Advances in spectroscopic techniques have led to an increase in the use of optical properties (absorbance and fluorescence) to assess dissolved organic matter (DOM) composition and infer sources and ...processing. However, little information is available to assess the impact of biological and photolytic processing on the optical properties of original DOM source materials. Over a 3.5 month laboratory study, we measured changes in commonly used optical properties and indices in DOM leached from peat soil, plants, and algae following biological and photochemical degradation to determine whether they provide unique signatures that can be linked to original DOM source. Changes in individual optical parameters varied by source material and process, with biodegradation and photodegradation often causing values to shift in opposite directions. Although values for different source materials frequently overlapped, multivariate statistical analyses showed that unique optical signatures could be linked to original DOM source material, with 17 optical properties determined by discriminant analysis to be significant (p < 0.05) in distinguishing between DOM source and environmental processing. These results demonstrate that inferring source material from optical properties is possible when parameters are evaluated in combination even after extensive biological and photochemical alteration.
In this paper, we estimate the impact of receiving an NIH grant on subsequent publications and citations. Our sample consists of all applications (unsuccessful as well as successful) to the NIH from ...1980 to 2000 for standard research grants (R01s). Both OLS and IV estimates show that receipt of an NIH research grant (worth roughly $1.7
million) leads to only one additional publication over the next five years, which corresponds to a 7% increase. The limited impact of NIH grants is consistent with a model in which the market for research funding is competitive, so that the loss of an NIH grant simply causes researchers to shift to another source of funding.
► We estimate the impact of NIH grant receipt on research output. ► Receiving an award modestly increases applicant research productivity. ► We find little evidence that an award displaces other NIH funding. ► Researchers may have access to other funding sources for high quality projects.
A retrospective review.
To characterize the risk factors for the development of major complications in 3-column osteotomies and determine whether the presence of a major complication affects ultimate ...clinical outcomes.
Three-column spinal osteotomies, including pedicle subtraction osteotomy (PSO) and vertebral column resection (VCR), are common techniques to correct severe and/or rigid spinal deformities.
Two hundred forty consecutive PSO (n = 156) and VCR (n = 84) procedures in 237 patients were performed at a single institution between 1995 and 2008. Of these, 105 patients (87 PSOs, 18 VCRs) had complete preoperative and minimum 2-year postoperative clinical outcomes data available for analysis. Using established criteria, we reported complications as major or minor and further stratified complications as surgical versus medical and permanent versus transient. Risk factors for complications and their effect on Scoliosis Research Society (SRS) clinical outcomes at baseline and at 2 years or more were assessed.
Major medical and surgical complications occurred at similar rates in both PSOs and VCRs (38%, 33 of 87 vs. 22%, 4 of 18; P = 0.28). Overall, 24.8% (26 of 105) experienced major surgical complications (3 permanent) and 15.2% (16 of 105) experienced major medical complications (4 permanent). Patients with PSO were older (53 vs. 29 yr; P < 0.001), had greater estimated blood loss (1867 vs. 1278 mL; P = 0.02), and showed a trend toward fewer fused levels (10.1 vs. 12.2; P = 0.06). Risk factors for major complications included preoperative sagittal imbalance of 40 mm or more (P = 0.01), age 60 years and older (P = 0.01), and the presence of 3 or more medical comorbidities (P = 0.04). Both groups improved significantly from baseline in SRS subscores; however, patients with PSO started off worse but improved more than VCRs in both the pain (+1.0 vs. +0.1; P < 0.001) and function (+0.6 vs. +0.2; P = 0.01) domains, with no differences in final satisfaction (4.1 vs. 4.3; P = 0.54). PSO and VCR patients with no complications had slightly higher satisfaction scores than patients with minor-only complications, major transient complications, and major permanent complications. There were no significant differences among the groups with respect to change in SRS subscores from baseline, and all complication groups improved significantly from baseline (P = 0.04).
Major complications occurred in 35% of 3-column osteotomies and at similar rates for both PSO (38%) and VCR (22%) procedures. The presence of a major complication did not affect the ultimate clinical outcomes at 2 years or more.
One long-standing motivation for low-income housing programs is the possibility that housing affordability and housing conditions generate externalities, including on children’s behavior and ...long-term life outcomes. We take advantage of a randomized housing voucher lottery in Chicago in 1997 to examine the long-term impact of housing assistance on a wide variety of child outcomes, including schooling, health, and criminal involvement. In contrast to most prior work focusing on families in public housing, we focus on families living in unsubsidized private housing at baseline, for whom voucher receipt generates large changes in both housing and nonhousing consumption. We find that the receipt of housing assistance has little, if any, impact on neighborhood or school quality or on a wide range of important child outcomes.
