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We evaluated bilateral femoral neck bone mineral densities (FNBMDs) in 32 men with poliomyelitis and their matched controls. Men with poliomyelitis had significantly lower FNBMD in both legs, and FNBMD was lowest in their shorter legs. Knee extensor strength and regular exercise were important predictive factors associated with decreased FNBMD.People with poliomyelitis (polio) are prone to leg fractures after mild trauma. The flaccid paralysis, asymmetric involvement, and underdeveloped growth of afflicted legs may lead to osteoporosis of either leg, characterized by different patterns. This study aimed to measure their femoral FNBMD and to explore the factors associated with changes in FNBMD in either leg.We did a prospective study to evaluate bilateral FNBMD with dual-energy X-ray absorptiometry in 32 men with polio (age range, 41-57 years; mean, 47 years) and 32 age- and body mass index-matched controls. Measuring the difference in leg length, we classified the legs of each polio subject as "longer" or "shorter." In addition, we chose the right leg of each control as a reference leg. We then used the Mann-Whitney U test to compare FNBMD of these three groups of legs and searched for the factors associated with FNBMD using stepwise multiple regression analyses.Compared to the reference leg, men with polio had significantly lower FNBMD in both their longer and shorter legs, by 13% and 23%, respectively. The difference in FNBMD between the two legs of polio subjects was significant. Knee extensor strength and regular exercise were two important factors associated with bilateral FNBMD in men with polio.Men with polio had lower bilateral FNBMD. FNBMD of the shorter leg should be the choice for predicting the risk of hip fracture in men with polio because on average, the shorter leg has lower BMD.

Sea salt particles are constantly produced from ocean surfaces by wave-wind interactions and removed by deposition and precipitation scavenging. These particles constitute the background aerosol for light scattering in the marine boundary layer. In this work, the thermodynamic and optical properties of sea salt aerosol particles generated from seawater samples are measured at 25°C as a function of relative humidity, using a single-particle levitation technique. Water activities, densities, and refractive indices of aqueous solution droplets containing a single salt NaCl, Na2SO4, MgCl2, or MgSO4 are also reported as a function of concentration. The light-scattering properties of the sea salt aerosol are modeled by the external mixture of these four salt systems selected to approximate the sea salt composition. Good agreements are obtained. It follows that in either visibility reduction or radiative forcing calculations, both freshly produced and aged sea salt aerosols may be modeled by external mixtures of the appropriate inorganic salts, whose solution properties are now available in the literature.

is monitored continuously using a capacitance manometer. The change in the particle’s composition as the temperature or relative humidity (RH) is varied is determined by measuring the mass-to-charge ratio (with an accuracy of1%). A vertically polarized HeNe laser is focused on the particle. The intensity of the scattered light is continuously monitored at a9 0 °angle from the incident laser, and the phase (solid or liquid) is determined from the Mie scattering. To assure uniform temperature, the electrodynamic trap and the interaction chamber are constructed of copper. The chamber is insulated with a vacuum shroud and is in contact with a liquid nitrogen reservoir via heat transfer straps. An automated feedback heating loop is used to control the temperature to better than 0.2 K. The temperature is monitored at two points, above and below the particle, with the difference kept to less than 0.3 K. The reported temperature is the average between the two points. The system can be used to perform experiments at constant temperature or to scan temperature at a prescribed rate. Both modes were utilized to obtain the data presented here. When the temperature was scanned, the water vapor pressure was maintained at equilibrium with ice, by coating the cell walls with ice. The entire pressure and temperature monitoring system was calibrated against the ice frost line. The results reported here represent observations of over20 particles.

The phase transformation and hydration of inorganic salt particles composed of alkaline earth metal nitrates, Ba(NO3)2, Sr(NO3)2, and Ca(NO3)2, are investigated in a quadrupole cell, in which a levitated single microparticle is in dynamic equilibrium with water vapor under controlled humidity conditions. Laser Raman and Mie scattering techniques are used to probe the chemical and physical states of the microparticle before and after phase transformation. Because of the high degree of supersaturation that only a suspended solution droplet can attain before solidifying, metastable states not predicted from bulk solution thermodynamics often result. Thus it is found that, except for Ba(NO3)2 particles which form the stable anhydrous crystalline state upon efflorescence, Sr(NO3)2 and Ca(NO3)2 droplets solidify to a metastable amorphous state that contains residual water persisting even in high vacuum. Raman spectra of the amorphous particles reveal that the nitrate ions form contact-ion pairs with the bivalen...

