Dynamics of a Pair of Interacting Spins Coupled to an Environmental Sea

We solve for the dynamics of a pair of spins, coupled to each other and also to an environmental sea of oscillators. The environment mediates an indirect interaction between the spins, causing both mutual coherence effects and dissipation. This model describes a wide variety of physical systems, ranging from 2 coupled microscopic systems (eg., magnetic impurities, bromophores, etc), to 2 coupled macroscopic quantum systems. We obtain analytic results for 3 regimes, viz., (i) The locked regime, where the 2 spins lock together; (ii) The correlated relaxation regime (mutually correlated incoherent relaxation); and (iii) The mutual coherence regime, with correlated damped oscillations. These results cover most of the parameter space of the system.Comment: 49 pages, To appear in Int J. Mod. Phys.

State Dependence and Alternative Explanations for Consumer Inertia

For many consumer packaged goods products, researchers have documented a form of state dependence whereby consumers become "loyal" to products they have consumed in the past. That is, consumers behave as though there is a utility premium from continuing to purchase the same product as they have purchased in the past or, equivalently, there is a psychological cost to switching products. However, it has not been established that this form of state dependence can be identified in the presence of consumer heterogeneity of an unknown form. Most importantly, before this inertia can be given a structural interpretation and used in policy experiments such as counterfactual pricing exercises,alternative explanations which might give rise to similar consumer behavior must be ruled out. We develop a flexible model of heterogeneity which can be given a semi-parametric interpretation and rule out alternative explanations for positive state dependence such as autocorrelated choice errors, consumer search, or consumer learning.

Broadband, unpolarized repumping and clearout light sources for Sr+^+ single-ion clocks

Future transportable optical clocks require compact and reliable light sources. Here, broadband, unpolarized repumper and state clearout sources for Sr+ single-ion optical clocks are reported. These turn-key devices require no frequency stabilization nor external modulators. They are fiber based, inexpensive, and compact. Key characteristics for clock operation are presented, including optical spectra, induced light shifts and required extinction ratios. Tests with an operating single-ion standard show a clearout efficiency of 100%. Compared to a laser-based repumper, the achievable fluorescence rates for ion detection are a few tens of per cent lower. The resulting ion kinetic temperature is 1--1.5 mK, near the Doppler limit of the ion system. Similar repumper light sources could be made for Ca+ (866 nm) and Ba+ (650 nm) using semiconductor gain media.Comment: 4 pages, 6 figure

Framing Expectations in Early HIV Cure Research

Language used to describe clinical research represents a powerful opportunity to educate volunteers. In the case of HIV cure research there is an emerging need to manage expectations by using the term ‘experiment’. Cure experiments are proof-of-concept studies designed to evaluate novel paradigms to reduce persistent HIV-1 reservoirs, without any expectation of medical benefit

Interface Equations for Capillary Rise in Random Environment

We consider the influence of quenched noise upon interface dynamics in 2D and 3D capillary rise with rough walls by using phase-field approach, where the local conservation of mass in the bulk is explicitly included. In the 2D case the disorder is assumed to be in the effective mobility coefficient, while in the 3D case we explicitly consider the influence of locally fluctuating geometry along a solid wall using a generalized curvilinear coordinate transformation. To obtain the equations of motion for meniscus and contact lines, we develop a systematic projection formalism which allows inclusion of disorder. Using this formalism, we derive linearized equations of motion for the meniscus and contact line variables, which become local in the Fourier space representation. These dispersion relations contain effective noise that is linearly proportional to the velocity. The deterministic parts of our dispersion relations agree with results obtained from other similar studies in the proper limits. However, the forms of the noise terms derived here are quantitatively different from the other studies

Variations of crop canopy spectral reflectance measurements under changing sky conditions

The possibility of using reflectance data collected under both cloudy and sunny conditions is studied. Extrenle values of red and far-red reflectances measured directly over bare soil and crop canopies during intermittently cloudy conditions can differ by more than 100 percent and 60 percent, respectively. Eliminating the irradiance variations by using only data collected under sunny conditions reduced such variation to within 1 percent for bare soil and to within 8 percent and 20 percent for crop canopy red and far-red reflectances, respectively. In general, the reflectances measured under cloudy conditions with relatively constant irradiance values are constant and approximately 10 percent larger than the ones measured at similar sun angles during sunny conditions. This result is independent of the species and the spectral regions under study

Field spectrometer to measure percent ground coverage and leaf area index of agriculture crops

Measurement of percent ground cover (PGC) and leaf area index (LAI) are required for crop modelling, yield estimation and for ground truth data in remote sensing studies. An instrument which traverses on a track above a crop and continuously measures the ratio of incident and reflected radiation at various wavelengths was developed and tested. Spectral irradiance and reflectance measurements were made at four wavelengths (647.8, 675.5, 739.9, 790.4 nm) at eight stages of growth of wheat and barley for three crop densities. Data provided information on the relations between spectral properties at selected wavelength and leaf area expansion at different growth stages. The spectral data were highly correlated with leaf area index measurements

Human Chromosomes: Evaluation of Processing Techniques for Scanning Electron Microscopy

Methods for scanning electron microscopy (SEM) of chromosomes have been developed in the last two decades. Technical limitations in the study of human chromosomes, however, have hindered the routine use of SEM in clinical and experimental human cytogenetics. We compared different methodologies, including metal impregnation, air drying and specimen coating. SEM preparation of human chromosomes in which osmium impregnation is mediated by tannic acid, yielded more reproducible results when compared with osmium impregnation protocols previously described. The level of osmium impregnation was systematically evaluated by imaging chromosomes in the backscattering mode. Critical point drying and a light gold-palladium coating were essential for appropriate secondary electron imaging of chromosomes. With this method, and in a preliminary quantitative analysis, we show that our SEM technique is mere sensitive than light microscopy for the detection of aphidicolin-induced fragile sites. This technical approach is useful for chromosomal studies requiring resolution higher than that obtained by light microscopy. Also, it allows the use of clinical and archival chromosomal samples prepared by routine cytogenetic techniques

Field spectrometer to measure percent ground coverage and leaf area index of agriculture crops [remote sensing]

Measurement of percent ground cover (PGC) and leaf area index (LAI) are required for crop modelling, yield estimati-on and for ground truth data in remote sensing studies. An instrument which traverses on a track above a crop and continuously measures the ratio of incident and reflected radiation at various wavelengths was developed and tested. Spectral irradiance and reflectance measurements were made at four wavelengths (647.8 , 675.5 , 739.9 , 790.4 nm) at eight stages of growth of wheat and barley for three crop densities. Data provided information on the relations between spectral properties at selected wavelength and leaf area expansion at different growth stages. The spectral data were highly correlated with leaf area index measurements

Solitary fibrous tumor arising in the mesentery: a case report

<p>Abstract</p> <p>Background</p> <p>Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm usually found in the pleura, soft tissues and visceral organs. We describe one case arising in the mesentery, which is an exceptional localization.</p> <p>Case presentation</p> <p>A 71-year-old man was referred to our establishment for a painless hypogastric mass. Further investigation revealed a vascular tumor, which was resected <it>en bloc</it>. Pathological findings confirmed solitary fibrous tumor of the mesentery.</p> <p>Conclusion</p> <p>This is the second case of solitary fibrous tumor of the small intestine mesentery ever reported. It was managed by <it>en bloc </it>resection and close follow up considering the high risk of recurrence. Investigation should be made regarding the use of adjuvant systemic therapy to improve long-term survival for these patients.</p