Insecurity for compact surfaces of positive genus

A pair of points in a riemannian manifold $M$ is secure if the geodesics between the points can be blocked by a finite number of point obstacles; otherwise the pair of points is insecure. A manifold is secure if all pairs of points in $M$ are secure. A manifold is insecure if there exists an insecure point pair, and totally insecure if all point pairs are insecure. Compact, flat manifolds are secure. A standing conjecture says that these are the only secure, compact riemannian manifolds. We prove this for surfaces of genus greater than zero. We also prove that a closed surface of genus greater than one with any riemannian metric and a closed surface of genus one with generic metric are totally insecure.Comment: 37 pages, 11 figure

Non Linear Current Response of a Many-Level Tunneling System: Higher Harmonics Generation

The fully nonlinear response of a many-level tunneling system to a strong alternating field of high frequency $\omega$ is studied in terms of the Schwinger-Keldysh nonequilibrium Green functions. The nonlinear time dependent tunneling current $I(t)$ is calculated exactly and its resonance structure is elucidated. In particular, it is shown that under certain reasonable conditions on the physical parameters, the Fourier component $I_{n}$ is sharply peaked at $n=\frac {\Delta E} {\hbar \omega}$, where $\Delta E$ is the spacing between two levels. This frequency multiplication results from the highly nonlinear process of $n$ photon absorption (or emission) by the tunneling system. It is also conjectured that this effect (which so far is studied mainly in the context of nonlinear optics) might be experimentally feasible.Comment: 28 pages, LaTex, 7 figures are available upon request from [email protected], submitted to Phys.Rev.

The measurement of commitment to work

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43493/1/11111_2004_Article_BF00972537.pd

Angiographic Pitfall: Duplicated Tapered A1 Segment of the Anterior Cerebral Artery Mimicking an Anterior Communicating Artery Aneurysm

We describe a misleading case of a partially occluded A1 segment duplication that mimicked an ACoA aneurysm on computed tomography angiography and conventional angiography and led to surgical intervention. The location of such an anomaly at the ACoA on the side of least hemodynamic stress may provide a clue to recognizing this variant

Omitting Routine Radiography of Traumatic Ankle Fractures After Initial 2-Week Follow-up Does Not Affect Outcomes The WARRIOR Trial: A Multicenter Randomized Controlled Trial

Background: The clinical consequences of routine follow-up radiographs for patients with ankle fracture are unclear, and their usefulness is disputed. The purpose of the present study was to determine if routine radiographs made at weeks 6 and 12 can be omitted without compromising clinical outcomes. Methods: This multicenter randomized controlled trial with a noninferiority design included 246 patients with an ankle fracture, 153 (62%) of whom received operative treatment. At 6 and 12 weeks of follow-up, patients in the routine-care group (n = 128) received routine radiographs whereas patients in the reduced-imaging group (n = 118) did not. The primary outcome was the Olerud-Molander Ankle Score (OMAS). Secondary outcomes were the American Academy of Orthopaedic Surgeons (AAOS) foot and ankle questionnaire, health-related quality of life (HRQoL) as measured with the EuroQol-5 Dimensions-3 Levels (EQ-5D-3L) and Short Form-36 (SF-36), complications, pain, health perception, self-perceived recovery, the number of radiographs, and the indications for radiographs to be made. The outcomes were assessed at baseline and at 6, 12, 26, and 52 weeks of follow-up. Data were analyzed with use of mixed models. Results: Reduced imaging was noninferior compared with routine care in terms of OMAS scores (difference [beta], -0.9; 95% confidence interval [CI], -6.2 to 4.4). AAOS scores, HRQoL, pain, health perception, and self-perceived recovery did not differ between groups. Patients in the reduced-imaging group received a median of 4 radiographs, whereas those in the routine-care group received a median of 5 radiographs (p < 0.05). The rates of complications were similar (27.1% [32 of 118] in the reduced-imaging group, compared with 22.7% [29 of 128] in the routine-care group, p = 0.42). The types of complications were also similar. Conclusions: Implementation of a reduced-imaging protocol following an ankle fracture has no measurable negative effects on functional outcome, pain, and complication rates during the first year of follow-up. The number of follow-up radiographs can be reduced by implementing this protocol.Trauma Surger

