Entanglement effects in capillary waves on liquid polymer films

Overdamped surface capillary wave relaxations on molten polymer films were measured using x-ray photon correlation spectroscopy. We found a transition from a single through a stretched to another single exponential regime as the temperature is decreased from well above to near the bulk glass transition temperature. A universal scaling of the dynamics was discovered over a wide range of film thicknesses, temperatures, and molecular weights (except in the multiple relaxation regime). These observations are justified by hydrodynamic theory and the time-temperature superposition principle by considering an effective viscosity instead of the bulk zero shear viscosity.

Newer forms of conventional ventilation for preterm newborns

Although life saving, mechanical ventilation can cause complications such as ventilator-induced lung injury and bronchopulmonary dysplasia in very preterm babies. The ventilator-induced lung injury is multi-factorial. There has been an introduction of a number of newer forms of mechanical ventilation, which are aimed to reduce such complications. These are based on sound physiologic principles and clinicians should familiarize themselves with these advances.

Review: Surfactant respiratory therapy using Surfaxin/sinapultide

Respiratory distress syndrome (RDS) is a leading cause of mortality and morbidity in preterm infants. Surfactant replacement therapy has been widely used to prevent and treat RDS in these newborns and has now become a standard of care. First-generation synthetic surfactants such as Exosurf did not contain any surfactant protein. This disadvantage was overcome with animal-derived surfactant preparations which contain specific proteins but has the limitation of being derived from animal sources. This has led to development of newer synthetic surfactants such as lucinactant (Surfaxin, Discovery Laboratories, Philadelphia) which contains the protein B mimic synthetic peptide, sinapultide. Recent phase 3 clinical trials with Surfaxin show promising results with similar efficacy as animal derived surfactants and yet avoiding the disadvantage associated with animal products. The purpose of this paper is to summarise results of recent clinical trials of Surfaxin use in newborns with RDS.

Thickness induced structural changes in polystyrene films

Changes to the structure of polystyrene melt films as measured through the spectrum of density fluctuations have been observed as a function of film thickness down to the polymer radius of gyration (Rg). Films thicker than 4Rg show bulklike density fluctuations. Thinner films exhibit a peak in S(q) near q=0 which grows with decreasing thickness. This peak is attributed to a decreased interpenetration of chains resulting in an enhanced compressibility. Measurements were made using small angle x-ray scattering in a standing wave geometry designed to enhance scattering from the interior of the film compared to interface scattering.

Partial crystallinity in alkyl side chain polymers dictates surface freezing

We have studied the structure of a novel crystalline surface monolayer on top of a disordered melt of the same material [poly(n-alkyl acrylate)s] using grazing incidence x-ray diffraction. The grazing incidence x-ray diffraction, surface tension, and bulk latent heat results show that side chains crystallize except the nine methylene units of the alkyl side chains closest to the polymer backbone. The partial crystallinity along with a thicker surface layer, due to the additional length of the linker group, explains why the difference between the surface order-to-disorder transition temperature and bulk melting temperature increases with a decrease in the length of the alkyl side chain.

Orocecal transit time in patients with celiac disease from North India: a case control study

AIM

The mechanisms responsible for bowel disturbances in celiac disease are still unknown. Small bowel motor abnormalities may be involved in this pathological condition; however, there is no study addressing small bowel transit in patients of celiac disease from Northern India.

METHOD

The mouth-to-cecum transit time was studied in 80 celiac patients and 80 age and sex matched apparently healthy controls.

RESULTS

Orocecal transit time in celiac patients was significantly delayed being 180+/-10.6 minutes (Mean+/-SE) as compared to 105+/-12.4 minutes in apparently healthy controls.

CONCLUSION

This prolonged orocecal transit time could be due to impaired small bowel function (deranged motility) in patients with celiac disease.

Squeeze-out of branched alkanes on graphite

We study squalane and heptamethylnonane (HMN) confined between a conducting atomic force microscope tip and a graphite surface. Solvation layering occurs for both liquids but marked differences in the squeeze out mechanics are observed for ordered or disordered monolayers. The squalane monolayer at 25 degrees C is an ordered solid, as verified by direct imaging, and the squeeze out can be modeled using elastic continuum mechanics. HMN is in a disordered state at 25 degrees C and cannot be modeled as a single elastic asperity even in solid-solid contact because HMN liquid is trapped in the contact zone.

Immediate respiratory management of the preterm infant

Infants born prematurely have underdeveloped lungs characterised by both morphological and biochemical abnormalities. Respiratory distress syndrome (RDS) is the leading cause of morbidity and mortality in this population. Both surfactant replacement therapy with mechanical ventilation and continuous positive airway pressure (CPAP) have been shown to be of benefit. However, considerable controversy exists about how best to use these therapies. This paper will review the pathophysiology of RDS and the evidence supporting each of these treatments.

