The role of induced contrast in images obtained using the environmental scanning electron microscope

Generation of contrast in images obtained using the environmental scanning electron microscope (ESEM) is explained by interpretation of images acquired using the gaseous secondary electron detector (GSED), ion current, and the Everhart-Thornley detector. We present a previously unreported contrast component in GSED and ion current images attributed to signal induction by changes in the concentration of positive ions in the ESEM chamber during image acquisition. Changes in positive ion concentration are caused by changes in electron emission from the sample during image acquisition and by a discrepancy between the drift velocities of negative and positive charge carriers in the imaging gas. The proposed signal generation mechanism is used to explain contrast reversal in images produced using the GSED and ion current signals and accounts for discrepancies in contrast observed, under some conditions, in these types of images. Combined with existing models of signal generation in the ESEM, the proposed model provides a basis for correct interpretation of ESEM images.     

Social role and patterns of symptomatic behaviors.

In an attempt to develop a more conceptually oriented system of psychiatric classification, the statistical relationships occurring among various symptomatic reactions were studied in 604 patients. The deviant reactions were organized into symptom clusters, and a test of their stability was made in another group of Ss. The 3 symptom clusters which emerged were "avoidance of others… self-indulgence and turning against others… [and] self-deprivation and turning against the self." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three dimensional solid-shell transition finite elements for heat conduction

This paper presents a finite element formulation for a special class of finite elements referred to as ‘Solid-Shell Transition Finite Elements’ for three dimensional heat conduction. The solid-shell transition elements are necessary in applications requiring the use of both three dimensional solid elements and the curved shell elements. These elements permit transition from the solid portion of the structure to the shell portion of the structure. A novel feature of the formulation presented here is that nodel temperatures as well as nodal temperature gradients are retained as primary variables. The element geometry is defined in terms of coordinates of the nodes as well as the nodal point normals for the nodes lying on the middle surface of the element. The temperature field with the element is approximated in terms of element approximation functions, nodal temperatures and nodal temperature gradients. The properties of the transition element are then derived using the weak formulation (or the quadratic functional) of the Fourier heat conduction equation in the Cartesian coordinate system and the element temperature approximation. The formulation presented here permits linear temperature distribution in the element thickness direction.

Convective boundaries as well as distributed heat flux is permitted on all six faces of the elements. Furthermore, the element formulation also permits internal heat generation and orthotropic material behavior. Numerical examples are presented firstly to illustrate the accuracy of the formulation and secondly to demonstrate its usefulness in practical application. Numerical results are also compared with the theoretical solutions.     

Control of very-long-wavelength infrared HgCdTe detector-cutoff wavelength

Hg_1-xCd_xTe is an important material for infrared (IR) detection applications where the bandgap of the alloy varies from semimetal to 1.4 eV. The large variation in bandgap energy with HgCdTe composition causes difficulty in controlling detector-cutoff wavelength, particularly for the long-wavelength IR and very-long-wavelength infrared (VLWIR, greater than 12 μm) spectral bands. Our ability to control the HgCdTe composition and compositional profile during growth by molecular beam epitaxy (MBE) is improved significantly by using automated feedback control from spectroscopic ellipsometry (SE) measurements, where the standard deviation in the error in composition has improved by a factor of 5, from σ=0.0081 to σ=0.0016. To improve our ability to predict cutoff wavelength from IR transmission measurements, we have used a model of the absorption in HgCdTe to revise our past empirical cutoff relationship to include the effect of compositional grading. We have achieved a mean detector-cutoff wavelength of 14.1 μm and standard deviation of σ=0.25 μm for a series of 19 processed layers with a target cutoff of 14 μm. The excellent control in VLWIR detector cutoff we have observed is attributed to automated compositional control and an improved cutoff-prediction model.     

Cerebral Cavernous Malformation Pathogenesis: Investigating Lesion Formation and Progression with Animal Models

Cerebral cavernous malformation (CCM) is a cerebromicrovascular disease that affects up to 0.5% of the population. Vessel dilation, decreased endothelial cell–cell contact, and loss of junctional complexes lead to loss of brain endothelial barrier integrity and hemorrhagic lesion formation. Leakage of hemorrhagic lesions results in patient symptoms and complications, including seizures, epilepsy, focal headaches, and hemorrhagic stroke. CCMs are classified as sporadic (sCCM) or familial (fCCM), associated with loss-of-function mutations in KRIT1/CCM1, CCM2, and PDCD10/CCM3. Identifying the CCM proteins has thrust the field forward by (1) revealing cellular processes and signaling pathways underlying fCCM pathogenesis, and (2) facilitating the development of animal models to study CCM protein function. CCM animal models range from various murine models to zebrafish models, with each model providing unique insights into CCM lesion development and progression. Additionally, these animal models serve as preclinical models to study therapeutic options for CCM treatment. This review briefly summarizes CCM disease pathology and the molecular functions of the CCM proteins, followed by an in-depth discussion of animal models used to study CCM pathogenesis and developing therapeutics.     

Direct Determination of ��-Hydroxy-��-Methylbutyrate (HMB) in Liquid Nutritional Products

A high performance liquid chromatography/ultraviolet method developed for the simple and direct determination of β-hydroxy-β-methylbutyrate (HMB) in liquid nutritional products and dietary supplements is described. Method suitability was defined by experimental assessments of linearity (r ² > 0.9999), precision (day-to-day RSD <1.5%), accuracy (spike recoveries = 98.1–102.4%, n = 28), selectivity (peak purity average = 99.8 ± 0.8%, n = 10; absence of interference verified by placebo analysis), and quantitation limit (90 mg/kg or 0.8 mM). The method provides for a simple, accurate, and precise quantification of HMB, when present at millimolar concentrations in liquid nutritional products and dietary supplements.     

Housing policy in remote Indigenous communities: how politics obstructs good policy

Abstract

When it comes to issues of housing policy, remote Indigenous housing often presents the extreme case. The failures of housing policy are most acute in remote Indigenous Australia, but despite the need to learn from the policy mistakes of the past, there has been little detailed analysis of the policy history. Through documentary and empirical analysis, we show that policies have either failed to be adapted to cultural and geographic contexts or, when they have been culturally responsive, they have lacked attention to the complexities of service delivery. Despite differences in policy settings, the long view is one of the normalization of Indigenous communities, although research points to the need for culturally appropriate arrangements. We argue that rather than politically motivated short-termism, governments need to develop a medium- to long-term approach that approaches policy solutions incrementally, builds capacity within the state and Indigenous communities, and is based on the evidence.     

Water Resources: The Delaware Basin

Philadelphia is in competition with New York City and Baltimore in staking a claim for the water resources it will need in the next half century and beyond. A new governmental organization having a delegation of both state and federal powers for continuous planning and for unified management and control of the water resources of the entire Delaware River Basin has been proposed; and a federal-state compact for its establishment is being negotiated.