Universal scaling laws of diffusion in a binary fluid mixture

A new universal scaling law relating the self-diffusivities of a binary fluid mixture and the excess entropies of its components is derived using mode coupling theory, reproducing the empirical scaling laws of Dzugutov [Nature (London) 381, 137 (1996)] and Hoyt et al. [Phys. Rev. Lett. 85, 594 (2000)] as special cases. The derived scaling laws are tested through numerical calculations for binary Lennard-Jones fluid mixtures for a wide range of physical parameters, and a very good correlation is observed. We have also arrived at a new universal scaling relationship between the cross-diffusivity and entropy for the first time.

Physiological response to the ambulatory performance of hand-rim and arm-crank propulsion systems

Two types of propulsion systems-the hand rim (HR) and the arm crank (AC)-are commonly used in wheelchair ambulation. The purpose of this study was to investigate the physiological response of the two propulsion systems under actual locomotive condition by the actual users. The energetics of locomotion manual wheelchair (HR propulsion) and arm-propelled three-wheeled chairs (AC-propelled) at their free chosen speed (FCS) were studied and compared. Thirty-four male subjects with dysfunctioning lower limbs; 17 manual wheelchair users and 17 arm-propelled three-wheeled chairs regular users volunteered to participate in the study. Speed (m.min-1), oxygen uptake (1 x min(-1)) and heart rate (b x min(-1)) were monitored during steady-state ambulation at FCS for 5 min. Oxygen consumption (VO2, ml x kg(-1) min(-1)), oxygen cost (VO2, ml x kg(-1) m(-1)), net locomotive energy cost (kcal kg(-1) km(-1)) and physiological cost index (b x m(-1)) were derived. The FCS of the AC propelled device is remarkably higher than the HR system, and the magnitude of the physiological variables of the AC propulsion system was significantly lower (p<0.001) in relation to the HR propulsion system, as revealed from the results of t test for two sample means at a significance level p=0.001. It can be inferred from the result that the AC propulsion system could be used for long distance rides with a higher speed required for outdoor ambulation and that the HR propulsion system is suitable only for indoor use, because of its excellent maneuverability where short-duration low-velocity ambulation is required.

Phase-transfer catalyst-induced changes in the absorption and fluorescence behavior of some electron donor-acceptor molecules

The quaternary ammonium salts find extensive use in a variety of chemical applications as surfactants and phase-transfer catalysts. Even though the interaction of the surfactants with various systems has been studied rather extensively, very little information is available on how the phase-transfer catalysts (PTC) interact with the dipolar systems in nonpolar media and how/whether these solubilizing agents affect the properties of the dissolved molecules. In this paper, the interaction of several tetraalkylammonium salts, commonly used as PTC, with a number of electron donor-acceptor (EDA) systems has been studied by absorption and fluorescence spectroscopy. The phase-transfer catalysts have been found to affect both the absorption and fluorescence properties of the EDA systems. The spectral changes of the EDA molecules induced by the tetraalkylammonium salts suggest the formation of an 1:1 complex between the two in nonpolar media. An electrostatic interaction between the phase-transfer catalysts (which exist as ion pairs in nonpolar media) and the dipolar molecules is shown to be the driving force for the formation of the complex. The dependence of the formation constant of the complex on the polarity of the media suggests a charge-transfer nature of the complex. It is shown that the anionic component of the salts serves as a source of electron to the positive end of the dipolar molecule, while the tetraalkylammonium cation, besides helping solubilization of its anionic counterpart in the nonpolar media, serves neutralizing the negative charge at the acceptor end of the EDA molecule. In effect, a cooperative influence of the cationic and anionic components of the PTC enhances the charge separation within the dipolar fluorophores. On the basis of the PTC-induced changes in the photophysical behavior of the EDA molecules, a possible structure for the 1:1 complex has been proposed. It has been concluded that a phase-transfer catalyst should not be treated as an innocuous substance that merely helps transfer of a polar substance from a polar to a nonpolar environment. Instead, it is demonstrated that the association of a PTC with a dipolar species can significantly change various properties of the latter.

Physical fitness training for wheelchair ambulation by the arm crank propulsion technique

OBJECTIVE

To observe the effect of endurance training on novice users of an arm-propelled three-wheeled chair (APTWC), powered by asynchronous arm crank propulsion, in actual locomotive conditions.

STUDY DESIGN

A continuous endurance training programme was administered by instructing subjects to propel themselves at free chosen speed (FCS) for 15 minutes, twice daily. Data were collected at two-week intervals consecutively and this was continued until the maximum beneficial effect was achieved.

SETTING

The study was conducted in outdoor settings similar to those the users encountered in their everyday life.

SUBJECTS

Twelve male paraplegics (below T10), age 30.5 +/- 8.59 years, weight 41.75 kg (+/- 5.76) recommended to use the APTWC as an ambulatory device.

