Seasonal slow slip in landslides as a window into the frictional rheology of creeping shear zones.

Whether Earth materials exhibit frictional creep or catastrophic failure is a crucial but unresolved problem in predicting landslide and earthquake hazards. Here, we show that field-scale observations of sliding velocity and pore water pressure at two creeping landslides are explained by velocity-strengthening friction, in close agreement with laboratory measurements on similar materials. This suggests that the rate-strengthening friction commonly measured in clay-rich materials may govern episodic slow slip in landslides, in addition to tectonic faults.

Foreshock properties illuminate nucleation processes of slow and fast laboratory earthquakes.

Understanding the connection between seismic activity and the earthquake nucleation process is a fundamental goal in earthquake seismology with important implications for earthquake early warning systems and forecasting. We use high-resolution acoustic emission (AE) waveform measurements from laboratory stick-slip experiments that span a spectrum of slow to fast slip rates to probe spatiotemporal properties of laboratory foreshocks and nucleation processes. We measure waveform similarity and pairwise differential travel-times (DTT) between AEs throughout the seismic cycle.

Ultralow frictional healing explains recurring slow slip events.

Plate motion on shallow subduction megathrusts is accommodated by a spectrum of tectonic slip modes. However, the frictional properties and conditions that sustain these diverse slip behaviors remain enigmatic. Frictional healing is one such property, which describes the degree of fault restrengthening between earthquakes.

Preferential Retention and Transport of Perfluorooctanesulfonic Acid in a Dolomite Aquifer.

Per- and polyfluoroalkyl substances (PFAS) can represent a significant human health risk if present in aquifers used as a drinking water source. Accurate assessment of PFAS exposure risks requires an improved understanding of field-scale PFAS transport in groundwater. Activities at a former firefighter training site in University Park, Pennsylvania introduced perfluorooctanesulfonic acid (PFOS) to the underlying dolomite aquifer.

Slow slip source characterized by lithological and geometric heterogeneity.

Slow slip events (SSEs) accommodate a significant proportion of tectonic plate motion at subduction zones, yet little is known about the faults that actually host them. The shallow depth (<2 km) of well-documented SSEs at the Hikurangi subduction zone offshore New Zealand offers a unique opportunity to link geophysical imaging of the subduction zone with direct access to incoming material that represents the megathrust fault rocks hosting slow slip. Two recent International Ocean Discovery Program Expeditions sampled this incoming material before it is entrained immediately down-dip along the shallow plate interface.

Recurring and triggered slow-slip events near the trench at the Nankai Trough subduction megathrust.

The discovery of slow earthquakes has revolutionized the field of earthquake seismology. Defining the locations of these events and the conditions that favor their occurrence provides important insights into the slip behavior of tectonic faults. We report on a family of recurring slow-slip events (SSEs) on the plate interface immediately seaward of repeated historical moment magnitude () 8 earthquake rupture areas offshore of Japan.

Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes.

Slow earthquakes represent an important conundrum in earthquake physics. While regular earthquakes are catastrophic events with rupture velocities governed by elastic wave speed, the processes that underlie slow fault slip phenomena, including recent discoveries of tremor, slow-slip and low-frequency earthquakes, are less understood. Theoretical models and sparse laboratory observations have provided insights, but the physics of slow fault rupture remain enigmatic.

Critically pressured free-gas reservoirs below gas-hydrate provinces.

Palaeoceanographic data have been used to suggest that methane hydrates play a significant role in global climate change. The mechanism by which methane is released during periods of global warming is, however, poorly understood. In particular, the size and role of the free-gas zone below gas-hydrate provinces remain relatively unconstrained, largely because the base of the free-gas zone is not a phase boundary and has thus defied systematic description.

Improving the prediction of outcome in severe acute closed head injury by using discriminant function analysis of normal auditory brainstem response latencies and amplitudes.

Object: The auditory brainstem response (ABR) is a useful addition to standard medical measures for predicting outcome in patients with severe acute closed head injury (ACHI). Limiting this success, however, is the poor predictive value of a so-called "normal" ABR. In this study the authors used discriminant function analysis (DFA) of ABR Wave I, III, and V latencies and amplitudes to improve the predictive accuracy of the normal ABR, both as a single measure and in combination with other standard medical measures.

Optic neuritis in an urban black African community.

Purpose: To describe the clinical profile of idiopathic optic neuritis in South African blacks.

Methods: South African black patients with acute isolated idiopathic optic neuritis, treated and followed for at least 3 months at a large medical centre, were studied. Exclusion criteria were other causes of optic neuropathy (such as ischaemic optic neuropathy, toxins or Leber's hereditary optic neuropathy); all causes of optic neuritis (such as HIV, neurosyphilis, sarcoid or connective tissue disease); neurological disease outside of the optic nerves; and any race other than South African black.

Demyelinating disorder of the central nervous system occurring in black South Africans.

Objectives: To investigate the nature and cause in eight black South African patients of a recurrent (multiphasic), remitting, and relapsing demyelinating disease of the CNS.

Methods: The clinical and laboratory investigations and radiological manifestations of these patients were documented.

