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M Baer

Publications and source records attributed to M Baer.

At least 19 recordsLinked to original sources
PubMed2006

D matrix analysis of the Renner-Teller effect: an accurate three-state diabatization for NH2.

Some time ago we published our first article on the Renner-Teller (RT) model to treat the electronic interaction for a triatomic molecule [J. Chem. Phys. 124, 081106 (2006)]. The main purpose of that Communication was to suggest considering the RT phenomenon as a topological effect, just like the Jahn-Teller phenomenon. However, whereas in the first publication we just summarized a few basic features to support that idea, here in the present article, we extend the topological approach and show that all the expected features that characterize a three (multi) state RT-type'3 system of a triatomic molecule can be studied and analyzed within the framework of that approach. This, among other things, enables us to employ the topological D matrix [Phys. Rev. A 62, 032506 (2000)] to determine, a priori, under what conditions a three-state system can be diabatized. The theoretical presentation is accompanied by a detailed numerical study as carried out for the HNH system. The D-matrix analysis shows that the two original electronic states 2A1 and 2B1 (evolving from the collinear degenerate Pi doublet), frequently used to study this Renner-Teller-type system, are insufficient for diabatization. This is true, in particular, for the stable ground-state configurations of the HNH molecule. However, by including just one additional electronic state--a B state (originating from a collinear Sigma state)--it is found that a rigorous, meaningful three-state diabatization can be carried out for large regions of configuration space, particularly for those, near the stable configuration of NH2. This opens the way for an accurate study of this important molecule even where the electronic angular momentum deviates significantly from an integer value.

Journal Article↗
PubMed2006

Renner-Teller nonadiabatic coupling terms: An ab-initio study of the HNH molecule.

In this Communication we present the first theoretical/numerical treatment of nonadiabatic coupling terms (NACT) that originate from the Renner-Teller (RT) model, namely, those that follow from the splitting of an electronic level of a linear molecule when it becomes bent. These two newly formed states are characterized by different symmetries and are designated as A and B. Our main findings: (1) The RT NACTs are quantized as long as they are calculated close enough to collinear configuration of the molecule (in this case HNH). Their value is tau = 1 (the Jahn-Teller values in similar situations, are tau = (1/2)). (2) Calculation of RT NACTs at bent configurations (i.e., at a distance from the linear axis) yield decreased values, sometimes by more than 50%. This last finding implies that in strongly bent configurations the two-state Hilbert subspace (formed by the above mentioned A and B states) is affected by upper states, most likely via Jahn-Teller conical intersections. (3) This study has also important practical implications. The fact that the RT NACTs decrease in (strongly) bent situations implies that analyzing spectroscopic data employing only the two Pi-states may not be sufficient in order to achieve the required accuracy.

Journal Article↗
PubMed2006

Two-state versus three-state quantization: an ab initio study of the three lower states of the {N,H2/A'} system.

In this article we present the first ab initio study of the conical intersections (cis) and their electronic nonadiabatic coupling terms (NACTs) for the {N,H2} system. Efforts were made to reveal the location of cis between the two lower, 1 2A' and 2 2A' states--to be designated as (1,2) cis--and the cis between the two upper, 2 2A' and 3 2A' states--to be designated as the (2,3) cis--of this system. We found that these cis are located along the collinear {NHH) arrangement. The study is carried out by analyzing two-state magnitudes such as the (1,2) and (2,3) adiabatic-to-diabatic transformation angles (known also as the mixing angles) and the corresponding topological phases (known also as the Berry phases or the Longuet-Higgins phases). In addition, a detailed three-state study is carried out. Here the emphasis is on driving the diagonal elements of the topological D matrix and analyzing situations for which the corresponding nonadiabatic coupling matrix is quantized. The reliability of two-state results is carefully examined by comparing them with corresponding outcomes derived for the three-state study. In addition we also calculated the potential-energy surfaces related to the two lower states and studied to what extent they are affected by the (1,2) ci. The results obtained in this treatment were found to be in full agreement with the NACT's calculations.

