Search for an annual modulation in a p-type Point Contact germanium dark matter detector.

Fifteen months of cumulative CoGeNT data are examined for indications of an annual modulation, a predicted signature of weakly interacting massive particle (WIMP) interactions. Presently available data support the presence of a modulated component of unknown origin, with parameters prima facie compatible with a galactic halo composed of light-mass WIMPs. Unoptimized estimators yield a statistical significance for a modulation of ∼2.8σ, limited by the short exposure.

Results from a search for light-mass dark matter with a p-type point contact germanium detector.

We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, a number of cosmogenic peaks can be observed for the first time. We discuss an irreducible excess of bulklike events below 3 keV in ionization energy. These could be caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible to determine their origin. Improved constraints are placed on a cosmological origin for the DAMA/LIBRA effect.

Decision trees for optimizing the minimum detectable concentration of radioxenon detectors.

We present a novel application of machine learning techniques to optimize the design of a radiation detection system. A decision tree-based algorithm is described which greedily optimizes partitioning of energy depositions based on a minimum detectable concentration metric - appropriate for radiation measurement. We apply this method to the task of optimizing sensitivity to radioxenon decays in the presence of a high rate of radon-progeny backgrounds (i.e., assuming no physical radon removal by traditional gas separation techniques). Assuming other backgrounds are negligible, and considering sensitivity to each xenon isotope separately (neglecting interference between isotopes), we find that, in general, high resolution readout and high spatial segmentation yield little additional capability to discriminate against radon backgrounds compared to simpler detector designs.

Background characterization of an ultra-low background liquid scintillation counter.

The Ultra-Low Background Liquid Scintillation Counter developed by Pacific Northwest National Laboratory will expand the application of liquid scintillation counting by enabling lower detection limits and smaller sample volumes. By reducing the overall count rate of the background environment approximately 2 orders of magnitude below that of commercially available systems, backgrounds on the order of tens of counts per day over an energy range of ~3-3600keV can be realized. Initial test results of the ULB LSC show promising results for ultra-low background detection with liquid scintillation counting.

Recent Bremsstrahlung-based assays of 210Pb in lead and comments on current availability of low-background lead in North America.

Low-background lead for radiation measurement shielding is often assayed for 210Pb to ensure acceptable backgrounds. Samples of lead assayed with a germanium spectrometer calibrated for bremsstrahlung-based assay of 210Pb provide a view into the 210Pb content of commercial lead in the U.S. (other than stockpiled Doe Run lead). Results suggest that the loss of lead smelting in the U.S. has eliminated the traditional supply of "low background" lead (~30Bqkg-1), and indicate current commercial supplies contain roughly an order of magnitude higher 210Pb levels.

Shielding concepts for low-background proportional counter arrays in surface laboratories.

Development of ultra low background gas proportional counters has made the contribution from naturally occurring radioactive isotopes - primarily α and ß activity in the uranium and thorium decay chains - inconsequential to instrumental sensitivity levels when measurements are performed in above ground surface laboratories. Simple lead shielding is enough to mitigate against gamma rays as gas proportional counters are already relatively insensitive to naturally occurring gamma radiation. The dominant background in these surface laboratory measurements using ultra low background gas proportional counters is due to cosmic ray generated muons, neutrons, and protons. Studies of measurements with ultra low background gas proportional counters in surface and underground laboratories as well as radiation transport Monte Carlo simulations suggest a preferred conceptual design to achieve the highest possible sensitivity from an array of low background gas proportional counters when operated in a surface laboratory. The basis for a low background gas proportional counter array and the preferred shielding configuration is reported, especially in relation to measurements of radioactive gases having low energy decays such as (37)Ar.

Development of a low-level (37)Ar calibration standard.

Argon-37 is an environmental signature of an underground nuclear explosion. Producing and quantifying low-level (37)Ar standards is an important step in the development of sensitive field measurement instruments. This paper describes progress at Pacific Northwest National Laboratory in developing a process to generate and quantify low-level (37)Ar standards, which can be used to calibrate sensitive field systems at activities consistent with soil background levels. This paper presents a discussion of the measurement analysis, along with assumptions and uncertainty estimates.