Results: Each patient had two or more acute attacks of demyelinating disease affecting the CNS.

New-onset seizures associated with HIV infection.

The authors studied new-onset seizures in 60 heterosexual black South African HIV-infected patients who had not used IV drugs. An intracranial space-occupying lesion was identified in 53% of patients, meningitis in 22%, and no additional cause in 25%. Of the patients with an identifiable cause, 64% had probable tuberculosis (tuberculoma or tuberculous meningitis).

The spectrum of HIV-1 related cancers in South Africa.

Despite the high prevalence of infection by the Human Immunodeficiency Virus (HIV) in South Africa, information on its association with cancer is sparse. Our study was carried out to examine the relationship between HIV and a number of cancer types or sites that are common in South Africa. A total of 4,883 subjects, presenting with a cancer or cardiovascular disease at the 3 tertiary referral hospitals in Johannesburg, were interviewed and had blood tested for HIV.

The clinical and genetic characteristics of spinocerebellar ataxia type 7 (SCA 7) in three Black South African families.

Objectives: Spinocerebellar ataxia type 7 is a rare autosomal dominant neurodegenerative disorder characterized by progressive cerebellar and retinal degeneration, described in various population groups in the literature. This is the first description from South Africa. The objective was to document the clinical and genetic characteristics of our patients and to determine concordance with other described cases.

Meningitis in a community with a high prevalence of tuberculosis and HIV infection.

Objectives: To evaluate the spectrum of aetiologies, and distinguishing clinical and laboratory features, of meningeal infection in a community with a high prevalence of tuberculosis (TB) and HIV infection.

Setting: A hospital serving mineworkers, originating from rural areas of Southern Africa.

Design: Prospective cohort of 60 consecutive lumbar punctures (LPs), performed for suspected meningitis.

Dual infective pathology in patients with cryptococcal meningitis.

Coinfection of the nervous system by two distinct nonviral organisms is uncommon and often undiagnosed. Medical teaching emphasizes that a single pathologic process should be sought; however, in the presence of severe immunocompromise this approach may not hold true. We describe seven HIV-1 seropositive patients with cryptococcal meningitis, three of whom had a proven nervous system infection with a second organism: concurrent tuberculous meningitis, a tuberculoma, and the first documented case of cryptococcal meningitis and neurosyphilis.

Huntington's disease confirmed by genetic testing in five African families.

Huntington's disease is an autosomal-dominant inherited progressive neurodegenerative disease associated with an expanded trinucleotide repeat (CAG) sequence on the short arm of chromosome 4. The disease is considered rare in Africans. We report five black South African families of different ethnic origin with proven expansions typical of Huntington's disease and discuss the possible origins of the disease in Africa.

High human immunodeficiency virus type 1 RNA load in the cerebrospinal fluid from patients with lymphocytic meningitis.

Thirty-seven matched cerebrospinal fluid (CSF) and plasma samples from 34 human immunodeficiency virus type 1 (HIV-1)-infected patients with suspected meningitis were analyzed for levels of HIV-1 RNA and markers of inflammation. Patients with tuberculous (n = 9) or cryptococcal (n = 6) meningitis had the highest CSF virus loads, which in many cases exceeded the levels in plasma, compared with patients with meningococcal meningitis (n = 3), aseptic meningitis (n = 8), tuberculoma (n = 2), or AIDS dementia complex (n = 4) or with normal lumbar punctures (n = 3). CSF virus load correlated significantly with the number of infiltrating lymphocytes (r = .

A double-blind controlled clinical trial of oxcarbazepine versus phenytoin in adults with previously untreated epilepsy.

In the last 5 years oxcarbazepine (OXC) has been registered in many countries for use as first-line and add-on treatment for partial seizures with or without secondarily generalized seizures (PS) and generalized tonic-clonic seizures without partial onset (GTCS). Its use as monotherapy in adults with newly diagnosed epilepsy was investigated in this double-blind, randomized, parallel-group comparison with phenytoin (PHT). A total of 287 adult patients, with either PS or GTCS, were randomized.

Multiple sclerosis in black South Africans and Zimbabweans.

Multiple sclerosis is rare among the indigenous black people of Africa. The first account of a black patient with multiple sclerosis in South Africa was published as late as 1987. Since then a search to find black patients with multiple sclerosis in Southern Africa has continued.

Vitelliform macular degeneration associated with mitochondrial myopathy.

A patient with mitochondrial myopathy is described. Examination of his fundus revealed bilateral vitelliform degeneration of the maculae. This lesion is a focal abnormality of the retinal pigment epithelium and may be a manifestation of the underlying mitochondrial disease.

Abnormal copper metabolism: another "non-Wilson's" case.

We describe a patient with extrapyramidal neurologic disease and an abnormal copper profile with hepatic copper accumulation, but no cirrhosis histologically, thus excluding a diagnosis of Wilson's disease (WD). We compared and highlighted the differences between similar previously reported cases of abnormal copper metabolism and true WD and suggest a spectrum of disease due to abnormal copper metabolism resulting in varied histochemical expression.