Conditional Lower Bounds for Space/Time Tradeoffs

In recent years much effort has been concentrated towards achieving polynomial time lower bounds on algorithms for solving various well-known problems. A useful technique for showing such lower bounds is to prove them conditionally based on well-studied hardness assumptions such as 3SUM, APSP, SETH, etc. This line of research helps to obtain a better understanding of the complexity inside P. A related question asks to prove conditional space lower bounds on data structures that are constructed to solve certain algorithmic tasks after an initial preprocessing stage. This question received little attention in previous research even though it has potential strong impact. In this paper we address this question and show that surprisingly many of the well-studied hard problems that are known to have conditional polynomial time lower bounds are also hard when concerning space. This hardness is shown as a tradeoff between the space consumed by the data structure and the time needed to answer queries. The tradeoff may be either smooth or admit one or more singularity points. We reveal interesting connections between different space hardness conjectures and present matching upper bounds. We also apply these hardness conjectures to both static and dynamic problems and prove their conditional space hardness. We believe that this novel framework of polynomial space conjectures can play an important role in expressing polynomial space lower bounds of many important algorithmic problems. Moreover, it seems that it can also help in achieving a better understanding of the hardness of their corresponding problems in terms of time

Antibiotic Spacers in Shoulder Arthroplasty: Comparison of Stemmed and Stemless Implants.

Background: Antibiotic spacers in shoulder periprosthetic joint infection deliver antibiotics locally and provide temporary stability. The purpose of this study was to evaluate differences between stemmed and stemless spacers. Methods: All spacers placed from 2011 to 2013 were identified. Stemless spacers were made by creating a spherical ball of cement placed in the joint space. Stemmed spacers had some portion in the humeral canal. Operative time, complications, reimplantation, reinfection, and range of motion were analyzed. Results: There were 37 spacers placed: 22 were stemless and 15 were stemmed. The stemless spacer population was older (70.9 ± 7.8 years vs. 62.8 ± 8.4 years, p = 0.006). The groups had a similar percentage of each gender (stemless group, 45% male vs. stemmed group, 40% male; p = 0.742), body mass index (stemless group, 29.1 ± 6.4 kg/m2 vs. stemmed group, 31.5 ± 8.3 kg/m2; p = 0.354) and Charlson Comorbidity Index (stemless group, 4.2 ± 1.2 vs. stemmed group, 4.2 ± 1.7; p = 0.958). Operative time was similar (stemless group, 127.5 ± 37.1 minutes vs. stemmed group, 130.5 ± 39.4 minutes). Two stemless group patients had self-resolving radial nerve palsies. Within the stemless group, 15 of 22 (68.2%) underwent reimplantation with 14 of 15 having forward elevation of 109° ± 23°. Within the stemmed group, 12 of 15 (80.0%, p = 0.427) underwent reimplantation with 8 of 12 having forward elevation of 94° ± 43° (range, 30° to 150°; p = 0.300). Two stemmed group patients had axillary nerve palsies, one of which self-resolved but the other did not. One patient sustained dislocation of reverse shoulder arthroplasty after reimplantation. One stemless group patient required an open reduction and glenosphere exchange of dislocated reverse shoulder arthroplasty at 6 weeks after reimplantation. Conclusions: Stemmed and stemless spacers had similar clinical outcomes. When analyzing all antibiotic spacers, over 70% were converted to revision arthroplasties. The results of this study do not suggest superiority of either stemmed or stemless antibiotic spacers

A COMPARATIVE STUDY BETWEEN BLADES AND STUDS IN FOOTBALL BOOTS

The incidence of non-contact injuries in football is high. A significant proportion of the blame is aimed at the footwear worn. Bladed design boots have attracted criticism, with high profile sports teams banning them amid fears of causing knee injury BBC, 2009). This study aimed to biomechanically compare a bladed boot design with a more conventional studded boot design to assess if either boot type produces a greater muscle response and suggest their potential for causing non-contact injury

Sunlight exposure is just one of the factors which influence Vitamin D status

© The Royal Society of Chemistry and Owner Societies. Studies on the determinants of vitamin D status have tended to concentrate on input-exposure to ultraviolet B radiation and the limited sources in food. Yet, vitamin D status, determined by circulating concentrations of 25-hydroxyvitamin D (25(OH)D), can vary quite markedly in groups of people with apparently similar inputs of vitamin D. There are small effects of polymorphisms in the genes for key proteins involved in vitamin D production and metabolism, including 7-dehydrocholesterol reductase, which converts 7-dehydrocholesterol, the precursor of vitamin D, to cholesterol, CYP2R1, the main 25-hydroxylase of vitamin D, GC, coding for the vitamin D binding protein which transports 25(OH)D and other metabolites in blood and CYP24A1, which 24-hydroxylates both 25(OH)D and the hormone, 1,25-dihydroxyvitamin D. 25(OH)D has a highly variable half-life in blood. There is evidence that the half-life of 25(OH)D is affected by calcium intake and some therapeutic agents. Fat tissue seems to serve as a sink for the parent vitamin D, which is released mainly when there are reductions in adiposity. Some evidence is presented to support the proposal that skeletal muscle provides a substantial site of sequestration of 25(OH)D, protecting this metabolite from degradation by the liver, which may help to explain why exercise, not just outdoors, is usually associated with better vitamin D status

Accuracy of Emergency Medical Services Dispatcher and Crew Diagnosis of Stroke in Clinical Practice.

