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The shift to multicore microprocessor architecture is likely to result in higher coolant flow requirements and thus exacerbate the problem of increasing data center energy consumption, also with respect to hotspot elimination. We present and experimentally prove a novel concept, for embedded, hotspot-targeted and energy efficient cooling of heterogeneous chip power landscapes. The rationally distributed, embedded microstructures presented here are able to adapt the heat transfer capability to a steady but non-uniform chip power map by passively throttling the flow in low heat flux areas. For the industrially acceptable limit on pressure drop of approximately 0.4 bar, the hotspot-targeted embedded liquid cooling (HT-ELC) designs are evaluated against a conservatively chosen conventional embedded liquid cooling (C-ELC) design and existing heat sinks in the literature. For an average steady-state heat flux of 150 W/cm 2 in core areas (hotspots) and 20 W/cm 2 over the remaining chip area (background), the chip temperature variation is reduced from 10 °C under the conventional cooling to 4 °C under the current hotspot targeted heat sink – a reduction of 57%. For heat fluxes of 300 and 24 W/cm 2 , the temperature variation is reduced by 30%. We show that the HT-ELC designs consume less than 0.3% of total chip power as pumping power to achieve this thermal performance, which the C-ELC design cannot match under all feasible levels of pumping power. Moreover, the HT-ELC designs achieve at least 70% improvement over the existing hotspot targeted heat sinks in terms of normalized chip temperature non-uniformity, without the need for any additional system level complexity, reducing reliability risks. [ABSTRACT FROM AUTHOR]

Large data centers today already account for nearly 1.31% of total electricity consumption with cooling responsible for roughly 33% of that energy consumption. This energy intensive cooling problem is exacerbated by the presence of hotspots in multicore microprocessors due to excess coolant flow requirement for thermal management. Here we present a novel liquid-cooling concept, for targeted, energy efficient cooling of hotspots through passively optimized microchannel structures etched into the backside of a chip (embedded liquid cooling or ELC architecture). We adopt an experimentally validated and computationally efficient modeling approach to predict the performance of our hotspot-targeted ELC design. The design is optimized for exemplar non-uniform chip power maps using Response Surface Methodology (RSM). For industrially acceptable limits of approximately 0.4 bar (40 kPa) on pressure drop and one percent of total chip power on pumping power, the optimized designs are computationally evaluated against a base, standard ELC design with uniform channel widths and uniform flow distribution. For an average steady-state heat flux of 150 W/cm 2 in core areas (hotspots) and 20 W/cm 2 over remaining chip area (background), the optimized design reduces the maximum chip temperature non-uniformity by 61% to 3.7 °C. For a higher average, steady-state hotspot heat flux of 300 W/cm 2 , the maximum temperature non-uniformity is reduced by 54% to 8.7 °C. It is shown that the base design requires a prohibitively high level of pumping power (about 2000 fold for 150 W/cm 2 case and 600 fold for 300 W/cm 2 case) to match the thermal performance of the optimized, hotspot-targeting designs. The pumping power requirement for optimized designs is only 0.23% and 0.17% of the total chip power for 150 W/cm 2 and 300 W/cm 2 hotspot heat flux respectively. Moreover, the optimized designs distribute the coolant flow without any external flow control devices and the performance is only marginally affected by the manifold geometry used to supply the coolant to the microchannel heat transfer structure. This also attests to the robustness of the optimized embedded microchannel structures. [ABSTRACT FROM AUTHOR]

