Yr In Duration Research Articles

The Black Hole Mass of the z = 2.805 Multiply Imaged Quasar SDSS J2222+2745 from Velocity-resolved Time Lags of the C iv Emission Line

Abstract We present the first results of a 4.5 yr monitoring campaign of the three bright images of multiply imaged z = 2.805 quasar SDSS J2222+2745 using the Gemini North Multi-Object Spectrograph and the Nordic Optical Telescope. We take advantage of gravitational time delays to construct light curves surpassing 6 yr in duration in the observed frame and achieve an average spectroscopic cadence of 10 days during the 8 months of visibility per season. Using multiple secondary calibrators and advanced reduction techniques, we achieve percent-level spectrophotometric precision and carry out an unprecedented reverberation mapping analysis, measuring both integrated and velocity-resolved time lags for the C iv emission line. The full line lags the continuum by τ cen = 36.5 − 3.9 + 2.9 rest-frame days. We combine our measurement with published C iv emission line lags and derive the r BLR − L relationship log 10 ​ ( τ / d a y ) = ( 0.99 ± 0.07 ) + ( 0.48 ± 0.03 ) log 10 ​ [ λ L λ ( 1350 A A ) / 10 44 e r g s − 1 ] with 0.30 ± 0.06 dex intrinsic scatter. The velocity-resolved lags are consistent with circular Keplerian orbits, with τ cen = 86.2 − 5.0 + 4.5 , 25 − 15 + 11 , and 7.5 − 3.5 + 4.2 rest-frame days for the core, blue wing, and red wing, respectively. Using σ line with the mean spectrum and assuming log 10 ( f mean , σ ) = 0.52 ± 0.26 , we derive log 10 ( M BH / M ⊙ ) = 8.63 ± 0.27 . Given the quality of the data, this system represents a unique benchmark for calibration of M BH estimators at high redshift. Future work will present dynamical modeling of the data to constrain the virial factor f and M BH.

Experimental droughts with rainout shelters: a methodological review

AbstractForecast increases in the frequency, intensity, and duration of droughts with climate change may have extreme and extensive ecological consequences. There are currently hundreds of published, ongoing, and new drought experiments worldwide aimed to assess ecological sensitivity to drought and identify the mechanisms governing resistance and resilience. To date, the results from these experiments have varied widely, and thus, patterns of drought sensitivities and the underlying mechanisms have been difficult to discern. Here we examined 89 published drought experiments, along with their associated historical precipitation records to (1) identify where and how drought experiments have been imposed, (2) determine the extremity of drought treatments in the context of historical climate, and (3) assess the influence of ambient precipitation variability on the magnitude of drought experiments. In general, drought experiments were most common in water‐limited ecosystems, such as grasslands, and were often short‐term, as 80% were 1–4 yr in duration. When placed in a historical context, the majority of drought experiments imposed extreme drought, with 61% below the 5th, and 43% below the 1st percentile of the 50‐yr annual precipitation distribution. We also determined that interannual precipitation variability had a large and potentially underappreciated effect on the magnitude of drought treatments due to the co‐varying nature of control and drought precipitation inputs. Thus, detecting significant ecological effects in drought experiments is strongly influenced by the interaction between experimental drought magnitude, precipitation variability, and key ecological thresholds. The patterns that emerged from this study have important implications for the design and interpretation of drought experiments and also highlight critical gaps in our understanding of the ecological effects of drought.

Epidural Steroid Injections, Conservative Treatment, or Combination Treatment for Cervical Radicular Pain

Background:Cervical radicular pain is a major cause of disability. No studies have been published comparing different types of nonsurgical therapy.Methods:A comparative-effectiveness study was performed in 169 patients with cervical radicular pain less than 4 yr in duration. Participants received no

Tolerability of sirolimus: a decade of experience at a single cardiac transplant center

