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Dissociative excitation of methanol (CH3OH) by electron impact leading to the production of O(1S) and CO(a3Π) has been studied in the energy range from threshold to 100 eV using a unique detector which is selectively sensitive to low energy metastable particles. Time of flight (TOF) techniques are used to separate atomic and molecular fragment species. Energy considerations have allowed certain excitation channels producing O(1S) to be identified.

A unique detector which is selectively sensitive to low energy metastable atoms, has been used to study the production of ground state N (2P) atoms following collisions of low energy (0-200 eV) electrons with molecular nitrogen. TOF techniques have revealed the existence of at least two distinct mechanisms yielding this dissociation product. Released kinetic energies in the dissociation have allowed positioning of the parent molecular states in the Franck-Condon region. This has allowed probable parent states, such as B' 3Σu¯, b' 1Σu+ and C' 3Πu, to be identified making use of recent theoretical calculations. Both direct and predissociation processes are shown to be involved.

A novel detector is described in which solid nitrogen at 17 K is used as the most significant element. Metastable particles impinge on this element and immediately transfer their internal energy to the solid nitrogen producing photons, via excimer formation or otherwise, whose wavelength depends on the metastable being detected and the energy transfer process. The performance of the instrument for the detection of atomic oxygen and molecular nitrogen metastables is discussed.

We have studied the excitation of metastable O(1D) following dissociative excitation of CO2 in the electron impact energy range from threshold to 400 eV. A solid Ne matrix at ∼20 K forms the heart of the detector. This is sensitive to the metastable species through the formation of excited excimers (NeO*), The resultant excimer radiation is readily detected, providing a means of measuring the production of the metastables. Using a pulsed electron beam and time-of-flight techniques, we have measured the O(1D) kinetic energy spectrum and its relative production cross sections as a function of electron impact energy. Threshold energy data are used to gain information about the excitation channels involved. In addition, an emission excitation function for the red photons, emitted in coincidence with the exciting electron pulse, has been measured in the 0–400 eV energy range.

A novel detector is described in which solid nitrogen at 17 K is used as the most significant element. Metastable particles impinge on this element and immediately transfer their internal energy to the solid nitrogen producing photons, via excimer formation or otherwise, whose wavelength depends on the metastable being detected and the energy transfer process. The performance of the instrument for the detection of atomic oxygen and molecular nitrogen metastables is discussed.

Metastable N-2 molecules produced by electron impact on N2 are detected using a unique solid nitrogen matrix detector. The time-of-flight system is shown to be selectively sensitive to a(1)Pi(g) and (1)Sigma(+)(g) or (1)Gamma(g) metastable species. The latter species had been identified theoretically previously but was detected experimentally for the first time in the present investigation. Their identification and excitation as a function of electron energy from threshold to 300 eV are presented. Comparison is made with the data obtained by other techniques. Published by AIP Publishing.

Dissociative excitation of thymine following electron impact was studied in the energy range up to 430 eV. Emissions in the vacuum ultra-violet spectral region below 150 nm were studied and found to be dominated by the hydrogen Lyman series. Emission cross section data reveal that Lyman-α excitation displays a broad maximum at an electron impact energy of 160 eV. The probability of extracting other excited atoms from the parent molecule is found to be insignificant. Possible excitation and dissociation mechanisms in the parent molecule are discussed.

The aim of this study was to compare the changes in hematological and biochemical parameters in race horses subjected to standardized field exercise tests. The tests were performed two times: in May, at the beginning of the racing season and then four months later. Ten horses were studied in May (5 Thoroughbreds and 5 Purebred Arabian horses). Eight horses were studied in September (4 Thoroughbreds and 4 Arabian horses). For each horse, venous blood samples were collected at rest, after warm-up, just after the end of each gallop, and 30 minutes after the end of the exercise. The concentration of blood lactic acid (LA) hemoglobin (Hb), plasma glucose (Glc), triacylglycerols (TG), glycerol, uric acid (UA), total protein, total thiobarbituric acid-reactive substances (TBARS), the activity of lactate dehydrogenase (LDH), kreatine kinase (CK) and aspartate aminotransferase (AST) and the total antioxidant status (TAS) were determined. The standardized field exercise test performed in September, in comparison to the first test, evoked the lowest increase in blood LA and plasma Glc and TG levels determined during exercise. The rapid return of elevated levels of LA, Hb and UA to their initial values was also observed in September, as compared to data obtained in May.

