode, the substrate is unibiased, and a mediator is used that shuttles between the ultramicroelectrode and the surface. The etching of semiconductors, the metal deposition and etching, the deposition of conducting polymers, and the patterning of org. and biomols. are treated for both the direct- and the feedback mode technique of the SECM. The achievable resoln. and the patterning rate are addressed. [on SciFinder(R)]
KL KOMPA and RD LEVINE. 2001. “A molecular logic gate.” PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 98, Pp. 410-414. Abstract
We propose a scheme for molecule-based information processing by combining well-studied spectroscopic techniques and recent results from chemical dynamics. Specifically it is discussed how optical transitions in single molecules can be used to rapidly perform classical (Boolean) logical operations. In the proposed way, a restricted number of states in a single molecule can act as a logical gate equivalent to at least two switches. it is argued that the four-level scheme can also be used to produce gain, because it allows an inversion, and not only a switching ability. The proposed scheme is quantum mechanical in that it takes advantage of the discrete nature of the energy revers but we here discuss the temporal evolution, with the use of the populations only. On a longer time range we suggest that the same scheme could be extended to perform quantum logic, and a tentative suggestion, based on an available experiment, is discussed. We believe that the pumping can provide a partial proof of principle, although this and similar experiments were not interpreted thus far in our terms.
We present a molecular-level theory for amphiphile packing in linear micelles, focusing on the early stages of micellar elongation, i.e., on small and ``intermediate-size'' micelles, whose endcaps are not yet molded into a final shape. The internal free energy of a micelle of given size and shape is expressed as an integral over local molecular packing free energies in different regions of the micelle. The free energy per molecule is expressed as a sum of interfacial (''opposing forces'') and chain conformational contributions, both depending on the local geometry. The equilibrium shape and energy of the micelle is determined by functional minimization of the total free energy. For amphiphiles exhibiting strong preference for packing in the cylindrical geometry, we show that the early stages of growth involve an energetic barrier, resulting in a ``gap'' in the micellar size distribution. That is, at low total amphiphile concentrations only small (globular) micelles appear in solution. Their concentration reaches a well-defined saturation value, beyond which, all added amphiphiles are incorporated in long micelles, whose ``non-interacting'' endcaps are well separated by the cylindrical middle part. This, ``second CMC'' behavior is demonstrated by numerical calculations of micellar size distributions and average aggregation numbers as a function of the total concentration. The conditions necessary for the appearance of a second CMC are analyzed theoretically, with explicit reference to the underlying molecular packing characteristics. In particular, it is shown that a necessary condition for the appearance of a sharply defined second CMC is that the endcap energies (of at least some) of the small or intermediate-size micelles must be considerably lower than the asymptotic (long micelle) value of this quantity. The diameter of the minimal, spherical micelles, as well as that of the final endcaps, is found to be larger than the diameter of the cylindrical body of the very long micelles. Our results are in good qualitative agreement with recent cryo-TEM imaging studies of micellar shape and growth, as well as with previous (less direct) experiments revealing second CMC behavior.
The adsorption of human IgG at the air/water interface was monitored both by the in situ radiotracer technique using [14C] labeled IgG and by surface tension measurements. The results reveal that adsorption of IgG from single protein systems displays bimodality due to mol. rearrangements at the interface. Above the threshold value of 1.5×10-2 mg/mL soln. concn., adsorbed IgG mols. reoriented from the side-on to the end-on configuration. The existence of a lag time which did not appear in Γ=f(t) curves, was obsd. in Π=f(t) relationships at low protein concns. and was due to the limits of the surface pressure technique to detect protein adsorption. The adsorption of native IgG was also carried out in the presence of a hydrophobized IgG obtained by grafting capryloyl residues to its lysine groups by reaction with N-hydroxysuccinimide ester of caprylic acid, which yielded 19 covalently bound alkyl chains to the IgG mol. (19C8-IgG). This modified IgG exhibited enhanced adsorption at the air/water interface, as manifested by its increased adsorption efficiency relative to the native protein. Sequential and competitive adsorption expts. from binary mixts. of native IgG and 19C8-IgG clearly demonstrate that the displacement of the native protein from the air/water interface strongly depended on the manner of how 19C8-IgG and native IgG competed with each other. When the two proteins competed simultaneously, 19C8-IgG predominantly occupied the available area but when native IgG was adsorbed first, for 2 h, the sequentially adsorbed 19C8-IgG was incapable of substantially displacing it from the interface. (c) 2001 Academic Press. [on SciFinder(R)]
AN Kluger, I Yaniv, and A Kuhberger. 2001. “Needs, Self-regulation, and Risk Preference.” 2nd Annual meeting of the Society of Personality and Social Psychology. San Antonio, TX.
