Possibilities for LWIR detectors using MBE-grown Si(/Si(1-x)Ge(x) structures

Traditionally, long wavelength infrared (LWIR) detection in Si-based structures has involved either extrinsic Si or Si/metal Schottky barrier devices. Molecular beam epitaxially (MBE) grown Si and Si/Si(1-x)Ge(x) heterostructures offer new possibilities for LWIR detection, including sensors based on intersubband transitions as well as improved conventional devices. The improvement in doping profile control of MBE in comparison with conventional chemical vapor deposited (CVD) Si films has resulted in the successful growth of extrinsic Si:Ga, blocked impurity-band conduction detectors. These structures exhibit a highly abrupt step change in dopant profile between detecting and blocking layers which is extremely difficult or impossible to achieve through conventional epitaxial growth techniques. Through alloying Si with Ge, Schottky barrier infrared detectors are possible, with barrier height values between those involving pure Si or Ge semiconducting materials alone. For both n-type and p-type structures, strain effects can split the band edges, thereby splitting the Schottky threshold and altering the spectral response. Measurements of photoresponse of n-type Au/Si(1-x)Ge(x) Schottky barriers demonstrate this effect. For intersubband multiquntum well (MQW) LWIR detection, Si(1-x)Ge(x)/Si detectors grown on Si substrates promise comparable absorption coefficients to that of the Ga(Al)As system while in addition offering the fundamental advantage of response to normally incident light as well as the practical advantage of Si-compatibility. Researchers grew Si(1-x)Ge(x)/Si MQW structures aimed at sensitivity to IR in the 8 to 12 micron region and longer, guided by recent theoretical work. Preliminary measurements of n- and p-type Si(1-x)Ge(x)/Si MQW structures are given

InAs/Ga(1-x)In(x)Sb superlattices for infrared detector applications

The successful growth of InAs/Ga(1-x)In(x)Sb superlattices and their optical and structural characterization is discussed. Samples were grown by molecular beam epitaxy at fairly low substrate temperatures (less than 400 C). Structural quality was assessed by reflection high energy electron difrraction, transmission electron microscopy, and x ray diffraction. Excellent structures were achieved for growth on thick, strain relaxed GaSb buffer layers on GaAs substrates, despite a residual threading dislocation density of 10(exp 9)cm(exp -2) originating at the GaSb/GaAs interface. Despite a lattice mismatch of 1.7 percent, InAs/Ga(0.75)In(0.25)Sb superlattices are observed to be free of misfit dislocations at the thicknesses examined here, owing to the close lattice match between the superlattice and GaSb, which evenly distributes compressive and tensile stresses between the InAs and Ga(0.75)In(0.25)Sb layers. Photoluminescence and photoconductivity measurements indicate that the energy gaps of the strain-layer superlattices are smaller than those of InAs/GaSb superlattices with the same layer thicknesses, and are in agreement with the theoretical predictions of Smith and Mailhiot. Energy gaps of 80 to 250 meV (15 to 5 microns) have been measured for InAs/Ga(0.75)In(0.25)Sb superlattices with 45 to 25 A/25 A layer thickness. Results demonstrate that far-infrared cutoff wavelengths are compatible with the thin superlattice layers required for strong optical absorption in type-II superlattices

Advances in the Diagnosis of Urothelial Neoplasia

Urothelial neoplasia is a unique cancer in that it consists of a spectrum of tumors with different biologic behaviors. The most common urothelial neoplasm is the low grade superficial papillary carcinoma or papilloma which may recur numerous times but does not result in significant morbidity or mortality. A variant of the superficial papillary carcinoma, which represents approximately 10% of the tumors, is the noninvasive papillary neoplasm which progresses to a less differentiated invasive transitional cell carcinoma (TCC). Considerable effort has been directed at identifying which of the superficial well differentiated papillary tumors will persist, recur and progress to invasive cancer Current approaches to identifying such tumors include cytogenetics, molecular biology, and flow cytometric DNA analysis. In the final group of bladder carcinomas, the high grade invasive neoplasms, evidence suggests that these life-threatening tumors arise de novo without identifiable precursors. Unfortunately, 75% to 90% of invasive TCCs are classified in this group, with the remaining minority progressing from preexisting recurrent superficial papillary carcinomas. Obviously the biologic behavior of these aggressive poorly differentiated tumors is life-threatening, and application of traditional diagnostic procedures and new technologies need to be directed at early diagnosis

Evaluation of Microbolometer-Based Thermography for Gossamer Space Structures

In August 2003, NASA's In-Space Propulsion Program contracted with our team to develop a prototype on-board Optical Diagnostics System (ODS) for solar sail flight tests. The ODS is intended to monitor sail deployment as well as structural and thermal behavior, and to validate computational models for use in designing future solar sail missions. This paper focuses on the thermography aspects of the ODS. A thermal model was developed to predict local sail temperature variations as a function of sail tilt to the sun, billow depth, and spectral optical properties of front and back sail surfaces. Temperature variations as small as 0.5 C can induce significant thermal strains that compare in magnitude to mechanical strains. These thermally induced strains may result in changes in shape and dynamics. The model also gave insight into the range and sensitivity required for in-flight thermal measurements and supported the development of an ABAQUS-coupled thermo-structural model. The paper also discusses three kinds of tests conducted to 1) determine the optical properties of candidate materials; 2) evaluate uncooled microbolometer-type infrared imagers; and 3) operate a prototype imager with the ODS baseline configuration. (Uncooled bolometers are less sensitive than cooled ones, but may be necessary because of restrictive ODS mass and power limits.) The team measured the spectral properties of several coated polymer samples at various angles of incidence. Two commercially available uncooled microbolometer imagers were compared, and it was found that reliable temperature measurements are feasible for both coated and uncoated sides of typical sail membrane materials

