Trace Actinide Signatures of a Bulk Neptunium Sample.

In nuclear forensic analyses, measurements of actinide elements in a sample can assist with identifying interdicted or unknown materials. While these radiochemical signatures have been extensively investigated in uranium materials, less is known about bulk neptunium samples. This paper describes the measurement of trace actinide concentrations and isotopic profiles in a 237Np oxide sample. Uranium, plutonium, americium, and curium concentrations and isotopic profiles in the sample were determined and deemed potentially useful for distinguishing different sources of 237Np. Several different potential radiochronometry systems were also investigated; discordant results indicate that the Np sample was never completely purified of other actinide elements, or that subsequent contamination of the sample occurred. Few prior studies of neptunium materials have been reported, and these data suggest that trace actinide constituents could provide unique signatures to identify material out of regulatory control.

Dural Venous Sinus Stent Placement Reduces Dosage Requirements for Carbonic Anhydrase Inhibitors in Patients with Idiopathic Intracranial Hypertension.

This retrospective single-center study evaluated the change in required dosage of acetazolamide and topiramate before and after dural venous sinus stent placement (VSSP) for idiopathic intracranial hypertension (IIH). Adults diagnosed with IIH who failed optimized medical management and were treated with VSSP were included. This study comprised 55 patients who underwent VSSP for the diagnosis of IIH. The median preprocedural dosage of acetazolamide and topiramate was 1,000 mg (range, 500-4,000 mg) and 100 mg (range, 0-200 mg), respectively, among patients able to tolerate the medications. The median postprocedural dosage of acetazolamide and topiramate was 375 mg (range, 0-4,000 mg), with a mean reduction of 52.9% (P = .001), and 0 mg (range, 0-200 mg), with a mean reduction of 45.9% (P = .005), respectively. Dural VSSP significantly reduced dosage requirements for acetazolamide and/or topiramate, potentially reducing the morbidity secondary to medication side effects.

Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk.

Dynamic models of the protoplanetary disk indicate there should be large-scale material transport in and out of the inner Solar System, but direct evidence for such transport is scarce. Here we show that the ε50Ti-ε54Cr-Δ17O systematics of large individual chondrules, which typically formed 2 to 3 My after the formation of the first solids in the Solar System, indicate certain meteorites (CV and CK chondrites) that formed in the outer Solar System accreted an assortment of both inner and outer Solar System materials, as well as material previously unidentified through the analysis of bulk meteorites. Mixing with primordial refractory components reveals a "missing reservoir" that bridges the gap between inner and outer Solar System materials. We also observe chondrules with positive ε50Ti and ε54Cr plot with a constant offset below the primitive chondrule mineral line (PCM), indicating that they are on the slope ∼1.0 in the oxygen three-isotope diagram. In contrast, chondrules with negative ε50Ti and ε54Cr increasingly deviate above from PCM line with increasing δ18O, suggesting that they are on a mixing trend with an ordinary chondrite-like isotope reservoir. Furthermore, the Δ17O-Mg# systematics of these chondrules indicate they formed in environments characterized by distinct abundances of dust and H2O ice. We posit that large-scale outward transport of nominally inner Solar System materials most likely occurred along the midplane associated with a viscously evolving disk and that CV and CK chondrules formed in local regions of enhanced gas pressure and dust density created by the formation of Jupiter.

Nuclear Sample Provenance and Age Determination Using Ruthenium Isotopes.

