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In contrast to other similar compounds, [FeCl2(C14H30N4)]PF6 is a monomer. Comparison with the mononuclear Fe2+ complex of the same ligand shows that the smaller Fe3+ ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxo dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra­aza­bicyclo­[6.6.2]hexa­decane prevent dimerization upon oxidation., The title compound, [FeCl2(C14H30N4)]PF6, contains Fe3+ coordinated by the four nitro­gen atoms of an ethyl­ene cross-bridged cyclam macrocycle and two cis chloride ligands in a distorted octa­hedral environment. In contrast to other similar compounds this is a monomer. Inter­molecular C—H⋯Cl inter­actions exist in the structure between the complex ions. Comparison with the mononuclear Fe2+ complex of the same ligand shows that the smaller Fe3+ ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra­aza­bicyclo­[6.6.2]hexa­decane prevent dimerization upon oxidation.

Uses a professional services setting to study the concept of factory focus. The rapid growth in the US of ambulatory surgery centres (surgicentres) provides an evolving illustration of focused factories in services. Because of the pressures of cost containment, most hospitals have segmented their surgical market, but have adapted their operations in a variety of ways. Some keep the inpatient and outpatient survery integrated in the same facility, while others choose a plant‐with‐a‐plant or a separate facility. Information concerning costs, organizational structure, achievement of the advantages and disadvantages of differentiation from inpatient surgery, service times, waiting times, customer services offered, and future plans were provided by 54 hospital‐owned ambulatory surgery centres. Despite a variety of structural arrangements, the responses were effectively classified by whether or not they shared operating rooms with inpatient surgery. Those who shared operating rooms reported significantly less achievement of the advantages and avoidance of the disadvantages of outpatient surgery. The shared facilities also reported longer waiting times, less patient contact and higher average facility charges, despite no significant differences in length of procedure nor volume of the seven most frequent procedures. Among the centre directors is the OR group, and 53 per cent favoured separation of the two surgical settings. All the directors with separated facilities favoured continued separation. The reasons given to justify integration emphasized economies of scale and safety, while those given for separation were customer‐service‐oriented.

Natural killer (NK) cells use killer immunoglobulin-like receptors (KIR) that bind to self-class I major histocompatibility complex (MHC) molecules to prevent killing of autologous cells. Mismatched allografts, which do not express recipient MHC class I molecules, can therefore be potential targets for NK-cell killing. In our living related-unrelated renal transplantation program, donor-recipient pairs vary in the amount of both HLA and KIR genes they share. This provides us with a unique opportunity to dissect the influence of KIR on NK-cell function after transplantation.Recipient NK cells were used in a cytotoxicity assay against donor peripheral blood mononuclear cells 2 days before, on the day of, and 3 days after transplantation. Results were correlated to HLA-KIR compatibility between donor and recipient.NK killing, in a direct ex vivo setting, was demonstrated to be HLA mismatch dependent. Recipient NK antidonor cytotoxicity was unaltered despite having received 2 days' treatment with cyclosporine A before transplantation. However, cytotoxicity increased 3 days after transplantation in 71% of recipients. Recipients exhibiting increased NK cytotoxicity against their donors after transplantation were found to possess more activating KIR genes specific for donor class I MHC molecules than those in whom killing activity did not increase (P0.04).NK cells are activated after transplantation despite quadruple immunosuppression, suggesting that recipient NK-cell cytotoxicity against the donor may be a previously unrecognized area of the rejection process, especially in poorly matched donor-recipient pairs where the recipient may not express the correct repertoire of inhibitory receptors to prevent killing of donor cells.

