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M L Senent

Publications and source records attributed to M L Senent.

10 recordsLinked to original sources
PubMed2006

Electronic structure calculations on the C4 cluster.

The ground and the electronically excited states of the C4 radical are studied using interaction configuration methods and large basis sets. Apart from the known isomers [l-C4(X(3)Sigmag (-)) and r-C4(X(1)Ag)], it is found that the ground singlet surface has two other stationary points: s-C4(X(1)Ag) and d-C4(X(1)A1). The d-C4 form is the third isomer of this cluster. The isomerization pathways from one form to the other show that deep potential wells are separating each minimum. Multireference configuration interaction studies of the electronic excited states reveal a high density of electronic states of these species in the 0-2 eV energy ranges. The high rovibrational levels of l-C4((3)Sigmau (-)) undergo predissociation processes via spin-orbit interactions with the neighboring (5)Sigmag + state.

Journal Article↗
PubMed2006

A simple variational-numerical approach to the ro-vibrational spectrum of diatomic molecules. An application to CH+.

We describe a simple way of obtaining numerically the manifold of energies for ro-vibrational transitions for a centrifugally distorted oscillator, starting from the potential energy of the non-rotating oscillator calculated by an accurate ab initio method. It is shown that the energies so obtained compare well with those obtained variationally. The species of astrophysical interest methylidyne ion, CH(+), has been selected as an example that allow us to show the computational efficiency of the method with respect to the variational one. It is applied for the determination of ro-vibrational levels up J=6, and the spectroscopic parameters corresponding to the ground electronic state X(1)Sigma(+). From the potential energy surface computed at the MRCI/cc-pV5Z level, the fundamental frequency, B(0) and D(0) are determined to be 2724.8, 13.85688 and -1.53322x10(-3)cm(-1), respectively. We provide also an estimation of anharmonic constants.

Algorithms↗
PubMed2001

Successful treatment of severe intra-abdominal bleeding associated with disseminated intravascular coagulation using recombinant activated factor VII.

Recombinant activated factor VII (rFVIIa) is indicated mainly for the treatment of patients with haemophilia and inhibitors. However, little information is available on the use of rFVIIa in the treatment of the severe bleeding associated with disseminated intravascular coagulation (DIC). We report a pregnant woman with DIC, who developed severe intra-abdominal bleeding after caesarean section. Despite treatment with fresh-frozen plasma, fibrinogen, platelet transfusions and surgery, the abdominal bleeding persisted and intravenous treatment with rFVIIa was initiated. The response to treatment was rapid, with control of the bleeding and resolution of the coagulopathy. No side-effects related to rFVIIa were noted. This case suggests a potential role for rFVIIa in the treatment of severe and refractory bleeding associated with DIC.

Acute Disease↗
PubMed2000

Theoretical and experimental study of the acetohydroxamic acid protonation: the solvent effect.

The mechanism of the protonation of acetohydroxamic acid is investigated comparing experimental results and ab initio calculations. Experimentally, the UV spectral curves were recorded at different temperatures, at constant dioxane/water concentration, and at very high concentrations of strong mineral acids. The process is followed by monitoring the changes in the UV curves with increasing acid concentration. The molecular structures and the solvation energies were calculated with the RHF, B3LYP, and MP2 methods. The solvent is treated as a continuum of uniform dielectric constant. The isolated molecule of acetohydroxamic acid exhibits two protonation sites, the carbonyl oxygen and the nitrogen atom. In dioxane/water mixture, the RHF calculations predict the existence of a third cation of low stability, where the proton is bonded to the OH oxygen. With the MP2 ab initio calculations, the free energies of the formation processes in solution of the two most stable cations, CH3COH-NHOH+ (O3H+) and CH3CO-NH2OH+ have been evaluated to be -160.2 kcalmol(-1) and -157.6 kcal mol(-1). The carbonyl site is the most active center in solution and in the gas phase. The carbonyl site is also the most active center in the UV measurements. Experimentally, the ionization constant was found to be pK(O3H+) = -2.21 at 298.15 K, after the elimination of the medium effects using the Cox-Yates equation for hight acidity levels. Experiments and ab initio calculations indicate that K(O3H+) decreases with the temperature.

