Book chapters will be unavailable on Saturday 24th August between 8am-12pm BST. This is for essential maintenance which will provide improved performance going forwards. Please accept our apologies for any inconvenience caused.
To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
While the distribution of the non-trivial zeros of the Riemann zeta function constitutes a central theme in Mathematics, nothing is known about the algebraic nature of these non-trivial zeros. In this article, we study the transcendental nature of sums of the form
where the sum is over the non-trivial zeros
is a rational function over algebraic numbers and
is a real algebraic number. In particular, we show that the function
has infinitely many zeros in
, at most one of which is algebraic. The transcendence tools required for studying
in the range
seem to be different from those in the range
, we have the following non-vanishing theorem: If for an integer
has a rational zero in
is the quadratic character associated with the imaginary quadratic field
. Finally, we consider analogous questions for elements in the Selberg class. Our proofs rest on results from analytic as well as transcendental number theory.
The existence of genotype by environment interaction (G*E) can cause a change in the ranking of bulls tested in one environment when their daughters are subsequently milked in another environment. If the degree of re-ranking is large, the genetic correlation between milk production in the two environments will be substantially less than 1.0, with the implication that proofs made in one environment may not be reliable predictors of proofs in the second environment. The aim of this study was to investigate the effect of increasing the difference between environments, defined on the basis of herd average milk yield, on the genetic correlation (rg) for milk, fat and protein yield in Holstein Friesian dairy cattle in Ireland.
Important differences exist between various databases in the digestibility of ruminant feed ingredients (INRA, 1989; MAFF, 1992). The objective of this experiment was to measure the digestibility of some the more important ruminant feed ingredients and the variation associated with them.
Interest is accruing in indicator traits as predictors of fertility which: 1) can be more easily recorded; 2) can be measured early in life; and, 3) possess a co-heritability that is larger than the heritability of the fertility traits. Potentially interesting indicator traits include body condition score (BCS) and body weight (BW). The objective of this study was to estimate genetic (co) variances between BCS, BCS change, BW, BW change, and fertility traits in dairy cattle.
Higher dry matter intakes (DMI) have been reported in dairy cows fed maize silage than in dairy cows fed grass silage. The objective of this experiment was to investigate this phenomenon by the measurement of digestibility and the determination of rumen outflow rates for both forages. The response in milk production of late lactation dairy cows to grass or maize silage was also measured.
Fourteen late lactation multiparous dairy cows (n = 7) were fed diets containing either grass silage (GS) (DM: 197g/kg; pH: 4.05; NDF: 642g/kg DM) or high starch maize silage (MS) (DM: 339g/kg; pH: 3.94; starch: 360g/kg DM; NDF: 442g/kg DM) ad-libitum plus 4kgs/hd/day of a dairy concentrate (233g CP/kg DM). Urea (460g N/kg DM) was used as a source of degradable protein (10g/kg DM) for the MS diet which also included straw (40g/kg DM). Dietary NDF equalled 542 and 423g/kg DM for the GS and MS diet.
Pre-1990 published responses to supplementation at pasture ranged from 0.4 to 0.6kg milk/kg concentrate fed. However since 1990 higher responses to concentrate supplementation at pasture have been published (Delaby 2001). The objective of this study was to determine if milk production responses of Holstein-Friesian dairy cows to concentrate supplementation at pasture are influenced by genetic merit (milk yield potential) in a spring calving grass based system of milk production.
Silicon nanoparticles are synthesized by very high frequency Plasma Enhanced Chemical Vapor Deposition (vhf-PECVD) in the gas phase. Pulsed plasmas are used to obtain particles with a narrow size distribution. The role of plasma OFF times is studied to tailor the size of the silicon nanoparticles. Various plasma OFF times are chosen, both longer- and shorter -than the residence time of the gases in the discharge. Time resolved optical emission spectroscopy (TROES) studies provide additional information about the growth precursor dynamics during plasma modulation. The size and the size distribution studies of the particles are done with transmission electron microscopy (TEM). These studies reveal that a plasma OFF time longer than the residence time is favorable for the formation of quantum sized silicon particles.