Balancing employee needs, project requirements and organisational priorities in team deployment

The 'people and performance' model asserts that performance is a sum of employee ability, motivation and opportunity (AMO). Despite extensive evidence of this people-performance link within manufacturing and many service sectors, studies within the construction industry are limited. Thus, a recent research project set out to explore the team deployment strategies of a large construction company with the view of establishing how a balance could be achieved between organisational strategic priorities, operational project requirements and individual employee needs and preferences. The findings suggested that project priorities often took precedence over the delivery of the strategic intentions of the organisation in meeting employees' individual needs. This approach is not sustainable in the long term because of the negative implications that such a policy had in relation to employee stress and staff turnover. It is suggested that a resourcing structure that takes into account the multiple facets of AMO may provide a more effective approach for balancing organisational strategic priorities, operational project requirements and individual employee needs and preferences more appropriately in the future

FGF19 Action in the Brain Induces Insulin-Independent Glucose Lowering

Insulin-independent glucose disposal (referred to as glucose effectiveness [GE]) is crucial for glucose homeostasis and, until recently, was thought to be invariable. However, GE is reduced in type 2 diabetes and markedly decreased in leptin-deficient ob/ob mice. Strategies aimed at increasing GE should therefore be capable of improving glucose tolerance in these animals. The gut-derived hormone FGF19 has previously been shown to exert potent antidiabetic effects in ob/ob mice. In ob/ob mice, we found that systemic FGF19 administration improved glucose tolerance through its action in the brain and that a single, low-dose i.c.v. injection of FGF19 dramatically improved glucose intolerance within 2 hours. Minimal model analysis of glucose and insulin data obtained during a frequently sampled i.v. glucose tolerance test showed that the antidiabetic effect of i.c.v. FGF19 was solely due to increased GE and not to changes of either insulin secretion or insulin sensitivity. The mechanism underlying this effect appears to involve increased metabolism of glucose to lactate. Together, these findings implicate the brain in the antidiabetic action of systemic FGF19 and establish the brain’s capacity to rapidly, potently, and selectively increase insulin-independent glucose disposal

Adverse outcomes and an immunosuppressed endotype in septic patients with reduced IFN-γ ELISpot

BACKGROUNDSepsis remains a major clinical challenge for which successful treatment requires greater precision in identifying patients at increased risk of adverse outcomes requiring different therapeutic approaches. Predicting clinical outcomes and immunological endotyping of septic patients generally relies on using blood protein or mRNA biomarkers, or static cell phenotyping. Here, we sought to determine whether functional immune responsiveness would yield improved precision.METHODSAn ex vivo whole-blood enzyme-linked immunosorbent spot (ELISpot) assay for cellular production of interferon γ (IFN-γ) was evaluated in 107 septic and 68 nonseptic patients from 5 academic health centers using blood samples collected on days 1, 4, and 7 following ICU admission.RESULTSCompared with 46 healthy participants, unstimulated and stimulated whole-blood IFN-γ expression was either increased or unchanged, respectively, in septic and nonseptic ICU patients. However, in septic patients who did not survive 180 days, stimulated whole-blood IFN-γ expression was significantly reduced on ICU days 1, 4, and 7 (all P \u3c 0.05), due to both significant reductions in total number of IFN-γ-producing cells and amount of IFN-γ produced per cell (all P \u3c 0.05). Importantly, IFN-γ total expression on days 1 and 4 after admission could discriminate 180-day mortality better than absolute lymphocyte count (ALC), IL-6, and procalcitonin. Septic patients with low IFN-γ expression were older and had lower ALCs and higher soluble PD-L1 and IL-10 concentrations, consistent with an immunosuppressed endotype.CONCLUSIONSA whole-blood IFN-γ ELISpot assay can both identify septic patients at increased risk of late mortality and identify immunosuppressed septic patients.TRIAL REGISTRYN/A.FUNDINGThis prospective, observational, multicenter clinical study was directly supported by National Institute of General Medical Sciences grant R01 GM-139046, including a supplement (R01 GM-139046-03S1) from 2022 to 2024

Understanding employee resourcing in construction organizations

In recent years the literature on employee resourcing has consistently advocated the importance of adopting a holistic, strategic approach to employee deployment decision making rather than adopting a reactive needs-based approach. This is particularly problematic in construction where the multi-project environment leads to constantly changing resource requirements and to changing demands over a project's life cycle. This can lead to inappropriate decisions, which fail to meet the longer-term needs of both construction organizations and their employees. A structured and comprehensive understanding of the current project team deployment practices within large construction organizations was developed. Project deployment practices were examined within seven case study contracting firms. The emergent themes that shaped the decision-making processes were grouped into five broad clusters comprising human resource planning, performance/career management, team deployment, employee involvement and training and development. The research confirms that a reactive and ad hoc approach to the function prevails within the firms investigated. This suggests a weak relationship between the deployment process and human resource planning, team deployment, performance management, employee involvement and training and development activities. It is suggested that strategic HR-business partnering could engender more transparent and productive relationships in this crucial area