Co-occurrence of superparamagnetism and anomalous hall effect in highly reduced cobalt-doped rutile TiO2-delta films

We report a detailed magnetic and structural analysis of highly reduced Co doped rutile TiO(2-delta) films displaying an anomalous Hall effect (AHE). The temperature and field dependence of magnetization, and transmission electron microscopy, clearly establish the presence of nanosized superparamagnetic cobalt clusters of approximately 8-10 nm size in the films at the interface. The co-occurrence of superparamagnetism and AHE raises questions regarding the use of the AHE as a test of the intrinsic nature of ferromagnetism in diluted magnetic semiconductors.

Multiferroic BaTiO3-CoFe2O4 Nanostructures

We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The films are epitaxial in-plane as well as out-of-plane with self-assembled hexagonal arrays of CoFe2O4 nanopillars embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and average spacing of 20 to 30 nanometers. Temperature-dependent magnetic measurements illustrate the coupling between the two order parameters, which is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show that the magnetoelectric coupling in such a nanostructure can be understood on the basis of the strong elastic interactions between the two phases.

Gene therapy. Therapeutic approaches and implications

The present article is an overview of gene therapy with an emphasis on different approaches and its implications in the clinic. Genetic interventions have been applied to the diagnosis of and therapy for an array of human diseases. The initial concept of gene therapy was focused on the treatment of genetic diseases. Subsequently, the field of gene therapy has been expanded, with a major focus on cancer. Although the results of early gene therapy-based clinical trials have been encouraging, there is a need for gene delivery vectors that feature reduced immunogenicity and improved targeting ability. The results of phases I/II clinical trials have suggested the important role of gene therapy as a versatile and powerful treatment tool, especially for human cancers. One reasonable expectation is that performing gene therapy at an earlier stage in the disease process or for minimal residual disease may be more advantageous.

Acellular and Glutaraldehyde-Preserved Tendon Allografts for Reconstruction of Superficial Digital Flexor Tendon in Bovines: Part II - Gross, Microscopic and Scanning Electron Microscopic Observations

Sixteen tenorrhaphies were performed at mid-metatarsal region in eight buffalo calves. A 2-cm long gap was created in the superficial digital flexor (SDF) tendon in all animals. The gap was immediately repaired with acellular grafts in animals of group I, 1% glutaraldehyde-preserved tendon allografts in group II, and in group III the defect was repaired with autografts (control group). The contralateral limb in each animal was operated after an interval of 60 days and the animals underwent the same procedure according to the designed groups. Gross observation revealed filling of host tendon-graft junction with fibrous connective tissue. Increased vascularity was seen in group I when compared with group II and III. Graft was resorbed in animals of group I and III, whereas partial absorption of graft was seen in group II. Histological observations on day 30 revealed restoration of cellularity in acellular graft and fragmentation and resorption of glutaraldehyde-preserved graft. Graft was replaced by newly formed fibrous connective tissue. Tissue reaction around polygalactin suture consisted of plasma cells, lymphocytes and macrophages. On day 90, most of the acellular graft was replaced by newly formed fibrous connective tissue. In group II the majority of graft portion remained at the site and was in a state of resorption. In the control group it was difficult to distinguish between the host tendon and the graft. Scanning electron microscopical observation showed densely packed neoformed tissue at host tendon-graft junction. Hydrolysis and invasion of connective tissue between polygalactin suture filaments, resorption of graft with cavity formation and dissolution of ground substance were observed.

Acellular and Glutaraldehyde-Preserved Tendon Allografts for Reconstruction of Superficial Digital Flexor Tendon in Bovines: Part I - Clinical, Radiological and Angiographical Observations

