Compact CMOS active quenching/recharge circuit for SPAD arrays

Avalanche diodes operating in Geiger mode are able to detect single photon events. They can be employed to photon counting and time-of-flight estimation. In order to ensure proper operation of these devices, the avalanche current must be rapidly quenched, and, later on, the initial equilibrium must be restored. In this paper, we present an active quenching/recharge circuit specially designed to be integrated in the form of an array of single-photon avalanche diode (SPAD) detectors. Active quenching and recharge provide benefits like an accurately controllable pulse width and afterpulsing reduction. In addition, this circuit yields one of the lowest reported area occupations and power consumptions. The quenching mechanism employed is based on a positive feedback loop that accelerates quenching right after sensing the avalanche current. We have employed a current starved inverter for the regulation of the hold-off time, which is more compact than other reported controllable delay implementations. This circuit has been fabricated in a standard 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology. The SPAD has a quasi-circular shape of 12 μm diameter active area. The fill factor is about 11%. The measured time resolution of the detector is 187 ps. The photon-detection efficiency (PDE) at 540 nm wavelength is about 5% at an excess voltage of 900 mV. The break-down voltage is 10.3 V. A dark count rate of 19 kHz is measured at room temperature. Worst case post-layout simulations show a 117 ps quenching and 280 ps restoring times. The dead time can be accurately tuned from 5 to 500 ns. The pulse-width jitter is below 1.8 ns when dead time is set to 40 ns.Ministerio de Economía y Competitividad TEC2012-38921-C02, IPT-2011-1625-430000, IPC-20111009 CDTIJunta de Andalucía TIC 2338-2013Office of Naval Research (USA) N00014141035

Minimum energy paths for conformational changes of viral capsids

In this work we study how a viral capsid can change conformation using techniques of Large Deviations Theory for stochastic differential equations. The viral capsid is a model of a complex system in which many units - the proteins forming the capsomers - interact by weak forces to form a structure with exceptional mechanical resistance. The destabilization of such a structure is interesting both per se, since it is related either to infection or maturation processes, and because it yields insights into the stability of complex structures in which the constitutive elements interact by weak attractive forces. We focus here on a simplified model of a dodecahederal viral capsid, and assume that the capsomers are rigid plaquettes with one degree of freedom each. We compute the most probable transition path from the closed capsid to the final configuration using minimum energy paths, and discuss the stability of intermediate states.Comment: 27 pages, 4 figures. New version, to appear in Physical Review

Some finite solvable groups with non-trivial lattice endomorphisms

The main purpose of this paper is to exhibit a doubly-infinite family of examples which are extensions of a p-group by a p′-group, with the action satisfying some conditions of Zappa (1951), arising from his study of dual-standard (meet-distributive) subgroups. The examples show that Zappa's conditions do not bound the nilpotency class (or even the derived length) of the p-group. The key to this work is found in closely related conditions of Hartley (published here for the first time). The examples use some exceptional relationships between primes

A 'Post-Carbon' Diplomacy? Japan's Southeast Asia Conundrum

In October 2020, Japanese prime minister Suga Yoshihide chose Vietnam and Indonesia as the destinations of his first official visit abroad. From a security standpoint, there is little doubt that the two countries play a crucial role in the Japanese–American grand strategy, launched by Suga’s predecessor, Abe Shinzō, of building a Free and Open Indo-Pacific to counter China’s assertiveness. Security, however, is just one element of a more intricate puzzle of competition and cooperation between Tokyo and Beijing in this region of Asia. Suga’s trip to Southeast Asia (SEA, hereafter) was also chosen as the occasion to unveil his government plans to make Japan carbon neutral (i.e., to slash the country’s emissions to a level that can be absorbed by nature) by 2050

“Greening” Speculative Urbanism?Space Politics and Model Circulation in South Korea and Vietnam’s Special Economic Zones

As products of the waves of deregulation and liberalization of trade and investments in the region in the 1980s and mid-1990s, special economic zones (SEZs) have emerged as an important tool of economic governance in East and Southeast Asia. Recently, governments and investors around the region, have favored multi-purpose SEZs conceived for land and real estate development which exhibit several similarities such as eliciting tourism as the main driver of local development and a declared “eco” and “green” configuration. The Incheon Free Economic Zone (IFEZ) in the Republic of Korea (ROK) and the Van Don SEZ in the Socialist Republic of Vietnam (SRV) are two illustrative cases of urban policy diffusion as a complex phenomenon combining the ROK’s increased international activism and SRV’s own institutional structure and preferences in terms of development goals. Based on a close reading of reports, official documents, qualitative interviews and site visits, this article will further contribute to the debate on the complexity of urban policy diffusion in contemporary East and Southeast Asia