Algorithms↗
PubMed2006

[Evaluation of duration for direct admission dispatch process in an urban area].

OBJECTIVE: In France, when physicians in ambulances take care of patients, they report medical status to the dispatch centre. Then the dispatching physician search for the available and appropriate hospital service to agree in directly receiving the patient. We attempted to evaluate this direct admission dispatch, in a urban area, with many health care facilities. STUDY DESIGN: Prospective evaluation. PATIENTS AND METHODS: All the files for out of hospital interventions with a dispatch process were included. Data collected and analysed were: main pathologies, started time and end time of direct admission dispatch process and number of services called before finding the right place. RESULTS: 959 patients files were included, 849 could be analysed. The average duration of direct admission dispatch process is 10 (+/-13) minutes. Traumatology speciality shows a longer dispatch process than medicine disease (p < 0.001), and this time increased during summer (p < 0.05). The other parameters did not influence this duration. CONCLUSION: The average duration of direct admission dispatch process is acceptable. The increased duration of direct admission dispatch process in some pathology during summer may induce a risk for the patients. This problem will be improved only when the management of the available bed for emergency traumatology, will be implemented a regional coordination.

Adult↗
PubMed2005

N-state adiabatic-to-diabatic transformation angle: theory and application.

In this article is discussed a new diabatization procedure which is expected to be reliable and, also, relatively easy to implement. This procedure takes into account the two main ingredients related to diabatization: (1) The size N of the smallest (relevant) group of states that forms a Hilbert subspace (this fact enforces the dimension of the adiabatic-to-diabatic transformation matrix to be N). (2) The total energy E which determines the number of open states, p, within this group of N states. The main emphasis in this manuscript is on the case that N is arbitrary but p is equal to 2. The various derivations as well as the final results are accompanied by numerical examples extracted from three- to five-state ab initio calculations for the H + H2 system.

Journal Article↗
PubMed2004

The impact of reduction in the benzene limit value in gasoline on airborne benzene, toluene and xylenes levels.

Background benzene, toluene, xylenes (BTX) average concentrations have been measured over the urban agglomeration of Toulouse, France, during both springtime and summer periods of 1999 and 2001. The benzene average amount over the two Toulouse campaigns in 1999 is equal to 2.2 microg/m(3), very close to the French air quality standard and well under the average value of 5 microg/m(3) recommended by European Economic Community countries, recognising that those regulations are given for a whole year. BTX pollution over Toulouse has, in particular, been produced by motor vehicle exhaust gases. For the study conducted during the same periods of 2001, benzene concentrations were within the French quality value in the whole area. This is because the benzene limit value contained in gasoline went from 5% to 1% since 2000 January 1. It will be important to measure benzene over annual periods in order to know its exact values over such a period and to observe its potential seasonal variations.

Journal Article↗
PubMed2004

A field theoretical approach to calculate electronic Born-Oppenheimer coupling terms.

In this paper we suggest to consider the spatial distribution of the Born-Oppenheimer nonadiabatic coupling terms as fields which are created by sources, located at degeneracy points, and which can be derived using the ordinary mathematical tools of field theory. It is shown that the curl-divergence equations as formed within a given Hilbert space [M. Baer, Chem. Phys. Lett. 35, 112 (1975)] can be converted into a set of inhomogeneous coupled Poisson equations which are solved for a given set of boundary conditions. The method is applied to the three-state Hilbert subspace of the H(3) system. The numerical results are compared with ab initio calculations for which a very encouraging fit is found.

Journal Article↗
PubMed2004

Derivation of the electronic nonadiabatic coupling field in molecular systems: an algebraic-vectorial approach.

