The effect of temperature, composition and alcohols on the microstructures of catanionic mixtures of sodium dodecylsulfate and cetyltrimethylammonium bromide in water.

The influence of mixing protocol, composition, temperature, ageing and added alcohols on the characteristics of the microstructures of sodium dodecylsulfate (SDS) + cetyltrimethylammonium bromide (CTAB) mixtures has been investigated in this paper. In this catanionic mixture (1 weight% total surfactant content) temperature induced microstructural transition occurs, which is (i) a micelle-to-vesicle transition (MVT) if αSDS (mole fraction of SDS) = 0.7, 0.8 or 0.9 and (ii) a vesicle-to-micelle transition (VMT) if αSDS = 0.1, 0.2 or 0.3. In the mixture of αSDS = 0.7, specific conductivity and dynamic light scattering measurements also support the occurrence of MVT. Transition electron microscopy and small angle neutron scattering measurements were also made to assess the characteristics of the microstructures. Alcohols added to the mixture of αSDS = 0.7 reduced the size of the vesicle, while only monohydric alcohols suppressed the temperature induced transition indicating that the number and location of -OH groups of the alcohols have a dramatic modulating influence on the structural transition occurring in catanionic mixtures. The influence of the alcohols is explained in terms of changes produced in the dielectric constant and hydrophobicity of the medium.

Effect of sodium salicylate and sodium deoxycholate on fibrillation of bovine serum albumin: comparison of fluorescence, SANS and DLS techniques.

The impact of biocompatible additives on the fibrillation and defibrillation of proteins provides valuable insight into the development of suitable formulations for the treatment of protein-related diseases or the storage of proteins in the laboratory. We have studied the effects of the addition of sodium deoxycholate (NaDC) and sodium salicylate (NaSal) on the fibrillation of bovine serum albumin (BSA) using fluorescence, circular dichroism, dynamic light scattering (DLS) and small angle neutron scattering (SANS). Spectroscopic studies indicate that the additives are adsorbed on the surfaces of proteins and change their secondary structures, irrespective of the sequence of addition. DLS and SANS studies show that the addition of either NaSal or NaDC to native proteins slows down or arrests the formation of fibrils. However, the additives do not defibrillate preformed fibrils when added after fibril formation. Thus, NaSal and NaDC can act as potential adjuvants for the prevention of fibril formation in BSA solutions.

Magnetic exchange interactions and non-Debye relaxation in spin-3/2 frustrated Kagomé magnet Co3V2O8.

We report the experimental determination of the magnetic exchange parameter (J/kB= 2.88 ± 0.02 K) for the Spin-3/2 ferromagnetic (FM) Kagomé lattice system: Co3V2O8using the temperature dependence of dc-magnetic susceptibilityχ(T) data by employing the fundamental Heisenberg linear chain model. Our results are quite consistent with the theoretically reported nearest neighbor dominant FM exchange coupling strengthJex-NN∼2.45 K. Five different magnetic phase transitions (6.2-11.2 K) and spin-flip transitions (9.6-7.7 kOe) have been probed using the∂(χT)/∂Tvs.T, heat capacity (CP-T) and differential isothermal magnetization curves. Among such sequence of transitions, the prominent ones being incommensurate antiferromagnetic (AFM) state at 11.2 K, commensurate AFM state at 8.8 K, and commensurate FM state across 6.2 K. All the successive magnetic phase transitions have been mapped onto a single H-T plane through which one can easily distinguish the above-mentioned different phases. The magnetic contribution of theCP-TnearTN(11.2 K) has been analyzed using the power-law expressionCM=A|T-TN|-αresulting in the critical exponentα= 0.18 ± 0.01 (0.15 ± 0.003) forTTN), respectively for the Co3V2O8. It is interesting to note that non-Debye type dipole relaxation is quite prominent in Co3V2O8and was evident from the Kohlrausch-Williams-Watts analysis of complex modulus and impedance spectra (0⩽ß⩽1). Mott's variable-range hopping of charge carriers process is evident through the resistivity analysis (ρac-T-1/4) in the temperature range 275 ∘C-350 ∘C. Moreover, the frequency-dependent analysis ofσac(ω) follows Jonscher's power law yielding two distinct activation energies (Ea∼0.37 and 2.29 eV) between the temperature range 39 ∘C-99 ∘C and 240 ∘C-321 ∘C.

