3D prompt gamma imaging for proton beam range verification.

We tested the ability of a single Compton camera (CC) to produce 3-dimensional (3D) images of prompt gammas (PGs) emitted during the irradiation of a tissue-equivalent plastic phantom with proton pencil beams for clinical doses delivered at clinical dose rates. PG measurements were made with a small prototype CC placed at three different locations along the proton beam path. We evaluated the ability of the CC to produce images at each location for two clinical scenarios: (1) the delivery of a single 2 Gy pencil beam from a hypo-fractionated treatment (~9 × 108 protons), and (2) a single pencil beam from a standard treatment (~1 × 108 protons). Additionally, the data measured at each location were combined to simulate measurements with a larger scale, clinical CC and its ability to image shifts in the Bragg peak (BP) range for both clinical scenarios. With our prototype CC, the location of the distal end of the BP could be seen with the CC placed up to 4 cm proximal or distal to the BP distal falloff. Using the data from the simulated full scale clinical CC, 3D images of the PG emission were produced with the delivery of as few as 1 × 108 protons, and shifts in the proton beam range as small as 2 mm could be detected for delivery of a 2 Gy spot. From these results we conclude that 3D PG imaging for proton range verification under clinical beam delivery conditions is possible with a single CC.

Feasibility Studies of a New Event Selection Method to Improve Spatial Resolution of Compton Imaging for Medical Applications.

A Compton imaging method for medical applications that includes new energy determination and data filtering techniques has been tested using several point sources with known emission lines. Using a prototype Compton camera, a distance-of-closest approach technique has been employed to determine the initial energy of the incoming γs and to ensure the reconstructed source position is within an acceptable distance from the known γ source location. Further analysis is done by implementing a Compton line filtering technique, keeping only those interactions whose deposited energy in the first interaction matches the theoretical energy deposition predicted by the Compton equation. Using this new event filtering method, we see improvements in the full width at half maximum in the lateral profiles of γ point sources of up to 70% over standard Compton imaging methods, as well as achievable spatial resolutions in the reconstructed images of better than 2 mm. In addition, this new Compton imaging method was able to reconstruct an extended source of γ rays emitted during irradiation of a water tank with a clinical proton radiotherapy beam.

Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay.

This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9 GWth nuclear reactors with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296 721 and 41 589 inverse ß decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55±0.04) ×10(-18) cm(2) GW(-1) day(-1) or (5.92±0.14) ×10(-43) cm(2) fission(-1). This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946±0.022 (0.991±0.023) relative to the flux predicted with the Huber-Mueller (ILL-Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2σ over the full energy range with a local significance of up to ∼4σ between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.

Electron Elevator: Excitations across the Band Gap via a Dynamical Gap State.

We use time-dependent density functional theory to study self-irradiated Si. We calculate the electronic stopping power of Si in Si by evaluating the energy transferred to the electrons per unit path length by an ion of kinetic energy from 1 eV to 100 keV moving through the host. Electronic stopping is found to be significant below the threshold velocity normally identified with transitions across the band gap. A structured crossover at low velocity exists in place of a hard threshold. An analysis of the time dependence of the transition rates using coupled linear rate equations enables one of the excitation mechanisms to be clearly identified: a defect state induced in the gap by the moving ion acts like an elevator and carries electrons across the band gap.

New measurement of antineutrino oscillation with the full detector configuration at Daya Bay.

We report a new measurement of electron antineutrino disappearance using the fully constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9×10^{5} GW_{th} ton days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six ^{241}Am-^{13}C radioactive calibration sources reduced the background by a factor of 2 for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of sin^{2}2θ_{13} and |Δm_{ee}^{2}| were halved as a result of these improvements. An analysis of the relative antineutrino rates and energy spectra between detectors gave sin^{2}2θ_{13}=0.084±0.005 and |Δm_{ee}^{2}|=(2.42±0.11)×10^{-3} eV^{2} in the three-neutrino framework.

Search for a light sterile neutrino at Daya Bay.

