Advancing Tests of Relativistic Gravity via Laser Ranging to Phobos

Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR's primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter $\gamma$, with an accuracy of two parts in $10^7$, thereby improving today's best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, $G$ and of the gravitational inverse square law at 1.5 AU distances--with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using laser ranging measurements of the distance between an Earth station and an active laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25 mJ, 10 ps pulses at 1 kHz, and receiving asynchronous 1 kHz pulses from earth via a 12 cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1 mm (3.3 ps) range precision. Existing satellite laser ranging (SLR) facilities--with appropriate augmentation--may be able to participate in PLR. Since Phobos' orbital period is about 8 hours, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 years of science operations. We discuss the PLR's science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission's primary objectives.Comment: 25 pages, 10 figures, 9 table

A case of brain abscess mimicking cystic brain tumor and showing intraoperative 5-aminolevulinic acid fluorescence: case report .

Intraoperative fluorescence diagnostics is proved highly sensitive and specific for surgery of highly malignant brain gliomas, meningiomas and metastases. The greatest capability of accumulating 5-ALA was found in oligodendrogliomas, piloid astrocytomas and gliomas with cystic components. In some cases, making the differential diagnosis between a cerebral cystic tumor and a brain abscess can be difficult due to the similarity of clinical and neuroimaging data. A 37 year old male was hospitalized in a local neurological hospital. On admission, he presented with headaches, nausea, episodic vomiting, and weakness in the left extremities. In the last few months the patient suffered from recurrent episods of sinusitis. Contrast-enhanced brain CT scans revealed a right parietal lobe lesion of irregular shape (70x35 mm) with perilesional contrast enhancement. Contrast-enhanced MRI showed a mass lesion, which was hypointense on T1 with a marked contrast accumulation at the periphery. To the differential diagnosis between the suspected abscess and malignant tumor, we used the method of intraoperative metabolic navigation with 5-ALA. To relive the severe tension of the brain tissue, a ultrasound-guided cyst puncture was carried out. As a result, a thick yellow purulent discharge (~30 mL) was drained. Microbiological analysis of cyst contents revealed the presence of the pathogenic Streptococcus alactolyticus in the abscess’s content. The 5-ALA-induced fluorescence can be successfully used in neurosurgery for the differential diagnosis between a intracerebral tumor cyst and an abscess in the brain