Conceptual Model for Cutoff Origin in Exotic Compact Objects

We propose a conceptual model for the closeness parameter $\epsilon$, which characterizes exotic compact objects (ECOs). To estimate $\epsilon$, a thin spherical dust shell is considered, which gravitationally contracts from a specific position $r(t_{0})$ to near its gravitational radius $r(t_{2})=r_{s} + \epsilon$, in a finite time $t_{2}$, measured in the frame of a fiducial observer (FIDO). For an external observer, the shell’s kinematics is characterized by two clearly distinguishable phases: one of rapid contraction, where the shell is far away from the gravitational radius, $r(t_{0})\gg r_{s}$, and a second phase quasi-stationary, $r(t)\sim r_{s}$, where all of the shell’s mass is concentrated around the associated horizon, such that for a FIDO, a black hole (BH)is undistinguishable from a shell configured as a black shell (BS). \\ In the semi-classical approximation $E\ll \kappa_{0}l_{p}^{2}$ and tends to zero when the observation time of collapse $t_{2}$, measured by FIDO, tends to infinity; $\kappa_{0}$ and $l_{p}$ are surface gravity and Planck length, respectively. The quantum effects are significant when $\epsilon\ll r(t_{2})$ and $\epsilon$ tends to $\kappa_{0}l_{p}^{2}$. \\ Without knowing details on quantum gravity, parameter $\epsilon$ is calculated, which, in general, allows distinguishing the ECOs from BHs. Specifically, a BS (ECO) is undistinguishable from a BH.

Impact of the Diurnal Radiation Contrast on the Contraction of Radius of Maximum Wind during Intensification of Hurricane Edouard (2014)

This work examines the impacts of the diurnal radiation contrast on the contraction rate of the radius of maximum wind (RMW) during intensification of Hurricane Edouard (2014) through convection-permitting simulations. Rapid contraction of RMW occurs both in the low and midlevels for the control run and the sensitivity run without solar insolation, while the tropical cyclone contracts more slowly in the low levels and later in the midlevels and thereafter fails to intensify continuously in the absence of the night phase, under weak vertical wind shear (~4 m s−1). The clouds at the top of the boundary layer absorb solar shortwave heating during the daytime, which enhanced the temperature inversion there and increased the convective inhibition, while nighttime destabilization and moistening in low levels through radiative cooling decrease convective inhibition and favor more convection inside the RMW than in the daytime phase. The budget analysis of the tangential wind tendency reveals that the greater positive radial vorticity flux inside of the RMW is the key RMW contraction mechanism in the boundary layer at night because of the enhanced convection. However, the greater positive vertical advection of tangential wind inside of the RMW dominates the RMW contraction in the midlevels.

The relationship between form and function throughout the history of excitation–contraction coupling

The concept of excitation–contraction coupling is almost as old as Journal of General Physiology. It was understood as early as the 1940s that a series of stereotyped events is responsible for the rapid contraction response of muscle fibers to an initial electrical event at the surface. These early developments, now lost in what seems to be the far past for most young investigators, have provided an endless source of experimental approaches. In this Milestone in Physiology, I describe in detail the experiments and concepts that introduced and established the field of excitation–contraction coupling in skeletal muscle. More recent advances are presented in an abbreviated form, as readers are likely to be familiar with recent work in the field.

Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454-m altitude

High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements, and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV was estimated by carbon monoxide rebreathing at SL, on every 4th day at HA, and 1 and 2 wk upon return to SL. Four weeks at HA increased Hbmass by 5.26% (range 2.5-11.1%; P < 0.001). The individual Hbmass increases commenced with up to 12 days of delay and reached a maximal rate of 4.04 ± 1.02 g/day after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20–24 days. Upon return to SL Hbmass decayed by −2.46 ± 2.3 g/day, reaching values similar to baseline after 2 wk. PV, aldosterone concentration, and renin activity were reduced at HA ( P < 0.001) while the total circulating protein mass remained unaffected. In summary, the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ∼3 wk. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data support that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure.