A new magneto-optical trap designed specifically for the measurement of absolute electron impact cross sections is described. Experimental results for electron impact total cross sections involving 6 2 S ground state Cs are presented over the energy range 5–200 eV. Significant disagreement is obtained between our experimental data and convergent close coupling (CCC) or Breit–Pauli R-matrix calculations at the lower energies. Above 100 eV our data overlap earlier measurements from this laboratory made with a completely different apparatus and agree well with the CCC results. A comparison is made with other measurements using more conventional techniques.

Using a time-of-flight technique, we have studied the production of neutral metastable fragments in collisions of electrons with neutral xenon clusters. The data reveal that at least six different processes are occurring, yielding fragments with most probable kinetic energies between 0.08 and 1.6 eV. Additional processes give rise to excited fragments that decay by vacuum ultraviolet photon emission, with a variety of lifetimes. Some excitation routes involve exciton excitation, followed by localization into a dimer state, and subsequent decay into the metastable atomic channel. Others involve localization into a bound dimer state, followed by infrared photon decay to a repulsive curve, with consequent production of energetic metastable fragments.

A novel xenon matrix surface detector is used to study the production of S(1S) atoms following controlled electron impact on CS2 over an energy range from threshold to 400 eV. A crossed-beam apparatus with a pulsed electron beam is used to obtain the time-of-flight, and hence energy spectra of S fragments. The absolute cross section for production of S(1S) reaches a maximum of 3.8 × 10−18 cm2 at an impact energy of 35 eV. The dissociation mechanism proposed by Kistopoulos et al (Kistopoulos T, Gebhardt C R and Rakitzis T P 2001 J. Chem. Phys. 115 9727) is confirmed.

A special matrix isolation detector, sensitive to S(1S0), has been used to study the dissociation of OCS into this fragment over an electron energy range from threshold to 400 eV. The maximum cross section occurs at an impact energy of 55 eV and has been measured to be 3.3×10-17 cm2. Time of flight spectroscopy has been used to monitor fragment kinetic energies. Optically allowed processes are observed to dominate the dissociation. Striking similarities between electron and 157 nm photon dissociation have been noted.

Laser-induced fluorescence (LIF) measurements of OH(X 2Π) production following electron impact on water have been carried out over an energy range from threshold to 300 eV. Data have been made absolute using existing measurements of OH(X) production via dissociative attachment. The cross section reaches a maximum value of 2.1×10−16 cm2 at an energy of 75 eV. Dipole-allowed processes are shown to dominate the production of OH(X) particularly via the A(1B1) repulsive state, though significant population of higher rotational levels is demonstrated, indicating the relevance of other channels as in photodissociation.

The polarization of Balmer-α radiation excited in collisions of electrons with atomic hydrogen is presented for an electron energy range from threshold to 1000 eV. Measurements are in good agreement with calculations carried out using either convergent-close-coupling or R-matrix with pseudo-states approaches. Cascade is demonstrated to have a significant effect. Balmer-α excitation function data are also presented. A previous measurement of the polarization of Balmer-α following dissociative excitation of H2 by electrons is confirmed and extended.

The interaction of electrons of carefully controlled energy with N2O molecules and clusters has been studied in a pulsed crossed-beam arrangement over the energy range from threshold to 200 eV. A variety of time-resolved techniques have been applied to isolate and study many of the dissociative excitation channels which occur. The data obtained are relatively insensitive to the degree of clustering in the target beam.

