Free H2O Research Articles

The relationship of fluid balance and sodium administration to cerebral edema formation and intracranial pressure in a porcine model of brain injury.

Fluid and sodium restriction have been advocated after brain injury as a means of controlling intracranial pressure (ICP). Recent clinical data showing no significant relationships between the amount of fluid infused or sodium administered (Na) and ICP question this practice. To analyze the relationship of amount of fluid, Na, and fluid balance to cerebral edema formation and ICP. A cryogenic brain injury with and without hemorrhagic shock was studied after 24 hours in swine (n = 35) randomized to receive either lactated Ringer's solution (LR) or hypertonic sodium lactate (HSL). Cerebral edema formation as indicated by cortical water content (CWC) was determined by measurement of specific gravity. There was a significant positive correlation between the following variables: (1) amount of fluid and ICP (r = 0.598; p < 0.01); (2) fluid balance and ICP (r = 0.684; p < 0.01); and (3) free water and ICP (r = 0.614; p < 0.01). There was a significant negative correlation between serum osmolarity and ICP (r = -0.654; p < 0.01). The study failed to demonstrate a significant correlation between Na and ICP, amount of fluid and CWC, or fluid balance and CWC. These data suggest that both the volume of fluid infused and the fluid balance do affect the ICP, but the amount of Na infused does not. The lack of a significant correlation between any of the independent variables and CWC suggests that their effect on ICP is not related to cerebral edema formation. These findings, combined with the observed significant positive correlation between free H2O infused and ICP, and the significant negative correlation between serum osmolarity and ICP, suggest that HSL resuscitation increases intracranial compliance after brain injury while LR decreases it. The data also suggest that free water restriction is warranted in patients with head injuries.

Characterization of Slightly Hydrated Ni(OH)2 by XPS

We report x-ray photoemission spectra (XPS) of slightly hydrated Ni(OH)2. XPS spectra were measured with the Physical Electronics Model 5400 x-ray photoelectron spectrometer using unmonochromatized Mg Kα x rays at two pass energy settings corresponding to analyzer energy resolutions of 1.34 and 0.54 eV. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution of 1.34 eV. Multiplexes of the C, O, and Ni photoemission lines, valence band region, as well as Ni LVV Auger lines were measured at an analzyer energy resolution of 0.54 eV. The slightly hydrated Ni(OH)2 sample was prepared by reacting stoichiometric Ni(NO3)2 with KOH in CO2 free H2O at 35 °C.

NMR studies of 1H NOEs in glycogen.

We have examined the cross-relaxation behavior among the protons of oyster glycogen using nuclear Overhauser enhancement (NOE). Steady-state and transient NOEs were generated using low-power CW irradiation and frequency-selective inversions. In D2O, saturation of glycogen H2 and H4' at 3.64 ppm gave a strong negative NOE (eta = -0.74) at H1. The NOE was similar to the value predicted by the correlation time (tau c) calculated from the T1 and T2 of glycogen H1 in D2O assuming an isotropic rigid motor dipole-dipole model. Selective inversion of H2 and H4' gave a transient NOE at H1. In D2O, selective inversion of H1 also led to negative transient NOEs in the H2 + H4', H3, and H5 resonances. The magnitude and rates of appearance of the NOEs in H3 and H5 were too large to arise from direct H1-H3 and H1-H5 dipolar interactions, but were consistent with very efficient cross-relaxation leading to large second-order NOEs. The glycogen H1 NOE in H2O was also studied. Replacement of D2O with H2O as solvent significantly reduced the steady-state NOE at H1 following saturation of H2 + H4'. Saturation of the water resonance caused a large negative NOE at H1 (eta = -0.55) consistent with our earlier study which indicated that there was no direct dipolar interaction between H1 and free H2O.

Vibration, rotation, and parity specific predissociation dynamics in asymmetric OH stretch excited ArH2O: A half collision study of resonant V–V energy transfer in a weakly bound complex