Sirolimus is used in cardiac transplant recipients to prevent rejection, progression of cardiac allograft vasculopathy, and renal dysfunction. However, sirolimus has many potential side effects and its tolerability when used outside of clinical trials is not well established. We describe a decade of experience with sirolimus in cardiac transplant recipients at our institution. We retrospectively reviewed records of all adult cardiac transplant recipients living between September 1999 and February 2010 (n = 329) and identified 67 patients (20%) who received sirolimus. The indications for sirolimus were cardiac allograft vasculopathy (67%), renal dysfunction (25%), rejection (4%), and intolerability of tacrolimus (3%). One-third of patients discontinued sirolimus at a median (25th, 75th percentiles) of 0.9 (0.2, 1.6) yr of duration. Over 70% of subjects experienced an adverse event attributed to sirolimus. Adverse events were associated with higher average sirolimus levels (9.1 ng/mL vs. 7.1 ng/mL, p = 0.004). We conclude that sirolimus is frequently used in cardiac transplant recipients (20%) and commonly causes side effects, often necessitating discontinuation. Higher average sirolimus levels were associated with adverse events, suggesting that tolerability may improve if levels are maintained within the lower end of the current therapeutic range; however, the improvement in tolerability would need to be balanced with the potential for decreased efficacy.

Greenhouse gases, climate change and the transition from coal to low-carbon electricity

A transition from the global system of coal-based electricity generation to low-greenhouse-gas-emission energy technologies is required to mitigate climate change in the long term. The use of current infrastructure to build this new low-emission system necessitates additional emissions of greenhouse gases, and the coal-based infrastructure will continue to emit substantial amounts of greenhouse gases as it is phased out. Furthermore, ocean thermal inertia delays the climate benefits of emissions reductions. By constructing a quantitative model of energy system transitions that includes life-cycle emissions and the central physics of greenhouse warming, we estimate the global warming expected to occur as a result of build-outs of new energy technologies ranging from 100 GWe to 10 TWe in size and 1–100 yr in duration. We show that rapid deployment of low-emission energy systems can do little to diminish the climate impacts in the first half of this century. Conservation, wind, solar, nuclear power, and possibly carbon capture and storage appear to be able to achieve substantial climate benefits in the second half of this century; however, natural gas cannot.

Exploring first-year undergraduate medical students' self-directed learning readiness to physiology

Medical students are expected to possess self-directed learning skills to pursue lifelong learning. Previous studies have reported that the readiness for self-directed learning depends on personal attributes as well as the curriculum followed in institutions. Melaka Manipal Medical College of Manipal University (Karnataka, India) offers a Bachelor of Medicine and Bachelor of Surgery (MBBS) twinning program that is of 5 yr in duration. Keeping in mind the amount of time that the curriculum has devoted for self-directed learning, we explored the self-directed learning readiness of first-year MBBS students (n = 130) using a self-directed learning readiness scale (SDLRS) and explored the correlation between SDLRS scores of high achievers, medium achievers, and low achievers with their academic performance in physiology examinations. Students were requested to respond to each item of the SDLRS on a Likert scale. Median scores of the three scales of the SDLRS were compared across the three groups of students using a Kruskall-Wallis test. SDLRS scores of the students (n = 130) were correlated with their marks in theory papers of first, second, and third block-end examinations using Spearmann's correlation coefficient. The mean item score for desire for learning was found to be higher followed by self-control and self-management. Data analyses showed significantly high (P < 0.03) median scores for self-control for high achievers compared with medium and low achievers. Between the groups, high achievers had a higher score for all the three scales of the SDLRS followed by low and medium achievers. SDLRS scores and academic performance of the three groups of students were found to exhibit a weak correlation. This study threw light on the fact that despite having a high desire for learning and ability of self-control, students need to be supported in their self-management skills.

