Ternary recombination of excited Ar+(P1/22) ions, established experimental results reinterpreted with a new extended model.

For many years, the recombination of excited ions of argon, Ar+(P1/22), has been assumed negligible under ambient conditions as compared to the recombination of ground-state ions, Ar+(P3/22). This opinion was confronted with detailed experimental results that seem to clearly support it. Here, we propose a new interpretation in light of our recent calculations, which shows that the recombination efficiency is comparable for both fine-structure states. Noteworthily, in our model leading to a picture consistent with the experiment, residual dimer ions emerge from Ar+(P1/22) due to non-adiabatic dynamics effects and interplay in measured data.

Dissociation of polycyclic aromatic hydrocarbons: molecular dynamics studies.

We present dynamical studies of the dissociation of polycyclic aromatic hydrocarbon (PAH) radical cations in their ground electronic states with significant internal energy. Molecular dynamics simulations are performed, the electronic structure being described on-the-fly at the self-consistent-charge density functional-based tight binding (SCC-DFTB) level of theory. The SCC-DFTB approach is first benchmarked against DFT results. Extensive simulations are achieved for naphthalene [Formula: see text], pyrene [Formula: see text] and coronene [Formula: see text] at several energies. Such studies enable one to derive significant trends on branching ratios, kinetics, structures and hints on the formation mechanism of the ejected neutral fragments. In particular, dependence of branching ratios on PAH size and energy were retrieved. The losses of H and C2H2 (recognized as the ethyne molecule) were identified as major dissociation channels. The H/C2H2 ratio was found to increase with PAH size and to decrease with energy. For [Formula: see text], which is the most interesting PAH from the astrophysical point of view, the loss of H was found as the quasi-only channel for an internal energy of 30 eV. Overall, in line with experimental trends, decreasing the internal energy or increasing the PAH size will favour the hydrogen loss channels with respect to carbonaceous fragments.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.

Fixation of 4-part fractures of the proximal humerus: Can we identify radiological criteria that support locking plates or IM nailing? Comparative, retrospective study of 107 cases.

INTRODUCTION: No objective criteria exist to help surgeons choose between IM nailing and plate fixation for 4-part fractures of the proximal humerus. The goal of this study was to identify radiological criteria that would make one technique a better choice than the other. MATERIAL AND METHODS: This was a comparative, multicentre, retrospective study of 54 cases of antegrade nailing and 53 cases of plating performed between 1st January 2009 and 31 December 2011 for 4-part fractures of the proximal humerus. All patients had a minimum radiological and clinical follow-up of 18 months. The functional outcomes were evaluated using the weighted Constant score; a poor result was defined as a weighted Constant score<70%. The following radiological criteria were evaluated during the preoperative assessment and at the last follow-up: initial displacement and reduction of humeral head and tuberosities; morphology of the medial column (i.e. calcar comminution, posteromedial hinge, size of metaphyseal head extension); occurrence of avascular necrosis (AVN). RESULTS: After an average follow-up of 42 months, the weighted Constant scores and rate of poor outcomes were 77% and 48% in the nail group and 81% and 38% in the plate group, respectively (ns). The humeral head was reduced into an anatomical position, valgus or varus in 57%, 30% and 13% of cases in the nail group, and 58%, 29% and 13% in the plate group, respectively. The tuberosities healed in an anatomical position in 72% of nail cases and 70% of plate cases (ns). Only the presence of a medial hinge preoperatively had an effect on the functional outcomes in the nail and plate groups: the weighted Constant scores (P=0.05) and rate of poor outcomes (P=0.02) were 82% and 52% in the nail group and 97% and 9% in the plate group, respectively. The complication rates were comparable: the rates of AVN and articular screw penetration were 17% and 11% in the nail group, and 15% and 11% in the plate group, respectively. The surgical revision rate was 18.5% in the nail group and 30% in the plate group. CONCLUSION: If the medial hinge is preserved, we recommend locking plate fixation. In other cases, either technique can be used as long as the general rules of internal fixation are applied: reduction of the tuberosities, varus correction and stabilization of the calcar area. LEVEL OF EVIDENCE: IV, retrospective study.

