Background rates of x-ray transition-edge sensor micro-calorimeters under a frequency domain multiplexing readout for solar axion-like particles' detection.

We report on the x-ray background rate measured with transition-edge sensors (TES) micro-calorimeters under frequency-domain multiplexing (FDM) readout as a possible technology for future experiments aiming at a direct detection of axion-like particles. Future axion helioscopes will make use of large magnets to convert axions into photons in the keV range and x-ray detectors to observe them. To achieve this, a detector array with high spectral performance and extremely low background is necessary. TES are single-photon, non-dispersive, high-resolution micro-calorimeters and represent a possible candidate for this application. We have been developing x-ray TES micro-calorimeters and an FDM readout technology in the framework of the space-borne x-ray astronomical observatories. We show that the current generation of our detectors is already a promising technology for a possible axion search experiment, having measured an x-ray background rate of 2.2(2) × 10-4 cm-2 s-1 keV-1 with a cryogenic demonstrator not optimized for this specific application. We then make a prospect to further improve the background rate down to the required value (<10-7 cm-2 s-1 keV-1) for an axion-search experiment, identifying no fundamental limits to reach such a level.

Performance and uniformity of a kilo-pixel array of Ti/Au transition-edge sensor microcalorimeters.

Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ray space observatories. These arrays are required to achieve an energy resolution ΔE < 3 eV full width at half maximum (FWHM) in the soft x-ray energy range. We are currently developing x-ray microcalorimeter arrays for use in the future laboratory and space-based x-ray astrophysics experiments and ground-based spectrometers. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with 140 × 30 µm2 Ti/Au TESs with the Au x-ray absorber. We report on extensive measurements on 60 pixels in order to show the uniformity of our large TES array. The averaged critical temperature is Tc = 89.5 ± 0.5 mK, and the variation across the array (∼1 cm) is less than 1.5 mK. We found a large region of detector's bias points between 20% and 40% of the normal-state resistance where the energy resolution is constantly lower than 3 eV. In particular, results show a summed x-ray spectral resolution ΔEFWHM = 2.50 ± 0.04 eV at a photon energy of 5.9 keV, measured in a single-pixel mode using a frequency domain multiplexing readout system developed at SRON/VTT at bias frequencies ranging from 1 MHz to 5 MHz. Moreover, we compare the logarithmic resistance sensitivity with respect to temperature and current (α and ß, respectively) and their correlation with the detector's noise parameter M, showing a homogeneous behavior for all the measured pixels in the array.

Frequency shift algorithm: Application to a frequency-domain multiplexing readout of x-ray transition-edge sensor microcalorimeters.

In the frequency-domain multiplexing (FDM) scheme, transition-edge sensors (TESs) are individually coupled to superconducting LC filters and AC biased at MHz frequencies through a common readout line. To make efficient use of the available readout bandwidth and to minimize the effect of non-linearities, the LC resonators are usually designed to be on a regular grid. The lithographic processes, however, pose a limit on the accuracy of the effective filter resonance frequencies. Off-resonance bias carriers could be used to suppress the impact of intermodulation distortions, which, nonetheless, would significantly affect the effective bias circuit and the detector spectral performance. In this paper, we present a frequency shift algorithm (FSA) to allow off-resonance readout of TESs, while preserving the on-resonance bias circuit and spectral performance, demonstrating its application to the FDM readout of an x-ray TES microcalorimeter array. We discuss the benefits in terms of mitigation of the impact of intermodulation distortions at the cost of increased bias voltage and the scalability of the algorithm to multi-pixel FDM readout. We show that with FSA, in the multi-pixel and frequencies shifted on-grid, the line noises due to intermodulation distortion are placed away from the sensitive region in the TES response and the x-ray performance is consistent with the single-pixel, on-resonance level.

Neurocognition and the Suicidal Process.

