Inelastic vibrational dynamics of CS in collision with H2 using a full-dimensional potential energy surface.

We report a six-dimensional (6D) potential energy surface (PES) for the CS-H2 system computed using high-level electronic structure theory and fitted using a hybrid invariant polynomial method. Full-dimensional quantum close-coupling scattering calculations have been carried out using this potential for rotational and, for the first time, vibrational quenching transitions of CS induced by H2. State-to-state cross sections and rate coefficients for rotational transitions in CS from rotational levels j1 = 0-5 in the ground vibrational state are compared with previous theoretical results obtained using a rigid-rotor approximation. For vibrational quenching, state-to-state and total cross sections and rate coefficients were calculated for the vibrational transitions in CS(v1 = 1,j1) + H2(v2 = 0,j2) → CS(v1' = 0,j1') + H2(v2' = 0,j2') collisions, for j1 = 0-5. Cross sections for collision energies in the range 1 to 3000 cm-1 and rate coefficients in the temperature range of 5 to 600 K are obtained for both para-H2 (j2 = 0) and ortho-H2 (j2 = 1) collision partners. Application of the computed results in astrophysics is also discussed.

Full-Dimensional Quantum Dynamics of SiO in Collision with H2.

We report the first full-dimensional potential energy surface (PES) and quantum mechanical close-coupling calculations for scattering of SiO due to H2. The full-dimensional interaction potential surface was computed using the explicitly correlated coupled-cluster (CCSD(T)-F12b) method and fitted using an invariant polynomial approach. Pure rotational quenching cross sections from initial states v1 = 0, j1 = 1-5 of SiO in collision with H2 are calculated for collision energies between 1.0 and 5000 cm-1. State-to-state rotational rate coefficients are calculated at temperatures between 5 and 1000 K. The rotational rate coefficients of SiO with para-H2 (p-H2) are compared with previous approximate results which were obtained using SiO-He PESs or scaled from SiO-He rate coefficients. Rovibrational state-to-state and total quenching cross sections and rate coefficients for initially excited SiO (v1 = 1, j1 = 0 and 1) in collisions with p-H2 (v2 = 0, j2 = 0) and ortho-H2 (o-H2) (v2 = 0, j2 = 1) are also obtained. The application of the current collisional rate coefficients to astrophysics is briefly discussed.

Full-dimensional quantum dynamics of rovibrationally inelastic scattering between CN and H2.

We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm-1. Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

Full-dimensional quantum dynamics of CO in collision with H2.

Inelastic scattering computations are presented for collisions of vibrationally and rotationally excited CO with H2 in full dimension. The computations utilize a newly developed six-dimensional potential energy surface (PES) and the previously reported four-dimensional V12 PES [P. Jankowski et al., J. Chem. Phys. 138, 084307 (2013)] and incorporate full angular-momentum coupling. At low collision energies, pure rotational excitation cross sections of CO by para-, ortho-, and normal-H2 are calculated and convolved to compare with recent measurements. Good agreement with the measured data is shown except for j1 = 0 → 1 excitation of CO for very low-energy para-H2 collisions. Rovibrational quenching results are presented for initially excited CO(v1j1) levels with v1 = 1, j1 = 1-5 and v1 = 2, j1 = 0 for collisions with para-H2 (v2 = 0, j2 = 0) and ortho-H2 (v2 = 0, j2 = 1) over the kinetic energy range 0.1-1000 cm(-1). The total quenching cross sections are found to have similar magnitudes, but increase (decrease) with j1 for collision energies above ∼300 cm(-1) (below ∼10 cm(-1)). Only minor differences are found between para- and ortho-H2 colliders for rovibrational and pure rotational transitions, except at very low collision energies. Likewise, pure rotational deexcitation of CO yields similar cross sections for the v1 = 0 and v1 = 1 vibrational levels, while rovibrational quenching from v1 = 2, j1 = 0 is a factor of ∼5 larger than that from v1 = 1, j1 = 0. Details on the PES, computed at the CCSD(T)/aug-cc-pV5Z level, and fitted with an invariant polynomial method, are also presented.

Diversity of nontypeable Haemophilus influenzae strains colonizing Australian Aboriginal and non-Aboriginal children.