An improved gas phase sampler and a recently developed nonenzymatic measurement method for H2O2 and HOCH2OOH(HMHP) are described. The gas phase sampler is equipped with a surfaceless intake to alleviate heterogeneous loss of H2O2 in the sampling line. The nonenzymatic method makes use of the aqueous phase Fention reaction for H2O2 measurement and is capable of speciation between H2O2 and HMHP, using a dual channel technique. By adding a third channel employing the well-established method of p-hydroxyphenylacetic acid (POHPAA) and horseradish peroxidase for total peroxide measurement, it is possible to differentiate H2O2, HMHP, and other organic peroxides, if present. The measurement technique was successfully deployed in a field study at George L. Smith III State Park, Georgia (82°20′W, 32°30′N). Preliminary data analysis indicates that the measured total peroxides range from 0.4 to ∼6 ppbv, depending on meteorological conditions, and that organic peroxides, mostly HMHP, constitute between 20 and 80% of the total peroxides. The work reported here represents the first continuous and real-time measurements for these peroxides in the atmosphere.

The polarization of Raman scattering from a single spherical droplet has been measured for the first time. Experiments are performed in a quadrupole cell, in which a charged liquid droplet is trapped by electro-dynamic forces. Raman scattering intensities at the 90° angle are measured for polarizations both parallel and perpendicular to that of the incident beam. The depolarization ratios thus obtained for the droplets are shown to be identical to those measured in the bulk samples. The present results indicate unequivocally that the depolarization ratio of Raman scattering is a molecular property and, as such, is not affected by the boundary conditions of the spherical droplets. Subsequently, the technique is applied to the chemical characterization of solution droplets. The presence of ion pairs in supersaturated strontium nitrate and bisulfate solutions is dramatically verified by distinct changes in the depolarization ratios.

An analytical technique for aerosol samples which utilizes the resonance Raman effect is described. The aerosol particles were generated at 50 kHz by a vibrating orifice. The nominal particle size was 45 µm in diameter. The visible lines (4579, 4765, 4880, and 5145 Å) of a continuous argon-ion laser were used as the excitation source. Within the coverage of the laser wavelengths, effects of pre-resonance, resonance, and post-resonance Raman scattering were studied. Under the resonance condition, the enhancement of p-nitrosodimethylaniline is 5.5 × 104 when compared to that of nitrate ions. The corresponding concentration of detection limit is 10−6 molar.

An experimental technique using individual aerosol particles for relative Raman scattering cross-section measurement is described. An electrostatically charged particle of known chemical composition, 10 to 15 µm in diameter, is suspended in an electrodynamic cell. A single line (4880 Å) from an argon-ion laser is selected to induce the Raman scattering. The minute size and free rotation of the suspended particle ensure uniform sample illumination. The present results show very good linearity between the scattering intensity ratio and the molar mixing ratio. Sodium nitrate, ammonium nitrate, sodium sulfate, and ammonium sulfate are examined, and their respective Raman cross sections relative to that of sodium nitrate are determined to be 1, 0.9, 0.61, and 0.94. The uncertainty in this work is estimated to be less than 10%.

Raman spectroscopy is applied to the physical and chemical characterization of an electrostatically charged single microparticle, which is trapped and suspended in an electrodynamic cell. The microparticle, 10 to 15 pm in diameter and composed of deliquescent salts, such as sulfates and nitrates, is present either as a solid particle or as a solution droplet under controlled humidity conditions. While the chemical composition of the microparticle is characterized by the distinct Raman shifts observed, the physical state is revealed by the Raman bandwidths. Since a solid microparticle under laser illumination is largely free from both the sample inhomogeneity and optical transmission degradation that are normally encountered in a single crystal or crystalline powders, it follows that single particle suspension is a unique experimental method for measuring relative Raman scattering cross-sections for solid compounds. Furthermore, a suspended solution droplet, which evaporates to attain high supersaturations inaccessible with bulk samples, provides an ideal condition for a spectroscopic investigation of solute-solute interactions in concentrated electrolyte solutions. Experimental results are presented, which illustrate the uniqueness and versatility of single particle Raman spectroscopy.

Interests in the gas phase oxidation reactions of organic sulfur compounds such as thiols, sulfides, and disulfides have become increasingly important due to their potential role in the formation of tropospheric and stratospheric sulfur containing aerosols. The rate constants for the reaction of OH with CH3SH and C2H5SH have been determined under pseudo‐first‐order conditions, using the discharge flow‐resonance fluorescence technique. The measured room temperature rate constants are (2.56±0.44)×10−11 and (3.67±0.18)×10−11 cm3 molecule−1 s−1 for CH3SH and C2H5SH, respectively. The CH3SH results are compared to those of previous studies, employing different experimental techniques.

