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Biomedical subjects

G Blumberg

Publications and source records attributed to G Blumberg.

At least 19 recordsLinked to original sources
PubMed2006

Quantum melting of the hole crystal in the spin ladder of Sr(14-x)CaxCu24O41.

We have used resonant soft x-ray scattering to study the effects of discommensuration on the hole Wigner crystal (HC) in the spin ladder Sr(14-x)CaxCu24O41 (SCCO). As the hole density is varied the HC forms only with the commensurate wave vectors L(L) = 1/5 and L(L) = 1/3; for incommensurate values it "melts." A simple scaling between L(L) and temperature is observed, tau1/3/tau1/5 = 5/3, indicating an inverse relationship between the interaction strength and wavelength. Our results suggest that SCCO contains hole pairs that are crystallized through an interplay between lattice commensuration and Coulomb repulsion, reminiscent of the "pair density wave" scenario.

Journal Article↗
PubMed2004

Crystallization of charge holes in the spin ladder of Sr14Cu24O41.

Determining the nature of the electronic phases that compete with superconductivity in high-transition-temperature (high-T(c)) superconductors is one of the deepest problems in condensed matter physics. One candidate is the 'stripe' phase, in which the charge carriers (holes) condense into rivers of charge that separate regions of antiferromagnetism. A related but lesser known system is the 'spin ladder', which consists of two coupled chains of magnetic ions forming an array of rungs. A doped ladder can be thought of as a high-T(c) material with lower dimensionality, and has been predicted to exhibit both superconductivity and an insulating 'hole crystal' phase in which the carriers are localized through many-body interactions. The competition between the two resembles that believed to operate between stripes and superconductivity in high-T(c) materials. Here we report the existence of a hole crystal in the doped spin ladder of Sr14Cu24O41 using a resonant X-ray scattering technique. This phase exists without a detectable distortion in the structural lattice, indicating that it arises from many-body electronic effects. Our measurements confirm theoretical predictions, and support the picture that proximity to charge ordered states is a general property of superconductivity in copper oxides.

Journal Article↗
PubMed2004

Magnetic order in lightly doped La2-xSrxCuO4.

We study long wavelength magnetic excitations in lightly doped La2-xSrxCuO4 (x</=0.03) detwinned crystals. The lowest energy magnetic anisotropy induced gap can be understood in terms of the antisymmetric spin interaction inside the antiferromagnetic (AF) phase. The second magnetic resonance, analyzed in terms of in-plane spin anisotropy, shows unconventional behavior within the AF state; it led to the discovery of collective spin excitations pertaining to a field induced magnetically ordered state. This state persists in a 9 T field to more than 100 K above the Néel temperature in x=0.01.

Journal Article↗
PubMed2003

Collective density-wave excitations in two-leg Sr14-xCaxCu24O41 ladders.

Raman measurements in the 1.5-20 cm(-1) energy range were performed on single crystals of Sr14-xCaxCu24O41. A quasielastic scattering peak (QEP) which softens with cooling is observed only in the polarization parallel to the ladder direction for samples with x=0, 8, and 12. The QEP is a Raman fingerprint of pinned collective density wave excitations screened by uncondensed carriers in the ladder structures. Our results suggest that transport in metallic samples, which is similar to transport in underdoped high-T(c) cuprates, is driven by a collective electronic response.

Journal Article↗
PubMed2002

Sliding density wave in Sr14Cu24O41 ladder compounds.

We used transport and Raman scattering measurements to identify the insulating state of self-doped spin (1/2) two-leg ladders of Sr14Cu24O41 as a weakly pinned, sliding density wave with nonlinear conductivity and a giant dielectric response that persists to remarkably high temperatures.

Journal Article↗
PubMed2002

Nonmonotonic d(x(2)-y(2)) superconducting order parameter in Nd2-xCexCuO4.