Nontypeable Haemophilus influenzae (NTHI) strains are responsible for respiratory-related infections which cause a significant burden of disease in Australian children. We previously identified a disparity in NTHI culture-defined carriage rates between Aboriginal and non-Aboriginal children (42% versus 11%). The aim of this study was to use molecular techniques to accurately determine the true NTHI carriage rates (excluding other culture-identical Haemophilus spp.) and assess whether the NTHI strain diversity correlates with the disparity in NTHI carriage rates. NTHI isolates were cultured from 595 nasopharyngeal aspirates collected longitudinally from asymptomatic Aboriginal (n=81) and non-Aboriginal (n=76) children aged 0 to 2 years living in the Kalgoorlie-Boulder region, Western Australia. NTHI-specific 16S rRNA gene PCR and PCR ribotyping were conducted on these isolates. Confirmation of NTHI by 16S rRNA gene PCR corrected the NTHI carriage rates from 42% to 36% in Aboriginal children and from 11% to 9% in non-Aboriginal children. A total of 75 different NTHI ribotypes were identified, with 51% unique to Aboriginal children and 13% unique to non-Aboriginal children (P<0.0001). The strain richness (proportion of different NTHI ribotypes) was similar for Aboriginal (19%, 65/346) and non-Aboriginal children (19%, 37/192) (P=0.909). Persistent carriage of the same ribotype was rare in the two groups, but colonization with multiple NTHI strains was more common in Aboriginal children than in non-Aboriginal children. True NTHI carriage was less than that estimated by culture. The Aboriginal children were more likely to carry unique and multiple NTHI strains, which may contribute to the chronicity of NTHI colonization and subsequent disease.

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study.

The dissociation of the hydroxymethyl radical, CH(2)OH, and its isotopolog, CD(2)OH, following the excitation of high OH stretch overtones is studied by quasi-classical molecular dynamics calculations using a global potential energy surface (PES) fitted to ab initio calculations. The PES includes CH(2)OH and CH(3)O minima, dissociation products, and all relevant barriers. Its analysis shows that the transition states for OH bond fission and isomerization are both very close in energy to the excited vibrational levels reached in recent experiments and involve significant geometry changes relative to the CH(2)OH equilibrium structure. The energies of key stationary points are refined using high-level electronic structure calculations. Vibrational energies and wavefunctions are computed by coupled anharmonic vibrational calculations. They show that high OH-stretch overtones are mixed with other modes. Consequently, trajectory calculations carried out at energies about ~3000 cm(-1) above the barriers reveal that despite initial excitation of the OH stretch, the direct OH bond fission is relatively slow (10 ps) and a considerable fraction of the radicals undergoes isomerization to the methoxy radical. The computed dissociation energies are: D(0)(CH(2)OH → CH(2)O + H) = 10,188 cm(-1), D(0)(CD(2)OH → CD(2)O + H) = 10,167 cm(-1), D(0)(CD(2)OH → CHDO + D) = 10,787 cm(-1). All are in excellent agreement with the experimental results. For CH(2)OH, the barriers for the direct OH bond fission and isomerization are: 14,205 and 13,839 cm(-1), respectively.

Chemistry. Beyond platonic molecules.

Molecular motion is influenced by quantum mechanics, which thus affect molecular properties such as their reactivity and the ease with which they isomerize. In his Perspective, Bowman describes recent theoretical advances that allow accurate quantum mechanical calculation of molecular motions for ever larger systems.

Theoretical and experimental rate constants for two isotopic modifications of the reaction h + h2.

Theoretical rate constants for two isotopic modifications of the simplest possible chemical reaction, namely, H + D(2) --> HD + D and D + H(2) --> HD + H, are presented. Experimental results, which have previously been obtained in the higher temperature regime by a shock tube technique, are combined with lower temperature results to give an experimental determination of the rate behavior over the large temperature range approximately 200 to 2000 K. It is now possible to assess the accuracy of ab initio potential energy surface calculations and to judge theoretical chemical kinetic methods.

Theoretical studies of the energetics and dynamics of chemical reactions.

Computational studies of basic chemical processes not only provide numbers for comparison with experiment or for use in modeling complex chemical phenomena such as combustion, but also provide insight into the fundamental factors that govern molecular structure and change which cannot be obtained from experiment alone. We summarize the results of three case studies, on HCO, OH + H(2), and O + C(2)H(2), which illustrate the range of problems that can be addressed by using modern theoretical techniques. In all cases, the potential energy surfaces were characterized by using ab initio electronic structure methods. Collisions between molecules leading to reaction or energy transer were described with quantum dynamical methods (HCO), classical trajectory techniques (HCO and OH + H(2)), and statistical methods (HCO, OH + H(2), and O + C(2)H(2)). We can anticipate dramatic increases in the scope of this work as new generations of computers are introduced and as new chemistry software is developed to exploit these computers.

