Research Experiences for Undergraduates

This paper explores the structural differences and relative goodness‐of‐fits of affine term structure models (ATSMs). Within the family of ATSMs there is a trade‐off between flexibility in modeling the conditional correlations and volatilities of the risk factors. This trade‐off is formalized by our classification of N ‐factor affine family into non‐nested subfamilies of models. Specializing to three‐factor ATSMs, our analysis suggests, based on theoretical considerations and empirical evidence, that some subfamilies of ATSMs are better suited than others to explaining historical interest rate behavior.

Updates to the American Cancer Society (ACS) guidelines regarding screening for the early detection of prostate, colorectal, and endometrial cancers, based on the recommendations of recent ACS workshops, are presented. Additionally, the authors review the "cancer-related check-up," clinical encounters that provide case-finding and health counseling opportunities. Finally, the ACS is issuing an updated narrative related to testing for early lung cancer detection for clinicians and individuals at high risk of lung cancer in light of emerging data on new imaging technologies. Although it is likely that current screening protocols will be supplanted in the future by newer, more effective technologies, the establishment of an organized and systematic approach to early cancer detection would lead to greater utilization of existing technology and greater progress in cancer control.

Barriers to international trade are known to be large but because of data limitations it is hard to measure them directly for a large number of countries over many years. To address this problem, I derive a micro‐founded measure of bilateral trade costs that indirectly infers trade frictions from observable trade data. I show that this trade cost measure is consistent with a broad range of leading trade theories including Ricardian and heterogeneous firms models. In an application I show that U.S. trade costs with major trading partners declined on average by about 40 between 1970 and 2000, with Mexico and Canada experiencing the biggest reductions . ( JEL F10, F15)

We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine the effective temperatures of 74 Galactic red supergiants (RSGs). The stars are mostly members of OB associations or clusters with known distances, allowing a critical comparison with modern stellar evolutionary tracks. We find we can achieve excellent matches between the observations and the reddened model fluxes and molecular transitions, although the atomic lines Ca I λ4226 and Ca II H and K are found to be unrealistically strong in the models. Our new effective temperature scale is significantly warmer than those in the literature, with the differences amounting to 400 K for the latest type M supergiants (i.e., M5 I). We show that the newly derived temperatures and bolometric corrections give much better agreement with stellar evolutionary tracks. This agreement provides a completely independent verification of our new temperature scale. The combination of effective temperature and bolometric luminosities allows us to calculate stellar radii; the coolest and most luminous stars (KW Sgr, Case 75, KY Cyg, HD 206936=μ Cep) have radii of roughly 1500 R ☉ (7 AU), in excellent accordance with the largest stellar radii predicted from current evolutionary theory, although smaller than that found by others for the binary VV Cep and for the peculiar star VY CMa. We find that similar results are obtained for the effective temperatures and bolometric luminosities using only the dereddened V - K colors, providing a powerful demonstration of the self-consistency of the MARCS models.

Zeolitic imidazolate frameworks (ZIFs) are hybrid organic-inorganic microporous materials that exhibit zeolite-like structures and can be synthesized with a wide range of pore sizes and chemical functionality. ZIFs as thin films and membranes are of interest for their applications in sensors and gas separation. Here, we report a method for ZIF film and membrane fabrication, based on support surface modification and in situ solvothermal growth, which has potential for general application to other ZIF membranes. Our simple surface modification method results in strong covalent bonds between α-Al(2)O(3) supports and imidazolate ligands, which promote the heterogeneous nucleation and growth of ZIF crystals. The microstructure of ZIF-8 films can be controlled by controlling the pH of the growth solution. ZIF-7 films were fabricated to demonstrate the potential for general applicability of our method. Finally, the separation performance of several ZIF-8 membranes was evaluated, revealing molecular sieving behavior with an ideal selectivity for H(2)/CH(4) of 13.