Isolated or predominant capitolunate osteoarthritis is the consequence of lunotriquetral dissociation. X-ray analysis of 22 consecutive cases.

Secondary osteoarthritis due to a scapholunate malalignment is well known, but is debatable in cases of lunotriquetral malalignment. It has been shown that lunotriquetral malalignment can lead to midcarpal osteoarthritis. The hypothesis of this retrospective study was that a relationship exists between the presence of midcarpal osteoarthritis and the presence of lunotriquetral malalignment. All patients with midcarpal osteoarthritis, isolated or predominant, treated between 1981 and 2013 were reviewed. Intracarpal angles were measured and the relative position of the carpal bones was analyzed by two examiners. Osteoarthritis of the wrist's joints was quantified in three stages. Diagnosis of static dissociative ligament lesion was made and correlated with the location of osteoarthritis. Twenty-two wrists in 20 patients (13 men and 7 women; mean age of 59 years) were included. The lunocapitate osteoarthritis was moderate in 6 cases and severe in 16 cases. The radioscaphoid osteoarthritis was moderate in 5 cases and severe in 1 case. Lunotriquetral malalignment was present in all cases; it was isolated in 8 cases and associated with scapholunate malalignment in 14 cases. In isolated lunotriquetral malalignment cases, midcarpal osteoarthritis was isolated or associated with degenerative lesions of lunotriquetral interval. Cases of perilunate instability in which the osteoarthritis is more severe in the midcarpal joint than in the radioscaphoid joint likely resulted from an injurying mechanism with ulnar beginning (ulnar-sided perilunate instability).

Ab initio transport coefficients of Ar⁺ ions in Ar for cold plasma jet modeling.

Collision cross sections and transport coefficients are calculated for Ar{+} ions, in the ground state {2}P_{3/2} and in the metastable state {2}P_{1/2}, colliding with their parent gas. Differential and integral collision cross sections are obtained using a numerical integration of the nuclear Schrödinger equation for several published interaction potentials. The Cohen-Schneider semi-empirical model is used for the inclusion of the spin-orbit interaction. The corresponding differential collision cross sections are then used in an optimized Monte Carlo code to calculate the ion transport coefficients for each initial ion state over a wide range of reduced electric field. Ion swarm data results are then compared with available experimental data for different proportions of ions in each state. This allows us to identify the most reliable interaction potential which reproduces ion transport coefficients falling within the experimental error bars. Such ion transport data will be used in electrohydrodynamic and chemical kinetic models of the low temperature plasma jet to quantify and to tune the active species production for a better use in biomedical applications.

Shoulder stabilization by modified Latarjet-Patte procedure: results at a minimum 10 years' follow-up, and role in the prevention of osteoarthritis.

INTRODUCTION: In 1995, our team modified the Latarjet-Patte procedure by associating "south-north" capsule retention with reinsertion to the edge of the glenoid cavity to the coracoid bone-block. HYPOTHESIS: The present minimum 10-year follow-up study tested the hypothesis that the rate of osteoarthritis could be reduced by the strictly extra-articular position of the bone-block and stability be enhanced by the associated Bankart effect. MATERIAL AND METHOD: Between January 1995 and December 2001, 78 shoulders were stabilized using the modified Latarjet-Patte procedure in 76 patients with a mean age at surgery of 26.7 years; 89.7% could be followed up, 82.8% of whom also had radiographic follow-up. Fifty-nine were sports players, including 25 at competition level. Stability was assessed on a questionnaire, any dislocation or subluxation being counted as recurrence. RESULTS: At a mean 13 years' follow-up (range, 10-15 years), there had been no revision surgery. Mean Duplay score was 82.6, mean Subjective Shoulder Value 91.9% and the satisfaction rate 98.5%. The recurrence rate was 1.4% and 10 patients reported residual apprehension. The osteoarthritis rate was 8.5%. Seven bone-blocks projected, but only one was associated with osteoarthritis (stage 1) (non-significant). There were 4 non-unions and 9 lyses, without instability or pain. DISCUSSION: The modified procedure provided a low rate of recurrence and an incidence of osteoarthritis (8.5%) much lower than in any other published series with a minimum 10 years' follow-up. The strictly extra-capsular situation of the bone-block appeared as an important factor in limiting long-term osteoarthritis. Capsule reinsertion also seemed to alleviate the radiologic complications. LEVEL OF EVIDENCE: IV, retrospective study.