Measurements of the ruthenium isotopic composition of nuclear samples could provide information about the method of sample production, sample irradiation history, and age. To investigate the feasibility and applicability of this idea, this study focuses on measurements of the ruthenium isotope composition of a nominally single-isotope 106Ru radioactivity standard, where the complications of environmental mixing are eliminated. The measurements of the 106Ru standards reveal unusual stable ruthenium isotopic compositions consistent with fissiogenic ruthenium. Three different lots of the material have been investigated, and the isotopic composition is found to be different for lot 1 as compared to lots 2 and 3, indicating a longer irradiation duration incurred during the production of lot 1. Through measurements of 106Ru and its 106Pd daughter, radiochronometry can be used to infer the ages of the samples. Lot 1 is older than lots 2 and 3 and was produced 4.91(5) years before the reference date of 1/1/21, approximately 2.7 years before lots 2 and 3. In an effort to better understand the sample production pathway, the isotopic measurements are compared with nuclear reactor simulations, which suggest that the material was generated by irradiation of a low-enriched uranium target material in a light water reactor. These findings have significant implications for nuclear treaty monitoring, providing an example of the power of ruthenium isotope measurements to discern details of sample origin and history.

Trace element geochemistry of coarse-grained angrites from Northwest Africa: Implications for their petrogenesis on the angrite parent body.

The angrites are a class of achondrites that encompass a wide range of igneous textures from quenched, volcanic, and subvolcanic stones to slowly cooled, plutonic rocks. The compositions of the various geochemical reservoirs generating this variety of rocks have not been investigated fully because historically the numbers and masses of angrites available for study have been quite small. However, the rapid increase in meteorites from Northwest Africa (NWA) has enabled a renewed opportunity for such an investigation. In particular, three samples, NWA 2999, 4590, and 4801, have provided a new window into our understanding of the origin and petrogenesis of the coarse-grained (plutonic) angrites. We report here the trace element abundances in individual mineral grains of pyroxene, plagioclase, olivine/kirschsteinite, and phosphate and in the whole-rock samples. We utilize these data to constrain the petrogenetic history of each of these samples on the angrite parent body (e.g., parental melt compositions and oxygen fugacity conditions) and assess genetic relationships to previously investigated angrites. The trace element abundances in each of the three coarse-grained angrites studied here indicate a unique history for each. The observed trace element abundances and patterns in NWA 2999 show similarities with previously studied fine-grained, volcanic angrites and potentially indicate a common geochemical source reservoir, even though NWA 2999 is temporally distinct from the volcanic angrites. In contrast, NWA 4590 has trace element characteristics analogous to other coarse-grained angrites (e.g., Lewis Cliff [LEW] 86010), suggesting that these samples originated from geochemically similar source reservoirs. The third angrite, NWA 4801, exhibits geochemical characteristics most similar to the plutonic, coarse-grained angrites, but also appears to have some affinities in its trace element characteristics to the volcanic, fine-grained angrites. This suggests that NWA 4801 may represent a petrogenetic link between two distinct geochemical reservoirs on the angrite parent body. In aggregate, the trace element distributions in these three plutonic angrites suggest that while they may have originated up to several million years after the fine-grained angrites, they sampled a range of source reservoirs on the angrite parent body. Some of these source reservoirs were likely similar to those of the fine-grained angrites, but others had distinct geochemical characteristics.

The impact and recovery of asteroid 2018 LA.

The June 2, 2018, impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve. 23 meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as a HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g/cm3, a relatively low albedo pv ~ 0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth-impacting orbit via the v6 resonance. The impact that ejected 2018 LA in an orbit towards Earth occurred 22.8 ± 3.8 Ma ago. Zircons record a concordant U-Pb age of 4563 ± 11 Ma and a consistent 207Pb/206Pb age of 4563 ± 6 Ma. A much younger Pb-Pb phosphate resetting age of 4234 ± 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta's Veneneia impact basin.

The fall, recovery, classification, and initial characterization of the Hamburg, Michigan H4 chondrite.

The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic 3He, 21Ne, and 38Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic 10Be concentration point to a small 40-60 cm diameter meteoroid. An 40Ar-39Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA-ICPMS give an average Pb-Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb-Pb phosphate age of 4535.3 ± 9.5 Ma and U-Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

Cerebral hemodynamics at altitude: effects of hyperventilation and acclimatization on cerebral blood flow and oxygenation.

