A low noise, high thermal stability, 0.1 K test facility for the Planck HFI bolometers

We are developing a facility which will be used to characterize the bolometric detectors for Planck, an ESA mission to investigate the Cosmic Microwave Background. The bolometers operate at 0.1 K, employing neutron-transmutation doped (NTD) Ge thermistors with resistances of several megohms to achieve NEPs~1×10^(–17) W Hz^(–1/2). Characterization of the intrinsic noise of the bolometers at frequencies as low as 0.010 Hz dictates a test apparatus thermal stability of 40 nK Hz^(–1/2) to that frequency. This temperature stability is achieved via a multi-stage isolation and control geometry with high resolution thermometry implemented with NTD Ge thermistors, JFET source followers, and dedicated lock-in amplifiers. The test facility accommodates 24 channels of differential signal readout, for measurement of bolometer V(I) characteristics and intrinsic noise. The test facility also provides for modulated radiation in the submillimeter band incident on the bolometers, for measurement of the optical speed-of-response; this illumination can be reduced below detectable limits without interrupting cryogenic operation. A commercial Oxford Instruments dilution refrigerator provides the cryogenic environment for the test facility

The emerging role of the principal as manager as it relates to the new philosophies and construction of teacher empowerment.

With the declining interest among college students toward preparation for occupations in the field of education, educational policy makers look toward establishing practices which will more adequately professionalize teaching. It is considered that empowerment will attract neophytes to the profession and also provide a challenge to the most able veterans to remain in the field. This study investigated the behaviors of a number of principals to determine if, in reality, these principals are utilizing behaviors which truly foster meaningful (being of great consequence) teacher empowerment in consequential decision-making situations (those which impact the quality of life in the school). The population surveyed includes all of the three hundred eighty-one principals working in the Southeast Educational Region of Massachusetts with two-hundred eight responding. Quantitative methodology was employed. This author constructed a questionnaire and the forced choice method was used to determine the extent to which principals employ behaviors which foster the creation or development of teacher empowerment. Personal and background information, along with the measure of degree of use of the identified behaviors which were gathered through the choice and comment survey items, were marginally tabulated to determine the manner in which the population distributes itself on the response alternatives for each of the items. Frequency and degree of behavior use, along with correlation of gender and levels of schools were analyzed. Through the construction of the questionnaire the specific behaviors used by principals in daily decision-making activities were identified. The response choices of usually, sometimes, and usually not, were utilized to identify the degree to which the activities are implemented by the administrators. A comment section on the questionnaire provided information which expanded and clarified the objective responses. Principals reported the highest percentages in areas where middle level empowerment behaviors existed on the continuum. Repeatedly, teachers have been most significantly included in decision-making activities in which the principal participates as a partner. This finding reflects the need of these principals to exert some degree of control over situations in their building. Principal behaviors of this type are an improvement over the autocratic approach but trust must develop between the parties before true teacher empowerment can exist

X-ray rocking curve study of Si-implanted GaAs, Si, and Ge

Crystalline properties of Si-implanted GaAs, Si, and Ge have been studied by Bragg case double-crystal x-ray diffraction. Sharp qualitative and quantitative differences were found between the damage in GaAs on one hand and Si and Ge on the other. In Si and Ge the number of defects and the strain increase linearly with dose up to the amorphous threshold. In GaAs the increase in these quantities is neither linear nor monotonic with dose. At a moderate damage level the GaAs crystal undergoes a transition from elastic to plastic behavior. This transition is accompanied by the creation of extended defects, which are not detected in Si or Ge