A search for light sterile neutrino mixing was performed with the first 217 days of data from the Daya Bay Reactor Antineutrino Experiment. The experiment's unique configuration of multiple baselines from six 2.9 GW(th) nuclear reactors to six antineutrino detectors deployed in two near (effective baselines 512 m and 561 m) and one far (1579 m) underground experimental halls makes it possible to test for oscillations to a fourth (sterile) neutrino in the 10(-3) eV(2)<|Δm(41)(2) |< 0.3 eV(2) range. The relative spectral distortion due to the disappearance of electron antineutrinos was found to be consistent with that of the three-flavor oscillation model. The derived limits on sin(2) 2θ(14) cover the 10(-3) eV(2) ≲ |Δm(41)(2)| ≲ 0.1 eV(2) region, which was largely unexplored.

Spectral measurement of electron antineutrino oscillation amplitude and frequency at Daya Bay.

A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9 GW(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3) eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(µµ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.

Measurement of muon antineutrino quasielastic scattering on a hydrocarbon target at Eν ~ 3.5 GeV.

We have isolated ν(µ) charged-current quasielastic (QE) interactions occurring in the segmented scintillator tracking region of the MINERvA detector running in the NuMI neutrino beam at Fermilab. We measure the flux-averaged differential cross section, dσ/dQ², and compare to several theoretical models of QE scattering. Good agreement is obtained with a model where the nucleon axial mass, M(A), is set to 0.99 GeV/c² but the nucleon vector form factors are modified to account for the observed enhancement, relative to the free nucleon case, of the cross section for the exchange of transversely polarized photons in electron-nucleus scattering. Our data at higher Q² favor this interpretation over an alternative in which the axial mass is increased.

Measurement of muon neutrino quasielastic scattering on a hydrocarbon target at Eν ~ 3.5 GeV.

We report a study of ν(µ) charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a µ- and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, dσ/dQ², and study the low energy particle content of the final state. Deviations are found between the measured dσ/dQ² and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state.

Observation of electron-antineutrino disappearance at Daya Bay.

The Daya Bay Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle θ(13) with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GWth reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43,000 ton-GWth-day live-time exposure in 55 days, 10,416 (80,376) electron-antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R=0.940±0.011(stat.)±0.004(syst.). A rate-only analysis finds sin(2)2θ(13)=0.092±0.016(stat.)±0.005(syst.) in a three-neutrino framework.

Pregnancy in HIV-infected teenagers in London.

OBJECTIVE: The aim of the study was to describe pregnancies in HIV-infected teenagers. METHODS: A review of the case notes of HIV-infected pregnant teenagers aged 13-19 years from 12 London hospitals was carried out for the period 2000-2007. RESULTS: There were 67 pregnancies in 58 young women, of whom one was known to have acquired HIV vertically. The overall mother-to-child transmission (MTCT) rate of HIV was 1.5% (one of 66). There were 66 live births. Median ages at HIV diagnosis and conception were 17 and 18 years, respectively. Sixty-three per cent of women were diagnosed with HIV infection through routine antenatal screening. Eighty-two per cent of pregnancies (41 of 50) were unplanned, with 65% of women (26 of 40) using no contraception. Forty-three per cent of the women (20 of 46) had a past history of a sexually transmitted infection (STI). In 63 pregnancies, antiretroviral therapy was started post-conception, with prevention of HIV MTCT the only indication in 81% of cases. Fifty-eight per cent of those on highly active antiretroviral therapy (HAART) had an undetectable HIV viral load by delivery. Eighty-seven per cent were uncomplicated pregnancies. Seventy-one per cent delivered by Caesarean section and 21% (14 of 64) had a preterm delivery (<37 weeks). In the 12 months after delivery, 45% of women received contraceptive advice and 25% of women became pregnant again. CONCLUSION: Obstetric and virological outcomes were favourable in this group of HIV-infected young women. However, the majority of pregnancies were unplanned with poor documentation of contraception use and advice and low rates of STI screening. A quarter of women conceived again within 12 months of delivery. Effective measures to reduce STIs, unplanned pregnancies and onward HIV transmission in HIV-infected teenagers are needed.