OBJECTIVE: Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy. METHODS: Peripheral (Spo2) and cerebral (Scto2) oxygenation, end-tidal carbon dioxide (ETCO2), and cerebral hemodynamics were studied in 12 subjects using transcranial Doppler and diffuse correlation spectroscopy (DCS) at 75 m and then 2 days and 7 days after ascending to 4559 m above sea level. After obtaining baseline measurements, subjects hyperventilated to reduce baseline ETCO2 by 50%, and a further set of measurements were obtained. RESULTS: Cerebral oxygenation and peripheral oxygenation showed a divergent response, with cerebral oxygenation decreasing at day 2 and decreasing further at day 7 at altitude, whereas peripheral oxygenation decreased on day 2 before partially rebounding on day 7. Cerebral oxygenation decreased after hyperventilation at sea level (Scto2 from 68.8% to 63.5%; P<.001), increased after hyperventilation after 2 days at altitude (Scto2 from 65.6% to 69.9%; P=.001), and did not change after hyperventilation after 7 days at altitude (Scto2 from 62.2% to 63.3%; P=.35). CONCLUSIONS: An intensification of the normal cerebral hypocapnic vasoconstrictive response occurred after partial acclimatization in the setting of divergent peripheral and cerebral oxygenation. This may help explain why hyperventilation fails to improve cerebral oxygenation after partial acclimatization as it does after initial ascent. The use of DCS is feasible at altitude and provides a direct measure of CBF indices with high temporal resolution.

Optimal approach to circumferential decompression and reconstruction for thoracic spine metastatic disease.

BACKGROUND: Circumferential decompression has been demonstrated to be the first-line therapy for patients with metastatic tumors in the thoracic spine requiring surgical intervention. However, there is significant debate regarding whether these tumors are best accessed anteriorly utilizing a thoracotomy or posteriorly. We used decision analysis to determine which approach yields greater health-related quality of life (QOL). METHODS: We searched Medline, Embase, and the Cochrane Library for relevant articles published between 1990 and 2011 on anterior and posterior approaches to metastatic disease in the thoracic spine. QOL values for major treatment outcomes were determined using the existing literature. Separate models were created for ambulatory and nonambulatory patients. A Monte Carlo simulation and sensitivity analyses were used to determine which treatment strategy resulted in the highest QOL. RESULTS: For ambulatory patients, an anterior approach resulted in a slightly higher QOL, and for nonambulatory patients, a posterior approach was favored, but these differences were not statistically significant. CONCLUSIONS: Using a decision-analytic model, we found no significant difference in QOL resulting from anterior versus posterior approaches to metastatic lesions in the thoracic spine. Decisions should instead be based on surgeon comfort, tumor characteristics, anatomy of the lesion, patient-related factors, and goals of the operation.

Response of brain oxygen to therapy correlates with long-term outcome after subarachnoid hemorrhage.

BACKGROUND: Brain oxygen (PbtO2) monitoring can help guide care of poor-grade aneurysmal subarachnoid hemorrhage (aSAH) patients. The relationship between PbtO2-directed therapy and long-term outcome is unclear. We hypothesized that responsiveness to PbtO2-directed interventions is associated with outcome. METHODS: Seventy-six aSAH patients who underwent PbtO2 monitoring were included. Long-term outcome [Glasgow Outcome Score-Extended (GOS-E) and modified Rankin Scale (mRS)] was ascertained using the social security death database and structured telephone interviews. Univariate and multivariate regression were used to identify variables that correlated with outcome. RESULTS: Data from 64 patients were analyzed (12 were lost to follow-up). There were 530 episodes of compromised PbtO2 (<20 mmHg) during a total of 7,174 h of monitor time treated with 1,052 interventions. Forty-two patients (66 %) survived to discharge. Median follow-up was 8.5 months (range 0.1-87). At most recent follow-up 35 (55 %) patients were alive, and 28 (44 %) had a favorable outcome (mRS ≤3). In multivariate ordinal regression analysis, only age and response to PbtO2-directed intervention correlated significantly with outcome. Increased age was associated with worse outcome (coeff. 0.8, 95 % CI 0.3-1.3, p = 0.003), and response to PbtO2-directed intervention was associated with improved outcome (coeff. -2.12, 95 % CI -4.0 to -0.26, p = 0.03). Patients with favorable outcomes had a 70 % mean rate of response to PbtO2-directed interventions whereas patients with poor outcomes had a 45 % response rate (p = 0.005). CONCLUSIONS: Response to PbtO2-directed intervention is associated with improved long-term functional outcome in aSAH patients.