Objective. In Northern Europeans, rheumatoid arthritis (RA) is strongly associated with a relatively conserved pentapeptide sequence of HLA–DRβ found notably in the HLA–DR4 subtypes Dw4 and Dw14 and in DR1. A previous serologic study of HLA class II polymorphism in a Greek population with RA failed to show significant associations with any antigen. Methods. We characterized HLA–DRB polymorphisms in Greek patients with RA and in control subjects by restriction fragment length polymorphism analysis. Allelic DRB subtypes were examined by polymerase chain reaction amplification and oligonucleotide hybridization. Results. DNA analysis in the RA patients showed that although individual HLA–DR allelic associations were weak, a relatively conserved HLA–DRβ motif was significantly associated with RA in this population of Greek patients. The third hypervariable region amino acid sequences QRRAA, QKRAA, or RRRAA were found in the HLA–DRβ1 of 43.5% of the RA patients versus 15.5% of the controls (unconnected P = 0.00004). Conclusion. Sequences shown to influence susceptibility to RA in patients in the UK also play a role in patients in Greece. However, 57% of Greek patients lack the putative HLA–DRβ motif, which suggests that considerable immunogenetic heterogeneity underlies disease susceptibility in this population.

Ambulatory surgery can be a win-win proposition for patients, physicians, payers, and even for hospitals. The main elements at risk are high costs and the traditional models of hospital-based surgical care. If hospitals delay their responses to the challenges of the free-standing surgicenter, the latter will become as common as the multispecialty group practice. Health care institutions need to address some questions in responding to this trend: how hospitals should act to transform their bureaucratic, inefficient systems; who should assume the leadership role; and how much autonomy and pluralism will be appropriate.

The infrared spectrum of CO chemisorbed on alumina‐supported Rh atoms has been investigated. In agreement with previous work, three types of adsorbed species have been clearly distinguished on the basis of their C–O stretching frequencies. Species I, assigned as Rh(CO)2, is formed only with Rh atoms which are isolated from each other. Species II, assigned as Rh–CO, and III, assigned as Rh2CO, are formed on Rh clusters having two or more Rh atoms. CO‐species II and III undergo interactions with neighbor CO species causing an increase in wave number as coverage increases. Based on infrared intensity measurements for species I, the OC–Rh–CO angle is ∼90°. Chemisorbed 13CO yields the expected infrared spectrum on Rh, and rapid isotopic exchange between 13CO(ads) and 12CO(g) is observed which cannot be explained by the observed rate of desorption of CO from the supported Rh surface.

Whereas the cardiorespiratory derangements of severe obesity have received careful scrutiny, the biochemical alterations unique to that state are not well known. This review will examine in morbidly obese patients the hepatic abnormalities related to morphology, function, and lipid metabolism. Altered xenobiotic biotransformation will then be discussed. Available studies in man will emphasize what is known about the biochemical aberrations exemplified by this abnormal biologic state.

A separation of the chemical shift tensor into physically meaningful “geometrical” and “chemical” contributions is presented and a comparison of model calculations with recently reported data on hydroxyl proton chemical shift tensors demonstrates, that for this system, the geometrical portion accounts for the qualitative features of the measured tensors.

The infrared spectrum of CO chemisorbed on alumina‐supported Rh surfaces has been studied following chemisorption at cryogenic temperatures. Major differences are observed in the distribution and spectroscopic character of chemisorbed CO species produced at low temperatures (110–170 K) compared to chemisorbed CO species produced on Rh at 295 K. It has been found that the species Rh(CO)2, formed on isolated Rh sites, is produced rapidly via an activated chemisorption process above ∼200 K. On more ’’crystalline’’ Rhx sites, containing chemisorbed CO, an activated CO adsorbate‐conversion process has been detected in which ?CO decreases by ∼50 cm−1 on warming the adsorbed layer above ∼265 K. Isotopic exchange between 13CO(g) and 12CO(ads) has been shown to occur rapidly at low temperature (∼200 K) for Rh(CO)2 species, whereas Rhx(CO) species exchange rapidly only at higher temperatures (≳250 K). These results, taken together, serve to confirm a model in which isolated Rh sites coexist on the alumina support w...

