The triviality problem for profinite completions

We prove that there is no algorithm that can determine whether or not a finitely presented group has a non-trivial finite quotient; indeed, this remains undecidable among the fundamental groups of compact, non-positively curved square complexes. We deduce that many other properties of groups are undecidable. For hyperbolic groups, there cannot exist algorithms to determine largeness, the existence of a linear representation with infinite image (over any infinite field), or the rank of the profinite completion.This is the accepted manuscript. The final version is available from Springer at http://dx.doi.org/10.1007/s00222-015-0578-

Negative immersions for one-relator groups

We prove a freeness theorem for low-rank subgroups of one-relator groups. Let F be a free group, and let w ∈ F be a nonprimitive element. The primitivity rank of w, π(w), is the smallest rank of a subgroup of F containing w as an imprimitive element. Then any subgroup of the one-relator group G = F/⟨⟨w⟩⟩ generated by fewer than π(w) elements is free. In particular, if π(w) > 2, then G does not contain any Baumslag–Solitar groups. The hypothesis that π(w) > 2 implies that the presentation complex X of the one-relator group G has negative immersions: if a compact, connected complex Y immerses into X and X(Y) ≥ 0, then Y Nielsen reduces to a graph. The freeness theorem is a consequence of a dependence theorem for free groups, which implies several classical facts about free and one-relator groups, including Magnus’ Freiheitssatz and theorems of Lyndon, Baumslag, Stallings, and Duncan–Howie. The dependence theorem strengthens Wise’s w-cycles conjecture, proved independently by the authors and Helfer–Wise, which implies that the one-relator complex X has nonpositive immersions when π(w) > 1

One-relator groups with torsion are coherent

We show that any one-relator group G = F/⟪w⟫ with torsion is coherent – i.e., that every finitely generated subgroup of G is finitely presented – answering a 1974 question of Baumslag in this case

Soft-tissue specimen shrinkage during the preparation for scanning electron microscopy

KIMThe amount of shrinkage and the scanning electron microscope appearance of specimens of rat tongue, soft palate and small intestine, dehydrated by air drying , the critical point technique, the camphene technique and freeze drying were compare

Generalized triangle groups, expanders, and a problem of Agol and Wise

Answering a question asked by Agol and Wise, we show that a desired stronger form of Wise's malnormal special quotient theorem does not hold. The counterexamples are generalizations of triangle groups, built using the Ramanujan graphs constructed by Lubotzky--Phillips--Sarnak

Pengaruh Ukuran Perusahaan, Return on Asset Dan Net Profit Margin Terhadap Perataan Laba (Income Smoothing) (Studi Pada Perusahaan Manufaktur Yang Terdaftar Di Bei 2012-2014)

The work of company needed by investors because could affect the willingness of investors to plant or withdraw their investments, instrument companies used in his work is earnings information. Earnings management is most used by companies is income smoothing. Agency theory the concept of income smoothing, pincipal and agents have motivation. This research to understand and explain; variable influence size firm, return on asset and the net profit margin partial against the income smoothing; variable influence size firm, return on asset and net profit margin simultaneously against the income smoothing. The kind of research used this research is an explanation with a quantitative approach. The variable in this research is size firm, return on asset and net profit margin as independent variables and income smoothing as dependent variable. This research used secondary data time series from the period 2012 to 2014. Data analysis method used is descriptive analysis and multiple linear regression analysis. The results of multiple linear regression analysis showed; there are partial effect between size firm variables, return on asset and net profit margin to the income smoothing; there is a partial effect between size firm variables, return on asset and net profit margin to the income smoothing

Delayed diagnosis of neuroschistosomiasis in a non-endemic country: A tertiary referral centre experience

BACKGROUND: Neuroschistosomiasis is a severe complication of schistosomiasis, triggered by the local immune reaction to egg deposition, with spinal cord involvement the most well recognised form. Early treatment with praziquantel and high dose steroids leads to a reduction of neurological sequelae. The rarity of this condition in returning travellers to high income countries can result in delayed diagnosis and treatment. We aimed to evaluate the diagnosis and management of neuroschistosomiasis in a UK national referral centre. MATERIALS AND METHODS: A retrospective review of confirmed clinical cases of spinal schistosomiasis referred to the Hospital for Tropical Diseases, UK, between January 2016 and January 2020 was undertaken. Electronic referral records were interrogated and patient demographic, clinical, laboratory, and radiological data collected. RESULTS: Four cases of neuroschistosomiasis were identified. The median age at diagnosis was 28 (range 21 to 50) with three male patients. All patients had epidemiological risk factors for schistosomiasis based on travel history and freshwater exposure; two in Uganda (River Nile), one in Malawi and one in Nigeria. All patients presented with features of transverse myelitis including back pain, leg weakness, paraesthesia and urinary dysfunction. The mean time from presentation to health services to definitive treatment was 42.5 days (range 16–74 days). Diagnosis was confirmed with CSF serology for schistosomiasis in all cases. Radiological features on MRI spine included enhancement focused predominantly in the lower thoracic spinal cord in three cases and the conus in one patient. All patients received a minimum of three days of oral praziquantel and high dose steroids. At three-month follow-up, one patient had complete resolution of symptoms and three had residual deficit; one patient was left with urinary and faecal incontinence, another had urinary retention, and the final patient has persistent leg pains and constipation. CONCLUSION: We observed a marked delay in diagnosis of neuroschistosomiasis in a non-endemic country. We advocate undertaking a thorough travel history, early use of imaging and CSF schistosomal serology to ensure early diagnosis of neuroschistosomiasis in patients presenting with consistent symptoms. If schistosomal diagnostics are not immediately available, presumptive treatment under the guidance of a tropical medicine specialist should be considered to minimize the risk of residual disability. We advocate for consensus guidelines to be produced and reporting to be performed in a uniform way for patients with spinal schistosomiasis

Effects of High Charge Densities in Multi-GEM Detectors

A comprehensive study, supported by systematic measurements and numerical computations, of the intrinsic limits of multi-GEM detectors when exposed to very high particle fluxes or operated at very large gains is presented. The observed variations of the gain, of the ion back-flow, and of the pulse height spectra are explained in terms of the effects of the spatial distribution of positive ions and their movement throughout the amplification structure. The intrinsic dynamic character of the processes involved imposes the use of a non-standard simulation tool for the interpretation of the measurements. Computations done with a Finite Element Analysis software reproduce the observed behaviour of the detector. The impact of this detailed description of the detector in extreme conditions is multiple: it clarifies some detector behaviours already observed, it helps in defining intrinsic limits of the GEM technology, and it suggests ways to extend them.Comment: 5 pages, 6 figures, 2015 IEEE Nuclear Science Symposiu