Quantum dynamics of CO-H2 in full dimensionality.

Accurate rate coefficients for molecular vibrational transitions due to collisions with H2, critical for interpreting infrared astronomical observations, are lacking for most molecules. Quantum calculations are the primary source of such data, but reliable values that consider all internal degrees of freedom of the collision complex have only been reported for H2-H2 due to the difficulty of the computations. Here we present essentially exact, full-dimensional dynamics computations for rovibrational quenching of CO due to H2 impact. Using a high-level six-dimensional potential surface, time-independent scattering calculations, within a full angular momentum coupling formulation, were performed for the de-excitation of vibrationally excited CO. Agreement with experimentally determined results confirms the accuracy of the potential and scattering computations, representing the largest of such calculations performed to date. This investigation advances computational quantum dynamical studies representing initial steps towards obtaining CO-H2 rovibrational quenching data needed for astrophysical modelling.

Rh erythroblastosis fetalis 1975.

Great advances have been made in the management of Rh erythroblastosis fetalis in the past two decades. Perinatal mortality has been reduced from 16.4% to 3.2%. However, perinatal mortality can only be reduced to zero if Rh erythroblastosis can be eradicated by prevention of Rh isoimmunization. Although prevention of Rh immunization by Rh immune globulin prophylaxis is now a reality, it does not appear that Rh immunization will be completely prevented with a single postdelivery injection. Antenatal treatment plus screening by the Kleihauer technique for massive transplacental hemorrhage may be necessary before complete suppression can be achieved. Low protein Rh immune globulin, and ultimately column-produced, very low protein, highly purified Rh immune globulin for intravenous use may prove to be the safest, most economical, and effective material for Rh prevention and total eradication of Rh erythroblastosis fetalis.

Failures of intravenous Rh immune globulin prophylaxis: an analysis of the reasons for such failures.

Universal administration of an ion exchange column prepared Rh immune globulin (RhIG-IV) antepartum at 28 weeks' gestation and postpartum to 9,295 Rh negative women delivering Rh positive babies has reduced the prevalence of Rh immunization from the expected 601 to 25 (a protection rate of 95.9%). Rh immunization, despite universal Rh prophylaxis, developed in 25 women; eight before antenatal prophylaxis was administered, 17 after antenatal prophylaxis was administered. Residual Rh immunization is caused by small fetal transplacental hemorrhages (TPH) (greater than or equal to 0.01 mL of fetal blood) before antenatal prophylaxis (15%) and by significant fetal TPH (greater than or equal to 0.05 mL of fetal blood) between 30 and 38 weeks' gestation (18%); TPH was too great, in some instances, for residual passive Rh antibody to give protection. Although a reduction of 62% (five of eight) of early Rh immunization and 82% (14 of 17) of later Rh immunization might be achieved by addition of 16 weeks' to 20 weeks' gestation and 34 weeks' gestation Rh prophylaxis; and a reduction of 84% overall (21 of 25) might be achieved by universal fetal TPH screening every 2 weeks from 10 weeks' gestation until delivery, with administration of RhIG when a small early fetal TPH or a significant later fetal TPH is detected, all of these programs are costly in terms of prevention of perinatal mortality and in terms of cost per quality adjusted life year gained. We believe that the costs outweigh the benefit that would be achieved. Therefore, a residual Rh immunization prevalence of 0.24% to 0.31% during or after each Rh positive pregnancy in patients at risk is to be expected despite universal 28 weeks' gestation antenatal and postnatal Rh prophylaxis.

Selective criteria for the microbiological examination of faecal specimens.

To assess the effectiveness of predetermined investigation criteria for the examination of faecal samples from inpatients, cultured stool specimens were prospectively examined for Salmonella spp, Shigella spp, Campylobacter spp and Clostridium difficile, and screened microscopically for intestinal parasites. Out of a total of 505 specimens, 421 (83%) fulfilled the criteria for examination for C difficile, 254 (50%) for Salmonella spp, Shigella spp, and Campylobacter spp, and 87 (17%) for intestinal parasites. Isolation rates for these organisms in those groups of patients where examination was indicated were 22.5% for C difficile and 9.1% for Salmonella spp, Shigella spp, and Campylobacter spp; the detection rate for parasites was 3.5%. In those patients where the criteria did not suggest investigation, the isolation or detection rates were 3.6% for C difficile, 0% for Salmonella spp, Shigella spp, and Campylobacter spp, and 1.7% for intestinal parasites, suggesting that the use of predetermined investigation criteria was effective.

