cssi/SciSciGPT-SciSciNet huggingface dataset:
Post-1969 immigration and the example of the insolvency of the Social Security system.

Advocates of immigration to save Social Security (S.S.) assume that a pay-as-you-go system will work over the long run. That assumption is not shared by the Social Security Board of Trustees. Reflection shows that it would entail ever-larger new cohorts of immigrants to support those who are retiring, in effect, a Ponzi scheme. In fact, the benefits structure of the S.S. system, which pays out proportionately more to low-wage earners than to high-wage earners relative to their contributions, taken together with the income profile of post-1969 immigrants, means that the more immigration which occurs, the deeper into insolvency the system falls.
Multiscale modeling of copper and copper/nickel nanofoams under compression

Abstract Pure metal nanofoams in the form of interconnected ligament networks have shown strong potential over the last few years in areas such as catalysts, batteries, and optics. However, they are often fragile and therefore difficult to integrate into engineering applications. For these reasons, a new class of materials, composite metallic nanofoams made of ligaments coated with thin metallic layers, have been proposed to solve these issue. The mechanical properties of these nanofoams depend on their relative density and their internal geometrical structure. In this work, we combine molecular dynamics (MD) and finite element method (FEM) to investigate the compressive behavior of nanofoams made of copper ligaments coated with nickel. We also investigate how this behavior relates to their microstructures. For that purpose, we built different types of representative cell structures, and atomistic simulations of multiaxial compression tests were performed to produce yield surfaces. Then the generated yield surfaces were curve fitted into a normalized model to obtain the shape parameters. Last, a plasticity model was introduced to study and compare their mechanical behavior under compression. The results suggest that the coating of the ligaments can improve the mechanical behavior of the nanofoams. They also reveal the importance and the limitations of the microstructural geometry on the strengthening of these structures. These findings can be used for the design of metallic nanofoams with tailored mechanical properties.
Diffusing Capacity Is an Independent Predictor of Outcomes in Pulmonary Hypertension Associated With COPD

Background Patients with COPD who experience pulmonary hypertension (PH) have worse mortality than those with COPD alone. Predictors of poor outcomes in COPD-PH are not well-described. Diffusing capacity of the lung (D lco ) assesses the integrity of the alveolar-capillary interface and thus may be a useful prognostic tool among those with COPD-PH. Research Question Using a single center registry, we sought to evaluate D lco as a predictor of mortality in a cohort of patients with COPD-PH. Study Design and Methods This retrospective cohort study analyzed 71 COPD-PH patients from the Johns Hopkins Pulmonary Hypertension Registry with right-sided heart catheterization (RHC)-proven PH and pulmonary function testing data within one year of diagnostic RHC. Transplant-free survival was calculated from index RHC. Adjusted transplant-free survival was modelled using Cox proportional hazard methods; age, pulmonary vascular resistance, FEV1, oxygen use, and N-terminal pro-brain natriuretic peptide were included as covariates. Results Overall unadjusted transplant-free 1-, 3-, and 5-year survivals were 87%, 60%, and 51%, respectively. Survival was associated with reduced D lco across the observed range of pulmonary artery pressures and pulmonary vascular resistance. Severe D lco impairment was associated with poorer survival (log-rank χ2 13.07) (P lco , mortality rates increased by 4% (hazard ratio, 1.04; 95% CI, 1.01-1.07). Interpretation Among patients with COPD-PH, severe gas transfer impairment is associated with higher mortality, even with adjustment for airflow obstruction and hemodynamics, which suggests that D lco may be a useful prognostic marker in this population. Future studies are needed to further investigate the association between D lco and morbidity and to determine the utility of D lco as a biomarker for disease risk and severity in COPD-PH.
Well-being and student–faculty interactions in higher education

The Organisation for Economic Co-operation and Development (OECD) calls for going beyond the measure of market strength to assess societal progress through a consideration of well-being. Research o...
Farey Trees Explain Sequential Effects in Choice Response Time

The latencies of successive two-alternative, forced-choice response times display intricately patterned sequential effects, or dependencies. They vary as a function of particular trial-histories, and in terms of the order and identity of previously presented stimuli and registered responses. This article tests a novel hypothesis that sequential effects are governed by dynamic principles, such as those entailed by a discrete sine-circle map adaptation of the Haken Kelso Bunz (HKB) bimanual coordination model. The model explained the sequential effects expressed in two classic sequential dependency data sets. It explained the rise of a repetition advantage, the acceleration of repeated affirmative responses, in tasks with faster paces. Likewise, the model successfully predicted an alternation advantage, the acceleration of interleaved affirmative and negative responses, when a task's pace slows and becomes more variable. Detailed analyses of five studies established oscillatory influences on sequential effects in the context of balanced and biased trial presentation rates, variable pacing, progressive and differential cognitive loads, and dyadic performance. Overall, the empirical patterns revealed lawful oscillatory constraints governing sequential effects in the time-course and accuracy of performance across a broad continuum of recognition and decision activities.
MALDI imaging mass spectrometry: an emerging tool in neurology