Separation of protactinium from uranium-niobium alloys for 231Pa-235U radiochronometry in nuclear forensic investigations.

The isolation and purification of protactinium from uranium materials is essential for 231Pa-235U radiochronometry, but separating Pa from uranium-niobium alloys, a common material in the nuclear fuel cycle, is challenging due to the chemical similarity of Pa and Nb. Here we present three resin chromatography separation techniques for isolating Pa from U and Nb which were independently developed by three different laboratories through ad hoc adaptations of standard operating procedures. Our results underscore the need for and value of purification methods suitable for a diversity of uranium-based materials to ensure the operational readiness of nuclear forensics laboratories. Supplementary Information: The online version contains supplementary material available at 10.1007/s10967-023-08928-y.

Anthropogenic uranium signatures in turtles, tortoises, and sea turtles from nuclear sites.

Chelonians (turtles, tortoises, and sea turtles) grow scute keratin in sequential layers over time. Once formed, scute keratin acts as an inert reservoir of environmental information. For chelonians inhabiting areas with legacy or modern nuclear activities, their scute has the potential to act as a time-stamped record of radionuclide contamination in the environment. Here, we measure bulk (i.e. homogenized scute) and sequential samples of chelonian scute from the Republic of the Marshall Islands and throughout the United States of America, including at the Barry M. Goldwater Air Force Range, southwestern Utah, the Savannah River Site, and the Oak Ridge Reservation. We identify legacy uranium (235U and 236U) contamination in bulk and sequential chelonian scute that matches known nuclear histories at these locations during the 20th century. Our results confirm that chelonians bioaccumulate uranium radionuclides and do so sequentially over time. This technique provides both a time series approach for reconstructing nuclear histories from significant past and present contexts throughout the world and the ability to use chelonians for long-term environmental monitoring programs (e.g. sea turtles at Enewetok and Bikini Atolls in the Republic of the Marshall Islands and in Japan near the Fukushima Daiichi reactors).

Cost-effectiveness of confirmatory techniques for the placement of lumbar pedicle screws.

OBJECT: There is considerable variation in the use of adjunctive technologies to confirm pedicle screw placement. Although there is literature to support the use of both neurophysiological monitoring and isocentric fluoroscopy to confirm pedicle screw positioning, there are no studies examining the cost-effectiveness of these technologies. This study compares the cost-effectiveness and efficacy of isocentric O-arm fluoroscopy, neurophysiological monitoring, and postoperative CT scanning after multilevel instrumented fusion for degenerative lumbar disease. METHODS: Retrospective data were collected from 4 spine surgeons who used 3 different strategies for monitoring of pedicle screw placement in multilevel lumbar degenerative disease. A decision analysis model was developed to analyze costs and outcomes of the 3 different monitoring strategies. A total of 448 surgeries performed between 2005 and 2010 were included, with 4 cases requiring repeat operation for malpositioned screws. A sample of 64 of these patients was chosen for structured interviews in which the EuroQol-5D questionnaire was used. Expected costs and quality-adjusted life years were calculated based on the incidence of repeat operation and its negative effect on quality of life and costs. RESULTS: The decision analysis model demonstrated that the O-arm monitoring strategy is significantly (p < 0.001) less costly than the strategy of postoperative CT scanning following intraoperative uniplanar fluoroscopy, which in turn is significantly (p < 0.001) less costly than neurophysiological monitoring. The differences in effectiveness of the different monitoring strategies are not significant (p = 0.92). CONCLUSIONS: Use of the O-arm for confirming pedicle screw placement is the least costly and therefore most cost-effective strategy of the 3 techniques analyzed.

