A multi-component Fermi surface in the vortex state of an underdoped high-Tc superconductor.

To understand the origin of superconductivity, it is crucial to ascertain the nature and origin of the primary carriers available to participate in pairing. Recent quantum oscillation experiments on high-transition-temperature (high-T(c)) copper oxide superconductors have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization. The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d-wave superconductivity. Here we report experiments on quantum oscillations in the magnetization (the de Haas-van Alphen effect) in superconducting YBa(2)Cu(3)O(6.51) that reveal more than one carrier pocket. In particular, we find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Importantly, characteristics of the multiple pockets within this more complete Fermi surface impose constraints on the wavevector of any underlying order and the location of the carriers in momentum space. These constraints enable us to construct a possible density-wave model with spiral or related modulated magnetic order, consistent with experimental observations.

High-magnetic-field lattice length changes in URu2Si2.

We report high-magnetic-field (up to 45 T) c-axis thermal-expansion and magnetostriction experiments on URu(2)Si(2) single crystals. The sample length change ΔL(c)(T(HO))/L(c) associated with the transition to the "hidden order" phase becomes increasingly discontinuous as the magnetic field is raised above 25 T. The reentrant ordered phase III is clearly observed in both the thermal expansion ΔL(c)(T)/L(c) and magnetostriction ΔL(c)(B)/L(c) above 36 T, in good agreement with previous results. The sample length is also discontinuous at the boundaries of this phase, mainly at the upper boundary. A change in the sign of the coefficient of thermal expansion α(c)=1/L(c)(∂ΔL(c)/∂T) is observed at the metamagnetic transition (B(M) ~ 38 T), which is likely related to the existence of a quantum critical end point.

Successive phase transitions and extended spin-excitation continuum in the S=1/2 triangular-lattice antiferromagnet Ba3CoSb2O9.

Using magnetic, thermal, and neutron measurements on single-crystal samples, we show that Ba3CoSb2O9 is a spin-1/2 triangular-lattice antiferromagnet with the c axis as the magnetic easy axis and two magnetic phase transitions bracketing an intermediate up-up-down phase in magnetic field applied along the c axis. A pronounced extensive neutron-scattering continuum above spin-wave excitations, observed below T(N), implies that the system is in close proximity to one of two spin-liquid states that have been predicted for a 2D triangular lattice.

Heavy holes as a precursor to superconductivity in antiferromagnetic CeIn3.

Numerous phenomenological parallels have been drawn between f- and d-electron systems in an attempt to understand their display of unconventional superconductivity. The microscopics of how electrons evolve from participation in large moment antiferromagnetism to superconductivity in these systems, however, remains a mystery. Knowing the origin of Cooper paired electrons in momentum space is a crucial prerequisite for understanding the pairing mechanism. Of special interest are pressure-induced superconductors CeIn(3) and CeRhIn(5) in which disparate magnetic and superconducting orders apparently coexist-arising from within the same f-electron degrees of freedom. Here, we present ambient pressure quantum oscillation measurements on CeIn(3) that crucially identify the electronic structure-potentially similar to high-temperature superconductors. Heavy hole pockets of f-character are revealed in CeIn(3), undergoing an unexpected effective mass divergence well before the antiferromagnetic critical field. We thus uncover the softening of a branch of quasiparticle excitations located away from the traditional spin fluctuation-dominated antiferromagnetic quantum critical point. The observed Fermi surface of dispersive f-electrons in CeIn(3) could potentially explain the emergence of Cooper pairs from within a strong moment antiferromagnet.

Magnetic enhancement of superconductivity from electron spin domains.

Since the discovery of superconductivity, there has been a drive to understand the mechanisms by which it occurs. The BCS (Bardeen-Cooper-Schrieffer) model successfully treats the electrons in conventional superconductors as pairs coupled by phonons (vibrational modes of oscillation) moving through the material, but there is as yet no accepted model for high-transition-temperature, organic or 'heavy fermion' superconductivity. Experiments that reveal unusual properties of those superconductors could therefore point the way to a deeper understanding of the underlying physics. In particular, the response of a material to a magnetic field can be revealing, because this usually reduces or quenches superconductivity. Here we report measurements of the heat capacity and magnetization that show that, for particular orientations of an external magnetic field, superconductivity in the heavy-fermion material CeCoIn(5) is enhanced through the magnetic moments (spins) of individual electrons. This enhancement occurs by fundamentally altering how the superconducting state forms, resulting in regions of superconductivity alternating with walls of spin-polarized unpaired electrons; this configuration lowers the free energy and allows superconductivity to remain stable. The large magnetic susceptibility of this material leads to an unusually strong coupling of the field to the electron spins, which dominates over the coupling to the electron orbits.