Peak Force Atomic Force Microscope is a new technique to characterize fragile materials such as nanoparticles with high accuracy with only one measurement. Unlike the tapping mode AFM, Peak Force AFM operates at a frequency below the resonant frequency of the cantilever. This allows for a direct control of the forces and avoids lateral forces that may damage the sample as in contact mode AFM. Furthermore, the performance characteristics of Peak Force AFM are suitable to work also in Tunneling AFM (TUNA) mode, enabling the study of the electrical properties of materials.
In this work SnS nanoparticles capped with tri-n-octylphosphine oxide (TOPO) have been characterized. By means of Peak Force AFM it is possible to measure simultaneously topography and current maps of nanoparticles, yielding information about the shape, size and the conductivity of even a single nanoparticle. The topography map clearly showed single nanoparticles with a size less than 5 nm and spherical shape. In the conductivity map it is possible to discern the same nanoparticles, the correlation with the topography map is evident. This confirms the conduction (though not calibrated) of SnS nanoparticles. This type of measurements has been repeated many times in order to check the reproducibility of this technique. Moreover, the same nanoparticles have been measured also by Torsional Resonant TUNA AFM in order to compare it with Peak Force AFM. By means of TR-TUNA it was possible to measure the topography of SnS nanoparticles capped with TOPO but not the current. Besides, the resolution of the topography map acquired by TR-TUNA AFM is inferior to Peak Force AFM. From this comparison it has been found that the conductivity of nanoparticles, even if they are capped with TOPO, can be measured by Peak Force AFM, a result that thus far has been difficult to achieve by other types of AFM.
Long-term tillage and fertilizer experiments were conducted in rice in kharif followed by lentil in dry subhumid Inceptisols at Varanasi and Faizabad; horse gram at Phulbani and linseed at Ranchi in moist subhumid Alfisols in rabi during 2001 to 2010. The study was conducted to assess the effect of conventional tillage (CT), low tillage + interculture (LT1) and low tillage + herbicide (LT2) together with 100% N (organic) (F1), 50% N (organic) + 50% N (inorganic) (F2) and 100% N (inorganic) (F3) on productivity, profitability, rainwater and energy use efficiencies. The results at Varanasi revealed that CT was superior with mean yield of 2389 kg ha−1, while F1 was superior with 2378 kg ha−1 in rice. At Faizabad, CT was superior with mean rice yield of 1851 kg ha−1 and lentil yield of 977 kg ha−1, while F1 was superior with 1704 and 993 kg ha−1 of rice and lentil, respectively. At Phulbani, F2 was superior with rice yield of 1170 kg ha−1. At Ranchi, F2 with rice yield of 986 kg ha−1 and F3 with linseed yield of 224 kg ha−1 were superior. The regression model of crop seasonal rainfall and yield deviations indicated an increasing trend in rice yield over mean (positive deviation) with increase in rainfall at all locations; while a decreasing trend (negative deviation) was found for lentil at Faizabad, horse gram at Phulbani and linseed at Ranchi. Based on economic analysis, CTF1 at Varanasi and Faizabad, CTF2 at Phulbani and LT2F2 at Ranchi were superior.
Pluvial lake deposits are found throughout western North America and are frequently used to reconstruct regional paleoclimate. In Death Valley, California, USA, we apply the beach particle technique (BPT) of Adams (2003), Sedimentology, 50, 565–577 and Adams (2004), Sedimentology, 51, 671–673 to Lake Manly deposits at the Beatty Junction Bar Complex (BJBC), Desolation Canyon, and Manly Terraces and calculate paleowind velocities of 14–27 m/s. These wind velocities are within the range of present-day wind velocities recorded in the surrounding area. Sedimentary structures and clast provenance at Desolation Canyon and the Manly Terraces indicate sediment transport from north to south. Lake level, based on the elevation of constructional features, indicates that the hill west of the BJBC was an island and that the BJBC spits formed during simple lake regression. The data are consistent with the hypothesis that the present wind regime (velocity and direction) formed the pluvial Lake Manly features.
