1,784 research outputs found
The White Roseâs Resistance to Nazism: The Influence of Friedrich Nietzsche
The White Rose was a non-violent resistance organization founded by students in Munich during the Second World War. Many scholars argue that religion influenced the group the most, but an analysis of their leaflets and correspondences highlights the influence that Friedrich Nietzsche had on the organization. Members of the White Rose, particularly Hans and Sophie Scholl, solidified their commitment to opposing Nazism by reading and discussing Friedrich Nietzsche. Nietzscheâs ideas shaped the foundational beliefs of the White Rose, including their belief that Germans could no longer ignore the crimes of the Nazi State. From 1942 to 1943, the White Rose anonymously distributed leaflets in Germany in an attempt to reach out to the German people and open their eyes to Nazi atrocities. By analyzing these leaflets, as well as journal entries and letters from the Hans and Sophie Scholl, it becomes quite evident that Nietzscheâs ideas on the âGood and Evil Dichotomyâ, the âHerd Mentalityâ, the âHigher Manâ, and âThe Shadowsâ are prevalent within the organizations writings. Through these ideas the White Rose attempted to use their leaflets to empower the German people to see where Hitler fit in the âGood and Evil Dichotomyâ, break from the âHerd Mentalityâ, find their âHigher Manâ, and escape from the suffocating grasp of âThe Shadowsâ to free not only themselves, but Germany as a whole
Point discharge in atmospheric electricity
Investigations of the current from an earth-connected point 0.002 cm in diameter, supported by masts at heights of 20m, 27m end 34m are described. Simultaneous measurements of the potential gradient at the ground to windward of the point, and wind speed at the point, indicate that the current can be represented by the equation I = K(W + C) (F - M) where I is the point discharge current in mioroamps W the wind speed in metres per second F the potential gradient in volts per metre M the onset value of the potential gradient (200 v/m at 20m, 135 v/m at 27m, l00 v/m at 34m) C and K are constants (C = 4 m/s and K = 2.56 x 10(^-4)”a per v/m per m/s at 27m) The general equation still holds when the potential gradient is measured 7m below the 34m mast but at 2m below the 20m point the equation is I = A(W + D) (F - M)(^n) where A and D are constants is dependent on wind speed. Measurements of point discharge currents down the trunk of a tree indicate that these are somewhat lower than those through a single point of corresponding height in similar conditions. The results are compared with those of previous workers and discrepancies are attributed to wind speed and wind direction effects, whilst good agreement is found between the present findings and the theoretical work of Chalmers and Mapleson (1955) and Chapman (1956). A reassessment of the Alti-Electrograph results of Simpson and scrase (1937) is made and suggests that the potential gradients measured by this means immediately below thunderclouds are of the earns order of magnitude as those measured by observers in aircraft (Gunnl953)
Statistical properties of a localization-delocalization transition induced by correlated disorder
The exact probability distributions of the resistance, the conductance and
the transmission are calculated for the one-dimensional Anderson model with
long-range correlated off-diagonal disorder at E=0. It is proved that despite
of the Anderson transition in 3D, the functional form of the resistance (and
its related variables) distribution function does not change when there exists
a Metal-Insulator transition induced by correlation between disorders.
Furthermore, we derive analytically all statistical moments of the resistance,
the transmission and the Lyapunov Exponent. The growth rate of the average and
typical resistance decreases when the Hurst exponent tends to its critical
value () from the insulating regime.
