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In primates, corpus luteum development involves both gonadotrophin stimulation and exposure to low density lipoprotein (LDL) delivered through vascularization of the granulosa cell-derived layer. These regulatory influences were modelled in vitro using granulosa cells obtained during in-vitro fertilization (IVF) cycles controlled with gonadotrophin releasing hormone (GnRH) analogue, human menopausal gonadotrophin (HMG) and human chorionic gonadotrophin (HCG). Granulosa cells were cultured in defined medium on extracellular matrix. Without gonadotrophin or LDL in the medium, progesterone production declined progressively. With LDL alone, there was a short-lived elevation of progesterone output which subsequently declined. Culture with HCG alone resulted in a relatively unchanged rate of steroid production over 5 days despite morphological development. This contrasted with a marked and sustained increase in progesterone output over the same time when granulosa cells were cultured with combined HCG/LDL. Cultures were challenged with combined HCG/LDL on day 5. Where initial incubation included HCG, the challenge resulted in a recovery of progesterone output to values comparable to those of granulosa cells exposed to continuous HCG/LDL. Initial incubation without gonadotrophin led to a reduced response. Results suggest that LDL delivery to granulosa cells of the early corpus luteum causes a short-lived period of progesterone production. Sustained luteinization of granulosa cells and maintenance of gonadotrophin responsiveness requires continued exposure to gonadotrophin in the luteal phase.

Focal left atrial (LA) tachycardias/ectopy (LATs) that may initiate atrial fibrillation (AF) are often difficult to initiate, non-sustained, and may have multiple origins, often in one or more pulmonary veins (PV). Thus, mapping with conventional techniques is often difficult. The authors tested the hypothesis that a non-contact mapping system capable of global simultaneous mapping of >3000 points in the LA, would facilitate ablation of LAT. The non-contact mapping system was able to rapidly identify the origin of human LATs and focal AF despite the infrequency and short duration of initiating ectopy and guide a conventional mapping catheter to successful ablation sites. The authors also observed that, although isoproterenol is the most successful method of initiating LATs, these originate from multiple sites and therefore appear to be of limited clinical significance.

The conduction characteristics of human ventricular tachycardias (VT) have not been fully defined. The authors used a non-contact system to map 11 reentrant VT in 8 patients. Propagation velocities and 3-dimensional angles of turn were calculated from Cartesian co-ordinates. The complete diastolic pathway (DP) was mapped in 7 VT patients. DP wavefront velocity was 0.82/spl plusmn/0.49 m/s. Significant changes (>5 degrees/mm) in trajectory of propagation (TOP) occurred within 8 DP segments, in which propagation slowed to 0.41/spl plusmn/0.11 m/s compared with 0.91/spl plusmn/0.16 m/s preceding (p

The pattern of left atrial (LA) activation during sinus rhythm (SR) in humans has not been delineated. The authors used a non-contact mapping system to analyze the patterns of left atrial (LA) activation during sinus rhythm and pacing. The system is capable of simultaneously reproducing more than 3,000 electrograms, which are superimposed on a virtual left atrial endocardium. Data were recorded in sinus rhythm and during pacing from the high right atrium, coronary sinus os, and right atrial septum. The authors demonstrate that during sinus rhythm, the LA activates mainly through posterior septal fibers, adjacent to the ostia of the right pulmonary veins. This suggests that, in humans, anterior interatrial connections including Bachmann's bundle may be less important than previously recognized.

Reviewing 780 in-vitro fertilization (IVF) cycles, where buserelin was commenced in the preceding luteal phase and human menopausal gonadotrophin on day 4 of the ensuing menses, 53 cycles were identified with sonolucent cysts (30-50 mm diameter). Of the latter 53 cycles, the serum oestradiol was significantly greater on day 4 in 22 cycles abandoned for poor follicular development than in 31 cycles which proceeded to oocyte retrieval (P less than 0.05). Of the 31 cycles proceeding to oocyte retrieval, nine had a day 4 serum oestradiol greater than 200 pmol/l (95th centile for day 4 oestradiol in patients without apparent cysts), and these cycles produced significantly fewer grade 1 embryos than the cycles with day 4 oestradiol levels less than or equal to 200 pmol/l (P less than 0.05). Six of the 53 cycles with cysts resulted in conception, and all of these cycles had a day 4 serum oestradiol less than 200 pmol/l. Among the 53 cycles with ovarian cysts, the serum progesterone on the day of abandonment in four cycles and on the day of human chorionic gonadotrophin administration in one non-abandoned cycle, was above the range established for 104 cycles without cysts. No significant difference was seen in day 4 serum androstenedione levels, and the day 4 serum progesterone was less than 5 nmol/l in all but one patient. Functional activity of ovarian cysts is associated with an adverse influence on IVF cycles.