Development of a low background liquid scintillation counter for a shallow underground laboratory.

Pacific Northwest National Laboratory has recently opened a shallow underground laboratory intended for measurement of low-concentration levels of radioactive isotopes in samples collected from the environment. The development of a low-background liquid scintillation counter is currently underway to further augment the measurement capabilities within this underground laboratory. Liquid scintillation counting is especially useful for measuring charged particle (e.g., ß and α) emitting isotopes with no (or very weak) gamma-ray yields. The combination of high-efficiency detection of charged particle emission in a liquid scintillation cocktail coupled with the low-background environment of an appropriately designed shield located in a clean underground laboratory provides the opportunity for increased-sensitivity measurements of a range of isotopes. To take advantage of the 35m-water-equivalent overburden of the underground laboratory, a series of simulations have evaluated the scintillation counter's shield design requirements to assess the possible background rate achievable. This report presents the design and background evaluation for a shallow underground, low background liquid scintillation counter design for sample measurements.

Effective cell support by repeat plateletpheresis of related donors on the IBM 2997 cell separator.

Forty-three non-HLA-matched donors provided 83 plateletpheresis products for 20 thrombocytopenic patients during a six-month period. The platelet product yield was 4.2 x 10(11) collected in 90 min. There was 26% cellular depletion of donor platelets and 20% depletion of donor lymphocyte per procedure. Males had a significantly greater lymphocyte depletion: 24% compared with 14% for females (P less than 0.05). There was no significant cellular depletion seen in 16 donors who underwent from two of a maximum of nine procedures. For these 16 donors, the time interval between procedures was a minimum of three days and a maximum of 100 days. Twelve refractory oncology patients received 49 plateletpheresis transfusions from 26 related donors. The mean corrected one-hour posttransfusion platelet increment was 18,300, and the mean corrected 20-hour posttransfusion platelet increment was 13,000. The results indicate that non-HLA-typed related plateletpheresis donors can safely undergo multiple procedures with the IBM 2997 Cell Separator and can effectively support their thrombocytopenic relatives who are unresponsive to random donor platelets.

Improved silver staining of nucleolar organiser regions in paraffin wax sections using an inverted incubation technique.

A new simple modification to the silver staining of nucleolar organiser regions (AgNORs) was devised which, by performing the incubation with the slide inverted, results in minimal undesirable background staining, a persistent problem. Inverted incubation is facilitated by the use of a commercially available plastic coverplate. This technique has several additional advantages over other published staining protocols. In particular, the method is straightforward, fast, and maintains a high degree of contrast between the background and the AgNORs.

The effect of hypoalbuminaemia, hyperbilirubinaemia and renal failure on serum fructosamine concentration in non-diabetic individuals.

We have investigated the effects of hypoalbuminaemia, hyperbilirubinaemia and renal failure on serum fructosamine concentration in 39 non-diabetic patients. All patients were hypoalbuminaemic (median serum albumin 25 g/l, range 12-34 g/l). Group 1 (n = 19) were patients with hypoalbuminaemia alone, group 2 (n = 7) with hypoalbuminaemia and impaired renal function (median serum creatinine 226 mumol/l, range 154-461 mumol/l) and group 3 (n = 13) were subjects with hypoalbuminaemia and hyperbilirubinaemia (median serum bilirubin 34 mumol/l, range 19-83 mumol/l). Serum fructosamine was significantly lower in all three groups compared to age-matched normoalbuminaemic controls, but there was no significant difference in fructosamine concentrations between the groups. There was a correlation between fructosamine concentration and serum albumin. (r = 0.82, p less than 0.001) in all three groups combined. Serum fructosamine did correlate with serum bilirubin in patients with normal renal function (r = 0.0, p less than 0.001). In patients with abnormal renal function there was no correlation between serum fructosamine and either urea (r = 0.22, ns) or creatinine (r = 0.31, ns). Albumin is the major factor affecting serum fructosamine concentrations. Moderate hyperbilirubinaemia does not affect fructosamine concentration. No difference in fructosamine concentration could be demonstrated in patients with renal failure.