In the metallic regime , the distributions become independent of
size. Therefore, the resistance and the transmission fluctuations do not
diverge with system size in the thermodynamic limit
Mammalian Sperm Motility: Observation and Theory
Mammalian spermatozoa motility is a subject of growing importance because of rising human infertility and the possibility of improving animal breeding. We highlight opportunities for fluid and continuum dynamics to provide novel insights concerning the mechanics of these specialized cells, especially during their remarkable journey to the egg. The biological structure of the motile sperm appendage, the flagellum, is described and placed in the context of the mechanics underlying the migration of mammalian sperm through the numerous environments of the female reproductive tract. This process demands certain specific changes to flagellar movement and motility for which further mechanical insight would be valuable, although this requires improved modeling capabilities, particularly to increase our understanding of sperm progression in vivo. We summarize current theoretical studies, highlighting the synergistic combination of imaging and theory in exploring sperm motility, and discuss the challenges for future observational and theoretical studies in understanding the underlying mechanics.\ud
Acronyms and Definitions\ud
Acrosome: the cap of the sperm head containing enzymes allowing penetration of the zona pellucida via the acrosome reaction\ud
Adenosine triphosphate (ATP): the currency unit of chemical energy transfer in living cells\ud
Axoneme: a phylogenetically conserved structure within the eukaryotic flagellum consisting of a ring of nine microtubule doublets and a central pair, frequently referred to as 9 + 2\ud
Bending moment density: the moment per unit length associated with flagellar bending; it can be divided into a hydrodynamic moment, an elastic moment (from the flagellar bending stiffness), an active moment (generated by dyneins exerting forces between adjacent microtubule doublets), and a passive moment resisting shear\ud
Capacitation: the physiological state of a sperm required for fertilization, which is accompanied by the motility patterns associated with hyperactivation, characterized in saline by high-amplitude asymmetric beating\ud
Central pair: a pair of microtubules along the length of the axoneme, symmetrically and slightly offset from the axoneme centerline\ud
Cumulus oophorus: the outer vestment of the mammalian egg consisting of hundreds of cells radiating out from the egg embedded within a non-Newtonian hyaluronic acid gel\ud
Dynein: a molecular motor within the axoneme, attached between adjacent microtubule doublets, that exerts a shearing force to induce axonemal bending\ud
Flagellum: a motile cellular appendage that drives the swimming of sperm and other cells; this article focuses on the eukaryotic flagellum\ud
Microtubule doublet: a pair of proteinaceous filament structures running the length of the axoneme; dyneins drive their bending, which induces flagellar motion\ud
Mid-piece: the region of a sperm flagellum with a mitochondrial sheath, where ATP is generated\ud
Oocyte: the egg\ud
Outer dense fibers and fibrous sheath: accessory structures reinforcing the mammalian sperm flagellum; the combined axoneme and accessory structures are referred to as 9+9+2\ud
Resistive-force theory: an approximation for the local drag of a slender filament element in Stokes flow (or a viscoelastic generalization thereof)\ud
Rheotaxis: directed motility in response to the influence of fluid flow\ud
Shear: in the context of the flagellum, the relative movement of adjacent microtubule doublets\ud
Slender-body theory: an improved approximation for the local drag on a slender filament element in Stokes flow (or a viscoelastic generalization thereof)\ud
Zona pellucida: a tough glycoprotein coat between the human egg and the cumulus oophorus, which a sperm must penetrate for successful fertilizatio
A Catalog of Absorption Lines in Eight HST/STIS E230M 1.0 < z < 1.7 Quasar Spectra
We have produced a catalog of line identifications and equivalent width
measurements for all absorption features in eight ultraviolet echelle quasar
spectra. These spectra were selected as having the highest signal-to-noise
among the HST/STIS spectra obtained with the E230M grating. We identify 56
metal-line systems toward the eight quasars, and present plots of detected
transitions, aligned in velocity-space. We found that about 1/4 - 1/3 of the
features in the Lya forest region, redward of the incidence of the Lyb forest,
are metal lines. High ionization transitions are common. We see both O VI and C
IV in 88 - 90% of the metal-line systems for which the spectra cover the
expected wavelength. Si III is seen in 58%, while low ionization absorption in
C II, Si II, and/or Al II is detected in 50% of the systems for which they are
covered. This catalog will facilitate future studies of the Lya forest and of
metal-line systems of various types.Comment: 13 pages, 2 figures, submitted to Monthly Notices of the Royal
Astronomical Society, a complete version with the appendix and all figures is
available at http://www.astro.psu.edu/users/misawa/pub/Paper/qalcat.pdf.g
The Deuterium Abundance in the z=0.7 absorber towards QSO PG1718+4807
We report a further analysis of the ratio of deuterium to hydrogen (D/H)
using HST spectra of the z=0.701 Lyman limit system towards the QSO PG1718+481.
Initial analyses of this absorber found it gave a high D/H value, 1.8 - 3.1
\times 10^{-4} (Webb et al. 1998), inconsistent with several higher redshift
measurements. It is thus important to critically examine this measurement. By
analysing the velocity widths of the DI, HI and metal lines present in this
system, Kirkman et al. (2001) report that the additional absorption in the blue
wing of the lya line can not be DI, with a confidence level of 98%. Here we
present a more detailed analysis, taking into account possible wavelength
shifts between the three sets of HST spectra used in the analysis. We find that
the constraints on this system are not as strong as those claimed by Kirkman et
al. The discrepancy between the parameters of the blue wing absorption and the
parameters expected for DI is marginally worse than 1 sigma.
Tytler et al.(1999) commented on the first analysis of Webb et
al.(1997,1998), reporting the presence of a contaminating lower redshift Lyman
limit system, with log[N(HI)] = 16.7 at z=0.602, which biases the N(HI)
estimate for the main system. Here we show that this absorber actually has
log[N(HI)] < 14.6 and does not impact on the estimate of N(HI) in the system of
interest at z = 0.701.