Bisphosphonate Use and Atypical Femoral Fractures: Getting Down to Brass Tacks

No doubt about it—times are rough for clinicians and their patients trying to make rational decisions about when and how to use (or stop) effective therapies for osteoporosis. On the one hand, we have increasingly clear evidence that bisphosphonates given to older women and men with osteoporosis [defined as an existing vertebral fracture or a bone mineral density (BMD) T-score less than 2.5] prevent future hip, vertebral, and non-spine fractures (1–3). Conversely, with help from the Internet, highprofile newspaper articles, and even the Food & Drug Administration (4), we seem to be reminded on a daily basis that bisphosphonates may cause serious harm, such as osteonecrosis of the jaw, atrial fibrillation, esophageal cancer, and spontaneous femur fractures. It is no wonder that patients are worried and openly share their angst about osteoporosis treatment with their doctors, while clinicians are equally worried about causing more harm than good. The numerous reports of the “unusual femur fractures” in particular have been disquieting; clinicians are not happy to hear that they may be responsible for causing the problem they thought they were treating to prevent. The worry that excessive bisphosphonate dosing or prolonged use might cause microdamage accumulation from oversuppression of bone remodeling and increase rather than decrease skeletal fragility is not new (5). Such concerns were voiced a decade ago (6) but seemed unlikely after the above-mentioned large fracture endpoint studies showed beneficial effects on fracture risk with few complications. The catch? Placebo-controlled fracture endpoint trials have been at most 3–5 yr in duration, so inferences about any effects of treatment beyond 5 yr, both beneficial and harmful, are lacking solid evidence. Numerous case reports of unusual fractures of the femur among bisphosphonate-treated women have appeared over the last 5 yr (7–9). These “atypical” fractures were subtrochanteric (below the lesser trochanter) or diaphyseal (above thedistalmetaphysis), occurredwith little trauma, and were characterized by transverse or nearly transverse “chalk-like” fracture lines as opposed to the more typical spiral or comminuted femoral shaft fractures. Subsequent reports highlighted the presence of prodromal thigh pain, bilateral involvement, the presence of other diseases such as rheumatoid arthritis and diabetes, and the concomitant use of other medications such as corticosteroids or proton pump inhibitors. Some reports, but certainly not all, suggest marked suppression of bone turnover as assessed by bone turnover markers and iliac crest histomorphometry (7). Even if causally related, these atypical fractures must be quite rare among women receiving bisphosphonate therapy for 3to 5-yr duration because the rates of all types of subtrochanteric and diaphyseal fractures were low and similar between placebo and bisphosphonate-treated women in a reanalysis of three large clinical trials (FIT, FLEX, and HORIZON) (10). Although the study is reassuring, an important limitation is that few women received more than 5 yr of bisphosphonate treatment, information on atypical features was not specifically collected, and for the most part only radiographic reports were reviewed. Large observational studies have also examined the relationship between bisphosphonate use and subtrochanteric or diaphyseal fractures (11). In this issue of JCEM, Abrahamsen et al. (12) extend their previous work using

Late Holocene phases of dome growth and Plinian activity at Guagua Pichincha volcano (Ecuador)

Since the eruption which affected Quito in AD 1660, Guagua Pichincha has been considered a hazardous volcano. Based on field studies and twenty 14C dates, this paper discusses the eruptive activity of this volcano, especially that of the last 2000 years. Three major Plinian eruptions with substantial pumice discharge occurred in the 1st century, the 10th century, and in AD 1660. The ages of organic paleosols and charcoal from block-and-ash flow and fallout deposits indicate that these eruptions occurred near the end of 100 to 200 year-long cycles of discontinuous activity which was comprised of dome growth episodes and minor pumice fallouts. The first cycle took place from ~ AD 1 to 140. The second one developed during the 9th and 10th centuries, lasted 150–180 yr, and included the largest Plinian event, with a VEI of 5. The third, historic cycle, about 200 yr in duration, includes pyroclastic episodes around AD 1450 and AD 1500, explosive activity between AD 1566 and AD 1582, possible precursors of the 1660 eruption in the early decades of the 17th century, and finally the 1660 eruption (VEI 4). A fourth event probably occurred around AD 500, but its authenticity requires confirmation. The Plinian events occurred at the end of these cycles which were separated by repose periods of at least 300 yr. Older volcanic activity of similar type occurred between ~ 4000 and ~ 3000 yr BP. Because ash fallout and related mudflows represent a serious hazard for Quito's metropolitan area, the significance of the increasing phreatic activity observed from 1981 to 1998, and the 1999–2001 magmatic episode of dome growth and collapse are discussed. These probably represent a short step in a longer evolution which may result in a major Plinian event in the future decades or in the next century, comparable to that which occurred during the 1st, 10th, and 17th centuries.