Knee pain after anterior cruciate ligament reconstruction: evaluation of a rehabilitation protocol.

INTRODUCTION: Anterior knee pain (AKP) is a rare and difficult complication following anterior cruciate ligament (ACL) reconstruction. This disabling pain is persistent with conventional rehabilitation protocols. The aim of this work is to validate a new rehabilitation protocol that may improve the patients and allow return to daily activities including sports. MATERIALS AND METHODS: Forty-three patients identified with functional AKP after ACL reconstruction was enrolled in the rehabilitation protocol between 2009 and 2011. The series included twenty-six patients with hamstring grafting and seventeen patients with patellar tendon transplant. This study compares the functional outcomes and pain scores before and after the isokinetic protocol until the last follow-up at an average of 25.7 months after surgery. The evaluation was performed according to the International Knee Documentation Committee (IKDC) and included a pain assessment using the visual analog scale. Statistical analysis used Student's t-test for unpaired data and the Pearson correlation test for the variables. The IKDC scores were compared by the Wilcoxon test. RESULTS: Functional outcomes and pain are significantly improved (p<0.0001). The average IKDC score improved with 28 points and the pain improved with 3.2 points on the visual analog scale (VAS). The results are correlated with the follow-up time (p=0.008) but not correlated with the delay between the surgery and the beginning of the isokinetic protocol. DISCUSSION: Isokinetic rehabilitation provides a significant improvement in the knee function as measured by the IKDC score and by the VAS, regardless of the painful period preceding the program. The function improvement continues after the end of the protocol, but the pain may not completely disappear. The isokinetic rehabilitation program may resume functional AKP related to muscular deficit and may be used as the starter of other physical therapy protocols. LEVEL OF EVIDENCE: IV.

Ion collision cross sections and transport coefficients extended to intermediate energies and reduced electric fields for He(2)(+) ions colliding with He.

This work is devoted to the calculation of transport coefficients for He(2)(+) ions in gaseous He at intermediate reduced electric fields. These swarm data are of great interest for a better understanding of the mechanisms of formation and propagation of the fast plasma bullets or ionization waves observed in dielectric barrier plasma jet devices. For transport data, the collision cross sections required are determined from several theoretical methods based on quantum, semiclassical, and hybrid approaches and a diatomics-in-molecules model for the potential energy surfaces of He(2)(+). The corresponding collision cross sections are then used in an optimized Monte Carlo code to calculate the ion transport coefficients over a wide range of reduced electric fields extending over the experimental range. Calculated transport coefficients are compared with available experimental data at low electric fields. Moreover, an extrapolation method is used in order to determine the reduced mobility for stronger fields. A critical discussion has been performed on the pertinence and the reliability of these different methods of determination of collision cross sections needed for the calculation of ion transport data. Such ion data will be used in electrohydrodynamic and chemical kinetic models of the low-temperature plasma jet to quantify and to tune the active species production for a better use in biomedical applications.

Lumbosacral arthrodesis for neuromuscular scoliosis using a simplified Jackson technique.

