Unusual Interplay between Superconductivity and Field-Induced Charge Order in YBa_{2}Cu_{3}O_{y}.

We present a detailed study of the temperature (T) and magnetic field (H) dependence of the electronic density of states (DOS) at the Fermi level, as deduced from specific heat and Knight shift measurements in underdoped YBa_{2}Cu_{3}O_{y}. We find that the DOS becomes field independent above a characteristic field H_{DOS}, and that the H_{DOS}(T) line displays an unusual inflection near the onset of the long-range 3D charge-density wave order. The unusual S shape of H_{DOS}(T) is suggestive of two mutually exclusive orders that eventually establish a form of cooperation in order to coexist at low T. On theoretical grounds, such a collaboration could result from the stabilization of a pair-density wave state, which calls for further investigation in this region of the phase diagram.

Evidence for nonlocal electrodynamics in planar Josephson junctions.

We study the temperature dependence of the critical current modulation I(c)(H) for two types of planar Josephson junctions: a low-Tc Nb/CuNi/Nb and a high-Tc YBa2Cu3O(7-δ) bicrystal grain-boundary junction. At low T both junctions exhibit a conventional behavior, described by the local sine-Gordon equation. However, at elevated T the behavior becomes qualitatively different: the I(c)(H) modulation field ΔH becomes almost T independent and neither ΔH nor the critical field for the penetration of Josephson vortices vanish at Tc. Such an unusual behavior is in good agreement with theoretical predictions for junctions with nonlocal electrodynamics. We extract absolute values of the London penetration depth λ from our data and show that a crossover from local to nonlocal electrodynamics occurs with increasing T when λ(T) becomes larger than the electrode thickness.

2D crystal structure and anisotropic magnetism of GdAu6.75-xAl0.5+x (x ≈ 0.54).

Exploration of the gold-rich part of the ternary Gd-Au-Al system afforded the intermetallic compound GdAu6.75-xAl0.5+x (x ≈ 0.54) which was structurally characterized by single crystal X-ray diffraction (Pnma, a = 18.7847(4) Å, b = 23.8208(5) Å, c = 5.3010(1) Å). GdAu6.75-xAl0.5+x crystallizes in a previously unknown structure type featuring layers of Gd2(Au, Al)29 and Gd2(Au, Al)28 clusters which are arranged as in a close-packing parallel to the ac plane. The Gd substructure corresponds to slightly corrugated 36 nets (dGd-Gd = 5.30-5.41 Å) which are stacked on top of each other along the b direction with alternating short (5.4, 5.6 Å, within layers) and long distances (6.4 Å, between layers). The title compound has been discussed with respect to a quasicrystal approximant (1/1 AC) GdAu5.3Al in the same system. The magnetic properties of GdAu6.75-xAl0.5+x were found to be reminiscent to those of some ternary ACs, with sharp peaks in the temperature dependent magnetization, and metamagnetic-like transitions. The material becomes antiferromagnetic below 25 K; magnetometry results suggest that the antiferromagnetic state is composed of ferromagnetic ac planes, coupled antiferromagnetically along the b direction.

Magnetoquantum oscillations in the specific heat of a topological Kondo insulator.

Surprisingly, magnetoquantum oscillations (MQOs) characteristic of a metal with a Fermi surface have been observed in measurements of the topological Kondo insulator SmB6. As these MQO have only been observed in measurements of magnetic torque (dHvA) and not in measurements of magnetoresistance (SdH), a debate has arisen as to whether the MQO are an extrinsic effect arising from rare-earth impurities, defects, and/or aluminum inclusions or an intrinsic effect revealing the existence of charge-neutral excitations. We report here the first observation of MQO in the low-temperature specific heat of SmB6. The observed frequencies and their angular dependence for these flux-grown samples are consistent with previous results based on magnetic torque for SmB6but the inferred effective masses are significantly larger than previously reported. Such oscillations can only be observed if the MQO are of bulk thermodynamic origin; the measured magnetic-field dependent oscillation amplitude and effective mass allow us to rule out suggestions of an extrinsic, aluminum inclusion-based origin for the MQO.

Detection of the phase shift from a single Abrikosov vortex.