Early thinking about cognitive process and suicidal behaviors tended to focus on the immediate situation surrounding the individual - typically the underlying psychiatric condition that was seen as leading to his or her distress. However, we now know that the cognitive processes involved in a range of suicidal thoughts and behaviors can exert a significant impact on the expression or development of these behaviors, even without an environmental stressor or psychiatric condition. In this chapter, we summarize theoretical perspectives that led to this realization and explore the current understanding of the link between cognition and suicide from recent research and clinical findings. We present these findings first by psychiatric disorder, then by cognitive domains, and finally by specific suicidal construct in order to highlight the importance of these factors in determining the role of cognition in the suicidal process.Within and across psychiatric disorders, certain cognitive processes - negativistic thinking, impulsivity, cognitive rigidity, and altered emotional processing - are frequently found to be linked to suicidal thoughts and behaviors. Overall cognitive performance, decreased processing speed, executive dysfunction, and negative biases in memory and attention have also been linked to suicidal thoughts and behaviors. However, these findings do not hold true for all populations. There seems to be a role both for cognitive distortions (such as hopelessness) and neurocognitive deficits (such as poor overall cognitive performance, slower processing speed, and executive dysfunction) in the suicidal process, which warrant further exploration both separately and together.

The aromatization of androgens by primary monolayer cultures of fetal rat hypothalamus.

Aromatization of [3H]androstenedione and [3H]19-hydroxyandrostenedione to [3H]estrone has been demonstrated to occur in one to two week old primary monolayer cultures of fetal rat hypothalamus. Three times more estrone is produced from 19-hydroxyandrostenedione than from androstenedione in four day incubations. Cultures treated with cytosine arabinoside have 50% less cellular protein and produce three times more estrone from either substrate than untreated cultures. Time course experiments using cultures treated with cytosine arabinoside indicate that aromatization of 19-hydroxyandrostenedione is linear for three days and can be quantitatively measured within the first two to eight hours of incubation.

Localization of aromatase and 5 alpha-reductase to neuronal and non-neuronal cells in the fetal rat hypothalamus.

Experiments were designed to identify the neural cell type(s) responsible for the aromatization and 5 alpha-reduction of androgens in the rat hypothalamus. Primary cultures of fetal rat hypothalamic cells, which had enhanced neuronal morphology, were treated at various times after plating with kainic acid (KA), a neurotoxic agent which selectively destroys neuronal cells. Neuronal morphology was disrupted in a time (0-6 days)- and dose (10(-4)-10(-2) M)-dependent fashion after KA treatment, with no apparent change in the appearance of the flattened, underlying non-neuronal cells. KA treatment for 4 days decreased aromatization by 94% in a dose-dependent fashion (10(-4)-10(-2) M KA), while 5 alpha-reduction declined by no more than 25%. A 6-day time course with 10(-3) M KA showed a dramatic decline in aromatization and no alteration in 5 alpha-reduction. In control experiments, substance P, a neuronal peptide, declined after KA treatment while the activity of glutamine synthetase, a glial enzyme, did not change. We conclude from these results that aromatase is localized primarily to neuronal cells in the hypothalamus while 5 alpha-reductase is confined primarily to non-neuronal cells.

Parental education related to adolescent stress-coping and substance use: development of a mediational model.

This research tested the relation of socioeconomic status (SES), indexed by parental education, to stress-coping variables and substance use in a sample of 1,391 adolescents. Lower education was related to higher level of adolescent substance use, lower levels of protective factors, and higher levels of risk factors. Mediation analyses indicated that the effect of education on adolescent substance use was mediated through relationships to parental support, academic competence, behavioral competence, negative life events, and friends' substance use. Moderation analyses indicated that adolescents from lower education families were more vulnerable to risk factors but also derived more benefit from protective factors. Multiple-group analysis indicated that moderation was attributable to larger paths in the lower education group for negative events and friends' use. Implications for the relation between SES and health risk are discussed.

Escalated substance use: a longitudinal grouping analysis from early to middle adolescence.

The authors surveyed a cohort of 1,184 adolescents in the 7th, 8th, and 9th grades. Measures of tobacco, alcohol, and marijuana use and of constructs from 3 theoretical models of substance use were obtained at each point. Clustering analysis for 3-wave substance use data indicated subgroups of nonusers, minimal experimenters, late starters, and escalators. Discriminant function analyses tested whether study variables differentiated the subgroups. One discriminant function accounted for the majority of between-group association; it had loadings for (high) life stress, nonadaptive coping, deviance-prone attitudes, and parental and peer substance use, and (low) parental support, academic competence, and behavioral control. Escalators were high on this function; late starters and experimenters had intermediate values; and nonusers were low on the function. Implications for theories of vulnerability to substance abuse are discussed.

