Source Of Excess Research Articles

No Fossil Disk in the T Tauri Multiple System V773 Tauri

We present new multiepoch near-infrared (NIR) and optical high angular resolution images of the V773 Tau pre-main-sequence triple system, a weak-line T Tauri star (WTTS) system in which the presence of an evolved, "fossil" protoplanetary disk has been inferred on the basis of a significant IR excess. Our images reveal a fourth object bound to the system, V773 Tau D. While it is much fainter than all other components at 2 μm, it is the brightest source in the system at 4.7 μm. We also present medium-resolution K-band adaptive optics spectroscopy of this object, which is featureless with the exception of a weak Brγ emission line. Based on this spectrum and on the spectral energy distribution (SED) of the system, we show that V773 Tau D is another member of the small class of "infrared companions" (IRCs) to T Tauri stars (TTSs). It is the least luminous, and probably the least massive, component of the system, as opposed to most other IRCs, which suggests that numerous low-luminosity IRCs such as V773 Tau D may still remain to be discovered. Furthermore, it is the source of the strong IR excess in the system. We therefore reject the interpretation of this excess as the signature of a fossil (or "passive") disk and further suggest that these systems may be much less frequent than previously thought. We further show that V773 Tau C is a variable classical TTS (CTTS) and that its motion provides a well-constrained orbital model. We show that V773 Tau D can be dynamically stable within this quadruple system if its orbit is highly inclined. Finally, V773 Tau is the first multiple system to display such a variety of evolutionary states (WTTS, CTTS, IRC), which may be the consequence of the strong star-star interactions in this compact quadruple system.

Maternal serum androgens in pregnant women with polycystic ovarian syndrome: possible implications in prenatal androgenization.

The aim of this study was to evaluate the peripheral serum androgen concentrations in normal and polycystic ovarian syndrome (PCOS) women during pregnancy, in order to establish if PCOS may induce gestational hyperandrogenism and therefore constitute a potential source of androgen excess for the fetus. Twenty pregnant PCOS (PPCOS) women and 26 normal pregnant (NP) women of similar age with singleton pregnancies were selected for the study. During gestational weeks 10-16 and 22-28, a 2 h, 75 g oral glucose tolerance test (OGTT) was performed. For the OGTT, glucose and insulin were measured in each sample and testosterone, androstenedione, dehydroepiandrosterone sulphate (DHEAS), estradiol, progesterone and sex hormone-binding globulin were determined in the fasting sample. In the first study period (gestational weeks 10-16), the levels of androstenedione, testosterone and DHEAS and the free androgen index tended to be higher in the PCOS group. These differences became significant in the second study period (gestational weeks 22-28). In this second period, 2 h insulin concentrations were also significantly higher in PPCOS than in NP women. The present study demonstrates a significant increase in androgen concentrations during pregnancy in PCOS women. We propose that these androgen concentrations could provide a potential source of androgen excess for the fetus, without leading to fetal virilization.

Rastreamento, Comprovação e Diferenciação Laboratorial do Hiperaldosteronismo Primário

Hiperaldosteronismo primário (HAP), antes considerado uma causa rara de hipertensão, pode corresponder, em séries recentes, a 5-10% da população de hipertensos. Embora alguns considerem o HAP como a principal causa de hipertensão secundária, outros recomendam cautela na análise desta recente "epidemia". As manifestações clássicas do excesso de aldosterona não estão sempre presentes no HAP, determinando como base para o seu rastreamento a relação aldosterona: renina plasmática (ng/dl:ng/ml/h). Hipertensos com valor desta relação > ou = 25 (e aldosterona >14ng/dl) devem prosseguir numa avaliação que inclui testes de supressão da aldosterona plasmática ou urinária (infusão de salina, administração de fludrocortisona ou dieta hipersódica). A ausência de supressão caracteriza autonomia da secreção de aldosterona e HAP, cujas principais etiologias são o adenoma adrenal (APA) e a hiperplasia bilateral ou hiperaldosteronismo idiopático (HAI). A diferenciação entre APA e HAI - obrigatória para direcionar a intervenção terapêutica -, fundamenta-se na ausência de resposta da aldosterona aos testes de estímulo da renina (teste postural, diuréticos ou dieta hipossódica) no primeiro e na hiperresposta, no último. A complementação diagnóstica inclui a avaliação por TC e, se necessário, cateterismo venoso bilateral com dosagem de aldosterona dos efluentes adrenais para confirmar a origem de seu excesso.