We probe a quantum mechanical phase rotation induced by a single Abrikosov vortex in a superconducting lead, using a Josephson junction, made at the edge of the lead, as a phase-sensitive detector. We observe that the vortex induces a Josephson phase shift equal to the polar angle of the vortex within the junction length. When the vortex is close to the junction it induces a π step in the Josephson phase difference, leading to a controllable and reversible switching of the junction into the 0-π state. This in turn results in an unusual Φ(0)/2 quantization of the flux in the junction. The vortex may hence act as a tunable "phase battery" for quantum electronics.

Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature.

Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-δ crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

Differential membrane-based nanocalorimeter for high-resolution measurements of low-temperature specific heat.

A differential, membrane-based nanocalorimeter for general specific heat studies of very small samples, ranging from 0.5 mg to sub-µg in mass, is described. The calorimeter operates over the temperature range from above room temperature down to 0.5 K. It consists of a pair of cells, each of which is a stack of heaters and thermometer in the center of a silicon nitride membrane, in total giving a background heat capacity less than 100 nJ/K at 300 K, decreasing to 10 pJ/K at 1 K. The device has several distinctive features: (i) The resistive thermometer, made of a Ge(1 - x)Au(x) alloy, displays a high dimensionless sensitivity ∣dlnR∕dlnT∣ ≳ 1 over the entire temperature range. (ii) The sample is placed in direct contact with the thermometer, which is allowed to self-heat. The thermometer can thus be operated at high dc current to increase the resolution. (iii) Data are acquired with a set of eight synchronized lock-in amplifiers measuring dc, 1st and 2nd harmonic signals of heaters and thermometer. This gives high resolution and allows continuous output adjustments without additional noise. (iv) Absolute accuracy is achieved via a variable-frequency-fixed-phase technique in which the measurement frequency is automatically adjusted during the measurements to account for the temperature variation of the sample heat capacity and the device thermal conductance. The performance of the calorimeter is illustrated by studying the heat capacity of a small Au sample and the specific heat of a 2.6 µg piece of superconducting Pb in various magnetic fields.

Gastric emptying in hereditary transthyretin amyloidosis: the impact of autonomic neuropathy.

BACKGROUND: Gastrointestinal (GI) complications are common in hereditary transthyretin amyloidosis and an autonomic dysfunction has been considered to explain these symptoms. The aim of this study was to investigate the impact of autonomic neuropathy on gastric emptying in hereditary transthyretin amyloidosis and to relate these findings to nutritional status, GI symptoms, gender, and age at disease onset. METHODS: Gastric emptying was evaluated with gastric emptying scintigraphy. Spectral analysis of the heart rate variability and cardiovascular responses after tilt test were used to assess the autonomic function. The nutritional status was evaluated with the modified body mass index (s-albumine × BMI). KEY RESULTS: Gastric retention was found in about one-third of the patients. A weak correlation was found between the scintigraphic gastric emptying rate and both the sympathetic (rs = -0.397, P < 0.001) and parasympathetic function (rs = -0.282, P = 0.002). The gastric emptying rate was slower in those with lower or both upper and lower GI symptoms compared with those without symptoms (median T(50) 123 vs 113 min, P = 0.042 and 192 vs 113 min, P = 0.003, respectively). Multiple logistic regression analysis showed that age of onset (OR 0.10, CI 0.02-0.52) and sympathetic dysfunction (OR 0.23, CI 0.10-0.51), but not gender (OR 0.76, CI 0.31-1.84) and parasympathetic dysfunction (OR 1.81, CI 0.72-4.56), contributed to gastric retention. CONCLUSIONS AND INFERENCES: Gastric retention is common in hereditary transthyretin amyloidosis early after onset. Autonomic neuropathy only weakly correlates with gastric retention and therefore additional factors must be involved.

Doping-induced change in the interlayer transport mechanism of Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} near the superconducting transition temperature.

We perform a detailed study of temperature, bias, and doping dependence of interlayer transport in the layered high temperature superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+delta}. We observe that the shape of interlayer characteristics in underdoped crystals exhibits a remarkable crossover at the superconducting transition temperature: from thermal activation-type above T_{c} to almost T-independent quantum tunneling-type below T_{c}. Our data provide insight into the nature of interlayer transport and indicate that its mechanism changes with doping: from the conventional single quasiparticle tunneling in overdoped to a progressively increasing Cooper pair contribution in underdoped crystals.

