Experimental characterization of SiCH+via single-photon ionization of gas-phase SiCH.

SiCH and its cation have consistently emerged as predicted species in models of silicon chemistry within the interstellar medium, although they remain unobserved in space. Hindered by their intrinsic instability, no spectroscopic insights have been gleaned concerning the SiCH+ cation. In this study, we present experimental measurements on the SiCH+ cation through single-photon ionization spectroscopy of the SiCH radical within the 8.0-11.0 eV range. Gas-phase SiCH radicals were generated through chemical reactions involving CHx (x = 0-3) and SiHy (y = 0-3) within a microwave discharge flow-tube reactor. Employing a double imaging photoelectron/photoion coincidence spectrometer on the DESIRS beamline at the SOLEIL synchrotron, we recorded mass-selected ion yield and photoelectron spectra. From the analysis of the photoelectron spectrum supported by ab initio calculations and Franck-Condon simulations, the adiabatic ionization energies for the transitions from the X2Π ground electronic state of SiCH toward the X+3Σ- and A+3Π electronic states of SiCH+ have been derived [8.935(6) and 10.664(6) eV, respectively, without spin-orbit correction]. The contribution from the less stable isomer HSiC has been explored in our analysis and ruled out in our experiments.

Single-photon ionization of SiC in the gas phase: experimental and ab initio characterization of SiC.

We report the first experimental observation of single-photon ionization transitions of the SiC radical between 8.0 and 11.0 eV performed on the DESIRS beamline at the SOLEIL synchrotron facility. The SiC radical, very difficult to synthesize in the gas phase, was produced through chemical reactions between CHx (x = 0-3) and SiHy (y = 0-3) in a continuous microwave discharge flow tube, the CHx and SiHy species being formed by successive hydrogen-atom abstractions induced by fluorine atoms on methane and silane, respectively. Mass-selected ion yield and photoelectron spectra were recorded as a function of photon energy using a double imaging photoelectron/photoion coincidence spectrometer. The photoelectron spectrum enables the first direct experimental determinations of the X+ 4Σ- ← X 3Π and 1+ 2Π â† X 3Π adiabatic ionization energies of SiC (8.978(10) eV and 10.216(24) eV, respectively). Calculated spectra based on Franck-Condon factors are compared with the experimental spectra. These spectra were obtained by solving the rovibrational Hamiltonian, using the potential energy curves calculated at the multireference single and double configuration interaction level with Davidson correction (MRCI + Q) and the aug-cc-pV5Z basis set. MRCI + Q calculations including the core and core-valence electron correlation were performed using the aug-cc-pCV6Z basis set to predict the spectroscopic properties of the six lowest electronic states of SiC+. Complete basis set extrapolations and relativistic energy corrections were also included in the determination of the energy differences characterizing the photoionization process. Using our experimental and theoretical results, we derived semi-experimental values for the five lowest ionization energies of SiC.

Precise localization of the motor nerve branches to the hamstring muscles: an aid to the conduct of neurolytic procedures.

OBJECTIVE: To identify the precise locations of the motor branches and motor points to the hamstring musculature and define these locations in relation to bony landmarks. DESIGN: Descriptive study of adult cadaver limb dissection. The number, location, and course of the motor branches and motor points to each hamstring muscle from the sciatic nerve were defined relative to bony landmarks. SETTING: Department of anatomy at a university school of medicine. PARTICIPANTS: Anatomic dissection of 30 adult cadaver limbs (17 individuals) was completed. Adult cadavers were selected randomly without regard to gender, age, and race. Exclusion criteria included femoral fracture, surgery, inability to obtain neutral position, and posterior thigh trauma. MAIN OUTCOME MEASURE: A descriptive anatomic study based on linear measures in centimeters from bony landmarks. RESULTS: Two zones located along a line from the ischial tuberosity to the lateral femoral condyle were observed to exist. Zone one, containing the first motor branch to the biceps long head and semitendinosus, is found at approximately 20% (6.9cm +/- 1.8 and 7.1cm +/- 2.2 from the ischial tuberosity, respectively) of femur length along the stated line. Zone two, containing the primary branch to the semimembranosus and the secondary branches to the biceps and semitendinosus, is found at approximately 33% (13.1cm +/- 3.6, 12.6cm +/- 3.9, and 14.3cm +/- 3.9 from the ischial tuberosity, respectively) of femur length. CONCLUSIONS: The drawing of one surface line, when combined with our anthropometric observations, should increase the ease and accuracy with which motor branch blocks to the hamstrings are performed.

National Pediatric Trauma Registry.

The National Pediatric Trauma Registry (NPTR) is a multi-institutional database designed to compile information concerning all aspects of pediatric trauma care. The registry is designed and operated in a manner that maximizes data accuracy and provides this information to all participating investigators. The growth of the database has allowed the NPTR to provide the first accurate epidemiologic description of pediatric trauma as a national disease, as well as to develop national norms for pediatric trauma care. The registry presently contains 10,177 patients, and is undergoing revisions (phase II) to allow a more focused evaluation of various aspects of the clinical care and rehabilitation of the pediatric trauma patient.

Use of polyglycolic acid mesh to confine particulate hydroxylapatite for augmentation of bone in the rat.

A preliminary report of the use of polyglycolic acid (PGA) mesh to contain particulate nonresorbable hydroxylapatite (HA) used for augmentation of bone in rats is presented. PGA mesh tubes, approximately 2 mm in diameter and 5 mm in length, were fabricated, filled with HA, and placed in surgically created subperiosteal pockets against the medial cortex of the tibia in rats. Specimens were obtained at two, six, 12, and 18 weeks. The results showed that when the HA was contained within the PGA mesh, severe displacement of particles was prevented and greater HA augmentation was possible. Absorption of the mesh took place between six and 12 weeks, after which the histologic features were the same as those seen when HA was implanted alone. Grossly, the implants appeared to hold firmly to bone even two weeks after implantation. A new, more efficacious delivery system is proposed for the augmentation of atrophic alveolar ridges using HA contained within PGA mesh tubes.