Dissociative excitation of SO2 by electron impact to produce excited oxygen fragments, in particular O (1S), has been studied in the energy range from threshold to 400 eV. Three processes leading to O (1S) production have been identified and the positions of the relevant repulsive states of SO2 in the Franck–Condon region have been determined. The multiplicities and symmetry characteristics of two of these states have also been established. The absolute cross section for production of O (1S) by all channels is measured to be 2.2 x 10-18 cm2 at 150 eV. The relative cross section for production of O (3p 3P and 3p 5P) from threshold to 400 eV has also been measured. The existence of a hitherto unidentified triplet state of SO2 that emits in the near infra red has been established. PACS No.: 34.80Gs

Total fragmentation of and has been studied as a function of incident energy over the range from threshold to 325 eV. A small subset of possible dissociation channels has been selected by making use of a novel solid xenon matrix detector which is selectively sensitive to metastable atoms. O-fragment kinetic energies and appearance potentials have been measured and significant isotopic effects are observed. Within the errors of the measurements the cross section for production from is the same as that from . The cross sections reach a maximum value of at 100 eV incident electron energy.

A variety of techniques have been applied to study the interaction of electrons with beams of CO2 molecules which are heavily clustered. Fragmentation of the clusters is monitored by detecting excited fragments directly or via the vacuum ultra-violet photons which they emit as they decay. The evidence obtained points to the conclusion that the excited molecules are essentially decoupled from the clusters during fragmentation. The shape of the excitation functions are indicative of the dominance of optically allowed processes in the initial interaction.PACS Nos.: 36.40+d and 34.80.GS

A detailed study has been made of electron impact induced fluorescence from Ar clusters. Use of suitable filters in the vacuum ultraviolet spectral region together with time-resolved techniques has enabled the dimer emission from the clusters to be investigated in detail. Excitation function measurements have revealed a number of processes leading to exciton production. Two-center collisions within the cluster appear to be significant. A close parallel to what is observed with solid Ar targets is noted.

Making use of a novel solid xenon matrix detector which is selectively sensitive to $\mathrm{O}(^{1}S_{0})$ metastable atoms, a new dissociation channel, via a $^{1}A_{1}$ repulsive state, has been uniquely identified following electron impact on ${\mathrm{D}}_{2}\mathrm{O}$ molecules. Careful measurements of the O fragment kinetic energies and appearance potentials have allowed partial reconstruction of the potential energy surface involved. The excitation function for production of $\mathrm{O}(^{1}S_{0})$ has a shape which is characteristic of an optically allowed transition in the parent molecule and has a maximum value of $1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}{\mathrm{cm}}^{2}$ at 100 eV incident electron energy.

Isotopically pure 202 Hg vapor, contained in a quartz cell, was irradiated with the 2572.5-A output from a frequency-doubled Ar + laser, which produced Hg 2 A 0 g ± excimer molecules by photoassociation followed by collisional relaxation. Simultaneously applied probe radiation from a ring laser, scanned over the range 4150–4400 A, gave rise to the H1 u ← A 0 g ± v′ = 1 ← v″ = 0 excitation bands consisting of about 490 rotational components. The bands were subjected to a rotational analysis which yielded spectroscopic constants that are compared with some previous data.

Molecular fluorescence of mercury has been known for over 60 years, and some of the important early experiments were carried out and interpreted in the 1930s at the University of Warsaw in Poland. It was not until the mid 1970s, that the continuum bands, emitted from excited mercury vapour, were properly assigned to the lowest electronic states of the Hg2 and Hg3 molecules. Comprehensive and quantitative information on the higher states of the Hg2 excimer has only become available during the past 15 years, largely as the result of flash photolysis experiments carried out in Cambridge, and our own studies of laser-induced fluorescence with time-resolution. We now report on our recent experiments, in which we used pump-and-probe methods to produce rotationally resolved excitation spectra of monoisotopic (202Hg)2. The rotational analyses of the observed structures yielded very accurate values of spectroscopic constants, and permitted some meaningful comparisons with "ab-initio" calculations of potential-energy diagrams.