Human umbilical cord mesenchymal stromal cells as an adjunct therapy with therapeutic hypothermia in a piglet model of perinatal asphyxia

Background: With therapeutic hypothermia (HT) for neonatal encephalopathy, disability rates are reduced, but not all babies benefit. Pre-clinical rodent studies suggest mesenchymal stromal cells (MSCs) augment HT protection. Aims:The authors studied the efficacy of intravenous (IV) or intranasal (IN) human umbilical cord-derived MSCs (huMSCs) as adjunct therapy to HT in a piglet model. Methods:A total of 17 newborn piglets underwent transient cerebral hypoxia-ischemia (HI) and were then randomized to (i) HT at 33.5C 113 h after HI (n=7), (ii) HT+IV huMSCs (30נ10(6) cells) at 24 h and 48 h after HI (n=5) or (iii) HT+IN huMSCs (30נ10(6) cells) at 24 h and 48 h after HI (n=5). Phosphorus-31 and hydrogen-1 magnetic resonance spectroscopy (MRS) was performed at 30 h and 72 h and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells and oligodendrocytes quantified. In two further piglets, 30נ10(6) IN PKH-labeled huMSCs were administered. Results:HI severity was similar between groups. Amplitude-integrated electroencephalogram (aEEG) recovery was more rapid for HT+IN huMSCs compared with HT from 25 h to 42 h and 49 h to 54 h (P 0.05). MRS phosphocreatine/inorganic phosphate was higher on day 2 in HT+IN huMSCs than HT (P=0.035). Comparing HT+IN huMSCs with HT and HT+IV huMSCs, there were increased OLIG2 counts in hippocampus (P=0.011 and 0.018, respectively), internal capsule (P=0.013 and 0.037, respectively) and periventricular white matter (P=0.15 for IN versus IV huMSCs). Reduced TUNEL-positive cells were seen in internal capsule with HT+IN huMSCs versus HT (P=0.05). PKH-labeled huMSCs were detected in the brain 12 h after IN administration. Conclusions:After global HI, compared with HT alone, the authors saw beneficial effects of HT+IN huMSCs administered at 24 h and 48 h (30נ10(6) cells/kg total dose) based on more rapid aEEG recovery, improved (31)P MRS brain energy metabolism and increased oligodendrocyte survival at 72 h

WARRIOR-trial - is routine radiography following the 2-week initial follow-up in trauma patients with wrist and ankle fractures necessary: study protocol for a randomized controlled trial

Background: Extremity fractures such as wrist and ankle fractures are a common and costly healthcare problem. The management of these fractures depends on fracture type and loss of congruity of the joint, resulting in cast immobilization or operative treatment. Loss of congruity or displacement leading to uneven joint loading, osteoarthritis and an increased probability of a poor functional outcome should be identified within the first 2 weeks post-trauma, based upon radiographs to determine optimal treatment. After this period, routine radiographs are scheduled for monitoring the bone-healing process. Current protocols describe imaging at 1, 2, 6 and 12 weeks post-trauma. However, it is questionable whether routine radiography following the initial follow-up (2-weeks post-trauma) is cost effective. Methods/design: In a multicenter randomized controlled trial, 697 patients aged 18 years or older will be included: 385 wrist fracture- and 312 ankle fracture patients. Patients will be randomized into two groups: Group 1 receives usual care, consisting of radiographs 1, 2, 6 and 12 weeks post-trauma; Group 2 receives radiographs beyond the initial follow-up only when clinically indicated. The primary outcome is the overall extremity-specific function. For wrist fractures, this includes the Disabilities of the Arm, Shoulder and Hand Score; for the ankle fractures, this includes the Olerud and Molander ankle score. Secondary outcomes include: healthcare cost, the specific function measured with the Patient Rated Wrist and Hand Evaluation for wrist fractures and American Academy of Orthopaedic Surgeons foot and ankle questionnaire for ankle fractures, pain-intensity, health-related quality of life, self-perceived recovery, and complications. Both groups will be monitored at 1, 2, and 6 weeks and 3, 6, and 12 months. Discussion: This study will provide data on (cost) effectiveness of routine radiography in the follow-up of wrist and ankle fractures, and could pave the way for a change in (inter)national protocols. Trial registration: Netherlands Trial Register NTR4610, registration date 22 June 2014