Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433

SS 433 is a microquasar, a stellar binary system that launches collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift in the apparent position of the gamma-ray emission from the parsec-scale jets. These observations trace the energetic electron population and indicate that inverse Compton scattering is the emission mechanism of the gamma rays. Our modeling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system, at distances of 25 to 30 parsecs, and that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons.

MYSTAT: A compact potentiostat/galvanostat for general electrochemistry measurements

An open-source potentiostat/galvanostat instrument design is introduced that provides the ability to take accurate measurements over a current range of ±200 mA and a potential range of ±12 V. The improved capability of the instrument compared to the previously published design upon which it is based makes it suitable for performing a wider range of electrochemical measurements including the ability to use larger working electrodes, study of high current density processes, study of electrochemistry in nonaqueous solutions and use in high voltage processes such as electrophoretic deposition. The instrument can be controlled from any computer capable of running the Python programming language, including a low-cost Raspberry Pi. Unlike many commercial potentiostat designs, the instrument is completely open-source, giving researchers the ability to modify the hardware and software as needed for custom measurement techniques. The low cost makes the instrument attractive for research and teaching laboratories in which multiple electrochemical measurements need to be carried out in parallel.

Further studies on the thiol groups of human haemoglobin

When the SH groups of various derivatives of human haemoglobin are converted into their mercuric mercaptides small changes are observed in the optical rotatory dispersion in the range 385-294mmu. These changes are proportionately greater for the reactive than for the unreactive SH groups. These observations have been interpreted in terms of the conformational changes that are likely to occur in the haemoglobin molecule on modification of the SH groups.

The disulphide bonds of human and rabbit gamma-globulins

1. The reaction of the disulphide bonds of the predominant species of human and rabbit gamma-globulins (the 7s gamma-globulins) with sulphite was studied in the presence and absence of denaturing agents and heavy-metal reagents. 2. The total number of bonds reacting/mol. of mol.wt. 160000 was approx. 18 for human and 20 for rabbit gamma-globulin. 3. Six S.S bonds/mol. of human and 6.5 S.S bonds/mol. of rabbit gamma-globulin reacted with sulphite alone at pH6. These appeared to include all the interchain S.S bonds. 4. The number of free SH groups was less than 0.2/mol. of human and less than 0.3/mol. of rabbit gamma-globulin.

A method for the estimation of thiol esters

1. A method is described for the estimation of thiol ester groups. The thiol ester is converted into the corresponding thiol by reaction with ammonia; the thiol is then titrated amperometrically with mercuric chloride. 2. The method may be used in the presence of SH and S.S groups. The SH groups are titrated at pH3 in the presence of excess of chloride; under these conditions thiol esters do not react with mercuric chloride. Thiol ester plus thiol is then estimated by titration after reaction with ammonia. Finally, titration after reaction with ammonia and sulphite gives the thiol ester plus thiol plus disulphide. 3. The procedure has been applied to glyceraldehyde phosphate dehydrogenase. The enzyme was found to contain 15-16 SH groups/mol. and no S.S groups. After reaction with acetyl phosphate 1.8-3.5 thiol ester groups were detected, the number depending on the conditions of acetylation. In the absence of bound NAD, the number of thiol ester groups formed was 1.8/mol., although a value of 2.9 labile acetyl groups/mol. was given by the method of Lipmann & Tuttle (1945). The presence of thiol ester groups in the S-(d-3-phosphoglyceryl)-enzyme was also demonstrated.

Interfacing the radiology information system to the modality: an integrated approach

The radiology information system (RIS) provides patient and examination information that is used in setting up and performing a radiologic procedure. In a digital imaging environment, information from the RIS can also be used to populate fields in the Digital Imaging and Communications in Medicine (DICOM) image header. Ideally, information from the RIS should be available at the modality at the time of the examination, and automatically be attached to the image in the appropriate DICOM fields before storage in the picture archiving and communications system (PACS). We have designed a highly integrated RIS interface for a digital radiography (DR) system. This interface employs browser technology to make RIS information conveniently available at the modality, and DICOM modality performed procedure step (MPPS) for RIS/DR information exchange. A novel feature of our approach is that a single display screen at the modality is used to alternatively display either the modality control window or the RIS window. Full access to RIS capabilities is available at the modality, including worklists and prior reports.

"I wouldn't have minded a wee one running about": miscarriage and the family

A sample of 27 women who had miscarried during the first trimester of pregnancy were interviewed and followed up over a 6 month period. The affective and practical support which they received from within their family was documented. The husband/partner and mother were found to be the main sources of support; the presence of young children was viewed positively, and the role of other family members was rather variable. Family support following miscarriage, while greatly appreciated, was found to be inadequate on a number of different counts.

Calcification of rachitic rat cartilage in vitro by extracellular matrix vesicles

Growth plate cartilage from rachitic rats was studied to assess the role in calcification of extracellular matrix vesicles, which are thought to participate in the initial stage of mineralization of connective tissue. The concentration of matrix vesicles and their distribution within the longitudinal septa was found to be normal in rats made rachitic by feeding by a diet low in vitamin D and phosphate for 3 weeks after weaning. Rachitic cartilage matrix did not contain circumvesicular clusters of apatite as does normal cartilage; however, occasional vesicles did enclose one or a few apatite needles. When slices of rachitic cartilage were incubated at 37 C in a metastable calcium phosphate solution ([Ca++] times [PO SEE ARTICLE] equals 3.5 mM identical to 2), apatite formation was initiated in association with matrix vesicles. Under these conditions, mineralization was prominent in the upper hypertrophic cartilage, where matrix vesicles became encrusted with apatite after only 2 to 3 hours of incubation. Vesicular apatite accumulation was inhibited by preheating the cartilage to 60 C for 30 minutes. Measurements of 45Ca uptake by rachitic cartilage slices from metastable calcium phosphates solution also indicated inhibition of calcification by heat. Light microscopic autoradiographs showed 45Ca localization primarily in the matrix of longitudinal septa and substantiated the inhibition site of mineralization in healing rachitic cartilage. The presence of apatite within rachitic vesicles prior to heating and the inhibition of vesicle calcification by heat suggests an active, enzymatically and mediated mechanism of vesicular calcification.

Protein-hydrocarbon interactions. Interactions of various proteins with pure decane

1. Solutions of a number of proteins were subjected to gentle agitation in the presence of small quantities of decane. 2. Some of the protein was lost from solution and adsorbed on the surface of the emulsion formed; at the same time some of the decane was bound to the protein remaining in solution. 3. The two processes were found to be related and a mechanism is proposed to explain the relationship. 4. With lysozyme and ribonuclease, the protein in the aqueous phase of an emulsion exhibited normal enzymic activity, whereas the fraction adsorbed on the interface was much less active but recovered activity on desorption.

Protein-hydrocarbon interactions. Interactions of various proteins with decane in the presence of alcohols

1. Solutions of proteins were subjected to gentle agitation in the presence of small quantities of decane containing different alcohols. 2. Some of the protein was lost from solution and adsorbed on the surface of the emulsion formed; at the same time some decane was bound to the protein remaining in solution. 3. Comparison of these results with those obtained with pure decane suggests that a mixed film of protein+alcohol is formed on the surface of the emulsion. 4. If the concentration of alcohol in decane is increased the amount of protein adsorbed on the emulsion is decreased. This phenomenon was used to compare the effect of different alcohols in disrupting the hydrophobic interactions between proteins and hydrocarbons.