Search

A model set of equations including Brownian rotation dynamics is proposed to investigate the role of rotation on the drift velocity of nanorods in the direction of an external field (such as electrical). Both inertial and non-inertial Brownian rotation are considered and the more realistic non-inertial shows more correlation between the rotational and translational motion. The average drift velocity is computed from the spatial trajectory for each path and the ensemble average and its confidence interval are computed from the average of 300 trajectories. The key parameter for the trajectories is the maximum rotational stopping distance, θSt. For a value of about 0.6 radians and a length of about 60 nm, the nanorod velocity is midway between the limiting value for the large and small value of θSt. The reduced velocity is found to depend on the length of the nanorod but not the diameter. A method of estimating the 3D observed mobility from the 1D simulations based on the reduced velocity is proposed. The experimental results of Gopalakrishnan et al. (2015) for 200 nm gold nanorods are consistent with an enhancement from rotation coupling for the gold nanorods ≥ 200 nm long in the free molecule limit. The effect of an elastic collision boundary condition is also considered.

Dynamic Spectrum Access (DSA) promises to be a shared spectrum technology that can alleviate the artificial spectrum crunch created by the static allocation of spectrum. There have been many studies on DSA systems in the literature. However, most of them are analyzed using simulation studies rather than analytical modeling. Analytical models are useful in evaluating performance of such systems quickly and easily. In this paper, we present an analytical model of an opportunistic DSA system. Using an alternating renewal process to represent primary user traffic of the DSA system and applying theory from survival analysis and stochastic process, we derive an expression to compute the white space utilization (WSU) of a DSA system for a general distribution of idle durations of primary traffic. Taking the exponential distribution as an example, we validate our analytical model by comparing its results to results obtained from two simulation experiments. One experiment uses idle durations generated from pseudorandom variates and the other uses data collected from a real Long-Term Evolution (LTE) system whose idle duration distribution is approximately exponential. Our analytical WSU results match closely with those from the first experiment and match reasonably well with those obtained from the second experiment.

The theoretical drift velocity of a randomly oriented nonspherical aerosol particles in an external field has been previously computed both in the limit of slow rotation and in the limit of fast rotation but not in the intermediate interval. The low rotation limit has been widely used to calculate the drift velocity for a range of nonspherical particles. The fast rotation limit, which is equivalent to the projected area method, has been used for molecular ions and agglomerates. A 1-D model equation containing the particle acceleration and an orientation dependent friction coefficient is proposed to predict the drift velocity between the two limits. This model has the essential physical phenomena without the complications of the 3-D treatment of the combined translation and rotation behavior. As an example, the drift velocity is computed for model parameters based on the friction tensor and rotational diffusion coefficient for circular cross section nanorods in the free molecular limit. For a momentum accommodation coefficient of 0.9 and a particle density of 1000 kg/m 3 , the largest percent deviation from the low rotation velocity limit is 14% and the deviation is at most 1% for nanorods of any length for diameters of 20 nm diameter or larger. Much larger changes in the velocity ratio are shown to occur if the momentum accommodation coefficient is reduced. Also, examples are given where the dimensionless rotation rate increases by about a factor of 7 from either a change in density or a change in the mean free path of the background gas. The results of recent experiments and model calculation of the collision cross section and mobilities of large molecular ions are discussed in regard to our model predictions on the effect of rotation on the drift velocity.

Background: Palliative care in Guatemala has received limited attention and research, resulting in an inadequate understanding of the needs of Guatemalans at the end-of-life (EOL). Guatemala ranks at the bottom of the Latin American Association for Palliative Care Index (Pastrana, Torres-Vigil, & DeLima, 2014). Women in the community have been identified as having an important spiritual role during EOL (Malcom, 2003; Miranda, 2007). Purpose: To understand EOL decision making, family involvement, and cultural/spiritual practices of rural Guatemalans. Methods: We conducted interviews with six Guatemalan families and one community leader in Spanish using a structured interview guide. Responses were translated into English and data was interpreted using content analysis. Findings: Relief from Suffering was the over-arching theme found through three support systems: the family, community rezadora, and priest. The family’s role was one of listening, making decisions, and providing love and care for the dying person. The community rezadora, a lay spiritual leader, was called upon to sing prayers and prepare the home altar, comforting the family and community. The priest’s role included the traditional sacraments. Physicians had some presence in EOL care, whereas nurses had no presence. Conclusions: International EOL training programs with Guatemalan nurses and families may be a valuable next step. Palliative nursing care in the US should consider incorporating cultural partners, such as the community rezadora. Further research on the role of rezadoras in the US would increase understanding of Guatemalan beliefs and practices. References Malcolm, T. (2003). Creating sacred space. National Catholic Reporter. Retrieved from http://natcath.org/NCR_Online/archives2/2003d/111403/111403k.htm Miranda, I. (2007). Faith formation with Hispanic/Latino families. Lifelong Faith, 1(2), 21-29. Retrieved from http://www.lifelongfaith.com/uploads/5/1/6/4/5164069/lifelong_faith_journal_1.2.pdf Pastrana,T., Torres-Vigil, I., & DeLima, L. (2014). Palliative care development in Latin America: an analysis using macro indicators. Palliative Medicine, 28(10), 1231-1238. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/24925578