Pump and probe methods of laser spectroscopy, applied to monoisotopic mercury vapor contained in a quartz cell, were used to study the rotationally resolved G0+u ← A0+g system of excitation bands of the (202Hg)2 excimer. Sixty-nine rovibronic bands containing over 5700 rotational peaks were recorded and analyzed, yielding accurate values of spectroscopic constants that were employed in constructing RKR models of potential curves for the two states, permitting comparison with ab initio calculations.

Isotopically pure 202 Hg vapor, contained in a quartz cell, was irradiated with the 2572.5 A output from a frequency-doubled Ar + laser, which produced Hg 2 A0 g ± excimer molecules by photoassociation followed by collisional relaxation. Simultaneously applied probe radiation from a ring laser, scanned over the range 4150–4650 A, gave rise to the H1 u ← A0 g + and H1 u ← A0 g − excitation spectra consisting of several hundred rotational components. Two previously unobserved rovibronic bands (one in each spectrum) were subjected to a rotational analysis which yielded spectroscopic constants that are compared with some previously reported values.

Isotopically pure 202Hg vapor, contained in a quartz cell, was irradiated with frequency-doubled 5140 A output from an Ar+ laser, which caused the formation of Hg2A0±g excimer molecules by photoassociation. Simultaneous probe radiation from a ring dye laser scanned over a range 5400–6000 A, produced the G0+u ← A0+g excitation spectrum which consists of several hundred well-resolved rotational components that have not been previously observed. Two vibronic bands were subjected to a rotational analysis which yielded spectroscopic constants that are compared with some previously reported values.

Production of metastable O(1D2) atoms following controlled electron impact on N2O and CO2 targets has been studied using a neon rare gas matrix detector operating at a temperature of

The doubly-excited 3Σ+u (4 3P, 4 3P) state of Zn2 was populated using pump and probe methods with time resolution. Structured excitation and fluorescence spectra were observed in the 300–330 nm region and are ascribed to 3Σ+u (4 3P, 4 3P)↔3Πg(4 3P) vibronic transitions, with partial resolution of the fine structure. An analysis of the spectra yielded the vibrational frequencies, relative energy, and relative equilibrium internuclear separations for the 3Σ+u and 3Πg states. The Zn2 excitation and fluorescence spectra contained a number of atomic lines whose origin was probed in a subsidiary experiment.

The 0 + u (4 1 P) state of Zn 2 was excited near the crossing of the 1 Σ + u (4 1 P) and 3 Π u (4 3 P) states, using pump and probe methods with time resolution. A structured excitation spectrum was observed in the 530–570 nm region and is ascribed to the 3 Π u (4 3 P)← 3 Π g (4 3 P) vibronic transitions. A fluorescence spectrum which was emitted in the 250–306 nm region is believed to arise from the 1 Σ + u →X 1 Σ + g bound—free decay. It consists of a “Condon internal diffraction pattern” whose profile suggests that it was emitted from a high vibrational level ( v ′ = 19) of the 1 Σ + u state.

The objective of the present study was to compare changes of blood parameters induced by the same work and performed in the same conditions in two racehorse breeds, Thoroughbred and Purebred Arabian. The effect of moderate-intensity exercise was studied in 20 stallions--ten Thoroughbreds, aged 2-3 years and the same number of Purebred Arabians, 3-4 years old. All the horses were administrated the same effort test consisting in 1200 m gallop at a speed typical of the daily training sessions. Three jugular venous blood samples were collected for each horse: at rest, just after the end of the gallop and after 30-minute rest. In the gathered blood, a hemoglobin (Hb) concentration was determined as well as plasma level of glucose (Glc), triacylglycerols (TG), glycerol, free fatty acids (FFA), total plasma proteins (TP) and the activity of creatine kinase (CK), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST). In the Arabian horses, an increase in levels of TP, glycerol, FFA and CK activity measured just after exercise was higher than that in Thoroughbreds. Similarly, after a 30-minute rest, a post-exercise rise of TP, AST, glycerol and FFA proved to be higher in the Arabian horses compared to that in the Thoroughbreds. Only TG plasma concentration measured 30 minutes following the effort was significantly lower in the Arabian horses than in Thoroughbreds. It can be concluded that the Thoroughbred horses adapted better to the effort test applied in this study as compared to the Purebred Arabian horses. The parameters related to lipid metabolism proved to be the most sensitive indicators of breed differences in relation to moderate-intensity exercise.

