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P W Anderson

Publications and source records attributed to P W Anderson.

At least 19 recordsLinked to original sources
PubMed2006

Determining the underlying Fermi surface of strongly correlated superconductors.

The notion of a Fermi surface (FS) is one of the most ingenious concepts developed by solid-state physicists during the past century. It plays a central role in our understanding of interacting electron systems. Extraordinary efforts have been undertaken, by both experiment and theory, to reveal the FS of the high-temperature superconductors, the most prominent class of strongly correlated superconductors. Here, we discuss some of the prevalent methods used to determine the FS and show that they generally lead to erroneous results close to half-filling and at low temperatures, because of the large superconducting gap (pseudogap) below (above) the superconducting transition temperature. Our findings provide a perspective on the interplay between strong correlations and superconductivity and highlight the importance of strong coupling theories for the characterization and determination of the underlying FS in angle-resolved photoemission spectroscopy experiments.

Journal Article↗
PubMed2006

Electronic structure of strongly correlated d-wave superconductors.

We study the electronic structure of a strongly correlated d-wave superconducting state. Combining a renormalized mean field theory with direct calculation of matrix elements, we obtain explicit analytical results for the nodal Fermi velocity upsilon(F), the Fermi wave vector k(F), and the momentum distribution n(k) as a function of hole doping in a Gutzwiller projected d-wave superconductor. We calculate the energy dispersion E(k) and spectral weight of the Gutzwiller-Bogoliubov quasiparticles and find that the spectral weight associated with the quasiparticle excitation at the antinodal point shows a nonmonotonic behavior as a function of doping. Results are compared to angle resolved photoemission spectroscopy of the high-temperature superconductors.

Journal Article↗
PubMed2006

Physics of the resonating valence bond (pseudogap) state of the doped mott insulator: spin-charge locking.

The properties of the pseudogap phase above T(C) of the high-T(C) cuprate superconductors are described by showing that the Anderson-Nambu SU(2) spinors of a resonating valence bond spin gap "lock" to those of the electron charge system because of the resulting improvement of kinetic energy. This enormously extends the range of the vortex liquid state in these materials. A heuristic description of the nonlocal electrodynamics of this pseudogap-vortex liquid state is proposed.

Journal Article↗
PubMed2005

Thermodynamics of an incommensurate quantum crystal.

We present a theory of the thermodynamics of an incommensurate quantum solid. The ground state of the solid is assumed to be an incommensurate crystal, with quantum zero-point vacancies and interstitials and thus a non-integer number of atoms per unit cell. We show that at low temperature T, the variation of the net vacancy concentration should be as T4 and that the first correction to the specific heat due to this varies as T7; these are quite consistent with experiments on solid helium-4. We also make some observations about the recent experimental reports of "supersolidity" in solid helium-4 that motivate a renewed interest in quantum crystals.

Journal Article↗
PubMed2001

Design and methods of the Raloxifene Use for The Heart (RUTH) study.

Raloxifene is a selective estrogen receptor modulator that lowers total and low-density lipoprotein (LDL) cholesterol, reduces the risk of vertebral fracture, and is associated with a reduced incidence of invasive breast cancer in postmenopausal women with osteoporosis. The Raloxifene Use for The Heart (RUTH) trial is designed to determine whether raloxifene 60 mg/day compared with placebo: (1) lowers the risk of the coronary events (coronary death, nonfatal myocardial infarction [MI], or hospitalized acute coronary syndromes other than MI); and (2) reduces the risk of invasive breast cancer in women at risk for a major coronary event. RUTH is a double-blind, placebo-controlled, randomized clinical trial of 10,101 postmenopausal women aged > or =55 years from 26 countries. Women are eligible for randomization if they are postmenopausal and have documented coronary heart disease (CHD), peripheral arterial disease, or multiple risk factors for CHD. Use of estrogen within the previous 6 months is an exclusion factor. The study will be terminated after a minimum of 1,670 participants experience a primary coronary end point. Secondary end points include cardiovascular death, myocardial revascularization, noncoronary arterial revascularization, stroke, all-cause hospitalization, all-cause mortality, all breast cancers, clinical fractures, and venous thromboembolic events, in addition to the individual components of the composite primary coronary end point. RUTH will provide important information about the risk-benefit ratio of raloxifene in preventing acute coronary events and invasive breast cancer, as well as information about the natural history of CHD in women at risk of major coronary events.