We present UBVRI photometry obtained from Mosaic images of M31 and M33 using the Kitt Peak National Observatory 4 m telescope. We describe our data reduction and automated photometry techniques in some detail, as we will shortly perform a similar analysis of other Local Group galaxies. The present study covered 2.2 deg 2 along the major axis of M31 and 0.8 deg 2 on M33, chosen so as to include all of the regions currently active in forming massive stars. We calibrated our data using photometry from the Lowell 1.1 m telescope, and this external method resulted in millimagnitude differences in the photometry of overlapping fields, providing some assurance that our photometry is reliable. The final catalog contains 371,781 and 146,622 stars in M31 and M33, respectively, where every star has a counterpart in (at least) the B , V , and R passbands. Our survey goes deep enough to achieve 1%-2% photometry at 21 mag (corresponding to stars more massive than 20 M ⊙ ) and achieves <10% errors at U ∼ B ∼ V ∼ R ∼ I ∼ 23 mag. Although our typical seeing was only modest (0 8-1 4, with median 1 0) by some standards, we find excellent correspondence between our catalog sources and those we see in our Hubble Space Telescope ACS data for OB48, a crowded region in M31. We compare our final photometry with that of others and find good agreement with the CCD catalog of M31 stars by Magnier et al., although our study covers twice the area and goes about 2 mag deeper. There is also excellent agreement with the CCD "DIRECT" surveys of M31 and M33. The photographic studies of others fare less well, particularly at the faint end in V , where accurate background subtraction is needed for good photometry. We provide cross-references to the stars confirmed as members by spectroscopy and compare the locations of these to the complete set in color-magnitude diagrams. While follow-up spectroscopy is needed for many projects, we demonstrate the success of our photometry in being able to distinguish M31/M33 members from foreground Galactic stars. Finally, we present the results of a single night of spectroscopy on the WIYN 3.5 m telescope, examining the brightest likely members of M31. The spectra identify 34 newly confirmed members, including B-A supergiants, the earliest O star known in M31, and two new luminous blue variable candidates whose spectra are similar to that of P Cygni.

This document was developed through the collaborative efforts of the Society of Critical Care Medicine, the American College of Chest Physicians, and the Association of Organ Procurement Organizations. Under the auspices of these societies, a multidisciplinary, multi-institutional task force was convened, incorporating expertise in critical care medicine, organ donor management, and transplantation. Members of the task force were divided into 13 subcommittees, each focused on one of the following general or organ-specific areas: death determination using neurologic criteria, donation after circulatory death determination, authorization process, general contraindications to donation, hemodynamic management, endocrine dysfunction and hormone replacement therapy, pediatric donor management, cardiac donation, lung donation, liver donation, kidney donation, small bowel donation, and pancreas donation. Subcommittees were charged with generating a series of management-related questions related to their topic. For each question, subcommittees provided a summary of relevant literature and specific recommendations. The specific recommendations were approved by all members of the task force and then assembled into a complete document. Because the available literature was overwhelmingly comprised of observational studies and case series, representing low-quality evidence, a decision was made that the document would assume the form of a consensus statement rather than a formally graded guideline. The goal of this document is to provide critical care practitioners with essential information and practical recommendations related to management of the potential organ donor, based on the available literature and expert consensus.

OBJECTIVE: We evaluated outcomes 12 months after trauma in terms of general health, satisfaction, and work status. METHODS: Two hundred forty-seven patients without severe neurotrauma were evaluated by interview during admission and by mailed self-report 6 and 12 months after trauma. Data were obtained from the Trauma Registry, interviews, and survey instruments. Baseline assessment was obtained with the Short Form 36 (SF36) and the Sickness Impact Profile (SIP) work scale. Outcome measures were the SF36, SIP work scale, Brief Symptom Inventory (BSI) depression scale, the Civilian Mississippi Scale for Posttraumatic Stress Disorder (PTSD), and a satisfaction questionnaire. Three regressions were determined for outcome. The dependent variables were general health and work status (linear) and satisfaction (logistic). Each regression controlled for baseline status and mental health, Injury Severity Score (ISS), and 12-month SF36 physical function before evaluating the effect of outcome mental health. RESULTS: Follow-up data were available for 75% of the patients at 6 months and 51% at 12 months. The mean age of patients was 37.2 +/- 0.9 years (+/-SEM), and 73% were male. Their average ISS was 13.9 +/- 0.6. Seventy percent of injuries were blunt force, 13.5 % were penetrating, and 16.5 % were burn injuries (mean total body surface area, 13.3 +/- 1.5%). Sixty-four percent of the patients had returned to work at 12 months. Follow-up SF36 mental health was associated with the dependent outcome in each regression. After controlling for baseline status and mental health, ISS, and outcome SF36 physical function, outcome mental health was associated with outcome SF36 general health (p < 0.001), SIP work status (p = 0.017), and satisfaction with recovery (p = 0.005). Outcome SF36 mental health was related to baseline mental health, 12-month PTSD and BSI depression scores, and increased drug and alcohol use. CONCLUSIONS: Twelve months after trauma, patients' work status, general health, and overall satisfaction with recovery are dependent on outcome mental health. This dependency persists despite measured baseline status, ISS, or physical recovery. The mental disease after trauma is attributable to poor mental health, the development of symptoms of PTSD and depression, and increased substance abuse. Trauma centers that fail to recognize, assess, and treat these injury-related mental health outcomes are not fully assisting their patients to return to optimal function.