High-energy and -protein diet increases brain and corticospinal tract growth in term and preterm infants after perinatal brain injury

OBJECTIVE

Our hypothesis was that infants with perinatal brain injury fail to thrive in the first postnatal year because of increased energy and protein requirements from deficits that accumulated during neonatal intensive care. Our aim was to assess whether dietary energy and protein input was a rate-limiting factor in brain and body growth in the first year after birth.

METHODS

We conducted a prospective, double-blind and randomized, 2-stage group sequential study and controlled for gestation, gender, and brain lesion. Neonates with perinatal brain damage were randomly allocated to receive either a high- (120% recommended average intake) or average (100% recommended average intake) energy and protein diet. The study began at term and continued for 12 months. Three-day dietary diaries estimated energy and protein intake. The primary outcome measure was growth of occipitofrontal circumference. Other measures were growth of axonal diameters in the corticospinal tract, which were estimated by using transcranial magnetic stimulation, weight gain, and length.

RESULTS

The study was terminated at the first analysis when the 16 subjects had completed the protocol, because the predetermined stopping criterion of >1 SD difference in occipitofrontal circumference at 12 months' corrected age in those receiving the higher-energy and -protein diet had been demonstrated. Axonal diameters in the corticospinal tract, length, and weight were also significantly increased.

CONCLUSIONS

These data support our hypothesis that infants with significant perinatal brain damage have increased nutritional requirements in the first postnatal year and suggest that decreased postnatal brain growth may exacerbate their impairment. There are no measures of cognitive ability at 12 months of age, and whether there will be any improvement in the status of these children, therefore, remains to be shown.

Study of small intestinal bacterial overgrowth in North Indian patients with irritable bowel syndrome: a case control study

BACKGROUND

Approximately 20% of the general population has irritable bowel syndrome. Despite this high prevalence, the cause of irritable bowel syndrome is unknown. There is no data available concerning the prevalence of small intestinal bacterial overgrowth in North Indian patients with irritable bowel syndrome.

AIM

This study evaluated the prevalence of small intestinal bacterial overgrowth in patients with irritable bowel syndrome compared with healthy controls.

METHODS

This study included 225 consecutive patients of irritable bowel syndrome between the ages 20 and 65 years attending the gastroenterology clinics. Diagnosis of irritable bowel syndrome was made according to the Rome II criteria. Small intestinal bacterial overgrowth was estimated by using the non-invasive glucose hydrogen breath test.

RESULTS

Of 225 patients of irritable bowel syndrome, 160 (71.1%) were male and 65 (28.9%) were female. Of 100 controls, 65 (65%) were male and 35 (35%) female. The prevalence of small intestinal bacterial overgrowth was 25 of 225 (11.1%) patients with irritable bowel syndrome and 1 of 100 (1%) in apparently healthy controls. This difference was statistically significant. The prevalence of small intestinal bacterial overgrowth in male and female patients was not significantly different.

CONCLUSION

This study indicates that the prevalence of small intestinal bacterial overgrowth in irritable bowel syndrome patients from North India is approximately 11.1%, which is lower than the reported prevalence.

Traumatic orbitomaxillary encephalocele

A rare case of occult traumatic intramaxillary encephalocele and intraorbital encephalocele without obvious connection to exterior is described

Small intestinal bacterial overgrowth in North Indian patients with celiac disease

BACKGROUND

Occasionally celiac patients continue to experience gastro-intestinal symptoms even with a gluten free diet. In these cases, small intestinal bacterial overgrowth may be one of the causes of the lack of response. Therefore, this prospective study was planned to determine the prevalence of small intestinal bacterial overgrowth in celiac patients.

MATERIALS AND METHODS

We studied 87 confirmed cases of celiac disease from North India and 87 age and sex matched controls. Celiac disease was confirmed by positive IgA antitissue transglutaminase on ELISA. 80 g glucose hydrogen breath test (non-invasive test) was performed to establish small intestinal bacterial overgrowth. Rise of more than 10 ppm in hydrogen concentration over baseline value within two hours was considered suggestive of small intestinal bacterial overgrowth.

RESULTS

Out of 87 patients with celiac disease, 49 were male and 38 were female. The mean (+/-SD) age for male patients was 26.3 +/- 16.3 years (range 14-59 years) and for female patients was 28.4 +/- 15.6 years (range 16-58 years). Amongst the controls, 52 (59.8%) were male and 35 (40.2%) were female. The mean (+/- SD) age for male controls was 27.6 +/- 14.5 years (range 15-57 years) and for female controls was 29.3 +/- 16.5 years (range 18-59 years). Hydrogen breath test was suggestive of bacterial overgrowth in 18 of the 87 (20.7%) celiac disease patients but not in any of the apparently healthy controls.

CONCLUSION

This study indicates that a large number of celiac patients from North India suffer from bacterial overgrowth which can be accordingly treated with antibiotics.