Ultrasound, computed tomography, and laboratory findings in the diagnosis of appendicitis.

PURPOSE: To determine the diagnostic accuracy and the clinical impact of ultrasound (US) and computed tomography (CT) in diagnosing appendicitis, and to evaluate the impact of laboratory tests on the treatment of acute appendicitis. MATERIAL AND METHODS: All patients who, during 2005, underwent an acute ultrasound or CT investigation due to suspected appendicitis, or were diagnosed and/or surgically treated for appendicitis at Umeå University Hospital, Umeå, were included. The type of radiological investigation, its findings, the choice of treatment, final diagnosis, C-reactive protein (CRP), leukocyte particle count (LPC), body temperature, age, and sex were recorded for each patient. The histological result from surgery was considered the gold standard. RESULTS: The material included 305 cases with an overall appendicitis prevalence of 58%. Fifty-two percent of the patients were female. The mean age was 29 years, with a total range of 2-94 years. Twenty percent (60/305) underwent a CT investigation, 40% (123/305) underwent an US investigation, 5% (14/305) underwent both a CT and an US investigation, and 35% (108/305) of patients did not undergo any radiological investigation at all. The sensitivities and specificities were 91% and 94% for CT, and 83% and 98% for US, respectively. The positive likelihood ratio was 15.1 and 45.5 for CT and US, and the negative likelihood ratio was 0.09 and 0.18 for CT and US, respectively. It was not possible to visualize the appendix in 31% of patients examined with US. The prevalence of appendicitis in this group was the same as the prevalence among patients where it was possible to see the appendix, i.e., 35%. The mean CRP for all patients with appendicitis was 59 (95% CI 10-491) mg/l, and the mean LPC was 11.1 (95% CI 2.6-28.1) x10(-9)/l. The mean LPC level was significantly higher for the appendicitis patients. Body temperature could not significantly verify or exclude appendicitis. The overall negative appendectomy rate was 9% (16/176), and it was higher in women, i.e., 11% (9/79). The negative appendectomy rate was slightly higher in the group that was examined by CT and/or US, i.e., 12% (8/69) compared to 7% (8/107) in the group not examined radiologically. CONCLUSION: Diagnostic accuracy was high for US as well as for CT. US was better for diagnosing positive findings, while CT was better for excluding diagnosis of appendicitis. The diagnostic accuracy of LPC, CRP, and body temperature was low. By combining findings from the radiological examination with the results from the clinical examination and laboratory values, a low negative appendectomy rate can be achieved.

Experimental evaluation of tube potential and contrast medium concentration for cholangiography.

Model cholangiographic experiments were performed in which the relationship between contrast medium concentration, duct diameter, calculus size and tube potential was analysed. The same degree of diagnostic reliability was obtained by increasing the tube potential as by diluting the contrast medium. A tube potential of 100 to 110 kV and a contrast medium concentration of 45 per cent were found to give the best result if the background density of the film was held constant.

Strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O(7-delta) single crystals.

Multiterminal transport measurements indicating a strongly correlated vortex liquid above the first order melting transition in untwinned YBa2Cu3O(7--delta) single crystals are presented. The correlation is found to be surprisingly stable for different weak variations of point disorder. We investigate the differences between intervortex and intravortex correlations in different contact geometries. The results are in agreement with the local conductivity model, with zero resistivity along straight vortex line segments.

Leakage from T tube tracts as determined by contrast radiology.

The continuity of the T tube tract on removal of the drain was studied by fluoroscopic examination in 51 patients. Leakage was found in 25 cases (abdominal cavity 7, wound drain 6, local cavity 11, combined abdominal and wound drain leakage 1). No correlation was found between the incidence of pyrexia or pain and the presence of leakage. These complications, noted in 10 patients, are probably explained by bacterial contamination of the bile in combination with the trauma caused by extraction of the tube.

Impact of gastrointestinal dysfunction on survival after liver transplantation for familial amyloidotic polyneuropathy.