Low energy polarized electronic Raman scattering of the electron-doped superconductor Nd2-x Ce x CuO4 ( x = 0.15, T(c) = 22 K) has revealed a nonmonotonic d(x(2)-y(2)) superconducting order parameter. It has a maximum gap of 4.4k(B)T(c) at Fermi surface intersections with an antiferromagnetic Brillouin zone (the "hot spots") and a smaller gap of 3.3k(B)T(c) at fermionic Brillouin zone boundaries. The gap enhancement in the vicinity of the hot spots emphasizes the role of antiferromagnetic fluctuations and the similarity in the origin of superconductivity for electron- and hole-doped cuprates.

Journal Article↗
PubMed2002

Attitudes of mothers toward their daughters' use of contraceptives in Israel.

The objective of the study was to examine mothers' knowledge about contraception, their attitudes to their daughters' use of contraception, and their communication with their daughters on the subject. A 20-item questionnaire was distributed in gynecological clinics throughout Israel for completion by women who had daughters over the age of 14 years. The questionnaire covered the mothers' demographic data, use of contraception, knowledge of contraception, attitude to their daughters' contraceptive use and sexual relationships, and communication with their daughters about contraception. Only 36% of the women received contraceptive information from physicians. Almost half felt their daughter should begin sexual relations when she felt she was ready; over two-thirds felt she should begin using contraception before or at the time of beginning sexual relations. Over three-quarters spoke with their daughters about contraception. Higher educational level of the mother was associated with high rate use of contraception by the mother, her support of earlier use of contraception by her daughter, a greater likelihood of her discussing contraception with her daughter, and a lesser likelihood to view contraceptives as dangerous to one's health. It is concluded that mothers of teenage daughters in Israel are involved in their daughters' decisions to begin sexual relations and the use of contraceptives. Their knowledge of contraception is adequate, although some gaps are still apparent. Clear correlation is found between higher educational level of the mothers and a more liberal attitude toward their daughters' sex life.

Adolescent↗
PubMed2002

The health-promoting behaviors and attitude towards menopause and hormone replacement therapy among women on dialysis.

The aim of this study was to assess the health-related behaviors, knowledge and attitude towards menopause and hormone replacement therapy (HRT) among women receiving dialysis treatment. The study population consisted of 44 women aged 55-75 years attending the dialysis unit. All women completed a 20-item questionnaire, which covered information on personal health-care habits, life style and attitude regarding menopause and HRT. The majority of participants were of desirable weight (body mass index < 25 kg/m2) and had a positive body image. About 80% had never smoked, and did not engage in regular physical activity. Over half underwent annual Pap smear, mammography, breast examination by a physician, and only a small minority performed breast self-examination. Surprisingly, 45% had used HRT in the past, but only 5% were current users. Although we expected postmenopausal women with a life-threatening disease to be more aware of personal health care than the general population, only a relatively small percentage of the study population safeguarded their health care, and used HRT. Stronger educational efforts may be needed to promote health-related behaviors and a positive attitude to health care, aging and menopause in this subgroup of patients.

Aged↗
PubMed2001

Spin dynamics of Sr14Cu24O41 two-leg ladder studied by Raman spectroscopy.

The two-magnon (2M) excitation at 3000 cm(-1) in Sr14Cu24O41 two-leg ladder is studied by Raman scattering. A slight anisotropy of the superexchange coupling J(perpendicular)/J(parallel) approximately 0.8 with J(parallel) = 110+/-20 meV is proposed from the analysis of the magnetic scattering. The resonant coupling across the charge transfer gap increases the 2M intensity by orders of magnitude. The anisotropy of Raman scattering is dependent upon the excitation energy. The 2M relaxation is found to be correlated with the temperature dependent electronic Raman continuum at low frequencies.