Cations↗
PubMed2000

Ab initio determination of the roto-torsional energy levels of hydrogen peroxide.

In the present paper, the roto-torsional energy levels of hydrogen peroxide are determined from ab initio calculations performed at the MP4(SDQ)/AUG-cc-pVTZ//MP4(SDQ)/cc-pVTZ+ ++ level. The rotational levels corresponding to the torsional states n = 0 and 1 are determined variationally up to J = 20. The flexible model used considers the roto-vibrational interactions. Symmetry conditions are included for classifying the levels and reducing the cost of diagonalization. Products of contracted torsional basis functions and top symmetric solutions are employed as basis functions. The calculated levels are in a very good agreement with the experimental data. In addition, the K-doubling has been obtained and the levels fitted to the top symmetric equations for determining the centrifugal distortion constants. The expectation values of the rotational constants at the lowest torsional levels are compared with the rotational constants arising from the experimental fit.

Energy Transfer↗
PubMed1998

[Lymphocyte subsets in blood donors].

OBJECTIVES: To establish the normal values among the different lymphocyte subsets in peripheral blood, measured by surface antigen expression, in healthy population. To observe if there are potential differences in respect of age, gender or sample origin. To compare the absolute lymphocyte number obtained with flow cytometry and with a cellular counter. MATERIAL AND METHODS: Longitudinal and prospective study performed with 100 samples of blood donors. Direct immunofluorescence with triple color staining was made on whole blood, red blood cells were then lysed and samples were analysed with a flow cytometer. The lymphocyte subsets studied were the T lymphocytes and their subsets (CD4 and CD8 lymphocytes), the B lymphocytes and Natural Killer cells population. The absolute lymphocyte count was performed with an automatic cellular counter. Donor data such as age, gender and origin were recorded and were statistically analysed. RESULTS: Normal ranges from the studied parameters are similar to other series. Comparison with gender, origin or age groups gave no significant difference, although there seems to be a tendency to decrease with the ageing of the population. Total absolute lymphocyte number did not differ between the results from the cellular counter or from the flow cytometer. CONCLUSIONS: We found no differences in the absolute lymphocyte number nor in the lymphocyte subsets studied (T lymphocytes, CD4 lymphocytes, CD8 lymphocytes, B lymphocytes and NK cells) with respect to gender, age or sample source. We have established reference ranges for our laboratory. We have not found significant differences in the absolute lymphocyte number measured with cell counter or with flow cytometer.

Adolescent↗
PubMed1996

[Detection of the PML/RAR alpha rearrangement in acute promyelocytic leukemia using a reverse PCR method].

AIMS: This study describes a molecular method of reverse transcription polymerase chain reaction (RT-PCR) to detect the rearrangement PML/RAR alpha in acute promyelocytic leukaemia (APL) in order to assess its specificity and sensibility, and to evaluate its utility in the characterization of APL patients. PATIENTS AND METHODS: Between January and June of 1995, 64 samples of bone marrow and peripheral blood stem cells (PBSC) cytapheresis were studied. There were 58 APL samples (23 patients: 10 samples obtained with disease activity, 43 samples in complete remission (CR) and 5 PBSC samples) and 6 control samples, of non-APL hematological neoplasms (3 other AML, 1 CML, 1 ALL, and 1 MDS). On the RNA obtained from the isolated mononuclear cells of each sample a conserved region of the PML/RAR alpha fusion gene was amplified by using a RT-PCR with specific primers. RESULTS: The sensitivity assays were performed by diluting PML/RAR alpha positive RNA samples into RNA of controls. The RT-PCR assay was capable to detect the PML/RAR alpha until an 1/1000 dilution in negative control RNA. Nine out of 58 APL samples failed in the amplification of the control gene, and were considered non-evaluable. None of the 6 control samples showed PML/RAR alpha rearrangement. Nine out of 10 APL samples with disease activity were positive for the presence of PML/RAR alpha (the non-positive sample was a non-evaluable one). Six out of 43 APL samples in CR showed the rearrangement, 3 of them corresponding to 2 patients who posteriory relapsed 12 and 19 months after 1st CR. The other 3 positive samples came from other 3 APL patients (24 months in 3rd CR, 14 months in 1st CR and early CR), who remained in CR at the end of the study. No relapse could be noted in patients with negative PCR samples. PML/RAR alpha was not found in any of the 5 APL PBSC samples studied. CONCLUSIONS: The RT-PCR method described here seems to be highly specific as it only detects this rearrangement in LPA patients. Furthermore, the presence of PML/RAR alpha in CR patients could be related to relapse. For all these reasons, this molecular method shows great usefulness and can be advocated, not only for assessing diagnosis, but for as monitoring minimal residual disease in the post remission follow up.