UNLABELLED: Treating patients with severe neuromuscular scoliosis by long spinal fusion improves their quality of life and provides significant comfort for the patient and caregivers. But lumbosacral (L5-S1) fusion is challenging in these patients because of the significant deformities that result in poor bone anchoring quality and a risk of impingement between the skin and implants. In 1993, Jackson described a L5-S1 fusion technique using S1 pedicle screws and intrasacral rods (implanted under X-ray guidance) that are linked to the construct above with connectors. The goal of this study was to evaluate the clinical and radiological results and the postoperative complications of a simplified version of this technique, which does not require connectors or X-ray guidance. MATERIALS AND METHODS: Thirty-three patients were evaluated with a minimum follow-up of 4years (average 82months). Frontal balance, sagittal balance, Cobb angle, sacral slope, lumbar lordosis and lateral pelvic tilt in the frontal plane were assessed on preoperative, postoperative and follow-up X-rays. Intraoperative and postoperative complications were recorded. RESULTS: Complete fusion was obtained in 32 patients. The average Cobb angle was 62° initially and was reduced to 20° after surgery and 24° at the final follow-up. The average lateral pelvic tilt was 10.3° (0 to 26°) initially; it was surgically corrected to an average of 7.5° (0 to 24°); the average secondary loss of correction was 1.2° (0 to 9°). The sacral slope was corrected to an average of 11.2°; an average of 0.2° had been lost at the last follow-up (0 to 18°). Although the average for lumbar lordosis was unchanged, the standard deviation went from 29° to 16° after the corrective surgery and 17° at the last follow-up, with large cluster of measurements around the average value of 40°. The deformity correction was comparable to the results with other techniques (Galveston, sacroiliac screws); the complication rate was similar but the non-union rate was lower. This simplified Jackson technique appears to be an effective, simple method for L5-S1 fusion to correct neuromuscular scoliosis as it provides stable results over time. LEVEL OF EVIDENCE: Level IV, retrospective study.

Shoulder hemiarthroplasty: outcomes and long-term survival analysis according to etiology.

BACKGROUND: The indications for hemiarthroplasty in glenohumeral joint diseases remain controversial and depend mainly on the original underlying diagnosis. Our objective was to investigate the influence of the primitive aetiology on long-term prosthesis survival and on the Constant-Murley score. MATERIALS AND METHODS: We studied 272 shoulders with the following diagnoses: fracture sequelae (n=73), primary osteoarthritis (n=67), cuff tear arthropathy (n=43), avascular necrosis (n=40), rheumatoid arthritis (n=31), and other (n=18). Of the 272 shoulders, 139 were evaluated after at least 8 years (mean follow-up, 134 months). In all, 30 prostheses required removal. Functional status was evaluated using the Constant-Murley score and survival rate using the Kaplan-Meier method with prosthesis removal or conversion to total arthroplasty as the endpoint. RESULTS: Ten-year prosthesis survival was 88.13% overall, 100% in the rheumatoid arthritis group, 94.9% in the avascular necrosis group, 94.2% in the primary osteoarthritis group, 81.5% in the cuff tear arthropathy group, and 76.8% in the fracture sequelae (P=0.05). The mean Constant-Murley score after 8 years or more was 70.1 in avascular necrosis, 60.7 in primary osteoarthritis, 57.7 in fracture sequelae, 55.3 in rheumatoid arthritis, and 46.2 in cuff tear arthropathy (P=0.0006). The complication rate with the initial population as the denominator was 24.7% in fracture sequelae, 18.6% in cuff tear arthropathy, 15% in avascular necrosis, 8.9% in primary osteoarthritis, and 3.2% in rheumatoid arthritis. CONCLUSIONS: The best indication for shoulder hemiarthroplasty is avascular necrosis and the worst indications are cuff tear and post-traumatic fracture sequellae. Rheumatoid arthritis and primary glenohumeral osteoarthritis are good indications in patients younger than 50 years of age. LEVEL OF EVIDENCE: Level IV, retrospective study.

Structural and spectroscopic study of the LiRb molecule beyond the Born-Oppenheimer approximation.