Neurological disease and disorders remain a large public health threat. Thus, research to improve early detection and/or develop more effective treatment approaches are necessary. Although there are many common techniques and imaging modalities utilized to study these diseases, existing approaches often require a label which can be costly and time consuming. Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) is a label-free, innovative and emerging technique that produces 2D ion density maps representing the distribution of an analyte(s) across a tissue section in relation to tissue histopathology. One main advantage of MALDI IMS over other imaging modalities is its ability to determine the spatial distribution of hundreds of analytes within a single imaging run, without the need for a label or any a priori knowledge. Within the field of neurology and disease there have been several impactful studies in which MALDI IMS has been utilized to better understand the cellular pathology of the disease and or severity. Furthermore, MALDI IMS has made it possible to map specific classes of analytes to regions of the brain that otherwise may have been lost using more traditional methods. This review will highlight key studies that demonstrate the potential of this technology to elucidate previously unknown phenomenon in neurological disease.
BICEP/Keck and Cosmological Attractors

We discuss implications of the latest BICEP/Keck data release for inflationary models, with special emphasis on the cosmological attractors which can describe all presently available inflation-related observational data.
Generation and Differentiation of Human iPS Cells

Perhaps one of the most significant achievements in science was the discovery of induced pluripotent stem (iPS) cells [1,2]. iPS cells are a type of pluripotent stem cell derived from adult somatic cells that have been genetically reprogrammed back to an embryonic stem-cell-like state through the forced expression of genes and factors important for maintaining the defining properties of embryonic stem (ES) cells [3]. Human iPS cells were first produced from human fibroblasts by two independent groups – the Yamanaka lab at Kyoto University and the Thomson lab at University of Wisconsin, Madison. iPS cells are similar to ES cells in many aspects, including the expression of ES cell markers, chromatin methylation patterns, embryoid body formation, teratoma formation, viable chimera formation, and pluripotency in differentiation. The basic concept of somatic cell reprogramming was discovered in the late nineties through the cell fusion and somatic cell nuclear transfer experiments [4–6]. Based on these findings, Shinya Yamanaka and his coworkers were able to show that mouse embryonic fibroblasts (MEFs) could be converted into germline-competent induced pluripotent stem cells by retroviral expression of four transcription factors: OCT4, SOX2, KLF4, and c-MYC [3,7]. The reprogramming process is based on the ectopic expression of these transcription factors, which initiate a rare reactivation of the endogenous pluripotency genes OCT4, SOX2, and NANOG [8]. This reactivation leads to a resetting of the epigenetic profile of a terminally differentiated somatic cell and activates the molecular circuitry of pluripotency [9,10]. Thereafter, the derived iPS cells are similar to embryonic stem cells with regard to their morphology, growth characteristics, differentiation capacities, and expression of various marker genes [11]. The transition from a somatic to a pluripotent state could be further enhanced through chromatinmodifying chemicals and microRNAs [12,13]. Subsequent studies revealed that the induction of pluripotency was also possible with different transcription factor combinations and could be improved by activation or inhibition of different signaling pathways [14–18]. The unique property of iPS cells to differentiate into all other cell types of the human body opened up new clinical perspectives for developing successful stem-cell-based therapies. However, the use of retroviral and lentiviral vectors for reprogramming carries a high risk of DNA incorporation into chromosomes and can lead to the disruption of gene transcription and tumor formation [19]. Therefore, it is important to develop further nonintegrating reprogramming techniques for future applications in the field of regenerative
Market Organizations for Controlling Smart Matter

We study the effectiveness of different organizations for maintaining a spatially extended physical system near an unstable configuration. Computational agents representing individual controllers hid to buy or sell power that is used to push the system to the desired unstable configuration. Simulation results show that this market mechanism leads to a stable control of an otherwise unstable system by focussing the power in those parts of the system where is most needed. Among our findings, we show that hierarchical organizations are best suited for successful control in terms of power consumption.
Impact of conjoint trajectories of body mass index and marijuana use on short sleep duration.

Background and Objectives We examined the association between the conjoint developmental trajectories of body mass index (BMI) and marijuana use from age 24 to age 32 and short sleep duration. Methods The participants included 158 African American male, 267 African American female, 166 Puerto Rican male, and 225 Puerto Rican female young adults (N = 816). Using Mplus, we obtained the conjoint trajectories of BMI and marijuana use. Logistic regression analyses examined the association between the conjoint trajectories and short sleep duration. Results Five conjoint trajectory groups were extracted: normal BMI and no or low marijuana use, obese and no or low marijuana use, morbidly obese and some marijuana use, normal BMI and high marijuana use, and obese and high marijuana use. Those in the obese and no or low marijuana use group, the morbidly obese and some marijuana use group, and the obese and high marijuana use group were more likely to report shorter sleep duration than those with normal BMI and no or low marijuana use group. Conclusions and Scientific Significance This study highlights the significance of examining joint trajectories over several developmental stages. In treating short sleep duration, we propose focusing on treating obesity, and also treating marijuana use if applicable. (Am J Addict 2014;23:176–183)
Blood lactate disappearance at various intensities of recovery exercise