Percutaneous transluminal coronary angioplasty was attempted with elective percutaneous intra-aortic balloon pump support in 21 patients (mean age 60 years, range 40-82; 18 males) with unstable angina (n = 2), multivessel coronary disease requiring multivessel angioplasty (n = 2), severe left ventricular dysfunction (ejection fraction 10-30%; n = 16) or ventricular fibrillation at diagnostic angiography (n = 1). Fourteen patients had 3-vessel disease (1 with vein grafts also diseased), 6 had 2-vessel disease and 1 had isolated left anterior descending disease. Twenty-five procedures were performed (one in 18 patients, two in 2 patients and three in one patient) on 42 lesions in 34 vessels/grafts. There was no angioplasty-related death. Successful dilatation was achieved in 38/42 lesions (90%) in 21/25 procedures (84%) without major complication. Three procedures were complicated: one by major coronary dissection without sequelae, one by haemodynamic deterioration due to distal occlusion and one by an unstable residual stenosis in the attempted vessel necessitating urgent bypass surgery. The only complication related to the intra-aortic balloon pump was local haematoma in 2 patients. In conclusion, elective intra-aortic balloon pump support may be safely used to stabilise high-risk patients undergoing coronary angioplasty, leading to a satisfactory primary success rate.

Future antitachycardia devices must be able to deliver a variety of therapies according to the requirements of the underlying arrhythmia. To ensure that appropriate treatment is prescribed the device must use a detection algorithm that is able to discriminate between multiple arrhythmias. Current criteria such as rate, change of rate, duration at high rate, and high rate stability are inadequate for this purpose. Many algorithms that evaluate the morphology of the endocardial electrogram are of too great a complexity to be incorporated in implantable devices that require real-time analysis without undue power consumption. In this study the sensitivity of a simple morphological technique (temporal electrogram analysis) is examined. The method sets threshold 'rails' above and below the isoelectric line and classifies ECG complexes according to the sequence and duration of rail excursions. A total of 27 ventricular tachyarrhythmias were induced in 25 patients (17 with a history of recurrent arrhythmias and eight undergoing risk stratification postmyocardial infarction). Temporal electrogram analysis (TEA), initially detected the onset of the ventricular arrhythmia in all patients whose surface ECG showed polymorphic or right bundle branch block pattern tachycardia, in 5/8 of cases with left bundle branch block pattern and in 4/5 of patients with concordant complexes across the precordial leads. After minor modifications the overall sensitivity of the method was improved to 95% (26/27 arrhythmias detected). TEA is a technique of low computational demands, which in this study, reliably discriminated between resting sinus rhythm and ventricular arrhythmias.

Biochemical monitoring was undertaken in 22 treatment cycles for women with normal ovarian function who underwent pituitary suppression with buserelin and administration of exogenous oestradiol (E2) and progesterone (P) for cryopreserved embryo transfer (ET). Eighteen transfers of 1-4 thawed embryos, on the third day of exposure to progesterone, resulted in five clinical pregnancies (27.8%) and one biochemical pregnancy. There was no difference between pregnant and non-pregnant patients in the number and quality of embryos transferred, age, weight or infertility diagnosis. Serum E2 level from days 10-17 (the late proliferative phase) of the therapy cycle were significantly higher in the pregnant group compared with the non-pregnant group (P less than 0.05--P less than 0.005). There were no significant differences in P levels between the two groups from the onset of progesterone administration to the end of the cycle. However, as might be expected, the mean E2/P molar ratio in the pregnant group was significantly higher at the time of ET (P less than 0.02). It is concluded that biochemical monitoring during the embryo replacement cycle is necessary to tailor drug dosages for individual requirements to achieve adequate E2 levels before ET. Alternative routes of oestradiol administration need to be considered in patients with poor E2 profiles.