Constraints on origin and evolution of Red Sea brines from helium and argon isotopes

Brines from three depressions along the axis of the Red Sea, the Atlantis II, the Discovery and the Kebrit Deep, were sampled and analyzed for helium and argon isotopes. We identified two principally different geochemical fingerprints that reflect the geological setting of the deeps. The Atlantis II and the Discovery brines originating from locations in the central Red Sea show 4He concentrations up to 1.2×10−5 cm3 STP g−1 and a 3He/4He ratio of 1.27×10−5. The MORB-like 3He/4He ratio is typical of an active hydrothermal vent system and clearly indicates a mantle origin of the helium component within the brines. 40Ar/36Ar ratios are as high as 305 implying that mantle-derived 40Ar excesses of up to 3% of the total argon concentration are present in the brines and transported along with the mantle helium signal. The mean (4He/40Ar)excess ratio of 2.1 is in agreement with the theoretical mantle production ratio. In the Kebrit Deep, located in the northern Red Sea, we found a helium excess of 5.7×10−7 cm3 STP g−1. The low 3He/4He ratio of 1×10−6 points to a predominantly radiogenic source of the helium excess with only a minor mantle contribution of approximately 9%. We propose a new scenario assuming that the Kebrit brine accumulates a diffusive helium flux that migrates from deeper sedimentary or crustal horizons. In contrast to the Atlantis II and Discovery Deep, the Kebrit brine shows no sign of an active hydrothermal input.

The presence of the 21-hydroxylase deficiency carrier status in hirsute women: phenotype-genotype correlations

Objective: To determine the role of heterozygosity for mutations in the 21-hydroxylase gene ( CYP21) in the pathogenesis of hyperandrogenism. Design: Controlled clinical study. Setting: Tertiary care institutional hospital. Patient(s): Forty hirsute women and 13 healthy control women. Intervention(s): The source of androgen excess was determined by the changes in serum testosterone levels in response to a single 3.75-mg IM dose of triptorelin. Main Outcome Measure(s): CYP21 molecular genetic analysis and serum 17-hydroxyprogesterone levels. Result(s): Eight patients and one control were heterozygous carriers of CYP21 mutations. Two patients with adrenal hyperandrogenism and one patient with ovarian hyperandrogenism, who carried the V281L mutation had an increased ACTH-stimulated 17-hydroxyprogesterone level (>4.1 ng/mL) that persisted during gonadal suppression. Another patient with adrenal hyperandrogenism carried the V281L mutation, and her ACTH-stimulated 17-hydroxyprogesterone level was elevated only during gonadal suppression. Four patients (three with idiopathic hirsutism, one with ovarian hyperandrogenism) and one control were carriers of CYP21 mutations typically associated with classic congenital adrenal hyperplasia but had normal basal and ACTH-stimulated 17-hydroxyprogesterone levels. Nine patients without CYP21 mutations had increased ACTH-stimulated 17-hydroxyprogesterone levels; these decreased to normal in six of the patients during gonadal suppression. Conclusion(s): The response of serum 17-hydroxyprogesterone to ACTH does not predict CYP21 carrier status. No clear concordance was found between the CYP21 genotype and the functional origin of androgen excess.

Keck Speckle Imaging of the White Dwarf G29-38: No Brown Dwarf Companion Detected

The white dwarf Giclas 29-38 has attracted much attention on account of its large infrared excess and the suggestion that excess might be due to a companion brown dwarf. We observed this object using speckle interferometry at the Keck telescope, obtaining diffraction-limited resolution (55 mas) at the K band, and found it unresolved. Assuming that the entire K-band excess is attributable to a single pointlike companion, we place an upper limit on the binary separation of 30 mas, or 0.42 AU at the star's distance of 14.1 pc. This result, combined with astroseismological data and other images of G29-38, supports the hypothesis that the source of the near-infrared excess is not a cool companion but a dust cloud.

