Complex dynamics in polymer nanocomposites

Polymer nanocomposites offer the potential to create a new type of hybrid material with unique thermal, optical, or electrical properties. Understanding their structure, phase behavior, and dynamics is crucial for realizing such potentials. In this work we provide an experimental insight into the dynamics of such composites in terms of the temperature, wave vector, and volume fraction of nanoparticles, using multispeckle synchrotron x-ray photon correlation spectroscopy measurements on gold nanoparticles embedded in polymethylmethacrylate. Detailed analysis of the intermediate scattering functions reveals possible existence of an intrinsic length scale for dynamic heterogeneity in polymer nanocomposites similar to that seen in other soft materials like colloidal gels and glasses.

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.

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.

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.

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.

Minimising ventilator induced lung injury in preterm infants

Ventilator induced lung injury continues to occur at an unacceptably high rate, which is inversely related to gestational age. Although the "new BPD" may not be entirely avoidable in the extremely premature infant, recognition of risk factors and adoption of an appropriate ventilatory strategy, along with continuous real time monitoring, may help to minimise lung damage. This paper will review the pathogenesis of ventilator induced lung injury and strategies that may mitigate it.

Colorectal neoplasm and acromegaly

The risk for colorectal carcinoma in acromegaly remains controversial. In our earlier study, we have demonstrated that the risk of colorectal carcinoma in Asian Indians with acromegaly is not increased and after this report, routine colonoscopy in our patients with acromegaly was abandoned. Subsequently, two consecutive young men aged 30 and 35, one 6 years after and other at the time of diagnosis of acromegaly had colorectal carcinoma respectively. None of them had family history of colonic neoplasm. These two younger patients with no other predisposition for colorectal neoplasm suggests that colonoscopy should be done in all patients with acromegaly at diagnosis and they should remain under surveillance.

Patients with gallstones develop gallbladder cancer at an earlier age

Significant proportions of Indian patients with gallbladder cancer are young. Multiple risk factors for gallbladder cancer are recognized among Indian patients. The effect of these risk factors on the age of development of gallbladder cancer is not known. We conducted a study to determine the influence of risk factors on the age at diagnosis of patients with gallbladder cancer and to assess the interactions between these risk factors. Patients with gallbladder cancer from two tertiary care institutions during the period 1994-2001 were prospectively studied. An ultrasound examination was done to look for the presence of gallstones. The influence of gender, gallstones, socio-economic status, smoking, residence in rural areas and in the Gangetic belt on the age at presentation was analysed using univariate analysis, logistic and linear regression analyses. The mean age of the 121 patients studied was 55+/-11.7 (SD) years. There were 51 (42%) patients aged less than 50 years. The younger patients (age < or =50 years) were more likely to have gallstones (88 versus 66%; P=0.008) and to have come from a lower socio-economic background (88 versus 71%; P=0.02) in comparison with older patients. However, there was no effect of the other risk factors. The independent determinants for younger age of patients with gallbladder cancer on logistic regression analysis were gallstones [odds ratio (OR) 4, 95% confidence interval (CI) 1.5-11; P=0.006] and lower socio-economic status (OR 3.1, 95% CI 1.1-8.6; P=0.03). On linear regression analysis, age at presentation was lowered by 5.6 years if there were associated gallstones. The mean age of patients with these two risk factors was significantly lower than that of those with one risk factor or no risk factor (52+/-12 years versus 57+/-11 years versus 61+/-9 years; P=0.007). In conclusion, the presence of gallstones and lower socio-economic status were both independently associated with a younger age at diagnosis of gallbladder cancer and their effect was additive.

Depth profile of uncompensated spins in an exchange bias system

We have used the unique spatial sensitivity of polarized neutron and soft x-ray beams in reflection geometry to measure the depth dependence of magnetization across the interface between a ferromagnet and an antiferromagnet. The net uncompensated magnetization near the interface responds to applied field, while uncompensated spins in the antiferromagnet bulk are pinned, thus providing a means to establish exchange bias.

Dietary fiber assessment of patients with irritable bowel syndrome from Northern India

BACKGROUND

Data on the absolute fiber intake and the source of dietary fiber intake in patients with irritable bowel syndrome (IBS) have been lacking in northern Indians.

OBJECTIVE

To find out the absolute fiber intake from different sources of food items in patients with IBS and healthy subjects from northern India.

METHODS

Using the 72-hour recall method, dietary intake of macronutrients and fiber was determined in 33 consecutive adult patients with IBS and 33 age- and gender-matched healthy controls.

RESULTS

The patients consumed lower amounts of macronutrients (protein 60.4 g vs 79.3 g, fat 47.7 g vs 65.7 g, and carbohydrates 294.6 g vs 339.8 g) and dietary fiber (8.1 g vs 15.7 g) than the control subjects. Though the patients consumed similar amount of pulses as the controls (46.6 [25.0] vs 46 [19.6] g/day), their fiber intake from pulses was lower (0.8 [0.7] vs 1.4 [0.9] g/day). The intake of fiber from vegetables and fruits was also significantly lower in patients (2.1 and 0.5 g/day, respectively) than in control subjects (5.8 and 3.9 g/day, respectively; p< 0.001 each).