A water vapor barrier layer is presented that is deposited entirely at temperatures below ∼100oC. Our method, using hot wire chemical vapor deposition (HWCVD), is effective in reducing the issue of pinholes in single layers of silicon nitride (SiNx) made at such low substrate temperatures. We succeeded in depositing an all hot-wire simple three-layer structure consisting of two low-temperature SiNx layers with a polymer layer in between, exhibiting a water vapor transmission rate (WVTR) as low as 5*10-6 g/m2/day, determined at a temperature of 60°C and a relative humidity of 90%. This WVTR is low enough for organic and polymer devices. In a second experiment the robustness of the barrier layer is shown with respect to environmental dust.
In this paper, we investigate a conjecture due to S. and P. Chowla and its generalization by Milnor. These are related to the delicate question of non-vanishing of
-functions associated to periodic functions at integers greater than 1. We report on some progress in relation to these conjectures. In a different vein, we link them to a conjecture of Zagier on multiple zeta values and also to linear independence of polylogarithms.
Direct deposition of polycrystalline silicon (poly-Si) thin films by the Hot Wire CVD method has been used for the first time for the fabrication of poly-Si top gate Thin Film Transistors (TFTs). The TFTs have a high electron mobility in saturation of up to 4 cm2V−1s−1 as well as a remarkably large ON/OFF ratio of up to 6 × 105.
The Si-H vibration in IR spectra of our device quality poly-Si films grown by hot-wire chemical vapour deposition (HWCVD) made at low wire temperature (Tw=1800 °C) is at 2000 cm−1 whereas in a poly-Si film made at high wire temperature (Tw=1900 °C) both 2000 cm−1 vibrations as well as 2100 cm−1 are observed. On the other hand, the Raman spectra (probing the upper part of the film) of Si-H stretching vibration measured for both these samples show only 2000 cm-1 mode. XTEM micrographs of these films show that whereas the low Tw film has a structure made of closely packed crystalline columns, the high Tw film has conical crystalline structures with amorphous region between them. The crystal cones meet each other towards the top of the film and form a closed structure. This is confirmed by Raman spectrum at 520 cm−1. We attribute the 2100 cm−1 mode to the Si-H bonds at the surface of the cones touching the amorphous regions. The Si-H vibration shifts to 2000 cm-1 when the crystalline cones coalesce with each other, as is the case in the upper part of both types of films.
The first competitive a-Si/poly-Si multibandgap tandem cells have been made in which the two intrinsic absorber layers are deposited by Hot Wire Chemical Vapor Deposition (HWCVD). These cells consist of two stacked n-i-p type solar cells on a plain stainless steel substrate using plasma deposited n- and p-type doped layers and Hot-Wire deposited intrinsic (i) layers, where the i-layer is either amorphous (band gap 1.8 eV) or polycrystalline (band gap 1.1 eV). In this tandem configuration, all doped layers are microcrystalline and the two intrinsic layers are made by decomposing mixtures of silane and hydrogen at hot filaments in the vicinity of the substrate. For the two layers we used individually optimized parameters, such as gas pressure, hydrogen dilution ratio, substrate temperature, filament temperature, and filament material. The solar cells do not comprise an enhanced back reflector, but feature a natural mechanism for light trapping, due to the texture of the (220) oriented poly-Si absorber layer and the fact that all subsequent layers are deposited conformally. The deposition rate for the throughput limiting step, the poly-Si i-layer, is ≍ 5-6 Å/s. This layer also determines the highest substrate temperature required during the preparation of these tandem cells (500 °C). The initial efficiency obtained for these tandem cells is 8.1 %. The total thickness of the silicon nip/nip structure is only 1.1 µm.
Thin films of Y-Ba-Cu-O have been prepared by rf diode sputtering from a single mixed-oxide powder target. The films were deposited on sapphire and cubic zirconia substrates, with the substrates either cooled, heated, or left to establish thermal equlibrium. The Cu content in the films decreased with increasing substrate temperature. Films having composition close to the desired 1–2–3 stoichiometry were fabricated either by enriching the target with CuO or by cooling the substrate. Using the latter approach, a single target was used for over 20 depositions yielding films that were uniform in composition (although slightly Cu-rich), and consistent from run to run. These films had as-deposited room temperature sheet resistances on the order of 100 kΩ. Subsequent annealing at temperatures up to 850 C resulted in films that were superconducting with an onset around 90 K and zero resistance at 50 K. The critical current was found to exceed 2000 A/cm2 at 4.2 K.