Long-term follow-up of a mandibular costochondral graft.

The long-term follow-up of a patient with unilateral mandibular condylar dysplasia and facial asymmetry, treated with a costochondral graft, is presented. The etiology of the deformity and the surgical treatment are discussed. A detailed review of the literature is included to introduce the reader to the biology and rationale for the use of costochondral grafts in growing patients.

A comparison of the cardiovascular and orofacial blood flow changes resulting from hypotension induced by sodium nitroprusside and adenosine triphosphate in the rat.

These experiments compared the cardiovascular effects and the alterations in orofacial blood flow resulting from hypotension induced with sodium nitroprusside and adenosine triphosphate infusions in 30 male rats. The authors found that sodium nitroprusside did not significantly change heart rate or cardiac output, while adenosine triphosphate caused a significant decrease in heart rate associated with a small increase in cardiac output. Both hypotensive agents produced similar profound decreases in total peripheral resistance. Blood flows to orofacial structures were qualitatively similar with both agents. Both adenosine triphosphate and sodium nitroprusside caused decreased flows to the maxilla and mandible. Sodium nitroprusside increased flows to masseter and suprahyoid muscles. Adenosine triphosphate caused increased flows to suprahyoid muscles but masseter muscle flows were not significantly changed. Tongue flows responded similarly to both agents, initially decreasing, then returning to normotensive levels. Finally, sodium nitroprusside-induced hypotension was associated with the development of tachyphylaxis in some animals, whereas no similar problem was observed with use of adenosine triphosphate. The demonstration of reduced blood flows to orofacial bony structures and the absence of resistance or tachyphylaxis during adenosine triphosphate-induced hypotension support its usefulness as a hypotensive agent during orthognathic and other surgery.

The image intensifier in oral and maxillofacial surgery.

The mobile image intensifier has been found useful in the removal of foreign bodies from both intraoral and extraoral sites. The safety of the machine has been verified, and a technique for its application is described. Additional uses for the machine are stated.

Mandibular movement during autorotation as a result of maxillary impaction surgery.

With increasing use of maxillary surgery to reduce vertical dimension, it would be appropriate to evaluate methods of predicting autorotation of the mandible. Experimental data derived from edentulous patients using metallic implants embedded in occlusal wax rims matched geometrically analyzed clinical data accumulated from twenty-three patients treated by maxillary impaction procedures. The center of rotation of mandibular autorotation during maxillary surgical impaction has been represented in the literature as the center of the condyle. Our evidence with lateral head films taken in centric occlusion supports a different instantaneous center of rotation located within the mastoid region. Modification of prediction tracing techniques by orthodontists and oral surgeons engaged in maxillary surgery could be indicated.

Blood flow to oral tissues: and experimental study with enflurane, sodium nitroprusside, and nitroglycerin.

Hypotensive anesthesia is currently being used in oral and maxillofacial surgery to reduce blood loss and provide a relatively bloodless surgical field. Radioactively labeled microspheres were used to determine and compare the hemodynamic effects of sodium nitroprusside (SNP), nitroglycerin (NTG), and deep enflurane anesthesia on oral tissues during controlled hypotension when compared with controls. Sodium nitroprusside and NTG produced significant reductions in blood flow to the maxilla, mandible, and tongue, while deep enflurane anesthesia did not. In the masseter and suprahyoid muscles, increases in tissue blood flow were found with SNP and enflurane. Nitroglycerin produced no significant change in blood flow in the masseter and the suprahyoid. These results demonstrate that in spite of a similar cardiac index with all agents tested, local oral blood flow varied significantly with the different agents tested. These differences in tissue blood flow suggest that SNP and NTG may be preferable to deep enflurane anesthesia for maxillary osteotomies to achieve greater flow reduction and diminish blood loss.

Below-knee orthosis: a wrap-around design for ankle-foot control.

Control of foot and ankle positions with orthotic appliances is generally more difficult to accomplish in children with spastic than flaccid paralytic disorders. Our new design for a custom molded plastic ankle-foot orthosis has proven superior to other designs in most applications. The appliance is vacuum molded from very thin polypropylene plastic and innerfaced with a foam material (Aliplast). The limb is enclosed completely in plastic with an anterior opening secured by several Velcro straps. Although the material is soft and pliable, the circumferential support provides remarkably rigid control of the limb. The orthosis has been successfully applied to children with polio, meningomyelocele and all forms of spastic and athetoid cerebral palsy. In addition to superior limb control, another advantage appears to be reflex inhibition of abnormal motor tone in may spastic patients. Patients have preferred this orthosis to those previously worn probably due to greater comfort. The limitation of adjustability of dorsiflexion can be compensated by heel or sole shoe lifts. Excessive heat created by the "wrap-around" design can be reduced by a thin cotton sock extended above the orthosis.

Cranial dislocation of mandibular condyle.

The ninth case of condylar dislocation into the middle cranial fossa is reported. The previously reported cases are reviewed and the clinical findings which they have in common are pointed out. Because difficulty in establishing the diagnosis seems to be the most serious aspect of this clinical entity, it is advised that films of the temporomandibular joint be taken more frequently. Finally, although treatment varied from physical therapy to intracranial condylectomy, our case of closed withdrawal of the condyle from the cranial fossa is the first case on record so treated.

A new technique for making a moulage.

A new technique for making a moulage has been described; it offers several significant advantages over standard techniques.