Blue-green algae: their excretion of iron-selective chelators enables them to dominate other algae.

During blue-green algal blooms, other algae can be completely suppressed. This ability of blue-green algae to suppress other algae may be determined by the abailability of iron. Iron deprivation induces the production of hydroxamate chelators, which appear to be the agent suppressing other algae.

Paget-Schroetter syndrome: A review and Algorithm (WASPS-IR).

Venous compression syndromes are rare and occur due to the entrapment of vein(s) in confined anatomical spaces bounded by osseous and non-osseous structures. Here we present a review of Paget-Schroetter Syndrome, an important cause of upper extremity of deep vein thrombosis, its associated clinical and radiological findings as well as treatment options.

Heavy fermions. Unconventional Fermi surface in an insulating state.

Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. The quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.

Arteriosclerosis obliterans in a rabbit model.

RATIONALE AND OBJECTIVES: The authors induced atherosclerotic occlusions in a rabbit model, using and comparing different experimental methods. METHODS: Lesions were induced in 40 femoral arteries in 20 rabbits. Four combinations of lesion induction methods were used: 1) drying of the endothelium with carbon dioxide gas; 2) gas-drying of the artery plus mechanical injury; 3) gas-drying plus induced thrombosis of the treated segment using thrombin; and 4) gas-drying, mechanical injury, and induced thrombosis. All rabbits were fed a high-fat, high-cholesterol diet for 1 to 2 months after lesion induction. RESULTS: Seventeen rabbits were available for follow-up. Sixty-eight percent (13 of 19) of femoral arteries treated with thrombin-induced thrombosis demonstrated atherosclerotic occlusions, compared with 27% of those that did not receive this treatment (4 of 15; P < .01). CONCLUSIONS: Thrombin-induced thrombotic occlusion of a segment of artery which has been de-endothelialized, followed by a high-fat, high cholesterol diet, results in a higher yield of experimental occlusive atherosclerosis in rabbits than is achievable by other methods.

O3-induced mucosa-linked airway muscle hyperresponsiveness in the guinea pig.

We investigated the effects of ozone exposure (3.0 ppm, 2 h) on the responsiveness of guinea pig airway muscle in vitro from animals developing bronchial hyperreactivity. Muscarinic reactivity in vivo was determined by measuring specific airway resistance (sRaw) in response to increasing concentrations of aerosolized acetylcholine (ACh) administered before and 30 min after exposure. Immediately after reactivity testing, multiple tracheal rings from ozone- and air-exposed animals were prepared and the contractile responses to increasing concentrations of substance P, ACh, or KCl were assessed in the presence of 10 microM indomethacin with or without 1 microM phosphoramidon, an inhibitor of neutral endopeptidase. Isometric force generation in vitro was measured on stimulation by cumulative concentrations of the agonists, and force generation (in g/cm2) was calculated after determination of muscle cross-sectional area. The smooth muscle of mucosa-intact airways from guinea pigs with ozone-induced bronchial hyper-reactivity proved to be hyperresponsive in vitro to substance P and ACh but not to KCl. Pretreatment with phosphoramidon abolished the increase in substance P responsiveness but had no effect on muscarinic hyperresponsiveness after ozone exposure. Furthermore, substance P responsiveness was not augmented in ozone-exposed airways in which the mucosa had been removed before testing in vitro. Likewise, muscarinic hyperresponsiveness was not present in ozone-exposed airways without mucosa. Our data indicate that airway smooth muscle responsiveness is increased in guinea pigs with ozone-induced bronchial hyperreactivity and suggest that this hyperresponsiveness may be linked to non-cyclooxygenase mucosa-derived factors.

A novel cell adhesion molecule, G-CAM, found on cultured rat glia.

Using a monoclonal antibody (mAb), designated AMP1, a novel cell adhesion molecule was identified on rat astrocytes and oligodendrocytes. When confluent monolayers of cultured rat astrocytes were labeled with AMP1, the antigen was discretely localized to the cell surface in regions of cell-cell contacts. The antibody did not label embryonic rat cortical neurons plated on monolayers of neonatal astrocytes, indicating that the antigen is neither present on cultured neurons nor does it reorganize on the glial surface under the neurons. On immunoblots of astrocytic or brain proteins, mAb AMP1 recognized a 106 kDa protein. In the present paper, data are presented demonstrating that the AMP1 antigen is a cell adhesion molecule and is distinct from all the known cell adhesion molecules present on astrocytes: N-CAM, N-cadherin, or members of the beta 1 integrin family. We have tentatively termed this molecule 'glial cell adhesion molecule' (G-CAM).