The 1:1 charge transfer salt of dimethyltetrathiotetracene (DMTTT) and of tetracyanoethylene (TCNE), C26H12N4S4 crystallizes from chlorobenzene in the monoclinic system, space group P2(l)/c with cell constants a = 11.136(2), b = 11.254(3), C = 17.280(4) A, beta = 96.56(2), V = 2151.4(9) A, Z = 4 and dcalc = 1.57 0 mg/nun. The structure is made up of dimers of DMTTT and TCNE, respectively. Polycrystalline samples of DMTTT/TCNE exhibit a weak paramagnetism which was studied by ESR techniques from 102 to 293 K. The ESR studies reveal anisotropie spectra which are best resolved in the temperature range 102 to 250 K. The spectra observed are those expected from a spin system which is described by an orthorhombic g-tensor. The isotropie g-value calculated from the observed anisotropie g-tensors falls between the isotropie g-values for DMTTT and TCNE. As the temperature is increased, the spectral width decreases suggesting motion of and/or an increase in the spin concentration. DMTTT/TCNE is a relatively poor electrical conductor which is consistent with its crystal structure.
The successful synthesis of dimethyltetrathiotetracene (DMTTT) has been achieved in our laboratory and an account of the details of the synthesis has been reported. Reported herein are studies of the physical properties of DMTTT and some of its chemistry. Both 1:1 and 2:1 DMTTTX charge transfer salts have been prepared and are in the process of being characterized in our laboratory. Comparisons of physical properties and the results of studies such as single crystal x-ray diffraction, solid state ESR spectra, cyclic voltammetry and electrical conductivity are reported. To date, these comparisons reveal considerable similarity between the properties of any given DMTTT charge transfer salt and its corresponding tetrathiotetracene (TTT) charge transfer salt.
Poly-silicon films have been prepared by hot-wire chemical vapour deposition (HWCVD) from hydrogen diluted silane gas at a low temperature (430 °C). The crystalline volume fraction is 95%. The grains have an average size of 70 nm and coalesce completely. The activation energy (0.54 eV) and the low carrier concentration (6.8 × 1010 cm−3) indicate the fully intrinsic nature of the films. The low (<1017 cm−3) defect density, the absence of 2100 cm−1 mode in infrared spectrum, the low activation energy of Hall mobility (0.012 eV) and the ambipolar diffusion length (LD) of 568 nm all indicate that the grain boundaries in the poly-Si:H films are indeed very thin. Preliminary n-i-p cells incorporating a poly-silicon i-layer yielded 3.15% efficiency and a current density of 18.2 mW/cm2 for only a 1.5 μm i-layer. In the solar cell, the conducting path is along the columnar grains ( (220) preferential orientation from XRD) and the carrier transport bypasses the grain boundary defects. This has been confirmed from the c-Si like optical absorption spectrum (measured by Dual Beam Photoconductivity in the cell configuration) at the low energy region. Inverted staggered thin-film transistors incorporating the poly-silicon layers showed transfer and output characteristics similar to those of state of the art a-Si:H TFTs : the saturation mobility is 0.4 cm2/Vs and the off current is approximately 10−11 A. This leads to the conclusion that the silicon near the SiO2 interface (the channel region) is still amorphous. This is illustrated by XTEM.
Wafer cleaning studies have been performed so as to understand the influence of acoustic (megasonic) energy on particle removal in dilute SC-1 solutions. Surface etching alone (up to 60Å) has been found to be insufficient to completely remove silicon nitride surface particles from native oxide surfaces in the absence of megasonics. For megasonic cleaning processes the minimum surface etching required for complete nitride particle removal is significantly lower (between 3–12Å) than for a non-megasonic process. The exact 'threshold' for surface etching will depend on the chemical nature of the particle/surface and the megasonics power. Megasonics energy does not appear to enhance chemical etching of the substrate, at least for silicon oxide substrates, however, it significantly improves particle removal. This data suggests that the particle removal process can benefit from both a thermally activated component (etching) as well as an acoustic component (cavitation/ acoustic streaming).