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Food and water are rewarding in part because they satisfy our internal needs1,2. Dopaminergic neurons in the ventral tegmental area (VTA) are activated by gustatory rewards3–5, but how animals learn to associate these oral cues with the delayed physiological effects of ingestion is unknown. Here we show that individual dopaminergic neurons in the VTA respond to detection of nutrients or water at specific stages of ingestion. A major subset of dopaminergic neurons tracks changes in systemic hydration that occur tens of minutes after thirsty mice drink water, whereas different dopaminergic neurons respond to nutrients in the gastrointestinal tract. We show that information about fluid balance is transmitted to the VTA by a hypothalamic pathway and then re-routed to downstream circuits that track the oral, gastrointestinal and post-absorptive stages of ingestion. To investigate the function of these signals, we used a paradigm in which a fluid’s oral and post-absorptive effects can be independently manipulated and temporally separated. We show that mice rapidly learn to prefer one fluid over another based solely on its rehydrating ability and that this post-ingestive learning is prevented if dopaminergic neurons in the VTA are selectively silenced after consumption. These findings reveal that the midbrain dopamine system contains subsystems that track different modalities and stages of ingestion, on timescales from seconds to tens of minutes, and that this information is used to drive learning about the consequences of ingestion.

Animals must learn through experience which foods are nutritious and should be consumed, and which are toxic and should be avoided. Enteroendocrine cells (EECs) are the principal chemosensors in the GI tract, but investigation of their role in behavior has been limited by the difficulty of selectively targeting these cells in vivo. Here we describe an intersectional genetic approach for manipulating EEC subtypes in behaving mice. We show that multiple EEC subtypes inhibit food intake but have different effects on learning. Conditioned flavor preference is driven by release of cholecystokinin whereas conditioned taste aversion is mediated by serotonin and substance P. These positive and negative valence signals are transmitted by vagal and spinal afferents, respectively. These findings establish a cellular basis for how chemosensing in the gut drives learning about food.

How neurons in the eye feed signals back to photoreceptors to optimize sensitivity to patterns of light appears mediated by one or more unconventional mechanisms. Via these mechanisms, horizontal cells control synaptic gain and enhance key aspects of temporal and spatial light adaptation, including center-surround receptive field antagonism. After the transduction of light energy into an electrical signal in photoreceptors, a major task in visual processing is transmission of an optimized signal to the follower neurons in the retina. For this to happen, the release of the excitatory neurotransmitter glutamate from photoreceptors is carefully regulated via feedback from horizontal cells, which acts like a thermostat to keep synaptic transmission in an optimal range during changes in light patterns and intensities. A recently described model that casts a classical neurotransmitter system together with ion transport mechanisms to adjust the alkaline milieu outside the synapse, is emphasized here. We review the new evidence showing how this novel inter-neuronal messaging system carries the feedback inhibition using two separate, but interwoven, regulated systems. It may be the complex interplay between these two signaling modalities, creating synaptic modulation-at-a-distance, that has made its definition difficult. The foundations of our understanding of the feedback mechanism from horizontal cells to photoreceptors have been long established: Horizontal cells have broad receptive fields, suitable for providing surround inhibition, their membrane potential regulates inhibition of photoreceptor voltage-gated calcium channels, and strong artificial pH buffering eliminates this action. This report compares and contrasts models of how these foundations are linked, focusing on a recent report of a novel action of GABA in mammals that shows tonic horizontal cell release of GABA activating chloride and bicarbonate permeable GABA autoreceptors. The membrane potential of horizontal cells provides the driving force for GABAR-mediated bicarbonate efflux, alkalinizing the cleft when horizontal cells are hyperpolarized by light or adding to their depolarization cells in darkness by contributing to cleft acidification via NHE-mediated proton efflux. This model reverses interpretations of earlier studies that were considered to rule out a role for GABA in feedback to cones.