Angina, Unstable↗
PubMed2001

Effects of raloxifene and hormone replacement therapy on markers of serum atherogenicity in healthy postmenopausal women.

OBJECTIVE: To determine the effect of raloxifene (RLX) and hormone replacement therapy (HRT) on non-high density lipoprotein cholesterol (non-HDL-C) levels and the apolipoprotein-B/apolipoprotein-A1 (apo-B/apo-A1) concentration ratio, markers of serum atherogenicity, in postmenopausal women. METHODS: Three hundred and ninety healthy postmenopausal women aged 45-72 years were enrolled in a double-blind, randomized, placebo-controlled, parallel trial at eight outpatient sites in the United States. Women were randomly assigned to receive continuous combined HRT (0.625 mg/day conjugated equine estrogen and 2.5 mg/day medroxyprogesterone acetate), 60 or 120 mg/day raloxifene, or placebo for 6 months. Serum concentrations of non-HDL cholesterol and the apo-B/apo-A1 concentration ratio were measured in serum samples obtained at baseline and at 6 months of treatment. RESULTS: At 6 months, non-HDL-C and apo-B/apo-A1 were significantly reduced by 60 mg/day RLX (10 and 11%, respectively), 120 mg/day RLX (9 and 12%, respectively) and HRT (10 and 12%, respectively), compared with placebo. The effect of all treatments to lower non-HDL-C and apo-B/apo-A1 was greatest in women with hypercholesterolemia (total-C>240 mg/dl) at baseline. Among women with undesirable (>160 mg/dl) non-HDL cholesterol at baseline, RLX and HRT lowered the percentage of these women remaining above this threshold after 6 months (placebo, 89%; 60 mg/day RLX, 61%; 120 mg/day RLX, 74%; HRT, 58%). Similar results were observed for women with high (>190 mg/dl) non-HDL cholesterol at baseline. CONCLUSION: In healthy postmenopausal women, RLX and HRT lower serum non-HDL-C and apo-B/apo-A1, indicators of serum atherogenicity, to a similar extent.

Aged↗
PubMed2001

Nature of spin excitations in two-dimensional mott insulators: undoped cuprates and other materials.

We investigate the excitation spectrum of a two-dimensional resonating valence bond (RVB) state. Treating the pi-flux phase with antiferromagnetic correlations as a variational ground state, we recover the long wavelength magnon as an "RVB exciton." However, this excitation does not exhaust the entire spectral weight and the high-energy spectrum is dominated by fermionic excitations. The latter can be observed directly by inelastic neutron scattering, and we predict their characteristic energy scales along different high symmetry directions in the magnetic Brillouin zone. We also interpret experimental results on two magnon Raman scattering and midinfrared absorption within this scenario.

Journal Article↗
PubMed2001

Giant enhancement of the thermal Hall conductivity kappa(xy) in the superconductor YBa(2)Cu(3)O(7).

In high-purity YBa(2)Cu(3)O(7), the (weak-field) thermal Hall conductivity kappa(xy) is observed to increase a thousand-fold between 90 and 30 K. The inferred quasiparticle lifetime tau increases a hundred-fold starting below 90 K, in disagreement with a recent photoemission experiment. We show that kappa(xy) exhibits a specific scaling behavior below approximately 30 K. This scaling may bear on the issue of whether Landau quantization of the quasiparticle states occurs.

Journal Article↗
PubMed2001

Effect of raloxifene on serum triglycerides in postmenopausal women: influence of predisposing factors for hypertriglyceridemia.