ABSTRACT We study the determinants of vertical integration in a new data set of over 750,000 firms from 93 countries. We present a number of theoretical predictions on the interactions between financial development, contracting costs, and the extent of vertical integration. Consistent with these predictions, contracting costs and financial development by themselves appear to have no effect on vertical integration. However, we find greater vertical integration in countries that have both greater contracting costs and greater financial development. We also show that countries with greater contracting costs are more vertically integrated in more capital‐intensive industries.

Nursing staff turnover has long been considered an important indicator of nursing home quality. However, turnover has never been reported on the Nursing Home Compare website, likely because of the lack of adequate data. On July 1, 2016, the Centers for Medicare and Medicaid Services began collecting auditable payroll-based daily staffing data for US nursing homes. We used 492 million nurse shifts from these data to calculate a novel turnover metric representing the percentage of hours of nursing staff care that turned over annually at each of 15,645 facilities. Mean and median annual turnover rates for total nursing staff were roughly 128 percent and 94 percent, respectively. Turnover rates were correlated with facility location, for-profit status, chain ownership, Medicaid patient census, and star ratings. Disseminating facilities' nursing staff turnover rates on Nursing Home Compare could provide important quality information for policy makers, payers, and consumers, and it may incentivize efforts to reduce turnover.

BACKGROUND: The frequency and prognostic influence of myocardial injury in patients with blunt chest trauma is controversial. We investigated the value of cardiac troponin I (cTn-I) and cardiac troponin T (cTn-T), highly specific markers of myocardial injury, to determine whether their measurement would improve the ability to detect myocardial contusion in stable patients with blunt chest trauma in comparison with conventional markers and whether they were associated with significantly worse late clinical outcome. METHODS AND RESULTS: Over an 18-month period, myocardial contusion was diagnosed in 26 of 94 patients (27.6%) with acute blunt chest trauma (motor vehicle crash; 81%), because of echocardiographic abnormalities (n = 12), electrocardiographic abnormalities (n = 29), or both. Patients with myocardial contusion had a significantly higher Injury Severity Score at the time of admission (p = 0.001) and a significantly longer hospital stay (p = 0.0008). All patients survived admission to hospital and were hemodynamically stable. None of the patients died or had severe in-hospital cardiac complications. The percentage of patients with elevated CK, (CK-MB/total CK) ratio, or CK-MB mass concentration was not significantly different between patients with or without myocardial contusion. However, there were significant differences between the two groups when we applied the commonly used threshold levels of CK-MB activity and myoglobin. The percentage of patients with elevated circulating cTn-I and cTn-T (> or = 0.1 microg/L) was significantly higher in patients with myocardial contusion (23% vs. 3%; p = 0.01 and 12% vs. 0%; p = 0.03, respectively). Complete changes in cTn-I and cTn-T correlated well (r = 0.91, p = 0.0001). Sensitivity, specificity, and negative and positive predictive values of cTn-I and cTn-T in predicting a myocardial contusion in blunt trauma patients were 23%, 97%, and 77%, 75%, and 12%, 100%, and 74%, 100%, respectively. Clinical follow-up was available in 83 patients (88%) (mean, 16 +/- 7.5 months). There were no deaths in either group directly attributed to cardiac complications. None of the patients had any long-term cardiac complications or myocardial failure related to blunt chest trauma. CONCLUSION: Although improved specificity of cTn-I and cTn-T compared with conventional markers, it should be emphasized that the main problem with cTn-I and cTn-T is low sensitivity as well as low predictive values in diagnosing myocardial contusion. cTn-I and cTn-T measurement is currently not an improved method in diagnosing blunt cardiac injury in hemodynamically stable patients. Moreover, there was no association of postmyocardial contusion cell injury and late outcome in these patients when cTn-I and cTn-T and other conventional markers were considered.