Interests in the gas‐phase oxidation of organic sulfur compounds have become increasingly evident due to the important roles that these compounds may play in combustion processes, atmospheric chemistry, and photochemical air pollution. The rate constants for the reaction of O(3P) with thiophene (C4H4S) have been determined for the first time under pseudo‐first‐order reaction conditions, using the discharge flow–resonance fluorescence technique. The measured rate constants over a temperature reange 262–448 K are well represented by the Arrhenius expression k = (3.34±0.34)×10−11exp[−(1130±60)/RT] cm3 molecule−1 s−1. However, a discontinuity in the Arrhenius plot is noted around 262 K. The results are discussed in terms of different reaction pathways and compared with other compounds having similar molecular structures and various reactivities.

Rate constants for the oxidation reactions of organic sulfur compounds have become increasingly important due to their potential role in the formation of tropospheric and stratospheric sulfate aerosols. The present study deals with the reaction of the ground state oxygen atom with dimethyl sulfide. A discharge fast flow–resonance fluorescence technique was used to follow the decay of O(3P) atoms in the presence of excess CH3SCH3 under pseudo‐first‐order conditions. Kinetic data, obtained over the temperature range 272 to 472 K, are well represented by the Arrhenius expression, kbi= (1.28±0.12) ×10−11 exp[(803±60)/RT] cm3 molecule−1 sec−1. The results are compared to those of previous studies which employed different experimental techniques.

An experimental technique described with which the growth rate of a single solution droplet by water vapor condensation can be repeatedly measured with high precision. The technique involves the use of an electrodynamic cell to suspend a NaCl solution droplet in water vapor and a CO2 laser to momentarily perturb the droplet-vapor equilibrium. The droplet size change during condensational growth is monitored with a tunable dye laser for a particular optical resonance due to Mie scattering. A consideration of the coupled heat and mass transfer processes during droplet growth indicates that the best agreement between theory and the experimental results is obtained with a condensation coefficient close to unity.

Thermodynamic properties of hydrated monobalent strontium ions in the gas phase were measured over the temperature range 38–400°C using high pressure mass spectrometry. Clusters up to 11 water molecules about a strontium ion were observed. The hydration enthalpies and entropies for the clusters, Sr(H2O)n, n?9 were derived from appropriate van’t Hoff plots. The exceptional stability of the clusters observed in the present study indicates the importance of valence electrons of the central ion in pormoting chemical bonding with the clustering water molecules.

Thermodynamic properties of hydrated monovalent lead ions in the gas phase were measured over the temperature range 2–144°C using high‐pressure mass spectrometry. Clusters of up to eight water molecules about a lead ion were observed. The hydration enthalpies and entropies for the clusters, Pb+(H2O)m, m≤ 6, are derived from appropriate van't Hoff plots. The implication of the data in terms of the bonding of the small clusters and the distribution of lead ions in the atmosphere are discussed.

The results of an experimental study of the behavior of fission products released from metallic uranium and a U-3.5%Mo alloy into helium and air are reported. A thermochromatographic technique for ...

Rate constants for the oxidation reactions of organic sulfur compounds have become increasingly important due to the potential role of these compounds in the formation of tropospheric and stratospheric sulfate aerosols. The present study deals with the reaction of the ground state oxygen atom with dimethyl disulfide (DMDS). The discharge fast flow–resonance fluorescence technique was used to monitor the decay of O(3P) concentration in the presence of excess CH3SSCH3 under pseudo‐first‐order conditions. Over a temperature range from 270 to 329 K, and a pressure range from 0.52 to 2.60 Torr, no variation of the rate constant with temperature and pressure was observed. The results are best represented by the temperature and pressure independent value of (2.12±0.22)×10−10 cm3 molecule−1 s−1, which is about one‐half the theoretical collision frequency. The zero activation energy for this reaction is discussed in terms of the temperature dependence of other sulfur compound–oxygen atom reactions reported in the ...

Interests in the gas phase oxidation of heterocyclic organic compounds containing oxygen, nitrogen, or sulfur have become increasingly evident due to the important roles that these compounds may play in combustion processes, atmospheric chemistry, and photochemical air pollution. The rate constants for the reactions of OH with furan (C4H4O) and thiophene (C4H4S) have been determined for the first time under pseudo‐first‐order conditions, using the discharge flow‐resonance fluorescence technique. The measured room temperature rate constants are (2.31±0.40)×10−13, (1.05±0.08)×10−10, and (4.77±0.63)×10−11 cm3/molecule−1 s−1 for ethane, furan, and thiophene, respectively. The results are discussed in terms of structural differences and probable reaction pathways.

Optical Mie scattering technique is applied in the study of the growth of a single saline solution droplet. A quadrupole particle chamber is used to suspend a charged sodium chloride solution droplet in a water vapor environment. The droplet-vapor equilibrium is momentarily shifted by the heating effect of an infrared laser and the subsequent condensational growth of this droplet is monitored by means of right angle Mie scattering. Simultaneous mass and heat transfer processes are considered, and the mass accommodation coefficient for water is deduced.