Abstract: A detailed thermo-hydrodynamic analysis of a hot water cooled manifold microchannel heat sink for electronic chip cooling is presented. The hot water cooling enables efficient recovery of heat dissipated by the even hotter chip by using hot water recovered from a secondary application. Contrary to usual expectation of laminar flow in electronic cooling, high flow rate and high fluid temperatures result in turbulent flow conditions in the inlet and outlet manifolds of the heat sink with predominantly laminar flow conditions in microchannels. To simulate these complex flow conditions, a three dimensional (3D) conjugate heat transfer model with turbulent flow is developed. Microchannel heat transfer structure is modeled as porous medium with permeability parameters extracted from a 3D model for a single microchannel. The energetic performance of the heat sink is analyzed in terms of 2nd law efficiency and sources of exergy destruction are identified by detailed local entropy generation analysis at low and high Reynolds number conditions of 2400 and 11200 respectively. This analysis shows that entropy generation due to heat transfer dominates the net entropy generation in the heat sink for both conditions. Although entropy generation due to viscous dissipation increases significantly with increased Reynolds number, it still contributes less than a third to the total entropy generated at high Reynolds numbers. Use of hot water reduces the heat transfer component of entropy generation significantly, thus leading to higher 2nd law efficiency. [Copyright &y& Elsevier]

Abstract: A novel framework is developed to determine the optimal operating conditions of water cooled microprocessor chips through a tradeoff between heat recovery from the coolant and the chip thermal reliability. For illustration, a manifold microchannel heat sink is evaluated experimentally and computationally. First, a single objective optimization is demonstrated by combining the heat recovery and chip reliability into a single parameter. Then, multi-objective optimizations are performed by using Pareto optimality and Multi-Criteria Design Analysis. Using conservative guidelines, these approaches suggest that for an optimal coolant flow rate of 1l/m, optimal coolant inlet temperature lies between 40 and 50°C. [Copyright &y& Elsevier]

Salmonella enterica serovar Heidelberg (American Type Culture Collection; ATCC 8326) was examined for the ability to adapt to the homologous stress of chlorine through exposure to increasing chlorine concentrations (25 ppm daily increments) in tryptic soy broth (TSB). The tested strain exhibited an acquired tolerance to chlorine in TSB with the tolerant cells growing in concentrations up to 400 ppm. In addition, the chlorine stressed cells displayed rugose morphology on tryptic soy agar (TSA) plates at 37°C. The minimum inhibitory concentration (MIC) of chlorine for adapted (rugose and smooth) cells was determined to be 550 ppm and 500 ppm, respectively whereas the MIC for the control was 450 ppm. The biofilm forming ability of the adapted and control cells were examined on both plastic and stainless steel surface at room temperature and 37°C. The rugose variant, in contrast to the smooth (adapted and control) showed the ability to form strong biofilms (P ≤ 0.05) on a plastic surface at room temperature and 37°C. Rugose cells compared to smooth and control attached more (P ≤ 0.05) to steel surfaces as well. The possibility of cross-adaptation was examined by exposing the adapted and control cells to different antibiotics according to the Clinical & Laboratory Standards Institute guidelines. Adapted cells exhibited reduced susceptibility to some of the antibiotics tested as compared to control. The findings of this study suggest that exposure to sublethal chlorine concentration during the sanitization procedure can result in tolerant Salmonella cells. Chlorine may confer cross-protection that aids in the survival of the tolerant population to other environmental stresses. [ABSTRACT FROM AUTHOR]