Numerous studies have reported that following intense exercise the rate of blood lactate (La) disappearance is greater during continuous aerobic work than during passive recovery. Recent work indicates that a combination of high- and low-intensity work may be optimal in reducing blood La. We tested this hypothesis by measuring the changes in blood La levels following maximal exercise during four different recovery patterns. Immediately following 50 S of maximal work, subjects (n = 7) performed one of the following recovery treatments for 40 min: 1) passive recovery (PR); 2) cycling at 35% maximal O2 uptake (VO2 max) (35% R); 3) cycling at 65% VO2 max (65% R); 4) cycling at 65% for 7 min followed by cycling at 35% for 33 min (CR). The treatment order was counterbalanced with each subject performing all treatments. Serial blood samples were obtained throughout recovery treatments and analyzed for La. The rate of blood La disappearance was significantly greater (P less than 0.05) in both the 35% R and CR when compared with either the 65% R or PR. No significant difference (P greater than 0.05) existed in the rate of blood La disappearance between the 35% R and CR. These data do not support the hypothesis that exercise recovery at a combination of intensities is superior to a recovery involving continuous submaximal exercise in lowering blood La following maximal work.
Fractional snow cover in the Colorado and Rio Grande basins, 1995–2002

[1] A cloud-masked fractional snow-covered area (SCA) product gridded at 1 km was developed from the advanced very high resolution radiometer for the Colorado River and upper Rio Grande basins for 1995–2002. Cloud cover limited SCA retrievals on any given 1-km2 pixel to on average once per week. There were sufficient cloud-free scenes to map SCA over at least part of the basins up to 21 days per month, with 3 months having only two scenes sufficiently cloud free to process. In the upper Colorado and upper Grande, SCA peaked in February–March. Maxima were 1–2 months earlier in the lower Colorado. Averaged over a month, as much as 32% of the upper Colorado and 5.5% of the lower Colorado were snow covered. Snow cover persisted longest at higher elevations for both wet and dry years. Interannual variability in snow cover persistence reflected wet-dry year differences. Compared with an operational (binary) SCA product produced by the National Operational Hydrologic Remote Sensing Center, the current products classify a lower fraction of pixels as having detectable snow and being cloud covered (5.5% for SCA and 6% for cloud), with greatest differences in January and June in complex, forested terrain. This satellite-derived subpixel determination of snow cover provides the potential for enhanced hydrologic forecast abilities in areas of complex, snow-dominated terrain. As an example, we merged the SCA product with interpolated ground-based snow water equivalent (SWE) to develop a SWE time series. This interpolated, masked SWE peaked in April, after SCA peaked and after some of the lower-elevation snow cover had melted.
Urban, Topographic and Diurnal Effects on Rainfall in the St. Louis Region

Abstract Analyses were made of the summer rainfall distribution (June-August) in 17 areas within the METROMEX network in St. Louis region. These were selected to represent areas subject to various types and degrees of inadvertent weather modification, plus a no-effect (control) area. The purpose was to determine the magnitude and relative intensity of urban and topographic effects on rain enhancement. Results indicated the urban enhancement was greater than that associated with hills and river bluffs in the experimental region. The urban enhancement maximized northeast of the St. Louis urban-industrial complex where it was computed to be approximately 30–35%. The bluffs effect was calculated to be approximately 14%, and the hill effect was 9% for all rainstorms combined during the five summers. The urban and topographic enhancements were most pronounced in heavy storms, defined as those producing gage amounts of 25 mm or more. The enhancement maximized in June in the region of maximum urban effect, but oc...
Testing the groupthink model: Effects of promotional leadership and conformity predisposition

Two hypotheses derived from groupthink theory were tested in a laboratory study which included measures of the full range of symptoms of groupthink, symptoms of a poor decision process, and decision quality. The hypothesis that groups whose leaders promoted their own preferred solutions would be more likely to fall victim to groupthink than groups with nonpromotional leaders received partial support. Groups with promotional leaders produced more symptoms of groupthink, discussed fewer facts, and reached a decision more quickly than groups with nonpromotional leaders. The hypothesis that groups composed of members who were predisposed to conform would be more likely to fall victim to groupthink than groups whose members were not predisposed to conform received no support. It is suggested that groupthink research is hampered by measurement problems.
Model for growth of binary alloys with fast surface equilibration