Liver transplantation is the only effective treatment of familial amyloidotic polyneuropathy type I (FAP). The aim of the present investigation was to identify factors at the time of submission for transplantation that had impact on survival, with special reference to gastrointestinal disturbances. All 28 liver-transplanted FAP patients evaluated at Umeå University Hospital were included in the study. A modified body mass index was used to assess nutritional status. Intestinal examinations were performed to diagnose bile acid malabsorption, gastric retention, and bacterial contamination of the small bowel. A significantly improved survival rate was found for patients in a good nutritional state (P = 0.002). Peripheral neurological symptoms were unrelated to survival, whereas increased mortality was found for patients with bile acid malabsorption (P < 0.05). Bacterial contamination and gastric retention were common complications of the disease. In conclusion, malabsorption and malnutrition have a profound impact on the outcome of liver transplantation for familial amyloidotic polyneuropathy.

Predictive value of prostate-specific antigen, tumour stage and tumour grade for the outcome of bone scintigraphy in patients with newly diagnosed prostate cancer.

OBJECTIVE: In order to evaluate the negative predictive value of a low prostate-specific antigen (PSA) for a positive bone scan, we performed a retrospective study in a patient material from the Umea region in Northern Sweden. We also evaluated whether different tumour grades could influence this predictive value. MATERIAL AND METHODS: Four-hundred-and-forty-six patients of newly diagnosed prostate cancer were reviewed. We analysed different levels of PSA, tumour grade, tumour stage and combinations of these parameters for their use in making a positive bone scintigraphy (BS) prediction. RESULTS: Among 214 patients with PSA <20 ng/ml, 9 showed a positive BS. When tumours of grades 2 and 3 were excluded, the number of positive BS predictions decreased to 6. For 350 of these 446 patients, a classification according to TNM was available; 162 of these 350 had a PSA value <20 ng/ml, and when this group comprised only small and well-differentiated tumours (T1-2, G1), only one of the remaining 81 patients had a positive BS result. CONCLUSIONS: We conclude that in most patients with small and well-differentiated tumours (T1-2, G1) and PSA <20, BS staging need not be carried out.

Quantitative bone scintigraphy. A methodological evaluation in prostate cancer.

PURPOSE: To evaluate a simple method for quantification of focal activity in bone scintigraphy (BS). MATERIAL AND METHODS: The gamma camera was calibrated using a phantom. Quantitative bone scintigraphy (QBS) was performed on 11 men recently diagnosed with prostate cancer (PCa), for whom routine BS showed involvement of the skeleton. Following endocrine therapy for 4 to 8 months, a second QBS was performed. Changes in QBS values were then compared to changes in serum levels of prostate-specific antigen (PSA). RESULTS: PSA response indicating regression of PCa was accompanied by a decrease in the QBS value in 8 of the 11 patients. The overall mean error of the QBS values was 15%. CONCLUSION: QBS according to this method is a relatively simple procedure that might contribute to objective evaluation of therapeutic effects in skeletal metastases, although its validity must be tested in a larger clinical material.

Serum amyloid P component scintigraphy in familial amyloid polyneuropathy: regression of visceral amyloid following liver transplantation.

Familial amyloid polyneuropathy (FAP) associated with transthyretin (TTR) mutations is the commonest type of hereditary amyloidosis. Plasma TTR is produced almost exclusively in the liver and orthotopic liver transplantation is the only available treatment, although the clinical outcome varies. Serum amyloid P component (SAP) scintigraphy is a method for identifying and quantitatively monitoring amyloid deposits in vivo, but it has not previously been used to study the outcome of visceral amyloid deposits in FAP following liver transplantation. Whole body scintigraphy following injection of iodine-123 labelled SAP was performed in 17 patients with FAP associated with TTR Met30 and in five asymptomatic gene carriers. Follow-up studies were performed in ten patients, eight of whom had undergone orthotopic liver transplantation 1-5 years beforehand. There was abnormal uptake of 123I-SAP in all FAP patients, including the kidneys in each case, the spleen in five cases and the adrenal glands in three cases. Renal amyloid deposits were also present in three of the asymptomatic carriers. Follow-up studies 1-5 years after liver transplantation showed that there had been substantial regression of the visceral amyloid deposits in two patients and modest improvement in three cases. The amyloid deposits were unchanged in two patients. In conclusion, 123I-SAP scintigraphy identified unsuspected visceral amyloid in each patient with FAP due to TTR Met30. The universal presence of renal amyloid probably underlies the high frequency of renal failure that occurs in FAP following liver transplantation. The variable capacity of patients to mobilise amyloid deposits following liver transplantation may contribute to their long-term clinical outcome.