The present study evaluated the efficacy of recently approved Salmonella lytic bacteriophage preparation (SalmoFresh™) in reducing Salmonella on chicken breast fillets, as a surface and dip application. The effectiveness of phage in combination with modified atmosphere packaging (MAP) and the ability of phage preparation in reducing Salmonella on chicken breast fillets at room temperature was also evaluated. Chicken breast fillets inoculated with a cocktail of Salmonella Typhimurium, S. Heidelberg, and S. Enteritidis were treated with bacteriophage (109 PFU/mL) as either a dip or surface treatment. The dip-treated samples were stored at 4°C aerobically and the surface-treated samples were stored under aerobic and MAP conditions (95% CO2/5% O2) at 4°C for 7 d. Immersion of Salmonella-inoculated chicken breast fillets in bacteriophage solution reduced Salmonella (P < 0.05) by 0.7 and 0.9 log CFU/g on d 0 and d 1 of storage, respectively. Surface treatment with phage significantly (P < 0.05) reduced Salmonella by 0.8, 0.8, and 1 log CFU/g on d 0, 1, and 7 of storage, respectively, under aerobic conditions. Higher reductions in Salmonella counts were achieved on chicken breast fillets when the samples were surface treated with phage and stored under MAP conditions. The Salmonella counts were reduced by 1.2, 1.1, and 1.2 log CFU/g on d 0, 1, and 7 of storage, respectively. Bacteriophage surface application on chicken breast fillets stored at room temperature reduced the Salmonella counts by 0.8, 0.9, and 0.4 log CFU/g after 0, 4, and 8 h, respectively, compared to the untreated positive control. These findings indicate that lytic phage preparation was effective in reducing Salmonella on chicken breast fillets stored under aerobic and modified atmosphere conditions. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the efficacy of X-ray irradiation on the inactivation of a 3-strain mixture of Salmonella enterica (S. Enteritidis E190-88, S. Typhimurium ATCC 14028, and S. Montevideo ATCC 8387) using an RS 2400 X-ray system on chicken breast fillets and shell eggs and to evaluate the effect of X-ray treatments on the shelf life of chicken breast fillets and shell eggs during 20 day storage at 5 °C (chicken breast fillets (25 g) or whole shell egg samples were treated with the 0.1 and 2.0 and 0.1 and 1.0 kGy, for chicken and shell eggs, respectively, and stored at 5 °C for 20 days. Samples were examined for psychrotrophs and mesophiles counts at 0, 5, 10, 15, and 20 days). In this study, the skin on chicken breast fillets (25 g) or whole shell egg (50 g) samples were inoculated by immersing in 0.1% peptone water that contained 10 8−9 CFU ml −1 of a 3-strain mixture of S. enterica for 1 min in a biosafety cabinet. The samples were then air dried at 22 °C for 30 min (to allow bacterial attachment) in the biosafety cabinet prior to X-ray treatments (0.0, 0.1, 0.5, 1.0, and 2.0 kGy). The surviving Salmonella populations on the chicken breast fillets and the shell egg samples were evaluated using a nonselective medium (tryptic soy agar) for 6 h with xylose lysine desoxycholate (XLD) (Difco, Becton Dickinson) selective medium overlay. The plates were then incubated for an additional 18 h at 37 °C. The colonies were counted and the results were expressed as log CFU/g or egg. The results indicated that the 0.5 kGy X-ray treatment significantly reduced the Salmonella population by 1.9 and 3.0 log reduction on chicken breast meat and shell egg samples, respectively, with greater than a 6 log CFU reduction being achieved with 2.0 and 1.0 kGy X-ray for chicken and shell eggs, respectively. Furthermore, treatment with X-ray significantly reduced the initial inherent microbiota on chicken breast fillets and shell eggs and inherent levels were significantly (p < 0.05) lower than the control sample throughout the shelf-life storage at 5 °C for 20 days. These results indicated that X-ray is a promising antimicrobial technology for the poultry and egg industries. [ABSTRACT FROM AUTHOR]