Transplacental fetal hemorrhage after amniocentesis.

A retrospective survey of Winnipeg Rh laboratory data from January 1, 1981 to December 31, 1984 determined that, despite placental localization, 2.6% of 974 women having amniocenteses performed at 16 to 18 weeks' gestation for genetic reasons and 2.3% of 1215 women having amniocenteses performed between 32 and 38 weeks' gestation had fetal-maternal transplacental hemorrhages greater than or equal to 0.1 mL of fetal red cells due to placental trauma. In 1.6 and 1.8%, respectively, the fetal transplacental hemorrhages were greater than or equal to 1 mL. Four of 99 alloimmunized women undergoing 257 amniocenteses for determination of severity of fetal erythroblastosis had fetal transplacental hemorrhages all greater than 5 mL of fetal red cells. The 1.9% incidence of fetal transplacental hemorrhages after amniocentesis in alloimmunized women is 83% less than the 11.2% incidence that occurred in the authors' institution from February 1963 to December 1966. However, in three of the four women, there was a very rapid rise in Rh antibody titer and increased severity of Rh fetal disease. Only the alloimmunized woman who meets strict criteria, indicating that her fetus is at risk of fetal death, should be subjected to amniocentesis, and then only after careful placental localization by ultrasound. Because fetal transplacental hemorrhages occur after amniocentesis despite ultrasound placental localization, 300 micrograms of Rh immune globulin should be administered to all unimmunized Rh negative women after amniocentesis.

Intrauterine fetal transfusions: Winnipeg 1982.

Perinatal survival after fetal transfusion in Winnipeg from February 1978 to June 1980 (52%-11 of 21 transfused) was worse than in the preceding 12-year period (70%-79 of 113 transfused). The cause was determined to be narrowing of the epidural transfusion catheter side hole opening diameters, which caused donor red cell hemolysis and hydrops fetalis. Catheter-induced red cell hemolysis was directly responsible for three perinatal deaths in this interval and probably contributed to two others. Catheter-induced red cell hemolysis was prevented completely by removal of the catheter tip and side hole openings, allowing donor red fell egress through the open end of the catheter. Following the institution of real-time ultrasound scan surveillance during and after intrauterine transfusion, survival for the interval from July 1980 to June 1982 was 92% (22 of 24 transfused), by far the series' best intrauterine transfusion survival rate. Hydropic fetal survival rate in the same period was 75% (six of eight transfused). With meticulous prenatal care, amniotic fluid delta OD450 measurements beginning at 20.5 weeks' gestation, and intrauterine transfusion carried out under ultrasound guidance, beginning as early as 22.5 weeks' gestation if necessary, the Rh Laboratory has achieved extremely satisfactory perinatal salvage following intrauterine transfusion. Intensive plasma exchange, as an adjunct to the above measures, should be reserved for the pregnant woman with a history of hydropic fetal death before 28 weeks' gestation.

Massive fetomaternal hemorrhage: Manitoba experience.

OBJECTIVE: To determine the incidence, size, and outcome of spontaneous massive fetomaternal transplacental hemorrhage in Manitoba. METHODS: The Kleihauer maternal-fetal screening records at the Rh Laboratory were reviewed for the period October 1970 to December 1992. Rh Laboratory correspondence for the 7-year period ending December 31, 1992, was reviewed to determine those instances of fetomaternal transplacental hemorrhage for which there was knowledge regarding fetal and neonatal outcome. RESULTS: Twenty-seven of 30,944 Rh-negative women undergoing routine Kleihauer screening at delivery had fetomaternal transplacental hemorrhages of at least 80 mL of fetal blood (incidence one in 1146 pregnancies); in 11 of the 27, the hemorrhages were 150 mL of blood or more (one in 2813 pregnancies). In non-routinely screened, selected maternal blood samples, sent because of unexplained fetal distress, fetal death, or neonatal anemia, 36 had evidence of fetomaternal transplacental hemorrhage of at least 80 mL of blood, 28 of which were in the 7-year period ending December 31, 1992 (one in 3893 pregnancies). Of these 28, 25 had hemorrhages of at least 150 mL of blood (one in 4360 pregnancies). Ascertainment of fetomaternal transplacental hemorrhage of 150 mL or more in women referred because of fetal or neonatal problems was 2813/4360 x 100 = 64.5%. Twenty-six cases in the final 7-year period had information regarding perinatal outcome. The incidence of adverse outcomes following massive fetomaternal transplacental hemorrhage was 46% (12 of 26). There were ten perinatal deaths, one infant death at 6 months, and one infant with spastic quadriplegia. CONCLUSIONS: Massive fetomaternal transplacental hemorrhage is uncommon but not rare, and subsequent adverse outcomes are common. A high index of suspicion with prompt investigation and appropriate management may improve the perinatal outcome following massive fetomaternal transplacental hemorrhage.

