Digital Tide Tables: A Necessity for Navigation in the Electronic Age

Tide Tables, produced by the relevant Hydrographic Offices, are a mandatory complement to navigational charts for any vessel sailing in tidal waters, i.e. in all the world's oceans and almost all of its seas. Until recently, they were almost exclusively in a printed form. However, the arrival and widespread use of personal computers is changing the status quo. Several digital tidal prediction programs of varying accuracy have appeared on the market, and Hydrographic Offices are being pressured to move into the electronic world as well. To date, only a few countries produce digital versions of authorized Tide Tables, with various levels of sophistication. The introduction of the Electronic Chart Display and Information System (ECDIS) is now emphasizing the need for digital tidal data, with more Hydrographic Offices expected to comply. Those mariners using electronic navigational charts now require digital tidal predictions as a companion to the digital ECDIS.Graphical representation of traditionally numeric tidal data is now practically "de rigueur" for Digital Tide Tables. With predictions for many secondary ports available with accuracy comparable to standard ports, the whole concept of "secondary" ports is challenged. Early versions of Digital Tide Tables had, at best, a relatively simple user menu with a listing of ports for which predictions were available. This is also changing, as Australia has already introduced a master geographical interface, showing the locations of available ports via several larger scale index charts.The second generation of Digital Tide Tables will include a "seamless" incorporation in the ECDIS to provide authorized (i.e. legal) tidal predictions on demand for real-time navigation. It is anticipated that the ECDIS community will enhance this further with spatial overlays and access to shore-based modelling of tidal heights and streams, as well as real-time water level measurements, where available

Gas of self-avoiding loops on the brickwork lattice

An exact calculation of the phase diagram for a loop gas model on the brickwork lattice is presented. The model includes a bending energy. In the dense limit, where all the lattice sites are occupied, a phase transition occuring at an asymmetric Lifshitz tricritical point is observed as the temperature associated with the bending energy is varied. Various critical exponents are calculated. At lower densities, two lines of transitions (in the Ising universality class) are observed, terminated by a tricritical point, where there is a change in the modulation of the correlation function. To each tricritical point an associated disorder line is found.Comment: 19 pages, 6 figures. to appear in J. Phys. A : Math. & Ge

Collision-Induced Non-Adiabatic Transitions Between The Ion-Pair States Of Molecular Iodine: A Challenge For Experiment And Theory

The ion-pair states of molecular iodine provide a unique system for studying the efficiency, selectivity, and mechanisms of collision-induced non-adiabatic transitions. Non-adiabatic transitions between the first-tier ion-pair states in collisions with molecular partners and rare gases are analyzed and discussed. The qualitative features of the rate constants and product state distributions under single collision conditions are summarized and interpreted in terms of appropriate theoretical approaches. Two mechanisms for the non-adiabatic transitions are clearly identified. The first, operative for collisions involving molecular partners possessing permanent or transition electrostatic moments, is highly selective. It connects the initially prepared level in the E 0(g)(+) electronic state with the near-resonant vibronic level of the D 0(u)(+) state with a minimum change of the total angular momentum. In an extreme quasi-resonant case when the gap between initial and final rovibronic level is less than 1 cm(-1), this mechanism has a giant cross section, 40 times that of a gas kinetic collision. An electrostatic model, which includes the coupling of the giant E-D transition dipole moment with a moment of the colliding partner and the semiclassical Born approximation, provides a plausible interpretation of this mechanism. A second mechanism is shown to govern collisions with rare gas atoms. It results in population of several ion-pair states and broad distributions over rovibronic levels. This mechanism is successfully interpreted by quantum scattering calculations based on the diatomics-in-molecule diabatic potential energy surfaces and coupling matrix elements. The calculations provide good agreement with experimental measurements and reveal different mechanisms for the population of different electronic states. Unexplained features of the non-adiabatic dynamics and directions of future work are outlined

Epidemiology of gastroschisis: A population-based study in California from 1995 to 2012.

BackgroundAlthough the incidence of gastroschisis is increasing, risk factors are not clearly identified.MethodsUsing the Linked Birth Database from the California Office of Statewide Health Planning and Development from 1995 to 2012, patients with gastroschisis were identified by ICD-9 diagnosis/procedure code or birth certificate designation. Logistic regressions examined demographics, birth factors, and maternal exposures on risk of gastroschisis.ResultsThe prevalence of gastroschisis was 2.7 cases per 10,000 live births. Patients with gastroschisis had no difference in fetal exposure to alcohol (p = 0.609), narcotics (p = 0.072), hallucinogenics (p = 0.239), or cocaine (p = 0.777), but had higher exposure to unspecified/other noxious substances (OR 3.27, p = 0.040; OR 2.02, p = 0.002). Gastroschisis was associated with low/very low birthweight (OR 5.08-16.21, p < 0.001) and preterm birth (OR 3.26-10.0, p < 0.001). Multivariable analysis showed lower risk in black (OR 0.44, p < 0.001), Asian/Pacific Islander (OR 0.76, p = 0.003), and Hispanic patients (OR 0.72, p < 0.001) compared to white patients. Risk was higher in rural areas (OR 1.24-1.76, p = 0.001). Compared to women age < 20, risk decreased with advancing maternal age (OR 0.49-OR 0.03, p < 0.001). Patients with gastroschisis had increased total charges ($336,270 vs.$9012, p < 0.001) and length of stay (38.1 vs. 2.9 days, p < 0.001). Mortality was 4.6%.ConclusionsThis is the largest population-based study summarizing current epidemiology of gastroschisis in California.Type of studyRetrospective comparative cohort study.Level of evidenceIII