Chromium Isotopic Evidence for Mixing of NC and CC Reservoirs in Polymict Ureilites: Implications for Dynamical Models of the Early Solar System.

Nucleosynthetic isotope anomalies show that the first few million years of solar system history were characterized by two distinct cosmochemical reservoirs, CC (carbonaceous chondrites and related differentiated meteorites) and NC (the terrestrial planets and all other groups of chondrites and differentiated meteorites), widely interpreted to correspond to the outer and inner solar system, respectively. At some point, however, bulk CC and NC materials became mixed, and several dynamical models offer explanations for how and when this occurred. We use xenoliths of CC materials in polymict ureilite (NC) breccias to test the applicability of such models. Polymict ureilites represent regolith on ureilitic asteroids but contain carbonaceous chondrite-like xenoliths. We present the first 54Cr isotope data for such clasts, which, combined with oxygen and hydrogen isotopes, show that they are unique CC materials that became mixed with NC materials in these breccias. It has been suggested that such xenoliths were implanted into ureilites by outer solar system bodies migrating into the inner solar system during the gaseous disk phase ~3-5 Myr after CAI, as in the "Grand Tack" model. However, combined textural, petrologic, and spectroscopic observations suggest that they were added to ureilitic regolith at ~50-60 Myr after CAI, along with ordinary, enstatite, and Rumuruti-type chondrites, as a result of breakup of multiple parent bodies in the asteroid belt at this time. This is consistent with models for an early instability of the giant planets. The C-type asteroids from which the xenoliths were derived were already present in inner solar system orbits.

A Randomized Phase 2 Study of Pembrolizumab With or Without Radiation in Patients With Recurrent or Metastatic Adenoid Cystic Carcinoma.

PURPOSE: We evaluated the safety and efficacy of pembrolizumab (pembro) ± radiation therapy (RT) in a phase 2 study among patients with progressive, metastatic adenoid cystic carcinoma (ACC). METHODS AND MATERIALS: Eligible patients had metastatic ACC with progression within the last year and ≥1 measurable lesion. Patients were randomized to pembro alone or with RT to 30 Gy in 5 fractions (pembroRT). The primary endpoint was objective response rate outside the RT field. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and local RT responses. RESULTS: We randomized 20 patients (10 per arm) from 2017 to 2018. We did not observe objective response outside of the radiation treatment field; stable disease (SD) was the best response in 12 (60%) patients and was not different per arm (7 pembro, 5 pembroRT, P = .65). A tumor growth rate decrease (TGR) of >25% was noted among 7 of 12 patients and >75% in 4 patients. There were local responses in the irradiated field among all evaluable pembroRT patients. Median PFS and OS were 4.5/not reached for pembroRT and 6.6 / 27.2 months for pembro patients. One patient developed grade 3 liver enzyme elevation after 27 cycles of therapy. Correlative analyses confirm low levels of programmed death-ligand 1 expression (PD-L1), and CD8 infiltrating T-cells. We identified associations between local response and both MYB/NFIB translocation and PD-L1 expression and between changes in systemic immune populations and RT. CONCLUSIONS: Pembrolizumab and pembroRT were well tolerated. We observed no objective responses, but 60% of patients with PD before the study achieved SD, the majority with decreased TGR and half (n = 10) with clinical benefit (SD >6 months). We observed favorable local responses within the RT field. Additional strategies are needed to further delay progression and effect response.

Circulating tumor cell analysis in locally advanced and metastatic squamous cell carcinoma of the head and neck.