Studies on the role of catecholamines in the regulation of the developmental pattern of hypothalamic aromatase.

Experiments were conducted to study the regulation of the developmental pattern of aromatase in the forebrain of the perinatal rat. Two experimental designs were used: aromatase measured in primary cultures of fetal hypothalamic cells and in cell-free preparations of forebrain tissue excised at varying ages. In cultured cells, aromatase decreased logarithmically at a slow rate (t1/2 = 7.8 days). Norepinephrine caused a pronounced dose (4 x 10(-6) M) and time-dependent (2-6 days) drop in aromatase without affecting the levels of 5 alpha-reductase or substance P. In isolated tissue, aromatase activity was compared with the concentrations of norepinephrine and dopamine in the forebrain of males vs females at different perinatal ages and in discrete forebrain areas at postnatal day 4. In no case was a sex difference in catecholamines seen. An overall developmental decline in aromatase was associated with developmental increases in catecholamine levels. Acute treatment with the beta-agonist, isoproterenol, had no effect on brain aromatase activity.

Activity and mood temperament as predictors of adolescent substance use: test of a self-regulation mediational model.

The authors tested a mediational model of temperament dimensions and substance use with a sample of 1,826 urban adolescents, M age 12.3 years. Five scales from the Revised Dimensions of Temperament Survey (DOTS-R) were administered together with measures of substance (tobacco, alcohol, marijuana) use and measures of related variables derived from a self-regulation model. Unique contributions to substance use were found for DOTS-R dimensions of high activity level (positively related) and positive mood (inversely related). High activity level and low positive mood were also related to lower levels of parental support. Analyses, including multiple regression and structural modeling, identified generalized self-control, maladaptive coping (anger and helplessness), novelty seeking, and affiliation with peer substance users as mediating the effect of temperament on substance use, with control for effects of parental support. Parental support was inversely related to substance use through several pathways. Implications for the theory of vulnerability are discussed.

Cholesterol screening in a community health promotion program: epidemiologic results from a biracial population.

The prevalence and interrelationship of high blood cholesterol levels with other cardiovascular disease risk factors were studied in a biracial suburb of New York City. Participants in community-based screenings to determine blood cholesterol levels have been predominantly white women in older age groups, highly educated and nonsmokers. To reach a more representative segment of a local population and promote healthy lifestyle behaviors, cholesterol screenings were conducted within an ongoing health promotion program in Mount Vernon, NY. Plasma cholesterol levels were determined for 5,011 participants, including 2,308 whites and 1,778 blacks. Of the men, 29 percent had high cholesterol levels; among women, it was 27 percent. Of the men with high levels, half had levels greater than 200 milligrams per deciliter, as did 55 percent of the women. After statistical adjustments were made for age and other risk factors for high blood cholesterol, mean cholesterol levels were higher for whites than blacks. The level for white men was 204 milligrams per deciliter; for women, 212. For black men, the level was 199 milligrams per deciliter; for women, 208, P < .10. Hispanic men had levels of 199, P < .10. The levels for Hispanic women (203 milligrams per deciliter) were significantly lower than that of white women. Among whites who smoked more than 1 pack of cigarettes per day, mean cholesterol levels were 11 milligrams per deciliter higher than for those who never smoked or were light smokers (0, 1-20 cigarettes per day, P < .10). There were too few who smoked more than 1 pack to test this association adequately among blacks. The mean cholesterol levels for hypertensive black men were 10 milligrams per deciliter greater than for black men with normal blood pressure (P<.10).

Substance use among Hispanic and non-Hispanic adolescents.

This study compared lifetime prevalence data on substance use with demographic and psychosocial variables among 2,821 Hispanic and non-Hispanic white students from two Southwestern cities. Study findings revealed that ethnic-racial background factors were not the strongest predictors of substance use. Rather, when the analyses accounted for school grades and for maternal education, non-Hispanic youth had higher lifetime substance use rates than Hispanic youth. Study findings suggest that preventive intervention and treatment efforts for substance abuse problems among adolescents should consider sociodemographic risk factors as well as ethnic-racial factors.

Implementation of a pilot school-site cholesterol reduction intervention.