BACKGROUND: Estrogen increases serum triglyceride (TG) levels and induces hypertriglyceridemia in susceptible women. The effect of raloxifene (RLX), a selective estrogen-receptor modulator, on serum TG has not been studied in detail. OBJECTIVE: The purpose of this study was to examine the effect of RLX on serum TG levels in postmenopausal women with and without osteoporosis, including those with predisposing factors for hypertriglyceridemia. METHODS: Fasting serum TG levels were assessed over 36 months in 2738 osteoporotic postmenopausal women (mean age, 67 years) assigned to placebo or RLX (60 or 120 mg/d) in an osteoporosis treatment trial and over 24 months in 1318 postmenopausal women without osteoporosis (mean age, 54 years) assigned to placebo or RLX (60 or 150 mg/d) in 3 osteoporosis prevention trials. RESULTS: In the osteoporosis treatment trial, the median serum TG concentration decreased in all groups, but significantly more in the placebo group (placebo, -3.4%; RLX 60 mg/d, -1.4%; RLX 120 mg/d, -1.3%; P = 0.002). In the osteoporosis prevention trials, the percentage change in median serum TG concentration was not significantly different among treatments (P = 0.22). Among women with varying degrees of hypertriglyceridemia at baseline (>2.82, >3.39, and >4.51 mmol/L), the median serum TG level at the end of the study decreased from baseline in all groups, with no significant differences among treatments (P > or = 0.13). The effect of RLX on serum TG level was not influenced by age, smoking status, use of alcohol, or presence of diabetes (P > or = 0.10 for all interactions). Among women in the highest tertile of body mass index (>26.4 kg/m2), RLX increased serum TG levels significantly compared with placebo (placebo, -3%; RLX 60 mg/d, 6%: RLX 120 mg/d, 4%; P < 0.05); the absolute increase from baseline with RLX in this subgroup was 0.05 mmol/L (4.4 mg/dL). CONCLUSIONS: RLX did not increase serum TG in postmenopausal women overall or among women with elevated TG levels or evidence of diabetes at baseline. TG levels increased slightly but statistically significantly in women in the upper tertile of body mass index who were treated with RLX.

Adult↗
PubMed2001

Monoclonal antibodies specific for Neisseria meningitidis group B polysaccharide and their peptide mimotopes.

From five mice immunized with Escherichia coli K1 bacteria, we produced 12 immunoglobulin M hybridomas secreting monoclonal antibodies (MAbs) that bind to Neisseria meningitidis group B (NMGB). The 12 MAbs also bound the capsular polysaccharide (PS) of E. coli K1 [which, like NMGB, is alpha(2-8)-linked polysialic acid (PSA)] and bound to EV36, a nonpathogenic E. coli K-12 strain producing alpha(2-8) PSA. Except for HmenB5, which cross-reacted with N. meningitidis group C, none of the MAbs bound to N. meningitidis groups A, C, and Y. Of the 12 MAbs, 6 were autoantibodies as defined by binding to CHP-134, a neuroblastoma cell line expressing short-chain alpha(2-8) PSA; five of these MAbs killed NMGB in the presence of rabbit complement, and two also killed NMGB with human complement. The other six MAbs, however, were nonautoreactive; all killed NMGB with rabbit complement, and five killed NMGB with human complement. To obtain peptide mimotopes of NMGB PS, four of the nonautoreactive MAbs (HmenB2, HmenB3, HmenB13, and HmenB14) were used to screen two types of phage libraries, one with a linear peptide of 7 amino acids and the other with a circular peptide of 7 amino acids inserted between two linked cysteines. We obtained 86 phage clones that bound to the screening MAb in the absence but not in the presence of E. coli K1 PSA in solution. The clones contained 31 linear and 4 circular mimotopes expressing unique sequences. These mimotopes nonrandomly expressed amino acids and were different from previously described mimotopes for NMGB PS. The new mimotopes may be useful in producing a vaccine(s) capable of eliciting anti-NMGB antibodies not reactive with neuronal tissue.

Amino Acid Sequence↗
PubMed2000

The effects of hormone replacement therapy and raloxifene on C-reactive protein and homocysteine in healthy postmenopausal women: a randomized, controlled trial.