Sixteen tenorrhaphies were performed at the mid-metatarsal region in eight buffalo calves under lignocaine epidural analgesia. A 2 cm long gap was created in the superficial digital flexor (SDF) tendon and immediately repaired with acellular grafts in animals of group I, 1% glutaraldehyde-preserved tendon allografts in group II. In group III, the defect was repaired with autografts. This group served as control. The contralateral limb in each animal was operated after an interval of 60 days and the animals underwent the same procedure according to the designed groups. Diclofenac sodium and Enrofloxacin was given post-operatively for 5 days. Clinical examination revealed significant increase (P < 0.05) in rectal temperature, heart and respiratory rate for 3-4 postoperative days in all the animals. Mild pain and exudation as well as early restoration of tendon gliding movements and weight-bearing were observed earlier in group I in comparison with group II. Air-tendograms revealed early organization, minimal adhesion formation and lesser thickening of tendon at the reconstructive site in the acellular group whereas in the glutaraldehyde group dense homogenous swelling with adhesions was seen along the flexors. Angiography on day 30 showed that the area of proximal and distal host tendon graft junction appeared hypervascularized, whereas the area occupied by the graft appeared relatively less vascularized. Normal vascularization was observed on day 90 in all the three groups.

A preliminary survey of central nervous system tumors in Tema, Ghana

BACKGROUND

In January 2000, the first ever neurosurgical program in Tema was established. This preliminary survey was conducted for the following purposes. 1) to determine the relative frequencies of the various histopathological types of CNS tumors. 2) To relate the occurrence of the various types of CNS tumors to age, sex, symptoms, neurologic findings and location. 3) to review the current use of neurodiagnostic modalities.

METHODS

A retrospective analysis of the records of 30 consecutive patients seen at T. I. N. with histologically proven CNS tumors was carried out. The following parameters were analysed; sex, age, symptoms, neurologic status, surgical procedure, histopathological diagnosis, pre and post operative Karnofsky rating.

RESULTS

30 patients (14M, 16F) constituted the series. Their mean age was 39.8 (R 2-72, SD, 18.7) years. The difference between the mean ages of patients with intracranial or spinal tumors was not significant (P>0.05). For intracranial tumors, there was a significant difference between the mean ages of those with infratentorial and supratentorial tumors. Spinal tumors constituted 13% of the series and they all presented with paraplegia. Eighty seven percent had intracranial tumors; of these 27% presented with headaches and 31% with seizures. Only 62% of patients with intracranial tumors presented with neurologic deficits. CT scanning was the diagnostic modality utilized in the diagnosis of all the intracranial tumors. Cerebral angiography was not obtained in any case. Myelography and post myelography CT scanning diagnosed all spinal tumors. Surgical procedures for CNS tumors constituted 23% of all neurosurgical surgical procedures performed during the study period. All patients with spinal tumors underwent laminectomy only. Sixty five percent of those with intracranial tumors underwent craniotomy; 34% underwent stereotactic biopsy. The most common intracranial tumor was high-grade astrocytoma (HGA), 23%. The left frontal lobe was the most common location of the intracranial tumors (54%), followed by the left temporal lobe (36%). No significant relationship was demonstrated in the brain tumor sites (P>0.05). At presentation, 46% of those with intracranial tumors had a karnofsky rating >70. One week after surgical intervention, this had increased to 62%. There was no significant relationship between tumor histopathology and preoperative or postoperative Karnofsky rating. The mortality rate in the first 10 days following intracranial tumor surgery was 8%; there were no deaths in the spine surgery group. The post operative complication rate for CNS tumor surgery was 11.5%.

CONCLUSION

Intracranial tumors are the most common type of CNS tumors in Tema. More than one third of patients with intracranial tumors presented without neurologic deficits. HGA is the most frequently seen intracranial tumor. All patients with spinal tumors presented with neurologic deficits, specifically paraplegia.