Journal Article↗
PubMed1997

Evolution of magnetic and superconducting fluctuations with doping of high-Tc superconductors

Electronic Raman scattering from high- and low-energy excitations was studied as a function of temperature, extent of hole doping, and energy of the incident photons in Bi2Sr2CaCu2O8+/-delta superconductors. For underdoped superconductors, short-range antiferromagnetic (AF) correlations were found to persist with hole doping, and doped single holes were found to be incoherent in the AF environment. Above the superconducting (SC) transition temperature Tc, the system exhibited a sharp Raman resonance of B1g symmetry and energy of 75 millielectron-volts and a pseudogap for electron-hole excitations below 75 millielectron-volts, a manifestation of a partially coherent state forming from doped incoherent quasi particles. The occupancy of the coherent state increases with cooling until phase ordering at Tc produces a global SC state.

Journal Article↗
PubMed1996

Women's attitudes towards menopause and hormone replacement therapy.

OBJECTIVES: To determine how women aged 50 years or more feel about menopause, and their knowledge, use of and attitude toward hormone replacement therapy (HRT). METHODS: All study participants resided in a single urban community in central Israel and were selected at random from the computerized government registry. Responses were collected by either telephone interview (n = 171) or mailed questionnaire (n = 41) and were analyzed for the group as a whole and by different demographic and attitudinal factors. RESULTS: Most (80%) of the women had a positive or neutral attitude to menopause. More than 80% had heard of HRT, 55% of whom from a physician. Of these, 12% were currently using HRT and 9.5% had done so in the past. Varied reasons were offered for starting or stopping treatment. CONCLUSIONS: Although the great majority of the participants had heard of HRT, and most of these had spoken about it with a doctor, only a small percentage were currently under therapy or had been in the past. We believe gynecologists should devote more effort to public education, in that those women who had discussed HRT with their physician were more likely to use it.

Aged↗
PubMed1996

Fetal oximetry monitoring: a new wonder or another mirage?

This review provides recent data and clinical opinions on a new technology in assessing fetal well-being during labor, the fetal pulse oximeter. Fetal pulse oximetry is potentially superior to electronic fetal heart rate monitoring because it allows direct assessment of both fetal oxygen status and fetal tissue perfusion. Several studies during recent years have demonstrated that fetal pulse oximetry during labor is feasible and accurate. On the other hand, these very same studies have demonstrated a few potential disadvantages and limitations of fetal oximetry. The main limitation seems to be a wide range of normal values. The correlation of fetal oximetry during labor with perinatal outcome and long-term newborn outcome has not yet been determined. In summary, fetal pulse oximetry during labor merits further randomized prospective studies, especially with regard to improvement of perinatal outcome.

Bias↗
PubMed1996

Impaired renal vasodilation and urinary cGMP excretion in Dahl salt-sensitive rats.

We previously have shown that Dahl salt-sensitive rats increase renal vascular resistance in response to excessive salt feeding before total peripheral resistance increases and hypertension occurs. Failure of renal vasculature to dilate, as normally occurs in Dahl salt-resistant rats fed a high salt diet, may play a role in the development of hypertension in Dahl salt-sensitive rats. We also showed that renal vasculature in salt-sensitive rats is hyperreactive to vasoconstrictors and hyporeactive to vasodilators. Atrial natriuretic peptide, by stimulating cell-bound receptors, and nitroprusside, by generating nitric oxide, cause renal vasodilation by generating cGMP. Studies were undertaken to determine whether defective renal vasodilation in Dahl salt-sensitive rats is due to impaired production of cGMP. We examined the influence of nitroprusside infusion and salt intake on renal vascular resistance and cGMP excretion in salt-sensitive rats. Results demonstrate that salt feeding and nitroprusside infusion increase cGMP excretion and decrease renal vascular resistance in salt-resistant rats (P < .01), and, although this relationship was less clear in salt-sensitive rats, there was a reciprocal relationship between renal vascular resistance and cGMP excretion in all animals studied. Salt feeding and nitroprusside infusion caused less of an increase in cGMP excretion in salt-sensitive than in salt-resistant rats (P < .01). In conclusion, these studies support the concept that impairment in cGMP generation may play a primary role in the inability of the kidneys of Dahl salt-sensitive rats to vasodilate in response to increased salt intake. Such an impairment could contribute to salt retention and the development of hypertension.

Animals↗