In this Communication it is suggested that various elements of the nonadiabatic coupling matrix, tau(jk)(s) are created by the singular nonadiabatic coupling terms of the system. Moreover, given the spatial distribution of these coupling terms in the close vicinity of their singularity points yields, according to this approach, the integrated intensity of the field at every point in the region of interest. To support these statements we consider the conical intersections of the three lower states of the H+H(2) system: From an ab initio treatment we obtain the nonadiabatic coupling terms around each conical intersection separately (at its close vicinity) and having those, create the field at every desired point employing vector-algebra. This approach is also used to calculate the intensity of the Curl of those matrix elements that lack their own sources [tau(13)(s) in the present case]. The final results are compared with relevant ab initio calculations.

Journal Article↗
PubMed2004

On the peculiarities of the diabatic framework: new insight.

In this article we consider the electronic diabatic presentation of a two-state system with the aim of earning insight regarding the distribution of conical intersections in a given region. In this process we revealed explicit relationship between the diabatic potentials and the locations of conical intersections. The study is accompanied with numerical examples as worked out for a model and ab initio potential energy surfaces of the Na+H2 system.

Journal Article↗
PubMed2004

On diabatization and the topological D-matrix: theory and numerical studies of the H + H2 system and the C2H2 molecule.

This article is divided into two main parts: (1) The theoretical part contains a new derivation of the topological matrix D (M. Baer and A. Alijah, Chem. Phys. Lett., 2000, 319, 489) which is based, solely, on the spatial dependent electronic manifold. This derivation enables more intimate relations between the adiabatic and the diabatic frameworks as is discussed in detail in the manuscript. (2) The numerical part is also divided into two parts: (a) In the first part we extend our previous study on the H + H2 system (G. Halasz, A. Vibok, A. M. Mebel and M. Baer, J. Chem. Phys., 2003, 118, 3052) by calculating the topological matrix for five states (instead of three) and for configuration spaces four times larger than before. These studies are expected to yield detailed information on the possibility of diabatization of this system. (b) We report on preliminary results concerning the C2H2 molecule. So far we established the existence of one (1,2) conical intersection and we have good reasons to believe that this system contains several (2,3) and (3,4) conical intersections as well.

Journal Article↗
PubMed2003

[Laboratory testing measurement of FIO2 delivered by Boussignac CPAP system with an input of 100% oxygen].

INTRODUCTION: CPAP (Continuous Positive Airway Pressure) is one of the treatments of the cardiogenic acute pulmonary edema (cAPE). Among the out-of-hospital used devices, Boussignac CPAP (Vygon) shows a good technical usability, but no analysis of delivered FIO2 is available. OBJECTIVE: To measure the FIO2 delivered to patient, using Boussignac CPAP with an input of 100 vol % oxygen. Type of study. - Measurement in a laboratory testing. MATERIAL AND METHOD: Measurement of delivered FIO2 in a three parameters environment: expiratory positive airway pressure (EPAP), respiratory rate (RR) and required oxygen flow (ROF). Laboratory test: 100 vol % oxygen input, with a ball-type flow regulator for oxygen 0-30 l x min(-1) (Mediline), Boussignac CPAP valve with manometer (Vygon), Michigan test lung, ventilator César (Taema), oxygen analysis (Servomex) with paramagnetic sensor, with a response time < 10 s, pneumotachographe (Fleisch v 2). RESULTS: Under 10 cmH2O EPAP, the required oxygen flow is < or = 30 l x min(-1). Measured FIO2 ranges from 70 to 100 vol %, for a volume per minute < or = 15 l x min(-1) except for a EPAP at 2.5 cmH2O with a rate = 10 c min(-1) and a tidal volume (VT) at 1500 ml where the measured FIO2 is 60 vol %. For a volume per minute > 15 l x min(-1) and < 20 l x min(-1), measured FIO2 ranges from 59 to 83 vol % depending on the variations of RR and VT. CONCLUSION: Boussignac CPAP with 100 vol % oxygen input, delivers high levels of FIO2, especially for volume per minute values usually met in cAPE. The needed oxygen flow is lower than what is usually required by other CPAP flow generators using the venturi effect that may be used in out-of-hospital medical care.

Manometry↗
PubMed2000

Generation of truncated C/EBPbeta isoforms by in vitro proteolysis.