Nuclear magnetic resonance (NMR) has long been a useful technique for the study of solids (1, 2). Within recent years, however, a number of advances have been made both along theoretical and experimental lines which hold promise to expand greatly the utility of nuclear magnetic resonance as an experimental technique for the study of physical and chemical phenomena in solids. Of particular importance are those techniques which are furnishing generally applicable means of measuring chemical shift tensors in solids for the first time. This review has been restricted to a discussion of those developing techniques which, among other possibilities, are allowing high resolution chemical shift tensor measurements in solids. No attempt will be made here for a definitive essay of the theoretical basis of these somewhat complex new techniques, but rather the emphasis will be placed on discussing the nature of the information they allow one to obtain on physical and chemical interactions within solid materials and what the present and future potentials and limitations of the techniques appear to be. Recent efforts in other aspects of solid state NMR have been reviewed (3-12), and the reader is particularly referred to the discussion of sample spinning techniques by Andrew (3), to the summary of theoretical developments in pulsed NMR by Mansfield (4), and to discussions of using NMR for the study of motional effects in solids (5-7) and of surface adsorbed species (8, 9). Additionally, attention is called to the development of more precise techniques for measuring moments of NMR lines by Lowe et al (13) and locating the center of such solid state lines by Kunitomo (14).

The production of chemical shift spectra of specific protons within polycrystalline solids is described by consideration of explicit double resonance pulse schemes which remove both heteronuclear and homonuclear dipolar interactions. These schemes present a means for characterization of both geometrical and electronic properties in the solid state. As an example of the selectivity of this technique we present results for the carbonyl proton of adsorbed formic acid on ammonium-Y zeolite. Finally, we report the amide bond length in acetanilide as an example of the use of selective proton observed heteronuclear dipolar modulated chemical shift spectra in structural determinations.

A double resonance multiple pulse nuclear magnetic resonance experiment is proposed and demonstrated which allows the use of heteronuclear dipolar interactions to determine geometrical, orientational, and motional information in polycrystalline solids. 13C–1H double resonance experiments are performed in polycrystalline benzene and calcium formate to demonstrate the capabilities of the technique in its present form.

Progressive saturation effects due to induction of two-quanta transitions in the quadrupolar-split levels of a spit, 3/2, (23Na) nucleus were studied by monitoring changes occuring in the 1/2 → − 1/2 magnetization after applying trains of identical pulses at various radiofrequencies and repetition rates. The variety of single- and double-quantum (DO) interconnected population effects observed in the experiments is explained by incorporating solutions of the ordinary two-level Bloch equations with those of the two-quanta, three-level Bloch-like equations (including off-resonance conditions) derived recently by Gold and Hahn. Small displacements of nuclear levels under DQ irradiation (analogous to the optical ac Stark shift) the cause rf power-dependent DQ frequency shifts are predicted for all spins I> 1, and explicit expressions are derived. Additional effects due to state mixing and to population transfer by satellite excitation are presented, and the relevance of DQ saturation to the recently developed double-resonance interferometric spectroscopy is discussed.

Markedly obese patients represent a unique subset of the population. The condition of obesity is related to physiological derangements of the cardiovascular system, deleterious effects of the mechanical and gas exchange function of the lung, severe biochemical derangements in the liver, and changes in normal endocrine functions. Therapy for and research efforts in obesity require a thorough understanding of the definition, measurement, and classification of obesity. The ability to assess pertinent physiological and biochemical alternations is a prerequisite for studying and caring for these patients. A subsequent review will address the biochemical derangements of morbid obesity. The present communication will focus on the physiologic derangements of the cardiopulmonary system unique to marked obesity.

