Heteronuclear molecules from matrix isolation sublimation and atomic diffusion.

We demonstrate the production of cryogenic beams of heteronuclear molecules from the matrix isolation sublimation (MISu) technique. A sapphire mirror serves as a substrate whereupon a solid Ne matrix is grown. Atoms of Li, H, Ca, and C are implanted into the matrix via subsequent laser ablation of different solid precursors such as Ca, Li, LiH, and graphite. The matrix is sublimated into vacuum generating a cryogenic beam of Ne carrying the previously isolated neutral atomic and molecular species. A compact and low energy electron source and time-of-flight mass spectrometer was designed to fit this system at low temperature. With electron ionization time-of-flight mass spectrometry, we analyze the species coming from MISu and demonstrate the formation of heteronuclear molecules in the matrix. In this first study, we produced LiCa from the sequential implantation of Li and Ca into the matrix and some clusters of CnLim after Li and C ablation. Also from ablation of a single LiH pellet, we observed clusters of LinHm. This novel technique opens up the opportunity to generate cryogenic beams of different molecules for precision physics and chemistry studies. Laser or microwave high resolution spectroscopy of a molecular beam benefits from low translational and rovibrational temperatures and forward velocities, such as the ones produced in this technique. Toward the prospect of enhancing the molecular formation, we introduce a new method to study the atomic diffusion of Li and Ca in the Ne matrix via laser spectroscopy during sublimation. We estimate a small diffusion coefficient at 7 K, but a surprisingly linear atomic dispersion during sublimation. The method is extensive to other species and matrices.

Cryogenic mount for mirror and piezoelectric actuator for an optical cavity.

We present the development of a mount that accommodates a mirror and a piezoelectric actuator with emphasis on physical needs for low temperature operation. The design uses a monolithic construction with flexure features that allow it to steadily hold the mirror and the piezoelectric actuator without glue and accommodate differential thermal contraction. The mount is small and lightweight, adding little heat capacity and inertia. It provides a pre-loading of the piezoelectric actuator as well as a good thermal connection to the mirror and a thermal short across the piezoelectric actuator. The performance of the assemblies has been tested by thermally cycling from room temperature down to 3 K more than a dozen times and over one hundred times to 77 K, without showing any derating. Such mounts are proposed for the cryogenic optical enhancement cavities of the ALPHA experiment at CERN for laser spectroscopy of antihydrogen and for hydrogen spectroscopy in our laboratory at UFRJ.

Kinetic Energy Release of the Singly and Doubly Charged Methylene Chloride Molecule: The Role of Fast Dissociation.

The center of mass kinetic energy release distribution (KERD) spectra of selected ionic fragments, formed through dissociative single and double photoionization of CH2Cl2 at photon energies around the Cl 2p edge, were extracted from the shape and width of the experimentally obtained time-of-flight (TOF) distributions. The KERD spectra exhibit either smooth profiles or structures, depending on the moiety and photon energy. In general, the heavier the ionic fragments, the lower their average KERDs are. In contrast, the light H(+) fragments are observed with kinetic energies centered around 4.5-5.5 eV, depending on the photon energy. It was observed that the change in the photon energy involves a change in the KERDs, indicating different processes or transitions taking place in the breakup process. In the particular case of double ionization with the ejection of two charged fragments, the KERDs present have characteristics compatible with the Coulombic fragmentation model. Intending to interpret the experimental data, singlet and triplet states at Cl 2p edge of the CH2Cl2 molecule, corresponding to the Cl (2p → 10a1*) and Cl (2p → 4b1*) transitions, were calculated at multiconfigurational self-consistent field (MCSCF) level and multireference configuration interaction (MRCI). These states were selected to form the spin-orbit coupling matrix elements, which after diagonalization result in a spin-orbit manifold. Minimum energy pathways for dissociation of the molecule were additionally calculated aiming to give support to the presence of the ultrafast dissociation mechanism in the molecular breakup.

Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption.

