404 research outputs found
A new method for the separation of androgens from estrogens and for the partition of estriol from the estrone-estradiol fraction: with special reference to the identification and quantitative microdetermination of estrogens by ultraviolet absorption spectrophotometry
It is recognized generally that a qualitative and quantitative knowledge of the excretion pattern of the urinary estrogens is one index to an understanding of the functional activity of the ovary and adrenal cortex. Obviously, such determinations may be useful also in evaluating the normal and abnormal functions of other physiologically related endocrine glands as well as of organs like the liver and kidneys. The clinical applications of these data are self-evident.
Various attempts have been made to circumvent the notoriously inaccurate values which have been obtained for the urinary estrogens by a variety of bioassay methods and calorimetric techniques (1, 2). The acknowledged shortcomings of these methods have led us to investigate the application of ultraviolet absorption spectrophotometry to the quantitative determination of the urinary estrogens in an attempt to develop an objective physical method for their accurate determination. It is known that the infra-red portion of the spectrum yields more differentially characteristic curves, but those of the ultraviolet range are more readily obtainable, and consequently better adapted to clinical use.
This communication is concerned with studies of the following aspects of the problem: (1) spectrophotometric identification and quantitative micro determination of crystalline estrogens; (2) detection by spectrophotometric assay of gross errors in current methods for extraction and partition of estrogens; (3) studies on the ultraviolet absorption of substances comprising the background material; (4) separation of the phenolic estrogens from the so called neutral steroid fraction; (5) separation of urinary estrogens from other urinary phenolic substances by steam distillation; (6) micro-Girard separation of estrone from estradiol; (7) an essentially new method for the extraction and partition of crystalline estrone, estradiol, and estriol, and their quantitative assay by ultraviolet spectrophotometry
Design requirements for laminar airflow clean rooms and devices
Laminar airflow and airborne contamination control concepts with clean room specifications and laminar flow facility design
Critical spin-flip scattering at the helimagnetic transition of MnSi
We report spherical neutron polarimetry (SNP) and discuss the spin-flip
scattering cross sections as well as the chiral fraction close to the
helimagnetic transition in MnSi. For our study, we have developed a
miniaturised SNP device that allows fast data collection when used in small
angle scattering geometry with an area detector. Critical spin-flip scattering
is found to be governed by chiral paramagnons that soften on a sphere in
momentum space. Carefully accounting for the incoherent spin-flip background,
we find that the resulting chiral fraction decreases gradually above the
helimagnetic transition reflecting a strongly renormalised chiral correlation
length with a temperature dependence in excellent quantitative agreement with
the Brazovskii theory for a fluctuation-induced first order transition.Comment: 5 pages, 3 figure
Neon Lights Up a Controversy: the Solar Ne/O Abundance
The standard solar model was so reliable that it could predict the existence
of the massive neutrino. Helioseismology measurements were so precise that they
could determine the depth of the convection zone. This agreement between theory
and observation was the envy of all astrophysics -- until recently when
sophisticated three-dimensional hydrodynamic calculations of the solar
atmosphere reduced the metal content by a factor of almost two. Antia & Basu
(2005) suggested that a higher value of the solar neon abundance, Ne/O = 0.52,
would resolve this controversy. Drake & Testa (2005) presented strong evidence
in favor of this idea from a sample of 21 Chandra stars with enhanced values of
the neon abundance, Ne/O = 0.41. In this paper, we have analyzed solar active
region spectra from the archive of the Flat Crystal Spectrometer on Solar
Maximum Mission, a NASA mission from the 1980s, as well as full-Sun spectra
from the pioneering days of X-ray astronomy in the 1960s. These data seem
consistent with the standard neon-to-oxygen abundance value, Ne/O = 0.15
(Grevesse & Sauval 1998). If these results prove to be correct, than the
enhanced-neon hypothesis will not resolve the current controversy.Comment: submitted to ApJ Letter
Efficacy of Online Training for Improving Camp Staff Competency
Preparing competent staff is a critical issue within the camp community. This quasi-experimental study examined the effectiveness of an online course for improving staff competency in camp healthcare practices among college-aged camp staff and a comparison group (N = 55). We hypothesized that working in camp would increase competency test scores due to opportunities for staff to experientially apply knowledge learned online. Hierarchical linear modeling was used to analyse the cross-level effects of a between-individuals factor (assignment to experimental or comparison group) and within-individual effects of time (pre-test, post-test #1, and post-test #2) on online course test scores. At post-test #2, the difference in average test scores between groups was ~30 points, with the treatment group scoring lower on average than the comparison group. Factors that may have influenced these findings are explored, including fatigue and the limited durability of online learning. Recommendations for research and practice are discussed
Linearly polarized GHz magnetization dynamics of spin helix modes in the ferrimagnetic insulator CuOSeO
Linear dichroism -- the polarization dependent absorption of electromagnetic
waves -- is routinely exploited in applications as diverse as structure
determination of DNA or polarization filters in optical technologies. Here
filamentary absorbers with a large length-to-width ratio are a prerequisite.
