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R Pillarisetty

Publications and source records attributed to R Pillarisetty.

14 recordsLinked to original sources
PubMed2005

Spin polarization dependence of the coulomb drag at large r(s).

We find that the temperature dependence of the drag resistivity between two dilute two-dimensional hole systems exhibits an unusual dependence upon spin polarization. Our main observation is that near the apparent metal-insulator transition, the temperature dependence of the drag, given by Talpha, weakens significantly with the application of a parallel magnetic field (B(||)), with alpha saturating at half its zero field value for B(||)>B(*), where B(*) is the polarization field.

Journal Article↗
PubMed2003

Role of density imbalance in an interacting bilayer hole system.

We study interacting GaAs hole bilayers in the limit of zero interlayer tunneling. When the layers have equal density, we observe a phase-coherent bilayer quantum Hall state (QHS) at a total filling factor nu=1, flanked by a reentrant insulating phase at nearby fillings which suggests the formation of a pinned, bilayer Wigner crystal. As we transfer charge from one layer to another, the phase-coherent QHS becomes stronger, evincing its robustness against charge imbalance, but the insulating phase disappears, suggesting that its stability requires the commensurability of the two layers.

Journal Article↗
PubMed2003

In-plane magnetodrag between dilute two-dimensional systems.

We performed in-plane magnetodrag measurements on dilute double layer two-dimensional hole systems, at in-plane magnetic fields that suppress the apparent metallic behavior, and to fields well above those required to fully spin polarize the system. When compared to the single layer magnetoresistance, the magnetodrag exhibits exactly the same qualitative behavior. In addition, we have found that the enhancement to the drag from the in-plane field exhibits a strong maximum when both layer densities are matched.

Journal Article↗
PubMed2002

Frictional drag between two dilute two-dimensional hole layers.

We report drag measurements on dilute double layer two-dimensional hole systems in the regime of r(s) = 19-39. We observed a strong enhancement of the drag over the simple Boltzmann calculations of Coulomb interaction, and deviations from the T2 dependence which cannot be explained by phonon-mediated, plasmon-enhanced, or disorder-related processes. We suggest that this deviation results from interaction effects in the dilute regime.

Journal Article↗
PubMed2002

Chondrocyte apoptosis following intraarticular fracture in humans.

OBJECTIVE: The primary objective of the present study was to establish the degree to which chondrocyte apoptosis occurs in vivo following intraarticular fractures in humans. DESIGN: Fracture cartilage specimens were obtained from patients undergoing surgical intervention for fractures of the articular surface of the proximal tibia. Normal proximal tibia cartilage specimens served as controls. Apoptotic chondrocytes were identified and quantified using TUNEL analysis. RESULTS: The percentage of TUNEL positive chondrocytes in the fractured articular cartilage specimens (mean 18.5%, range 1-44%) was found to be an order of magnitude higher than the percentage observed in control specimens (mean 1.9%, range 0-4%). CONCLUSIONS: The percentage of TUNEL positive chondrocytes following intraarticular fracture is much higher than that reported for chronic degenerative conditions such as osteoarthritis and rheumatoid arthritis. These data provide strong evidence that chondrocyte apoptosis is a consequence of intraarticular fracture and suggest that chondrocyte apoptosis may play a particularly significant role in the subsequent development of post-traumatic arthritis.

Adult↗
PubMed1977

Immunological regulation of spontaneous antibodies to DNA and RNA. II. Sequential switch from IgM to IgG in NZB/NZW F1 mice.

Serial serum samples from NZB/NZW F1 mice were studied by sucrose density gradient ultracentrifugation and filter radioimmunoassay for the immunoglobulin class of antibodies to double-stranded DNA and single-stranded RNA (Poly A). These antibodies occur spontaneously during the course of an autoimmune disease resembling systemic lupus erythematosus. Study of serum samples at 2-week intervals showed the sequential appearance of 19S followed by 7S anti-nucleic acid antibodies, an earlier commitment to 7S antibodies in female compared to male mice, and an independent and unrelated switching mechanism (19S-7S) for antibodies to DNA and Poly A. The more severe disease in female mice is correlated with an earlier appearance of 7S anti-DNA antibodies. This sequential and ordered appearance of antibodies to nucleic acids is discussed in relation to possible immunologic regulatory mechanisms.

