Dynamics of chromosome movement

(1) At mitotic prophase unravelling of the chromosome spiral occurs without actual increase in length.(2) The opening out of the secondary split is at mid -prophase. The actual split most probably does not coincide with the opening out of the sister chromatids during mitosis.(3) The commencement of mitosis is the fission of genes and this must occur during the resting stage.(4) The single structure of prophase spiral at mitosis is due to the close association of the homologous genes, chromomeres, and chromatids. The cause of the association is homology, most probably physicochemical in nature.(5) Unravelling of the chromosome spiral is a condition sine qua non for the building up of the matrix of each chromonema'separately.(6) Contraction operates from the undivided attachment constriction. This force acts upon the matrix, causing it to decrease gradually in length. The chromonema does not shorten but adjusts itself by forming a spiral. This structure can be recognised in the prophase of the following division (persist - ance of chromosome individuality).(7) The tertiary split at metaphase was not found in Vicia, Tulipa and Allium. Anaphase separation is due to repulsion which operates between two homologous attachment constrictions.(8) The loci of pairing at zygotene between homologous chromosomes are at random, but always include groups of chromomeres. Polarisation is caused by special attraction between the ends of chromosomes and centrosomes or nuclear Dole. It is most probably genetical in its or(9) At pachytene the homologous chromosomes twist around each other.(10) The opening out of the secondary split is at the end of pachytene.(11) The general rule of pairing - that association always occurs between pairs of homologues, and repulsion always between pairs of paired homologous constituents, - is demonstrated by several observations.(12) At the end of pachytene, attraction and contraction produce a torsion. The secondary split introduces the repulsion and as a result of the interaction of these forces, breaks occur. The fusion of partner chromatids produces the chiasma.(13) Chiasma frequency is not related to the size of the bivalents.(14) The decrease in the number of chiasmata from diplotene to metaphase is caused by two repulsions . The first is general, operating between pairs of paired chromatids; the second is specific and acts between two corresponding homologous attachment constrictions. If the latter is greater, the result of interaction is movement of the chiasmata, towards the distal end.(15) The following data supply evidence in favour of Janssens' chiasmatype hypothesis: (a) Pairing of unequal chromosomes; (b) Interlocking of bivalents at meiotic pro - :phase. (ç) Twisting of sister chromatids on both sides of chiasmata; (d) Decrease in genetical crossing -over parallel to a similar decrease in chiasma frequency.(16) The terminal association of bivalents depends upon a special affinity between terminal chromomeres. If intercalary chromomeres become terminal by trans - location, they attain this special affinity.(17) The movement of chromosomes towards the equatorial plate is a result of repulsion operating between poles and attachment constrictions only.(18) Metaphase equilibrium is a result of repulsion between poles and attachments and between attachmen of similar and dissimilar chromosomes.(19) In some cases the interal affinity of chromosomes will interact with the other forces and determine the mitotic or meiotic metaphase pattern, as it is the case in secondary association and somatic pairing.(20) The spindle mechanism is necessary for normal chromosome movements before and after metaphase. It guides the chromosomes by their attachment constriction towards equilibrium either at the metaphase plate or at the poles. The spindle can be formed only in a normal cytoplasmic environment.(21) At anaphase there is a second period of equilibrium where the repulsion between the corresponding attachment constrictions and poles is equal. Further separation is due to the expansion of the inter-chromosomal spindle, for which new evidence is put forward.(22) At anaphase there is no repulsion between the similar or dissimilar attachments migrating towards the same pole. Repulsion exists only between the corresponding homologous attachment constrictions.(23) The similarity between effects of forces operating at mitotic and meiotic division and those which act in an electro-magnetic field indicates a close relationship in the nature of those forces

Electron beam driven alkali metal atom source for loading a magneto-optical trap in a cryogenic environment

We present a versatile and compact electron beam driven source for alkali metal atoms, which can be implemented in cryostats. With a heat load of less than 10mW, the heat dissipation normalized to the atoms loaded into the magneto-optical Trap (MOT), is about a factor 1000 smaller than for a typical alkali metal dispenser. The measured linear scaling of the MOT loading rate with electron current observed in the experiments, indicates that electron stimulated desorption is the corresponding mechanism to release the atoms.Comment: 5 pages, 3 figure

