The long reach of DNA sequence heterogeneity in diffusive processes

Many biological processes involve one dimensional diffusion over a correlated inhomogeneous energy landscape with a correlation length $\xi_c$. Typical examples are specific protein target location on DNA, nucleosome repositioning, or DNA translocation through a nanopore, in all cases with $\xi_c\approx$ 10 nm. We investigate such transport processes by the mean first passage time (MFPT) formalism, and find diffusion times which exhibit strong sample to sample fluctuations. For a a displacement $N$, the average MFPT is diffusive, while its standard deviation over the ensemble of energy profiles scales as $N^{3/2}$ with a large prefactor. Fluctuations are thus dominant for displacements smaller than a characteristic $N_c \gg \xi_c$: typical values are much less than the mean, and governed by an anomalous diffusion rule. Potential biological consequences of such random walks, composed of rapid scans in the vicinity of favorable energy valleys and occasional jumps to further valleys, is discussed

A simple high-sensitivity technique for purity analysis of xenon gas

We report on the development and performance of a high-sensitivity purity-analysis technique for gaseous xenon. The gas is sampled at macroscopic pressure from the system of interest using a UHV leak valve. The xenon present in the sample is removed with a liquid-nitrogen cold trap, and the remaining impurities are observed with a standard vacuum mass-spectroscopy device. Using calibrated samples of xenon gas spiked with known levels of impurities, we find that the minimum detectable levels of N2, O2, and methane are 1 ppb, 160 ppt, and 60 ppt respectively. This represents an improvement of about a factor of 10,000 compared to measurements performed without a coldtrap.Comment: 20 pages, 5 figure

Estimates for practical quantum cryptography

In this article I present a protocol for quantum cryptography which is secure against attacks on individual signals. It is based on the Bennett-Brassard protocol of 1984 (BB84). The security proof is complete as far as the use of single photons as signal states is concerned. Emphasis is given to the practicability of the resulting protocol. For each run of the quantum key distribution the security statement gives the probability of a successful key generation and the probability for an eavesdropper's knowledge, measured as change in Shannon entropy, to be below a specified maximal value.Comment: Authentication scheme corrected. Other improvements of presentatio

Gay father surrogacy families: relationships with surrogates and egg donors and parental disclosure of children's origins.

OBJECTIVE: To study the nature and quality of relationships between gay father families and their surrogates and egg donors and parental disclosure of children's origins. DESIGN: Cross-sectional study. SETTING: Family homes. PATIENT(S): Parents in 40 gay father families with 3-9-year-old children born through surrogacy. INTERVENTION(S): Administration of a semistructured interview. MAIN OUTCOME MEASURE(S): Relationships between parents, children, surrogates, and egg donors and parental disclosure of children's origins were examined using a semistructured interview. RESULT(S): The majority of fathers were content with the level of contact they had with the surrogate, with those who were discontent wanting more contact. Fathers were more likely to maintain relationships with surrogates than egg donors, and almost all families had started the process of talking to their children about their origins, with the level of detail and children's understanding increasing with the age of the child. CONCLUSION(S): In gay father surrogacy families with young children, relationships between parents, children, surrogates, and egg donors are generally positive.Wellcome Trust (Grant ID:097857/Z/11/Z)This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.fertnstert.2016.08.01

Mechanical Ventilation to Minimize Progression of Lung Injury in Acute Respiratory Failure

Mechanical Ventilation (MV) is used to sustain life in patients with acute respiratory failure. A major concern in mechanically ventilated patients is the risk of Ventilator-Induced Lung Injury (VILI), which is partially prevented by lung protective ventilation. Spontaneously breathing, non-intubated, patients with acute respiratory failure may have a high respiratory drive and breathe with large tidal volumes and potentially injurious transpulmonary pressure swings. In patients with existing lung injury, regional forces generated by the respiratory muscles may lead to injurious effects on a regional level. In addition, the increase in transmural pulmonary vascular pressure swings caused by inspiratory effort may worsen vascular leakage. Recent data suggest that these patients may develop lung injury that is similar to the VILI observed in mechanically ventilated patients. As such, we argue that application of a lung protective ventilation, today best applied with sedation and endotracheal intubation, might be considered a prophylactic therapy, rather than just a supportive therapy, to minimize the progression of lung injury from a form of patient-self inflicted lung injury (P-SILI). This has important implications for the management of these patients