Nonlinear strain effects in ion-implanted GaAs

The nonlinear production of strain in (100) GaAs by room-temperature ion implantation has been studied. Ions of Ne, Si, and Te were used, with energies of 300, 300, and 500 keV, respectively. Doses ranged up to those required for amorphization. Strains were monitored by x-ray double-crystal diffractometry. Rocking curves were recorded about the (400) Bragg condition and detailed depth profiles of strain perpendicular to the sample surface, epsilon[perpendicular](x), found by fitting the rocking curves with a kinematic model. These were compared with calculated profiles of the density of energy deposited in nuclear interactions, rhoE(x). Rocking curves were also recorded about the (422) Bragg condition for selected samples, to monitor strain in the directionparallel with their surfaces. At low doses, epsilon[perpendicular](x) is a linear function of rhoE(x). At doses sufficient to create strains exceeding about 0.3%, strong nonlinearities are evident and strain profiles depart significantly from the rhoE(x) curves. For the Ne and Si implantations, the profiles tend to saturate at 0.4%–0.5% over a depth of ~4000 Å. At higher doses a narrow (~2000 Å), sharply peaked region develops, with strains up to 1.5%. At still higher doses this region becomes amorphous. The Te-implanted samples do not experience appreciable saturation; rather a sharply peaked profile develops, and grows with dose to amorphicity. Curves of epsilon[perpendicular] vs rhoE were extracted by comparison of epsilon[perpendicular](x) and rhoE(x) profiles. These demonstrated that for each ion species epsilon[perpendicular] is a unique function of rhoE at all depths. Although this function has the same general form for all three implantations, the curves differ from species to species. Above epsilon[perpendicular]=0.3%, epsilon[perpendicular] increases sublinearly with rhoE for all three implanted ions. For Ne and Si, epsilon[perpendicular] becomes almost constant at 0.4%, beginning at rhoE~0.15 eV/Å^3. The strain epsilon[perpendicular] starts increasing again with rhoE at about 0.7 eV/Å^3 for Ne and 0.3 eV/Å^3 for Si, until the GaAs goes amorphous. The curve for Te shows only a slight inflection at epsilon[perpendicular]~0.3%, continuing to increase with rhoE to amorphicity. Parallel strains in the Si-implanted samples were not more than 0.02% at all values of rhoE

The connection between slums and COVID-19 cases in Jakarta, Indonesia : a case study of Kapuk Urban Village

COVID-19 has spread world-wide, and with multiple health, social, and economic ramifications. These present a formidable challenge for those belonging to vulnerable communities, such as those living in slums. There is now a growing literature urging attention to this challenge. However, few studies have examined the actual lived realities within these areas using direct, observational research, notwithstanding commentary elsewhere that such close attention is necessary to ensure effective action. This study took this approach in relation to a particular case-study, Kapuk Urban Village, in Jakarta, Indonesia. Drawing on an existing schema involving three spatial scales of slum areas (environs, settlement, and object), the research confirms how different built and socio-economic features can exacerbate vulnerability, and COVID-19 transmission. We also add to the body of knowledge by contributing a dimension of ‘ground-level’ research engagement. We conclude by discussing related ideas around ensuring community resilience and effective policy implementation, and recommend an “urban acupuncture” approach to encourage government regulations and actions better tailored to such communities

Strain in GaAs by low-dose ion implantation

The production of strain in (100) GaAs by low-dose ion implantation has been investigated. Implantations were conducted at room temperature with ions of He, B, C, Ne, Si, P, and Te. Energies were between 100 and 500 keV, and each species was implanted over a range of doses sufficient to create perpendicular strain below 0.3%. The perpendicular strains epsilon [perpendicular] were measured by x-ray double-crystal diffractometry about the (400) Bragg condition. Detailed depth profiles of epsilon[perpendicular] were obtained by fitting the resulting rocking curves with a kinematic model for the diffraction. For all implantations the maximum in the epsilon[perpendicular] distribution was found approximately from the separation of the lowest-angle prominent oscillation from the substrate peak. The depth profiles of perpendicular strain had the same shape as the calculated profiles of energy deposited per ion by nuclear collisions, FD. The maximum perpendicular strains scaled linearly with the dose phi of the implanted ions for all ion species. Also the ratio of maximum strain to dose was found to vary linearly with FD over more than 2 orders of magnitude in FD. We therefore conclude that epsilon[perpendicular]=KphiFD at all depths, where K is a constant. The value of K was found to be (5±1)×10^−2 Å^3/eV. Our results suggest that this holds for any ion species in the mass range 4–128 amu, with energy in the hundreds of keV, implanted into (100) GaAs at room temperature, provided the maximum strain is less than 0.3%

Mass Drug Administration and beyond: how can we strengthen health systems to deliver complex interventions to eliminate neglected tropical diseases?