Adiabatic and diabatic potential energy curves and the permanent and transition dipole moments of the low-lying electronic states of the LiRb molecule dissociating into Rb(5s, 5p, 4d, 6s, 6p, 5d, 7s, 6d) + Li(2s, 2p) have been investigated. The molecular calculations are performed with an ab initio approach based on nonempirical pseudopotentials for Rb(+) and Li(+) cores, parametrized l-dependent core polarization potentials and full configuration interaction calculations. The derived spectroscopic constants (R(e), D(e), T(e), ω(e), ω(e)x(e), and B(e)) of the ground state and lower excited states are in good agreement with the available theoretical works. However, the 8-10(1)Σ(+), 8-10(3)Σ(+), 6(1,3)Π, and 3(1,3)Δ excited states are studied for the first time. In addition, to the potential energy, accurate permanent and transition dipole moments have been determined for a wide interval of internuclear distances. The permanent dipole moment of LiRb has revealed ionic characters both relating to electron transfer and yielding Li(-)Rb(+) and Li(+)Rb(-) arrangements. The diabatic potential energy for the (1,3)Σ(+), (1,3)Π, and (1,3)Δ symmetries has been performed for this molecule for the first time. The diabatization method is based on variational effective Hamiltonian theory and effective metric, where the adiabatic and diabatic states are connected by an appropriate unitary transformation.

Theoretical study of the LiCs molecule: adiabatic and diabatic potential energy and dipole moment.

For nearly all the states dissociating into Cs (6s, 6p, 5d, 7s, 7p, 6d, 8s) and Li (2s, 2p, 3s), we present an extensive adiabatic study for (1,3)Sigma(+), (1,3)Pi, and (1,3)Delta symmetries of the LiCs molecule. We have used an ab initio approach based on nonempirical pseudopotentials, parametrized l-dependent polarization potentials, and full configuration interaction calculations. A diabatisation procedure based on the effective Hamiltonian theory and an effective metric is used to produce the quasi-diabatic potential energy for all studied states. The spectroscopic constants (R(e), D(e), T(e), omega(e), omega(e)x(e), and B(e)) of these states are derived and compared with the available theoretical and experimental works. In addition to the potential energies, accurate permanent and transition dipole moment have been determined for a wide range of internuclear distances. The adiabatic permanent dipole moment for the first 10 (1)Sigma(+) electronic states has revealed ionic characters relating to electron transfer and yielding both Li(-)Cs(+) and Li(+)Cs(-) arrangements. The quasi-diabatic permanent moments show linear behaviors, especially at intermediate and large distance. The transition dipole moment between neighbor states has revealed many peaks located around the avoided crossing positions.

The D 1Sigma+ state of 7LiH: comparison of observations with vibronic theory.

The excited D (1)Sigma(+) electronic state of (7)LiH has been observed up to near its dissociation limit by a pulsed optical-optical double resonance fluorescence depletion spectroscopic technique. An extensive vibronic calculation has been performed with a diabatic approach with purely potential couplings involving a set of eight diabatic states of (1)Sigma(+) symmetry, corresponding to seven neutral states and one ionic state. Twenty-six new vibrational levels have been observed. Both the derived vibrational energy spacings and the vibronic ones are similarly irregular. The observed spectral linewidths and vibronic resonance widths are found to vary similarly with increasing energy. Observed asymmetric spectral lineshapes may be attributed to the strong radial couplings between the discrete levels of the D (1)Sigma(+) electronic state and the continuum states of the C (1)Sigma(+) electronic state. The mutual agreement between the spectral results and the vibronic results demonstrates that the D (1)Sigma(+) electronic state of (7)LiH is better characterized by the vibronic approach.

Isomerization dynamics and thermodynamics of ionic argon clusters.