Multiple forms of the transcriptional regulator CCAAT/enhancer-binding protein beta (C/EBPbeta) with molecular masses of approximately 38, 34, 20, and 14 kDa have been observed in cell extracts. It has been proposed that these proteins arise by alternative initiation at in-frame AUG codons. The truncated C/EBPbeta isoforms (p14 and p20/LIP) lack transactivation domains but retain DNA-binding and dimerization sequences and are therefore assumed to function as competitive inhibitors of C/EBP-mediated transcription in vivo. By comparing various extraction procedures to analyze endogenous and overexpressed C/EBPbeta proteins, we determined that p20-C/EBPbeta is generated predominantly by in vitro proteolytic cleavage during isolation from cells and that p14-C/EBPbeta is produced exclusively by this mechanism. In transfected cells, the full-length (p34 and p38) isoforms but not the truncated proteins were detectable in the cytoplasm, indicating that the latter are not primary translation products. In addition, the C/EBPbeta leucine zipper dimerization domain was essential for the appearance of the truncated species, demonstrating that protein folding or dimerization are critical determinants of proteolytic sensitivity. Our findings suggest that the presence of truncated C/EBPbeta proteins in cell extracts must be interpreted with caution and that assumptions about the in vivo relevance of these isoforms should be re-evaluated.

CCAAT-Enhancer-Binding Proteins↗
PubMed2000

The C/EBP bZIP domain can mediate lipopolysaccharide induction of the proinflammatory cytokines interleukin-6 and monocyte chemoattractant protein-1.

C/EBPalpha, beta, and delta are all expressed by bone marrow-derived macrophages. Ectopic expression of any of these transcription factors is sufficient to confer lipopolysaccharide (LPS)-inducible expression of interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) to a B lymphoblast cell line, which normally lacks C/EBP factors and does not display LPS induction of proinflammatory cytokines. Thus, the activities of C/EBPalpha, beta, and delta are redundant in regard to expression of IL-6 and MCP-1. Surprisingly, the bZIP region of C/EBPbeta, which lacks any previously described activation domains, can also confer LPS-inducible expression of IL-6 and MCP-1 in stable transfectants. Transient transfections reveal that the bZIP regions of C/EBPbeta, C/EBPdelta, and, to a lesser extent, C/EBPalpha can activate the IL-6 promoter and augment its induction by LPS. Furthermore, the transdominant inhibitor, LIP, can activate expression from the IL-6 promoter. The ability of the C/EBPbeta bZIP region to activate the IL-6 promoter in transient transfections is completely dependent upon an intact NF-kappaB-binding site, supporting a model where the bZIP protein primarily functions to augment the activity of NF-kappaB. Replacement of the leucine zipper of C/EBPbeta with that of GCN4 yields a chimeric protein that can dimerize and specifically bind to a C/EBP consensus sequence, but shows a markedly reduced ability to activate IL-6 and MCP-1 expression. These results implicate the leucine zipper domain in some function other than dimerization with known C/EBP family members, and suggest that C/EBP redundancy in regulating cytokine expression may result from their highly related bZIP regions.

Animals↗
PubMed1999

Tissue plasminogen activator (tPA) as therapy for hepatotoxicity following bone marrow transplantation.

The treatment of established veno-occlusive disease (VOD) of the liver with tissue plasminogen activator (tPA) has been disappointing. In attempts to improve upon these results we identified a subgroup of patients with consistently elevated bilirubin levels who did not meet conventional criteria for VOD (Susp VOD) but who had a significant risk of later developing clinical VOD. In January 1994 we began to treat patients who developed Susp VOD with tPA rather than waiting until they developed clinical VOD. We now report on the results of the first 37 patients who ultimately developed clinical VOD and received tPA therapy prior to Susp VOD, or at the time they had established VOD. Significant bleeding complications occurred in 13 (35%) patients but resolved with discontinuation of therapy in all but one. We found that patients treated early in the course of hepatotoxicity prior to the development of overt VOD had a significantly higher response rate and 100 day survival than patients treated at the time of established VOD. Given the poor results seen in treating late VOD, we suggest that early treatment with tPA may improve the outcome in patients who develop signs of hepatotoxicity following marrow transplantation.