Achieving the 2020 goals for Neglected Tropical Diseases (NTDs) requires scale-up of Mass Drug Administration (MDA) which will require long-term commitment of national and global financing partners, strengthening national capacity and, at the community level, systems to monitor and evaluate activities and impact. For some settings and diseases, MDA is not appropriate and alternative interventions are required. Operational research is necessary to identify how existing MDA networks can deliver this more complex range of interventions equitably. The final stages of the different global programmes to eliminate NTDs require eliminating foci of transmission which are likely to persist in complex and remote rural settings. Operational research is required to identify how current tools and practices might be adapted to locate and eliminate these hard-to-reach foci. Chronic disabilities caused by NTDs will persist after transmission of pathogens ceases. Development and delivery of sustainable services to reduce the NTD-related disability is an urgent public health priority. LSTM and its partners are world leaders in developing and delivering interventions to control vector-borne NTDs and malaria, particularly in hard-to-reach settings in Africa. Our experience, partnerships and research capacity allows us to serve as a hub for developing, supporting, monitoring and evaluating global programmes to eliminate NTDs

Efficient computation of high index Sturm-Liouville eigenvalues for problems in physics

Finding the eigenvalues of a Sturm-Liouville problem can be a computationally challenging task, especially when a large set of eigenvalues is computed, or just when particularly large eigenvalues are sought. This is a consequence of the highly oscillatory behaviour of the solutions corresponding to high eigenvalues, which forces a naive integrator to take increasingly smaller steps. We will discuss some techniques that yield uniform approximation over the whole eigenvalue spectrum and can take large steps even for high eigenvalues. In particular, we will focus on methods based on coefficient approximation which replace the coefficient functions of the Sturm-Liouville problem by simpler approximations and then solve the approximating problem. The use of (modified) Magnus or Neumann integrators allows to extend the coefficient approximation idea to higher order methods

Preliminary performance measurements of bolometers for the Planck high-frequency instrument

We report on the characterization of bolometers fabricated at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2007. The HFI is a multicolor focal plane which consists of 48 bolometers operated at 100mK. Each bolometer is mounted to a feedhorn-filter assembly which defines one of six frequency bands centered between 100-857GHz. Four detectors in each of six bands are coupled to both linear polarizations and thus measure the total intensity. In addition, eight detectors in each of 3 bands (143, 217, and 353GHz) couple only to a single linear polarization and thus provide measurements of the Stokes parameters, Q and U, as well the total intensity. The detectors are required to achieve a Noise Equivalent Power (NEP) at or below the background limit ∼ 10^(-17)W/√Hz for the telescope and time constants of a few ms, short enough to resolve point sources as the 5 to 9 arc-minute beams move across the sky in great circles at 1 rpm. The bolometers are tested at 100mK in a commercial dilution refrigerator with a custom built thermal control system to regulate the heat sink with precision < 100nK/√Hz. The 100mK tests include dark electrical characterization of the load curves, optical and electrical measurement of the thermal time constants and measurement of the noise spectral density from 0.01 to 10Hz for up to 24 bolometers simultaneously

Diagnosis of carbonation induced corrosion initiation and progression in reinforced concrete structures using piezo-impedance transducers

In addition to chloride induced corrosion, the other commonly occurring type of rebar corrosion in reinforced concrete structures is that induced by the ingress of atmospheric carbon dioxide into concrete, commonly referred to as ‘carbonation induced corrosion’. This paper presents a new approach for detecting the onset and quantifying the level of carbonation induced rebar corrosion. The approach is based on the changes in the mechanical impedance parameters acquired using the electro-mechanical coupling of a piezoelectric lead zirconate titanate (PZT) ceramic patch bonded to the surface of the rebar. The approach is non-destructive and is demonstrated though accelerated tests on reinforced concrete specimens subjected to controlled carbon dioxide exposure for a period spanning over 230 days. The equivalent stiffness parameter, extracted from the frequency response of the admittance signatures of the PZT patch, is found to increase with penetration of carbon dioxide inside the surface and the consequent carbonation, an observation that is correlated with phenolphthalein staining. After the onset of rebar corrosion, the equivalent stiffness parameter exhibited a reduction in magnitude over time, providing a clear indication of the occurrence of corrosion and the results are correlated with scanning electron microscope images and Raman spectroscopy measurements. The average rate of corrosion is determined using the equivalent mass parameter. The use of PZT ceramic transducers, therefore, provides an alternate and effective technique for diagnosis of carbonation induced rebar corrosion initiation and progression in reinforced concrete structures non-destructively