Intermediate mass excess of dilepton production in heavy ion collisions at relativistic energies

Dielectron mass spectra are examined for various nuclear reactions recently measured by the DLS Collaboration. A detailed description is given of all dilepton channels included in the transport model UrQMD 1.0, i.e., Dalitz decays of ${\ensuremath{\pi}}^{0},\ensuremath{\eta},\ensuremath{\omega},{\ensuremath{\eta}}^{\ensuremath{'}}$ mesons and of the $\ensuremath{\Delta}(1232)$ resonance, direct decays of vector mesons and $\mathrm{pn}$ bremsstrahlung. The microscopic calculations reproduce data for light systems fairly well, but tend to underestimate the data in $\mathrm{pp}$ at high energies and in $\mathrm{pd}$ at low energies. These conventional sources, however, cannot explain the recently reported enhancement for nucleus-nucleus collisions in the mass region $0.15\mathrm{ }\mathrm{GeV}<~{M}_{{e}^{+}{e}^{\ensuremath{-}}}<~0.6\mathrm{ }\mathrm{GeV}.$ Chiral scaling and $\ensuremath{\omega}$ meson broadening in the medium are investigated as a source of this mass excess. They also cannot explain the recent DLS data.

NGC 4258: A Compact Central Infrared Source Revealed

We present high-resolution (~06) near-infrared Keck observations that probe the optically obscured nucleus of NGC 4258 (M 106), which is believed to contain a 3.6 × 107 M☉ black hole. The images show a compact central source at K (2.21 μm) and H (1.65 μm). To determine the strength of the compact component against the stellar background, we normalized the J (1.25 μm) surface brightness profile, which is taken to be dominated by the bulge stars, to the K and H profiles at 200 pc and subtracted it out. The normalization constant in each case agrees well with the outer colors of highly inclined spirals. The compact source has a measured K flux of 4.5 mJy and an H flux of 1.1 mJy. After making reasonable assumptions about the intrinsic energy distribution of the central source based on optical polarimetry and X-ray measurements, we derive a reddening to the source of AV ~ 17 mag. When corrected for this extinction, the IR (1.5-3.5 μm) luminosity is ~2 × 107 L☉. The corresponding X-ray (2-10 keV) luminosity is ~107 L☉, while the central source has been estimated at ~102 L☉ in the radio. We suggest on the basis of the polarimetric evidence that the source of the near-infrared excess is nonthermal, although the possibility of thermal emission by dust grains in the inferred torus cannot be ruled out.

Primary aldosteronism: Adrenal venous sampling

In primary aldosteronism, high-resolution adrenal computed tomography (CT) increasingly identifies subtle anatomic abnormalities. To interpret the functional significance of adrenal micronodular changes on CT scan, we have reevaluated selective adrenal venous sampling. Thirty-four patients with primary aldosteronism were selected prospectively for adrenal venous sampling on the basis of CT findings: normal findings or minimal thickening of an adrenal limb (n = 15), unilateral microadenoma (n = 6), bilateral adrenal nodules (n = 9), or atypical unilateral adrenal macroadenoma (n = 4). Both adrenal veins were catheterized in 33 of 34 patients. Six (40%) of 15 patients with normal or minimal adrenal limb thickening had a unilateral source of aldosterone. Six patients with apparent unilateral microadenoma had ipsilateral aldosterone-producing adenomas. Four (44%) of nine patients with bilateral adrenal masses had a unilateral source of aldosterone secretion. Three of four patients with unilateral atypical adrenal macroadenomas had ipsilateral aldosterone-producing adenomas. A unilateral source of aldosterone excess may be found in selected patients with adrenal glands that appear normal or show a minimally expanded adrenal limb on CT scan. Findings on adrenal venous sampling are crucial in determining the source of aldosterone excess in patients with bilateral adrenal masses or atypical-appearing macroadenomas.

Quantification of gas fluxes from the subcontinental mantle: The example of Laacher See, a maar lake in Germany

