Арагонитовые и кальцитовые жеоды из пещеры Ботовская

В статье описываются необычные вторичные минеральные образования, обнаруженные в Ботовской пещере в Восточной Сибири, которые представляют собой жеоды, выполненные арагонитом, а в отдельных случаях – кальцитом. Приведены два предположения о формирование жеод: за счет стекающих растворов, размывающих рыхлые пещерные отложения и заполняющих образовавшиеся пустоты, в которых затем происходила кристаллизация минералов, и за счет растворения центрального тела сформированных ранее конкреций и последующего отложения арагонита и кальцита в получившейся полости. Впоследствии жеоды были вскрыты при выносе из пещеры большого объема осадков водными потоками. Вследствие особенностей своей морфологии и генезиса данные образования могут рассматриваться как новый тип спелеотем.У статті описуються незвичайні вторинні мінеральні утворення, виявлені у Ботовской печері у Східному Сибіру, якими є жеоди, виповнені арагонітом, а в окремих випадках - кальцитом. Наведені два припущення про формування жеод: за рахунок стікаючих розчинів, що розмивають пухкі печерні відклади і заповнюють порожнини, що утворилися, в яких потім відбувалася кристалізація мінералів, і за рахунок розчинення центрального тіла сформованих раніше конкрецій і подальшого відкладення арагоніту і кальциту у порожнини, що утворилися. Згодом жеоди були розкриті при винесенні з печери великого об'єму відкладень водними потоками. Внаслідок особливостей своєї морфології і генезису ці утворення можуть розглядатися як новий тип спелеотем.The article describes unusual secondary mineral formation found in Botovskaya Cave in Eastern Siberia, which are geodes, lined byaragonite and, in some cases, by calcite. Two assumptions of the geode formation are put forward: 1) at the expense of draining solutions that erode loose sediments and fill formed cavities, where then mineral crystallization occurs; 2) at the expense of dissolution of the central body of concretions formed earlier, followed by precipitation of aragonite and calcite in the cavity formed. Later on, the geodes were uncovered during erosion of large volumes of sediments by water flows. Due to peculiar features of their morphology and genesis, these formations can be regarded as a new type of speleothems

Chemical Genetic Inhibition of Mps1 in Stable Human Cell Lines Reveals Novel Aspects of Mps1 Function in Mitosis

Proper execution of chromosome segregation relies on tight control of attachment of chromosomes to spindle microtubules. This is monitored by the mitotic checkpoint that allows chromosome segregation only when all chromosomes are stably attached. Proper functioning of the attachment and checkpoint processes is thus important to prevent chromosomal instability. Both processes rely on the mitotic kinase Mps1.We present here two cell lines in which endogenous Mps1 has been stably replaced with a mutant kinase (Mps1-as) that is specifically inhibited by bulky PP1 analogs. Mps1 inhibition in these cell lines is highly penetrant and reversible. Timed inhibition during bipolar spindle assembly shows that Mps1 is critical for attachment error-correction and confirms its role in Aurora B regulation. We furthermore show that Mps1 has multiple controls over mitotic checkpoint activity. Mps1 inhibition precludes Mad1 localization to unattached kinetochores but also accelerates mitosis. This acceleration correlates with absence of detectable mitotic checkpoint complex after Mps1 inhibition. Finally, we show that short-term inhibition of Mps1 catalytic activity is sufficient to kill cells.Mps1 is involved in the regulation of multiple key processes that ensure correct chromosome segregation and is a promising target for inhibition in anti-cancer strategies. We report here two cell lines that allow specific and highly penetrant inhibition of Mps1 in a reproducible manner through the use of chemical genetics. Using these cell lines we confirm previously suggested roles for Mps1 activity in mitosis, present evidence for novel functions and examine cell viability after short and prolonged Mps1 inhibition. These cell lines present the best cellular model system to date for investigations into Mps1 biology and the effects of penetrance and duration of Mps1 inhibition on cell viability

Square root singularity in the viscosity of neutral colloidal suspensions at large frequencies