Conventional and solid state proton nuclear magnetic resonance (NMR) techniques have been used to examine water molecules in the channels of a single crystal of cordierite, (Mg, Fe)_2Al_4Si_5O_(18), as a function of temperature, magnetic field, and orientation. Only one type of water was found rather than water in two distinct rigid orientations which were indicated by earlier infrared spectral studies. However, the measured dipolar splittings indicate that this water is in rapid motion. Shifts in the dipolar doublet due to Fe^(2+) impurities indicate that the water molecules are not moving among adjacent channel sites along a channel cavity. A two-site hopping model is proposed involving the major residence time spent with the hydrogen-hydrogen vector parallel to the channels, a minor residence time spent with the hydrogen-hydrogen vector perpendicular to the channels, and a short time (

The chemical shift tensor for the carboxylic proton in potassium hydrogen malonate has been determined from a proton multiple pulse experiment carried out at 270 MHz. Both the values of the averaged chemical shift relative to tetramethylsilane (TMS), ?=−20.5 (5) and the chemical anisotropy, Δσ=27.6 (6), are consistent with the very strong hydrogen bond found for the carboxylic proton in KHCH2(COO)2. The directions of the eigenvectors are similar to those found for proton chemical shift tensors determined for other hydrogen‐bonded systems, i.e., the z‐principal axis is fairly close to the O⋅⋅⋅H⋅⋅⋅O vector off by 9 (2) °, and the x‐principal axis is close to the normal of the plane defined by the carboxylic groups [off by 8 (2) °].

A single resonance, multiple pulse nuclear magnetic resonance experiment is proposed and demonstrated which produces a homonuclear dipolar modulation of a chemical shift powder pattern. The correlation generated between the homonuclear dipolar Hamiltonian and the chemical shift Hamiltonian can be used to determine the relative orientation of the chemical shift principal axis frame to the molecular frame. The experimental scheme is applied to determine the orientation of the proton–proton vector in a CCl3COOH dimer relative to the chemical shift tensor of the hydrogen‐bonded proton.

Proton-magnetic-resonance data are presented for twenty different plasma-deposited amorphous-silicon---hydrogen films. The two-phase compositional inhomogeneity observed in these films is found to be independent of film thickness down to less than 1 \ensuremath{\mu}m. Models for various structural configurations show that these films contain heavily monohydride-clustered regions such as vacancies and voids, as well as ${(\mathrm{Si}{\mathrm{H}}_{2})}_{n}$ and Si${\mathrm{H}}_{3}$ local bonding configurations. The films also contain regions in which monohydride groups are distributed at random. Based on changes in a film whose proton NMR line shapes are metastable as deposited, a model based on strain relief is proposed for film development which explains the ubiquitous presence of the two-phase inhomogeneity. Examination of the changes in proton NMR data as a function of deposition conditions furnishes new insight on the role Si${\mathrm{H}}_{2}$ and $\mathrm{Si}{{\mathrm{H}}_{x}}^{+}$ groups have in models for the gas-phase reactions involved in the developing films. Finally, $p$- or $n$-type doping is found to increase the hydrogen content of the films, and, under heavy $p$-type doping with diborane, boron clustering may occur within the films.

The results of a nuclear-magnetic-resonance experiment are presented which directly demonstrate the spinor character of a spin-1/2 nucleus, C-13. The interferometric spectroscopic technique used and its potential applications are discussed.

This North Carolina case study addresses the migration of anesthesiologists into subspecialty, clinical areas of anesthesiology over a 4 year period (1984 to 1987). Three hundred fourteen members of the North Carolina Society of Anesthesiologists (NCSA) were surveyed using a one-page questionnaire. The response rate was 93.6%. The questionnaire elicited data to characterize the magnitude of change in anesthesiologist manpower, to assess emerging subspecialization, to describe the flux of anesthesiologists entering and leaving practice, and to detail evolving modes of practice. Results indicated a net increase in manpower averaging 8.8% per year in academic programs, whereas clinical community practitioners increased physician positions at a rate three times the former (27% increase per year). Of 184 anesthesiologists recruited to North Carolina over 4 years, 75 different residency programs were represented; 48% of new anesthesiologists were from southern educational programs and 44% entered practice with fellowships (i.e., postgraduate year 4 to 5). The principal fellowship was cardiac (33%). Subspecialty areas were represented in all 53 reporting clinical practices. The principal practice mode emerging was hospital-based, same day surgery (85%) followed by pediatric anesthesia (81 %), perioperative pain management (68%), obstetric anesthesia (63%), and an anesthesia “clinic” (54%). Respondents expected additional practice options over the next 3 years with anesthesia for ambulatory diagnostic and therapeutic modalities projected to emerge at the fastest rate. In conclusion, anesthesiologists in North Carolina seem to be filling unmet needs in obstetric and cardiac anesthesia, critical care, ambulatory surgery, and pain therapy units. These observations may represent a vignette of the national scene.