In this study, we design and implement two algorithms for dynamic spectrum access that are based on survival analysis. They use a non-parametric estimate of the cumulative hazard function to predict the remaining idle time available for secondary transmission subject to the constraint of a preset probability of successful completion. In addition to theoretical performance analysis of the algorithms, we evaluate them using data collected from a long term evolution band to model primary user activity to demonstrate their effectiveness in real-world scenarios, even at fine time scales. The algorithms are run in different configurations, i.e., they are trained and run on a few combinations of data sets. Our results show that as long as the cumulative hazard functions are fairly similar across datasets, the algorithms can be trained on one dataset and run on that of another without any significant degradation of performance. The algorithms achieve fairly high white space utilization and have a measured probability of interference that is at or below the preset threshold.

In this paper, it is shown under conditions associated with the moment problem that a sequence of product moments uniquely determines a conditional expectation of two random variables. Then, a numerical procedure is derived to reconstruct a conditional expectation in terms of a sequence of its product moments.

In this study, we design and implement two algorithms for dynamic spectrum access (DSA) that are based on survival analysis. They use a non-parametric estimate of the cumulative hazard function to predict the remaining idle time available for secondary transmission subject to the constraint of a preset probability of successful completion. To show that the algorithms are effective in real-world scenarios even at fine time scales, we evaluate their performance using data collected from an LTE band to model primary user activity. The algorithms are run in different configurations, i.e., they are trained and run on a few combinations of data sets. Our results show that as long as the cumulative hazard functions are fairly similar across datasets, the algorithms can be trained on one day's dataset and run on that of another day's without any significant degradation of performance. The algorithms achieve fairly high white space utilization and have a measured probability of interference which always stays below the preset threshold.

Curve registration problems in data analysis and computer vision can often be reduced to the problem of matching two functions defined on an interval. Dynamic Programming (DP) is an effective approach to solve this problem. In this paper, we propose a DP algorithm that runs in O(N) time to compute optimal diffeomorphisms for elastic registration of curves with N nodes. This algorithm contrasts favorably with other DP algorithms used for this problem: the commonly used algorithm of quadratic time complexity, and the algorithm that guarantees a globally optimal solution with O(N4) time complexity. Key to our computational efficiency is the savings achieved by reducing our search space, focusing on thin strips around graphs of estimates of optimal diffeomorphism. Estimates and strips are obtained with a multigrid approach: an optimal diffeomorphism obtained from a lower resolution grid using DP is progressively projected to ones of higher resolution until full resolution is attained. Additionally, our DP algorithm is designed so that it can handle nonuniformly discretized curves. This enables us to realize further savings in computations, since in the case of complicated curves requiring large numbers of nodes for a high-fidelity representation, we can distribute curve nodes adaptively, focusing nodes in parts of high variation. We demonstrate effectiveness of our DP algorithm on several registration problems in elastic shape analysis, and functional data analysis.

At 450mm wafer area, the first Cu BEOL module process was demonstrated with a single damascene structure using low-k ILD, TiN metal hard mask and guided 20nm half-pitched lamella BCP DSA patterning. It showed the potential opportunities, technical feasibility and further challenges for coming needs for 450mm equipment.

In this article an accurate confidence interval is derived when the results of a small number of possibly biased experimental methods are combined for the determination of an unknown quantity called the consensus mean. ANOVA and a simple hierarchical Bayesian analysis of variance with locally uniform priors result in confidence intervals too wide for precision metrology. Often when deciding on experimental methods, scientists choose methods in such a way that the truth lies between the extremes of the method means. Combining this additional information with experimental data, an interval more accurate than the ANOVA interval and the simple hierarchical Bayesian interval is obtained. The estimate obtained falls within the ISO guidelines, and the mean and standard deviation used to derive the confidence interval are shown to be the posterior mean and variance of a fully Bayesian procedure.