Animals↗
PubMed1975

Anti-nucleic acid antibodies in systemic lupus erythematosus patients and their families. Incidence and correlation with lymphocytotoxic antibodies.

Anti-RNA antibodies were found in 82% of 28 systemic lupus erythematosus (SLE) probands and in 16% of 124 of their family members. The incidence in 76 control family members was only 5%. In the SLE family members, the antibodies were found exclusively in 21% of the 94 close household contacts of the probands. The incidence of anti-native DNA (nDNA) antibodies was 68% for the SLE probands. The incidence of anti-nDNA antibodies in close household contacts of the probands was 6%, which was not significantly different from the 1% incidence found in control families. Lymphocytotoxic antibodies occurred in 57% of the SLE family members as a whole and in 68% of the close household contacts. In the SLE probands, lymphocytotoxic antibodies correlated with anti-single-stranded RNA (poly A) and anti-nDNA but not with anti-double-stranded RNA (poly A-poly U). On the other hand, lymphocytotoxic antibodies in the household contacts correlated with anti-double-stranded RNA (poly A-poly U) but not with anti-poly A or anti-nDNA. The anti-RNA antibodies were present in consanguineous household contacts but not in nonconsanguineous household contacts. These findings strengthen the hypothesis that both an environmental agent, possibly a virus, as well as the genetic response are important in the pathogenesis of SLE. Family members may therefore be a logical population in whom to search for specific antibodies to a viral agent.

Adult↗
PubMed1975

Independent appearance of anti-thymocyte and anti-RNA antibodies in NZB/NZW F1 mice.

NZB and NZB/NZW (B/W) mice were studied for natural thymocytoxic autoantibody(NTA) and antibody to reovirus RNA by cytotoxicity and radioimmunoassay respectively.NZB mice developed NTA by 2-3 months of age. RNA antibodies appeared later if atall. NTA and anti-RNA were present in B/W mice starting at 4-5 months and increased in frequency with age. Either activity could appear first and could be present without the other. Thus, all four possible patterns of autoantibody occurrence were found. NTA and anti-RNA in 12-month B/W sera were separable by sucrose density gradient ultracentrifugation; NTA is a 19S IgM antibody whereas anti-RNA is 7S.

Animals↗
PubMed1975

Acceleration of autoimmunity in NZB/NZW F1 mice by graft-versus-host disease.

Chronic graft-versus-host (GVH) disease was induced in NZB/NZW F1 (B/W) hybrid female mice by the weekly injection of parental NZB spleen cells. Control mice received injections of syngeneic spleen cells only. The mice were assayed for antibodies to [3H]DNA and [3H]polyadenylic-polyuridylic acid by a cellulose ester filter radioimmunoassay, and for antibody to thymocytes by a cytotoxicity method. GVH disease accelerated the development of all three antibodies in B/W mice. In addition, sucrose density gradient ultracentrifugation of pooled sera suggested that an accelerated switch from 19S to 7S anti-DNA production may be an early effect of GVH. The mechanism of acceleration is discussed in terms of immunological and viral factors generated by the GVH reaction.

Animals↗
PubMed1973

Monoclonal macroglobulinemia in NZB-NZW F1 mice.

Serum monoclonal macroglobulins were detected in over 30% of NZB/NZW F(1) mice greater than 11 mo of age. The monoclonal nature of the IgM was shown by restricted electrophoretic mobility, characteristic appearance on immunoelectrophoresis, restriction to a single light chain type, and ability to induce anti-idiotypic antisera. The monoclonal macroglobulins were separated from antibodies to DNA and RNA that migrated in the 7S region of sucrose gradients. Enlarged lymph nodes were often present in mice with monoclonal IgM, and a transplantable IgM-producing lymphoid tumor was established from the spleen of one animal.

Animals↗