The spectrum of neutrons at 60 hg m(-2)

The rate of neutron interactions was measured for the energy range 7.5 to 60 MeV, using a 3.85 kg cell of liquid scintillator. The neutrons are selected by pulse shape discrimination, with anticoincidence counters used to reduce interference from muons transversing the scintillator. The observed flux is interpreted in terms of neutrons produced from environmental uranium and thorium, those resulting from the capture of negative muons in nuclei and those from fast muon interactions

The great outdoors: how a green exercise environment can benefit all

The studies of human and environment interactions usually consider the extremes of environment on individuals or how humans affect the environment. It is well known that physical activity improves both physiological and psychological well-being, but further evidence is required to ascertain how different environments influence and shape health. This review considers the declining levels of physical activity, particularly in the Western world, and how the environment may help motivate and facilitate physical activity. It also addresses the additional physiological and mental health benefits that appear to occur when exercise is performed in an outdoor environment. However, people's connectedness to nature appears to be changing and this has important implications as to how humans are now interacting with nature. Barriers exist, and it is important that these are considered when discussing how to make exercise in the outdoors accessible and beneficial for all. The synergistic combination of exercise and exposure to nature and thus the 'great outdoors' could be used as a powerful tool to help fight the growing incidence of both physical inactivity and non-communicable disease. © 2013 Gladwell et al.; licensee BioMed Central Ltd

Selective Cytotoxicity of Rhodium Metalloinsertors in Mismatch Repair-Deficient Cells

Mismatches in DNA occur naturally during replication and as a result of endogenous DNA damaging agents, but the mismatch repair (MMR) pathway acts to correct mismatches before subsequent rounds of replication. Rhodium metalloinsertors bind to DNA mismatches with high affinity and specificity and represent a promising strategy to target mismatches in cells. Here we examine the biological fate of rhodium metalloinsertors bearing dipyridylamine ancillary ligands in cells deficient in MMR versus those that are MMR-proficient. These complexes are shown to exhibit accelerated cellular uptake which permits the observation of various cellular responses, including disruption of the cell cycle, monitored by flow cytometry assays, and induction of necrosis, monitored by dye exclusion and caspase inhibition assays, that occur preferentially in the MMR-deficient cell line. These cellular responses provide insight into the mechanisms underlying the selective activity of this novel class of targeted anticancer agents

Modal Analysis of the Orion Capsule Two Parachute System

As discussed in Ref [1], it is apparent from flight tests that the system made up of two main parachutes and a capsule can undergo several distinct dynamical behaviors. The most significant and problematic of these is the pendulum mode in which the system develops a pronounced swinging motion with an amplitude of up to 24 deg. Large excursions away from vertical by the capsule could cause it to strike the ground at a large horizontal or vertical speed and jeopardize the safety of the astronauts during a crewed mission. In reference [1], Ali et al. summarized a series of efforts taken by the Capsule Parachute Assembly System (CPAS) Program to understand and mitigate the pendulum issue. The period of oscillation and location of the system's pivot point are determined from post-flight analysis. Other noticeable but benign modes include: 1) flyout (scissors) mode, where the parachutes move back and forth symmetrically with respect to the vertical axis similar to the motion of a pair of scissors; 2) maypole mode, where the two parachutes circle around the vertical axis at a nearly constant radius and period; and 3) breathing mode, in which deformation of the non-rigid canopies affects the axial acceleration of the system in an oscillatory manner. Because these modes are relatively harm- less, little effort has been devoted to analyzing them in comparison with the pendulum motion. Motions of the actual system made up of two parachutes and a capsule are extremely complicated due to nonlinearities and flexibility effects. Often it is difficult to obtain insight into the fundamental dynamics of the system by examining results from a multi-body simulation based on nonlinear equations of motion (EOMs). As a part of this study, the dynamics of each mode observed during flight is derived from first principles on an individual basis by making numerous simplifications along the way. The intent is to gain a better understanding into the behavior of the complex multi-body system by studying the reduced set of differential equations associated with each mode. This approach is analogous to the traditional modal analysis technique used to study airplane flight dynamics, in which the full nonlinear behavior of the airframe is decomposed into the phugoid and short period modes for the longitudinal dynamics and the spiral, roll-subsidence, and dutch-roll modes for the lateral dynamics. It is important to note that the study does not address the mechanisms that cause the system to transition from one mode to another, nor does it discuss motions during which two or more modes occur simultaneously