Blood pressure, heart rate, and respiratory rate were recorded in 24 subjects during 3 9-minute measurement sessions in which they petted an unknown dog, petted a dog with whom a companion bond had been established, or read quietly. Based on the findings of this study, several conclusions were drawn: (1) There is a significant difference in changes over time in both systolic and diastolic blood pressure between petting a dog with whom a companion bond has been established and petting a dog with whom no bond exists; (2) the decreases in both systolic and diastolic blood pressure that occur during petting a dog with whom a companion bond has been established parallel the relaxation effect of quiet reading; and (3) there is a " greeting response" to the entry of a dog with whom a companion bond has been established, which results in significantly higher systolic and diastolic pressures than the response either to an unknown dog or to reading.

Vascular endothelial growth factor (VEGF), a major regulator of angiogenesis, has therapeutic benefit in animal models of coronary or limb ischemia. However, the hemodynamic effects of VEGF have not been investigated. We examined the effects of VEGF on hemodynamics and cardiac performance. Mean arterial pressure (MAP), heart rate (HR), cardiac output, stroke volume, left ventricular (LV) dP/dt, and hematocrit were measured before and after intravenous injection of VEGF in conscious, instrumented rats. VEGF caused a dose-dependent reduction in MAP and an associated increase in HR. VEGF (250 micrograms/kg) significantly decreased cardiac output and stroke volume without affecting the inotropic state of the left ventricle, as determined by dP/dt. VEGF significantly increased hematocrit. Furthermore, VEGF did not affect contractility or HR in the isolated rat heart in vitro. The data suggest that the VEGF-induced decrease in cardiac output is due to reduced stroke volume, which may be caused by a decrease in venous return rather than a direct effect on myocardial contractility. In addition, pretreatment with N omega-nitro-L-arginine methyl-ester (L-NAME), a nitric oxide (NO) synthase inhibitor, significantly attenuated the depressor and tachycardic responses to VEGF, suggesting that VEGF-induced hypotension may be mediated by NO.

This study examines the nature and value of undergraduate students’ experiences with the academic library. The data represent responses from more than 300,000 students between 1984 and 2002 to the College Student Experiences Questionnaire. Although library use did not appear to make independent contributions to desirable outcomes of college, such experiences were related to important educationally valuable activities. Because the emphasis a campus places on information literacy is a strong predictor of students becoming information literate, librarians should redouble their collaborative efforts to promote the value of information literacy and help create opportunities for students to evaluate the quality of the information they obtain.

Received from the Department of Anesthesiology, Cook County Hospital and Hektoen Institute, Chicago, Illinois; and Northwestern University School of Medicine; accepted for publication February 12, 1964.

Hemolysis caused by flow-induced mechanical damage to red blood cells is still a problem in medical devices such as ventricular assist devices (VADs), artificial lungs, and mechanical heart valves. A number of different models have been proposed by different research groups for calculating the hemolysis, and of these, the power law-based models (HI(%)=Ct(α)τ(β)) have proved the most popular because of their ease of use and applicability to a wide range of devices. However, within this power law category of models there are a number of different implementations. The aim of this work was to evaluate different power law-based models by calculating hemolysis in a specifically designed shearing device and a clinical VAD, and comparing the estimated results with experimental measurements of the hemolysis in these two devices. Both the Eulerian scalar transport and all the Lagrangian models had fairly large percentage of errors compared with the experiments (minimum Eulerian 91% and minimum Lagrangian 57%) showing they could not accurately predict the magnitude of the hemolysis. However, the Eulerian approach had large correlation coefficients (>0.99) showing that this method can predict relative hemolysis, which would be useful in comparative analysis, for example, for ranking different devices or for design optimization studies.