GC/MS analysis of m-hydroxybenzoylecgonine in urine. Forensic implication in cocaine use.

m-Hydroxybenzoylecgonine (m-OH-BE) and d3-m- hydroxybenzoylecgonine (d3-m-OH-BE) have been synthesized, and a GC/MS procedure with d3-m-OH-BE as internal standard has been developed. Among 24 human urine specimens that were positive for BE, all of them have shown detectable levels of m-OH-BE with 75% of the specimens exceeding the LoQ (5 ng/mL), compared with only 50% of the specimens containing detectable levels of EME. The presence of m-OH-BE in urine suggested that this metabolite may serve as a valuable marker of cocaine use in addition to BE and EME.

Hearing results in pediatric patients with chronic otitis media after ossicular reconstruction with partial ossicular replacement prostheses and total ossicular replacement prostheses.

OBJECTIVE: To examine hearing results in pediatric patients after ossicular reconstruction with partial ossicular replacement prostheses (PORPs) and total ossicular replacement prostheses (TORPs) in children with chronic otitis media. METHODS: A retrospective chart review was performed on 55 pediatric patients with chronic otitis media who underwent ossicular reconstruction from 1991 to 1998. Patients' audiograms were evaluated preoperatively and postoperatively for pure-tone average (PTA), air-bone gap (ABG), speech reception threshold (SRT), method of ossicular reconstruction, and management of the mastoid. RESULTS: Twenty-seven patients underwent ossicular reconstruction with TORPs. The average preoperative ABG was 40.1 dB, and the average postoperative ABG was 31.6 dB. Forty-one percent of the children improved their PTA greater than 10 dB postoperatively, and 52% of children did not change their ABG by more than 10 dB postoperatively. Nineteen percent of children with TORPs had a postoperative ABG less than 20 dB, and 44% of children with TORPs had a postoperative ABG less than 30 dB. Twenty-eight patients underwent ossicular reconstruction with PORPs. The average preoperative ABG was 29.7 dB, and the average postoperative ABG was 22.5 dB. Thirty-two percent of patients improved their PTA by greater than 10 dB, while 57% of children with PORPs did not change their ABG by more than 10 dB postoperatively. Forty-three percent of children with PORPs had an ABG of less than 20 dB postoperatively, and 71% of children with PORPs had a postoperative ABG less than or equal to 30 dB. CONCLUSIONS: Children who underwent ossicular reconstruction with PORPs had slightly better postoperative hearing than did children with TORPs. Postoperative hearing was essentially unchanged in approximately 55% of both groups. Preoperative hearing levels may be the most important factor determining postoperative hearing in nonstaged surgery for children with chronic otitis media Long-term hearing results in children with single-stage surgery were not as good as those reported in the literature for staged surgery. Severe mucosal disease and eustachian tube dysfunction may contribute to poorer hearing results in children.

Effects of preoperative embolization on glomus jugulare tumors.

The charts of 35 patients were reviewed retrospectively to determine the effects of embolization on glomus jugulare tumors. Eighteen patients underwent embolization; 17 did not. All tumors were removed with a type A infratemporal fossa approach. The charts were evaluated for operative blood loss, operative time, length of hospitalization, new postoperative cranial nerve deficits and recurrence of tumor. Embolized patients had significantly less operative blood loss and operative time. Embolization did not affect length of hospitalization or reduce the incidence of new postoperative cranial nerve deficits. The surgeon's experience also plays a central role in reducing operative blood loss and operative time. The potential risks of embolization must be considered in the treatment regimen of glomus jugulare tumors.

Stapedectomy in the pediatric patient.

The purpose of this study was to evaluate and compare the results of stapedectomy in pediatric patients with otosclerosis and tympanosclerosis. A retrospective review of 14 patients (15 ears) who underwent stapedectomy from 1993 to 1995 was conducted. In 5 ears stapedectomy for tympanosclerosis was performed; 9 patients had otosclerosis and 1 had Treacher Collins syndrome. Patients were evaluated for preoperative and postoperative air-bone gaps, preoperative and postoperative speech reception thresholds, postoperative air conduction hearing improvement, and preoperative and postoperative speech discrimination. Children with otosclerosis who underwent stapedectomies had an average postoperative air-bone gap of 16 dB with an average air conduction hearing improvement of 17.6 dB. Children with tympanosclerosis who underwent stapedectomies had an average air-bone gap of 14 dB with an average air conduction hearing improvement of 28 dB. Stapedectomy is a safe and effective treatment for otosclerosis and tympanosclerosis in pediatric patients.

Vascular ultrasound in the intensive care unit.