Evolution of the Understanding of Premature Ejaculation: Historical Perspectives

The perception of lifelong premature ejaculation (PE) has evolved from that of a relatively obscure complaint to one of a relatively common syndrome with a neurobiological component. During the last century, four historical periods, each about 30 yr in duration, can be distinguished. In these periods PE was regarded according to the major prevailing viewpoint of mental disorders, that is, from phenomenological, psychoanalytic, behavioral, and neurobiological points of view. Although the influences of these different periods on the medical approach to PE are still present today, recent scientific evidence suggests that lifelong PE is related to an imbalance in central serotonin neurotransmission. A basic premise for further research remains an evidence-based definition of PE. Such an evidence-based definition is essential to ensure accurate and reproducible clinical outcomes.

Tiotropium as essential maintenance therapy in COPD

Over the past decade, several large-scale clinical trials have been performed to assess the impact of pharmacological treatments on patient-centred outcomes such as dyspnoea, exercise tolerance, exacerbations and health-related quality of life (HRQoL) in patients with chronic obstructive pulmonary disease (COPD). Tiotropium, a once-daily inhaled anticholinergic agent that works through prolonged muscarinic M₃ receptor blockade, has consistently been shown to provide sustained improvements in lung function parameters. Furthermore, several prospective trials have shown that tiotropium improves exercise tolerance and augments the beneficial effects of pulmonary rehabilitation. Beyond these important physiological outcomes, tiotropium has been shown to reduce dyspnoea, decrease the frequency of exacerbations and improve HRQoL in studies of ≤1 yr in duration. Such improvements in patient-centred outcomes may allow patients to increase their activity levels, thereby interrupting the downward spiral of chronic inactivity that leads to physical deconditioning and further reductions in exercise tolerance. Recently, combination therapies of two long-acting bronchodilators have been examined more closely regarding their potential to provide patients with superior symptom relief compared with that provided by single-agent therapy. Because maintenance treatment with tiotropium provides consistent and sustained improvements in many relevant clinical outcomes of chronic obstructive pulmonary disease, it may reduce the progression of the disease. This hypothesis is being tested in the ongoing Understanding the Potential Long-term Impacts on Function with Tiotropium (UPLIFT) trial.

Are Ultraluminous X‐Ray Sources Intermediate‐Mass Black Holes Accreting from Molecular Clouds?

The origin and nature of ultraluminous X-ray sources (ULXs) is a contentious and controversial topic. There are ongoing debates about the masses of the objects responsible, their sources of mass for accretion, and their relation to stellar populations in galaxies. A new picture of these objects is proposed in which they are intermediate-mass black holes confined to the disks of their host galaxies and accreting from the interstellar medium. They are then preferentially found in or near molecular clouds. This model correctly predicts the shape of the observed luminosity function and requires only a very small fraction of the baryonic mass of a galaxy to be in the form of intermediate-mass black holes. Because the X-rays they produce strongly heat nearby interstellar gas and because they move relatively rapidly in and out of dense regions, ULXs are predicted to have brief episodes of high luminosity, perhaps ~105 yr in duration, but they may recur many times.

Carbon sequestration in western Canadian peat highly sensitive to Holocene wet-dry climate cycles at millennial timescales

A high-resolution fen peat record and 79 basal peat dates from paludified peatlands in continental western Canada provide evidence for cyclic change in moisture conditions and in peat carbon accumulation. The ash-free bulk density, a proxy for degree of peat decomposition and thus moisture conditions, shows periodicities at both millennial (from 1500 to 2190 yr, with a mean of 1785 yr) and century scales (386 yr and 667 yr). Wet periods of 200–600 yr in duration, especially at ~6900, 5500 and 4000 cal. BP, correlate with rapid peat accumulation, new peatland initiation and declines in the rate of increase of atmospheric CO2 concentrations. The wet periods in western North America are coeval with warm periods in the North Atlantic, a phasing relationship that has been documented in other published palaeorecords for the glacial period and late Holocene, probably in response to variations in solar activity. These results indicate a strong connection between climate and the global carbon cycle at the millennial scale, mediated in part by peatland dynamics. This is the first demonstration that peatland carbon sequestration rates are highly sensitive even to minor climatic fluctuations, which are too small to produce detectable changes in major species in the peatland. That global atmospheric CO2 concentrations have in the past responded to these changes in peatland dynamics implies a strong potential for peatlands to be a major player in affecting future global change.