I argue that some important preemptive causal chains cannot be accommodated by a consequentialist framework. While the literature of the last two decades has discussed the question of ethical deliberation in cases of irrelevant outcome, I construct a different case that directly concentrates on the 'comparative' assumption that underlies consequentialism. The flaw that would be exposed in case consequentialism cannot successfully deal with some types of overdetermination would, therefore, pertain not only to the 'implications' of consequentialist reasoning, but to the reasoning itself, when it is predicated (as it is) on comparison limited only to the relative value of states of affairs. Consequentialism would thus be exposed as relying on a notion of comparison that does not encompass some moral elements that we expect it to include.
A highly flexible, automatic sequential-injection stripping anal. (SISA) system was developed and applied for monitoring the levels of Hg in aq. solns. using a chem. modified electrode. The prepn. of the modified electrode comprises spin coating of an EtOH soln. of poly(4-vinylpyridine) and Kryptofix-222 onto a glassy C electrode (GCE) followed by crosslinking the polymer. The anal. is based on the anodic stripping voltammetry of Hg using differential pulse voltammetry. A sequence of 36 operations was needed to complete a full cycle of cleaning, calibration and anal. [on SciFinder(R)]
Background. The extra length obtained by skeletonizing the internal thoracic arteries (ITAs) enables versatile use of in situ bilateral ITAs for coronary artery bypass grafting, as the longer skeletonized right ITA more easily reaches the anastomotic site on the left anterior descending coronary artery. Methods. Between April 1996 and November 1999, 365 consecutive patients underwent revascularization with bilateral in situ ITAs (29% of 1,250 grafting procedures performed with both ITAs in our department during this period). The right ITA was routed anterior to the aorta to graft the left anterior descending coronary artery, and the in situ left ITA was used to graft circumflex branches. Right coronary artery branches were grafted with right gastroepiploic artery or saphenous vein graft. The right ITA crossed the midline above the aorta at the most cranial point to avoid damage in case of a repeat sternotomy in the future. Results. The operative mortality rate was 2.2% (8 patients). P
A large series of publications1-9 has proposed that cationic peptides from leukocytes kill bacteria primarily by causing a depolarization of their membranes leading to enhanced permeability. One group of cationic peptides from human neutrophils was even coined bactericidal/permeability-increasing proteins.3Surprisingly, however, none of a large series of other publications that had proposed a concept that cationic agents from neutrophils might be bactericidal also by virtue of their capacity to activate the bacterial autolytic wall enzymes (muramidases), leading to bacteriolysis and cell death,10-22 has ever been cited in any of the publications by the leading authors in this field of research.1-9
For the information of your readers, there exist a series of 16 publications since 1974 entitled “Effect of leukocyte hydrolases on bacteria” and several additional publications on the same subject under different titles, many of them published in journals covered by Medline; the references contain a selected list of these.10-22 24 These had proposed that many of the highly cationic agents either present in plasma or generated by activated phagocytes (eg, lysozymes, PLA2, elastase, cathepsin G, myeloperoxidase, bactericidal/permeability-increasing proteins, defensins, etc) might kill bacteria not simply by acting on the membranes to cause depolarization and enhanced permeability1-7 but also by an indirect mechanism. This involves a deregulation, by the cationic agents, of the anionic and amphiphilic regulators of the autolytic wall enzymes(muramidases) (lipoteichoic acid in Gram-positives and Forssman antigens in Gram-negatives)16 17 23-25 resulting in hydrolysis of the peptidoglycan, in bacteriolysis, and in cell death. It is of great clinical importance that the bacteriolysis-inducing activity of cationic agents mimics that of beta-lactam antibiotics.26 Furthermore, the observations that a variety of highly negatively charged, sulfated anionic agents can act as potent inhibitors of the cationic agent– and beta-lactam–induced bacteriolysis11 12 14 16 17 27-30further stress the importance of the autolytic systems in bacterial killing. This phenomenon might also be of great clinical significance especially in selecting measures to control postinfectious sequelae that undoubtedly are triggered by the release of bacterial components, especially following bacteriolysis.
Regrettably, attempts to bring these issues to the awareness of the leading investigators in the field of cationic proteins1-9and of clinicians involved is the clinical aspects of sepsis control have not been successful.
If the concept that cationic agents might be bactericidal also because of their bacteriolysis-inducing properties is reasonable and scientifically sound, it is expected that publications describing this phenomenon should be cited by authors studying the bactericidal effects of cationic agents. If on the other hand one deems that this concept is for some reason erroneous, nonsensical, and scientifically unacceptable, such publications should definitely be cited but properly discussed, challenged, and even also ridiculed. But it is totally unacceptable and unreasonable that such publications be simply ignored!