Vertical and horizontal distributions of helium and neon isotopes were measured in the water of Laacher See, a maar lake in the East Eifel volcanic field in Germany. Neon is in approximate atmospheric equilibrium throughout the lake, but the concentrations of both helium isotopes increase with depth and reach values of up to 10 ( 4He) and 50 ( 3He) times the atmospheric equilibrium concentration. The isotopic ratio of the helium excess, R ex = 3He ex/ 4He ex, is (7.42 ± 0.03) · 10 −6, i.e., R ex/ R a = 5.36 ± 0.02, where R a = 1.384·10 −6 is the isotopic ratio in air. This indicates the presence of mantle-derived helium. Laacher See is thermally stratified during the summer. It acts as an almost perfect trap for injected gases. The helium concentration in the hypolimnion (deep water) approximately doubled from May to September 1991 yielding a mean 4He-flux of (10 ± 2) · 10 12 atoms m −2 s −1. This value is 30 times smaller than in Lake Nyos, Cameroon, but 20 times larger than in Crater Lake, USA. Release of bubbles of nearly pure CO 2 (>99%) observable in shallow waters at the eastern shore, as well as detected by divers in about 30 m depth, was identified as an important source of the helium excess in the lake. If carefully sampled by divers to avoid air contamination, the bubbles exhibit mantle influenced isotopic signatures not only for helium, but also for neon and argon ( 20Ne/ 22Ne = 9.92 ± 0.03; 40Ar/ 36Ar = 391 ± 4). Based on the elemental ratios of carbon, neon, and argon to 3He, the fluxes of volatiles from the mantle into Laacher See are determined as 7.4·10 7 atoms m −2 s −1 for 3He, 13·10 7 atoms m −2 s −1 for 20Ne, 26·10 7 atoms m −2 s −1 for 361Ar, and 6.4·10 17 molecules m −2 s −1 for CO 2. Non-atmospheric neon was also found in the well “Wallenborn” in the West Eifel volcanic field with a 20Ne/ 22Ne-ratio as high as 11.21 ± 0.06.

Near- and mid-infrared imaging of the planetary nebulae BD +30 deg 3639 and IC 418

We present near- and mid-IR images of the planetary nebulae BD +30 deg 3639 and IC 418, with a unique combination of high spatial and spectral resolution. The mid-IR images were obtained with MIRAC, a new IR array camera. For BD +30 deg 3639, the mid-IR images at 10.0, 11.2, 12.4, 12.8, and 13.2 microns have allowed us to separate the various spectral emission components such as the broad UIR features, the 12.8-micron forbidden Ne II emission feature, and continuum emission, to determine the distribution of these components in the nebula. For IC 418, we have obtained high-resolution images in both the near- and mid-IR. The images in the near-IR at J, H, and K are important for determining the source of the IR excess; one component of the excess is located near the central star. We have also imaged the halo emission at H and K, which has been detected in earlier studies, and have determined its spatial extent. The mid-IR images at 9.8 and 11.7 microns show continuum emission coincident with the ionized zone and suggest that SiC emission originates from the region near the central star.

Adrenal androgen abnormalities in women with late onset and persistent acne.

Androgens are an essential prerequisite for the development of acne. The present study was undertaken to characterize the androgen status of women with late onset and persistent acne only and, using the dexamethasone (dex) suppression test, to identify the source(s) of the androgen excess. We measured serum levels of total testosterone (T), free testosterone (FT), androstenedione (delta 4A), dihydrotestosterone (DHT), dehydroepiandrosterone sulphate (DHEA-S) and sex hormone binding globulin (SHBG) in 34 healthy control subjects, in 34 women with mild acne and in 29 women with moderate or severe acne. Serum FT, DHT and DHEA-S levels in patients of both acne groups were significantly higher than those in the control subjects. The other hormone levels showed no significant differences between patients and control subjects, and there were no significant differences between the two acne groups in any of the androgen levels. In order to evaluate the ovarian and adrenal contributions to serum androgens in the acne patients, the serum levels of delta 4A, T, DHT and DHEA-S were measured prior to and following 2 weeks of dex therapy. Following the dex test, the DHT and T of adrenal origin were significantly higher in the acne patients than in the control subjects. These results suggest that, in acne patients, hyperandrogenaemia is likely to develop as a result of adrenal androgen excess. In addition, since abnormally high androgen levels are frequently seen in late onset and persist acne, it seems that this condition is likely to be a sign of hyperandrogenism.

Photometry and spectroscopy of the very close early type binary SV Centauri

view Abstract Citations (15) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometry and Spectroscopy of the Very Close Early Type Binary SV Centauri Rucinski, S. M. ; Baade, D. ; Lu, W. X. ; Udalski, A. Abstract New high-quality observations of this unusual early type contact binary are presented. BVRI photometry of SV Cen provides a precise moment of minimum in March 1990. From high-resolution profiles of the He I line at 492.1 nm a new, improved set of orbital parameters was derived. Intrinsic line profile variability was not detected in either component and both photometry and spectroscopy. Low-noise spectra of the region around He II 468.6 nm showed no feature at any orbital phase, thus not giving a clue on the location of the source of a far-UV flux excess previously inferred from IUE observations. Since, for technical reasons, simultaneous EUV spectrophotometry with the Voyager spacecraft was lost, the temperature of this possible ultrahot spot could not be further constrained. Publication: The Astronomical Journal Pub Date: February 1992 DOI: 10.1086/116084 Bibcode: 1992AJ....103..573R Keywords: B Stars; Binary Stars; Stellar Spectrophotometry; Ultraviolet Astronomy; Centaurus Constellation; Extreme Ultraviolet Radiation; Helium; Light Curve; Stellar Evolution; Stellar Orbits; Astrophysics; BINARIES: CLOSE; BINARIES: SPECTROSCOPIC full text sources ADS | data products SIMBAD (3)