This study identifies a group of 87 patients, who demonstrated a 'poor' response to a standard buserelin/human menopausal gonadotrophin (HMG) regime. The subsequent outcome in 61 of these 'poor' responders when treated with a higher dose of HMG to achieve a satisfactory response was compared with 250 patients, who showed a 'good' response to the standard regime. 'Poor' responders were significantly older than 'good' responders (P less than 0.001), but no significant difference was demonstrated in the indication for in-vitro fertilization (IVF). Even on higher doses of HMG, 'poor' responders took longer for their follicles to achieve maturity than the 'good' responders (P less than 0.01). 'Poor' responders produced 8.9 oocytes per oocyte collection compared to 11.8 in the 'good' responders (P less than 0.01). The fertilization rate was significantly lower in the 'poor' responders compared to the 'good' responders (P less than 0.01). Although there was no significant difference in morphometric grading between 'poor' responder embryos and 'good' responder embryos, the rate of cell division was significantly slower in embryos of the 'poor' responders than the 'good' responders (P less than 0.01). The pregnancy rate per oocyte retrieval was 9% in the 'poor' responders compared to 29% in the 'good' responders (P less than 0.01). The implantation rate in the 'poor' responders was 4.4% compared to 16.1% in the 'good' responders (P less than 0.001).

The circulating levels of placental protein 14 (PP14) and progesterone were measured in three pregnancies resulting from the transfer of cryopreserved embryos. Two of these women had suppressed ovarian activity as a result of pituitary down-regulation with the luteinizing hormone-releasing hormone agonist (buserelin) prior to treatment with exogenous oestradiol and progesterone. After 14 days of oral oestradiol treatment and if the endometrial thickness was greater than 7 mm, progesterone was given intramuscularly for a further 14 days with embryo transfer on the third day of this treatment. On confirmation of pregnancy by human chorionic gonadotrophin analysis, progesterone administration was altered to transvaginal pessaries for maintenance of adequate progesterone levels and endometrial support. In the two women with ovarian suppression, PP14 levels remained below the 2.5th centile of the normal range for pregnancy. In the third pregnancy, embryo transfer was performed 3 days after a spontaneous luteinizing hormone surge in a normal menstrual cycle. In this pregnancy, PP14 levels were within the normal range. Ultrasonic examination confirmed three normal ongoing singleton pregnancies. These results suggest that the majority of PP14 production in normal pregnancy is under ovarian or anterior pituitary control and that the influence of progesterone is of a secondary nature.

Approximate coupled channel scattering calculations are performed for model systems comprising a closed-shell atom colliding with rigid rotor diatomic homo- and hetero-nuclear molecules. Differential and total cross-sections for rotational scattering with several different interaction potentials are given for p-H2 and MuH + He, at a fixed total collision energy, and for LiF + Ar with a fixed emperical potential but varying collision energy. Conclusions are drawn concerning the effect on the cross-sections of the variations made.

Close-coupling calculations with 121 channels at an energy of 155 cm-1 have been made for the rotational scattering of LiF by Ar, using a Lennard-Jones type potential with long range anisotropic terms. Integral cross sections for transitions (jmj )→(j′mj′ ) are given for j = 0, 1, 2, 3, 4 and j′ = 0, 1, 2, 3, 4, 5, and also for the j = 0→8 and j = 0 → 10 transitions. Differential cross sections were obtained for Δj = 1 and j = 0, 1, 2, 3, and for j = 1 →1, 1 →3, 0 →2 and 3 →3 transitions. Rotated scattering amplitudes were used to obtain integral cross sections by numerical integration, but these show little evidence that for Δj ≠ 0 the Δm = 0 transition has a relatively large cross section along an axis perpendicular to the bisector of the angle between the initial and final relative velocity vectors. Certain rules for Δm are suggested, and a comparison with experimental results for (Ar, LiF) and (Ar, CsF) is given.

Close-coupling calculations at 500 cm −1 for the system (Ar,LiH) are used to obtain scattering amplitudes and cross sections for the rotational transitions j = 1 to j' = 0, 2, 3, 4, 5, j = 2 to j' = 3 and j = 3 to j' = 4. The degeneracy-averaged cross sections are in reasonable agreement with experiment for two different simple model potentials. Values for m -dependent cross sections with respect to two frames of reference are compared with various rules for Δ m and with the previous results for (Ar,LiH).