We study a simple growth model for (d+1)-dimensional films of binary alloys in which atoms are allowed to interact and equilibrate at the surface, but are frozen in the bulk. The resulting crystal is highly anisotropic: Correlations perpendicular to the growth direction are identical to a d-dimensional two-layer system in equilibrium, while parallel correlations generally reflect the dynamics of an Ising system. For stronger in-plane interactions, the correlation volumes change from oblate to highly prolate shapes near a critical demixing or ordering transition. In d=1, the critical exponent z relating the scaling of the two correlation lengths varies continuously with the chemical interactions.
Cancer and non-cancer risk assessment : not so different if you consider mechanisms

Default risk assessment procedures use threshold models for non-carcinogens and a non-threshold model for carcinogens. This a priori distinction reflects the fact that the default procedures do not consider mechanisms of action of specific chemicals. When mechanisms are considered, the distinction is not necessary. Starting with the premise that the goal of risk assessment is to identify actual risk for specific chemicals, three major, generic components of the overall mechanism translating exposure into a response of regulatory interest are identified. These are the specific mechanisms linking (1) exposure with dose to target tissue, (2) target tissue dose with short-term responses such as cytolethality or mutation, and (3) short-term responses with ensuing long-term responses such as cancer or cirrhosis. (Short-term responses may be regulatory end points of interest, or they may be intermediate steps on the way to longer-term sequelae). On-going research on formaldehyde and chloroform is described to illustrate how these three components of the overall mechanism can be examined experimentally and used in specific models. The impact of mechanism-based risk assessment on uncertainty is also considered. Uncertainty is a function of the extent to which the model used for risk assessment misspecifies the actual mechanism of action for the chemical in question. There is a trade-off between (a) mechanism-based models that may reduce uncertainty but are expensive and time-consuming to develop and (b) default models that are not chemical-specific but can be used with minimal data sets. Experience with mechanism-based risk assessment may allow modification of default procedures to minimize this trade-off. A future default procedure for carcinogen risk assessment might allow specification of mode of action. For example, while DNA reactive-carcinogens would still be assumed to have linear low-dose risk, carcinogens acting through purely cytotoxic mechanisms might be assumed to have sharply non-linear or even threshold dose-response curves.
Functional distinctions between IMP dehydrogenase genes in providing mycophenolate resistance and guanine prototrophy to yeast

IMP dehydrogenase (IMPDH) catalyzes the rate-limiting step in the de novo synthesis of GTP. Yeast with mutations in the transcription elongation machinery are sensitive to inhibitors of this enzyme such as 6-azauracil and mycophenolic acid, at least partly because of their inability to transcriptionally induce IMPDH. To understand the molecular basis of this drug-sensitive phenotype, we have dissected the expression and function of a four-gene family in yeast called IMD1 through IMD4. We show here that these family members are distinct, despite a high degree of amino acid identity between the proteins they encode. Extrachromosomal copies of IMD1, IMD3, or IMD4 could not rescue the drug-sensitive phenotype of IMD2 deletants. When overexpressed, IMD3 or IMD4 weakly compensated for deletion of IMD2. IMD1 is transcriptionally silent and bears critical amino acid substitutions compared with IMD2 that destroy its function, offering strong evidence that it is a pseudogene. The simultaneous deletion of all four IMD genes was lethal unless growth media were supplemented with guanine. This suggests that there are no other essential functions of the IMPDH homologs aside from IMP dehydrogenase activity. Although neither IMD3 nor IMD4 could confer drug resistance to cells lacking IMD2, either alone was sufficient to confer guanine prototrophy. The special function of IMD2 was provided by its ability to be transcriptionally induced and the probable intrinsic drug resistance of its enzymatic activity.
Paravertebral approach to the brachial plexus: an anatomic improvement in technique

In the early 1920s, Kappis developed blocks of the spinal nerves at all levels of the vertebral column, including blocks of the the cervical and brachial plexis.1 Because the vertebral artery and vein are anterior to these nerves, he advocated a posterior rather than lateral approach. Probably due to penetration of the paraspinal extensor muscles of the neck, these blocks were painful and remained little used until Pippa’s 1990 report of a modified approach to the brachial plexus.2 We describe a modification of the techniques introduced by Kappis and Pippa, which minimizes the pain associated with this approach to the brachial plexus by inserting the needle between the levator scapulae and trapezius muscles.3 Secondarily we describe catheter insertion for continuous brachial plexus nerve block using a “stimulating catheter.”
IN VITRO COMPARISON OF FRAGMENTATION EFFICIENCY OF FLEXIBLE PNEUMATIC LITHOTRIPSY USING 2 FLEXIBLE URETEROSCOPES