Para ArH2O complexes are detected via slit jet direct absorption spectroscopy using continuous wave difference frequency generation of high resolution tunable IR in the 3780 cm−1 v3=1←0 asymmetric OH stretch region. P/R and Q branch transitions on the Π(101,v3=1)←Σ(000,v3=0) band are observed, which derive oscillator strength from the 101←000 v3=1←0 transition in free H2O and access upper states of e and f parity, respectively. Frequency shifts in the f parity levels (Q branch), and both frequency shifts and predissociation broadened linewidths in the e parity levels (P/R branch) are evidenced in the spectrum, unambiguously characteristic of an avoided crossing in the vicinity of J′=6 with a second, near resonant vibration–internal rotation state in ArH2O. From detailed analysis of the avoided crossing, this perturbing state is assigned to a symmetric (v1=1) OH stretch+internal rotor state in ArH2O, which resonantly mixes with the IR laser prepared asymmetric (v3=1) OH stretch by resonant ‘‘half collisional’’ V→V transfer with the Ar atom. The striking parity dependence of the observed predissociation linewidths results from energy conservation and the symmetries of the asymptotic Ar+H2O (v1=1) states; the e parity levels can dissociate to the ground 000 rotor level of H2O (v1=1), whereas the f parity levels can access at lowest the 111 rotor level, therefore releasing insufficient energy to rupture the van der Waals bond. The data establishes a clear upper limit on the dissociation bond strength for para ArH2O, and place spectroscopic constraints on the promoting internal rotor state in ArH2O (v1=1). A simple local mode theory of half collision induced mixing between symmetric and asymmetric stretch excitation in H2O is presented. The model predicts a coupling which is proportional to three factors, (i) a ‘‘steric’’ term which describes the overlap of initial/final internal rotor wave functions in the ArH2O angular geometry conductive to energy transfer, (ii) a ‘‘collisional’’ term which depends on the van der Waals stretching frequency and reduced mass, and (iii) an intramolecular V→V term to describe the ‘‘rephasing’’ of the OH local modes that characterizes the collisional transformation between asymmetric and symmetric stretch vibrations. All the parameters in the model are accessible from the high resolution van der Waals spectra, and the resulting predictions are in surprisingly good agreement with the coupling spectroscopically determined from the perturbation analysis. The high efficiency of the predissociation dynamics is also qualitatively consistent with the near gas kinetic v3↔v1 energy transfer observed by Finzi et al. [J. Chem. Phys. 63, 2285 (1975)] in thermally averaged H2O(v1,v3)+Ar collisions. In summary, analysis of the J and parity dependent predissociation linewidths and frequency shifts in a van der Waals near-IR spectrum of ArH2O offers an unusually detailed glimpse at collision induced intramolecular V–V transfer in vibrationally excited H2O from a half collision perspective.

Slit-jet near-infrared spectroscopy and internal rotor dynamics of the ArH2O van der Waals complex: An angular potential-energy surface for internal H2O rotation

Near-infrared vibration-rotation spectra of jet-cooled Ar-H2O complexes are detected for the first time via direct absorption of tunable difference frequency infrared radiation in a slit supersonic expansion source. Transitions from both the lowest para and ortho complexes are observed which correlate to 000 and 101 rotational levels of free H2O, respectively, and permit spectroscopic characterization of the complex in both the ground (ν3=0) and asymmetric stretch excited (ν3=1) levels. From hot bands involving excited internal rotor states correlating with the 101 H2O rotational level, we determine the Σe(101)-Πf(101) energy splitting to be 11.3333(3) cm−1 (J=1). In conjunction with far-infrared measurements of the Σ(110)-Π(101) and Π(110)-Σ(101) energy splittings, this information permits determination of a two-dimensional (2D) angular potential-energy surface of the complex as a function of the H2O orientation. The barriers to internal rotation of an ArH2O differ for in-plane (19 cm−1) and out-of-plane (33 cm−1 ) rotation of the H2O subunit. However, both barriers are only slightly higher than the ground-state energies and, hence, the behavior of H2O in the complex is that of a nearly free rotor. Agreement with recent ab initio calculations by Chalasinski et al. [J. Chem. Phys. 94, 2807 (1991)], as well as with 3D fits solely to far-infrared data by Cohen and Saykally [J. Chem. Phys. 94, 7991 (1991)], is remarkably good. Predictions based on this angular potential-energy surface are made for the internal rotor states of ArHDO and ArD2O and compared with recent far-infrared measurements by Suzuki et al. [J. Phys. Chem. 94, 824 (1991)].