Elastic and inelastic differential cross-sections for the rotational scattering of p-H2 and MuH by He at a single collision energy are calculated with potential surfaces obtained by varying the parameters in a model potential. The importance of the attractive and repulsive terms in the potential, and of the available kinetic energy in the different channels is demonstrated, and it is shown that the whole potential surface determines the scattering cross-sections. Inelastic and elastic scattering are compared, and the differences between the rotational scattering of homonuclear and heteronuclear homopolar molecules are ascribed to the molecular constants rather than to the numbers of open channels.

Extended gaussian basis set ab initio molecular orbital calculations, both with and without configuration interaction, have been made for the polarizability components of CsF, using the distant charge finite field method. Preliminary calculations to obtain a suitable basis were made for the polarizability of LiF and for the dipole and quadrupole moments of LiF, RbF and CsF. A revised value is suggested for the quadrupole moment of RbF. The polarizability anisotropy of CsF is compared with previous empirical values.

To assist the interpretation of polarized rotational scattering experiments from states ( j, m ) to ( j, m' ), differential and total cross sections obtained from close-coupling calculations are given for m values corresponding to j ⩽ 3 in collisions between LiF and Ar at 20 cm −1 . The hypothesis ¦ m ¦-¦ m' ¦= 0 is proposed for the most likely transition, as an extension of the Δ m = 0 rule.

Calculations of the energies for various geometries of Li3, involving linear and perpendicular approaches of a Li atom to a Li2 molecule, are described. The basis set was of double zeta plus polarization contracted gaussian orbitals, and both a single configuration restricted Hartree—Fock function, and a five configuration function were used. The perpendicular approach was found to give the lowest energy, and the most stable form of Li3 is estimated to be about 10 kcal/mole lower in energy than Li + Li2.

Quasi-degenerate many-body perturbation theory with a multi-configuration reference space is used to obtain potential curves for the ground and excited electronic states of Li 2 , LiNa and Na 2 . Correlation contributions are analyzed and the effect of potential curve crossing on laser action is discussed.

A calculation by the self-consistent MO method of the UV spectra of thiophene, 2,2′-, 3,3′-, and 2,3′-dithienyl is described. For the dithienyls the local energy method developed by Longuet-Higgins and Murrell is applied. Only the π-electrons are considered explicitly and the zero differential overlap approximation is used. Values are given for the transition energies and oscillator strengths of thiophene, the dithienyls and some cyclopentadithiophenes, and for the angles of twist of the dithienyls in non-polar solution. For thiophene a reasonable charge distribution is obtained and the bond-orders lead to bond lengths in good agreement with experiment.

Experimental values for 1H and 19F nuclear shielding anisotropies obtained from solid state, nematic phase, and molecular beam measurements are reviewed. Certain discrepancies are pointed out. An anisotropy operator is defined as a sum of two operators corresponding to the Lamb and high frequency terms. Approximations to the high frequency operator are given. Scales of absolute shielding constants are obtained, so that the magnitudes of the anisotropies can be discussed on the basis of non-empirical and semi-empirical calculations, and of the experimental results. The hypothesis due to Ramsey that the potential is constant for a given nucleus in different molecules is used to obtain approximate values for the Lamb term in the nuclear shielding constant. The distinction between shielding in large and small molecules is stressed. For the fluoromethanes and fluorobenzene the results of CNDO/2 molecular orbital calculations are used for a qualitative discussion of the anisotropies.

Data on the diagmagnetic anisotropies of C-C and C-H bonds obtained by measurements of chemical shifts, crystal diamagnetic susceptibilities, and Cotton-Mouton constants are discussed. It is suggested that for both C-C and C-H bonds the absolute value of the transverse susceptibility is greater than the absolute value of the longitudinal susceptibility. A relation for the anisotropy of a straight chain paraffin in terms of the bond anisotropies is derived. It is concluded that the crystal susceptibilities and Cotton-Mouton constants can be explained if the C-H bond anisotropy is greater than about one-half of the C-C bond anisotropy. It is suggested that values for the bond anisotropies obtained from proton chemical shifts are too high, owing to other contributions to the proton shielding, and to the breakdown of the classical magnetic dipole equation. Values for the C-C and C-H bond anisotropies consistent with the available data are given.