The developing retina expresses multiple bHLH transcription factors. Their precise functions and interactions in uncommitted retinal progenitors remain to be fully elucidated. Here, we investigate the roles of bHLH factors ATOH7 and Neurog2 in developing human ES cell-derived 3D retinal organoids. Single cell transcriptome analyses identify three states of proliferating retinal progenitors: pre-neurogenic, neurogenic, and cell cycle-exiting progenitors. Each shows different expression profile of bHLH factors. The distinct cell cycle-exiting progenitors feed into a postmitotic heterozygous neuroblast pool that gives rise to early born neuronal lineages. Elevating ATOH7 or Neurog2 expression accelerates the transition from the pre-neurogenic to the neurogenic state, and expands the exiting progenitor and neuroblast populations. In addition, ATOH7 and Neurog2 significantly, yet differentially, enhance retinal ganglion cell and cone photoreceptor production. Moreover, single cell transcriptome analyses reveal that ATOH7 and Neurog2 assert positive autoregulation, suppress key bHLH factors associated with the neurogenic progenitors, and elevate bHLH factors expressed by exiting progenitors and differentiating neuroblasts. This study thus provides novel insight regarding how ATOH7 and Neurog2 impact human retinal progenitor behaviors and neuroblast fate choices.

Author(s): Crawford, Emily D; Acosta, Irene; Ahyong, Vida; Anderson, Erika C; Arevalo, Shaun; Asarnow, Daniel; Axelrod, Shannon; Ayscue, Patrick; Azimi, Camillia S; Azumaya, Caleigh M; Bachl, Stefanie; Bachmutsky, Iris; Bhaduri, Aparna; Brown, Jeremy Bancroft; Batson, Joshua; Behnert, Astrid; Boileau, Ryan M; Bollam, Saumya R; Bonny, Alain R; Booth, David; Borja, Michael Jerico B; Brown, David; Buie, Bryan; Burnett, Cassandra E; Byrnes, Lauren E; Cabral, Katelyn A; Cabrera, Joana P; Caldera, Saharai; Canales, Gabriela; Castaneda, Gloria R; Chan, Agnes Protacio; Chang, Christopher R; Charles-Orszag, Arthur; Cheung, Carly; Chio, Unseng; Chow, Eric D; Citron, Y Rose; Cohen, Allison; Cohn, Lillian B; Chiu, Charles; Cole, Mitchel A; Conrad, Daniel N; Constantino, Angela; Cote, Andrew; Crayton-Hall, Tre'Jon; Darmanis, Spyros; Detweiler, Angela M; Dial, Rebekah L; Dong, Shen; Duarte, Elias M; Dynerman, David; Egger, Rebecca; Fanton, Alison; Frumm, Stacey M; Fu, Becky Xu Hua; Garcia, Valentina E; Garcia, Julie; Gladkova, Christina; Goldman, Miriam; Gomez-Sjoberg, Rafael; Gordon, M Grace; Grove, James CR; Gupta, Shweta; Haddjeri-Hopkins, Alexis; Hadley, Pierce; Haliburton, John; Hao, Samantha L; Hartoularos, George; Herrera, Nadia; Hilberg, Melissa; Ho, Kit Ying E; Hoppe, Nicholas; Hosseinzadeh, Shayan; Howard, Conor J; Hussmann, Jeffrey A; Hwang, Elizabeth; Ingebrigtsen, Danielle; Jackson, Julia R; Jowhar, Ziad M; Kain, Danielle; Kim, James YS; Kistler, Amy; Kreutzfeld, Oriana; Kulsuptrakul, Jessie; Kung, Andrew F