Neutron interferometry using a single modulated phase grating.

Neutron grating interferometry provides information on phase and small-angle scatter in addition to attenuation. Previously, phase grating moiré interferometers (PGMI) with two or three phase gratings have been developed. These phase-grating systems use the moiré far-field technique to avoid the need for high-aspect absorption gratings used in Talbot-Lau interferometers (TLI) that reduce the neutron flux reaching the detector. We first demonstrate, through theory and simulations, a novel phase grating interferometer system for cold neutrons that requires a single modulated phase grating (MPG) for phase-contrast imaging, as opposed to the two or three phase gratings in previously employed PGMI systems. The theory shows the dual modulation of MPG with a large period and a smaller carrier pitch P, resulting in large fringes at the detector. The theory was compared to the full Sommerfeld-Rayleigh diffraction integral simulator. Then, we proceeded to compare the MPG system to experiments in the literature that use a two-phase-grating-based PGMI with best-case visibility of around 39%. The simulations of the MPG system show improved visibility in comparison to that of the two-phase-grating-based PGMI. An MPG with a modulation period of 300 µm, the pitch of 2 µm, and grating heights with a phase modulation of (π,0, illuminated by a monochromatic beam produces visibility of 94.2% with a comparable source-to-detector distance (SDD) as the two-phase-grating-based PGMI. Phase sensitivity, another important performance metric of the grating interferometer, was compared to values available in the literature, viz. the conventional TLI with the phase sensitivity of 4.5 × 103 for an SDD of 3.5 m and a beam wavelength of 0.44 nm. For a range of modulation periods, the MPG system provides comparable or greater theoretical maximum phase sensitivity of 4.1 × 103 to 10.0 × 103 for SDDs of up to 3.5 m. This proposed MPG system appears capable of providing high-performance PGMI that obviates the need for the alignment of two phase gratings.

Aggregation behavior of sodium dioctylsulfosuccinate in aqueous ethylene glycol medium. A case of hydrogen bonding between surfactant and solvent and its manifestation in the surface tension isotherm.

The dependence of critical micelle concentration (cmc) of sodium dioctylsulfosuccinate (AOT) on the amount of ethylene glycol (EG) in water + EG medium was reported to be unusual and different from that of other surfactants to the extent that the cmc of AOT in EG is lower than in water. It is yet to be understood why AOT behaves so in water + EG medium, although AOT is known to have some special properties. Hence in the present study cmc of AOT in water + EG medium in the range from 0 to 100% (by weight) EG is measured by using surface tension and fluorescence emission methods. In contrast to what was reported, this study revealed that with respect to EG amount the cmc of AOT follows the general trend and AOT has higher cmc in EG than in water. On the other hand, it was surprisingly found that a break in the surface tension isotherm occurs in the premicellar region when the amount of EG exceeds 50% rendering a bisigmoidal shape to the surface tension isotherm. UV spectral study showed that AOT and EG undergo hydrogen bonding in the premicellar region when the EG amount is ≥50% and this hydrogen bonding becomes less on adding NaCl. The density functional theory calculations also showed formation of hydrogen bonds between EG and AOT through the sulfonate group of AOT providing thereby support to the experimental findings. The calculations predicted a highly stable AOT-EG-H(2)O trimer complex with a binding energy of -37.93 kcal mol(-1). The present system is an example, which is first of its kind, of a case where hydrogen bonding with surfactant and solvent molecules results in a surface tension break.

Micellar shape driven counterion binding. Small-angle neutron scattering study of AOT micelle.

Sodium dioctylsulfosuccinate (AOT) micelle has a special counterion binding behavior in aqueous electrolyte medium, viz., the counterion binding constant (ß) abruptly increases by 2-fold at about 0.015 mol dm(-3) NaCl concentration (c*), but not in sodium salicylate (NaSa) solution. Since counterions affect the structure and performance of ionic surfactants, ascertaining the cause for the sudden shift in the ß value of AOT micelle is of fundamental importance. In this study the special counterion binding behavior of AOT micelle has been ascertained at 40 °C by carrying out surface tension, zeta potential, and fluorescence emission (pyrene probe) measurements. The results of the small-angle neutron scattering experiment carried out at 40 °C showed that at c* the shape of AOT micelle changes from prolate spheroid to rodlike in NaCl solution, but not in NaSa solution, thus establishing micellar shape change as responsible for the abrupt change in ß value. The absence of sudden shift in ß of AOT micelle in NaSa solution is attributed to the binding of salicylate coanion to AOT micelle through hydrophobic interaction.