Gravitational-wave luminosity of binary neutron stars mergers

We study the gravitational-wave peak luminosity and radiated energy of quasicircular neutron star mergers using a large sample of numerical relativity simulations with different binary parameters and input physics. The peak luminosity for all the binaries can be described in terms of the mass ratio and of the leading-order post-Newtonian tidal parameter solely. The mergers resulting in a prompt collapse to black hole have largest peak luminosities. However, the largest amount of energy per unit mass is radiated by mergers that produce a hypermassive neutron star or a massive neutron star remnant. We quantify the gravitational-wave luminosity of binary neutron star merger events, and set upper limits on the radiated energy and the remnant angular momentum from these events. We find that there is an empirical universal relation connecting the total gravitational radiation and the angular momentum of the remnant. Our results constrain the final spin of the remnant black-hole and also indicate that stable neutron star remnant forms with super-Keplerian angular momentum.Comment: 5 pages, 4 figure

Defining the Cellular and Molecular Basis of Spondyloepiphyseal dysplasia tarda

One third of the proteome is transported in membrane-encapsulated vesicles from the endoplasmic reticulum (ER) to the Golgi apparatus en route to the plasma membrane, other intracellular organelles and the extracellular matrix. After folding, newly synthesized proteins reach the Golgi apparatus through COPII carriers. COPII vesicles bud from sub-domains of the ER, named ER exit sites (ERES) and are composed of five rapidly cycling proteins: the small GTPase Sar1, the inner coat (Sec23/Sec24) and the outer layer (Sec13/31). The efficiency of COPII cycling is dispensable for the transport of small soluble cargoes or trans- membrane cargoes, yet is mandatory for the exit of “extra-size” proteins, such as procollagens. To facilitate the incorporation of procollagens into nascent COPII carriers, several adaptors work in cooperation at ERES. One of them is sedlin, a small protein that acts as a co-GAP for Sar1, thus increasing its kinetics. The idea that sedlin is important for collagen transport is enforced by the evidence that a rare Mendelian disorder, Spondyloepiphyseal dysplasia tarda (SEDT), is caused by sedlin mutations in which the main clinical manifestation is an alteration in collagen deposition. With the aim to clarify sedlin functions in membrane trafficking, I followed two different approaches: (1) biochemical analysis of sedlin interactors and (2) the generation of a sedlin KO medaka model. Using mass spectroscopy approaches, several proteins were shown to interact with sedlin of which one of the most significant was CLIC1. Subsequent experiments showed that deletion of CLIC1 delayed protein secretion. Furthermore, this work showed that CLIC1 and sedlin, as well as the COPII inner coat, take part in the integrated stress response (IRS). Upon perturbations that change cellular homeostasis such as heat shock, redox stress or unfolded protein accumulation, cells activate signalling pathways that result in translation inhibition by sequestering free mRNAs and ribonucleoproteins in cytosolic aggregates named stress granules (SGs). I demonstrated that SGs control secretion by recruiting key components of ER-to- Golgi trafficking and thus inhibit anterograde transport. This suggested that the ISR regulates protein metabolism on two levels: translationally and post- translationally, by sequestering mRNAs and inhibiting protein export from the ER, respectively. Additionally, by using TALEN technology, I edited the sedlin gene in medaka to create a SEDLIN KO stable line (Sedl-/-). Sedl-/- fish have severe skeletal defects, which are similar to those observed in human SEDT patients, and die soon after birth suggesting that sedlin has an essential role in early postnatal medaka growth. To investigate the molecular pathways altered in sedlin-/- vertebrates I performed a Transcriptomic analysis on whole larvae highlighting that eye and cartilage are the two most affected organs and led to the hypothesis of a common pathogenetic mechanism. These findings provide evidence that sedlin is involved in different molecular pathways and when mutated can contribute to the pathogenesis of SEDT. Thus, my thesis work has shed light on a new control mechanism that involves ER-to-Golgi transport and establishes the first SEDT animal model, a suitable tool to find SEDT correctors