Guanabenz: A centrally acting, natriuretic antihypertensive drug

Guanabenz is acutely natriuretic and diuretic in saline expanded animals. In man, guanabenz has not resulted in sodium retention as seen with other comparable antihypertensives. To directly define the action of guanabenz on sodium and water excretion in man, we performed clearance studies during water diuresis on eight hypertensive subjects under metabolic balance conditions. Each subject underwent three studies: 1) baseline study: no drug, a water diuresis study; this was followed by a saline load (= 2% BW); 2) acute study (24 hr after baseline): 16 mg guanabenz PO; and 3) chronic study: after one week of guanabenz 8 mg PO BID. In the acute guanabenz studies there were: 1) no changes in GFR or ERPF; 2) an increase in both sodium excretion and fractional sodium excretion; 3) a rise in free H2O clearance (CH2O) and (CH2O/GFR) X 100%. These findings were not sustained in the chronic guanabenz studies. We conclude that in man (preconditioned with prior saline loading) guanabenz is acutely natriuretic and water diuretic. These effects are due to decreased tubular sodium and water reabsorption, probably related to inhibition of alpha adrenergic activity. The data are consistent with selectively reduced renal sympathetic activity affecting sodium transport and provide a basis for the absence of edema and sodium retention associated with guanabenz therapy.

Structure and fluxional behaviour of some aqua-complexes of rhodium(III) and iridium(III)

The single-crystal X-ray structure of trans,mer-[IrCl2(H2O)(PMe2Ph)3][ClO4] confirms a structure based on 1H and 31P-{1H} n.m.r. spectroscopy. The weakly bonded H2O ligand is trans to PMe2Ph, a ligand with a strong trans influence, and has a long Ir–O bond [2.1 89(6)Å] and a short Ir–P bond [2.249(3)Å]trans to it. The phosphine ligand site exchange, apparent in the n.m.r. spectra of this compound and its rhodium analogue, is a result of rate-determining H2O dissociation to give the five-co-ordinate intermediates [MCl2(PMe2Ph)3]+(M = Rh or Ir), which are probably squarepyramidal species undergoing rapid pseudo-rotation. The rates of PMe2Ph exchange and the rates of exchange of free and co-ordinated H2O are similar in each case but greater for Rh than Ir.

Relics of H2O fluid inclusions in mantle-derived olivine

In olivine of upper mantle derivation, CO2 is the most commonly reported species of fluid1. Despite its great importance in the upper mantle2, H2O has rarely been reported (refs 3, 4 and E. Roedder, personal communication). Here we report that possible relics of H2O-rich fluid inclusions have been found in olivine of dunite from the alpine-type Iwanai-dake complex, northern Japan. These inclusions now consist mainly of serpentine and brucite, which may be the products of the reaction, olivine + H2O = serpentine + brucite, in a closed system. The abundance of such inclusions suggests that the Iwanai-dake complex may have been derived from the upper mantle in conditions in which some free H2O was available, such as the mantle wedge above a subduction zone.

INDOMETHACIN AND RENAL FUNCTION: THE EFFECTS OF ADDITION OF LOW-DOSE DOPAMINE

The renal function changes induced by indomethacin during treatment of patent ductus arteriosus often preclude its use. To determine if concommitent low-dose dopamine improved renal function, we studied renal parameters in Beagle puppies. The animals were sedated; tracheostomy was performed and mechanical ventilation begun. The femoral artery and vein were catheterized and the right ureter isolated and catheterized for urine collection. Four groups were studied: controls, indomethacin treated, dopamine treated, and indomethacin and dopamine treated. Each animal was allowed to serve as its own control at time 0-120 min. At time 120 the treated animals received .2 mg/kg indomethacin intravenously and/or 4 mcg/kg/min dopamine by continuous intravenous infusion. Time 120-240 served as the next collection period. All animals received constant fluid intake. Blood pressure, heart rate and blood gases remained stable. Glomerular filtration rate (GFR), sodium para-aminohippurate (PAH) clearance, fractional sodium (Na) excretion, osmolar and free H2O clearance were obtained. GFR was significantly decreased (p<.05) in animals that received indomethacin alone, and unchanged in the groups receiving dopamine, dopamine and indomethacin and controls. There was a trend (p<.1) indicating fractional Na excretion decreased only in the group receiving indomethacin. This data suggests that low-dose dopamine may improve renal parameters when used with indomethacin.