The stream of visual information sent from photoreceptors to second-order bipolar cells is intercepted by laterally interacting horizontal cells that generate feedback to optimize and improve the efficiency of signal transmission. The mechanisms underlying the regulation of graded photoreceptor synaptic output in this nonspiking network have remained elusive. Here, we analyze with patch clamp recording the novel mechanisms by which horizontal cells control pH in the synaptic cleft to modulate photoreceptor neurotransmitter release. First, we show that mammalian horizontal cells respond to their own GABA release and that the results of this autaptic action affect cone voltage-gated Ca2+ channel (CaV channel) gating through changes in pH. As a proof-of-principle, we demonstrate that chemogenetic manipulation of horizontal cells with exogenous anion channel expression mimics GABA-mediated cone CaV channel inhibition. Activation of these GABA receptor anion channels can depolarize horizontal cells and increase cleft acidity via Na+/H+ exchanger (NHE) proton extrusion, which results in inhibition of cone CaV channels. This action is effectively counteracted when horizontal cells are sufficiently hyperpolarized by increased GABA receptor (GABAR)-mediated HCO3- efflux, alkalinizing the cleft and disinhibiting cone CaV channels. This demonstrates how hybrid actions of GABA operate in parallel to effect voltage-dependent pH changes, a novel mechanism for regulating synaptic output.

Outdoor air pollution is a major environmental health problem throughout the world. In particular, exposure to particulate matter (PM) has been associated with the development and exacerbation of several respiratory diseases, including asthma. Although the adverse health effects of PM have been demonstrated for many years, the underlying mechanisms have not been fully identified. In this review, we focus on the role of the lung epithelium and specifically highlight multiple cytokines in PM-induced respiratory responses. We describe the available literature on the topic including in vitro studies, findings in humans (ie observations in human cohorts, human controlled exposure and ex vivo studies) and in vivo animal studies. In brief, it has been shown that exposure to PM modulates the airway epithelium and promotes the production of several cytokines, including IL-1, IL-6, IL-8, IL-25, IL-33, TNF-α, TSLP and GM-CSF. Further, we propose that PM-induced type 2-promoting cytokines are important mediators in the acute and aggravating effects of PM on airway inflammation. Targeting these cytokines could therefore be a new approach in the treatment of asthma.

This work presents data obtained from an investigation into muon stimulated neutron emission in combination with the technique of muon scattering tomography. Initial measurements in lead of the neutron emission measured a half-life of 56.9 ± 6.63 ns which is three standard deviations lower than expected, with the error primarily attributed to prompt X-ray emission. A hypothetical detector, based on a muon scattering tomography prototype at AWE was used to examine the data expected from an integrated system. A lifetime 81 ± 3 ns was obtained here. Alongside this a portable muon trigger detector has been developed which aims to be implemented in a deployable muon scattering tomography system. The portable detector successfully measures muons to an accuracy of 20%.

Muon scattering tomography techniques can be used to image the contents of an enclosed volume by measuring the scattering angle of cosmic ray muons as they pass through a volume using particle tracking detectors. The magnitude of the observed muon scatter varies with the density of the objects within a volume, therefore the technique is well suited to distinguishing dense (high-Z) materials from lower density (low-Z) materials. AWE has been investigating muon scattering tomography techniques for use in the identification of special nuclear material (SNM) in transit cargo for a number of years. As part of this work AWE and our partner institutions have plate chamber technology, and a software suite of reconstruction tools and Monte Carlo simulations that we have used to quantify the capability and limitations of muon tomography techniques for SNM identification. Recent work at AWE has focused on the development of portable detector technologies for the imaging of objects and packages at unfixed locations. It is envisaged that portable detectors will be positioned to the sides of the screened objects rather than at the top and bottom with the object in the centre. This work has involved the further development of our Monte Carlo models to provide a more detailed of the horizontal muon flux and the implementation of new tracking algorithms to identify muons coming from either side of the tracking system. Part of this work has also involved investigating the use of portable wire chamber and silicon tracking detectors. Our work has also focused on examining the potential improvements to image quality afforded by the detection of spallation neutrons from muon interactions inside an object. The work presented will provide an overview of these recent developments and draw conclusions on the use of muon scattering tomography techniques for deployable security imaging applications.

The Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) on NASA's Terra platform has been widely used in geological and other science studies. In support of ASTER studies, a library of natural and man-made materials was compiled as the ASTER Spectral Library v1.2 and made available from http://speclib.jpl.nasa.gov . The library is a collection of contributions in a standard format with ancillary data from the Jet Propulsion Laboratory (JPL), Johns Hopkins University (JHU) and the United States Geological Survey (USGS). A new version of the library (v2.0) is now available online or via CD, which includes major additions to the mineral and rock spectra. The ASTER library provides a comprehensive collection of over 2300 spectra of a wide variety of materials covering the wavelength range 0.4–15.4 µm.

Horizontal cells form the first laterally interacting network of inhibitory interneurons in the retina. Dopamine released onto horizontal cells under photic and circadian control modulates horizontal cell function. Using isolated, identified horizontal cells from a connexin-57-iCre × ROSA26-tdTomato transgenic mouse line, we investigated dopaminergic modulation of calcium channel currents ( ICa) with whole cell patch-clamp techniques. Dopamine (10 μM) blocked 27% of steady-state ICa, an action blunted to 9% in the presence of the L-type Ca channel blocker verapamil (50 μM). The dopamine type 1 receptor (D1R) agonist SKF38393 (20 μM) inhibited ICaby 24%. The D1R antagonist SCH23390 (20 μM) reduced dopamine and SKF38393 inhibition. Dopamine slowed ICaactivation, blocking ICaby 38% early in a voltage step. Enhanced early inhibition of ICawas eliminated by applying voltage prepulses to +120 mV for 100 ms, increasing ICaby 31% and 11% for early and steady-state currents, respectively. Voltage-dependent facilitation of ICaand block of dopamine inhibition after preincubation with a Gβγ-blocking peptide suggested involvement of Gβγ proteins in the D1R-mediated modulation. When the G protein activator guanosine 5′- O-(3-thiotriphosphate) (GTPγS) was added intracellularly, ICawas smaller and showed the same slowed kinetics seen during D1R activation. With GTPγS in the pipette, additional block of ICaby dopamine was only 6%. Strong depolarizing voltage prepulses restored the GTPγS-reduced early ICaamplitude by 36% and steady-state ICaamplitude by 3%. These results suggest that dopaminergic inhibition of ICavia D1Rs is primarily mediated through the action of Gβγ proteins in horizontal cells.

Background Although the prominent role of TH2 cells in type 2 immune responses is well established, the newly identified type 2 innate lymphoid cells (ILC2s) can also contribute to orchestration of allergic responses. Several experimental and epidemiologic studies have provided evidence that allergen-induced airway responses can be further enhanced on exposure to environmental pollutants, such as diesel exhaust particles (DEPs). However, the components and pathways responsible remain incompletely known. Objective We sought to investigate the relative contribution of ILC2 and adaptive TH2 cell responses in a murine model of DEP-enhanced allergic airway inflammation. Methods Wild-type, Gata-3+/nlslacZ (Gata-3–haploinsufficient), RAR-related orphan receptor α (RORα)fl/flIL7RCre (ILC2-deficient), and recombination-activating gene (Rag) 2−/− mice were challenged with saline, DEPs, or house dust mite (HDM) or DEP+HDM. Airway hyperresponsiveness, as well as inflammation, and intracellular cytokine expression in ILC2s and TH2 cells in the bronchoalveolar lavage fluid and lung tissue were assessed. Results Concomitant DEP+HDM exposure significantly enhanced allergic airway inflammation, as characterized by increased airway eosinophilia, goblet cell metaplasia, accumulation of ILC2s and TH2 cells, type 2 cytokine production, and airway hyperresponsiveness compared with sole DEPs or HDM. Reduced Gata-3 expression decreased the number of functional ILC2s and TH2 cells in DEP+HDM-exposed mice, resulting in an impaired DEP-enhanced allergic airway inflammation. Interestingly, although the DEP-enhanced allergic inflammation was marginally reduced in ILC2-deficient mice that received combined DEP+HDM, it was abolished in DEP+HDM-exposed Rag2−/− mice. Conclusion These data indicate that dysregulation of ILC2s and TH2 cells attenuates DEP-enhanced allergic airway inflammation. In addition, a crucial role for the adaptive immune system was shown on concomitant DEP+HDM exposure., Graphical abstract