Adenovirus-mediated transfer of the PTEN gene inhibits human colorectal cancer growth in vitro and in vivo

The tumor-suppressor gene PTEN encodes a multifunctional phosphatase that is mutated in a variety of human cancers. PTEN inhibits the phosphatidylinositol 3-kinase pathway and downstream functions, including activation of Akt/protein kinase B (PKB), cell survival, and cell proliferation in tumor cells carrying mutant- or deletion-type PTEN. In such tumor cells, enforced expression of PTEN decreases cell proliferation through cell-cycle arrest at G1 phase accompanied, in some cases, by induction of apoptosis. More recently, the tumor-suppressive effect of PTEN has been reported in ovarian and thyroid tumors that are wild type for PTEN. In the present study, we examined the tumor-suppressive effect of PTEN in human colorectal cancer cells that are wild type for PTEN. Adenoviral-mediated transfer of PTEN (Ad-PTEN) suppressed cell growth and induced apoptosis significantly in colorectal cancer cells (DLD-1, HT29, and SW480) carrying wtPTEN than in normal colon fibroblast cells (CCD-18Co) carrying wtPTEN. This suppression was induced through downregulation of the Akt/PKB pathway, dephosphorylation of focal adhesion kinase (FAK) and mitogen-activated protein kinase (MAPK) and cell-cycle arrest at the G2/M phase, but not the G1 phase. Furthermore, treatment of human colorectal tumor xenografts (HT-29, and SW480) with Ad-PTEN resulted in significant (P=0.01) suppression of tumor growth. These results indicate that Ad-PTEN exerts its tumor-suppressive effect on colorectal cancer cells through inhibition of cell-cycle progression and induction of cell death. Thus Ad-PTEN may be a potential therapeutic for treatment of colorectal cancers.

Synthesis, spectra, dioxygen affinity and antifungal activity of Ru(III) Schiff base complexes

The reaction of ruthenium(III) complexes, [RuX(3)(EPh(3))(3)] (E=As, X=Cl or Br; E=P, X=Cl) and [RuBr(3)(PPh(3))(2)(CH(3)OH)] with bidendate Schiff base ligands derived by condensing salicylaldehyde with methylamine (Hsalmet), cyclohexylamine (Hsalchx), 2-aminopyridine (Hsalampy) have been carried out. The complexes were characterized by analytical and spectral studies (IR, electronic and EPR) and are formulated as [RuX(EPh(3))(LL')(2)] (where LL'=monobasic bidentate Schiff base ligand; E=P or As, X=Cl or Br). An octahedral geometry has been tentatively proposed for the new complexes. Dioxygen affinity of some of the Ru(III) Schiff base complexes was studied by cyclic voltammetry. The representative Schiff bases and their complexes were tested in vitro to evaluate their activity against fungi, namely, Aspergillus flavus (A. flavus) and Fusarium species.

Analysis of axially polarized piezoelectric cylinders with arbitrary boundary conditions on flat surfaces

A method to analyze axially polarized piezoelectric ceramic cylinders with arbitrary length to radius ratio and arbitrary boundary conditions on the flat surfaces is presented. The method is based on the use of functions that individually exactly satisfy the axisymmetric equations of motion and the Gauss electrostatic conditions. The axial and radial components of displacement and the potential are expressed as weighted sums of these functions. The functions form complete sets in the radial direction and arbitrary boundary conditions can, therefore, be satisfied on the flat surfaces. On the curved surface, certain uniform boundary conditions can be exactly satisfied. The weights are easily determined by using the orthogonal property of the functions. The input electrical admittance is a function of only the average boundary conditions and is very easily determined. Several special cases and numerical results are presented for electrically and mechanically excited cylinders to illustrate the method. The series expressions for displacements, potential, and stress converge rapidly and they are in good agreement with results obtained using ATILA--a finite element program. The method can be extended to analyze hollow cylinders with arbitrary boundary conditions on all surfaces.

Epitaxial BiFeO3 multiferroic thin film heterostructures

Enhancement of polarization and related properties in heteroepitaxially constrained thin films of the ferroelectromagnet, BiFeO3, is reported. Structure analysis indicates that the crystal structure of film is monoclinic in contrast to bulk, which is rhombohedral. The films display a room-temperature spontaneous polarization (50 to 60 microcoulombs per square centimeter) almost an order of magnitude higher than that of the bulk (6.1 microcoulombs per square centimeter). The observed enhancement is corroborated by first-principles calculations and found to originate from a high sensitivity of the polarization to small changes in lattice parameters. The films also exhibit enhanced thickness-dependent magnetism compared with the bulk. These enhanced and combined functional responses in thin film form present an opportunity to create and implement thin film devices that actively couple the magnetic and ferroelectric order parameters.