The measurement of the amount of water in oils is of significant economic importance to the industrial community, particularly to the electric power and crude oil industries. The amount of water in transformer oils is critical to their normal function and the amount of water in crude oils affects the cost of the crude oil at the well head, the pipeline, and the refinery. Water in oil Certified Reference Materials (CRM) are essential for the accurate calibration of instruments that are used by these industries. Three NIST Standard Reference Materials (SRMs) have been prepared for this purpose. The water in these oils has been measured by both coulometric and volumetric Karl Fischer methods. The compounds (such as sulfur compounds) that interfere with the Karl Fischer reaction (interfering substances) and inflate the values for water by also reacting with iodine have been measured coulometrically. The measured water content of Reference Material (RM) 8506a Transformer Oil is 12.1+/-1.9 mg kg(-1) (plus an additional 6.2+/-0.9 mg kg(-1) of interfering substances). The measured water content of SRM 2722 Sweet Crude Oil, is 99+/-6 mg kg(-1) (plus an additional 5+/-2 mg kg(-1) of interfering substances). The measured water content of SRM 2721 Sour Crude Oil, is 134+/-18 mg kg(-1) plus an additional 807+/-43 mg kg(-1) of interfering substances. Interlaboratory studies conducted with these oil samples (using SRM 2890, water saturated 1-octanol, as a calibrant) are reported. Some of the possible sources of bias in these measurements were identified, These include: improperly calibrated instruments, inability to measure the calibrant accurately, Karl Fischer reagent selection, and volatilization of the interfering substances in SRM 2721.

The time that it takes an occupant population to reach safety when descending a stairwell during building evacuations is typically estimated by measureable engineering variables such as stair geometry, speed, density, and pre-observation delay. In turn, engineering models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. As part of a program to better understand occupant movement and behavior during building emergencies, the Engineering Laboratory at the National Institute of Standards and Technology has collected stair movement data during fire drill evacuations of office and residential buildings. These data collections are intended to provide a better understanding of this principal building egress feature and develop a technical foundation for future codes and standards requirements. Fire drill evacuation data has been collected in 14 buildings (11 office buildings and 3 residential buildings) ranging from six to 62 stories in height that included a range of stair widths and occupant densities. A total of more than 22,000 individual measurements are included in the data set. This paper provides details of the data collected and an analysis of the data. The intention is to better understand movement during stairwell evacuations and provide data to test the predictive capability of building egress models. While mean and standard deviation of the distribution of movement speeds in the current study of 0.44 m/s ± 0.19 m/s are observed to be quite similar to the range of values in previous studies, mean local movement speeds as occupants traverse down the stairs are seen to vary widely within a given stairwell, ranging from 0.10 m/s ± 0.008 m/s to 1.7 m/s ± 0.13 m/s. These data provide confirmation of the adequacy of existing literature values typically used for occupant movement speeds and provide updated data for use in egress modeling or other engineering calculations.

Conformance testing is considered from a statistical point of view. An s-confidence interval is found for the reliability that an implementation of a software package complies with specifications of a standard. Determination of whether it complies depends on a conformance test, which is written directly from the standard. Although the conformance test is written directly from the standard it does not test all possible software parameter-settings that invoke the standard. Thus, statistical inference is necessary. A general s-confidence interval for the reliability is given when the specification requires that the implementation passes all the tests in the conformance test suite. The conformance test is made of disjoint homogeneous partitions. The failure probability of the software is based on a weighted linear combination of the partition failure probabilities. An example is included.

A method to determine arbitrary moments of aerosol size distributions from differential mobility analyzer measurements has been proposed. The proposed method is based on a modification of the algorithm developed by Knutson and Whitby to calculate the moments of electrical mobility distributions. For this modification, the electrical mobility and the charge distribution have been approximately expressed by power functions of the particle diameter. To evaluate the validity of the approximation, we have carried out numerical simulations for typical size distributions. We have found that for typical narrowly distributed aerosols such as polystyrene latex particles and particles that arise in the tandem differential mobility analyzer configuration, the distribution parameters can be accurately determined by this method. For a log-normally distributed aerosol, the accuracy of the distribution parameters determined by this method has been evaluated as a function of the geometric standard deviation. We have also ...

The calculus of residues is one of the many beautiful tools that comes out of the field of complex variables. The calculus of residues is applied, together with the inversion formula for characteristic functions, to compute the non-gamma probability density function for the sum of gamma variates with different shape parameters. The distribution of the sum of gamma variates is needed in problems in statistical inference, as well as stochastic processes. This derivation seems more elegant than previous methods for deriving the density function of such a sum. Furthermore, the numerical computation is straightforward, especially in any symbolic computer language.