Insulin detemir under steady-state conditions: no accumulation and constant metabolic effect over time with twice daily administration in subjects with Type 1 diabetes.

AIMS: This study investigated the pharmacodynamic and pharmacokinetic characteristics of the novel long-acting insulin analogue insulin detemir (IDet) under single-dose and steady-state conditions in comparison with those of NPH insulin at steady state. METHODS: Twenty-five subjects with Type 1 diabetes [seven females, 18 males, mean age (+/- sd) 39 +/- 12 years, body mass index 24 +/- 3 kg/m(2)] participated in three 24-h glucose clamps. IDet or NPH were given at 12-h intervals in fixed, individualized doses. The first clamp assessed the metabolic effect of NPH at steady state, the second investigated the effect of two single injections of IDet. Subjects continued IDet treatment for 7-14 days, after which the third clamp was performed to investigate IDet at steady state. RESULTS: At steady state, the metabolic effect of IDet was constant over 24 h while a clear peak in the metabolic effect [expressed as glucose infusion rates (GIR)] was observed with NPH after each injection. The fluctuation in the metabolic effect (maximum GIR divided by the average of the GIR values at the interval ends) was significantly lower in the second 12 h of the experiments with IDet under steady-state conditions compared with NPH (fluctuation(12-24 h) 1.27 +/- 0.17 vs. 1.56 +/- 0.72, P < 0.05). The overall metabolic effect of IDet at steady state was comparable with that of NPH [GIR-area under curve (AUC)(0-24 h): 5697 +/- 1861 vs. 5929 +/- 1965 mg/kg] whereas a significantly lower effect (5187 +/- 1784 mg/kg, P = 0.01 vs. steady state) was observed following the first two IDet injections. GIR values at the end of clamp day 2 (first doses) and clamp day 3 (steady state) were comparable [GIR(trough 24 h) 3.7 +/- 1.7 vs. 3.8 +/- 1.6 mg/(kg x min) NS], indicating that IDet had reached steady state after the first two injections. CONCLUSIONS: IDet administered twice daily reached steady state after the second injection and showed a constant metabolic effect over time under steady-state conditions. This should facilitate basal insulin substitution and decrease the risk of hypoglycaemia in insulin-treated subjects.

Comparison of three multiple injection regimens for Type 1 diabetes: morning plus dinner or bedtime administration of insulin detemir vs. morning plus bedtime NPH insulin.

AIMS: This trial investigated the efficacy and safety of two different administration-time regimens with insulin detemir (IDet) to that of a conventional basal insulin regimen with NPH insulin (NPH). METHODS: This multinational, 16-week, open, parallel group trial included 400 people with Type 1 diabetes mellitus (DM) randomized to IDet either morning and before dinner (IDetmorn+din) or morning and bedtime (IDetmorn+bed), or to NPH morning and bedtime (NPHmorn+bed), all in combination with mealtime insulin aspart (IAsp). RESULTS: HbA1c was comparable between the three groups after 16 weeks (P = 0.64), with reductions of 0.39-0.49% points. Lower fasting plasma glucose (FPG) was observed with IDetmorn+din and IDetmorn+bed compared with NPHmorn+bed (9.8 and 9.1 vs. 11.1 mmol/l, P = 0.006), whereas the IDet groups did not differ (P = 0.15). Within-person variation in self-measured FPG was significantly lower for both IDet regimens (sd IDetmorn+din 2.5, IDetmorn+bed 2.6 mmol/l) than for NPHmorn+bed (sd 3.1 mmol/l, P < 0.001), but was comparable between the IDet groups (P = 0.48). Ten-point plasma glucose profiles were lower between dinner and breakfast in the IDetmorn+din group (P = 0.043), compared with the two other groups. Risk of overall and nocturnal hypoglycaemia was similar for the three groups. Lower mean bodyweight was observed with IDet compared with NPH after 16 weeks (difference: (IDetmorn+din)-1.3 kg, P < 0.001, (IDetmorn+bed)-0.6 kg, P = 0.050). CONCLUSIONS: Both IDet regimens were well tolerated and provided lower and less variable glucose levels with no, or less, weight gain than NPH at comparable HbA1c. IDet can be administered either at dinner or bedtime, with similar glycaemic control according to the need of the individual person.

