Molecular theory of the static dielectric constant of dipolar fluids.

The link between the static dielectric constant and the microscopic intermolecular interactions is the Kirkwood g1 factor, which depends on the orientational structure of the fluid. Over the years, there have been several attempts to provide an accurate description of the orientational structure of dipolar fluids using molecular theories. However, these approaches were either limited to mean-field approximations for the pair correlation function or, more recently, limited to adjusting the orientational dependence to simulation data. Here, we derive a theory for the dielectric constant of dipolar hard-sphere fluids using the augmented modified mean-field approximation. Qualitative agreement is achieved throughout all relevant thermodynamic states, as demonstrated by a comparison with simulation data from the literature. Excellent quantitative agreement can be obtained using a single empirical scaling factor, the physical origin of which is analyzed and accounted for. In order to predict the dielectric constant of the Stockmayer fluid (Lennard-Jones plus dipole potential), we use an adjusted version of the expression for the dipolar hard-sphere fluid. Comparing theoretical predictions with newly generated simulation data, we show that it is possible to obtain excellent agreement with simulation by performing the calculations at a corresponding state using the same scaling factor. Finally, we compare the theoretical orientational structure of the Stockmayer fluid with that obtained from simulations. The simulated structure is calculated following a post-processing methodology that we introduce by deriving an original expression that relates the proposed theory to the histogram of relative dipole angles.

Pseudo hard-sphere potential for use in continuous molecular-dynamics simulation of spherical and chain molecules.

We present a continuous pseudo-hard-sphere potential based on a cut-and-shifted Mie (generalized Lennard-Jones) potential with exponents (50, 49). Using this potential one can mimic the volumetric, structural, and dynamic properties of the discontinuous hard-sphere potential over the whole fluid range. The continuous pseudo potential has the advantage that it may be incorporated directly into off-the-shelf molecular-dynamics code, allowing the user to capitalise on existing hardware and software advances. Simulation results for the compressibility factor of the fluid and solid phases of our pseudo hard spheres are presented and compared both to the Carnahan-Starling equation of state of the fluid and published data, the differences being indistinguishable within simulation uncertainty. The specific form of the potential is employed to simulate flexible chains formed from these pseudo hard spheres at contact (pearl-necklace model) for m(c) = 4, 5, 7, 8, 16, 20, 100, 201, and 500 monomer segments. The compressibility factor of the chains per unit of monomer, m(c), approaches a limiting value at reasonably small values, m(c) < 50, as predicted by Wertheim's first order thermodynamic perturbation theory. Simulation results are also presented for highly asymmetric mixtures of pseudo hard spheres, with diameter ratios of 3:1, 5:1, 20:1 over the whole composition range.

Outcome of diabetic pregnancies in Waikato: five year experience.

The outcome of diabetic pregnancies in Waikato Hospital from 1979-1984 was reviewed. Overall perinatal mortality in the 61 deliveries was 69/1000 births but in the 38 deliveries whose antenatal care included close diabetic control, the perinatal mortality was 26/1000 births. The national perinatal mortality has improved from 12.2/1000 births in 1979 to 9.6/1000 in 1983 (provisional) with an overall rate of 11.0/1000 births. Improved outcome of diabetic pregnancies both in terms of reduced perinatal mortality and reduced neonatal and maternal complications depends on meticulous blood glucose control throughout pregnancy.

The transient nephrotic syndrome of pregnancy.

The transient nephrotic syndrome was observed in 24 pregnancies in 23 patients, over a five-year period, in a base hospital obstetric unit. The clinical and biochemical features of this syndrome were similar to the nephrotic syndrome observed in non-pregnant patients. In only half the episodes was the patient a primigravida. In three multigravida patients, previous pregnancies were normal. In 10 of the 24 pregnancies, a perinatal death occurred. A bad fetal prognosis was associated with an early onset of the nephrotic syndrome. Of 11 pregnancies in nine patients occurring after the pregnancy complicated by the transient nephrotic syndrome, seven were normal. One pregnancy was complicated by heavy proteinuria, one by hypertension and intra-uterine death, one by an hydatidiform mole, and one was terminated.