Lifetime data on stress rupture of copper joints made with certain lead-free solders suggest that specimens under 'stress below a certain threshold' run indefinitely without failure. A commonly used model for this type of data is the Weibull inverse power law that includes a threshold. If the threshold is unknown, this estimation problem presents several difficulties for statistical treatment. The largest problem is: as the threshold approaches the minimum of the data (stresses) the likelihood approaches infinity, thus there is no global maximum. A modified maximum likelihood approach, in the spirit of Cohen is used to resolve this problem. The method is similar to Cohen's, but interesting differences occur for censored data. The results show that modifications of the Cohen method produce estimates of the parameters in the Weibull inverse power threshold law.

The transfer function for the Differential Mobility Analyzer (DMA) is derived based on particle trajectories for both nondiffusing particles and diffusing particles. The effect of particle diffusion is assessed by using a Monte-Carlo method for particles of sizes 1, 3, 10, 30, and 100 nm. This approach includes both the effect of wall losses and axial diffusion. The range of validity of the Stolzenburg analysis is assessed by comparing his transfer function, the peak of his transfer function, and its dimensionless width with similar calculations based on the Monte-Carlo. For particle sizes smaller than 10 nm, the Monte-Carlo method indicates large wall losses, which result in a reduction in the peak of the transfer function by as much as a factor of 10 to 30, sensitivity to the flow-field, and skewness of the transfer function. It is shown that Stolzenburg's approximate formula for the standard deviation of the width of the transfer function agrees with Monte-Carlo simulations for particle sizes of 3 nm a...

English This article analyses trends in public employment in Britain since the I970s, comparing them with the postwar pattern of trends up to that period. The most striking development has been the dramatic decline in public employment in ‘industrial’ activities through the reduction of staff in existing industries and, since 1979, the continuing privatisation or contracting out of industrial activities. Decline elsewhere has been less dramatic and far from universal, and is in part due to the transfer of activities to a nominally private, but government-funded and regulated, quasi-public sector. Evidence for a move towards a ‘post-modern’ structure of public employment is mixed. There has been a move towards contracting and quasi-contracting, but in many cases this is a different means of transmitting bureaucratic regulation. There has been a changing relative distribution towards more part-time and casual work, with a heavy gender bias. Britain does seem to be special among OECD countries in the sharp decline in general government employment in relation to total employment since the late 1980s, but this is largely due to the removal of some education functions from local government to nominally private bodies, and the reclassification of most health service employees.

The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health (NIH), has developed a Standard Reference Material (SRM) to support technology development in metabolomics research. SRM 1950 Metabolites in Human Plasma is intended to have metabolite concentrations that are representative of those found in adult human plasma. The plasma used in the preparation of SRM 1950 was collected from both male and female donors, and donor ethnicity targets were selected based upon the ethnic makeup of the U.S. population. Metabolomics research is diverse in terms of both instrumentation and scientific goals. This SRM was designed to apply broadly to the field, not toward specific applications. Therefore, concentrations of approximately 100 analytes, including amino acids, fatty acids, trace elements, vitamins, hormones, selenoproteins, clinical markers, and perfluorinated compounds (PFCs), were determined. Value assignment measurements were performed by NIST and the Centers for Disease Control and Prevention (CDC). SRM 1950 is the first reference material developed specifically for metabolomics research.

Image cytometry has emerged as a valuable in vitro screening tool and advances in automated microscopy have made it possible to readily analyze large cellular populations of image data. The purpose of this paper is to illustrate the viability of using cell shape to test equality of cell populations based on image data. Shape space theory is reviewed, from which differences between shapes can be quantified in terms of geodesic distance. Several multivariate nonparametric statistical hypothesis tests are adapted to test equality of cell populations. It is illustrated that geodesic distance can be a better feature than cell spread area and roundness in distinguishing between cell populations. Tests based on geodesic distance are able to detect natural perturbations of cells, whereas Kolmogorov-Smirnov tests based on area and roundness are not.

The conventional industrial practice to correct (recalibrate) measuring instruments according to a fixed schedule (calibration interval) may waste money when the schedule is too tight or may provide a false sense of control when the schedule is too relaxed. Also, this approach may not generate data on real-time measurement errors that are crucial to draw management's attention to measurement concerns. We propose that the measurement process be interrupted according to an economically sensible schedule to check (interim test) the real-time errors with well-characterized check standards. When the observed error with the check standard exceeds an economic control limit, the measuring instrument should be corrected; otherwise correction is not needed. The proposed approach to limit the uncertainty of a measurement process is simple, sensible and generic. More important, it saves money by limiting the loss due to measurement error and the cost of control.