The incidence of high-energy radiation onto icy surfaces constitutes an important route for leading new neutral or ionized molecular species back to the gas phase in interstellar and circumstellar environments, especially where thermal desorption is negligible. In order to simulate such processes, an acetonitrile ice (CH3CN) frozen at 120 K is bombarded by high energy electrons, and the desorbing positive ions are analyzed by time-of-flight mass spectrometry (TOF-MS). Several fragment and cluster ions were identified, including the Hn=1-3(+), CHn=0-3(+)/NHn=0-1(+); C2Hn=0-3(+)/CHn=0-3N(+), C2Hn=0-6N(+) ion series and the ion clusters (CH3CN)n=1-2(+) and (CH3CN)n=1-2H(+). The energy dependence on the positive ion desorption yield indicates that ion desorption is initiated by Coulomb explosion following Auger electronic decay. The results presented here suggest that non-thermal desorption processes, such as desorption induced by electronic transitions (DIET) may be responsible for delivering neutral and ionic fragments from simple nitrile-bearing ices to the gas-phase, contributing to the production of more complex molecules. The derived desorption yields per electron impact may contribute to chemical evolution models in different cold astrophysical objects, especially where the abundance of CH3CN is expected to be high.

Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules.

We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H2 are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

Strong Electronic Selectivity in the Shallow Core Excitation of the CH2Cl2 Molecule.

The photoexcitation and multiphotoionization of the dichloromethane molecule have been studied for photons with energies from 100 eV to the Cl 2p edge, using the time-of-flight multicoincidence technique and synchrotron radiation. The electronic de-excitation gives rise to one to three electrons and an ionic molecule that decays onto smaller moieties through several fragmentation channels. To discern the channels, sets of fragments have been dispersed in time, measured in coincidence, and recorded as a function of incident photon energy. The chlorine ion, Cl(+), has the highest intensity around and above the Cl 2p edge, while the CHnCl(+) ion, corresponding to the loss of one neutral chlorine atom, dominates the mass spectra in the valence region. In addition, strong electronic selectivity has been observed for the core-excited molecule.

Ionization and fragmentation of methane induced by 40 eV to 480 eV synchrotron radiation: from valence to beyond core electron ionization.

Photoionization and fragmentation of gaseous methane induced by tunable synchrotron radiation were investigated in a wide energy range, from 40 eV up to 480 eV. We report electron-ion coincidence experiments by measuring the relative partial-ion yields and precursor-specific relative yields for individual fragment ions and for ion fragment pairs as a function of photon energy. The fragmentation patterns are discussed with emphasis on the transition behavior of the bond breaking reactions and of the hydrogen rearrangements from valence to core electron ionization. Below the C 1s threshold, a comparison between photon induced dissociation and electron impact data showed that the ionic fragments formation depends for both projectiles on the same final electronic state reached upon ionization.

Source of slow lithium atoms from Ne or H2 matrix isolation sublimation.

We have studied, via laser absorption spectroscopy, the velocity distribution of (7)Li atoms released from cryogenic matrices of solid neon or molecular hydrogen. The Li atoms are implanted into the Ne or H(2) matrices--grown onto a sapphire substrate--by laser ablation of a solid Li or LiH precursor. A heat pulse is then applied to the sapphire substrate sublimating the matrix together with the isolated atoms. With a NiCr film resistor deposited directly onto the sapphire substrate we are able to transfer high instantaneous power to the matrix, thus reaching a fast sublimation regime. In this regime the Li atoms can get entrained in the released matrix gas, and we were also able to achieve matrix sublimation times down to 10 µs for both H(2) or Ne matrix, enabling us to proceed with the trapping of the species of our interest such as atomic hydrogen, lithium, and molecules. The sublimation of the H(2) matrix, with its large center-of-mass velocity, provides evidence for a new regime of one-dimensional thermalization. The laser ablated Li seems to penetrate the H(2) matrix deeper than it does in Ne.

Electron-recoil ion and recoil ion-projectile coincidence techniques applied to obtain absolute partial collision cross sections.