Meta-analyses of therapies for postmenopausal osteoporosis. V. Meta-analysis of the efficacy of hormone replacement therapy in treating and preventing osteoporosis in postmenopausal women.

To review the effect of hormone replacement therapy (HRT) on bone density and fractures in postmenopausal women. We searched MEDLINE and EMBASE from 1966 to 1999, the Cochrane Controlled Register, citations of relevant articles, and proceedings of international meetings for eligible randomized controlled trials. We contacted osteoporosis investigators to identify additional studies, and primary authors for unpublished data. We included 57 studies that randomized postmenopausal women to HRT or a control (placebo or calcium/vitamin D) and were of at least 1 yr in duration. Seven of these studies reported fractures. For each study, three independent reviewers assessed the methodological quality and abstracted the data. HRT showed a trend toward reduced incidence of vertebral fractures [relative risk (RR) 0.66, 95% confidence interval (CI) 0.41-1.07; 5 trials] and nonvertebral fractures (RR 0.87, 95% CI 0.71-1.08; 6 trials). HRT had a consistent effect on bone mineral density (BMD) at all sites. The difference between HRT and control in the percent change in bone density at 2 yr was 6.76 (5.83, 7.89; 21 trials) at the lumbar spine and 4.53 (3.68, 5.36; 14 trials) and 4.12 (3.45, 4.80; 9 trials) at the forearm and femoral neck, respectively. HRT has a consistent, favorable and large effect on bone density at all sites. The data show a nonsignificant trend toward a reduced incidence in vertebral and nonvertebral fractures.

VLA Observations of the Nearby Merger NGC 4038/4039: H [CSC]ii[/CSC] Regions and Supernova Remnants in the “Antennae”

We present 6 and 4 cm radio images of the inner disks of the nearby merger pair NGC 4038 and NGC 4039 at resolutions between ~ 1'' and 26, or ~ 100 and 260 pc. We detect numerous compact radio sources embedded in more diffuse radio emission; the compact radio sources produce ~ 12% and ~ 25% of the 6 and 4 cm radio emission in the system, respectively. The strongest radio continuum emission occurs between the galaxies, at an optically unremarkable location near but not coincident with an extremely red cluster detected by Whitmore & Schweizer. The radio peak is at a location of intense star formation (as detected in the mid-IR) and of dense molecular gas. We identify 115 individual compact 6 cm radio sources and 63 individual 4 cm sources in the system, to a limiting luminosity of ~ 2 × 1018 W Hz-1, or ~ 4 times the luminosity of Cas A; 90% of the 6 cm sources and 67% of the 4 cm sources are unresolved in these observations. Of the strongest sources, for which the flux densities are large enough to measure spectral indices with reasonable errors, one-third have nominally flat radio spectra, indicating that they are dominated by thermal radio emission from H II regions, and two-thirds have nominally steep spectra dominated by nonthermal emission from supernova remnants. For the compact sources dominated by thermal emission, we derive typical masses of 104 to 105 M⊙ in massive young stars. Using reasonable assumptions about source sizes, we estimate associated ionized gas masses of 103 to 104 M⊙. A comparison with the ~ (2–5) × 103 M⊙ typical optical clusters detected recently by Whitmore et al. suggests that the thermal radio sources detected here may be composed of tens of these typical young star clusters or else that they are more like the individual massive 105–106 M⊙ Whitmore et al. clusters. The strongest thermal radio source is associated with none of the Whitmore et al. clusters but is coincident with strong CO and 15 μm emission, implying that massive star clusters are still enshrouded by dust in this region. The second strongest thermal source is near several optical clusters, suggesting that these clusters are just now emerging from their birth cloud and are clearing away the surrounding material. Estimates of stellar ages and sound speeds indicate that we do not see star formation propagating in this system; rather, the star formation sequence is probably related to more global properties of the interaction. From the steep-spectrum sources, we derive a total system supernova rate of 0.2–0.3 yr-1, about an order of magnitude larger than that expected from the currently observed O star population. This suggests that a large number of O stars may have formed in the system in a short-lived burst, less than 106 yr in duration and about 3–4 Myr ago.