Although obese patients have been shown to represent a particularly high risk group with respect to hypoxemia both pre and postoperatively, no data exist to delineate the intraoperative arterial oxygenation pattern of these patients. Furthermore, no one has studied the effects of a change in operative position or a subdiaphragmatic laparotomy pack on arterial oxygenation (PaO2). Sixty-four adults undergoing jejunoileal bypass for morbid exogenous obesity, with a mean weight of 142.0 +/- 31.4 kg and a mean age of 33.3 +/- 10.4 years, were studied. Twenty-five patients (Group I) were maintained in the supine position throughout the operative procedure, while the remaining 39 patients (Group II) were changed to a 15 degrees head down position 15 minutes after a control blood sample was taken. Four additional markedly obese patients were studied to determine the effect of an abdominal pack of PaO2 values. The following findings were demonstrated: 1) 40% oxygen did not uniformly produce adequate arterial oxygenation for intra-abdominal surgery in otherwise healthy obese patients; 2) placement of a subdiaphragmatic abdominal laparotomy pack without a change in operative position resulted in a consistent fall in PaO2 in each patient to less than 65 mm Hg even though 40% oxygen was being administered; and 3) a change from supine to a 15 degrees head down operative position resulted in a significant (P less than 0.001) reduction in mean PaO2 (73.0 +/- 26.3 mm Hg). Seventy-seven per cent of these patients demonstrated PaO2 values of less than 80 mm Hg on 40% oxygen. Because of these findings, serious consideration should be given to the routine use of the Trendelenberg position intraoperatively in obese patients. However, if one elects this posture, prudence would dictate careful monitoring and maintenance of arterial oxygenation. Certainly, in obese patients, the intraoperative combination of the head down position and a subdiaphragmatic laparotomy pack should be avoided. In addition, since our data were collected in obese but otherwise healthy, young patients free of cardiorespiratory disease, special attention should be directed at the continuous measurement of arterial oxygenation in the older obese patient with either intrinsic dysfunction of vital organs (heart, lung, liver, kidney) or surgical disorders (peritonitis, sepsis).

There is currently no published chromatographic assay for the fentanyl family of analgesics. This study reports the development of a sensitive, precise, and accurate gas chromatographic method for the determination of fentanyl and its analogues in human plasma. Sensitivity attained for fentanyl and sufentanil was 0.1 ng/mL plasma with an average coefficient of variation of 4.5%. Calibration curve correlation coefficients of 0.99% or greater were consistently obtained. Average recovery of drug into the final extract exceeded 80% and was independent of fentanyl concentration. The required degree of specificity was obtained by selective extraction, use of the nitrogen/phosphorous detector, and chromatographic resolution. This method appears suitable for clinical studies of fentanyl and its derivatives in man.

The results of nuclear magnetic resonance (NMR) spectroscopy have been analyzed with respect to previous infrared studies of CO adsorbed on Rh dispersed on Al2O3 to quantify the site distribution and to describe the adsorbed state. The 13C NMR spectra account for all the 13CO adsorbed on a 2.2% Rh on Al2O3 substrate. Although the spectra from the different adsorbed states of CO overlap, the line shapes may be separated into two components based on differences in the 13C spin–lattice relaxation times. These two components have been assigned to the 13CO dicarbonyl formed on single Rh atoms and to 13CO adsorbed on Rh rafts. The component attributed to the CO adsorbed on the raft sites is further separated into linear and bridged CO state contributions based on chemical shift information, yielding a quantitative distribution of the three adsorbed states of CO on Rh. The 13CO distribution is used to estimate the molar integrated intensities of the infrared spectrum of 13CO on Rh at high coverage and to determi...