We present in detail an alternative experimental set-up and data analysis, based on the electron-recoil ion and recoil ion-projectile coincidence techniques, that enable the measurement of partial pure ionization and partial charge exchange cross sections for an effusive gas jet set-up, where the absolute target density and recoil ion efficiency cannot be measured directly. The method is applied to the ionization of helium atoms due to collision with partially stripped C(3 +) projectiles. In order to check the method, the results are compared to data available in the literature where the target density and recoil ion detection efficiency were measured directly. The pure ionization channel is compared to the electron capture channel.

Genetics of ethylene biosynthesis and restriction fragment length polymorphisms (RFLPs) of ACC oxidase and synthase genes in melon ( Cucumis melo L.).

We investigated the genetics of ethylene biosynthesis and its linkage to the RFLPs of the ACC oxidase and synthase genes in melon ( Cucumis melo L.). The results suggested that the A(0) and B(0) fragments of RFLP-MEL1 of the ACC oxidase gene were two alleles from a single locus, as were the B and C fragments of RFLP-MEACS1 of the ACC synthase gene. The B(0) allele seemed to be partially dominant over the A(0) allele, whereas B and C alleles appeared to map to quantitative trait loci (QTLs), which most likely contributed to ethylene production. Both RFLPs were linked to ethylene production rates, but they were not linked to each other. The interaction effects of the ACC oxidase and synthase genes on ethylene production were revealed by segregation of RFLP-MEL1 and RFLP-MEACS1. The results of single-copy-reconstruction assays suggested that the ACC oxidase gene is a single copy, whereas the ACC synthase gene is a component of a multigene family in the melon genome. The abscission phenotype appeared to be controlled by an independent locus, with the abscission (full-slip) allele dominant over the non-abscission (not full-slip) allele. These results may facilitate efforts toward mapping the quantitative trait loci (QTLs) of ethylene production. The RFLPs may be used in marker-assisted selection in developing melons with a more-desirable low ethylene production rate for enhancing postharvest storage life.

The pelvic plexus and antireflux surgery: topographical findings and clinical consequences.

PURPOSE: Voiding dysfunction and urinary retention are rare complications of antireflux surgery. As mainly reported after bilateral antireflux surgery with extravesical technique, bladder insufficiency has been suspected to be caused by intraoperative damage to neural structures. We studied the topography of the pelvic plexus and assessed the injury to the plexus resulting from antireflux surgery. MATERIALS AND METHODS: Human cadavers fixed with Thiel solution were used for dissection. The superior hypogastric plexus and hypogastric nerves were identified as the pathway to the pelvic plexus. After dissecting the surrounding fatty tissue the S2 to S4 nerves and efferent nerve bundles from the pelvic plexus were identified. RESULTS: The main portion of the pelvic plexus was located about 1.5 cm. dorsal and medial to the ureterovesical junction. The bundles of the pelvic plexus ended at the distal ureter, trigone and rectum. When simulating an antireflux procedure, there was a high risk of injury to the pelvic plexus and its efferent nerves if dissection was performed distal to the ureter and dorsal trigone. CONCLUSIONS: Careful dissection close to the ureter avoids inadvertent injury to the pelvic plexus. To minimize the risk of voiding dysfunction bilateral antireflux surgery should be performed at 2 sessions unless the operative technique allows preservation of the neural structures.

A modified Spalteholz technique with preservation of the histology.

The Spalteholz technique for producing clear macroscopic specimens was introduced 100 years ago, and is still in use today because it immediately provides transparent three-dimensional specimens. The classical clearing procedure with peroxide severely damages formalin-fixed tissue and inhibits further investigation on a histological level. We, therefore, wanted to make a transparent specimen by a modified Spalteholz method and chose the human larynx as an example of a large specimen. Its blood vessels were injected with gelatin, the specimen treated with acetone and peracetic acid and subjected to freeze substitution. After complete dehydration, benzyl benzoate and dimethylphthalate were used for impregnation. The cleared specimen satisfactorily revealed the laryngeal blood vessels and such structures as muscles, cartilage and the thyroid gland. The histology of the laryngeal glands, thyroid tissue, and infrahyoid muscle fibres was preserved. Tissue shrinkage became apparent with subsequent steps of the clearing procedure. We conclude that our modifications maintain the transparency of the specimen and allow histological investigation. The herein described technique thus constitutes an improvement of the classical Spalteholz technique.