Ultrasonography plays an increasingly important role in the evaluation of the vascular system. It is especially useful for the intensive care patient because of its ability to be performed at the patient's bedside, as well as the relatively high frequency of vascular complications in the ICU. Ultrasonography is the method of choice for evaluation of deep vein thromboembolic disease of the lower extremity in all patients, demonstrating excellent sensitivity and specificity for this condition. It also should be the initial method of evaluating upper extremity deep vein thrombosis. It may be limited in this assessment, however, because it does not reliably demonstrate the central subclavian and innominate veins, and therefore may be inadequate for evaluation of malfunctioning central venous catheters. Ultrasonography can reliably identify the presence of abdominal aortic aneurysms, although computed tomography is better able to demonstrate location and extent of these lesions. Finally, ultrasonography can be used to diagnose complications of arterial catheterization and, in selected patients, may direct compression of pseudoaneurysms, resulting in thrombosis and thereby averting surgical repair.

Mal de debarquement syndrome: a forgotten entity?

Mal de debarquement syndrome is defined by a persistent sensation of rocking and swaying commonly felt with sea travel that is first noted on return to land. Mal de debarquement syndrome is not to be confused with seasickness, which causes nausea, vomiting, diaphoresis, and headache. Four female patients with mal de debarquement syndrome are reviewed. Mal de debarquement is normally a short-lived phenomenon. The need for extensive evaluations may be avoided by an awareness of this entity.

MRI of the facial nerve during paralysis.

Gadolinium-enhanced MRI was used to evaluate 10 patients with Bell's palsy and one patient with facial paralysis secondary to Lyme disease. Nine of the eleven patients showed increased signal intensity of their facial nerve with gadolinium-enhanced MRI. In all nine patients, the facial nerve was involved at the labyrinthine, geniculate ganglion and proximal tympanic portions of the facial nerve, while two of the nine patients also had involvement of the mastoid segment of the facial nerve. Patients whose facial nerve enhancement was limited to the labyrinthine, geniculate ganglion and proximal tympanic facial nerve ultimately had complete return of facial function. Patients whose facial nerve enhanced in the mastoid segment experienced incomplete return of facial function. Gadolinium is effective in localizing the site of inflammation during facial paralysis. Those patients with enhancement localized to the labyrinthine, geniculate ganglion and proximal tympanic segments were more likely to regain complete facial function. In contrast, patients who had enhancement of the mastoid segment of the facial nerve had poorer prognoses for complete return of facial function.

Magnetic resonance imaging of the facial nerve during Bell's palsy.

Twenty-five patients with Bell's palsy were evaluated to assess the efficacy of gadolinium (Gd+)-enhanced MRI in determining: (1) the site of facial nerve enhancement, (2) the relationship between EMG findings and Gd+ MRIs, and (3) the usefulness of Gd+ MRI in predicting recovery of facial function. Eighteen of twenty-five patients had enhancement of the facial nerve during Gd+ MRI whereas seven did not. The most common areas of facial nerve enhancement were the labyrinthine, geniculate ganglion, and proximal tympanic segments of the facial nerve. EMGs were performed on ten patients who lost nerve excitability. The segments of facial nerve enhanced during Gd+ MRI varied in location and intensity in patients who maintained nerve excitability and in patients who lost nerve excitability. There was no correlation between EMG findings and location of facial nerve enhancement in patients who lost nerve excitability. The location of facial nerve enhancement during Gd+ MRI was not useful in predicting recovery of facial paralysis.

Hearing results in pediatric patients after canal-wall-up and canal-wall-down mastoid surgery.

Hearing results were studied in pediatric patients after canal-wall-up and canal-wall-down mastoid surgery in a private practice setting. A retrospective chart review was performed on 69 patients who underwent surgery from 1991-1995. Twenty-six patients underwent canal-wall-up mastoidectomies, and 43 patients underwent canal-wall-down mastoidectomies. Various types of ossicular reconstruction were performed in patients in both groups. Hearing was evaluated for preoperative and postoperative pure-tone averages, speech-reception thresholds, and air-bone gaps for the various types of ossicular reconstruction. Patients with canal-wall-up mastoidectomies and an intact ossicular chain had an average postoperative air-bone gap of 15 dB, whereas reconstruction of the ossicular chain (regardless of technique) resulted in an average postoperative air-bone gap of 19 dB. Patients with canal-wall-down mastoidectomies and an intact ossicular chain had an average air-bone gap of 15 dB, while all techniques of ossicular reconstruction had an average air-bone gap of 29 dB. Canal-wall-up and canal-wall-down mastoid surgeries in pediatric patients have similar hearing results. Variables other than hearing should be used to make treatment decisions regarding the canal wall in pediatric candidates for mastoid surgery.