Dynamics of ferroelastic domains in ferroelectric thin films

Dynamics of domain interfaces in a broad range of functional thin-film materials is an area of great current interest. In ferroelectric thin films, a significantly enhanced piezoelectric response should be observed if non-180 degrees domain walls were to switch under electric field excitation. However, in continuous thin films they are clamped by the substrate, and therefore their contribution to the piezoelectric response is limited. In this paper we show that when the ferroelectric layer is patterned into discrete islands using a focused ion beam, the clamping effect is significantly reduced, thereby facilitating the movement of ferroelastic walls. Piezo-response scanning force microscopy images of such islands in PbZr0.2Ti0.8O3 thin films clearly point out that the 90 degrees domain walls can move. Capacitors 1 microm2 show a doubling of the remanent polarization at voltages higher than approximately 15 V, associated with 90 degrees domain switching, coupled with a d33 piezoelectric coefficient of approximately 250 pm V-1 at remanence, which is approximately three times the predicted value of 87 pm V-1 for a single domain single crystal.

Historical pollution trends in coastal environments of India

Seventeen sediment cores were collected from different coastal ecosystems of Tamil Nadu, India that include coastal lagoon (Pulicat), polluted rivers in Chennai (Adyar and Cooum), Coral reef (Gulf of Mannar) and a perennial river (Tamiraparani). Radiometric dating has been used to determine the modern sedimentation rates in these ecosystems. The Pulicat Lake and the polluted rivers (Adyar and Cooum) yield an average sediment accumulation rate of 12.34 and 7.85 mm yr(-1), respectively. In the Gulf of Mannar coral reef, the sedimentation rate averages 17.37 mm yr(-1), while the rate in Tamiraparani River is 11.00 mm yr(-1). In the Tamiraparani River basin, the deposition rates were an order of magnitude higher when compared to the erosion rates, which may be due to bank erosion and the intense human activity. In general high rates of sedimentation observed in the coastal ecosystems not only reflect the capacity of the coastal regions as sinks for trace metals but also denote increased input of pollutants into the coastal environments in the recent past. The deposition rates of heavy metals--Fe, Mn, Zn, Cu, Cr and Ni in the depth profiles have been computed using sedimentation rates and their distribution is discussed. It can be seen that the mean deposition rates of all the measured elements in the Tamil Nadu coastal ecosystems are high compared with rates determined for the sediments of the deltaic regions of India and the Bay of Bengal.

An evaluation of level of oxidative stress and protein glycation in nondiabetic undialyzed chronic renal failure patients

BACKGROUND

Chronic renal failure (CRF) patients on prolonged dialysis and with diabetes have been found to have significant alteration in their antioxidant status and protein glycation, but little is known about the same in nondiabetic undialyzed CRF patients. This study was performed to evaluate (a) the levels of oxidative stress and protein glycation in nondiabetic undialyzed CRF patients and (b) the possible influence of oxidative stress on protein glycation.

DESIGN AND METHODS

A case control study was performed on 23 nondiabetic undialyzed CRF patients and 17 control subjects. The concentrations of total plasma ascorbic acid, whole blood reduced glutathione (GSH) and plasma lipid peroxides were measured to evaluate the antioxidant status and oxidative stress. The protein glycation was measured from plasma fructosamine normalized for albumin concentrations. A partial correlation analysis was carried out to analyze the effect of oxidative stress parameters on protein glycation.

RESULTS

A compromised nonenzymatic defense against free-radical generation was evidenced by decreased concentrations of whole blood GSH and plasma ascorbic acid. The concentrations of lipid peroxides, fructosamine and fructosamine/albumin ratio were significantly (p<0.05) higher in the CRF group when compared with controls. The partial correlation analysis revealed that oxidative stress influences protein glycation in CRF patients.

CONCLUSIONS

Increased oxidative stress might have a role in promoting protein glycation in nondiabetic undialyzed CRF patients. The reduction of oxidative stress and protein glycation might open new therapeutic approaches in treating CRF patients.