Prevalence of Spontaneous Asymptomatic Facial Nerve Canal Meningoceles: A Retrospective Review.

BACKGROUND AND PURPOSE: The prevalence of patent facial nerve canals and meningoceles along the facial nerve course is unknown. This study aimed to assess the frequency of such findings in asymptomatic patients. MATERIALS AND METHODS: A retrospective review was completed of patients with high-resolution MR imaging of the temporal bone whose clinical presentations were unrelated to facial nerve pathology. Facial nerve canals were assessed for the presence of fluid along each segment and meningoceles within either the labyrinthine segment (fluid-filled distention, ≥1.0-mm diameter) or geniculate ganglion fossa (fluid-filled distention, ≥2.0-mm diameter). If a meningocele was noted, images were assessed for signs of CSF leak. RESULTS: Of 204 patients, 36 (17.6%) had fluid in the labyrinthine segment of the facial nerve canal and 40 (19.6%) had fluid in the geniculate ganglion fossa. Five (2.5%) had meningoceles of the geniculate ganglion fossa; no meningoceles of the labyrinthine segment of the canal were observed. No significant difference was observed in the ages of patients with fluid in the labyrinthine segment of the canal or geniculate ganglion compared with those without fluid (P = .177 and P = .896, respectively). Of the patients with a meningocele, one had a partially empty sella and none had imaging evidence of CSF leak or intracranial hypotension. CONCLUSIONS: Fluid within the labyrinthine and geniculate segments of the facial nerve canal is relatively common. Geniculate ganglion meningoceles are also observed, though less frequently. Such findings should be considered of little clinical importance without radiologic evidence of CSF otorrhea, meningitis, or facial nerve palsy.

Linear stability, transient energy growth, and the role of viscosity stratification in compressible plane Couette flow.

Linear stability and the nonmodal transient energy growth in compressible plane Couette flow are investigated for two prototype mean flows: (a) the uniform shear flow with constant viscosity, and (b) the nonuniform shear flow with stratified viscosity. Both mean flows are linearly unstable for a range of supersonic Mach numbers (M). For a given M , the critical Reynolds number (Re) is significantly smaller for the uniform shear flow than its nonuniform shear counterpart; for a given Re, the dominant instability (over all streamwise wave numbers, alpha ) of each mean flow belongs to different modes for a range of supersonic M . An analysis of perturbation energy reveals that the instability is primarily caused by an excess transfer of energy from mean flow to perturbations. It is shown that the energy transfer from mean flow occurs close to the moving top wall for "mode I" instability, whereas it occurs in the bulk of the flow domain for "mode II." For the nonmodal transient growth analysis, it is shown that the maximum temporal amplification of perturbation energy, G(max), and the corresponding time scale are significantly larger for the uniform shear case compared to those for its nonuniform counterpart. For alpha=0 , the linear stability operator can be partitioned into L ~ L+Re(2) L(p), and the Re-dependent operator L(p) is shown to have a negligibly small contribution to perturbation energy which is responsible for the validity of the well-known quadratic-scaling law in uniform shear flow: G(t/Re) ~ Re(2). In contrast, the dominance of L(p) is responsible for the invalidity of this scaling law in nonuniform shear flow. An inviscid reduced model, based on Ellingsen-Palm-type solution, has been shown to capture all salient features of transient energy growth of full viscous problem. For both modal and nonmodal instability, it is shown that the viscosity stratification of the underlying mean flow would lead to a delayed transition in compressible Couette flow.

Coexisting exchange bias effect and ferroelectricity in geometrically frustrated ZnCr2O4.