BACKGROUND: Accurate recognition of stroke symptoms by Emergency Medical Services (EMS) is necessary for timely care of acute stroke patients. We assessed the accuracy of stroke diagnosis by EMS in clinical practice in a major US city. METHODS AND RESULTS: Philadelphia Fire Department data were merged with data from a single comprehensive stroke center to identify patients diagnosed with stroke or TIA from 9/2009 to 10/2012. Sensitivity and positive predictive value (PPV) were calculated. Multivariable logistic regression identified variables associated with correct EMS diagnosis. There were 709 total cases, with 400 having a discharge diagnosis of stroke or TIA. EMS crew sensitivity was 57.5% and PPV was 69.1%. EMS crew identified 80.2% of strokes with National Institutes of Health Stroke Scale (NIHSS) ≥5 and symptom durationmodel, correct EMS crew diagnosis was positively associated with NIHSS (NIHSS 5-9, OR 2.62, 95% CI 1.41-4.89; NIHSS ≥10, OR 4.56, 95% CI 2.29-9.09) and weakness (OR 2.28, 95% CI 1.35-3.85), and negatively associated with symptom duration \u3e270 min (OR 0.41, 95% CI 0.25-0.68). EMS dispatchers identified 90 stroke cases that the EMS crew missed. EMS dispatcher or crew identified stroke with sensitivity of 80% and PPV of 50.9%, and EMS dispatcher or crew identified 90.5% of patients with NIHSS ≥5 and symptom duration \u3c6 \u3eh. CONCLUSION: Prehospital diagnosis of stroke has limited sensitivity, resulting in a high proportion of missed stroke cases. Dispatchers identified many strokes that EMS crews did not. Incorporating EMS dispatcher impression into regional protocols may maximize the effectiveness of hospital destination selection and pre-notification

A Survey of Expert Opinion Regarding Rotator Cuff Repair.

Many patients with rotator cuff tears have questions for their surgeons regarding the surgical procedure, perioperative management, restrictions, therapy, and ability to work after a rotator cuff repair. The purpose of our study was to determine common clinical practices among experts regarding rotator cuff repair and to assist them in counseling patients. We surveyed 372 members of the American Shoulder and Elbow Surgeons (ASES) and the Association of Clinical Elbow and Shoulder Surgeons (ACESS); 111 members (29.8%) completed all or part of the survey, and 92.8% of the respondents answered every question. A consensus response (\u3e50% agreement) was achieved on 49% (24 of 49) of the questions. Variability in responses likely reflects the fact that clinical practices have evolved over time based on clinical experience

Computational evidence for an early, amplified systemic inflammation program in polytrauma patients with severe extremity injuries

Extremity and soft tissue injuries contribute significantly to inflammation and adverse in-hospital outcomes for trauma survivors; accordingly, we examined the complex association between clinical outcomes inflammatory responses in this setting using in silico tools. Two stringently propensity-matched, moderately/severely injured (Injury Severity Score > 16) patient sub-cohorts of ~30 patients each were derived retrospectively from a cohort of 472 blunt trauma survivors and segregated based on their degree of extremity injury severity (above or below 3 on the Abbreviated Injury Scale). Serial blood samples were analyzed for 31 plasma inflammatory mediators. In addition to standard statistical analyses, Dynamic Network Analysis (DyNA) and Principal Component Analysis (PCA) were used to model systemic inflammation following trauma. Patients in the severe extremity injury sub-cohort experienced longer intensive care unit length of stay (LOS), total LOS, and days on a mechanical ventilator, with higher Marshall Multiple Organ Dysfunction (MOD) Scores over the first 7 days post-injury as compared to the mild/moderate extremity injury sub-cohort. The higher severity cohort had statistically significant elevated lactate, base deficit, and creatine phosphokinase on first blood draw, along with significant changes in multiple circulating inflammatory mediators. DyNA pointed to a sustained role for type 17 immunity in both sub-cohorts, along with IFN-γ in the severe extremity injury group. DyNA network complexity increased over 7 days post-injury in the severe injury group, while generally decreasing over this same time period in the mild/moderate injury group. PCA suggested a more robust activation of multiple pathways in the severe extremity injury group as compared to the mild/moderate injury group. These studies thus point to the possibility of self-sustaining inflammation following severe extremity injury vs. resolving inflammation following less severe extremity injury