CONCLUSION

Total dietary fiber intake and intake of fiber from vegetables, fruits and pulses are lower in patients with IBS from northern India than in control subjects.

Comparison of cough of 2 and 3 weeks to improve detection of smear-positive tuberculosis cases among out-patients in India

SETTING

Governmental health facilities in six districts of India.

OBJECTIVE

To estimate the prevalence of cough and to compare the detection of smear-positive tuberculosis (TB) among out-patients with cough of > or =2 or > or =3 weeks.

DESIGN

Trained health workers questioned each out-patient for presence of cough. Those with cough > or =2 weeks underwent sputum microscopy.

RESULTS

Of 55561 out-patients interviewed, 2210 (4%) had cough > or =2 weeks, of whom 267 had sputum-positive TB, compared to 182/1370 with cough > or =3 weeks. The 31% who did not spontaneously complain of cough were less likely to be sputum-positive than those who did (45/680 [7%] vs. 222/1530 [15%], P < 0.001), but they accounted for 45/267 smear-positive cases. Using cough > or =2 weeks as the screening criterion, the estimated number of smears performed per day at each primary and secondary health care facility was respectively 8 and 19, compared to 5 and 12 using cough > or =3 weeks.

CONCLUSION

The detection of smear-positive TB cases can be substantially improved by actively eliciting history of cough from all out-patients, and by changing the screening criterion for performing sputum microscopy among out-patients from cough > or =3 weeks to > or =2 weeks. Before implementing this change nationally, its programmatic feasibility should be assessed.

Four-unit-cell superstructure in the optimally doped YBa2Cu3O6.92 superconductor

Diffuse x-ray scattering measurements reveal that the optimally doped YBa2Cu3O6.92 superconductor is intrinsically modulated due to the formation of a kinetically limited 4-unit-cell superlattice, q(0)=(1/4, 0, 0), along the shorter Cu-Cu bonds. The superlattice consists of large anisotropic displacements of Cu, Ba, and O atoms, respectively, which are correlated over approximately 3-6 unit cells in the ab plane, and appears to be consistent with the presence of an O-ordered "ortho-IV" phase. Long-range strains emanating from these modulated regions generate an inhomogeneous lattice which may play a fundamentally important role in the electronic properties of yttrium-barium-copper-oxides.

Severe acute bleeding from portal colopathy controlled by somatostatin: a case report

Portal hypertensive colopathy (PHC) is a recently described entity in patients with portal hypertension which can cause even life-threatening lower gastrointestinal bleeding. In contrast to variceal bleed, there is no standardized treatment for the control of bleeding from these lesions. We report a case of alcoholic cirrhosis with portal hypertension, in whom bleeding from colonic angiodysplasia-like lesions was effectively controlled by somatostatin infusion.

Hemobilia as presenting manifestation of polyarteritis nodosa

Polyarteritis nodosa (PAN) is a multisystem necrotizing inflammatory vasculitis of medium-sized muscular arteries. Hepatobiliary complications secondary to thrombosis or aneurysm formation in PAN are rare and are associated with poor outcome. We describe an 18-year-old man with PAN who presented with hemobilia secondary to rupture of a hepatic artery aneurysm, which was successfully managed with coil embolization followed by immunosuppressive therapy.

Association of ulcerative colitis with pulmonary sarcoidosis, subcutaneous lipomatosis and appendiceal adenocarcinoma

We report a 52-year-old man with left-sided ulcerative colitis for 5 years and pulmonary sarcoidosis diagnosed 3 years back. He presented with subcutaneous lipomatosis and a right iliac fossa mass, which was diagnosed histologically as appendiceal adenocarcinoma. He was treated with right hemicolectomy, followed by chemotherapy.

Diagnostic evaluation of extrapulmonary tuberculosis by fine needle aspiraton (FNA) supplemented with AFB smear and culture

One hundred forty-three patients, 72 males and 71 females, with extrapulmonary tuberculosis were aspirated and subjected to cytological (Ziehl-Neelsen stain) examination and culture in Lowenstein-Jensen media. Routine haematological examination and Mantoux test were done in all the cases, x-ray chest in 112, skeletal x-ray in 3 relevant cases and sputum was examined for AFB in 16 cases where pulmonary tuberculosis was associated/suspected with extrapulmonary tuberculosis. HIV status was evaluated in 51 cases and 9 (7.64%) were seropositive. FNA cytology in 102 cases (71.3%) had caseating epithelioid granulomas while smear for AFB was positive in 57 cases (39.8%). Both culture and smear were positive in 29 (20.2%) cases. Combining both smear and culture yielded positive results in 47.5% cases. It was observed that AFB positivity was higher in untreated patients and with HIV positive cases. Further more, the triad of FNAC, AFB smear and culture were cheaper, foolproof and confirmatory than costlier tests like TB IgG, IgM, RTPCR and BACTEC.