Concomitant occurrence of exchange bias effect and ferroelectric order is revealed in antiferromagnetic spinel ZnCr2O4. The exchange bias effect is observed below antiferromagnetic Neél temperature (T N) with a reasonable value of exchange bias field ([Formula: see text] Oe at 2 K). Intriguingly, the [Formula: see text] ratio is found unusually high as ∼2.2, where H C is the coercivity. This indicates that large H C is not always primary for obtaining large exchange bias effect. Ferroelectric order is observed at T N, where non-centrosymmetric magnetic structure with [Formula: see text] space group associated with the magnetoelectric coupling correlates the ferroelectric order, proposing that, ZnCr2O4 is an improper multiferroic material. Rare occurrence of exchange bias effect and ferroelectric order in ZnCr2O4 attracts the community for fundamental interest and draws special attention in designing new materials for possible electric field control of exchange bias effect.

Estimation of the Rigid-Body Motion from Three-Dimensional Images Using a Generalized Center-of-Mass Points Approach.

We present an analytical method for the estimation of rigid-body motion in sets of three-dimensional SPECT and PET slices. This method utilizes mathematically defined generalized center-of-mass points in images, requiring no segmentation. It can be applied to compensation of the rigid-body motion in both SPECT and PET, once a series of 3D tomographic images are available. We generalized the formula for the center-of-mass to obtain a family of points co-moving with the object's rigid-body motion. From the family of possible points we chose the best three points which resulted in the minimum root-mean-square difference between images as the generalized center-of-mass points for use in estimating motion. The estimated motion was used to sum the sets of tomographic images, or incorporated in the iterative reconstruction to correct for motion during reconstruction of the combined projection data. For comparison, the principle-axes method was also applied to estimate the rigid-body motion from the same tomographic images. To evaluate our method for different noise levels, we performed simulations with the MCAT phantom. We observed that though noise degraded the motion-detection accuracy, our method helped in reducing the motion artifact both visually and quantitatively. We also acquired four sets of the emission and transmission data of the Data Spectrum Anthropomorphic Phantom positioned at four different locations and/or orientations. From these we generated a composite acquisition simulating periodic phantom movements during acquisition. The simulated motion was calculated from the generalized center-of-mass points calculated from the tomographic images reconstructed from individual acquisitions. We determined that motion-compensation greatly reduced the motion artifact. Finally, in a simulation with the gated MCAT phantom, an exaggerated rigid-body motion was applied to the end-systolic frame. The motion was estimated from the end-diastolic and end-systolic images, and used to sum them into a summed image without obvious artifact. Compared to the principle-axes method, in two of the three comparisons with anthropomorphic phantom data our method estimated the motion in closer agreement to than of the Polaris system than the principal-axes method, while the principle-axes method gave a more accurate estimation of motion in most cases for the MCAT simulations. As an image-driven approach, our method assumes angularly complete data sets for each state of motion. We expect this method to be applied in correction of respiratory motion in respiratory gated SPECT, and respiratory or other rigid-body motion in PET.

The tau mutation in the Syrian hamster differentially reprograms the circadian clock in the SCN and peripheral tissues.

The hypothalamic suprachiasmatic nuclei (SCN), the principal circadian oscillator in mammals, are synchronized to the solar day by the light-dark cycle, and in turn, they coordinate circadian oscillations in peripheral tissues. The tau mutation in the Syrian hamster is caused by a point mutation leading to a deficiency in the ability of Casein Kinase 1epsilon to phosphorylate its targets, including circadian PER proteins. How this accelerates circadian period in neural tissues is not known, nor is its impact on peripheral circadian oscillators established. We show that this mutation has no effect on per mRNA expression nor the nuclear accumulation of PER proteins in the SCN. It does, however, accelerate the clearance of PER proteins from the nucleus to an extent sufficient to explain the shortened circadian period of behavioral rhythms. The mutation also has novel, unanticipated consequences for circadian timing in the periphery, including tissue-specific phase advances and/or reduced amplitude of circadian gene expression. The results suggest that the tau mutation accelerates a specific phase, during mid-late subjective night of the SCN circadian feedback loop, rather than cause a global compression of the entire cycle. This reprogrammed output from the clock is associated with peripheral desynchrony, which in turn could account for impaired growth and metabolic efficiency of the mutant.

8pter-p23 deletion is associated with racial differences in prostate cancer outcome.