Effect of metformin and rosiglitazone in a prepubertal boy with Alström syndrome

Alström syndrome (AS) is an autosomal recessive disorder characterized by progressive pigmentary retinopathy, sensorineural hearing loss, fatty liver infiltration, obesity, insulin resistance and early-onset type 2 diabetes mellitus (DM2). Early onset of insulin resistance and DM2 are key components of this syndrome.

AIM

To study the effect of early initiation of the insulin sensitizer metformin combined with rosiglitazone in a patient with AS with impaired glucose tolerance.

PATIENT

An 8 year-old boy with AS presented with acanthosis nigricans and insulin resistance at the age of 6 years. He had progressive excessive weight gain from 9 months of age. By the age of 1 year he developed photosensitivity, blindness and nystagmus. At the age of 5.5 years, his body mass index (BMI) was above the 95th percentile. He developed impaired glucose tolerance at 6 years of age and treatment with metformin was initiated. After 8 months of treatment with metformin he developed DM2. The dose of metformin was increased, and rosiglitazone added.

METHODS

A 2-hour oral glucose tolerance test (OGTT) and a rapid intravenous glucose tolerance test (IVGTT) were performed before treatment was initiated, after treatment with metformin and at the end of 1 year of combination therapy with metformin and rosiglitazone to calculate quantitative insulin sensitivity check index (QUICKI) and acute insulin response (AIR). For mutation analysis, all exons and splice site sequences of the ALMS1 gene were amplified and sequenced.

RESULTS

Metformin treatment alone at the stage of impaired glucose tolerance did not prevent progression to DM2. However, metformin at a higher dose and in combination with rosiglitazone resulted in improvement of pancreatic beta-cell function, shown by markedly improved first-phase insulin response to glucose measured by AIR. The patient was found to have two heterozygous nonsense mutations in ALMS1, 8008 C-->T Ter, R2670X, and 11449 C-->T Ter, Q3817X. These alterations cause premature stops and result in a truncated ALMS1 protein.

CONCLUSION

We suggest that early initiation of combined therapy comprising a high dose of metformin plus rosiglitazone may be valuable in managing insulin resistance and DM2 in children with AS.

Partially wetting thin liquid films: structure and dynamics studied with coherent x rays

We studied the surface structure of thin liquid films vapor deposited on solid substrates in a partial wetting situation by means of coherent x-ray scattering. No dynamics has been observed showing the absence of capillary waves on liquid films partially wetting a substrate. Instead an exponential form of the height-height correlation function has been found pointing toward a solidlike behavior of the thin liquid films at large length scales. The exact surface structure and degree of replication with the substrate depend on the deposition rate of the molecules.

Solvation and squeeze out of hexadecane on graphite

We have performed simultaneous force and conductivity measurement of hexadecane liquid confined between a conducting atomic force microscope tip and a graphite surface. Both the current and the force data reveal discrete solvation layering of the hexadecane near the surface. We typically observe that the current does not vary with load in a simple way as the layer closest to the surface is compressed, but increases markedly prior to the expulsion of material from the tip-sample gap. We infer that even for a nanoscale asperity there is conformation change of the confined hexadecane under the tip apex prior to squeeze out of the molecules.

Evidence for viscoelastic effects in surface capillary waves of molten polymer films

The surface dynamics of supported ultrathin polystyrene films with thickness comparable to the radius of gyration were investigated by surface sensitive x-ray photon correlation spectroscopy. We show for the first time that the conventional model of capillary waves on a viscous liquid has to be modified to include the effects of a shear modulus in order to explain both static and dynamic scattering data from ultrathin molten polymer films.

Isolation and characterization of microsomal omega-6-desaturase gene (fad2-1) from soybean

A genomic DNA sequence (fad2-1) encoding seed specific microsomal 0-6 desaturase was isolated from soybean (Glycine max. L cv. Pusa-9702). A positive genomic clone of 1852 nucleotides containing a single uninterrupted 3' end exonic region with an ORF of 1140 bp encoding a peptide of 379 amino acids, a complete 3' UTR of 206 bp and 86 bp of 5' UTR interrupted by a single intron of 420 bp was obtained on screening the sub-genomic library of soybean. Southern blots revealed at least two copies of the gene per haploid genome. Analysis of the translated product showed the presence of three histidine boxes, with the general sequence HXXXH and five probable transmembrane segments reported to be involved in substrate specificity.

Volume-targeted ventilation of newborns

Traditional management of neonatal respiratory failure has been accomplished with mechanical ventilation delivered by time-cycled, pressure-limited techniques. Although easy to use, this modality results in the delivery of tidal volumes that vary according to pulmonary compliance. In contrast, volume-targeted ventilation delivers a selected tidal volume at variable peak inspiratory pressure, resulting in consistent tidal volume delivery, even in the face of changing compliance. This article reviews salient features of volume-targeted ventilation and a review of the evidence base.