The purpose of the present paper is to highlight important aspects of the
analysis which were not explored in previous studies, and hence help refine the
methods used in future analyses of D/H in quasar spectra.Comment: 11 pages, 9 figures. Accepted by MNRA
QSO 0130-4021: A third QSO showing a low Deuterium to Hydrogen Abundance Ratio
We have discovered a third quasar absorption system which is consistent with
a low deuterium to hydrogen abundance ratio, D/H = 3.4 times 10^-5. The z ~ 2.8
partial Lyman limit system towards QSO 0130-4021 provides the strongest
evidence to date against large D/H ratios because the H I absorption, which
consists of a single high column density component with unsaturated high order
Lyman series lines, is readily modeled -- a task which is more complex in other
D/H systems. We have obtained twenty-two hours of spectra from the HIRES
spectrograph on the W.M. Keck telescope, which allow a detailed description of
the Hydrogen. We see excess absorption on the blue wing of the H I Lyman alpha
line, near the expected position of Deuterium. However, we find that Deuterium
cannot explain all of the excess absorption, and hence there must be
contamination by additional absorption, probably H I. This extra H I can
account for most or all of the absorption at the D position, and hence D/H = 0
is allowed. We find an upper limit of D/H < 6.7 times 10^-5 in this system,
consistent with the value of D/H ~ 3.4 times 10^-5 deduced towards QSO
1009+2956 and QSO 1937-1009 by Burles and Tytler (1998a, 1998b). This
absorption system shows only weak metal line absorption, and we estimate [Si/H]
< -2.6 -- indicating that the D/H ratio of the system is likely primordial. All
four of the known high redshift absorption line systems simple enough to
provide useful limits on D are consistent with D/H = 3.4 +/- 0.25 times 10^-5.
Conversely, this QSO provides the third case which is inconsistent with much
larger values.Comment: 18 pages, 5 figures, submitted to Ap
McKay matrices for finite-dimensional Hopf algebras
For a finite-dimensional Hopf algebra , the McKay matrix of an -module encodes the relations for tensoring the simple -modules with . We prove results about the eigenvalues and the right and left (generalized) eigenvectors of by relating them to characters. We show how the projective McKay matrix obtained by tensoring the projective indecomposable modules of with is related to the McKay matrix of the dual module of . We illustrate these results for the Drinfeld double of the Taft algebra by deriving expressions for the eigenvalues and eigenvectors of and in terms of several kinds of Chebyshev polynomials. For the matrix that encodes the fusion rules for tensoring with a basis of projective indecomposable -modules for the image of the Cartan map, we show that the eigenvalues and eigenvectors also have such Chebyshev expressions
Human sperm accumulation near surfaces: a simulation study
A hybrid boundary integral/slender body algorithm for modelling flagellar cell motility is presented. The algorithm uses the boundary element method to represent the âwedge-shapedâ head of the human sperm cell and a slender body theory representation of the flagellum. The head morphology is specified carefully due to its significant effect on the force and torque balance and hence movement of the free-swimming cell. The technique is used to investigate the mechanisms for the accumulation of human spermatozoa near surfaces. Sperm swimming in an infinite fluid, and near a plane boundary, with prescribed planar and three-dimensional flagellar waveforms are simulated. Both planar and âelliptical helicoidâ beating cells are predicted to accumulate at distances of approximately 8.5â22 ÎŒm from surfaces, for flagellar beating with angular wavenumber of 3Ï to 4Ï. Planar beating cells with wavenumber of approximately 2.4Ï or greater are predicted to accumulate at a finite distance, while cells with wavenumber of approximately 2Ï or less are predicted to escape from the surface, likely due to the breakdown of the stable swimming configuration. In the stable swimming trajectory the cell has a small angle of inclination away from the surface, no greater than approximately 0.5°. The trapping effect need not depend on specialized non-planar components of the flagellar beat but rather is a consequence of force and torque balance and the physical effect of the image systems in a no-slip plane boundary. The effect is relatively weak, so that a cell initially one body length from the surface and inclined at an angle of 4°â6° towards the surface will not be trapped but will rather be deflected from the surface. Cells performing rolling motility, where the flagellum sweeps out a âconical envelopeâ, are predicted to align with the surface provided that they approach with sufficiently steep angle. However simulation of cells swimming against a surface in such a configuration is not possible in the present framework. Simulated human sperm cells performing a planar beat with inclination between the beat plane and the plane-of-flattening of the head were not predicted to glide along surfaces, as has been observed in mouse sperm. Instead, cells initially with the head approximately 1.5â3 ÎŒm from the surface were predicted to turn away and escape. The simulation model was also used to examine rolling motility due to elliptical helicoid flagellar beating. The head was found to rotate by approximately 240° over one beat cycle and due to the time-varying torques associated with the flagellar beat was found to exhibit âloopingâ as has been observed in cells swimming against coverslips
- âŠ