The asymptotic frequency $\omega$, dependence of the dynamic viscosity of neutral hard sphere colloidal suspensions is shown to be of the form $\eta_0 A(\phi) (\omega \tau_P)^{-1/2}$, where $A(\phi)$ has been determined as a function of the volume fraction $\phi$, for all concentrations in the fluid range, $\eta_0$ is the solvent viscosity and $\tau_P$ the P\'{e}clet time. For a soft potential it is shown that, to leading order steepness, the asymptotic behavior is the same as that for the hard sphere potential and a condition for the cross-over behavior to $1/\omega \tau_P$ is given. Our result for the hard sphere potential generalizes a result of Cichocki and Felderhof obtained at low concentrations and agrees well with the experiments of van der Werff et al, if the usual Stokes-Einstein diffusion coefficient $D_0$ in the Smoluchowski operator is consistently replaced by the short-time self diffusion coefficient $D_s(\phi)$ for non-dilute colloidal suspensions.Comment: 18 pages LaTeX, 1 postscript figur

Markov Random Field Segmentation of Brain MR Images

We describe a fully-automatic 3D-segmentation technique for brain MR images. Using Markov random fields the segmentation algorithm captures three important MR features, i.e. non-parametric distributions of tissue intensities, neighborhood correlations and signal inhomogeneities. Detailed simulations and real MR images demonstrate the performance of the segmentation algorithm. The impact of noise, inhomogeneity, smoothing and structure thickness is analyzed quantitatively. Even single echo MR images are well classified into gray matter, white matter, cerebrospinal fluid, scalp-bone and background. A simulated annealing and an iterated conditional modes implementation are presented. Keywords: Magnetic Resonance Imaging, Segmentation, Markov Random FieldsComment: 34 pages, 10 figures; the paper (published in 1997) has introduced the concept of Markov random field to the segmentation of medical MR images. For the published version see http://dx.doi.org/10.1109/42.65088

Chromosomal Instability by Inefficient Mps1 Auto-Activation Due to a Weakened Mitotic Checkpoint and Lagging Chromosomes

BACKGROUND: Chromosomal instability (CIN), a feature widely shared by cells from solid tumors, is caused by occasional chromosome missegregations during cell division. Two of the causes of CIN are weakened mitotic checkpoint signaling and persistent merotelic attachments that result in lagging chromosomes during anaphase. PRINCIPAL FINDINGS: Here we identify an autophosphorylation event on Mps1 that is required to prevent these two causes of CIN. Mps1 is phosphorylated in mitotic cells on at least 7 residues, 4 of which by autophosphorylation. One of these, T676, resides in the activation loop of the kinase domain and a mutant that cannot be phosphorylated on T676 is less active than wild-type Mps1 but is not kinase-dead. Strikingly, cells in which endogenous Mps1 was replaced with this mutant are viable but missegregate chromosomes frequently. Anaphase is initiated in the presence of misaligned and lagging chromosomes, indicative of a weakened checkpoint and persistent merotelic attachments, respectively. CONCLUSIONS/SIGNIFICANCE: We propose that full activity of Mps1 is essential for maintaining chromosomal stability by allowing resolution of merotelic attachments and to ensure that single kinetochores achieve the strength of checkpoint signaling sufficient to prevent premature anaphase onset and chromosomal instability. To our knowledge, phosphorylation of T676 on Mps1 is the first post-translational modification in human cells of which the absence causes checkpoint weakening and CIN without affecting cell viability

Properties of commonly used calcium phosphate cements in trauma and orthopaedic surgery

Introduction Half of the population sustains at least one fracture during their lifetime, and the majority of these fractures heal successfully. Successful fracture healing requires the following five elements; (i) osteogenic cells (e.g., osteoblasts), (ii) osteoinductive stimuli (e.g., bone morphogenetic proteins); (iii) an osteoconductive matrix; (iv) adequate blood and nutrient supply, and (v) sufficient mechanical support. One or more elements can be compromised due to the existence of a bone defect. Bone defects are treated with bone grafts in order to avoid insufficient fracture healing. Insufficient fracture healing is encountered in 5–10% of the fractures, resulting in delayed union, malunion, or non-union