Whilst the performance of small THGEMs is well known, here we consider the challenges in scaling these up to large area charge readouts. We first verify the expected gain of larger THGEMs by reporting experimental Townsend coefficients for a 10 cm diameter THGEM in low-pressure CF$_4$. Large area 50 cm by 50 cm THGEMs were sourced from a commercial PCB supplier and geometrical imperfections were observed which we quantified using an optical camera setup. The large area THGEMs were experimentally characterised at Boulby Underground Laboratory through a series of gain calibrations and alpha spectrum measurements. ANSYS, Magboltz and Garfield++ simulations of the design of a TPC based on the large area THGEMs are presented. We also consider their implications for directional dark matter research and potential applications within nuclear security., Comment: 18 pages, 22 figures

Ultralarge sale integrated circuit designs require multiple metal wiring layers for the formation of the device interconnections. Surface planarization and the deposition of high quality insulating films are critical fabrication steps related to the manufacture of these circuits. Planarization and dielectric deposition can be accomplished simultaneously using a spin-on process with hydrogen silsesquioxane (HSQ) resin to deposit amorphous SiO:H dielectric films. The use of this material in device manufacturing has increased as a result of the material's good planarization properties, eliminating the need for etchback procedures. More recently, it has been observed that HSQ-based films also provide the added benefit of relative permittivity less than SiO 2 , which helps to minimize electrical delay. In order to obtain optimum properties from this material, tight process control and knowledge of the material's chemical behavior are necessary. Studies of the precursor material, film formation, and film properties have been performed. Also it is found that structural and compositional changes in the precursor during the film forming process play an important role in establishing the beneficial properties observed in HSQ-based dielectric films.

Patient characteristics and cytogenetics of acute myeloid leukaemia (AML) in clinical trials do not reflect that of the general population. There has not been a large population-based study that has examined cytogenetic features and outcomes of AML in Australia.Investigation of epidemiological, prognostic, treatment and outcome data in adults diagnosed with AML in Western Australia between 1991 and 2005.Patients were identified utilising the Western Australia Cancer Registry, cytogenetic databases and hospital inpatient discharge diagnoses. Data were retrospectively collected from patients presenting to tertiary hospitals on patient characteristics, karyotype, induction therapy, remission, transplantation and survival.A total of 987 patients with AML was identified, of which 91% (898) attended a tertiary hospital. Median age was 67 years and 45% of cases represented secondary AML. Cytogenetic analysis was available in 81% of patients. Frequent karyotypes were normal (38.8%), complex (13.8%) and -7/add(7q)/del(7q) (12.1%). Aggressive therapy was initiated in 62.6%. Less than 15% were enrolled in clinical trials. Overall 16.5% received a stem cell transplant. Median overall survival for all patients was 5.6 months. In patients treated aggressively, complete remission was achieved in 56.9% and median overall survival was 12.2 months. Age, secondary disease and karyotype were significantly predictive of remission and overall survival.Age distribution, remission and survival rates were comparable with published population-based studies. High median age was reflected in the rate of secondary AML and trial eligibility. These findings highlight the need for prospective data collection.