Dissociative excitation of thymine into excited atomic fragments has been studied in the electron impact energy range from threshold to 435 eV. The main features in the spectrum are the H Lyman series lines.

Excitation of metastable molecular N2 by electron impact has been studied in the impact energy range from threshold to 300 eV using time-of-flight techniques and a novel solid matrix detector.

An atom trapping technique for determining absolute, total ionization cross sections (TICS) out of an excited atom is presented. The unique feature of our method is in utilizing Doppler cooling of neutral atoms to determine ionization cross sections. This fluorescence-monitoring experiment, which is a variant of the ``trap loss'' technique, has enabled us to obtain the experimental electron impact ionization cross sections out of the Cs $6\phantom{\rule{0.2em}{0ex}}^{2}{P}_{3∕2}$ state between $7\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and $400\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. CCC, RMPS, and Born theoretical results are also presented for both the ground and excited states of cesium and rubidium. In the low energy region $(l11\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ where best agreement between these excited state measurements and theory might be expected, a discrepancy of approximately a factor of five is observed. Above this energy there are significant contributions to the TICS from both autoionization and multiple ionization.

The first time observed excitation spectrum of the C11(51P1) ← X10+(51S0) transition in CdHe van der Waals molecules is reported. Vibrational spectrum in the UV region (2286.0–2296 A) was excited in a continuous molecular-jet-expansion beam of CdHe seeded in helium using an in-house-built nitrogen-dye laser system. The excitation spectrum exhibits two vibrational components ( v ′ ← v ″ = 0 ) highly broadened by means of unresolved rotational structure and some additional contributions of “hot-bands” componenets ( v ′ ← v ″ = 1 ) . The last effect is due to an extremely small separation of the vibrational levels in the ground X10+ state of the CdHe molecule, where v ′ = 0 vibrational level is separated from v ″ = 0 by merely 6.0 cm−1. It follows therefore that even in an extremely cold environment (Tv ≈ 10 K) of a jet-expansion beam the population of v ″ = 1 level is feasible, due to some residual collisions, and hence the v ′ ← v ′ = 1 transitions are highly probable. The assignment of vibrational bands and numerical analysis of the spectrum was based and obtained with the aid of a rigorous computer simulation of the C11 ← X10+ transition including the impact of rotational structure and hot-bands contributions. As a result we obtained optical potential parameters of the C11(51P1) state of CdHe molecule which are further discussed in terms of our recent (and only existing) experimental results regarding the X10+, B1(53P1) and A0+(53P1) states of CdHe as well as in terms of ab initio calculations results.

The aim of this study was to compare changes in epinephrine (E), norepinephrine (NE) and dopamine (DA) levels in blood plasma of two racehorses breeds: Arabian and Thoroughbred during moderate intensity exercise performed in the same conditions. The increase in plasma E level just after exercise was higher in Thoroughbreds than in Arabians. During the whole test, the Arabians showed the higher levels of NE and DA as compared to those found in Thoroughbreds.

A special xenon matrix detector has been used to study the production of S(1S) following controlled electron impact on thiophosgene (Cl2CS) targets over an electron energy range from threshold to 400 eV. Time-of-flight spectroscopy has been used to measure S(1S) fragment kinetic energies. Fragments with energies in excess of 1 eV have been observed. The absolute cross section for S(1S) production reaches a maximum of [1.05+/-0.35] x 10(-18) cm2 at approximately 125 eV impact energy. Two different fragmentation processes, involving triplet and singlet excited states of the parent Cl2CS molecule, have been identified.