The principal components of the 13C NMR chemical shift tensors of metal carbonyls containing between one and six metal atoms were determined from their powder patterns. The tensors of terminally bound CO groups are highly anisotropic (380±60 ppm) and nearly axially symmetric. The tensors of bridging CO groups are much less anisotropic, due to significant asymmetry in the electron orbitals about the C–O internuclear axis. The tensors vary only slightly for different transition metals. There is no intramolecular rearrangement of the metal carbonyls in the solid state at frequencies greater than 10 kHz, except in Fe3(CO)12.

A single‐coil (solenoid), nuclear magnetic double resonance sample probe, suited for a wide variety of solid state studies, is described. It was designed to be used in double resonance experiments where it is necessary to generate intense rf magnetic fields (rotating components with amplitudes ∼50 G) at two widely spaced frequencies and simultaneously to detect microvolt‐level signals. Designs for operation over the 12–270 MHz frequency range are discussed.

A review of the experimental capabilities presently available for the modification of spin Hamiltonians normally encountered in solids has been presented to illustrate the control the still-developing high-resolution, solid state NMR techniques furnish. Examples have been discussed to furnish insight into how such schemes can be used to control the time developemnt of a nuclear spin system to allow a detailed characterization of both the electronic and molecular-frame structure near a nuclear site. While the examples specifically discussed have been chosen from areas of current activity, they are only examples of present efforts, and future developments in this field will undoubtedly furnish many more such examples since the concepts upon which these techniques are based are quite general, and there exists great flexibility for the development of specific experimental schemes for a given problem. (Author)

Forty-eight markedly obese patients for elective jejunoileal bypass were studied during spontaneous ventilation preoperatively and then postoperatively after 2 to 4 hours and on each of days 1 to 5 to determine the effect of the operative incision (midline versus transverse) on the alveolar-arterial oxygen tension difference (A-aDO2). Compared with control (Pre-op.) A-aDO2, there was a significant increase in A-aDO2 in all patients, beginning in the postanesthetic recovery area and continuing through postoperative (P.O.) day 4. Comparing the mean increase in A-aDO2 (P.O.-Pre-op.) between the two incision groups, patients with a midline incision had a significantly greater (p smaller than 0.001) increase in A-aDO2 on control (Pre-op.) value by day 5. The authors conclude that in markedly obese subjects, the midline incision can be expected to result in both more profound and more prolonged reduction in arterial oxygenation postoperatively.

Correlations between parameters characterizing the proton chemical shift tensors for O–H⋅⋅⋅O bonded protons in solids and O⋅⋅⋅O hydrogen bond distances and deuterium quadrupole coupling constants (e2qQ/h) are presented. The isotropic value of the chemical shift correlates very well with both RO⋅⋅⋅O and e2qQ/h, whereas the correlations involving the chemical shift anisotropy show much more scatter. A quantitative agreement is found with theoretical calculations performed by Ditchfield.

Proton magnetic resonance data are presented for plasma-deposited amorphous Si:H as a function of annealing temperature up to 650°C. The data indicate that hydrogen diffuses internally before major evolution occurs, that transfer of hydrogen occurs from a heavily clustered phase to a dilute phase coincident with evolution and that evolution occurs initially from the heavily clustered phase. Comparison with infrared data indicates that the heavily clustered phase can be either SiH x ( x = 2,3) or SiH.

Gastric secretory function was studied in 20 morbidly obese patients both before and after jejuno-ileal bypass. The mean postoperative weight loss was 99.2 pounds during a mean postoperative followup period of 12.6 months. The gastric secretory values we studied included basal and histalogstimulated volume, pH, concentration, and output. No statistically significant changes were observed in any of these variables. Therefore it is suggested that jejuno-ileal bypass, as performed for morbid obesity, is probably not an ulcerogenic procedure.

