Gene liked to commonest cancer Mutations in the human version of patched, a gene first identified in a fruit fly developmental pathway, cause a hereditary skin cancer and may contribute to sporadic skin cancers, too. The fruit fly has proven itself an adept teacher of genetics, Matthew scott of standford university school of medicine and Allen bale of Yale identified the gene at fault in a rare inherited disease, called Gorlin's or basal cell nevus syndrome which occurs in about 1/100000 people and predisposes its victims to both developmental abnormalities and a variety of cancers, esp basal cell carcinoma. The errant gene was first identified in the fruit fly. The human version of a gene called "oatched" a member of a key developmental control pathway that helps determine how different tissues are laid out in the embryonic fly. /*---------------------------------------------------------------------*/ Bose-Einstein Condensates Display Their First Tricks. A year ago, this month 6/5/1995 University of Colorado and NIST (Nat. Institute of Standards and Technology) in Boulder created a new state of matter : a Bose-Einstein condensate, in which a cloud of atoms is cooled so close to absolute zero that their quantum-mechanical waves merge. In effect, the atoms act like a single macroscopic particle- one that still obeys the microscopic laws of quantum physics. But with barely 1000 atoms in condensate that lasted just a few seconds, the colorado team could do no more than say they'd done it. Since that first triumph, it's gone from " a little bit of condensate squirting out of a tap and everyone cheering" "to seeing these macroscopic condensates, millions of atoms, and the first quantitative experiments; the ability to directly photograph them, manipulate them,squeeze them , quash them and even make them ring. The progress was on display last month at a symposium on Bose condensates. Wolfgang Ketterle reported developing a new atom trap that can create condensates of 5 million sodium atoms, shaped like elfin cigars a 1/3 of a millimeter long, that survive for a half minute. With the new trap , along with a technique the MIT workers have developed for imaging condensates without destroying them, the MIT and colorado groups are well on their way to studying this new state of matter. They may even be on the way to putting it to work iin atomic lasers, which would do for atoms what lasers do for light and take the world of atomic manipulation and measurement to levels of precision and accuracy never before seen. Before the atom laser was just a pipe dream. but the existence of these bose condensates makes it a reality. So far, only the MIT and boulder team as are making this kind of headway after the NIST university of colorado announcement last year, researchers speculated that any physicist might quickly concoct a Bose condensate with $50,000 in equipment and a little expertise. That seemed reasonable when reports of successful condensates followed from two other groups that had long been pursuing them, one led by Randy hulet at rice university and the other by ketterle at MIT. But since then no one else has been able to create a cloud of atoms cold and dense enough to form a Bose condensate, and even hulet says that it is only now that his group has compelling evidence for a condensate. Ketterle have adapted a trap designed by MIT physicist David Pritchard, rolling on a cloverleaf arrangement of magnetic coils to create a magnetic field that doesn't fall to zero and doesn't need to be rotated or plugged. As a result the new trap is simplest than the cone-shaped ones. and it also confines the atoms more tightly opening the way to long-lived, million-atom condensates. Size and stability allow for probing of properties. They managed to ring the condensate like a bell by suddenly changing the electromagnetic potential of the trap. The way to think of it is a standing sound wave. The condensate is a little blob, and you can get a sound wave, which sets up a standing wave, and you can then measure the frequency of different modes. Superfluids offer virtually no resistance to motion, they have no viscosity so a superfluid condensate should ring indefinitely. How do you image on . ? Photons give energy to the condensate. MIT has tuned a resonant frequency laser , photons refracted by the atoms in the condensate make an image. The cloud as a perfectly clear glass marble, it doesn't absorb light it just redirects it like a lens. With the right kind of push they will turn a Bose condensate into an atomic laser a coherent focused beam in which all the atoms like photons in a laser beam have identical quantum mechanical wave functions. Ketterle points out that his team has already created a primitive atomic laser just by turning off their magnetic trap and letting the condensate fall. Its a pulse of coherent matter. In a certain sense it is a valid to call it a pulsed atom atomic laser. A useful atomic laser would propel the pulse of coherent matter with a laser or by gently launching it with a magnetic field - a magnetic sling Such lasers could be used to lay down atoms on a substrate with extraordinary precision, a technology that could conceivably replace photolithography, the current technique for laying out microcircuitry. They would also hold promise for building atomic interferometers, measuring devices that - because the wavelengths of atoms are much smaller than those of light could be used for making measurements far more precise than can be made with laser interferometry. If you want to do something demanding with light you just use coherent light, a laser. If you want to do something demanding with atomic beams you will use a coherent beam of atoms an atom laser. /*---------------------------------------------------------------------*/ Microscopic particle motions in strongly coupled dusty plasmas The microscopic particle motions from the crystal to the disordered state of a dusty plasma with micrometer sized silicon dioxide particle suspensions in a radio-frequency glow discharge system were studied through an optical microimaging