The effectiveness of recently approved Salmonella lytic bacteriophage preparation (SalmoFresh™) in reducing Salmonella in vitro and on chicken breast fillets was examined in combination with lauric arginate (LAE) or cetylpyridinium chloride (CPC). In another experiment, a sequential spray application of this bacteriophage (phage) solution on Salmonella inoculated chicken skin after a 20 s dip in chemical antimicrobials (LAE, CPC, peracetic acid, or chlorine) was also examined in reducing Salmonella counts on chicken skin. The application of phage in combination with CPC or LAE reduced S. Typhimurium, S. Heidelberg, and S. Enteritidis up to 5 log units in vitro at 4 °C. On chicken breast fillets, phage in combination with CPC or LAE resulted in significant (p < 0.05) reductions of Salmonella ranging from 0.5 to 1.3 log CFU/g as compared to control up to 7 days of refrigerated storage. When phage was applied sequentially with chemical antimicrobials, all the treatments resulted in significant reductions of Salmonella . The application of chlorine (30 ppm) and PAA (400 ppm) followed by phage spray (10 9 PFU/ml) resulted in highest Salmonella reductions of 1.6–1.7 and 2.2–2.5 log CFU/cm 2 , respectively. In conclusion, the surface applications of phage in combination with LAE or CPC significantly reduced Salmonella counts on chicken breast fillets. However, higher reductions in Salmonella counts were achieved on chicken skin by the sequential application of chemical antimicrobials followed by phage spray. The sequential application of chlorine, PAA, and phage can provide additional hurdles to reduce Salmonella on fresh poultry carcasses or cut up parts. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the antimicrobial efficacy of lauric arginate (LAE) against Campylobacter jejuni (in broth and on chicken breast fillets) and spoilage microorganisms (on chicken breast fillets). In vitro antimicrobial activity of LAE was determined by treating C. jejuni (in pure culture) with 0 (control), 50, 100, and 200 mg/L of LAE solutions at 4°C for 2 h. Inoculated chicken samples with C. jejuni were treated with 0, 200, and 400 mg/kg of LAE, packaged, and stored at 4°C for 7 d for determining the efficacy of LAE against C. jejuni on meat. Noninoculated skinless chicken breast fillet samples were treated with 0, 200, and 400 mg/kg of LAE and were used for analysis of LAE treatments on growth of mesophilic and psychrotrophic organisms on d 0, 3, 9, and 14 during storage at 4°C. Lauric arginate was highly effective against C. jejuni in vitro with no detectable survivors. Lauric arginate significantly (P ⩽ 0.05) reduced C. jejuni counts on chicken breast fillets with 200 and 400 mg/kg treatments. Lauric arginate at 400 mg/L gave a maximum reduction of ∼1.5 log cfu/g of C. jejuni during 7 d of storage at 4°C without any change in pH of meat. Treating chicken breast fillets with 400 mg/kg of LAE caused 2.3 log cfu/g reduction of psychrotrophs (P ⩽ 0.05) compared with the control on d 0 of storage. However, no difference existed (P ⩾ 0.05) in the growth of psychrotrophs on chicken breast fillets after treatment with 200 and 400 mg/kg of LAE compared with the control after 3 d. The LAE treatments had no effect (P ⩾ 0.05) on growth of mesophilic organisms. The results of the study indicated that LAE is effective in reducing C. jejuni on chicken breast fillets. [ABSTRACT FROM AUTHOR]

In the present study, low concentrations of carvacrol (0.025 to 0.2%) and lauric arginate (LAE; 25 to 200 ppm) were tested at 4, 22, and 45°C in a broth model, and higher concentrations of carvacrol (0.1 to 5%) and LAE (200 to 5,000 ppm) were tested individually and in combination at 4°C in 3 different ground turkey samples (with 15, 7, and 1% fat con-tent) for their effectiveness against a 3-strain mixture of Salmonella. A low concentration of 25 ppm of LAE or 0.025% carvacrol had no effect on Salmonella in a broth model, but their mixture showed a synergistic action by reducing 6 log cfu/mL Salmonella counts to a nondetectable level within 30 min of exposure. The US Food and Drug Administration-recommended 200 ppm of LAE was not sufficient for Salmonella reductions in ground turkey when applied internally. High concentra-tions of 2,000 to 5,000 ppm of LAE or 1 to 2% carvacrol were needed to reduce Salmonella counts by 2 to 5 log cfu/g in ground turkey by internal application. No spe-cific relationship existed between fat content and LAE or carvacrol concentrations for Salmonella reductions. For example, 2,000 ppm of LAE could reduce Salmo-nella counts by 4 log cfu/g in 1% fat-containing turkey samples but very similar ~1.5 log cfu/g reductions in both 7 and 15% fat-containing ground turkey samples. For the total microbial load, about 2,000 ppm of LAE or 2% of carvacrol treatments were needed to achieve 2 to 3 log (P < 0.05) cfu/g reductions in different turkey samples. A mixture of 1% carvacrol and 2,000 ppni of LAE exhibited a synergistic action in ground turkey containing 7% fat by reducing the Salmonella counts by 4 log cfu/g, which was not found with individual antimicrobial treatments. [ABSTRACT FROM AUTHOR]