Unfortunately, the avoidance of relevant citations and the disregard for concepts that might perhaps not “fit” current dogma and beliefs have reached epidemic levels. This is how pioneering publications proposing “novel approaches and ideas”16 17 29 30 to explain additional mechanisms of microbial killing might be lost forever. More importantly, these concepts will probably never reach the attention of clinicians interested in the pathogenesis of inflammation, infection, postinfectious sequelae, and the mechanisms of host defense.29-31
But what is even more disturbing, concerning, and unacceptable is that the expert referees selected by the editorial boards of journals and who should have been knowledgeable of the relevant literature failed to alert the authors to the existence of key publications on bacteriolysis so relevant to the subject of the papers and of the reviews they had been assigned to judge.
Am I wrong to assume that the task of a journal's editorial board is to ensure that all viewpoints and ideas, both “conventional” and nonconventional, be equally represented? Excuses either that limitations to the number of references permissible were the reason for not citing basic and pioneering publications or that the authors had been “instructed” to discuss only a narrow field of research and to disregard others fields with direct relevance are unacceptable.
A failure to give credit to relevant papers is also unacademic, self-defeating, unethical, and therefore unacceptable by all standards. Furthermore, are papers older than 15 years, or so, already passéand, therefore, unworthy of being acknowledged?
As we enter the third millennium, we witness the rapid continuation of the unprecedented explosion of scientific information. Today, we are fortunate to have access to Medline and to electronic journals covering the mammoth fields of biological sciences. It presumably assures us that we can no longer miss important relevant recent publications crucial to the continuation of our original line of research. Unfortunately, we witness today a dangerous trend that despite having access to Index Medicus and additional abstracting systems covering the literature prior to 1960, younger investigators tend to refrain from citing "older" publications, assuming that they are already passe. Obviously, it necessitates spending time in libraries. But who, in these "modern" computerized days, has time to wait?
Over the last few years, I tried to find out what was behind this behavior. I took the liberty of writing to authors who published papers in my own field of research and who failed to cite crucial key publications from the pre-Medline era, without which I believe they cannot even start to understand the evolution of their own current research.
The following are only several of the responses I received:
"I do not read the Journals which you claimed had included papers relevant for my research paper."
"I was unaware of the publications you proposed, but will be happy to read them if you can send them to me. I might consider citing them in my future review on the subject."
"Restrictions over the numbers of reference permissible prevented me from citing the proposed articles."
"The library at my university gives me a hard time trying to retrieve older literature."
"The focus of my article was to narrow down only on the most relevant current information available on the subject."
"Reviews covering the topic of my current investigations had recently been published." (However, no such review was cited by the author.)
"I do not have the time to comment on your thoughts in a scholarly fashion. However, bear in mind that the papers you had listed have not gone completely unnoticed." (Really?)
"You will recognize that it is not easy to find papers from several years unless they are cited by others, as there is literally too much information about"
"As a newcomer to this field of research, I neglected to read relatively old articles and I restricted myself to critically report the most common views on the subject. Besides, I was unable to receive the older articles you mentioned, because they are unavailable in the library of our relatively new university."
"I had, as you guessed, not seen your work. I am unfamiliar with most of the journals in which you publish—-and also I am not an immunologist."
The following is also a reminder how certain line of research might become extinct. A review on the role of proteinases in tissue damage concluded that proteinases might also synergize with oxidants and with additional pro-inflammatory agents. Yet, publications since 1960 which had described this phenomenon had not been included either in this particular paper or in any of the papers on the subject.
A main line of research had proposed that cationic proteins from leukocytes might kill bacteria by altering the permeability of their membranes. Yet, none of a very large series of investigations by others since the early 1970s, which had proposed an alternative possible mechanism suggesting that cationic proteins might kill microorganisms also by their ability to induce bacteriolysis, are ever cited anywhere.
Because of a change in nomenclature, pioneering investigations from 1951-1957, which had described the properties and mechanisms of action of bacterial cell-sensitizing agents (HF), had literally been eliminated because today this factor is called lipoteichoic acid (LTA). One simple sentence, and including proper citations stressing that LTA was previously called HF, might have sufficed to prevent unnecessary repetitions of the same experiments.
The following proposals might be adopted by editorial boards of journals to assure and also fight against the "disregard syndrome." (i) Every paper should include an introductory historical coverage of the "pioneering" investigations on which the current research is based. (ii) Emeriti professors, who might have read "older investigations" in a particular field of research, be nominated as referees. This might also stimulate emeriti professors to be reinvolved in the activities of the scientific community. (iii) A "Letters to the Editor" section in every Journal be established where authors can alert their readers to the existence of "old" literature on the subject. (iv) To combat the unacceptable attitude where publications which do not "fit" current thoughts and ideas are simply concealed from the modern reader. This is unethical and also self-defeating. Only a strong stand by Editorial Boards against the "disregard syndrome" might help to advance honest science.