Nanoscale phenomena in synthetic functional oxide heterostructures

This paper reviews nanoscale phenomena such as polarization relaxation dynamics and piezoelectric characterization in model ferroelectric thin films and nanostructures using voltage-modulated scanning force microscopy. Using this technique we show the three-dimensional reconstruction of the polarization vector in lead zirconate titanate (PZT) thin films. Second, the time-dependent relaxation of remanent polarization in epitaxial PZT ferroelectric thin films, containing a uniform two-dimensional grid of 90 degrees domains (c-axis in the plane of the film), has been investigated extensively. The 90 degrees domain walls preferentially nucleate the 180 degrees reverse domains during relaxation. Relaxation occurs through the nucleation and growth of reverse 180 degrees domains, which subsequently coalesce and consume the entire region as a function of relaxation time. In addition we also present results on investigation of the relaxation phenomenon on a very local scale, where pinning and bowing of domain walls has been observed. We also show how this technique is used for obtaining quantitative information on piezoelectric constants and by engineering special structures, and how we realize ultrahigh values of piezoconstants. Last, we also show direct hysteresis measurements on nanoscale capacitors, where there is no observable loss of polarization in capacitors as small as 0.16 microm2 in area.

Distribution of natural and anthropogenic radionuclides in soil and beach sand samples of Kalpakkam (India) using hyper pure germanium (HPGe) gamma ray spectrometry

Pre-operational survey at Kalpakkam coast, indicated elevated gamma background radiation levels in the range of 100-4000 nGy h(-1) over the large tracts of the coastal sands due to the presence of pockets of monazite mineral in beach sands. In view of the prevalence of monazite, a systematic gamma spectrometric study of distribution of natural radionuclides in soil and beach sand samples collected from the terrestrial and coastal environment of Kalpakkam was performed and concentrations of primordial radionuclides such as 238U, 232Th and 40K and anthropogenic radionuclide 137Cs were determined. The concentrations of 238U, 232Th and 40K in soil samples were 5-71, 15-776 and 200-854 Bq kg(-1) dry, respectively. In beach sand samples, 238U, 232Th and 40K contents varied in the range of 36-258, 352-3872 and 324-405 Bq kg(-1) dry, respectively. The total absorbed gamma dose rate in air due to the presence of 238U, 232Th and 40K in Kalpakkam soil samples varied between 24 and 556 nGy h(-1) with a mean of 103 nGy h(-1). The contribution to the total absorbed gamma dose rate in air in the decreasing order was due to the presence of 232Th (76.4%), followed by 40K (16.9%) and 238U (6.7%) in Kalpakkam soils. However, in beach areas of Kalpakkam, the presence of 232Th in beach sand contributed maximum (94.0%) to the total absorbed gamma dose rate in air followed by 238U (4.7%) and minimum contribution was by 40K (1.3%). 137Cs in Kalpakkam soils ranged from < or = 1.0 to 2.8 Bq kg(-1) dry, which was 1-3 order of magnitude less than the concentration of primordial radionuclides in soil.

Epidemiology of dengue in Sri Lanka before and after the emergence of epidemic dengue hemorrhagic fever

Before 1989, dengue epidemiology in Sri Lanka was characterized by frequent transmission of all four dengue serotypes but a low incidence of dengue hemorrhagic fever (DHF). After 1989, cases of DHF dramatically increased. Here we present the results of epidemiologic studies conducted in Colombo, Sri Lanka before and after epidemic emergence of DHF in 1989. We compared the proportion of dengue cases among people with fever attending clinics from 1980 to 1984 and in 1997 and 1998 to determine if an increase in dengue transmission was associated with more DHF cases being reported. We also compared the relative distribution of dengue virus serotypes circulating in Colombo before and after the emergence of DHF. We detected no significant differences in dengue as a proportion of fever cases or in serotype distribution between the pre and post-DHF periods. We conclude that an increase in virus transmission or a change in circulating serotypes does not explain the epidemic emergence of DHF in Sri Lanka.