ABSTRACT Purpose: Pneumatic lithotripsy has been shown to be an effective and safe intracorporeal lithotripsy modality for renal and ureteral calculi, capable of fragmenting stones of all compositions. We determined the in vitro stone fragmentation abilities of the 0.5 mm flexible pneumatic lithotripsy probe when inserted through the working channel of 2, 7.5Fr flexible ureteroscope designs (straight working channel and offset working channel at approximately 30 degrees from the long axis of the endoscope). The velocity and displacement of the pneumatic probe tip were also evaluated with the probe inserted through each endoscope. Materials and Methods: The 0.5 mm (1.5Fr) stainless steel probe was tested at 5 deflection angles, namely 0, 12, 24, 33 and 48 degrees, at a pneumatic pressure of 2.5 bar when inserted through the offset and straight working channel ureteroscopes. A noncontact optical laser system was used to measure or calculate the displacement and velocity of the 0.5 mm probe tip at each angle of deflection with the 2 ureteroscopes. Fragmentation at all deflection angles was assessed using plaster of Paris stone phantoms with the pneumatic device on continuous mode at 2.5 bar pressure for 30 seconds. Stones were weighed after each fragmentation cycle and the percent weight lost was determined. Comparisons were made between the 2 ureteroscopes at each angle. Results: Probe tip displacement was significantly better through the straight channel ureteroscope with 30% improvement at all angles tested compared to the offset channel. Moreover, a substantial decrement in tip displacement was noted as the angle of deflection increased regardless of the endoscope used. Conversely tip velocity was relatively unchanged throughout the study and it was equivalent from straight to offset channel measurements. Phantom stone fragmentation correlated inversely with the severity of the deflection angle. An approximately 80% loss of fragmentation ability was noted as the angle increased from 0 to 48 degrees. Although the pneumatic device performed better through the straight channel scope, a similar percent loss in fragmentation from 0 to 48 degrees was seen when using either endoscope. Conclusions: The flexible pneumatic 0.5 mm lithotripsy probe appears to be best used through a straight channel flexible ureteroscope, out performing use through the offset channel scope at all angles of deflection. Tip displacement and fragmentation ability were inversely related to the degree of active deflection as the angle increased from 0 to 48 degrees. Use of the flexible pneumatic probe to aid in managing renal or proximal ureteral calculi may be limited until an improved probe can be developed, allowing complete and unencumbered fragmentation throughout all angles of deflection.
Identifying and correcting Java programming errors for introductory computer science students

Programming in Java can be a daunting task for introductory students, one that is only compounded by the cryptic compiler error messages they see when they first start to write actual code. This article details a project conducted by faculty and advanced students in the creation of an educational tool for Java programming, called Expresso. This paper discusses some existing programming tools, explains their drawbacks, and describes why Expresso is different. We also include a detailed list of typical errors made by novice programmers, used in the construction of the Expresso tool.
The dynamics of planetary magnetospheres

Abstract Mercury, Earth, Jupiter, Saturn, Uranus, Neptune, and the moon, Ganymede, have presently-active internal dynamos while Venus, Mars, at least two of the Galilean moons, the Earth's moon, comets and asteroids do not. These active dynamos produce magnetic fields that have sufficient strength to stand off the pressure of the exterior plasma environment. Because of changes in these exterior plasma environments these magnetospheres are very dynamic. The jovian magnetosphere includes a strong time-varying energy source that adds to the dynamics of its magnetosphere and produces a quite different circulation pattern than that found at Earth and, presumably, Mercury. Not only intrinsic planetary magnetic fields produce magnetospheres but also unmagnetized planets. Venus, Mars and comets have induced magnetospheres associated with the solar wind interaction with their atmospheres. Cometary magnetospheres, parts of which can be remotely sensed, exhibit spectacular disruptions called tail disconnections. Even the atmosphereless bodies with weak magnetic fields can interact with the solar wind. Small magnetic anomalies on the moon and possibly asteroids cause weak deflections of the solar wind. The dynamics of these various magnetospheres provide a rich spectrum of behavior which we review herein.
New Numerical Procedure for Impedance Eduction in Ducts Containing Mean Flow

A new impedance eduction method is presented and validated against a benchmark method, and the effects of measurement uncertainty errors on the impedances educedwith this newmethod are assessed.Unique features of the newmethod include the following: 1) the upstream and downstream boundary conditions contain higher-order duct modes, 2) the impedance spectra of unique nonuniform test liners on opposite walls may be educed simultaneously, and 3) the measured data for the impedance eduction are acquired only at the source and duct termination planes. The validation exercise is performedwith a rigid-wall insert and a conventional liner over a range of frequencies and flowMach numbers in the NASALangleyResearchCenter’s grazing flow impedance tube. The primary conclusions of the study are that the impedance spectra of the rigid-wall insert and the conventional liner that were educed from the newmethod are in very good agreement with those that were educed by using the benchmarkmethod. However, the effects of measurement uncertainty on the educed impedance are greater at the lower frequencies and the higher Mach numbers for the newmethod. All indications are that this occurs because the newmethod 1) uses significantly less data to perform the impedance eduction than the benchmark and 2) is currently based on a rather crude approximation to the measured pressure gradient, which is more sensitive to the refractive effects of the boundary layer than the measured lower-wall pressure that is required in the benchmark method.
Vascular bubbles and droplets for drug delivery