Secondary hyperparathyroidism: Diagnosis of site of recurrence

Persistent or recurrent hyperparathyroidism after total parathyroidectomy with forearm implant may be caused by hyperplastic grafted tissue, residual parathyroid tissue left in the neck or the presence of a supernumerary gland not found during surgery. A correct assessment of graft function is needed to localize the source of hormone excess and to avoid an unnecessary neck reoperation in cases of graft dependent hyperparathyroidism. In 12 patients with relapsing hyperparathyroidism after total parathyroidectomy with forearm implant, total ischemic blockade of the arm bearing the parathyroid graft produced a "transitory implantectomy" with a significant reduction of serum levels of intact PTH in those with graft hyperfunction. In 6 patients with proved supernumerary glands, total ischemia of the graft was not followed by significant changes in intact PTH. Hyperparathyroidism was reversed after surgical resection of the parathyroid implants in the 6 patients with positive responses to the ischemic maneuver. A repeat neck reoperation removing cervical or mediastinal supernumerary glands was followed by control of recurrent hyperparathyroidism in the 6 patients with a negative response to the ischemic blockade. Total ischemic blockade of the arm bearing the parathyroid graft is a valuable method for a correct assessment of graft function after total parathyroidectomy with forearm autotransplantation.

Age-related changes in 11β-hydroxyandrostenedione concentration in normal and osteoporotic women

The secretion of dehydroepiandrosterone (DHEA) and its sulfate is known to decline gradually with advancing age. Furthermore DHEA is known to be significantly lower in osteoporotic subjects than in normals. Recently 11β-hydroxyandrostenedione (11-OHA) has been proposed as an important indicator of the adrenal source of hormone excess in different hyperandrogenic states. In the present study we measured 11-OHA in 224 normal women aged 20–79 yr and 130 osteoporotic women aged 40–79 yr. RIA of 11-OHA was performed with highly specific antiserum raised in rabbits. The mean 11-OHA serum concentration was 2.20±0.90 ng/ml in normal women and 1.75±0.58 ng/ml in osteoporotic women. In contrast to DHEA there was no age-related decrease in 11-OHA serum concentrations in normal and osteoporotic women. Osteoporotic subjects showed statistically significantly lower 11-OHA serum concentrations than normal women. Therefore low serum 11-OHA might represent a further risk factor for osteoporosis.

Hyperandrogenism in Peripubertal Girls

Androgens arise from either adrenal or ovarian secretion or by peripheral conversion of secreted precursors. The adrenals and ovaries normally contribute about equally to testosterone and AD production. DHAS is the major adrenal 17-KS. Testosterone is the major circulating form of androgen. More than 96% of plasma testosterone is bound to SHBG; the free testosterone seems to be the bioavailable fraction. Hyperandrogenism must be considered in any girl with premature or excessive development of public hair or acne, menstrual irregularity (whether it be oligo-amenorrhea or dysfunctional uterine bleeding), or obesity. The most common cause of premature public hair development (pubarche) is premature adrenarche. The most common cause of hyperandrogenism presenting in a teenage girl is polycystic ovary syndrome. However, the differential diagnosis includes "exaggerated adrenarche," late-onset congenital adrenal hyperplasia, virilizing tumors, Cushing's syndrome, hyperprolactinemia, acromegaly, and abnormalities of androgen action or of metabolism. The plasma free testosterone is a more sensitive indicator of hyperandrogenism than is the total testosterone concentration. The pattern of response of plasma free testosterone, DHAS, and cortisol to dex-suppression testing is diagnostic of the source of androgen excess. Most hyperandrogenic adolescents will be found to have PCOS. The treatment is chosen according to particular symptoms, such as menstrual irregularity, hirsutism, or obesity.