Methane emissions from a coastal lagoon: Vembanad Lake, West Coast, India

An attempt has been made to estimate methane fluxes from a tropical coastal wetland the Vembanad Lake, a lagoon along the West Coast of India. It has been found that Vembanad Lake contributes significant amount of methane to the atmosphere. Average emissions varied spatially within the lake. Methane emissions were 193.2 +/- 24.5 mg m(-2) h(-1) at Kumaragam (fresh water) as compared to 9.3 +/- 9.6 mgm(-2) h(-1) at Pullot (brackish water) site. Seasonal variation was significant between pre- and post-monsoons. Soil temperature, time of the day, salinity sediment organic carbon, all control the rate of methane emissions from the Vembanad Lake.

Determination of butyl-, phenyl-, octyl- and tributylmonomethyltin compounds in a marine environment (Bay of Bengal, India) using gas chromatography-inductively coupled plasma mass spectrometry

Organotin compounds (butyl-, phenyl-, octyl- and tributylmonomethyltin) and inorganic tin were quantified in sea-water and sediments from two harbours and several locations on the southeast coast of India using highly sensitive and selective gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS), adopting new extraction and analytical techniques with extremely low detection limits (water, 0.019-0.85 pg l(-1); sediment, 0.23-0.48 ng g(-1)). The concentrations of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in sea-water from Tuticorin harbour varied from 0.64 to 4.97, 3.0 to 26.8 and 0.3 to 30.4 ng Sn l(-1), respectively. MBT, DBT and TBT in sediments from harbour areas ranged from 1.6 to 393, 1.3 to 394 and ND (not detected) to 1280 ng Sn g(-1) (dry weight), respectively. Natural methylation in both harbours was established by quantifying tributylmonomethyltin (TBMMT) residues (sea-water, ND-0.19 ng Sn l(-1); sediment, ND-765 ng Sn g(-1) dry weight). In sea-water, octyltins were also determined as monooctyltin (MOT) > dioctyltin (DOT) > trioctyltin (TOT). Butyltin contamination in commercial harbours is evident, but other coastal waters are not contaminated with organotin residues. The high concentration of inorganic tin in estuarine sediment indicates an elevated rate of debutylation in the estuarine environment. Both methylation and debutylation of TBT in Chennai harbour were greater than in Tuticorin harbour. A significant correlation (r2 = 0.75) between total butyltin and organic carbon contents in sediment was found. To our knowledge, this is the first report on the distribution of butyltins and methylated butyltin in sea-water and sediment and octyltins in sea-water in the Indian marine environment.

The turkey transcription factor Pit-1/GHF-1 can activate the turkey prolactin and growth hormone gene promoters in vitro but is not detectable in lactotrophs in vivo

The transcription factor Pit-1/GHF-1 plays an important role in regulating the prolactin (Prl) and growth hormone (GH) genes in mammals. In this study, the role that Pit-1 plays in regulating the prolactin and growth hormone genes in avian species was examined by cotransfection assays and immunofluorescence staining of pituitary sections. In cotransfection assays, turkey Pit-1 activated the turkey Prl, turkey GH, and rat Prl promoters 3.8-, 3.7-, and 12.5-fold, respectively. This activation was comparable to rat Pit-1 activation of these same promoters. A point mutation in the turkey Pit-1 cDNA, which changed leu-219 to ser-219, resulted in a 2-, 2-, and 10-fold reduction in the activation of the turkey Prl, turkey GH, and rat Prl promoters, respectively. Unexpectedly, coexpression of tPit-1 (leu-219) and tPit-1(ser-219) activated turkey Prl and rat Prl promoters 9.4- and 35.9-fold, respectively, but had no effect on the turkey GH promoter. Dual-label immunofluorescence analysis of turkey pituitary sections revealed that Pit-1 was not detectable in prolactin-staining cells but was detectable in GH-staining cells. Taken together, these data indicate that in the domestic turkey, Pit-1 can activate the turkey Prl promoter in vitro, but does not appear to play a role in regulating Prl gene expression in vivo. Pit-1, however, still likely plays a role in regulating GH gene expression.