Raised liver associated enzyme activity and post-prandial bile acid concentrations in sera from treated diabetic outpatients.

Aspartate aminotransferase, alanine aminotransferase and gamma-glutamyl transferase activities were measured in sera from 411 diabetic outpatients and were raised in 26 (6.4%), 34 (8.3%) and 62 (15.2%) patients, respectively. Serum total bile acid concentrations were raised in 4 patients (1%). Percentage glycated hemoglobin A1, serum fructosamine concentration and plasma glucose concentration were also measured. No relationship between the presence of raised enzyme activity and mature age, short duration of diabetic treatment regimen or glycemic control was found. Twenty-six patients with an alanine aminotransferase activity greater than 60 U/l were reviewed at 23 +/- 6.5 weeks. The activity of this enzyme had fallen to within the reference interval in 15 (58%). In the other 11 patients, its median activity was 75 U/l (range 51-181 U/l). Median gamma-glutamyl transferase activity had risen in these 11 patients from 78 U/l to 93 U/l (P less than 0.01). No statistical differences in treatment regimen or glycemic control were found between these two groups. Raised liver-associated enzyme activity in treated stabilised diabetic outpatients should therefore not be attributed to poor glycemic control or diabetic treatment regimen.

Long-term performance of the fructosamine assay.

We have investigated the long-term performance of the fructosamine assay based on secondary glycated protein standards and attempted to define the interpretation of varying degrees of increase in fructosamine concentration in comparison to haemoglobin A1 (HbA1) values both in insulin dependent (IDDM) and non-insulin dependent (NIDDM) diabetic patients. Between-batch imprecision of fructosamine over 5 months was (CV) 2.5% at 2.09 mmol/L, 2.8% at 3.52 mmol/L and 3.6% at 4.14 mmol/L. Variation of fructosamine concentration in vivo in stable diabetic patients monitored over 8-18 weeks was 2.3% to 7.1%. Fructosamine correlated with HbA1 both in IDDM (n = 110, r = 0.701, P less than 0.001) and NIDDM (n = 71, r = 0.764, P less than 0.001). Specificity and sensitivity of fructosamine for the prediction of degree of control assessed on the basis of HbA1 level (cut-off point for good vs. poor control, HbA1 = 10%) was determined. In NIDDM, specificity above 90% was achieved at a fructosamine concentration of 3.4 mmol/L with a corresponding sensitivity of 64.1%. 22.5% of patients were classified differently on the basis of fructosamine as compared to HbA1. In IDDM, specificity over 90% was achieved at 3.8% mmol/L fructosamine with a sensitivity of 35%. Discordancy rate between HbA1 and fructosamine based assessment of control was 31.8%. The assessment of diabetic control based on fructosamine may be different from that based on HbA1, particularly in IDDM. Fructosamine and HbA1 should be used as complementary rather than alternative tests.

Ceravital revisited: lessons to be learned.

OBJECTIVE: To report the long-term results in a series of ossiculoplasties using Ceravital prostheses. STUDY DESIGN: Retrospective case review. SETTING: District general hospital. PATIENTS: Ossiculoplasties using Ceravital prostheses were performed in 25 patients with a mean age of 39 years. Cholesteatoma was present in 9 cases and absent in 16 cases before surgery. The reconstruction was single stage in 23 cases and second stage in 2 cases. MAIN OUTCOME MEASURES: Hearing gain and prosthesis-related complications. The mean length of follow-up was 6 years 6 months. RESULTS: In the short term, the mean air-bone gap improved from 43 dB preoperatively to 24 dB 6 months postoperatively. In the long term, the results were as follows: good in 4 cases, absorption of the prosthesis in 9 cases, slippage of the prosthesis in 4 cases, extrusion of the prosthesis in 3 cases, atelectasis of the tympanic membrane in 2 cases, and unknown in 3 cases. The mean time for complications to become apparent was 6 years 4 months for absorption, 3 years 3 months for extrusion, 7 months for slippage, and 1 year 9 months for atelectasis. Revision surgery was performed on 11 of the 18 cases in which the results were poor. CONCLUSIONS: Ceravital prostheses highlight the potential complication of absorption of ossicular prostheses. Absorption takes much longer to become apparent than other complications such as extrusion, slippage, or atelectasis. The much higher rate of absorption in this series than in previous series with shorter follow-up times suggests that the rate of absorption increases significantly over time.