The cellular mechanisms underlying feedback signaling from horizontal cells to photoreceptors, important for formation of receptive field surrounds of early visual neurons, remain unsettled. Mammalian horizontal cells express a complement of synaptic proteins that are necessary and sufficient for calcium-dependent exocytosis of inhibitory neurotransmitters at their contacts with photoreceptor terminals, suggesting that they are capable of releasing GABA via vesicular release. To test if horizontal cell vesicular release is involved in feedback signaling, we perturbed inhibitory neurotransmission in these cells by targeted deletion of the vesicular GABA transporter (VGAT), the protein responsible for uptake of inhibitory transmitter by synaptic vesicles. To manipulate horizontal cells selectively, an iCre mouse line with Cre recombinase expression controlled by connexin57 (Cx57) regulatory elements was generated. In Cx57-iCre mouse retina, only horizontal cells expressed Cre protein and its expression occurred in all retinal regions. After crossing with a VGATflox/flox mouse line, VGAT was selectively eliminated from horizontal cells, which was confirmed immunohistochemically. Voltage-gated ion channel currents in horizontal cells of Cx57-VGAT -/- mice were the same as Cx57-VGAT+/+ controls, as were the cells’ responses to the ionotropic glutamate receptor agonist, kainate, but the response to the GABAA receptor agonist, muscimol, in Cx57-VGAT -/- mice was larger. In contrast, feedback inhibition of photoreceptor calcium channels, which in control animals is induced by horizontal cell depolarization, was completely absent in Cx57-VGAT -/- mice. The results suggest that vesicular release of GABA from horizontal cells is required for feedback inhibition of photoreceptors. Significance Statement: Feedback inhibition by horizontal cells regulates the photoreceptor calcium channels responsible for the release of the neurotransmitter, glutamate. This feedback inhibition contributes to the formation of the receptive field surrounds of early visual neurons, important for contrast sensitivity and color opponency in vision. The cellular mechanisms underlying feedback inhibition are not fully understood. One disputed mechanism for mammalian horizontal cell inhibitory output involves the vesicular release of the inhibitory neurotransmitter, GABA. By deleting selectively the transporter that normally loads GABA into vesicles in horizontal cells, we show that horizontal cells lose their ability to modulate photoreceptor calcium signals. These findings implicate a role for the vesicular release of GABA in mediating inhibitory feedback.

Low‐temperature growth processes are needed in order to fully exploit the potential of GexSi1−x/Si heterostructures. Remote plasma‐enhanced chemical vapor deposition has been successful for silicon homoepitaxy at substrate temperatures as low as 150 °C. We report the growth of GexSi1−x/Si heterostructures with values of x between 0.07 and 0.73, and at substrate temperatures of 305 and 450 °C. The films grown at 450 °C have excellent crystallinity, low defect densities, and very abrupt interfaces, while films grown at 305 °C have degraded crystallinity.

Silane (S1H4), a pyrophoric gas, is the most widely used gas for the growth of dielectric films used in integrated circuit manufacturing. The industry has extensive experience in the handling of silane, but as process throughput continues to increase, so to do the concerns regarding safety and implementation issues involving this material. Trimethylsilane ((CH3)3SiH) is a non-pyrophoric organosilicon gas which can be used as a safe replacement for silane. Its material properties allow for standard packaging and quick integration into plasma deposition processes. The use of a non-pyrophoric gas will increase safety and process equipment uptime. By direct comparison to silane based processes, it is demonstrated that high quality films of silicon dioxide and silicon nitride can be deposited from trimethylsilane. In addition, hard, inert amorphous silicon carbide films can be deposited using the gas as a single precursor.

The Performance Rating Table (PRT) is introduced as a means to separate mask-wearer performance by causative factors. The PRT shows which mask factors require design attention and how the mask affects different users.

The Joint Services Operational Requirements (JSOR) for vision, communications, respiration, thermal, personal support, compatibility and psychological factors are presented in this summary. The body of the report provides the test methods used with other pertinent information. The test equipment and cost of equipment are provided with recommendations for selection of the test and the equipment. The Recommendation section provides a synopsis of the findings and suggested equipment the advanced protective systems integration laboratory may want to evaluate for use with advanced mask design.