A school-based cholesterol reduction intervention was offered to primary grade students in two New York City public schools. Subjects were participating in the "Know Your Body" school health program which includes an annual cholesterol screening for all students. Students with total serum cholesterol values greater than 170 mg/dl were eligible for a workshop designed to teach students to identify the amount and type of fat and fiber in various foods and to recognize the negative health consequences of eating a diet high in cholesterol and saturated fat as well as the benefits of eating a diet high in complex carbohydrate and fiber. Thirty-four students completed the five-session behavioral group intervention. Following the workshop, mean total cholesterol for the 34 intervention participants fell 9.0% from baseline (196.9 mg/dl to 179.1 mg/dl). Cholesterol levels decreased 6.6% for a matched sample of comparison subjects (n = 118) participating only in the "Know Your Body" program. While several methodological limitations existed in this pilot study, the results suggest school-site cholesterol reduction interventions for high-risk individuals are feasible, cost-effective, and potentially efficacious.

Responsibilities, roles & staffing patterns of nurse practitioners in the neonatal intensive care unit.

PURPOSE: To describe the unique contribution of the NP in caring for critically ill infants through the study of NP responsibilities, roles, staffing patterns, and patient profiles. DESIGN: This prospective descriptive study was conducted in conjunction with a regional multi-site outcomes study. METHODS: Data were collected at five regional level II/III NICUs in Massachusetts and Rhode Island. Twenty-two NPs were surveyed. Existing data on outcomes of 2,146 very low birth weight infants were used to describe patient profiles. NP care was defined as assignment to an NP at admission. Illness severity was measured using the Score of Neonatal Acute Physiology (SNAP). RESULTS: NP roles included all levels of NICU care as well as antepartal consultation, delivery room management, transport, and outpatient follow-up. NPs were equally involved with patients of all degrees of complexity and birthweights. Patient assignments were most often made by a rotational system with the resident/fellow or by complexity of infant with the NP in some NICUs caring for sicker smaller babies. CLINICAL IMPLICATIONS: This study documents a blended model of NP MD care in the NICU with each provider bringing unique strengths to the team. Nurse practitioners working in the NICU provide an invaluable contribution in terms of parent support and teaching, post NICU follow-up care, and professional education and research. The NP role in the NICU should not be viewed as a substitution for resident physicians.

Symbiosis therapy: the potential of using human protozoa for molecular therapy.

The concept of symbiosis is proposed as a disease therapy model. It is hypothesized that protozoa that live naturally in human tissues can be genetically modified for the production and delivery of therapeutic proteins. Approximately 30 identified species of protozoa live in a variety of human tissues, both intracellularly and extracellularly. Leishmania, one species of human protozoa, has been genetically altered for conditional auxotrophy and has shown no pathology in both mouse and nonhuman primate safety tests. Several species of protozoa have been transfected with a variety of genes and have successfully manufactured active foreign proteins. Protozoa have biochemical mechanisms to glycosylate proteins. Human protozoa have evolved sophisticated mechanisms for evading immune rejection and can sometimes persist for the lifetime of the host. Symbiosis therapy does not involve genetic alteration of the host and is potentially fully reversible. Research on treating genetic diseases is currently ongoing. For example, there is a group of more than 40 genetic diseases, lysosomal storage diseases, which result from defects in lysosomal enzymes primarily in macrophages. Leishmania specifically targets the lysosomal compartment of the macrophage and therefore may be the optimal vector for treatment of many of these diseases.

Stress-coping factors in adolescent substance use: test of ethnic and gender differences in samples of urban adolescents.

Investigated group differences in the relationship between stress-coping variables and substance (cigarette, alcohol, and marijuana) use with samples of inner-city students in sixth through eighth grades (N = 1,289) and metropolitan-area students in seventh through ninth grades (N = 1,702). Measures included affect, life events, parental support, and coping patterns. African-American adolescents had the lowest rate of substance use, Hispanics were intermediate, and Whites had the highest rate; there was no gender difference in overall substance use. Multiple regression analysis showed the strength of predictive relationships for stress-coping variables was lower for African Americans and was greatest for Whites; four methodological tests showed these differences were not attributable to statistical artifacts. Hispanic adolescents showed greater vulnerability than Whites at younger ages but this effect reversed at later ages. Implications for prevention research are discussed.