The role of stethoscopes in the transmission of hospital infections

Stethoscopes are one of the most commonly used medical devices and have been reported to be potential sources of hospital acquired infections. In this study, we aimed to find out the bacterial contamination of stethoscopes used by health-care staff. Swab samples were taken from the surface of the diaphragm of the stethoscopes used by health personnel in four hospitals including three secondline and one third-line health care institution in Turkey. The samples were inoculated onto bacteriological and mycological media. For identification of the microorganisms, conventional methods and Vitek2 (Biomérieux) were performed. Swab samples were taken from 121 stethoscopes. We found bacterial and fungal contamination on 92 (76%) of the stethoscopes. 15 out 90 (16.3%) had potential pathogens including methicillin susceptible Staphylococcus aureus (5), methicillin resistance Staphylococcus aureus (4), Escherichia coli (3), Acinetobacter baumannii, Acinetobacter haemolyticus and Enterococcus spp. Of the 121 health-care persons, only 61 regularly cleaned their stethoscopes by various disinfectants. The statistical difference between the two groups in terms of pathogen and microorganism isolation was not determined (p>0.05). Although stethoscopes are uncritical medical devices, they could contain pathogen microorganisms and they might be a potential source of hospital acquired infections.Key words: Stethoscopes, hospital infections, Staphylococcus aureus

Continuously Tunable Emission in Inverted Type-I CdS/CdSe Core/Crown Semiconductor Nanoplatelets

The synthesis and unique tunable optical properties of core/crown nanoplatelets having an inverted Type-I heterostructure are presented. Here, colloidal 2D CdS/CdSe heteronanoplatelets are grown with thickness of four monolayers using seed-mediated method. In this work, it is shown that the emission peak of the resulting CdS/CdSe heteronanoplatelets can be continuously spectrally tuned between the peak emission wavelengths of the core only CdS nanoplatelets (421 nm) and CdSe nanoplatelets (515 nm) having the same vertical thickness. In these inverted Type-I nanoplatelets, the unique continuous tunable emission is enabled by adjusting the lateral width of the CdSe crown, having a narrower bandgap, around the core CdS nanoplatelet, having a wider bandgap, as a result of the controlled lateral quantum confinement in the crown region additional to the pure vertical confinement. As a proof-of-concept demonstration, a white light generation is shown by using color conversion with these CdS/CdSe heteronanoplatelets having finely tuned thin crowns, resulting in a color rendering index of 80. The robust control of the electronic structure in such inverted Type-I heteronanoplatelets achieved by tailoring the lateral extent of the crown coating around the core template presents a new enabling pathway for bandgap engineering in solution-processed quantum wells

Phenomenology, Astrophysics and Cosmology of Theories with Sub-Millimeter Dimensions and TeV Scale Quantum Gravity

We recently proposed a solution to the hierarchy problem not relying on low-energy supersymmetry or technicolor. Instead, the problem is nullified by bringing quantum gravity down to the TeV scale. This is accomplished by the presence of $n \geq 2$ new dimensions of sub-millimeter size, with the SM fields localised on a 3-brane in the higher dimensional space. In this paper we systematically study the experimental viability of this scenario. Constraints arise both from strong quantum gravitational effects at the TeV scale, and more importantly from the production of massless higher dimensional gravitons with TeV suppressed couplings. Theories with $n>2$ are safe due mainly to the infrared softness of higher dimensional gravity. For $n=2$, the six dimensional Planck scale must be pushed above $\sim 30$ TeV to avoid cooling SN1987A and distortions of the diffuse photon background. Nevertheless, the particular implementation of our framework within type I string theory can evade all constraints, for any $n \geq 2$, with string scale $m_s \sim 1$ TeV. We also explore novel phenomena resulting from the existence of new states propagating in the higher dimensional space. The Peccei-Quinn solution to the strong CP problem is revived with a weak scale axion in the bulk. Gauge fields in the bulk can mediate repulsive forces $\sim 10^6 - 10^8$ times stronger than gravity at sub-mm distances, and may help stabilize the proton. Higher-dimensional gravitons produced on our brane and captured on a different "fat" brane can provide a natural dark matter candidate.Comment: 51 pages, late

Neutrino Masses from Large Extra Dimensions

Recently it was proposed that the standard model (SM) degrees of freedom reside on a $(3+1)$-dimensional wall or ``3-brane'' embedded in a higher-dimensional spacetime. Furthermore, in this picture it is possible for the fundamental Planck mass \mst to be as small as the weak scale \mst\simeq O(\tev) and the observed weakness of gravity at long distances is due the existence of new sub-millimeter spatial dimensions. We show that in this picture it is natural to expect neutrino masses to occur in the 10^{-1} - 10^{-4}\ev range, despite the lack of any fundamental scale higher than \mst. Such suppressed neutrino masses are not the result of a see-saw, but have intrinsically higher-dimensional explanations. We explore two possibilities. The first mechanism identifies any massless bulk fermions as right-handed neutrinos. These give naturally small Dirac masses for the same reason that gravity is weak at long distances in this framework. The second mechanism takes advantage of the large {\it infrared} desert: the space in the extra dimensions. Here, small Majorana neutrino masses are generated by breaking lepton number on distant branes.Comment: 17 pages, late