Adenoma in the middle ear: a report of two cases.

Middle-ear adenoma has been reported only in small numbers by surgeons. The few large series reported have been presented by histopathologists. We add two cases of middle-ear adenoma to the published literature, together with pre-, per- and post-operative imaging of one case, as a demonstration of this rare clinical entity. We discuss the pathology of middle-ear adenoma, its diagnosis and treatment, and suggest ways of improving its management.

Experimental constraints on a dark matter origin for the DAMA annual modulation effect.

A claim for evidence of dark matter interactions in the DAMA experiment has been recently reinforced. We employ a new type of germanium detector to conclusively rule out a standard isothermal galactic halo of weakly interacting massive particles as the explanation for the annual modulation effect leading to the claim. Bounds are similarly imposed on a suggestion that dark pseudoscalars might lead to the effect. We describe the sensitivity to light dark matter particles achievable with our device, in particular, to next-to-minimal supersymmetric model candidates.

Mobile laboratory unit based on the Kodak Ektachem DT system.

We evaluated the Kodak Ektachem DT system (DT60, DTE, DTSC modules), using it as a mobile laboratory unit (MLU) in different hospital settings. Imprecision of 19 assays performed with the system and correlation with routine methods in the main laboratory were assessed. The system was then transported to different departments within the hospital, where limited test profiles were offered and the time taken to produce results was recorded. It proved practicable to offer a six-test electrolyte profile to a five-bed intensive-care unit but not to an 18-bed renal unit, where more selective analysis would be required. In a low-throughput outpatient clinic (five patients per hour) it was feasible to provide a six-test on-site profile on every patient, whereas the maximum number of tests was four in a high-throughput clinic (10 patients per hour). The cost of providing a flexible extra-laboratory biochemistry service must be balanced against the benefit of having on-site results, e.g., fewer outpatient-clinic visits.

An effective method for the preparation of leukocyte-poor platelets.

Febrile transfusion reactions are encountered occasionally in patients receiving platelet concentrates that contain contaminating leukocytes. To remove heavier cellular elements, a 400-ml platelet pooling bg with tapered sides and a pouch at the base was designed to trap these cells after centrifugation. Two versions of this bag were tested: the initial prototype with a 3-ml pouch and a modified version with a 4-ml pouch. Platelet concentrates were pooled in batches of 6 per bag and, after sampling, were centrifuged between 186 and 600 x g for 7 to 10 minutes. The pouch on each bag was then clamped off, and samples from the primary bag were withdrawn so tht the percentage of cellular elements remaining could be determined. At optimal centrifugation conditions (390 x g for 10 minutes) with the initial prototype of the bag, average cellular decreases were: leukocytes, 75.9 percent; red cells, 84.1 percent; and platelets, 9.8 percent. Twenty-two components prepared in this manner were infused into 12 patients with histories of febrile transfusion reactions. Febrile reactions were markedly reduced or absent in ten patients, a strong febrile reaction due to incorrect component preparation occurred in one, and a marked allergic reaction occurred in one. The 4-ml pouch gave much better production results with greater than 95 percent leukocyte removal and less than 5 percent platelet loss. This system removes sufficient leukocytes from platelet concentrates that the risk of febrile transfusion reactions is reduced significantly.