Adolescent↗
PubMed1999

Parallel phase I studies of daunorubicin given with cytarabine and etoposide with or without the multidrug resistance modulator PSC-833 in previously untreated patients 60 years of age or older with acute myeloid leukemia: results of cancer and leukemia group B study 9420.

PURPOSE: The Cancer and Leukemia Group B conducted parallel phase I trials of cytarabine, daunorubicin, and etoposide (ADE) with or without PSC-833 (P), a modulator of p-glycoprotein-mediated multidrug resistance. PATIENTS AND METHODS: One hundred ten newly diagnosed patients > or = 60 years of age with de novo acute myeloid leukemia (AML) were treated. All patients received cytarabine by continuous infusion for 7 days at 100 mg/m(2)/d. The starting dose of daunorubicin was 30 mg/m(2)/d for 3 days. Etoposide was administered at a dose of 100 mg/m(2)/d for 3 days, except in the last cohort administered ADEP, who received 60 mg/m(2). PSC-833 was given intravenously with a loading dose of 1.5 mg/kg over 2 hours and a simultaneous continuous infusion of 10 mg/kg/d continued until 24 hours after the last dose of daunorubicin or etoposide. RESULTS: There was no toxicity attributed to the PSC-833. Dose-limiting toxicity was primarily gastrointestinal (diarrhea, mucositis in the ADEP group). The estimated maximum-tolerated doses, calculated using a logistic regression model, were daunorubicin 40 mg/m(2)/d for 3 days with etoposide 60 mg/m(2) for 3 days in the ADEP group and daunorubicin 60 mg/m(2)/d for 3 days and etoposide 100 mg/m(2)/d for 3 days in the ADE group. Twenty-one (48%) of 44 patients achieved complete remission with ADE, compared with 29 (44%) of 66 patients treated with ADEP. CONCLUSION: It is necessary to decrease the doses of daunorubicin and etoposide when they are administered with PSC-833, presumably because of the effect of the modulator on the pharmacokinetics of these agents. A phase III trial comparing the regimens derived from this phase I trial has recently begun.

Acute Disease↗
PubMed1999

Concurrent administration of rhesus rotavirus tetravalent (RRV-TV) vaccine with pentavalent diphtheria-pertussis-tetanus-Haemophilus influenzae beta-inactivated polio and hepatitis B vaccines.

To investigate the incorporation of oral rhesus-human reassortant rotavirus tetravalent (RRV-TV) vaccine into a routine immunization programme, RRV-TV or oral placebo was coadministered with a pentavalent diphtheria-tetanus-whole-cell pertussis-Haemophilus influenzae b (Hib)-inactivated polio vaccine and hepatitis B vaccine following a 3-4-5-mo schedule in a double-blind trial involving 249 infants. Seroconversion rates after 3 doses of rotavirus vaccine were 80% for rotavirus immunoglobulin A (IgA) and 93% for RRV neutralizing antibodies. Rotavirus vaccine did not interfere with the immune responses to diphtheria, tetanus, pertussis, Hib, poliovirus 1, 2 and 3, or hepatitis B. Following the first, second and third doses of vaccine, fever >38 degrees C on the day of vaccination was seen in 31%, 24% and 24%, respectively, with no difference between RRV-TV- and placebo-vaccinated children. This fever was presumably due to the whole-cell pertussis vaccine. Those vaccinees who received concomitant RRV-TV vaccine had another peak of fever around d 4 after the first dose, when 25% of them had fever >38 degrees C and 3% >39 degrees C. It is concluded that RRV-TV rotavirus vaccine can be given concurrently with other childhood immunizations following a 3-4-5-mo vaccination schedule. However, febrile reactions to RRV-TV rotavirus vaccine are common when the first dose is given at the age of 3 mo.

Antibody Formation↗