For magnetization dynamics in the few GHz frequency regime strictly linear
dichroism was not observed for more than eight decades. Here, we show that the
bulk chiral magnet CuOSeO exhibits linearly polarized magnetization
dynamics at an unexpectedly small frequency of about 2 GHz. Unlike optical
filters that are assembled from filamentary absorbers, the magnet provides
linear polarization as a bulk material for an extremely wide range of
length-to-width ratios. In addition, the polarization plane of a given mode can
be switched by 90 via a tiny variation in width. Our findings shed a
new light on magnetization dynamics in that ferrimagnetic ordering combined
with anisotropic exchange interaction offers strictly linear polarization and
cross-polarized modes for a broad spectrum of sample shapes. The discovery
allows for novel design rules and optimization of microwave-to-magnon
transduction in emerging microwave technologies.Comment: 20 pages, 4 figure
The Cooperative Extension Program Development Model: Adapting to a Changing Context
For over 100 years, Cooperative Extension in the United States has used a consistently articulated program development model including program planning, design and implementation, and evaluation that involves stakeholders in the process. This issue of the Journal of Human Sciences and Extension examines the history and evolution of the program development model for successful Extension work and adaptations to that model that have emerged due to the changing educational context. This issue provides information on how elements of the model have changed over the last 100 years; delves into contemporary issues and challenges; and provides important analysis, implications, lessons learned, and applications for current and future success of Extension programs. In this article, we provide a definition of a program, the rationale for using a program development model in Extension work, the Extension Program Development Model, other program development models used by Extension professionals, and the changing context surrounding Extension work that impacts the Program Development Model
Emergent Lorentz symmetry with vanishing velocity in a critical two-subband quantum wire
We consider a quantum wire with two subbands of spin-polarized electrons in
the presence of strong interactions. We focus on the quantum phase transition
when the second subband starts to get filled as a function of gate voltage.
Performing a one-loop renormalization group (RG) analysis of the effective
Hamiltonian, we identify the critical fixed-point theory as a conformal field
theory having an enhanced SU(2) symmetry and central charge 3/2. While the
fixed point is Lorentz invariant, the effective 'speed of light' nevertheless
vanishes at low energies due to marginally irrelevant operators leading to a
diverging critical specific heat coefficient.Comment: 4 pages, 3 figures, minor changes, published versio
Universal signatures of the metamagnetic quantum critical endpoint: Application to CeRu2Si2
A quantum critical endpoint related to a metamagnetic transition causes
distinct signatures in the thermodynamic quantities of a compound. We argue
that, irrespective of the microscopic details of the considered material, the
diverging differential susceptibility combined with the Ising symmetry of the
endpoint give rise to a number of characteristic metamagnetic phenomena. In the
presence of a magnetoelastic coupling, one finds a correspondence of
susceptibility, magnetostriction and compressibility and, as a result, a
pronounced crystal softening, a diverging Grueneisen parameter, a sign change
of thermal expansion alpha(H), and a minimum in the specific heat coefficient
gamma(H). We illustrate these signatures and their relation on the metamagnetic
crossover at 8 T in the prototypical heavy-fermion system CeRu2Si2.Comment: 8 pages, 6 figures, v2: changed title, minor modification
Multiscale quantum criticality: Pomeranchuk instability in isotropic metals
As a paradigmatic example of multi-scale quantum criticality, we consider the
Pomeranchuk instability of an isotropic Fermi liquid in two spatial dimensions,
d=2. The corresponding Ginzburg-Landau theory for the quadrupolar fluctuations
of the Fermi surface consists of two coupled modes, critical at the same point,
and characterized by different dynamical exponents: one being ballistic with
dynamical exponent z=2 and the other one is Landau-damped with z=3, thus giving
rise to multiple dynamical scales. We find that at temperature T=0, the
ballistic mode governs the low-energy structure of the theory as it possesses
the smaller effective dimension d+z. Its self-interaction leads to logarithmic
singularities, which we treat with the help of the renormalization group. At
finite temperature, the coexistence of two different dynamical scales gives
rise to a modified quantum-to-classical crossover. It extends over a
parametrically large regime with intricate interactions of quantum and
classical fluctuations leading to a universal T-dependence of the correlation
length independent of the interaction amplitude. The multiple scales are also
reflected in the phase diagram and in the critical thermodynamics. In
particular, we find that the latter cannot be interpreted in terms of only a
single dynamical exponent: whereas, e.g., the critical specific heat is
determined by the z=3 mode, the critical compressibility is found to be
dominated by the z=2 fluctuations.Comment: 15 pages, 6 figures; (v2) RG implementation with arbitrary dynamical
exponent z, discussion on fixed-points adde
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