This study estimates the effects of means-tested housing programs on labor supply using data from a randomized housing voucher wait-list lottery in Chicago. Economic theory is ambiguous about the ...expected sign of any labor supply response. We find that among working-age; able-bodied adults, housing voucher use reduces labor force participation by around 4 percentage points (6 percent) and quarterly earnings by $329 (10 percent), and increases Temporary Assistance for Needy Families program participation by around 2 percentage points (15 percent). We find no evidence that the housing-specific mechanisms hypothesized to promote work, such as neighborhood quality or residential stability, are important empirically.
Can principals identify effective teachers? Jacob, Brian A; Lefgren, Lars
Journal of labor economics,
2008, 20080100, 2008-01-00, 20080101, Letnik:
26, Številka:
1
Journal Article
Recenzirano
We examine how well principals can distinguish between more and less effective teachers. To put principal evaluations in context, we compare them with the traditional determinants of teacher ...compensation—education and experience—as well as value‐added measures of teacher effectiveness based on student achievement gains. We present “out‐of‐sample” predictions that mitigate concerns that the teacher quality and student achievement measures are determined simultaneously. We find that principals can generally identify teachers who produce the largest and smallest standardized achievement gains but have far less ability to distinguish between teachers in the middle of this distribution.
► We employ a regression discontinuity design to identify the impact of NIH postdoctoral fellowship receipt on subsequent research productivity. ► We find that receipt of an NIH postdoctoral ...fellowship significantly increases the probability that a new PhD will successfully make the transition to a research career and the number of articles published in the 10 years following grant receipt. ► Our estimates are likely a lower bound of the total social benefit associated with NIH fellowships.
In this paper, we estimate the impact of receiving an NIH postdoctoral training grant on subsequent publications and citations. Our sample consists of all applications for NIH postdoctoral training grants (unsuccessful as well as successful) from 1980 to 2000. Both ordinary least squares and regression discontinuity estimates show that receipt of an NIH postdoctoral fellowship leads to about one additional publication over the next five years, which reflects a 20% increase in research productivity.
School choice has become an increasingly prominent strategy for enhancing academic achievement. To evaluate the impact on participants, we exploit randomized lotteries that determine high school ...admission in the Chicago Public Schools. Compared to those students who lose lotteries, students who win attend high schools that are better in a number of dimensions, including peer achievement and attainment levels. Nonetheless, we find little evidence that winning a lottery provides any systematic benefit across a wide variety of traditional academic measures. Lottery winners do, however, experience improvements on a subset of nontraditional outcome measures, such as self-reported disciplinary incidents and arrest rates.
Saturn’s moon Enceladus has an ice-covered ocean; a plume of material erupts from cracks in the ice. The plume contains chemical signatures of water-rock interaction between the ocean and a rocky ...core. We used the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft to detect molecular hydrogen in the plume. By using the instrument’s open-source mode, background processes of hydrogen production in the instrument were minimized and quantified, enabling the identification of a statistically significant signal of hydrogen native to Enceladus. We find that the most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials. The relatively high hydrogen abundance in the plume signals thermodynamic disequilibrium that favors the formation of methane from CO₂ in Enceladus’ ocean.
This article presents multi-band direct-conversion receivers (RXs) with frequency-translated negative feedback. The forward path includes a low-noise transconductance amplifier (LNTA) followed by ...four-phase passive mixers that drive baseband amplifiers. A feedback path employs tunable resistor banks attached to additional four-phase passive mixers, allowing tunable, frequency-selective input matching around a wide range of local oscillator (LO) frequencies. The passive mixers are driven by 25% duty-cycle, non-overlapping quadrature LO waveforms, and two different methods are presented for generating such waveforms. Two RX variants, differing in their LO generation schemes, are fabricated in 45-nm SOI CMOS. The first operates from 6 to 30 GHz, exhibiting greater than 25-dB gain and 4.1-10.5-dB noise figure (NF). A second operates from 10 to 50 GHz, achieving greater than 18-dB gain with 7.1-17-dB NF across the band. For either version, the instantaneous bandwidth is 960 MHz for the highest gain setting and 1375 MHz with reduced gain, measured at 10 GHz LO. The in- band third-order intercept point (IIP3) is −5.4 dBm, the in- band IIP2 is +16.5 dBm, and the out-of-band 1-dB blocker compression is greater than −15 dBm. The RX core consumes 71 mW, while LO circuitry in each variant consumes 48-182 and 72-262 mW from 10 to 50 and 6 to 30 GHz, respectively.
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