Effect of maternal cold exposure and nutrient restriction on insulin-like growth factor sensitivity in adipose tissue of newborn sheep

Adipose tissue mass in the newborn is determined in part by insulin-like growth factor (IGF)s, which are dependent on the maternal nutritional and metabolic environment during late gestation. The present study was designed to determine whether maternal cold exposure (CE) commencing in mid gestation could modulate some of the adaptive effects of nutrient restriction in late gestation on adipose tissue endocrine sensitivity in the resulting offspring. Twenty eight pregnant sheep were entered into the study and were either shorn, i.e. cold exposed, from 70 days gestation (term = 147 days), or remained unshorn, and were fed either their total calculated metabolisable energy (ME) requirements for body weight and pregnancy from 110 days gestation or 50% of this amount (n=7 per group). Adipose tissue was sampled from the offspring at one day of age and the mRNA abundance for IGF-I, II their receptors (R) and GH secretagogue receptor-1a (GHSR-1a) were determined. CE mothers produced larger offspring with more perirenal adipose tissue, an adaptation prevented by maternal nutrient restriction. Nutrient restriction in unshorn mothers increased IGF-I and IIR mRNA abundance. The mRNA abundances for IGF-I, II and IIR in adipose tissue were reduced by CE, adaptations independent of maternal food intake, whereas CE plus nutrient restriction increased GHSR-1a mRNA. In conclusion, maternal nutrient restriction with or without CE has very different effects on IGF sensitivity of adipose tissue and may act to ensure adequate fat stores are present in the newborn in the face of very different maternal endocrine and metabolic environments

Cardiovascular risk factors from diagnosis in children with type 1 diabetes mellitus: a longitudinal cohort study

BACKGROUND: For childhood onset type 1 diabetes (T1D), the pathogenesis of atherosclerosis is greatly accelerated and results in early cardiovascular disease (CVD) and increased mortality. However, cardioprotective interventions in this age group are not routinely undertaken. AIMS: To document prevalence of cardiovascular risk factors from diagnosis of childhood T1D and their relationship with disease duration and ethnicity. METHODS: Routinely collected clinical records for 565 children with T1D were retrospectively analyzed. Data were collected from diagnosis and at routine check-ups at pediatric diabetes clinics across Barts Health National Health Service Trust. Age at diagnosis was 8.5 years (0.9–19.4). Mean follow-up 4.3 years (0–10.8). 48% were boys and 60% were non-white. Linear longitudinal mixed effects models were used to evaluate relationships between risk factors and diabetes duration. RESULTS: CVD risk factors were present at first screening; 33.8% of children were overweight or obese, 20.5% were hypertensive (elevated diastolic blood pressure (BP)) and total cholesterol, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol were abnormal in 63.5%, 34.2% and 22.0%, respectively. Significant associations between diabetes duration and annual increases of body mass index (0.6 kg/m2), BP (0.1 SD score) and lipids (0.02–0.06 mmol/L) were noted. Annual increases were significantly higher in black children for BP and Bangladeshi children for lipids. Bangladeshi children also had greatest baseline levels. CONCLUSIONS: CVD risk factors are present in up to 60% of children at diagnosis of T1D and increase in prevalence during the early years of the disease. Commencing screening in younger children and prioritizing appropriate advice and attention to ethnic variation when calculating risk should be considered

Frustrated quantum Heisenberg ferrimagnetic chains

We study the ground-state properties of weakly frustrated Heisenberg ferrimagnetic chains with nearest and next-nearest neighbor antiferromagnetic exchange interactions and two types of alternating sublattice spins S_1 > S_2, using 1/S spin-wave expansions, density-matrix renormalization group, and exact- diagonalization techniques. It is argued that the zero-point spin fluctuations completely destroy the classical commensurate- incommensurate continuous transition. Instead, the long-range ferrimagnetic state disappears through a discontinuous transition to a singlet state at a larger value of the frustration parameter. In the ferrimagnetic phase we find a disorder point marking the onset of incommensurate real-space short-range spin-spin correlations.Comment: 16 pages (LaTex 2.09), 6 eps figure

Density-Matrix Spectra of Solvable Fermionic Systems

We consider non-interacting fermions on a lattice and give a general result for the reduced density matrices corresponding to parts of the system. This allows to calculate their spectra, which are essential in the DMRG method, by diagonalizing small matrices. We discuss these spectra and their typical features for various fermionic quantum chains and for the two-dimensional tight-binding model.Comment: 12 pages and 9 figure