BACKGROUND: Circulating tumors cells (CTCs) are considered an early step towards metastasis and have been linked to poor prognosis in several types of cancer. CTCs in squamous cell carcinoma of the head and neck (SCCHN) have an unclear role. METHODS: In this prospective study, patients with locally advanced or metastatic SCCHN had CTC counts assessed before starting systemic treatment using the CellSearch System. Select cases also had sequential CTC evaluation. Presence of CTCs was correlated with patient characteristics and outcomes. RESULTS: Forty-eight patients enrolled, and 36 had evaluable clinical data and baseline CTC counts. Twenty-five patients had locally advanced disease (LAD) and 11 had metastatic disease. ≥1 CTCs were detected in six patients with LAD (24%) and four with metastatic disease (36%). On univariate analysis, smoking was associated with CTCs. CONCLUSION: CTCs are not associated with prognosis in patients with LAD and metastatic disease; however, they are present in this patient population, and ≥1 CTCs is associated with a history of smoking. LEVEL OF EVIDENCE: 1b; individual prospective cohort study.

Thalamic deep brain stimulation for midbrain tremor secondary to cystic degeneration of the brainstem.

OBJECTIVE: Tremor resulting from damage to midbrain structures is poorly understood and often difficult to treat. The authors report a case of cystic degeneration of the brainstem with resultant Holmes-like tremor which was successfully treated using a stimulating electrode placed in the contralateral ventralis intermedius nucleus (VIM) of the thalamus. CLINICAL PRESENTATION: A 31-year-old man presented with a multilobulated, multiseptated lesion of the upper brainstem diagnosed after subacute onset of headaches. The patient subsequently developed an incapacitating left-upper-extremity tremor refractory to medical treatment. INTERVENTION: The patient underwent implantation of a deep brain stimulator in the VIM with symptomatic and functional improvement. CONCLUSIONS: Deep brain stimulation is an effective and safe intervention for tremor of unusual etiology. Electrode placement should be based on an understanding of the structure-function relationships underlying the various and distinct types of tremor.

The origin of the unique achondrite Northwest Africa 6704: Constraints from petrology, chemistry and Re-Os, O and Ti isotope systematics.

Northwest Africa (NWA) 6704 is a unique achondrite characterized by a near-chondritic major element composition with a remarkably intact igneous texture. To investigate the origin of this unique achondrite, we have conducted a combined petrologic, chemical, and 187Re-187Os, O, and Ti isotopic study. The meteorite consists of orthopyroxene megacrysts (En55-57Wo3-4Fs40-42; Fe/Mn = 1.4) up to 1.7 cm in length with finer interstices of olivine (Fa50-53; Fe/Mn = 1.1-2.1), chromite (Cr# ~ 0.94), awaruite, sulfides, plagioclase (Ab92An5Or3) and merrillite. The results of morphology, lattice orientation analysis, and mineral chemistry indicate that orthopyroxene megacrysts were originally hollow dendrites that most likely crystallized under high super-saturation and super-cooling conditions (1-102 °C/h), whereas the other phases crystallized between branches of the dendrites in the order of awaruite, chromite → olivine → merrillite → plagioclase. In spite of the inferred high supersaturation, the remarkably large size of orthopyroxene can be explained as a result of crystallization from a melt containing a limited number of nuclei that are preserved as orthopyroxene megacryst cores having high Mg# or including vermicular olivine. The Re-Os isotope data for bulk and metal fractions yield an isochron age of 4576 ± 250 Ma, consistent with only limited open system behavior of highly siderophile elements (HSE) since formation. The bulk chemical composition is characterized by broadly chondritic absolute abundances and only weakly fractionated chondrite-normalized patterns for HSE and rare earth elements (REE), together with substantial depletion of highly volatile elements relative to chondrites. The HSE and REE characteristics indicate that the parental melt and its protolith had not undergone significant segregation of metals, sulfides, or silicate minerals. These combined results suggest that a chondritic precursor to NWA 6704 was heated well above its liquidus temperature so that highly volatile elements were lost and the generated melt initially contained few nuclei of relict orthopyroxene, but the melting and subsequent crystallization took place on a timescale too short to allow magmatic differentiation. Such rapid melting and crystallization might occur as a result of impact on an undifferentiated asteroid. The O-Ti isotope systematics (Δ17O = -1.052 ± 0.004, 2 SD; ε50Ti = 2.28 ± 0.23, 2 SD) indicate that the NWA 6704 parent body sampled the same isotopic reservoirs in the solar nebula as the carbonaceous chondrite parent bodies. This is consistent with carbonaceous chondrite-like refractory element abundances and oxygen fugacity (FMQ = -2.6) in NWA 6704. Yet, the Si/Mg ratio of NWA 6704 is remarkably higher than those of carbonaceous chondrites, suggesting significant nebular fractionation of forsterite in its provenance.