Amniotomy shortens the induction delivery interval

Amniotomy or Artificial rupture of membrane is commonly performed procedure in obstetrics. It induces and or accelerates the progress of labour. It is done by artificial rupture of forebag of amniotic membrane. It causes local increase of prostaglandin which interact with collagenous framework and matrix of cervix, converting it from a rigid structure to a soft distensible organ. Release of amniotic fluid shortens muscle bundles of myometrium, strength and duration of contractions are thereby increased and more rapid contraction sequence follows. For this purpose amniotomy as a method of induction of labour may benefit in the way of reducing time interval and operative intervention. This study was conducted with the aim and objectives to evaluate cases in terms of indication, determine amnitomy delivery interval, analyze outcome of amniotomy in labour, find out cases needed for intervention during the process and detect any maternal and fetal complication that may arise as a result of amniotomy. This cross-sectional study was undertaken among 110 cases in Sir Sallimullah Medical College and Mitford Hospital over a period of one year from December’1999 to December’2000. Out of 110 patients 58 patients were multigravida and 52 were primigravida and their mean age was 25.3 years. Amniotomy was done in these patient with mean cervical dilatation of 3.9 cm. Amniotomy alone was done in 88 cases. Mean amniotomy-delivery interval was 4 hours 54 minutes and 90(81.8%) patients delivered normally; 89.1% babies were healthy. Amniotomy can not be used in remote areas of our country. Though it may shorten labour by augmentation and may contribute in reducing maternal morbidity and mortality but there is potential risk of cord prolapse, abruption placenta, risk of infection, so it can be done in institution with proper supervision. DOI: http://dx.doi.org/10.3329/cbmj.v2i2.16702 Community Based Medical Journal 2013 July: Vol.02 No 02: 67-70

Security Risks to IT Supply Chains under Economic Stress

Information technology (IT) supply chains are subject to security risks even during the most stable of economic times, However, when economies come under stress due to brisk growth or rapid contraction, IT supply chains become greater targets for nefarious players, be they employees, hackers, terrorists or nation states, for a variety of reasons. Maintaining both cyber and physical security of owned systems and facilities, over which you have direct control, is difficult and expensive enough under normal conditions. However, attempting to preserve adequate levels of security over third parties, be they process outsourcers, product vendors or contractors, is much more challenging and can be extremely costly in time, money and resources. It is also fraught with organizational, social, economic, political, geographical and contractual challenges. In this paper, the authors list a broad range of potential IT-related security risks and suggest how they might become exacerbated during times of economic stress. Mitigation of these risks may call for extreme measures. Some actions are reasonable and straightforward to implement, whereas others require substantial effort and indeed may not be achievable under current legal and regulatory conditions. The authors offer recommendations for overcoming manageable hurdles, and suggest how some reduction in risk might be attained even in situations where ready solutions are not yet available.

Blood Clots Are Rapidly Assembled Hemodynamic Sensors: Flow Arrest Triggers Intraluminal Thrombus Contraction.