The spectroscopy of the 3 Σ + g (4 3 P, 4 3 P) state in Zn 2 was studied by pump and probe methods with time resolution. Structured excitation and fluorescence spectra that were observed in the 266–277 nm region, are assigned as due to 3 Σ + g (4 3 P, 4 3 P) ↔ 3 Σ + u (4 3 P, 4 1 S) vibronic transitions. Vibrational analysis of the spectra yielded the vibrational frequencies, relative energies, and relative equilibrium internuclear separations for the two states.

The 3 Π u (4 3 P, 4 3 P) state of the Zn 2 excimer was excited by pump-and-probe irradiation of Zn vapor in a quartz cell. The resulting structured fluorescence and excitation spectra, which were recorded in the 270–290 nm spectral region, are interpreted as arising from 3 Π u (4 3 P, 4 3 P)↔ 3 Π g (4 3 P, 4 1 S) vibronic transitions. An analysis of the vibrational structures yielded the vibrational frequencies, relative energies, and relative equilibrium internuclear separations for the 3 Π u and 3 Π g states.

A structured excitation spectrum of Zn2 in the 420–470 nm region was registered in zinc vapor subjected to pump-and-probe excitation as the emitted bound—free fluorescence was monitored at 274 nm. The excitation and fluorescence spectra were interpreted as due to transitions involving the 1Σ+u (5 1S), 3Πg (4 3P), and X1Σ+g (4 1S0) states. An analysis of the vibrational structure yielded vibrational constants and relative energies for the 1Σ+u and 3Πg states.

In this study, the authors present the biochemical, morphologic, and physiological analyses of a transgenic mouse model for retinal degeneration slow (RDS)-mediated retinitis pigmentosa caused by a proline 216 to leucine (P216L) amino acid substitution in rds/peripherin.The authors assembled a mutant rds transgene that encodes rds/peripherin with a P216L substitution. Transgenic mice were generated on wild-type (+/+), heterozygous (rds-/+), and homozygous (rds-/rds-) null genetic backgrounds. These mice were analyzed biochemically, by light and electron microscopy, and by electroretinography.In P216L-transgenic mice on a +/- background, the authors observed expression-level-dependent photoreceptor degeneration and outer-segment shortening. Expression of the P216L transgene on an rds-/+ background resulted in more severe photoreceptor degeneration and outer-segment dysplasia than seen in nontransgenic rds-/+ mutants. Severely dysplastic outer segments were detectable in P216L transgenics on an rds-/rds-null background. The reduction in b-wave amplitudes by electroretinography were well correlated with the degree of photoreceptor degeneration, but not outer-segment dysplasia in these different rds mutants.The phenotype in P216L-transgenic mice on an rds-/+ genetic background probably is caused by a combination of two genetic mechanisms: a direct dominant effect of the P216L substituted protein, and a reduction in the level of normal rds/peripherin. The expression pattern of the normal and mutant genes in these animals is similar to that predicted for humans with RDS-mediated autosomal-dominant retinitis pigmentosa. These mice may thus be considered an animal model for this disease.

Summary The aim of the following study was the comparison of phospholipase A2 (PLA2) activity and fatty acids content in cows with and without retained fetal membranes. The activity of the enzyme and levels of fatty acids were measured in maternal and fetal placental tissues obtained from cows immediately after spontaneous parturition without (group A) and with (group B) retained fetal membranes. PLA2 activity was statistically significantly (P < 0.05) higher in group A than in group B, and was significantly lower in the fetal part than in the maternal part of placenta in both groups. The content of the examined fatty acids –- myristic (14:0), palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (18:1), linolenic (18:3), arachidic (20:0), arachidonic (20:4, AA) –- was higher in group A than in B. Concentration of linoleic acid (18:2) showed the opposite relationship. There was a positive correlation between enzyme activity and content of determined fatty acids. The results seem to confirm the hypothesis that the arachidonic acid pathway is altered in cases of retained placenta in cows.