Intrauterine transfusion in an Rh-immunized twin pregnancy: a case report of successful outcome and a review of the literature.

Fifteen sets of twins have been reported among 2331 pregnancies complicated by Rh alloimmunization of sufficient severity to warrant intrauterine transfusions. Four of the 15 sets were managed in Winnipeg, Canada. One of the four is described in detail in the present report. Serial amniocenteses (N = 15) and intrauterine transfusions (N = 8) were used in the management of the dizygous affected twin fetuses with a favorable outcome. Factors contributing to the survival of the twins are described.

Maternal Kell blood group alloimmunization.

BACKGROUND: Two recent paper have provided conflicting views regarding the severity of Kell hemolytic disease of the newborn. METHODS: We reviewed our experience during 1944-1990 with pregnant Kell-alloimmunized Manitoban women and similar women referred from outside of Manitoba. RESULTS: Between 1944-1990, 311 Kell-immunized Manitoban women had 459 pregnancies, of which 63 ended in abortion or stillbirth unrelated to anti-Kell. Of the infants born, 376 were unaffected and 20 were affected. Twelve did not require treatment; two needed phototherapy, one required a simple transfusion, and one an exchange transfusion. One died of kernicterus and three were hydropic and died; all four deaths occurred between 1948-1954. Fourteen Kell-immunized women with 16 pregnancies were referred from outside Manitoba. Eleven had a history of Kell hydropic fetuses and ten had hydropic fetuses at referral. Five of the hydropic fetuses survived and five died. Five women had Kell-negative infants correctly predicted by amniocentesis (two) and by fetal blood sampling (three). Serial amniotic fluid delta OD 450 readings were 83-89% accurate in predicting the presence and severity of Kell hemolytic disease. Life-threatening inaccuracies occurred, primarily in the early and middle second trimester. CONCLUSIONS: Kell hemolytic disease, although rare, may be as severe as Rh(D) hemolytic disease when it does occur. When there is a history of hydrops or the father is Kell-positive and the maternal anti-Kell indirect antiglobulin titer is 8 or greater, amniocentesis should be performed at 16-20 weeks' gestation. Fetal blood sampling followed by fetal intravascular transfusion is indicated if delta OD 450 readings approach the 65% level in modified zone 2 of Liley or if amniocentesis is precluded because of an anterior placenta and there is a history of hydrops or ultrasound evidence of fetal hemolytic disease.

Fetomaternal hemorrhage following funipuncture: increase in severity of maternal red-cell alloimmunization.

OBJECTIVE: To determine the prevalence of fetomaternal transplacental hemorrhage after funipuncture and its effect on maternal red-cell alloantibody levels. METHODS: The prevalence and size of transplacental hemorrhages at the Health Sciences Centre were studied in two groups of patients: 174 women who were not alloimmunized or were carrying fetuses whose red cells were negative for the antigen to which they were immunized, and 122 women who were alloimmunized and carrying fetuses whose red cells were positive for the antigen to which they were immunized. In the alloimmunized group with affected fetuses, we surveyed the incidence of maternal antibody increase in titer by two or more doubling dilutions and the Rh(D) antibody increase (in microgram/mL of serum) of more than 50% after funipuncture. RESULTS: One hundred of the 174 women (57.5%) in the nonimmunized group and 69 of the 122 women (56.6%) in the immunized group had evidence of transplacental hemorrhages ranging in volume from 0.03 mL to greater than 5 mL of fetal red blood cells. In the latter group, antibody titer increases of 2 to 9 and doubling dilutions occurred in 37 of 74 women (50%) in whom such measurements were carried out. Increases of anti-D exceeding 50% occurred in 44 of 53 women (83%) in whom quantitative measurements were assayed. CONCLUSION: Funipuncture carries a high risk of fetal transplacental hemorrhage. In the immunized woman carrying an antigen-positive fetus, this will increase the level of her antibody and probably increase the severity of hemolytic disease in her fetus. In alloimmunized women, funipuncture should rarely be carried out to determine the fetal antigen status. Serial amniocenteses combined with careful serial ultrasound observation of the fetus are safer. Funipuncture should not be done in alloimmunized women before the cord vessels are of adequate size to allow immediate intravascular fetal transfusion, if required.