Lower within-subject variability of fasting blood glucose and reduced weight gain with insulin detemir compared to NPH insulin in patients with type 2 diabetes.

AIM: The aim of this study was to compare the efficacy and safety of a basal-bolus insulin regimen comprising either insulin detemir or neural protamine hagedorn (NPH) insulin in combination with mealtime insulin aspart in patients with type 2 diabetes. METHODS: This was a 26-week, multinational, open-label, parallel group trial with 505 patients with type 2 diabetes (mean age, 60.4 +/- 8.6 years; mean BMI, 30.4 +/- 5.3 kg/m(2); mean HbA(1c), 7.9 +/- 1.3%). Patients, randomized 2:1 to insulin detemir or NPH insulin, received basal insulin either once or twice daily according to their pretrial insulin treatment and insulin aspart at mealtimes. RESULTS: After 26 weeks of treatment, significant reductions in HbA(1c) were observed for insulin detemir (0.2%-points, p = 0.004) and NPH insulin (0.4%-points; p = 0.0001); HbA(1c) levels were comparable at study end (insulin detemir, 7.6%; NPH insulin, 7.5%). The number of basal insulin injections administered per day had no effect on HbA(1c) levels (p = 0.50). Nine-point self-measured blood glucose (SMBG) profiles were similar for the two treatment groups (p = 0.58), as were reductions in fasting plasma glucose (FPG) (insulin detemir, 0.5 mmol/l; NPH insulin, 0.6 mmol/l). At study end, FPG concentrations were similar for the two treatment groups (p = 0.66). By contrast, within-subject day-to-day variation in fasting SMBG was significantly lower with insulin detemir (p = 0.021). Moreover, patients receiving insulin detemir gained significantly less body weight than those who were administered NPH insulin (1.0 and 1.8 kg, respectively, p = 0.017). The frequency of adverse events and the risk of hypoglycaemia were comparable for the two treatment groups. CONCLUSIONS: Patients with type 2 diabetes, treated for 26 weeks with insulin detemir plus insulin aspart at mealtimes, experienced comparable glycaemic control but significantly lower within-subject variability and less weight gain compared to patients treated with NPH insulin and insulin aspart. Insulin detemir was well tolerated and had a similar safety profile to NPH insulin.

Insulin detemir used in basal-bolus therapy in people with type 1 diabetes is associated with a lower risk of nocturnal hypoglycaemia and less weight gain over 12 months in comparison to NPH insulin.

AIM: The aim of this study was to compare the long-term safety and efficacy of twice-daily insulin detemir or NPH insulin as the basal component of basal-bolus therapy in people with type 1 diabetes. METHODS: A multicentre, open-label, parallel-group study was conducted over 12 months and completed by 308 people (from an original randomized cohort of 428). Patients were randomized in a 2:1 ratio to receive insulin detemir or NPH insulin before breakfast and dinner, with insulin aspart at mealtimes. RESULTS: Glycaemic control improved in both groups with HbA(1c) decreasing by 0.64 and 0.56% point in the insulin detemir and NPH insulin groups, reaching baseline-adjusted final values of 7.53 +/- 0.10% and 7.59 +/- 0.13%, respectively. No significant difference was apparent between treatments in terms of HbA(1c), fasting plasma glucose or 9-point blood glucose profiles. Fewer hypoglycaemic events (major and minor) occurred in association with insulin detemir compared with NPH insulin, but the overall hypoglycaemic risk did not differ statistically significantly (RR for detemir, 0.78 [0.56-1.08]). However, the risk of nocturnal hypoglycaemia during the maintenance phase (month 2-12) was 32% lower in the detemir group (p = 0.02) and lower in every month. This risk reduction remained statistically significant after correction for HbA(1c). After 12 months, baseline-adjusted mean body weight was significantly lower in the insulin detemir group than in the NPH insulin group (p < 0.001). CONCLUSIONS: In long-term basal-bolus therapy, insulin detemir with insulin aspart as mealtime insulin is well tolerated and reduces the risks of nocturnal hypoglycaemia and weight gain compared to NPH insulin.

