Study of the effects of dust, relative humidity, and temperature on solar PV performance in Doha: Comparison between monocrystalline and amorphous PVS

The sensitivity of various solar photovoltaic technologies to dust, temperature, and relative humidity is investigated for Doha's environment. Results obtained show that monocrystalline photovoltaics (PVs) have efficiencies as high as 85% compared to 70% for amorphous ones. Also, dust accumulation degrades more critically the efficiency of amorphous and monocrystalline silicon PVs than the panel's temperature or relative humidity. In addition, the results show that amorphous PVs are more affected by temperature and relative humidity than monocrystalline PVs. However, amorphous PVs prove to be more robust against dust settlement than monocrystalline PVs and hence are more suitable for implementation in desert climates like Doha unless cleaning strategies are devised. It was estimated that 100 days of dust accumulation over monocrystalline PV panels, caused the efficiency to decrease by around 10%. This limitation makes solar PVs to represent an unreliable source of power for unattended or remote devices and thus strongly suggests the challenge of cleaning the panel's surface regularly or injecting technical modifications. Furthermore, the study suggests operating solar PV plants in Doha from 11:00 am to 02:00 pm to optimize production.Scopu

Proline is required for male gametophyte development in Arabidopsis

<p>Abstract</p> <p>Background</p> <p>In crosses between the proline-deficient mutant homozygous for <it>p5cs1</it> and heterozygous for <it>p5cs2 (p5cs1 p5cs2/P5CS2)</it>, used as male, and different Arabidopsis mutants, used as females, the <it>p5cs2</it> mutant allele was rarely transmitted to the outcrossed progeny, suggesting that the fertility of the male gametophyte carrying mutations in both <it>P5CS1</it> and <it>P5CS2</it> is severely compromised.</p> <p>Results</p> <p>To confirm the fertility defects of pollen from <it>p5cs1 p5cs2/P5CS2</it> mutants, transmission of mutant alleles through pollen was tested in two ways. First, the number of progeny inheriting a dominant sulfadiazine resistance marker linked to <it>p5cs2</it> was determined. Second, the number of <it>p5cs2/p5cs2</it> embryos was determined. A ratio of resistant to susceptible plantlets close to 50%, and the absence of aborted embryos were consistent with the hypothesis that the male gametophyte carrying both <it>p5cs1</it> and <it>p5cs2</it> alleles is rarely transmitted to the offspring. In addition, in reciprocal crosses with wild type, about 50% of the <it>p5cs2</it> mutant alleles were transmitted to the sporophytic generation when <it>p5cs1 p5cs2/P5CS2</it> was used as a female, while less than 1% of the <it>p5cs2</it> alleles could be transmitted to the outcrossed progeny when <it>p5cs1 p5cs2/P5CS2</it> was used as a male. Morphological and functional analysis of mutant pollen revealed a population of small, degenerated, and unviable pollen grains, indicating that the mutant homozygous for <it>p5cs1</it> and heterozygous for <it>p5cs2</it> is impaired in pollen development, and suggesting a role for proline in male gametophyte development. Consistent with these findings, we found that pollen from <it>p5cs1</it> homozygous mutants, display defects similar to, but less pronounced than pollen from <it>p5cs1 p5cs2/P5CS2</it> mutants. Finally, we show that pollen from <it>p5cs1 p5cs2/P5CS2</it> plants contains less proline than wild type and that exogenous proline supplied from the beginning of another development can partially complement both morphological and functional pollen defects.</p> <p>Conclusions</p> <p>Our data show that the development of the male gametophyte carrying mutations in both <it>P5CS1</it> and <it>P5CS2</it> is severely compromised, and indicate that proline is required for pollen development and transmission.</p

Branching vs. Linear Time: Final Showdown

The discussion of the relative merits of linear- versus branching-time frameworks goes back to early 1980s. One of the beliefs dominating this discussion has been that &quot;while specifying is easier in LTL (linear-temporal logic), verification is easier for CTL (branching-temporal logic)&quot;. Indeed, the restricted syntax of CTL limits its expressive power and many important behaviors (e.g., strong fairness) can not be specified in CTL. On the other hand, while model checking for CTL can be done in time that is linear in the size of the specification, it takes time that is exponential in the specification for LTL. Because of these arguments, and for historical reasons, the dominant temporal specification language in industrial use is CTL