New chronology for the late Paleocene thermal maximum and its environmental implications

The late Paleocene thermal maximum (LPTM) is associated with a brief, but intense, interval of global warming and a massive perturbation of the global carbon cycle. We have developed a new orbital chronology for Ocean Drilling Program (ODP) Site 690 (Weddell Sea, Southern Ocean) by using spectral analysis of high-resolution geochemical records. The LPTM interval spans 11 precessional cycles yielding a duration of 210 to 220 k.y. The δ 13 C anomaly associated with the LPTM has a magnitude of about −2.5‰ to −3‰; we show that about −2‰ of the excursion occurs within two steps that each were less than 1000 yr in duration. The remainder developed through a series of steps over ∼52 k.y. The timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates, punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial. Further, we are able to correlate the records between ODP Sites 690 and 1051 (western North Atlantic) on the scale of 21 k.y. cycles, which demonstrates that the details of the δ 13 C excursion are recognizable between distant sites. Comparison of cycle records at Sites 690 and 1051 suggests that sediment representing the interval ∼30 k.y. just prior to and at the onset of the LPTM are missing in the latter location. This unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k.y. of the start of the LPTM.

Etiological diagnosis of primary adrenal insufficiency using an original flowchart of immune and biochemical markers.

Approximately 70-80% of cases of primary adrenal insufficiency are classified as idiopathic. An effective protocol for the etiological diagnosis of primary adrenal insufficiency is needed to ensure correct patient management. With the aim of developing an algorithm for the etiological diagnosis of primary adrenal insufficiency, we studied 56 Italian patients with nonsurgical primary adrenal insufficiency and 24 French patients with X-linked adrenoleukodystrophy (ALD) for serum levels of adrenal cortex, steroid-21-hydroxylase (21OHAb), islet cell (ICA), glutamate decarboxylase (GAD65Ab), IA2/ICA512 (ICA512Ab), thyroid peroxidase (TPOAb) autoantibodies, and plasmatic concentrations of very long chain fatty acids (VLCFA). High levels of 21OH and adrenal cortex antibodies were found in 35/42 (83%) and 17/42 (40%) Italian patients with idiopathic adrenal insufficiency, respectively. Levels of adrenal autoantibodies correlated inversely with disease duration (P < 0.0001). Elevated VLCFA were found in 4/42 (10%) idiopathic patients. A total of 34/35 (97%) idiopathic patients with a disease duration of less than 20 yr was positive for either 21OHSAb or elevated levels of VLCFA. None of 14 patients with posttuberculosis adrenal insufficiency had elevated levels of either adrenal antibodies or VLCFA. ICA, GAD65Ab, ICA512Ab, and TPOAb were found in 6/56 (11%), 8/56 (14%), 4/56 (7%), and 23/56 (41%) patients, respectively. None of 24 French ALD patients with adrenal insufficiency was positive for organ-specific autoantibodies. The measuring of 21OH antibodies and plasma VLCFA levels enabled a correct diagnosis of autoimmune (89%) and ALD (8%) in 97% of patients with idiopathic primary adrenal insufficiency of less than 20 yr of duration. The results of our study have important therapeutic and prognostic implications.

Duration and Structure of the Past Four Interglaciations

Reanalysis and additional dating of the Devils Hole δ18O paleotemperature record confirm that the last interglaciation in the Great Basin (the continental analog of marine isotopic substage 5e) lasted ∼22,000 yr, consistent with the Vostok paleotemperature record which suggests a duration of ∼19,000 yr for this event in Antarctica. The three preceding interglaciations in the Devils Hole record (analogs of marine isotopic substages 7e, 9c, and 11c) range from 20,000 to 26,000 yr in duration. A ∼20,000-yr duration for the last interglaciation is consistent with TIMS uranium-series dated sea-level high stands. Thus, the widely held view that interglaciations were of 11,000- to 13,000-yr duration and constituted only about 10% of mid-to-late Pleistocene climatic cycles needs reexamination. The warmest portion of each interglaciation in the Devils Hole time series is marked by a δ18O plateau, signifying apparent climatic stability for periods of 10,000- to 15,000-yr duration.