Deep venous thrombosis: detection by using indirect CT venography. The Pulmonary Angiography-Indirect CT Venography Cooperative Group.

PURPOSE: To assess the clinical benefits of performing indirect computed tomographic (CT) venography after pulmonary CT angiography to detect deep venous thrombosis (DVT) in patients suspected of having a pulmonary embolism. MATERIALS AND METHODS: The authors prospectively enrolled 541 consecutive patients who underwent pulmonary CT angiography for suspected pulmonary embolism at seven institutions. Using a protocol that optimizes venous enhancement without additional contrast material injection, the authors obtained contiguous images from the pelvis to the popliteal fossa. Ultrasonography (US) also was performed in 116 patients. RESULTS: DVT was found at indirect CT venography in 45 (8%), and pulmonary embolism was found at pulmonary CT angiography in 91 (17%) of 541 patients. Among the 45 patients with DVT, DVT occurred in 16 patients who had no pulmonary embolism at pulmonary CT angiography, which increased the diagnosis of thromboembolic disease by 18%. Among 116 patients who underwent US and indirect CT venography, 15 had DVT at US, and in all 15, DVT also was seen at indirect CT venography. In four additional cases, DVT was seen at only indirect CT venography. CONCLUSION: Among patients suspected to have pulmonary embolism, a substantial number had DVT in the absence of pulmonary embolism. Combined pulmonary CT angiography-indirect CT venography can depict these cases with accuracy comparable to that of US and thus could have a significant effect on patient care.

The status of middle level HIV/STD education as assessed by state and local education agencies.

During spring 1998 RAD Educational Programs, in cooperation with the National Middle School Association, conducted a needs assessment of middle level HIV/STD prevention programs from the perspective of representatives from state education agencies (SEA) and local education agencies (LEA). Data were collected from 84% of states (SEAs) and 88% of cities (LEAs) funded by CDC to conduct HIV/STD prevention activities. A range of activities are occurring in school-based HIV/STD prevention for early adolescents in grades 5-8. However, a prevailing characteristic among states was the high degree to which local control and local decision making affects programming in schools. Needs of SEAs and LEAs are similar as reflected by the need for continued improvement of middle level HIV/STD prevention education. A concrete result was the multitude of requests for effective HIV/STD curricula for middle level students. In addition, administrators shared similar needs for an increase in time allotment for health instruction. Most SEAs (65%) and LEAs (77%) believed that time for health education in the classroom would increase if a nation-wide mandate existed resulting in appropriate standards and assessments for all middle level and high school students.

[Histological biomorphosis of human heart valve. II. Morphometric studies]. / Zur histologischen Biomorphose menschlicher Herzklappen. II. Morphometrische Untersuchungen.

Previous polarization-microscopical measurements combined with silver-staining methods at histological sections of the bicuspid valve and the tricuspid valve in the region of fibrosa showed (similar to that of the corresponding tendinous cords) for middle-aged persons a distinct difference in the collagen composition in comparison between high pressure vs. low pressure system. The aim of the current study was the morphometric investigation of the collagen composition, of the relative content of total collagen (measured as relative number of total collagen fibers per measuring area), and of the cell-collagen relation in dependence of age and possibly on sex in the high and low pressure system, respectively. Tissue samples of atrioventricular valves of 67 probands of both sexes were available. The probands were healthy with regard to heart and circulation and distributed in 3 age groups (1st to 2nd decade, 3rd to 5th decade, and 6th to 9th decade). After corresponding preliminary treatment, the histological sections of tissue samples were evaluated by a suitable combination of polarization-microscopical, immuno-histochemical, and morphometrical methodology. The thickness of the heart valves was measured by microscopic image analysis. A rise of the number of fibers per measuring area (ma) for both sexes and both valves was observed with increasing age. The slopes of the linear regression curves and the mean values of the numbers of collagenous fibers/ma (for each age group) were different between both sexes. They depend upon the valve considered. Analogous to these results, the differentiated statements were possible to the number of fibers/ma and to the percentages of the fiber species by the distinction between the collagen types I and III in the fibrosa of the heart valves. Whereas the relative numbers of fibers/ma rose with increasing age, the number of cell (fibroblasts, fibrocytes) nuclei for both valves and sexes slightly decreased. For the latter, there was no difference between high and low pressure system in contrast to the collagenous fibers. The opposite age-dependent behavior of the collagenous fibers and of their producing cells during the biomorphosis of the heart valves could be explained with the collagen turn-over.