Using an in vitro incubation system, the role of the cyclic AMP-dependent protein kinase A (PKA) pathway in the regulation of the in situ activity of tyrosine hydroxylase (TH) was studied in the hypothalamuses of young and aged ovariectomized rats. Hypothalamic tissue was incubated for 60 min in medium containing 3-hydroxybenzylhydrazine dihydrochloride, a dihydroxyphenylalanine (DOPA) decarboxylase inhibitor, and various agents that modify the activity of the PKA pathway. At the end of the incubation, the tissue was homogenized and analyzed for DOPA and TH mass. The in situ molar activity of TH was expressed as the moles of DOPA accumulating in the tissue per mole of TH per hour. Forskolin, an activator of adenylyl cyclase and the cyclic AMP agonist, (Sp)-cyclic adenosine 3',5'-monophosphothioate, significantly (P.01) increased the in situ molar activity of TH in the hypothalamic dopaminergic (DAergic) neurons of both young and aged rats. Theophylline, a phosphodiesterase inhibitor, did not affect the TH molar activity in the hypothalamuses of aged animals but did significantly (P.001) increase its activity in those of young rats. When vasoactive intestinal peptide was evaluated, the TH molar activity was significantly (P.005) increased in the hypothalamuses of young rats but not in those of aged rats. It was suggested that the deficiency of DA secretion by hypothalamic DAergic neurons of aged rats may be the result of insufficient activation of PKA caused by failure of transduction of an extracellular signal to activate adenylyl cyclase and produce cyclic AMP.

Fragment-specific detection following electron or photon dissociation of molecules is often an essential element for accurate characterization of the dissociation pathways and energetics. Previously, a Xe matrix has proved to be a sensitive and selective detector for oxygen or sulphur 1S0 metastable atoms. In the present work the use and performance of other rare gas matrices for metastable particle detection is evaluated and quantified.

Absolute photoemission cross section data have been measured for the dissociative excitation of H2S by electrons in the impact energy range from threshold to 300 eV. Emissions in the vacuum ultraviolet spectral region have been observed and quantified using emission from H2 as a secondary standard. Numerous dissociation pathways have been identified. H2S data are important in a wide range of situations such as plasma physics, interstellar space and blood flow in humans.

A novel, simplified procedure for the removal of DNA template from newly synthesized RNA is described. The method avoids the use of DNase and involves extraction of the RNA transcription products at acid pH using either phenol or phenol: chloroform:guanidinium thiocyanate mixture. Both procedures are as effective as DNase digestion in removing DNA template, but are free of the hazard of RNA degradation, are highly reproducible and remove proteins at the same time.

The role of prolactin and of estradiol and progesterone in the control of the biosynthetic and secretory activity of TIDA neurons has been investigated in the following animal models: young female rats, aged female rats, and young male rats. The indices of TIDA neuronal function employed were a) mass of TH in neurites in the ME, b) total in situ activity of TH in the ME, c) in situ molar activity of TH in the ME, and d) secretion of dopamine into hypophysial portal blood. It was found that prolactin in high concentration in the circulation and in the CSF had little, if any, effect on the mass of TH in the ME. However, a high concentration of prolactin in either the circulation or in the CSF stimulated significantly the in situ TH activity in the ME whether expressed in terms of total activity per ME or activity per mole of TH. The stimulation of TH activity with prolactin was prevented by immunoneutralization of circulating prolactin. A high concentration of prolactin in the CSF was as effective in stimulating TH activity in the ME of rats with intact pituitary glands as in hypophysectomized rats. In addition to prolactin, treatment of animals with intact pituitaries with a combination of estradiol and progesterone markedly stimulated the total in situ activity of TH of the ME as well as the in situ molar activity of TH of the ME, but neither estradiol nor progesterone alone had an effect on TH activity. Hypophysectomy abolished the stimulatory action of estradiol and progesterone on TH activity of the ME. In addition to the in situ activity of TH in the ME, estradiol-progesterone treatment stimulated the secretion of dopamine into hypophysial portal blood. Neither estradiol nor progesterone alone affected dopamine secretion by TIDA neurons. We conclude that exposure to high concentrations of prolactin or to both estradiol and progesterone stimulate the biosynthetic and secretory activity of TIDA neurons. These hormones are effective in old rats and well as young rats and in males as well as females.