Cation influence on the structure and electron density of water in some Men+�H2O complexes

The cation influence on the water molecule in the Li+·H2O, Be2+·H2O, Mg2+·H2O and A13+·H2O complexes has been studied by means of quantum-mechanical ab initio calculations. A number of general trends are noted. (1) The calculated equilibrium water O-H distances increase with increasing binding energies, i.e. in the order Li+, Mg2+, Be2+, Al3+. The H-O-H angles differ by about ±1 ° from the calculated equilibrium angle for the free H2O molecule; the variation has no systematic trend. (2) The electron density redistribution accompanying the change in the internal H2O geometry in these complexes is considerably smaller than the redistribution brought about by the direct influence of the external field. (3) The harmonic O-H stretching force constant decreases with increased cation-water bonding. (4) The qualitative features of the density changes are very similar for the four complexes. The magnitudes of the interactions follow the relation Li+ < Mg2+ < Be2+≲ Al3+. An increased polarization of the H2O molecule occurs with electron migration from the H atoms towards the O atom and an accumulation of electron charge approximately at the centre of the Men+—O bond, especially in Be2+·H2O and A13+·H2O. An electron deficiency is found in the lone-pair region.

Depolarisation thermocurrents in frozen aqueous solutions of glucose

The dielectric behaviour of frozen aqueous solutions of glucose was studied by the depolarisation thermocurrent (DTC) method in the temperature range 85-250K and over a wide range of concentrations (0.005-1.5 mol. litre-1), to obtain information on the state of water in the solutions. Two predominant peaks were observed at temperatures of about 125-130 and 225K, respectively. The low-temperature DTC peak was studied in detail, using several techniques offered by the DTC method. The peak was attributed to polarisation of free and hydration H2O molecules. The results show the existence of a continuous transition from hydration to free H2O molecules in solutions with molar solute concentrations up to about 0.7 mol. litre-1, and the presence of only hydration H2O molecules in solutions with higher concentrations.

Proton NMR study of the orientation and motion of H2O in Na β′′ alumina

Proton NMR measurements in nearly dry Na β\ alumina crystals display a Pake doublet due to H2O molecules. At 300 K the angular dependence of the Pake splitting shows the time average orientation of the water HH vectors is parallel to the crystal c axis. Measurements at 133 K, where motional averaging is removed, demonstrate that HH is tilted from c by 5° to 13°. The frequency splitting of the doublet shows that the HH distance is between 1.65 and 1.71 Å, longer than in free H2O. Above 250 K, line narrowing indicates the H2O are translationally diffusing while maintaining their orientation. A model of this motion is suggested. The chemical shift anisotropy of the H2O is found to be in agreement with previous measurements of H2O in ice and gypsum.

Etude, par Spectroscopie de Vibration, du Composé 4HNO3·H2O dans les Etats Cristallisé, Vitreux et Liquide Mise en Evidence du Trihydrogénotétranitrate d'Oxonium

AbstractThe IR and Raman spectra of the mixture 4HNO3 · H2O in crystal, glassy and liquid states have been investigated in the frequency range 4000–50 cm−1. The crystal is the oxonium trihydrogentetranitrate where the oxonium ion is practically free (ν(OH) = 3480 and 3385 cm−1). In the trlhydrogentetranitrate ion the charge is not localized. In the glassy and liquid states, four species have been characterized: (1) the oxonium trihydrogentetranitrate; (2) the free molecular association H2O …︁ (HONO2) (νOH(H2O)= 3550 cm−1 and ν OH(HNO3)=2930 cm−1); (3) the free ionic pair (H2OH)+…︁(ONO2)− (ν(OHO)= 2700 cm−1, ν1(NO3−)=1030 cm−1) and (4) free HNO3 molecules (ν(NOH)=926 cm−1).

Dielectric studies of zeolite systems. Part 2.—Ag-X zeolite with dipolar and non-dipolar absorbates

Studies have been made over the range 6 Hz to 130 kHz and 170 to 450 K of dielectric absorptions in Ag-X zeolite evacuated at 10–5 Torr and 520 K and also with controlled contents of H2O, NH3, CH3CN or C6H6: adsorption isotherms were measured simultaneously. Introduction of a Teflon film with the compacted dielectric disc gave blocking-electrode conditions when the d.c. conductance was disturbingly large. In addition to this d.c. ionic conductance a separate dielectric absorption (I) was measured in the zeolite itself and further distinct processes, absorption II and III were characterized both in frequency and intensity (via Fuoss–Kirkwood parameters) and in activation enthalpy and entropy terms (via Eyring parameters). Processes I and II arise from ion-jumping within the lattice and are discussed in relation to their most probable mechanisms. Absorption III in Ag-X/H2O is due to H2O reorientation: it appears (sharply) at H2O contents above 160 molecules per unit cell and has an effective strength (µeff≈ 1.8 D) equivalent to that of the free H2O molecule.