INTERVENTION

The propulsion speed (metres per minute), peak heart rate (beats per minute) and oxygen uptake (litres per minute) were measured in consecutive sessions at two-week intervals. Physiological cost index (beats m(-1)), oxygen consumption (ml kg(-1) min(-1)) and oxygen cost (ml kg(-1) m(-1)) were derived to assess fitness level.

RESULTS

Significant changes were observed in the variables following endurance training for 12 weeks. The propulsion speed increased considerably and the cardiorespiratory parameters were found to be reduced. One-way analysis of variance was done for each parameter separately for seven sets of readings taken to assess the overall change over the study period of 12 weeks. The F-ratios were found to be significant (p < 0.01) in each case, except for body weight and oxygen uptake. The pairwise comparison of the biweekly results of the parameters which showed an overall significant change over the study period revealed that after the first two weeks there was considerable change (p < 0.01) for all the parameters. The trend was upward for speed and downward for the other cardiovascular stress parameters. These trends continued until the 10th week showing significant change, after which the values become stable as was revealed by thestatistical tests (p > 0.05). The percentage difference in the mean values from the initial stage (before training) to the 12th week ranged from 10.44% in the case of heart rate to 69.70% in the case of propulsion speed.

CONCLUSION

Self-ambulation at free chosen speed regularly for 10-12 weeks provides efficiency and improves fitness status required for wheelchairs driven by an asynchronous arm crank propulsion technique and no special exercise programme is required.

Photochemical E (trans)-->Z (cis) isomerization in substituted 1-naphthylacrylates

Substituted naphthylacrylates, 1-3, not showing rotamerism have been synthesized with a view to study photochemical E (trans)-->Z (cis) isomerization. Photostationary state composition of the isomers upon direct excitation, triplet sensitized isomerization, quantum yield of isomerization, and steady state and time-resolved fluorescence behavior have been studied for these naphthylacrylates. The direct excitations of the compounds yield high Z (approximately 80%) isomer composition, whereas the triplet sensitization results in less Z (approximately 20%) isomer composition. This indicates that the singlet pathway is very efficient in converting the E isomer to the Z isomer. The naphthylacrylates 1 and 2 exhibit structured fluorescence at room temperature in hexane and upon changing the solvent to CH3CN; the structure of the fluorescence is lost, indicating that the singlet excited-state develops a polar character in a polar environment. The polar nature of the singlet excited state becomes more clear in the case of 3 from its fluorescence solvatochromism. The naphthylacrylates did not exhibit excitation wavelength-dependent fluorescence at room temperature suggesting that the ground state conformers (rotamers) are not involved. Fluorescence lifetimes measured for these compounds displayed biexponential behavior, which is explained using a two-state model.

Long-term mortality and morbidity of transfusion-associated non-A, non-B, and type C hepatitis: A National Heart, Lung, and Blood Institute collaborative study

Persons with non-A, non-B hepatitis (cases) identified in 5 transfusion studies in the early 1970s have been followed ever since and compared for outcome with matched, transfused, non-hepatitis controls from the same studies. Previously, we reported no difference in all-cause mortality but slightly increased liver-related mortality between these cohorts after 18 years follow-up. We now present mortality and morbidity data after approximately 25 years of follow-up, restricted to the 3 studies with archived original sera. All-cause mortality was 67% among 222 hepatitis C-related cases and 65% among 377 controls (P = NS). Liver-related mortality was 4.1% and 1.3%, respectively (P =.05). Of 129 living persons with previously diagnosed transfusion-associated hepatitis (TAH), 90 (70%) had proven TAH-C, and 39 (30%), non-A-G hepatitis. Follow-up of the 90 TAH-C cases revealed viremia with chronic hepatitis in 38%, viremia without chronic hepatitis in 39%, anti-HCV without viremia in 17%, and no residual HCV markers in 7%. Thirty-five percent of 20 TAH-C patients biopsied for biochemically defined chronic hepatitis displayed cirrhosis, representing 17% of all those originally HCV-infected. Clinically evident liver disease was observed in 86% with cirrhosis but in only 23% with chronic hepatitis alone. Thirty percent of non-A, non-B hepatitis cases were unrelated to hepatitis viruses A,B,C, and G, suggesting another unidentified agent. In conclusion, all-cause mortality approximately 25 years after acute TAH-C is high but is no different between cases and controls. Liver-related mortality attributable to chronic hepatitis C, though low (<3%), is significantly higher among the cases. Among living patients originally HCV-infected, 23% have spontaneously lost HCV RNA.