Abstract 2164 During thrombosis or hemostasis under flow conditions, platelets rapidly deposit at a site of vascular injury and quickly become mechanically connected to the vessel wall and subendothelium.1 This interwoven assembly prevents further blood loss by platelet-mediated clot contraction and stiffening.2 We utilized two microfluidic devices to investigate clot contraction dynamics in the presence or absence of transthrombus permeation (ΔP=23.5 mm Hg). Unlike many previous in vitro clot contraction studies, these devices incorporate the critical mechanical and biological thrombi properties that can only be obtained under hemodynamic conditions. In our permeation device, platelet deposits were formed for 10 min with embedded 50 nm fluorescent beads as fiduciary markers (inlet wall shear rate of 1130 s−1). Following the thrombus formation, the flow was switched without interruption to buffer for 4.5 min and then flow was completely stopped. Unexpectedly, the 20-μm thick platelet layer underwent massive platelet retraction upon flow cessation (Fig. 1A). The upstream and downstream edge contraction rates were measured throughout the buffer flow period and after flow stoppage (Fig. 1B). Contraction rates 1 to 2 min after flow cessation significantly increased by 6.5-fold (upstream region) and 4.6-fold (downstream region) (P<0.05), compared to the rate during buffer flow. The restructuring of the thrombus upstream and downstream edges by 2 min post flow cessation resulted in contractile trajectories of embedded beads towards the center of the thrombus mass (Fig. 1C). Comparisons of the time dependent contraction data in the Y and Z direction at upstream and downstream positions of the clot demonstrated increased contraction rates after flow cessation (Fig. 1D). In our rigid wall microfluidic device we investigated the role of soluble autocrine mediators. We added 1 μM SQ-29,548 (TXA2 receptor antagonist) or 10 μM MRS-2179 and 50 μM 2-MeSAMP (P2Y1 and P2Y12 platelet receptors, respectively) to examine the effects of ADP and TXA2. Following platelet deposition and 7 min of buffer/antagonist perfusion, flow was stopped and total contraction was measured with time. Both antagonists significantly reduced the total clot contraction as compared to buffer. ADP antagonists had the largest effect, reducing the total contraction nearly 75% over 7 min, whereas TXA2 antagonist reduced the contraction by 44%. These findings demonstrate ADP (from dense granules) and TXA2 from activated cyclooxygenase-1 (COX1) were the mediators of the triggered contraction response upon flow cessation. Flow dilution of these platelet autocrine mediators during intraluminal clotting balances the platelet contractile apparatus with prevailing hemodynamics, a newly defined flow sensing mechanism to regulate clot function. Figure 1. Flow arrest triggers clot contraction. A thrombus formed in the absence of thrombin and presence of fluorescent 50 nm beads was rinsed with Ca2+ buffer for 4.5 min before the cessation of flow caused a rapid contraction. The outline of a pre-retracted thrombus (t'=−1 min) shows the inward retraction of the thrombus following flow stoppage (t'=0 to 2 min) (A). Contraction rate of the upstream and downstream sections of the thrombus were measured before and after flow arrest (n=3 donors) (B). Trajectories of the 50 nm beads represent the contractile response of the thrombus at upstream (red, n=6), middle (blue, n=3), and downstream (green, n=6) locations (C). Stopping the flow caused a significant increase in contraction rate in the Y and Z directions. To quantify these rates, the times before (0–2 min) and after flow cessation (0–1 min, 1–2 min) were monitored for bead velocity in the three sections of the thrombus (D). Downstream contraction rate in Y direction is shown as absolute value for contraction toward the middle region. *, P<0.01; error bars indicate mean ± SD. Figure 1. Flow arrest triggers clot contraction. A thrombus formed in the absence of thrombin and presence of fluorescent 50 nm beads was rinsed with Ca2+ buffer for 4.5 min before the cessation of flow caused a rapid contraction. The outline of a pre-retracted thrombus (t'=−1 min) shows the inward retraction of the thrombus following flow stoppage (t'=0 to 2 min) (A). Contraction rate of the upstream and downstream sections of the thrombus were measured before and after flow arrest (n=3 donors) (B). Trajectories of the 50 nm beads represent the contractile response of the thrombus at upstream (red, n=6), middle (blue, n=3), and downstream (green, n=6) locations (C). Stopping the flow caused a significant increase in contraction rate in the Y and Z directions. To quantify these rates, the times before (0–2 min) and after flow cessation (0–1 min, 1–2 min) were monitored for bead velocity in the three sections of the thrombus (D). Downstream contraction rate in Y direction is shown as absolute value for contraction toward the middle region. *, P<0.01; error bars indicate mean ± SD. Disclosures: No relevant conflicts of interest to declare.