Two-point density correlations of quasicondensates in free expansion

We measure the two-point density correlation function of freely expanding quasicondensates in the weakly interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge gradually during expansion as a result of initial phase fluctuations present in the trapped quasicondensate. Asymptotically, they are governed by the thermal coherence length of the system. Our measurements take place in an intermediate regime where density correlations are related to near-field diffraction effects and anomalous correlations play an important role. Comparison with a recent theoretical approach described by Imambekov et al. yields good agreement with our experimental results and shows that density correlations can be used for thermometry of quasicondensates.Comment: 4 pages, 4 figures, minor change

Strong magnetic coupling of an ultracold gas to a superconducting waveguide cavity

Placing an ensemble of $10^6$ ultracold atoms in the near field of a superconducting coplanar waveguide resonator (CPWR) with $Q \sim 10^6$ one can achieve strong coupling between a single microwave photon in the CPWR and a collective hyperfine qubit state in the ensemble with $g_\textit{eff} / {2 \pi} \sim 40$ kHz larger than the cavity line width of ${\kappa}/{2 \pi} \sim 7$ kHz. Integrated on an atomchip such a system constitutes a hybrid quantum device, which also can be used to interconnect solid-state and atomic qubits, to study and control atomic motion via the microwave field, observe microwave super-radiance, build an integrated micro maser or even cool the resonator field via the atoms

Two-point phase correlations of a one-dimensional bosonic Josephson junction

We realize a one-dimensional Josephson junction using quantum degenerate Bose gases in a tunable double well potential on an atom chip. Matter wave interferometry gives direct access to the relative phase field, which reflects the interplay of thermally driven fluctuations and phase locking due to tunneling. The thermal equilibrium state is characterized by probing the full statistical distribution function of the two-point phase correlation. Comparison to a stochastic model allows to measure the coupling strength and temperature and hence a full characterization of the system

Stochastic optimization of a cold atom experiment using a genetic algorithm

We employ an evolutionary algorithm to automatically optimize different stages of a cold atom experiment without human intervention. This approach closes the loop between computer based experimental control systems and automatic real time analysis and can be applied to a wide range of experimental situations. The genetic algorithm quickly and reliably converges to the most performing parameter set independent of the starting population. Especially in many-dimensional or connected parameter spaces the automatic optimization outperforms a manual search.Comment: 4 pages, 3 figure

Single-particle-sensitive imaging of freely propagating ultracold atoms

We present a novel imaging system for ultracold quantum gases in expansion. After release from a confining potential, atoms fall through a sheet of resonant excitation laser light and the emitted fluorescence photons are imaged onto an amplified CCD camera using a high numerical aperture optical system. The imaging system reaches an extraordinary dynamic range, not attainable with conventional absorption imaging. We demonstrate single-atom detection for dilute atomic clouds with high efficiency where at the same time dense Bose-Einstein condensates can be imaged without saturation or distortion. The spatial resolution can reach the sampling limit as given by the 8 \mu m pixel size in object space. Pulsed operation of the detector allows for slice images, a first step toward a 3D tomography of the measured object. The scheme can easily be implemented for any atomic species and all optical components are situated outside the vacuum system. As a first application we perform thermometry on rubidium Bose-Einstein condensates created on an atom chip.Comment: 24 pages, 10 figures. v2: as publishe

Chitin Modulates Innate Immune Responses of Keratinocytes

Chitin, after cellulose the second most abundant polysaccharide in nature, is an essential component of exoskeletons of crabs, shrimps and insects and protects these organisms from harsh conditions in their environment. Unexpectedly, chitin has been found to activate innate immune cells and to elicit murine airway inflammation. The skin represents the outer barrier of the human host defense and is in frequent contact with chitin-bearing organisms, such as house-dust mites or flies. The effects of chitin on keratinocytes, however, are poorly understood. We hypothesized that chitin stimulates keratinocytes and thereby modulates the innate immune response of the skin. Here we show that chitin is bioactive on primary and immortalized keratinocytes by triggering production of pro-inflammatory cytokines and chemokines. Chitin stimulation further induced the expression of the Toll-like receptor (TLR) TLR4 on keratinocytes at mRNA and protein level. Chitin-induced effects were mainly abrogated when TLR2 was blocked, suggesting that TLR2 senses chitin on keratinocytes. We speculate that chitin-bearing organisms modulate the innate immune response towards pathogens by upregulating secretion of cytokines and chemokines and expression of MyD88-associated TLRs, two major components of innate immunity. The clinical relevance of this mechanism remains to be defined

Feasibility and acceptance of electronic quality of life assessment in general practice: an implementation study

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