Fluorescence properties and photophysics of the sulfoindocyanine Cy3 linked covalently to DNA.

The sulfoindocyanine Cy3 is one of the most commonly used fluorescent dyes in the investigation of the structure and dynamics of nucleic acids by means of fluorescence methods. In this work, we report the fluorescence and photophysical properties of Cy3 attached covalently to single-stranded and duplex DNA. Steady-state and time-resolved fluorescence techniques were used to determine fluorescence quantum yields, emission lifetimes, and fluorescence anisotropy decays. The existence of a transient photoisomer was investigated by means of transient absorption techniques. The fluorescence quantum yield of Cy3 is highest when attached to the 5' terminus of single-stranded DNA (Cy3-5' ssDNA), and decreases by a factor of 2.4 when the complementary strand is annealed to form duplex DNA (Cy3-5' dsDNA). Substantial differences were also observed between the 5'-modified strands and strands modified through an internal amino-modified deoxy uridine. The fluorescence decay of Cy3 became multiexponential upon conjugation to DNA. The longest lifetime was observed for Cy3-5' ssDNA, where about 50% of the decay is dominated by a 2.0-ns lifetime. This value is more than 10 times larger than the fluorescence lifetime of the free dye in solution. These observations are interpreted in terms of a model where the molecule undergoes a trans-cis isomerization reaction from the first excited state. We observed that the activation energy for photoisomerization depends strongly on the microenvironment in which the dye is located. The unusually high activation energy measured for Cy3-5' ssDNA is an indication of dye-ssDNA interactions. In fact, the time-resolved fluorescence anisotropy decay of this sample is dominated by a 2.5-ns rotational correlation time, which evidences the lack of rotational freedom of the dye around the linker that separates it from the terminal 5' phosphate. The remarkable variations in the photophysical properties of Cy3-DNA constructs demonstrate that caution should be used when Cy3 is used in studies employing DNA conjugates.

Trends in Resident Operative Teaching Opportunities for Treatment of Intracranial Aneurysms.

OBJECTIVE: The International Subarachnoid Aneurysm Trial heralded a paradigm shift in the treatment of intracranial aneurysms. During this same time frame, neurosurgical training programs increased in size and scope. The present study examines the impact of trends in surgical clipping and the endovascular treatment of intracranial aneurysms, over one decade, and the neurosurgical resident complement on the resident teaching environment using the Nationwide Inpatient Sample (NIS). METHODS: The NIS was used to estimate the number of aneurysms treated with either surgical clipping and endovascular methods from 2002 through 2011 at teaching institutions. Teaching opportunities per year per resident or chief resident were calculated as the ratio of the number of specified cases to the average number of neurosurgical trainees by year. Annualized trends were assessed. RESULTS: Over the study period, the percent change in odds of occurrence of a clipped ruptured aneurysm was -15.6% per year (P < 0.001) and of ruptured aneurysms undergoing endovascular treatment was 18.7% per year (P < 0.001) within teaching institutions. This corresponded to a decline in teaching opportunities for clipped ruptured aneurysms for both residents and chief residents (P < 0.001). In contrast, teaching opportunities for endovascular treatment of both ruptured and unruptured aneurysms increased dramatically over the study period. CONCLUSIONS: There has been a significant decrease in opportunity for operative exposure to craniotomy for ruptured aneurysm clipping over the past decade, whereas the volume of endovascular procedures for aneurysms has dramatically increased, highlighting the need for a shift in training strategy for those neurosurgeons graduating from residency desiring to subspecialize in neurovascular neurosurgery.