Spanning tree generating functions and Mahler measures

We define the notion of a spanning tree generating function (STGF) $\sum a_n z^n$, which gives the spanning tree constant when evaluated at $z=1,$ and gives the lattice Green function (LGF) when differentiated. By making use of known results for logarithmic Mahler measures of certain Laurent polynomials, and proving new results, we express the STGFs as hypergeometric functions for all regular two and three dimensional lattices (and one higher-dimensional lattice). This gives closed form expressions for the spanning tree constants for all such lattices, which were previously largely unknown in all but one three-dimensional case. We show for all lattices that these can also be represented as Dirichlet $L$-series. Making the connection between spanning tree generating functions and lattice Green functions produces integral identities and hypergeometric connections, some of which appear to be new.Comment: 26 pages. Dedicated to F Y Wu on the occasion of his 80th birthday. This version has additional references, additional calculations, and minor correction

Side impact motor vehicle crashes: driver, passenger, vehicle and crash characteristics for fatally and nonfatally-injured rear-seated adults

Background Most studies of rear-seated occupants have focused on or included pediatric occupants which may not translate to adults. This study examines passenger, driver, vehicle and crash characteristics for rear-seated adult occupants involved in side crashes. Methods The National Automotive Sampling System General Estimates System (NASS/GES) for calendar years 2011–2014 was used with accompanying weights to examine the occupant, vehicle and crash characteristics associated with injury in rear-seated adults (n = 395,504) involved in a side crash. A weighted subpopulation analysis includes occupants travelling in a vehicle with an IIHS safety rating (n = 39,208), which was used to control for vehicle safety. Statistical analysis used Chi-square tests and multilevel multivariable logistic regression. Unadjusted and adjusted odds ratios (ORs) are reported with 95 % confidence intervals (95 % CIs). Results Rear-seated occupants on the same side as the crash impact were more likely to be severely/fatally injured than occupants seated on the opposite side (Multivariable adjusted OR: 2.54, 95 % CI: 2.31–2.79), as were those in angle crashes (Multivariable adjusted OR: 10.85, 95 % CI: 9.24–12.73). Rear-seated occupants of belted drivers were 3.28 times more likely to be belted compared to rear-seated occupants of an unbelted driver. In a subpopulation analysis of all same-side crashes, unrestrained occupants were 5.96 times more likely to be severely/fatally injured compared to restrained occupants. Conclusion Restraint use was protective for rear-seated adult occupants involved in side crashes, including those in same-side crashes. Angle and same-side crashes are associated with increased injury severity

Side impact motor vehicle crashes: driver, passenger, vehicle and crash characteristics for fatally and nonfatally-injured rear-seated adults

Background Most studies of rear-seated occupants have focused on or included pediatric occupants which may not translate to adults. This study examines passenger, driver, vehicle and crash characteristics for rear-seated adult occupants involved in side crashes. Methods The National Automotive Sampling System General Estimates System (NASS/GES) for calendar years 2011–2014 was used with accompanying weights to examine the occupant, vehicle and crash characteristics associated with injury in rear-seated adults (n = 395,504) involved in a side crash. A weighted subpopulation analysis includes occupants travelling in a vehicle with an IIHS safety rating (n = 39,208), which was used to control for vehicle safety. Statistical analysis used Chi-square tests and multilevel multivariable logistic regression. Unadjusted and adjusted odds ratios (ORs) are reported with 95 % confidence intervals (95 % CIs). Results Rear-seated occupants on the same side as the crash impact were more likely to be severely/fatally injured than occupants seated on the opposite side (Multivariable adjusted OR: 2.54, 95 % CI: 2.31–2.79), as were those in angle crashes (Multivariable adjusted OR: 10.85, 95 % CI: 9.24–12.73). Rear-seated occupants of belted drivers were 3.28 times more likely to be belted compared to rear-seated occupants of an unbelted driver. In a subpopulation analysis of all same-side crashes, unrestrained occupants were 5.96 times more likely to be severely/fatally injured compared to restrained occupants. Conclusion Restraint use was protective for rear-seated adult occupants involved in side crashes, including those in same-side crashes. Angle and same-side crashes are associated with increased injury severity

Can Preschoolers be Health Messengers to Promote Breast Health among Chinese Americans?