The dynamics and thermodynamics of small Ar(n) (+) clusters, n=3, 6, and 9, are investigated using molecular dynamics (MD) and exchange Monte Carlo (MC) simulations. A diatomic-in-molecule Hamiltonian provides an accurate model for the electronic ground state potential energy surface. The microcanonical caloric curves calculated from MD and MC methods are shown to agree with each other, provided that the rigorous conservation of angular momentum is accounted for in the phase space density of the MC simulations. The previously proposed projective partition of the kinetic energy is used to assist MD simulations in interpreting the cluster dynamics in terms of inertial, internal, and external modes. The thermal behavior is correlated with the nature of the charged core in the cluster by computing a dedicated charge localization order parameter. We also perform systematic quenches to establish a connection with the various isomers. We find that the Ar(3) (+) cluster is very stable in its linear ground state geometry up to about 300 K, and then isomerizes to a T-shaped isomer in which a quasineutral atom lies around a charged dimer. In Ar(6) (+) and Ar(9) (+), the covalent trimer core is solvated by neutral atoms, and the weakly bound solvent shell melts at much lower energies, occasionally leading to a tetramer or pentamer core with weakly charged extremities. At high energies the core itself becomes metastable and the cluster transforms into Ar(2) (+) solvated by a fluid of neutral argon atoms.

Temperature measurement from the translational kinetic energy release distribution in cluster dissociation: a theoretical investigation.

Unimolecular dissociation of neutral and charged argon clusters is theoretically investigated in the context of calorimetric measurements. The temperature of the product cluster is estimated from the distribution of the translational kinetic energy released (KER), assumed to have the form f(epsilon) approximately epsilon(alpha) exp(-epsilon/k(B)T). Phase space theory (PST) in its orbiting transition state (OTS) version is validated by comparing its predictions to the results of large-scale molecular dynamics simulations. The temperatures estimated from the KER distributions are seen to be generally lower than the actual microcanonical temperature computed from independent Monte Carlo simulations of the product cluster at thermal equilibrium. On the basis of these deviations, the various approximations leading from the rigorous PST/OTS treatment to the assumed exponential form are critically discussed. In the case of Ar(n)(+) clusters, the use of a quantum diatomic-in-molecules Hamiltonian constructed from recent ab initio calculations reveals some possible inadequacies of the 1/r(4) ion/dipole interaction at intermediate distances due to some residual charge transfer.

Building-block approach for determining low-frequency normal modes of macromolecules.

Normal mode analysis of proteins of various sizes, ranging from 46 (crambin) up to 858 residues (dimeric citrate synthase) were performed, by using standard approaches, as well as a recently proposed method that rests on the hypothesis that low-frequency normal modes of proteins can be described as pure rigid-body motions of blocks of consecutive amino-acid residues. Such a hypothesis is strongly supported by our results, because we show that the latter method, named RTB, yields very accurate approximations for the low-frequency normal modes of all proteins considered. Moreover, the quality of the normal modes thus obtained depends very little on the way the polypeptidic chain is split into blocks. Noteworthy, with six amino-acids per block, the normal modes are almost as accurate as with a single amino-acid per block. In this case, for a protein of n residues and N atoms, the RTB method requires the diagonalization of an n x n matrix, whereas standard procedures require the diagonalization of a 3N x 3N matrix. Being a fast method, our approach can be useful for normal mode analyses of large systems, paving the way for further developments and applications in contexts for which the normal modes are needed frequently, as for example during molecular dynamics calculations.

Tamizaje de marcadores para hepatitis B pre y post-vacunación en el hospital de C. del Uruguay, Argentina / Screening of the hepatitis B markers before and after vaccination at the C. del Uruguay's hospital, Argentina