A double resonance technique designed to allow study of quadrupolar interactions in nonintegral spin systems is described using both theoretical calculations and experimental data. The interferometric technique involves indirect detection of quadrupolar‐broadened satellites by observation of only the central 1/2↔−1/2 transition. Changes in the phase factor of one wavefunction in a multilevel quadrupolar split spin system are monitored by observation of the free‐induction decay of the central transition, while a 360° pulse at a second (search) frequency is applied. Particular consideration is given to the accurate reproduction of an inhomogeneously broadened satellite, and several spectroscopic schemes are compared theoretically and tested experimentally using the 23Na satellites in single‐crystal sodium nitrate. Emphasis was placed on the important roles of H1 broadening and coherence transfer to the double quantum states.

Serum levels of inorganic fluoride, trifluoroacetic acid, and bromide ion were measured at various time intervals following two hours of halothane anesthesia in 17 morbidly obese and eight nonobese patients. Ionic fluoride, a marker of reductive halothane metabolism, increased in the obese but not the nonobese patients. This is of concern since reductive halothane metabolism is associated with hepatoxicity in animals. In addition, serum bromide levels were higher after 48 h in the obese patients compared to the nonobese patients (mean +/- SE, 1,311 +/- 114 vs. 787 +/- 115 microM, P less than 0.01). Sedative levels of bromide were not attained in any patient. Peak trifluoroacetic acid levels were similar in the two patient groups. Sex age, medication intake, and smoking history had no influence on the halothane metabolite levels found in this study.

The interaction of H2CO with alumina‐supported Rh has been studied by transmission infrared spectroscopy. It has been shown that isolated Rh atoms catalyze the decomposition of H2CO to produce carbonyl hydride species HxRh–CO (x=1,2). Species of the type Rh(HCO) and Rh(HCOH) are not observed to form in detectable amounts. Hydride bonding to rhodium carbonyl species is associated with electron donation to Rh causing a decrease in ?CO due to electron donation into 2π*‐CO orbitals. Hydride displacement by CO may occur on exposure to CO(g). The conversion of the species H–Rh(CO)2 to H–Rh(CO) has been followed spectroscopically during desorption.

The multiple pulse nuclear magnetic resonance techniques have been used to measure the 19F chemical shift, or nuclear magnetic shielding, tensor in a series of Group II difluorides. For the cubic difluorides measured values relative to a C6F6 reference are: CaF2, −61 ppm; SrF2, −82; BaF2, −154 ppm; CdF2, +33 ppm; and HgF2, +32 ppm. For the two noncubic difluorides principal values of the chemical shift tensors relative to C6F6 are; for MgF2, +13, +28, and +43 ppm; and for ZnF2, +15, +38, and +59 ppm. The chemical shifts from the cubic difluorides were found to correlate well with electronegativities and a covalency parameter calculated from electron spin resonance superhyperfine interaction parameters. A theoretical calculation of the chemical shift tensor for MgF2 is presented and give good agreement with the experimental data, accounting for 90% of the chemical shift anisotropy.

A low power (100 W) pulse spectrometer is described for work in solids, and the use of the spectrometer for performing the Waugh ``line narrowing'' multiple pulse experiments is demonstrated and discussed in detail. The performance of these measurements with a low power spectrometer is made possible by controlling the nature of the transient responses of tuned circuits within the spectrometer, and means for nullifying the effects of such transients on the effective rotation axis of an rf pulse are presented.

Volume and pH of Gastric Juice in Obese Patients ROBERT VAUGHAN;SPOMENKO BAUER;LESLIE WISE; Anesthesiology

The chemical shift tenson for the water molecule in α‐oxalic acid dihydrate was measured using a multiple pulse, NMR technique. The high resolution proton speclia were recorded at room temperature.(AIP)