Magnetism in all-carbon nanostructures with negative gaussian curvature

The electronic and magnetic properties of an sp2 bonded all-carbon nanostructure, consisting of a nanotube junction structurally related to schwarzite, were investigated. The spin density functional theory was used during the investigation. The electronic structure of different tetrapods was calculated using the density functional theory within the local spin density approximation (LSDA). It was found that particular systems, which were related to schwarzite and contain no under-coordinated carbon atoms, carry a net magnetic moment in the ground state. The effect of edge termination on the net magnetic moment of the tetrapod was also studied.open13713

Generating Small Numbers by Tunneling in Multi-Throat Compactifications

A generic F-theory compactification containing many D3 branes develops multiple brane throats. The interaction of observers residing inside different throats involves tunneling suppression and, as a result, is very weak. This suggests a new mechanism for generating small numbers in Nature. One application is to the hierarchy problem: large supersymmetry breaking near the unification scale inside a shallow throat causes TeV-scale SUSY-breaking inside the standard-model throat. Another application, inspired by nuclear-decay, is in designing naturally long-lived particles: a cold dark matter particle residing near the standard model brane decays to an approximate CFT-state of a longer throat within a Hubble time. This suggests that most of the mass of the universe today could consist of CFT-matter and may soften structure formation at sub-galactic scales. The tunneling calculation demonstrates that the coupling between two throats is dominated by higher dimensional modes and consequently is much larger than a naive application of holography might suggest.Comment: 55 pages, 2 figures, v2: typo correcte

Proizvodnja limunske kiseline pomoću kvasaca uzgojenih na podlogama s glicerolom, dobivenim pri proizvodnji biodizela

The possibility of using glycerol and glycerol-containing waste from biodiesel manufacture as a carbon and energy source for microbiological production of citric acid has been studied. Acid formation on the selective media had previously been tested in 66 yeast strains of different genera (Candida, Pichia, Saccharomyces, Torulopsis and Yarrowia). Under growth limitation by nitrogen, 41 strains (belonging mainly to species Yarrowia lipolytica) produced acids; unlike 25 strains of the genera Debaryomyces, Candida, Pichia, Saccharomyces and Torulopsis. Among the 41 acid-producing strains, mutant strain Yarrowia lipolytica N15 was selected since it was able to produce citric acid presumably in high amounts. The citric acid production by the selected strain was studied in dependence on the medium pH, aeration and concentration of glycerol. Under optimal conditions, the mutant Y. lipolytica N15 produced up to 98 g/L of citric acid when grown in a fermentor with the medium containing pure glycerol, and 71 g/L of citric acid when grown on glycerol-containing waste. The effect of growth phases on physiological peculiarities of the citric acid producer was discussed.Ispitana je mogućnost uporabe glicerola i otpada bogatoga glicerolom, dobivenih pri proizvodnji biodizela, kao izvora ugljika i energije za mikrobnu proizvodnju limunske kiseline. Prethodno je ispitana proizvodnja limunske kiseline na selektivnim podlogama pomoću 66 sojeva kvasaca različitih vrsta (Candida, Pichia, Saccharomyces, Torulopsis i Yarrowia). Pri smanjenim koncentracijama dušika 41 soj (uglavnom vrste Yarrowia lipolytica) mogao je proizvesti limunsku kiselinu, dok 25 sojeva vrsta Debaryomyces, Candida, Pichiа, Saccharomyces i Torulopsis to nije moglo. Od 41 soja odabran je mutant Yarrowia lipolytica N15, jer je mogao proizvesti veliku količinu limunske kiseline. Ispitan je utjecaj pH-vrijednosti podloge, prozračivanja tijekom reakcije i koncentracije glicerola u podlozi na proizvodnju limunske kiseline pomoću toga soja. U optimalnim uvjetima u fermentoru mutant Yarrowia lipolytica N15 proizveo je do 98 g/L limunske kiseline na podlozi sa čistim glicerolom, a do 71 g/L limunske kiseline na podlozi s otpadom bogatim glicerolom. U radu se raspravlja i o utjecaju faze rasta na fiziološke značajke kvasaca pri proizvodnji limunske kiseline

Substrate-based atom waveguide using guided two-color evanescent light fields

We propose a dipole-force linear waveguide which confines neutral atoms up to lambda/2 above a microfabricated single-mode dielectric optical guide. The optical guide carries far blue-detuned light in the horizontally-polarized TE mode and far red-detuned light in the vertically-polarized TM mode, with both modes close to optical cut-off. A trapping minimum in the transverse plane is formed above the optical guide due to the differing evanescent decay lengths of the two modes. This design allows manufacture of mechanically stable atom-optical elements on a substrate. We calculate the full vector bound modes for an arbitrary guide shape using two-dimensional non-uniform finite elements in the frequency-domain, allowing us to optimize atom waveguide properties. We find that a rectangular optical guide of 0.8um by 0.2um carrying 6mW of total laser power (detuning +-15nm about the D2 line) gives a trap depth of 200uK for cesium atoms (m_F = 0), transverse oscillation frequencies of f_x = 40kHz and f_y = 160kHz, collection area ~ 1um^2 and coherence time of 9ms. We discuss the effects of non-zero m_F, surface interactions, heating rate, the substrate refractive index, and the limits on waveguide bending radius.Comment: 12 pages, 4 figures, revtex, submitted to Phys. Rev. A Replaced: final version accepted by PRA v.61 Feb 2000. (2 paragraphs added