Study of a zirconium getter for purification of xenon gas

Oxygen, nitrogen and methane purification efficiencies for a common zirconium getter are measured in 1050 Torr of xenon gas. Starting with impurity concentrations near 10^{-6} g/g, the outlet impurity level is found to be less than 120*10^{-12} g/g for O2 and less than 950*10^{-12} g/g for N2. For methane we find residual contamination of the purified gas at concentrations varying over three orders of magnitude, depending on the purifier temperature and the gas flow rate. A slight reduction in the purifier's methane efficiency is observed after 13 mg of this impurity has been absorbed, which we attribute to partial exhaustion of the purifier's capacity for this species. We also find that the purifier's ability to absorb N2 and methane can be extinguished long before any decrease in O2 performance is observed, and slower flow rates should be employed for xenon purification due to the cooling effect that the heavy gas has on the getter.Comment: 14 pages, 5 figure

A Xenon Condenser with a Remote Liquid Storage Vessel

We describe the design and operation of a system for xenon liquefaction in which the condenser is separated from the liquid storage vessel. The condenser is cooled by a pulse tube cryocooler, while the vessel is cooled only by the liquid xenon itself. This arrangement facilitates liquid particle detector research by allowing easy access to the upper and lower flanges of the vessel. We find that an external xenon gas pump is useful for increasing the rate at which cooling power is delivered to the vessel, and we present measurements of the power and efficiency of the apparatus.Comment: 22 pages, 7 figures Corrected typos in authors lis

APPLICATION OF MODIFYING ALLOYING ALLOY CONTAINING NANOSIZED POWDERS OF ACTIVE ELEMENTS IN PRODUCTION OF HIGH-STRENGTH CAST IRON WITH GLOBULAR GRAPHITE

Scientific and practical interest is the application of alloying alloy-modifiers for secondary treatment of high-strength cast iron to stabilize the process of spheroidization graphite and achieving higher physical-mechanical properties of castings. The peculiarity of the high-strength cast irons manufacturing technology is their tendency to supercooling during solidification in the mold. This leads to the formation of shrinkage defects and structurally free cementite, especially in thin-walled sections of the finished castings. To minimize these effects in foundry practice during production of ductile iron the secondary inoculation is widely used. In this regard, the question of the choice of the additives with effective impact not only on the graphitization process but also on the formation of the metallic base of ductile iron is relevant. The aim of the present work is to study the peculiarities of structure formation in cast iron with nodular graphite when alloying alloy-modifier based on tin with additions of nanoparticles of titanium carbide, yttrium oxide and graphite nano-pipes is used for secondary treatment. Melting of iron in laboratory conditions was performed in crucible induction furnace IST-006 with an acid lining held. Spheroidizing treatment of melt was realized with magnesium containing alloying alloy FeSiMg7 by means of ladle method. Secondary treatment of high strength cast iron was carried out by addition of alloying alloy-modifier in an amount of 0.1% to the bottom of the pouring ladle. Cast samples for chemical composition analysis, study of microstructure, technological and mechanical properties of the resultant alloy were made. Studies have shown that the secondary treatment of high strength cast iron with developed modifier-alloying alloy results in formation of the perlite metallic base due to the tin impact and nodular graphite with regular shape under the influence of titanium carbide, yttrium oxide and graphite nano-pipes. The tendency of high strength cast iron to «white cast iron» formation has been minimized, and the mechanical properties of the alloy produced correspond to HSCI80

A prototype vector magnetic field monitoring system for a neutron electric dipole moment experiment

We present results from a first demonstration of a magnetic field monitoring system for a neutron electric dipole moment experiment. The system is designed to reconstruct the vector components of the magnetic field in the interior measurement region solely from exterior measurements