Deletions of chromosome sequences mapping to the short arm of chromosome 8 have been observed frequently in a variety of human cancers. A small number of studies have suggested that the terminal portion of the short arm of chromosome 8, 8pter-p23, may be deleted independently of other portions of 8p in human tumors, and that deletion of the 8pter-p23 region may be correlated with poor prognosis. The aim of the present study was to physically define the minimal region of 8pter-p23 deletion and to define the frequency and prognostic significance of 8pter-p23 loss in human prostate tumors. DNA was purified from normal and tumor tissues of 45 radical prostatectomy specimens and amplified for 15 highly polymorphic microsatellite sequences, 13 spanning 8pter-p23 and 2 proximal 8p markers. Allelic loss of 8p sequences was observed in 28 of 45 (62%) tumors examined. Of these, approximately half (12 of 28; 43%) demonstrated independent loss of the 8pter-p23 region, with several tumors defining a 5-cM minimal region of deletion spanning D8S264-D8S1824-D8S1781-D8S262-D8S1798. When serum prostate-specific antigen was used as a surrogate end point marker for survival, 8pter-p23 loss was significantly associated with reduced disease-free progression (log-rank P = 0.0426). Moreover, loss of the 8pter-p23 region was significantly associated with poor survival for American Caucasian (log-rank P = 0.0024) but not African-American (log-rank P = 0.5832) prostate cancer patients. These studies suggest that independent deletion of 8pter-p23 is differentially associated with disease recurrence and poor outcome in American Caucasian but not African-American prostate cancer patients.

Cognitive function in younger type II diabetes.

OBJECTIVE: To examine central nervous system involvement as a possible complication of diabetes by performing a comprehensive neuropsychological evaluation of relatively young (age < 55 years) NIDDM patients and a group of control subjects. RESEARCH DESIGN AND METHODS: A cross-sectional comparative study of 28 patients, with duration of diabetes 5-18 years (mean +/- SD +/- 3.2 years), screened for acceptable glycemic control and absence of hypoglycemia on the day of examination, compared with 28 demographically similar, nondiabetic control subjects. Neuropsychometric tests performed were Mini-Mental Status Examination (MMSE), Neurobehavioral Cognitive Status Examination (NCSE), and P300 latencies (endogenous evoked potentials). RESULTS: Seven (25.0%) patients reported history suggestive of cognitive impairment during day-to-day activities, and 17 (60.7%) had distal symmetrical polyneuropathy. Average P300 latencies were significantly delayed among the diabetic patients compared with the control subjects (349.5 +/- 28.2 vs. 312.9 +/- 19.3 ms; t = 5.68, P < 0.001). Although there was no significant difference in MMSE scores, compared with control subjects significantly more patients had impairment in NCSE tests of attention (chi 2 = 7.38, P < 0.01), repetition (chi 2 = 4.073, P < 0.05), and memory (chi 2 = 5.83, P < 0.05), while there was no significant difference in tests of comprehension, naming, construction, and calculation. Duration of diabetes, HbA1c levels, and the presence of distal symmetrical polyneuropathy among patients each did not correlate with any of the parameters of cognitive function evaluated. Higher blood glucose levels during the electrophysiological testing were associated with less delay in P300 latencies among the patients. CONCLUSIONS: Central nervous system impairment, manifesting as mild impairments in certain cognitive skills, should be recognized as a possible complication of long-standing NIDDM, even in relatively younger individuals.

Peptidylprolyl isomerase A (PPIA) as a preferred internal control over GAPDH and beta-actin in quantitative RNA analyses.

A good internal control is critical in all quantitative analyses of gene expression. Levels of bet-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and peptidylprolyl isomerase A (PPIA) were analyzed in 78 samples (data obtained from our laboratory and from a publicly available database at http://www.ncbi.nlm.nih.gov/SAGE/). These libraries included cell lines and tissues from brain, breast, colon, kidney, ovary, pancreas, prostate, skin, and vascular origin. The level of PPIA mRNA is the most constant among the three genes. Hence, our study suggests that PPIA is a better internal control than beta-actin or GAPDH, the two most commonly used internal controls.

MnPcS4: a new MRI contrast enhancing agent for tumor localisation in mice.