Tunnel switch diode based on AlSb/GaSb heterojunctions

We report on tunnel switch diodes based on AlSb barriers and GaSb p–n junctions grown by molecular beam epitaxy. These were the devices with thyristor like switching in the GaSb/AlSb system. The characteristic "S" shaped current–voltage curve was found to occur for structures with AlSb barriers less than 300 Å thick. The switching voltage and current density exhibited less sensitivity to barrier and epilayer thickness than was predicted by the punch-through model. The results were correlated with drift diffusion simulations which have been modified to account for the presence of a tunneling contact

A benign, low Z electron capture agent for negative ion TPCs

We have identified nitromethane (CH$_3$NO$_2$) as an effective electron capture agent for negative ion TPCs (NITPCs). We present drift velocity and longitudinal diffusion measurements for negative ion gas mixtures using nitromethane as the capture agent. Not only is nitromethane substantially more benign than the only other identified capture agent, CS$_2$, but its low atomic number will enable the use of the NITPC as a photoelectric X{}-ray polarimeter in the 1{}-10 keV band

Low-background temperature sensors fabricated on parylene substrates

Temperature sensors fabricated from ultra-low radioactivity materials have been developed for low-background experiments searching for neutrinoless double-beta decay and the interactions of WIMP dark matter. The sensors consist of electrical traces photolithographically-patterned onto substrates of vapor-deposited parylene. They are demonstrated to function as expected, to do so reliably and robustly, and to be highly radio-pure. This work is a proof-of-concept study of a technology that can be applied to broad class of electronic circuits used in low-background experiments

A cross-sectional study of physical activity behaviour and associations with wellbeing during the UK coronavirus lockdown

This study assessed physical activity (PA) and wellbeing during lockdown. UK adults reported their PA in the previous week, perception of PA importance (more, less, same) and wellbeing, depression, anxiety and stress. One-way ANOVA compared PA and wellbeing by PA importance. The ‘less’ importance group did less PA than the ‘more’ and ‘same’ (p < 0.05) importance group; and scored worse on all wellbeing measures than the ‘same’ importance group (p < 0.01). They also had worse wellbeing, depression and anxiety than the ‘more’ importance group (p < 0.05). Strategies to overcome the impact of the pandemic should aim to increase PA

Possible Local Spiral Counterparts to Compact Blue Galaxies at Intermediate Redshift

We identify nearby disk galaxies with optical structural parameters similar to those of intermediate-redshift compact blue galaxies. By comparing HI and optical emission-line widths, we show that the optical widths substantially underestimate the true kinematic widths of the local galaxies. By analogy, optical emission-line widths may underrepresent the masses of intermediate-z compact objects. For the nearby galaxies, the compact blue morphology is the result of tidally-triggered central star formation: we argue that interactions and minor mergers may cause apparently compact morphology at higher redshift.Comment: 5 pages, uses emulateapj5 and psfig. To appear in ApJ

Theoretical studies of Si and GaAs surfaces and initial steps in the oxidation

Using ab initio quantum chemical methods (generalized valence bond), we examine (i) the electronic states of Si (111) and GaAs (110) surface, (ii) the relaxation of the Si (111) surface, (iii) the reconstruction of the GaAs surface, (iv) the initial steps in the chemisorption of O_2 on Si (111), and (v) the bonding of O atom to Ga and As centers