system. Small amplitude random motion around the lattice stiets of the crystal state, relative domain motion with varying boundaries, cooperative hopping the liquid state and highly disordered motion with increasing radio-frequency power were observed. Chaotic states with different spatial scales under the coherent and stochastic coupling between dust particles and self organized background plasma fluctuations were also demonstrated. /*---------------------------------------------------------------------*/ High resolution molecular spectroscopy of Van der Walls clusters in Liquid Helium Droplets. Van der walls clusters of SF6 prepared in He-4 droplets (4000atoms). Diode lasers measure high resolution infrared spectra of these clusters in the vicinity of v3 vibrational mode. Rotational strucutre was observed, indicated that the embedded species rotate nearly freely, though they had been cooled to a temperature of 0.37K. Results show droplet are superfluid . /*---------------------------------------------------------------------*/ Nonequilibrium Structures in Condensed Systems. Condense molecular systems form regular structures that become more ordered when the temperature is decreased. Strong external activation leads to qualitative changes in the system's behavior and to the emergence of new nonequilibrium structures. A striking example of this by Tabe and Yokoyama for traveling waves in Langmuir Blodgettf films. Nonequilibrium structures have long been observed in low-density systems, such as in the Belousov-Zhabotinsky reaction. concentrations are low, so physical interactions can be neglected. The system resembles an ideal gas . A similar situation is found in semiconductors, where electrons and holes represent a reactive gas like subsystem inside a solid crystal. Pattern formation in these "ideal" systems is described by reaction-diffusion models. Nonequilibrium structures can also appear in condensed systems of particles with attractive interaction. Here, external activation must act against cohesion, which is reasponsible for formation of an equilibrium thermodynamic strucutre; a higher activation is generally needed to produce structural changes. So that kinetic processes can efficiently compete with physical interactions between the particles and thus influence the microscopic organization of a system, the system must be structurally labile. Structural lability is a feature of soft matter condensed molecular systems with relatively weak interactions between particles. Examples include polymer gels and liquid crystals, lipid membranes or vesicles, Langmuir-blodgett films, thin liquid films on solid surfaces and adsorbate layers on metals. Nonequilibrium structures, directly interfering with the equilibrium organization,, are much more likely to form. nonequilibrium structures can generally be divided into stationary and time-dependent types. Stationary nonequilibrium structures have basically the same morphology as do equilibrium structures; that is they represent periodic or disordered patterns of stripes or certain domain arrays. The properties of equilibrium structures, such as the spatial size of domains or the array period, are determined only by the energy of interactions between the molecules. In contrast, the properties of nonequilibrium structures are controlled by kinetic parameters, which specify the rates of diffusion, relaxation, or reactions. Therefore, although the Turing patterns or the spots in reaction-diffusion systems may have the same shapes as equilibrium patterns formed by bubbles in thin films of magnetic garnets they belong to a different class of physical phenomena. They are accompanied by dissipation of energy; therefore, their generation of maintenance requires permanent energy or mass supply Stable periodic oscillations, self-supported propagation of waves, and formation of complex wave patterns or even turbulence represent the kinds of behavior that are not possible at thermal equilibrium . Here the difference in the properties of equilibrium and nonequilibrium systems becomes most spectacular. Time dependent patterns are propagating fronts or pulses, rotating spiral waves, pacemakers or traveling spots. Analysis and experiment for reaction-diffusion systems Examples of condensed systems in which nonequilibrium pattern formation is accompanied by a changed in the microscopic organization or by phase transitions are known. Tabe and Yokoyama reported traveling waves in illuminated Langmuir-Blodgett monolayers. Such insoluble monomolecular layers are formed at the air-water interface by amphiphilic molecules possessing a permanent electric dipole moment. At thermal equilibrium, complicated domain structures -s tripes forming a labyrinthine pattern or bubbles ordered in hexagonal arrays- have previously been observed in these films. Illumination with linearly polarized light at a wave length suitable to induce trans-cis isomerizations was found to cause a significant change in the equilibrium stripe pattern. Its spatial profile became modified and at a sufficiently high light intensity, the pattern broke down into a nonequilibrium stationary granular texture consisting of randomly oriented domains of 10micrometers or less in diameter. When the illumination was shut off, the initial equilibrium pattern of stripes was recovered. At the light intensities preceding formation of a random granular texture, traveling periodic orientational waves were observed. The wave velocity was typically of the order 50mm/s and only slightly depended on the incident light power. Occasionally propagating solitary waves were also seen. The importance of this discovery goes beyond a particular experiment. It shows that the kinds of nonequilibrium spatiotemporal organization, which were previously seen for chemical reactions in liquid solutions or at catalytic surfaces, are also possible in monomolecular organic films. Their existence also possesses the question whether similar nonequilibrium structures may be observed in other condensed organic systems, such as lipid membranes, playing a fundamental role in biological processes.