Women’s limited knowledge about breast cancer screening (BCS), combined with differences in Eastern and Western disease prevention concepts, may contribute to late-stage breast cancer diagnosis among minorities. Children can be conduits of knowledge transfer to adults. This pilot study tested the use of a culturally-tailored theatrical preschool performance in increasing Chinese American women’s knowledge of BCS guidelines. Chinese preschool children relayed BCS guidelines through a culturally-tailored theatrical performance. Data were collected from 177 Chinese American women (84% foreign-born) who completed pre- and post-performance surveys. Findings suggested that promoting BCS guidelines through a culturally-tailored preschool theatrical performance significantly increased participants’ knowledge of the guidelines. Interventions involving young children as change agents to deliver simple health messages such as BCS guidelines are feasible and promising to increase knowledge and desired behavioral change within the target population. Further empirical investigations are warranted in larger randomized controlled trials

Restraint use and risky driving behaviors across drug types and drug and alcohol combinations for drivers involved in a fatal motor vehicle collision on U.S. roadways

Background While driving impaired is a well-recognized risk factor for motor vehicle (MV) crash, recent trends in recreational drug use and abuse may pose increased threats to occupant safety. This study examines mechanisms through which drug and/or alcohol combinations contribute to fatal MV crash. Methods The Fatality Analysis Reporting System (FARS) for 2008–2013 was used to examine drugs, alcohol, driver restraint use, driver violations/errors and other behaviors of drivers of passenger vehicles who were tested for both alcohol and drugs (n = 79,932). Statistical analysis was based on Chi-square tests and multivariable logistic regression. Associations of restraint use and other outcomes with alcohol and drug use were measured by estimated odds ratios (ORs) and 95 % confidence intervals (95 % CIs). Results More than half (54.8 %) of the study population were positive for drugs or alcohol at the time of crash. Approximately half of drivers were belted, but this varied from 67.1 % (unimpaired) to 33.0 % (drugs plus alcohol). Compared to the unimpaired, the odds of a driver being unbelted varied: alcohol and cannabis (OR 3.70, 95 % CI 3.44–3.97), alcohol only (3.50,3.36–3.65), stimulants (2.13,1.91–2.38), depressants (2.09,1.89–2.31), narcotics (1.84,1.67–2.02) and cannabis only (1.55,1.43–1.67). Compared to belted drivers, unbelted drivers were over 4 times more likely to die. Driving violations varied across drug/drug alcohol combinations. Speed-related violations were higher for drivers positive for stimulants, alcohol, cannabis, and cannabis plus alcohol, with a more than two fold increase for alcohol and cannabis (2.36, 2.05, 2.71). Conclusions Mechanisms through which drugs, alcohol and substance combinations produce increased risks to occupant safety include lowered restraint use and increases in risky driving behaviors, including speeding, lane, passing, turning and signal/sign violations

Restraint use and risky driving behaviors across drug types and drug and alcohol combinations for drivers involved in a fatal motor vehicle collision on U.S. roadways

Background While driving impaired is a well-recognized risk factor for motor vehicle (MV) crash, recent trends in recreational drug use and abuse may pose increased threats to occupant safety. This study examines mechanisms through which drug and/or alcohol combinations contribute to fatal MV crash. Methods The Fatality Analysis Reporting System (FARS) for 2008–2013 was used to examine drugs, alcohol, driver restraint use, driver violations/errors and other behaviors of drivers of passenger vehicles who were tested for both alcohol and drugs (n = 79,932). Statistical analysis was based on Chi-square tests and multivariable logistic regression. Associations of restraint use and other outcomes with alcohol and drug use were measured by estimated odds ratios (ORs) and 95 % confidence intervals (95 % CIs). Results More than half (54.8 %) of the study population were positive for drugs or alcohol at the time of crash. Approximately half of drivers were belted, but this varied from 67.1 % (unimpaired) to 33.0 % (drugs plus alcohol). Compared to the unimpaired, the odds of a driver being unbelted varied: alcohol and cannabis (OR 3.70, 95 % CI 3.44–3.97), alcohol only (3.50,3.36–3.65), stimulants (2.13,1.91–2.38), depressants (2.09,1.89–2.31), narcotics (1.84,1.67–2.02) and cannabis only (1.55,1.43–1.67). Compared to belted drivers, unbelted drivers were over 4 times more likely to die. Driving violations varied across drug/drug alcohol combinations. Speed-related violations were higher for drivers positive for stimulants, alcohol, cannabis, and cannabis plus alcohol, with a more than two fold increase for alcohol and cannabis (2.36, 2.05, 2.71). Conclusions Mechanisms through which drugs, alcohol and substance combinations produce increased risks to occupant safety include lowered restraint use and increases in risky driving behaviors, including speeding, lane, passing, turning and signal/sign violations