Strand-plain evidence for late Holocene lake-level variations in Lake Michigan

Lake level is a primary control on shoreline behavior in Lake Michigan. The historical record from lake-level gauges is the most accurate source of information on past lake levels, but the short duration of the record does not permit the recognition of long-term patterns of lake-level change (longer than a decade or two). To extend the record of lake-level change, the internal architecture and timing of development of five strand plains of late Holocene beach ridges along the Lake Michigan coastline were studied. Relative lake-level curves for each site were constructed by determining the elevation of foreshore (swash zone) sediments in the beach ridges and by dating basal wetland sediments in the swales between ridges. These curves detect long-term (30+ yr) lake-level variations and differential isostatic adjustments over the past 4700 yr at a greater resolution than achieved by other studies. The average timing of beach-ridge development for all sites is between 29 and 38 yr/ridge. This correspondence occurs in spite of the embayments containing the strand plains being different in size, orientation, hydrographic regime, and available sediment type and caliber. If not coincidental, all sites responded to a lake-level fluctuation of a little more than three decades in duration and a range of 0.5 to 0.6 m. Most pronounced in the relative lake-level curves is a fluctuation of 120–180 yr in duration. This ≈150 yr variation is defined by groups of four to six ridges that show a rise and fall in foreshore elevations of 0.5 to 1.5 m within the group. The 150 yr variation can be correlated between sites in the Lake Michigan basin. The ≈30 and 150 yr fluctuations are superimposed on a long-term loss of water to the Lake Michigan basin and differential rates of isostatic adjustment.

Measurement of the degree of smoothing in sediment paleomagnetic secular variation records: an example from late Quaternary deep-sea sediments of the Bermuda Rise, western North Atlantic Ocean

Replicate paleomagnetic secular variation (PSV) records for the last 15,000 yr have been recovered from two deep-sea sediment gravity cores on the Bermuda Rise, western North Atlantic Ocean. The records have been correlated using several different parameters and dated by correlation to a nearby piston core which has a high-resolution 14C chronology. The PSV records are systematically subdued with respect to the expected local magnetic field variability during the Holocene, when sedimentation rates were about 10 cm/kyr. During the Late Pleistocene, when sedimentation rates were a factor of 2–3 higher, the PSV variability was significantly larger. We attribute this to smoothing of the PSV records by a depositional/post-depositional remanence (DRM/PDRM) acquisition process with a 10–20 cm lock-in interval. The degree of PSV smoothing was evaluated by comparing the VGP angular dispersion and vector spectral content of the Bermuda Rise cores with high-resolution PSV records from North America and Great Britain. These results suggest a 50% reduction in the DRM/PDRM recording of vector variability during the Holocene on the Bermuda Rise, with most of the PSV reduction occurring for features of less than 2000 yr in duration. We can reproduce the subdued PSV pattern with a mathematical model that simulates the site DRM/PDRM remanence acquisition process. Finally, the replicate gravity cores document that PSV records may be reproducible on a local scale, even though they only retain a low-pass filtered record of true magnetic field variability.

Islet cell cytoplasmic autoantibody reactivity to glutamate decarboxylase in insulin-dependent diabetes.

Individuals with or at risk for insulin-dependent diabetes (IDD) frequently have autoantibodies against an islet cell cytoplasmic (ICA) antigen thought to be a sialoglycolipid. However, we now report that preabsorption of ICA-positive sera with recombinant glutamate decarboxylase (human GAD 65 and/or GAD 67) reduced or blocked the ICA reactivity of 5/18 (27%) new-onset IDD patients and 7/18 (39%) prediabetics. Interestingly, nondiabetic subjects with ICA of > or = 5 yr in duration had GAD-reactive ICA significantly more often (16/24, 67%, P < 0.04) than the diabetic groups. ICA reactivity to GAD was not related to serum ICA titer nor the age of the individual, and in all cases tested was blocked by GAD 65 or GAD 67 with equivalent efficiency. The ICA observed in 21/25 (84%) IDD patients with ICA long after clinical onset of disease (9-42 yr) was reactive to GAD. A natural history analysis of three individuals showed conversions from ICA which was reactive to GAD to a non-GAD-reactive ICA nearer to their clinical onsets of IDD. This study further defines the autoantigens reactive to ICA, and suggests that, whereas ICA that are not reactive to GAD may identify an advanced and more prognostic lesion, GAD-reactive ICA may typify the early or inductive lesion that may or may not progress to clinically significant beta cell injury.