Superfluidity in a doped helium droplet.

Path-integral Monte Carlo calculations of the superfluid density throughout 4He droplets doped with linear impurities are presented. After deriving a local estimator for the superfluid density distribution, we find a decreased superfluid response in the cylindrically symmetric region of the first solvation layer. The helium in this region has a superfluid transition temperature similar to that of a two-dimensional helium system and may be responsible for previously unexplained experimental Q-branch measurements.

Bose-Einstein condensation at a helium surface.

A path integral Monte Carlo method was used to calculate the Bose-Einstein condensate fraction at the surface of a helium film at T = 0.77 K, as a function of density. Moving from the center of the slab to the surface, the condensate fraction was found to initially increase with decreasing density to a maximum value of 0.9 before decreasing. Long wavelength density correlations were observed in the static structure factor at the surface of the slab. Finally, a surface dispersion relation was calculated from imaginary-time density-density correlations.

Clinical profile of the novel sulphonylurea glimepiride.

Glimepiride is a new generation sulphonylurea being prudently characterized in more than 2000 NIDDM patients. It has a short onset of action and a long duration of action. The same pharmacodynamic effect as with traditional sulphonylureas is achieved with secretion of less insulin, suggesting a possible extrapancreatic action. Glimepiride is given once daily in doses from 1-8 mg/day. 100% absolute bioavailability and the absence of a food interaction guarantee highly reproducible pharmacokinetics. Glimepiride is a remarkably safe drug especially in NIDDM patients at high risk e.g. the renally impaired, elderly or physically very active person. Hypoglycemia is less frequent in the first weeks of treatment than with glibenclamide. Ongoing studies are investigating the possible beneficial clinical effect of its different binding behavior to the potassium channel, especially in the heart.

Clinical profile of glimepiride.

In order to achieve appropriate blood glucose control, the treatment of non-insulin dependent (NIDDM) Type II diabetes usually starts with diet and exercise. If this still results in insufficient metabolic control, oral hypoglycaemic drugs or insulin are added to the non-pharmacological measures. Sulphonylureas have been used successfully as oral hypoglycaemic agents since the 1950s but there are aspects where medication could be better adjusted to the patients' needs. Preclinical investigations on animals and in vitro studies with glimepiride (HOE490), a new sulphonylurea, suggested some benefit over sulphonylureas currently available, including lower dosage, rapid onset and long duration of action, lower insulin and C-peptide levels, possibly due to less stimulation of insulin secretion and more pronounced extrapancreatic effects. The clinical relevance of these findings were studied in clinical trials. 19 phase II and 4 phase III clinical studies, in a total of about 3750 Type II diabetic patients, established efficacy and safety of glimepiride in comparison to placebo and glibenclamide and showed its therapeutic value. 1 mg per day induced a marked blood glucose reduction (FPG 2.4 mmol/l; HbA1c 1.2%) which could be enhanced by increasing the dose to the maximum effective 4 and 8 mg daily. In patients, glimepiride had a more rapid onset of action than glibenclamide, with a long duration of action. Glimepiride achieved metabolic control with the lowest dose (1-8 mg daily) of all the sulphonylureas. In addition, it maintained a more physiological regulation of insulin secretion than glibenclamide during physical exercise, suggesting that there may be less risk of hypoglycaemia with glimepiride.(ABSTRACT TRUNCATED AT 250 WORDS)