Restraint use and injury in forward and rear-facing infants and toddlers involved in a fatal motor vehicle crash on a U. S. Roadway

Background Use of appropriate child passenger safety restraints reduces injury in infants, with rear facing restraints favored over forward facing. In 2011, the American Academy of Pediatrics (AAP) began recommending that infants and children under the age of 2 years be restrained in a rear-facing seat installed in the vehicle’s rear seat. This study examines the practice of rear-facing restraints pre- and post-AAP recommendations for children under 2 years. Methods Data from the Fatality Analysis Reporting System (FARS) from 2008 to 2015 were used to examine restraint status and injuries in rear-seated infants and toddlers aged 0 to less than 2 years involved in fatal collisions (n = 4966). Subpopulation analyses were conducted on 1557 children with seat facing direction recorded. Multivariable logistic regression was used to generate odds ratios (OR) with 95% confidence intervals (CI). Covariates considered for inclusion in the multivariable model included passenger characteristics (age, gender, seating position), driver characteristics (age, gender, seat belt status, alcohol status, drug status, previous traffic violations), vehicle characteristics (vehicle type), and crash-level characteristics (day/night, weekday/weekend, rush hour, expressway/surface street, urban/rural). Results Approximately 6.7% (330 of 4996) of infants and toddlers were unrestrained with mortality that was approximately triple that of restrained infants (40.0% vs 13.7%, P < 0.0001). In multivariable adjusted models, predictors of an infant being unrestrained included unrestrained driver (OR: 3.17, 95% CI: 2.38–4.21), driver aged less than 20 years (OR: 2.18, 95% CI: 1.42–3.34), driver alcohol use (OR: 2.21, 95% CI: 1.42–3.44), center-seated infant (OR: 1.55, 95% CI: 1.19–2.03) and weekday crash (OR: 1.52, 95% CI: 1.12–2.01). Of all rear-seated children whose restraint status were reported (4966), rear-facing restraint use increased from 5.0% to 23.2% between 2008 and 2015 (P < 0.0001). The odds of rear-facing restraint use increased after introduction of the AAP guideline among infants aged 0 to < 1 year old (OR: 2.12, 95% CI: 1.46–3.10) and among toddlers aged 1 to < 2 years old (OR: 1.97, 95% CI: 1.03–3.79). Conclusion Trends in the use of rear-facing child restraints improved over the timeframe of this study, but remain low despite the introduction of AAP guidelines and the strengthening of child restraint laws

Localized magnetoplasmon modes arising from broken translational symmetry in semiconductor superlattices

The electromagnetic propagator associated with the localized collective magnetoplasmon excitations in a semiconductor superlattice with broken translational symmetry, is calculated analytically within linear response theory. We discuss the properties of these collective excitations in both radiative and non-radiative regimes of the electromagnetic spectra. We find that low frequency retarded modes arise when the surface density of carriers at the symmetry breaking layer is lower than the density at the remaining layers. Otherwise a doublet of localized, high-frequency magnetoplasmon-like modes occurs.Comment: Revtex file + separate pdf figure

Influence of Gap Extrema on the Tunneling Conductance Near an Impurity in an Anisotropic Superconductor

Changes: figures added in postscript form, Eq. (7) and various typos corrected. We examine the effect of an impurity on the nearby tunneling conductance in an anisotropically-gapped superconductor. The variation of the conductance has pronounced spatial dependence which depends strongly on the Fermi surface location of gap extrema. In particular, different gap symmetries produce profoundly different spatial features in the conductance. These effects may be detectable with an STM measurement on the surface of a high-temperature superconductor.Comment: 12 pages (revtex) + 3 figures (included - postscript), NSF-ITP-93-8

Primordial galactic magnetic fields from domain walls at the QCD phase transition

We propose a mechanism to generate large-scale magnetic fields with correlation lengths of 100 kpc. Domain walls with QCD scale internal structure form and coalesce obtaining Hubble scale correlations and align nucleon spins. Due to strong CP violation, nucleons in these walls have anomalous electric and magnetic dipole moments and thus the walls are ferromagnetic. This induces electromagnetic fields with Hubble size correlations. The same CP violation also induces a maximal helicity (Chern-Simons) correlated through the Hubble volume which supports an inverse cascade allowing the initial correlations to grow to 100 kpc today. We estimate the generated electromagnetic fields in terms of the QCD parameters and discuss the effects of the resulting fields.Comment: 5 pages, REVTex. Published versio