This paper develops asymptotic optimality theory for statistical treatment rules in smooth parametric and semiparametric models. Manski (2000, 2002, 2004) and Dehejia (2005) have argued that the problem of choosing treatments to maximize social welfare is distinct from the point estimation and hypothesis testing problems usually considered in the treatment effects literature, and advocate formal analysis of decision procedures that map empirical data into treatment choices. We develop large-sample approximations to statistical treatment assignment problems using the limits of experiments framework. We then consider some different loss functions and derive treatment assignment rules that are asymptotically optimal under average and minmax risk criteria.

The dentate nucleus of the cerebellum may appear as hyperintense on unenhanced T1 magnetic resonance images (MRIs) of the brain. Recently, T1 signal hyperintensity has received attention owing to data on the association of this finding with the history of multiple injections of gadolinium-based contrast agents, specifically gadodiamide, in patients with multiple sclerosis and brain metastases. We conducted a retrospective study on patients with a meningioma who had routinely undergone follow-up enhanced MRI scans with gadodiamide. Across a time interval of 18 months (from January 2013 to July 2014), we identified 102 consecutive patients eligible for this study. A significant increase in T1 hyperintensity of the dentate nuclei of the cerebellum on nonenhanced scans was observed between the first and the last MRI in the group of patients with a history of at least 6 enhanced MRI scans (P < 0.01), whereas no differences were observed in the group with 1 to 5 enhanced MRI scans (P = 0.74). Further research is necessary to shed light on the mechanism of the T1 hyperintensity as well as on the histological and microstructural appearance of the dentate nucleus after multiple intravenous injections of gadodiamide. The finding raises the question of substantial dechelation of this agent in patients with normal renal function.

If society's goal is to increase people's feelings of well‐being, economic growth in itself will not do the job. Full employment and a generous and comprehensive social safety net do increase happiness. Such policies are arguably affordable not only in higher income nations but also in countries that account for most of the population of the less‐developed world. These conclusions are suggested by an analysis of a wide range of evidence on happiness in countries throughout the world . ( JEL I31, I38, O21, F20, D60, E60)

In a previous paper on the Magellanic Clouds, we demonstrated that coeval clusters provide a powerful tool for probing the progenitor masses of Wolf-Rayet (W-R) stars and luminous blue variables (LBVs). Here we extend this work to the higher metallicity regions of the Milky Way, studying 12 Galactic clusters. We present new spectral types for the unevolved stars and use these, plus data from the literature, to construct H-R diagrams. We find that all but two of the clusters are highly coeval, with the highest mass stars having formed over a period of less than 1 Myr. The turnoff masses show that at Milky Way metallicities some W-R stars (of early WN type) come from stars with masses as low as 20–25 M ⊙ . Other early-type WN stars appears to have evolved from high masses, suggesting that a large range of masses evolve through an early WN stage. On the other hand, WN7 stars are found only in clusters with very high turnoff masses, over 120 M ⊙ . Similarly, the LBVs are only found in clusters with the highest turnoff masses, as we found in the Magellanic Clouds, providing very strong evidence that LBVs are a normal stage in the evolution of the most massive stars. Although clusters containing WN7 stars and LBVs can be as young as 1 Myr, we argue that these objects are evolved, and that the young age simply reflects the very high masses that characterize the progenitors of such stars. In particular, we show that the LBV η Car appears to be coeval with the rest of the Trumpler 14/16 complex. Although the WC stars in the Magellanic Clouds were found in clusters with turnoff masses as low as 45 M ⊙ , the three Galactic WC stars in our sample are all found in clusters with high turnoff masses (>70 M ⊙ ); whether this difference is significant or due to small number statistics remains to be seen. The bolometric corrections of Galactic W-R stars are hard to establish using the cluster turnoff method but are consistent with the "standard model" of Hillier.