Bone Marrow↗
PubMed1992

[Progression to AIDS among HIV-seropositive hemophiliacs].

PURPOSE: To assess the incidence of AIDS, along with its origin and mortality rate, in a group of sero-positive haemophiliacs with long follow-up. MATERIAL AND METHODS: The progression into AIDS in 94 HIV-seropositive haemophiliacs (88 with haemophilia A and 6 with haemophilia B) followed since 1986 has been analyzed. The mean age was 19 years and 64% of the patients had severe haemophilia. All of them had been previously treated with non virus-inactivated factor concentrates. Was detected HIV antigen in 13 of them and 32 were treated with zidovudine. Actuarial analysis started from seroconversion date or from the first positive result and the average observation time was 90 months (5-97). RESULTS: Sixteen patients developed AIDS, resulting in an eight-years accumulative actuarial indice of about 24%. AIDS incidence was lower (p less than 0.0001) in haemophilia A (21%) than in haemophilia B (67%). The eight-years progression rate to AIDS showed a significant dependence on patient age, it being higher in patients aged greater than 30 (77%) than in those aged 15-30 (30%) and less than 15 (9%). Patients who presented CD4+ counts lower than 0.5 x 10(9)/L or CD4/CD8 ratios lower than 0.5 at the beginning of the observation period had a greater 8-year AIDS incidence (63% and 57% respectively) than the remaining patients (16% and 12%). At AIDS diagnosis, all patients had CD4+ lymphocyte counts lower than 0.2 x 10(9)/L, two had detectable HIV antigenaemia and six had been previously treated with zidovudine. The cause of AIDS was an opportunistic infection in all the cases namely, P. carinii pneumonia and candidiasis, but no secondary neoplasia was registered. Nineteen patients died during the follow-up, 12 because of AIDS and 7 because of other reasons unrelated to HIV-infection. CONCLUSION: Our results suggest that 25% of the haemophiliacs will develop AIDS eight years after seroconversion, and a decreasing incidence is not observed. Lower progression rate to AIDS in children than in adults is confirmed.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Transfusion management of a patient with multiple anti-erythrocyte antibodies (anti-c + anti-K + anti-Fyb + anti-Jkb) subjected to a valvular reoperation using extracorporeal circulation].

A woman with multiple anti-red cell antibodies (anti-c, anti-K, anti-Jkb, anti-Fyb) due to previous transfusions was admitted to the hospital for valvular replacement. To ensure enough transfusional supply, a high number of packed red cell units was typed and screened prior to previous operation. Haemorrhagic complications developing during surgery led to transfusion of 32 blood units, 20 of them compatible. Besides this, measures directed to prevent complications derived from haemolytic disease were instituted. These included intravenous fluids and diuretics to maintain circulatory integrity and improve renal cortical blood flow. High-dose gammaglobulin was also administered in an attempt to decrease extravascular haemolysis. Despite therapy, severe adult distress respiratory syndrome caused patient's death nine days after surgery. We remark the need of storing frozen blood of low-frequency phenotypes in blood banks to face significant transfusional problems, providing sufficient numbers of antibody-compatible blood.

Agglutinins↗