Manganese-tetrasulfonated phthalocyanine (MnPcS4) has been evaluated as a potential contrast agent in Magnetic resonance imaging (MRI) for tumor localisation in mice. MnPcS4 showed favourable molar relaxivity, much better than Gd-DTPA and comparable to tetrasulfonated manganese complex of porphyrin (TPPS4). Tumors showed selective retention of the metal complex (dye) with the peak value reached at 24 hours following intravenous administration. Dye concentration in tumors remained consistently higher than either kidney or muscle tissue both at 1 and 24 hours and a 10-fold increase in tumor-to-muscle ratio over the control was seen at 24 hr. Normal liver tissue, however, showed higher concentration than tumor at all times during the study. A linear correlation was found between longitudinal relaxation rate (1/T1) and the corresponding concentration of MnPcS4 in various tissues. MR imaging done in animals using 1.5 T superconducting clinical imager showed a mean percent increase in signal intensity of 131.8% (SD +/- 32.86) in the tumor and a 70% increase in tumor-to-muscle ratio over the pretreatment value, at 24 hr. The results suggest that MnPcS4 is a potential tumor-selective contrast agent in MRI.

A scanning electron microscope study of Raillietascaris varani (Baylis et Daubney, 1922) (Nematoda: Ascaridioidea).

The Raillietascaris varani (Baylis et Daubney, 1922), parasitic in the Indian monitor lizard, Varanus monitor (L.), was studied by scanning electron microscopy (SEM). A surface topography of the worm, especially the head and male tail, were described, illustrated and discussed with regard to the available data on this species, and also other species of ascaridoid nematodes. The present study confirms the previous observations from Sprent (1985), and also provides some additional information concerning the microtopography of the worm which might be useful in comparative studies on the Ascaridoidea.

Defining and measuring quality of diabetes care.

The literature on diabetes mellitus has increasingly focused on the quality of diabetes care and its measurement. Serious and widespread quality problems exist throughout American medicine. Current efforts to improve will not succeed unless we undertake a major, systematic effort to overhaul how we deliver health care services, educate and train clinicians, and assess and improve quality. This article defines the components of quality of diabetes care provision and discusses approaches to their measurement individually and globally.

Butanol solubilization in aqueous F127 solution: investigating the enhanced micellar solvation and consequent improvement in gelation characteristics.

Pluronics(®) are an important class of non-ionic surfactants because of their rich phase behavior and numerous industrial and biomedical applications. F127, an FDA approved Pluronic(®) is the most prominent member amongst them owing to its potential uses as vehicle for drug delivery and template for the fabrication of mesoporous materials. A cubic micellar gel formed by this copolymer above 15 wt% concentration is the commonly used form of self assembled structure for these applications. In this manuscript we report SANS, fluorescence and rheological studies on the effect of n-butanol on gelation characteristics of aqueous F127 solutions. The studies show that solubilization of n-butanol results in a large increase in viscosity of micellar solution at a fixed copolymer concentration, and leads to the formation of stiff gel at F127 concentration as low as 9 wt%. SANS and fluorescence studies attribute this to enhancement in micellar solvation due to solubilization of n-butanol. Quite interestingly, SANS studies show that n-butanol induced F127 gels form at significantly lower micellar volume fraction than the pure F127 gels. The observed improvement in gelation characteristics can have important bearing with the application in making mesoporous materials since n-butanol is used as co-surfactant to control pore size of such structures formed with F127 gels as template.

Additive induced core and corona specific dehydration and ensuing growth and interaction of Pluronic F127 micelles.

Pluronic F127 is considered to be the most prominent member amongst Pluronics owing to its uses in the fields of drug delivery and fabrication of mesoporous materials. Though extensive studies were carried out on the phase behavior of this copolymer, the effect of additives on restructuring and growth processes of its micelles is not understood yet. In this manuscript we report DLS, SANS, fluorescence and rheological studies on the effects of NaCl and butan-1-ol on the properties of Pluronic F127 micelles in the aqueous medium. The studies show that corona specific micellar dehydration by NaCl induces inter micellar attraction and consequent formation of micellar clusters. Core specific micellar dehydration by butan-1-ol on the other hand, brings about sphere-to-rod micellar shape transition on approaching the cloud point of copolymer solutions. A room temperature sphere-to-rod shape transition of Pluronic F127 micelles can also be induced in the combined presence of butan-1-ol and NaCl. Observation of such micellar shape transition in aqueous Pluronic F127 system is first of its kind, which can have important bearing with their application in mesoporous structure formation and drug delivery.