Se estudió entre 1993 y 1995 la prevalencia para tres marcadores de hapatitis B (antiHBs, AgHBs y antiHBc) en 382 de 402 (95 por ciento) empleados del hospital público de C. del Uruguay, por presunción de unaincidencia elevada y la necesidad de identificar subgrupos de mayor riesgo, con un muestreo único transversal. Se utilizó la prueba de inmunosorción enzimática (ELISA), y se siguió la respuesta inmune a la vacuna por DNA-recombinante para un mínimo de tres y hasta cuatro dosis, mediante el dosaje de anti HBs. Los resultados muestran una prevalencia general prevacunación para al menos algún marcador de 5,6 por ciento (de 2,9 a 16,7 por ciento según profesiones) y para sólo el anti HBc de 4,2 por ciento. La seroprevalencia positiva del personal fue significativamente mayor en los servicios de odontología, laboratorio, pediatría, cirugía y guardia, en ese orden, que entre el personal de los servicios (p < 0,05). No se encontró asociación con el sexo, edad, antigüedad en el servicio, condición familiar, intervenciones quirúrgicas, transfusiones ni enfermedades crónicas, pero sí con las aplicaciones endovenosas de medicamentos recibidas. El 70 por ciento de los seropositivos eran médicos, personal de enfermería, de laboratorio e instrumentadores, y el resto personal administrativo de servicios y auxiliares. La asociación con la frecuencia de contacto sanguíneo o de mucosas expuestas resultó significativa (p < 0,05). Con respecto a la respuesta inmune frente a la vacunación, el 93,4 por ciento respondieron satisfactoriamente luego de la tercera dosis, y el 100 por ciento luego de la cuarta. El 80 por ciento del personal que requiriera una cuarta dosis, tenían una antigüedad media de 15,5 ñ 2,3 años en el servicio de radiología, en ausencia de otros factores, lo que sugiere la posibilidad de un grupo con depresión inmunológica. En la población estudiada la magnitud de la respuesta inmune o el retardo en la misma no aparece asociada con la edad, el sexo, los otros lugares de desempeño, el hábito de fumar, enfermedades crónicas o la obesidad

Tamizaje de marcadores para hepatitis B pre y post-vacunación en el hospital de C. del Uruguay, Argentina / Screening of the hepatitis B markers before and after vaccination at the C. del Uruguays hospital, Argentina

Se estudió entre 1993 y 1995 la prevalencia para tres marcadores de hapatitis B (antiHBs, AgHBs y antiHBc) en 382 de 402 (95 por ciento) empleados del hospital público de C. del Uruguay, por presunción de unaincidencia elevada y la necesidad de identificar subgrupos de mayor riesgo, con un muestreo único transversal. Se utilizó la prueba de inmunosorción enzimática (ELISA), y se siguió la respuesta inmune a la vacuna por DNA-recombinante para un mínimo de tres y hasta cuatro dosis, mediante el dosaje de anti HBs. Los resultados muestran una prevalencia general prevacunación para al menos algún marcador de 5,6 por ciento (de 2,9 a 16,7 por ciento según profesiones) y para sólo el anti HBc de 4,2 por ciento. La seroprevalencia positiva del personal fue significativamente mayor en los servicios de odontología, laboratorio, pediatría, cirugía y guardia, en ese orden, que entre el personal de los servicios (p < 0,05). No se encontró asociación con el sexo, edad, antig³edad en el servicio, condición familiar, intervenciones quirúrgicas, transfusiones ni enfermedades crónicas, pero sí con las aplicaciones endovenosas de medicamentos recibidas. El 70 por ciento de los seropositivos eran médicos, personal de enfermería, de laboratorio e instrumentadores, y el resto personal administrativo de servicios y auxiliares. La asociación con la frecuencia de contacto sanguíneo o de mucosas expuestas resultó significativa (p < 0,05). Con respecto a la respuesta inmune frente a la vacunación, el 93,4 por ciento respondieron satisfactoriamente luego de la tercera dosis, y el 100 por ciento luego de la cuarta. El 80 por ciento del personal que requiriera una cuarta dosis, tenían una antig³edad media de 15,5 ñ 2,3 años en el servicio de radiología, en ausencia de otros factores, lo que sugiere la posibilidad de un grupo con depresión inmunológica. En la población estudiada la magnitud de la respuesta inmune o el retardo en la misma no aparece asociada con la edad, el sexo, los otros lugares de desempeño, el hábito de fumar, enfermedades crónicas o la obesidad (AU)