On the complexity of edge labelings for trees

AbstractGiven a tree T with n edges and a set W of n weights, we deal with labelings of the edges of T with weights from W, optimizing certain objective functions. For some of these functions the optimization problem is shown to be NP-complete (e.g., finding a labeling with minimal diameter), and for others we find polynomial-time algorithms (e.g., finding a labeling with minimal average distance)

Neurotrauma: 2022 update

The year 2021 was highlighted by many notable advancements in the field of neurotrauma and associated neuropathology. After a thorough review of the new literature, we call attention to what we feel are among the most impactful studies and publications. In brief, 2021 was marked by published consensus papers related to the diagnosis of chronic traumatic encephalopathy (CTE) and its clinical counterpart, traumatic encephalopathy syndrome. There was also progress toward our understanding of the impact of traumatic brain injury (TBI) on the general population, and how strongly CTE pathology may, or may not, commonly underlie long term clinical sequelae following TBI. Next, a critical new study has identified that acetylated tau protein, which has been found to be increased in the brains of Alzheimer’s disease and CTE patients, can be induced by TBI, is neurotoxic, and that its reduction via already-existent therapeutics is neuroprotective. There are also several important updates that pertain to military and blast TBI, particularly as they pertain to establishing causality of interface astroglial scarring. In addition, and for the first time, a specific signature for diffuse axonal injury has been identified in ex vivo tissues using multidimensional magnetic resonance imaging, providing promise for the clinical diagnosis of this lesion. Finally, several important radiologic studies from 2021 have highlighted long-standing structural reductions in a number of brain regions following both mild and severe TBI, emphasizing the need for neuropathologic correlation. We end by highlighting an editorial piece discussing how TBI is portrayed in entertainment media and how this impacts public perception of TBI and its consequences

A New Method for Searching for Free Fractional Charge Particles in Bulk Matter

We present a new experimental method for searching for free fractional charge in bulk matter; this new method derives from the traditional Millikan liquid drop method, but allows the use of much larger drops, 20 to 100 mm in diameter, compared to the traditional method that uses drops less than 15 mm in diameter. These larger drops provide the substantial advantage that it is then much easier to consistently generate drops containing liquid suspensions of powdered meteorites and other special minerals. These materials are of great importance in bulk searches for fractional charge particles that may have been produced in the early universe.Comment: 17 pages, 5 figures in a singl PDF file (created from WORD Doc.). Submitted to Review of Scientific Instrument

Changing Traditions: Supervision, Co-Teaching, and Lessons Learned in a Professional Development School Partnership

Considering how long societies have been educating their youth, the history of teacher education is relatively brief. The first efforts to provide systematic education for teachers with some kind of practical experience occurred in Rheims, France, in the late 17th century when Jean Baptiste De La Salle opened the first normal school

Distinct subsets of unmyelinated primary sensory fibers mediate behavioral responses to noxious thermal and mechanical stimuli

Behavioral responses to painful stimuli require peripheral sensory neurons called nociceptors. Electrophysiological studies show that most C-fiber nociceptors are polymodal (i.e., respond to multiple noxious stimulus modalities, such as mechanical and thermal); nevertheless, these stimuli are perceived as distinct. Therefore, it is believed that discrimination among these modalities only occurs at spinal or supraspinal levels of processing. Here, we provide evidence to the contrary. Genetic ablation in adulthood of unmyelinated sensory neurons expressing the G protein-coupled receptor Mrgprd reduces behavioral sensitivity to noxious mechanical stimuli but not to heat or cold stimuli. Conversely, pharmacological ablation of the central branches of TRPV1+ nociceptors, which constitute a nonoverlapping population, selectively abolishes noxious heat pain sensitivity. Combined elimination of both populations yielded an additive phenotype with no additional behavioral deficits, ruling out a redundant contribution of these populations to heat and mechanical pain sensitivity. This double-dissociation suggests that the brain can distinguish different noxious stimulus modalities from the earliest stages of sensory processing

Is the Top Quark Really Heavier than the WW Boson?

Scalar induced top decays may drastically suppress $B(t\to \ell\nu + jet)$ and still hide the top below $M_W$. The $p\bar p$ collider experiments should enlarge the scope and study the $m_t - B(t\to\ell\nu j)$ plane. Specific model signatures such as $t\to ch^0\to cb\bar b$ (multiple high $p_T$ $b$-jets) and $t\to bH^+\to bc\bar s$, $b\tau^+\nu$ (with $B(t\to b\tau\nu) \ \raisebox{-.5ex}{\rlap{$\sim$}} \raisebox{.4ex}{$<$}\ 1/3$) should be explored. Without ruling out these possibilities, isolated lepton signals in the future might actually be due to the 4th generation$t^\prime$or$b^\prime$ quark, while top quark and toponium physics could still turn up at LEP-II.Comment: 11 pages (RevTex), 3 figures (not included), NTUTH-93-0

Narrowing the window for millicharged particles by CMB anisotropy

We calculate the cosmic microwave background (CMB) anisotropy spectrum in models with millicharged particles of electric charge q\sim 10^{-6}-10^{-1} in units of electron charge. We find that a large region of the parameter space for the millicharged particles exists where their effect on the CMB spectrum is similar to the effect of baryons. Using WMAP data on the CMB anisotropy and assuming Big Bang nucleosynthesis value for the baryon abundance we find that only a small fraction of cold dark matter, Omega_{mcp}h_0^2 < 0.007 (at 95% CL), may consists of millicharged particles with the parameters (charge and mass) from this region. This bound significantly narrows the allowed range of the parameters of millicharged particles. In models without paraphoton millicharged particles are now excluded as a dark matter candidate. We also speculate that recent observation of 511 keV gamma-rays from the Galactic bulge may be an indication that a (small) fraction of CDM is comprised of the millicharged particles.Comment: 10 pages, 3 figures; v2: journal version, references adde