Modification of biophysical properties of lung epithelial Na(+) channels by dexamethasone

There is considerable interest in identifying the basic mechanisms by which dexamethasone alters ion transport across the adult alveolar epithelium. Herein, we incubated synchronized A549 cells, a human alveolar epithelial cell line, with dexamethasone (1 microM) for 24-48 h. When normalized to HPRT (a housekeeping gene), A549 beta- and gamma-subunit mRNA levels for the human amiloride-sensitive epithelial sodium channel (hENaC), assessed by RT-PCR, increased by 1.6- and 17-fold respectively, compared with control values (P < 0.05). These changes were abolished by actinomycin D, indicating transcriptional regulation. Western blotting studies revealed that dexamethasone also increased expression of beta- and gamma-hENaC protein levels. In contrast, alpha-hENaC mRNA increased by onefold (P > 0.05) and alpha-hENaC protein level was unchanged. Incubation of A549 cells with dexamethasone increased their whole cell amiloride-sensitive sodium currents twofold and decreased the K(0.5) for amiloride from 833 +/- 69 to 22 +/- 5.4 nM (mean +/- SE; P < 0.01). Single channel recordings in the cell-attached mode showed that dexamethasone treatment increased single channel open time and open probability threefold and decreased channel conductance from 8.63 +/- 0.036 to 4. 4 +/- 0.027 pS (mean +/- SE; P < 0.01). We concluded that dexamethasone modulates the amiloride-sensitive Na(+) channels by differentially regulating the expression of beta- and gamma-subunits at the mRNA and protein levels in the human A549 cell line, with little effect on alpha-hENaC subunit.

Aberrant processing of oxidative DNA damage in systemic lupus erythematosus

Defective DNA damage processing has been reported in systemic lupus erythematosus (SLE). Vitamin C may modulate formation/removal of the oxidative DNA lesion 8-oxo-2'-deoxyguanosine (8-oxodG). Baseline levels of 8-oxodG measured in SLE serum, urine and PBMC DNA did not differ significantly from healthy subjects. In contrast to healthy subjects, no significant decrease in PBMC 8-oxodG or increase in urinary 8-oxodG was noted in vitamin C supplemented SLE patients. A significant, although attenuated, increase in serum 8-oxodG was detected in SLE patients, compared to healthy subjects. These data support putative abnormalities in the repair/processing of 8-oxodG in SLE.

Evaluation of ambulatory performance of the arm propelled three-wheeled chair using heart rate as a control index

PURPOSE

The Arm propelled three wheeled chair (APTWC) is in common use in the economically poor countries for outdoor ambulation, the propulsion force of which is exerted by arm cranking in asynchronous fashion. The purpose of the study was to assess the ambulatory performance of the users of the device using heart rate as a control index, at graded speeds.

METHOD

Fifteen regular users of APTWC male with paraplegia and poliomyelitis were ambulated at seven different graded speeds in outdoor settings and the resting and ambulatory heart rate was measured during steady state and then physiological cost index and comfortable speed of propulsion was computed.

RESULTS

The physiological strain, linear regression of the relationship between heart rate and speed with correlation coefficient of r = 0.86 (p < 0.001), polynomial regression of the relationship between physiological cost index (PCI) and speed with correlation coefficient of r = 0.83 (p < 0.001) and comfortable speed of propulsion (120 m/min) was reported.

CONCLUSIONS

Heart rate can be used to evaluate the ambulatory performance of the device, quantifying energy economy for outcome evaluation and decision making for clinical recommendation.

Biophysical properties and molecular characterization of amiloride-sensitive sodium channels in A549 cells

Amiloride-sensitive Na(+) channels, present in fetal and adult alveolar epithelial type II (ATII) cells, play a critical role in the reabsorption of fetal fluid shortly after birth and in limiting the extent of alveolar edema across the adult lung. Because of the difficulty in isolating and culturing ATII cells, there is considerable interest in characterizing the properties of ion channels and their response to injury of ATII cell-like cell lines such as A549 that derive from a human alveolar cell carcinoma. A549 cells were shown to contain alpha-, beta-, and gamma-epithelial Na(+) channel mRNAs. In the whole cell mode of the patch-clamp technique (bath, 145 mM Na(+); pipette, 145 mM K(+)), A549 cells exhibited inward Na(+) currents reversibly inhibited by amiloride, with an inhibition constant of 0.83 microM. Ion substitution studies showed that these channels were moderately selective for Na(+) (Na(+)-to-K(+) permeability ratio = 6:1). Inward Na(+) currents were activated by forskolin (10 microM) and inhibited by nitric oxide (300 nM) and cGMP. Recordings in cell-attached mode revealed the presence of an amiloride-sensitive Na(+) channel with a unitary conductance of 8.6 +/- 0.04 (SE) pS. Channel activity was increased by forskolin and decreased by nitric oxide and the cGMP analog 8-bromo-cGMP. These data demonstrate that A549 cells contain amiloride-sensitive Na(+) channels with biophysical properties similar to those of ATII cells.

Development of amphotericin B loaded nanoparticles

Amphotericin B loaded nanoparticles were successfully prepared by in-situ emulsion polymerization technique using Ethylcyanoacrylate monomer. Scanning Electron Micrographs (SEM) of the nanoparticles showed that the particles were spherical and discrete. Average particle size analysis of two samples were found to be within the range of 475.3 +/- 91.68 to 479.75 +/- 105.49 nm. Thus the particles formed were within the colloidal range. With increase in monomer concentration, the percentages of drug adsorbed on the surface of nanoparticles were also increased. At the optimum concentration of Ethylcyanoacrylate (21.6 microliters/ml), 72.1% of Amphotericin B was adsorbed.