Radioimmunoscintigraphy with a novel monoclonal antiprostate antibody (E4): an experimental study in nude mice.

BACKGROUND: Prostate cancer is one of the leading causes of death among men, despite achievements in diagnosis and therapy. Radioimmunolocalization and radioimmunotherapy of malignant tumors have demonstrated increasing potential and may become useful tools in the management of prostate cancer. METHODS: Nude mice were inoculated subcutaneously with cells from the poorly differentiated human prostate cancer cell line DU-145. The intact monoclonal antibody (MoAb) E4 and an intact anticytokeratin-8 MoAb, TS1, used for comparison were labeled with 125I and injected intraperitoneally (i.p.) in the mice. Repetitive quantitative scintigraphic recordings were performed during 1 month. The mice were killed at Day 29 after injection of the radiolabeled MoAb. The tumors and the organs were dissected and weighed. The remaining activity was measured in a gamma well counter. One part of the tumor was immediately fixed in Bouin's solution for autoradiography and the other in formaldehyde for microscopy. RESULTS: The study demonstrated significant radioimmunolocalization of the MoAb E4 into the DU-145 prostate tumor tissue in the animal model, with an average radiation dose of 0.08 Gy/MBq in the tumor. TS1 localized preferentially in necrotic parts of the tumor, yielding a tumor dose of 0.02 Gy/MBq. CONCLUSIONS: The MoAb E4 is a promising radiotracer for prostate cancer and may be used in radioimmunotherapy. As in earlier studies, TS1 shows significant radioimmunolocalization into necrotic tumor tissue, which also exists in prostate cancer.

Radioimmunotherapy of DU-145 tumours in nude mice--a pilot study with E4, a novel monoclonal antibody against prostate cancer.

The anti-tumour effect of the 131I-labelled antiprostate monoclonal antibody (MAb) E4 was studied in an experimental model with 41 nude mice, subcutaneously xenografted with a human prostate cancer cell line (DU-145). The mice were divided into four study groups, i.e. one receiving single and another repeated injections of the radiolabelled MAb. A third group was injected with non-labelled MAb, and the fourth served as an untreated control group. The tumour volumes increased similarly in all groups during the 27-day observation period. The tumour tissue was morphologically disintegrated in the group that received repeated radioimmunotherapy (RIT). The tumours from this group contained large fluid-filled cystic parts and demonstrated pronounced cellular and subcellular polymorphism in the remaining viable tumour tissue. The untreated control tumours and single therapy tumours remained solid. The proportion of the total tumour volume that consisted of viable tumour cells, as determined by morphometric techniques, was significantly lower in the 131I-E4-treated groups. The use of 131I-labelled E4 MAb has thus demonstrated a promising therapeutic potential.

Radioimmunoscintigraphy using an anti-prostate monoclonal antibody (E4): a dosimetric evaluation.

The aim of this study was to evaluate different strategies to increase the tumour radiation dose for experimental radioimmunotherapy using 125I-labelled monoclonal antibody (MAb) E4 in a nude mice model xenografted with DU-145 tumours. The effects from a single injection of the 125I-labelled MAb E4, the same total amount of radiolabelled MAb E4 divided into three repeated injections, and the effect of pre-targeting with non-labelled MAb E4 for reducing the amount of shed antigen were investigated. Based on repetitive quantitative radioimmunoscintigraphies, calculation of the tumour radiation dose delivered from the 125I-nuclide was performed for each strategy. The single injection strategy without pretargeting rendered the highest mean tumour radiation dose, i.e. 0.23 Gy/MBq. Pretargeting with non-labelled MAb E4 before a single injection of [125I]E4 resulted in a slightly lower mean tumour radiation dose, i.e. 0.19 Gy/MBq, compared to the single injection alone. An even lower mean tumour radiation dose, i.e. 0.14 Gy/MBq, was obtained when the same total administered amount of activity was divided into three separate injections given in 10-day intervals. We concluded that the single injection strategy is the most efficient when using MAb E4 in this tumour model. The tumour radiation doses were not increased by dividing the same amount of activity into three injections or by pretargeting with non-labelled MAb E4.