Localized drug delivery has many potential benefits for a number of therapeutic applications. Microbubbles and microdroplets are potential vehicles for localized drug delivery. This article provides an overview of biofluid mechanics related to microbubbles and microdroplets, and reviews recent developments in their application for drug delivery. Particular attention is devoted to acoustically-activated microdroplets.
Separation of Spermatogenic Cell Types Using STA-PUT Velocity Sedimentation

Mammalian spermatogenesis is a complex differentiation process that occurs in several stages in the seminiferous tubules of the testes. Currently, there is no reliable cell culture system allowing for spermatogenic differentiation in vitro, and most biological studies of spermatogenic cells require tissue harvest from animal models like the mouse and rat. Because the testis contains numerous cell types--both non-spermatogenic (Leydig, Sertoli, myeloid, and epithelial cells) and spermatogenic (spermatogonia, spermatocytes, round spermatids, condensing spermatids and spermatozoa)--studies of the biological mechanisms involved in spermatogenesis require the isolation and enrichment of these different cell types. The STA-PUT method allows for the separation of a heterogeneous population of cells--in this case, from the testes--through a linear BSA gradient. Individual cell types sediment with different sedimentation velocity according to cell size, and fractions enriched for different cell types can be collected and utilized in further analyses. While the STA-PUT method does not result in highly pure fractions of cell types, e.g. as can be obtained with certain cell sorting methods, it does provide a much higher yield of total cells in each fraction (~1 x 10(8) cells/spermatogenic cell type from a starting population of 7-8 x 10(8) cells). This high yield method requires only specialized glassware and can be performed in any cold room or large refrigerator, making it an ideal method for labs that have limited access to specialized equipment like a fluorescence activated cell sorter (FACS) or elutriator.
The calibration of scanning monochromators for the measurement of absolute irradiance.

Certain approximations commonly used in the absolute calibration of a scanning monochromator are examined in terms of the response of the instrument to a monochromatic input. The absolute irradiance due to any spectral feature in the neighborhood of λ0 is commonly computed from the expression W = AB(λ0)/H(λ0), where A is the area of the spectral feature as recorded by the monochromator output trace, B(λ) is the spectral irradiance of a standard source, and H(λ) is the response of the monochromator to B(λ) when the monochromator corresponds to wavelength λ. As an example, approximations used in justifying such calculations are examined and applied to an Ebert 0.5-m monochromator. For the case chosen, the approximation is shown to be valid to an accuracy of 1.5% to 2%, depending upon assumptions made in the calculation. It is found that the most serious error for this example is introduced by changes in the sensitivity of the monochromator over a wavelength interval comparable with that of the spectral feature under investigation. A second source of error is found to be the change in the irradiance of the standard source over a wavelength interval comparable to the instrument resolving power.
No cofactor effect on equilibrium unfolding of Desulfovibrio desulfuricans flavodoxin.

Abstract Flavodoxins are proteins with an α/β doubly wound topology that mediate electron transfer through a non-covalently bound flavin mononucleotide (FMN). The FMN moiety binds strongly to folded flavodoxin ( K D =0.1 nM, oxidized FMN). To study the effect of this organic cofactor on the conformational stability, we have characterized apo and holo forms of Desulfovibrio desulfuricans flavodoxin by GuHCl-induced denaturation. The unfolding reactions for both holo- and apo-flavodoxin are reversible. However, the unfolding curves monitored by far-UV circular dichroism and fluorescence spectroscopy do not coincide. For both apo- and holo-flavodoxin, a native-like intermediate (with altered tryptophan fluorescence but secondary structure as the folded form) is present at low GuHCl concentrations. There is no effect on the flavodoxin stability imposed by the presence of the FMN cofactor (Δ G =20(±2) and 19(±1) kJ/mol for holo- and apo-flavodoxin, respectively). A thermodynamic cycle, connecting FMN binding to folded and unfolded flavodoxin with the unfolding free energies for apo- and holo-flavodoxin, suggests that the binding strength of FMN to unfolded flavodoxin must be very high ( K D =0.2 nM). In agreement, we discovered that the FMN remains coordinated to the polypeptide upon unfolding.
Comparative stimulatory and anti-mitotic effects of levamisole and its metabolite OMPI on thymocytes

Abstract The activity of 2-oxo-3-[2-mercaptoethyl]-5-phenylimidazolidine (OMPI), a possible active metabolite of levamisole, was compared in vitro to that of its parent compound levamisole. In cultures of Con A-stimulated murine thymocytes, OMPI was ten-fold more potent than levamisole, with peak responses at 10 μg/ml and 100 μg/ml, respectively. It shortened the cell cycle time comparably to levamisole; however, it was less effective in the recruitment of thymocytes into a proliferative pathway. OMPI was also found to be more potent than levamisole in inhibition of proliferation in the presence of 2-mercaptoethanol. OMPI, added for 3 h to a 2-mercaptoethanol-enhanced culture, was able to tra[ cells in metaphase as effectively as vinblastine or colcemid, but levamisole had no anti-mitotic activity. However, when levamisole was cultured with cells, and 2-mercaptoethanol added for the final 3 h, levamisole was as effective as OMPI in causing a mitotic block. High dose inhibition by OMPI or levamisole in the absence of 2-mercaptoethanol did not lead to mitotic blockage. These results suggest that, in vitro , levamisole is transformed into an agent with OMPI-like activity, and, in the presence of 2-mercaptoethanol, both OMPI and the levamisole transformation product can cause a mitotic block, presumably by effects on microtubules.
S-matrix method for the numerical determination of bound states.