The approximate self-consistent molecular orbital method CNDO/2 is applied to calculations on all the valency electrons of some fluorobenzenes and fluoronitrobenzenes. The charge distribution, which shows σ-electron acceptance and π-electron donation by the fluorine atoms, is in accordance with general chemical ideas. It leads to satisfactory values for the dipole moments of the fluorobenzenes and slightly less good values for the fluoronitrobenzenes. The spin densities on the carbon, nitrogen and oxygen atoms obtained for the anions of the fluoronitrobenzenes by the unrestricted form of the method give a satisfactory representation of the experimental hyperfine splitting constants. The elements of the bond order matrix are used with the average energy approximation and theoretical values for r -3 integrals to obtain relative shielding constants for the fluorine nuclei. The assumption made by other workers that the σ-electron terms are effectively constant for the fluorobenzenes is found to be justified. ...

The gamma-ray spectrum of 2.3 day Np239 has been studied with high-resolution lithium-drifted germanium spectrometers, and twelve new gamma rays of low intensity have been identified. Ten of these are characterized as the de-excitation spectrum of a K= 1 2 band based at 469.8 keV in Pu239. The decoupling parameter (a) of this band is found to be 0.48. A comparison is made of the experimental and theoretical photon relative transition intensities and reasonable agreement is obtained for the case: K 1 = 1 2 , b E1 =0 . The properties of this band are consistent with those expected for Nilsson state 1 2 − [501]. Estimates of the log ft values of Np239 beta decay to levels of the new band are made and are discussed in terms of the states involved.

Many methods of sorting can be used in an electronic universal digital computer. Different sorting problems require different processes, not only for efficiency of sorting, but also to preserve such order as already exists in the data. The sorting methods known to the author are described in the paper, and their effectiveness is evaluated in various types of sorting problem.Since the possibility of using many different methods of sorting arose only recently, with the advent of the electronic computer, there is no generally accepted precise terminology. An attempt is made in the paper to introduce new terms where they are needed.The sorting methods described employ a digital computer with magnetic-tape external storage, and attention is given to the organization of transfers between the computer and the tapes, and the management of tape-reel changes.

A self-consistent molecular orbital perturbation method suitable for use with the CNDO/2 approximations is formulated. The first-order perturbed equation is solved with an electric field perturbation for several molecules, and the polarizabilities are obtained. The results are too low, particularly for polarizabilities along short molecular axes, with a valency orbital basis set. The inclusion of 2p orbitals on hydrogen atoms gives improved results; but it is concluded that additional basis orbitals on other atoms are required for a valid interpretation of polarizabilities.

In order to assist experimental assignments in olefinic and aromatic fluorine compounds, fluorine nuclear coupling constants have been obtained from the first-order self-consistent perturbation theory equation with the INDO molecular orbital approximation in a series of fluoro-substituted furans. There is a clear distinction between the magnitudes and signs for the four fluorine coupling positions; the importance of the orbital and spin-dipolar contributions is very clear. Tentative signs are suggested for all the coupling constants.

Koopmans' theorem ionization potentials from ab initio gaussian basis set calculations on cis, trans and skew forms of HOOH and HSSH are compared with experimental values from photoelectron spectroscopy.

Ab initio calculations with a double zeta contracted gaussian basis are used to discuss the ionization potentials of o-, m- and p-difluorobenzene, and the correlation with benzene. Interpretations of the experimental X-ray and UV photoelectron spectra are given.

Ionization potentials calculated by the valency electron self-consistent molecular method CNDO/2 for BF 3 , HCHO, O 3 , N 2 , CO, the fluoromethanes, and some fluorobenzenes are compared with experimental values obtained by photo-electron and ultraviolet spectroscopy.

Values of vicinal fluorine nuclear coupling constants for the stable rotamers of (CH2F)2, CHF2, CH2F, (CHF2)2 and CF3. CH2F are obtained from the first-order self-consistent perturbation theory equation with the INDO molecular orbital approximations. A clear distinction is found between gauche and trans values. A comparison with experimental values for similar compounds is made.