We have used polyclonal and monoclonal antibodies raised against calf thymus profilin to localize the corresponding protein in translocating, spreading, and stationary rat fibroblasts. Immunofluorescence of whole cells and immunogold labeling on ventral membranes of lysis-squirted cells showed that profilin was markedly enriched in the highly dynamic lamellipodia or pseudopodial lobes. Within these regions, a significant fraction was colocalized with dynamic actin filaments organized in actin ribs, cortical filaments, or stress fiber-like bundles, and little profilin was found in membrane areas appearing free of actin. In contrast, stress fibers of stationary cells as well as actin arcs and ring-like bundles of spreading and migrating cells showed very little label. These results are discussed in context with the proposed role of profilin in regional membrane dynamics typical for fibroblasts and are compared to previous data (Hartwig et al.: J. Cell Biol. 109:1571-1579, 1989) on profilin distribution in platelets and granulocytes.

The density of misfit dislocations in GexSi1−x films has been measured as a function of deposition temperature and r-f plasma power in Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD). The misfit dislocation density decreases as the deposition temperature is lowered from 450°C to 410°C. As the plasma power is increased from 6.6 to 16W, the dislocation density peaks at lOW and then decreases with increasing power.

An all-fiber (6x6) optical shutter switch matrix with the control system for microwave phased array has been demonstrated. The device offers the advantages of integrated configuration, low cost, low power consumption, small size, and light weight. The maximum extinction ratio (among 36 individual pixel) of this switch matrix at 840 nm is 24.2 dB, and the switching time is less than 120 microsec. In addition to phased array application, this low cost switch matrix is extremely attractive for fiber optic switching networks.

A reliable contact diffusion barrier has been successfully formed by sintering in N2 a physically sputtered W/Ti bilayer. This barrier system is designed for use in 1.0‐μm Al/W/TiNy/TiSz/n+ and p+)Si very large scale integrated complementary metal–oxide semiconductor contacts. The structure of this barrier metallization layer has been physically characterized by Auger electron spectroscopy, Rutherford backscattering spectroscopy, secondary neutral mass spectrometry, and secondary ion mass spectrometry.

The high-strength, nickel-base alloy X-750 is susceptible to stress-corrosion cracking (SCC) in high-purity, deaerated water. Crack initiation occurs at high temperatures [>400°F (204 °C)]. Crack propagation occurs in both high-temperature and low-temperature [

A proposed new method for soil surface compaction based on the principle of pressure waves as a source of energy is described. This method, which has been termed the foamed propellant method for soil compaction, has a formulation containing hydrazine, ammonium perchlorate, and a foaming agent, hydrolized protein base foam liquid. The mechanics of this new compaction technique are relatively simple, with a blanket of the foamed propellant system placed on the surface of the soil to be compacted and then detonated. The results of using the foamed propellant system to compact loose cohesionless soils are presented and evaluated. This includes some preliminary investigation of the influence of both surface area and multiple detonation on compaction control parameters. The results of this investigation to date (1964) show conclusively that this new compaction is effective in increasing the density of the soil to depths of as much as 15 in. below the surface for sandy soils, sand-gravel mixtures, and predominantly silty soil containing little clay. Laboratory blast pressure measurements are also examined and presented.

Ion-thinned longitudinal sections of a third molar were observed by bright- and dark-field electron microscopy. In bright field, the hydroxyapatite crystallites in enamel appeared as long rods, but, when observed in dark field, the crystallites were rectangular, with a mean length of 321 A.

Thin foils of high purity aluminium and an Al-Al2O3 SAP type of alloy were oxidised in a specially designed hot stage specimen chamber in an electron microscope. Below 450 C, amorphous aluminium oxide formed on the foil surface and was first detectable at foil edges, holes, and pits. Islands of aluminium then nucleated in this amorphous oxide. The aluminium islands displayed either a lateral growth with eventual coalescence with other islands, or a reoxidation process which caused the islands to disappear. The aluminium island formation was determined to be related to the presence of the electron beam. A mechanism based upon electron charging due to the electron beam was proposed to explain the nucleation, growth, coalescence, disappearance, and geometry of the aluminium islands.