C-Reactive protein and homocysteine are independent risk factors for the development of cardiovascular disease. This study compared the effects of hormone replacement therapy (HRT) and raloxifene on serum C-reactive protein and homocysteine levels as markers of cardiovascular risk in healthy postmenopausal women. Healthy postmenopausal women (n = 390) were enrolled in a double blind, randomized, placebo-controlled, 6-month trial at eight out-patient sites in the United States. Women were randomly assigned to receive continuous combined HRT (0.625 mg/day conjugated equine estrogen and 2.5 mg/day medroxyprogesterone acetate), raloxifene (60 or 120 mg/day), or placebo for 6 months. C-Reactive protein and homocysteine were measured in baseline and 6-month serum samples. HRT increased C-reactive protein levels by 84% (P<0.001), whereas raloxifene (60 and 120 mg/day) had no significant effect (-6% and -4%;, respectively; P>0.2). Raloxifene (60 and 120 mg/day) significantly lowered serum levels ofhomocysteine by 8% (P = 0.014) and 6% (P = 0.024), respectively, similar to the 7% (P = 0.014) reduction obtained with HRT. We conclude that HRT and raloxifene lower serum homocysteine levels to a comparable extent in postmenopausal women. Whereas cardiovascular risk predicted by C-reactive protein in healthy postmenopausal women is not influenced by raloxifene, the relationship between elevated C-reactive protein levels with HRT and cardiovascular disease events requires further study.

Aged↗
PubMed1998

Effects of raloxifene on serum lipids and coagulation factors in healthy postmenopausal women.

CONTEXT: Raloxifene is a selective estrogen receptor modulator that has estrogen-agonistic effects on bone and estrogen-antagonistic effects on breast and uterus. OBJECTIVE: To identify the effects of raloxifene on markers of cardiovascular risk in postmenopausal women, and to compare them with those induced by hormone replacement therapy (HRT). DESIGN: Double-blind, randomized, parallel trial. SETTING: Eight sites in the United States. PARTICIPANTS: 390 healthy postmenopausal women recruited by advertisement. INTERVENTION: Participants were randomized to receive 1 of 4 treatments: raloxifene, 60 mg/d; raloxifene, 120 mg/d; HRT (conjugated equine estrogen, 0.625 mg/d, and medroxyprogesterone acetate, 2.5 mg/d); or placebo. MAIN OUTCOME MEASURES: Change and percent change from baseline of lipid levels and coagulation parameters after 3 months and 6 months of treatment. RESULTS: At the last visit completed, compared with placebo, both dosages of raloxifene significantly lowered low-density lipoprotein cholesterol (LDL-C) by 12% (P < .001), similar to the 14% reduction with HRT (P < .001). Both dosages of raloxifene significantly lowered lipoprotein(a) by 7% to 8% (P < .001), less than the 19% decrease with HRT (P<.001). Raloxifene increased high-density lipoprotein-2 cholesterol (HDL2-C) by 15% to 17% (P < .05), less than the 33% increase with HRT (P < .001). Raloxifene did not significantly change high-density lipoprotein cholesterol (HDL-C), triglycerides, or plasminogen activator inhibitor-1 (PAI-1); whereas HRT increased HDL-C by 11% and triglycerides by 20%, and decreased PAI-1 by 29% (for all, P < .001). Raloxifene significantly lowered fibrinogen by 12% to 14% (P < .001), unlike HRT, which had no effect. Neither treatment changed fibrinopeptide A or prothrombin fragment 1 and 2. CONCLUSIONS: Raloxifene favorably alters biochemical markers of cardiovascular risk by decreasing LDL-C, fibrinogen, and lipoprotein(a), and by increasing HDL2-C without raising triglycerides. In contrast to HRT, raloxifene had no effect on HDL-C and PAI-1, and a lesser effect on HDL2-C and lipoprotein(a). Further clinical trials are necessary to determine whether these favorable biochemical effects are associated with protection against cardiovascular disease.

Aged↗
PubMed1998

Hormone and nonhormone therapy for the maintenance of postmenopausal health: the need for randomized controlled trials of estrogen and raloxifene.

Multiple health benefits have been postulated for the long-term use of hormone therapy in postmenopausal women, most notably for prevention of osteoporotic fractures and coronary heart disease, as well as several risks, including cancer of the breast and uterus and venous thromboembolism. Cardiovascular disease is the most common cause of death among postmenopausal women. If real, the reduction in risk of coronary heart disease by hormone use suggested by observational studies would likely outweigh the risks. The decision to initiate and maintain hormone therapy is complicated by uncertainties about estrogen's true benefits and risks. Raloxifene, a selective estrogen receptor modulator (SERM), appears to have many of the benefits of estrogen without the cancer risks. It is not known if SERMs can provide significant cardiovascular protection. This article reviews the relation of use of postmenopausal hormones and raloxifene to women's health and addresses the need for large randomized trials to quantify the effect of both postmenopausal estrogen and raloxifene on cardiovascular health.