Evidence of heterogeneous mechanisms in lipoprotein lipid alterations in hyperandrogenic women

Fifty-one hyperandrogenic women had their lipoprotein lipid profiles determined. Free and albumin-bound testosterone was associated with triglycerides and with high-density lipoprotein cholesterol independent of fasting insulin levels, percent ideal body weight, and waist/hip ratio. To gain insight into mechanisms of these lipid alterations, the women were subgrouped according to apparent source of androgen excess. Whereas all groups had low levels of high-density lipoprotein-2 cholesterol and high triglyceride concentrations, only in those with high luteinizing hormone-to-follicle-stimulating hormone ratios was free and albumin-bound testosterone associated with triglycerides and high-density lipoprotein cholesterol independent of fasting insulin levels. Relationships between percent ideal body weight and waist/hip ratios, free and albumin-bound testosterone, sex hormone binding globulin, fasting insulin and 2-hour insulin levels and blood pressure are not significant in all subgroups, suggesting differing endocrinological influences and differing mechanisms for lipoprotein lipid alterations.

Lipoprotein lipids in women with androgen excess: independent associations with increased insulin and androgen

Concentrations of triglycerides are increased and concentrations of high-density lipoprotein (HDL) cholesterol are low in women with hyperandrogenism. These alterations could be related to excessive androgen or estrogen, to hyperinsulinism, or to a combination of these abnormalities. We examined their independent influences on lipids in 21 women with hyperandrogenism, subgrouped according to apparent source of androgen excess. Results for lipid, androgen, and insulin did not differ among subgroups, so these data were pooled. Free plus albumin-bound testosterone (uT) was correlated with triglycerides (r = 0.69, P less than 0.01) and HDL cholesterol (r = -0.56, P less than 0.01). Both triglycerides (r = 0.66, P less than 0.01) and HDL cholesterol (r = -0.48, P less than 0.05) were also correlated with insulin measured during fasting. Partial correlation revealed that, after adjusting for insulin, lipids were associated with uT. This suggests that androgen excess is independently related to lipid excess. Insulin also was correlated with lipids when adjusted for uT. Free plus albumin-bound estradiol was not associated with any of the lipids. We conclude that altered lipids in women with hyperandrogenism result from the independent effects of androgen and insulin.

The ovary-suppression test in the evaluation of hyperandrogenemia

Forty hyperandrogenemic women were investigated in order to determine whether the source of androgen excess could be attached to a dysfunction of the ovary or the adrenal cortex with a higher degree of accuracy when both steroid-producing organs were subjected to a supposedly specific suppression test. Dexamethasone (DXM) was administered at a dose of 2 mg for 2 days. The ovary-suppression test (OST) was carried out after a combined preparation containing 35 micrograms of ethinyl estradiol and 2 mg of cyproterone acetate (EE-CPA) had been taken for 2-3 weeks. Before and after the tests, the serum levels of testosterone (T), free testosterone (fT), DHEA-S and SHBG were determined. Serum T was lowered by DXM and EE-CPA to the same degree: the latter was more effective with respect to fT. DHEA-S responded much better to DXM than to EE-CPA. The basal level of SHBG was below the lower limit of the norm in 45% of the women. This indicates that hyperandrogenemia can be associated with normal and subnormal levels of SHBG. T and/or fT were elevated in all 40 women. DHEA-S was higher than normal in only 22 of the 40. DXM normalized the DHEA-S level in all but 1 case. In another 18 women, serum T and fT remained unaffected by DXM. This indicates an ovarian source of androgen excess in these cases. The number of cases was reduced from 18 to 4 when the OST was carried out. Even though DXM and EE-CPA are not completely organ-specific in action, the combination of both suppression tests seems to allow a higher degree of discrimination to be made between an ovarian and an adrenal component of hyperandrogenemia than is possible with either test alone.

Message Discrimination

Some 15 years ago, investigators Clarke and Kline proposed message discrimination as an alternative open-ended measure of media exposure. This study examined its use in a multicity health campaign project. It addressed three issues: message recall patterns as a function of instrument length and sociodemographic variables; types of messages recalled; and interviewer effects. Analysis suggested that three open-ended “question cycles” were sufficient to capture the majority of respondents' message recall and that respondents did not recall different types of messages earlier or later in the instrument's administration. The major argument that message discrimination as a technique is less biased against those with less formal education received qualified support. The study also lent qualified support to the conclusion that interviewers were a source of excess but controllable variability in this open-ended survey method.