A rapid numerical technique for the determination of bound states of a partial-wave-projected Schroedinger equation is presented. First, one needs to integrate the equation only outwards as in the scattering case, and second, the number of trials necessary to determine the eigenenergy and the corresponding eigenfunction is considerably less than in the usual method. As a nontrivial example of the technique, bound states are calculated in the exchange approximation for the e-/He+ system and l equals 1 partial wave.
Sex hormone receptor binding, progestin selectivity, and the new oral contraceptives

The desired biologic effect of pro9estins used in OCs is progestational activity. Undesired pharmacologic properties such as androgenic activity are not necessary for contraception and increase the potential for adverse effects. A selective progestin has progestational effects at relatively low concentrations or doses and androgenic effects at only relatively high concentrations or doses. The degree to which progestational activity is maximized and androgenic activity is minimized is a measure of a progestin's selectivity. The ratio of its affinity for progesterone receptors to its affinity for androgen receptors is the selectivity index. To minimize the androgenic side effects associated with the older progestins, the doses used in OCs have been reduced over the years. These dose reductions have decreased the potential for undesired androgenic effects but also have negatively affected cycle control. Three new progestins, norgestimate desogestrel, and gestodene, have relatively greater affinity for rogesterone receptors than for androgen receptors when compared with the older agents, permitting a reduction in androgenic side effects without the need for further dose reduction. Preclinical receptor-binding studies and animal pharmacologis studies have documented the higher selectivity indexes of these new progestins. Their higher ratios of progestational to androgenic activity provide the basis for the reduction in androgenic adverse effects observed with their clinical use.
Radio Frequency-Activated Nanoliposomes for Controlled Combination Drug Delivery

This work was conducted in order to design, characterize, and evaluate stable liposomes containing the hydrophobic drug raloxifene HCl (RAL) and hydrophilic doxycycline HCl (DOX), two potentially synergistic agents for treating osteoporosis and other bone lesions, in conjunction with a radio frequency-induced, hydrophobic magnetic nanoparticle-dependent triggering mechanism for drug release. Both drugs were successfully incorporated into liposomes by lipid film hydration, although combination drug loading compromised liposome stability. Liposome stability was improved by reducing the drug load and by including Pluronics® (PL) in the formulations. DOX did not appear to interact with the phospholipid membranes comprising the liposomes, and its release was maximized in the presence of radio frequency (RF) heating. In contrast, differential scanning calorimetry (DSC) and phosphorus-31 nuclear magnetic resonance (31P-NMR) analysis revealed that RAL developed strong interactions with the phospholipid membranes, most notably with lipid phosphate head groups, resulting in significant changes in membrane thermodynamics. Likewise, RAL release from liposomes was minimal, even in the presence of RF heating. These studies may offer useful insights into the design and optimization of multidrug containing liposomes. The effects of RAL on liposome characteristics and drug release performance underscore the importance of appropriate physical-chemical analysis in order to identify and characterize drug-lipid interactions that may profoundly affect liposome properties and performance early in the formulation development process.
Regulation of membrane type-matrix metalloproteinases.

Pericellular proteolysis is a hallmark of tumor cell metastasis. The membrane type (MT)-matrix metalloproteinases (MMPs) constitute a distinctive group of membrane-bound MMPs that are central mediators of surface proteolytic events that regulate tumor cell motility, metastasis and angiogenesis. As membrane-tethered proteases, the MT-MMPs exhibit unique regulatory mechanisms and interactions with metalloproteinase inhibitors and other relevant molecules. This review will focus on new emerging information on the mechanisms that regulate MT-MMP processing, activity and inhibition, and their significance for enzyme function in the tumor microenvironment.
Active and passive millimeter- and sub-millimeter-wave imaging

ABSTRACT We have developed several millimeter/submillimeter/terahertz systems to study active and passive imaging and associated phenomenology. Fo r measuring the transmission and scattering pr operties of materials, we have developed a dual rotary stage scattering system with active illumination an d a Fourier Transform spectrometer. For imaging studies, we have developed a system based on a 12-inch diameter raster-scanned mirror. By interchange of active sources and both heterodyne and bolometric detectors, this system can be used in a variety of active and passive configurations. The laboratory measurements are used as inputs for, and model calibration and validation of, a terahertz imaging system performance model used to evaluate different imaging modalities for concealed weapon identification. In this paper, we will present examples of transmission and scattering meas urements for common clothing as well as active imaging results that used a 640 GHz source and receiver. Keywords: terahertz, imaging, active, passive, millimeter-wav e, submillimeter-wave, transmi ssion, reflection, scattering
The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules

A micro-reactor system (approximately 0.5–1 mm inner diameter by 2–3 cm in length) coupled with photoionization mass spectrometry and matrix isolation/infrared spectroscopy diagnostics is described. Short residence time flow reactors (roughly ≤ 100 μs) combined with suitable diagnostic tools have the potential to allow observation of unimolecular decomposition processes with minimum interference from secondary reactions. However, achieving the short residence times desired requires very small micro-reactors that are difficult to characterise experimentally because of their size. In this article the benefits of using these micro-reactors are presented along with some details of the systems employed. This is followed by some general flow considerations and then some simple analyses to illustrate particular features of the flow. Finally, computational fluid dynamics simulations are used to explore the flow and chemical behaviour of the reactors in detail. Some findings include: (1) The reactor operates in th...
A general formulation of the theory of wire ropes

This paper presents a general formulation of the nonlinear and linear analysis of wire ropes. In the formulation, wires, strands, and wire ropes are all considered as a kind of identical structure characterized by seven stiffness and deformation constants, and as such they can be used, in the same way, as component elements in some layered general structures. Based on such a point of view, the general formulation thus developed can be used to analyze wire ropes of various complex cross sections, and to analyze simple wire strands as well.
Effects of endophyte infection on drought stress tolerance of Lolium perenne accessions from the Mediterranean region

Abstract Perennial ryegrass (Lolium perenne) is a cool-season grass species that is often infected by the leaf-inhabiting endophyte Neotyphodium lolii. This particular endophyte is asexual and has the potential to impact host survival, growth and reproduction. The objective was to assess the potential costs or benefits of endophyte infection on drought stress tolerance of native perennial ryegrass accessions originally collected from Italy, Morocco, Tunisia, and Turkey. Sixty infected (E+) individuals from each accession were planted in a greenhouse. Half of these individuals were treated with a systemic fungicide to eliminate the endophyte (E−). For two drought periods water was withheld for 10–14 days and then allowed a one week recovery period following each. In some accessions under drought, E+ plants had more tillers, greater tiller lengths, total dry mass and green shoot mass than E− plants, suggesting a positive effect of endophyte infection on host growth. Total tiller length and the number of tillers showed significant population × treatment × infection interactions for 4 of 6 populations. This work is one of the few that documents the effects of endophyte infection for a common forage grass species from wild populations native to its distributional range. The results demonstrate that endophyte infection can help ameliorate abiotic stress such as drought and there may be a selective advantage for grasses from certain Mediterranean regions.
Backbone and side-chain resonance assignments of the membrane localization domain from Pasteurella multocida toxin.

1H, 13C, and 15N chemical shift assignments are presented for the isolated four-helical bundle membrane localization domain (MLD) from Pasteurella multocida toxin (PMT) in its solution state. We have assigned 99 % of all backbone and side-chain carbon atoms, including 99 % of all backbone residues excluding proline amide nitrogens. Secondary chemical shift analysis using TALOS+ demonstrates four helices, which align with those observed within the MLD in the crystal structure of the C-terminus of PMT (PDB 2EBF) and confirm the use of the available crystal structures as templates for the isolated MLDs.
Hormonal and dim light effects in retinal photodamage.

—Exposure of albino rats to continuous visible dim light results in the rapid. but graded. loss of photoreceptor cells. The age at which albino rats are exposed to light influences the degree of photoreceptor damage. The severity of cell destruction per unit exposure time gradually increases in rats exposed at different ages from postweaning to adulthood, and by 8 weeks of age, reduction in the thickness of the outer nuclear layer (photoreceptor cell nuclei) is highly significant. The period of increasing susceptibility to light damage is coincident with the occurrence of sexual maturation, which suggests a relationship between photoreceptor destruction and the maturation of the pituitary gland-gonadal axis. To determine whether the absence of the pituitary gland and ovarian hormones influences photoreceptor damage, animals were either hypophysectomized or ovariectomized and exposed to continuous illumination for up to 45 days. The degree of photoreceptor destruction is significantly reduced in operated, as compared with sham-operated control, rats exposed to an identical light regimen. Small, physiologic doses of estradiol reverse the protective effects of ovariectomy, but larger, pharmacologic doses do not. Retinal damage is significantly enhanced by injection of pituitary homogenates during the light-exposure period and by transplantation of pituitary glands under the kidney capsule of rats in which the pituitary has been removed. Pituitary glands transplanted in this location produce high levels of prolactin, while other pituitary hormones are found at unusually low, and sometimes nonfunctional, levels. Prolactin administration to rats during the light exposure period effectively reverses the protection afforded by removal of the pituitary gland. Pituitary gland hormones as well as hormones from some of the pituitary target organs, appear to have a regulatory influence on the severity of light-induced photoreceptor damage in this species.