Cardiovascular Diseases↗
PubMed1997

The baboon as a nonhuman primate model for assessing the effects of maternal immunization with Haemophilus influenzae type b polysaccharide vaccines.

These studies were performed to assess the utility of the baboon as a nonhuman primate model to evaluate vaccines for use in humans. Specifically, we examined the antibody response of baboons immunized during the third trimester of pregnancy with Haemophilus influenzae type b (Hib) polyribosylribitol phosphate (PRP) conjugate and unconjugated polysaccharide vaccines. Some of the vaccinated mothers failed to respond to a single immunization with unconjugated Hib PRP. Specific Hib PRP immunoglobulin G (IgG) but not IgM antibodies cross the baboon placenta and are detected in the offspring. Higher-titer baboon anti-Hib PRP did not express two previously defined cross-reactive human anti-Hib PRP idiotypes and was biased towards lambda light-chain expression. Spectrotype analysis indicated that baboon anti-Hib PRP was restricted in heterogeneity and oligoclonal.

Animals↗
PubMed1996

Insulin and angiotensin II are additive in stimulating TGF-beta 1 and matrix mRNAs in mesangial cells.

Angiotensin II (Ang II) and insulin are implicated in the mesangial cell hypertrophy and excessive accumulation of mesangial matrix seen in glomerulosclerosis. Therefore, the effects of Ang II with and without insulin on mRNA levels of several important extracellular matrix genes and transforming growth factor beta-1 (TGF-beta 1) were examined. Ang II alone (1 microM) added to quiescent, murine mesangial cells in serum-free, insulin-free media slightly but not significantly increased TGF-beta 1, fibronectin, collagen I, collagen IV and laminin message levels. The slight elevations in message expression were reversed by losartan, suggesting that these modest effects are mediated by the AT-1 receptor. Ang II alone also had no significant effects on TGF-beta 1 and extracellular matrix message levels in quiescent rat mesangial cells. In contrast, significant increases in mRNA for collagen 1 (6-fold), collagen IV (4-fold), fibronectin 1 (4-fold) and TGF-beta 1 (2-fold) were seen with insulin alone (10(-6)M) in rat mesangial cells, and a dose-response effect could be demonstrated for insulin (10(-9) to 10(-6)M). Ang II plus insulin further significantly increased collagen I (9-fold), collagen IV (9-fold), fibronectin 1 (5-fold) and TGF-beta 1 (3-fold) message expression. These effects were partially reversed in the presence of losartan. The Northern analyses were supported by measurements of active and total TGF-beta 1 activity (pg/ml/ 5 x 10(6) cells): 1145 +/- 76 and 1960 +/- 199, serum free control; 1121 +/- 92 and 1932 +/- 214, Ang II (10(-6)M); 4589 +/- 103 (P < 0.001 vs. control) and 11071 +/- 1952 (P < 0.01 vs. control), insulin (10(-6)M); and 6881 +/- 183 (P < 0.001 vs. control) and 16626 +/- 1435 (P < 0.01 vs. control), insulin plus Ang II. These results suggest that insulin, itself, significantly increases TGF-beta 1 and extracellular matrix gene expression in rat mesangial cells. Ang II alone has modest effects, while Ang II and insulin have additive effects. To explain the mechanism of these additive effects, we investigated the action of Ang II on insulin signaling and the effect of insulin on Ang II AT1 receptor mRNA expression. Ang II did not enhance insulin-induced insulin receptor substrate-1 (IRS-1) phosporylation or phosphatidylinositol3 (PI-3) kinase activity, but did enhance insulin-induced mitogen activated protein (MAP) kinase activity. Insulin increased message levels of AT1 receptor by twofold. These results suggest that enhancement of MAP kinase activity and AT1 receptor regulation by insulin may contribute to the additive effects of insulin and Ang II in mesangial cells.

Angiotensin II↗