Texas non-donor-hospital project: a program to increase organ donation in community and rural hospitals.

Identifying and recovering donors from community and rural hospitals present a challenge to organ procurement organizations. A study of non-donor hospitals in the United States was undertaken at Johns Hopkins University, which identified 31 hospitals (in one service area) with the facilities to accommodate organ donation, though an organ donor had not been produced in 3 years. The purpose of this study was to determine whether donors could be produced from these hospitals. A large, geographically dispersed OPO initiated a program consisting of (1) in-house coordinators, and (2) routine notification of all hospital deaths. Following implementation of this program, organ donation increased 387% among the targeted 25 hospitals. The number of hospitals producing at least 1 organ donor increased 133%. The number of organs recovered in the project increased 449%. In-house coordinators, by identifying potential donors and facilitating an organ donor awareness program, can increase the number of organ donors in hospitals with low, but real, donor potential.

Epidemiologic evaluation of encephalitic listeriosis in goats.

OBJECTIVE: To evaluate host and environmental factors associated with the development of encephalitic listeriosis in goats. DESIGN: Retrospective analysis of diagnostic laboratory records and survey of veterinarians and goat producers. SAMPLE POPULATION: 355 goat herds accessible through laboratory records; 38 veterinarians who treated goats and 76 goat producers. PROCEDURE: Data regarding breed and use for goats affected with encephalitic listeriosis were obtained from surveys and case follow-up information. Listeria monocytogenes isolates from the brains of 7 affected goats were serotyped and subjected to DNA restriction analysis. RESULTS: Odds ratio for the development of encephalitis listeriosis in Angora (mohair-producing) goats was 22.9 by use of diagnostic laboratory records. Survey also revealed a high prevalence in herds of Angora and other breeds that subsisted on woody browse, although Angora goats feeding predominantly on hay or pasture were not affected. Listeria monocytogenes isolates from 4 Angora goats in 3 herds differed in DNA restriction patterns, although the pattern was identical in 3 other goats from another herd. CLINICAL IMPLICATIONS: Encephalitic listeriosis can be observed in all goat breeds, but a lifestyle of heavy browse consumption seems important to the development of disease in some herds.

Effect of Re-17 mutant Salmonella typhimurium bacterin toxoid on clinical coliform mastitis.

The objective of this study was to test the hypothesis that the incidence and severity of clinical coliform mastitis could be decreased by Re-17 mutant Salmonella typhimurium bacterin toxoid. Holstein-Friesian cows from two Arizona dairies were selected for this study based on July through November projected calving dates; peak lactation occurred during the period of highest rainfall and peak environmental stress. The cows were randomly assigned to either a vaccinate or a control group, and 1292 cows were paired by herd, parity, calving date, and milk yield. The 646 vaccinates were injected twice during the third trimester of pregnancy with an Re-17 mutant S. typhimurium bacterin toxoid, and the 646 controls were not vaccinated. Vaccinated cows had significantly fewer clinical cases of coliform mastitis with positive coliform cultures and had lower culling rate from coliform mastitis than control cows during the first 5 mo of lactation. During the same period, the mortality rate from clinical coliform mastitis was 75% less in the vaccinated clinical coliform mastitic group than in the control group. Incidence of mastitis increased with advancing parity. The Re-17 mutant Salmonella typhimurium bacterin toxoid provided cross-protection against coliform mastitis; incidence and severity of clinical coliform mastitis were significantly lowered during the first 5 mo of lactation.